2021 publications citing ADF

First author: Southern, SA, NMR Response of the Tetrel Bond Donor,
Abstract: The tetrel elements (group 14) have the capacity to act as electrophilic sites and participate in structure-directing noncovalent tetrel bonds. We establish here the experimental response of several NMR interaction tensors to tetrel bonding via a range of Sn-119 and Cl-35 solid-state NMR experiments carried out in applied magnetic fields ranging from 4.7 to 21.1 T. Experimentally measured isotropic (1)J(Sn-119, Cl-35) coupling constants and Cl-35 nuclear quadrupolar coupling constants (C-Q) in a series of cocrystals of triphenyltin chloride, wherein tin acts as the tetrel bond donor atom, correlate with the experimental Sn center dot center dot center dot O tetrel bond length. Remarkably, the formation of moderately strong tetrel bonds to Ph3SnCl results in substantial reductions in (1)J(Sn-119, Cl-35) and CQ by 27-45 and 20-36%, respectively. The experimental findings are reproduced by periodic gauge-including projector-augmented wave density functional theory (DFT) calculations as well as spin-orbit relativistic zeroth-order regular approximation DFT calculations. The trend established here in J couplings parallels that for hydrogen bond donors, providing experimental evidence for the analogy between the two classes of interactions. Tin chemical shift tensors and computed magnetic shielding tensors correlate less well with structure, suggesting that these are less suitable measures of tetrel bond strength. These results contribute to the elucidation of important analogies and differences between tetrel bonds and related classes of noncovalent interactions such as hydrogen bonds and halogen bonds. This work provides new insights, which should prove to be useful in future studies of related crystalline or amorphous systems featuring tetrel bonds and/or tetrel-halogen moieties such as halide perovskites and related photovoltaic and optoelectronic materials.

First author: Ferrier, MG, Unsaturated Sulfur Crown Ethers Can Extract Mercury(II) and Show Promise for Future Copernicium(II) Studies: A Combined Experimental and Computational Study,
INORGANIC CHEMISTRY, 61, 807, (2022)
Abstract: The unsaturated hexathia-18-crown-6 (UHT18C6) molecule was investigated for the extraction of Hg(II) in HCl and HNO3 media. This extractant can be directly compared to the recently studied saturated hexathia-18-crown-6 (HT18C6). The default conformation of the S lone pairs in UHT18C6 is endodentate, where the pocket of the charge density, according to the crystal structures, is oriented toward the center of the ring, which should allow better extraction for Hg(II) compared to the exodentate HT18C6. Batch study experiments showed that Hg(II) had better extraction at low acid molarity (ca. 99% in HCl and ca. 95% in HNO3), while almost no extraction was observed above 0.4 M HCl and 4 M HNO3 (<5%). Speciation studies were conducted with the goal of delineating a plausible extraction mechanism. Density functional theory calculations including relativistic effects were carried out on both Hg(II)-encapsulated HT18C6 and UHT18C6 complexes to shed light on the binding strength and the nature of bonding. Our calculations offer insights into the extraction mechanism. In addition to Hg(II), calculations were performed on the hypothetical divalent Cn(II) ion, and showed that HT18C6 and UHT18C6 could extract Cn(II). Finally, the extraction kinetics were explored to assess whether this crown can extract the short-lived Cn(II) species in a future online experiment.

First author: de Simone, M, Study of the Electronic Structure of M-2(CH2CMe3)(6) (M = Mo, W) by Photoelectron Spectroscopy and Density Functional Theory,
ORGANOMETALLICS, 61, 807, (2022)
Abstract: The valence electronic structures of two dinuclear alkyl compounds containing sigma(2)pi(4) triple bonds between group 6 metals, viz., M-2(CH2CMe3)(6) (M = Mo, W), have been investigated using a combination of molecular orbital theory and variable photon energy photoelectron spectroscopy (PES). Density functional theory (DFT) calculations using PBEO-dDsC functionals, which include dispersion forces, have been performed on the title compounds as well as several closely related M2X6 (M = Mo, W) compounds. The DFT calculations on the dinuclear neopentyl complexes are in excellent agreement with the solid-state structures, measured PES spectra, and ultraviolet-visible (UV-vis) spectra. The top nine filled orbitals in both cases are associated with M-M and M-C bonding. The orbital energy pattern conforms to that anticipated for a D-3d (staggered) M2C6 skeleton. For both Mo and W, the highest-energy pair of orbitals are of e(u) (pi) symmetry, followed by one of a(1g) (sigma) symmetry, and comprise the metal-metal triple bond. The orbital energies are higher for W than for Mo, and the separation between the pi and sigma orbitals is greater for W, reflecting a greater relativistic stabilization of the tungsten 6s orbital compared to that of the Mo 5s orbital. The spin-orbit splitting in the pi ionization of W-2(CH2CMe3)(6) has been resolved and successfully modeled. A graphical comparison of valence orbital energies for Mo2X6, where X = CH2CMe3, NMe2, and OCH2CMe3, shows how the Mo-Mo pi and sigma levels vary as a function of the ligand set.

First author: Gao, JX, A promising strategy for increasing phosphorescent quantum yield: The ligand 10-cyclic chelate of the tetradentate Pt(II) complex,
Abstract: In this paper, the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to deeply investigate the photophysical properties and radiative and non-radiative processes of tetradentate Pt(II) complexes with 10- and 11-cyclic chelate ligands. According to the calculated results, the cyclization of ligand can distinctly influence on the emission wavelengths of complexes. In addition, due to the larger spin density, spin-orbit coupling (SOC) matrix element, and smaller metal-centered d-d excited states ((MC)-M-3) character, singlet-triplet splitting energy ( increment E(S-n – T-1)), the radiation rate constant ( kr = 5.9E + 04) of the 10-cyclic chelate ligand complex is significantly higher than that of the 11-cyclic chelate ligand complex ( kr = 1.9E + 04). In the case of temperature-dependent non-radiative process, compared with 11-cyclic chelate ligand complex, 10-cyclic chelate ligand complex should possess the larger non-radiative rate because of the lower energy barrier from the excited state to (MC)-M-3. What’s more, the 10-cyclic chelate ligand complex has small Huang-Rhys factor, which suggests that the 10-cyclic chelate ligand complex has better rigidity and color purity. This investigation could provide some useful information for designing the high-performance organic light-emitting diode (OLED) materials.

First author: Kojima, Y, Synthesis and n-Type Semiconducting Properties of Bis(dioxaborin) Compounds Containing a pi-Extended 2,2 ‘-Bithiophene Structure,
Abstract: Bis(dioxaborin) compounds containing pi-conjugated systems have been studied as n-type semiconductors for organic field-effect transistors (OFETs). In this study, with the aim of investigating the effect of the extension of the pi-conjugation on the n-type semiconducting properties and stability of bis(dioxaborin) compounds, we synthesized new compounds containing 2,2 ‘-bithiophene derivatives extended with an olefin or an acetylene spacer. The absorption maxima of the compounds containing olefin spacers were greatly red-shifted compared with those of the original compound without a pi-spacer. The newly synthesized compounds exhibited high electron affinity, and the olefin spacers effectively reduced the on-site Coulomb repulsion in the two-electron reduction of the compounds. An OFET fabricated using one of these compounds having a layer-by-layer crystal structure exhibited n-type semiconductor behavior with a low threshold voltage, most likely due to the small on-site Coulomb repulsion. The electron-transporting properties were investigated by theoretical calculations based on the Marcus theory.

First author: Zheng, HB, Investigation on micro-mechanism of palm oil as natural ester insulating oil for overheating thermal fault analysis of transformers,
HIGH VOLTAGE, 17, 807, (2022)
Abstract: In order to explore the pyrolysis mechanism of palm oil as the natural ester insulating liquid from the molecular aspect, the ReaxFF reactive force field was used to simulate the pyrolysis process of palm oil. Firstly, the molecular models of the four main molecules of palm oil-tripalmitin, trilinolein, triolein, and tristearin-are constructed via density functional theory (DFT). Secondly, the vibrational frequencies of the four molecules are calculated, so as to calculate the infrared (IR) spectra. Thirdly, molecular dynamics (MD) simulations employing the ReaxFF method are performed to simulate the pyrolysis reaction of the palm oil system under different temperatures, so as to observe the generation pathways of major products used in the dissolved gas analysis (DGA) in the transformer thermal fault analysis. Finally, hydrogen bonds in the pyrolysis process are counted. It is found that the number of hydrogen bonds gradually increased with the increase of pyrolysis time and pyrolysis temperature. It reveals why the life of the insulating paper immersed with natural esters is prolonged, and why the breakdown voltage is reduced slowly in the actual experiment from another perspective. This study can provide theoretical guidance and effective reference for the thermal fault analysis of an insulating liquid using palm oil as raw material.

First author: Golzadeh, B, On the nature of M-L bond and the puckering of some B-heterocyclic carbenes and silylenes in their relevant complexes with coinage metals: A theoretical quest,
Abstract: Boron heterocyclic divalents (BHEs; E=C, Si) are organometallic ligands, and their coordination chemistry with transition metals, particularly coinage (G11) metals (Cu, Ag, Au), is interesting. Here, quantum chemical calculations at M06/def2-tzvp level of theory are performed to study the BHEs; E=C, Si along with BP86/TZ2P level of theory for the calculation of its corresponding complexes of coinage metals (X2BHE-MCl; M=Cu(I), Ag(I), Au(I)) with selected halogen and alkyl side groups (X=F, Cl, Br, Me, iPr, tBu). Results display that the interaction energies (Delta E-int) for E-M bond in X2BHE-MCl complexes (M=Cu(I), Au(I), Ag(I); E=C, Si; X=F, Cl, Br, Me, iPr, tBu) are significant and follow the familiar trend for the G11 transition metals as Au(I) > Cu(I) > Ag(I). The nature of E-M bond in the complexes is evaluated using natural bond orbital (NBO), energy decomposition analysis (EDA), and excited transition state-natural orbitals for chemical valance (ETS-NOCV). The interaction energy (E-int) in X2BHE-MCl complexes studied here is largely electrostatic, and this feature accounts for about 65% of the total interaction energy. Furthermore, it is found that in carbene (1(X)-MCl) complexes with electron-withdrawing side groups (X=F, Cl, Br), the group 11 metals form stronger bonds with X2BHEs rather than their corresponding silylenes (2(X)-MCl). The comparison of EDA-NOCV results for E-M bond with the same M atom and X side groups in 1(X)-MCl and 2(X)-MCl indicates that the silylenes are typically stronger s donors and weaker p acceptors than the corresponding carbene ligands.

First author: Yao, FP, The inhibition of p-hydroxyphenyl hydroxyl group in residual lignin on enzymatic hydrolysis of cellulose and its underlying mechanism,
Abstract: ABSTR A C T The controlling factors of the inhibition on enzymatic hydrolysis caused by residual lignin were identified with molecular level understanding of the mechanism. Residual lignin samples with different properties were isolated, characterized and added into the enzymatic hydrolysis of Avicel. It was found that the phenolic hydroxyl group (OH) was the main inhibitor in residual lignin, and the p-hydroxyphenyl OH was the crucial sub-structure that exhibited the highest inhibition and non-productive adsorption, ascribing to its higher electrophilicity and lower steric hindrance. The H-bond interaction and n -n stacking between phenolic OH of lignin and phenolic OH of tyrosine on the planar face of carbohydrate binding module of cellulase were probably responsible for the non-productive adsorption. The binding sites of H-bonds may be the H in phenolic OH of lignin and the O in phenolic OH of tyrosine, respectively, and that of the n -n stacking may be the benzene rings of them.

First author: Liu, HY, Pyrene Core-based Dopant-free Hole Transporting Materials for Perovskite Solar Cells: A Theoretical Design and Experimental Verification,
Abstract: Hole transport materials (HTMs) are an indispensable part of perovskite solar cells (PSCs), and the role of HTMs in improving the performance of PSCs is worth highlighting. In this work, an efficient triphenylamine-based HTM (HY4) is constructed by introducing a fused aromatic core. Theoretical calculated results reveal that the introduced pyrene core in HY4 with a better planarity than the parental HTM (H101 is conducive to promote the intermolecular pi-pi stacking and reduce the reorganization energy in the hole transferring process. Experimental characterization further confirms that HY4 exhibits matched energy levels, high hole mobility, smooth film morphology, and extraordinary hole extraction ability. Therefore, dopant-free HY4-based PSC devices can achieve a higher power conversion efficiency of 16.62% than a dopant-free H101-based device (14.92%). This work demonstrates that incorporating a fused aromatic core in HTMs is a promising strategy to improve device performance.

First author: Pietrzak, M, Photoinduced and ground state conversions in a cyclic beta-thioxoketone,
RSC ADVANCES, 12, 681, (2021)
Abstract: The photochemistry of a cyclic beta-thioxoketone (2-methyl-1-(2-thioxycyclohexyppropan-1-one (MTPO)) is investigated by NMR, UV, and IR experiments supported by DFT calculations. MTPO exists as a tautomeric mixture of an enol and a thiol form. Irradiation at Low temperature Led to a cis-trans isomerization of the thiol form resulting in a rather unusual enethiol (3). This is followed by a transfer of the isopropyl methine proton onto the carbonyl carbon resulting in yet another enethiol isomer (4). The photoconversion mechanisms without water present are discussed. Photochemical experiments at ambient temperature showed involvement of water in the excited state and resulted in another ketoform (5). The same species was also obtained when the products of the Low temperature experiments were kept in the dark at ambient temperature.

First author: Hansen, T, How Solvation Influences the S(N)2 versus E2 Competition,
Abstract: We have quantum chemically investigated how solvation influences the competition between the S(N)2 and E2 pathways of the model F- + C2H5Cl reaction. The system is solvated in a stepwise manner by going from the gas phase, then via microsolvation of one to three explicit solvent molecules, then last to bulk solvation using relativistic density functional theory at (COSMO)-ZORA-OLYP/QZ4P. We explain how and why the mechanistic pathway of the system shifts from E2 in the gas phase to S(N)2 upon strong solvation of the Lewis base (i.e., nucleophile/protophile). The E2 pathway is preferred under weak solvation of the system by dichloromethane, whereas a switch in reactivity from E2 to S(N)2 is observed under strong solvation by water. Our activation strain and Kohn-Sham molecular orbital analyses reveal that solvation of the Lewis base has a significant impact on the strength of the Lewis base. We show how strong solvation furnishes a weaker Lewis base that is unable to overcome the high characteristic distortivity associated with the E2 pathway, and thus the S(N)2 pathway becomes viable.

First author: Sattarova, AF, Quantum-chemical approaches in the study of fullerene and its derivatives by the example of the most typical cycloaddition reactions: A review,
Abstract: In the past two decades, quantum chemistry has become an indispensable tool for the reliable interpretation of experimental measurements of a wide range of molecular properties of fullerene and its derivatives. Among the modern quantum-chemical methods of analysis, preference is given to the density functional theory. This review describes the computational studies that demonstrate rather comprehensively the prospects of quantum-chemical calculations in many fields of the chemistry of fullerene and its derivatives, such as geometric parameters, stability of structures, molecular spectroscopic properties, electronic structures, the nature of bonds, thermochemistry, and simulation of the kinetics and mechanism of processes. The review focuses on the most typical cycloaddition reactions such as Diels-Alder, Prato and Bingel-Hirsch reactions. The general trends of scientific studies in this area are also discussed and a wide range of references is provided where the readers can find technical details of computational approaches that may be of interest for them.

First author: Hu, SX, Electronic Structures and Properties of Bimetallic Plutonium Group 13 Carbonyl Compounds [XPuCO] (X = B, Al, and Ga),
INORGANIC CHEMISTRY, 60, 18794, (2021)
Abstract: Bonding features of heterobimetallic complexes containing f-block elements are fundamental content in actinide chemistry. In order to account for the structural periodicity of the X-Pu carbonyls and the formation of chemical bonds between bimetallic plutonium and group 13 carbonyl compounds, we report a comprehensively quantum-chemical study of the electronic structure and properties of XPuCO (X = B, Al, and Ga). With increasing atomic radii of the group 13 elements, the XPuCO structure alternates from cyclic [PuCBO] to linear [AlCPuO] and [GaCPuO]. The bonding analysis indicates that the donor-acceptor model is the best description for bonding interactions of metal and ligands with different donation patterns of CBO -> Pu and XC -> PuO (X = Al and Ga). The apparent XC <- PuO backdonation increases the C-Pu bond strength markedly and stabilizes the linear geometry of [AlCPuO] and [GaCPuO], while spin-orbit coupling is found to be significant in the stabilization of [PuCBO]. The ground electron configurations and natural orbital analysis indicate that cyclic [PuCBO] and linear [XCPuO] (X = Al and Ga) are considered as complexes of Pu(III) and Pu(V), respectively. The trend presents a valuable insight for the 5f/6d-np bonding interactions, especially for the fundamental understanding of transuranic elements.

First author: Liang, JW, Square tetravalent chalcogen bonds in dimeric aggregates: a joint crystallographic survey and theoretical study,
CRYSTENGCOMM, 24, 975, (2022)
Abstract: Chalcogen bonds (ChBs) involving hypervalent chalcogen atoms have been the target of several recent crystallographic and theoretical studies. In this study, we first gathered a large number of crystal structures containing a four-membered synthon with double tetravalent ChMIDLINE HORIZONTAL ELLIPSISO contacts were initially gathered from the Cambridge Structural Database. Then, a series of dimeric complexes of tetravalent chalcogenoxide species were selected to model such square interactions found in the crystals. In addition, atoms in molecules, noncovalent interaction index, natural bond orbital, and energy decomposition analyses were also employed to characterize these interactions. Square tetravalent ChBs show primary electrostatic character and become stronger with increasing atomic polarizability (S < Se < Te), similar to conventional divalent ChBs. In general, strong electron-withdrawing groups have a stronger effect on the sigma-hole intensity of the chalcogen atoms than the basicity of the interacting O atoms, leading to enhanced tetravalent ChB interactions. We hope that the results reported herein will promote the application of hypervalent ChBs in crystal engineering and materials design.

First author: Jana, G, XNgNSi (X = HCC, F; Ng = Kr, Xe, Rn): A New Class of Metastable Insertion Compounds Containing Ng-C/F and Ng-N Bonds and Possible Isomerization therein,
Abstract: Recently, astronomically important silaisocyanoacetylene (HCCNSi) possessing a large dipole moment has been detected for the first time with the help of crossed molecular beam experiments. Quantum chemical computations at higher levels of theory have also been performed to characterize the transient species. In this study, we have analyzed the equilibrium geometry, stability, reactivity, and energetics as well as the nature of bonding in the noble gas (Ng) inserted HCCNSi compound. We have also considered its F analogue to understand the influence of the most electronegative atom in the compound. Metastable behavior of the XNgNSi compounds (X = HCC, F; Ng = Kr-Rn) is examined by calculating thermochemical parameters like free energy change (Delta G) and zero-point-energy-corrected dissociation energy (D-0) at 298 K for all possible two-body (2B) and three-body (3B) (both neutral as well as ionic) dissociation channels using coupled-cluster theory [CCSD (T)] in addition to density functional theory (DFT) as well as second order Moller-Plesset perturbation theory (MP2). The set of predicted compounds is found to be endergonic in nature, having high positive free energy change suggesting the thermochemical stability of the compounds except for the 2B Ng-release paths. Though thermodynamically feasible, they are kinetically protected with very high activation free energy barriers. Interestingly, the release of Ng from the parent moiety XNgNSi produces the XSiN isomer, by 180 degrees flipping of the NSi moiety. This can also be seen in the dynamical simulation carried out with the help of atom-centered density matrix propagation (ADMP) technique at 2000K for 1 ps. The bonding in Ng-C, Ng-F, and Ng-N bonds of the studied compounds is analyzed and described with the aid of natural bond orbital (NBO), topological parameters computed using atoms-in-molecules theory (AIM), energy decomposition analysis (EDA), and adaptive natural density partitioning (AdNDP) methods. The natural charge distribution on the constituent atoms suggests that the compounds can be partitioned into both ways of representations, viz., neutral radical as well as ionic fragments. Lastly, the reactivity of the compounds is scrutinized using certain reactivity descriptors calculated within the domain of conceptual density functional theory (CDFT).

First author: Weller, S, A P-Functionalized [3]Ferrocenophane with a Dynamic SPS-Bridge,
Abstract: Ferrocene-1,1 ‘-dithiol reacts with PCl3 and P(NMe2)(3) to give [3]ferrocenophanes with SPS-ansa-bridges comprising potentially reactive P-Cl and P-N bonds at the central bridge atom. The products were characterized by NMR data and single-crystal XRD studies. The P-chloro-derivative exists both in the solid state and in solution as a mixture of two energetically nearly degenerate conformers with different stereochemical disposition of the ansa-bridge. Activation parameters for the dynamic equilibration between both isomers in solution were determined by dynamic NMR spectroscopy. Computational studies suggest that the isomerization proceeds via a torsional motion of the bridging SPS-unit rather than via configuration inversion at the phosphorus atom.

First author: Gorantla, SMNVT, EDA-NOCV Calculation for Efficient N-2 Binding to the Reduced Ni3S8 Complex: Estimation of Ni-N-2 Intrinsic Interaction Energies,
ACS OMEGA, 6, 33389, (2021)
Abstract: The binding of the dinitrogen molecule to the metal center is the first and crucial step toward dinitrogen activation. Favorable interaction energies are desired by chemists and biochemists to study model complexes in the laboratory. An electrochemically reduced form of a previously isolated sulfur-bridged Ni3S8 complex is inferred to bind N-2 at multiple Ni centers, and this bonded N-2 undergoes reductive protonation to produce hydrazine (N2H4) as the product in the presence of a proton donor. Density functional theory (DFT) calculations and quantum theory of atoms in molecules (QTAIM) analysis have been carried out to shed light on the nature of N-2 binding to an anionic trinuclear Ni3S8 complex. Additionally, energy decomposition analysis with the combination of natural orbital for chemical valence (EDA-NOCV) analysis has been performed to estimate the pairwise interaction energies between the Ni center and the N-2 molecule under experimental conditions.

First author: Gorantla, SMNVT, Estimations of Fe-N-2 Intrinsic Interaction Energies of Iron-Sulfur/Nitrogen-Carbon Sites: A Deeper Bonding Insight by EDA-NOCV Analysis of a Model Complex of the Nitrogenase Cofactor,
ACS OMEGA, 6, 33932, (2021)
Abstract: The MoFe7S9C1- unit of the nitrogenase cofactor (FeMoco) attracts chemists and biochemists due to its unusual ability to bind aerial dinitrogen (N-2) at ambient condition and catalytically convert it into ammonia (NH3). The mode of N-2 binding and its reaction pathways are yet not clear. An important conclusion has been made based on the very recent synthesis and isolation of model Fe(I/0)-complexes with sulfur-donor ligands under the cleavage of one Fe-S bond followed by binding of N-2 at the Fe(0) center. These complexes are structurally relevant to the nitrogenase cofactor (MoFe7S9C1-). Herein, we report the EDA-NOCV analyses and NICS calculations of the dinitrogen-bonded dianionic complex Fe-0-N-2 (1) (having a C-Ar <- Fe pi-bond) and monoanionic complex Fe-I-N-2 (2) (having a C-Ar -Fe sigma-bond) to provide a deeper insight into the Fe-N-2 interacting orbitals and corresponding pairwise interaction energies (EDA-NOCV = energy decomposition analysis coupled with natural orbital for chemical valence; NICS = nucleus-independent chemical shifts). The orbital interaction in the Fe-N-2 bond is significantly larger than Coulombic interactions, with major pairwise contributions coming from d(Fe) orbitals to the empty pi* orbitals of N, (three Fe -> N-2). Delta E-int values are in the range of -61 to -77 kcal mol(-1). Very interestingly, NICS calculations have been carried out for the fragments before and after binding of the N-2 molecule. The computed sigma- and pi-aromaticity values are attributed to the position of the Fe atoms, oxidation states of Fe centers, and Fe-C bond lengths of these two complexes.

First author: Comas-Vila, G, Accurate Fe-57 Mossbauer Parameters from General Gaussian Basis Sets,
Abstract: The prediction of isomer shifts in Fe-57 Mossbauer spectra is typically achieved by building calibration lines using the values of the density at the nuclear position. Using Slater-type orbital basis or large and specific Gaussian-type orbital basis has been thus far mandatory to achieve accurate predictions with density functional theory methods. In this work, we show that replacing the value of the density at the nucleus by the density integrated in a sphere of radius 0.06 au centered on the Fe nuclei yields excellent calibration lines (r(2) = 0.976) with a high predictive power (q(2) = 0.975, MAE = 0.055 mm.s(-1)) while using the conventional def2-TZVP basis set and X-ray geometrical parameters. Our data set comprises 69 Fe-57-containing compounds and 103 signals. We also find B3LYP performing significantly better than the PW91 functional.

First author: Conquest, OJ, Calculating Entropies of Large Molecules in Aqueous Phase,
Abstract: Entropy benchmarking of different sized molecules in aqueous phase is carried out for known solvation models, where we compare geometry and solvation cavity packing parameters, which allows us to improve the accuracy of the obtained entropy values using empirical corrections. A comparison of solvation entropy models is conducted for a benchmarking set of 56 molecules, showing how an accurate description of cavitation entropy and its hindrance on other entropy values is important for large-sized solute molecules. Finally, we compare reaction free energies with entropies calculated using the most accurate solvation model considered, where we demonstrate a significant improvement in the accuracy relative to experimental values.

First author: Wilson, TR, Electron Density Geometry and the Quantum Theory of Atoms in Molecules,
Abstract: A novel form of charge density analysis, that of isosurface curvature redistribution, is formulated and applied to the toy problem of carbonyl oxygen activation in formaldehyde. The isosurface representation of the electron charge density allows us to incorporate the rigorous geometric constraints of closed surfaces toward the analysis and chemical interpretation of the charge density response to perturbations. Visual inspection of 2D isosurface motion resulting from applied external electric fields reveals how the isosurface curvature flows within and between atoms and that a molecule can be uniquely and completely partitioned into chemically significant regions of positive and negative curvatures. These concepts reveal that carbonyl oxygen activation proceeds primarily through curvature and charge redistribution within rather than between Bader atoms. Using gradient bundle analysis-the partitioning of formaldehyde into infinitesimal volume elements bounded by QTAIM zero-flux surfaces-the observations from visual isosurface inspection are verified. The results of the formaldehyde carbonyl analysis are then shown to be transferable to the substrate carbonyl in the ketosteroid isomerase enzyme, laying the groundwork for extending this approach to the problems of enzymatic catalysis.

First author: Stennett, CR, Designing a Solution-Stable Distannene: The Decisive Role of London Dispersion Effects in the Structure and Properties of {Sn(C6H2-2,4,6-Cy-3)(2) 2 (Cy = Cyclohexyl),
Abstract: The reaction of 1 equiv of the dimeric lithium salt of a new London dispersion effect donor ligand {Li(C6H2-2,4,6-Cy-3)center dot OEt2}(2) (Cy = cyclohexyl) with SnCl2 afforded the distannene {Sn(C6H2-2,4,6-Cy-3)(2)}(2) (1). The distannene remains dimeric in solution, as indicated by its room-temperature 119Sn NMR signal (delta = 361.3 ppm) and its electronic spectrum, which is invariant over the temperature range of -10 to 100 degrees C. The formation of the distannene, which has a short Sn-Sn distance of 2.7005(7) A and greatly enhanced stability in solution compared to that of other distannenes, is due to increased interligand London dispersion (LD) attraction arising from multiple close approaches of ligand C-H moieties across the Sn-Sn bond. DFT-D4 calculations revealed a dispersion stabilization of dimer 1 of 38 kcal mol(-1) and a dimerization free energy of Delta G(dimer) = -6 kcal mol(-1). In contrast, the reaction of 2 equiv of the similarly shaped but less bulky, less hydrogen-rich Li(C6H2-2,4,6-Ph-3)center dot(OEt2)(2) with SnCl2 yielded the monomeric stannylene Sn(C6H2-2,4,6-Ph-3)(2) (2), which is unstable in solution at ambient temperature.

First author: Maria, L, Experimental and Computational Study of a Tetraazamacrocycle Bis(aryloxide) Uranyl Complex and of the Analogues {E=U=NR}2+(E = O and NR),
INORGANIC CHEMISTRY, 143, 21478, (2021)
Abstract: The reaction of [U(K6-{(t-Bu2ArO)2Me2-cyclam})I][I] (H2{(t-Bu2ArO)2Me2-cyclam} = 1,8-bis(2-hydroxy-3,5-di-tertbutyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane) with 2 equiv of NaNO2 in acetonitrile results in the isolation of the uranyl complex [UO2{(t-Bu2ArO)2Me2-cyclam}] (3) in 31% yield, which was fully characterized, including by single-crystal X-ray diffraction. Density functional theory (DFT) computations were performed to evaluate and compare the level of covalency within the U=E bonds in 3 and in the analogous trans-bis(imido) [U(K4-{(t-Bu2ArO)2Me2-cyclam})(NPh)2] (1) and trans-oxido-imido [U(K4{(t-Bu2ArO)2Me2-cyclam})(O)(NPh)] (2) complexes. Natural bond orbital (NBO) analysis allowed us to determine the mixing covalency parameter A, showing that in 2, where both U-Ooxido and U-Nimido bonds are present, the U-Nimido bond registers more covalency with regard to 1, and the opposite is seen for U-Ooxido with respect to 3. However, the covalency driven by orbital overlap in the U-Nimido bond is slightly higher in 1 than in 2. The 15N-labeled complexes [U(K4-{(t-Bu2ArO)2Me2-cyclam})(15NPh)2] (1-15N) and [U(K4-{(t-Bu2ArO)2Me2-cyclam})(O)(15NPh)] (2-15N) were prepared and analyzed by solution 15N NMR spectroscopy. The calculated and experimental 15N chemical shifts are in good agreement, displaying the same trend of SN (1-15N) > SN (2-15N) and reveal that the 15N chemical shift may serve as a probe for the covalency of the U=NR bond.

First author: Guda, AA, Understanding X-ray absorption spectra by means of descriptors and machine learning algorithms,
Abstract: X-ray absorption near-edge structure (XANES) spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom. However, the quantitative analysis of these spectra is not straightforward. Even with the most recent advances in this area, for a given spectrum, it is not clear a priori which structural parameters can be refined and how uncertainties should be estimated. Here, we present an alternative concept for the analysis of XANES spectra, which is based on machine learning algorithms and establishes the relationship between intuitive descriptors of spectra, such as edge position, intensities, positions, and curvatures of minima and maxima on the one hand, and those related to the local atomic and electronic structure which are the coordination numbers, bond distances and angles and oxidation state on the other hand. This approach overcoms the problem of the systematic difference between theoretical and experimental spectra. Furthermore, the numerical relations can be expressed in analytical formulas providing a simple and fast tool to extract structural parameters based on the spectral shape. The methodology was successfully applied to experimental data for the multicomponent Fe:SiO2 system and reference iron compounds, demonstrating the high prediction quality for both the theoretical validation sets and experimental data.

First author: Komissarov, L, Improving the Silicon Interactions of GFN-xTB,
Abstract: A general-purpose density functional tight binding method, the GFN-xTB model is gaining increased popularity in accurate simulations that are out of scope for conventional ab initio formalisms. We show that in its original GFN1-xTB parametrization, organosilicon compounds are described poorly. This issue is addressed by re-fitting the model’s silicon parameters to a data set of 10 000 reference compounds, geometry-optimized with the revPBE functional. The resulting GFN1(Si)-xTB parametrization shows improved accuracy in the prediction of system energies, nuclear forces, and geometries and should be considered for all applications of the GFN-xTB Hamiltonian to systems that contain silicon.

First author: Castro-Ocampo, O, Understanding hydroxyl radicals addition to CO2 on alpha-Fe2O3 (110) surface photocatalyst for organic compounds production,
FUEL, 310, 5931, (2022)
Abstract: In this work, Density Functional Theory (DFT) calculations were performed to assess the photo-catalytic properties of hematite (alpha-Fe2O3) and the atomistic modeling of the CO2 conversion mechanism to organic molecules on such a surface. The reaction pathways for the CO2 simulated photo-transformation were modeled with the string method. The reaction mechanism obtained by DFT calculations evidenced the H2O2 molecules reduction instead of the CO2 reduction at the first step, inducing center dot OH radical formation. The following CO2 activation is induced by the addition of the center dot OH radical through one of the pi* bonds of CO2 molecule, unlike the commonly reported CO2 reduction, resulting in the bicarbonate anion. The emergence of carbonic acid is followed by carbon reduction reactions up to methanol. According to the adsorption energies and topological analysis of the bond critical points, the intermediates exhibited closed-shell interactions with the hematite surface. Electronic structure properties were evaluated at the DFT+U+J level. Opto-electronic parameters were also evaluated experimentally; giving validity to the results obtained by the DFT. This work also shows the first theoretical insight into the conversion of CO2 with H2O2 into H2CO3, HCOOH, CH2O and CH3OH on the hematite (1 1 0) surface. Additionally, to support the theoretical elucidation, a mixture of iron oxides (Fe2O3 – FeOOH) nanoparticles were prepared in accordance to recent published results suggesting a heterogeneous catalytic process, instead a homogeneous Fenton’s method to evaluate the photocatalytic properties and the redox-potential to degrade CO2. One of the predominant phases observed in the iron oxide mixture corresponds to hematite. Moreover, the photocatalytic process of CO2 conversion with iron oxide nanoparticles was experimentally performed. The formation of methanol was evidenced via FTIR analysis.

First author: Cai, HX, CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties,
INORGANIC CHEMISTRY, 60, 18859, (2021)
Abstract: Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO2, which to some extent resolves the environmental concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, [b-ONO]M CCH3 (THF)(2) ([b-ONO] = {(C6H4 [C(CF3)(2)O])(2)N}(3-); M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO2 cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The M C moiety in the complexes turns out to be the active site for the [2 + 2] cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M-C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M-O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.

First author: Wisofsky, GK, Ligation of Boratabenzene and 9-Borataphenanthrene to Coinage Metals,
INORGANIC CHEMISTRY, 60, 18981, (2021)
Abstract: The reactions of boratabenzene and borataphenanthrene anions with group 11 Ph3PMCl reagents furnished eta(2) coordination complexes, with the exception of the copper boratabenzene species that adopted an mode. The binding of arene ligands to copper in an eta(6) manner is rare, and altering the ancillary ligand on copper to an N-heterocyclic carbene switched the binding of the boratabenzene to eta(2), indicating that such ligands are capable of vacating coordination sites. The eta(2) coordination complexes bind side-on, akin to olefins, via a borataalkene unit, although with the carbon atom much more proximal to the metal center than boron.

First author: Colaco, MC, Janusene as a silver ion scavenger: insights from computation,
NEW JOURNAL OF CHEMISTRY, 46, 2393, (2022)
Abstract: Janusene is a [3,3]ortho-cyclophane that possesses four aromatic moieties of which two are held together in a quasi-parallel or in a cleft-shaped arrangement. The multiple coordination sites available in janusene were tested by bonding of Ag+ ions in different positions of the janusene structure, leading to 35 systems. Our results evidence that janusene is able to stabilize up to five Ag+ ions simultaneously. Due to the symmetric coordination positions, several isomers have been obtained with systems containing up to 4 Ag+ ions. Janusene-Ag+ interactions, for all systems, are partially covalent in nature, mainly stabilized by Delta E-orb and Delta E-ele interactions. MEP isosurfaces reveal that the different Ag+ coordination modifies the janusene electron density, thus modulating the reactivity of its rings. Janusene is also able to stabilize, by approximate to-130 kcal mol(-1), a [AgAMIDLINE HORIZONTAL ELLIPSISAgB](2+) interaction at short distances, in the cleft between facial rings. Interestingly, these interactions are enhanced by coordination of other Ag+ ions, increasing the lateral rings’ orbital interactions to the stabilization of the [AgAMIDLINE HORIZONTAL ELLIPSISAgB](2+) interaction. This study reveals the presence of some unusual and previously unexplored features of janusene’s electronic structure.

First author: Portela, S, Nature of C-I…pi Halogen Bonding and its Role in Organocatalysis,
Abstract: The nature of the C-I…pi halogen bonding and its mode of activation in organocatalysis have been quantitatively explored in detail by means of Density Functional Theory (DFT) calculations. To this end, the uncatalyzed homo-[4+2]-cycloaddition reaction involving 2-alkenylindoles is compared to the analogous process mediated by iodine-substituted azolium salts. It is found that the catalysts establish relatively strong C-I…pi noncovalent interactions with the indole reactant, which are characterized by a high degree of covalency. This interaction results in a significant acceleration of the cycloaddition by lowering the activation barrier up to 6 kcal/mol with respect to the uncatalyzed reaction. The calculations predict that this barrier can be further reduced by increasing the electrophilicity of the catalyst. Our quantitative analyses reveal that the origin of the catalysis is found mainly in a significant reduction of the steric (Pauli) repulsion between the diene and dienophile, therefore confirming the generality of the recently introduced Pauli-repulsion lowering concept.

First author: Sahadevan, SA, Combined Experimental/Theoretical Study on the Luminescent Properties of Homoleptic/Heteroleptic Erbium(III) Anilate-Based 2D Coordination Polymers,
INORGANIC CHEMISTRY, 60, 17765, (2021)
Abstract: The synthesis, structural and photophysical characterization, and theoretical studies on homo/heteroleptic neutral 2D-layered coordination polymers (CPs), obtained by combining the Er-III in ion with chlorocyananilate (ClCNAn) and/or tetrafluoroterephthalate (F4BDC) linkers, are herein reported. The structure of the heteroleptic Er-III-based CP, formulated as [Er-2(CICNAn)(2)(F4BDC)(DMSO)(6)](n) (1) is also reported. 1 crystallizes in the triclinic P1 space group, and the structure consists of neutral 2D layers formed by Er-III ions linked through the two linkers oriented in such a way that the neighboring 2D layers are eclipsed along the a axis, leading to parallelogram-like cavities. Photophysical measurements highlight the prominent role of chlorocyananilate linkers as optical antennas toward lanthanide ions, while wave-function-theory analysis supports the experimental findings, providing evidence for the effect of ligand substitution on the luminescence properties of homo/heteroleptic 2D CPs.

First author: Sojka, M, Supramolecular Coronation of Platinum(II) Complexes by Macrocycles: Structure, Relativistic DFT Calculations, and Biological Effects,
INORGANIC CHEMISTRY, 60, 17911, (2021)
Abstract: Platinum-based anticancer drugs are actively developed utilizing lipophilic ligands or drug carriers for the efficient penetration of biomembranes, reduction of side effects, and tumor targeting. We report the development of a supramolecular host-guest system built on cationic platinum(II) compounds bearing ligands anchored in the cavity of the macrocyclic host. The host-guest binding and hydrolysis process on the platinum core were investigated in detail by using NMR, MS, X-ray diffraction, and relativistic DFT calculations. The encapsulation process in cucurbit[7]uril unequivocally promotes the stability of hydrolyzed dicationic cis-[Pt-II(NH3)(2)(H2O)(NH2-R)](2+) compared to its trans isomer. Biological screening on the ovarian cancer lines A2780 and A2780/CP shows time-dependent toxicity. Notably, the reported complex and its beta-cyclodextrin (beta-CD) assembly achieve the same cellular uptake as cisplatin and cisplatin@beta-CD, respectively, while maintaining a significantly lower toxicity profile.

First author: Pruszkowska, K, Effect of Diamine Bridge on Reactivity of Tetradentate ONNO Nickel(II) Complexes,
CHEMPHYSCHEM, 23, 17911, (2022)
Abstract: Two new square planar ONNO nickel(II) complexes C2_core and C3_core have been synthesized and characterized by single crystal X-ray diffraction, NMR spectroscopy, thermogravimetry, and DFT calculations. The experimental results revealed the effect of the length of diamine bridge in the ligand on the behavior of the studied complexes in the reaction with N-heterocyclic aromatic amines, while DFT calculations provided a basis for the rationalization of this observation. The complex with propylenediamine bridge (C3_core) readily reacts with pyridine and its derivatives to form high-spin (paramagnetic) complexes with octahedral geometry as characterized by X-ray diffraction; electron-donating substituents on the pyridine ring facilitate the coordination of axial ligands. In contrast, the complex with ethylenediamine bridge (C2_core) does not undergo such a reaction because of the high deformation energy of the core required for the formation of C2_Py complex.

First author: Andreeva, IV, Commodity Chemicals and Fuels from Biomass: Thermodynamic Properties of Levoglucosan Derivatives,
Abstract: Cellulose-derived platform chemicals offer viable substitutes for most petroleum-based polymers and also enable the development of novel functional materials. In the focus of this work are thermophysical and thermochemical studies of dihydro-levoglucosenone (Cyrene) and levoglucosenone, which are considered as potential “green” replacements for industrial polar aprotic solvents. The densities, viscosities, absolute vapor pressures, and combustion energies of cyrene and levoglucosenone were measured in this work. The thermodynamic properties of levoglucosan derivatives are reliable for thermochemical calculations and used to calculate reaction enthalpies of valorization of the cellulose component of biomass. These enthalpies of reaction are useful in the further optimization and development of sustainable syntheses of commodity chemicals and fuels from biomass. The data provided in this work will aid researchers and engineers as the use of these new solvents grows.

First author: Zhou, X, Evaluation of Computational Chemistry Methods for Predicting Redox Potentials of Quinone-Based Cathodes for Li-Ion Batteries,
BATTERIES-BASEL, 7, 17183, (2021)
Abstract: High-throughput computational screening (HTCS) is an effective tool to accelerate the discovery of active materials for Li-ion batteries. For the evaluation of organic cathode materials, the effectiveness of HTCS depends on the accuracy of the employed chemical descriptors and their computing cost. This work was focused on evaluating the performance of computational chemistry methods, including semi-empirical quantum mechanics (SEQM), density-functional tight-binding (DFTB), and density functional theory (DFT), for the prediction of the redox potentials of quinone-based cathode materials for Li-ion batteries. In addition, we evaluated the accuracy of three energy-related descriptors: (1) the redox reaction energy, (2) the lowest unoccupied molecular orbital (LUMO) energy of reactant molecules, and (3) the highest occupied molecular orbital (HOMO) energy of lithiated product molecules. Among them, the LUMO energy of the reactant compounds, regardless of the level of theory used for its calculation, showed the best performance as a descriptor for the prediction of experimental redox potentials. This finding contrasts with our earlier results on the calculation of quinone redox potentials in aqueous media for redox flow batteries, for which the redox reaction energy was the best descriptor. Furthermore, the combination of geometry optimization using low-level methods (e.g., SEQM or DFTB) followed by energy calculation with DFT yielded accuracy as good as the full optimization of geometry using the DFT calculations. Thus, the proposed calculation scheme is useful for both the optimum use of computational resources and the systematic generation of robust calculation data on quinone-based cathode compounds for the training of data-driven material discovery models.

First author: Alnoman, RB, Synthesis and Computational Characterization of Organic UV-Dyes for Cosensitization of Transparent Dye-Sensitized Solar Cells,
MOLECULES, 26, 17183, (2021)
Abstract: The fabrication of colorless and see-through dye-sensitized solar cells (DSCs) requires the photosensitizers to have little or no absorption in the visible light region of the solar spectrum. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled, since most transparent DSCs are showing low PCE when compared to colorful and opaque DSCs. One strategy to increase PCE is applying two cosensitizers with selective conversion of the UV and NIR radiation, therefore, the non-visible part only is absorbed. In this study, we report synthesis of novel five UV-selective absorbers, based on diimide and Schiff bases incorporating carboxyl and pyridyl anchoring groups. A systematic computational investigation using density functional theory (DFT) and time-dependent DFT approaches was employed to evaluate their prospect of application in transparent DSCs. Experimental UV/Vis absorption spectra showed that all dyes exhibit an absorption band covering the mid/near-UV region of solar spectrum, with a bathochromic shift and a hyperchromic shifts for Py-1 dye. Computational results showed that the studied dyes satisfied the basic photophysical and energetics requirements of operating DSC as well as the stability and thermodynamical spontaneity of adsorption onto surface of TiO2. However, results revealed outperformance of the thienothiophene core-containing Py-1 UV-dye, owing to its advantageous structural attributes, improved conjugation, intense emission, large Stokes shift and maximum charge transferred to the anchor. Chemical compatibility of Py-1 dye was then theoretically investigated as a potential cosensitizer of a reference VG20-C2 NIR-dye. By the judicious selection of pyridyl anchor-based UV-absorber (Py-1) and carboxyl anchor-based NIR-absorber (VG20), the advantage of the optical complementarity and selectivity of different TiO2-adsorption-site (Lewis- and Bronsted-acidic) can be achieved. An improved overall PCE is estimated accordingly.

First author: Rodriguez-Jimenez, JA, On the doping of the Ga12As12 cluster with groups p and d atomic impurities,
Abstract: We report a theoretical study of how the physical and chemical properties of the Ga12As12 cluster change upon doping with atomic impurities of groups p and d. Calculations were performed within the density functional theory with the generalized gradient approximation to the exchange and correlation energy functional. We consider the Ga11As12X and Ga12As11X doped clusters, where X is an atomic impurity (from B-P, Al-Cl, Cr-Cu and Mo-Ag in their respective series) that substitutes either a Ga or an As atom at. We found that, in general, the substitution of a Ga atom is a more exothermic process than the substitution of an As one, in accordance with experimental reports on doped GaAs bulk. Some of the transition metal dopants (Cr, Mn, Fe, Mo and Tc) interact in such a way that the magnetic moment of the clusters is enhanced. We discuss the doping effect by analyzing the structural changes, binding energies per atom, HOMO-LUMO gaps, and relevant vertical chemical descriptors.

First author: Conradie, J, Understanding Hyperporphyrin Spectra: TDDFT Calculations on Diprotonated Tetrakis(p-aminophenyl)porphyrin,
Abstract: A detailed TDDFT study (with all-electron STO-TZ2P basis sets and the COSMO solvation model) has been carried out on the effect of diprotonation on the UV-vis-NIR spectra of free-base tetraphenylporphyrin and tetrakis(p-aminophenyl)porphyrin. The diprotonated forms have been modeled as their bis-formate complexes, i.e., as so-called porphyrin diacids. The dramatic redshift of the Q-band of the TAPP diacid has been explained in terms of an elevated “a(2u)” HOMO and lowered LUMOs, both reflecting infusion of aminophenyl character into the otherwise classic Gouterman-type frontier MOs. The exercise has also yielded valuable information on the performance of different exchange-correlation functionals. Thus, the hybrid B3LYP functional was found to yield a substantially better description of key spectral features, especially the diprotonation-induced redshifts, than the pure OLYP functional. Use of the range-separated CAMY-B3LYP functional, on the other hand, did not result in improvements relative to B3LYP.

First author: Ghosh, A, The Dog That Didn’t Bark: A New Interpretation of Hypsoporphyrin Spectra and the Question of Hypsocorroles,
Abstract: Nearly a half-century after Gouterman classified the UV-vis-NIR spectra of porphyrin derivatives as normal, hyper, or hypso, we propose a heretofore unsuspected “mechanism” underlying hypso spectra. Hypsoporphyrins, which exhibit blueshifted optical spectra relative to normal porphyrins (such as Zn porphyrins), typically involve d(n) transition metal ions, where n > 6. The spectral blueshifts have been traditionally ascribed to elevated porphyrin e(g) LUMO (lowest unoccupied molecular orbital) energy levels as a result of antibonding interactions with metal d(pi) orbitals. Herein, we have found instead that the blueshifts reflect a lowering of the a(2u) HOMO (highest occupied molecular orbital) energy levels. Electronegative metals such as Pd and Pt transfer smaller quantities of electron density to the porphyrin nitrogens, compared to a more electropositive metal such as Zn. With large amplitudes at the porphyrin nitrogens, the a(2u) HOMOs of Pd(II) and Pt(II) porphyrins accordingly exhibit lower orbital energies than those of Zn(II) porphyrins, thus explaining the hypso effect. Hypso spectra are also observed for corroles: compared with six-coordinate Al(III) corroles, which may be thought of exhibiting normal spectra, Au(III) corroles, for instance, exhibit blueshifted or hypso spectra.

First author: Stevanovic, N, Cu(II), Mn(II) and Zn(II) complexes of hydrazones with a quaternary ammonium moiety: synthesis, experimental and theoretical characterization and cytotoxic activity,
DALTON TRANSACTIONS, 51, 185, (2021)
Abstract: In this paper, Cu(II), Mn(II) and Zn(II) complexes with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride ((HLCl)-Cl-1) were synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and DFT calculations. In all three complexes, a ligand (L-1) is coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Cu(II) and Zn(II) form mononuclear penta-coordinated complexes (CuL1(N-3)(CH3-OH)]BF4 and (ZnL1(N-3)(2)], respectively, while Mn(II) forms a binuclear (Mn2L21(mu-(1.1)-N-3)(2)(N-3)(2)]center dot 2CH(3)OH complex, with unusual distorted trigonal-prismatic geometry around the metal centers. The antimicrobial activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two yeasts and one fungal strain. The binuclear Mn(II) complex showed antifungal activity of similar intensity to amphotericin B. Based on the results of the brine shrimp test and DPPH radical scavenging activity, the most active Cu (II) and Mn(II) complexes were selected for evaluation of cytotoxic activity against five malignant cancer cell lines (HeLa, A375, MCF7, PC-3 and A549) and one normal cell line HaCaT. Both complexes showed significant activity. It should be pointed out that the activity of the Mn(ii) complex against the MCF7 breast cancer cell line is only slightly weaker than that of cisplatin, but with selectivity to the tumor cell line in comparison to normal HaCaT cells, which is non-existent in the case of cisplatin.

First author: Maturana, RG, Nature of hydride and halide encapsulation in Ag-8 cages: insights from the structure and interaction energy of [Ag-8(X){S2P((OPr)-Pr-i)(2)}(6)](+) (X = H-, F-, Cl-, Br-, I-) from relativistic DFT calculations,
Abstract: Unraveling the different contributing terms to an efficient anion encapsulation is a relevant issue for further understanding of the underlying factors governing the formation of endohedral species. Herein, we explore the favorable encapsulation of hydride and halide anions in the [Ag-8(X){S2P(OPr)(2)}(6)](+) (X- = H, 1, F, 2, Cl, 3, Br, 4, and, I, 5) series on the basis of relativistic DFT-D level of theory. The resulting Ag-s-X interaction is sizable, which decreases along the series: -232.2 (1) > -192.1 (2) > -165.5 (3) > -158.0 (4) > -144.2 kcal mol(-1) (5), denoting a more favorable inclusion of hydride and fluoride anions within the silver cage. Such interaction is mainly stabilized by the high contribution from electrostatic type interactions (80.9 av%), with a lesser contribution from charge-transfer (17.4 av%) and london type interactions (1.7 av%). Moreover, the ionic character of the electrostatic contributions decreases from 90.7% for hydride to 68.6% for the iodide counterpart, in line with the decrease in hardness according to the Pearson’s acid-base concept (HSAB) owing to the major role of higher electrostatic interaction terms related to the softer (Lewis) bases. Lastly, the [Ag-8{S2P(OPr)(2)}(6)](2+) duster is able to adapt its geometry in order to maximize the interaction towards respective monoatomic anion, exhibiting structural flexibility. Such insights shed Light on the physical reasoning necessary for a better understanding of the different stabilizing and destabilizing contributions related to metal-based cavities towards favorable incorporation of different monoatomic anions.

First author: Cortes, I, Rationalizing the influence of alpha-cationic phospholes on pi-catalysis,
DALTON TRANSACTIONS, 50, 18036, (2021)
Abstract: The physical factors behind the experimentally observed high activity of gold(i)-catalysts having an alpha-cationic phosphole as a ligand have been computationally explored. To this end, the gold(i)-catalysed hydroarylation reactions of phenylacetylene and mesitylene involving both neutral and cationic phosphole as well as phosphine ligands have been quantitatively analyzed in detail with the help of the activation strain model of reactivity in combination with the energy decomposition analysis method. It is found that the cationic phosphole ligands induce a dramatic change in both the geometry and the electronic structure of the initially formed pi-complex which significantly enhances its electrophilicity. This results in an enhancement of the key pi(mesitylene) -> pi*(LAu-acetylene complex) molecular orbital interaction which is the main factor responsible for the activating effect of these cationic ligands.

First author: Anaridha, S, Comparative theoretical analysis using DFT & MP2 calculations, ADMET profiling and docking studies of the drug telotristat ethyl,
Abstract: The title drug, Ethyl(2S)-2-amino-3-(4{2-amino-6-[(1R)-1-[4-chloro-2-(3-methyl-1H-pyrazol-1-yl) phenyl]-2,2,2-trifluoroethoxy] pyrimidin-4-yl}phenyl)propanoate was reported for carcinoid syndrome diarrhea and approved by FDA in the year 2017. DFT (B3LYP) and Moller-Plesset Second Order (MP2) quantum chemical calculations in the 631G basis set were used to optimize the drug and evaluate the global and local reactivity descriptors. Molecular docking was performed against the tryptophan hydroxylase-1 inhibitor protein to study the binding interactions of the drug with the protein and rationalize the structure-activity relationship. The bond length between drug and protein established the presence of good binding with more interaction or reactivity. Fukui functions were invoked to describe the reactivity and stability of the drug molecule. ADMET profiling of the drug molecule predicts poor solubility and limited absorption in the gastrointestinal tract. BOILED Egg representation displayed low absorption, impermeability to the Blood-Brain barrier, and induced P-gp Substrate. Descriptor parameters were compared between DFT and MP2 optimized structures for each atom, and the most reactive and stable atoms were reported. The current research focuses on the structural and bioactive properties of the title molecule. The study was conducted further to find suitable reactivity centers. This aspect would help to evaluate more reactivity patterns of such types of molecules in future.

First author: Maity, B, Mechanistic Understanding of Arylation vs Alkylation of Aliphatic C-sp3-H Bonds by Decatungstate-Nickel Catalysis,
ACS CATALYSIS, 11, 13973, (2021)
Abstract: Computational analysis of the arylation of aliphatic C-sp3-H bonds catalyzed by decatungstate-nickel validates the reaction mechanism and provides valuable insights into how to accomplish the corresponding alkylation. Our analysis indicates that the light-excited decatungstate photocatalyst activates one of the C-sp3-H bonds by a hydrogen atom transfer reaction involving the bridging O atoms of decatungstate. The generated alkyl radical reacts with a bipyridine-based Ni catalytic species to form a Ni-I-alkyl intermediate. Oxidative addition of aryl bromide to this intermediate leads to a Ni-III complex, from which the cross coupling product is liberated via reductive elimination. We also investigated the corresponding prototype reaction where the aryl bromide is replaced by an alkyl bromide, which suggested a too high energy barrier for the oxidative addition of the alkyl bromide to the Ni-I-alkyl intermediate. Variation of the steric and electronic properties of the bipyridine ligand suggests that steric encumbrance in the 6,6 ‘ position can promote oxidative addition of the alkyl bromide as verified by ad hoc experimental tests.

First author: George, G, Reactivity of the superhalogen/superalkali ion encapsulating C-60 fullerenes,
DALTON TRANSACTIONS, 51, 203, (2021)
Abstract: The Diels-Alder cycloaddition reaction between 1,3-cyclohexadiene and a series of C-60 fullerenes with encapsulated (super)alkali/(super)halogen species (Li+@C-60, Li2F+@C-60, Cl-@C-60, and LiF2-@C-60) was explored by means of DFT calculations. The reactivity of the ion encapsulating systems was compared to that of the parent C-60 fullerene. Significant enhancement in reactivity was found for cation-encapsulating Li+/Li2F+@C-60 complexes. The cycloadduct formed by LiF2-@C-60 was found to be the most thermodynamically favorable among the studied ones. In contrast, encapsulation of Cl- anions disfavors the cycloaddition reaction both kinetically and thermodynamically. Higher activation energy barrier and less stability of the reaction product in the case of Cl-@C-60 were associated with the higher deformation energies of the fullerene cage and the lower interaction energy between the reactants in comparison with the other studied complexes.

First author: Wang, J, Theoretical probing of twenty-coordinate actinide-centered boron molecular drums,
Abstract: The exploration of metal-doped boron clusters has a great significance in the design of high coordination number (CN) compounds. Actinide-doped boron clusters are probable candidates for achieving high CNs. In this work, we systematically explored a series of actinide metal atom (U, Np, and Pu) doped B-20 boron clusters An@B-20 (An = U, Np, and Pu) by global minimum structural searches and density functional theory (DFT). Each An@B-20 cluster is confirmed to be a twenty-coordinate complex, which is the highest CN obtained in the chemistry of actinide-doped boron clusters so far. The predicted global minima of An@B-20 are tubular structures with actinide atoms as centers, which can be considered as boron molecular drums. In An@B-20, U@B-20 has a relatively high symmetry of C-2, while both Np@B-20 and Pu@B-20 exhibit C-1 symmetry. Extensive bonding analysis demonstrates that An@B-20 has sigma and pi delocalized bonding, and the U-B bonds possess a relatively higher covalency than the Np-B and Pu-B bonds, resulting in the higher formation energy of U@B-20. Therefore, the covalent character of An-B bonding may be crucial for the formation of these high CN actinide-centered boron clusters. These results deepen our understanding of actinide metal doped boron clusters and provide new clues for developing stable high CN boron-based nanomaterials.

First author: Morales-Guevara, R, The role of substituted pyridine Schiff bases as ancillary ligands in the optical properties of a new series of fac-rhenium(i) tricarbonyl complexes: a theoretical view,
RSC ADVANCES, 11, 37181, (2021)
Abstract: Over the last few years, luminescent Re(i) tricarbonyl complexes have been increasingly proposed as fluorophores suitable for fluorescence microscopy to visualize biological structures and cells. In this sense, incorporating an asymmetrical pyridine Schiff base (PSB) as the ancillary ligand strongly modifies the staining and luminescent properties of Re(i) tricarbonyl complexes. In this work, we analyzed two series of Re(i) tricarbonyl complexes with their respective PSB ligands: (1) fac-[Re(CO)(3)(2,2′-bpy)(PSB)](1+) and (2) fac-[Re(CO)(3)(4,4′-bis(ethoxycarbonyl)-2,2′-bpy)(PSB)](1+), where the PSB exhibits substitutions at positions 4 or 6 in the phenolic ring with methyl or halogen substituents. Thus, we performed computational relativistic DFT and TDDFT studies to determine their optical properties. The ten complexes analyzed showed absorption in the visible light range. Furthermore, our analyses, including zero-field splitting (ZFS), allowed us to determine that the low-lying excited state locates below the (LLCT)-L-3 states. Interestingly, seven of the ten analyzed complexes, whose corresponding PSB harbors an intramolecular hydrogen bond (IHB), exhibited luminescent emission that could be suitable for biological purposes: large Stokes shift, emission in the range 600-700 nm and tau in the order of 10(-2) to 10(-3) s. Conversely, the three complexes lacking the IHB due to two halogen substituents in the corresponding PSB showed a predicted emission with the lowest triplet excited state energy entering the NIR region. The main differences in the complexes’ photophysical behavior have been explained by the energy gap law and time-resolved luminescence. These results emphasize the importance of choosing suitable substituents at the 4 and 6 positions in the phenolic ring of the PSB, which determine the presence of the IHB since they modulate the luminescence properties of the Re(i) core. Therefore, this study could predict Re(i) tricarbonyl complexes’ properties, considering the desired emission features for biological and other applications.

First author: Milovanovic, MR, The Thermochemistry of Alkyne Insertion into a Palladacycle Outlines the Solvation Conundrum in DFT,
Abstract: In an effort to determine the thermochemistry of established organometallic transformation, the well documented reaction of alkynes with a palladacycle was investigated by isothermal titration calorimetry (ITC). Although the mechanism of the insertion of unsaturated substrates into the Pd-C bond of cyclopalladated compounds is known, no information is available so far about their thermochemistry. The enthalpies of the reactions of Ph-C equivalent to C-Ph and MeOC(O)-C equivalent to C(O)COMe with the bisacetonitrilo salt of the N,N-benzylamine palladacycle were determined by ITC in chlorobenzene after having optimized the conditions to ensure that only the double and a single insertion of alkynes were occurring respectively. The reaction energy profile established by DFT for the double insertion process involving Ph-C equivalent to C-Ph confirmed earlier conclusions on the rate determining character of the first insertion. Further computations of reaction enthalpies reveal significant discrepancies between ITC and DFT-D/continuum solvation enthalpies, that are suspected to arise from an unexpected explicit noncovalent interaction of PhCl with the components of the reaction.

First author: Guda, A, Excited-state structure of copper phenanthroline-based photosensitizers,
Abstract: Cu diimine complexes present a noble metal free alternative to classical Ru, Re, Ir and Pt based photosensitizers in solution photochemistry, photoelectrochemical or dye-sensitized solar cells. Optimization of these dyes requires understanding of factors governing the key photochemical properties: excited state lifetime and emission quantum yield. The involvement of exciplex formation in the deactivation of the photoexcited state is a key question. We investigate the excited-state structure of [Cu(dmp)(2)](+) and [Cu(dsbtmp)(2)](+) (dmp = 2,9-dimethyl-1,10-phenanthroline, dsbtmp = 2,9-di-sec-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline) using pump-probe X-ray absorption spectroscopy (XAS) and DFT. Features of XAS that distinguish flattened tetrahedral site and 5-coordinated geometry with an additional solvent near Cu(ii) center are identified. Pump-probe XAS demonstrates that for both complexes the excited state is 4-coordinated. For [Cu(dmp)(2)](+) the exciplex is 0.24 eV higher in energy than the flattened triplet state, therefore it can be involved in deactivation pathways as a non-observable state that forms slower than it decays. For [Cu(dsbtmp)(2)](+) the excited-state structure is characterized by Cu-N distances of 1.98 and 2.07 angstrom and minor distortions, leading to a 3 orders of magnitude longer excited-state lifetime.

First author: Li, XY, Two-dimensional bipolar magnetic semiconductors with high Curie-temperature and electrically controllable spin polarization realized in exfoliated Cr(pyrazine)(2) monolayers,
Abstract: Exploring two-dimensional (2D) magnetic semiconductors with room-temperature magnetic ordering and electrically controllable spin-polarization is a highly desirable but challenging task for nano-spintronics. Here, through first-principles calculations, we propose to realize such a material by exfoliating the recently synthesized organometallic layered crystal Li-0.7[Cr(pyz)(2)]Cl-0.7 center dot 0.25(THF) (pyz=pyrazine, THF=tetrahydrofuran). The feasibility of exfoliation is confirmed by the rather low exfoliation energy of 0.27 J m(-2), even smaller than that of graphite. In exfoliated Cr(pyz)(2) monolayers, each pyrazine ring grabs one electron from the Cr atom to become a radical anion, and then a strong d-p direct-exchange magnetic interaction emerges between Cr cations and pyrazine radicals, resulting in room-temperature ferrimagnetism with a Curie temperature of 342 K. Moreover, the Cr(pyz)(2) monolayer is revealed to be an intrinsic bipolar magnetic semiconductor where electrical doping can induce half-metallic conduction with controllable spin-polarization direction.

First author: Wei, J, Computational Insight into the Ligand Effect on the Original Activity of Rh-Catalyzed Formaldehyde Hydroformylation,
Abstract: This study performs a computational examination of the effect of the ligand nature on the Rh-L interaction and of the formaldehyde hydroformylation for substituted rhodium-carbonyl catalysts using a range of realistic mono-and bidentate ligands (CO, P(OMe)(3), PPh3, DMI, and DPPE). The energy decomposition analysis of the Rh-L bond suggests the bidentate ligand, DPPE, shows the strongest interaction with Rh. The pi-accepting capacity of monodentate ligands follows the sequence CO > P(OMe)(3) > PPh3 > DMI. Analysis of the potential energy surface reveals the sigma-donor ligands serve to increase the energy of the active anionic complex [Rh(CO)(3)L](-). No clear correlation has been found between the CO insertion/hydrogenolysis energy barrier and electronic properties of ligands, while the H-2 oxidative addition barrier increases with increasing the ligand’s electron donating capacity. The investigation on the effect of the ligand (PPh3) coordination number demonstrates that the three-coordinated catalyst exhibits the highest energy barrier, and the influence of ligand steric hindrance on the H-2 oxidative addition can be ignorable.

First author: Liu, TJ, Semimetallic square-octagon two-dimensional polymer with high mobility,
PHYSICAL REVIEW B, 104, 25514, (2021)
Abstract: The electronic properties of pi-conjugated two-dimensional (2D) polymers near the Fermi level are determined by structural topology and chemical composition. Thus tight-binding (TB) calculations of the corresponding fundamental network can be used to explore the parameter space to find configurations with intriguing properties before designing the atomistic 2D polymer network. The vertex-transitive fes lattice, which is also called a square-octagon, 4-8, or 4.82 lattice, is rich in interesting topological features including Dirac points and flat bands. Herein, we study its electronic and topological properties within the TB framework using representative parameters for chemical systems. Secondly, we demonstrate that the rational implementation of band structure features obtained from TB calculations in 2D polymers is feasible with a family of 2D polymers possessing fes structure. A one-to-one band structure correspondence between the fundamental network and 2D polymers is found. Moreover, changing the relative length of linkers connecting the triangulene units in the 2D polymers reflects tuning of hopping parameters in the TB model. These perturbations allow sizable local band gaps to open at various positions in the Brillouin zone. From analysis of the Berry curvature flux, none of the polymers exhibits a large topologically nontrivial band gap. However, we find a particular configuration of semimetallic characteristics with separate electron and hole pockets, which possess very low effective masses both for electrons (as small as m*e = 0.05) and for holes (as small as m*h = 0.01).

First author: Breton, GW, Competition between the stabilizing effects of saturated alkyl substituents and pi bonds on complexes of silver ion (Ag+) with alkenes,
Abstract: The coordination of Ag+ ions to alkenes is of both theoretical and practical interest. While much attention has been paid to how the nature of the C=C pi bond affects the coordinative process, little attention has been directed toward the effect of saturated side chains on complex stabilization despite experimental evidence suggesting its importance. Calculations employing the M06-2X DFT functional have revealed that saturated chains can exhibit as powerful a stabilizing effect on Ag+/alkene complex formation as increased alkyl substitution about the C=C bond. Natural bond orbital (NBO) analysis confirms the mechanism of stabilization to be that of agostic interactions of properly-oriented CH sigma-bonds in the saturated chain with the Ag+ ion. Analysis by the extended transition state energy decomposition approach with the natural orbital for chemical valence method (ETS-NOCV) and the reduced density gradient (RDG) model were used to better characterize the nature of the interaction as a near equivalent combination of electrostatic and orbital interactions.

First author: Hill, A, Positional and Conformational Isomerism in Hydroxybenzoic Acid: A Core-Level Study and Comparison with Phenol and Benzoic Acid,
Abstract: Three positional isomers of hydroxybenzoic acid, as well as phenol and benzoic acid, were studied using core-level photoemission and X-ray absorption spectroscopies, supported by quantum chemical calculations. While 2-hydroxybenzoic (salicylic) acid exists as a single conformer with an internal hydrogen bond, 3- and 4-hydroxybenzoic acids are mixtures of multiple conformers. The effects due to isomerism are clearly seen in the C 1s and O 1s photoelectron spectra, whereas the conformational effects on the binding energies are less pronounced. The O 1s photoelectron spectrum of salicylic acid is significantly different from that of the other two isomers, providing a signature of the hydrogen bond. In contrast, the oxygen K edge X-ray absorption spectra of the three hydroxybenzoic acids show only minor differences. The salicylic acid absorption spectrum at the carbon K edge shows a more resolved vibrational structure than the spectra of the other molecules, which can be explained in part by the existence of a single conformer. Our theoretical study of vibrational excitations in the lowest C 1s absorption bands of salicylic and 4-hydroxybenzoic acids indicates that the observed structure can be assigned to 0-0 lines of various electronic transitions since most of the totally symmetric vibrational modes with sufficiently large frequencies to be resolved are predicted to be inactive. Significant sensitivity of the C 1s excitations in 3-hydroxybenzoic acid to rotational conformerism was predicted but not observed due to spectral crowding.

First author: Gan, W, The reactivity of Nb-n(+) clusters with acetylene and ethylene to produce a cubic aromatic metal carbide Nb4C4+,
NEW JOURNAL OF CHEMISTRY, 45, 21844, (2021)
Abstract: The study of clusters with strongly size-dependent properties has attracted extensive attention due to their potential applications in building new materials. Utilizing a home-made multiple-ion laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer, we have studied the reactions of niobium cationic clusters with acetylene and ethylene. It is observed that dehydrogenation dominates the reaction process, and Nb4C4+ shows up prominently in the mass spectra. Quantum chemistry calculations reveal that the most stable structure of Nb4C4+ corresponds to a slightly distorted cubic structure with D-2d symmetry, with reasonable stability pertaining to its cubic aromaticity. We illustrate the dehydrogenation reaction paths of Nb-4(+) + 2C(2)H(2) to form the prominent Nb4C4+ product, along with the highly exothermic reactions to produce H-2.

First author: Komoda, R, Effect of Gas Pressure on Hydrogen Environment Embrittlement of Carbon Steel A106 in Carbon Monoxide Mixed Hydrogen Gas,
Abstract: The addition of a small volume fraction of carbon monoxide (CO) gas to pure gaseous H-2 potentially mitigates the susceptibility of steel to hydrogen environment embrittlement (HEE). The effect of environmental gas pressure on the mitigation of HEEs by a mixture of H-2 and CO was examined in this study. Fracture toughness tests of an ASTM A106 pipe carbon steel were carried out in H-2 gas containing CO. The environmental gas pressures at which the fracture toughness tests were conducted were 0.6, 1.0 and 4.0 MPa. The addition of a certain concentration of CO to H-2 gas completely prevented HEE. The CO concentration achieving complete HEE prevention increased with an enhancement of the environmental gas pressure. Molecular dynamics (MD) simulations were further conducted to interpret the experimental results based on the interactions of H-2 and CO with the Fe surface in conjunction with the effect of gas pressure. The MD simulations revealed that the dissociation rate of dihydrogen molecules to atomic hydrogen on the Fe surface significantly increased with an elevation of the gas pressure, whereas the adsorption rate of CO on the Fe surface was almost independent of the gas pressure. These results suggest that the increase in the gas pressure relatively promotes hydrogen uptake into the material in the presence of CO, which accounts for the experimental results showing that the CO concentration achieving complete HEE prevention increased with the elevation of the gas pressure.

First author: Zhu, HD, High spin polarized Fe-2 cluster combined with vicinal nonmetallic sites for catalytic ammonia synthesis from a theoretical perspective,
Abstract: An Fe-2 catalyst combined with the vicinal nonmetallic sites may break the Bronsted-Evans-Polanyi limitation and lead to a more efficient ammonia synthesis than previously reported. Our theoretical calculations show that the Fe-2 catalyst supported on graphitic carbon nitride (Fe-2/mpg-C3N4) strongly favors hydrogenation of *N-2 to form *NHNH2 species, which leads to low energy barriers for N-H formation (0.47 eV) and N-N dissociation (0.50 eV). In addition, B-N Lewis pairs constructed on the mpg-C3N4 serve as nonmetallic sites that enable heterolysis of the H-H bond to overcome the relatively high energy barrier of hydrogen transfer. Through a comprehensive study of Fe-n/mpg-C3N4 (n = 2, 3, 4) and Fe (211) catalysts, we conclude that synergistic Fe-2 catalyst shows a significant advantage due to its high spin polarization and thus can avoid harsh reaction conditions for the thermal conversion of N-2 to NH3.

First author: Kreuter, F, Surface functionalization with nonalternant aromatic compounds: a computational study of azulene and naphthalene on Si(001),
Abstract: Nonalternant aromatic pi-electron systems show promises for surface functionalization due to their unusual electronic structure. Based on our previous experiences for metal surfaces, we investigate the adsorption structures, adsorption dynamics and bonding characteristics of azulene and its alternant aromatic isomer naphthalene on the Si(001) surface. Using a combination of density functional theory, ab initio molecular dynamics, reaction path sampling and bonding analysis with the energy decomposition analysis for extended systems, we show that azulene shows direct adsorption paths into several, strongly bonded chemisorbed final structures with up to four covalent carbon-silicon bonds which can be described in a donor-acceptor and a shared-electron bonding picture nearly equivalently. Naphthalene also shows these tetra-sigma-type bonding structures in accordance with an earlier study. But the adsorption path is pseudo-direct here with a precursor intermediate bonded via one aromatic ring and strong indications for a narrow adsorption funnel. The four surface-adsorbate bonds formed lead for both adsorbates to a strong corrugation and a loss of aromaticity.

First author: Sanchez-Gonzalez, A, From groove binding to intercalation: unravelling the weak interactions and other factors modulating the modes of interaction between methylated phenanthroline-based drugs and duplex DNA,
Abstract: Several antitumor drugs base their cytotoxicity on their capacity to intercalate between base pairs of DNA. Nevertheless, it has been established that the mechanism of intercalation of drugs in DNA starts with the prior groove binding mode of interaction of the drug with DNA. Sometimes, for some kind of flat small molecules, groove binding does not produce any cytotoxic effect and the fast transition of such flat small molecules to the cytotoxic intercalation mode is desirable. This is the case of methylated phenanthroline (phen) derivatives, where, changes in the substitution in the position and number of methyl groups determine their capability as cytotoxic compounds and, therefore, it is a way for the modulation of cytotoxic effects. In this work, we studied this modulation by means of the interaction of the [Pt(en)(phen)](2+) complex and several derivatives by methylation of phen in different number and position and the d(GTCGAC)(2) DNA hexamer via groove binding using PM6-DH2 and DFT-D methods. The analysis of the geometries, electronic structure and energetics of the studied systems was compared to experimental works to gain insight into the relation structure-interaction for the studied systems with cytotoxicity. The trends are explained by means of the Non-Covalent Interaction (NCI) index, the Energy Decomposition Analysis (EDA) and solvation contributions. Our results are in agreement with the experiments, in which the methylation of position 4 of phen seems to favour the interaction via groove binding thus making the transition to the intercalation cytotoxic mode difficult. Looking at the NCI results, these interactions come not only from the CH/pi and CH/n interactions of the methyl group in position 4 but also from the ethylenediamine (en) ligand, whose orientation in the Pt complex was found in such a way that it produces a high number of weak interactions with DNA, especially with the sugar and phosphate backbone.

First author: Li, LK, Highly efficient carbazolylgold(iii) dendrimers based on thermally activated delayed fluorescence and their application in solution-processed organic light-emitting devices,
CHEMICAL SCIENCE, 12, 14833, (2021)
Abstract: A new class of C<^>C<^>N ligand-containing carbazolylgold(iii) dendrimers has been designed and synthesized. High photoluminescence quantum yields of up to 82% in solid-state thin films and large radiative decay rate constants in the order of 10(5) s(-1) are observed. These gold(iii) dendrimers are found to exhibit thermally activated delayed fluorescence (TADF), as supported by variable-temperature emission spectroscopy, time-resolved photoluminescence decay and computational studies. Solution-processed organic light-emitting diodes (OLEDs) based on these gold(iii) dendrimers have been fabricated, which exhibit a maximum current efficiency of 52.6 cd A(-1), maximum external quantum efficiency of 15.8% and high power efficiency of 41.3 lm W-1. The operational stability of these OLEDs has also been recorded, with the devices based on zero- and second-generation dendrimers showing maximum half-lifetimes of 1305 and 322 h at 100 cd m(-2), respectively, representing the first demonstration of operationally stable solution-processed OLEDs based on gold(iii) dendrimers.

First author: Poater, J, Path-dependency of energy decomposition analysis & the elusive nature of bonding,
Abstract: Here, we provide evidence of the path-dependency of the energy components of the energy decomposition analysis scheme, EDA, by studying a set of thirty-one closed-shell model systems with the D-2h symmetry point group. For each system, we computed EDA components from nine different pathways and numerically showed that the relative magnitudes of the components differ substantially from one path to the other. Not surprisingly, yet unfortunately, the most significant variations in the relative magnitudes of the EDA components appear in the case of species with bonds within the grey zone of covalency and ionicity. We further discussed that the role of anions and their effect on arbitrary Pauli repulsion energy components affects the nature of bonding defined by EDA. The outcome variation by the selected partitioning scheme of EDA might bring arbitrariness when a careful comparison is overlooked.

First author: Pnevskaya, AY, First Principal Simulation of Palladium Nanocatalysts Surfaces,
Abstract: Palladium nanocatalysts are widely used in a number of industrially relevant hydrogenation reactions. Understanding the processes that occur at the surface of the catalysts during these reactions is a problem of high scientific and industrial importance. This work is devoted to the theoretical study of atomic and electronic structure of palladium (111) and (100) surfaces, and the structures of a series of hydrocarbon, which are potential intermediates of ethylene and acetylene hydrogenation/dehydrogenation reactions. It was found that in (111) surface after geometry relaxation, interplanar distances at the surface are bigger than those in the bulk, while the opposite effect is observed for (100) surface. It was shows that the above effect is reproduced in both Projector Augmented Wave method and with using Slater Type Orbitals. The effect is stronger in Generalized Gradient Approximation than in Local Density Approximation. On the obtained surfaces, 11 hydrocarbon molecules and radicals were relaxed and the probably of their formation at different surfaces was estimated. The obtained results provide important insights on the fundamental processes of hydrocarbon adsorption on palladium nanoparticles.

First author: De Vleeschouwer, F, A Combined Experimental/Quantum-Chemical Study of Tetrel, Pnictogen, and Chalcogen Bonds of Linear Triatomic Molecules,
MOLECULES, 26, 1270, (2021)
Abstract: Linear triatomic molecules (CO2, N2O, and OCS) are scrutinized for their propensity to form perpendicular tetrel (CO2 and OCS) or pnictogen (N2O) bonds with Lewis bases (dimethyl ether and trimethyl amine) as compared with their tendency to form end-on chalcogen bonds. Comparison of the IR spectra of the complexes with the corresponding monomers in cryogenic solutions in liquid argon enables to determine the stoichiometry and the nature of the complexes. In the present cases, perpendicular tetrel and pnictogen 1:1 complexes are identified mainly on the basis of the lifting of the degenerate nu 2 bending mode with the appearance of both a blue and a red shift. Van & PRIME;t Hoff plots of equilibrium constants as a function of temperature lead to complexation enthalpies that, when converted to complexation energies, form the first series of experimental complexation energies on sp(1) tetrel bonds in the literature, directly comparable to quantum-chemically obtained values. Their order of magnitude corresponds with what can be expected on the basis of experimental work on halogen and chalcogen bonds and previous computational work on tetrel bonds. Both the order of magnitude and sequence are in fair agreement with both CCSD(T) and DFA calculations, certainly when taking into account the small differences in complexation energies of the different complexes (often not more than a few kJ mol(-1)) and the experimental error. It should, however, be noted that the OCS chalcogen complexes are not identified experimentally, most probably owing to entropic effects. For a given Lewis base, the stability sequence of the complexes is first successfully interpreted via a classical electrostatic quadrupole-dipole moment model, highlighting the importance of the magnitude and sign of the quadrupole moment of the Lewis acid. This approach is validated by a subsequent analysis of the molecular electrostatic potential, scrutinizing the sigma and pi holes, as well as the evolution in preference for chalcogen versus tetrel bonds when passing to “higher ” chalcogens in agreement with the evolution of the quadrupole moment. The energy decomposition analysis gives further support to the importance/dominance of electrostatic effects, as it turns out to be the largest attractive term in all cases considered, followed by the orbital interaction and the dispersion term. The natural orbitals for chemical valence highlight the sequence of charge transfer in the orbital interaction term, which is dominated by an electron-donating effect of the N or O lone-pair(s) of the base to the central atom of the triatomics, with its value being lower than in the case of comparable halogen bonding situations. The effect is appreciably larger for TMA, in line with its much higher basicity than DME, explaining the comparable complexation energies for DME and TMA despite the much larger dipole moment for DME.

First author: Ulantikov, AA, Thermally Controlled Synthesis of Octahedral Rhenium Clusters with 4,4 ‘-Bipyridine and CN- Apical Ligands,
SYMMETRY-BASEL, 13, 1270, (2021)
Abstract: The selective preparation, structural and spectroscopic study of two new rhenium cluster complexes trans-[Re6S8(bpy)(4)(CN)(2)] and trans-[Re6S8(bpy)(2)(CN)(4)](2-) (bpy = 4,4 & PRIME;-bipyridine) obtained by reactions of corresponding hexarhenium cyanohalides with molten bpy are reported. The complexes were crystallized as solvates, displaying supramolecular structures based on cluster units linked by numerous weak interactions with bpy molecules. The molecular compound trans-[Re6S8(bpy)(4)(CN)(2)] (1) is insoluble in water and common organic solvents, while the ionic compound trans-Cs1.7K0.3[Re6S8(bpy)(2)(CN)(4)] (2) is somewhat soluble in DMSO, DMF and N-methylpyrrolidone. The presence of the redox-active ligand bpy leads to the occurrence of multi-electron reduction transitions in a solution of 2 at moderate potential values. The ambidentate CN- ligand is the secondary functional group, which has potential for the synthesis of coordination polymers based on the new cluster complexes. In addition, both new compounds show a weak red luminescence, which is characteristic of complexes with a {Re6S8}(2+) cluster core.

First author: Jung, CK, Thermodynamic Description of Interfaces Applying the 2PT Method on ReaxFF Molecular Dynamics Simulations,
Abstract: The interface between liquid water and the Pt(111) metal surface is characterized structurally and thermodynamically via reactive MD simulations within the ReaxFF framework. The formation of a distinct buckled adsorbate layer and subsequent wetting layers is tracked via the course of the water’s density and the distribution of the H2O molecules with increasing distance to the metal surface. Hereby, also the two-phase thermodynamics (2PT) method has been utilized for studying the course of entropy as well as the translational, rotational, and vibrational entropic contributions throughout the Pt(111)vertical bar H2O interface. A significant reduction of the entropy compared to the bulk value is observed in the adsorbate layer (S = 31.05 +/- 2.48 J/mol K) along with a density of 3.26 +/- 0.06 g/cm(3). The O-O interlayer distribution allows for direct tracing of the water ordering and a quantified comparison to the ideal hexagonal adlayer. While the adsorbate layer at the Pt surface shows the occurrence of hexagonal motifs, this near-order is already weakened in the wetting layers. Bulk behavior is reached at 15 angstrom distance from the Pt(111) metal. Introducing an electric field of 0.1 V/angstrom prolongs the ordering effect of the metal surface into the liquid water.

First author: Inoue, H, Solid-State Structures and Photoluminescence of Lamellar Architectures of Cu(I) and Ag(I) Paddlewheel Clusters with Hydrogen-Bonded Polar Guests,
MOLECULES, 26, 24663, (2021)
Abstract: Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu-6(Hmna)(6)]center dot 7DMF (1 center dot 7DMF) and [Ag-6(Hmna)(6)]center dot 8DMSO (2 center dot 8DMSO), where H(2)mna = 2-mercaptonicotininc acid, DMF = N,N’-dimethylformamide, and DMSO = dimethyl sulfoxide. The solvated clusters, together with their fully desolvated forms 1 and 2, have been characterized by FTIR, UV-Vis diffuse reflectance spectroscopy, TG-DTA analysis, and DFT calculations. Crystal structures of two solvated clusters 1 center dot 7DMF and 2 center dot 8DMSO have been unambiguously determined by single-crystal X-ray diffraction analysis. Six carboxylic groups appended on the clusters trap solvent guests, DMF or DMSO, through H-bonds. As a result, alternately stacked lamellar architectures comprising of a paddlewheel cluster layer and H-bonded solvent layer are formed. Upon UV illumination (lambda(ex) = 365 nm), the solvated hexasilver(I) cluster 2 center dot 8DMSO gives intense greenish-yellow photoluminescence in the solid state (lambda(PL) = 545 nm, phi(PL) = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1 center dot 7DMF displays PL in the near-IR region (lambda(PL) = 765 nm, phi(PL) = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (phi(PL) < 0.01) is observed. The desorption-sorption response was studied by the solid-state PL spectroscopy. Non-covalent interactions in the crystal including intermolecular H-bonds, CH...pi interactions, and pi...pi stack were found to play decisive roles in the creation of the lamellar architectures, small-molecule trap-and-release behavior, and guest-induced luminescence enhancement.

First author: Sangolkar, AA, Structure, Stability, Properties, and Application of Atomically Thin Coinage Metal Flatland in Graphene Pore: A Density Functional Theory Calculation,
Abstract: 2D metals are emerging materials in the 2D nanomaterials family and a rapid development is seen in the past few years. The properties of material that play a crucial role to determine their application in various fields need to be explored. Herein, a patch consisting of seven to nine coinage metal (Cu, Ag, and Au) atoms is created in the pore of graphene. Electronic properties, work function, and the interaction energy using periodic energy decomposition analysis (pEDA) of the materials are calculated using density functional theory (DFT). Carbon monoxide (CO) adsorption studies on these surfaces are also performed. All the metal atoms are found to align themselves in hexagonal arrangement in the graphene pore. All the materials with an exception of eight-Au-patched graphene are found to be metallic. The eight-Au-patched graphene is a low bandgap semiconductor exhibiting a direct bandgap of 0.23 eV. CO molecule adsorbs strongly on Cu-patched surfaces in comparison to Ag- and Au-patched surfaces. The interaction energy of CO is observed to be higher on seven-Cu-patched graphene as compared with Ag- and Au-patched graphene.

First author: Jha, R, Effect of confinement on the behavior of superhalogen and superalkali,
Abstract: Superalkalis (SA) are excellent reducing agents due to their lower ionization energies than alkalis and alkaline earth metals. On the other hand, superhalogens(SH) behave as powerful oxidizing agents because of their high electron affinity(EA) than that of Cl which has the highest electron affinity in the periodic table. In this article we have shown that these properties of superhalogen/superalkali get changed in a confined environment created by fullerenes cages with different sizes. It has been observed that while the electron affinity of superhalogen decreases, ionization energies(IE) of superalkali increases. Steric effect is predominant between host and guest in smaller fullerenes whereas van der Waals interaction gradually increases in bigger fullerenes.

First author: Fukushima, K, Excited-state theorem in both case of a nuclear potential and a more general external potential in correspondence to the Hohenberg-Kohn theorem,
Abstract: This paper is mainly aimed at presenting an excited-state theorem in both case of a nuclear potential and a more general external potential, in correspondence to the Hohenberg-Kohn (HK) theorem for the static ground state. The author uses the second-quantized scheme employed by HK. The electron field operator is expanded in terms of complete functions. State vectors are represented by electron occupation numbers of each basis state described by the complete function. The main idea is that for the electronic density as a function of spatial coordinates, the author found a one-to-one correspondence between the electronic density and a state vector via occupation numbers. It is found that in an atom and a more general system, there exists a one-to-one correspondence between the electronic density and external potential when the eigenenergy is specified. Thus, the theorem corresponding to the Hohenberg-Kohn theorem is presented for all states at the same level. The advantages and secondary works are as follows: (1) the Kohn-Sham formalism is extended to excited states with the electronic relaxation; (2) in the Schro spacing diaeresis dinger picture all time-dependent state vectors are derived within DFT; and (3) for simple cases numerical calculations were performed.

First author: Strianese, M, Imidazo-pyridine-based zinc(ii) complexes as fluorescent hydrogen sulfide probes,
DALTON TRANSACTIONS, 50, 17075, (2021)
Abstract: In this work we explore the interaction of HS- with a family of fluorescent zinc complexes. In particular we selected a family of complexes with N,O-bidentate ligands aiming at assessing whether the zinc-chelating ligand plays a role in influencing the reactivity of HS- with the complexes under investigation. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS- binds the zinc center of all the complexes included in this study. The results highlight the potential of the devised systems to be used as HS-/H2S fluorescent sensors via a coordinative-based approach. To shed light on the species formed in solution when HS-/H2S interacts with the title complexes and aiming to rationalize the photophysical properties of the sensing constructs, we performed a computational analysis based on the time dependent density functional theory (TD-DFT). Preliminary bio-imaging experiments were also performed and the results indicate the potential of this class of compounds as probes for the detection of H2S in living cells.

First author: du Fosse, I, Effect of Ligands and Solvents on the Stability of Electron Charged CdSe Colloidal Quantum Dots,
Abstract: Many colloidal quantum dot (QD)-based devices involve charging of the QD, either via intentional electronic doping or via electrical charge injection or photoexcitation. Previous research has shown that this charging can give rise to undesirable electrochemical surface reactions, leading to the formation of localized in-gap states. However, little is known about the factors that influence the stability of charged QDs against surface oxidation or reduction. Here, we use density functional theory to investigate the effect of various ligands and solvents on the reduction of surface Cd in negatively charged CdSe QDs. We find that X-type ligands can lead to significant shifts in the energy of the band edges but that the in-gap state related to reduced surface Cd is shifted in the same direction. As a result, shifting the band edges to higher energies does not necessarily lead to less stable electron charging. However, subtle changes in the local electrostatic environment lead to a clear correlation between the position of the in-gap state in the bandgap and the energy gained upon surface reduction. Binding ligands directly to the Cd sites most prone to reduction was found to greatly enhance the stability of the electron charged QDs. We find that ligands bind much more weakly after reduction of the Cd site, leading to a loss in binding energy that makes charge localization no longer energetically favorable. Lastly, we show that increasing the polarity of the solvent also increases the stability of QDs charged with electrons. These results highlight the complexity of surface reduction reactions in QDs and provide valuable strategies for improving the stability of charged QDs.

First author: Wang, MH, Planar hexacoordinate gallium,
CHEMICAL SCIENCE, 12, 15067, (2021)
Abstract: We report the first planar hexacoordinate gallium (phGa) center in the global minimum of the GaBe6Au6+ cluster which has a star-like D-6h geometry with (1)A(1g) electronic state, possessing a central gallium atom encompassed by a Be-6 hexagon and each Be-Be edge is further capped by an Au atom. The electronic delocalization resulting in double aromaticity (both sigma and pi) provides electronic stability in the planar form of the GaBe6Au6+ cluster. The high kinetic stability of the title cluster is also understood by Born-Oppenheimer molecular dynamics simulations. The energy decomposition analysis in combination with the ‘natural orbitals for chemical valence’ theory reveals that the bonding in the GaBe6Au6+ cluster is best expressed as the doublet Ga atom with 4s(2)4p(perpendicular to)(1) electronic configuration forming an electron-sharing pi bond with the doublet Be6Au6+ moiety followed by Ga(s)->[Be6Au6+] sigma-backdonation and two sets of Ga(p(||))<-[Be6Au6+] sigma-donations.

First author: Deghiche, A, Effect of the stearic acid-modified TiO2 on PLA nanocomposites: Morphological and thermal properties at the microscopic scale,
Abstract: In this work, a route is developed to synthesize nanocomposites based on polylactic acid (PLA) and stearic acid-modified TiO2 nanoparticles (TiO2-SA). The nanocomposite is prepared in two steps by solution and melt methods. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), as well as Thermogravimetric Analysis (TGA) are used to characterize the synthesized materials. Quantum chemical calculations are carried out by means of density functional theory (DFT) calculations, Blends study and AIM analysis, to investigate the role of Stearic Acid (SA) on the nanocomposite PLA/TiO2 at microscopic level. FTIR analysis confirms the functionalization of TiO2 nanoparticles by stearic acid (SA). The DSC results illustrates the overall TiO2 effect in reducing the glass transition temperature Tg (from 58 degrees to 52 degrees C) and the rise in the crystallinity degree (from 0.19 degrees to 7.18 degrees C) where the 5% of nanoparticle shows the optimum result. This could be attributed to the fact that TiO2-SA acts as a nucleating agent, as confirmed also by XRD patterns. TGA analysis shows that the thermal stability of PLA decreases by the addition of TiO2-SA and this effect is monothonic with TiO2 content where the 1% nanoparticle shows the most thermally stable formulation. Simulations at atomic level confirmed the dispersion of treated TiO2 in the matrix. In particular, SA plays the role of electron donor with PLA and TiO2, increasing the miscibility between them by a strong hydrogen bond. The main results obtained allow considering SA as a valid option for the functionalization of TiO2 before inclusion in PLA matrix.

First author: Cao, GJ, Electronic structures and bonding properties of MSi12- anions (M = V, Nb, and Ta),
Abstract: Here we have reported a relativistic quantum chemical study on electronic structures and bonding characteristics of MSi12- anions (M = V, Nb and Ta). One electron from extra electron, five ones from the central Ta atom, and 12 valence electrons from the Si atoms can be viewed as an 18e system with six sets of sigma or pi orbitals. EDA-NOCV calculations reveal that TaSi12- anion is formed by the electron-sharing interactions and a weak dative bond which comes from sigma orbital of Si-12-donation into the s orbital of Ta. It has stronger bonding interactions when compared with Ta’s lighter homologues due to the larger relativistic effect of Ta.

First author: Findik, V, Origins of the photoinitiation capacity of aromatic thiols as photoinitiatiors: a computational study,
Abstract: In this work, we report the photophysical properties of three thiol derivatives, commonly used as photoinitiators in thiol-ene free radical polymerization, the ultimate goal being to rationalize the main reason behind the photoinitiation efficiency. For this aim, time dependent density functional theory is used to simulate the absorption spectra of alkyl thiol (R-SH), thiophenol (PhSH) and p-(trifluoromethyl) thiophenol (p-CF3PhSH), describe their excited state topologies, and explore their potential energy surfaces along the S-H dissociation. Excited state calculations have shown that the S-H photolysis is achieved through the triplet excited states following intersystem crossing from the originally populated singlet manifolds. More specifically, while in aromatic thiol derivatives dissociation is mainly triplet-state mediated, the first excited singlet state and first triplet state of alkyl thiol are both dissociative and hence potentially capable of generating the photoinduced radical species. We have also justified the experimental findings concerning the photoinitiator efficiency considering both their potential energy surface topologies and the absorption intensity, in the lowest energy region.

First author: Ho, PC, Iso-Tellurazolium-N-Phenoxides: A Family of Te center dot center dot center dot O Chalcogen-Bonding Supramolecular Building Blocks,
INORGANIC CHEMISTRY, 60, 16726, (2021)
Abstract: Formal substitution of the oxygen atom of an isotellurazole N-oxide with deprotonated (ortho, meta, and para)hydroxyphenyl groups generated molecules that readily aggregate through Te center dot center dot center dot O chalcogen bonding (ChB) interactions. The molecules undergo autoassociation in solution, as shown by variable temperature (VT) H-1 NMR experiments and paralleling the behavior of iso-tellurazole N-oxides. Judicious adjustment of crystallization conditions enabled the isolation of either polymeric or macrocyclic aggregates. Among the latter, the ortho compound assembled a calixarene-like trimer, while the para isomer built a macrocyclic tetramer akin to a molecular square. The Te center dot center dot center dot O ChB distances in these structures range from 2.13 to 2.17 angstrom, comparable to those in the structures of iso-tellurazole N-oxides. DFT calculations estimate that the corresponding Te center dot center dot center dot O ChB energies are between – 122 and -195 kJ mol(-1) in model dimers and suggest that macrocyclic aggregation enhances these interactions.

First author: Blokker, E, The Chemical Bond: When Atom Size Instead of Electronegativity Difference Determines Trend in Bond Strength,
Abstract: We have quantum chemically analyzed element-element bonds of archetypal HnX-YHn molecules (X, Y=C, N, O, F, Si, P, S, Cl, Br, I), using density functional theory. One purpose is to obtain a set of consistent homolytic bond dissociation energies (BDE) for establishing accurate trends across the periodic table. The main objective is to elucidate the underlying physical factors behind these chemical bonding trends. On one hand, we confirm that, along a period (e. g., from C-C to C-F), bonds strengthen because the electronegativity difference across the bond increases. But, down a period, our findings constitute a paradigm shift. From C-F to C-I, for example, bonds do become weaker, however, not because of the decreasing electronegativity difference. Instead, we show that the effective atom size (via steric Pauli repulsion) is the causal factor behind bond weakening in this series, and behind the weakening in orbital interactions at the equilibrium distance. We discuss the actual bonding mechanism and the importance of analyzing this mechanism as a function of the bond distance.

First author: Miloserdov, FM, Bonding and Reactivity of a Pair of Neutral and Cationic Heterobimetallic RuZn2 Complexes,
INORGANIC CHEMISTRY, 60, 16256, (2021)
Abstract: A combined experimental and computational study of the structure and reactivity of two [RuZn2Me2] complexes, neutral [Ru(PPh3)(Ph2PC6H4)(2)(ZnMe)(2)] (2) and cationic [Ru(PPh3)(2)(Ph2PC6H4)(ZnMe)(2)][BArF4] ([BArF4] = [B{3,5-(CF3)(2)C6H3}(4)]) (3), is presented. Structural and computational analyses indicate these complexes are best formulated as containing discrete ZnMe ligands in which direct Ru-Zn bonding is complemented by weaker Zn center dot center dot center dot Zn interactions. The latter are stronger in 2, and both complexes exhibit an additional Zn center dot center dot center dot C-aryl interaction with a cyclometalated phosphine ligand, this being stronger in 3. Both 2 and 3 show diverse reactivity under thermolysis and with Lewis bases ((PBu3)-Bu-n, PCy3, and IMes). With 3, all three Lewis bases result in the loss of [ZnMe](+). In contrast, 2 undergoes PPh3 substitution with (PBu3)-Bu-n, but with IMes, loss of ZnMe2 occurs to form [Ru(PPh3)(C6H4PPh2)(C6H4PPhC6H4Zn(IMes))H] (7). The reaction of 3 with H-2 affords the cationic trihydride complex [Ru(PPh3)(2)(ZnMe)(2)(H)(3)][BAr4F] (12). Computational analyses indicate that both 12 and 7 feature bridging hydrides that are biased toward Ru over Zn.

First author: Ebenezer, C, Does the length of the alkyl chain affect the complexation and selectivity of phenanthroline-derived phosphonate ligands?-Answers from DFT calculations,
POLYHEDRON, 210, 16256, (2021)
Abstract: The soft-hard-donor-combined phosphonate-based ligands are one of the popular extractants for the separation of actinide from lanthanide in nuclear waste management. Among them, tetradentate phenanthroline-derived phosphonate (POPhen) ligands attract much attention. A recent report suggests that n-butyl substituted POPhen shows better portioning behaviour compared to its ethyl derivative. However, the effect of the alkyl chain on the extraction and complexation behaviour is yet to be explored. We addressed this issue by designing POPhen ligands with alkyl chains of different lengths (methyl to n-hexyl) using DFT calculations. Results show that the n-butyl substituted ligand has an excellent extraction capability with high selectivity towards Am(III) over Eu(III) ion. Electronic structure studies demonstrate that M-N and M-O bond lengths are greater in the Eu complexes than the corresponding Am complexes. Atoms in Molecules analysis was done on the optimized geometries to ascertain the nature of interactions present in these ML(NO3)3 complexes. In addition, bond order analysis reiterates that the n-butyl substituted ligand is having a better extraction ability towards Am(III) ions through higher M-O and M-N bond orders. The calculated separation factor of the ligand with n-butyl substitution is greater than that of other ligands. Increasing the length of the alkyl chain until the n-butyl increases the selectivity and binding, beyond which, the chain length is not of much use in improving the selectivity as well as the binding ability of these POPhen ligands. This work brings out an ideal alkyl chain length (n-butyl) required for better binding and extraction capability of POPhen ligands. Overall this computational study sheds light on the need for tailoring ligands with optimum alkyl chain for effective lanthanide/actinide separation.

First author: Srivastava, A, New deep eutectic solvents based on imidazolium cation: Probing redox speciation of uranium oxides by electrochemical and theoretical simulations,
Abstract: Two new deep eutectic solvents, different from hitherto known and based on common choline chloride, were prepared. 1-methyl-3-decylimidazolium bromide mixed with hydrogen bond donors, malonic acid and diglycolic acid to form DES. Dissolution of uranium oxides (UO3 and UO2) was explored in both of them and characterization of the resultant solutions was carried out by IR, TGA and UV-Vis spectroscopy. Redox speciation of dissolved uranium oxides was probed in these redox-active DES through cyclic voltammetry, differential pulse voltammetry and in situ spectroelectrochemical measurements. Interestingly, the formation of uranium oxo species was observed through the dissolution of UO3 in both the DES. The electrochemical characteristics viz. redox thermodynamics (peak potential and formal redox potential), transport property (diffusion coefficient D0), heterogeneous electron transfer kinetic parameters (alpha n and k0) and mechanistic electron transfer of the dissolved uranium species in two DES were investigated. The speciation of uranium was decoded through the electronic absorption spectra of uranium in its lower oxidation states [U(V) and U(IV)] acquired through in situ spectroelectrochemical electrolysis with varying cathodic potentials. Studies were also carried out using Molecular Dynamics (MD) and density functional theory (DFT) simulations to authenticate the electrochemical outcomes and to acquire the binding energy, optimized structure and molecular orbital diagram of dissolved uranium species. Further, the MD simulation sheds light on the probable equatorial coordinating atoms of dissolved uranium species. This is the first report, to the best of our knowledge, on imidazolium-based DES and actinide ions.

First author: Smak, P, The catalytic reaction mechanism of tyrosylprotein sulfotransferase-1,
Abstract: Tyrosine sulfation alters the biological activity of many proteins involved in different physiological and pathophysiological conditions, such as non-specific immune reaction, response to inflammation and ischemia, targeting of leukocytes and stem cells, or the formation of cancer metastases. Tyrosine sulfation is catalyzed by the enzymes tyrosylprotein sulfotransferases (TPST). In this study, we used QM/MM Car-Parrinello metadynamics simulations together with QM/MM potential energy calculations to investigate the catalytic mechanism of isoform TPST-1. The structural changes along the reaction coordinate are analyzed and discussed. Furthermore, both the methods supported the S(N)2 type of catalytic mechanism. The reaction barrier obtained from CPMD metadynamics was 12.8 kcal mol(-1), and the potential energy scan led to reaction barriers of 11.6 kcal mol(-1) and 13.7 kcal mol(-1) with the B3LYP and OPBE functional, respectively. The comparison of the two methods (metadynamics and potential energy scan) may be helpful for future mechanistic studies. The insight into the reaction mechanism of TPST-1 might help with the rational design of transition-state TPST inhibitors.

First author: Petralanda, U, Fast Intrinsic Emission Quenching in Cs4PbBr6 Nanocrystals,
NANO LETTERS, 21, 8619, (2021)
Abstract: Cs4PbBr6 (0D) nanocrystals at room temperature have both been reported as nonemissive and green-emissive systems in conflicting reports, with no consensus regarding both the origin of the green emission and the emission quenching mechanism. Here, via ab initio molecular dynamics (AIMD) simulations and temperature-dependent photoluminescence (PL) spectroscopy, we show that the PL in these 0D metal halides is thermally quenched well below 300 K via strong electron-phonon coupling. To unravel the source of green emission reported for bulk 0D systems, we further study two previously suggested candidate green emitters: (i) a Br vacancy, which we demonstrate to present a strong thermal emission quenching at room temperature; (ii) an impurity, based on octahedral connectivity, that succeeds in suppressing nonradiative quenching via a reduced electron-phonon coupling in the corner-shared lead bromide octahedral network. These findings contribute to unveiling the mechanism behind the temperature-dependent PL in lead halide materials of different dimensionality.

First author: Sobiech, TA, Stable pseudo[3]rotaxanes with strong positive binding cooperativity based on shape-persistent aromatic oligoamide macrocycles,
Abstract: New aromatic oligoamide macrocycles with C-3-symmetry bind a bipyridinium guest (G) to form compact pseudo[3]rotaxanes involving interesting enthalpic and entropic contributions. The observed high stabilities and strong positive binding cooperativity are found in few other host-guest systems.

First author: Javid, F, Hydrothermal deconstruction of two antibiotics (amoxicillin and metronidazole),
Abstract: Pharmaceutical waste contributes to the contamination of land and water. Often without efficacious protocols for disposal, these toxic wastes are a threat to the environment. This study used non-catalytic hydrothermal destruction to elucidate the degradation of two antibiotics. The antibiotics, amoxicillin and metronidazole with an initial concentration of 800 and 400 mg/L, respectively, were subjected to 60 min hydrothermal deconstruction at temperatures varying between 200 and 350 degrees C. A reduction in the chemical oxygen demand (COD) (up to 94.8%) was observed for amoxicillin deconstruction; metronidazole deconstruction showed 83.9% COD reduction. Short-chain and volatile fatty acids, primarily acetic acid, were generated during the deconstruction process. Amoxicillin achieved complete degradation at 250 degrees C after 5 min, whereas metronidazole achieved 99% degradation at 350 degrees C after 5 min. Ammonia nitrogen content (NH3-N) of up to 10.5 mg/L was traced for amoxicillin deconstruction, and 29.8 mg/L for metronidazole deconstruction. A reactive force field (ReaxFF) molecular dynamic simulation proposed that the hydroxyl radicals were accountable for the degradation of amoxicillin and metronidazole. The results suggest the potential of hydrothermal deconstruction to resolve the issues presented by antibiotics by their deconstruction in an environmentally benign manner.

First author: Ye, ZR, Theoretical Insights into the Separation of Am(III)/Eu(III) by Hydrophilic Sulfonated Ligands,
INORGANIC CHEMISTRY, 60, 16409, (2021)
Abstract: In this work, we focused on the separation of Am(III)/Eu(III) with four hydrophilic sulfonated ligands (L) based on the framework of phenanthroline and bipyridine through scalar relativistic density functional theory. We studied the electronic structures of [ML(NO3)(3)] (M = Am, Eu) complexes and the bonding nature between metal and ligands as well as evaluated the separation selectivity of Am(III)/Eu(III). The tetrasulfonated ligand L-2 with a bipyridine framework has the strongest complexing ability for metal ions probably because of the better solubility and flexible skeleton. The disulfonated ligand L-1 has the highest Am(III)/Eu(III) selectivity, which is attributed to the covalent difference between the Am-N and Eu-N bonds based on the quantum theory of atoms in the molecule analysis. Thermodynamic analysis shows that the four hydrophilic sulfonated ligands are more selective toward Am(III) over Eu(III). In addition, these hydrophilic sulfonated ligands show better complexing ability and Am(III)/Eu(III) selectivity compared to the corresponding hydrophobic nonsulfonated ones. This work provides theoretical support for the separation of Am(III)/Eu(III) using hydrophilic sulfonated ligands.

First author: Dumpala, RMR, The aqueous interaction of neodymium with two omni existent biomoieties – a mechanistic understanding by experimental and theoretical studies,
DALTON TRANSACTIONS, 50, 16191, (2021)
Abstract: Neodymium (Nd), a technologically important metal ion, has emerged as a major contaminant in aquatic systems in recent years owing to its surge in electrical and electronic applications as a permanent magnet. The chelating molecules present in hydro- and biospheres could substantially enhance its absorption and lead to transportation and migration of Nd from the source. The mechanistic understanding of the Nd interaction with naturally relevant biomoieties present in flora and fauna is of primitive importance to estimate the toxicological effects of the metal ion. The present studies aimed at understanding the aquatic interaction of Nd with two biomoieties namely pyrazine-2-carboxylic acid (P2C) and pyrazine-2,3-dicarboxylic acid (P23C) by multiple experimental determinations and theoretical estimations. Potentiometry and spectrophotometry were employed to determine the aquatic speciation and thermodynamic stability of the complexes. Both techniques supported the formation of MLi (i = 1-4) complexes by Nd(iii) with P2C and MLi (i = 1-3) complexes with P23C. The Nd-P23C complexes are more stable than the Nd-P2C complexes for ML formation, while the opposite trend is observed for the ML2 and ML3 complexes. Titration calorimetry was used to determine the enthalpies of complexation which was found to be exothermic and majorly favored by entropy contributions. The formation of the Nd(iii)-P2C complexes is more exothermic than that of the respective Nd(iii)-P23C complexes. Density functional theory was employed for the geometry optimization of the predicted complexes and for the estimation of the bond distances and partial charges on the coordinating atoms in the optimized geometries. Experimental insights provide crucial inputs at the macro (thermodynamic) level and theoretical calculations help in understanding the complexation process at the molecular level.

First author: Hanada, T, DFT-Based investigation of Amic-Acid extractants and their application to the recovery of Ni and Co from spent automotive Lithium-Ion batteries,
Abstract: To establish more efficient and environmentally friendly lithium-ion battery (LiB) recycling processes, novel extractants derived from amino acids that enable better separation of Ni and Co were explored using density functional theory (DFT) calculations. DFT calculations and experimental validation indicated that of the three coordination sites-namely amine, amide, and carboxyl groups in the amic-acid ligands-the bond strength of the central amine group to the metal determines the Ni and Co separation performance. Based on the findings, the glycine-derived amic-acid extractant N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) was applied for the recovery of Ni and Co from a spent automotive LiB leachate. Preferential and mutual recovery of Ni and Co from manganese by the D2EHAG-based recycling process was demonstrated. This study provides insights into the design of extractants that enable the mutual separation of Ni, Co, and Mn, and indicates the suitability of amic-acid extractants for LiB recycling processes.

First author: Tang, Z, XEDA, a fast and multipurpose energy decomposition analysis program,
Abstract: A fast and multipurpose energy decomposition analysis (EDA) program, called XEDA, is introduced for quantitative analysis of intermolecular interactions. This program contains a series of variational EDA methods, including LMO-EDA, GKS-EDA and their extensions, to analyze non-covalent interactions and strong chemical bonds in various environments. XEDA is highly efficient with a similar computational scaling of single point energy calculations. Its efficiency and universality are validated by a series of test examples including van der Waals interactions, hydrogen bonds, radical-radical interactions and strong covalent bonds.

First author: Carlotto, S, cis-[(eta(5)-C5H5)Fe(eta(1)-CO)(mu-CO)](2), the poor relative between cis and trans tautomers. A theoretical study of the gas-phase Fe L-3-edge and C and O K-edge XAS of trans-/cis-[(eta(5)-C5H5)Fe(eta(1)-CO)(mu-CO)](2),
Abstract: The relative stability of trans-[(eta(5)-C5H5)Fe(eta(1)-CO)(mu-CO)](2) (trans-I) and cis-I tautomers in a vacuum and in solvents with different dielectric constants (epsilon) has been investigated by exploiting density functional theory (DFT). Theoretical results indicate that, in agreement with experimental evidence, trans-I is more stable than cis-I in a vacuum (similar to 1.5 kcal mol(-1); epsilon = 1), while the opposite is true in media with epsilon > 7. Differently from solution, DFT outcomes pertaining to the vapor-phase cis-I &leftrightarrows; trans-I equilibrium at T = 368 K, the temperature at which the Fe L-2,L-3-edges and the C and O K-edge X-ray absorption spectroscopy (XAS) data of I have been recorded, ultimately indicate the trans-I predominance (similar to 93%). Compositions, oscillator strengths (f) and excitation energy (EE) values of cis-I transitions substantially mirror those of trans-I; nevertheless, the weighted cis-If(EE) distributions negligibly contribute to the diverse simulated XA spectra of I.

First author: Tiekink, EH, How Lewis Acids Catalyze Ene Reactions,
Abstract: The catalytic effect of various Lewis acids (LAs) on the ene reaction between propene (ene) and but-3-en-2-one (enophile) was studied quantum chemically using density functional theory and with coupled-cluster theory. The studied LAs efficiently accelerate the ene reaction by lowering the reaction barrier up to 12 kcal mol(-1) compared to the uncatalyzed reaction. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal that coordination of a LA catalyst to the enophile decreases the reaction barrier of the ene reaction by inducing an asymmetry in the pi-electronic system, which increases the asynchronicity and hence relieves the otherwise highly destabilizing activation strain and Pauli repulsion between the closed-shell filled pi-orbitals of the ene and enophile. In all, these findings further demonstrate the generality of the Pauli-lowering catalysis concept.

First author: Lbadaoui-Darvas, M, Molecular simulations of interfacial systems: challenges, applications and future perspectives,
MOLECULAR SIMULATION, 2021, 5275, (2021)
Abstract: We present a comprehensive review of methods and applications of molecular simulations of interfacial systems. We give a detailed overview of the main techniques and major challenges in the following aspects of solid and fluid surfaces: adsorption at solid surfaces, interfacial transport and surface-to-bulk partitioning. We summarise methods to estimate macroscopic properties interfaces (adsorption isotherms, surface tension and contact angle) and ways to extract quantitative information about fluctuating liquid surfaces. We demonstrate the usage of these methods on recent applications from the fields of atmospheric science, material science and biophysics. The two main goals of this review are: (i) to provide guidance in practical questions, such as choosing software, force field, level of theory, system geometry, and finding the appropriate selective surface analysis methods based on the type of the interface and the nature of the physical problem to be studied; and (ii) to highlight domains where molecular simulations can bring about substantial advances in our understanding in important questions of applied science as a function of future method development and adaptation for applied fields.

First author: Lehtola, S, Straightforward and Accurate Automatic Auxiliary Basis Set Generation for Molecular Calculations with Atomic Orbital Basis Sets,
Abstract: Density fitting (DF), also known as the resolution of the identity (RI), is a widely used technique in quantum chemical calculations with various types of atomic basis sets.Gaussian-type orbitals, Slater-type orbitals, as well as numerical atomic orbitals-to speed up density functional, Hartree-Fock (HF), and post-HF calculations. Traditionally, custom auxiliary basis sets are hand-optimized for each orbital basis set; however, some automatic schemes have also been suggested. In this work, we propose a simple yet numerically stable automated scheme for forming auxiliary basis sets with the help of a pivoted Cholesky decomposition, which is applicable to any type of atomic basis function. We exemplify the scheme with proof-of-concept calculations with Gaussian basis sets and show that the proposed approach leads to negligible DF/RI errors in HF and second-order Moller-Plesset (MP2) total energies of the non-multireference part of the W4-17 test set when used with orbital basis sets of at least polarized triple-zeta quality. The results are promising for future applications employing Slater-type orbitals or numerical atomic orbitals, as well as schemes based on the use of local fitting approaches. Global fitting approaches can also be used, in which case the high-angular-momentum functions produced by the present scheme can be truncated to minimize the computational cost.

First author: Meng, GH, Theoretical Insights into the Carrier Mobility Anisotropy of Organic-Inorganic Perovskite ABI(3) (A = CH3NH3 and HC(NH2)(2); B = Pb and Sn),
Abstract: High mobility, which is closely relevant to crystal structures, is one of the predominant advantages of organicinorganic halide perovskites. However, the carrier mobility anisotropies for photoelectric materials HC(NH2)(2)SnI3, HC(NH2)(2)PbI3, and CH3NH3SnI3 parallel to the representative crystal planes are still unknown. According to the density functional theory and Marcus theory, we focus on carrier mobility anisotropy by simulating the intermolecular electronic coupling integral V and the internal reorganization energy. parallel to different low-index crystal planes. Results indicate that the electrons and holes of HC(NH2)(2)PbI3 exhibit transport orientation consistency along the (101), (010), (111), and (001) crystal planes. However, inconsistency was observed along the (110) crystal planes (an angle of 65 degrees between electron and hole movements). The electrons and holes in HC(NH2)(2)SnI3 reflect transport orientation consistency along the (001) and (101) crystal planes, while inconsistency was observed along the (110) and (111) crystal planes (the angles fluctuate from 40 to 65 degrees between the carrier movements). The carriers in CH3NH3SnI3 exhibit transport orientation consistency along the (110) and (101) crystal planes, while inconsistencies were observed along the (010), (001), and (111) crystal planes (the angles fluctuate from 45 to 65 degrees between the carrier transport). This study emphasizes the theoretical guidance of controllable oriented fabrication for perovskites.

First author: Zhang, SM, Theoretical insights into the substitution effect of phenanthroline derivative ligands on the extraction of Mo (VI),
Abstract: With the rapid development of nuclear medical imaging, the production of Mo-99 has attracted much attention, because the important medical isotope Tc-99m can be obtained from Mo-99. N,N’-diethyl-N,N’-ditolyl-2,9-diamidel,10-phenanthroline (Et-Tol-DAPhen) has been proven to be an excellent ligand for the extraction of U (VI), while there are still few reports on the extraction of Mo(VI) using this ligand. To investigate the coordination structures of MoO22+ with Et-Tol-DAPhen, we carried out theoretical calculations using scalar relativistic density functional theory (DFT). The analyses of Wiberg indices (WBIs), quantum theory of atoms in molecules (QTAIM) and natural orbitals of chemical valence (NOCV) indicate that the MoO22+ have stronger complexation ability with O atoms compared to N atoms. The bonds between MoO22+ ions and ligands are mainly ionic interactions. The analyses of EDA and the most negative binding energy indicates that complex [MoO2L(NO3)](+) is energetically favorable and Et-Tol-DAPhen has also good extraction ability for MoO22+. Moreover, although both the electron-donating and electron-withdrawing groups have slightly effect on the electronic structures of the [MoO2L(NO3)](+) complexes, Et-Tol-DAPhen modified by the electron-donating group can enhance the extraction ability of MoO22+. This study is helpful to understand the complexation behavior of Et-Tol-DAPhen with MoO22+ and provides useful structural and thermodynamic information for the MoO22+ extraction with phenanthroline derivative ligands.

First author: Li, YY, Achieving a Favorable Activation of the C-F Bond over the C-H Bond in Five- and Six-Membered Ring Complexes by a Coordination and Aromaticity Dually Driven Strategy,
ORGANOMETALLICS, 40, 3397, (2021)
Abstract: Activating the C-F bond (the strongest sigma bond to carbon) is particularly challenging, let alone in a selective fashion when a weaker C-H bond is present in the same species. Herein, we demonstrate a novel strategy to achieve a thermodynamically and kinetically favorable activation of the C-F bond over the CH bond dually driven by coordination and aromaticity via density functional theory calculations. Specifically, the bond dissociation energies (BDEs) of the C-H bond in 5-fluoro-1,2,3,4-tetramethylcyclopenta-1,3-diene increase remarkably after its coordination to the metal centers (Co, Rh, and Ir), whereas the BDE changes in the C-F bond of Rh and Ir complexes are insignificant. The C-F bond activation of the Co system has the lowest energy barrier and the largest exergonicity due to significant weakening of the C-F bond of reactants after coordination. Aromaticity is found to play an important role in stabilizing the transition states and products during the reactions, which is indicated by gradually increased multicenter index values along the intrinsic reaction coordinate. In addition, stronger electrostatic attraction in the transition states between the metal center and F over the H atom could be another factor for the lower reaction barrier of the C-F bond activation. All these findings provide a fundamental understanding of competitive activation of the C-F and C-H bonds, inviting experimental chemists’ verification.

First author: Yakovlev, IA, Nitric oxide release and related light-induced cytotoxicity of ruthenium nitrosyls with coordinated nicotinate derivatives,
DALTON TRANSACTIONS, 50, 13516, (2021)
Abstract: The synthetic approaches for the preparation of trans(NO,OH)-cis(NO2,NO2)-[RuNO(L)(2)(NO2)(2)OH], where L = ethyl nicotinate (I) and methyl nicotinate (II), are reported. The structures of the complexes are characterized by X-ray diffraction and analyzed by Hirshfeld surface analysis. Both compounds show a nitric oxide release reaction under 445 or 532 nm irradiation of dimethyl sulfoxide (DMSO) solutions, which is studied by combined ultraviolet-visible- (UV-vis), infrared- (IR), and electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations. The charge transfer from the OH-Ru-NO chain and nitrite ligands to the antibonding orbitals of Ru-NO is responsible for the photocleavage of the ruthenium-nitrosyl bond. The elimination of NO leads to a side reaction, namely the protonation of the parent hydroxyl compound. The cytotoxicity and photo-induced cytotoxicity investigations of both compounds on the breast adenocarcinoma cell line MCF-7 reveal that (I) and (II) are cytotoxic with IC50 values of 27.5 +/- 2.8 mu M and 23.3 +/- 0.3 mu M, respectively. Moreover, (I) shows an increase of the toxicity after light irradiation by 7 times (IC50 = 4.1 +/- 0.1), which makes it a prominent target for deeper biological investigations.

First author: De Marco, R, Synthesis, Structural Characterization and Antiproliferative Activity of Gold(I) and Gold(III) Complexes Bearing Thioether-Functionalized N-Heterocyclic Carbenes,
Abstract: A series of gold(I) and gold(III) complexes with N-heterocyclic carbene ligands functionalized with a pendant thioether group (NHC-SR) was synthesized with straightforward procedures and characterized in solution with NMR spectroscopy and ESI-MS spectrometry, as well as in the solid state by means of single crystal X-ray diffraction analysis. Selected experimental aspects were rationalized through relativistic DFT calculations. The gold(I) and gold(III) complexes displayed moderate in vitro cytotoxicity towards breast cancer cells MCF7.

First author: Majid, A, Layered silicon carbide: a novel anode material for lithium ion batteries,
NEW JOURNAL OF CHEMISTRY, 45, 19105, (2021)
Abstract: The structural stability of carbon and the high theoretical capacity of silicon was the motivation for investigating the prospects of layered silicon carbide (SiC). The density functional theory (DFT) based computations and first-principles molecular dynamics (MD) simulations were performed to determine the likelihood of being able to use 2D SiC layers as a lithium intercalation compound. The calculations were performed using dispersion corrected exchange correlation and this revealed the stability of the layers, and the transfer of charge from Li to the host during intercalation was at a maximum storage capacity of 699 mA h g(-1). The layers offered better flexibility, a higher rate capability and a three times larger capacity when compared to graphite bilayers. The diffusion barrier calculated here, with a small energy barrier of 0.40 eV, illustrated a good rate capability. The findings and comparison with graphite revealed that layered SiC is an appropriate anode material for used in lithium ion batteries (LIBs) because of its structural firmness, high electronic conductivity, low diffusion barrier and high storage capacity.

First author: Xu, S, Theoretical Insight into 20-Electron Transition Metal Complexes (C5H5)(2)TM(E1E2)(2) (TM = Cr, Mo, W; E1E2 = CO, N-2, BF): Stabilities, Electronic Structures, and Bonding Nature,
Abstract: A systematic first-principles study is performed to investigate the 20-electron transition metal complexes (C5H5)(2)TM(E1E2)(2) (TM = Cr, Mo, W; E1E2 = CO, N-2, BF). For the thermodynamic stable (C5H5)(2)TM(E1E2)(2) complexes (TM = Cr, Mo, W; E1E2 = CO, BF), their 20-electron nature is derived from their occupied nonbonding molecular orbital mainly donated by ligands. Furthermore, the nature of the TM-E-1 bond is thoroughly analyzed by the energy decomposition analysis (EDA) method. The absolute value of interaction energies (|Delta E-int|) between (C5H5)(2)TM(E1E2) and E1E2 has the same trend as the corresponding bond dissociation energy and Wiberg bond orders of TM-E-1 bonds, following the order W > Mo > Cr with same ligands and BF > CO with same TM. The largest contribution to the Delta E-int values is the repulsive term Delta E-Pauli. Similar contributions from covalent and electrostatic terms to the TM-E-1 bonds are found, which can be described as the classic dative bond with nearly same sigma and pi contributions.

First author: Brault, P, Insight into acetylene plasma deposition using molecular dynamics simulations,
Abstract: Molecular dynamics simulations are carried out for studying the growth and properties of polymers from pure acetylene plasma. A mixture of H, C2H, and C2H2 is the initial composition used for running the molecular dynamics simulations. The resulting films are characterized by determining the bond order, [H]/[C] ratio, and simulated infrared spectrum. The latter is qualitatively compared with three different experiments: IR peak identification and positions are recovered.

First author: Chen, YM, Theoretical insights into the possible applications of amidoxime-based adsorbents in neptunium and plutonium separation,
DALTON TRANSACTIONS, 50, 15576, (2021)
Abstract: Efficient separation of neptunium and plutonium from spent nuclear fuel is essential for advanced nuclear fuel cycles. At present, the development of effective actinide separation ligands has become a top priority. As common adsorbents for extracting uranium from seawater, amidoxime-based adsorbents may also be able to separate actinides from high-level liquid waste (HLLW). In this work, the complexation of Np(iv,v,vi) and Pu(iv) and alkyl chains (R = C13H26) modified with amidoximate (AO(-)) and carboxyl (Ac-) functional groups was systematically studied by quantum chemical calculations. For all the studied complexing species, the RAc- and RAO(-) ligands act as monodentate or bidentate ligands. Complexes with AO(-) groups show higher covalency of the metal-ligand bonding than the analogues with Ac- groups, in line with the binding energy analysis. Bonding analysis verifies that these amidoxime/carboxyl-based adsorbents possess higher coordination affinity toward Pu(iv) than toward Np(iv), and the Np(vi) complexes have stronger covalent interactions than Np(v). According to thermodynamic analysis, these adsorbents have the ability to separate Np(iv,v,vi) and Pu(iv), and also exhibit potential performance for partitioning Pu(iv) from Np(iv) under acidic conditions. This work can help to deeply understand the interaction between transuranium elements and amidoxime-based adsorbents, and provide a theoretical basis for the separation of actinides with amidoxime-based adsorbents.

First author: Seo, Y, [Pd(4-R3Si-IPr)(allyl)Cl]/K2CO3/EtOH: A highly effective catalytic system for the Suzuki-Miyaura cross-coupling reaction,
Abstract: A series of R3Si-NHC-Pd complexes 1Pd-7Pd was successfully tested as a pre-catalyst for the Suzuki-Miyaura cross-coupling reaction of aryl chlorides and arylboronic acid derivatives to form a wide range of valuable biphenyl products. Use of the readily available weakly basic potassium carbonate as a base and the highly polar protic ethanol as the reaction solvent gave the target coupling products in good-to-excellent yields. The experimental data pointed to the crucial importance of the preliminary pre-catalyst activation step [i.e., the conversion of Pd(II) to Pd(0)], which is remarkably facilitated by the electron-donating trialkylsilyl groups on the NHC ligands of 1Pd-7Pd, thereby rendering them superior compared to the commercially available IPr-Pd complexes. Computational analysis revealed the mechanism of the Pd(II)-> Pd(0) activation step, demonstrating the critical role of the reaction solvent and the base in the preference of our 1Pd-7Pd pre-catalysts, for which this step is both thermodynamically and kinetically more feasible.

First author: Crespo, DM, Interacting Quantum Atoms Method for Crystalline Solids,
Abstract: An implementation of the Interacting Quantum Atoms method for crystals is presented. It provides a real space energy decomposition of the energy of crystals in which all energy components are physically meaningful. The new package ChemInt enables one to compute intra-atomic and inter-atomic energies, as well as electron population measures used for quantitative description of chemical bonds in crystals. The implementation is tested and applied to characteristic molecular and crystalline systems with different types of bonding.

First author: Petrov, PA, Cyclometallation of the Dimethylamide Ligand in the Reaction of Ta(NMe2)(5) with CS2,
Abstract: The reaction of Ta(NMe2)(5) with CS2 resulted in the isolation of azametallacyclopropane complex [Ta((Me)Dtc)(3)(eta(2)-CH2NMe)] (I, (Me)Dtc = dimethyldithiocarbamate), which was characterized by X-ray diffraction in the solvent-free form and as a toluene solvate (CCDC nos. 2005837 (I), 2049693 (I center dot 0.5C(7)H(8))) and by NMR spectroscopy and DFT calculations.

First author: Menant, S, Polarisation of Electron Density and Electronic Effects: Revisiting the Carbon-Halogen Bonds,
MOLECULES, 26, 657, (2021)
Abstract: Electronic effects (inductive and mesomeric) are of fundamental importance to understand the reactivity and selectivity of a molecule. In this article, polarisation temperature is used as a principal index to describe how electronic effects propagate in halogeno-alkanes and halogeno-alkenes. It is found that as chain length increases, polarisation temperature decreases. As expected, polarisation is much larger for alkenes than for alkanes. Finally, the polarisation mode of the carbon-fluorine bond is found to be quite different and might explain the unusual reactivity of fluoride compounds.

First author: Novak, M, N-Donor stabilized tin(II) cations as efficient ROP catalysts for the synthesis of linear and star-shaped PLAs via the activated monomer mechanism,
DALTON TRANSACTIONS, 50, 16039, (2021)
Abstract: alpha-Iminopyridine ligands L-1(2-(CH=N(C6H2-2,4,6-Ph-3))C5H4N), L-2 (2-(CH=N(C6H2-2,4,6-tBu(3)))C5H4N) and L-3 (1,2-(C5H4N-2-CH=N)(2)CH2CH2) differing by the steric demand of the substituent on the imine CH=N group and by the number of donating nitrogen atoms were utilized to initiate a Lewis base mediated ionization of SnCl2 in an effort to prepare ionic tin(II) species [L1-3 -> SnCl][SnCl3]. The reaction of L-1 and L-2 with SnCl2 led to the formation of neutral adducts [L-1 -> SnCl2] (2) and [L-2 -> SnCl2] (3). The preparation of the desired ionic compounds was achieved by subsequent reactions of 2 and 3 with an equivalent of SnCl2 or GaCl3. In contrast, ligand L-3 containing four donor nitrogen atoms showed the ability to ionize SnCl2 and also Sn(OTf)(2), yielding [L-3 -> SnCl][SnCl3] (7) and [L-3 -> Sn(H2O)][OTf](2) (8). The study thus revealed that the reaction is dependent on the type of the ligand. The prepared complexes 4-8 together with the previously reported [{2-((CH3)C=N(C6H3-2,6-iPr(2)))-6-CH3O-C5H3N}SnCl][SnCl3] (1) were tested as catalysts for the ROP of L-lactide, which could operate via an activated monomer mechanism. Finally, a DFT computational study was performed to evaluate the steric and electronic properties of the ionic tin(II) species 1 and 4-8 together with their ability to interact with the L-lactide monomer.

First author: Sprague-Klein, EA, Modulating the Electron Affinity of Small Bipyridyl Molecules on Single Gold Nanoparticles for Plasmon-Driven Electron Transfer,
Abstract: Developing controlled platforms for plasmon-driven chemistry is of great importance in catalytic reactions at the nanoscale. We report anion radical formation for five bipyridyl complexes of varying degrees of electron affinity utilizing optically focused intraband (594 nm) and interband (532 nm) pump excitation of single gold nanoparticles. The surface-enhanced Raman scattering (SERS) of anion radicals for the five nonresonant adsorbed molecules, 2,2′-bipyridine (22BPY), 4,4′-bipyridine (44BPY), trans-1,2-bis(4-pyridyl)ethylene (BPE), 1,2-bis(4-pyridyl)acetylene (BPA), and 1,2-bis(4-pyridyl)ethane (BPEt), were detected using localized surface-plasmon resonance (LSPR) excitation with 785 nm. The electron affinity of the five bipyridyl complexes were determined using electrochemistry. Molecules with low electron affinity experienced higher instances of radical anion formation under a plasmon-coupled intraband electron transfer excitation (594 nm), whereas molecules with high electron affinity showed a preference for anion radical formation under direct interband electron transfer excitation (532 nm). The lowest unoccupied molecular orbital (LUMO) energy levels for low electron affinity surface-bound molecules (22BPY, BPEt) are on average similar to 0.43 eV higher than high electron affinity surface-bound molecules (BPA, BPE, 44BPY), as calculated using time-dependent density functional theory, elucidating the importance of plasmon coupling to energy levels that facilitate charge transfer pathways. We also show the ability to “activate” high versus low electron affinity single nanoparticles with the choice of pump excitation wavelength. The findings show the complex interplay between molecular electron affinity, orbital overlap with the density of states of the plasmonic metal, and excitation energetics of the pump laser wavelength. Potential applications of this work include enhanced control over molecular scale catalysis, biosensor design, and solar energy capture.

First author: Chattaraj, S, Role of O Substitution in Expanded Porphyrins on Uranyl Complexation: Orbital- and Density-Based Analyses,
INORGANIC CHEMISTRY, 60, 15351, (2021)
Abstract: Search for new U(VI) sequestering macrocyclic ligands is an important area of research due to manifold applications. Besides hard- or soft-donor-based ligands, mixed-donor ligands are also gaining popularity in achieving optimized performances. However, how the combination of hard-soft-donor centers alters the bonding interactions with U(VI) is still not well-understood. Moreover, a consensus is yet to be reached on the nature and role of underlying covalent interactions in mixed N,O-donor ligands. In this work, using the relativistic density functional theory (DFT), we attempted to address these intriguing issues by investigating the subtle change in bonding characteristics of the uranyl ion upon binding with an expanded porphyrin, viz. sapphyrin, with subsequent O substitutions at the cavity. The results obtained from a range of modern analysis tools suggest that in the O-substituted sapphyrin variants, UO22+ prefers to bind with N over O, and an increase in the number of O-donor sites at the cavity prompts UO22+ to have a better interaction with the rest of the N-donor-centers. Although O donors are involved in more numbers of mixed molecular orbitals, the variation in the amplitude of overlap and the better sigma-donation ability favor N to have stronger bonding interactions with uranyl. Molecular orbital (MO) and density of states (DOS) analyses show favorable participation of U(d), and the involvement of U(f) orbitals in bonding is of a low extent but non-negligible. Although electrostatic interaction dominates at U-O/N bonds in the equatorial plane, the quantum theory of atoms in molecules descriptors, MO analysis, and overlap-integral calculations confirm the presence of underlying near-degeneracy-driven covalent interactions.

First author: Nabil, E, Optimizing the Cosensitization Effect of SQ02 Dye on BP-2 Dye-Sensitized Solar Cells: A Computational Quantum Chemical Study,
Abstract: Cosensitization of the semiconducting electrode in dye-sensitized solar cells (DSCs), with two or more light-harvesting dyes, is a chemical fabrication method that aims to achieve a panchromatic absorption spectrum emulating that of the solar emission spectrum. In this paper, SQ02 and BP-2 cosensitizers have been investigated, as isolated monomers/dimer and adsorbed monomers/dimer on the TiO2 (101) anatase surface, by employing density functional theory (DFT) and time-dependent DFT calculations. Computed results showed that the dominant electron injection pathway is direct injection from each dye into the conduction band of TiO2. The almost complete spectral overlap between the simulated absorption spectrum of BP-2 and fluorescence emissions of SQ02 implies that excitation energy transfer occurs between cosensitizers via the trivial reabsorption mechanism. However, the results showed very limited unidirectional intermolecular charge transfer (CT) from SQ02 dye to BP-2 dye (0.04 vertical bar e(-)vertical bar). Therefore, this study also presents a stepwise molecular engineering of BP-2 dye, aiming at optimizing the cosensitization functionality. First, 14 redesigned dye candidates are reported to identify dyes with photophysical properties matching the requirements for efficient DSCs. Second, the four most promising dyes are shortlisted for testing as cosensitizers with the SQ02 dye. The molecular design factors of cosensitization that need validation are chemical compatibility, availability of CT between cosensitizers, and complementarity of the absorption spectra. This screening suggests the judicious choice of the modeled difluorenyl amine donor-based dye (BP-D4) as a very promising cosensitizer. In particular, the SQ02/BP-D4 dimer showed 10 times larger (0.53 vertical bar e(-)vertical bar) unidirectional CT than that of SQ02/BP-2 dimer, in addition to the maximum increased electron population of acceptor moieties upon photoexcitation.

First author: Shakourian-Fard, M, Density functional theory investigation into the interaction of deep eutectic solvents with amino acids,
Abstract: Processing of amino acids (AAs) is a very cost-intensive process. Recently, Li et al. used supported liquid membranes (SLMs) based on deep eutectic solvents (DESs) for amino-acid extraction and found that [choline chloride][p-Toluenesulfonic acid] aChCl][p-TSA])) DES was efficiently separating Tryptophan (Trp (center dot)) amino acid. Inspired by the study, here we investigate the interaction of [ChCl] [p-TSA] DES with three forms of amino acids, including neutral(center dot), cationic(+), and anionic(-) forms using density functional theory (DFT) method at the M06-2X/6-311++G(d,p) level of theory. Our results indicate that the interaction of AAs(center dot/+/-) with [ChCl] [p-TSA] DES is governed by the hydrogen bonding interactions, which is consistent with the findings of H-1 NMR spectra by Li et al. Thermochemistry calculations indicate that the formation of [ChCl] [p-TSA]…AAs(center dot/+/-) complexes is an exothermic and favorable reaction and proceeds spontaneously. Among the three forms of AAs(center dot/+/-), cationic forms (AAs(+)) exhibited the most tendency to interact with the [ChCl][p-TSA] DES. The binding energy (Delta E-b) calculations show that Trp(center dot) has the strongest interaction with [ChCl][p-TSA] DES among the AAs(center dot), in agreement with the experimental results reported in the literature. The Gly(+) and Val(-) also have the highest Delta E-b value with [ChCl][pTSA] DES. A comparison between the calculated free energies and the extraction efficiency (%) reported by Li et al. for extraction of AAs(center dot) by [ChCl] [p-TSA] DES indicates that the higher the free energy value, the higher is the extraction efficiency (%) of neutral AAs(center dot). Furthermore, the natural bond orbital (NBO) analysis, atoms in molecules (AIM) theory, and noncovalent interaction (NCI) plots were performed to determine the nature and strength of hydrogen bonding interactions between the [ChCl][p-TSA] DES and AAs(center dot/+/-). These analyses indicate that the O-H..D, O-H…[Cl] , and N-H…[Cl] interactions in the complexes are stronger than the N-H…O and C-H…O interactions. Energy decomposition analysis (EDA) method revealed that the charged AAs(+/-) have a greater tendency to interact with [ChCl][p-TSA] DES due to the presence of positive and negative charges on the AAs(+/-), which leads to increased strength in the electrostatic interactions between the AAs(+/-) and [ChCl][p-TSA] DES.

First author: Kiran, B, Trapping of H-2(-) in aluminum hydride, Al4H14-,
Abstract: Ever since our first experimental and computational identification of Al4H6 as a boron analog [X. Li et al., Science 315, 356 (2007)], studies on aluminum hydrides unveiled a richer pattern of structural motifs. These include aluminum-rich hydrides, which follow shell closing electron counting models; stoichiometric clusters (called baby crystals), which structurally correspond to the bulk alane; and more. In this regard, a mass spectral identification of unusually high intense peak of Al4H14-, which has two hydrogen atoms beyond stoichiometry, has remained mostly unresolved [X. Li et al., J. Chem. Phys. 132, 241103 (2010)]. In this Communication, with the help of global minima methods and density functional theory-based calculations, we identify the lowest energy bound structure with a unique Al-H-H-Al bonding. Our electronic structural analysis reveals that two Al2H6 units trap a transient, metastable H-2(-). In other words, three stable molecules, two Al2H6 and an H-2, are held together by a single electron. Our studies provide a pathway to stabilize transient species by making them part of a more extensive system.

First author: Khanna, SN, The superatomic state beyond conventional magic numbers: Ligated metal chalcogenide superatoms,
Abstract: The field of cluster science is drawing increasing attention due to the strong size and composition-dependent properties of clusters and the exciting prospect of clusters serving as the building blocks for materials with tailored properties. However, identifying a unifying central paradigm that provides a framework for classifying and understanding the diverse behaviors is an outstanding challenge. One such central paradigm is the superatom concept that was developed for metallic and ligand-protected metallic clusters. The periodic electronic and geometric closed shells in clusters result in their properties being based on the stability they gain when they achieve closed shells. This stabilization results in the clusters having a well-defined valence, allowing them to be classified as superatoms-thus extending the Periodic Table to a third dimension. This Perspective focuses on extending the superatomic concept to ligated metal-chalcogen clusters that have recently been synthesized in solutions and form assemblies with counterions that have wide-ranging applications. Here, we illustrate that the periodic patterns emerge in the electronic structure of ligated metal-chalcogenide clusters. The stabilization gained by the closing of their electronic shells allows for the prediction of their redox properties. Further investigations reveal how the selection of ligands may control the redox properties of the superatoms. These ligated clusters may serve as chemical dopants for two-dimensional semiconductors to control their transport characteristics. Superatomic molecules of multiple metal-chalcogen superatoms allow for the formation of nano-p-n junctions ideal for directed transport and photon harvesting. This Perspective outlines future developments, including the synthesis of magnetic superatoms.

First author: Galley, SS, Using Redox-Active Ligands to Generate Actinide Ligand Radical Species,
INORGANIC CHEMISTRY, 60, 15242, (2021)
Abstract: Using a redox-active dioxophenoxazine ligand, DOPO (DOPO = 2,4,6,8-tetra-tert-butyl-1-oxo-1H-phenoxazine-9-olate), a family of actinide (U, Th, Np, and Pu) and Hf tris(ligand) coordination compounds was synthesized. The full characterization of these species using H-1 NMR spectroscopy, electronic absorption spectroscopy, SQUID magnetometry, and X-ray crystallography showed that these compounds are analogous and exist in the form M(DOPOq)(2)(DOPOsq), where two ligands are of the oxidized quinone form (DOPOq) and the third is of the reduced semiquinone (DOPOsq) form. The electronic structures of these complexes were further investigated using CASSCF calculations, which revealed electronic structures consistent with metals in the +4 formal oxidation state and one unpaired electron localized on one ligand in each complex. Furthermore, f orbitals of the early actinides show a sizable bonding overlap with the ligand 2p orbitals. Notably, this is the first example of a plutonium-ligand radical species and a rare example of magnetic data being recorded for a homogeneous plutonium coordination complex.

First author: Zhang, ZF, Significant Insight into the Origin of Reaction Barriers Determining Dihydrogen Activation by G13-P-P (G13=Group 13 Element) and G15-P-Ga (G15=Group 15 Element) Frustrated Lewis Pairs,
INORGANIC CHEMISTRY, 60, 15253, (2021)
Abstract: The heterolytic cleavage of H-2 by multiply bonded phosphorus-bridged G13-P-P-Rea (G13 = B, Al, Ga, In, and Tl) and G15-P-Ga-Rea (G15 = N, P, As, Sb, and Bi) frustrated Lewis pairs (FLPs) has been theoretically investigated using density functional theory calculations. For the above nine FLP-type molecules, our theoretical findings suggest that only Al-P-P-Rea, Ga-P-P-Rea, and InP-P-Rea can undergo the energetically feasible H-2 activation reaction from kinetic and thermodynamic viewpoints. Our study based on the activation strain model (ASM) reveals that gaining a better orbital overlap between G13-P-P-Rea and G15-P-Ga-Rea molecules and H-2 affected the reaction barriers through the atomic radius of G13 and G15. According to our energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) results, the bonding of these H-2 activation reactions involving G13-P-P-Rea and G15-P-Ga-Rea is dominated by the donor-acceptor interaction (singlet-singlet interaction) rather than the electron-sharing interaction (triplet-triplet interaction). Moreover, our EDA-NOCV evidence reveals that the best description for the above bonding situations is the lone pair(G15) -> sigma*(H-2) interaction rather than the empty p-pi-orbital(G13) <- sigma(H-2) interaction. In particular, the findings in this work based on theoretically calculated geometries and the corresponding relative free energies of the stationary points combined with the results from the above sophisticated methods nicely agree with the famous Hammond postulate.

First author: Wen, CT, 2Ch-2N Square Chalcogen Bonds between Pairs of Radicals: A Case Study of 1,2,3,5-Dichalcogenadiazolyl Derivatives,
Abstract: Specific 2Ch-2N square interactions between pairs of heterocyclic rings have been the target of many recent crystallographic and computational studies. According to our search of the Cambridge Structural Database (CSD), a number of crystal structures of the derivatives of 1,2,3,5-dichalcogenadiazolyl (DChDA) radicals, which consist of 2Ch-2N square motifs in the dimer units, were extracted. On the basis of the CSD survey results, a set of dimeric complexes of DChDA-based radicals with diverse aryl substituents at the 4-position were selected to model such squares. Similar to that in conventional chalcogen bonds, 2Ch-2N square interactions become stronger as the atomic size of chalcogens increases. Both the orbital term and electrostatics contribute significantly to the attraction of these interactions, while the dispersion contribution is small but unneglectable. Some five-membered aryl substituents, such as imidazole, thiazole, and oxazole, produce markedly enhanced square interactions, leading to a pronounced influence on the distribution of spin populations on DChDA rings.

First author: Du, JZ, Exceptional uranium(VI)-nitride triple bond covalency from N-15 nuclear magnetic resonance spectroscopy and quantum chemical analysis,
Abstract: Determining the nature and extent of covalency of early actinide chemical bonding is a fundamentally important challenge. Recently, X-ray absorption, electron paramagnetic, and nuclear magnetic resonance spectroscopic studies have probed actinide-ligand covalency, largely confirming the paradigm of early actinide bonding varying from ionic to polarised-covalent, with this range sitting on the continuum between ionic lanthanide and more covalent d transition metal analogues. Here, we report measurement of the covalency of a terminal uranium(VI)-nitride by N-15 nuclear magnetic resonance spectroscopy, and find an exceptional nitride chemical shift and chemical shift anisotropy. This redefines the N-15 nuclear magnetic resonance spectroscopy parameter space, and experimentally confirms a prior computational prediction that the uranium(VI)-nitride triple bond is not only highly covalent, but, more so than d transition metal analogues. These results enable construction of general, predictive metal-ligand N-15 chemical shift-bond order correlations, and reframe our understanding of actinide chemical bonding to guide future studies.

First author: Orenha, RP, Design of supramolecular systems capable of recognizing anions uniquely by aliphatic C-HMIDLINE HORIZONTAL ELLIPSISanion hydrogen bonds: theoretical insights,
NEW JOURNAL OF CHEMISTRY, 45, 19584, (2021)
Abstract: Anions perform several important functions in biological processes. Thus, structures that are able to interact with anions are of great relevance. Here, light is shed on the main characteristics of the bonds between the anions chloride (Cl-), bromide (Br-) and nitrite (NO2-) and the -CH groups of trioxane structures non-substituted and polarized by the ligands (i) -CH3, (ii) -CH2Cl, (iii) -CHCl2, and (iv) -CCl3. There is a less attractive recognition of the anions Cl-, Br- and NO2- using trioxane substituted by the -CH3 groups compared to the receptors non-substituted due to the destabilization of the electrostatic interactions C-HMIDLINE HORIZONTAL ELLIPSIS(Cl-, Br- and NO2-). The presence of electron withdrawing groups in the receptor structure improves the interaction with the anions through more favorable sigma bonds between the -CH groups and anions Cl-, Br- and NO2-. The anion NO2- is recognized with (i) more favorable and (ii) similar energy and rate by receptors containing (i) -CH3 and (ii) -CH2Cl, -CHCl2 or -CCl3, compared to anions Cl- and Br-. The lower values of the Pauli repulsion contribution in receptorsMIDLINE HORIZONTAL ELLIPSISCl- bonds when compared to the interactions receptorsMIDLINE HORIZONTAL ELLIPSISBr- explain the more favorable recognition of the anion Cl- in relation to Br-. The larger recognition rate of the anion Cl- regarding to anion Br- is determined by more favorable electrostatic and orbital interactions. These data provide relevant information about the recognition of anions using C-H bonds and can be used to guide the development of new receptors.

First author: Zaccaria, F, How Divalent Cations Interact with the Internal Channel Site of Guanine Quadruplexes,
CHEMPHYSCHEM, 22, 2286, (2021)
Abstract: The formation of guanine quadruplexes (GQ) in DNA is crucial in telomere homeostasis and regulation of gene expression. Pollution metals can interfere with these DNA superstructures upon coordination. In this work, we study the affinity of the internal GQ channel site towards alkaline earth metal (Mg2+, Ca2+, Sr2+, and Ba2+), and (post-)transition metal (Zn2+, Cd2+, Hg2+, and Pb2+) cations using density functional theory computations. We find that divalent cations generally bind to the GQ cavity with a higher affinity than conventional monovalent cations (e. g. K+). Importantly, we establish the nature of the cation-GQ interaction and highlight the relationship between ionic and nuclear charge, and the electrostatic and covalent interactions. The covalent interaction strength plays an important role in the cation affinity and can be traced back to the relative stabilization of cations’ unoccupied atomic orbitals. Overall, our findings contribute to a deeper understanding of how pollution metals could induce genomic instability.

First author: Garain, BC, Delineating Conformation Control in the Photophysical Behaviour of a Molecular Donor-Acceptor-Donor Triad,
CHEMPHYSCHEM, 22, 2297, (2021)
Abstract: Mechanochromic luminescent materials, exhibiting a change in luminescence behavior under external stimuli have emerged as one of the promising candidates for upcoming efficient OLEDs. Recently mechanochromic luminescence was reported in a donor-acceptor-donor (D-A-D) triad featuring two phenothiazine units separated by a dibenzo[a,j]phenazine motif. The triad follows different emissive routes ranging from phosphorescence to TADF based on the conformational switching of the D units. In this article, we investigate such conformation-dependent photophysical behavior of this triad through theoretical calculations. By analyzing the nature of ground state, excited state and factors determining the reverse ISC crossing rates associated with the relative orientation of the D and A units, we delineate the effect of the conformational changes on their photophysical properties. Our findings reveal that axial orientation of both the donor groups enhances the overlap between HOMO and LUMO leading to a large singlet-triplet gap (Delta EST ) which drives phosphorescence emission. On the contrary, the equatorial orientation of the donor groups minimizes Delta EST to facilitate rISC making the conformers TADF active. The role of several geometric factors affecting the photophysical properties of the conformers is also highlighted. Finally, we show how to regulate the population difference among the conformers by functionalizing the triad to harvest the maximum TADF efficiency.

First author: Dutta, S, Computational Exploration of Mechanistic Avenues in Metal-Free CO2 Reduction to CO by Disilyne Bisphosphine Adduct and Phosphonium Silaylide,
Abstract: Recent years have seen a growing interest in metal-free CO2 activation by silylenes, silylones, and silanones. However, compared to mononuclear silicon species, CO2 reduction mediated by dinuclear silicon compounds, especially disilynes, has been less explored. We have carried out extensive computational investigations to explore the mechanistic avenues in CO2 reduction to CO by donor-stabilized disilyne bisphosphine adduct (R1(M)) and phosphonium silaylide (R2) using density functional theory calculations. Theoretical calculations suggest that R1(M) exhibits donor-stabilized bis(silylene) bonding features with unusual Si-Si multiple bonding. Various modes of CO2 coordination to R1(M) have been investigated and the coordination of CO2 by the carbon center to R1(M) is found to be kinetically more facile than that by oxygen involving only one or both the silicon centers. Both the theoretically predicted reaction mechanisms of R1(M) and R2-mediated CO2 reduction reveal the crucial role of silicon-centered lone pairs in CO2 activations and generation of key intermediates possessing enormous strain in the Si-C-O ring, which plays the pivotal role in CO extrusion.

First author: Huynh, W, Solid-state B-11 NMR studies of coinage metal complexes containing a phosphine substituted diboraanthracene ligand,
DALTON TRANSACTIONS, 50, 14855, (2021)
Abstract: Transition metal interactions with Lewis acids (M -> Z linkages) are fundamentally interesting and practically important. The most common Z-type ligands contain boron, which contains an NMR active B-11 nucleus. We measured solid-state B-11{H-1} NMR spectra of copper, silver, and gold complexes containing a phosphine substituted 9,10-diboraanthracene ligand (B2P2) that contain planar boron centers and weak M -> BR3 linkages ([(B2P2)M][BAr4F] (M = Cu (1), Ag (2), Au (3)) characterized by large quadrupolar coupling (C-Q) values (4.4-4.7 MHz) and large span (omega) values (93-139 ppm). However, the solid-state B-11{H-1} NMR spectrum of K[Au(B2P2)](-) (4), which contains tetrahedral borons, is narrow and characterized by small C-Q and omega values. DFT analysis of 1-4 shows that C-Q and omega are expected to be large for planar boron environments and small for tetrahedral boron, and that the presence of a M -> BR3 linkage relates to the reduction in C-Q and B-11 NMR shielding properties. Thus solid-state B-11 NMR spectroscopy contains valuable information about M -> BR3 linkages in complexes containing the B2P2 ligand.

First author: Juneau, A, Exploring Curious Covalent Bonding: Raman Identification and Thermodynamics of Perpendicular and Parallel Pancake Bonding (Pimers) of Ethyl Viologen Radical Cation Dimers,
Abstract: Viologen radical cations can dimerize in solutions, and the resulting “pimers” were predicted to assemble into parallel and perpendicular conformers by density functional theory (DFT) calculations. Using resonance Raman, we could identify both perpendicular and parallel forms of ethyl viologen dimers. The distinction between the two forms was accomplished by studying the formation of a host-guest complex with gamma-cyclodextrin. The dimers perpendicular form was excluded due to the host cavity size, and gamma-cyclodextrin addition caused a decrease in peak intensities at 1171, 1511, and 1602 cm(-1) that could be assigned to the perpendicular form. DFT modeling of the vibrational spectra under preresonance conditions allowed us to assign the remaining vibrational modes for the parallel and perpendicular forms. Using variable-temperature UV-vis, the bond dissociation energy (Delta H) for this pancake-bonded dimer was measured as 13.1 +/- 0.2 kcal/mol. This type of covalent pancake bonding is a challenge to properly describe using DFT methods. Previously, B97D was found to best describe the Delta G of this dimerization (Angew. Chem. 2017, 129, 9563-9567), but this method underestimates the Delta H by 6 kcal/mol. Of the 11 functionals tested, we found that B3LYP with Grimme’s D3 dispersion effect can best reproduce the Delta H. Energy decomposition analysis of the bonding energy showed that solvation effects were the most important contributor-polar solvents are needed to overcome the Coulomb repulsion between the two positively charged monomers. Dispersion effects are second in importance and appear larger than the favorable orbital interaction obtained by singly occupied molecular orbital (SOMO)-SOMO orbital overlap. This study brings forth important insights into the curious cases of covalent bonding between two pi-delocalized radicals.

First author: Wu, JJ, Coordination anion effects on the geometry and magnetic interaction of binuclear Dy-2 single-molecule magnets,
DALTON TRANSACTIONS, 50, 15027, (2021)
Abstract: Two new dimeric dysprosium(iii) complexes, [Dy-2(HL)(2)(SCN)(2)]center dot 2CH(3)CN (1) and [Dy-2(HL)(2)(NO3)(2)]center dot 2CH(3)CN center dot 2H(2)O (2), have been assembled using the H3L multidentate ligand (H3L = 2,2′-((((2-hydroxy-5-methyl-1,3-phenylene)bis(methylene))bis((pyridin-2-ylmethyl)azanediyl))bis(methylene))diphenol). The use of different coordination anions for the two complexes results in distinct coordination geometries of the metal sites. The Dy centers in complexes 1 and 2 display capped octahedron and triangular dodecahedron coordination geometries, respectively. Consequently, the two compounds exhibit distinct dc and ac magnetic properties. Complex 1 behaves as a single molecule magnet (SMM) while no SMM behavior is observed for complex 2. Although complexes 1 and 2 possess a similar core of Dy2O2, their different coordination anions lead to two distinct magnetic interactions, namely ferromagnetic and antiferromagnetic, respectively. Ab initio calculations reveal that these interactions may result from strong intramolecular dipolar couplings that are ferromagnetic for 1 but antiferromagnetic for 2, while exchange couplings are antiferromagnetic in both cases.

First author: Kim, SY, Effects of substituents on the intermolecular interaction, morphology, and charge transport of novel bis-lactam-based molecules,
Abstract: To elucidate the origin of high charge carrier mobility in bis-lactam compounds with twisted geometries, we designed and synthesized a series of 3,7-diphenyl-1,5-dioctyl-1,5-naphthyridine-2,6-dione (NTDP) derivatives bearing various substituents (i.e., OCH3, CH3, H, F, and Cl) in the end-capping phenyl rings. Despite the distinct dihedral angle between the 1,5-naphthyridine-2,6-dione (NTD) core and the end-capping groups, all of the derivatives formed rigid molecular structures and the delocalized highest occupied molecular orbitals (HOMOs), which could lead to high charge transport properties. Among the derivatives, the fluorinated NTDP molecule (NTDP-F) exhibited the highest hole mobility of 0.54 cm(2) V-1 s(-1) in vacuum-deposited organic field-effect transistors (OFETs) due to the strong intermolecular interaction, high crystallinity, and two-dimensional (2D) terrace-like morphology in the thin-film. Furthermore, the twisted geometry of NTDP-F allowed facile solution processability resulting in a high hole mobility of up to 0.27 cm(2) V-1 s(-1) in solution-processed OFETs.

First author: Koley, D, Isomerization of Functionalized Olefins by Using the Dinuclear Catalyst [Pd-I(mu-Br)((PBu3)-Bu-t)](2): A Mechanistic Study,
Abstract: In a combined experimental and computational study, the isomerization activity of the dinuclear palladium(I) complex [Pd-I(mu-Br)((PBu3)-Bu-t)](2) towards allyl arenes, esters, amides, ethers, and alcohols has been investigated. The calculated energy profiles for catalyst activation for two alternative dinuclear and mononuclear catalytic cycles, and for catalyst deactivation are in good agreement with the experimental results. Comparison of experimentally observed E/Z ratios at incomplete conversion with calculated kinetic selectivities revealed that a substantial amount of product must form via the dinuclear pathway, in which the isomerization is promoted cooperatively by two palladium centers. The dissociation barrier towards mononuclear Pd species is relatively high, and once the catalyst enters the energetically more favorable mononuclear pathway, only a low barrier has to be overcome towards irreversible deactivation.

First author: Fang, Y, Glaser Coupling of Substituted Anthracene Diynes on a Non-metallic Surface at the Vapor-Solid Interface,
Abstract: The direct polymerization via irreversible C-C coupling on inert substrates will give access to new low-dimensional advanced functional materials and simplify their industrial fabrication. In this work, we present our initial results in the application of Glaser coupling to the direct on-surface polymerization of a model diacetylene compound at the solid-vapor interface. The self-assembly of the monomer and polymerization products was characterized using scanning tunneling microscopy (STM). In addition, selected optical properties and the electronic structure of all compounds were investigated.

First author: Zanca, F, Computational techniques for characterisation of electrically conductive MOFs: quantum calculations and machine learning approaches,
Abstract: The customisability of metal-organic frameworks (MOFs) has attracted exponentially growing interest in the realm of materials science. Because of their porous nature, MOF research has been primarily focused on gas storage and separation. More recent investigations into MOFs have realised promising electronic characteristics suitable for applications in electrocatalysis, resistive sensing and energy storage. Despite high porosity and presence of organic linkers, – properties that contribute to the electrical insulating properties of most MOFs – several strategies have been developed to construct MOFs with high conductivity. These recent findings serve as strong encouragement that the incorporation of charge transport chemistries into MOFs leads to structures that exhibit conductive behaviour. However, our understanding behind the nature of conductivity in MOFs is not yet explicitly evident. The development of outstanding conductive MOFs would be greatly accelerated if we had an atomistic-level understanding of how low-energy charge transport pathways can be installed in MOFs. In this context, computational quantum mechanical methods can produce rich electronic structure details with sufficient accuracy to provide insights towards MOFs’ conductive behaviour. An emerging alternative design strategy is the use of machine learning to accelerate the way we screen and discover new conductive materials. In this review, we summarise the most widely used quantum mechanical techniques to characterise important band structure parameters and compare them with experimental measurements in the MOF literature. We also highlight the current state of the art in machine learning assisted screening of MOFs for their conductive properties and discuss the opportunities and challenges which lie ahead in this exciting field.

First author: Mechachti, F, Predicted structure and selectivity of 3d transition metal complexes with glutamic N,N-bis(carboxymethyl) acid,
NEW JOURNAL OF CHEMISTRY, 45, 18366, (2021)
Abstract: The complexation of transition metals with a rather new aminopolycarboxilic ligand, the glutamic N,N-bis(carboxymethyl) acid (GLDA) is investigated using the density functional at the PBE/TPZ level of theory. In order to predict the selectivity of metals and to gain insight into factors influencing the calculated log K values, the GLDA ligand is studied in the gas phase and in solvent with the electrostatic COSMO model. In the absence of crystallographic data, most complexes prefer a pentacoordinated structure in gas phase. On the contrary, in presence of solvent the two structures can coexist, copper excepted, which does not adopt the octahedral form. Good correlations are found between the experimental thermodynamic values and several calculated parameters such as charge transfer, bond descriptors, or bonding free energy energies. The obtained calculations show that, copper excepted, the complexes are octahedral and for a selective separation of cations, the copper cation will be the first to be efficiently complexed.

First author: Wodrich, MD, Methoxycyclization of 1,5-Enynes by Coinage Metal Catalysts: Is Gold Always Superior?,
HELVETICA CHIMICA ACTA, 104, 18366, (2021)
Abstract: Au(I) catalysts promote the intramolecular cycloisomerization of 1,n-enynes, as well as facilitate reactions with alcohols, characteristics that have led to their wide-spread in the synthesis of complex natural products. Literature reports of Cu and Ag species catalyzing the same or similar reactions are much less common. Here, we utilize molecular volcano plots to assess the activity of 45 coinage metal phosphine/phosphite catalysts possessing a variety of stereoelectronic properties for the methoxycyclization reaction of a prototypical 1,5-enyne. Our analysis reveals that the intrinsic properties of gold allow it to be coupled with a wide range of ligands, all of which exhibit high catalytic activity. On the other hand, the coupling of silver and copper with more traditional phosphines, such as triphenylphosphine, leads to catalysts with diminished catalytic ability. The activity of Ag and Cu species, however, can be enhanced by appending ligands with strong pi-accepting character, which shifts these species closer to the volcano peak.

First author: Darquie, B, Valence-shell photoelectron circular dichroism of ruthenium(iii)-tris-(acetylacetonato) gas-phase enantiomers,
Abstract: Chiral transition-metal complexes are of interest in many fields ranging from asymmetric catalysis and molecular materials science to optoelectronic applications or fundamental physics including parity violation effects. We present here a combined theoretical and experimental investigation of gas-phase valence-shell photoelectron circular dichroism (PECD) on the challenging open-shell ruthenium(iii)-tris-(acetylacetonato) complex, Ru(acac)(3). Enantiomerically pure Delta- or ?-Ru(acac)(3), characterized by electronic circular dichroism (ECD), were vaporized and adiabatically expanded to produce a supersonic beam and photoionized by circularly-polarized VUV light from the DESIRS beamline at Synchrotron SOLEIL. Photoelectron spectroscopy (PES) and PECD experiments were conducted using a double imaging electron/ion coincidence spectrometer, and compared to density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The open-shell character of Ru(acac)(3), which is not taken into account in our DFT approach, is expected to give rise to a wide multiplet structure, which is not resolved in our PES signals but whose presence might be inferred from the additional striking features observed in the PECD curves. Nevertheless, the DFT-based assignment of the electronic bands leads to the characterisation of the ionized orbitals. In line with other recent works, the results confirm that PECD persists independently on the localization and/or on the achiral or chiral nature of the initial orbital, but is rather a probe of the molecular potential as a whole. Overall, the measured PECD signals on Ru(acac)(3), a system exhibiting D-3 propeller-type chirality, are of similar magnitude compared to those on asymmetric-carbon-based chiral organic molecules which constitute the vast majority of species investigated so far, thus suggesting that PECD is a universal mechanism, inherent to any type of chirality.

First author: Muhasina, PV, Correlation between bonding, philicity and substituent effects in cyclopropenylidenes,
Abstract: The electronic structure and bonding of cyclopropenylidenes with different substituents at the olefinic position viz., -H (1), electron-withdrawing groups (-CHO (2) and -COOH (3)) and electron-donating groups (-N(CH3)2 (4) and -N(iPr)2 (5)), have been explored at the M06/def2-TZVPP//BP86/def2-TZVPP level of theory. The ground state of cyclopropenylidenes 1 – 5 is a singlet 2 pi-aromatic system with a considerable singlet-triplet energy gap. The geometrical and electronic structure analyses indicate that the nucleophilicity of the carbene lone pair increases when substituents change from electron-withdrawing to electron-donating groups. The energy decomposition analysis combined with natural orbitals for chemical valence (EDA-NOCV) analysis indicates that the bonding interaction between the carbene carbon and the -C2R2 fragment in the parent cyclopropenylidene (1) can be best represented by two electron-sharing sigma-bonds and a donor-acceptor pi-bond from -C2R2 fragment to the carbene carbon. The pz-orbital on the carbene carbon atom is susceptible to nucleophilic attack if the incoming nucleophile is stronger than the pi -MO of the acetylenic fragment. When the substituents change to electron-withdrawing groups, -CHO (2) and -COOH (3), the sigma-bonds turn into donor-acceptor interactions. The py and pz-orbitals on the carbene carbon atom are accepting electrons from the acetylenic fragment. Hence these orbitals are susceptible to nucleophilic attack. On the other hand, when the substituents change to electrondonating groups, -N(CH3)2 (4) and -N(iPr)2 (5), the best bonding situation changes into one electron-sharing sigma-bond and pi-bond along with one donor-acceptor sigma-bond from -C2R2 fragment to the carbene carbon. The py-orbital is accepting electrons from the acetylenic fragment. Hence, py-orbital is susceptible to nucleophilic attack, which in turn leads to Ccarbene-C bond cleavage. These bonding descriptions are in agreement with the experimental isolation of several derivatives of cyclopropenylidene.

First author: Kaiser, W, Iodide vs Chloride: The Impact of Different Lead Halides on the Solution Chemistry of Perovskite Precursors,
Abstract: Controlled perovskite growth from solution is crucial for efficient optoelectronic applications and requires a deep understanding of the perovskite precursor chemistry. The so-called “chlorine route” to lead-iodide perovskite, using PbCl2 or MACl additive as a precursor, is frequently employed to form homogeneous perovskite layers by retarding perovskite crystallization. To understand the role of chlorine-containing lead precursors in solution, we analyze the chemical interaction of PbCl2 and PbI2 precursors with commonly employed solvents (gamma-butyrolactone (GBL), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)) by combining first-principles simulations and experimental UV-vis spectroscopy in diluted precursor solutions. Ab initio molecular dynamics simulations reveal reduced solvation and an increased free energy barrier of lead-halide bond dissociation of PbCl2 compared to PbI2 with chlorine acting as a stronger ligand, which, in turn, limits the solvent coordination. In contrast to PbI2, PbCl2 absorption spectra lack signatures of high-valent [PbCln](2-n) complexes and show low sensitivity on the employed solvent, as confirmed by combined UV-vis and excited-state time-dependent density functional theory (TD-DFT) analysis. Altogether, our data suggest the presence of residual chlorine coordinated to Pb even in the presence of high iodine excess, which may retard the perovskite growth and could also lead to chlorine incorporation within the lead-iodide perovskite crystal.

First author: Matsumoto, RA, Investigating the Accuracy of Water Models through the Van Hove Correlation Function,
Abstract: We present molecular-simulation-based calculations of the Van Hove correlation function (VHF) of water using multiple modeling approaches: classical molecular dynamics with simple three-site non-polarizable models, with a polarizable model, and with a reactive force field; density functional tight-binding molecular dynamics; and ab initio molecular dynamics. Due to the many orders of magnitude difference in the computational cost of these approaches, we investigate how small and short the simulations can be while still yielding sufficiently accurate and interpretable results for the VHF. We investigate the accuracy of the different models by comparing them to recently published inelastic X-ray scattering measurements of the VHF. We find that all of the models exhibit qualitative agreement with the experiments, and in some models and for some properties, the agreement is quantitative. This work lays the foundation for future simulation approaches to calculating the VHF for aqueous solutions in bulk and under nanoconfinement.

First author: Orenha, RP, Designing boron and metal complexes for fluoride recognition: a computational perspective,
Abstract: Fluoride anions (F-) may have beneficial or harmful effects on the environment depending on their concentration. Here, we shed light on F- recognition by compounds containing boron, tellurium and antimony, which were experimentally demonstrated to be capable of interacting with the F- ion in a partially aqueous medium. Boron and metal complexes recognize F- anions primarily using electrostatic energy along with important contributions from orbital interaction energy. The natural orbitals for chemical valence (NOCV) methodology indicates that the main orbital interactions behind fluoride recognition are sigma bonds between the receptors and the F- anions. The charged receptors, which provide (i) two B atoms, (ii) one B atom and one Sb atom, or (iii) one B atom and one Te atom to directly interact with the F- ions, appear to be some of the best structures for the recognition of F- anions. This is supported by the combination of favorable electrostatic and sigma bond interactions. Overall, the presence of electron donor groups, such as -CH3 and -OH, in the receptor structure destabilizes the fluoride recognition because it decreases the attractive electrostatic energy and increases the Pauli repulsion energy in the receptorMIDLINE HORIZONTAL ELLIPSISF- bonds. Notably, electron acceptor groups, for example, -CN and -NO2, in the receptor structure favor the interaction with the F- ions, due to the improvement of the electrostatic and sigma bond interactions. This study opens the way to find the main features of a receptor for F- recognition.

First author: Yao, YR, Crystallographic Characterization of U@C-2n (2n=82-86): Insights about Metal-Cage Interactions for Mono-metallofullerenes,
Abstract: Endohedral mono-metallofullerenes are the prototypes to understand the fundamental nature and the unique interactions between the encapsulated metals and the fullerene cages. Herein, we report the crystallographic characterizations of four new U-based mono-metallofullerenes, namely, U@C-s(6)-C-82, U@C-2(8)-C-84, U@C-s(15)-C-84, and U@C-1(12)-C-86, among which the chiral cages C-2(8)-C-84 and C-1(12)-C-86 have never been previously reported for either endohedral or empty fullerenes. Symmetrical patterns, such as indacene, sumanene, and phenalene, and charge transfer are found to determine the metal positions inside the fullerene cages. In addition, a new finding concerning the metal positions inside the cages reveals that the encapsulated metal ions are always located on symmetry planes of the fullerene cages, as long as the fullerene cages possess mirror planes. DFT calculations show that the metal-fullerene motif interaction determines the stability of the metal position. In fullerenes containing symmetry planes, the metal prefers to occupy a symmetrical arrangement with respect to the interacting motifs, which share one of their symmetry planes with the fullerene. In all computationally analyzed fullerenes containing at least one symmetry plane, the actinide was found to be located on the mirror plane. This finding provides new insights into the nature of metal-cage interactions and gives new guidelines for structural determinations using crystallographic and theoretical methods.

First author: Chapple, PM, Bonding analysis in ytterbium(II) distannyl and related tetryls,
DALTON TRANSACTIONS, 50, 14273, (2021)
Abstract: The syntheses of the ytterbium(s) distannyl [Yb{Sn(SiMe3)(3)}(2)center dot(thf)(4)] (Yb-Sn) and of its digermyl analogue [Yb{Ge(SiMe3)(3)}(2)center dot(thf)(3)] (Yb-Ge) are presented. The compounds were characterised by multinuclear high-resolution solution NMR spectroscopy, including Yb-171 NMR, and by X-ray diffraction crystallography. The bonding and electronic properties of the two complexes, along with those of the known ytterbium(II) disilyl derivative [Yb{Si(SiMe3)(3)}(2)center dot(thf)(3)) (Yb-Si) and those of the congeneric calcium distannyl [Ca{Sn(SiMe3)(3)}(2)center dot(thf)(4)] (Ca-Sn), were investigated in detail by DFT calculations. This analysis points at a primarily ionic Yb-tetrel bonding, with a small covalent contribution, attributed principally to the 5d(Yb) participation. This weak covalent character is found to be larger for the distannyl Yb-Sn than for its lighter Si-and Ge-derivatives. The covalent component is also found to be greater in Yb-Sn than in Ca-Sn, due to the availability of the 5d(Yb) orbitals for bonding.

First author: Shen, J, Electron transport properties of PAl12-based cluster complexes,
NANOSCALE ADVANCES, 3, 6888, (2021)
Abstract: The electronic transport properties of PAl12-based cluster complexes are investigated by density functional theory (DFT) in combination with the non-equilibrium Green’s function (NEGF) method. Joining two PAl12 clusters via a germanium linker creates a stable semiconducting complex with a large HOMO-LUMO gap. Sequential attachment of an electron-donating ligand, N-ethyl-2-pyrrolidone, to one of the two linked clusters results in the shifting of the electronic spectrum of the ligated cluster while the energy levels of the unligated cluster are mostly unchanged. Using this approach, one can eventually align the HOMO of the ligated cluster to the LUMO of the non-ligated cluster, thereby significantly reducing the HOMO-LUMO gap of the complex. As a result, the transport properties of the complex are highly dependent on the number of attached ligands. Although a single ligand is observed to generally decrease the current, the inclusion of two or more ligands shows a significant increase in the amount of current at most voltages. The resulting increase of the current can be attributed to two factors, first the reduction in the HOMO-LUMO gap due to ligand attachment which has moved the transmission orbitals into the bias window. Secondly, when two or more ligands are attached to the complex, the HOMOs become delocalized across the scattering region, and this significantly enhances the currents.

First author: Bista, D, Interfacial magnetism in a fused superatomic cluster [Co6Se8(PEt3)(5)](2),
NANOSCALE, 13, 15763, (2021)
Abstract: An isolated Co6Se8(PEt3)(6) cluster is non-magnetic; however, we find that a magnetic unit can be formed by fusing two Co6Se8(PEt3)(5) superatoms into a [Co6Se8(PEt3)(5)](2) dimer. Theoretical studies indicate that the dumbbell-shaped [Co6Se8(PEt3)(5)](2) dimer has a spin moment of 2 mu(B), and the spin density is primarily localized at the interfacial Co-sites where two clusters are fused into a dimer. The dimer has a low ionization energy of 4.17 eV, allowing the dimer to donate charge to C-70 during the formation of a cluster assembled material, as seen in recent experiments by Nuckolls and co-workers. The donation of charge causes the dimer’s magnetic moment to drop from 2 mu(B) to 1 mu(B). We hypothesize that adding electrons to the dimer, such as doping impurities to the crystal lattice, may enhance the magnetic moment by neutralizing the charged cluster. This reveals a strategy for stabilizing magnetic moments in ligated cluster assemblies.

First author: Li, QZ, Unraveling the Nucleation Process from a Au(I)-SR Complex to Transition-Size Nanoclusters,
Abstract: Atomically precise noble metal nanoclusters provide a critical benchmark for the fundamental research of the origin of condensed matter because they retain the original state of the metal bonds. Also, knowledge about the transition from organometallic complexes to a nanoclusters is important for understanding the structural evolution of the nanoclusters, particularly their nucleation mechanism. Herein, three transition-size gold nanoclusters are prepared via a controlled diphosphine-mediated top-down routine. Starting from small-size nanoclusters, three new nanoclusters including Au-13(SAdm)(8)(L-4)(2)(BPh4) (Au-13), Au-14(S-c-C6H11)(10)L-4 (Au-14), and Au-16(S-c-C6H11)(11)L-Ph* (Au-16) are obtained by controlled clipping on the surface and kernel of initial nanoclusters. Combining their atomically precise structures with DFT theoretical calculations, the overall atom-by-atom structural evolution process from Au-12(SR)(12) (0 e(-)) to Au-18(SR)(14) (4 e(-)) is mapped out. In addition, studies on their electronic structures show that the evolution from an organometallic complex to nanoclusters is accompanied by a dramatic decrease in the HOMO-LUMO gaps. Most importantly, the formation of the first Au-Au bond is captured in the “Au4S4 to Au-5” nucleation process from Au-12(SR)(12) complex to the Au-13 nanocluster. This work provides a deep insight into the origin of inner core in Au NCs and their structural transition relationship with metal complexes.

First author: Murillo, J, Actinide arene-metalates: ion pairing effects on the electronic structure of unsupported uranium-arenide sandwich complexes,
CHEMICAL SCIENCE, 12, 13360, (2021)
Abstract: Addition of [UI2(THF)(3)(mu-OMe)](2).THF (2.THF) to THF solutions containing 6 equiv. of K[C14H10] generates the heteroleptic dimeric complexes [K(18-crown-6)(THF)(2)](2)[U(eta(6)-C14H10)(eta(4)-C14H10)(mu-OMe)](2).4THF (1(18C6).4THF) and {[K(THF)(3)][U(eta(6)-C14H10)(eta(4)-C14H10)(mu-OMe)]}(2) (1(THF)) upon crystallization of the products in THF in the presence or absence of 18-crown-6, respectively. Both 1(18C6).4THF and 1(THF) are thermally stable in the solid-state at room temperature; however, after crystallization, they become insoluble in THF or DME solutions and instead gradually decompose upon standing. X-ray diffraction analysis reveals 1(18C6).4THF and 1(THF) to be structurally similar, possessing uranium centres sandwiched between bent anthracenide ligands of mixed tetrahapto and hexahapto ligation modes. Yet, the two complexes are distinguished by the close contact potassium-arenide ion pairing that is seen in 1(THF) but absent in 1(18C6).4THF, which is observed to have a significant effect on the electronic characteristics of the two complexes. Structural analysis, SQUID magnetometry data, XANES spectral characterization, and computational analyses are generally consistent with U(iv) formal assignments for the metal centres in both 1(18C6).4THF and 1(THF), though noticeable differences are detected between the two species. For instance, the effective magnetic moment of 1(THF) (3.74 mu(B)) is significantly lower than that of 1(18C6).4THF (4.40 mu(B)) at 300 K. Furthermore, the XANES data shows the U L-III-edge absorption energy for 1(THF) to be 0.9 eV higher than that of 1(18C6).4THF, suggestive of more oxidized metal centres in the former. Of note, CASSCF calculations on the model complex {[U(eta(6)-C14H10)(eta(4)-C14H10)(mu-OMe)](2)}(2-) (1*) shows highly polarized uranium-arenide interactions defined by pi-type bonds where the metal contributions are primarily comprised by the 6d-orbitals (7.3 +/- 0.6%) with minor participation from the 5f-orbitals (1.5 +/- 0.5%). These unique complexes provide new insights into actinide-arenide bonding interactions and show the sensitivity of the electronic structures of the uranium atoms to coordination sphere effects.

First author: Stolyarova, ED, Blue-to-red light triggered nitric oxide release in cytotoxic/cytostatic ruthenium nitrosyl complexes bearing biomimetic ligands,
Abstract: The nitrosyl complexes trans(L,L)-[RuNO(L)2Cl3] (L = indazole (I) and imidazole (II)) were synthesized and comprehensively characterized including by single crystal X-ray diffraction. Both compounds exhibit lightinduced NO release under blue or green light (445, 532 nm) irradiation of DMSO solutions, complex (I) also shows NO release under red 638 nm irradiation, which is in the range of phototherapeutic window (600-1100 nm). The photolysis was investigated by spectroscopic (UV-vis, IR, EPR) and electrochemical (CV) techniques, and it was shown that NO can be activated by both light excitation or electrochemically. Performed DFT calculations allow to reveal possible charge transfers responsible for the NO activation. The dynamics of ruthenium species after irradiation consists of a transformation of [Ru3+(DMSO)(L)2Cl3] complex to a more stable [Ru2+(DMSO)(L)2Cl3]- product. The cytotoxic test of both complexes against breast adenocarcinoma cell line MCF-7 shows, imidazole complex (II) exhibits cytostatic action at concentrations higher than 25 mu M, while indazole complex (I) is highly cytotoxic with IC50 value of 3.1 +/- 0.6 mu M, which is an order of magnitude higher than the activity of cisplatin. New knowledge open the prospects for the design and synthesis of prominent compounds trans(L,L)-[RuNO(L)2Cl3], where the nature of L influences the photo-sensitive and cytotoxic properties of the resulted complexes.

First author: Wulf, T, B12X11(H-2)(-): exploring the limits of isotopologue selectivity of hydrogen adsorption,
RSC ADVANCES, 11, 28466, (2021)
Abstract: We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of B12X11- (X = H, F, Cl, Br, I, CN) using ab initio quantum chemistry. With a Gibbs free energy of H-2 attachment reaching up to 80 kJ mol(-1) (Delta G at 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H-2 adsorption sites. Differences of the zero-point energy of attachment average 5.0 kJ mol(-1) between D-2 and H-2 and 2.7 kJ mol(-1) between HD and H-2, resulting in hypothetical isotopologue selectivities as high as 2.0 and 1.5, respectively, even at 300 K. Interestingly, even though attachment energies vary substantially according to the chemical nature of X, isotopologue selectivities remain very similar. We find that the H-H activation is so strong that it likely results in the instantaneous heterolytic dissociation of H-2 in all cases (except, possibly, for X = H), highlighting the extremely electrophilic nature of B12X11- despite its negative charge. Unfortunately, this high reactivity also makes B12X11- unsuitable for practical application in the field of dihydrogen isotopologue separation. Thus, this example stresses the two-edged nature of strong H-2 affinity, yielding a higher isotopologue selectivity on the one hand but risking dissociation on the other, and helps define a window of adsorption energies into which a material for selective adsorption near room temperature should ideally fall.

First author: Berezin, AS, A brightly emissive halomanganates(II) with triphenylphosphonium cation: Synthesis, luminescence, and up-conversion phenomena,
DYES AND PIGMENTS, 196, 28466, (2021)
Abstract: A series of [HL](2)[MnX4] [X = I, Br, Cl] tetrahalomanganates with triphenylphosphonium cation has been designed and investigated in photophysics and EPR terms. At room temperature, the solid complexes exhibit a remarkably bright green phosphorescence (lambda(max) = 525 nm-555 nm) resulted from the Mn(II) d -d transitions (T-4(1) -> (6)A(1)) with high quantum efficiency (>50%) and a short lifetime of the iodomanganate complex (approximate to 41 mu s). Under infrared excitation (lambda(Ex) = 780 nm) the complexes exhibit unusually luminescence in the visible region (lambda(max) approximate to 500 nm). The EPR spectra of complexes are characterized by the deviation of the g-factor from the ge free electron value and by the high value of the zero-field splitting parameters on account of the spin-orbit coupling. The correlations between the luminescence and magnetic properties of the title complexes are discussed.

First author: Wellala, NPN, Decomposition pathways and mitigation strategies for highly-stable hydroxyphenazine flow battery anolytes,
Abstract: Aqueous organic redox flow batteries are a promising technology for large-scale energy storage. The stability of the redox active organic molecules is increasingly being recognized as one of the major hurdles. Upon extended flow battery cycling, 7,8-dihydroxyphenazine-2 sulfonic acid (DHPS) undergoes desulfonation and reduction of a phenolic C-O bond to yield a mixture of 7/8-hydroxyphenazine-2-sulfonic acid, as well as hydrogenation of the aromatic ring system. Density functional theory (DFT) analysis of the charged DHPS, its ring-hydrogenated products, and variably substituted hydroxy phenazines has led to the development of a series of dihydroxylated phenazine isomers which provide insight into the effects of substitution pattern on solubility and stability. Seven dihydroxyphenazine (DHP) isomers were synthesized and their solubilities, electrochemical properties, flow battery cycling performance, and degradation pathways have been investigated. Based on theoretical and experimental results, hydroxyl substitution at the 1, 4, 6 and 9 positions yields highly stable derivatives, while substitution at the 2, 3, 7, and 8 positions results in unstable derivatives. Flow cells of 1,4- and 1,6-DHPs coupled with ferro/ferricyanide achieved high stabilities, with temporal capacity loss of 0.029 and 0.031% per day, respectively. Decomposition of 1,8- and 2,7-DHPs were found to arise from irreversible hydrogen rearrangement (tautomerization), yielding redox-inactive species. These results provide a detailed understanding of decomposition pathways and mitigation strategies for phenazine-based anolytes, and can provide general design guidelines for the development of stable redox-active organics.

First author: Nottoli, T, A black-box, general purpose quadratic self-consistent field code with and without Cholesky decomposition of the two-electron integrals,
MOLECULAR PHYSICS, 119, 21918, (2021)
Abstract: We present the implementation of a quadratically convergent self-consistent field (QCSCF) algorithm based on an adaptive trust-radius optimisation scheme for restricted open-shell Hartree-Fock (ROHF), restricted Hartree-Fock (RHF), and unrestricted Hartree-Fock (UHF) references. The algorithm can exploit Cholesky decomposition (CD) of the two-electron integrals to allow calculations on larger systems. The most important feature of the QCSCF code lies in its black-box nature – probably the most important quality desired by a generic user. As shown for pilot applications, it does not require one to tune the self-consistent field (SCF) parameters (damping, Pulay’s DIIS, and other similar techniques) in difficult-to-converge molecules. Also, it can be used to obtain a very tight convergence with extended basis sets – a situation often needed when computing high-order molecular properties – where the standard SCF algorithm starts to oscillate. Nevertheless, trouble may appear even with a QCSCF solver. In this respect, we discuss what can go wrong, focusing on the multiple UHF solutions of ortho-benzyne.

First author: Robinson, S, Reactions of organoplatinum complexes with dimethylamine-borane,
NEW JOURNAL OF CHEMISTRY, 45, 14965, (2021)
Abstract: The reactions of dimethylamine-borane with platinum(ii) or platinum(iv) triflate complexes gave, not the anticipated sigma-complexes, but the respective hydridoplatinum complexes. The reaction with [Pt(OTf)Me-3(NN)], with NN = 2,2 ‘-bipyridine (bipy) and 4,4 ‘-di-t-butyl-2,2 ‘-bipyridine (bu(2)bipy), gave the rare stable bridging hydridoplatinum(iv) complexes [mu-H{PtMe3(NN)}(2)][OTf] and the reaction with [Pt(O2CCF3)Me(NN)] gave the unstable hydridoplatinum(ii) complex [PtHMe(NN)]. The unstable hydridoplatinum(ii) complexes could be trapped by reaction with methyl acrylate by forming the insertion products [PtCl(CHMeCO2Me)(bipy)] and [Pt(CHMeCO2Me)(2)(bipy)]. The complex [PtCl(CHMeCO2Me)(bipy)] reacted with methyl iodide to give [PtClIMe(CHMeCO2Me)(bipy)], by cis oxidative addition, and the presence of two chiral centers in the product platinum(iv) complex allowed a detailed stereochemical pathway to be proposed.

First author: Illobre, PG, Time-Resolved Excited-State Analysis of Molecular Electron Dynamics by TDDFT and Bethe-Salpeter Equation Formalisms,
Abstract: In this work, a theoretical and computational set of tools to study and analyze time-resolved electron dynamics in molecules, under the influence of one or more external pulses, is presented. By coupling electronic-structure methods with the resolution of the time-dependent Schrodinger equation, we developed and implemented the time-resolved induced density of the electronic wavepacket, the time-resolved formulation of the differential projection density of states (Delta PDOS), and of transition contribution map (TCM) to look at the single-electron orbital occupation and localization change in time. Moreover, to further quantify the possible charge transfer, we also defined the energy-integrated Delta PDOS and the fragment-projected TCM. We have used time-dependent density-functional theory (TDDFT), as implemented in ADF software, and the Bethe-Salpeter equation, as provided by MolGW package, for the description of the electronic excited states. This suite of postprocessing tools also provides the time evolution of the electronic states of the system of interest. To illustrate the usefulness of these postprocessing tools, excited-state populations have been computed for HBDI (the chromophore of GFP) and DNQDI molecules interacting with a sequence of two pulses. Time-resolved descriptors have been applied to study the time-resolved electron dynamics of HBDI, DNQDI, LiCN (being a model system for dipole switching upon highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) electronic excitation), and Ag-22. The computational analysis tools presented in this article can be employed to help the interpretation of fast and ultrafast spectroscopies on molecular, supramolecular, and composite systems.

First author: Liu, YQ, E E triple bonds (E = Group 13) promoted by charge transfer from alkali metals,
NEW JOURNAL OF CHEMISTRY, 45, 18392, (2021)
Abstract: We report herein evidence of E E triple bonds (E = Group 13) promoted by the perpendicularly surrounding M-4 (M = Li and Na) motifs. The global minimum of E2M4 (E = B, Al, and Ga) is a D-4h -symmetry structure where E-E is surrounded perpendicularly by square M-4 motifs, whereas the C-s-symmetry structure formed by E-E-M surrounded partially by M-3 motifs is the lowest-energy structure for E = In and TI. Chemical bonding reveals that strong charge transfer from M-4 to E-2 dimer not only provides efficient elec-trons to form E E triple bonds, but also the resulting electrostatic interactions between M-4 and E-2 play a driving force to stabilize these intriguing triply bonded species.

First author: Vermeeren, P, Origin of asynchronicity in Diels-Alder reactions,
Abstract: Asynchronicity in Diels-Alder reactions plays a crucial role in determining the height of the reaction barrier. Currently, the origin of asynchronicity is ascribed to the stronger orbital interaction between the diene and the terminal carbon of an asymmetric dienophile, which shortens the corresponding newly formed C-C bond and hence induces asynchronicity in the reaction. Here, we show, using the activation strain model and Kohn-Sham molecular orbital theory at ZORA-BP86/TZ2P, that this rationale behind asynchronicity is incorrect. We, in fact, found that following a more asynchronous reaction mode costs favorable HOMO-LUMO orbital overlap and, therefore, weakens (not strengthens) these orbital interactions. Instead, it is the Pauli repulsion that induces asynchronicity in Diels-Alder reactions. An asynchronous reaction pathway also lowers repulsive occupied-occupied orbital overlap which, therefore, reduces the unfavorable Pauli repulsion. As soon as this mechanism of reducing Pauli repulsion dominates, the reaction begins to deviate from synchronicity and adopts an asynchronous mode. The eventual degree of asynchronicity, as observed in the transition state of a Diels-Alder reaction, is ultimately achieved when the gain in stability, as a response to the reduced Pauli repulsion, balances with the loss of favorable orbital interactions.

First author: Wentz, KE, Reactions of 9-Carbene-9-Borafluorene Monoanion and Selenium: Synthesis of Boryl-Substituted Selenides and Diselenides,
INORGANIC CHEMISTRY, 60, 13941, (2021)
Abstract: Reactions of 9-carbene-9-borafluorene monoanion (1) with elemental selenium and selenium-containing reagents are reported. When compound 1 is reacted with grey selenium in THF, various boryl-substituted selenides and diselenides are produced (2-6), including molecules resulting from migration of the carbene ligand Dipp group (Dipp = 2,6-diisopropylphenyl). However, when a similar reaction between 1 and grey selenium is performed in toluene in the presence of 18-crown-6, boryl-substituted selenide 7 is obtained as the sole boron-containing product. As compound 7 is the monomeric variant of organoselenide 3, 18-crown-6 promotes both product selectivity and solubility in a nonpolar solvent. Diselenide 5, which features a trans-bent B-Se-Se-B core, was directly isolated via reaction of 1 with Se2Cl2 in THF. Computational modeling suggests that the formation of 5 proceeds via a radical mechanism. This was supported by an experiment demonstrating that the CAAC-borafluorene radical also reacts with SeCl2 to yield 5 [CAAC = (2,6-diisopropylphenyl)-4,4-diethyl2,2-dimethyl-pyrrolidin-5-ylidene]. Energy decomposition analysis of 5 indicates a covalent borafluorene-diselenide bond (Delta E-int, -168.9 kcal mol(-1)). All of the new compounds were fully characterized via single-crystal X-ray diffraction and multinuclear nuclear magnetic resonance (H-1, C-13, B-11, and Se-77).

First author: Cheng, AH, Charge “Skin Behavior” of Gold Superatoms,
Abstract: In this work, we investigate the relationship between the charge distribution and electron occupation by exploring neutral gold superatoms Au, and their anion structures [Au-n](-) (n = 13, 55, and 147). It is shown that there exists “skin behavior” of charge distribution for gold superatoms. For the neutral Au-n, there are negative charges of -0.1 e, -0.54 e, and -1.16 e distributed in the surface area of 1D(5) SAMOs of Au-13, 1F(12) 1G(15) SAMOs of Au-55, and 2D(6) 1H(22) 2F(14) 1I(6) 3S(2) 1J(6) 1I(8) 1J(4) 3P(1) SAMOs of Au-147, respectively. For the anion [Au-n](-), more negative charges of -1.08 e, -1.55 e, and -2.14 e are distributed in the surface area of 1D SAMO of [Au-13](-), 1G SAMO of [Au-55](-), and 3P SAMO of [Au-147](-). In addition, adding an electron will cause the SAMOs rearrangement and enhance the geometric symmetry of superatoms, especially in [Au-13](-) and [Au-55](-). Our findings provide a new perspective on microelectronic structure in understanding the skin effects.

First author: Vazquez-Lima, H, Heavy-element-ligand covalence: ligand noninnocence in molybdenum and tungsten Viking-helmet Corroles,
DALTON TRANSACTIONS, 50, 12843, (2021)
Abstract: Extensive DFT calculations with several exchange-correlation functionals indicate that molybdenum-dichlorido Viking helmet corroles are noninnocent with significant Mo-IV-corrole(2-) character. The effect is mediated by a Mo(4d)-corrole(pi) orbital interaction similar to that postulated for MnCl, FeCl and FeNO corroles. The effect also appears to operate in tungsten-dichlorido corroles but is weaker relative to that for Mo. In contrast, MoO triarylcorroles do not exhibit a significant degree of corrole radical character. Furthermore, the Soret absorption maxima of a series of MoCl2 tris(para-X-phenyl)corrole derivatives were found to redshift dramatically with increasing electron-donating character of the para substituent X, essentially clinching the case for a noninnocent macrocycle in MoCl2 corroles.

First author: Cheng, M, Shedding Light on the Role of Chemical Bond in Catalysis of Nitrogen Fixation,
ADVANCED MATERIALS, 33, 12843, (2021)
Abstract: Ammonia (NH3) and nitrates are essential for human society because of their widespread utilization for producing medicines, fibers, fertilizers, etc. In recent years, the development on nitrogen fixation under mild reaction conditions has attracted much attention. However, the very low conversion efficiency and ambiguous catalytic mechanism remain the major hurdles for the research of nitrogen fixation. This review aims to clarify the role of chemical bond in catalytic nitrogen fixation by summarizing and analyzing the recent development of nitrogen fixation research. In detail, the atomic-scale mechanism of nitrogen fixation reaction, the various methods to improve the nitrogen fixation performance, and the computational investigation of nitrogen fixation are discussed, all from a chemical bond perspective. It is hoped that this review could trigger more profound pondering and deeper exploration in the field of catalytic nitrogen fixation.

First author: Senthooran, R, Discrete Oligomers and Polymers of Chloride Monohydrate Can Form in Encapsulated Environments: Structures and Infrared Spectra of [Cl-4(H2O)(4)](4-) and {[Cl(H2O)](-)}(infinity),
CHEMPLUSCHEM, 86, 1297, (2021)
Abstract: A discrete tetrachloride tetrahydrate cluster, [Cl-4(H2O)(4)](4-), was obtained with a partially-fluorinated triaminocyclopropenium cation, [C-3(N(CH2CF3)(2))(NEt2)(NPr2)](+). The cluster consists of a [Cl-2(H2O)(2)](2-) square with each Cl- coordinated by another H2O bridged to another Cl-. A 1D polymer of chloride monohydrate, {[Cl(H2O)](-)}(infinity), was obtained with [C-3(N(CH2CF3)(2))(2)(NBuMe)](+). The tetrameric and polymeric structures were found to be computationally-unstable in the gas phase which indicates that an encapsulated environment is essential for their isolation. DFT and DFTB calculations were carried out on gas-phase [Cl-4(H2O)(4)](4-) to assist the infrared assignments. Anharmonically-corrected B3LYP transition frequencies were in close agreement with experiment, but DFTB models were only appropriate for qualitative interpretation. Solid-state DFTB calculations allowed the vibrational modes to be assigned. The results found are consistent with “discrete” chloride hydrates.

First author: Weatherly, J, On the calculation of the electrostatic potential, electric field and electric field gradient from the aspherical pseudoatom model. II. Evaluation of the properties in an infinite crystal,
Abstract: The previously reported exact potential and multipole moment (EP/MM) method for fast and precise evaluation of the intermolecular electrostatic interaction energies in molecular crystals using the pseudoatom representation of the electron density [Nguyen, Macchi & Volkov (2020), Acta Cryst. A76, 630-651] has been extended to the calculation of the electrostatic potential (ESP), electric field (EF) and electric field gradient (EFG) in an infinite crystal. The presented approach combines an efficient Ewald-type summation (ES) of atomic multipoles up to the hexadecapolar level in direct and reciprocal spaces with corrections for (i) the net polarization of the sample (the ‘surface term’) due to a net dipole moment of the crystallographic unit cell (if present) and (ii) the short-range electron-density penetration effects. The rederived and reported closed-form expressions for all terms in the ES algorithm have been augmented by the expressions for the surface term available in the literature [Stenhammar, Trulsson & Linse (2011), J. Chem. Phys. 134, 224104] and the exact potential expressions reported in a previous study [Volkov, King, Coppens & Farrugia (2006), Acta Cryst. A62, 400-408]. The resulting algorithm, coded using Fortran in the XDPROP module of the software package XD, was tested on several small molecular crystal systems (formamide, benzene, L-dopa, paracetamol, amino acids etc.) and compared with a series of EP/MM-based direct-space summations (DS) performed within a certain number of unit cells generated along both the positive and negative crystallographic directions. The EP/MMbased ES technique allows for a noticeably more precise determination of the EF and EFG and significantly better precision of the evaluated ESP when compared with the DS calculations, even when the latter include contributions from an array of symmetry-equivalent atoms generated within four additional unit cells along each crystallographic direction. In terms of computational performance, the ES/EP/MM method is significantly faster than the DS calculations performed within the extended unit-cell limits but trails the DS calculations within the reduced summation ranges. Nonetheless, the described EP/MM-based ES algorithm is superior to the direct-space summations as it does not require the user to monitor continuously the convergence of the evaluated properties as a function of the summation limits and offers a better precision-performance balance.

First author: Javid, F, Subcritical hydrothermal deconstruction of two hormones (adrenaline and progesterone) in pharmaceutical waste,
Abstract: This study investigates the subcritical hydrothermal deconstruction of adrenaline and progesterone. The hormones were subjected to 60 min hydrothermal deconstruction in the presence of oxygen at temperatures between 200 degrees C and 350 degrees C. A significant reduction in the chemical oxygen demand (COD) was observed for adrenaline (85.1%) progesterone deconstruction (80.2%). Complete deconstruction of adrenaline was achieved at 250 degrees C for 5 min, whereas progesterone was completely degraded at 300 degrees C after 15 min. Volatile fatty acids, predominantly acetic acid, and ammonia nitrogen (NH3-N) were produced during the deconstruction process. A reactive force field (ReaxFF) molecular dynamic simulation implied that the production of hydroxyl radicals could play a role in the deconstruction of adrenaline and progesterone. The results confirm that hydrothermal deconstruction is a feasible and environmentally benign method to eliminate hormones from pharmaceutical waste.

First author: Poltev, V, Understanding the Origin of Structural Diversity of DNA Double Helix,
COMPUTATION, 9, 399, (2021)
Abstract: Deciphering the contribution of DNA subunits to the variability of its 3D structure represents an important step toward the elucidation of DNA functions at the atomic level. In the pursuit of that goal, our previous studies revealed that the essential conformational characteristics of the most populated “canonic” BI and AI conformational families of Watson-Crick duplexes, including the sequence dependence of their 3D structure, preexist in the local energy minima of the elemental single-chain fragments, deoxydinucleoside monophosphates (dDMPs). Those computations have uncovered important sequence-dependent regularity in the superposition of neighbor bases. The present work expands our studies to new minimal fragments of DNA with Watson-Crick nucleoside pairs that differ from canonic families in the torsion angles of the sugar-phosphate backbone (SPB). To address this objective, computations have been performed on dDMPs, cdDMPs (complementary dDMPs), and minimal fragments of SPBs of respective systems by using methods of molecular and quantum mechanics. These computations reveal that the conformations of dDMPs and cdDMPs having torsion angles of SPB corresponding to the local energy minima of separate minimal units of SPB exhibit sequence-dependent characteristics representative of canonic families. In contrast, conformations of dDMP and cdDMP with SPB torsions being far from the local minima of separate SPB units exhibit more complex sequence dependence.

First author: Turlik, A, Origin of Increased Reactivity in Rhenium-Mediated Cycloadditions of Tetrazines,
Abstract: Pyridyl tetrazines coordinated to metals like rhenium have been shown to be more reactive in [4 + 2] cycloadditions than their uncomplexed counterparts. Using density functional theory calculations, we found a more favorable interaction energy caused by stronger orbital interactions as the origin of this increased reactivity. Additionally, the high regioselectivity is due to a greater degree of charge stabilization in the transition state, leading to the major product.

First author: Silva, DR, Dipolar repulsion in alpha-halocarbonyl compounds revisited,
Abstract: The concept of dipolar repulsion has been widely used to explain several phenomena in organic chemistry, including the conformational preferences of carbonyl compounds. This model, in which atoms and bonds are viewed as point charges and dipole moment vectors, respectively, is however oversimplified. To provide a causal model rooted in quantitative molecular orbital theory, we have analyzed the rotational isomerism of haloacetaldehydes OHC-CH2X (X = F, Cl, Br, I), using relativistic density functional theory. We have found that the overall trend in the rotational energy profiles is set by the combined effects of Pauli repulsion (introducing a barrier around gauche that separates minima at syn and anti), orbital interactions (which can pull the anti minimum towards anticlinal to maximize hyperconjugation), and electrostatic interactions. Only for X = F, not for X = Cl-I, electrostatic interactions push the preference from syn to anti. Our bonding analyses show how this trend is related to the compact nature of F versus the more diffuse nature of the heavier halogens.

First author: Grabowski, SJ, A-X center dot center dot center dot sigma Interactions-Halogen Bonds with sigma-Electrons as the Lewis Base Centre,
MOLECULES, 26, 20883, (2021)
Abstract: CCSD(T)/aug-cc-pVTZ//omega B97XD/aug-cc-pVTZ calculations were performed for halogen-bonded complexes. Here, the molecular hydrogen, cyclopropane, cyclobutane and cyclopentane act as Lewis base units that interact through the electrons of the H-H or C-C sigma-bond. The FCCH, ClCCH, BrCCH and ICCH species, as well as the F-2, Cl-2, Br-2 and I-2 molecular halogens, act as Lewis acid units in these complexes, interacting through the sigma-hole localised at the halogen centre. The Quantum Theory of Atoms in Molecules (QTAIM), the Natural Bond Orbital (NBO) and the Energy Decomposition Analysis (EDA) approaches were applied to analyse these aforementioned complexes. These complexes may be classified as linked by A-X center dot center dot center dot sigma halogen bonds, where A = C, X (halogen). However, distinct properties of these halogen bonds are observed that depend partly on the kind of electron donor: dihydrogen, cyclopropane, or another cycloalkane. Examples of similar interactions that occur in crystals are presented; Cambridge Structural Database (CSD) searches were carried out to find species linked by the A-X center dot center dot center dot sigma halogen bonds.

First author: Khireche, M, Understanding the chemical bonding in sandwich complexes of transition metals coordinated to nine-membered rings: energy decomposition analysis and the donor-acceptor charge transfers,
Abstract: DFT calculations on sandwich complexes of the type (C9H9)(2)M and (C6N3H6)(2)M (M = Sc-Ni) are carried out in gas phase and tetrahydrofurane solvent (THF) using BP86 and B3LYP functionals. The nine-membered (C9H9)(-) and (C6N3H6)(-) ligand anions behave differently regarding their coordination to the M2+ metal cation. The computed structural and energetic parameters are weakly influenced by the inclusion of THF solvent. We report that the metal-ligand separation are sensitive to the electron-donation and electron pi-backdonation as highlighted by the populations of the occupied and empty orbitals of the [(C9H9)(-)](2) and [(C6N3H6)(-)](2) anions and the electronic configuration of the M2+ cation. The results showed that the [(C9H9)(-)](2) and [(C6N3H6)(-)](2) ligands behave differently in terms of bonding, coordination mode and donation and pi-backdonation properties in relationship with the metal cation radius, the number of the atoms involved in the coordination and their nature (either carbon or nitrogen atoms). The interactions are dominated by electrostatic and orbital terms each contributing approximately half into the total attractive energy. The donor-acceptor between NBOs identified within the NEDA scheme show the importance of sigma -> LP charge transfers contrary to those related to LP -> sigma* ones in line with their occupations and second perturbative energy E-2.

First author: Sengupta, T, Developing Efficient Suzuki Cross-Coupling Catalysts by Doping Palladium Clusters with Silver,
ACS CATALYSIS, 11, 11459, (2021)
Abstract: It is shown that doping of a Pd duster by Ag atoms can provide an efficient catalyst for the Suzuki-Miyaura cross-coupling reactions. We demonstrate this intriguing possibility by considering a model reaction involving bromobenzene and phenylboronic acid as reagents where the reaction involves oxidation, transmetallation, and reduction steps. We have examined the reaction barriers of all three steps for a conventional ligated Pd catalyst, a nearly icosahedral Pd-13 cluster, and a monosilver-doped Pd12Ag duster using gradient-corrected density functional theory. It is observed that the reaction carried out on the Pd sites adjacent to an Ag atom in a Pd12Ag cluster shows substantially lower barriers for the oxidation and reduction steps compared to the conventional ligated Pd catalyst and the pure Pd-13 cluster. A detailed analysis indicates that the Ag site donates charge to the neighboring Pd site. While such a donation may have been expected to reduce the barrier for the oxidative step, the lowering of the barrier for the reduction step indicates that the respective sites not only act as a donor but can also serve as an acceptor for the reduction step. Furthermore, because of the differential donor-acceptor characteristic of the Ag and Pd atoms, it is observed that the barrier heights of the redox steps are primarily dependent on the chosen active site. The calculated results show that by altering the atom (Ag or Pd) at the active site of the reaction, the activation energies of the redox steps can either be reduced or increased. This shows that the active sites of a bimetallic cluster-like Pd12Ag can be utilized to control the barrier heights of suitable chemical reactions. The relative trend of the barrier heights for both clusters is also observed to be predictable by the conceptual density functional theory. Previous studies in our group have indicated that the reaction barriers for Pd-n clusters can be lowered by supporting them on reduced graphene. We, therefore, propose that silver-doped Pd-n clusters may provide an even better catalyst.

First author: Makkar, P, A review on the use of DFT for the prediction of the properties of nanomaterials,
RSC ADVANCES, 11, 27897, (2021)
Abstract: Nanostructured materials have gained immense attraction because of their extraordinary properties compared to the bulk materials to be used in a plethora of applications in myriad fields. In this review article, we have discussed how the Density Functional Theory (DFT) calculation can be used to explain some of the properties of nanomaterials. With some specific examples here, it has been shown that how closely the different properties of nanomaterials (such as optical, optoelectronics, catalytic and magnetic) predicted by DFT calculations match well with the experimentally determined values. Some examples were discussed in detail to inspire the experimental scientists to conduct DFT-based calculations along with the experiments to derive a better understanding of the experimentally obtained results as well as to predict the properties of the nanomaterial. We have pointed out the challenges associated with DFT, and potential future perspectives of this new exciting field.

First author: Gupta, P, Coke resistant catalyst for hydrogen production in a versatile, multi-fuel, reformer,
JOURNAL OF CATALYSIS, 402, 177, (2021)
Abstract: Distributed H-2 generation coupled with CO2 capture has the potential to deliver clean fuel for transportation purposes, especially in remote communities. Here we present a novel potassium doped Ni-Pt/alumina catalyst which shows remarkable activity and stability for oxidative steam reforming of multiple fuels. At an optimum potassium loading of 5 wt%, the catalyst was found to be stable for at least 42 h time-on-stream, with frequent start-up and shut-down. The catalyst provided nearly identical conversions of methanol, gasoline and diesel, H-2 yield and production rates, demonstrating the flexibility of this catalyst for different feedstocks. Potassium doping in the alumina matrix created higher pore surface area, stabilized the Ni ensemble from sintering at high temperatures and prevented nucleation of coke on the Ni surface, making it coke resistant. A K-Al-Si-O type species that formed during the support synthesis along with presence of Pt species on the surface are believed to be the reasons for the stability of catalyst.

First author: Javid, F, Hydrothermal deconstruction of local anesthetics (bupivacaine and lignocaine) in pharmaceutical waste,
Abstract: Pharmaceutical waste is highly toxic; its disposal is problematic. This study aimed to investigate the non-catalytic hydrothermal deconstruction of local anesthetics and their packaging materials and to gain some insight into the mechanisms of degradation. The widely used local anesthetics bupivacaine and lignocaine with initial concentrations of 400 and 800 mg/L, respectively, were subjected to 60 min hydrothermal treatment at temperatures ranging between 200 and 350 degrees C. A reduction in the chemical oxygen demand (COD) was observed for the bupivacaine (up to 91.3%), and lignocaine (up to 87.8%) samples. Short-chain and volatile fatty acids, predominantly acetic acid, were produced from the hydrothermal process. Complete degradation of lignocaine was achieved at 200 degrees C after 30 min, whereas bupivacaine was completely degraded at 250 degrees C after 10 min. Nitrogen in the form of ammonia (NH3-N) was detected in the degradation products of both bupivacaine (up to 28.2 mg/L) and lignocaine (up to 60 mg/L). Packaging materials make up a substantial part of pharmaceutical waste. Complete deconstruction of packaging waste was achieved by hydrothermal deconstruction, with the resulting mixture having a total chemical oxygen demand (tCOD) of 784 mg/L and soluble chemical oxygen demand (sCOD) of 732.6 mg/L. The total suspended solids (TSS) were reduced by 93%. Complete deconstruction of a mixture of packaging and pharmaceutical waste was achieved at 300 degrees C after 60 min. The reactive force field (ReaxFF) molecular dynamic simulation suggested that hydroxyl radicals were responsible for the degradation of bupivacaine and lignocaine. The findings indicate the potential for hydrothermal processing to address the problems caused by local anesthetics and the associated packaging materials in pharmaceutical waste.

First author: Andreeva, IV, Glycerol valorisation towards biofuel additivities: Thermodynamic studies of glycerol ethers,
Abstract: Glycerol (and activated forms such as epichlorohydrin) provide a versatile substrate for the design and synthesis of new, bio-derived compounds that can have uses in key contemporary applications such as CO2 capture, plastics recycling, and green chemistry in general. Upon etherification of one or more alcohols the glycerol skeleton, the thermophysical properties of the resultant substances change dramatically compared to glycerol. Most notably, the viscosity of glycerol-derived diethers and triethers is reduced by 2-3 orders of magnitude, however, this also corresponds to increased volatility. Determining properties of these new compounds is a key consideration for engineering process design. Here, for the first time we report a comprehensive study on the vapor pressures, heat capacities, and enthalpies of vaporization of symmetric 1,3-diethers of glycerol and provide a group additivity model for estimating the enthalpies of vaporization. The properties of these glycerol-derived solvents are compared to other compounds with similar structures.

First author: Majid, A, Photoinjection and carrier recombination kinetics in photoanode based on (TM)FeO3 adsorbed TiO2 quantum dots,
Abstract: The work being reported was carried out with motivation to address the issues being faced by DSSC by designing organic dye attached to (TM)FeO3/TiO2 structures (where TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) using first principles methods. The structural and electronic properties of (TiO2)54 quantum dot (QD), clusters (TM)FeO3, adsorbed (TM)FeO3/(TiO2)54 and dye attached (TiO2)54/(TM)FeO3 structures are described in detail. The structural stability of the clusters exhibited consistent trend in such a way that the cluster CuFeO3 is most stable whereas ZnFeO3 is least stable structure. The band gap of the QD is reduced after adsorption of the clusters to make harvesting of solar light in visible region except (TiO2)54/Fe2O3 and (TiO2)54/ZnFeO3 which are found active in infrared region of electromagnetic spectrum. The value of recombination rate is decreased whereas the electron injection rate is increased after adsorption of (TM)FeO3 on the QD.

First author: Pnevskaya, AY, Experimental and Theoretical Investigation of Ethylene and 1-MCP Binding Sites in HKUST-1 Metal-Organic Framework,
Abstract: Selective binding of ethylene and ethylene action inhibitor in nanoporous materials can provide new strategies for harvest preservation technologies. In this work, we investigate the process of ethylene and 1-methylcyclopropene (1-MCP), also known as ethylene action inhibitor, binding on HKUST-1, a metal-organic framework (MOF) with open copper sites. For the first time, in situ infrared spectroscopy combined with theoretical simulations was used to obtain the three-dimensional structure of ethylene and 1-MCP bound to Cu-sites of HKUST-1. Time-resolved infrared spectra were collected to selectively determine the rates of ethylene desorption from Cu-sites and estimate its binding energies which were also compared with theoretical results. Not only a successful investigation of ethylene binding sites in HKUST-1 is presented but also a methodology that can be extended to study ethylene/1-MCP storage and release in porous materials with open metal sites which is relevant to the harvest preservation technology.

First author: Das, S, Uncovering the Activity of Alkaline Earth Metal Hydrogenation Catalysis Through Molecular Volcano Plots,
TOPICS IN CATALYSIS, 65, 289, (2022)
Abstract: Recent advances in alkaline earth (Ae) metal hydrogenation catalysis have broadened the spectrum of potential catalysts to include candidates from the main group, providing a sustainable alternative to the commonly used transition metals. Although Ae-amides have already been demonstrated to catalyze hydrogenation of imines and alkenes, a lucid understanding of how different metal/ligand combinations influence the catalytic activity is yet to be established. In this article, we use linear scaling relationships and molecular volcano plots to assess the potential of the Ae metal-based catalysts for the hydrogenation of alkenes. By analyzing combinations of eight metals (mono-, bi-, tri-, and tetravalent) and seven ligands, we delineate the impact of metal-ligand interplay on the hydrogenation activity. Our findings highlight that the catalytic activity is majorly determined by the charge and the size of the metal ions. While bivalent Ae metal cations delicately regulate the binding and the release of the reactants and the products, respectively, providing the right balance for this reaction, ligands play only a minor role in determining their catalytic activity. We show how volcano plots can be utilized for the rapid screening of prospective Ae catalysts to establish a guideline to achieve maximum activity in facilitating the hydrogenation process.

First author: Sathiyamoorthy, VN, Intermolecular interactions in microhydrated ribonucleoside and deoxyribonucleoside: A computational study,
Abstract: The nature of interactions between the ribonucleoside and deoxyribonucleoside with water molecule was examined employing the dispersion corrected density functional theory and wave functional analysis. In the nucleosides, the water binds with the 5 ‘-OH hydrogen and N3 nitrogen or N7-H group. In the deoxynucleosides, the water binds through 3 ‘-OH and N3 nitrogen or carbonyl oxygen. The interaction energy, binding energy, hydration entropy and enthalpy do not show any appreciable change for the nucleoside-water complexes, emulating the experimental findings. Electrostatic potential analysis shows that the most positive region is observed near the 5 ‘-OH hydrogen atom of the ribose unit in nucleosides. In deoxynucleosides, the 3 ‘-OH hydrogen has V-s,V-max values equivalent to 5 ‘-OH hydrogen atom. Hence, the water binds with the 3 ‘-OH hydrogen and the nucleobase. QTAIM analysis shows the presence of medium-strength hydrogen bonds between water and nucleoside. In deoxynucleoside-water complexes, in addition to the 3 ‘-OH hydrogen bonding with water, the nearby 2 ‘ C-H in ribose unit bonds with oxygen in the water molecule. QTAIM and EDA analysis show the intermolecular bonds are noncovalent and electrostatic dominant. The 2D RDG plot shows, additional spikes due to the interaction of 2 ‘ C hydrogen with water oxygen. The 3D spatial diagram shows the existence of several green patches in the deoxynucleoside-water complexes, associated with the weak van der Waal’s interactions which make them more stable.

First author: Goto, S, Revealing the internal heavy chalcogen atom effect on the photophysics of the dibenzo[a,j]phenazine-cored donor-acceptor-donor triad,
Abstract: A new twisted donor-acceptor-donor (D-A-D) multi-photofunctional organic molecule comprising phenoselenazine as the electron donor (Ds) and dibenzo[a,j]phenazine (DBPHZ) as the electron acceptor (A) has been developed. The developed selenium-incorporated D-A-D compound features multi-color polymorphism, distinct mechanochromic luminescence, chemically-stimulated luminochromism, thermally-activated delayed fluorescence, and room-temperature phosphorescence. The internal heavy atom effect on the photophysical properties of the D-A-D system has been investigated through a comparison with the physicochemical properties of a previously developed sulfur analogue and a tellurium analogue.

First author: Czernetzki, C, A Neutral Beryllium(I) Radical,
Abstract: The reduction of a cyclic alkyl(amino)carbene (CAAC)-stabilized organoberyllium chloride yields the first neutral beryllium radical, which was characterized by EPR, IR, and UV/Vis spectroscopy, X-ray crystallography, and DFT calculations.

First author: Boronski, JT, A crystalline tri-thorium cluster with sigma-aromatic metal-metal bonding,
NATURE, 598, 72, (2021)
Abstract: Metal-metal bonding is a widely studied area of chemistry(1-3), and has become a mature field spanning numerous d transition metal and main group complexes(4-7). By contrast, actinide-actinide bonding, which is predicted to be weak(8), is currently restricted to spectroscopically detected gas-phase U-2 and Th-2 (refs. (9,10)), U2H2 and U2H4 in frozen matrices at 6-7 K (refs. (11,12)), or fullerene-encapsulated U-2 (ref. (13)). Furthermore, attempts to prepare thorium-thorium bonds in frozen matrices have produced only ThHn (n = 1-4)(14). Thus, there are no isolable actinide-actinide bonds under normal conditions. Computational investigations have explored the probable nature of actinide-actinide bonding(15), concentrating on localized sigma-, pi-, and delta-bonding models paralleling d transition metal analogues, but predictions in relativistic regimes are challenging and have remained experimentally unverified. Here, we report thorium-thorium bonding in a crystalline cluster, prepared and isolated under normal experimental conditions. The cluster exhibits a diamagnetic, closed-shell singlet ground state with a valence-delocalized three-centre-two-electron sigma-aromatic bond(16,17) that is counter to the focus of previous theoretical predictions. The experimental discovery of actinide sigma-aromatic bonding adds to main group and d transition metal analogues, extending delocalized sigma-aromatic bonding to the heaviest elements in the periodic table and to principal quantum number six, and constitutes a new approach to elaborate actinide-actinide bonding.

First author: Ghosh, B, Understanding, Modulating, and Leveraging Transannular M -> Z Interactions,
INORGANIC CHEMISTRY, 60, 12790, (2021)
Abstract: Density functional theory calculations have been performed on metallatranes featuring a group 13 elements at the bridgehead position to understand the factors that influence the nature of the M center dot center dot center dot Z (M = Fe, Co, Ni; Z = Al, Ga, In) interaction present in these complexes and the resultant reactivity at the metal center. The strength of the M center dot center dot center dot Z interaction increases with the increase in the size and polarizability of the bridgehead group 13 elements. The calculated reaction free energies (Delta G degrees values) for binding of different Lewis bases to the metallatranes are found to be significantly more exergonic for the larger In(III) ions. Quantum theory of atoms in molecules calculations reveal the covalent nature of the M center dot center dot center dot Z interactions, while the EDA-NOCV analysis indicates the strong binding ability of these metallatranes not only to different sigma-donor and pi-acceptor ligands but also to relatively inert species, such as N-2.

First author: Zhao, XT, Endohedral group-14-element clusters TM@E-9 (TM = Co, Ni, Cu; E = Ge, Sn, Pb) and their low-dimensional nanostructures: a first-principles study,
Abstract: Endohedral group14-based clusters with the encapsulation of a transition metal, which are termed [TM@E-m](n-) (TM = transition metal and E = group-14 elements), have lots of potential applications and have been used as interesting building blocks in materials science. Nevertheless, their electronic structures and stability mechanism remain unclear. In this paper, we systematically study the geometries, electronic structures, and bonding properties of [TM@E-9](n-) clusters which are the smallest endohedral group-14-based clusters synthesized so far, by using density functional theory (DFT) calculations. The calculation results reveal the important role of TMs in affecting the structures and bonding interactions in the [TM@E-9](n-) cluster. In the presence of a TM, the cluster geometry could change from a monocapped square antiprism (C-4v) for empty [E-9](4-) cages to a tricapped trigonal prismatic geometry (D-3h) for [TM@E-9](n-). By using the energy decomposition analysis (EDA) method, the bonding properties between the endohedral TM and E-9 cluster have been thoroughly investigated. It was found that the origin of stability of these clusters is from the large electrostatic attraction with significantly reduced Pauli repulsion. In the case of orbital interactions, the pi back-donations from d orbitals of the TM to the cluster make important contributions. More interestingly, the 1D-chain and 2D-sheet nanostructures based on the [Ni@E-9] cluster have been theoretically predicted. The band structure and density of states analysis revealed that all of these nanostructures are metallic and their excellent thermodynamic stability has been confirmed by using ab initio molecular dynamics (AIMD) simulations.

First author: Havenridge, S, Deciphering the dual emission in the photoluminescence of Au14Cd(SR)(12): A theoretical study using TDDFT and TDDFT plus TB,
Abstract: Determining excited state processes for small nanoclusters, specifically gold, aids in our ability to fine-tune luminescent materials and optical devices. Using TDDFT and TDDFT + TB, we present a detailed theoretical explanation for the dual emission peaks displayed in Au14Cd(S-Adm)(12) (Adm = adamantane). As dual emission is relatively rare, we decipher whether the mechanism originates from two different excited states or from two different minima on the same excited state surface. This unique mechanism, which proposes that the dual emission results from two minima on the first excited state, stems from geometrical changes in the bi-tetrahedron core during the emission process.

First author: Margiotta, E, SARS-CoV spike proteins can compete for electrolytes in physiological fluids according to structure-based quantum-chemical calculations,
Abstract: The trimeric spike (S) glycoprotein is the trojan horse and the stronghold of the severe acute respiratory syndrome coronaviruses. Although several structures of the S-protein have been solved, a complete understanding of all its functions is still lacking. Our multi-approach study, based on the combination of structural experimental data and quantum-chemical DFT calculations, led to identify a sequestration site for sodium, potassium and chloride ions within the central cavity of both the SARS-CoV-1 and SARS-CoV-2 spike proteins. The same region was found as strictly conserved, even among the sequences of the bat-respective coronaviruses. Due to the prominent role of the main three electrolytes at many levels, and their possible implication in the molecular mechanisms of COVID-19 disease, our study can take the lead in important discoveries related to the SARS-CoV-2 biology, as well as in the design of novel effective therapeutic strategies.

First author: Roeleveld, JJ, Computational Evaluation of Me2TCCP as Lewis acid,
CHEMPHYSCHEM, 22, 2099, (2021)
Abstract: Supramolecular adducts between dimethyl-2,2,3,3-tetracyanocyclopropane (Me2TCCP) with 21 small (polar) molecules and 10 anions were computed with DFT (B3LYP-D3/def2-TZVP). Their optimized geometries were used to obtain interaction energies, and perform energy decomposition and ‘atoms-in-molecules’ analyses. A set of 38 other adducts were also evaluated for comparison purposes. Selected examples were further scrutinized by inspection of the molecular electrostatic potential maps, Noncovalent Interaction index plots, the Laplacian, the orbital interactions, and by estimating the Gibbs free energy of complexation in hexane solution. These calculations divulge the thermodynamic feasibility of Me2TCCP adducts and show that complexation is typically driven by dispersion with less polarized partners, but by orbital interactions when more polarized or anionic guests are deployed. Most Me2TCCP adducts are more stable than simple hydrogen bonding with water, but less stable than traditional Lewis adducts involving Me3B, or a strong halogen bond such as with Br-2. Several bonding analyses showed that the locus of interaction is found near the electron poor sp(3)-hydridized (NC)(2)C-C(CN)(2) carbon atoms. An empty hybrid sigma*/pi* orbital on Me2TCCP was identified that can be held responsible for the stability of the most stable adducts due to donor-acceptor interactions.

First author: Them, K, Parahydrogen-Induced Polarization Relayed via Proton Exchange,
Abstract: The hyperpolarization of nuclear spins is a game-changing technology that enables hitherto inaccessible applications for magnetic resonance in chemistry and biomedicine. Despite significant advances and discoveries in the past, however, the quest to establish efficient and effective hyperpolarization methods continues. Here, we describe a new method that combines the advantages of direct parahydrogenation, high polarization (P), fast reaction, and low cost with the broad applicability of polarization transfer via proton exchange. We identified the system propargyl alcohol + pH(2) -> allyl alcohol to yield H-1 polarization in excess of P approximate to 13% by using only 50% enriched pH(2) at a pressure of approximate to 1 bar. The polarization was then successfully relayed via proton exchange from ally! alcohol to various target molecules. The polarizations of water and alcohols (as target molecules) approached P approximate to 1% even at high molar concentrations of 100 mM. Lactate, glucose, and pyruvic acid were also polarized, but to a lesser extent. Several potential improvements of the methodology are discussed. Thus, the parahydrogen-induced hyperpolarization relayed via proton exchange (PHIP-X) is a promising approach to polarize numerous molecules which participate in proton exchange and support new applications for magnetic resonance.

First author: Yakovlev, IA, Nitric oxide release and related light-induced cytotoxicity of ruthenium nitrosyls with coordinated nicotinate derivatives,
DALTON TRANSACTIONS, 143, 13694, (2021)
Abstract: The synthetic approaches for the preparation of trans(NO,OH)-cis(NO2 ,NO2)-[RuNO(L)(2)(NO2)(2)OH], where L = ethyl nicotinate (I) and methyl nicotinate (II), are reported. The structures of the complexes are characterized by X-ray diffraction and analyzed by Hirshfeld surface analysis. Both compounds show a nitric oxide release reaction under 445 or 532 nm irradiation of dimethyl sulfoxide (DMSO) solutions, which is studied by combined ultraviolet-visible- (UV-vis), infrared- (IR), and electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations. The charge transfer from the OH-Ru-NO chain and nitrite ligands to the antibonding orbitals of Ru-NO is responsible for the photocleavage of the ruthenium-nitrosyl bond. The elimination of NO leads to a side reaction, namely the protonation of the parent hydroxyl compound. The cytotoxicity and photo-induced cytotoxicity investigations of both compounds on the breast adenocarcinoma cell line MCF-7 reveal that (I) and (II) are cytotoxic with IC50 values of 27.5 +/- 2.8 mu M and 23.3 +/- 0.3 mu M, respectively. Moreover, (I) shows an increase of the toxicity after light irradiation by 7 times (IC50 = 4.1 +/- 0.1), which makes it a prominent target for deeper biological investigations.

First author: Krishnadas, KR, Raman Spectroscopic Fingerprints of Atomically Precise Ligand Protected Noble Metal Clusters: Au-38(PET)(24) and Au38-xAgx(PET)(24),
SMALL, 17, 13694, (2021)
Abstract: Distinct Raman spectroscopic signatures of the metal core of atomically precise, ligand-protected noble metal nanoclusters are reported using Au-38(PET)(24) and Au38-xAgx(PET)(24) (PET = 2-phenylethanethiolate, -SC2H4C6H5) as model systems. The fingerprint Raman features (occurring <200 cm(-1)) of these clusters arise due to the vibrations involving metal atoms of their Au-23 or Au23-xAgx cores. A distinct core breathing vibrational mode of the Au-23 core has been observed at 90 cm(-1). Whereas the breathing mode shifts to higher frequencies with increasing Ag content of the cluster, the vibrational signatures due to the outer metal-ligand staple motifs (between 200 and 500 cm(-1)) do not shift significantly. DFT calculations furthermore reveal weak Raman bands at higher frequencies compared to the breathing mode, which are associated mostly with the rattling of two central gold atoms of the bi-icosahedral Au-23 core. These vibrations are also observed in the experimental spectrum. The study indicates that low-frequency Raman spectra are a characteristic fingerprint of atomically precise clusters, just as electronic absorption spectroscopy, in contrast to the spectrum associated with the ligand shell, which is observed at higher frequencies.

First author: Kovacs, A, Metal-ligand interactions in complexes of cyclen-based ligands with Bi and Ac,
STRUCTURAL CHEMISTRY, 32, 1719, (2021)
Abstract: The structural and bonding properties of Bi and Ac complexes with cyclen-based chelating ligands have been studied using relativistic DFT calculations in conjunction with TZ2P all-electron basis sets. Besides the parent cyclen ligand, the study has covered its extensions with pyridine-type (L-py), carboxylate (DOTA, DOTPA), picolinate (MeDO2PA) and phosphonate (DOTMP) pendant arms. The effect of the cyclen ring size has been probed by increasing it from [12]aneN(4) to [16]aneN(4). Additional extensions in the DOTA complexes included the H2O ligand at the 9th coordination site as well as the p-SCN-Bn substituent (a popular linker to the targeting vector). The study focuses on the complex stability, the nature of bonding and the differences between Ac and Bi in the complexes. The metal-ligand interactions have been analysed by the Extended Transition State method combined with Natural Orbitals of Chemical Valence theory and Quantum Theory of Atoms in Molecules models.

First author: Ghorai, S, Comparison of RNC Coupling and CO Coupling Mediated by Cr-Cr Quintuple Bond and B-B Multiple Bonds: Main Group Metallomimetics,
Abstract: A theoretical analysis of reductive coupling of isocyanide and CO mediated by a Cr-Cr quintuple bonded complex and B-B multiple bonded complexes shows how the difference in donor-acceptor capability of isocyanide and CO ligands controls the product distributions. In the case of CO, the Cr-Cr quintuple bonded complex is unable to show C-C coupling due to the high pi- back bonding possibility of CO and the reaction follows the singlet potential energy surface throughout, whereas, in the case of isocyanide, less pi- back bonding possibility allows the reactions to undergo a spin transition and gives a series of products with different spin multiplicities. Similarly, reactions of B-B multiple bonded complexes with CO and isocyanides are also controlled by donor-acceptor capabilities of ligands, and the C-C coupling takes place by changing the oxidation state of the boron centers from +I to +II, in contrast to the classical main group mediated reactions where stable oxidation states are always preserved. This part of the main group chemistry which is dominated by donor-acceptor bonding interaction is more likely to follow transition metal behavior.

First author: Cui, ZH, Linear Group 13 E equivalent to E Triple Bonds in E2Li62+,
CHEMPHYSCHEM, 22, 1996, (2021)
Abstract: The triply bonded heavier main-group compounds have a textbook trans-bent geometry, in contrast to a familiar linear form found for the lightest analogues. Strikingly, the unexpected linear group 13 E equivalent to E triple bonds were herein found in the D-4h-symmetry E2Li62+ clusters, and they possess a large barrier (>18.0 kcal/mol) towards the dissociation of Li+. The perfectly surrounded Li-4 motifs and two linear coordinated Li atoms strongly suppress the increasing nonbonded electron density of heavier E atoms, making two degenerate pi bonds and one multi-center sigma bond in linear heavier main-group triple bonds. The surrounding Li-6 motifs not only creates an effective electronic structure to form a linear E equivalent to E triple bond, but the resulting electrostatic interactions account for the highly stable global E2Li62+ clusters.

First author: Osthues, H, Covalent photofunctionalization and electronic repair of 2H-MoS(2)via nitrogen incorporation,
Abstract: A route towards covalent functionalization of chemically inert 2H-MoS2 exploiting sulfur vacancies is explored by means of (TD)DFT and GW/BSE calculations. Functionalization via nitrogen incorporation at sulfur vacancies is shown to result in more stable covalent binding than via thiol incorporation. In this way, defective monolayer MoS2 is repaired and the quasiparticle band structure as well as the remarkable optical properties of pristine MoS2 are restored. Hence, defect-free functionalization with various molecules is possible. Our results for covalently attached azobenzene, as a prominent photo-switch, pave the way to create photoresponsive two-dimensional (2D) materials.

First author: Kondinski, A, Polyoxoplatinates as covalently dynamic electron sponges and molecular electronics materials,
NANOSCALE ADVANCES, 3, 5663, (2021)
Abstract: In organic systems, dynamic covalent chemistry provides an adaptive approach (i.e., “covalent dynamics”) where thermodynamic equilibria are used to tailor structural and electronic changes in molecular assemblies. The covalent dynamics finds utility in the design of novel self-healing materials, sensors, and actuators. Herein, using density functional theory (DFT) we explore the structural, electronic and transport properties of the Pt-based polyoxometalate (POM) [PtIII12O8(SO4)(12)](4-) and its derivatives. The latter POM has six redox responsive {O-Pt-Pt-O} moieties and prospects for storage of up to twelve electrons, thus exemplifying how dynamic covalent chemistry may manifest itself in fully inorganic systems. Simulations of the Au/POM/Au junction show that the electron conduction strongly depends on the redox of the POM but more weakly on its rotations with respect to the Au surface. Moreover, the POM shows promising spin-polarized current behaviour, which can be modulated using bias and gate voltages.

First author: Kwon, H, Pyrolysis of bio-derived dioxolane fuels: A ReaxFF molecular dynamics study,
FUEL, 306, 5663, (2021)
Abstract: Alkyl-substituted 1,3-dioxolanes, including 4,5-dimethyl-2-pentan-3-yl-1,3-dioxolane (Fuel 1), 4,5-dimethyl-2pentyl-1,3-dioxolane (Fuel 2), and 2-(heptan-3-yl)-4,5-dimethyl-1,3-dioxolane (Fuel 3), have been recently suggested as potential biodiesels. In this paper, we investigate the initial pyrolysis of the alkyl-substituted 1,3dioxolanes at high temperatures using ReaxFF molecular dynamics (MD) simulations. We analyze the decomposition rate, reaction mechanism, and product distribution in the pyrolysis of the three alkyl 1,3-dioxlanes. The three fuels primarily decompose to 4,5-dimethyl-1,3-dioxolane radical and hydrocarbons derived from the alkyl side-chains. The further decomposition of 4,5-dimethyl-1,3-dioxolane radical primarily leads to 2-C4H8 and CO2 within a few decomposition steps. The hydrocarbon product distribution is significantly affected by the molecular structure of the alkyl side-chain, which would have a strong influence on the sooting tendency of these fuels. The ReaxFF simulations predict that the order of sooting tendency would be Fuel 3 > Fuel 1 > Fuel 2, which agrees with the measured sooting tendency trend. Based on the pyrolysis mechanism identified by ReaxFF, we propose a new alkyl dioxolane, 4-hexyl-5-methyl-1,3-dioxolane (Fuel 4), which might produce even less soot, by modifying the molecular structure of Fuel 2. Our ReaxFF simulation shows that Fuel 4 produce much less C4H8, an effective non-aromatic soot precursor, than Fuel 2. Moreover, more carbon atoms are bonded to each oxygen atom in Fuel 4 than Fuel 2, which would help reduce soot yield by removing more carbon atoms from the soot-producing pool of species. The major decomposition pathways identified in this work can be used to develop chemical kinetic models for 1,3-dioxolane based compounds, as biodiesel components, applicable to combustion engine simulations. We also demonstrate that the chemical kinetic insight offered by ReaxFF simulations can be used to design new fuel molecules with more desired properties.

First author: Bista, D, Massive dipoles across the metal-semiconductor cluster interface: towards chemically controlled rectification,
Abstract: An interface between a metallic cluster (MgAl12) and a semiconducting cluster (Re6Se8(PMe3)(5)) is shown to be marked by a massive dipole reminiscent of a dipolar layer leading to a Schottky barrier at metal-semiconductor interfaces. The metallic cluster MgAl12 with a valence electron count of 38 electrons is two electrons short of 40 electrons needed to complete its electronic shells in a superatomic model and is marked by a significant electron affinity of 2.99 eV. On the other hand, the metal-chalcogenide semiconducting cluster Re6Se8(PMe3)(5), consisting of a Re6Se8 core ligated with five trimethylphosphine ligands, is highly stable in the +2 charge-state owing to its electronic shell closure, and has a low ionization energy of 3.3 eV. The composite cluster Re6Se8(PMe3)(5)-MgAl12 formed by combining the MgAl12 cluster through the unligated site of Re6Se8(PMe3)(5) exhibits a massive dipole moment of 28.38 D resulting from a charge flow from Re6Se8(PMe3)(5) to the MgAl12 cluster. The highest occupied molecular orbital (HOMO) of the composite cluster is on the MgAl12 side, which is 0.53 eV below the lowest unoccupied molecular orbital (LUMO) localized on the Re6Se8(PMe3)(5) cluster, reminiscent of a Schottky barrier at metal-semiconductor interfaces. Therefore, the combination can act as a rectifier, and an application of a voltage of approximately 4.1 V via a homogeneous external electric field is needed to overcome the barrier aligning the two states: the HOMO in MgAl12 with the LUMO in Re6Se8(PMe3)(5). Apart from the bias voltage, the barrier can also be reduced by attaching ligands to the metallic cluster, which provides chemical control over rectification. Finally, the fused cluster is shown to be capable of separating electron-hole pairs with minimal recombination, offering the potential for photovoltaic applications.

First author: Jiang, W, Dielectric Constant Engineering of Organic Semiconductors: Effect of Planarity and Conjugation Length,
Abstract: Bulk heterojunction organic solar cells continue to show steady photoconversion efficiency improvements. However, single component organic solar cells are a particularly attractive alternative due to the relative simplicity of device manufacture. It has been proposed that organic semiconductors with a high dielectric constant (approximate to 10) could give rise to spontaneous free charge carrier generation upon photoexcitation. In this manuscript, factors are explored that affect the dielectric constant of organic semiconductors, particularly the optical-frequency dielectric constant. The properties of monomers, dimers and trimers of two isoelectronic families of materials that have acceptor units composed of one or two dicyanovinylbenzothiadiazole moieties and one to three donor units are compared. The donor components are composed of either fluorenyl or cyclopentadithiophene moieties with the same glycol-based solubilizing groups. It is found that chromophore planarity and orientation with respect to the substrate, and film density affect the optical and electronic properties of the materials, especially the high-frequency dielectric constant. The results also indicate that delocalization of the highest occupied and lowest unoccupied molecular orbitals is a critical factor. The dimer with two dicyanovinylbenzothiadiazole moieties and two dithienocyclopentadiene units is found to have the highest optical frequency dielectric constant and overall performance.

First author: Thomas, MG, Tuning the structure of disulfonated phenanthroline based ligands for effective separation of Am(III)/Eu(III) ions : A DFT investigation,
Abstract: The disulfonated N,N’-diphenyl-2,9-diamide-1,10-phenanthroline (DS-Ph-DAPhen) ligand, is recently added to the list of efficient water-soluble heterocyclic ligands for the separation of actinides from lanthanides in nuclear waste management. This ligand contains phenyl sulfonate group which improves the solubility in aqueous medium. To understand the role of sulfonate group in selective binding of Am3+ over Eu3+ ions, a systematic investigation is executed on the designed disulfonated N,N’-diethyl-N,N’-diphenyl-2,9-diamide-1,10-phenanthroline (DS-Et-Ph-DAPhen) ligands. Here, we provide insights into the nature of metal-ligand bond in ML(NO3)(3) complexes [M = Am and Eu] to trace the origin of selectivity in the separation process using scalar relativistic ZORA/DFT calculations. The quantum theory of atoms in molecules (QTAIM) and energy decomposition analysis (EDA) are carried out to understand the stabilizing interactions and binding energies of these ML(NO3)(3) complexes respectively. Results reveal that DS-Et-Ph-DAPhen ligands show preferential binding to Am3+ where M-O bond length is shorter and stronger than that of M-N bonds. Computed separation factors indicate that meta-substitution is most favourable for extraction. Overall this study brings out the importance of sulfonate group in the stripping of Am3+ from Eu3+ and will shed light on the structural role played by sulfonate moiety for the nuclear waste treatment.

First author: Anderson, JSM, Non-Nuclear maxima and the universality of Bright Wilson’s justification of the first Hohenberg Kohn theorem revisited,
CHEMICAL PHYSICS LETTERS, 780, 18975, (2021)
Abstract: The Kato cusp condition involves a spherically-averaged derivative of the electron density with respect to distance from a given nucleus weighted by the electron density at that nucleus. This “Kato ratio” is shown analytically to vanish at all points of the electron density (and of the underlying external potential) that do not exhibit a singularity including non-nuclear maxima/attractors (NNM/NNAs). Using prototypical test cases, the analytical result is confirmed numerically. This result, while quite simply demonstrated and possibly tacitly known, could not be located in the literature to the best of the authors’ efforts. Since the Kato ratio is zero at a NNM/NNA, this saves the DFT plausibility argument of E. Bright Wilson. The consideration of these ideas in excited electronic states is discussed.

First author: Mafune, F, Dissociative adsorption of NO introduces flexibility in gas phase Rh-6(+) clusters leading to a rich isomeric distribution,
CHEMICAL PHYSICS LETTERS, 780, 18975, (2021)
Abstract: The adsorption of an NO molecule on a Rh-6(+) gas phase cluster was investigated based on a wide screening of the geometrical and spin isomers by density functional theory calculations. For molecular adsorption, several different on-top adsorption forms were found in a wider energy range. For dissociative adsorption, a characteristic adsorption form was found, which has many more geometrical and spin isomers than the other adsorption forms. These isomers can exist because of the relative flexible geometric structure, in which a Rh atom is connected to pyramidal Rh5 through two hinge-like connections formed by the N and O atoms.

First author: Nagata, M, Fused-Nonacyclic Multi-Resonance Delayed Fluorescence Emitter Based on Ladder-Thiaborin Exhibiting Narrowband Sky-Blue Emission with Accelerated Reverse Intersystem Crossing,
Abstract: Developing organic luminophores with unique capability of strong narrowband emission is both crucial and challenging for the further advancement of organic light-emitting diodes (OLEDs). Herein, a nanographitic fused-nonacyclic pi-system (BSBS-N1), which was strategically embedded with multiple boron, nitrogen, and sulfur atoms, was developed as a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter. Narrowband sky-blue emission with a peak at 478 nm, full width at half maximum of 24 nm, and photoluminescence quantum yield of 89 % was obtained with BSBS-N1. Additionally, the spin-orbit coupling was enhanced by incorporating two sulfur atoms, thereby facilitating the spin-flipping process between the excited triplet and singlet states. OLEDs based on BSBS-N1 as a sky-blue MR-TADF emitter achieved a high maximum external electroluminescence quantum efficiency of 21.0 %, with improved efficiency roll-off.

First author: An, M, Analysis of the role of Cu for improving the reactivity of Cu-modified Fe2O3 oxygen carriers in the chemical looping gasification process with coal,
FUEL, 305, 20280, (2021)
Abstract: The design and optimization of high-performance oxygen carriers (OCs) are the key to the industrialization of chemical looping gasification processes. The addition of Cu to Fe-based OCs has been demonstrated to improve their reaction performance. However, the operative mechanisms behind this improvement, which must be understood for making accurate predictions and designing optimum Fe-Cu composite OCs, remain poorly understood. The present work addresses this issue by systematically investigating the gasification reactivity of Cumodified Fe2O3 OCs with molar ratios of CuO/Fe2O3 in the range of 0.2-1.8 fabricated by mechanical mixing and calcination. The obtained Cu-modified Fe2O3 OCs are characterized by an array of methods, and employed in a fluidized bed reactor for conducting chemical looping gasification experiments with coal. The results indicate that the replacement of Fe with Cu atoms in the Fe2O3 lattice, resulting in the formation of CuxFe3-xO4, is the key feature in the improved reaction performance of Cu-modified Fe2O3 OCs. The effect of introducing Cu into the Fe2O3 OCs on the H-2-OC reduction reaction is analyzed computationally from a molecular perspective based on density functional theory. The introduction of Cu is thereby demonstrated to improve the reactivity of Fe2O3 fundamentally by altering the reaction pathway of Fe2O3 and decreasing the reaction energy barrier between H-2 molecules and the OC. This understanding of the mechanisms by which Cu affects the reactivity of Cu-modified Fe2O3 OCs provides significant support for the controllable preparation of highly active OCs, and thereby facilitates the industrial development of chemical looping gasification processes.

First author: Mtshali, Z, Electrochemical study of the Mn(II/III) oxidation of tris (polypyridine)manganese(II) complexes,
ELECTROCHIMICA ACTA, 391, 20280, (2021)
Abstract: The electrochemical behaviour of a series of tris(polypyridine)manganese(II) complexes containing substituents ranging from electron withdrawing (Cl) to electron donating (OMe) is presented. The Mn(II/III) redox couple shows irreversible behaviour with large peak potential separations and small peak current ratios. A density functional theory (DFT) study shows the unstable oxidized Mn(III) complex to be either a high spin Jahn-Teller distorted ( S = 2) or an intermediate spin ( S = 1) species. Geometry distortion or electron rearrangement upon oxidation provides possible reasons for the observed irreversible electrochemical behaviour of the Mn(II/III) redox couple. A linear relationship obtained between the DFT calculated solvent phase (acetonitrile) highest molecular orbital energies and experimental reduction potentials (1/2(Epa + Epc) – obtained experimentally in acetonitrile for complexes 1 -7 in this study) were used to predict the experimental reduction potentials of related complexes (1/2(Epa + Epc) of complexes 8 -10 (previously published) accurately within 0.04 V of the published data.

First author: Koridon, E, Orbital transformations to reduce the 1-norm of the electronic structure Hamiltonian for quantum computing applications,
Abstract: Reducing the complexity of quantum algorithms to treat quantum chemistry problems is essential to demonstrate an eventual quantum advantage of noisy-intermediate scale quantum devices over their classical counterpart. Significant improvements have been made recently to simulate the time-evolution operator U(t) = e(i (H) over cap >t), where (H) over cap is the electronic structure Hamiltonian, or to simulate (H) over cap directly (when written as a linear combination of unitaries) by using block encoding or qubitization techniques. A fundamental measure quantifying the practical implementation complexity of these quantum algorithms is the so-called 1-norm of the qubit representation of the Hamiltonian, which can be reduced by writing the Hamiltonian in factorized or tensor-hypercontracted forms, for instance. In this paper, we investigate the effect of classical preoptimization of the electronic structure Hamiltonian representation, via single-particle basis transformation, on the 1-norm. Specifically, we employ several localization schemes and benchmark the 1-norm of several systems of different sizes (number of atoms and active space sizes). We also derive a formula for the 1-norm as a function of the electronic integrals and use this quantity as a cost function for an orbital-optimization scheme that improves over localization schemes. This paper gives more insights about the importance of the 1-norm in quantum computing for quantum chemistry and provides simple ways of decreasing its value to reduce the complexity of quantum algorithms.

First author: Nandi, A, Boron Tunneling in the “Weak” Bond-Stretch Isomerization of N-B Lewis Adducts,
CHEMPHYSCHEM, 22, 1857, (2021)
Abstract: Some nitrile-boron halide adducts exhibit a double-well potential energy surface with two distinct minima: a “long bond” geometry (LB, a van der Waals interaction mostly based on electrostatics, but including a residual charge transfer component) and a “short bond” structure (SB, a covalent dative bond). This behavior can be considered as a “weak” form of bond stretch isomerism. Our computations reveal that complexes RCN-BX3 (R=CH3, FCH2, BrCH2, and X=Cl, Br) exhibit a fast interconversion from LB to SB geometries even close to the absolute zero thanks to a boron atom tunneling mechanism. The computed half-lives of the meta-stable LB compounds vary between minutes to nanoseconds at cryogenic conditions. Accordingly, we predict that the long bond structures are practically impossible to isolate or characterize, which agrees with previous matrix-isolation experiments.

First author: Olejniczak, M, Relativistic frozen density embedding calculations of solvent effects on the nuclear magnetic resonance shielding constants of transition metal nuclei,
Abstract: Nuclear magnetic resonance shielding constants of transition metals in solvated complexes are computed at the relativistic density functional theory (DFT) level. The solvent effects evaluated with subsystem-DFT approaches are compared with the reference solvent shifts predicted from supermolecular calculations. Two subsystem-DFT approaches are analyzed-in the standard frozen density embedding (FDE) scheme the transition metal complexes are embedded in an environment of solvent molecules whose density is kept frozen, in the second approach the densities of the complex and of its environment are relaxed in the “freeze-and-thaw” procedure. The latter approach improves the description of the solvent effects in most cases, nevertheless the FDE deficiencies are rather large in some cases.

First author: Curtis, CJ, Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione,
INORGANIC CHEMISTRY, 60, 12457, (2021)
Abstract: Oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. Although the stabilization of radicals within oligopyrrolic pi systems is more common for macrocyclic ligands, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transitionmetal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven S dimerization to form a hydroxo-bridged binuclear complex in the presence of water or triethylamine. Electrochemical, spectroelectrochemical, and computational analyses of the binuclear complex indicate the accessibility of two quasi-reversible ligand-centered reduction processes. The product of a two-electron chemical reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltocenium salt features a folded dianionic complex that maintains the hydroxo bridges between the divalent palladium centers. X-band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a diradical with spin density almost entirely located on the two dipyrrindione ligands. As established from the EPR temperature dependence, the associated exchange coupling is weak and antiferromagnetic (J approximate to -2.5 K), which results in a predominantly triplet state at the temperatures at which the measurements have been performed.

First author: Asaro, F, beta-Fluorinated Paraconic Acid Derivatives: Synthesis and Fluorine Stereoelectronic Effects,
Abstract: New methods for the introduction of fluoro substituents are in great demand, owing to the present importance of fluorinated bioactive compounds. Here we report a simple strategy for the synthesis of a new class of beta-fluorinated paraconic acid derivatives. Methyl and ethyl hexanoyl succinates were fluorinated by Selectfluor (R), then reduced by a mild reducing agent in acidic medium, thus partially suppressing the HF elimination reaction. The diastereomeric beta-fluoro-gamma-lactones afforded by lactonization of the fluorinated hydroxydiesters were separated by column chromatography. Their stereochemistry was assessed by means of F-19{H-1}-HOESY NMR measurements. The relationship between the remarkable F-19 chemical shift difference (20 ppm) and configuration difference was elucidated by two-component relativistic DFT calculations. Both the quick survey of conformers stability based on molecular mechanics in the RDKit environment and the DFT geometry optimizations at the scalar ZORA TZ2P/BLYP level, revealed that for the (2R,3R) diastereomer the gamma-lactone ring adopts one prevalent envelope conformation, whereas for the (2R,3S) one both envelope conformations must be taken into consideration.

First author: Lv, CD, Mechanism and Selectivity of Cyclopropanation of 3-Alkenyl-oxindoles with Sulfoxonium Ylides Catalyzed by a Chiral N,N’-Dioxide-Mg(II) Complex,
Abstract: The mechanism and stereoselectivity of an asymmetric cyclopropanation reaction between 3-alkenyl-oxindole and sulfoxonium ylide catalyzed by a chiral N,N’-dioxide-Mg(II) complex were explored using the B3LYP-D3(BJ) functional and the def2-TZVP basis set. The noncatalytic reaction occurred via a stepwise mechanism, with activation barriers of 21.6-23.5 kcal mol(-1). The C-2-C-alpha bond formed followed by the carbanion S(N)2 substitution, constructing a three-membered ring in spiro-cyclopropyl oxindoles, accompanied by the release of dimethylsulfoxide. The electron-withdrawing N-protecting t-butyloxy carbonyl (Boc) and acetyl (Ac) groups in isatin enhanced the local electrophilicity of the C2 atom and the repulsion between the two COPh groups in the reactants, contributing to high reactivity as well as good diastereoselectivity results. The N-Boc-3-phenacylideneoxindole coordinated to the chiral ligand (L-PiPr(2)) in a bidentate fashion, forming a hexacoordinate-Mg(II) complex as the reactive species. The origin of enantioselectivity was from the shielding effect of 2,6-diisopropylphenyl groups in the ligand toward the si-face of oxindole. The repulsion between the SO(CH3)(2) and COPh groups in 3-alkenyl-oxindole and the neighboring ortho-iPr group in the ligand directed the re-face of ylide to attack the re-face of oxindole preferably, contributing to the high diastereoselectivity of the product. A metal-ion-ligand matching relationship was important for a good asymmetric induction effect of the chiral N,N’-dioxide-metal catalyst. A large chiral cavity in the Zn(II) catalyst weakened the shielding effect of 2,6-diisopropylphenyl groups in the ligand toward the prochiral face of oxindole, leading to inferior enantioselectivity observed in the experiment.

First author: Garain, BC, Intersystem Crossing in Boron-Based Donor-Spiro-Acceptor Organic Chromophore: A Detailed Theoretical Study,
Abstract: Intersystem crossing and reverse intersystem crossing (rISC) processes were investigated in a boron-based donor-spiro-acceptor organic chromophore which shows thermally activated delayed fluorescence. Due to the perpendicular arrangement between donor and acceptor moieties, the HOMO and the LUMO are spatially separated, and the compound shows charge transfer (CT) transitions. We found both S-1 and T-1 excited states are CT in nature (i.e., electron and hole wave functions are localized on acceptor and donor units, respectively) and T-2, which is higher in energy than S-1 and T-1, is locally excited in nature (i.e., both electron and hole wave functions are localized on an acceptor unit). Because of the same nature of excitation (i.e., CT here), the spin-orbit coupling matrix element between S-1 and T-1 is very low and insignificant exciton conversion occurs from the T-1 state to the S-1 state (and vice versa). Our combined time-dependent density functional theory and quantum dynamics simulation shows that the rISC process from the T-1 state to the S-1 state can be enhanced by the presence of a nearby local excited triplet state (i.e., T-2 state here). A smaller gap between the T-1 and T-2 states efficiently establishes the rISC route.

First author: Dong, X, Tuning structural preference of negatively charged B16 by ionically or covalently interacting with alkali and coinage metals,
CHEMICAL PHYSICS, 550, 6674, (2021)
Abstract: The planar ribbon form is the lowest-energy structure of the neutral and negatively charged B16 clusters, especially planar B162- with ten delocalized pi electrons is viewed as an all-boron naphthalene, whereas the doped B16TM- by transition metals unexpectedly exhibit the high coordinated TM-centered tubular structures. We found herein a totally different picture in B16M- /B16TM-(M = Li, Na, K; TM = Ag, Au) doped by s-block metals (being isoelectronic to B162-) relative to the reported B16-based clusters. A new quasi-planar trapezoid structure is predicted to be a global minimum, where B16TM- (TM = Ag, Au) presents chemistry similar to that of hydrogen in its bonding to boron. The chemical bonding and structural integrity of the quasi-planar trapezoid structure is not altered significantly in B16M-, suggesting its stability and viability as a promising building block for boron-assembled nanomaterials.

First author: Fedik, N, Band Gap Engineering and 14 Electron Superatoms in 2D Superoctahedral Boranes B4X2 (B, N, P, As, Sb),
Abstract: Band gap tuning in 2D monolayers is one of the most attractive approaches in design and production of new atomically thin semiconductors. Following our recent computational design of stable two-dimensional octahedral boranes, we present comprehensive computational study of electronic structure, stability and properties of members belonging to family B4X2 (X = B, N, P, As, Sb). We select 15 group atoms (pnictogens) as apical substituents to stabilize quasi-octahedral units by delocalized bonding and create interlayer “pressure” caused by vertically aligned lone pairs. We first substitute apical B atoms by N and then go down the 15 group to capture electronic structure trends. B -> N substitution opens band gap, while further substitution consistently narrows band gap. We revealed elegant band gap trend which is inversely proportional to the size of octahedral units. Thus, old as world isoelectronic substitution could be used for band gap engineering in superoctahedral 2D boranes and other monolayers. We also discovered superatomic bonding in B4As2 and B4P2 octahedra which agrees with their exceptional stability (up to 800 K) and magnetic response properties. Remarkably, both B4As2 and B4P2 units have 14 valence electrons, making them exceptional examples of stable nonconventional electron count of spherical aromaticity. Alongside with a considerable negative formation energy and phonon stability, B4As2 has extremely low exfoliation energy of 0.02 eV/atom implying probability of synthetic route from a putative bulk material. It gives a strong basis to believe in possibility of experimental fabrication of B4As2 monolayer which can serve as alternative to MoS2 and silicon.

First author: Grabowski, SJ, Classification of So-Called Non-Covalent Interactions Based on VSEPR Model,
MOLECULES, 26, 17280, (2021)
Abstract: The variety of interactions have been analyzed in numerous studies. They are often compared with the hydrogen bond that is crucial in numerous chemical and biological processes. One can mention such interactions as the halogen bond, pnicogen bond, and others that may be classified as sigma-hole bonds. However, not only sigma-holes may act as Lewis acid centers. Numerous species are characterized by the occurrence of pi-holes, which also may play a role of the electron acceptor. The situation is complicated since numerous interactions, such as the pnicogen bond or the chalcogen bond, for example, may be classified as a sigma-hole bond or pi-hole bond; it ultimately depends on the configuration at the Lewis acid centre. The disadvantage of classifications of interactions is also connected with their names, derived from the names of groups such as halogen and tetrel bonds or from single elements such as hydrogen and carbon bonds. The chaos is aggravated by the properties of elements. For example, a hydrogen atom can act as the Lewis acid or as the Lewis base site if it is positively or negatively charged, respectively. Hence names of the corresponding interactions occur in literature, namely hydrogen bonds and hydride bonds. There are other numerous disadvantages connected with classifications and names of interactions; these are discussed in this study. Several studies show that the majority of interactions are ruled by the same mechanisms related to the electron charge shifts, and that the occurrence of numerous interactions leads to specific changes in geometries of interacting species. These changes follow the rules of the valence-shell electron-pair repulsion model (VSEPR). That is why the simple classification of interactions based on VSEPR is proposed here. This classification is still open since numerous processes and interactions not discussed in this study may be included within it.

First author: Sanchez-Gonzalez, A, New Insights on the Interaction of Phenanthroline Based Ligands and Metal Complexes and Polyoxometalates with Duplex DNA and G-Quadruplexes,
MOLECULES, 26, 17280, (2021)
Abstract: This work provides new insights from our team regarding advances in targeting canonical and non-canonical nucleic acid structures. This modality of medical treatment is used as a form of molecular medicine specifically against the growth of cancer cells. Nevertheless, because of increasing concerns about bacterial antibiotic resistance, this medical strategy is also being explored in this field. Up to three strategies for the use of DNA as target have been studied in our research lines during the last few years: (1) the intercalation of phenanthroline derivatives with duplex DNA; (2) the interaction of metal complexes containing phenanthroline with G-quadruplexes; and (3) the activity of Mo polyoxometalates and other Mo-oxo species as artificial phosphoesterases to catalyze the hydrolysis of phosphoester bonds in DNA. We demonstrate some promising computational results concerning the favorable interaction of these small molecules with DNA that could correspond to cytotoxic effects against tumoral cells and microorganisms. Therefore, our results open the door for the pharmaceutical and medical applications of the compounds we propose.

First author: Lewinska, A, Antiradical Properties of N-Oxide Surfactants-Two in One,
Abstract: Surfactants are molecules that lower surface or interfacial tension, and thus they are broadly used as detergents, wetting agents, emulsifiers, foaming agents, or dispersants. However, for modern applications, substances that can perform more than one function are desired. In this study we evaluated antioxidant properties of two homological series of N-oxide surfactants: monocephalic 3-(alkanoylamino)propyldimethylamine-N-oxides and dicephalic N,N-bis[3,3 ‘-(dimethylamino)propyl]alkylamide di-N-oxides. Their antiradical properties were tested against stable radicals using electron paramagnetic resonance (EPR) and UV-vis spectroscopy. The experimental investigation was supported by theoretical density functional theory (DFT) and ab initio modeling of the X-H bonds dissociation enthalpies, ionization potentials, and Gibbs free energies for radical scavenging reactions. The evaluation was supplemented with a study of biological activity. We found that the mono- and di-N-oxides are capable of scavenging reactive radicals; however, the dicephalic surfactants are more efficient than their linear analogues.

First author: Neto, ANC, ZORA all-electron double zeta basis sets for the elements from H to Xe: application in atomic and molecular property calculations,
Abstract: From the segmented all-electron basis set of double zeta valence quality plus polarization functions (DZP) for the elements from H to Xe, the zeroth-order regular approximation (ZORA) is used to generate a DZP-ZORA basis set, i.e., the contraction coefficients of the DZP set are re-optimized using the minimum ZORA energy criterion. To properly describe electrons distant from the nuclei, a diffuse function is added to each atomic symmetry (s, p, d, and f). The later basis set is designated as DZP-ZORA augmented. To test the effectiveness of the basis sets developed in this work, calculations of ionization energies and mean dipole polarizabilities of some elements are performed using the ZORA-CCSD(T) method. At the same level of theory, bond lengths, dissociation energies, and harmonic vibrational frequencies of some diatoms are also reported. Comparison with experimental data and recommended values available in the literature is made. Except for polarizability, scalar relativistic effects are estimated for the other properties. The performances of the ZORA and second-order Douglas-Kroll-Hess Hamiltonians are evaluated.

First author: Mikhailov, AA, Photoinduced linkage isomers in a model ruthenium nitrosyl complex: Identification and assignment of vibrational modes,
Abstract: Photoinduced NO-linkage isomers were investigated in the solid state of labelled trans-[Ru((NO)-N-14/15)(py(4))F](ClO4)(2) complex by combined IR-spectroscopy and DFT calculations. Based on the experimental data and the DFT calculations of this isotopically labelled (NO)-N-14/15 nitrosyl compound, we present a complete assignment of the vibrational bands of three nitrosyl linkage isomers in a range from 4000 to 200 cm(-1). The calculated IR-spectra match well with the experimental data allowing reliable assignment of the vibrational bands. The structural change from the Ru-NO (GS) to the Ru-ON (MS1) and Ru-eta(2)-(NO) (MS2) linkage configuration leads to the downshift of the nu(NO) and nu(Ru-(NO)) bands, and a corresponding increase of the energy of the nu(Ru-F) band. The shift of the bands corresponds to the change of the Ru(NO) and Ru-F bond lengths: increase of the Ru-(NO) bond length leads to the decrease of the energy of the nu(Ru-(NO)) band; decrease of the Ru-F bond length leads to the increase of the energy of the nu(Ru-F) band. These observations can be extrapolated to the family of related nitrosyl complexes and therefore be used for the qualitative prediction of the Ru-(NO) and Ru-Ltrans-to-NO bond lengths of different linkage isomers in the framework of one complex. While the formation of linkage isomers is a reversible process, long-time irradiation sometimes induces irreversible reactions such as the release of NO. Here, we show that the photolysis of trans-[Ru((NO)-N-14/15)(py(4))F](ClO4)(2) in KBr pellets may lead to the release of nitrous oxide N2O, conceivably through the formation of a {Ru-(kappa(2)-ONNO)} intermediate.

First author: Yin, BQ, Probing Cluster-pi Interactions between Cu-n(-) and C2H2/C2H4 for Gas Separation,
Abstract: Copper-related materials are used for separation of ethylene and acetylene gases in chemistry; however, the precise mechanism regarding selectivity is elusive to be fully understood. Here, we have conducted a joint experimental and theoretical study of the Cu-n(-) (n = 7-30) clusters in reacting with C2H4 and C2H2. It is found that all of the Cu-n(-) clusters readily react with C2H2, giving rise to C2H2-addition products; however, Cu-18(-) and Cu-19(-) do not react with C2H4. We illustrate the superatomic stability of Cu-18(-) and advocate its availability to separate C2H4 from C2H2. Further, we demonstrate the atomically precise mechanism regarding selectivity by fully unveiling the size-dependent cluster-pi interactions.

First author: Khan, MI, Computational insights of alkali metal (Li / Na / K) atom decorated buckled bismuthene for hydrogen storage,
Abstract: The mechanism of hydrogen molecule adsorption on 2D buckled bismuthene (b-Bi) monolayer decorated with alkali metal atoms was studied using density functional theory based first principles calculations. The decorated atoms Li, Na and K exhibited distribution on surface of b-Bi monolayer with increasing binding energy of 2.6 eV, 2.9 eV and 3.6 eV respectively. The adsorption of H-2 molecule on the slabs appeared stable which was further improved upon inclusion of van der Waals interactions. The adsorption behaviour of H-2 molecules on the decorated slabs is physisorption whereas the slabs were able to bind up to five H-2 molecules. The average adsorption energy per H-2 molecules are in range of 0.1-0.2 eV which is good for practical applications. The molecular dynamics simulation also confirmed the thermodynamic stabilities of five H-2 molecules adsorbed on the decorated slabs. The storage capacity values are found 2.24 wt %, 2.1 wt %, and 2 wt %, for respective cases of Li, Na and K atoms decorated b-Bi. The analysis of the adsorbed cases pointed to electrostatic interaction of Li and H-2 molecule. The adsorption energies, binding energies, charge analysis, structural stability, density of states, and hydrogen adsorption percentage specifies that the decorated b-Bi may serve as an efficient hydrogen storage material and could be an effective medium to interact with hydrogen molecules at room temperature.

First author: Yuan, SF, Rod-Shaped Silver Supercluster Unveiling Strong Electron Coupling between Substituent Icosahedral Units,
Abstract: The first linear silver supercluster based on icosahedral Ag-13 units has been constructed via bridging of dpa ligands: Ag-61(dpa)(27)(SbF6)(4) (Hdpa = dipyridylamine) (Ag-61). Single-crystal X-ray diffraction reveals that this rod-shaped cluster consists of four vertex-sharing Ag-13 icosahedra in a linear arrangement. This Ag-61 cluster represents the longest one-dimensional metal nanocluster with a resolved structure. Unprecedented electron coupling develops between their constituent Ag-13 units. Theoretical studies disclose that the stabilities of the two superclusters are dictated by a strong interaction between the Ag-13 units as well as the ligand effect of the dpa-Ag motifs. The quantum size effect accounts for the significant enhancement of the metal-related absorptions and the red shift at the near-infrared region as the length of the cluster increases. This work sheds light on the evolution of one-dimensional materials and an understanding of the electronic communication between the constituent clusters.

First author: Kryuchkova, NA, Electronic structure and stability of hexanuclear complex [Cu-6(hfa)(4)(dpm)(4)(OH)(4)],
Abstract: Interatomic interactions and charge state of atoms in hexanuclear complex [Cu-6(hfa)(4)(dpm)(4)(OH)(4)] have been studied by the methods of quantum chemistry and X-ray photoelectron spectroscopy (XPS). The shape and energy position of the Cu2p(3/2)-lines indicate that all copper atoms state could be interpreted as Cu2+. It was also analyzed the quantum chemical and XPS data on atomic charge distribution for monoligandic bis-beta-diketonate Cu(hfa)(2) and Cu(dpm)(2) complexes. The comparison of calculated and experimental data for monoligandic and hexanuclear complexes revealed the electronic density redistribution on the oxygen and copper atoms in 1 due to the charge transfer interaction between Cu(hfa)(2)- and Cu(dpm)-fragments with participation of the bridging OH-groups, which was confirmed by NBO analysis.

First author: Wu, F, Fate of Cobaltacycles in Cp*Co-Mediated C-H Bond Functionalization Catalysis: Cobaltacycles May Collapse upon Oxidation via Co(IV) Species,
ORGANOMETALLICS, 40, 2624, (2021)
Abstract: Recent reports have identified Cp*Co-based complexes to be powerful catalysts for aromatic C-H bond activation under oxidative conditions. However, little is known about the speciation of Cp*Co species during catalysis. We now show that key intermediates, Cp*Co-III metallacycles derived from 2-phenylpyridine (phpy-H), react swiftly in solution with one-electron oxidants to irreversibly collapse by a cyclocondensation of the organic ligands to afford cationic alkaloids in yields of >70%. A low-temperature EPR analysis of a mixture of the cobaltacycle with the tritylium cation reveals the signatures of trityl and Co(IV)-centered radicals. Electrochemical analyses show that the oxidation of these cobaltacycles is irreversible and gives rise to several products in various amounts, among which the most salient ones are a cationic alkaloid resulting from the cyclocondensation of the phpy and Cp* ligands and the dimeric cation {[Cp*Co](2) (mu-I)(3)}(+). DFT investigations of relevant noncovalent interactions using QTAIM-based NCI plots and intrinsic bond strength indexes suggest a ligand-dependent predisposition by “NCI-coding” for the Co(IV)-templated cyclocondensation, the computed reaction network energy profile for which supports the key roles of a short-lived Co(IV) metallacycle and of a range of triplet state organocobalt intermediates.

First author: Ceylan, YS, Hydride- and halide-substituted Au-9(PH3)(8)(3+) nanoclusters: similar absorption spectra disguise distinct geometries and electronic structures,
Abstract: Ligands dramatically affect the electronic structure of gold nanoclusters (NCs) and provide a useful handle to tune the properties required for nanomaterials that have high performance for important functions like catalysis. Recently, questions have arisen about the nature of the interactions of hydride and halide ligands with Au NCs: hydride and halide ligands have similar effects on the absorption spectra of Au-9 NCs, which suggested that the interactions of the two classes of ligands with the Au core may be similar. Here, we elucidate the interactions of halide and hydride ligands with phosphine-protected gold clusters via theoretical investigations. The computed absorption spectra using time-dependent density functional theory are in reasonable agreement with the experimental spectra, confirming that the computational methods are capturing the ligand-metal interactions accurately. Despite the similarities in the absorption spectra, the hydride and halide ligands have distinct geometric and electronic effects. The hydride ligand behaves as a metal dopant and contributes its two electrons to the number of superatomic electrons, while the halides act as electron-withdrawing ligands and do not change the number of superatomic electrons. Clarifying the binding modes of these ligands will aid in future efforts to use ligand derivatization as a powerful tool to rationally design Au NCs for use in functional materials.

First author: Karmakar, A, Uncovering Halogen Mixing and Octahedral Dynamics in Cs2SnX6 by Multinuclear Magnetic Resonance Spectroscopy,
CHEMISTRY OF MATERIALS, 33, 6078, (2021)
Abstract: Cs2SnX6 (X = Cl, Br, and I) compounds have emerged as promising lead-free and ambient-stable materials for photovoltaic and optoelectronic applications. To advance these promising materials, it is crucial to determine the correlations between physical properties and their local structure and dynamics. Solid-state NMR spectroscopy of multiple NMR-active nuclei (Cs-133, Sn-119, and Cl-35) in these cesium tin(IV) halides has been used to reveal the atomic structure, which plays a key role in the materials’ optical properties. The Sn-119 NMR chemical shifts span approximately 4000 ppm, and the Sn-119 spin-lattice relaxation times span 3 orders of magnitude when the halogen goes from chlorine to iodine in these diamagnetic compounds. Moreover, ultrawideline Cl-35 NMR spectroscopy of Cs2SnCl6 indicates an axially symmetric chlorine electric field gradient tensor with a large quadrupolar coupling constant of ca. 32 MHz, suggesting the presence of a chlorine moiety that is directly attached to Sn(IV) ions. Variable-temperature Sn-119 spin-lattice relaxation time measurements support the presence of dynamics of octahedral SnI6 units in Cs2SnI6. We further show that complete mixed-halide solid solutions of Cs(2)SnCl(x)Br(6-x )and Cs2SnBrxI6-x (0 <= x <= 6) form at any halogen compositional ratio. Sn-119 and Cs-133 NMR spectroscopy resolve the unique local SnClnBr6-n and SnBrnI6-n (n = 0-6) octahedral and CsBrmI12-m (m = 0-12) cuboctahedral environments in the mixed-halide samples. The experimentally observed Sn-119 NMR results are consistent with magnetic shielding parameters obtained by density functional theory computations that were obtained to model the random halogen distribution in mixed-halide analogues. Finally, we demonstrate the difference in the local structures and the optical absorption properties of Cs2SnI6 samples prepared by solvent-assisted and solvent-free synthesis routes.

First author: Islas, R, Metallaborazines: To Be or Not To Be Delocalized,
ACS OMEGA, 6, 19629, (2021)
Abstract: In the current work, the analysis of the electronic delocalization of some metallacycles, based on borazine, was realized by employing magnetic criteria, such as the induced magnetic field and magnetically induced current densities, and electronic criteria, such as adaptative natural density partitioning and the analysis of molecular orbitals. The current metallaborazines were generated from isoelectronic substitutions. The main question is whether the electronic delocalization increases or decreases. The results showed that metal-N bonded borazines could be cataloged as delocalized compounds. On the other hand, the metal-B bonded borazines could be cataloged as nonaromatic (or weak aromatic) compounds based on the results of this analysis.

First author: Persaud, RR, Computational Study of Triphosphine-Ligated Cu(I) Catalysts for Hydrogenation of CO2 to Formate,
Abstract: The catalyzed hydrogenation of CO2 to formate via a triphosphine-ligated Cu(I) was studied computationally at the density functional theory level in the presence of a self-consistent reaction field. Of the four functionals benchmarked, M06 was generally in the best agreement with the available experimentally estimated values. Two bases, DBU and TBD, were studied in the context of two proposed mechanisms in the MeCN solvent. Activation of H-2 was explored by using LCu(DBU)(+) to form LCuH. Dissociation of a ligand arm results in higher barriers to form the key hydride complex, LCuH. The preferred mechanism passes through a transition state, where the H-2 has one H atom interacting with the copper center and the other H atom interacting with the N atom of the base, similar to H2 insertion into a frustrated Lewis pair. There is no significant difference between the choice of a base, DBU or TBD, with respect to the proposed mechanisms. We propose that the experimentally observed differences between DBU and TBD reactivities for this mechanism are due to off-pathway changes.

First author: Jaegers, NR, Impact of Hydration on Supported V2O5/TiO2 Catalysts as Explored by Magnetic Resonance Spectroscopy,
Abstract: Supported vanadium oxide catalysts are important industrial materials for a wide array of chemical transformations. The condition of surface hydration is of particular interest as a reflection of the state of freshly manufactured catalysts prior to their activation in catalytic reactors or under the conditions of photocatalysis where surface vanadia are exposed to moisture. Under such conditions, the surface vanadia species undergo structural changes, as evidenced by V-51 magic-angle spinning nuclear magnetic resonance (V-51 MAS NMR) in this study. For low surface vanadia densities on titania, a modest trend toward the formation of dimeric and oligomeric vanadia species was observed under hydrated conditions when compared to the corresponding dehydrated catalyst, which contains a large abundance of monomeric vanadia species. The incorporation of tungsten oxide into the V2O5/TiO2 catalyst with low surface vanadia density, however, is found to better stabilize the surface vanadia species on the titania support upon hydration than its tungsta-free counterpart. This stabilization is not an intrinsic property of more extensively oligomerized surface vanadia species in the presence of tungsten oxide, which is evidenced by the conditions of high concentrations of surface vanadia oligomers on titania that exhibit dramatic structural changes upon hydration. At high surface vanadia coverage under hydrated environments, the simultaneous observation of polycrystalline V2O5 nanoparticles and a mobile phase of surface vanadia species is apparent, where vanadia species are dissolved in a thin hydration layer on the titania support. These new findings have broad implications on the behavior of other metal-oxide species on high surface oxide supports under hydrated conditions.

First author: Price, JS, Reactions of manganese silyl dihydride complexes with CO2,
POLYHEDRON, 206, 16766, (2021)
Abstract: Under mild conditions (room temperature, 1.1 atm. of CO2), the silyl dihydride complexes [(dmpe)2MnH2(SiHR2)] {R = Ph (1Ph2); Et (1Et2)} reacted rapidly and quantitatively with carbon dioxide to afford [(dmpe)2MnH2{Si(x1-O2CH)R2)}] {R = Ph (2Ph2); Et (2Et2)}; the products of apparent CO2 insertion into the terminal Si-H bond. In addition, room temperature reactions of [(dmpe)2MnH2(SiH2R)] {R = Ph (1Ph); nBu (1Bu)} with CO2 (1.1 atm.) yielded [(dmpe)2MnH2{Si(x1-O2CH)2R)}] {R = Ph (3Ph); nBu (3Bu)} containing two formate substituents on silicon. The latter reactions proceeded in a stepwise fashion, rapidly forming [(dmpe)2MnH2{SiH(x1-O2CH)R}] {R = Ph (4Ph); nBu (4Bu)} intermediates, which then slowly converted into 3Ph and 3Bu. During the syntheses of 3Ph and 3Bu, significant amounts of H2 and previously reported [(dmpe)2Mn (CO)(x1-O2CH)] (5) were also formed. The reaction of [(dmpe)2MnD2(SiH2nBu)] (d2-1Bu) with CO2 was carried out, yielding d2-3Bu as the major reaction product, predominantly (>95%) as [(dmpe)2MnD2{Si(x1-O2CH)2nBu}] featuring two deuteride ligands. DFT calculations to probe the relative energies of silicate [(dmpe)2Mn(r/3H2SiR3)], trans-hydrosilane/hydride (trans-[(dmpe)2MnH(H-SiR3)]), trans-dihydrogen/silyl (trans-[(dmpe)2Mn (H2)(SiR3)]), and lateral-dihydrogen/silyl (cis-[(dmpe)2Mn(H2)(SiR3)]) isomers of 2Ph2, 3Ph, and 4Ph are also reported; the lowest energy structures of 2Ph2 and 3Ph are those of the silicate isomers, consistent with the NMR spectra obtained for 2R2 and 3R. Also, compound 2Ph2 was isolated, and crystallized as the silicate isomer; the solid state structure of 2Ph2 is qualitatively analogous to that of 1Ph2, but the Mn-Si bond in 2Ph2 is significantly shorter {2.2876(7) angstrom vs 2.3176(3) angstrom}.

First author: Cabrera-Trujillo, JJ, Factors Controlling the Aluminum(I)-meta-Selective C-H Activation in Arenes,
Abstract: The so far poorly understood factors controlling the complete meta-selectivity observed in the C-H activation reactions of alkylarenes promoted by aluminyl anions have been explored in detail by means of Density Functional Theory calculations. To this end, a combination of state-of-the-art computational methods, namely the activation strain model of reactivity and energy decomposition analysis, has been applied to quantitatively unveil the origin of the selectivity of the transformation as well as the influence of the associated potassium cation. It is found that the selectivity takes place during the initial nucleophilic addition step where the key LP(Al)->pi*(C=C) molecular orbital interaction is more stabilizing for the meta-pathway, which results in a stronger interaction between the reactants along the entire transformation.

First author: Mason, MM, Prediction of An(III)/Ln(III) Separation by 1,2,4-Triazinylpyridine Derivatives,
Abstract: The effect of frustrated Lewis donors on metal selectivity between actinides and lanthanides was studied using a series of novel organic ligands. Structures and thermodynamic energies were predicted in the gas phase, in water, and in butanol using 9-coordinate, explicitly solvated (H2O) Eu, Gd, Am, and Cm in the +III oxidation state as reactants in the formation of complexes with 2-(6-[1,2,4]-triazin-3-yl-pyridin-2-yl)-1H-indole (Core 1), 3-[6-(2H-pyrazol-3-yl)pyridin-2-yl]-1,2,4-triazine (Core 2), and several derivatives. These complexations were studied using density functional theory (DFT) incorporating scalar relativistic effects on the actinides and lanthanides using a small core pseudopotential and corresponding basis set. A self-consistent reaction field approach was used to model the effect of water and butanol as solvents. Coordination preferences and metal selectivity are predicted for each ligand. Several ligands are predicted to have a high degree of selectivity, particularly when a low ionization potential in the ligand permits charge transfer to Eu(III), reducing it to Eu(II) and creating a half-filled f(7) shell. Reasonable separation is predicted between Cm(III) and Gd(III) with Core 1 ligands, possibly due to ligand donor frustration. This separation is largely absent from Core 2 ligands, which are predicted to lose their frustration due to proton transfer from the 2N to the 3N position of the pyrazole component of the ligands via tautomerization.

First author: Wonanke, ADD, Role of Host-Guest Interaction in Understanding Polymerisation in Metal-Organic Frameworks,
Abstract: Metal-organic frameworks, MOFs, offer an effective template for polymerisation of polymers with precisely controlled structures within the sub-nanometre scales. However, synthetic difficulties such as monomer infiltration, detailed understanding of polymerisation mechanisms within the MOF nanochannels and the mechanism for removing the MOF template post polymerisation have prevented wide scale implementation of polymerisation in MOFs. This is partly due to the significant lack in understanding of the energetic and atomic-scale intermolecular interactions between the monomers and the MOFs. Consequently in this study, we explore the interaction of varied concentration of styrene, and 3,4-ethylenedioxythiophene (EDOT), at the surface and in the nanochannel of Zn-2(1,4-ndc)(2) (dabco), where 1,4-ndc = 1,4-naphthalenedicarboxylate and dabco = 1,4-diazabicyclo[2.2.2]octane. Our results showed that the interactions between monomers are stronger in the nanochannels than at the surfaces of the MOF. Moreover, the MOF-monomer interactions are strongest in the nanochannels and increase with the number of monomers. However, as the number of monomers increases, the monomers turn to bind more strongly at the surface leading to a potential agglomeration of the monomers at the surface.

First author: Rodriguez-Kessler, PL, Evaluation of ultrasmall coinage metal M-13(dppe)(6) M = Cu, Ag, and Au clusters. Bonding, structural and optical properties from relativistic DFT calculations,
Abstract: Ultrasmall ligand-protected clusters are prototypical species for evaluating the variation at the bottom of the nanoscale range. Here we explored the ultrasmall gold-phosphine M-13(dppe)(6) cluster, as a prototypical framework to gain insights into the fundamental similarities and differences between Au, Ag, and Cu, in the 1-3 nm size range, via relativistic DFT calculations. Different charge states involving 8- and 10-cluster electron (ce) species with a 1S(2)1P(6) and 1S(2)1P(6)1D(2) configuration, leading to structural modification in the Au species between Au-13(dppm)(6)(5+) and Au-13(dppm)(6)(3+), respectively. Furthermore, this structural distortion of the M-13 core is found to occur to a lower degree for the calculated Ag and Cu counterparts. Interestingly, optical properties exhibit similar main patterns along with the series, inducing a blue-shift for silver and copper, in comparison to the gold parent cluster. For 10-ce species, the main features of 8-ce are retained with the appearance of several weak transitions in the range. The ligand-core interaction is enhanced for gold counterparts and decreased for lighter counterparts resulting in the Au > Cu > Ag trend for the interaction stabilization. Hence, the Ag and Cu counterparts of the Au-13(dppm)(6) cluster appear as useful alternatives, which can be further explored towards different cluster alternatives for building blocks for nanostructured materials.

First author: Yakimov, A, DNP-SENS Formulation Protocols To Study Surface Sites in Ziegler-Natta Catalyst MgCl2 Supports Modified with Internal Donors,
Abstract: Heterogeneous Ziegler-Natta propylene polymerization catalysts are today responsible for the production of over 90% of polypropylene worldwide. These catalysts comprise an organic internal donor (ID) that coordinates to the MgCl2 support and is key for the formation of active sites with high stereoselectivity. Yet, little is experimentally known about the details of the interaction between the internal donor and the support. Of various spectroscopic techniques, C-13 magic angle spinning solid-state NMR spectroscopy should be a method of choice. However, NMR spectroscopy displays intrinsic low sensitivity, which becomes more critical when addressing surface sites that correspond to only a fraction of the sample (1-2%), hence the difficulty to implement the powerful 2D NMR approaches that enable detailed structure determination. In order to increase the sensitivity of NMR and for surface sites in particular, dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS) was developed to reveal the structural details of surface sites. Here, we use this approach to study the interaction of selected internal donors (1,3-dimethoxy-2,2-dimethylpropane, diisobutylphthalate, di-n-butylphthalate) with the MgCl2 support. Toward this goal, we first investigated factors affecting DNP enhancements for signals corresponding to the internal donor on the support and developed so-called DNP formulation protocol- sample preparation procedure that leads to highest DNP enhancements. Scanning through the effects of internal donor loading, the number of -CH3 groups in the internal donor and their deuteration, as well as MgCl2 particle size allowed us to achieve surface DNP enhancements of 40 on a 600 MHz NMR spectrometer, which corresponds to 1600-fold experimental time savings. This opened up a possibility for remarkably fast 1D and 2D NMR experiments such as H-1-C-13 HETCOR NMR, H-2 MAS NMR, and H{Cl-35} REDOR MAS NMR. Analysis of the results has helped to reveal the NMR signatures of internal donors on the support and to obtain valuable information about the reorientation of the internal donor and its distance to the surface of the support.

First author: Sang, S, Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation,
Abstract: Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M-H bonds that are either too weak to efficiently activate H-2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co-H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H-2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H-2 via HAT.

First author: Tosato, M, Copper Coordination Chemistry of Sulfur Pendant Cyclen Derivatives: An Attempt to Hinder the Reductive-Induced Demetalation in Cu-64/67 Radiopharmaceuticals,
INORGANIC CHEMISTRY, 60, 11530, (2021)
Abstract: The Cu2+ complexes formed by a series of cyclen derivatives bearing sulfur pendant arms, 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), and 1,7-bis[2-(methylsulfanyl)ethyl]-4,10-diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S), were studied in aqueous solution at 25 degrees C from thermodynamic and structural points of view to evaluate their potential as chelators for copper radioisotopes. UV-vis spectrophotometric out-of-cell titrations under strongly acidic conditions, direct in-cell UV-vis titrations, potentiometric measurements at pH >4, and spectrophotometric Ag+-Cu2+ competition experiments were performed to evaluate the stoichiometry and stability constants of the Cu2+ complexes. A highly stable 1:1 metal-to-ligand complex (CuL) was found in solution at all pH values for all chelators, and for DO2A2S, protonated species were also detected under acidic conditions. The structures of the Cu2+ complexes in aqueous solution were investigated by UV-vis and electron paramagnetic resonance (EPR), and the results were supported by relativistic density functional theory (DFT) calculations. Isomers were detected that differed from their coordination modes. Crystals of [Cu(DO4S)(NO3)].NO3 and [Cu(DO2A2S)] suitable for X-ray diffraction were obtained. Cyclic voltammetry (CV) experiments highlighted the remarkable stability of the copper complexes with reference to dissociation upon reduction from Cu2+ to Cu+ on the CV time scale. The Cu+ complexes were generated in situ by electrolysis and examined by NMR spectroscopy. DFT calculations gave further structural insights. These results demonstrate that the investigated sulfur-containing chelators are promising candidates for application in copper-based radiopharmaceuticals. In this connection, the high stability of both Cu2+ and Cu+ complexes can represent a key parameter for avoiding in vivo demetalation after bioinduced reduction to Cu+, often observed for other well-known chelators that can stabilize only Cu2+.

First author: Fowler, PW, Periodoannulenes: A Generalized Annulene-within-an-Annulene Paradigm for Combined sigma and pi Ring Currents,
Abstract: Periodoannulene molecules and ions CxIxq in planar geometry offer examples of systems with the potential for outer sigma and inner pi ring-current double aromaticity, given a sufficient overlap of tangential p(sigma)-orbital manifolds on the large atoms of the outer cycle. Previous theoretical work indicated concentric diatropic currents in the dication C6I62+. Ab initio ipsocentric calculations support an account in terms of frontier-orbital selection rules for current contributions in C6I62+ (and radical C6I6+, implicated in recent experimental work on the oxidation of periodobenzene). A sigma/pi analogue of the annulene-within-an-annulene model is applied here to period() systems based on cyclooctatetraene. Model species C8I8q with charges q = 0, +1, +2, +4, -2 and structures constrained to a planar D-4h symmetry exhibit maps with all combinations of sigma/pi con- and counter-rotation, comprising global sigma ring currents on the iodine perimeter and central pi ring currents on the carbocycle. All can be rationalized by the separate application of the tropicity selection rules to the two subsystems, whether in singlet or triplet states.

First author: Poltarak, P, New O-centered titanium chalcohalide: synthesis and structure of Ti4O(Se-2)(4)Br-6,
Abstract: New O-centered tetranuclear titanium complex Ti4O(Se-2)(4)Br-6 has been prepared from TiSe1.73, Se, SeO2 and Br-2 at moderate temperature by ampule synthesis. Its X-ray crystal structure (monoclinic space group P2(1)/c, a=9.4850(2), b=11.4667(2), c=19.1413(5)angstrom, beta=92.0080(10)degrees, Z=4, V=2080.56(8)angstrom(3)) includes molecular complex Ti4O(Se-2)(4)Br-6 based on fragment {Ti-4(mu(4)-O)} coordinated by diselenide (Se-2)(2-) and bromide bridging ligands. Ti4O(Se-2)(4)Br-6 is a new member of family of O-centered tetranuclear complexes with the fragment {M-4(mu(4)-O)(Q(2))(4)} (M=Ti, Nb, Ta; Q=S, Se, Te); here we discuss its synthetic features, crystal and electronic structure.

First author: Meng, QY, Synthesis and Characterization of Two Isomers of Th@C-82: Th@C-2v(9)-C-82 and Th@C-2(5)-C-82,
INORGANIC CHEMISTRY, 60, 11496, (2021)
Abstract: Actinide endohedral fullerenes have demonstrated remarkably different physicochemical properties compared to their lanthanide analogues. In this work, two novel isomers of Th@C-82 were successfully synthesized, isolated, and fully characterized by mass spectrometry, X-ray single crystallography, UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry. The molecular structures of the two isomers were determined unambiguously as Th@C-2v(9)-C-82 and Th@C-2(5)-C-82 by single-crystal X-ray diffraction analysis. Raman and UV-vis-NIR spectroscopies further confirm the assignment of the cage isomers. Electrochemical gaps suggest that both Th@C-2v(9)-C-82 and Th@ C-2(5)-C-82 possess a stable closed-shell electronic structure. The computational results further confirm that Th@C-2v(9)-C-82 and Th@ C-2(5)-C-82 exhibit a unique four-electron charge transfer from the metal to the carbon cage and are among the most abundant isomers of Th@C-82.

First author: Menzel, JP, Efficient workflow for the investigation of the catalytic cycle of water oxidation catalysts: Combining GFN-xTB and density functional theory,
Abstract: Photocatalytic water oxidation remains the bottleneck in many artificial photosynthesis devices. The efficiency of this challenging process is inherently linked to the thermodynamic and electronic properties of the chromophore and the water oxidation catalyst (WOC). Computational investigations can facilitate the search for favorable chromophore-catalyst combinations. However, this remains a demanding task due to the requirements on the computational method that should be able to correctly describe different spin and oxidation states of the transition metal, the influence of solvation and the different rates of the charge transfer and water oxidation processes. To determine a suitable method with favorable cost/accuracy ratios, the full catalytic cycle of a molecular ruthenium based WOC is investigated using different computational methods, including density functional theory (DFT) with different functionals (GGA, Hybrid, Double Hybrid) as well as the semi-empirical tight binding approach GFN-xTB. A workflow with low computational cost is proposed that combines GFN-xTB and DFT and provides reliable results. GFN-xTB geometries and frequencies combined with single-point DFT energies give free energy changes along the catalytic cycle that closely follow the full DFT results and show satisfactory agreement with experiment, while significantly decreasing the computational cost. This workflow allows for cost efficient determination of energetic, thermodynamic and dynamic properties of WOCs.

First author: Lu, YS, Theoretical insights into origin of graphene oxide acidity and relating behavior of oxygen-containing groups in water,
CARBON, 183, 355, (2021)
Abstract: Understanding the acidic characteristics of graphene oxide (GO) and the relating deprotonation and proton transfer behaviors of oxygen-containing functional groups in the water environment is of great significance for the application of GO nanoscale materials. In this study, firstly, the density functional theory (DFT) method was applied to compute the explicit acidity constant (pK(a)) of the carboxyl and hydroxyl groups on GOs. The good consistency of our results with experiments approves the applicability of the designed thermodynamic cycles for computing the pK(a) of GOs. Secondly, the thermodynamics and kinetics of the deprotonation reactions of GOs in the presence of hydroxyl anions were investigated, quantitatively revealing that it is the carboxyl groups that mainly contribute to the surface charge acquisition of GO. Lastly, specific intramolecular proton transfer pathways were studied energetically, demonstrating that the proton is easily transferred between the adjacent hydroxyl group and the epoxy group on GO basal plane. This process could cause a change in the distribution of surface charge on GO surface, which will be very critical in understanding the surface properties of GOs.

First author: Majid, A, On the prospects of layeredness in tantalum pentoxide,
Abstract: First principles calculations were carried out at different levels of theory to study the structural and electronic properties of Ta2O5 in bulk and slab periodicities. The material behaves as 2D layered material in slab periodicities with the average intra-layer Ta-O bond length 1.7 -1.9 angstrom and average interlayer distance 2.35 angstrom. The investigations also involved periodic energy decomposition analysis (pEDA), potential energy surface (PES) and phonon structure calculations. The electronic properties reveals that conduction band of the material comprises of Ta-d whereas the valence band is of O-p states. The bulk and monolayer are direct band gap semiconductors having respective values of band gap as 0.20 eV and 1.6 eV whereas the material with increase in number of layers exhibited metallic nature due to Ta-d states at Fermi level. The material stabilized as layered with calculated value of exfoliation energy as 30 meV/atom.

First author: Pitesa, T, Combined Surface-Hopping, Dyson Orbital, and B-Spline Approach for the Computation of Time-Resolved Photoelectron Spectroscopy Signals: The Internal Conversion in Pyrazine,
Abstract: A computational protocol for simulating time-resolved photoelectron signals of medium-sized molecules is presented. The procedure is based on a trajectory surface-hopping description of the excited-state dynamics and a combined Dyson orbital and multicenter B-spline approach for the computation of cross sections and asymmetry parameters. The accuracy of the procedure has been illustrated for the case of ultrafast internal conversion of gas-phase pyrazine excited to the B-1(2u)(pi pi*) state. The simulated spectra and the asymmetry map are compared to the experimental data, and a very good agreement was obtained without applying any energy-dependent rescaling or broadening. An interesting side result of this work is the finding that the signature of the 1A(u)(n pi*) state is indistinguishable from that of the B-1(3u)(n pi*) state in the time-resolved photoelectron spectrum. By locating four symmetrically equivalent minima on the lowest-excited (S-1) adiabatic potential energy surface of pyrazine, we revealed the strong vibronic coupling of the (1)A(u)(n pi*) and B-1(3u)(n pi*) states near the S-1 <- S-0 band origin.

First author: Wang, XL, Effect of One-Coordinated Atoms on the Electronic and Optical Properties of ZnSe Clusters,
ACS OMEGA, 6, 18711, (2021)
Abstract: To understand the influence of one-coordinated Zn and Se atoms on the structures, electronic, and optical properties of ZnSe clusters, we investigate the Zn37Se20 clusters employing first-principles theoretical calculations. The Zn37Se20 cluster, constructed from the InP nanocrystal structure, possesses a Zn21Se20 core and 16 one-coordinated surface atoms. The effect of one-coordinated atoms is studied by adding or removing one-coordinated atoms of the Zn37Se20 cluster. The calculations show that the modifications of one-coordinated atoms change slightly the coordination states and bond lengths of the atoms on the cluster surface. The clusters with the same core structure and different amounts of one-coordinated atoms have similar optical spectra, suggesting the importance of the cluster core structure in their optical properties.

First author: Piatek, J, Toward Sustainable Li-Ion Battery Recycling: Green Metal-Organic Framework as a Molecular Sieve for the Selective Separation of Cobalt and Nickel,
Abstract: The growing demand for Li-ion batteries (LIBs) has made their postconsumer recycling an imperative need toward the recovery of valuable metals, such as cobalt and nickel. Nevertheless, their recovery and separation from active cathode materials in LIBs, via an efficient and environmentally friendly process, have remained a challenge. In this work, we approach a simple and green method for the selective separation of nickel ions from mixed cobalt-nickel aqueous solutions under mild conditions. We discovered that the bioinspired microporous metal-organic framework (MOF) SU-101 is a selective sorbent toward Ni2+ ions at pH 5-7 but does not adsorb Co2+ ions. According to the Freundlich isotherm, the adsorption capacity toward Ni2+ reached 100.9 mg.g(-1), while a near-zero adsorption capacity was found for Co2+ ions. Ni2+ removal from aqueous solutions was performed under mild conditions (22 degrees C and pH 5), with a high yield up to 96%. The presence of Ni2+ ions adsorbed on the surface of the material has been proven by solid-state H-1 nuclear magnetic resonance spectroscopy. Finally, the separation of Ni2+ from Co2+ from binary solutions was obtained with approximately 30% yield for Ni2+, with a near-zero adsorption of Co2+, which has been demonstrated by UV-vis spectroscopy. The ion adsorption process of Ni2+ and Co2+ ions was additionally studied by means of classical molecular dynamics calculations (force fields), which showed that the Ni2+ ions were more prone to enter the MOF canals by replacing some of their coordinated water molecules. These results offer a green pathway toward the recycling and separation of valuable metals from cobalt-containing LIBs while providing a sustainable route for waste valorization in a circular economy.

First author: Moitra, T, Capturing Correlation Effects on Photoionization Dynamics,
Abstract: A highly correlated combination of the equation-ofmotion coupled cluster (EOM-CC) Dyson orbital and the multicentric B-spline time-dependent density functional theory (TDDFT)-based approach is proposed and implemented within the single-channel approximation to describe molecular photoionization processes. The twofold objective of the approach is to capture interchannel coupling effects, missing in the B-spline DFT treatment, and to explore the response of Dyson orbitals to strong correlation effects and its influence on the photoionization observables. We validate our scheme by computing partial cross sections, branching ratios, asymmetry parameters, and molecular frame photoelectron angular distributions of simple molecules. Finally, the method has been applied to the study of photoelectron spectra of the Ni(C3H5)(2) molecule, where giant correlation effects completely destroy the Koopmans picture.

First author: Braband, H, Relativity as a Synthesis Design Principle: A Comparative Study of [3+2] Cycloaddition of Technetium(VII) and Rhenium(VII) Trioxo Complexes with Olefins,
INORGANIC CHEMISTRY, 60, 11090, (2021)
Abstract: The difference in [3 + 2] cycloaddition reactivity between fac[MO3(tacn)](+) (M = Re, Tc-99; tacn = 1,4,7-triazacyclononane) complexes has been reexamined with a selection of unsaturated substrates including sodium 4-vinylbenzenesulfonate, norbornene, 2-butyne, and 2-methyl- 3-butyn-2-ol (2MByOH). None of the substrates was found to react with the Re cation in water at room temperature, whereas the Tc-99 reagent cleanly yielded the [3 + 2] cycloadducts. Interestingly, a bis-adduct was obtained as the sole product for 2MByOH, reflecting the high reactivity of a (TcO)-Tc-99-enediolato monoadduct. On the basis of scalar relativistic and nonrelativistic density functional theory calculations of the reaction pathways, the dramatic difference in reactivity between the two metals has now been substantially attributed to differences in relativistic effects, which are much larger for the 5d metal. Furthermore, scalar-relativistic Delta G values were found to decrease along the series propene > norbornene > 2-butyne > dimethylketene, indicating major variations in the thermodynamic driving force as a function of the unsaturated substrate. The suggestion is made that scalar-relativistic effects, consisting of greater destabilization of the valence electrons of the 5d elements compared with those of the 4d elements, be viewed as a new design principle for novel (99)mTc/Re radiopharmaceuticals, as well as more generally in heavyelement coordination chemistry.

First author: Gange, GB, Metal-Free Bond Activation by Carboranyl Diphosphines,
Abstract: We report metal-free bond activation by the carboranyl diphosphine 1-(PBu2)-Bu-t-2-(PPr2)-Pr-i-C2B10H10. This main group element system contains basic binding sites and possesses the ability to cycle through two-electron redox states. The reported reactions with selected main group hydrides and alcohols occur via the formal oxidation of the phosphine groups and concomitant reduction of the boron cage. These transformations, which are driven by the cooperation between the electron-donating exohedral substituents and the electron-accepting cluster, differ from those of “regular” phosphines and are reminiscent of oxidative addition to transition metal centers, thus representing a new approach to metal-free bond activation.

First author: Das, P, Substituent Effects on Electride Characteristics of Mg-2(eta(5)-C5H5)(2): A Theoretical Study,
Abstract: An ab initio study has been carried out on the substituted binuclear sandwich complexes of Mg-2(eta(5)-C5H5)(2). We have checked whether the substitution destroys the electride properties of a complex, as it needs to satisfy several stringent criteria to obtain the status of an electride. The thermochemical results show that the complexes are stable at room temperature and 1 atm pressure. From the analysis of the various electron density descriptors and the natural bond orbital (NBO) for all the complexes, it is confirmed that the Mg-Mg bonds are covalent and the metal-ligand bonds are ionic in nature. The charges on each Mg atom in the studied complexes are +1. Analysis of the electron density descriptors shows the presence of a non-nuclear attractor (NNA) at the middle of the bond formed by the two Mg atoms when attached to the ligands. The electride characteristics are exhibited by all of the designed complexes. We also report the aromaticity behavior and reactivity descriptors of these complexes. The electride characteristics of Mg-2(eta(5)-C5H5)(2) complex get affected on substitution, as both the NNA population and the nonlinear optical properties (NLO) of the complexes are changed.

First author: Jin, JY, Infrared Spectroscopy and Bonding of the B(NN)(3)(+) and B-2(NN)(3,4)(+) Cation Complexes,
Abstract: The boron-dinitrogen cation complexes B(NN)(3)(+) and B-2(NN)(3,4)(+) are produced in the gas phase and are studied by infrared photodissociation spectroscopy in the N-N stretching vibrational frequency region. The geometric and electronic structures are determined by comparison of the experimental spectra with density functional theory calculations. The B(NN)(3)(+) cation is characterized to have a closed-shell singlet ground state with planar D-3h symmetry. The B-2(NN)(3)(+) cation is determined to have a B=B bonded (NN)(2)BBNN structure with C-2v symmetry. Two isomers of the B-2(NN)(4)(+) cation contribute to the experimental spectrum. One is a N-2-tagged complex involving a B-2(NN)(3)(+) core ion. Another one is a B-B bonded B-2(NN)(4)(+) complex with a planar D-2h structure. Bonding analyses reveal that the B-NN interactions in these complexes come mainly from covalent orbital interactions, with the NN -> B sigma donation being stronger than the B -> NN pi back-donation.

First author: Wang, J, Theoretical Study on the Structural-photophysical Relationships of Tetra-Pt Phosphorescent Emitters,
Abstract: Quantitative comprehension of the photophysical process is essential for developing novel highly efficient emitters. Improving the photoluminescence quantum efficiency of Pt (II) complexes is the key to their application as emitters in organic light-emitting diodes (OLEDs). With the help of density functional theory (DFT) calculation, the current contribution addresses the microscopic mechanisms of phosphorescence for Pt (II) complexes including calculations of the spin-orbit couplings integrals, radiative lifetime, rate constants, transition dipole moments, and intersystem crossing (ISC) channels. We found that pushing electrons in N -> Pt direction can effectively shield the non-radiative decay process, thereby improving the phosphorescence emission efficiency. This work would provide useful insight into the molecular engineering for high-efficient emitters.

First author: Sarwono, YP, Solutions of Atomic and Molecular Schrodinger Equations with One-dimensional Function Approach,
Abstract: Rigorous numerical techniques to solve the Schrodinger equation are both interesting and desirable, particularly with one that can include new features beyond the standard methods. In this article, we review one-dimensional function( ID function) approach developed recently by us to obtain the solutions of the Schrodinger equations of atomic and molecular systems where one-dimensional basis functions have been applied to separate components. A uniform real-space grid representation of the electronic wavefunctions is employed; hence, a refinement technique of residual vector correction can be implemented. The ID function approach facilitates such convenient numerical integrations that many problems related with the many-electron multi-center potential molecular integrals are circumvented. The converged energy is obtained from a strictly upper bound one, while the obtained two-electron Schrodinger wavefunction exhibits the electron correlation effect on one-electron distribution. Different from density functional theory or Hartree-Fock with the assumed particle-separability, the obtained solution treats more accurately many-body effect of electron correlation found in the electron-electron repulsion energy.

First author: Higuchi, C, Energy Decomposition Analysis of the Adhesive Interaction between an Epoxy Resin Layer and a Silica Surface,
LANGMUIR, 37, 8417, (2021)
Abstract: We investigate the adhesive interaction energy (Delta E-int) between an epoxy resin and a silica surface using pair interaction energy decomposition analysis (PIEDA), which decomposes Delta E-int into four components: electrostatic (Delta E-es), exchange repulsion (Delta E-ex), charge-transfer (Delta E-ct), and dispersion (Delta E-disp) energies based on quantum chemistry. Our previous study with PIEDA showed that synergistic effects of Delta E-es and Delta E-disp are critical at the interface between an epoxy resin fragment and a hydrophilic surface. The present study is designed to show in detail that the synergistic effects are significant at the interface between an epoxy layer model consisting of 20 epoxy monomers and a hydrophilic silica surface. The ratio of the dispersion energies to the total interaction energies of the layer model shows good agreement with experimental values, that is, the dispersion ratio of the work of adhesion (Wad). The 20 epoxy molecules in the layer model are investigated individually to closely correlate the four decomposed energies with their structural features. Our energy-decomposition analyses show that H-bonding and OH-pi interactions play important roles at the interface between an epoxy resin and a silica surface. PIEDA calculations for the epoxy layer model also show that the region 3.6 angstrom from the silica surface accounts for more than 99% of the total interaction energies.

First author: Forster, A, GW100: A Slater-Type Orbital Perspective,
Abstract: We calculate complete basis set (CBS) limitextrapolated ionization potentials (IPs) and electron affinities (EA) with Slater-type basis sets for the molecules in the GW100 database. To this end, we present two new Slater-type orbital (STO) basis sets of triple-(TZ) and quadruple-zeta (QZ) quality, whose polarization is adequate for correlated-electron methods and which contain extra diffuse functions to be able to correctly calculate EAs of molecules with a positive lowest unoccupied molecular orbital (LUMO). We demonstrate that going from TZ to QZ quality consistently reduces the basis set error of our computed IPs and EAs, and we conclude that a good estimate of these quantities at the CBS limit can be obtained by extrapolation. With mean absolute deviations (MAD) from 70 to 85 meV, our CBS limit-extrapolated IP are in good agreement with results from FHI-AIMS, TURBOMOLE, VASP, and WEST, while they differ by more than 130 meV on average from nanoGW. With a MAD of 160 meV, our EA are also in good agreement with the WEST code. Especially for systems with positive LUMOs, the agreement is excellent. With respect to other codes, the STO-type basis sets generally underestimate EAs of small molecules with strongly bound LUMOs. With 62 meV for IPs and 93 meV for EAs, we find much better agreement with CBS limit-extrapolated results from FHI-AIMS for a set of 250 medium to large organic molecules.

First author: Pandit, V, A solution-processed bis-tridentate iridium(iii) complex-cored dendrimer for green OLEDs,
Abstract: We report the first example of a solution-processable dendronised bis-tridentate iridium(iii) complex composed of a bis(imidazolyl)phenyl ligand with a first-generation biphenyl dendron containing t-butyl surface groups and a 2-pyrazolyl-6-phenylpyridine co-ligand. The non-dendronised analogue and the dendrimer were found to emit green light. Both complexes were found to have a solution photoluminescence quantum yield [PLQY (phi)] of similar to 70% in toluene. The PLQY of both complexes was reduced in the neat film due to intermolecular quenching. However, the dendrimer retained a higher portion of its PLQY (phi = 22% versus 9%) in the neat film due to the dendrons partially shielding the emissive iridium(iii) complex at its core. The solid-state intermolecular interchromophore interactions of the dendronised complex were suppressed by blending with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and the PLQY increased to 65%. The non-dendronised material had insufficient solubility to enable it to be solution processed to form films of sufficient thickness and quality to be used as the emissive material in an organic light-emitting diode (OLED). In contrast, the dendronised complex was amenable to solution coating techniques and simple two-layer OLEDs comprising a neat dendrimer film or films with 10 wt% of the dendrimer in TCTA and an electron transport layer showed green emission with maximum external quantum efficiency of 4.5% and 10.7%, respectively.

First author: Liu, Y, Theoretical Insights into Transplutonium Element Separation with Electronically Modulated Phenanthroline-Derived Bis-Triazine Ligands,
INORGANIC CHEMISTRY, 60, 10267, (2021)
Abstract: In the process of spent fuel reprocessing, it is highly difficult to extract transplutonium elements from adjacent actinides. A deep understanding of the electronic structure of transplutonium complexes is essential for development of steady ligands for in-group separation of transplutonium actinides. In this work, we have systematically explored the potential in-group separation ability of transplutonium elements of typical quadridentate N-donor ligands (phenanthroline-derived bis-triazine, BTPhen derivatives) through quasi-relativistic density functional theory (DFT). Our calculations demonstrate that ligands with electron-donating groups have stronger coordination abilities, and the substitutions of Br and phenol at the 4-position of the 1,10-phenanthroline have a higher effect on the ligand than those at the 5-position. Bonding analysis indicates that the covalent interaction of An(3+) complexes becomes stronger from Am to Cf apart from Cm, which is because the energy of the 5f orbital gradually decreases and becomes energy-degenerate with the 2p orbitals of ligands. The most negative values of binding energies indicate the higher stability of Cf3+ complexes, in line with the larger covalency in the Cf-L bonds compared with An-L (An = Am, Cm, Bk). In addition, electron-donating group phenol can enhance the covalent interaction between ligands and heavy actinides. Consequently, the extraction ability of ligands with electron-donating substituents for heavy actinides is generally stronger than other ligands. Nevertheless, these ligands exhibit diverse separation abilities to in-group actinide recovery. Therefore, the enhancement of covalency does not necessarily lead to the improvement of separation ability, which may be caused by different extraction abilities. Compared with the tetradentate N, O-donor ligands (2,9-diamide-1,10-phenanthrolinel, DAPhen derivatives), species with BTPhen ligands display stronger covalent interaction and higher extraction capacity. In terms of in-group separation ability, the BTPhen ligands seem to have advantages in separation of californium from curium, while the DAPhen ligands possess stronger abilities to separate americium from curium. These results may afford some afflatus for the development of effective agents for in-group separation of transplutonium elements.

First author: Xie, WY, Constructing the bonding interactions between endohedral metallofullerene superatoms by embedded atomic regulation,
Abstract: We present a possible principle that controls intercluster bonding through embedding different kinds of actinide atoms into the centre of fullerenes, thereby exhibiting different bonding forms. Moreover, these superatoms maintain the robustness of electronic structures.

First author: Fagan, JW, Toward quantitative electronic structure in small gold nanoclusters,
Abstract: Ligand-protected gold nanoclusters (AuNCs) feature a dense but finite electronic structure that can be rationalized using qualitative descriptions such as the well-known superatomic model and predicted using quantum chemical calculations. However, the lack of well-resolved experimental probes of a AuNC electronic structure has made the task of evaluating the accuracy of electronic structure descriptions challenging. We compare electronic absorption spectra computed using time-dependent density functional theory to recently collected high resolution experimental spectra of Au-9(PPh3)(8)(3+) and Au-8(PPh3)(7)(2+) AuNCs with strikingly similar features. After applying a simple scaling correction, the computed spectrum of Au-8(PPh3)(7)(2+) yields a suitable match, allowing us to assign low-energy metal-metal transitions in the experimental spectrum. No similar match is obtained after following the same procedure for two previously reported isomers for Au-9(PPh3)(8)(3+), suggesting either a deficiency in the calculations or the presence of an additional isomer. Instead, we propose assignments for Au-9(PPh3)(8)(3+) based off of similarities Au-8(PPh3)(7)(2+). We further model these clusters using a simple particle-in-a-box analysis for an asymmetrical ellipsoidal superatomic core, which allows us to reproduce the same transitions and extract an effective core size and shape that agrees well with that expected from crystal structures. This suggests that the superatomic model, which is typically employed to explain the qualitative features of nanocluster electronic structures, remains valid even for small AuNCs with highly aspherical cores.

First author: Gorantla, SMNVT, Energy Decomposition Analysis Coupled with Natural Orbitals for Chemical Valence and Nucleus-Independent Chemical Shift Analysis of Bonding, Stability, and Aromaticity of Functionalized Fulvenes: A Bonding Insight,
ACS OMEGA, 6, 17798, (2021)
Abstract: The Donor base ligand-stabilized cyclopentadienyl-carbene compounds L-C5H4 (L = H2C, aAAC; (CO2Me)(2)C, Py; aNHC, NHC, PPh3; SNHC; aAAC = acyclic alkyl(amino) carbene, aNHC = acyclic N-hetero cyclic carbene, NHC = cyclic N-hetero cyclic carbene, SNHC = saturated N-hetero cyclic carbene, Py = pyridine) (1a-1d, 2a-2c, 3) have been theoretically investigated by energy decomposition analysis coupled with natural orbitals for chemical valence calculation. Among all these compounds, aNHC = C5H4 (2a) and Ph3P=C5H4 (2c) had been reported five decades ago. The bonding analysis of compounds with the general formula L = C5H4 (1a-1d) [L = (H2C, aAAC, (CO2Me)(2)C, Py] showed that they possess one electron-sharing sigma bond and electron-sharing pi bond between L and C5H4 neutral fragments in their triplet states as expected. Interestingly, the bonding scenarios have completely changed for L = aNHC, NHC, PPh3, SNHC. The aNHC analogue (2a) prefers to form one electron-sharing sigma bond (C-L-CC5H4) and dative pi bond (C-L <- CC5H4) between cationic (aNHC)(+) and anionic C5H4- fragments in their doublet states. Similar bonding scenarios have been observed for NHC (2b) and PPh3 (2c) (P-L-CC5H4, P-L <- CC5H4) analogues. In contrast, the SNHC and C5H4 neutral fragments of SNHC = C5H4 (3) prefer to form a dative s bond (C-SNHC. C-C5H4) and a dative p bond (C-SNHC <- C-C5H4) in their singlet states. The pyridine analogue 1d is quite different from 2c from the bonding and aromaticity point of view. The nucleus-independent chemical shifts of all the abovementioned species (1-3) corresponding to aromaticity have been computed using the gauge-independent atomic orbital approach.

First author: Guo, MD, Gas-phase synthesis and deposition of metal-bipyridine complex [M-bpy(1-2)](+) (M = Ag, Cu),
Abstract: Controllable synthesis of organometallic clusters in the gas phase is a topic of reasonable interest with precisely tunable properties depending on sizes, compositions, and intra-cluster charge-transfer interactions. Here, we have prepared small Ag-n(+) and Cu-n(+) clusters by using a customized magnetron sputtering (MagS) source and observed the gas-phase reactions with 2,2 ‘-bipyridine. It is found that the small silver and copper clusters readily react with bipyridine and form products of [M-bpy(1-2)](+) (M = Ag, Cu). Quantum chemistry calculations reveal that the bipyridine in both [Ag-bpy(1-2)](+) and [Cu-bpy(1-2)](+) takes on cis-conformation with altered N-C-C-N dihedral angles, which is in contrast to the trans-conformation of a free 2,2 ‘-bipyridine molecule itself. In order to unveil the principle of conformational transition, we have fully studied the interactions between the nitrogen atoms of bipyridine and the cationic Ag+ and Cu+, calculated the donor-acceptor orbital overlaps, and analyzed the correlation of their frontier molecular orbital energy levels. Furthermore, by using a soft-landing strategy, we have managed to deposit the [Cu-bpy(2)](+) complex onto the glass substrates coated with Ag nanoparticles, and recorded the surface-enhanced Raman scattering spectra.

First author: Bellucci, N, Bis(CBT)palladium(II) Derivatives (CBT = m-carborane-1-thiolate): Synthesis, Molecular Structure, and Physicochemical Properties of cis-[(bipy)Pd(CBT)(2)] and trans-[(py)(2)Pd(CBT)(2)],
INORGANIC CHEMISTRY, 60, 10478, (2021)
Abstract: The new synthesized Pd-II complex cis-[(bipy)Pd(CBT)(2)] (bipy = 2,2′-bipyridyl; CBT = m-carborane-1-thiolate anion), which is a potential BNCT (boron neutron capture therapy) agent and of structure elucidated by single-crystal X-ray work, has been studied by infrared (IR) and ultraviolet-visible light (UV-vis) spectra and its properties compared with those of the previously reported and also the structurally characterized analogue trans-[(py)(2)Pd(CBT)(2)]. This trans species, prepared via a direct method, was previously isolated from a pyridine solution, consequent to the occurring releasing of the external Pd(CBT)(2) moieties of the porphyrazine macrocycle [{Pd-(CBT)(2)} 4LZn]center dot xH(2)O (L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]-porphyrazinato anion), which is an active photosensitizer in photodynamic therapy (PDT) and a potential bimodal PDT/BNCT agent. The UV-vis spectral behavior of both cis and trans species in CHCl3 solution and in the gas phase has been examined in detail by density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies devoted to explain their distinct behavior observed in the region of 400-500 nm, as determined by the presence in the cis structure of a vicinal arrangement of the two CBT groups, an ensemble of results closely similar to those observed for the macrocycles [{Pd(CBT)(2)}(4)LM]center dot xH(2)O (M = Mg-II(H2O), Zn-II, Pd-II). It has also been experimentally proved the tendency of the cis isomer in CHCl3/pyridine solution to be changed to the respective trans analogue, with conversion occurring in two steps, as interpreted by detailed DFT studies.

First author: Shyama, M, Adsorption properties of amino acid-based ionic liquids (AAILs) on edge fluorinated graphene surface – a DFT study,
MOLECULAR SIMULATION, 47, 1066, (2021)
Abstract: We have investigated the adsorption properties of amino acid-based ionic liquids (AAILs) on edge fluorinated graphene surface (FG). Adsorption of organic ILs on the FG surface occurs via hydrogen bonds (X-H center dot center dot center dot FC), electrostatic interactions, and pi center dot center dot center dot pi interactions. There are large charge transfers between the interfaces, primarily from the lone pair of the fluorine (C-F bond) to the X-H (X = C, N, O) bond of both cations/anions AAILs. These non-conventional reversible hydrogen bridges are essential in surface interactions. However, substantial charge transfer occurs to cations and anions in both aromatic and aliphatic systems, respectively. Interestingly, aromatic AAILs are firmly physisorbed than aliphatic ILs. The inclusion of dispersion corrections increases the accuracy of total binding energy contributions from multiple adsorption interactions and predicts the complex’s kinetic stability. Molar volume values determine the materiality of AAIL/FG to bulk systems.

First author: Escayola, S, Chelation enforcing a dual gold configuration in the catalytic hydroxyphenoxylation of alkynes,
Abstract: The functionalization of alkynes by Au (N-heterocyclic carbene, NHC) complexes via the hydrophenoxylation reaction is a paradigm for the discussion between mono and dual metal catalysis. With the aim of mimicking the framework containing two gold units, achieved with molecular boxes, two NHC ligands were joined here with a chelated chain and this motif was examined in the hydrophenoxylation/hydroalkoxylation reactions through DFT calculations. This synthetic motif transforms the standard hydrophenoxylation intermolecular reaction from an inter- into an intra-molecular nucleophilic attack, when forming the C-O bond. Various chain lengths were tested with regard to the coordination of the alkyne to the cationic NHC-gold(I) center.

First author: Spivak, M, Gating the conductance of extended metal atom chains: a computational analysis of Ru-3(dpa)(4)(NCS)(2) and [Ru-3(npa)(4)(NCS)(2)],
Abstract: The effects of a gate potential on the conductance of two members of the EMAC family, Ru-3(dpa)(4)(NCS)(2) and its asymmetric analogue, [Ru-3(npa)(4)(NCS)(2)](+), are explored with a density functional approach combined with non-equilibrium Green’s functions. From a computational perspective, the inclusion of an electrochemical gate potential represents a significant challenge because the periodic treatment of the electrode surface resists the formation of charged species. However, it is possible to mimic the effects of the electrochemical gate by including a very electropositive or electronegative atom in the unit cell that will effectively reduce or oxidize the molecule under study. In this contribution we compare this approach to the more conventional application of a solid-state gate potential, and show that both generate broadly comparable results. For two extended metal atom chain (EMAC) compounds, Ru-3(dpa)(4)(NCS)(2) and [Ru-3(npa)(4)(NCS)(2)], we show that the presence of a gate potential shifts the molecular energy levels in a predictable way relative to the Fermi level, with distinct peaks in the conductance trace emerging as these levels enter the bias window.

Abstract: Four novel rhenium cluster complexes with the general formula trans-[Re(6)Q(8)(ppy)(4)X-2]center dot n(ppy) (Q = S, Se; X = Cl, Br; ppy = 4-phenylpyridine) are obtained by the interaction of salts Cs-n[Re(6)Q(8)X(6)]center dot 2H(2)O (Q = S, n = 4; Q = Se, n = 3; X = Cl or Br) with a 4-phenylpyridine melt. The single-crystal XRD study shows that the structures of these compounds contain molecular fragments trans-[Re(6)Q(8)(ppy)(4)X-2] packed together with 4-phenylpyridine solvate molecules and connected with these molecules by weak interactions, including hydrogen bonds and pi-stacking of aromatic rings. It is shown that different halide and chalcogenide ligands of the cluster complex form different types of packing. The obtained compounds are insoluble in water and in organic solvents. The crystal samples are luminescent in the red region with emission peaks at 708-718 nm, quantum yields of 0.01-0.03, and emission lifetimes of similar to 4 mu s. The electronic structure of these compounds contains ligand-centered LUMO-LUMO+3 levels localized between metal-centered HOMO and LUMO+4 levels.

First author: Schmitt-Monreal, D, Density-Based Many-Body Expansion as an Efficient and Accurate Quantum-Chemical Fragmentation Method: Application to Water Clusters,
Abstract: Fragmentation methods based on the many-body expansion offer an attractive approach for the quantum-chemical treatment of large molecular systems, such as molecular clusters and crystals. Conventionally, the many-body expansion is performed for the total energy, but such an energy-based many-body expansion often suffers from a slow convergence with respect to the expansion order. For systems that show strong polarization effects such as water clusters, this can render the energy-based many-body expansion infeasible. Here, we establish a density-based many-body expansion as a promising alternative approach. By performing the many-body expansion for the electron density instead of the total energy and inserting the resulting total electron density into the total energy functional of density functional theory, one can derive a density-based energy correction, which in principle accounts for all higher-order polarization effects. Here, we systematically assess the accuracy of such a density-based many-body expansion for test sets of water clusters. We show that already a density-based two-body expansion is able to reproduce interaction energies per fragment within chemical accuracy and is able to accurately predict the energetic ordering as well as the relative interaction energies of different isomers of water clusters.

First author: Khan, MI, Intercalation of Lithium inside Bilayer Buckled Borophene: A First Principles Prospective,
Abstract: It is keen wish of scientists to develop anode materials having low volume expansion and large capacity with high mobility. Therefore, lithium (Li) has been intercalated in bilayer buckled borophene to improved the adsorption energy, theoretical capacity, open circuit voltage (OCV), diffusion barrier, and structural stability. Here, we investigated the bilayer b-borophene as anode material for Li-ion batteries using first principle calculations. The intercalation of Li preserved the metallic nature of borophene and no volume expansion was found for a fully lithiated structure. This theoretical capacity of 1859 mAh/g, diffusion barrier 80 eV, and OCV 0.08 V indicate that intercalation improves said parameters compared to commercially used Graphene and prove it as a potential candidate for anode material in Li-ion batteries.

First author: Berezin, AS, A Halomanganates(II) with P,P’-Diprotonated Bis(2-Diphenylphosphinophenyl)ether: Wavelength-Excitation Dependence of the Quantum Yield and Role of the Non-Covalent Interactions,
Abstract: A [H(2)DPEphos][MnX4] [X = Br, Cl] tetrahalomanganates(II) with P,P’-diprotonated bis[2-(diphenylphosphino)phenyl]ether cation has been designed and investigated in photophysics and EPR terms. The complexes exhibit a green luminescence resulted from the Mn(II) d-d transitions (T-4(1)->(6)A(1)) with the wavelength-excitation dependence of the quantum yield. The solid [H(2)DPEphos][MnBr4] complex exhibits a bright green phosphorescence (lambda(max) = 515 nm) with the high luminescence quantum yield depending on the excitation energy whereas the solid [H(2)DPEphos][MnCl4] complex exhibits a very weak phosphorescence (lambda(max) = 523 nm). The unexpected shorter luminescence lifetime for the [H(2)DPEphos][MnCl4] than for the [H(2)DPEphos][MnBr4] at 300 K can be a result of the higher non-radiative relaxation contribution. On the one hand, the non-covalent PH horizontal ellipsis X(Mn) interactions quench the manganese(II) luminescence. On the other hand, the PH horizontal ellipsis X(Mn) interactions are a pathway of the excitation transfer from [H(2)DPEphos](2+) to [MnX4](2-).

First author: Fornari, RP, A Computational Protocol Combining DFT and Cheminformatics for Prediction of pH-Dependent Redox Potentials,
MOLECULES, 26, 4144, (2021)
Abstract: Discovering new materials for energy storage requires reliable and efficient protocols for predicting key properties of unknown compounds. In the context of the search for new organic electrolytes for redox flow batteries, we present and validate a robust procedure to calculate the redox potentials of organic molecules at any pH value, using widely available quantum chemistry and cheminformatics methods. Using a consistent experimental data set for validation, we explore and compare a few different methods for calculating reaction free energies, the treatment of solvation, and the effect of pH on redox potentials. We find that the B3LYP hybrid functional with the COSMO solvation method, in conjunction with thermal contributions evaluated from BLYP gas-phase harmonic frequencies, yields a good prediction of pH = 0 redox potentials at a moderate computational cost. To predict how the potentials are affected by pH, we propose an improved version of the Alberty-Legendre transform that allows the construction of a more realistic Pourbaix diagram by taking into account how the protonation state changes with pH.

First author: Gholamian, F, Effects of electric fields on Be-7 half-life,
CHINESE PHYSICS C, 45, 4144, (2021)
Abstract: First-principle calculations based on the density functional theory (DFT) method are adopted to investigate the influence of a strong electric field on the Be-7 half-life. Accordingly, electronic structures of Be and BeO are examined in the presence of a homogeneous electric field. The electron density at the nucleus is estimated upon the geometry optimization. Our computations for the Be metal indicate a 0.02% increase in the decay rate of the Be-7 nucleus, corresponding to a 0.02% decrease in the Be-7 half-life, both at 5.14 V/angstrom (0.1 a.u.). Furthermore, it is determined that the decay rate of Be-7 is not considerably altered up to 3.6 V/angstrom in the BeO structure. Our results show that the screening energy of the electron can be dependent on the applied electric field strength. Furthermore, we predict variations in the Coulomb potential at the Be-7 nucleus due to electric field application.

First author: Galembeck, SE, Through-Bond and Through-Space Interactions in [2,2]Cyclophanes,
Abstract: The interpretation of the distortions of the electron distribution in [2,2]cyclophanes (22-CPs) is controversial. Some studies indicate that there is an accumulation of electron density (p) outside the cavity of 22-CPs. The nature of through-space (ts) interaction is still under debate. The relative importance of ts and through-bond (tb) is an open question. In an attempt to clarify these points, we have investigated five 22-CPs and their corresponding toluene dimers by molecular orbitals analysis, electron density difference analysis, some topological analysis of p (quantum theory of atoms in molecules (QTAIM), electron localization function (ELF) and noncovalent interactions (NCI)), and energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV). p is concentrated inside the inter-ring region. All the analyses indicated that ts is predominant. The ts is composed by attractive dispersion and Pauli repulsion, with a small covalent contribution. Except for 1 and 6, all the compounds present inter-ring bond paths.

First author: Ren, YX, Efficient blue thermally activated delayed fluorescence emitters showing very fast reverse intersystem crossing,
Abstract: We report a highly efficient blue thermally activated delayed fluorescence (TADF) emitter, namely, MCz-TXO. MCz-TXO exhibits close energy level matching of the three states: charge transfer (CT) and locally excited triplet states, and a CT singlet state. Owing to the good energy level matching and heavy atom effect of sulfur in the molecular structure, MCz-TXO shows very large experimental rate constant of reverse intersystem crossing (k (RISC)) of similar to 2 x 10(8) s(-1). This is one of the largest k (RISC) values among all reported pure organic TADF emitters. The MCz-TXO based organic light-emitting diodes exhibit blue emission with maximum external quantum efficiency of 17.4%.

First author: Shyama, M, Complexes of criegee intermediate CH2OO with CO, CO2, H2O, SO2, NO2, CH3OH, HCOOH and CH3CH(3)CO molecules – A DFT study on bonding, energetics and spectra,
Abstract: Using high-level quantum chemical methods like CBS-QB3, CCSD(T), PBEPBE, the bonding and energy of the criegee intermediate (CI) CH2OO complexes, with atmospherically abundant gas molecules like H2O, CO, CO2, SO2, NO2, HCOOH, CH3OH and CH3CH3CO are studied. The interaction of CIs with these molecules results in hydrogen-bonded reaction complexes due to the zwitterionic character of CIs. Our findings indicate that CIs interact strongly with HCOOH, CH3OH, H2O and are weakly bonded to CO and CO2. The bonded complex of CIs with SO2 results in heteroozonide adduct. Energy decomposition analysis (EDA) reveals that the weakest interaction of CI with CO differs by 14 kcal/mol from that of the strongest criegee-HCOOH complex. EDA results augment well with the nature of bonding and charge transfer mechanism. Notably, exchange-correlation (XC) energy contributes maximum towards the interaction. Our IR analysis results suggest that CH2 and O-O stretching frequencies of CIs are red-shifted with large charge transfers where distinct CH2 symmetric modes increase the rate in hydrogen-bonded criegee reaction complexes. The electronic transitions in UV absorption spectra show that the excitation wavelengths of CIs complexes with the atmospheric molecules is red-shifted.

First author: Jayaweera, HDAC, Free three-dimensional carborane carbanions,
CHEMICAL SCIENCE, 12, 10441, (2021)
Abstract: Carbon atom functionalization via generation of carbanions is the cornerstone of carborane chemistry. In this work, we report the synthesis and structural characterization of free ortho-carboranyl [C2B10H11](-), a three-dimensional inorganic analog of the elusive phenyl anion that features a “naked” carbanion center. The first example of a stable, discrete C(H)-deprotonated carborane anion was isolated as a completely separated ion pair with a crown ether-encapsulated potassium cation. An analogous approach led to the isolation and structural characterization of a doubly deprotonated 1,1 ‘-bis(o-carborane) anion [C2B10H10](2)(2-), which is the first example of a discrete molecular dicarbanion. These reactive carbanions are key intermediates in carbon vertex chemistry of carborane clusters.

First author: Yang, H, Predictions of Chemical Shifts for Reactive Intermediates in CO2 Reduction under Operando Conditions,
Abstract: The electroreduction of CO2 into value-added products is a significant step toward closing the global carbon loop, but its performance remains far from meeting the requirement of any practical application. The insufficient understanding of the reaction mechanism is one of the major causes that impede future development. Although several possible reaction pathways have been proposed, significant debates exist due to the lack of experimental support. In this work, we provide opportunities for experiments to validate the reaction mechanism by providing predictions of the core-level shifts (CLS) of reactive intermediates, which can be verified by the X-ray photoelectron spectroscopy (XPS) data in the experiment. We first validated our methods from benchmark calculations of cases with reliable experiments, from which we reach consistent predictions with experimental results. Then, we conduct theoretical calculations under conditions close to the operando experimental ones and predict the C 1s CLS of 20 reactive intermediates in the CO2 reduction reaction (CO2RR) to CH4 and C2H4 on a Cu(100) catalyst by carefully including solvation effects and applied voltage (U). The results presented in this work should be guidelines for future experiments to verify and interpret the reaction mechanism of CO2RR.

First author: Bhattacharya, L, Promising small molecule Pechmann dye analogue donors with low interfacial charge recombination for photovoltaic application: A DFT study,
Abstract: A series of donor-acceptor-donor (D-A-D) type small molecule (SM) donors containing Pechmann dye analogues (N, S, O) are designed and their geometrical, optoelectronic, charge transport, and photovoltaic properties are investigated using density functional theory (DFT). The structural modification of the donor backbone has been performed via additional sp(2)-nitrogen heteroatom incorporation in the Pechmann analogue acceptor cores. The N-heteroatom containing SM donors are found to be more air-stable due to having relatively deeper HOMO/LUMO levels than their unsubstituted counterparts. The maximum computed open-circuit voltage (V-oc) is 1.53 V for the N-heteroatom substituted O-Pechmann core based donor. The designed donors are expected to harvest photon energy efficiently as their simulated absorption spectra lie in the visible region (575-724 nm). The N-heteroatom incorporation plays a significant role in lowering the charge recombination rate (K-CR) and increasing the charge separation rate (K-CS) at the SM donor/PC61BM interface. The ratio of interfacial K-CS and K-CR is found to be improved by 10(4) – 10(10) times after sp(2)-nitrogen substitution in the Pechmann analogue cores. The maximum predicted power conversion efficiencies (PCEs) using the Scharber diagram reach up to similar to 9% for the S-analogue of the Pechmann dye core based donor. This study sheds light on promising SM donors based on Pechmann dye analogues with low interfacial charge recombination rates and high charge separation rates and also demonstrates the impact of structural modification of Pechmann dye analogue cores on air-stability and overall photovoltaic performance.

First author: Zhao, RD, Quasi-four-component method with numeric atom-centered orbitals for relativistic density functional simulations of molecules and solids,
PHYSICAL REVIEW B, 103, 31554, (2021)
Abstract: We describe and benchmark the quasi-four-component (Q4C) approach to relativistic density functional simulations of molecules and solids, using precise, numerically tabulated atom-centered orbital (NAO) basis sets to discretize Dirac’s equation. The Q4C approach initially projects the atomic solution to (electron-only) positive-energy states and eventually deals with only two components but retains the precision of traditional four-component (4C) relativistic methods. While Q4C inherently reduces the dimension of the Hamiltonian matrix in diagonalization, the adoption of localized NAO basis functions in solids further limits the computational demand in real space operations, promising a pathway to investigate large and complex systems containing heavy elements with the precision of a 4C method. Here, we first perform validation and benchmark calculations for cohesive properties of a set of diatomic molecules and of previously established periodic model systems (i.e., silver halides). Then we report Q4C relativistic energy band structure benchmarks for a series of 103 periodic materials, including chemical elements up to Bi, and providing quantitative comparisons with more approximate scalar-relativistic and spin-orbit coupled treatments. Finally, we demonstrate the applicability of the method to band structure calculations of simple and complex hybrid organic-inorganic perovskites containing Pb and Bi, i.e., Cs2AgBiCl6 and a larger system (containing 94 atoms per unit cell), (4-FPEA)(2)PbI4 .The effect of full Q4C, compared with scalar relativity, on binding energies can be significant even for relatively light p-orbital bonded main group elements such as Br and I-i.e., 0.3 and 0.6 eV for Br-2 and I-2 binding energies, respectively.

First author: Reant, BLL, Si-29 NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency,
Abstract: We report the use of Si-29 NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s- and f-block metal-silicon bonds. The complexes [M(SitBu(3))(2)(THF)(2)(THF)(x)] (1-M: M = Mg, Ca, Yb, x = 0; M = Sm, Eu, x = 1) and [M(SitBu(2)Me)(2)(THF)(2)(THF)(x)] (2-M: M = Mg, x = 0; M = Ca, Sm, Eu, Yb, x = 1) have been synthesized and characterized. DFT calculations and Si-29 NMR spectroscopic analyses of 1-M and 2-M (M = Mg, Ca, Yb, No, the last in silico due to experimental unavailability) together with known {Si(SiMe3)(3)}(-)-, {Si(SiMe2H)(3)}(-)-, and {SiPh3}(-)-substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound Si-29 NMR isotropic chemical shifts, delta(Si), span a wide (similar to 225 ppm) range when the metal is kept constant, and direct, linear correlations are found between dSi and computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency. The calculations reveal dominant s- and d-orbital character in the bonding of these silanide complexes, with no significant f-orbital contributions. The dSi is determined, relatively, by paramagnetic shielding for a given metal when the silanide is varied but by the spin-orbit shielding term when the metal is varied for a given ligand. The calculations suggest a covalency ordering of No(II) > Yb(II) > Ca(II) approximate to Mg(II), challenging the traditional view of late actinide chemical bonding being equivalent to that of the late lanthanides.

First author: Shao, Y, Two-Channel Model for Electron Transfer in a Dye-Catalyst-Dye Supramolecular Complex for Photocatalytic Water Splitting,
CHEMSUSCHEM, 14, 3155, (2021)
Abstract: To improve the performance of dye-sensitized photoelectrochemical cell (DS-PEC) devices for splitting water, the tailoring of the photocatalytic four-photon water oxidation half-reaction represents a principle challenge of fundamental significance. In this study, a Ru-based water oxidation catalyst (WOC) covalently bound to two 2,6-diethoxy-1,4,5,8-diimide-naphthalene (NDI) dye functionalities provides comparable driving forces and channels for electron transfer. Constrained ab initio molecular dynamics simulations are performed to investigate the photocatalytic cycle of this two-channel model for photocatalytic water splitting. The introduction of a second light-harvesting dye in the Ru-based dye-WOC-dye supramolecular complex enables two separate parallel electron-transfer channels, leading to a five-step catalytic cycle with three intermediates and two doubly oxidized states. The total spin S=1 is conserved during the catalytic process and the system with opposite spin on the oxidized NDI proceeds from the Ru=O intermediate to the final Ru-O-2 intermediate with a triplet molecular O-3(2) ligand that is eventually released into the environment. The in-depth insight into the proposed photocatalytic cycle of the two-channel model provides a strategy for the development of novel high-efficiency supramolecular complexes for DS-PEC devices with buildup and conservation of spin multiplicity along the reaction coordinate as a design principle.

First author: Mattioli, G, Water-biomolecule clusters studied by photoemission spectroscopy and multilevel atomistic simulations: hydration or solvation?,
Abstract: The properties of mixed water-uracil nanoaggregates have been probed by core electron-photoemission measurements to investigate supramolecular assembly in the gas phase driven by weak interactions. The interpretation of the measurements has been assisted by multilevel atomistic simulations, based on semi-empirical tight-binding and DFT-based methods. Our protocol established a positive-feedback loop between experimental and computational techniques, which has enabled a sound and detailed atomistic description of such complex heterogeneous molecular aggregates. Among biomolecules, uracil offers interesting and generalized skeletal features; its structure encompasses an alternation of hydrophilic H-bond donor and acceptor sites and hydrophobic moieties, typical in biomolecular systems, that induces a supramolecular core-shell-like organization of the mixed clusters with a water core and an uracil shell. This structure is far from typical models of both solid-state hydration, with water molecules in defined positions, or liquid solvation, where disconnected uracil molecules are completely surrounded by water.

First author: Klein, BA, Expanding the NMR toolkit for biological solids: oxygen-17 enriched Fmoc-amino acids,
NEW JOURNAL OF CHEMISTRY, 45, 12384, (2021)
Abstract: We report the solid-state O-17 NMR parameters for five previously uncharacterized N-alpha-fluoren-9-yl-methoxycarbonyl-O-t-butyl (Fmoc) protected amino acids. These molecules are critical to constructing synthetic biological systems, like peptides, and provide an avenue for introducing O-17 as an NMR probe nucleus. A multiple-turnover reaction was used to efficiently O-17 label the carboxylic acid moieties of Fmoc-l-isoleucine, Fmoc-l-tryptophan, Fmoc-l-proline, Fmoc-l-tyrosine and Fmoc-l-threonine. Magic-angle spinning (MAS) and non-spinning NMR spectra were obtained at two magnetic field strengths (14.1 and 21.1 T) and the quadrupolar and chemical shift parameters for the carbonyl and hydroxyl sites were determined. Computed NMR parameters using density functional theory (DFT) were found to be in good agreement with experimental results, supporting the identification of minor unprotonated species present. This work continues to highlight O-17 as a sensitive probe nucleus of its local environment and reinforces the importance of developing solid-state O-17 NMR techniques to expand the analytical NMR toolkit for exploring biologically relevant molecules.

First author: Kinoshita, T, Enhancement of Near-Infrared Singlet-Triplet Absorption of Ru(II) Sensitizers for Improving Conversion Efficiency of Solar Cells,
Abstract: Panchromatic photoenergy conversion is one of the most important challenges in the field of solar energy conversion. However, many materials that absorb near-infrared (NIR) light possess a short excitation lifetime, which is often disadvantageous for the energy conversion process. Although the utilization of spin-forbidden transitions is an effective solution to overcome this problem, its absorption coefficient is small. This study proposes a series of phosphine-coordinated Ru(II) sensitizers, denoted as DX4 and DX5, as a carboxy-thiophene anchoring functional group into wideband Ru(II) sensitizers to improve the spin-forbidden transition intensity in the NIR region and the characteristics of dye-sensitized solar cells (DSSCs) that utilize these sensitizers. Isomers DX4 and DX5 with two carboxy-anchoring groups at different positions are synthesized, and their optical properties are analyzed. The incorporation of DX4 and DX5 led to an increase of approximately 20% in the singlet-triplet absorption intensity in the NIR region compared to that obtained using DX6, which does not contain a carboxy-thiophene group. In addition, the difference in the adsorption behavior observed when using DX4 and DX5 on TiO2 surface is analyzed using UV-vis spectroscopy and density functional theory. The results showed that the molecular orientation on the TiO2 surface changed depending on the position of the anchoring groups. Even though the terpyridine ligand with a carboxy-thiophene group has a highly planar pi-conjugated system, the carboxy-thiophene group protected by the methyl ester inhibited the aggregation of the molecule. The DSSCs using DX4 showed panchromatic photoelectric conversion up to 1000 nm, and DX4 achieved an energy conversion efficiency of 10.2%.

First author: Wu, XH, The pivotal alkyne group in the mutual size-conversion of with nanoclusters,
DALTON TRANSACTIONS, 50, 10113, (2021)
Abstract: Herein, density functional theory (DFT) calculations were performed to elucidate the mechanism of the reversible single atom size conversion between [Au-10(DMPP)(4)(C6H11C C)](3+) and [Au-9(DMPP)(4)](3+) (DMPP is 2,2′-bis-(dimethylphosphino)-1,1′-biphenyl, the simplified, theoretical model of the experimentally used 2,2′-bis-(diphenylphosphino)-1,1′-binaphthyl). The presence of a unique alkyne group is pivotal to the nucleophilic attack of the phosphine ligand on the electron-deficient Au-10 core. After that, a formal ligand exchange and facile 1,2-P (of the diphosphine ligand) transfer occur to generate the Au-9 cluster product. By contrast, the absence of the alkyne group results in a relatively electron-rich Au-9 core, and thus an electrophilic attack of the Au(alkyne) complex on the most electron-rich metal sites occurs first. After that, the Au(alkyne) migration on the cluster surface, 1,2-P transfer and core-reconstruction occur successively to generate the thermodynamically highly stable Au-10 cluster product.

First author: Meng, XX, Asymmetric [2+2] cycloaddition of isatin with ketene catalyzed by N, N ‘-dioxide-Sc(III) complex: Mechanism and selectivity,
MOLECULAR CATALYSIS, 510, 10113, (2021)
Abstract: The mechanism and stereoselectivity of the phenylethylketene with isatin catalyzed by a chiral N,N’-dioxide-Sc (III) complex were studied at the B3LYP-D3(BJ)/6-311G(d,p)//B3LYP-D3(BJ)/def2-SVP(SMD,CH2Cl2) theoretical level. The calculations indicated that the reaction occurred in a one-step but asynchronous manner. The fourmembered product was formed by nucleophilic attack of the electron-rich O(2) atom in the N-benzylisatin toward the electron-deficient C(beta) atom in ketene in the initial stage of reaction, which was responsible to the high regioselectivity of the cycloaddition. The pi-pi stacking interaction between two deformed reactants stabilized the corresponding transition state, affording the enantiomer with S,R-configuration as major product in background reactions. The N-benzylisatin coordinated to the Sc3+ in bidentate manner, forming a hexacoordinated scandiumcomplex reactive species in the catalytic process. Different from the non-catalytic reaction, the C-alpha-C-1 bond was formed prior to the construction of C-beta-O-2 bond. The ortho-iPr in the aniline of chiral N,N’-dioxide ligand shielded re-face of isatin, and induced the ketene to attack the isatin from less hindered si-face, leading to good enantioselectivity of product. Suffering from the steric repulsion from benzyl group in N-benzylisatin, the phenylethylketene substrate preferred to approach the si-face of N-benzylisatin with its re-face, affording predominant product with S,S-configuration. Variation of substituent in reactants and ligand structure would modify the shielding degree of ortho-iPr toward prochiral face of isatin, adjusting the stereoselectivity.

First author: Huo, EF, Quantum chemical modeling, synthesis, spectroscopic (FT-IR, excited States, UV-Vis) studies, FMO, QTAIM, NBO and NLO analyses of two new azo derivatives,
Abstract: In this research, we report the results of experimental and density functional theory (DFT)/timedependent DFT analyses of two new azo derivatives that absorb light in the visible range: (E)-2((4-(diethylamino)phenyl)diazenyl)-6-methoxy-3-methylbenzo[d]thiazol-3-ium ( I ) and N,N-diethyl-4-((6methoxybenzo[d]thiazol-2-yl)diazenyl)aniline ( II ) in the presence of water ( I ) and chloroform ( II ). The molecular geometry and excited states of the compounds were investigated, and their natural bond orbital, frontier molecular orbital, quantum theory of atoms in molecules, and nonlinear optical (NLO) parameters were calculated. In addition, Fourier-transform infrared, nuclear magnetic resonance, and ultraviolet/visible spectral parameters were generated from the derived structures and compared to experimental spectral parameters. The practical applicability of the azo derivatives was investigated by determining their electronic and NLO properties, which demonstrated that both molecules have potential for optoelectronic and photonic applications. A high degree of approximation between the calculated and experimental results was demonstrated.

First author: Bettens, T, Towards the understanding of halogenation in peptide hydrogels: a quantum chemical approach,
MATERIALS ADVANCES, 2, 4792, (2021)
Abstract: Non-covalent interactions involving aromatic rings play a central role in many areas of modern chemistry. In medicinal and bioorganic chemistry, the intermolecular interactions between the aromatic side chains of amino acids, such as phenylalanine and tyrosine, are of great interest. To enhance the affinity between such aromatic side chains, halogenation is a promising modification strategy. In the current work, the nature and strength of halogenated pi-pi stacked phenylalanine (Phe) dimers have been investigated using density functional theory, energy decomposition analyses and the non-covalent interaction (NCI) method. Our analysis shows that increasing the degree of halogenation enhances the strength of the stacking interactions and, moreover, the heavier halides (Cl, Br and I) lead to stronger interactions compared to the lighter F. This effect was traced back to local secondary interactions of the halide with the aliphatic C-H bonds of the phenylalanine side chain. Based on the computational findings, a set of peptide hydrogelators was synthesized, and the resulting hydrogel properties were further investigated via dynamic rheometry. Experimental observations can be correlated to the trends found in the theoretical analysis, suggesting that local interactions indeed play a noticeable role in enhancing peptide-based hydrogel strength.

First author: Go, W, Synergistic inhibition effects of hydrophilic monomeric substances on CH4 hydrate as revealed by experimental and computational approaches,
Abstract: In this study, urea (U), acetamide (A), and glycine (G), which are easily decomposable, were suggested as kinetic hydrate inhibitors (KHIs) and potential synergists for CH4 hydrate. The inhibition performance of these substances was evaluated by measuring the onset temperature of CH4 hydrate via both a stirred high-pressure autoclave and a non-stirred high-pressure micro-differential scanning calorimeter. In addition, two quantum mechanics approaches of COnductor-like Screening MOdel for Real Solvents (COSMO-RS) and quantum theory of atoms in molecules (QTAIM), were used to examine the hydrophilicity of the inhibitor candidates and to elucidate the synergism of the inhibitor mixtures. The sigma-profile and sigma-potential analyses using COSMO-RS indicated that the three monomeric substances have a significant potential as gas hydrate inhibitors by forming hydrogen bonds with host water molecules. The experimental results demonstrated that glycine was the best KHI among the three candidates, and either of two combinations (U + A, U + G, and A + G) had synergistic inhibition effects on CH4 hydrate. The A + G mixture showed the lowest onset temperature, i.e., the best synergism. QTAIM analysis showed that when two different inhibitor molecules were bound to the bi-cage hydrate structure, the absolute value of hydrogen bond energy between inhibitors and water molecules was larger compared to the attachment of two identical inhibitor molecules. The overall combined experimental and computational analyses not only suggest the possibility of hydrophilic monomeric substances as potent KHIs but also offer a new way to reveal the mechanism of hydrate inhibition.

First author: Zarate, X, Structure and electronic properties of benzimidazole and cycloheptaimidazole gold N-heterocyclic carbenes,
POLYHEDRON, 205, 4792, (2021)
Abstract: Two related families (one previously experimentally reported and another theoretically proposed) of gold benzimidazole (family 1) and cycloheptaimidazole (family 2) N-heterocyclic carbenes were studied due to the potential application in medicinal chemistry and the resurgence of Au based catalysis. Both families show interesting aromatic properties, which were calculated computationally using the Nucleus Independent Chemical Shift (NICS) indexes, Electron Localization Function (ELF) and the Electrostatic Potential Surface (EPS) maps. The calculation of the NICS indexes, the ELF values and EPS showed that there is a small difference between both families of studied complexes, where family 1 is slightly more aromatic that family 2. Both families showed that the carbene ring has sigma aromaticity, while the six or seven membered rings showed pi aromaticity. To study their spectroscopic properties, Time-Dependent Density Functional Theory (TD-DFT) calculations were performed. These calculations showed that there is almost no contribution from the metal to the observed UV-Vis transitions (all of them showed Ligand to Ligand Charge Transfer (LLCT) character), due to the high stability that the molecular orbitals (MOs) of the gold atom have in the complex.

First author: Jegan, G, Exploring long-chain hexaalkyl phosphoramides for actinide extraction: A combined experimental and theoretical investigation,
INORGANICA CHIMICA ACTA, 525, 4792, (2021)
Abstract: The strong basic nature and amenability of three nitrogen subunits of hexaalkyl phosphoramides (HalP) make them as potential extractants for the recovery of actinides by solvent extraction. The six alkyl groups present in the molecule improve the selectivity and physico-chemical properties (density, solubility, interfacial tension, etc.) of the extractants. In this regard, higher homologs of hexaalkyl phosphoramides such as hexaamyl phosphoramide (HAPA) and hexahexyl phosphoramide (HHPA) were evaluated for the extraction of actinides and fission products. HAPA and HHPA were synthesized in considerable yield by condensation reaction between phosphoryl chloride (POCl3) and the corresponding dialkyl amine. The synthesized compound was purified by column chromatography and characterized by spectroscopic techniques such as NMR (H1, C13, and P31) and IR. The extraction behavior of U(VI), Th(IV), and Pu(IV) was investigated as a function of aqueous phase nitric acid concentration for both the phosphoramides. In addition, physico-chemical properties such as density, solubility of phosphoramides in water and solubility of water in phosphoramides were measured. Results of phosphoramides were compared with the 1.1 M TBP/n-DD under identical conditions. The DFT calculations were performed to study the complexation behavior of phosphoramides with U and Pu. The computed complexation energy for metal-ligand complexes is consistent with the trend established by experimentally measured distribution ratios.

First author: Zeng, Y, Impact of Ligands on Structural and Optical Properties of Ag-29 Nanoclusters,
Abstract: A ligand exchange strategy has been employed to understand the role of ligands on the structural and optical properties of atomically precise 29 atom silver nanoclusters (NCs). By ligand optimization, similar to 44-fold quantum yield (QY) enhancement of Ag-29(BDT)(12-x)(DHLA)(x) NCs (x = 1-6) was achieved, where BDT and DHLA refer to 1,3-benzene-dithiol and dihydrolipoic acid, respectively. High-resolution mass spectrometry was used to monitor ligand exchange, and structures of the different NCs were obtained through density functional theory (DFT). The DFT results from Ag-29(BDT)(11)(DHLA) NCs were further experimentally verified through collisional cross-section (CCS) analysis using ion mobility mass spectrometry (IM MS). An excellent match in predicted CCS values and optical properties with the respective experimental data led to a likely structure of Ag-29(DHLA)(12) NCs consisting of an icosahedral core with an Ag16S24 shell. Combining the experimental observation with DFT structural analysis of a series of atomically precise NCs, Ag29-yAuy(BDT)(12-x)(DHLA)(x) (where y, x = 0,0; 0,1; 0,12 and 1,12; respectively), it was found that while the metal core is responsible for the origin of photoluminescence (PL), ligands play vital roles in determining their resultant PLQY.

First author: Stasyuk, AJ, Photoinduced electron transfer in mechanically interlocked suit[3]ane systems,
Abstract: Suitanes, a new class of two-component mechanically interlocked systems, have recently been developed. In this work, we report a detailed study of photoinduced electron-transfer processes in suit[3]anes consisting of a 3-fold symmetric pyridinium-based (HC6+center dot 6PF(6)(-) ) cage and substituted benzotrithiophenes, as well as other polycyclic aromatic guests. Our analysis of the electronic properties of these complexes shows that electron transfer is favorable for complexes of HC6+center dot 6PF(6)(-) with strong donors, such as thiatruxene, benzotrithiophenes, and benzotrifuran. The photoinduced electron transfer for these complexes occurs on the picosecond time scale. On the contrary, electron transfer does not occur in complexes of HC6+center dot 6PF(6)(-) with benzotristhiazole and benzotrisoxazole. Our results open perspectives for the future design of mechanically interlocked systems for application in photovoltaic devices.

First author: Mayer, M, Relevance of pi-Backbonding for the Reactivity of Electrophilic Anions [B12X11](-) (X=F, Cl, Br, I, CN),
Abstract: Electrophilic anions of type [B12X11] posses a vacant positive boron binding site within the anion. In a comparatitve experimental and theoretical study, the reactivity of [B12X11](-) with X=F, Cl, Br, I, CN is characterized towards different nucleophiles: (i) noble gases (NGs) as sigma-donors and (ii) CO/N-2 as sigma-donor-pi-acceptors. Temperature-dependent formation of [B12X11](-) indicates the enthalpy order (X=CN)>(X=Cl)approximate to(X=Br)>(X=I)approximate to(X=F) almost independent of the NG in good agreement with calculated trends. The observed order is explained by an interplay of the electron deficiency of the vacant boron site in [B12X11](-) and steric effects. The binding of CO and N-2 to [B12X11](-) is significantly stronger. The B3LYP 0 K attachment enthapies follow the order (X=F)>(X=CN)>(X=Cl)>(X=Br)>(X=I), in contrast to the NG series. The bonding motifs of [B12X11CO] and [B12X11N2](-) were characterized using cryogenic ion trap vibrational spectroscopy by focusing on the CO and N-2 stretching frequencies nu(CO) and nu(N2), respectively. Observed shifts of nu(CO) and nu(N2) are explained by an interplay between electrostatic effects (blue shift), due to the positive partial charge, and by pi-backdonation (red shift). Energy decomposition analysis and analysis of natural orbitals for chemical valence support all conclusions based on the experimental results. This establishes a rational understanding of [B12X11](-) reactivety dependent on the substituent X and provides first systematic data on pi-backdonation from delocalized sigma-electron systems of closo-borate anions.

First author: Zhao, ND, Fabrication of cellulose@Mg(OH)(2) composite filter via interfacial bonding and its trapping effect for heavy metal ions,
Abstract: The utilization of renewable biomass cellulose in treating pollution of heavy metal ions (HMIs) is one of overarching and appealing strategies, because it simultaneously satisfies sustainable development and resolves everincreasing environmental issue. In this regard, the composite cellulose@Mg(OH)(2) was prepared via a facile method and explored for its use as water treatment agent. It is demonstrated that the smaller and thinner hexagonal Mg(OH)(2) flakes are constructed onto the cellulose substrate by self-assembling; two components are chemically coupled via hydrogen bonds and Mg-Oc (cellulose oxygen) dative bonds; what’s more, the coupling of cellulose with Mg(OH)(2) (101) facet is much more preferential than with (001) facet. The resultant composite material shows remarkable HMI removal performance: large capacities of 734.9, 595.8 and 1473.1 mg g(-1) for Cd2+, Cu2+ and Pb2+, respectively. Further assisted by good shaping property of the cellulose substrate, the composite is capable of being made into filter, which practically separates HMIs and purifies wastewater with high removal efficiency (99.99%) for Cd2+ even after operating for 110 days and potable water can be obtained. The mechanism is delineated with removal models and characterizations of HMI-recovered products.

First author: Novotny, J, Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes,
INORGANIC CHEMISTRY, 60, 9368, (2021)
Abstract: Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal-ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded C-13 NMR resonances for these compounds in the range of 900-1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)(3) and square-planar Cu(acac)(2) compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the C-13 NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)(3) compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions.

First author: Grabowski, SJ, The coordination of beryllium and magnesium centres in half-sandwich and sandwich compounds,
Abstract: BP86-D3/TZ2P calculations were performed on half-sandwich and sandwich beryllium and magnesium moieties. The Cp–Be2+-X- and Cp–Mg2+-X-, half-sandwich species are considered, where X = Cl or Br while Cp marks the cyclopentadienyl, C5H5-, or pentamethylcyclopentadienyl, C5Me5-, anion; the C5H5- -Be2+-C5H5- and C5H5–Mg2+- C5H5- sandwich species are analysed. The Quantum Theory of Atoms in Molecules (QTAIM), the Natural Bond Orbitals (NBO) and the Energy Decomposition Analysis (EDA) approaches were also applied to analyse these systems. The results of calculations show that beryllium and magnesium species are governed mainly by electrostatic interactions but a covalent character of interactions is also pronounced, more for beryllium systems than for magnesium ones. The EDA calculations show that the Cp-Be and Cp-Mg interactions are stronger and “more covalent” than the corresponding Be-X and Mg-X interactions. The Cambridge Structural Database (CSD) searches were carried out to find half-sandwich and sandwich beryllium and magnesium species that correspond to systems analysed theoretically here.

First author: Becca, JC, A discrete interaction model/quantum mechanical method for simulating surface-enhanced Raman spectroscopy in solution,
Abstract: Since surface-enhanced Raman scattering (SERS) is of considerable interest for sensing applications in aqueous solution, the role that solvent plays in the spectroscopy must be understood. However, these efforts are hindered due to a lack of simulation approaches for modeling solvent in SERS. In this work, we present an atomistic electrodynamics-quantum mechanical method to simulate SERS in aqueous solution based on the discrete interaction model/quantum mechanical method. This method combines an atomistic electrodynamics model of the nanoparticle with a time-dependent density functional theory description of the molecule and a polarizable embedding method for the solvent. The explicit treatment of solvent molecules and nanoparticles results in a large number of polarizable dipoles that need to be considered. To reduce the computational cost, a simple cut-off based approach has been implemented to limit the number of dipoles that need to be treated without sacrificing accuracy. As a test of this method, we have studied how solvent affects the SERS of pyridine in the junction between two nanoparticles in aqueous solution. We find that the solvent leads to an enhanced SERS due to an increased local field at the position of the pyridine. We further demonstrate the importance of both image field and local field effects in determining the enhancements and the spectral signatures. Our results show the importance of describing the local environment due to the solvent molecules when modeling SERS. Published under an exclusive license by AIP Publishing.

First author: Yu, VWZ, Accurate frozen core approximation for all-electron density-functional theory,
Abstract: We implement and benchmark the frozen core approximation, a technique commonly adopted in electronic structure theory to reduce the computational cost by means of mathematically fixing the chemically inactive core electron states. The accuracy and efficiency of this approach are well controlled by a single parameter, the number of frozen orbitals. Explicit corrections for the frozen core orbitals and the unfrozen valence orbitals are introduced, safeguarding against seemingly minor numerical deviations from the assumed orthonormality conditions of the basis functions. A speedup of over twofold can be achieved for the diagonalization step in all-electron density-functional theory simulations containing heavy elements, without any accuracy degradation in terms of the electron density, total energy, and atomic forces. This is demonstrated in a benchmark study covering 103 materials across the Periodic Table and a large-scale simulation of CsPbBr3 with 2560 atoms. Our study provides a rigorous benchmark of the precision of the frozen core approximation (sub-meV per atom for frozen core orbitals below -200 eV) for a wide range of test cases and for chemical elements ranging from Li to Po. The algorithms discussed here are implemented in the open-source Electronic Structure Infrastructure software package.

First author: Yang, X, Unsupported Lanthanide-Transition Metal Bonds: Ionic vs Polar Covalent?,
INORGANIC CHEMISTRY, 60, 9394, (2021)
Abstract: Lanthanide-transition metal complexes continue to be of interest, not only because of their synthetic challenge but also of their promising magnetic properties. Computational work examining the chemical bonding between lanthanides and transition metals in PyCp(2)Ln-TMCp(CO)(2) (DyPyCp22- = [2,6-(CH2C5H3)(2)C5H3N](2-)) reveals strong Ln-TM dative bonds. Gas-phase optimized geometries are in good agreement with experimental structures at the density functional theory (DFT) level with large-core pseudopotentials. From La to Lu, there is a small increase in the bond dissociation energy, as well as a decrease in Ln-Fe bond lengths. Energy decomposition analyses attribute this trend to an increase in the electrostatic contribution from the decreasing bond length and a modest increase in the orbital contribution. The natural bond orbital analysis clearly indicates that 3d(6) “lone pairs” in the [FeCp(CO)(2)](-) fragment act as a Lewis bases donating nearly 0.5 electron to Ln virtual orbitals of mainly d character. The interfragment bonding was also quantified by the quantum theory of atoms in molecules, which indicates that the Ln-Fe bond is more covalent than the Ca-Fe bond in the hypothetical CpCa-FeCp(CO)(2) but less covalent than the Zn-Fe bond in the hypothetical CpZn-FeCp(CO)(2). Further comparisons suggest that to the [PyCp(2)Ln](+) cation the [FeCp(CO)(2)](-) anion appears much like a halide. Overall, these Ln-TM dative bonds appear to have strong electrostatic contributions as well as significant orbital mixing and dispersion contributions

First author: Jensen, F, Computational Chemistry: The Exciting Opportunities and the Boring Details,
Abstract: Computational chemistry has emerged as a sub-field in science over the last five decades, not at least due to the amazing increase in computational resources. Equally important, however, is the continuing developments of theoretical methods and in software technology. The refinement of theoretical models moves forward at a steady pace, but at times takes a radical turn in new directions. Computational chemistry methods are now integrated elements in many research fields and are routine tools for non-experts. The plethora of different models, however, forms a bewildering jungle of choices, often resulting in practitioners defaulting to the tried and true. The present contribution contains some personal reflections on the development of computational chemistry methods over the last four decades, with special focus on the development of basis sets and density functional methods.

First author: Warm, K, Stable, but still reactive – investigations on the effects of Lewis acid binding on copper nitrene intermediates,
Abstract: Copper nitrenes are proposed as reactive intermediates in a number of copper mediated aziridination and amination reactions. However, the isolation and characterization of such intermediates have proved challenging because of their transient nature. One successful approach for the stabilization of the copper-nitrene cores is the employment of a redox innocent Lewis acid (LA) like Sc3+. We herein report the stabilization of two transient copper nitrene species 3 and 4 in the absence of LAs by employing electronegative -CF3 and -NO2 groups in the nitrene substituent. Detailed investigations of the spectroscopic properties of 3 and 4 by theoretical and experimental methods, and a comparison of their reactivities in presence and absence of LAs provide some vital insights into the effect of LAs on the geometric and electronic structures of the copper nitrenes.

First author: Bououden, W, Surface adsorption of Crizotinib on carbon and boron nitride nanotubes as Anti-Cancer drug Carriers: COSMO-RS and DFT molecular insights,
Abstract: In this study, the adsorption mechanisms and interactions between the anticancer molecule Crizotinib (CZT) on the surfaces of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) are investigated. The investigations are carried out using the density functional theory (DFT) and the conductor-like screening model for real solvents (COSMO-RS). The quantum molecular descriptors (QMD) are also computed to explain the drug-carrier interaction mechanism and energy of adsorption. The negative adsorption energies of the complex drug-CNT indicate that adsorption is exothermic. The electrophilicity index of the drug-CNT system is five times greater than that of the drug-BNNT, demonstrating the higher stability of the CNTs with respect to BNNT. Moreover, a stronger interaction is observed for CZT-CNT, using the COSMO-RS method. A solvation study in water also reveals that the CZT-CNT complex is more soluble than CZT-BNNT. Finally, a quantum theory of atoms in molecules (QTAIM) analysis is also applied to investigate the nature of the intermolecular interactions. Based on the obtained results, it can be concluded that CNTs are more stable and better carriers than BNNTs when applied for CZT drug delivery in biological media.

First author: Avagliano, D, QM/MM Nonadiabatic Dynamics: the SHARC/COBRAMM Approach,
Abstract: We present the SHARC/COBRAMM approach to enable easy and efficient excited-state dynamics simulations at different levels of electronic structure theory in the presence of complex environments using a quantum mechanics/molecular mechanics (QM/MM) setup. SHARC is a trajectory surface-hoping method that can incorporate the simultaneous effects of nonadiabatic and spin-orbit couplings in the excited-state dynamics of molecular systems. COBRAMM allows ground- and excited-state QM/MM calculations using a subtractive scheme, with electrostatic embedding and a hydrogen link-atom approach. The combination of both free and open-source program packages provides a modular and extensive framework to model nonadiabatic processes after light irradiation from the atomistic scale to the nano-scale. As an example, the relaxation of acrolein from S-1 to T-1 in solution is provided.

First author: Heshmat, M, Lewis Acidity of Carbon in Activated Carbonyl Group vs. B(C6F5)(3) for Metal-Free Catalysis of Hydrogenation of Carbonyl Compounds,
CHEMPHYSCHEM, 22, 1535, (2021)
Abstract: In this work, using DFT calculations, we investigated Lewis acidities of carbon (in activated carbonyl group) in comparison to the B(C6F5)(3) in combination with dioxane as the Lewis base (LB) for metal-free catalysis of heterolytic H-2 splitting and hydrogenation of carbonyl compounds. We found that in case of carbon as the Lewis acid (LA) the reaction is controlled by frontier molecular orbital interactions between the H-2 and LA-LB fragments at shorter distances. The steric effects can be reduced by electrophilic substitutions on the carbonyl carbon. Synergic combination between stronger orbital interactions and reduced steric effects can lower the barrier of the H-2 splitting below 10 kcal/mol. With the B(C6F5)(3), the H-2 splitting is controlled by electrostatic interactions, which cause to form an early transition state. An advantage of employing Lewis acidity of the activated carbonyl carbon for hydrogenation is that the hydride-type attack and hydrogenation of the C=O bond occur in a single step throughout H-2 splitting. Hence, stronger Lewis acidity of the C(C=O) reinforces hydrogenation without prohibition of the hydride delivery.

First author: Li, XN, Unveiling the In Situ Generation of a Monovalent Fe(I) Site in the Single-Fe-Atom Catalyst for Electrochemical CO2 Reduction,
ACS CATALYSIS, 11, 7292, (2021)
Abstract: Atomically dispersed single-atom catalysts are among the most attractive electrocatalysts for the CO2 reduction reaction (CRR). To elucidate the origin of the exceptional activity of atomically dispersed Fe-N-C catalyst in CRR, we have performed operando Fe-57 Mossbauer spectroscopic studies on a model single-Fe-atom catalyst with a well-defined N coordination environment. Combining with operando X-ray absorption spectroscopy, the in situ-generated four pyrrolic nitrogen atom-coordinated low-spin Fe(I) (LS FeIN4) featuring monovalent iron is identified as the reactive center for the conversion of CO2 to CO. Furthermore, density functional theory calculations reveal that the optimal binding strength of CO2 to the LS (FeN4)-N-I site, with strong orbital interactions between the singly occupied d(z)(2) orbital of the Fe(I) site and the singly occupied pi* orbital of [COOH] fragment, is the key factor for the excellent CRR performance.

First author: Goszczycki, P, The origin of conformational solvatochromism in phenylmethylidene-bis (pyrrolo[2,3-b]quinoxaline) derivative,
DYES AND PIGMENTS, 193, 7292, (2021)
Abstract: Phenylmethylidene-bis(pyrrolo[2,3-b]quinoxaline) derivative (1) was synthesized by the reaction between the 3-thiobenzoylpyrrolo[2,3-b]quinoxaline (SPQ) and a secondary amine or NaOH in DMF solution. The obtained compound was characterized by single crystal X-ray diffraction, which indicated the presence of pair of P and M helical enantiomers in the crystal structure. Molecules of 1 showed positive solvatochromism, with about 40 nm bathochromic shift. The theoretical calculations showed that the solvatochromism of the investigated compound depends on the conformational changes induced by the formation of the hydrogen bond with a strong acceptor. These conformational changes described by the angle between chromophore planes correlate with the solvent polarity.

First author: Rinaldi-Neto, F, Anti-melanoma effect of ruthenium(II)-diphosphine complexes containing naphthoquinone ligand,
Abstract: The use of natural products as potential ligands has been explored as a strategy in the development of metal-based chemotherapy. Since ruthenium complexes are promising alternatives to traditional antitumor agents, this study evaluated the anti-melanoma potential of two ruthenium(II) complexes containing the naphthoquinone ligands lapachol (lap), [Ru(lap)(dppm)(2)]PF6, and lawsone (law), [Ru(law)(dppm)(2)]PF6, in addition to the bis(diphenylphosphino)methane (dppm) ligand, referred to as complexes (1) and (2), respectively, using a syngeneic murine melanoma model. Activation of the apoptotic pathway by the treatments was assessed by immunohistochemistry in tumor tissue. Additionally, toxicity of the treatments was evaluated by variation in body and organ weight, quantification of biochemical indicators of renal damage, and genotoxicity in bone marrow and hepatocytes. First, the antiproliferative activity of (1) and (2) was observed in B16F10 cells, with IC50 values of 2.78 and 1.68 mu M, respectively. The results obtained in mice showed that, unlike complex (1), (2) possesses significant anti-melanoma activity demonstrated by a reduction in tumor volume and mass (88.42%), as well as in mitosis frequency (83.86%). Additionally, complex (2) increased the levels of cleaved caspase-3, inducing tumor cell apoptosis. When compared to the metallodrug cisplatin, complex (2) exhibited similar anti-melanoma activity and lower toxicity considering all parameters evaluated. In silico studies demonstrated no difference in the binding energy of the naphthoquinone complex between complexes (1) and (2). However, the complex containing the lawsone ligand has a lower molar volume, which may be important for interactions with minor DNA grooves. The present results demonstrate the antitumor efficiency of complex (2) and a significantly lower systemic toxicity compared to cisplatin.

First author: Jana, G, H-2 adsorption by noble gas insertion compounds: A computational study,
Abstract: In order to find a solution of energy-related problems, sophisticated hydrogen storing materials are needed as hydrogen is an abundant and environment friendly fuel. We have investigated the hydrogen storage potential of Ng inserted metal acetylide and metal cyanide compounds (metal = Cu, Ag and Au) at the omega B97X-D/cc-pVTZ-PP level of theory. Due to the difference in electronegativity and formal charge on metal atoms in the insertion compounds, the interaction with the hydrogen molecule is expected to be different. The adsorption energies, the free energy of adsorption, natural charges on atomic centers/moieties are obtained through the natural population analysis, and energy decomposition analysis has also been carried out for nH(2)…MNgCCH and nH(2)…MNgCN (n = 1-3). The hydrogen adsorption capacity of the strongest and the weakest cases has also been investigated. Both the insertion compounds, MNgCCH and MNgCN, are found to adsorb a maximum of three hydrogen molecules on the metal site. The single H-2 adsorbed minimum energy structures of studied compounds show a “Tshaped” orientation while double H-2 adsorbed minimum energy structures are of “Y- shaped” geometry and those of tricoordinated structures resemble “Td-like” shape. The negative value of Gibbs free energy change suggests the thermodynamical spontaneity of the hydrogen adsorption process.

First author: Nogara, PA, Methylmercury Can Facilitate the Formation of Dehydroalanine in Selenoenzymes: Insight from DFT Molecular Modeling,
Abstract: Experimental studies have indicated that electrophilic mercury forms (e.g., methylmercury, MeHg+) can accelerate the breakage of selenocysteine in vitro. Particularly, in 2009, Khan et al. (Environ. Toxicol. Chem. 2009, 28, 1567-1577) proposed a mechanism for the degradation of a free methylmercury selenocysteinate complex that was theoretically supported by Asaduzzaman et al. (Inorg. Chem. 2010, 50, 2366-2372). However, little is known about the fate of methylmercury selenocysteinate complexes embedded in an enzyme, especially in conditions of oxidative stress in which methylmercury target enzymes operate. Here, an accurate computational study on molecular models (level of theory: COSMO-ZORA-BLYP-D3(BJ)/TZ2P) was carried out to investigate the formation of dehydroalanine (Dha) in selenoenzymes, which irreversibly impairs their function. Methylselenocysteine as well as methylcysteine and methyltellurocysteine were included to gain insight on the peculiar behavior of selenium. Dha forms in a two-step process, i.e., the oxidation of the chalcogen nucleus followed by a syn-elimination leading to the alkene and the chalcogenic acid. The effect of an excess of hydrogen peroxide, which may lead to the formation of chalcogenones before the elimination, and of MeHg+, a severe toxicant targeting selenoproteins, which leads to the formation of methylmercury selenocysteinate, are also studied with the aim of assessing whether these pathological conditions facilitate the formation of Dha. Indeed, elimination occurs after chalcogen oxidation and MeHg+ facilitates the process. These results indicate a possible mechanism of toxicity of MeHg+ in selenoproteins.

First author: Taylor, JO, Effect of the 2-R-AIIyl and Chloride Ligands on the Cathodic Paths of [Mo(eta(3)-2-R-allyl)(alpha-diimine)(CO)(2)Cl] (R = H, CH3; alpha-diimine=6,6 ‘-Dimethyl-2,2 ‘-bipyridine, Bis(p-tolylimino)acenaphthene),
ORGANOMETALLICS, 40, 1598, (2021)
Abstract: The new, formally Mo(II) complexes [Mo(eta(3)-2-Rallyl)(6,6′-dmbipy)(CO)(2)Cl] (6,6′-dmbipy = 6,6′-dimethyl-2,2′-bipyridine; 2-R-allyl = allyl for R = H, 2-methallyl for R = CH3) and [Mo(eta(3)-2-methallyl)(pTol-bian)(CO)(2)Cl] (pTol-bian = bis-(p-tolylimino)acenaphthene) share, in this rare case, the same structural type. The effect of the anionic pi-donor ligand X (Cl- vs NCS-) and the 2-R-allyl substituents on the cathodic behavior was explored. Both ligands play a significant role at all stages of the reduction path. While 2e(-)-reduced [Mo(eta(3)-allyl)(6,6′-dmbipy)-(CO)(2)](-) is inert when it is ECE-generated from [Mo(eta(3)-allyl)(6,6′-dmbipy)(CO)(2)(NCS)], the Cl- ligand promotes Mo-Mo dimerization by facilitating the nucleophilic attack of [Mo(eta(3)-allyl)(6,6′-dmbipy)(CO)(2)](-) at the parent complex at ambient temperature. The replacement of the allyl ligand by 2-methallyl has a similar effect. The Cl-/2-methallyl ligand assembly destabilizes even primary radical anions of the complex containing the strongly ir-accepting pTol-Bian ligand. Under argon, the cathodic paths of [Mo(eta(3)-2-R-allyl)(6,6′-dmbipy)(CO)(2)Cl] terminate at ambient temperature with 5-coordinate [Mo(6,6′-dmbipy)(CO)(3)](2-) instead of [Mo(eta(3)-2-R-allyl)(6,6′-dmbipy)(CO)(2)](-), which is stabilized in chilled electrolyte. [Mo(eta(3)-allyl)(6,6′-dmbipy)(CO)(2)](-) catalyzes CO2 reduction only when it is generated at the second cathodic wave of the parent complex, while [Mo(eta(3)-2-methallyl)(6,6′-dmbipy)(CO)(2)](-) is already moderately active at the first cathodic wave. This behavior is fully consistent with absent dimerization under argon on the cyclic voltammetric time scale. The electrocatalytic generation of CO and formate is hampered by the irreversible formation of anionic tricarbonyl complexes replacing reactive [Mo(eta(3)-2-methallyl)(6,6′-dmbipy)(CO)(2)](2) along the cathodic route.

First author: Kim, CL, Purely organic phosphorescent organic light emitting diodes using alkyl modified phenoselenazine,
Abstract: Purely organic phosphorescent emitters have been developed with the incorporation of alkyl substituents into the N-phenylphenoselenazine core. The new emitter displayed efficient phosphorescence in amorphous film and featured pure phosphorescence in electroluminescence devices due to strong spin-orbit coupling for triplet to singlet transition. The steric bulk of the alkyl substituent, which could hamper triplet-exciton-quenching, is found to be essential for high efficiency of the device, and the tert-butyl group induces the highest external quantum efficiency (EQE) of 9.0%.

First author: Rousset, E, Molecular engineering for optical properties of 5-substituted-1,10-phenanthroline-based Ru(II) complexes,
DALTON TRANSACTIONS, 50, 10119, (2021)
Abstract: A series of homo- and heteroleptic Ru(II) complexes [Ru(phen)(3-n)(phen-X)(n))(PF6)(2) (n = 0-3, X = CN, epoxy, H, NH2) were prepared and characterized. The influence of electron-withdrawing or electron-releasing substituents of the 1,10-phenanthroline ligands on the photo-physical properties was evaluated. It reveals fundamental interests in the fine tuning of redox potentials and photo-physical characteristics, depending both on the nature of the substitution of the ligand, and on the symmetry of the related homo- or heteroleptic complex. These complexes exhibit linear absorption and two-photon absorption (2PA) cross-sections over a broad range of wavelength (700-900 nm) due to absorption in the intra-ligand charge transfer (ILCT) and the metal-to-ligand charge transfer (MLCT) bands. These 2PA properties were more particularly investigated in the 700-1000 spectral range for a family of complexes bearing electro-donating ligands (phen-NH2).

First author: Shyama, M, Cation-Anion Interactions, Stability, and IR Spectra of Dicationic Amino Acid-Based Ionic Liquids Probed Using Density Functional Theory,
Abstract: In this work, we have theoretically studied the dicationic ionic liquids (DILs) constructed from geminal methylimidazolium dication with varying amino acid anions and spacers using density functional theory. Amino acid-based DILs form via strong C-H center dot center dot center dot O hydrogen bonds. These hydrogen bonds have a significant role in stabilizing the DILs. The higher cation-anion interaction energy in the order of covalent bond energy and liquid density of DILs imply higher thermal stability than their mono analogues. The C-H stretching frequencies are above 3100 cm(-1) in all complexes and form a signature for DILs. Interestingly, aliphatic and aromatic amino acid anions show similar molecular properties. Overall, the DILs formed from amino acids exhibit high stability and large surface tension and are chemically non-toxic; hence, they can replace inorganic DILs.

First author: Zhao, MF, Electron momentum spectroscopy study on inner orbitals of methyl iodide,
Abstract: The binding energy spectrum and electron momentum profiles of the inner orbitals of methyl iodide have been measured using an electron momentum spectrometer at the impact energy of 1200 eV plus binding energy. Two peaks in the binding energy spectrum, arising from the spin-orbit splitting, are observed and the corresponding electron momentum profiles are obtained. Relativistic density functional calculations are performed to elucidate the experimental electron momentum profiles of two spin-orbit splitting components, showing agreement with each other except for the intensity in low momentum region. The measured high intensity in the low momentum region can be further explained by the distorted wave calculation.

First author: Szymanski, S, In Silico Studies on Sennidines-Natural Dianthrones from Senna,
BIOLOGY-BASEL, 10, 281, (2021)
Abstract: Simple Summary The study determines the spatial structure and intramolecular interactions of sennidines-natural pharmaceutical substances present in Senna species. The calculations predict many sennidin conformers with similar energy but the gauche conformation will be present in the plant material. The lowest energy structure that is most likely to be found in plant material is characterized by the presence of OHO hydrogen bonds formed by hydroxyl groups and carbonyl oxygen. The sanidin molecule can be easily breakdown into monoanthrones because of elongation of the single C-C bond linking the anthrone moieties and reduced bond dissociation energy. The work contains data on theoretical, vibrational and electron excitation spectra, which can be used in the analysis of experimental samples. The rapid development of technology allows for more accurate research of biological systems with the use of in silico methods. One of the tools is the quantum-chemical method used for determining the structure, properties and interactions of molecules of great pharmacological importance. The accuracy of theoretical models is increasing and can be a real help in biology, chemistry and pharmacy. The aim of the study is to determine the spatial structure and intramolecular interactions of sennidines-natural pharmaceutical substances present in Senna species. Calculations carried out in the gas-phase and in the solvent model, compared with the available experimental data indicate the possibility of sennidines to form conformers. QTAIM and NCI analysis suggests the presence of many intramolecular interactions in the sennidin structure. Taking into account the lowest energy optimized structure, it can be predicted that the sennidin in the gauche conformation will be present in the plant material. The single C-C bond connecting the anthrone moieties is elongated and its reduced Bond Dissociation Energy (BDE) could be the cause of an easy breakdown of the sennidin molecule into monoanthrones. This work contains data on theoretical, vibrational and electron excitation spectra, which can be used in the analysis of experimental samples.

First author: Nakai, H, Development of Linear-Scaling Relativistic Quantum Chemistry Covering the Periodic Table,
Abstract: This Award Account focuses on the author’s studies on the theoretical developments of two-component (2c) relativistic quantum chemistry calculations for large systems with high efficiency and high accuracy, with a review of related studies as the background. The local unitary transformation scheme allows the linear-scaling computation cost to be applied to construct a 2c Hamiltonian, such as an infinite-order two-component version. The divide-and-conquer scheme can lead to linear-scaling computation costs to apply not only a Hartree-Fock (HF) method but also post-HF methods such as the second-order Moller-Plesset perturbation and couple cluster theory with singles and doubles for the 2c Hamiltonian in addition to a non-relativistic version. The frozen core potential scheme can naturally connect pseudopotential calculations with all-electron calculations. The accompanying coordinate expansion with a transfer recurrence relation scheme provides an efficient algorithm for the rapid evaluation of electron repulsion integrals for systems including heavy elements, the orbitals of which have long contractions and high angular momenta, such as f- and g-orbitals. Illustrative applications will help readers realize the advantages and usefulness of these schemes.

First author: Apostolidis, C, Tris-{Hydridotris(1-pyrazolyl)borato}lanthanide Complexes: Synthesis, Spectroscopy, Crystal Structure and Bonding Properties,
INORGANICS, 9, 1664, (2021)
Abstract: Complexes of trivalent lanthanides (Ln) with the hydridotris(1-pyrazolyl)borato (Tp) ligand Ln[eta(3)-HB(N2C3H3)(3)](3) (LnTp(3)) were subjected to a joint experimental-theoretical analysis. X-ray diffraction experiments have been performed on CeTp(3), NdTp(3), SmTp(3), GdTp(3), and TbTp(3) in the nine-fold coordination and on DyTp(3), HoTp(3), ErTp(3), TmTp(3), YbTp(3), and LuTp(3) in the eight-fold coordination form. Density functional theory (DFT) calculations were carried out for all 15 LnTp(3) complexes. They extended the X-ray diffraction data available on the LnTp(3) compounds and facilitated a straightforward interpretation of trends in the structural parameters. As a result of the joint analysis, significant steric strain in the equatorial coordination sites of the nine-coordinate structures was recognized. Trends in the bonding properties were elucidated by energy decomposition and quantum theory of atoms in molecules (QTAIM) analysis of the electron density distribution. These results revealed the major electrostatic character of the Ln … Tp bonding and fine variation of charge transfer effects across the Ln row.

First author: Wang, XY, Van der Waals enhanced interfacial interaction in cellulose/zinc oxide nanocomposite coupled by graphitic carbon nitride,
CARBOHYDRATE POLYMERS, 268, 1664, (2021)
Abstract: In-depth understanding of interfacial property is the key to guiding the synthesis of biomass composites with desired performance. However, the exploration is of great challenge due to limitations of experimental techniques in locating hydrogen, requiring large/good crystals and detecting a weak interaction like van der Waals (vdW). Herein, we experimentally and computationally investigated the composite cellulose/zinc oxide/g-C3N4. Hydrothermal synthesis afforded cellulose/ZnO, and then fabricated the ternary composite by adding g-C3N4 under ultrasonic condition. Three components are found to co-exist in the composite, and the ZnO nanoparticle is attaching to cellulose and coupling with g-C3N4. These experimental findings were corroborated by relativistic DFT calculations. The interfacial coupling is elaborated as contributions of dative bonds, hydrogen bonds and vdW interaction. The vdW is increased by a factor of 4.23 in the ZnO/g-C3N4 interface. This improves electronhole separation and offers prospective application of the composite in photocatalysis, antibacteria and gas sensing.

First author: Ryzhikov, MR, Chirality and Relativistic Effects in Os-3(CO)(12),
MOLECULES, 26, 1664, (2021)
Abstract: The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os-3(CO)(12) with D-3h and D-3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os-3(CO)(12) corresponds to the D-3 symmetry and thus may be characterized either as left-twisted (D-3S) or right-twisted (D-3R). The D-3S <-> D-3R transitions occur through the D-3h transition state with an activation barrier of similar to 10(-14) kJ/mol. Parity violation energy difference (PVED) between D-3(S) and D-3R states equals to similar to 5 x 10(-10) kJ/mol. An unusual three-center exchange interaction was found inside the {Os-3} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.

First author: Mekapothula, S, Supramolecular Chromatographic Separation of C-60 and C-70 Fullerenes: Flash Column Chromatography vs. High Pressure Liquid Chromatography,
Abstract: A silica-bound C-butylpyrogallol[4]arene chromatographic stationary phase was prepared and characterised by thermogravimetric analysis, scanning electron microscopy, NMR and mass spectrometry. The chromatographic performance was investigated by using C-60 and C-70 fullerenes in reverse phase mode via flash column and high-pressure liquid chromatography (HPLC). The resulting new stationary phase was observed to demonstrate size-selective molecular recognition as postulated from our in-silico studies. The silica-bound C-butylpyrogallol[4]arene flash and HPLC stationary phases were able to separate a C-60- and C-70-fullerene mixture more effectively than an RP-C-18 stationary phase. The presence of toluene in the mobile phase plays a significant role in achieving symmetrical peaks in flash column chromatography.

First author: Stasyuk, OA, [10]CPP-Based Inclusion Complexes of Charged Fulleropyrrolidines. Effect of the Charge Location on the Photoinduced Electron Transfer,
Abstract: A number of non-covalently bound donor-acceptor dyads, consisting of C-60 as the electron acceptor and cycloparaphenylene (CPP) as the electron donor, have been reported. A hypsochromic shift of the charge transfer (CT) band in polar medium has been found in [10]CPP superset of Li+@C-60. To explore this anomalous effect, we study inclusion complexes [10]CPP superset of Li+@C-60-MP, [10]CPP superset of C-60-MPH+, and [10]CPP superset of C-60-PPyMe+ formed by fulleropyrrolidine derivatives and [10]CPP using the DFT/TDDFT approach. We show that the introduction of a positively charged fragment into fullerene stabilizes CT states that become the lowest-lying excited states. These charge-separated states can be generated by the decay of locally excited states on a nanosecond to picosecond time scale. The distance of the charged fragment to the center of the fullerenic cage and its accessibility to the solvent determine the strength of the hypsochromic shift.

First author: Gholamian, F, Change in Be-7 half-life in host media,
CHINESE PHYSICS C, 45, 8737, (2021)
Abstract: First-principle calculations within the density functional theory framework are used to study the probability of electron capture for the Be-7 nucleus. For this purpose, electron density at the Be-7 nucleus is computed in Al, Au, Pd, Pt, and Pb environments. Our results show that the half-life of Be-7 is changed by implanting Be-7 in host environments. Electron affinity of the media and confinement effects are responsible for the change in the half-life of Be-7 nucleus. Moreover, electric potential at the Be-7 nucleus is calculated. Results show that variations in electric potential are usually consistent with those in electron density at the Be-7 nucleus.

First author: Pan, S, Bonding in M(NHBMe)(2) and M[Mn(CO)(5)](2) complexes (M=Zn, Cd, Hg; NHBMe=(HCNMe)(2)B): divalent group 12 metals with zero oxidation state,
Abstract: Quantum chemical studies using density functional theory were carried out on M(NHBMe)(2) and M[Mn(CO)(5)](2) (M=Zn, Cd, Hg) complexes. The calculations suggest that M(NHBMe)(2) and M[Mn(CO)(5)](2) have D-2d and D-4d symmetry, respectively, with a (1)A(1) electronic ground state. The bond dissociation energies of the ligands have the order of Zn > Cd > Hg. A thorough bonding analysis using charge and energy decomposition methods suggests that the title complexes are best represented as NHBMe&leftrightarrows;M-0 reversible arrow NHBMe and Mn(CO)(5)&leftrightarrows;M-0 reversible arrow Mn(CO)(5) where the metal atom M in the electronic ground state with an ns(2) electron configuration is bonded to the (NHBMe)(2) and [Mn(CO)(5)](2) ligands through donor-acceptor interaction. These experimentally known complexes are the first examples of mononuclear complexes with divalent group 12 metals with zero oxidation state that are stable at ambient condition. These complexes represent the rare situation where the ligands act as a strong acceptor and the metal center acts as strong donor. The relativistic effect of Hg leads to a weaker electron donating strength of the 6s orbital, which explains the trend of the bond dissociation energy.

First author: Muravieva, VK, Synthesis, Structure, and Spectroscopic Study of Redox-Active Heterometallic Cluster-Based Complexes [Re5MoSe8(CN)(6)](n),
INORGANIC CHEMISTRY, 60, 8838, (2021)
Abstract: The heterometallic cluster-based compound K-5[Re5MoSe8(CN)(6)] was obtained by high-temperature reaction from a mixture of ReSe2 and MoSe2 in molten potassium cyanide. The redox behavior of the [Re5MoSe8(CN)(6)](5-) cluster anion was studied by cyclic voltammetry in aqueous and organic media showing two reversible one- electron-redox transitions with E-1/2 of -0.462 and 0.357 V versus Ag/AgCl in CH3CN. Aqueous media potentials were found to be noticeably shifted to higher values because of solvation. Chemically accessible potentials allowed us to structurally isolate and characterize the [Re5MoSe8(CN)(6)]n (n = 3-, 4-, and 5-) cluster complex in several charge states with corresponding cluster skeletal electron (CSE) numbers ranging from 24 to 22. The electronic absorption of the [Re5MoSe8(CN)(6)](n) cluster complex varies significantly upon a change of the CSE number, especially in the visible and near-IR regions. The local cluster core distortion upon electron removal was confirmed by density functional theory calculation, while the overall geometry of the cluster anion remained practically unaltered.

First author: Lin, PP, Unveiling the effects of substituents on the packing motif and the carrier transport of dinaphtho-thieno-thiophene (DNTT)-based materials,
NEW JOURNAL OF CHEMISTRY, 45, 11552, (2021)
Abstract: Molecular modification plays an important role in tuning the packing motif and charge transport in organic semiconductor materials. In particular, electron-withdrawing substituents and functional heteroatoms have seen a recent surge of interest. Here, we modeled four crystal structures of dinaphtho-thieno-thiophene (DNTT) derivatives with the trifluoromethyl (-CF3) group and heteroatoms (O- and N-atoms), and elaborately delineated the impact of intermolecular interactions to establish the relationship between microscopic molecular structures and macroscopic solid-state packing. The effects of -CF3, O-, and N-atom positions on the charge transport properties were systematically investigated via multi-scale theoretical simulations. The results show that the reorganization energy and frontier molecular orbital energy levels are more sensitive to the positions of O- and N-atoms than the -CF3 position. Significantly, the substitution of heteroatoms on the terminal benzene ring can lead to ambipolar materials after introducing -CF3. The cooperative effect of -CF3, O-, and N-atom substitution can transform the molecular packing from herringbone-stacking to pi-stacking. The simultaneous introduction of -CF3 in the trans-position and O-, and N-atoms in the terminal benzene ring can bring the most compact packing and more hydrogen bonds. Besides, the transfer integral fluctuation caused by the position of -CF3 is more intense than that of O- and N-atoms, which originated from the long- and short-axis sliding motions that act as “killer” phonon modes. Our work shows that suitable substituent engineering on p-channel materials might simultaneously realize changes in molecular packing and carrier transport, paving the way toward designing higher-performance specific ambipolar transport materials.

First author: Theetharappan, M, A Water-Soluble Schiff Base Turn-on Fluorescent Chemosensor for the Detection of Al3+ and Zn2+ Ions at the Nanomolar Level: Application in Live-Cell Imaging,
Abstract: A water-soluble Schiff base, 2,3-bis((E)-(2-hydroxy-3-methoxybenzylidene)amino) propanoic acid (ODA) prepared by condensing o-vanillin and DL-2,3-diaminopropionic acid was evaluated as an efficient “turn on” fluorescent chemosensor for the selective recognition of Al3+ and Zn2+ ions in presence of several interfering metal ions (detection limit; for Al3+ = 1.82 nM, Zn2+ = 7.06 nM). The probe also shows a selective chromogenic behavior towards Al3+ and Zn2+ ions that the naked eye can view. The binding stoichiometry was determined using H-1-NMR titration and ESI-MS spectrometry. The sensing mechanism is due to the inhibition of ESIPT and isomerization of -C=N of ODA on complexation with Al3+/Zn2+. The intramolecular hydrogen bonding energy and the critical bond energy in ODA-Al3+/Zn2+ were calculated using QTAIM analysis. The Thin Layer Chromatography (TLC) plates and strip papers loaded with ODA were used to test the practical applications for sensing Al3+ and Zn2+ ions. Moreover, the probe has been used for live-cell imaging to detect Al3+ and Zn2+ ions in hepatoma C3A and human glioblastoma U87 cells.

First author: Heijmans, K, Development of a reactive force field for CaCl2 center dot nH(2)O, and the application to thermochemical energy storage,
Abstract: Calcium chloride salt hydrates (CaCl2 center dot nH2O) have a high potential to be used as thermochemical storage material (TCM). However, specific material properties – e.g., slow diffusion, low thermal conductivity, melting temperature, and crystal stability – inhibits further implementation as robust TCM. Inherent bulk crystal defects like cracks, pores, and grain boundaries promoted during the (de) hydration cycle of the TCM, affect these material properties. Reactive force field molecular dynamics (ReaxFF-MD) is used to investigate CaCl2 center dot nH2O (physical and chemical) properties, as well as the effect of crystal defects on them. In this sense, a new ReaxFF force field is developed, which can describe stable CaCl2 center dot nH2O structures, accurate descriptions of crystal surface energies, and multiple material indicators like charges, reaction enthalpies, and radial distribution functions. The new force field is further used to investigate the thermal conductivity, dehydration echanisms/kinetics, and crack formation upon heating of the crystal. The thermal conductivity is found to be 1.1 and 0.5 W/mK for respectively CaCl2 and CaCl2 center dot 2H2O, which is in good agreement with experimental results. Additionally, we investigated the influence of grain boundaries and the salts’ anisotropic crystal morphology and found that both grain boundaries and the typical layered structure in z-direction lower the thermal conductivity. By investigating dehydration mechanisms, it is shown that initial dehydration is 1.9-2.5 times lower in the z-direction, also due to the typical layered morphology. For all directions, superficial dehydrated CaCl2 layers impede dehydration of core layers, but cracks and pores significantly promote it. These molecular-scale findings reveal nanoscale opportunities that could benefit the TCM.

First author: Yonezawa, AF, Stability Changes in Iridium Nanoclusters via Monoxide Adsorption: A DFT Study within the van der Waals Corrections,
Abstract: Small iridium nanoclusters are prominent subnanometric systems for catalysis-related applications, mainly because of a large surface-to-volume ratio, noncoalescence feature, and tunable properties, which are completely influenced by the number of atoms, geometry, and molecular interaction with the chemical environment. Herein, we investigate the interaction between Ir-n nanoclusters (n = 2-7) and polluting molecules, CO, NO, and SO, using van der Waals D3 corrected density functional theory calculations. Starting from a representative structural set, we determine the growth pattern of the lowest energy unprotected Ir-n nanoclusters, which is based on open structural motifs, and from the adsorption of a XO (X = C, N, and S) molecule, the preferred high-symmetric adsorption sites were determined, dominated by the onefold top site. For protected systems, 4XO/Ir-4 and 6XO/Ir-6, we found a reduction in the total magnetic moment, while the equilibrium bonds of the nanoclusters expanded (contracted) due to mCO and mNO (mSO) adsorption, with exceptions for systems with large structural distortions (4SO/Ir-4 and 6NO/Ir-6). Meanwhile, the C-O and N-O (S-O) bond strength decreases (increases) following an increase (decrease) in the C-O and N-O (S-O) distances upon adsorption. We show, through energetic analysis, that for the different chemical environments, relative stability changes occur from the most stable unprotected nanoclusters, planar square (Ir-4), and prism (Ir-6) to higher energy isomers. The change in the stability order between the two competing protected systems is feasible if the balance between the interaction energy (additive term) and distortion energies (nonadditive terms) compensates for the relative total energies of the unprotected configurations. For all systems, the interaction energy is the main reason responsible for stability alterations, except for 4SO/Ir-4, where the main contribution is from a small penalty due to Ir-4 distortions upon adsorption, and for 4NO/Ir-4, where the energetic effects from the adsorption do not overcome the difference between the binding energies of the unprotected nanoclusters. Finally, from energy decomposition and Hirshfeld charge analysis, we find a predominant covalent nature of the physical contributions in mOX…Ir-n interactions with a cationic core (Ir-n) and an anionic shell (XO coverage).

First author: Sorbelli, D, Tuning the Gold(I)-Carbon sigma Bond in Gold-Alkynyl Complexes through Structural Modifications of the NHC Ancillary Ligand: Effect on Spectroscopic Observables and Reactivity,
Abstract: Understanding the features of the gold(I)-carbon sigma bond and its modulation induced by an ancillary ligand has become fundamental for the purposes of ligand design, due to the increasing interest towards gold(I)-alkynyl complexes and their wide range of applications. We carry out a systematic computational analysis of 16 gold(I)-acetylide complexes bearing different N-Heterocyclic Carbenes (NHCs) as ancillary ligands [NHC-Au(I)-CCH]. The results show that the strength and features of the Au-C bond can be efficiently tuned by performing specific structural modifications on the NHC, enabling a more efficient pi communication between the alkynyl and the ancillary ligand. We also demonstrate that the effect of the bond modulation can be revealed via NMR spectroscopy, as highlighted by the tight correlation between the computed nuclear shielding constants and the bonding parameters. Finally, we show that, for the dual-gold-catalyzed Bergman cyclization as case study, suitable structural modifications on the NHC ligand, which modulate the pi-acidity of the metal fragment sigma-coordinated to an enediyne substrate, could affect the reaction barrier and the thermodynamic stability of the product. All the reported results can be well rationalized in the framework of distortion/interaction analysis, which has been recently extended to the dual (sigma,pi-type) Au catalytic systems by Alabugin et al (J. Am. Chem. Soc. 2017, 137, 3406-3416).

First author: Ramirez, M, Origins of Endo Selectivity in Diels-Alder Reactions of Cyclic Allene Dienophiles,
Abstract: Strained cyclic allenes, first discovered in 1966 by Wittig and co-workers, have recently emerged as valuable synthetic building blocks. Previous experimental investigations, and computations reported here, demonstrate that the Diels-Alder reactions of furans and pyrroles with 1,2-cyclohexadiene and oxa- and azaheterocyclic analogs proceed with endo selectivity. This endo selectivity gives the adduct with the allylic saturated carbon of the cyclic allene endo to the diene carbons. The selectivity is very general and useful in synthetic applications. Our computational study establishes the origins of this endo selectivity. We analyze the helical frontier molecular orbitals of strained cyclic allenes and show how secondary orbital and electrostatic effects influence stereoselectivity. The LUMO of carbon-3 of the allene (C-3 is not involved in primary orbital interactions) interacts in a stabilizing fashion with the HOMO of the diene in such a way that the carbon of the cyclic allene attached to C-1 favors the endo position in the transition state. The furan LUMO, allene HOMO interaction reinforces this preference. These mechanistic studies are expected to prompt the further use of long-avoided strained cyclic allenes in chemical synthesis.

First author: Zarroug, R, Decavanadate salts of piperidine and triethanolamine: A combined experimental and theoretical study,
Abstract: Two novel decavanadate salts with organic cations, (C5H12N)(4)[H2V10O28]center dot 3.25H(2)O (I) and (C6H12N(OH)(3))(2)[H4V10O28]center dot 10H(2)O (II), have been synthesized in aqueous solution and characterized by IR, UV-Vis spectroscopies, EDX-SEM and single crystal X-Ray diffraction completed by DFT calculations. The asymmetric unit of (C5H12N)(4) [H2V10O28]center dot 3.25H(2)O is composed of one decavanadate [H(2)V(10)O(2)8](4-), four piperidinium cations and water molecules. The structures of (II) is based on one decavanadate cluster, two triethanolaminum cations (TEAH)(+) and ten water molecules. The cohesion of the crystal packing in both compounds is provided by a complex network of N-H center dot center dot center dot O, O-w-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds involving water molecules and organic molecules as well as vander Waals interactions for the connection between the organic molecules. The IR spectra confirmed the presence of organic cations, decavanadate (V10O28)(6-) groups and water molecules. The UV-Vis diffuse reflectance spectrum shows that these compounds exhibit semiconducting behavior with an optical band gap of 2.22 eV and 2.13 eV, respectively for compound (I) and (II). Furthermore the Hirshfeld surface analysis shed more light on the intermolecular interactions occurring in the two crystals and the structure-properties relationships.

First author: Srivastava, A, New Greener and Sustainable Methodology for Direct Sequestering and Analysis of Uranium Using a Maline Supramolecular Scaffold and Mechanistic Understanding through Speciation and Interaction Studies,
Abstract: Research, based on the development of an economical innovative green technology, is the quintessential requirement for the advancement of the nuclear fuel cycle (NFC). The present studies show that Maline, with a preorganized supramolecular scaffold, would be considered as the workhorse for its potential efficacy in diverse facets of the NFC, specifically as an elegant metal hijacker for processing of uranium (U) matrices, designer solvent for green analysis of U, and a promising U chelator for a greener alternative for the cleanup of U contamination. Seven U matrices (UO3, UN, UO2, Rb2U(SO4)(3), U metal, U3Si2, and (U, Pu)O-2) were dissolved in Maline without any external additives and cyclic voltammetry was performed to investigate the redox speciation, viz., redox thermodynamics (E-p and E-f) and kinetic (D-0, k(0), and an) parameters and mechanistic electron transfer of the dissolved U species. To get an insight into the molecular speciation, the structural analysis on UO3 dissolved in Maline was conducted by extended X-ray absorption fine structure, which indicates an interesting observation of the formation of UO22+ kind of species with malonic acid and H2O at equatorial coordination. Molecular dynamics and density functional theory simulations were carried out to acquire diffusion, optimized structure, binding energy, and molecular orbital diagram of U species in Maline, to corroborate the experimental results and to shed light on the hydrogen-bond network in Maline with aqueous dilution. The interaction of uranyl with Maline was probed by luminescence, absorption spectroscopy, and calorimetry titration. Green analysis methodology was developed based on Maline digestion followed by voltammetric determination of U in nuclear material samples. Green chemistry metrics were evaluated to authenticate the greener aspects of the present methodology. The present developed methodology of direct sequestration and analysis of U matrices represents an appropriate replacement of the existing method, viz., hazardous acidic processing of U matrices followed by biamperometry analysis.

First author: Swanson, WB, Direct experimental P-31 2D DOSY NMR evidence for oligomerization of transition-metal substituted polyoxotungstates in nonpolar solvents,
POLYHEDRON, 204, 7846, (2021)
Abstract: Transition-metal substituted polyoxotungstates (TMSPOTs) dissolved in toluene, where they form surfactant encapsulated clusters (SEC), have been recognized as potential catalysts for carbon dioxide activation. Therefore, their detailed structures in toluene are of great interest. This paper reports the first direct experimental evidence, based on 31-P 2D DOSY NMR, for the oligomerization of TMSPOTs in dry toluene. Two kinds of experiments are described in this paper. First, the 31-P 2D DOSY NMR data in aqueous solutions confirmed the reliability of 31-P 2D DOSY NMR for the determination of diffusion coefficients for the phospho-polyoxotungstates (P-POT) of various shapes. Second, 31-P 2D DOSY NMR for toluene solutions of tetraheptylammonium (THA) salts of cobalt- and nickel- substituted Keggin POTs (PW11Co and PW11Ni) and Weakley Co-POTs (P2W18Co4) showed the existence in the solution of polyoxotungstates with various sizes. For Keggin POTs (with one exchangeable water molecule) the slower and faster diffusing species were identified as the dimers and monomers, respectively. For Weakley POTs, with two exchangeable water molecules, the slower diffusing species is much greater than a dimer. The experimental results are in agreement with the results determined computationally using DFT method.

First author: Celis-Barros, C, Computational Investigation of the Bonding in [(eta(5)-Cp ‘)(3) (eta(1)-Cp ‘)M](1-) (M = Pu, U, Ce),
ORGANOMETALLICS, 40, 1577, (2021)
Abstract: Despite the similar ionic radii for Ce3+, U3+, and Pu3+, [(eta(5)-Cp’)(3)(eta(1) -Cp’)Ce](1-) (Cp’ = C5H4SiMe3, 1-Ce) displays a significantly longer eta(1)-Cp’ distance in the solid state compared to the U3+ and Pu3+ analogues. To better understand this observation, a theoretical investigation was undertaken to examine the differences in bonding between the actinides 1-Pu and 1-U and how they compare with 1-Ce. The results show that although the bonding is largely ionic and dominated by ligand (2p)-metal (6d/Sd) interactions, the polarization of Sf orbitals plays a significant role for 1-Pu and 1-U compared to the 4f-orbitals of 1-Ce. The lack of Ce(4f) interactions is compensated for by increased participation of the Ce(5d) orbitals relative to the actinide 6d orbitals, particularly for the sigma-bound eta(1)-Cp’ ligand. The use of multiple theoretical approaches including topological, localization, and energy decomposition approaches shows that 1-Pu and 1-U are very similar in covalent character compared to 1-Ce, though the composition and energy of the different interactions suggest that 1-U presents the strongest overall interactions.

First author: Cui, XL, Computational Mechanistic Study of Bronsted Acid-Catalyzed Unsymmetrical 1,2,4,5-Tetrazines Synthesis,
Abstract: Density functional theory (DFT) calculations were conducted to gain insight into the reaction mechanism of the Bronsted acid-catalyzed unsymmetrical 1,2,4,5-tetrazine synthesis. Various possible reaction pathways were considered, and the most favorable one can be characterized via sequential six steps, including addition of DCM to hydrazine 1 giving complex IM4, N-H bond activation in IM4 mediated by sulfur, AcOH-assisted substitution of 3 with sulfur-activated hydrazine 2, HNO2-assisted addition of nitrile to intermediate 8, cyclization, and intramolecular elimination leading to the final product 7. Among the six steps, sulfur activation of IM4 N-H bond is found to be the ratedetermining step (RDS). The mechanism rationalizes the experimental observation that 2 equiv of sulfur leads to the best yield of product. Furthermore, we disclosed that the Bronsted acid additives (i.e., acetic acid and nitrous acid) served triple roles as catalyst, proton shuttle, and hydrogen bond donor and acceptor in the whole catalysis.

First author: Wohner, K, Strong Binding of Noble Gases to [B12X11](-): A Theoretical Study,
Abstract: We systematically explore the stability and properties of [B(12)X(11)NG](-) adducts resulting from the binding of noble gas atoms to anionic [B12X11](-) clusters in the gas phase of mass spectrometers. [B12X11](-) can be obtained by stripping one X- off the icosahedral closo-dodecaborate dianion [B12X12](2-). We study the binding of the noble gas atoms He, N; Ar, Kr, and Xe to [B12X11](-) with substituents X = F, Cl, Br, I, and CN. While He cannot be captured by these clusters and Ne only binds at low temperatures, the complexes with the heavier noble gas atoms Ar, Kr, and Xe show appreciable complexation energies and exceed 1 eV at room temperature in the case of [B-12(CN)(11)Xe](-). The predicted B-NG equilibrium distance in the complexes with Ar, Kr, and Xe is only 0.10-0.25 angstrom longer than the sum of the covalent radii of the two corresponding atoms, and a significant charge transfer from the noble gas atom to the icosahedral B 12 cage is observed.

First author: Alkan, F, Understanding the Effect of Symmetry Breaking on Plasmon Coupling from TDDFT,
Abstract: We perform a time-dependent density functional theory (TDDFT) investigation for the optical properties of nanorod assemblies for different sizes (Ag-10, Ag-59, and Ag-139), interparticle distances, and orientations with a focus on the effect of symmetry breaking via an angle on plasmon coupling. For the model systems, the angle (theta) between the particles is varied between 0 and 180 degrees, where theta = 0 degrees and theta = 180 degrees correspond to symmetric side-by-side and end-to-end orientations of the nanorods, respectively. Our analysis reveals that for a sufficiently large interparticle distance (r > 0.7 nm), where the wave-function overlap between monomers is negligible, TDDFT results agree quite well with the predictions of the dipole-dipole interaction model for the intensity of the different modes of coupled plasmons. For smaller gap distances (0.4-0.5 nm), a charge-transfer plasmon (CTP) mode occurs for the symmetry broken case of the Ag-10 dimer. For the assemblies of larger nanorods, however, the CTP mode is predicted to be less pronounced, especially for the cases where the deviation from the end-to-end geometry is larger than 30 degrees. The orbital overlap and configuration-interaction analyses show that these results are related to the fact that the relative overlap strength between monomeric energy levels is significantly reduced for symmetry-broken orientations of larger nanorods.

First author: Vinogradova, KA, Coordination-induced emission enhancement in copper(i) iodide coordination polymers supported by 2-(alkylsulfanyl)pyrimidines,
DALTON TRANSACTIONS, 50, 9317, (2021)
Abstract: First examples of copper(i) complexes with 2-(alkylsulfanyl)pyrimidine ligands have been synthesized. Reactions of copper(i) iodide with 2-(methylsulfanyl)pyrimidine (L-1) in various metal-to-ligand molar ratios in MeCN afford a ladder-type coordination polymer [(Cu2LI2)-I-1](n) with polymeric chains built from double-stranded (Cu2I2)(n) ribbons supported on both sides by mu(2)-N,S-L-1 molecules. Although the second ligand, 2-(ethylsulfanyl)pyrimidine (L-2), differs from L-1 only by a methylene group, its reactions with copper(i) iodide in MeCN yield not only a congenerous coordination polymer, [(Cu2LI2)-I-2](n), but also [(CuLI)-I-2](n), in which a similar (Cu2I2)(n) ribbon is decorated by N-monodentate L-2 molecules. Absorption spectra of all compounds represent an interplay of metal + iodine-to-ligand charge transfer (XMLCT) and ligand-centered (LC) and cluster-centered (CC) transitions, while the emission occurs from the excited states of XMLCT nature. The luminescence of [(Cu2LI2)-I-1](n) and [(Cu2LI2)-I-2](n) is blue-shifted and greatly enhanced in comparison with that of [(CuLI)-I-2](n) (quantum yields: 89% and 68% for [(Cu2LI2)-I-1](n) and [(Cu2LI2)-I-2](n) vs. 23% for [(CuLI)-I-2](n) at 77 K), which can be associated with a more rigid mu(2)-N,S coordination of 2-(alkylsulfanyl)pyrimidine ligands in [(Cu2LI2)-I-1](n) and [(Cu2LI2)-I-2](n) leading to a less distorted T-1 state.

First author: Staron, J, Tuning the activity of known drugs via the introduction of halogen atoms, a case study of SERT ligands – Fluoxetine and fluvoxamine,
Abstract: The selective serotonin reuptake inhibitors (SSRIs), acting at the serotonin transporter (SERT), are one of the most widely prescribed antidepressant medications. All five approved SSRIs possess either fluorine or chlorine atoms, and there is a limited number of reports describing their analogs with heavier halogens, i.e., bromine and iodine. To elucidate the role of halogen atoms in the binding of SSRIs to SERT, we designed a series of 22 fluoxetine and fluvoxamine analogs substituted with fluorine, chlorine, bromine, and iodine atoms, differently arranged on the phenyl ring. The obtained biological activity data, supported by a thorough in silico binding mode analysis, allowed the identification of two partners for halogen bond interactions: the backbone carbonyl oxygen atoms of E493 and T497. Additionally, compounds with heavier halogen atoms were found to bind with the SERT via a distinctly different binding mode, a result not presented elsewhere. The subsequent analysis of the prepared XSAR sets showed that E493 and T497 participated in the largest number of formed halogen bonds. The XSAR library analysis led to the synthesis of two of the most active compounds (3,4-diCl-fluoxetine 42, SERT K-i = 5 nM and 3,4-diCl-fluvoxamine 46, SERT K-i = 9 nM, fluoxetine SERT K-i = 31 nM, fluvoxamine SERT K-i = 458 nM). We present an example of the successful use of a rational methodology to analyze binding and design more active compounds by halogen atom introduction. ‘XSAR library analysis’, a new tool in medicinal chemistry, was instrumental in identifying optimal halogen atom substitution.

First author: Sruthi, PK, Pentavalent P center dot center dot center dot N phosphorus bonding in the heterodimers of POCl3 center dot center dot center dot nitrogen bases: Evidence from matrix isolation infrared spectroscopy and Ab initio computations,
Abstract: The present work explores the P center dot center dot center dot N phosphorus bonding with phosphoryl chloride (POCl3) prototype against a series of nitrogen bases such as ammonia (NH3), aniline (C6H5NH2), and pyridine (C5H5N), arranged in increasing order of basicity. Experiments were performed in N-2 and Ar matrixes at low temperatures and the structure of dimers was elucidated by infrared spectroscopy. Though N-H center dot center dot center dot O hydrogen bonding is expected to dominate in POCl3-NH(3)dimer due to the presence of phosphoryl oxygen, the phosphorus bonded P center dot center dot center dot N interaction plays a non-trivial role in determining the structure of the dimer with a distortion in the hydrogen bonding angle. With a severe distortion in the hydrogen bonding angle, the P center dot center dot center dot N phosphorus bonding completely influences the structure of POCl3-C(6)H(5)NH(2)dimer. A strong P center dot center dot center dot N interaction was noticed in the case of POCl3-C5H5N dimer with a co-operative C-H center dot center dot center dot O hydrogen bonding stabilization. The scanning of complete potential energy surface of POCl3 with nitrogen bases divulged competing structures,which are stabilized through Cl center dot center dot center dot N halogen bonding interaction in the case of POCl3-NH3 dimer and P center dot center dot center dot pi phosphorus bonding for POCl3-C6H5NH2 and POCl3-C5H5N dimers. The distinctive features of the interaction prevailing in the heterodimers involving POCl3-nitrogen bases were examined using electrostatic potential mapping along with natural orbital, energy decomposition and non covalent interaction analyses. In addition to P center dot center dot center dot N interaction, a faint P center dot center dot center dot sigma interaction in which bonding sigma(N-H) orbital interacts with phosphorus of POCl3 also was discerned in POCl3-NH3 and POCl3-C6H5NH2 dimers. Though the nitrogen atom of these bases (NH3,C6H5NH2, and C5H5N) cannot qualify to be acknowledged as pnicogens, due to the donation of the lone pair of electrons on nitrogen in these systems towards hydrogen bonding make it electron deficient. As a result, a surprising pnicogen character, though feeble, is witnessed on these nitrogen atoms, the observation of which is reported with caution.

First author: Vermeeren, P, Chemical reactivity from an activation strain perspective,
Abstract: Chemical reactions are ubiquitous in the universe, they are at the core of life, and they are essential for industrial processes. The drive for a deep understanding of how something occurs, in this case, the mechanism of a chemical reaction and the factors controlling its reactivity, is intrinsically valuable and an innate quality of humans. The level of insight and degree of understanding afforded by computational chemistry cannot be understated. The activation strain model is one of the most powerful tools in our arsenal to obtain unparalleled insight into reactivity. The relative energy of interacting reactants is evaluated along a reaction energy profile and related to the rigidity of the reactants’ molecular structure and the strength of the stabilizing interactions between the deformed reactants: Delta E(zeta) = Delta E-strain(zeta) + Delta E-int(zeta). Owing to the connectedness between the activation strain model and Kohn-Sham molecular orbital theory, one is able to obtain a causal relationship between both the sterics and electronics of the reactants and their mutual reactivity. Only when this is accomplished one can eclipse the phenomenological explanations that are commonplace in the literature and textbooks and begin to rationally tune and optimize chemical transformations. We showcase how the activation strain model is the ideal tool to elucidate fundamental organic reactions, the activation of small molecules by metallylenes, and the cycloaddition reactivity of cyclic diene- and dipolarophiles.

First author: Jia, YH, Tetrahedral Pt-10(-) Cluster with Unique Beta Aromaticity and Superatomic Feature in Mimicking Methane,
Abstract: Utilizing a customized metal cluster source in tandem with a flow tube reactor and a reflectron time-of-flight mass spectrometer, we have obtained well-resolved pure metal clusters Pt-n(-) and observed their gas-phase reactions with a few small gas molecules. Interestingly, the remarkable inertness of Pt-10(-) was repeatedly observed in different reactions. Meanwhile, we have determined the structure of Pt-10(-) within a regular tetrahedron. Considering that Pt possesses 5d(9)6s(1) electron configuration, the tetrahedral Pt-10(-) exhibits unexpected stability at neither a magic number of valence electrons nor a shell closure of geometric structure. Comprehensive theoretical calculations unveil the stability of Pt-10(-) is significantly associated with the all-metal aromaticity. In addition to the classical total aromaticity, which is mainly due to 6s electrons, there is unique beta-aromaticity ascribed to spin-polarized beta 5d electrons pertaining to singly occupied multicenter bonds. Further, we demonstrate the superatomic feature of such a transition metal cluster Pt-10(-), as Pt-6@Pt-4(-), in mimicking methane.

First author: Wang, RY, Understanding the Electronic Structure and Stability of BnXn0/2- (n=4, 6; X = H, F, Cl, Br, I, At, Ts) Clusters(dagger),
Abstract: Main observation and conclusion

First author: Banerjee, S, Preparation and Reactivity Studies of Four and Five coordinated Amidinate Aluminum Compounds,
Abstract: Synthesis of four and five coordinated aluminum amidinate (PhC((NBu)-Bu-t)(2)=L) compounds are reported herein along with their single-crystal X-ray structures and detailed characterizations using both, experimental and computational techniques. LAlCl2 (1) and L2AlCl (2) were synthesized by treating AlCl3 with PhC((NBu)-Bu-t)(2)Li in an equivalent ratio of 1 : 1 and 1 : 2, respectively. [LAl(C2H5)Cl] (3) was prepared from a reaction of AlCl2(C2H5) with PhC((NBu)-Bu-t)(2)Li in an equivalent ratio of 1 : 1. Reactivity of 3, an amidinate based organo-aluminum compound is explored for the various reactions. 3 produced [LAl(C2H5)(mu-F)](2) (4) on treatment with Me3SnF. Interestingly, [LAl(C2H5)Cl] (3) was converted to [LAlCl(mu-OEt)](2) (5) when refluxed in Et2O. 3 gives the monomeric and neutral cyclic (alkyl)(amino) carbene (cAAC) based radical [LAl(C2H5)(cAAC)] (6) on reduction with KC8 in the presence of cAAC.

First author: Morgan, HWT, Open Shells in Endohedral Clusters: Structure and Bonding in the [Fe-2@Ge-16](4-) Anion and Comparison to Isostructural [Co-2@Ge-16](4-),
Abstract: The anionic cluster [Fe-2@Ge-16](4-) has been characterized and shown to be isostructural to the known D-2h-symmetric alpha isomer of the cobalt analogue [Co-2@ Ge-16](4-). Together with the known pair of compounds [Co@Ge-10](3-) and [Fe@Ge-10](3-), the title compound completes a set of four closely related germanium clusters that allow us to explore how the metal-metal and metal-cage interactions evolve as a function of size and of the identity of the metal. The results of spin-unrestricted density functional theory (DFT) and multiconfigurational self-consistent field (MC-SCF) calculations present a consistent picture of the electronic structure where transfer of electron density from the metal to the cage is significant, particularly in the Fe clusters where the exchange stabilization of unpaired spin density is an important driving force.

First author: Kulichenko, M, Double sigma-Aromaticity in a Planar Zinc-Doped Gold Cluster: Au9Zn-,
Abstract: The strong relativistic effects result in many interesting chemical and physical properties for gold and gold compounds. One of the most surprising findings has been that small gold clusters prefer planar structures. Dopants can be used to tune the electronic and structural properties of gold nanoclusters. Here we report an experimental and theoretical investigation of a Zn-doped gold cluster, Au9Zn-. Photoelectron spectroscopy reveals that Au9Zn- is a highly stable electronic system with an electron binding energy of 4.27 eV. Quantum chemical studies show that the global minimum of Au9Zn- has a D-3h structure with a closed-shell electron configuration ((1)A(1)’), which can be viewed as replacing the central Au atom by Zn in the open-shell parent Au-10(-) cluster. The high electronic stability of Au9Zn- is corroborated by its extremely large HOMO-LUMO gap of 3.3 eV. Chemical bonding analyses revealed that the D-3h Au9Zn- are bonded by two sets of delocalized sigma bonds, giving rise to double sigma aromaticity and its remarkable stability. Two planar low-lying isomers are also observed, corresponding to a similar triangular structure with the Zn atom on the edge and another one with one of the corner Au atoms moved to the edge of the triangle.

First author: Benaissa, H, Exploring “Triazole-Thiourea” Based Ligands for the Self-Assembly of Photoluminescent Hg(II) Coordination Compounds,
CRYSTAL GROWTH & DESIGN, 21, 3562, (2021)
Abstract: This study represents the first explorative investigation on the supramolecular structural diversity in Hg(II) coordination chemistry with triazole-thiourea ligands leading to a variety of mononuclear, binuclear, and coordination polymers: {[Hg(L1)(2)(L1(-))(2)]} (1), {[Hg-2(L1)(2)(mu(2)-I)(2)I-2]center dot DMSO} (2), {[Hg-(L2)(mu(2)-I)I]center dot MeOH}(proportional to)(3), {[Hg-2(mu-L3(-))4(])}(proportional to) (4), {[HgCl(L4(-)) L4]center dot MeOH} (5), {[Hg-2(L4)(2)(mu(2)-I)(2)(I)(2)]center dot 2MeOH} (6), {[Hg-2(mu(2)-L5(-))(4)]}(proportional to) (7), {[Hg-2(mu(2)-Cl)(2)(L6(-))(2)(L6)(2)]} (8), {[Hg-2(mu(2)-Br)(2)(L6(-))(2)(L6)(2)]} (9), and {[Hg-2(mu(2)-I)(2)(L6(-))(2)(L6)(2)]} (10). A reaction mechanism was suggested for the unexpected ligand rearrangement occurring in {[Hg2I3(mu(3)-L5′)]}(proportional to) (11). The ligands were fully characterized including by X-ray crystallography and computational means. This includes six new triazole-thiourea based ligands, namely, 1-R-3-(4H-1,2,4-triazol-4-yl)thiourea (where R = methyl (L1), ethyl (L2), propyl (L3), isopropyl (L4), and its polymorph (L4-poly), allyl (L5), ethyl acetate (L6), and its solvate (L6_MeOH)). Under UV light excitation, 7, 10, and 11 exhibit visible photoluminescence of wide origin, ranging from ligand-centered (LC) fluorescence combined with organic-ligand-to-metal charge transfer (LMCT) emissive states in 7 and 10, up to halide-to-metal charge transfer (XMCT) combined with halide-to-ligand charge transfer (XLCT) emissive states in 11. The variable emission mechanisms in the obtained coordination polymers were elucidated by experimental proofs confronted with theoretical calculations of the electronic densities of states, proving that Hg(II) halide coordination polymers involving flexible 1,2,4-triazole-based ligands form a promising class of luminescent molecular materials.

First author: Cantero-Lopez, P, The role of zero-field splitting and pi-stacking interaction of different nitrogen-donor ligands on the optical properties of luminescent rhenium tricarbonyl complexes,
NEW JOURNAL OF CHEMISTRY, 45, 11192, (2021)
Abstract: Rhenium tricarbonyl complexes are among the most important classes of coordination compounds in inorganic chemistry. Exploring their luminescent excited states, the lowest singlet (S-1) and lowest triplet (T-1), is an important topic to understand their interesting photophysical behavior and potential applications in organic light-emitting diodes (OLEDs). In this work, a systematic evaluation of the role of zero-field splitting (ZFS) and the geometric arrangement of different nitrogen-donor ligands, including pi-stacking interactions, in five selected rhenium luminescent complexes was performed. The optical properties have been deeply discussed using relativistic quantum mechanics methods and other theoretical approaches. Spin-orbit coupling TDDFT (SOC-TDDFT) calculations showed an excellent prediction of emission properties. The zero-field splitting (ZFS) values were relatively large, verifying the presence of the (MLCT)-M-3 state in the transition character of T1 and efficient spin-orbit coupling (SOC). The introduction of two nitrogen-donor ligands introduced pi-stacking interactions that produced a synergistic effect between the ligands and the metal center, promoting blueshift emissions and higher rate constants for T-1-S-0 transition mediated by SOC.

First author: Rodriguez-Kessler, PL, Exploring the Size-Dependent Hydrogen Storage Property on Ti-Doped B-n Clusters by Diatomic Deposition: Temperature Controlled H-2 Release,
Abstract: The hydrogen storage properties of Ti-doped B-n (n=3-12) clusters are investigated by using the “diatomic deposition method” with further evaluation by density functional theory computations. The results show that TiBn (n=7-9) clusters possess the ability to storage up to four H-2 molecules, reaching a mass fraction of 6.12%. Further, the hydrogen release temperature is analyzed by molecular dynamics simulations with a variable temperature. It turns out that the TiB7 and TiB9 clusters release the H-2 molecules at T less than or similar to 700 K, while TiB8 requires higher temperature due to stronger interactions with the H-2 molecules, confirmed by the electronic density of states. The size-dependent properties and odd-even nuclearity on the clusters can be useful for applications with controlled temperature. These results serve for further design of novel materials with reversible and controlled hydrogen storage properties based on TiB7/TiB9 motifs. Additionally, new lower-energy isomers for TiB4 and TiB9 clusters were found within the accuracy of the all-electron triple-zeta Slater [slater type orbital (STO)-Triple-zeta basis set(TZP)] basis set.

First author: Paramasivam, K, New luminescent tetracoordinate boron complexes: an in-depth experimental and theoretical characterisation and their application in OLEDs,
Abstract: A group of new tetracoordinate mononuclear 2-(N-phenylformimino)pyrrolyl boron chelates [BX2{kappa N-2,N ‘-NC4H3-2-C(H)N-C6H5}] (X = F 3; mesityl (2,4,6-trimethylphenyl, Mes) 4; C(6)F(5)5; X-2 = 1,1 ‘-biphenyl-2,2 ‘-diyl 6) and the related binuclear complex [(C6F5)(2)B{kappa N-2,N ‘-NC4H3-2-C(H)N-C6H4-N C(H)-C4H3N-kappa N-2,N ‘}B(C6F5)(2)] 7 were synthesised via metathetic exchange reactions of sodium 2-(N-phenylformimino)pyrrolyl with BF3 center dot Et2O (3), BMes(2)F (4) and 9-chloro-9-borafluorene (6), whereas 5 and 7 were obtained from the acid-base reactions between the corresponding neutral ligand precursors, respectively 2-(N-phenylformimino)pyrrole (1) and 1,4-(HNC4H3-C(H) N)(2)-C6H4 (2), with B(C6F5)(2)OEt. These complexes were designed to evaluate the influence of the boron co-ligands on the molecular properties of the corresponding 2-iminopyrrolyl tetrahedral boron derivatives, particularly on luminescence. Compounds 3-7 were photophysically characterised in solution and in solid state, exhibiting blue to yellowish-green emissions and fluorescence quantum yields (phi(f)) up to 0.40. The exception was complex 4, which revealed full fluorescence quenching owing to a dynamic equilibrium involving the bidentate (tetracoordinate) 2-iminopyrrolyl boron complex and the corresponding monodentate (tricoordinate) species. DFT and TDDFT studies were carried out, considering the effect of solvent and also of dispersion forces, in order to elucidate the change in geometries of compounds 3-7 from the ground to the singlet excited state, to understand the dynamic equilibrium of 4, to ascribe electronic transitions, and to rationalise the observed luminescence and also the main trends of thermal stabilities. These complexes were applied in organic light-emitting diodes (OLEDs), the ones based on complex 6 showing the best performances (maximum luminance of 170 cd m(-2) and electroluminescence efficiency of 0.037 cd A(-1)).

First author: Alemayehu, AB, Rhenium Corrole Dimers: Electrochemical Insights into the Nature of the Metal-Metal Quadruple Bond,
INORGANIC CHEMISTRY, 60, 8315, (2021)
Abstract: The interaction of free-base triarylcorroles with Re-2(CO)(10) in 1,2-dichlorobenzene in the presence of 2,6-lutidine at 180 degrees C under strict anerobic conditions afforded approximately 10% yields of rhenium corrole dimers. The compounds exhibited diamagnetic H-1-NMR spectra consistent with a metal-metal quadruple bond with a sigma(2)pi(4)delta(2) orbital occupancy. One of the compounds proved amenable to single-crystal X-ray structure determination, yielding a metal-metal distance of similar to 2.24 angstrom, essentially identical to that in triple-bonded osmium corrole dimers. On the other hand, the electrochemical properties of Re and Os corrole dimers proved to be radically different. Thus, the reduction potentials of the Re corrole dimers are some 800 mV upshifted relative to those of their Os counterparts. Stated differently, the Re corrole dimers are dramatically easier to reduce, reflecting electron addition to delta* versus pi* molecular orbitals for Re and Os corrole dimers, respectively. The data also imply electrochemical HOMO-LUMO gaps of only 1.0-1.1 V for rhenium corrole dimers, compared with values of 1.85-1.90 V for their Os counterparts. These HOMO-LUMO gaps rank among the first such values reported for quadruple-bonded transition-metal dimers for any type of supporting ligand, porphyrin-type or not.

First author: Wang, JY, Coordination-driven assembly of actinide-organic polyrotaxanes involving crown ether macrocycles,
Abstract: Research on synthesizing new coordination-driven polyrotaxanes as well as regulating their structural diversity contributes to the success of macrocycle-based supramolecular materials. In this work, we describe the synthesis of a new kind of actinide-organic polyrotaxane involving crown ether macrocycles for the first time. Crystal structures of two uranyl polyrotaxane compounds, UCER-1 and UCER-2, as well as a third non-polyrotaxane compound UON-1, have been determined, and the formation mechanism of actinide-organic polyrotaxanes is discussed in terms of factors affecting the assembly process. A comparison of the reaction conditions and the corresponding outcomes suggests the necessity of a host-guest pseudorotaxane linker for the successful construction of targeted actinide-organic polyrotaxanes. The coordination of different coordination atoms, especially bromide ions and uranyl ions, is analyzed in detail through theoretical calculations. As an extension of cucurbituril-based uranyl-organic polyrotaxanes, the introduction of crown ether macrocycles as a new supramolecular element brings a different kind of actinide polyrotaxane with intriguing molecular structures and supramolecular assembly behaviours, and will, we believe, expand the research scope of actinide rotaxane coordination polymers.

First author: Venkataramanan, NS, A computational study on the complexation of bisbenzimidazolyl derivatives with cucurbituril and cyclohexylcucurbituril,
Abstract: The binding properties of 1, omega-bisbenzimidazolyl derivatives with cucurbit[6]uril (Q[6]) and cyclohexanocucurbit[ 6]uril (Cy6Q[6]) host, for 1: 1 stoichiometry, have been studied using density functional theory. The distance between the two benimidazole acidic hydrogen’s along with the flexible butyl spacer group play a vital role in the complexation with host. The energetic analysis exhibits strong complexation ability of guests with Q[6] than Cy6Q[6] host. The computed enthalpy and free energy change were negative indicating the encapsulation process to be spontaneous and thermodynamically favorable and enthalpy driven. The global reactivity descriptors based charge transfer calculations show that charge transfer occurs from the guest to host molecule which was supported by the electron density difference map. The main factors for the higher stability of stable complex was the presence of C-H center dot center dot center dot center dot O=C hydrogen bonding interactions in addition to the weak C center dot center dot center dot O, C center dot center dot center dot N, N center dot center dot center dot O, C center dot center dot center dot H, H center dot center dot center dot N type of interactions. AIM topological parameters and NCI analysis reveals the existence of weak interaction, mainly of electrostatic in nature and more number of hydrogen bonds are present in stable complexes. EDA analysis demonstrates the presence of noncovalent and electrostatic interaction with partial covalent character in the encapsulated complexes. The lower stability of Cy6Q[6] complexes compare to Q[6] are due to the presence of positive V-s,V- max values of cyclohexanone methylene hydrogen’s on Cy6Q[6] host.

First author: Filho, JBG, Selective visible-light-driven toxicity breakdown of nerve agent simulant methyl paraoxon over a photoactive nanofabric,
Abstract: An efficient photocatalytic nanofabric (NbOFe-NF) based on polycaprolactone (PCL) and immobilized iron niobate (NbOFe) nanoparticles was produced through the electrospinning technique and applied to the photo degradation of methyl paraoxon (MP), a highly neurotoxic chemical warfare simulant. Photocatalytic tests were conducted in the absence of any solvent, relying only on the fabric, substrate, and visible light radiation. As a result, an excellent conversion of 94.5 % of MP was obtained in 48 h of photocatalysis. Furthermore, the photoactive nanofabric proved to be extremely selective, converting MP and its original organophosphate product into less toxic compounds. This entire process was exclusively photocatalytic, through h(+) and O center dot H produced from ambient humidity.

First author: Pandeya, P, Nonradiative relaxation dynamics in the [Au25-nAgn(SH)(18)](-1) (n=1, 12, 25) thiolate-protected nanoclusters,
Abstract: Evaluation of the electron-nuclear dynamics and relaxation mechanisms of gold and silver nanoclusters and their alloys is important for future photocatalytic, light harvesting, and photoluminescence applications of these systems. In this work, the effect of silver doping on the nonradiative excited state relaxation dynamics of the atomically precise thiolate-protected gold nanocluster [Au25-nAgn(SH)(18)](-1) (n = 1, 12, 25) is studied theoretically. Time-dependent density functional theory is used to study excited states lying in the energy range 0.0-2.5 eV. The fewest switches surface hopping method with decoherence correction was used to investigate the dynamics of these states. The HOMO-LUMO gap increases significantly upon doping of 12 silver atoms but decreases for the pure silver nanocluster. Doped clusters show a different response for ground state population increase lifetimes and excited state population decay times in comparison to the undoped system. The ground state recovery times of the S-1-S-6 states in the first excited peak were found to be longer for [Au13Ag12(SH)(18)](-1) than the corresponding recovery times of other studied nanoclusters, suggesting that this partially doped nanocluster is best for preserving electrons in an excited state. The decay time constants were in the range of 2.0-20 ps for the six lowest energy excited states. Among the higher excited states, S-7 has the slowest decay time constant although it occurs more quickly than S-1 decay. Overall, these clusters follow common decay time constant trends and relaxation mechanisms due to the similarities in their electronic structures.

First author: Lu, HJ, Visible colorimetric dosimetry of UV and ionizing radiations by a dual-module photochromic nanocluster,
Abstract: Radiation dosimeters displaying conspicuous response of irradiance are highly desirable, owing to the growing demand of monitoring high-energy radiation and environmental exposure. Herein, we present a case of dosimetry based on a discrete nanocluster, [Th-6(OH)(4)(O)(4)(H2O)(6)](TPC)(8)(HCOO)(4).4DMF.H2O (Th-SINAP-100), by judiciously incorporating heavy Th-6 polynuclear centers as radiation attenuator and organic linkers as photo-responsive sensor. Interestingly, dual-module photochromic transitions upon multiple external stimuli including UV, beta -ray, and gamma -ray are integrated into this single material. The striking color change, and more significantly, the visible color transition of luminescence in response to accumulating radiation dose allow an on-site quantitative platform for naked-eye detection of ionization radiations over a broad range (1-80 kGy). Single crystal X-ray diffraction and density functional theory calculations reveal that the dual-module photochromism can be attributed to the (TPC)-> pi*(TPC) intermolecular charge transfer driven by enhanced pi-pi stacking interaction between the adjacent TPC moieties upon irradiation. Radiation dosimeters that measure ionizing radiations over a broad range and allow for direct readout are desirable. Here, the authors present a dual-mode photochromic thorium-based metal-organic nanocluster that enables direct visible colorimetric dosimetry of UV, beta -ray, and gamma -ray radiation.

First author: Brault, P, Insight into plasma degradation of paracetamol in water using a reactive molecular dynamics approach,
Abstract: Plasma-produced reactive oxygen and nitrogen species are expected to promote micropollutant degradation in water and more generally in liquids. Among these species, the hydroxyl radical (HO center dot) is recognized as being the most efficient. Molecular dynamics simulations were carried out to determine the reaction steps of HO center dot interaction with the paracetamol molecule in water, a pharmaceutical residue that is frequently detected in surface and tap water and is well documented. Calculations were performed at various temperatures to determine the oxidation pathways, and the intermediate and final products were identified. Assuming a ratio of 10% HO center dot in water, it was found that a local temperature of 2500 K is required to decompose paracetamol to CO, H2O, NH3, and C2H2.

First author: Brunken, C, Automated Construction of Quantum-Classical Hybrid Models,
Abstract: We present a protocol for the fully automated construction of quantum mechanical (QM)-classical hybrid models by extending our previously reported approach on self-parametrizing system-focused atomistic models (SFAMs) [Brunken, C.; Reiher, M. J. Chem. Theory Comput. 2020, 16, 3, 1646-1665]. In this QM/SFAM approach, the size and composition of the QM region are evaluated in an automated manner based on first principles so that the hybrid model describes the atomic forces in the center of the QM region accurately. This entails the automated construction and evaluation of differently sized QM regions with a bearable computational overhead that needs to be paid for automated validation procedures. Applying SFAM for the classical part of the model eliminates any dependence on pre-existing parameters due to its system-focused quantum mechanically derived parametrization. Hence, QM/SFAM is capable of delivering high fidelity and complete automation. Furthermore, since SFAM parameters are generated for the whole system, our ansatz allows for a convenient redefinition of the QM region during a molecular exploration. For this purpose, a local reparametrization scheme is introduced, which efficiently generates additional classical parameters on the fly when new covalent bonds are formed (or broken) and moved to the classical region.

First author: Sen, S, Understanding the Relation between Structural and Spectral Properties of Light-Harvesting Complex II,
Abstract: Light-harvesting complex II (LHCII) is a pigment-protein complex present in higher plants and green algae. LHCII represents the main site of light absorption, and its role is to transfer the excitation energy toward the photosynthetic reaction centers, where primary energy conversion reactions take place. The optical properties of LHCII are known to depend on protein conformation. However, the relation between the structural and spectroscopic properties of the pigments is not fully understood yet. In this respect, previous classical molecular dynamics simulations of LHCII in a model membrane [Sci. Rep. 2015, 5, 1-10] have shown that the configuration and excitonic coupling of a chlorophyll (Chl) dimer functioning as the main terminal emitter of the complex are particularly sensitive to conformational changes. Here, we use quantum chemistry calculations to investigate in greater detail the effect of pigment-pigment interactions on the excited-state landscape. While most previous studies have used a local picture in which electrons are localized on single pigments, here we achieve a more accurate description of the Chl dimer by adopting a supramolecular picture where time-dependent density functional theory is applied to the whole system at once. Our results show that specific dimer configurations characterized by shorter inter-pigment distances can result in a sizable intensity decrease (up to 36%) of the Chl absorption bands in the visible spectral region. Such a decrease can be predicted only when accounting for Chl-Chl charge-transfer excitations, which is possible using the above-mentioned supramolecular approach. The charge-transfer character of the excitations is quantified by two types of analyses: one focusing on the composition of the excitations and the other directly on the observable total absorption intensities.

First author: Batista, PR, Solvent effect on the Pt-195 NMR properties in pyridonate-bridged Pt-III dinuclear complex derivatives investigated by ab initio molecular dynamics and localized orbital analysis,
Abstract: An ab initio molecular dynamics investigation of the solvent effect (water) on the structural parameters, Pt-195 NMR spin-spin coupling constants (SSCCs) and chemical shifts of a series of pyridonate-bridged Pt-III dinuclear complexes is performed using Kohn-Sham (KS) Car-Parrinello molecular dynamics (CPMD) and relativistic hybrid KS NMR calculations. The indirect solvent effect (via structural changes) has a dramatic effect on the (1)J(PtPt) SSCCs. The complexes exhibit a strong trans influence in solution, where the Pt-Pt bond lengthens with increasing axial ligand sigma-donor strength. In the diaqua complex, where the solvent effect is more pronounced, the SSCCs averaged for CPMD configurations with explicit plus implicit solvation agree much better with the experimental data, while the calculations for static geometry and CPMD unsolvated configurations show large deviations with respect to experiment. The combination of CPMD with hybrid KS NMR calculations provides a much more realistic computational model that reproduces the large magnitudes of (1)J(PtPt) and Pt-195 chemical shifts. An analysis of (1)J(PtPt) in terms of localized and canonical orbitals shows that the SSCCs are driven by changes in the s-character of the natural atomic orbitals of Pt atoms, which affect the ‘Fermi contact’ mechanism.

First author: Sun, XQ, Theoretical investigations on the charge transport properties of anthracene derivatives with aryl substituents at the 2,6-position-thermally stable “herringbone” stacking motifs,
Abstract: High-performance organic semiconductor materials based on the small aromatic anthracene-core and its derivatives develop comparatively slowly due to the lack of a profound understanding of the influence of chemical modifications on their charge-transfer properties. Herein, the electronic properties and the charge transport characteristics of several typical anthracene-based derivatives with aryl groups substituted at the 2,6-site are systematically investigated by multi-scale simulation methods including Molecular Dynamics (MD) simulation and the full quantum nuclear tunneling model in the framework of density functional theory (DFT). To elucidate the origin of different charge transport properties of these anthracene-based materials, analysis of the molecular stacking and noncovalent intermolecular interaction caused by different substituents was carried out. The results indicate that the electron and hole injection capabilities and the air oxidation stability of the anthracene derivatives are greatly improved when the size of the aryl substituent increases. In addition, the incorporation of 2,6-site aryl substituents can inhibit the stretching vibration of the anthracene-core during charge transport, and allow molecular packing along the long axis (a-axis of DPA and BDBFAnt, and c-axis of dNaAnt) with almost no slippage, and the main transport channels remain unchanged, exhibiting more isotropic 2D transport properties. It should be emphasized that the edge-to-face dimers with smallest dihedral angles are closest to the thermally stable dimer model, with relatively larger pi-orbital distributions in transmission channels (dimer 1, 2) and the largest spatial overlap, resulting in the largest hole transfer integral in DPA (V-h1/h2 = 57 meV). Although the analysis of the thermal disorder effect shows a phonon scattering effect, the maximum hole mobility of the DPA molecule is still as high as 1.5 cm(2) V-1 s(-1).

First author: Fugel, M, On the Role of Hydrogen Bonding in Gas-Phase S(N)2 Reactions at Silicon,
Abstract: ( )The shape of the potential energy surface (PES) of gas-phase S(N)2 reactions at silicon is determined by the type of nucleophile, the leaving group, and substituents which remain bonded to silicon. In this study, we present PES scans along the reaction coordinate of six symmetrical S(N)2 reactions: X- + SiR3X -> XSiR3 + X-, where X = Cl or F and R = H, Me, or OMe. While the fluorine systems and the CISiH3Cl system only give single-well PESs, CISiMe3Cl and CISi(OMe)(3)Cl give triple- and double-well PESs with stable pre- and post-reaction complexes. A complementary bonding analysis (energy decomposition analysis, quantum theory of atoms in molecules, and natural bond orbitals) reveals that the leaving group (X-) is stabilized by hydrogen bonding in the XSiMe3X and XSi(OMe)(3)X systems. It is shown that this so far neglected stabilizing contribution, along with sigma-hole bonding, is responsible for the shapes of the PESs of ClSiMe3Cl and CISi(OMe)(3)Cl in the gas phase.

First author: Zhang, ZY, A short-range disordered defect in the double layer ice,
Abstract: A localized, metastable, 5775-type defect is uncovered in the double-layer ice with and without Au(111) support from density functional theory calculations. Without destroying the total number conservation of the hydrogen bonds in the hexagonal ice, the defect only dislocates the molecules by 0.08 angstrom associated with a 3.27% difference of the interaction energy. The high energy barrier, low quantum tunneling and thermal transporting probabilities hindered the transformation from the 6666 to the 5775 structures. This finding indicates that the defected ice is stable, and it tends to form during the ice growth instead of post-grown process.

First author: Yuan, NN, Modulation of Fe-based oxygen carriers by low concentration doping of Cu in chemical looping process: Reactivity and mechanism based on experiments combined with DFT calculations,
POWDER TECHNOLOGY, 388, 474, (2021)
Abstract: Fe-based oxygen carriers (OCs) are currently the crucial material basis for chemical looping technology to realize industrial applications. However, the relatively low reactivity of pure Fe-based OCs limits their extensive applications. One strategy to enhance reactivity in the chemical looping process is the introduction of another metallic element by doping. This study prepared a series of Fe-based OCs (Cu2xFe2(1-x)O3) with low concentration doping of Cu. The reaction mechanism and reactivity modulation of Cu2xFe2(1-x)O3 OCs in the chemical looping process were systematically investigated by means of experiments and density function theory (DFT) calculations. Activation energies for Cu2xFe2(1-x)O3 ranging between 72 and 37 kJ/mol were detected using H-2 and the thermogravimetric analyzer (TGA) test, indicating enhanced reactivity in the chemical looping process as compared with that of pure Fe-based OCs of 84 kJ/mol. Thus, the low concentration doping of Cu can effectively improve the reactivity of Fe-based OCs. Furthermore, comprehensive DFT calculations upon the transition state indicated the reaction energy barrier for Cu2xFe2(1-x)O3 with different doping concentration and configurations to be in the range of 1.68-1.02 eV, lower than that of pure Fe2O3 of 2.30 eV. The Cu doping and the modulation of the reaction pathways are important reasons for the enhanced reactivity of Cu2xFe2(1-x)O3 OCs. Additionally, this study proposed a lattice oxygen release mechanism of Cu2xFe2(1-x)O3 OCs during chemical looping combustion.

First author: Suta, M, The angular overlap model of ligand field theory for f elements: An intuitive approach building bridges between theory and experiment,
Abstract: Lanthanoid ions are well-known for their characteristic optical and magnetic properties interesting for a wide range of applications. Most of these properties show a subtle dependence on the surrounding ligands. Unlike the transition metal ions with their often encountered octahedral or tetrahedral coordination in compounds, rare earth ions are typically found in coordination geometries with low symmetries and high coordination numbers. The quantitative treatment of the ligand field in the so-called Wybourne scheme then becomes overparametrized and not readily insightful but merely a technical tool. In this review, we want to present the alternative approach by the chemically intuitive angular overlap model (AOM) of ligand field theory that is independent from symmetry and allows to decompose any coordination geometry into its separate metal-ligand bonds with well-known bonding character. It is the goal of this review to demonstrate its strength in the semi-quantitative description of opto-magnetic properties of the rare earth ions on carefully selected examples from practice. Finally, we compare the AOM to conventional Wybourne-parametrized ligand field theory and show how the two schemes of ligand field theory are related to one another. Overall, this review offers a perspective on future approaches to ligand field calculations with f elements with the benefit of full transparency and intuitive understanding rather than technical fitting.

First author: Rajani, P, Does the basicity of phosphoryl oxygen change with alkyl chain length in phosphate ligands?,
Abstract: The effect of alkyl chain length on the basicity of phosphoryl oxygen in phosphate ligands is investigated in the present study. In all ligands except PH3O, a negative hyperconjugation interaction has been observed resulting from the interaction between the filled pi (P–O) and sigma*(PR) orbitals. This hyperconjugation interaction reduces the phosphoryl group’s electron density and is found identical in all ligands. The NBO, AIM and ELF electronic structure analysis revealed no evidence for the correlation between the basicity of phosphoryl oxygen atom and alkyl chain length in phosphate ligands.

First author: Rajabpour, S, Development and Applications of ReaxFF Reactive Force Fields for Group-III Gas-Phase Precursors and Surface Reactions with Graphene in Metal-Organic Chemical Vapor Deposition Synthesis,
Abstract: Two-dimensional (2D) materials exhibit a wide range of optical, electronic, and quantum properties divergent from their bulk counterparts. To realize scalable 2D materials, metal-organic chemical vapor deposition (MOCVD) is often used. Here, we report two ReaxFF reactive force fields, GaCH-2020 and InCH2020, which were developed to investigate the MOCVD gas-phase reactions of Ga and In film growth from trimethylgallium (TMGa) and trimethylindium (TMIn) precursors, respectively, and the surface interactions of TMGa and TMIn with graphene. The newly developed force fields were applied to determine the optimal conditions for the thermal decomposition of TMGa/TMIn to achieve Ga/In nanoclusters with low impurities. Additionally, the cluster formation of Ga/In on a graphene substrate with different vacancies and edges was studied. It was found that a graphene with Ga-functionalized monovacancies could help conduct directional Ga cluster growth via covalent bonds. Moreover, under specific growth conditions, we found that Ga atoms growing on armchairedged graphene not only exhibited a superior growth ratio to In atoms but also produced a widely spread 2D thin layer between graphene edges.

First author: Zhu, YH, MS-CASPT2 studies on the mechanistic photophysics of tellurium-substituted guanine and cytosine,
Abstract: Sulfur-substituted nucleobases are highly promising photosensitizers that are widely used in photodynamic therapy, and there are numerous studies exploring their unique photophysical behaviors. However, relevant photophysical investigations on selenium and tellurium substitutions are still rare. Herein, the high-level multistate complete-active-space second-order perturbation (MS-CASPT2) method was performed for the first time to explore the excited-state relaxation processes of tellurium-substituted guanine (TeG) and cytosine (TeC). Based on the electronic state properties in the Franck-Condon (FC) region, we found that the lowest five (S-0, S-1, S-2, T-1, and T-2) and six (S-0, S-1, S-2, T-1, T-2 and T-3) states will participate in the nonadiabatic transition processes of TeG and TeC systems, respectively. In these electronic states, two kinds of minimum and intersection structures (i.e., planar and twisted structures) were obtained for both TeG and TeC systems. The linearly interpolated internal coordinate (LIIC) paths and spin-orbit coupling (SOC) constants revealed several possible planar and twisted excited-state decay channels, which could lead the systems to the lowest reactive triplet state of T-1. Small energy barriers in the T-1 state will trap the TeG and TeC systems for a while before they finally populate to the ground state. Although tellurium substitution would further redshift the absorption wavelength and enhance the intersystem crossing (ISC) rate to the T-1 state compared with sulfur and selenium substitutions, the rapid ISC process of T-1 -> S-0 may make it a less effective photosensitizer to sensitize the molecular oxygen. We believe our present work will provide important mechanistic insights into the photophysics of tellurium-substituted nucleobases.

First author: Bessen, N, Extraction of the trivalent transplutonium actinides americium through einsteinium by the sulfur donor Cyanex 301,
Abstract: In the extraction of lanthanides by the sulfur donor ligand, Cyanex 301 (HC301, bis(2,4,4-trimethylpentyl)dithiophosphinic acid), a transition in the coordination mode of extracted complexes has been observed between Eu and Gd. The light lanthanides La-Eu tend to be extracted as inner sphere complexes with HC301 directly coordinating the metal whereas the second half of the series Gd-Lu have a tendency to be extracted as outer sphere complexes. Without extended actinide studies, spanning the transplutonium actinides, it was unclear if a similar change in the extraction mechanism occurs in the actinide series. To assess this, solvent extraction studies were completed examining the slope dependence of the actinides and lathanides in the presence of varied nitrate and acid concentrations. Significant variation in the slope dependences was not observed for either the actinides or the lanthanides as pC(H+) varied, however, the nitrate dependence and neodymium spectroscopy data suggest that the formation of outer sphere complexes is suppressed by higher nitrate concentrations. This suppression of outer sphere complexes enhanced the extraction of lanthanides, but not the actinides and suggests that the actinides form inner sphere complexes. Therefore, the HC301 separations chemistry observed thus far suggest differences in the chemistry of the actinides and lanthanides continues to persist deep into the actinide series.

First author: Tang, JW, Regulating Interfacial Coupling and Electron Transport for Efficient Electron-Transporting Materials,
Abstract: Herein, naphthalimide derivative NDI-ID, a promising organic electron-transporting material (ETM), is used as a model molecular skeleton to investigate how the electron transport of organic ETMs and the interfacial coupling between organic ETM and perovskite are regulated by intermolecular van der Waals interactions. As shown in our computations, the van der Waals interactions between ETM and perovskite are strengthened considerably by the pi-extended modification of naphthalimide derivatives, enhancing the ETM-perovskite interfacial coupling and thus accelerating electron extraction and transfer from perovskites to ETMs by coupling of lead pi-orbitals in perovskites with pi-conjugated antibonding orbitals of ETMs. Meanwhile, the ETM intermolecular pi-pi interactions are also significantly enhanced, which stabilizes the face-to-face stacking between ETM molecules. The enhancement of the ETM intermolecular pi-pi interactions and the ETM-perovskite interfacial coupling improve remarkably the performance of ETMs. Modified naphthalimide derivative, NF2X-ID, has a very high electron mobility of 0.386 cm(2 )V(-1) s(-1), about 2 orders of magnitude larger than 0.00614 cm(2 )V(-1) s(-1) of NDI-ID. The present work provides theoretical guidance for the design of ETMs with excellent performance.

First author: Schneck, F, Solvent dependent C-H Bond Strength in a Nickel Pincer Complex,
Abstract: Metal coordination can substantially weaken the bond strength of X-H bonds in coordinated ligands. Despite the importance for redox catalysis, this phenomenon is surprisingly scarcely examined for C-H bonds of organometallic compounds. We here report a nickel(I) pincer complex with a remote methylene group in the ligand backbone that exhibits an unusually solvent dependent C-H bond dissociation free energy (BDFEC-H). Structural and thermochemical characterization in MeCN and THF indicates that the BDFEC-H strongly depends on solvent binding to the metal within the Ni-II/Ni-I redox couple.

First author: Fatima, M, Synthesis, characterization, antioxidant, DNA binding and density functional studies of novel bisamides,
Abstract: Bisamides N-1,N-3-bis(4-(4-nitrophenoxy)phenyl)isophthalamide (BA1), N-1,N-4 -bis(4-(4-nitrophenoxy) phenyl)terephthalamide (BA2) and 1,1′-bis(4-(4-nitrophenoxy)phenyl) ferrocenylamide (BA3) were synthesized from 4-(4-nitrophenoxy)aniline and isophthaloyl dichloride, terephthaloyl dichloride and 1,1′-dicarbonylchloride ferrocene respectively. The synthesized compounds were characterized from spectroscopic (FTIR), NMR (H-1, C-13) and single crystal X-ray analyses. The compound N-1,N-3-bis(4-(4-nitrophenoxy)phenyl)isophthalamide crystallized in triclinic system having space group P-1. The biological worth of the compounds was assessed by performing drug-DNA binding and DPPH free radical scavenging activity investigations. The results of the compounds indicate significant drug-DNA interaction. All the synthesized compounds exhibit intercalation mode of interaction. The greater value of binding interaction is observed for BA2 and its intercalation into DNA structure is more facile than BA1 and BA3. DPPH free radical scavenging activity analysis has shown the highest activity for BA1 (55%), moderate activity for BA2 (45%) while lowest for BA3 (40%). Density functional theory has been employed to study the structure-property ramifications in the bisamides; results reveal a sterling concurrence in the experimental and theoretical structural parameters. A comprehensive bonding inspection of each compound has also been executed by Bader’s AIM analysis to gain an insight into inter and intra-molecular interactions.

First author: Mahmoudi, G, Solvent-Induced Formation of Novel Ni(II) Complexes Derived from Bis-Thiosemicarbazone Ligand: An Insight from Experimental and Theoretical Investigations,
Abstract: In this work, we report solvent-induced complexation properties of a new N2S2 tetradentate bis-thiosemicarbazone ligand (H2LI), prepared by the condensation of 4-phenylthiosemicarbazide with bis-aldehyde, namely 2,2′-(ethane-1,2-diylbis(oxy)dibenzaldehyde, towards nickel(II). Using ethanol as a reaction medium allowed the isolation of a discrete mononuclear homoleptic complex [NiLI] (1), for which its crystal structure contains three independent molecules, namely 1-I, 1-II, and 1-III, in the asymmetric unit. The doubly deprotonated ligand L-I in the structure of 1 is coordinated in a cis-manner through the azomethine nitrogen atoms and the thiocarbonyl sulfur atoms. The coordination geometry around metal centers in all the three crystallographically independent molecules of 1 is best described as the seesaw structure. Interestingly, using methanol as a reaction medium in the same synthesis allowed for the isolation of a discrete mononuclear homoleptic complex [Ni(L-II)(2)] (2), where L-II is a monodeprotonated ligand 2-(2-(2-(2-(dimethoxymethyl)phenoxy)ethoxy)benzylidene)-N-phenylhydrazine-1-carbothioamide (HLII). The ligand L-II was formed in situ from the reaction of L-I with methanol upon coordination to the metal center under synthetic conditions. In the structure of 2, two ligands L-II are coordinated in a trans-manner through the azomethine nitrogen atom and the thiocarbonyl sulfur atom, also yielding a seesaw coordination geometry around the metal center. The charge and energy decomposition scheme ETS-NOCV allows for the conclusion that both structures are stabilized by a bunch of London dispersion-driven intermolecular interactions, including predominantly N-H center dot center dot center dot S and N-H center dot center dot center dot O hydrogen bonds in 1 and 2, respectively; they are further augmented by less typical C-H center dot center dot center dot X (where X = S, N, O, pi), CH center dot center dot center dot HC, pi center dot center dot center dot pi stacking and the most striking, attractive long-range intermolecular C-H center dot center dot center dot Ni preagostic interactions. The latter are found to be determined by both stabilizing Coulomb forces and an exchange-correlation contribution as revealed by the IQA energy decomposition scheme. Interestingly, the analogous long-range C-H center dot center dot center dot S interactions are characterized by a repulsive Coulomb contribution and the prevailing attractive exchange-correlation constituent. The electron density of the delocalized bonds (EDDB) method shows that the nickel(II) atom shares only similar to 0.8 vertical bar e vertical bar due to the sigma-conjugation with the adjacent in-plane atoms, demonstrating a very weak sigma-metalloaromatic character.

First author: Anchique, L, Predicting the Adsorption of Amoxicillin and Ibuprofen on Chitosan and Graphene Oxide Materials: A Density Functional Theory Study,
POLYMERS, 13, 1478, (2021)
Abstract: The occurrence, persistence, and accumulation of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) represent a new environmental problem due to their harmful effects on human and aquatic life. A suitable absorbent for a particular type of pollutant does not necessarily absorb other types of compounds, so knowing the compatibility between a particular pollutant and a potential absorbent before experimentation seems to be fundamental. In this work, the molecular interactions between some pharmaceuticals (amoxicillin, ibuprofen, and tetracycline derivatives) with two potential absorbers, chitosan and graphene oxide models (pyrene, GO-1, and coronene, GO-2), were studied using the omega B97X-D/6-311G(2d,p) level of theory. The energetic interaction order found was amoxicillin/chitosan > amoxicillin/GO-1 > amoxicillin/GO-2 > ibuprofen/chitosan > ibuprofen/GO-2 > ibuprofen/GO-1, the negative sign for the interaction energy in all complex formations confirms good compatibility, while the size of E-int between 24-34 kcal/mol indicates physisorption processes. Moreover, the free energies of complex formation were negative, confirming the spontaneity of the processes. The larger interaction of amoxicillin Gos, compared to ibuprofen Gos, is consistent with previously reported experimental results, demonstrating the exceptional predictability of these methods. The second-order perturbation theory analysis shows that the amoxicillin complexes are mainly driven by hydrogen bonds, while van der Waals interactions with chitosan and hydrophobic interactions with graphene oxides are modelled for the ibuprofen complexes. Energy decomposition analysis (EDA) shows that electrostatic energy is a major contributor to the stabilization energy in all cases. The results obtained in this work promote the use of graphene oxides and chitosan as potential adsorbents for the removal of these emerging pollutants from water.

First author: Chacon, P, Modeling Adsorption and Optical Properties for the Design of CO2 Photocatalytic Metal-Organic Frameworks,
MOLECULES, 26, 1478, (2021)
Abstract: Four Metal-Organic Frameworks (MOFs) were modeled (IRMOF-C-BF2, IRMOF-C-(2)-BF2, IRMOF-C’-BF2, and IRMOF-C-CH2BF2) based on IRMOF-1. A series of linkers, based on Frustrated Lewis Pairs and coumarin moieties, were attached to IRMOF-1 to obtain MOFs with photocatalytic properties. Four different linkers were used: (a) a BF2 attached to a coumarin moiety at position 3, (b) two BF2 attached to a coumarin moiety in positions 3 and 7, (c) a BF2 attached in the coumarin moiety at position 7, and (d) a CH2BF2 attached at position 3. An analysis of the adsorption properties of H-2, CO2, H2O and possible CO2 photocatalytic capabilities was performed by means of computational modeling using Density Functional Theory (DFT), Time-Dependent Density Functional (TD-DFT) methods, and periodic quantum chemical wave function approach. The results show that the proposed linkers are good enough to improve the CO2 adsorption, to hold better bulk properties, and obtain satisfactory optical properties in comparison with IRMOF-1 by itself.

First author: Krawczyk, MS, The Crystal Structure and Intermolecular Interactions in Fenamic Acids-Acridine Complexes,
MOLECULES, 26, 1478, (2021)
Abstract: In order to improve pharmaceutical properties of drugs, complexes are synthesized as combinations with other chemical substances. The complexes of fenamic acid and its derivatives, such as mefenamic-, tolfenamic- and flufenamic acid, with acridine were obtained and the X-ray structures were discussed. Formation of the crystals is determined by the presence of the intermolecular O-(HN)-N- horizontal ellipsis hydrogen bond that occur between fenamic acids and acridine. Intermolecular interactions stabilizing the crystals such as pi( horizontal ellipsis )pi stacking, C-(HX)-X- horizontal ellipsis (X = O, Cl) intermolecular hydrogen bonds as well as C-H- horizontal ellipsis pi and other dispersive interactions were analyzed by theoretical methods: the quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) approaches.

First author: Ribaudo, G, Selenoxide Elimination Triggers Enamine Hydrolysis to Primary and Secondary Amines: A Combined Experimental and Theoretical Investigation,
MOLECULES, 26, 1478, (2021)
Abstract: We discuss a novel selenium-based reaction mechanism consisting in a selenoxide elimination-triggered enamine hydrolysis. This one-pot model reaction was studied for a set of substrates. Under oxidative conditions, we observed and characterized the formation of primary and secondary amines as elimination products of such compounds, paving the way for a novel strategy to selectively release bioactive molecules. The underlying mechanism was investigated using NMR, mass spectrometry and density functional theory (DFT).

First author: Galdeano, M, Theoretical Characterization of New Frustrated Lewis Pairs for Responsive Materials,
POLYMERS, 13, 1478, (2021)
Abstract: In recent years, responsive materials including dynamic bonds have been widely acclaimed due to their expectation to pilot advanced materials. Within these materials, synthetic polymers have shown to be good candidates. Recently, the so-called frustrated Lewis pairs (FLP) have been used to create responsive materials. Concretely, the activation of diethyl azodicarboxylate (DEAD) by a triphenylborane (TPB) and triphenylphosphine (TPP) based FLP has been recently exploited for the production of dynamic cross-links. In this work, we computationally explore the underlying dynamic chemistry in these materials, in order to understand the nature and reversibility of the interaction between the FLP and DEAD. With this goal in mind, we first characterize the acidity and basicity of several TPB and TPP derivatives using different substituents, such as electron-donating and electron-withdrawing groups. Our results show that strong electron-donating groups increase the acidity of TPB and decrease the basicity of TPP. However, the FLP-DEAD interaction is not mainly dominated by the influence of these substituents in the acidity or basicity of the TPB or TPP systems, but by attractive or repulsive forces between substituents such as hydrogen bonds or steric effects. Based on these results, a new material is proposed based on FLP-DEAD complexes.

First author: Ostrowski, JPA, Synthesis and Characterisation of Molecular Polarised-Covalent Thorium-Rhenium and -Ruthenium Bonds,
INORGANICS, 9, 1478, (2021)
Abstract: Separate reactions of [Th{N(CH2CH2NSiMe2But)(2)(CH2CH2NSi(Me)(Bu-t)(mu-CH2)](2) (1) with [Re(eta(5)-C5H5)(2)(H)] (2) or [Ru(eta(5)-C5H5)(H)(CO)(2)] (3) produced, by alkane elimination, [Th(Tren(DMBS))Re(eta(5)-C5H5)(2)] (ThRe, Tren(DMBS) = {N(CH2CH2NSiMe2But)(3)}(3-)), and [Th(Tren(DMBS))Ru(eta(5)-C5H5)(CO)(2)] (ThRu), which were isolated in crystalline yields of 71% and 62%, respectively. Complex ThRe is the first example of a molecular Th-Re bond to be structurally characterised, and ThRu is only the second example of a structurally authenticated Th-Ru bond. By comparison to isostructural U-analogues, quantum chemical calculations, which are validated by IR and Raman spectroscopic data, suggest that the Th-Re and Th-Ru bonds reported here are more ionic than the corresponding U-Re and U-Ru bonds.

First author: Sergeieva, T, Chemical Bonding in Silicon Carbonyl Complexes,
Abstract: Although silylene-carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re-evaluated to explain the origins of their remarkable stability within the Kohn-Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor-acceptor interaction: a sigma-donation from the sigma(CO) into the empty p-orbital of silicon, and a pi-back donation from the sp(2) lone pair of silicon into the pi*(CO) antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si-CO compounds, however, is another pi-back donation from a perpendicular bonding R-Si sigma-orbital into the pi*(CO) antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the pi-back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene-carbonyl chemistry.

First author: Vermeeren, P, Lewis Acid-Catalyzed Diels-Alder Reactions: Reactivity Trends across the Periodic Table,
Abstract: The catalytic effect of various weakly interacting Lewis acids (LAs) across the periodic table, based on hydrogen (Group 1), pnictogen (Group 15), chalcogen (Group 16), and halogen (Group 17) bonds, on the Diels-Alder cycloaddition reaction between 1,3-butadiene and methyl acrylate was studied quantum chemically by using relativistic density functional theory. Weakly interacting LAs accelerate the Diels-Alder reaction by lowering the reaction barrier up to 3 kcal mol(-1) compared to the uncatalyzed reaction. The reaction barriers systematically increase from halogen., the latter have the least catalytic effect. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal that these LAs lower the Diels-Alder reaction barrier by increasing the asynchronicity of the reaction to relieve the otherwise destabilizing Pauli repulsion between the closed-shell filled pi-orbitals of diene and dienophile. Notably, the reactivity can be further enhanced on going from a Period 3 to a Period 5 LA, as these species amplify the asynchronicity of the Diels-Alder reaction due to a stronger binding to the dienophile. These findings again demonstrate the generality of the Pauli repulsion-lowering catalysis concept.

First author: Sabatelli, F, Monitoring of the Pre-Equilibrium Step in the Alkyne Hydration Reaction Catalyzed by Au(III) Complexes: A Computational Study Based on Experimental Evidences,
MOLECULES, 26, 10610, (2021)
Abstract: The coordination ability of the [(ppy)Au(IPr)](2+) fragment [ppy = 2-phenylpyridine, IPr = 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene] towards different anionic and neutral X ligands (X = Cl-, BF4-, OTf-, H2O, 2-butyne, 3-hexyne) commonly involved in the crucial pre-equilibrium step of the alkyne hydration reaction is computationally investigated to shed light on unexpected experimental observations on its catalytic activity. Experiment reveals that BF4- and OTf- have very similar coordination ability towards [(ppy)Au(IPr)](2+) and slightly less than water, whereas the alkyne complex could not be observed in solution at least at the NMR sensitivity. Due to the steric hindrance/dispersion interaction balance between X and IPr, the [(ppy)Au(IPr)](2+) fragment is computationally found to be much less selective than a model [(ppy)Au(NHC)](2+) (NHC = 1,3-dimethylimidazol-2-ylidene) fragment towards the different ligands, in particular OTf- and BF4-, in agreement with experiment. Effect of the ancillary ligand substitution demonstrates that the coordination ability of Au(III) is quantitatively strongly affected by the nature of the ligands (even more than the net charge of the complex) and that all the investigated gold fragments coordinate to alkynes more strongly than H2O. Remarkably, a stabilization of the water-coordinating species with respect to the alkyne-coordinating one can only be achieved within a microsolvation model, which reconciles theory with experiment. All the results reported here suggest that both the Au(III) fragment coordination ability and its proper computational modelling in the experimental conditions are fundamental issues for the design of efficient catalysts.

First author: Bijou, D, Synthesis and Thermal Behavior of Heteroleptic gamma-Substituted Acetylacetonate-Alkoxides of Titanium,
Abstract: A series of heteroleptic titanium derivatives of general formula [Ti(OiPr)(2)(R-acac)(2)] with acetylacetonate ligands modified in the internal (gamma- or 3-) position by different substituents (R=OAc, NO2, Me, Et, Cl, Br) has been synthesized and completely characterized by liquid multinuclear NMR and FTIR. The influence of the nature of the group on the thermal stability of the different complexes was studied by thermogravimetric analysis (TGA) and gave the following decreasing stability ranking: H

First author: Kanj, AB, Chirality Remote Control in Nanoporous Materials by Circularly Polarized Light,
Abstract: The ability to dynamically control chirality remains a grand challenge in chemistry. Although many molecules possess chiral isomers, lacking their isolation, for instance during photoisomerization, results in racemic mixtures with suppressed enantiospecific chiral properties. Here, we present a nanoporous solid in which chirality and enantioselective enrichment is induced by circularly polarized light (CPL). The material is based on photoswitchable fluorinated azobenzenes attached to the scaffold of a crystalline metal-organic framework (MOF). The azobenzene undergoes trans-to-cis-photoisomerization upon irradiation with green light and reverts back to trans upon violet light. While each moiety in cis conformation is chiral, we show the trans isomer also possesses a nonplanar, chiral conformation. During photoisomerization with unpolarized light, no enantiomeric enrichment is observed and both isomers, R- and S-cis as well as R- and S-trans, respectively, are formed in identical quantities. In contrast, CPL causes chiral photoresolution, resulting in an optically active material. Right-CPL selectively excites R-cis and R-trans enantiomers, producing a MOF with enriched S-enantiomers, and vice versa. The induction of optical activity is reversible and only depends on the light-handedness. As shown by first-principle DFT calculations, while both, trans and cis, are stabilized in nonplanar, chiral conformations in the MOF, the trans isomer adopts a planar, achiral form in solution, as verified experimentally. This shows that the chiral photoresolution is enabled by the linker reticulation in the MOF. Our study demonstrates the induction of chirality and optical activity in solid materials by CPL and opens new opportunities for chiral resolution and information storage with CPL.

First author: Mukherjee, K, Machine learning and descriptor selection for the computational discovery of metal-organic frameworks,
Abstract: Metal-organic frameworks (MOFs), crystalline materials with high internal surface area and pore volume, have demonstrated great potential for many applications. In the past decade, as large number of MOFs have come into existence, there has been an effort to model them using computers. High-throughput screening techniques in tandem with molecular simulations or ab-initio calculations are being used to calculate their properties. However, the number of MOFs that can be hypothetically created are in the millions, and thoughcomputer simulations have shown remarkable accuracy, we cannot deploy them for all structures due to their high-computational cost. In this regard, machine learning (ML)-based algorithms have proven to be effective in predicting material properties and reducing the need for expensive calculations. Adopting this methodology can save time and allow researchers to explore materials in unchartered chemical space, thus ushering an era of high-throughput in-silico material design using ML. In this work, we present what is ML, its associated workflow, selecting descriptors, and how it can help build reliable models for discovering MOFs. We present somepopular and novel ones. Thereafter, we review some of the recent studies with respect to ML-based implementation for MOF discovery emphasizing descriptors selected and the workflow adopted.

First author: Lu, XQ, Half-Sandwich LaBn-/0 (n=14-17): pi Dually Aromatic Lanthanide Boride Complexes with Multicenter Fluxional Bonds,
Abstract: Novel lanthanide boride complexes with unique structural and bonding patterns have been observed in recent experiments. Based on extensive first-principles theory calculations, we predict herein the possible existence of half-sandwich C-2v LaB14- (1), C-1 LaB15 (2), C-5v LaB16- (3), and C-s LaB17 (4) which all contain a La center coordinated by a bowl-like B-n ligand (n = 14-17). Detailed bonding analyses indicate that effective d-p coordination interactions exist between the La center and B-n ligand, making these half-sandwich complexes pi dually aromatic in nature. Energy decomposition analyses reveal that electrostatic (50.2%) and covalent (49.8%) interactions contribute almost equally to the overall attraction in LaB14- (1), with the La centre serving as both electron donor and acceptor. Molecular dynamics simulations show that both LaB14- (1) (La[B-4 (c) B-10](-)) and LaB17 (4) (La[B (c) B-5 (c) B-11]) with multicenter fluxional bonds behave like Wankel motors at finite temperatures.

First author: Egidi, F, A polarizable three-layer frozen density embedding/molecular mechanics approach,
Abstract: We present a novel multilayer polarizable embedding approach in which the system is divided into three portions, two of which are treated using density functional theory and their interaction is based on frozen density embedding (FDE) theory, and both also mutually interact with a polarizable classical layer described using an atomistic model based on fluctuating charges (FQ). The efficacy of the model is demonstrated by extending the formalism to linear response properties and applying it to the simulation of the excitation energies of organic molecules in aqueous solution, where the solute and the first solvation shell are treated using FDE, while the rest of the solvent is modeled using FQ charges.

First author: Zheng, J, Phosphorescent Metal Rotaxane-like Bimetallic Ag/Au Clusters,
Abstract: A series of Ag/Au clusters have been synthesized by reacting the p-acidic cyclic trinuclear Ag(I) pyrazolate and its Au(I) analogue with 3-substituted phenylacetylene. Single-crystal X-ray studies reveal that these 13-atom bimetallic clusters are anionic and isostructural, featuring a rotaxane-like architecture with a “rod-in-belt” fashion. Interestingly, the Ag/Au clusters exhibit high-energy phosphorescence tunable from blue to cyan through the modulation of the substituents on the phenylacetylene ligand. Albeit a small amount doping of Au, an over 23-fold boost in phosphorescence quantum yield is observed for these heterometallic clusters compared with their homometallic Ag(I) analogue. Together with our previously reported Ag/Cu clusters capable of furnishing low-energy phosphorescence through the modulation of the Cu-doping amount, we have completed the luminescence puzzle of bimetallic Ag/M clusters with phosphorescence emissions that cover the entire visible-light region. Further computational studies suggest cooperative effects of electrostatic attraction and metal-metal interaction on the modulation of emission color and the stabilization of the rod-in-belt rotaxane structure.

First author: Jiang, YR, Gaseous cyclodextrin-closo-dodecaborate complexes chi CD center dot B12X122- (chi = alpha, beta, and gamma; X = F, Cl, Br, and I): electronic structures and intramolecular interactions,
Abstract: A fundamental understanding of cyclodextrin-closo-dodecaborate inclusion complexes is of great interest in supramolecular chemistry. Herein, we report a systematic investigation on the electronic structures and intramolecular interactions of perhalogenated closo-dodecaborate dianions B12X122- (X = F, Cl, Br and I) binding to alpha-, beta-, and gamma-cyclodextrins (CDs) in the gas phase using combined negative ion photoelectron spectroscopy (NIPES) and density functional theory (DFT) calculations. The vertical detachment energy (VDE) of each complex and electronic stabilization of each dianion due to the CD binding (Delta VDE, relative to the corresponding isolated B12X122-) are determined from the experiments along alpha-, beta- and gamma-CD in the form of VDE (Delta VDE): 4.00 (2.10), 4.33 (2.43), and 4.30 (2.40) eV in X = F; 4.09 (1.14), 4.64 (1.69), and 4.69 (1.74) eV in X = Cl; 4.11 (0.91), 4.58 (1.38), and 4.70 (1.50) eV in X = Br; and 3.54 (0.74), 3.88 (1.08), and 4.05 (1.25) eV in X = I, respectively. All complexes have significantly higher VDEs than the corresponding isolated dodecaborate dianions with Delta VDE spanning from 0.74 eV at (alpha, I) to 2.43 eV at (beta, F), sensitive to both host CD size and guest substituent X. DFT-optimized complex structures indicate that all B12X122- prefer binding to the wide openings of CDs with the insertion depth and binding motif strongly dependent on the CD size and halogen X. Dodecaborate anions with heavy halogens, i.e., X = Cl, Br, and I, are found outside of alpha-CD, while B12F122- is completely wrapped by gamma-CD. Partial embedment of B12X122- into CDs is observed for the other complexes via multipronged B-XMIDLINE HORIZONTAL ELLIPSISH-O/C interlocking patterns. The simulated spectra based on the density of states agree well with those of the experiments and the calculated VDEs well reproduce the experimental trends. Molecular orbital analyses suggest that the spectral features at low binding energies originated from electrons detached from the dodecaborate dianion, while those at higher binding energies are derived from electron detachment from CDs. Energy decomposition analyses reveal that the electrostatic interaction plays a dominating role in contributing to the host-guest interactions for the X = F series partially due to the formation of a O/C-HMIDLINE HORIZONTAL ELLIPSISX-B hydrogen bonding network, and the dispersion forces gradually become important with the increase of halogen size.

First author: Geng, LJ, Spin accommodation and reactivity of nickel clusters with oxygen: Aromatic and magnetic metalloxocube Ni13O8 +/-,
NANO RESEARCH, 14, 4822, (2021)
Abstract: Due to challenges in preparing pure metal clusters and in controlling reactions, the oxides produced by metal clusters reacting with oxygen are often different from traditional ion-molecule products in the gas phase and their reactivity pattern is also largely unveiled yet. In this work, utilizing a customized Re-TOFMS having a home-made cluster source and a flow tube reactor, we have observed the gaseous reactions of Ni-n(+/-) clusters with oxygen and found magic clusters of Ni13O8 +/- that dominate the mass distributions. By quantum chemistry calculations, we find that both Ni13O8- and Ni13O8+ clusters bear a regular cubic structure with 8 oxygen anchoring the eight angles, however, they have rather different spin accommodations. The Ni13O8- clusters have 15 unpaired spin-up electrons exhibiting cubic aromaticity and decent ferromagnetism, while the Ni13O8+ clusters take a lower-spin ground state (11 unpaired electrons), with spin-down population on the central Ni atom pertaining to ferrimagnetism. This is a class of metalloxocube clusters that hold properties of aromaticity and ferromagnetism/ferrimagnetism charcterized by a few spin electrons, which embodies the bonding nature of superatomic compounds and enables to develop cluster-genetic materials of multi-functionality.

First author: Ricciarelli, D, Energy vs Charge Transfer in Manganese-Doped Lead Halide Perovskites,
ACS ENERGY LETTERS, 6, 1869, (2021)
Abstract: Mn-doped lead halide perovskites exhibit long-lived dopant luminescence and enhanced host excitonic quantum yield. The contention between energy and charge transfer in sensitizing dopant luminescence in Mn-doped perovskites is investigated by state-of-the-art DFT calculations on APbX(3) perovskites (X = Cl, Br, and I). We quantitatively simulate the electronic structure of Mn-doped perovskites in various charge and spin states, providing a structural/mechanistic analysis of Mn sensitization as a function of the perovskite composition. Our analysis supports both energy- and charge-transfer mechanisms, with the latter probably preferred in Mn:CsPbCl3 due to small energy barriers and avoidance of spin and orbital restrictions. An essential factor determining the dopant luminescence quantum yield in the case of charge transfer is the energetics of intermediate oxidized species, while bandgap resonance can well explain energy transfer. Both aspects are mediated by perovskite host band edge energetics, which is tuned in turn by the nature of the halide X.

First author: Zhuang, JX, Characterization of a strong covalent Th3+-Th3+ bond inside an I-h(7)-C-80 fullerene cage,
Abstract: The nature of the actinide-actinide bonds is of fundamental importance to understand the electronic structure of the 5f elements. It has attracted considerable theoretical attention, but little is known experimentally as the synthesis of these chemical bonds remains extremely challenging. Herein, we report a strong covalent Th-Th bond formed between two rarely accessible Th3+ ions, stabilized inside a fullerene cage nanocontainer as Th-2@I-h(7)-C-80. This compound is synthesized using the arc-discharge method and fully characterized using several techniques. The single-crystal X-Ray diffraction analysis determines that the two Th atoms are separated by 3.816 angstrom. Both experimental and quantum-chemical results show that the two Th atoms have formal charges of +3 and confirm the presence of a strong covalent Th-Th bond inside I-h(7)-C-80. Moreover, density functional theory and ab initio multireference calculations suggest that the overlap between the 7s/6d hybrid thorium orbitals is so large that the bond still exists at Th-Th separations larger than 6 angstrom. This work demonstrates the authenticity of covalent actinide metal-metal bonds in a stable compound and deepens our fundamental understanding of f element metal bonds.

First author: Ali, B, A new class of Dy-III-SIMs associated with a guanidine-based ligand,
DALTON TRANSACTIONS, 50, 5146, (2021)
Abstract: A family of four mononuclear Dy-III complexes of the guanidine-based ligand L [L = tris(2-hydroxybenzylidene)triaminoguanidine] with formulas [DyLCl2(DMF)(2)]center dot DMF center dot CH3OH (1), [DyL2(CH3OH)(2)]Br center dot H2O center dot 3CH(3)OH (2), [DyL2(H2O)(2)]SCN center dot 3H(2)O center dot CH3OH (3) and [DyL2(CH3OH)(2)]SCN center dot CH3CN center dot CH3OH (4) were successfully prepared by varying reaction conditions. Complex 1 is seven-coordinate, with three N2O from ligand L along with two equatorially trapped DMF molecules and two axial Cl- anions, adopting pentagonal bipyramidal D-5h symmetry. Complexes 2-4 have somewhat similar structures with six donor N4O2 sites from two ligands and two O from corresponding solvent molecules, featuring a N4O4 octa-coordinate environment with triangular dodecahedron D-2d symmetry. Magnetic investigations indicated that complex 1 did not demonstrate single-molecule magnetic behavior, while complexes 2-4 were single-ion magnets (SIMs) under zero applied DC field with the effective energy barriers (U-eff) of 207.3 (2), 222.5 (3) and 311.7 K (4), respectively. The different types of coordinated solvent molecules and counter anions caused changes in intermolecular interactions and coordination geometries that severely affected their magnetic dynamics. The magnetic behaviors of these complexes were investigated through complete-active space self-consistent field (CASSCF) calculations with the inclusion of spin-orbit effects. Calculations revealed that the measured differences in magnetic behaviors originated mainly from intermolecular and crystal-packing effects as isolated complexes 1-4 have almost identical electronic and magnetic properties.

First author: Orenha, RP, The design of anion-pi interactions and hydrogen bonds for the recognition of chloride, bromide and nitrate anions,
Abstract: The role of anions in several biochemical processes has given rise to enormous interest in the identification/exploration of compounds with the potential ability to recognize anions. Here, an anthracene-squaramide conjugated compound, O2C4[NH(C14H10)][(NH(C6H6)], has been modified through the substitutions (i) H -> F and (ii) H -> OH at the anthracene and benzene rings to improve the capabilities of these structures for recognizing chloride, bromide, and nitrate anions. Through an energy decomposition analysis method, the recognition of the anions is chiefly identified as a non-covalent process. H -> F substitutions at the benzene ring and, principally, the anthracene ring favor anion recognition, since H -> F substitutions create a pi-acid region in the aromatic ring, as indicated based on the molecular electrostatic potential surfaces. Similarly, H -> OH substitutions also improve the recognition of anions, which is related to the establishment of partly covalent chemical bonds of the form O-HMIDLINE HORIZONTAL ELLIPSIS(Cl-, Br- and O-), which are verified based on the quantitative analysis of the maximum and minimum values of the molecular electrostatic potential surfaces and the quantum theory of atoms in molecules method. The presence of large electron density has a key role in the recognition of Cl- anions, and the more favorable electrostatic interactions between the anthracene structure and Br- anions, relative to NO3- anions, mean that receptorMIDLINE HORIZONTAL ELLIPSISBr- interactions are more attractive than receptorMIDLINE HORIZONTAL ELLIPSISNO3- ones. These data can contribute to the design of structures with the relevant abilities to interact with anions.

First author: Petrov, PA, Paramagnetic Rhenium Iodide Cluster with N-Heterocyclic Carbene,
INORGANIC CHEMISTRY, 60, 6746, (2021)
Abstract: triangulo-Trirhenium nonaiodide Re3I9 reacts with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) to produce the novel 13-electron paramagnetic cluster Re3I8(IMes)(2), which was characterized by means of X-ray diffraction analysis, ESR spectroscopy, magnetometry, and quantum chemistry.

First author: Zierkiewicz, W, Competition between Inter and Intramolecular Tetrel Bonds: Theoretical Studies Complemented by CSD Survey,
CHEMPHYSCHEM, 60, 6746, (2021)
Abstract: Crystal structures document the ability of a TF3 group (T=Si, Ge, Sn, Pb) situated on a naphthalene system to engage in an intramolecular tetrel bond (TB) with an amino group on the adjoining ring. Ab initio calculations evaluate the strength of this bond and evaluate whether it can influence the ability of the T atom to engage in a second, intermolecular TB with another nucleophile. A very strong CN- anionic base can approach the T either along the extension of a T-C or T-F bond and form a strong TB with an interaction energy approaching 100 kcal/mol, although this bond is weakened a bit by the presence of the internal T…N bond. The much less potent NCH base engages in a correspondingly longer and weaker TB, less than 10 kcal/mol. Such an intermolecular TB is weakened by the presence of the internal TB, to the point that it only occurs for the two heavier tetrel atoms Sn and Pb.

First author: Bessen, NP, Complexation of Lanthanides and Heavy Actinides with Aqueous Sulfur-Donating Ligands,
INORGANIC CHEMISTRY, 60, 6125, (2021)
Abstract: The separation of trivalent lanthanides and actinides is challenging because of their similar sizes and charge densities. S-donating extractants have shown significant selectivity for trivalent actinides over lanthanides, with single-stage americium/lanthanide separation efficiencies for some thiol-based extractants reported at >99.999%. While such separations could transform the nuclear waste management landscape, these systems are often limited by the hydrolytic and radiolytic stability of the extractant. Progress away from thiol-based systems is limited by the poorly understood and complex interactions of these extractants in organic phases, where molecular aggregation and micelle formation obfuscates assessment of the metal-extractant coordination environment. Because S-donating thioethers are generally more resistant to hydrolysis and oxidation and the aqueous phase coordination chemistry is anticipated to lack complications brought on by micelle formation, we have considered three thioethers, 2,2′-thiodiacetic acid (TDA), (2R,5S)-tetrahydrothiophene-2,5-dicarboxylic acid, and 2,5-thiophenedicarboxylic acid (TPA), as possible trivalent actinide selective reagents. Formation constants, extended X-ray absorption fine structure spectroscopy, and computational studies were completed for thioether complexes with a variety of trivalent lanthanides and actinides including Nd, Eu, Tb, Am, Cm, Bk, and Cf. TPA was found to have moderately higher selectivity for the actinides because of its ability to bind actinides in a different manner than lanthanides, but the utility of TPA is limited by poor water solubility and high rigidity. While significant competition with water for the metal center limits the efficacy of aqueous-based thioethers for separations, the characterization of these solution-phase, S-containing lanthanide and actinide complexes is the most comprehensively available in the literature to date. This is due to the breadth of lanthanides and actinides considered as well as the techniques deployed and serves as a platform for the further development of S-containing reagents for actinide separations. Additionally, this paper reports on the first bond lengths for Cf and Bk with a neutral S donor.

First author: Gusakov, EA, The first representative of a new class of charge transfer complexes in o-quinone series for organic semiconductors,
Abstract: The first representative of a new class of charge transfer complexes for organic semiconductors was synthesized. The reaction of p-nitroaniline (PNA) with [1,10]-phenanthroline-5,6-dione (PD) results in the formation of a stable molecular charge transfer (CT) complex PNA(3)-PD2 in a ratio of 3:2. The structure of the molecular CT complex PNA(3)-PD2 was established by X-ray diffraction studies. Using the density functional theory method, it is shown that several types of intermolecular interactions are realized in the complex: between the PNA amino group and the nitro group of another PNA molecule, carbonyl groups, and PD nitrogen atoms. Complex PNA(3)-PD2 is stable only in solid form. The diffuse reflectance UV-vis spectrum of PNA(3)-PD2 crystal powder is characterized by the intense weakly structured long-wavelength absorption band up to 650 nm. Quantum chemical calculations of the electronic structure have shown that the complex PNA(3)-PD2 is a straight-band semiconductor with a band gap of 2.11 eV.

First author: Gorantla, SMNVT, Stabilization of group 14 elements E = C, Si, Ge by heterobileptic ligands cAAC, MCOn with push-pull mechanism,
Abstract: The stability and bonding of a series of hetero-diatomic molecules with general formula (cAAC)E-M(CO)(n), where cAAC = cyclic alkyl(amino) carbene; E = group 14 elements (C, Si, and Ge); M = transition metal (Ni, Fe, and Cr) have been studied by quantum chemical calculations using density functional theory (DFT) and energy decomposition analysis-natural orbital chemical valence (EDA-NOCV). The equilibrium geometries were calculated at the BP86/def2-TZVPP level of theory. The tri-coordinated group 14 complex (1a, 4a, and 7a) in which one of the CO groups is migrated to the central group 14 element from adjacent metal is theoretically found to be more stable when the central atom (E) is carbon. On the other hand, the two-coordinate group 14 element containing metal-complexes (2, 5, 8, 3, 6, and 9) are found to be more stable with their corresponding heavier analogues. The electronic structures of all the molecules have been analyzed by molecular orbital, topological analysis of electron density and natural bond orbital (NBO) analysis at the M06/def2-TZVPP//BP86/def2-TZVPP level of theory. The nature of the cAAC-E and E M bonds has been studied by EDA-NOCV calculations at BP86-D3(BJ)/TZ2P level of theory. The EDA analysis suggests that the bonding of cAAC-C(CO) can be best represented by electron sharing sigma and pi interactions, whereas, C(CO)-M(CO)(n-1) by dative s and p interactions. On the other hand, EDA-NOCV calculations suggests both dative s and p interactions for cAAC-E and E-M(CO)(n) bonds of the corresponding Si and Ge analogues having stronger sigma(-) and relatively weaker pi-bonds. The topological analysis of electron density supports the closed-shell interaction for the Si and Ge complexes and open-shell interaction for the carbon complexes. The calculated proton affinity and hydride affinity values corroborated well with the present bonding description. This class of complexes might act as efficient future catalysts for different organic transformations due to the presence of electron rich group 14 element and metal carbonyl.

First author: Verma, A, ReaxFF reactive molecular dynamics simulations to study the interfacial dynamics between defective h-BN nanosheets and water nanodroplets,
Abstract: In this work, the authors have developed a reactive force field (ReaxFF) to investigate the effect of water molecules on the interfacial interactions with vacancy defective hexagonal boron nitride (h-BN) nanosheets by introducing parameters suitable for the B/N/O/H chemistry. Initially, molecular dynamics simulations were performed to validate the structural stability and hydrophobic nature of h-BN nanosheets. The water molecule dissociation mechanism in the vicinity of vacancy defective h-BN nanosheets was investigated, and it was shown that the terminal nitrogen and boron atoms bond with a hydrogen atom and hydroxyl group, respectively. Furthermore, it is predicted that the water molecules arrange themselves in layers when compressed in between two h-BN nanosheets, and the h-BN nanosheet fracture nucleates from the vacancy defect site. Simulations at elevated temperatures were carried out to explore the water molecule trajectory near the functionalized h-BN pores, and it was observed that the intermolecular hydrogen bonds lead to agglomeration of water molecules near these pores when the temperature was lowered to room temperature. The study was extended to observe the effect of pore sizes and temperatures on the contact angle made by a water nanodroplet on h-BN nanosheets, and it was concluded that the contact angle would be less at higher temperatures and larger pore sizes. This study provides important information for the use of h-BN nanosheets in nanodevices for water desalination and underwater applications, as these h-BN nanosheets possess the desired adsorption capability and structural stability.

First author: Garcia-Orduna, P, Origin of the Ir-Si bond shortening in Ir-NSiN complexes,
DALTON TRANSACTIONS, 50, 5951, (2021)
Abstract: The Ir-Si bond distances reported for Ir-(fac-kappa(3)-NSiNOPy) and Ir-(fac-kappa(3)-NSiN4MeOPy) species (NSiNOPy = bis(pyridine-2-yloxy)methylsilyl and NSiN4MeOPy = bis(4-methyl-pyridine-2-yloxy)methylsily) are in the range of 2.220-2.235 angstrom. These values are in the lowest limit of the Ir-Si bond distances found in the Cambridge Structural Database (CSD). To understand the origin of such remarkable shortening, a computational study of the bonding situation of representative examples of Ir-(fac-kappa(3)-NSiN) species has been carried out. It is found that the Ir-Si bond can be described as an electron-sharing (i.e. covalent) bond. Despite that, this bond is highly polarized and as a result, the contribution of the electrostatic attractions to the bonding is rather significant. Indeed, there exists a linear relationship (R-2 = 0.97) between the Ir-Si bond distance and the extent of the computed electrostatic interactions, which indicates that the ionic contribution to the bonding is mainly responsible for the observed Ir-Si bond shortening.

First author: Koenis, MAJ, Vibrational circular dichroism studies of exceptionally strong chirality inducers in liquid crystals,
Abstract: 7,7 ‘-Disubstituted 2,2 ‘-methylenedioxy-1,1 ‘-binaphthyls are highly efficient chirality inducers in nematic liquid crystals. The absolute configuration of these compounds is, however, hard to determine as they only crystallize as racemic mixtures. In this work a Vibrational Circular Dichroism (VCD) study is reported that provides an unambiguous determination of the absolute configuration of these compounds. An in-depth General Coupled Oscillator (GCO) analysis of the source of the VCD signal reveals that the unusual structure of these binaphthyl compounds inherently leads to strong and robust VCD bands. Combined with linear transit calculations, our VCD studies allow for the determination of key structural parameters.

First author: Ebenezer, C, Tailoring the selectivity of phenanthroline derivatives for the partitioning of trivalent Am/Eu ions – a relativistic DFT study,
Abstract: In the past few years, phenanthroline-based ligands have become an attractive target for the partitioning of trivalent actinides (Ac) from lanthanides (Ln) in nuclear waste management. However, designing efficient ligands for selectively trapping radioactive minor actinides requires complete knowledge of the structure-property relationship to understand the solvent extraction processes in a better way. Therefore, a series of CyMe(4)BTPhen (2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline) derivatives with a five-membered aliphatic ring and a six-membered aliphatic ring have been considered and their complexes with americium and europium [ML(NO3)(3) (L = 1-6)] are studied using scalar relativistic ZORA/DFT calculations. Herein, we envisage the effect of change of a six-membered aliphatic ring to a five-membered aliphatic ring along with the role of substitution of a phenol group on the CyMe(4)BTPhen ligand. All ligands show preferential binding towards Am3+ as compared to the Eu3+ ion. The calculated thermodynamic properties and the separation factors indicate that the five-membered aliphatic ring has the highest selectivity for the Am3+ ion. Energy decomposition analysis has been carried out to understand the total binding energy with its various energy components, while the nature of interactions between metal and ligand is addressed by QTAIM analysis. The results reveal that ligands with six-membered aliphatic rings and phenol substitution at the 5 and 6 positions are the best bet for stripping actinide ions compared to other designed ligands. In summary, this study offers insights into the structure-binding ability relationship to design efficient candidates for nuclear waste management.

First author: Shi, YR, First-principles investigation of electronic and charge transport properties of pyrazinacenes and their structural relatives,
Abstract: Acenes, as organic electronic materials, have attracted great interest, while heteroacenes and their derivatives are rarely studied. This paper is aimed at chemical and physical properties, including the structural, electronic, and charge transport properties of a series of pyrazinacene materials based on quantum chemistry calculations. Based on the single-crystal structures, reorganization energies, and charge transfer integral, the electron mobility reaches 8.667 cm2 V-1 s-1 by introducing electron-withdrawing groups into pyrazinacenes, which can be regarded as an N-type organic semiconductor. The pyrazinacenes have high thermal stability and high charge mobility, which indicate that they are promising candidate materials for organic semiconductor devices.

First author: Zheng, XJ, Relativistic DFT Probe for Reaction Energies and Electronic/Bonding Properties of Polypyrrolic Hetero-Bimetallic Actinide Complexes: Effects of Uranyl endo-Oxo Functionalization,
INORGANIC CHEMISTRY, 60, 5747, (2021)
Abstract: A series of hetero-bimetallic actinide complexes of the Schiff-base polypyrrolic macrocycle (L), featuring cation-cation interactions (CCIs), were systematically investigated using relativistic density functional theory (DFT). The tetrahydrofuran (THF) solvated complex [(THF)((OUOUIV)-O-VI)(THF)(L)](2+) has high reaction free energy (Delta(r)G), and its replacement with electron-donating iodine promotes the reaction thermodynamics to obtain uranyl iodide [(I)((OUOUIV)-O-VI)(I)(L)](2+) (U-VI-U-IV). Retaining this coordination geometry, calculations have been extended to other An(IV) (An = Th, Pa, Np, Pu), i.e., for the substitution of U(IV) to obtain U-VI-An(IV). As a consequence, the reaction free energy is appreciably lowered, suggesting the thermodynamic feasibility for the experimental synthesis of these bimetallic complexes. Among all U-VI-An(IV), the electron-spin density and high-lying occupied orbitals of U-VI-Pa-IV show a large extent of electron transfer from electron-rich Pa(IV) to electron-deficient U(VI), leading to a more stable U-V-Pa-V oxidation state. Additionally, the shortest bond distance and the comparatively negative E-int of the Pa-O-endo bond suggest more positive and negative charges (Q) of Pa and endo-oxo atoms, respectively. As a result of the enhanced Pa-O-endo bond and strong CCI in U-VI-Pa-IV along with the corresponding lowest reaction free energy among all of the optimized complexes, uranyl species is a better candidate for the experimental synthesis in the ultimate context of environmental remediation.

First author: Pineiro, RP, Raman and DFT Study of the H2S Scavenger Reaction of HET-TRZ under Simulated Contactor Tower Conditions,
Abstract: Raman spectroscopy is a rapid and noninvasive analytical technique used for the analysis of complex materials in complex matrices. Herein, we report for the first time a combined Raman-DFT study to assign all the vibrational modes associated with the most important species involved in the H2S scavenger reaction of HET-triazine under simulated contactor tower conditions. In doing so, we have defined specific peaks or Raman identifier bands (RIBs) to get a complete reaction profile of the H2S removal process. Our methodology was able to identify the presence of the elusive 2,2′-(1,3,5-thiadiazine-3,5-diyl)di(ethan-1-ol) (TDZ) intermediate and also provided evidence supporting the formation of the sulfur polymeric deposit from the 2-(1,3,5-dithiazinan-5-yl)ethan-1-ol (DTZ) byproduct.

First author: Yarovoy, SS, Stabilization of Re-3(7+)/Re-3(8+) Metalloclusters by Cyanide Ligands in New Trinuclear Rhenium Cluster Complexes [{Re3X3}(CN)(9)](4-)/[{Re3X3}(CN)(9)](5-) (X = Br or I),
INORGANIC CHEMISTRY, 60, 5980, (2021)
Abstract: The interaction of rhenium(III) halides Re3Br9 and Re3I9 with aqueous solution of sodium cyanide resulted in the formation of the first trinuclear halide-cyanide rhenium cluster complexes [{Re3X3}(CN)(9)](5-)/[{Re3X3}(CN)(9)](4-) (X = Br or I) crystallized as salts of the compositions Cs4Na[{Re3Br3}(CN)(9)]center dot 5.25H(2)O (1), Cs4Na[{Re3I3}(CN)(9)]center dot 6H(2)O (2), Cs-4[{Re3Br3}-(CN)(9)]center dot 2H(2)O center dot 0.5CsCl (3), and Cs-4[{Re3I3}(CN)(9)]center dot(4). All of the compounds are stable in air in the solid state and in aqueous solution. The substitution of apical halide ligands in the parent compounds Re3X9 by cyanides led to reduction of the original metallocluster Re-3(9+) (12 cluster valence electrons (CVEs)) to Re-3(7+) (14 CVEs), forming the compounds 1 and 2. The apical CN- ligands affect the electronic structure of the Re-3 metallocluster stabilizing reduced form. Complexes 1 and 2 represent the first examples of triangular rhenium clusters with the Re-3(7+) metallocluster. The reaction of 1 and 2 with H2O2 resulted in formation of compounds 3 and 4 with the formal charge of the Re-3 metallocluster equal to 8+, and no further oxidation to Re-3(9+) occurred. The compounds were characterized by the X-ray diffraction analysis, NMR and UV-vis spectroscopies, mass spectrometry, cyclic voltammetry, and magnetic susceptibility measurements.

First author: Carrasco-Busturia, D, Ab initio Molecular Dynamics Investigations of the Speciation and Reactivity of Deep Eutectic Electrolytes in Aluminum Batteries,
CHEMSUSCHEM, 14, 2034, (2021)
Abstract: Deep eutectic solvents (DESs) have emerged as an alternative for conventional ionic liquids in aluminum batteries. Elucidating DESs composition is fundamental to understand aluminum electrodeposition in the battery anode. Despite numerous experimental efforts, the speciation of these DESs remains elusive. This work shows how ab initio molecular dynamics (AIMD) simulations can shed light on the molecular composition of DESs. For the particular example of AlCl3:urea, one of the most popular DESs, we carried out a systematic AIMD study, showing how an excess of AlCl3 in the AlCl3:urea mixture promotes the stability of ionic species vs neutral ones and also favors the reactivity in the system. These two facts explain the experimentally observed enhanced electrochemical activity in salt-rich DESs. We also observe the transfer of simple [AlClx(urea)(y)] clusters between different species in the liquid, giving rise to free [AlCl4](-) units. The small size of these [AlCl4](-) units favors the transport of ionic species towards the anode, facilitating the electrodeposition of aluminum.

First author: Berezin, AS, A family of brightly emissive homo- and mixed-halomanganates(II): The effect of halide on optical and magnetic properties,
JOURNAL OF LUMINESCENCE, 236, 2034, (2021)
Abstract: A series of homo- and mixed-halide Mn(II) complexes of (MMTP)2[MnX4] [X = I, Br, Cl; MMTP is 1-methyl-2(methylthio)pyridin-1-ium] and (MMTP)2[MnI2X2] types [X = Br, Cl] has been synthesized and studied in terms of photoluminescent and EPR spectroscopies. At ambient temperature, the complexes obtained in the solid state exhibit an bright green phosphorescence stemmed from the Mn(II)-centered d-d transitions (4T1 -> 6A1). The homohalide complexes, (MMTP)2[MnX4], have a quantum yield of luminescence (and lifetime) of 83% (38 mu s), 100% (270 mu s), and 44% (2850 mu s) at 300 K for X = I, Br, and Cl, respectively. Owing to iodide-enhanced spinorbital coupling in [MnI2X2]2- anion, the phosphorescence quantum efficiency increases and is close to unity; whereas lifetime significantly decreases and is unusually short (54-64 mu s). Except for (MMTP)2[MnCl4], the EPR spectra of the obtained complexes are characterized by the significant deviation of the g-factor from the ge freeelectron value and by the high value of the zero-field splitting parameters on account of the spin-orbit coupling. The correlations between the luminescence and magnetic properties of the title complexes are discussed.

First author: Khetrapal, NS, How O-2-Binding Affects Structural Evolution of Medium Even-Sized Gold Clusters Au-n(-) (n=20-34),
Abstract: We report the first joint anion photoelectron spectroscopy and theoretical study on how O-2-binding affects the structures of medium even-sized gold clusters, Au-n(-)(n = 20-34), a special size region that entails a variety of distinct structures. Under the temperature conditions in the current photoelectron spectroscopy experiment, O(2)(-)bound gold clusters were observed only for n = 22-24 and 34. Nevertheless, O-2 binding with the clusters in the size range of n = 20-34 can be still predicted based on the obtained global-minimum structures. Consequently, a series of structural transitions, from the pyramidal to fused-planar to core-shell structures, are either identified or predicted for the AunO2- clusters, where the O-2-binding is in either superoxo or peroxo fashion. The identified global-minimum structures of AunO2- (n = 20-34) also allow us to gain improved understanding of why the clusters Au-n(-)(n = 26-32) are less reactive with O-2 in comparison to others.

First author: Arias-Olivares, D, In Silico Analysis of the Electronic Delocalization in Some Double Fused-Ring Metallabenzenes,
ACS OMEGA, 6, 9887, (2021)
Abstract: In the current work, some metallabenzenes with one and several fused rings were analyzed in terms of their electronic delocalization. These fused-ring metallabenzenes are known as metallabenzenoids, and their aromatic character is not free of controversy. The systems of the current work were designed from crystallographic data of some synthesized molecules, and their electronic delocalization (aromaticity) was computationally examined in terms of the molecular orbital analysis (Huckel’s rule), the induced magnetic field, and ring currents. The computational evidence allows us to understand if these molecules are or are not aromatic compounds.

First author: Liu, X, Super-strong interactions between multivalent anions and graphene,
CHINESE PHYSICS B, 30, 9887, (2021)
Abstract: Based on the density functional theory (DFT) calculations, we showed that the interactions between different valence anions (PO43-, CH3PO42-, (CH3)(2)PO4-) and graphene significantly increased as the valence of anion increased from negative monovalence to negative trivalence. The adsorption energy of (CH3)(2)PO4- on the electron-rich graphene flake (C84H24) is -8.3 kcal/mol. The adsorption energy of CH3PO42- on the electron-rich graphene flake (C84H24) is -48.0 kcal/mol, which is about six times that of (CH3)(2)PO4- adsorption on electron-rich graphene flake (C84H24) and is even much larger than that of CO32- adsorption on electron-deficient aromatic ring C6F6 (-28.4 kcal/mol). The adsorption energy of PO43- on the electron-rich graphene flake (C84H24) is -159.2 kcal/mol, which is about 20 times that of (CH3)(2)PO4- adsorption on the graphene flake (C84H24). The super-strong adsorption energy is mainly attributed to the orbital interactions between multivalent anions and graphene. This work provides new insights for understanding the interaction between multivalent anions and pi-electron-rich carbon-based nanomaterials and is helpful for the design of graphene-based DNA biosensor.

First author: Chong, DOP, Computational Study of the Electron Spectra of Vapor-Phase Indole and Four Azaindoles,
MOLECULES, 26, 9887, (2021)
Abstract: After geometry optimization, the electron spectra of indole and four azaindoles are calculated by density functional theory. Available experimental photoemission and excitation data for indole and 7-azaindole are used to compare with the theoretical values. The results for the other azaindoles are presented as predictions to help the interpretation of experimental spectra when they become available.

First author: Portela, S, Nature of the Hydrogen Bond Enhanced Halogen Bond,
MOLECULES, 26, 9887, (2021)
Abstract: The factors responsible for the enhancement of the halogen bond by an adjacent hydrogen bond have been quantitatively explored by means of state-of-the-art computational methods. It is found that the strength of a halogen bond is enhanced by ca. 3 kcal/mol when the halogen donor simultaneously operates as a halogen bond donor and a hydrogen bond acceptor. This enhancement is the result of both stronger electrostatic and orbital interactions between the XB donor and the XB acceptor, which indicates a significant degree of covalency in these halogen bonds. In addition, the halogen bond strength can be easily tuned by modifying the electron density of the aryl group of the XB donor as well as the acidity of the hydrogen atoms responsible for the hydrogen bond.

First author: Correa, S, Hybrid Materials Based on Magnetic Iron Oxides with Benzothiazole Derivatives: A Plausible Potential Spectroscopy Probe,
Abstract: Rare diseases affect a small part of the population, and the most affected are children. Because of the low availability of patients for testing, the pharmaceutical industry cannot develop drugs for the diagnosis of many of these orphan diseases. In this sense, the use of benzothiazole compounds that are highly selective and can act as spectroscopy probes, especially the compound 2-(4 ‘-aminophenyl)benzothiazole (ABT), has been highlighted. This article reports the design of potential contrast agents based on ABT and iron to develop a new material with an efficient mechanism to raise the relaxation rate, facilitating diagnosis. The ABT/delta-FeOOH hybrid material was prepared by grafting (N-(4′-aminophenyl) benzothiazole-2-bromoacetamide) on the surface of the iron oxyhydroxide particles. FTIR spectra confirmed the material formations of the hybrid material ABT/delta-FeOOH. SEM analysis checked the covering of nanoflakes’ surfaces in relation to the morphology of the samples. The theoretical calculations test a better binding mode of compound with iron oxyhydroxide. Theoretical findings show the radical capture mechanism in the stabilization of this new material. In this context, Fe3+ ions are an electron acceptor from the organic phase.

First author: Takeda, Y, Palladium-Catalyzed Regioselective and Stereospecific Ring-Opening Suzuki-Miyaura Arylative Cross-Coupling of 2-Arylazetidines with Arylboronic Acids,
Abstract: We have developed a palladium-catalyzed regioselective and enantiospecific ring-opening Suzuki-Miyaura arylative cross-coupling of N-tosyl-2-arylazetidines to give enantioenriched 3,3-diarylpropylamines. This reaction represents an example of transition-metal-catalyzed ring-opening cross-coupling using azetidines as a non-classical alkyl electrophile. Density functional theory rationalized the mechanism of the full catalytic cycle, which consists of the selectivity-determining ring opening of the azetidine, reaction with water, rate-determining transmetalation, and reductive elimination. Transition states of the selectivity-determining ring-opening step were systematically determined by the multi-component artificial force induced reaction (MC-AFIR) method to explain the regioselectivity of the reaction.

First author: He, JJ, Guanidine-Amide-Catalyzed Aza-Henry Reaction of Isatin-Derived Ketimines: Origin of Selectivity and New Catalyst Design,
MOLECULES, 26, 2796, (2021)
Abstract: Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral guanidine-amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine-amide catalyst; (ii) formation of C-C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh3 group in guanidine as well as N-Boc group in ketimine raised the Pauli repulsion energy (Delta E-Pauli) and the strain energy (Delta E-strain) of reacting species in the unfavorable si-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH3NO2 by decreasing the energy barrier in the deprotonation step. The repulsion between the N-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C-C bond formation along the si-face attack pathway, leading to the formation of R-configuration product. A possible synthetic route for the new catalyst is also suggested.

First author: Fujisaki, M, Effects of thermal expansion and degeneracy on ambipolar carrier mobility of non-peripherally hexyl-substituted phthalocyanine,
Abstract: The origin of the negative temperature dependence of carrier mobility in a crystal phase of 1,4,8,11,15,18,22,25-octahexylphthalocyanine was studied by utilizing a charge transport simulation based on Marcus theory and density functional theory. In order to understand the unique negative temperature dependence of carrier mobility, the theoretical calculation was carried out by taking the thermal expansion of the lattice parameters into consideration. The calculated hole mobility exhibited the similar temperature dependence as the experimental results. In the electron mobility calculation, the negative temperature dependence could be simulated by considering the degeneracy of lowest unoccupied molecular orbitals as well as the thermal expansion.

First author: Kowalski, K, From NWChem to NWChemEx: Evolving with the Computational Chemistry Landscape,
CHEMICAL REVIEWS, 121, 4962, (2021)
Abstract: Since the advent of the first computers, chemists have been at the forefront of using computers to understand and solve complex chemical problems. As the hardware and software have evolved, so have the theoretical and computational chemistry methods and algorithms. Parallel computers clearly changed the common computing paradigm in the late 1970s and 80s, and the field has again seen a paradigm shift with the advent of graphical processing units. This review explores the challenges and some of the solutions in transforming software from the terascale to the petascale and now to the upcoming exascale computers. While discussing the field in general, NWCHEM and its redesign, NWCHEMEX, will be highlighted as one of the early codesign projects to take advantage of massively parallel computers and emerging software standards to enable large scientific challenges to be tackled.

First author: Zhu, JJ, Synthesis and Evaluation of Charge Transport Property of Ethynylene-Bridged Anthracene Oligomers,
Abstract: A set of ethynylene-bridged anthracene oligomers from monomer to tetramer is synthesized and characterized. The red-shifts in the UV-vis absorption and fluorescence spectra indicate the pi-extension with elongation of the linear chain. Cyclic voltammetric measurements suggest that their highest occupied molecular orbitals are located lower than -5.0 eV, indicating high air stability. Single-crystal X-ray analysis of a trimer needle crystal indicates that anthracene units display a twisted arrangement, adopting a face-to-face packing structure. The dip-coating method with a very slow pulling rate provides crystalline films of dimer and trimer. The top-contact bottom-gate organic field-effect transistor devices reveal that trimer shows better charge transport property (8.0 x 10(-3) cm(2) V-1 s(-1)) than dimer (8.9 x 10(-4) cm(2) V-1 s(-1)). Furthermore, the single-crystal field-effect transistor of trimer shows mobility up to 0.14 cm(2) V-1 s(-1), which is higher than that of tetramer (3.3 x 10(-2) cm(2) V-1 s(-1)). This is likely due to the larger amount of defects in tetramer crystals that are caused by the free rotation of ethynylene units, while the trimer achieves a good balance between the effective pi-conjugation and defectless crystal formation.

First author: Liu, N, Hexachloroethane dechlorination in sulfide-containing aqueous solutions catalyzed by nitrogen-doped carbon materials,
Abstract: This study demonstrated that nitrogen-doped carbon materials (NCMs) could effectively catalyze the chlorine elimination process in hexachloroethane (HCA) declorination in sulfide-containing environments for the first time. The k(obs) values of HCA dechlorination by sulfide in the presence of 10 mg/L NCMs were higher than that of no mediator at pH 7.3 by one or two orders of magnitude. The catalytic capabilities of NCMs on HCA dechlorination were evident in common ranges of natural pH (5.3-8.9) and it could be accelerated by the increase of pH but be suppressed by the presence of dissolved humic acid. Moreover, NCMs exhibited much better catalytic capability on HCA dechlorination compared to the carbon materials, mainly owing to the combined contributions of pyridine N, including enhanced nucleophilic attack to HCA molecule by generating newborn C-S-S and activation of HCA molecule by elongating C-CI bonds. The functions of pyridine N in micron-sized NCMs with mesopores were better than in nano-sized NCMs on HCA dechlorination. These findings displayed the potential of NCMs, when released into sulfide-containing environments, may significantly increase the dechlorination of chlorinated aliphatic hydrocarbons.

First author: Majid, A, Iodide Adsorption on Transition-Metal-Doped SiC Monolayers: A Density Functional Theory Based Bonding Analysis,
Abstract: The exploration of platinum-free counter electrode (CE) materials is a hot area of research related to dye-sensitized solar cells. This work reports the potential of 3d and 4d transition-metal-doped SiC monolayers for use as CEs studied via periodic energy decomposition analysis. Adsorption of iodide was carried out to check the catalytic activity of the doped slabs, reactivity, energetics, and bonding properties of the doped slabs. The interaction energy was computed through Pauli, electrostatic, and orbital energy terms. Preparation energy, found using structurally and electrically unperturbed fragments, was examined in detail to reveal the relative value of the slabs. Comparative analysis revealed that Ti:SiC and Zr:SiC slabs have superior catalytic properties to a Pt slab.

First author: Wada, Y, Acceleration of Reverse Intersystem Crossing using Different Types of Charge Transfer States,
Abstract: There is a need to boost the rate constant of reverse intersystem crossing (k(RISC)) in thermally activated delayed fluorescence (TADF) materials for applications to organic light-emitting diodes. Recently, energy level matching of the locally excited state (LE) and charge transfer state (CT) has been reported to enhance k(RISC). In this study, we conceptually demonstrate that k(RISC) can be improved even between CT states without LE states, through the use of different types of CT states. On the basis of this concept, we design a new compound, named DMAC-bPmT, where two phenyl groups of a well-known TADF material DMAC-TRZ are substituted by pyrimidine groups. Theoretical calculations indicated that the energy levels of the different CT states of DMAC-bPmT are very close and enhanced spin orbit coupling may be expected between them. As predicted, DMAC-bPmT experimentally exhibited a k(RISC) three times as high as that of DMAC-TRZ.

First author: Bai, YY, Redox-Induced Interconversion of Two Au-8 Nanoclusters: the Mechanism and the Structure-Bond Dissociation Activity Correlations,
INORGANIC CHEMISTRY, 60, 5724, (2021)
Abstract: The interconversion of atomically precise nanoclusters represents an excellent platform to understand the structural correlations of nanomaterials at the atomic level. Herein, density functional theory calculations were performed to elucidate the mechanism of the redox-induced interconversion of [Au-8(dppp)(4)](2+) and [Au-8(dppp)(4)Cl-2](2+) (dppp is short for 1,3-bis(diphenylphosphino)propane) nanoclusters. Reduction is the driving force for the conversion of [Au-8(dppp)(4)Cl-2](2+) to [Au-8(dppp)(4)](2+), while the Au-Au and first Au-Cl bond dissociations occur asynchronously on the two different corner Au atoms to avoid the formation of an electron-deficient Au atom. By contrast, the reduced electron density of [Au-8(dppp)(4)](2+) by oxidation with O-2 weakens the outmost Au-Au bond therein and facilitates the coordination of the electron-rich chloride(s). The reduction- and oxidation-induced activations, respectively, of Au-Cl and Au-Au bonds and the elucidated principles on the structure-activity correlations might also be generalized to other size conversions upon redox treatment.

First author: Sun, XF, Investigating phosphorescence capability of halogen-substituted metal-free organic molecules: A theoretical study,
Abstract: The radiative and non-radiative decay processes of five compounds are investigated through a comprehensive computational approach, for the aim of investigating the effect of different halogen substituents to the phosphorescent emission. Their optimal configurations at the ground (S-0) and lowest triplet excited (T-1) states are obtained and the calculated phosphorescent emission spectra are comparable with the experimental values. For 1,4-di(9H-carbazol-9-yl)benzene (PDCz), the electronic transition is between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), while for the four halides, the electronic transitions are attributed to several molecular orbitals. According to calculations, 9,9′-(2,5-diiodo-1,4-phenylene)bis(9H-carbazole) (PDICz) possesses the largest radiative decay rate constant (k(r)) and non-radiative decay rate constant (k(nr)), which can be attributed to the strong spin-orbital coupling from the heavy iodine atom. However, the phosphorescent quantum efficiency (Phi) of PDICz is lower than that of 9,9′-(2,5-dibromo-1,4-phenylene)bis(9H-carbazole) (PDBCz), implying that a comprehensive consideration is necessary. Furthermore, by analyzing the vibrational mode, we have confirmed that the reorganization energies are also influenced by the different halogen atoms. While the dominated factor that determines the kr and knr comes from the spin-orbital coupling. We expect that our research findings will be beneficial to the newly designed organic phosphorescent materials in the future.

First author: Wei, ZM, Excited state dynamics of BODIPY-based acceptor-donor-acceptor systems: a combined experimental and computational study,
Abstract: Donor-bridge-acceptor systems based on boron dipyrromethene (BODIPY) are attractive candidates for bio-imagining and sensing applications because of their sensitivity to temperature, micro-viscosity and solvent polarity. The optimization of the properties of such molecular sensors requires a detailed knowledge of the relation between the structure and the photophysical behavior in different environments. In this work we have investigated the excited-state dynamics of three acceptor-donor-acceptor molecules based on benzodithiophene and BODIPY in solvents of different polarities using a combination of ultrafast spectroscopy and DFT-based electronic structure calculations. Transient absorption spectra show that upon photoexcitation an initial excited species with an induced absorption band in the near-infrared regime is formed independent of the solvent polarity. The subsequent photophysical processes strongly depend on the solvent polarity. In non-polar toluene this initial excited state undergoes a structural relaxation leading to a delocalized state with partial charge transfer character, while in the more polar tetrahydrofuran a fully charge separated state is formed. The results clearly show how factors such as donor-acceptor distance and restricted rotational motion by steric hindrance can be used to tune the excited state photophysics to optimize such systems for specific applications.

First author: Vermeeren, P, How metallylenes activate small molecules,
CHEMICAL SCIENCE, 12, 4526, (2021)
Abstract: We have studied the activation of dihydrogen by metallylenes using relativistic density functional theory (DFT). Our detailed activation strain and Kohn-Sham molecular orbital analyses have quantified the physical factors behind the decreased reactivity of the metallylene on going down Group 14, from carbenes to stannylenes. Along this series, the reactivity decreases due to a worsening of the back-donation interaction between the filled lone-pair orbital of the metallylene and the sigma*-orbital of H-2, which, therefore, reduces the metallylene-substrate interaction and increases the reaction barrier. As the metallylene ligand is varied from nitrogen to phosphorus to arsenic a significant rate enhancement is observed for the activation of H-2 due to (i) a reduced steric (Pauli) repulsion between the metallylene and the substrate; and (ii) less activation strain, as the metallylene becomes increasingly more predistorted. Using a rationally designed metallylene with an optimal Group 14 atom and ligand combination, we show that a number of small molecules (i.e. HCN, CO2, H-2, NH3) may also be readily activated. For the first time, we show the ability of our H-2 activated designer metallylenes to hydrogenate unsaturated hydrocarbons. The results presented herein will serve as a guide for the rational design of metallylenes toward the activation of small molecules and subsequent reactions.

First author: Chatterjee, M, Variable electronic structure and spin distribution in bis(2,2 ‘-bipyridine)-metal complexes (M = Ru or Os) of 4,5-dioxido- and 4,5-diimido-pyrene,
DALTON TRANSACTIONS, 50, 4191, (2021)
Abstract: The odd-electron compounds [M(bpy)(2)(L-1)](ClO4) M = Ru ([1](ClO4)) or Os ([2](ClO4)), and the even-electron species [M(bpy)(2)(H2L2)](ClO4)(2), M = Ru ([3](ClO4)(2)) or Os ([4](ClO4)(2)) were obtained from pyrene-4,5-dione, L-1, or 4,5-diaminopyrene, H4L2, and were characterised structurally, electrochemically and spectroscopically. Experimental and computational analysis (TD-DFT) revealed rather different electronic structures and spin distributions of the paramagnetic monocations 1(+)-4(+). EPR investigations and electronic absorption studies exhibit increasing metal contributions to the singly occupied MO along the series 1(+) < 3(+) < 4(+) < 2(+), illustrated by g value and long-wavelength absorbance. In addition to variations of the metal (Ru,Os) and the donor atoms (O,NH) the extension of the pi system of the semiquinone-type ligand has a large effect on the electronic structure of the paramagnetic cations.

First author: Bi, TG, The Li-F-H ternary system at high pressures,
Abstract: Evolutionary crystal structure prediction searches have been employed to explore the ternary Li-F-H system at 300 GPa. Metastable phases were uncovered within the static lattice approximation, with LiF3H2, LiF2H, Li3F4H, LiF4H4, Li2F3H, and LiF3H lying within 50 meV/atom of the 0 K convex hull. All of these phases contain HnFn+1- (n = 1, 2) anions and Li+ cations. Other structural motifs such as LiF slabs, H3+ molecules, and F delta- ions are present in some of the low enthalpy Li-F-H structures. The bonding within the HnFn+1- molecules, which may be bent or linear, symmetric or asymmetric, is analyzed. The five phases closest to the hull are insulators, while LiF3H is metallic and predicted to have a vanishingly small superconducting critical temperature. Li3F4H is predicted to be stable at zero pressure. This study lays the foundation for future investigations of the role of temperature and anharmonicity on the stability and properties of compounds and alloys in the Li-F-H ternary system.

First author: Chen, PP, Computational Exploration of Ambiphilic Reactivity of Azides and Sustmann’s Paradigmatic Parabola,
Abstract: We examine the theoretical underpinnings of the seminal discoveries by Reiner Sustmann about the ambiphilic nature of Huisgen’s phenyl azide cycloadditions. Density functional calculations with omega B97X-D and B2PLYP-D3 reproduce the experimental data and provide insights into ambiphilic control of reactivity. Distortion/interaction-activation strain and energy decomposition analyses show why Sustmann’s use of dipolarophile ionization potential is such a powerful predictor of reactivity. We add to Sustmann’s data set several modern distortion-accelerated dipolarophiles used in bioorthogonal chemistry to show how these fit into the orbital energy criteria that are often used to understand cycloaddition reactivity. We show why such a simple indicator of reactivity is a powerful predictor of reaction rates that are actually controlled by a combination of distortion energies, charge transfer, closed-shell repulsion, polarization, and electrostatic effects.

First author: Portela, S, Catalysis by Bidentate Iodine(III)-Based Halogen Donors: Surpassing the Activity of Strong Lewis Acids,
Abstract: The poorly understood mode of activation and catalysis of bidentate iodine(III)-based halogen donors have been quantitatively explored in detail by means of state-of-the-art computational methods. To this end, the uncatalyzed Diels-Alder cycloaddition reaction between cyclohexadiene and methyl vinyl ketone is compared to the analogous process mediated by a bidentate iodine(III)-organocatalyst and by related, highly active iodine(I) species. It is found that the bidentate iodine(III)-catalyst accelerates the cycloaddition by lowering the reaction barrier up to 10 kcal mol(-1) compared to the parent uncatalyzed reaction. Our quantitative analyses reveal that the origin of the catalysis is found in a significant reduction of the steric (Pauli) repulsion between the diene and dienophile, which originates from both a more asynchronous reaction mode and a significant polarization of the p-system of the dienophile away from the incoming diene. Notably, the activity of the iodine(III)-catalyst can be further enhanced by increasing the electrophilic nature of the system. Thus, novel systems are designed whose activity actually surpasses that of strong Lewis acids such as BF3.

First author: Mai, NL, Elastic and thermodynamic properties of the major clinker phases of Portland cement: Insights from first principles calculations,
Abstract: Portland based cement is one of the most popular materials used in the civil and construction applications. Reliable computational methods to provide an insight into the underlying mechanics of the major phases of this material are of great interest for cement design. The present work investigated the performance of density functional theory (DFT) calculations using the PBE-D2 method to predict the mechanical, thermodynamic properties of four major phases namely Alite C3S, Belite C2S, tricalcium aluminate C(3)A and tetracalcium aluminoferrite C(4)AF. The calculated elastic properties were in a good agreement with available experimental data. In addition, a deeper insight into the electron density of state, spinpolarization, atomic charge, as well as free energy and entropy properties were also presented. Further development is necessary to improve the established DFT models for predicting the mechanical properties of the ferrite phase of Portland clinker.

First author: Du, QY, Single O Atom Doped Ag Cluster Cations for CO Oxidation: An O-Doped Superatom Ag15O+ with Remarkable Stability,
Abstract: Silver-based materials are reported to have remarkable catalytic activity toward CO oxidation after O-2 pretreatment, which are less expensive in comparison with conventional catalysts such as gold and platinum. However, the regulatory role of atomic O that is inevitably present on silver surface remains unclear due to the complicated circumstances in condensed phases. Here we investigated CO oxidation on silver clusters doped by a single O atom AgnO(+) (n = 7-11, 15, 19, 22) by experimental mass spectrometry combined with ab initio calculations. We found two types of O species having high cluster size selectivity and determining the oxidation products. A higher d-band center of AgnO(+) leads to larger reaction barrier. Remarkably, an extremely stable Ag15O+ superatom with a unique meteor dart structure and satisfying the 18 valence electrons configuration (1S(2)1P(6)1D(10)2S(0)) was discovered, which is the first reported O-doped transition metal cluster with superatomic character. This work provides important knowledge for balancing the stability and activity of silver-based catalysts at atomic precision for oxidation reactions.

First author: Carreno, A, New Cationic fac-[Re(CO)(3)(deeb)B2](+) Complex, Where B2 Is a Benzimidazole Derivative, as a Potential New Luminescent Dye for Proteins Separated by SDS-PAGE,
Abstract: Sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) can be used to separate proteins based mainly on their size such as in denaturing gels. Different staining methods have been reported to observe proteins in the gel matrix, where the most used dyes are generally anionic. Anionic dyes allow for interactions with protonated amino acids, retaining the dye in the proteins. Fluorescent staining is an alternative technique considered to be sensitive, safe, and versatile. Some anionic complexes based on d(6) transition metals have been used for this purpose, where cationic dyes have been less explored in this context. In this work, we synthesized and characterized a new monocationic rhenium complex fac-[Re(CO)(3)(deeb)B2](+) (where deeb is 4,4 ‘-bis(ethoxycarbonyl)-2,2 ‘-bpy and B2 is 2,4-di-tert-butyl-6-(3H-imidazo[4,5-c]pyridine-2-yl)phenol). We carried out a structural characterization of this complex by MS+, FTIR, H-1 NMR, D2O exchange, and HHCOSY. Moreover, we carried out UV-Vis, luminescence, and cyclic voltammetry experiments to understand the effect of ligands on the complex’s electronic structure. We also performed relativistic theoretical calculations using the B3LYP/TZ2P level of theory and R-TDDFT within a dielectric continuum model (COSMO) to better understand electronic transitions and optical properties. We finally assessed the potential of fac-[Re(CO)(3)(deeb)B2](+) (as well as the precursor fac-Re(CO)(3)(deeb)Br and the free ligand B2) to stain proteins separated by SDS-PAGE. We found that only fac-[Re(CO)(3)(deeb)B2](+) proved viable to be directly used as a luminescent dye for proteins, presumably due to its interaction with negatively charged residues in proteins and by weak interactions provided by B2. In addition, fac-[Re(CO)(3)(deeb)B2](+) seems to interact preferentially with proteins and not with the gel matrix despite the presence of sodium dodecyl sulfate (SDS). In future applications, these alternative cationic complexes might be used alone or in combination with more traditional anionic compounds to generate counterion dye stains to improve the process.

First author: Gao, Y, Fully Active Nitrogen Energetic Chains Mg-2(N-5)(2)N-2[Mg-2(N-5)(2)N-2](n) under Ambient Conditions,
Abstract: Pentazolate anion cyclo-N-5(-)) is a high energy density unit that has been synthesized. However, how to make cyclo-N complexes stable under ambient condition, without the presence of nonenergetic components, such as H3O+ and NH4+, has always been a challenge. In this work, a fully active nitrogen energetic chain Mg-2(N-5)(2)N-2[Mg-2(N-5)(2)N-2](n) (denoted as ANEC(n), n >= 1) is reported, which has high nitrogen content up to 78%. More importantly, first-principles calculations and molecular dynamics simulations confirm the stability of this structure without external supports. Further electronic structure analysis indicates that the charge transfer from Mg to cyclo-N-5(-) leads to strong covalent bonds, which promotes the stability of cyclo-N-5(-) the chain structures. This finding can contribute to rational design and synthesis of novel high-energy density materials.

First author: Ciancaleoni, G, Assessing the Orbital Contribution in the “Spodium Bond” by Natural Orbital for Chemical Valence-Charge Displacement Analysis,
INORGANIC CHEMISTRY, 60, 4683, (2021)
Abstract: The term “spodium bond” (SpB) has been recently proposed to describe the noncoordinative interaction that can be established between a polarized group 12 metal and a mild Lewis base (LB). Most of the systems showing short metal-donor distances compatible with SpB are characterized by the coexistence of multiple weak interactions, including hydrogen and halogen bonding, making the assessment of real importance of SpB difficult. Here, we show that the relative importance of each contribution can be probed by dissecting the orbital component of the interaction through the extended transition state-natural orbital for chemical valence-charge displacement analysis (ETS-NOCV-CD). The latter gives useful information about relative energies and electrons involved, for model systems ([(thiourea)(2)MX2]center dot center dot center dot LB; M = Zn, Cd, and Hg; X = Cl and I; and LB = CH2S, CH2O, CH3CN, and CO) and a variety of structures extracted from experimentally characterized adducts, allowing us to demonstrate the lack of a direct correlation between a favorable metal-base distance and the presence of an orbital contribution for the SpB.

First author: Inostroza-Rivera, R, Zintl Lewis Superacids: Al(Ge9L3)(3) (L = H, CH3, CHO, CN),
Abstract: In quest of a Zintl ion-based Lewis superacids, Al(Ge9L3)(3) {L = H, CH3, CHO and CN} compounds have been designed and their properties have been studied within the framework of conceptual density functional theory-based reactivity descriptors. Superacid property has been identified for these complexes as per the fluoride ion affinity (FIA) values. Studies reveal that Al[Ge-9(CN)(3)](3) and Al[Ge-9(CH3)(3)](3) behave like superacids as their FIA exceeds the value of SbF5, which is considered as the strongest Lewis acid. It has been observed that the ligand plays an important role in reactivity as well as in Lewis acidic property.

First author: Verevkin, SP, Webbing a network of reliable thermochemistry around lignin building blocks: tri-methoxy-benzenes,
RSC ADVANCES, 11, 10727, (2021)
Abstract: Methoxy-substituted benzenes are the simplest fragments from the lignin separation feedstock. Extensive experimental thermochemical studies of these compounds were carried out, including vapor pressure measurements, combustion and differential scanning calorimetry. These data were evaluated using empirical, semi-empirical and quantum chemical methods. The consistent sets of evaluated thermodynamic data were used to design the method for predicting enthalpies of vaporisation and enthalpies of formation of di- and tri-substituted benzenes. It has been found that the agglomeration of substituents on the benzene ring has dramatic consequences for the energetics of the molecule (in terms of the enthalpy of formation), as well as for the energetics of intermolecular interactions (in terms of the enthalpy of vaporisation). These observations are essential to reliably assess the energetics of the molecules that appear in reaction products of lignin transformations in value-adding chemicals and materials.

First author: Tretyakov, EV, 2-(8-Iodonaphthalen-1-yl)-Substituted Nitronyl Nitroxide: Suppressed Reactivity of Iodine Atom and Unusual Temperature Dynamics of the EPR Spectrum,
Abstract: While developing methods for obtaining high-spin graphene nanostructures, we carried out a model cross-coupling reaction between 1,8-diiodonaphthalene and an organogold derivative of a nitronyl nitroxide. It was found that only one iodine atom reacted, leading to the corresponding 8-iodonaphthalen-1-yl-substituted nitronyl nitroxide. The latter was successfully isolated as two polymorphic modifications, whose X-ray structural analysis revealed a strong distortion of the paramagnet’s geometry in comparison with a noniodinated analog. Moreover, the spatial proximity of the heavy iodine atom and the paramagnetic moiety resulted in unprecedented temperature dynamics of the EPR spectrum. To clarify these dynamics, quantum chemical calculations were performed using the exact two-component relativistic X2C method with the self-consistent account of spin-orbit coupling in conjunction with the B3LYP functional and relativistic STO-type basis set. These computations predicted a reasonable a(iso)(I-127) value that can affect the EPR spectrum. Substitution of the second iodine atom would lead to the formation of a diradical with a 1,8-naphthalenediyl bridge, whose structure and magnetic properties were analyzed at the DFT level. Two stable conformations of the diradical with strongly distorted geometry were identified. In both conformations, calculations predict a ferromagnetic exchange between the paramagnetic centers with J=8 and 14 cm(-1) (H=-2 J.S1S2).

First author: Wang, GY, Barrierless HONO and HOS(O)(2)-NO2 Formation via NH3-Promoted Oxidation of SO2 by NO2,
Abstract: In the troposphere, the knowledge about nitrous acid (HONO) sources is incomplete. The missing source of sulfate and fine particles cannot be explained during haze events. Air quality models cannot predict high levels of secondary fine-particle pollution. Despite extensive studies, one challenging issue in atmospheric chemistry is identifying the source of HONO. Here, we present direct ab initio molecular dynamics simulation evidence and typical air pollution events of the formation of gaseous HONO, nitrogen dioxide/hydrogen sulfite (HOS(O)(2)-NO2 or NO2-HSO3) from nitrogen dioxide (NO2), sulfur dioxide (SO2), water (H2O), and ammonia (NH3) molecules in a proportion of 2:1:3:3. The reactions show a new mechanism for the formation of HONO and NO2-HSO3 in the troposphere, especially when the concentration of NO2, SO2, H2O, and NH3 is high (e.g., 2:1:3:3 or higher) in the air. Contrary to the proportion NO2, SO2, H2O, and NH3 equaling to 1:1:3:1 and 1:1:3:2, the proportion (2:1:3:3) enables barrierless reactions and weak interactions between molecules via the formation of HONO, NO2HSO3, and NH3/H2O. In addition, field observations are carried out, and the measured data are summarized. Correlation analysis supported the conversion of NO2 to HONO during observational studies. The weak interactions promote proton transfer, resulting in the generation of HONO, NO2-HSO3, and NH3/H2O pairs.

First author: Haroon, M, Prediction of NLO response of substituted organoimido hexamolybedate: First theoretical framework based on p-anisidine adduct [Mo6O18(p-MeOC6H4N)](2-),
Abstract: The second-order nonlinear optical (NLO) responses and dipole polarizabilities of p-anisidine adduct (imido derivative of hexamolybdates/polyoxometalates/POMs/Cluster) are studied by means of time dependent density functional (TDDFT) calculations. A substantial molecular second-order NLO response has been noticed in these organic-inorganic hybrid compounds, particularly [Mo6O17 cis-(p-MeOC6H4N)(2)](2-) (system 2) and [Mo6O18 pMeOC(6)H(4)N](2-) (system 1) having static second-order polarizability (beta(vec)) calculated to be 1949.60 au and 1565.10 au respectively. Both p-anisidine and cis-(p-anisidine) are found to be preferred choice over the trans-(p-anisidine) adduct. There is a fair probability for these systems to be selected as efficient second-order nonlinear optical materials. The movement of charge transfer from p-anisidine to hexamolybdate cluster (D-A) along the yaxis suggests molybdenum cluster acts as an acceptor (A) whereas p-anisidine working as a donor (D) in all the studied systems which is responsible for NLO response in such adducts. An incremental increase in the computed beta(vec) values were evaluated by incorporation of an electron donor (Metalloporphyrin) instead of p-anisidine. Furthermore, substitution of Fe over Zn in Metalloporphyrin cage has enhanced the optical nonlinearity. This research effort offers a significant understanding into metal (Fe/Zn) to metal (Mo) charge transfer through imidolinkage in hexamolybdates, which has been found to be an efficient mode to enhance NLO response as a prime example in modulation of optoelectronics.

First author: Arrue, L, Boron-noble gas covalent bonds in borenium and boronium compounds,
Abstract: The capability of the BH2+ parent cation to bind noble gases (Ng) has been evaluated. The results show its potential to form borenium (BH(2)Ng(+)) and boronium (BH(2)Ng(2)(+)) cations. Conformational search using the recently developed AUTOMATON program and Coalescence Kick method, in addition to thermochemical and Born-Oppenheimer molecular dynamics (BOMD) calculations, were performed. Results show that compounds containing Ng = Ar-Rn are thermodynamically and kinetically stable. Furthermore, it was found that the B-Ng bond has high dissociation energy values at both DFT and CCSD(T) levels suggesting a strong interaction. The nature of the chemical bond has been assessed according to the Quantum Theory of Atoms in Molecules (QTAIM), Natural Bond Orbital Theory (NBO) and Energy decomposition Analysis (EDA). Negative values of local energy density H(r(c)) and high values of the Wiberg bond Index (WBI) reveal its covalent nature that is confirmed by localized natural bond orbitals with 2.0 |e| occupations. Additionally, it could be observed that the orbital term (Delta E-orb) is the most important component (84.6-90.1%) of the interaction energy between the parent BH2+ and Ng atoms, supporting the polar covalent nature of the B-Ng bond.

First author: Jiang, ZY, Expanded Inverse-Sandwich Complexes of Lanthanum Borides: La2B10- and La2B11-,
Abstract: Inverse-sandwich structures have been observed recently for dilanthanide boride clusters, in which two Ln atoms sandwich a monocyclic B-x ring for x = 7-9. An interesting question is if larger Bx rings are possible to form such inverse-sandwich clusters. Here we address this question by investigating La2B10- and La2B11- using photoelectron spectroscopy and ab initio quantum chemical calculations. Photoelectron spectra of La2B10- and La2B11- show complicated, but well-resolved, spectral features that are used to compare with theoretical calculations. We have found that global minimum structures of the two clusters are based on the octa-boron ring. The global minimum of La2B10- consists of two chiral enantiomers with C-1 symmetry, which can be viewed as adding a B-2 unit off-plane to the B-8 ring, whereas that of La2B11- can be viewed as adding a B-3 unit in-plane to the B-8 ring in a second coordination shell. Chemical bonding analyses reveal localized B- B bonds on the edge of the clusters and delocalized bonds in the expanded boron frameworks. The interactions between the La atoms and the boron frameworks include the unique (d-p)delta bonding, which was found to be the key for inverse-sandwich complexes with monocyclic boron rings. The current study confirms that the largest monocyclic boron ring to form the inversesandwich structures is B-9 and provide insights into the structural evolutions of larger lanthanide boride clusters.

First author: Su, GL, A bifunctional iminophosphorane squaramide catalyzed enantioselective synthesis of hydroquinazolines via intramolecular aza-Michael reaction to alpha,beta-unsaturated esters,
CHEMICAL SCIENCE, 12, 6064, (2021)
Abstract: An efficient synthesis of enantioenriched hydroquinazoline cores via a novel bifunctional iminophosphorane squaramide catalyzed intramolecular aza-Michael reaction of urea-linked alpha,beta-unsaturated esters is described. The methodology exhibits a high degree of functional group tolerance around the forming hydroquinazoline aryl core and wide structural variance on the nucleophilic N atom of the urea moiety. Excellent yields (up to 99%) and high enantioselectivities (up to 97 : 3 er) using both aromatic and less acidic aliphatic ureas were realized. The potential industrial applicability of the transformation was demonstrated in a 20 mmol scale-up experiment using an adjusted catalyst loading of 2 mol%. The origin of enantioselectivity and reactivity enhancement provided by the squaramide motif has been uncovered computationally using density functional theory (DFT) calculations, combined with the activation strain model (ASM) and energy decomposition analysis (EDA).

First author: Bylaska, EJ, Quantum Solvers for Plane-Wave Hamiltonians: Abridging Virtual Spaces Through the Optimization of Pairwise Correlations,
Abstract: For many-body methods such as MCSCF and CASSCF, in which the number of one-electron orbitals is optimized and independent of the basis set used, there are no problems with using plane-wave basis sets. However, for methods currently used in quantum computing such as select configuration interaction (CI) and coupled cluster (CC) methods, it is necessary to have a virtual space that is able to capture a significant amount of electron-electron correlation in the system. The virtual orbitals in a pseudopotential plane-wave Hartree-Fock calculation, because of Coulomb repulsion, are often scattering states that interact very weakly with the filled orbitals. As a result, very little correlation energy is captured from them. The use of virtual spaces derived from the one-electron operators has also been tried, and while some correlations are captured, the amount is quite low. To overcome these limitations, we have been developing new classes of algorithms to define virtual spaces by optimizing orbitals from small pairwise CI Hamiltonians, which we term as correlation optimized virtual orbitals with the abbreviation COVOs. With these procedures, we have been able to derive virtual spaces, containing only a few orbitals, which are able to capture a significant amount of correlation. The focus in this manuscript is on using these derived basis sets to target full CI (FCI) quality results for H-2 on near-term quantum computers. However, the initial results for this approach were promising. We were able to obtain good agreement with FCI/cc-pVTZ results for this system with just 4 virtual orbitals, using both FCI and quantum simulations. The quality of the results using COVOs suggests that it may be possible to use them in other many-body approaches, including coupled cluster and Moller-Plesset perturbation theories, and open up the door to many-body calculations for pseudopotential plane-wave basis set methods.

First author: Scherer, TM, Analysis of Multiple Redox Sites in Complexes [M(C5Me5)(Q)(NO)](n), M=Ru or Os, Q=o-Quinones,
Abstract: Neutral complexes [M-II(C5Me5)(Q(2-))(NO+)] with M=Ru or Os and the catecholates Q(2-) with 3,5-di-tert-butyl (dtbc) or 3,4,5,6-tetrachloro substituents (tcc) were identified with the oxidation and charge states indicated. Reversible electron transfer was analyzed spectroelectrochemically (EPR, UV-vis-NIR, IR), supported by DFT calculations. Reversible reduction was observed for [Ru(C5Me5)(tcc)(NO)] to occur on the nitrosyl ligand to yield the NO radical complex [Ru-II(C5Me5)(tcc(2-))(NO.)](-), whereas the stepwise oxidation yielded o-semiquinone cations, [M-II(C5Me5)(Q(.-))(NO+)](+), and dications. The metals remained in the stable low-spin d(6) states, Ru-II and Os-II, respectively. Redox potentials were found to depend strongly on the donor or acceptor substitution pattern at Q(n).

First author: Zhou, XQ, Rollover Cyclometalation vs Nitrogen Coordination in Tetrapyridyl Anticancer Gold(III) Complexes: Effect on Protein Interaction and Toxicity,
JACS AU, 1, 380, (2021)
Abstract: In this work, a pair of gold(III) complexes derived from the analogous tetrapyridyl ligands H(2)biqbpy1 and H(2)biqbpy2 was prepared: the rollover, bis-cyclometalated [Au(biqbpy1)Cl ([1]Cl) and its isomer [Au(biqbpy2)Cl ([2]Cl). In [1](+), two pyridyl rings coordinate to the metal via a Au-C bond ((CNNC)-N-boolean AND-N-boolean AND-C-boolean AND coordination) and the two noncoordinated amine bridges of the ligand remain protonated, while in [2](+) all four pyridyl rings of the ligand coordinate to the metal via a Au-N bond ((NNNN)-N-boolean AND-N-boolean AND-N-boolean AND coordination), but both amine bridges are deprotonated. As a result, both complexes are monocationic, which allowed comparison of the sole effect of cyclometalation on the chemistry, protein interaction, and anticancer properties of the gold(III) compounds. Due to their identical monocationic charge and similar molecular shape, both complexes [1]Cl and [2]Cl displaced reference radioligand [H-3]dofetilide equally well from cell membranes expressing the K(v)11.1 (hERG) potassium channel, and more so than the tetrapyridyl ligands H(2)biqbpy1 and H(2)biqbpy2. By contrast, cyclometalation rendered [1]Cl coordinatively stable in the presence of biological thiols, while [2]Cl was reduced by a millimolar concentration of glutathione into metastable Au(I) species releasing the free ligand H(2)biqbpy2 and TrxR-inhibiting Au+ ions. The redox stability of [1]Cl dramatically decreased its thioredoxin reductase (TrxR) inhibition properties, compared to [2]Cl. On the other hand, unlike [2]Cl, [1]Cl aggregated into nanoparticles in FCS-containing medium, which resulted in much more efficient gold cellular uptake. [1]Cl had much more selective anticancer properties than [2]Cl and cisplatin, as it was almost 10 times more cytotoxic to human cancer cells (A549, A431, A375, and MCF7) than to noncancerous cells (MRC5). Mechanistic studies highlight the strikingly different mode of action of the two compounds: while for [1]Cl high gold cellular uptake, nuclear DNA damage, and interaction with hERG may contribute to cell killing, for [2]Cl extracellular reduction released TrxR-inhibiting Au+ ions that were taken up in minute amounts in the cytosol, and a toxic tetrapyridyl ligand also capable of binding to hERG. These results demonstrate that bis-cyclometalation is an appealing method to improve the redox stability of Au(III) compounds and to develop gold-based cytotoxic compounds that do not rely on TrxR inhibition to kill cancer cells.

First author: Aramburu, JA, Key Role of Deep Orbitals in the d(x2-y2)-d(3z2-r2) Gap in Tetragonal Complexes and 10Dq,
Abstract: Using first-principles calculations, we show that the origin of the intrinsic a(1g)(similar to 3z(2) – r(2))-b(1g)(similar to x(2) – y(2)) splitting, Delta(int), in tetragonal transition-metal complexes and the variations of the cubic field splitting, 10Dq, with the metal-ligand distance, R, are much more subtle than commonly thought. As a main novelty, the key role played by covalent bonding with deep valence ligand levels and thus the inadequacy of too simple models often used for the present goal is stressed. Taking as a guide the isolated D-4h CUF64- complex, it is proved that Delta(int), essentially arises from bonding with deep 2s(F) orbitals despite them lying similar to 23 eV below 2p(F) orbitals. This conclusion, although surprising, is also supported by results on octahedral fluoride complexes where the contribution to 10Dq splitting from bonding with 2s(F) orbitals is behind its strong R dependence, stressing that explanations based on the crystal-field approach are simply meaningless.

First author: Lingas, R, Aromaticity of ortho and meta 8-Cycloparaphenylene and Their Dications: Induced Magnetic Field Analysis with Localized and Delocalized Orbitals in Strained Nanohoops,
CHEMPHYSCHEM, 22, 741, (2021)
Abstract: Dications of cycloparaphenyles ([n]CPPs) are known to exhibit in-plane global aromaticity, contained in a nanobelt structure. Recently synthesized ortho and meta isomers of [n]CPPs break the radial symmetry of pi structure incorporating perpendicular oriented pi orbitals. Herein we set to explore the aromaticity of neutral and dicationic ortho and meta isomers of [8]CPP by dissecting the induced magnetic field to contributions of the twofold radial/perpendicular pi system using delocalized canonical molecular orbitals (CMO), and introducing the natural localized molecular orbitals (NLMO) analysis with DFT methods. The dications sustain a reduced global aromatic character of the radial pi system under a perpendicular orientation of the external field which declines from ortho to meta isomer and reinforces local aromaticity of ortho ring while it destroys aromaticity of meta ring. Aromaticity variations are determined by symmetry governed rotational excitations of frontier pi orbitals. The parallel orientation reveals a substantial reduction of local aromaticity verified with NICS pi analysis and electron delocalization indices.

First author: Pan, SD, Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO)(5)}(2)](+) (M=Cu, Ag, Au),
Abstract: Syntheses of the copper and gold complexes [Cu{Fe(CO)(5)}(2)][SbF6] and [Au{Fe(CO)(5)}(2)][HOB{3,5-(CF3)(2)C6H3}(3)] containing the homoleptic carbonyl cations [M{Fe(CO)(5)}(2)](+) (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu2Fe, Ag2Fe and Au2Fe complexes [Cu{Fe(CO)(5)}(2)][SbF6], [Ag{Fe(CO)(5)}(2)][SbF6] and [Au{Fe(CO)(5)}(2)][HOB{3,5-(CF3)(2)C6H3}(3)] are also given. The silver and gold cations [M{Fe(CO)(5)}(2)](+) (M=Ag, Au) possess a nearly linear Fe-M-Fe’ moiety but the Fe-Cu-Fe’ in [Cu{Fe(CO)(5)}(2)][SbF6] exhibits a significant bending angle of 147 degrees due to the strong interaction with the [SbF6](-) anion. The Fe(CO)(5) ligands adopt a distorted square-pyramidal geometry in the cations [M{Fe(CO)(5)}(2)](+), with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO)(5)}(2)](+) (M=Cu, Ag, Au) gives equilibrium structures with linear Fe-M-Fe’ fragments and D-2 symmetry for the copper and silver cations and D-4d symmetry for the gold cation. There is nearly free rotation of the Fe(CO)(5) ligands around the Fe-M-Fe’ axis. The calculated bond dissociation energies for the loss of both Fe(CO)(5) ligands from the cations [M{Fe(CO)(5)}(2)](+) show the order M=Au (D-e=137.2 kcal mol(-1))>Cu (D-e=109.0 kcal mol(-1))>Ag (D-e=92.4 kcal mol(-1)). The QTAIM analysis shows bond paths and bond critical points for the M-Fe linkage but not between M and the CO ligands. The EDA-NOCV calculations suggest that the [Fe(CO)(5)]-> M+<-[Fe(CO)(5)] donation is significantly stronger than the [Fe(CO)(5)]<- M+->[Fe(CO)(5)] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO)(5) ligands into the vacant (n)s and (n)p AOs of M+ and five components for the backdonation from the occupied (n-1)d AOs of M+ into vacant ligand orbitals.

First author: Lipin, R, Theoretical evaluation of mixed N-, O- donor based TMPhenDA ligand in selective complexation with actinide (III) ions over lanthanide (III) ions,
Abstract: Separation of trivalent actinides An(III) from lanthanide Ln(III) is an extremely challenging task in handling nuclearwastes due to their similar chemical behaviours. Though many designed organic ligands have been used for the separation of Ln(III) from An(III) over the years, selectivity and efficiency is still a matter of concern. This drives us to formulate new efficient ligands, in which mixed -N, -O donor ligands are one of the most emerging and promising agents in separation of An(III) from Ln(III). In this work, recently reported TMPhenDA ligand has been investigated for their complexation behaviour with An(III) (U, Am, Cm) and Ln(III) (Nd, Eu, Gd) ions using scalar relativistic ZORA/DFT calculations. Computed bond parameters show that the An(III) ions bind strongly to the ligand than the lanthanide ions. Bond order and QTAIM analyses have been done on the optimized geometries to understand the bonding situation present in the M3+ TMPhenDA complexes. Further, energy decomposition analysis is taken up to assign the percentage covalency of M-N and M-O bonds in these complexes to estimate the strength of these bonds. Overall, this computational investigation provides an in-depth understanding on the preferential selectivity of the ligand with An(III) over Ln(III) using DFT calculations.

First author: Srivastava, R, Application of Optimization Algorithms in Clusters,
Abstract: The structural characterization of clusters or nanoparticles is essential to rationalize their size and composition-dependent properties. As experiments alone could not provide complete picture of cluster structures, so independent theoretical investigations are needed to find out a detail description of the geometric arrangement and corresponding properties of the clusters. The potential energy surfaces (PES) are explored to find several minima with an ultimate goal of locating the global minima (GM) for the clusters. Optimization algorithms, such as genetic algorithm (GA), basin hopping method and its variants, self-consistent basin-to-deformed-basin mapping, heuristic algorithm combined with the surface and interior operators (HA-SIO), fast annealing evolutionary algorithm (FAEA), random tunneling algorithm (RTA), and dynamic lattice searching (DLS) have been developed to solve the geometrical isomers in pure elemental clusters. Various model or empirical potentials (EPs) as Lennard-Jones (LJ), Born-Mayer, Gupta, Sutton-Chen, and Murrell-Mottram potentials are used to describe the bonding in different type of clusters. Due to existence of a large number of homotops in nanoalloys, genetic algorithm, basin-hopping algorithm, modified adaptive immune optimization algorithm (AIOA), evolutionary algorithm (EA), kick method and Knowledge Led Master Code (KLMC) are also used. In this review the optimization algorithms, computational techniques and accuracy of results obtained by using these mechanisms for different types of clusters will be discussed.

First author: Sanyal, S, Nature of halogen bond adducts of carbones with XCF3 (X = Cl, Br, I) species,
POLYHEDRON, 200, 6936, (2021)
Abstract: Quantum chemical calculations have been utilized to study the covalent character of halogen bonding in addition complexes of trifluorohalomethanes XCF3 (X = Cl, Br, I) with well-studied electron-pair-donor divalent C(0) compounds C(NHC)(2), NHC-C-CO, NHC-C-PH3 and PPh3-C-CO [NHC =N-heterocyclic carbene, (CHNH)(2)C]. The geometries of the complexes in which the dicoordinated carbon molecules bind as ligands to one and two XCF3 moieties, respectively, have been optimized to analyze the strength and nature of bond formation using energy decomposition analysis and natural bond orbital calculations. Addition of one XCF3 to the carbones occurs through the lone pair having a orbital character in the plane of the L -> C <- L' bond, while the addition of a subsequent XCF3 leads to the carbone acquiring a tetrahedral geometry. The bond dissociation energy (BDE) for removing ICF3 from one of the carbone adducts is higher than for ClCF3 or BrCF3, while the BDE for the second XCF3 is clearly less than for the first dissociation. Even though electrostatic interactions are known to dominate in halogen bonding, we find considerable contributions from orbital and dispersion interactions.

First author: Zhang, NX, Theoretical prediction of chiral actinide endohedral borospherenes,
NEW JOURNAL OF CHEMISTRY, 45, 6803, (2021)
Abstract: Recently, the observation of the first axially chiral borospherenes (B-39(-)) enriched the members of the boron cluster family, and opened the door to axially chiral boron cages. Herein, we theoretically predicted a series of chiral borospherenes by actinide metal (An) encapsulation, which are new chiral members of the borospherene family. Theoretical calculations demonstrate that the C-2 neutral and charged Ac- and Th-B-39 boron clusters (Ac@B-39, [Ac@B-39](2+), and Th@B-39, [Th@B-39](3+)) are the most stable structures, and each borospherene possesses degenerate enantiomers, in accordance with the chiral borospherenes B-39(-). In contrast, the global minimum structures of Cf embedded borospherenes have no symmetry (C-1). All the chiral actinoborospherenes [An@B-39](n+) (An = Ac, n = 0, 2; An = Th, n = 0, 3) possess high formation energies, especially C-2 [Th@B-39](3+). Bonding analysis shows that each complex of [Ac@B-39](n+) and [Th@B-39](n+) has the characteristic of sigma + pi double delocalization, and the Th-B bonds possess relatively higher covalency than the Ac-B bonds, resulting in the higher formation energy of C-2 [Th@B-39](3+). Therefore, the covalent character of An-B bonding may be essential for the formation of these chiral actinoborospherenes. This work extends the chiral borospherenes to actinide metal-doped chiral borospherenes, and sheds light on the design of chiral metalloborospherenes.

First author: Wada, Y, Efficient Direct Reverse Intersystem Crossing between Charge Transfer-Type Singlet and Triplet States in a Purely Organic Molecule,
CHEMPHYSCHEM, 22, 625, (2021)
Abstract: In the field of organic light-emitting diodes, thermally activated delayed fluorescence (TADF) materials have achieved great performance. The key factor for this performance is the small energy gap (Delta E-ST) between the lowest triplet (T-1) and singlet excited (S-1) states, which can be realized in a well-separated donor-acceptor system. Such systems are likely to possess similar charge transfer (CT)-type T-1 and S-1 states. Recent investigations have suggested that the intervention of other type-states, such as locally excited triplet state(s), is necessary for efficient reverse intersystem crossing (RISC). Here, we theoretically and experimentally demonstrate that our blue TADF material exhibits efficient RISC even between singlet CT and triplet CT states without any additional states. The key factor is dynamic flexibility of the torsion angle between the donor and acceptor, which enhances spin-orbit coupling even between the charge transfer-type T-1 and S-1 states, without sacrificing the small Delta E-ST. This results in excellent photoluminescence and electroluminescence performances in all the host materials we investigate, with sky-blue to deep-blue emissions. Among the hosts investigated, the deepest blue emission with CIE coordinates of (0.15, 0.16) and the highest EQE(MAX) of 23.9 % are achieved simultaneously.

First author: Zhang, BH, From luminescence quenching to high-efficiency phosphorescence: a theoretical study on the monomeric and dimeric forms of platinum(ii) complexes with both 2-pyridylimidazol-2-ylidene and bipyrazolate chelates,
Abstract: To develop solid-state light-emitting materials with high luminescence efficiency, determining the potential photophysics and luminescence mechanisms of the aggregation state remains a challenge and a priority. Here, we apply density functional theory to study the photophysical properties of a series of square planar Pt(ii) complexes in both monomeric and dimeric forms. We reveal that four monomeric Pt(ii) complexes are dominated by triplet ligand-to-ligand charge-transfer, and the lack of the triplet metal-to-ligand charge-transfer feature results in weak spin-orbit coupling (SOC), which leads to limited radiative rates; moreover, calculated nonradiative transition rates are one or two orders of magnitude higher than those radiative rates because a large amount of reorganization energy caused by the vibration of the bipyrazolate (bipz) ligand cannot be readily suppressed in the monomeric form. Therefore, four monomers exhibit photoluminescence quenching in CH2Cl2 solution in both theoretical calculations and experiments. However, in the solid state, the intense luminescence phenomenon indicates obviously distinct properties between the monomer and aggregation. We carried out a dimer model to interpret that the interaction of PtMIDLINE HORIZONTAL ELLIPSISPt induces a metal-metal-to-ligand charge-transfer excimeric state, which leads more metal components to participate in the charge transfer and enhance the SOC effect. At the same time, the ligand vibration can be significantly reduced by the shortened distance, and there is a strong pi-pi packing interaction in the dimer; thus, an excellent quantum yield can be achieved in aggregation. In addition, we disclose that introducing bulky substituents bearing electron-donating groups at R ‘ and R ” positions have little effect on the properties of the monomers; however, there is a benefit of restricting the internal reorganization energy through the intermolecular interaction when packing in the solid state. Therefore, substitutions can be tuned to improve the properties of monomers (such as emission energy and reorganization energy). We hope that our work will shine some light on Pt(ii) emitters in the fabrication of efficient OLEDs.

First author: Fonseca, J, Flexible amorphous metal-organic frameworks with pi Lewis acidic pore surface for selective adsorptive separations,
DALTON TRANSACTIONS, 50, 3145, (2021)
Abstract: Selective separation of light hydrocarbons (LHs) and adsorption of volatile organic compounds (VOCs) remain expensive and complex scientific challenges in the petrochemical industry. Shape-selective adsorbent materials can cost-effectively face these demands. Two new porous, dynamic and amorphous metal-organic frameworks (MOFs), NEU-3 [= Zn(PMDA)(Py)(2)] and NEU-4 [= Fe(PMDA)(Py)(2)] are disclosed. These MOFs along with NEU-1c [= Zn(BPDI)(Py)(2)] and NEU-2 [= Fe(BPDI)(Py)(2)] display an electron-deficient pore surface due to predesigned pi-electron-deficient ligands. They are unique smart guest-responsive materials owing to their pi Lewis acidic pore surface and presumably their framework flexibility. A variety of effective adsorptions and adsorptive separations is achieved by using beds of NEU-1c, NEU-2, NEU-3 and NEU-4. Promising for further investigations into the petrochemical industry, NEU-4 shows ultrahigh benzene adsorption, recognition capability, selectivity for benzene over its analogues, and high stability and regenerability.

First author: Abedi, M, Synthesis, structure, magnetic properties and DFT study of a dinuclear copper(II) macrocyclic complex containing acetate groups,
INORGANICA CHIMICA ACTA, 520, 3145, (2021)
Abstract: Synthesis, spectroscopic characterizations and single crystal X-ray structure of a new dinuclear Copper(II) complex of the form [Cu2L(?-O-OAc)(OAc)2](PF6) are reported. The molecular structure of the complex indicates that acetate ions coordinate to metals in different types, as a unidentate ligand, as a chelating ligand and in arrangement involving chelation and bridging. The metal centers in this complex are five coordinated with two different geometries (trigonal bipyramid and square pyramidal). Magnetic measurements show the presence of a strong Cu?Cu antiferromagnetic interaction. Moreover, density functional theory (DFT) calculations were performed to deeper analysis of the structure and vibrational properties of the synthesized complex. An interesting result is failure of DFT and second order M?ller-Plesset perturbation (MP2) methods for prediction of antiferromagnetic coupling in the synthesized complex which introduces its as a new challenging material for future computational chemistry investigations.

First author: Gao, YJ, Predicting Excited-State and Luminescence Properties of a Cyclometalated Iridium(III) Complex: Quantum Mechanics/Molecular Mechanics Study,
Abstract: The excited-state and luminescence properties of a cyclometalated Ir(III) complex with two (CN)-N-boolean AND ligands ((CN)-N-boolean AND = 2-(2-4-difluorophenyl)pyridine, F(2)ppy) and one acyclic diamino carbene (ADC) ancillary ligand have been investigated by employing computational chemistry methods. We also considered the environmental effects on excited-state properties in CH2Cl2 solution and crystal. The less overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) can reduce the energy gap Delta E-ST between the lowest excited singlet and triplet states. The calculated fluorescence emission peak (S-1 -> S-0) matches with the experimental values in two media. The small Delta E-ST and proper spin-orbit coupling matrix elements (SOCMEs) facilitate the reverse intersystem crossing (rISC) processes from T-1 to S-1 states. Moreover, the forward ISC process takes precedence over transient fluorescence emission and reverse ISC process is also faster than the corresponding phosphorescence emission. This effect may be observed both in the dichloromethane solution and in crystal. By absorbing thermal energy, the excitons of T-1 states upconvert to S-1 states and then radiate energy from S1 states. As a consequence, this Ir complex displays typical characteristics of thermally activated delayed fluorescence (TADF) emitters, and it promises to be the first example of Ir complex with TADF.

First author: Alkorta, I, A C-13 chemical shifts study of iodopyrazoles: experimental results and relativistic and non-relativistic calculations,
Abstract: This work reports the C-13 chemical shifts of 49 iodopyrazoles and the N-15 chemical shifts of 6 iodopyrazoles, most of them from the literature but a number of significant cases from the present work. Most experimental data were from solution studies but some of them correspond to the solid state (CPMAS). The calculations include non-relativistic calculations (nr-GIAO) and relativistic ones (ZORA, mDKS/B3LYP/VDZ and mDKS/B3LYP/VTZ). In the case of NH-pyrazoles, problems of tautomerism and desmotropy arise that have been also studied. The manuscript is dedicated to develop some equations containing corrections for heavy atoms to predict C-13 and N-15 chemical shifts.

First author: Kim, S, Tuning Orbital Symmetry of Iridium Nitrenoid Enables Catalytic Diastereo- and Enantioselective Alkene Difunctionalizations,
Abstract: Among the central themes in synthetic chemistry is the establishment of novel strategies that usher in the development of more efficient and mild reactions and also expand the chemical space for asymmetric catalysis. Herein, we present an approach to revitalize the Cp*Ir(kappa(2)-LX) system as a catalyst toward alkene difunctionalizations via a nitrenoid-mediated pathway. A key strategy is tuning the orbital symmetry of the key Ir nitrenoid intermediates by ligand modification to impart the desired catalytic activity with the suppression of catalyst deactivation. On the basis of a frontier molecular orbital (FMO) analysis, we systematically engineered a new catalyst system capable of a stepwise nitrenoid transfer to allow for nucleophile incorporation. Using the catalytic protocol, a range of difunctionalized lactams can be produced in a diastereoselective manner with various nucleophiles. Mechanistic investigations revealed that the ligand plays a crucial role in both nitrenoid-delivery and stereoselectivity-determining steps. The current mechanistic platform also enabled the development of new asymmetric methods for introducing two-point chirality in (oxyallcyl)lactam products with excellent enantioselectivity.

First author: Riedel, R, Superalkali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents,
Abstract: The nature of anionic alkali metals in solution is traditionally thought to be “gaslike” and unperturbed. In contrast to this noninteracting picture, we present experimental and computational data herein that support ion pairing in alkalide solutions. Concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering results are consistent with the presence of superalkali-alkalide ion pairs in solution, whose stability and properties have been further investigated by DFT calculations. Our temperature dependent alkali metal NMR measurements reveal that the dynamics of the alkalide species is both reversible and thermally activated suggesting a complicated exchange process for the ion paired species. The results of this study go beyond a picture of alkalides being a “gaslike” anion in solution and highlight the significance of the interaction of the alkalide with its complex countercation (superalkali).

First author: Khan, MI, Computational study of borophene/boron nitride (B/BN) interface as a promising gas sensor for industrial affiliated gasses,
Abstract: This study was planned to probe the adsorption properties of industrial affiliated gases CO, NO, CO2, NO2, and NH3 on the surface of Borophene/Boron Nitride (B/BN) interface for gas sensing applications. The investigations carried out using density functional theory (DFT) and involving the van der Waals dispersion revealed that all studied gas molecules except CO2 showed chemisorption behavior. Fascinatingly, the computed energies of adsorption are favourable than borophene as well as other reported 2D materials. The electronic properties are improved for the interface than the pristine borophene and the metallic character remained preserved after adsorption of the gases. Moreover, validation of stronger binding is done with the help of Hirshfeld charge analysis. The calculations exhibited significant change in the transmission for the interface when compared with the pristine interface. In this study, we analyzed the adsorption energies, adsorption configurations, and charge transfer, electronic density of states, transmission properties, vibrational frequencies, and effect of humidity of the mentioned systems. The outcomes of the work are expected to strengthen the plausibility of (B/BN) interfacebased gas sensing device.

First author: Jian, J, Do Sulfonamides Interact with Aromatic Rings?,
Abstract: Aromatic rings form energetically favorable interactions with many polar groups in chemical and biological systems. Recent molecular studies have shown that sulfonamides can chelate metal ions and form hydrogen bonds, however, it is presently not established whether the polar sulfonamide functionality also interacts with aromatic rings. Here, synthetic, spectroscopic, structural, and quantum chemical analyses on 2,6-diarylbenzenesulfonamides are reported, in which two flanking aromatic rings are positioned close to the central sulfonamide moiety. Fine-tuning the aromatic character by substituents on the flanking rings leads to linear trends in acidity and proton affinity of sulfonamides. This physical-organic chemistry study demonstrates that aromatic rings have a capacity to stabilize sulfonamides via through-space NH-pi interactions. These results have implications in rational drug design targeting electron-rich aromatic rings in proteins.

First author: Vermeeren, P, Not Carbon s-p Hybridization, but Coordination Number Determines C-H and C-C Bond Length,
Abstract: A fundamental and ubiquitous phenomenon in chemistry is the contraction of both C-H and C-C bonds as the carbon atoms involved vary, in s-p hybridization, along sp(3) to sp(2) to sp. Our quantum chemical bonding analyses based on Kohn-Sham molecular orbital theory show that the generally accepted rationale behind this trend is incorrect. Inspection of the molecular orbitals and their corresponding orbital overlaps reveals that the above-mentioned shortening in C-H and C-C bonds is not determined by an increasing amount of s-character at the carbon atom in these bonds. Instead, we establish that this structural trend is caused by a diminishing steric (Pauli) repulsion between substituents around the pertinent carbon atom, as the coordination number decreases along sp(3) to sp(2) to sp.

First author: Zheng, HB, Investigation of the palm oil-solubility in naphthenic insulating oil using density functional theory and COSMO-RS,
Abstract: This paper first uses density functional theory combined with the method of quantum chemistry calculations to obtain the electrostatic potential surfaces of the four main triglyceride molecules in palm oil and the water molecule, which reveals the reactivities of triglyceride molecules and the water molecule from a microscopic perspective. In addition, the conductor-like screening model for real solutions (COSMO-RS) method is used to calculate the ?-profile of the main active components of naphthenic mineral oil and the four main triglycerides in palm oil. Then, the COSMO-RS model of the triglyceride-hydrocarbon system is constructed, which theoretically predicts the solubility of the four main triglyceride molecules tripalmitin, tristearin, triolein, and trilinolein in mineral oil. The results show that triglyceride molecules and the mineral oil molecules have similar intermolecular forces, so triglyceride molecules can easily dissolve into the mineral oil. The results of this paper can provide theoretical reference and calculation support for the development of new-type mixed insulating oil for transformers.

First author: Shaik, S, Valence Bond Theory-Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects,
MOLECULES, 26, 7074, (2021)
Abstract: This essay describes the successive births of valence bond (VB) theory during 1916-1931. The alternative molecular orbital (MO) theory was born in the late 1920s. The presence of two seemingly different descriptions of molecules by the two theories led to struggles between the main proponents, Linus Pauling and Robert Mulliken, and their supporters. Until the 1950s, VB theory was dominant, and then it was eclipsed by MO theory. The struggles will be discussed, as well as the new dawn of VB theory, and its future.

First author: Broclawik, E, Zeolites at the Molecular Level: What Can Be Learned from Molecular Modeling,
MOLECULES, 26, 7074, (2021)
Abstract: This review puts the development of molecular modeling methods in the context of their applications to zeolitic active sites. We attempt to highlight the utmost necessity of close cooperation between theory and experiment, resulting both in advances in computational methods and in progress in experimental techniques.

First author: Komarovskikh, A, Structure and EPR investigation of Cu(II) bifluoride complexes with zwitterionic N-hydroxyimidazole ligands,
INORGANICA CHIMICA ACTA, 517, 7074, (2021)
Abstract: Copper(II) bifluoride complexes with zwitterionic N-hydroxyimidazole ligands 1-hydroxy-4methyl-2-(pyridin-2yl)-5-phenylimidazole (HL1) and 1-hydroxy-2-(pyridin-2-yl)-4,5,6,7-tetrahydrobenzimidazole (HL2) were synthesized as a result of reaction of copper(II) fluoride dihydrate with corresponding ligand (metal-to-ligand ratio equal to 1:2) in hydrofluoric acid. The X-ray crystal structures of two compounds CuL12(HF2)2 and [CuL22(HF2)]2?(H2F3)?(H1.4F2.4) were solved. Solvent molecules enter the crystal structures stabilizing them due to the formation of hydrogen bonds. Both of the complexes were investigated with the EPR technique giving the spectra with S = 1/2, gxx = 2.06(1), gyy = 2.11(1), gzz = 2.21(1) and S = 1, gxx = 2.07(1), gyy = 2.07(1), gzz = 2.24 (1), |D| = 61.6(5) mT, |E| = 0 (5) mT, respectively. The magnetic susceptibility measurements results correlate with EPR data. The calculations were performed in the framework of DFT theory; the g-tensors calculated are in good agreement with experimentally obtained.

First author: Dyduch, K, Theoretical Study on Epoxide Ring-opening in CO2/Epoxide Copolymerization Catalyzed by Bifunctional Salen-Type Cobalt(III) Complexes: Influence of Stereoelectronic Factors,
CATALYSTS, 11, 7074, (2021)
Abstract: Propylene oxide (PO) binding and ring-opening reaction with the bifunctional CO2/epoxide copolymerization catalyst, based on the Co(III)-salcy complex including two quaternary ammonium salts with n-butyl substituents (N+-chains) were investigated by Density Functional Theory (DFT) calculations and compared with the model systems without the N+-chains. The importance of the different possible stereoisomers and the stereoselectivity of these processes for (S)- and (R)-enantiomers of PO were considered. To explore the conformational space for the real catalyst, a complex approach, developed previously was applied. The calculations for the model systems directly demonstrate that PO-ring opening proceeds preferentially in trans catalysts’ configuration and no participation of cis-beta isomers is viable; nucleophilic attack at the methylene-carbon atom is preferred over that at methine-carbon atom. For the real bifunctional catalyst, with the (S,S)-configuration of cyclohexane, the results indicate a preference of (R)-PO ring-opening over (S)-PO ring-opening (ca. 6:5). Concerning stereoisomers resulting from the orientation of N+-chains in the real catalyst, different groups of structures participate in the ring-opening reaction for (R)-PO, and different for (S)-PO. The high population of nonreactive complexes of (R)-PO may be the key factor responsible for decreasing the activity of the analyzed catalyst in the epoxide ring-opening reaction.

First author: Sola, M, The energy components of the extended transition state energy decomposition analysis are path functions: the case of water tetramer,
Abstract: A recent paper (Phys. Chem. Chem. Phys. 2020, 22:22,459) shows that the energy components of the extended transition state energy decomposition analysis (ETS-EDA) are path functions, and therefore, they are not uniquely defined. In this work, we apply the ETS-EDA to analyse all possible dissociation paths of the water tetramer to four free water molecules. Our results confirm that the energy components of the ETS-EDA are path functions. However, they also show that differences among energy components obtained for the different paths are relatively small, and therefore, we conclude that the information obtained from an ETS-EDA can be used to discuss the nature of chemical bonds and analyse the origin of isomerization energies and energy barriers. However, if a given process can be attained by means of different and chemically reasonable paths, we recommend to perform the ETS-EDA of a given reaction for all different paths to confirm that energy components of the ETS-EDA do not differ very much from one path to another.

First author: Khan, MI, A computational study of intercalation of streptozotocin (STZ) into DNA base pairs,
Abstract: Deoxyribonucleic acid (DNA) drug intercalation is a well-known phenomenon for the treatment of cancer. Streptozotocin (STZ) is a drug agent containing toxic properties that make it good in the pancreatic cancer. The main objective of this study is the intercalation of the anticancer drug into the stacked base pair of DNA sequence with ATGC using a density functional theory (DFT) code named as ADF-Molecule. ADF code implements DFT using the Slater-type orbitals (STO) for computational analysis of atomic and molecular structures. All the calculations were carried out with the GGA and hybrid exchange correlation functional with TZ2P basis sets. It was captivatingly studied that during the intercalation process, the bonds between the DNA base pairs broken. Moreover, during the process of intercalation, the free radicals are considered responsible for disturbance in the base configurations. It was determined that the disturbances that occurred in the base pairs lead to discontinuity in the replication of that particular sequence in the DNA strand.

First author: Gao, HF, Understanding endohedral behaviors of ten-electron atomic and cluster system inside C-60 from first-principles,
Abstract: Endohedral fullerenes with remarkable properties and various potential applications currently constitute a focus area of interest in nanocarbon science. Recently reported endohedral fullerenes exhibiting fine-tuned properties are highly desirable for realizing enhanced functionality. This work systematically investigates endohedral fullerenes containing various atomic or cluster species with ten electrons inside C-60 (termed X-10e@C-60) by density functional theory calculations. In particular, the nature of the interaction between the ten-electron species and fullerene cage in X-10e@C-60 has been discussed in detail considering the reduced density gradient, energy decomposition analysis, charge transfer, and orbital interaction analysis. The molecular electrostatic potential evidence in this study shows that endohedral fullerenes with neutral, cationic, and anionic species have the similar surfaces with C-60, C-60(+), and C-60(-), respectively. And the dominating attractive contributions were different for the neutral, cationic, and anionic X-10e@C-60 systems during the physical process.

First author: Lancheros, A, Modulation of CO2 adsorption in novel pillar-layered MOFs based on carboxylate-pyrazole flexible linker,
DALTON TRANSACTIONS, 50, 2880, (2021)
Abstract: Metal-organic frameworks (MOFs) have attracted significant attention as sorbents due to their high surface area, tunable pore volume and pore size, coordinatively unsaturated metal sites, and ability to install desired functional groups by post-synthetic modification. Herein, we report three new MOFs with pillar-paddlewheel structures that have been synthesized solvothermally from the mixture of the carboxylate-pyrazole flexible linker (H2L), 4,4-bipyridine (BPY)/triethylenediamine (DABCO), and Zn(ii)/Cu(ii) ions. The MOFs obtained, namely [Zn-II(L)BPY], [Cu-II(L)BPY], and [Cu-II(L)DABCO], exhibit two-fold interpenetration and dinuclear paddle-wheel nodes. The Zn(ii)/Cu(ii) cations are coordinated by two equatorial L linkers that result in two-dimensional sheets which in turn are pillared by BPY or DABCO in the perpendicular direction to obtain a neutral three-dimensional framework that shows one-dimensional square channels. The three pillar-layered MOFs were characterized as microporous materials showing high crystalline stability after activation at 120 degrees C and CO2 adsorption. All MOFs contain uncoordinated Lewis basic pyrazole nitrogen atoms in the framework which have an affinity toward CO2 and hence could potentially serve as CO2 adsorption material. The CO2 uptake capacity was initially enhanced by replacing Zn with Cu and then replacing the pillar, going from BPY to DABCO. Overall, all the MOFs exhibit low isosteric heat (Q(st)) of adsorption which signifies an advantage due to the energy required for the adsorption and regeneration processes.

First author: Chen, X, Theoretical study on the molecular stacking interactions and charge transport properties of triazasumanene crystals – from explanation to prediction,
Abstract: Computational analyses of the solid-state properties of triazasumanene (TAS), a C-3-symmetric nitrogen-doped sumanene derivative, were carried out in this work. The present studies are mainly divided into two parts. In the first part, we demonstrated the differences in the interactions of the crystal packing between the racemic and the homochiral structures: the former having perpendicular columnar packing and the latter forming slipped helical packing. Two geometries of the TAS monomer, a theoretically optimized structure under vacuum and an X-ray crystal structure in experiment, were compared. It can be found that it is not the total interaction energy, but the local interactions (mainly the electrostatic interactions) of the molecular dimer that dominate the columnar stacking conformation. The second part involves the investigation of the potential charge transport properties of the crystals according to the semiclassical Marcus theory with the hopping mechanism using the simple dimer model. The charge transfer integrals of the two sets of dimers, racemic and homochiral dimer models, were compared as well. The calculation results show that the TAS racemic crystal was predicted to have an advantage of hole transport properties. The perpendicular columnar stacking of the homochiral conformation should essentially have better charge transport properties than the racemic conformation. It is reasonable to employ the simple dimer model built using optimized monomers under vacuum for the purpose of the prediction of the molecular packing conformation by IES calculation and the charge transport properties of the perpendicular columnar-stacking crystal. Our work provides a simple approach to the deep understanding of the structure-property relationship of bowl-shaped molecular systems in theory. It can help to facilitate the design and preparation of heteroatom-doped sumanene derivatives with perpendicular columnar stacking crystals as novel organic semiconductor materials.

First author: Wysokinski, R, Anion-anion and anion-neutral triel bonds,
Abstract: The ability of a TrCl4- anion (Tr = Al, Ga, In, Tl) to engage in a triel bond with both a neutral NH3 and CN- anion is assessed by ab initio quantum calculations in both the gas phase and in aqueous medium. Despite the absence of a positive sigma or pi-hole on the Lewis acid, strong triel bonds can be formed with either base. The complexation involves an internal restructuring of the tetrahedral TrCl4- monomer into a trigonal bipyramid shape, where the base can occupy either an axial or equatorial position. Although this rearrangement requires a substantial investment of energy, it aids the complexation by imparting a much more positive MEP to the site that is to be occupied by the base. Complexation with the neutral base is exothermic in the gas phase and even more so in water where interaction energies can exceed 30 kcal mol(-1). Despite the long-range coulombic repulsion between any pair of anions, CN- can also engage in a strong triel bond with TrCl4-. In the gas phase, complexation is endothermic, but dissociation of the metastable dimer is obstructed by an energy barrier. The situation is entirely different in solution, with large negative interaction energies of as much as -50 kcal mol(-1). The complexation remains an exothermic process even after the large monomer deformation energy is factored in.

First author: He, TF, Impact of.EST on Delayed Fluorescence Rate, Lifetime, and Intensity Ratio of Tetrahedral Cu(I) Complexes: Theoretical Simulation in Solution and Solid Phases,
Abstract: Profound understanding of the luminescence mechanism and structure-property relationship is vital for Cu(I) thermally activated delayed fluorescence (TADF) emitters. Herein, we theoretically simulated luminescent behavior in both solution and solid phases for two Cu(I) complexes and found the following: (i) The strengthened spin-orbit coupling (SOC) effect by more d(x)(-y)(2)(2) orbital contributions and well-restricted structural distortion via remarkable intramolecular interaction in [Cu(dmp)(POP)](+) enable the emission at room temperature to be a mixture of direct phosphorescence (10%) and TADF (90%). (ii) Benefiting from enhanced steric hindrance and the electron-donating ability of the paracyclophane group, the narrowed S-1-T-1 energy separation (Delta E-ST) in [Cu(dmp)(phanephos)](+) accelerates the reverse intersystem crossing, promoting the TADF rate (1.88 x 10(5) s(-1)) and intensity ratio (98.3%). These results indicate that the small Delta E-ST is superior for reducing the lifetime and that the strong SOC stimulates the phosphorescence to compete with TADF, which are both conducive to avoiding collision-induced exciton quenching and reducing the roll-off in devices.

First author: Confer, MP, Solubility thermodynamics of amine boranes in polar solvents,
Abstract: Amine boranes are solid hydrogen storage materials and are difficult to transport within systems unless dissolved in solvents. The solubility and free energy of solution were experimentally determined for ammonia borane, methylamine borane, dimethylamine borane, trimethylamine borane, and tert-butylamine borane in methanol, ethanol, 1propanol, 2-propanol, acetonitrile, dimethyl sulfoxide, and tetrahydrofuran. The solubilities of ammonia borane/methylamine borane mixtures in methanol were also measured. The enthalpy of solution was experimentally determined for ammonia borane, methyl amine borane, dimethylamine borane, and 30/70 wt% ammonia borane/methylamine borane eutectic in four different solvents: methanol, ethanol, acetonitrile, and dimethyl sulfoxide. For all solutes, dimethyl sulfoxide solutions were the most exothermic or least endothermic. Increased methyl-substitution on the amine led to more endothermic processes. For methanol, ethanol, and acetonitrile, the entropy of solution increased as solubility increased. The entropy of solution for ammonia borane dissolving in dimethyl sulfoxide is negative. COSMO-RS solubility calculations using density functional theory optimized geometries agree relatively well with experimental values for amine borane materials dissolved in polar solvents.

First author: Gharibnejad, H, A multi-center quadrature scheme for the molecular continuum?,
Abstract: A common way to evaluate electronic integrals for polyatomic molecules is to use Becke’s partitioning scheme (Becke and Chem, 1988) in conjunction with overlapping grids centered at each atomic site. The Becke scheme was designed for integrands that fall off rapidly at large distances, such as those approximating bound electronic states. When applied to states in the electronic continuum, however, Becke scheme exhibits slow convergence and it is highly redundant. Here, we present a modified version of Becke scheme that is applicable to functions of the electronic continuum, such as those involved in molecular photoionization and electron-molecule scattering, and which ensures convergence and efficiency comparable to those realized in the calculation of bound states. In this modified scheme, the atomic weights already present in Becke’s partition are smoothly switched off within a range of few bond lengths from their respective nuclei, and complemented by an asymptotically unitary weight. The atomic integrals are evaluated on small spherical grids, centered on each atom, with size commensurate to the support of the corresponding atomic weight. The residual integral of the interstitial and long-range region is evaluated with a central master grid. The accuracy of the method is demonstrated by evaluating integrals involving integrands containing Gaussian Type Orbitals and Yukawa potentials, on the atomic sites, as well as spherical Bessel functions centered on the master grid. These functions are representative of those encountered in realistic electron-scattering and photoionization calculations in polyatomic molecules.

First author: Silva, DR, The Gauche Effect in XCH2CH2X Revisited,
CHEMPHYSCHEM, 22, 641, (2021)
Abstract: We have quantum chemically investigated the rotational isomerism of 1,2-dihaloethanes XCH2CH2X (X = F, Cl, Br, I) at ZORA-BP86-D3(BJ)/QZ4P. Our Kohn-Sham molecular orbital (KS-MO) analyses reveal that hyperconjugative orbital interactions favor the gauche conformation in all cases (X = F-I), not only for X = F as in the current model of this so-called gauche effect. We show that, instead, it is the interplay of hyperconjugation with Pauli repulsion between lone-pair-type orbitals on the halogen substituents that constitutes the causal mechanism for the gauche effect. Thus, only in the case of the relatively small fluorine atoms, steric Pauli repulsion is too weak to overrule the gauche preference of the hyperconjugative orbital interactions. For the larger halogens, X…X steric Pauli repulsion becomes sufficiently destabilizing to shift the energetic preference from gauche to anti, despite the opposite preference of hyperconjugation.

First author: Murugesan, V, Accelerated design of vanadium redox flow battery electrolytes through tunable solvation chemistry,
Abstract: Operational stability of electrolytes is a persistent impediment in building redox flow battery technology. Stabilizing multiple vanadium oxidation states in aqueous solution is a primary challenge in designing reliable large-scale vanadium redox flow batteries (VRBs). Here we demonstrate that rationally selected ionic additives can stabilize the aqua vanadium solvate structures through preferential bonding and molecular interactions despite their relatively low concentrations (<= 0.1 M). The competing cations (NH4+ and Mg2+) and bonding anions (SO42-, PO43-, and Cl-) introduced by bi-additives are used to tune the vanadium solvation chemistry and design an optimal electrolyte for VRB technology. Such molecular engineering of VRB electrolytes results in enhancement of the operational temperature window by 180% and energy density by more than 30% relative to traditional electrolytes. This work demonstrates that tunable solvation chemistry is a promising pathway to engineer an optimal electrolyte for targeted electrochemical systems.

First author: Das, AK, One-Dimensional Silver-Thiolate Cluster-Assembly: Effect of Argentophilic Interactions on Excited-State Dynamics,
Abstract: We report the synthesis, crystal structure, and electronic structure calculations of a one-dimensional silver-thiolate cluster-assembled and its ultrafast spectroscopic investigation. Experiments and theory find the material to have a significant gap as the HOMO-LUMO absorption corresponds to 2.69 eV, and the defect-free structure is calculated to have a gap of 2.82 eV. Cluster models demonstrate that the gap energy is length-dependent. Theoretical studies identify a nonbonding metallophilic interaction that exists between two Ag atoms in adjacent strings that helps to stabilize the chain structure. Transient absorption spectroscopy reveals that the electron dynamics is a mixture of the behavior of cluster and nanoparticle, with the material having a 346 fs ground-state relaxation like a cluster, and the electron dynamics is dominated by electron-phonon coupling with a decay time of 1.5 ps, unlike the isolated cluster whose decay is mostly radiative.

First author: Wang, YT, High-temperature pyrolysis of isoprenoid hydrocarbon p-menthane using ReaxFF molecular dynamics simulation,
Abstract: The pyrolysis chemistry of p-menthane, a promising ?drop-in? fuel of bio-derived isoprenoid hydrocarbon, has not been well understood especially under high temperatures. In this work, the pyrolysis of p-menthane is further investigated using molecular dynamics simulations with the reactive force-field interatomic potential (ReaxFF) under 2600 K. It is found that the scission of isopropyl and the ring-open reaction in the site adjacent to the isopropyl are two predominant initiations of p-menthane decomposition in our simulations. The main generation and consumption channels of important products, such as methane and ethylene, are also tracked by the straightforward scrutinize on simulation trajectories. In addition, a detailed reaction scheme of the hightemperature pyrolysis is proposed. The apparent activation energy calculated from our reactive molecular dynamics simulations in the temperature range from 2200 K to 3000 K is 232 kJ mol- 1, which is reasonably consistent with our experimental result of 225 ? 5 kJ mol- 1. In summary, the simulation results provided by ReaxFF are helpful to explain pyrolysis processes readily, which is the effective verification and extension of previous experimental studies.

First author: Sruthi, PK, Exploring pentavalent phosphorous bonding in phosphoryl chloride-halocarbon heterodimers at low temperatures and ab initio Computations,
CHEMICAL PHYSICS, 545, 2154, (2021)
Abstract: In this work, POCl3 prototype was examined with competing hydrogen, halogen, tetrel and pnicogen (phosphorus) bonding partners under isolated conditions at low temperatures, which were supported by quantum chemical calculations. Computations on 1:1 heterodimer of POCl3-CH2Cl2 indicated that the multiple competing interactions were found to co-exist in all the heterodimers. Of the eight possible POCl3-CH2Cl2 dimers, the experimentally important global minimum structure (PDCM-I) has a strong hydrogen bonding interaction with co-operative pentavalent phosphorus bonding. If hydrogen bonding is hampered with chlorine substitutions in the interacting partner and as with illustrative POCl3-CCl4 dimer model, phosphorus bonding seems to dominate with co-operative halogen bonding interaction in the experimentally relevant ground state geometry (PCTC-I). Experimental evidence for the formation of the PDCM-I and PCTC-I heterodimers were discerned in Ar and N-2 matrixes using infrared spectroscopy.

First author: Simeral, ML, Effects of Conformational Variation on Structural Insights from Solution-Phase Surface-Enhanced Raman Spectroscopy,
Abstract: Surface-enhanced Raman scattering (SERS) spectra contain information on the chemical structure on nanoparticle surfaces through the position and alignment of molecules with the electromagnetic near field. Time-dependent density functional theory (TDDFT) can provide the Raman tensors needed for a detailed interpretation of SERS spectra. Here, the impact of molecular conformations on SERS spectra is considered. TDDFT calculations of the surfactant cetyltrimethylammonium bromide with five conformers produced more accurate unenhanced Raman spectra than a simple all-trans structure. The calculations and measurements also demonstrated a loss of structural information in the CH2/CH3 scissor vibration band at 1450 cm(-1) in the SERS spectra. To study lipid bilayers, TDDFT calculations on conformers of methyl phosphorylcholine and cis-5-decene served as models for the symmetric choline stretch in the lipid headgroup and the C=C stretch in the acyl chains of 1,2-oleoyl-glycero-3-phosphocholine. Conformer considerations enabled a measurement of the distribution of double-bond orientations with an order parameter of S-C=C = 0.53.

First author: Gorantla, SMNVT, Bonding and Stability of C6F4 Bridged by Bis-Carbenes: EDA-NOCV Analysis of (L)(2)C6F4 [L = SNHCDip, cAAC(Me)],
Abstract: The donor base ligand stabilized compound (L)(2)C6F4 [1 for L=saturated N-heterocyclic carbene (SNHCDip) and 2 for L=cyclic alkyl(amino) carbene (cAAC(Me))] has been investigated by energy decomposition analysis (EDA) coupled with natural orbital for chemical valence (NOCV) calculation. The bonding analysis of 1 has revealed that (SNHCDip)(2)(+) prefers to form an electron sharing sigma-bond, a dative sigma-bond and two dative pi-bonds with the central C6F4- unit in their doublet states. In contrast, (cAAC(Me))(2) forms two electron sharing sigma-bonds and two electron sharing pi-bonds with the neutral C6F4 unit of 2 in their quintet states.

First author: Gao, Y, Stabilization of hydrated Ac-III cation: the role of superatom states in actinium-water bonding,
CHEMICAL SCIENCE, 12, 2655, (2021)
Abstract: Ac-225-based radiopharmaceuticals have the potential to become invaluable in designated cancer therapy. However, the limited understanding of the solution chemistry and bonding properties of actinium has hindered the development of existing and emerging targeted radiotherapeutics, which also poses a significant challenge in the discovery of new agents. Herein, we report the geometric and electronic structural properties of hydrated Ac-III cations in the [Ac-III(H2O)(n)](3+) (n = 4-11) complexes in aqueous solution and gas-phase using density functional theory. We found that nine water molecules coordinated to the Ac-III cation is the most stable complex due to an enhanced hydration Gibbs free energy. This complex adopts a closed-shell 18-electron configuration (1S(2)1P(6)1D(10)) of a superatom state, which indicates a non-negligible covalent character and involves H2O -> Ac-III sigma donation interaction between s-/p-/d-type atomic orbitals of the Ac atom and 2p atomic orbitals of the O atoms. Furthermore, potentially existing 10-coordinated complexes need to overcome an energy barrier (>0.10 eV) caused by hydrogen bonding to convert to 9-coordination. These results imply the importance of superatom states in actinide chemistry generally, and specifically in Ac-III solution chemistry, and highlight the conversion mechanism between different coordination numbers.

First author: Mattei, CA, Solid-state versus solution investigation of a luminescent chiral BINOL-derived bisphosphate single-molecule magnet,
Abstract: The enantiopure coordination polymer [Dy(hfac)(3)((S/R)-L)](n) ([(S/R)-1](n)) involving a BINOL-derived bisphosphate ligand (S/R)-L is reported. Paramagnetic NMR and computational investigations demonstrated the formation of mononuclear species [(S/R)-1] in CH2Cl2 solution and its optimized structure was determined. The experimental electronic circular dichroism signals of (S/R)-L were strongly enhanced after metal coordination [(S/R)-1]. Both polymeric and mononuclear structures displayed field-induced Single-Molecule Magnet (SMM) behaviour with similar multi-relaxation processes due to the retention of crystal-field splitting determined by CASSCF calculations, despite the strong structural transformation between the two media. The HOMO -> LUMO transition of the (S)-L ligand induced the classical Dy(iii) emission at 77 K that was correlated with the magnetic properties. [(S)-1](n) is described as one-dimensional assembly of chiral luminescent Single-Ion Magnets (SIMs).

First author: Vasconcellos-Dias, M, New heptacoordinate tungsten(II) complexes with ?-diimine ligands in the catalytic oxidation of multifunctional olefins,
Abstract: New tungsten(II) and molybdenum(II) heptacoordinate complexes [MX2(CO)3(LY)] (MXLy: M = W, Mo; X = Br, I; LY = C5H4NCY = N(CH2)2CH3 with Y = H (L1), Me (L2), Ph (L3)) were synthesized and characterized by spectroscopic techniques and elemental analysis. The two tungsten complexes WXL1 (X = Br, I) were also structurally characterized by single crystal X-ray diffraction. The metal coordination environment is in both a distorted capped octahedron. The complexes with L1 and L2 ligands were grafted in MCM-41, after functionalization of the ligands with a Si(OEt)3 group. The new materials were characterized by elemental analysis, N2 adsorption isotherms, 29Si MAS and 13C MAS NMR. The tungsten(II) complexes and materials were the first examples of this type reported. All complexes and materials were tested as homogeneous and heterogeneous catalysts in the oxidation of multifunctional olefins (cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, geraniol, S-limonene, and 1-octene), with tert-butyl hydroperoxide (TBHP) as oxidant. The molybdenum(II) catalyst precursors are in general very active, reaching 99% conversion and 100% selectivity in the epoxidation of trans-hex-3-en-1-ol. Their performance is comparable with that of the [Mo(?3-C3H5)X(CO)2(LY)] complexes, but it increases with immobilization. On the other hand, most of the W(II) complexes display an activity similar or inferior to that of the Mo(II) analogues and it decreases after they are supported in MCM-41. DFT calculations show that tungsten complexes and iodide ligands are more easily oxidized from M(II) to M(VI) than molybdenum ones, while the energies of relevant species in the catalytic cycle are very similar for all complexes, making the theoretical rationalization of experimental catalytic data difficult.

First author: Chen, DQ, cis-beta-Ru(II)heteroatom-stabilized-carbene complexes supported by tetradentate Schiff-base salen ligand,
POLYHEDRON, 199, 947, (2021)
Abstract: A panel of stable ruthenium carbene complexes bearing a tetradentate salen ligand, with their carbene-C atom adjacent to heteroatom, were synthesized from cis-beta-Ru(II)-bis(CO) complex by reacting with the corresponding carbene precursors. These carbene complexes, which were fully characterized by elemental analysis, NMR, IR spectroscopy and X-ray-crystal structure determination, all adopt a cis-beta configuration; the heteroatom (N or O) adjacent to the carbene C atom contributes to the high stability of these complexes both in solution and in solid state. DFT calculations were also performed to gain insight into the Ru-C-carbene bonds.

First author: Gorantla, SMNVT, Bonding and stability of donor ligand-supported heavier analogues of cyanogen halides (L ‘)PSi(X)(L),
RSC ADVANCES, 11, 6586, (2021)
Abstract: Fluoro- and chloro-phosphasilynes [X-Si=P (X = F, Cl)] belong to a class of illusive chemical species which are expected to have Si=P multiple bonds. Theoretical investigations of the bonding and stability of the corresponding Lewis base-stabilized species (L ‘)PSi(X)(L) [L ‘ = cAAC(Me) (cyclic alkyl(amino) carbene); L = cAAC(Me), NHCMe (N-heterocyclic carbene), PMe3, aAAC (acyclic alkyl(amino) carbene); X = Cl, F] have been studied using the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) method. The variation of the ligands (L) on the Si-atom leads to different bonding scenarios depending on their sigma-donation and pi-back acceptance properties. The ligands with higher lying HOMOs prefer profoundly different bonding scenarios than the ligands with lower lying HOMOs. The type of halogen (Cl or F) on the Si-atom was also found to have a significant influence on the overall bonding scenario. The reasonably higher value and endergonic nature of the dissociation energies along with the appreciable HOMO-LUMO energy gap may corroborate to the synthetic viability of the homo and heteroleptic ligand-stabilized elusive PSi(Cl/F) species in the laboratory.

First author: Shakourian-Fard, M, A DFT study of the adsorption of deep eutectic solvents onto graphene and defective graphene nanoflakes,
Abstract: The interaction of four deep choline chloride-derived eutectic solvents (DESs) with both graphene nanoflakes (GNF) and its defective double-vacancy and Stone-Wales forms (DV-GNF and SW-GNF), was evaluated using density functional theory (DFT). The presence of defects increases the adsorption energy of DESs, following the order DESnDV-GNF > DESnSW-GNF > DESnGNF. Non-covalent interaction and energy decomposition analyses show that the interactions are noncovalent and dominated by dispersive forces. Furthermore, we find that the presence of aromatic moieties in the DESs increases the van der Waals interactions with the surfaces. These interactions decrease the HOMO-LUMO (E-g) energy gap of the surfaces and thus increase reactivity. Reactivity parameter calculations indicate that the chemical potential (mu) and chemical hardness (eta) of the complexes follow the order DESn GNF > DESnSW-GNF > DESnDV-GNF. This order is reversed for the global softness (S) and electrophilicity index (omega). Time-dependent DFT (TD-DFT) calculations predict that the adsorption of DESs onto DV-GNF and SW-GNF should red shift absorption, while the absorption spectrum of GNF surface remains unchanged upon DES adsorption. The biggest changes in the absorption spectra are observed upon adsorption of DESs on the DV-GNF surface due to the stronger affinity of the DESs for this surface.

First author: Zhang, Q, A quantitative evaluation of computational methods to accelerate the study of alloxazine-derived electroactive compounds for energy storage,
SCIENTIFIC REPORTS, 11, 6586, (2021)
Abstract: Alloxazines are a promising class of organic electroactive compounds for application in aqueous redox flow batteries (ARFBs), whose redox properties need to be tuned further for higher performance. High-throughput computational screening (HTCS) enables rational and time-efficient study of energy storage compounds. We compared the performance of computational chemistry methods, including the force field based molecular mechanics, semi-empirical quantum mechanics, density functional tight binding, and density functional theory, on the basis of their accuracy and computational cost in predicting the redox potentials of alloxazines. Various energy-based descriptors, including the redox reaction energies and the frontier orbital energies of the reactant and product molecules, were considered. We found that the lowest unoccupied molecular orbital (LUMO) energy of the reactant molecules is the best performing chemical descriptor for alloxazines, which is in contrast to other classes of energy storage compounds, such as quinones that we reported earlier. Notably, we present a flexible in silico approach to accelerate both the singly and the HTCS studies, therewithal considering the level of accuracy versus measured electrochemical data, which is readily applicable for the discovery of alloxazine-derived organic compounds for energy storage in ARFBs.

First author: Xu, C, Revisiting the pi-Back-Donation in the NHC-B B-NHC Molecule,
Abstract: As the first thermal stable molecule with a B B bond, the diboryne complex protected by N-heterocyclic carbene ligands (NHC-B B-NHC) has attracted much interest. Researchers point out that pi-backdonation highly stabilizes the B B bond besides a-donation, both of which are induced by NHC ligands. In this work, details of the pi-back-donation are revisited by using DFT calculations. There are two delocalized pi* orbitals in NHC, and the symmetry of one e orbital is highly adaptive to then orbitals in B B bond, whereas the other cannot be involved in the A-back-donation. In staggered configuration, two orthogonal pi orbitals of B B interact with this pi* orbital in each NHC ligand, respectively, to form R-back-donations in both sides. This interaction has proven to be more intensive than pi-conjunction, resulting in the lower energy of the staggered isomer compared with the eclipsed one containing greater pi-conjunction. Moreover, intensity of the pi-back-donation can be enhanced by reducing the energy levels of the matched pi* orbitals in ligands, which gives references for the design of stable diborynes.

First author: Santos, LA, A Quantitative Molecular Orbital Perspective of the Chalcogen Bond,
CHEMISTRYOPEN, 10, 391, (2021)
Abstract: We have quantum chemically analyzed the structure and stability of archetypal chalcogen-bonded model complexes D(2)Ch…A(-) (Ch = O, S, Se, Te; D, A = F, Cl, Br) using relativistic density functional theory at ZORA-M06/QZ4P. Our purpose is twofold: (i) to compute accurate trends in chalcogen-bond strength based on a set of consistent data; and (ii) to rationalize these trends in terms of detailed analyses of the bonding mechanism based on quantitative Kohn-Sham molecular orbital (KS-MO) theory in combination with a canonical energy decomposition analysis (EDA). At odds with the commonly accepted view of chalcogen bonding as a predominantly electrostatic phenomenon, we find that chalcogen bonds, just as hydrogen and halogen bonds, have a significant covalent character stemming from strong HOMO-LUMO interactions. Besides providing significantly to the bond strength, these orbital interactions are also manifested by the structural distortions they induce as well as the associated charge transfer from A(-) to D(2)Ch.

First author: Barboza, CA, Structural, electronic and magnetic properties of copper(I) cubic clusters,
POLYHEDRON, 195, 391, (2021)
Abstract: We report the molecular and electronic structure, and the calculated electronic excitation energies, using the time dependent density functional methodologies (TD-DFT), and the induced magnetic field (B-i) of a series of Cu(I) dithiolato and diselenolato species of formula [Cu-8(L)(6)]. They are composed by eight copper atoms forming a Cu-8 cube and six bidentate ligands (L), where twelve chalcogen atoms (Q) bridging the edges of the copper cube, in such a way that chalcogen atoms describe an icosahedron, enclosing a cubic [Cu8(mu-Q(12))](4) core of T-h symmetry. The Q…Q bite distance is similar in all clusters, without being influenced by the Cu-Cu distance, suggesting the existence of metallophilic interactions that stabilize the cluster structure. Despite of the structural similarities, the electronic structure of these clusters present some differences which are magnified on their optical properties. Excitation energies and their composition depend on the nature of each different ligand in these clusters, according to CT(lambda(M) )index to determine the ligand to metal (LM) or metal to ligand charge transfer (MLCT) character of each calculated electronic transition. The magnetic properties calculations show the importance to separate the magnetic response into their individual components (B-i with i = x, y, z, iso), and diamagnetic and paramagnetic contributions to understand the differences according to the type of ligand on the cluster structure.

First author: Wanjari, PJ, Quantum chemical study in exploring the role of donor -> acceptor interactions in 1,3-bis carbene-stabilized guanidinium cations,
Abstract: Guanidinium species are highly basic and hence mostly exist in cationic state. Because these cations carry electron-deficient centers, they can be stabilized with the help of electron-donating ligands like N-heterocyclic carbenes. A few novel guanidinium cationic species stabilized by electron-donating ligands were designed and quantum chemically evaluated. It was shown that strong hydrogen bonds and tautomerism are the important characteristics of these species. Further, the possibility of donor -> acceptor coordination interactions in these species have been explored between the electron-donating carbenes and the central guanidinium unit. The results suggest that the title compounds can be considered as ligand-stabilized guanidinium cations similar to the ligand-stabilized N+ and N-3(+) centers.

First author: Wolter, M, Systematic Partitioning of Proteins for Quantum-Chemical Fragmentation Methods Using Graph Algorithms,
Abstract: Quantum-chemical fragmentation methods offer an efficient approach for the treatment of large proteins, in particular if local target quantities such as protein-ligand interaction energies, enzymatic reaction energies, or spectroscopic properties of embedded chromophores are sought. However, the accuracy that is achievable for such local target quantities intricately depends on how the protein is partitioned into smaller fragments. While the commonly employed naive approach of using fragments with a fixed size is widely used, it can result in large and unpredictable errors when varying the fragment size. Here, we present a systematic partitioning scheme that aims at minimizing the fragmentation error of a local target quantity for a given maximum fragment size. To this end, we construct a weighted graph representation of the protein, in which the amino acids constitute the nodes. These nodes are connected by edges weighted with an estimate for the fragmentation error that is expected when cutting this edge. This allows us to employ graph partitioning algorithms provided by computer science to determine near-optimal partitions of the protein. We apply this scheme to a test set of six proteins representing various prototypical applications of quantum-chemical fragmentation methods using a simplified molecular fractionation with conjugate caps (MFCC) approach with hydrogen caps. We show that our graph-based scheme consistently improves upon the naive approach.

First author: Madabeni, A, Effect of Methylmercury Binding on the Peroxide-Reducing Potential of Cysteine and Selenocysteine,
INORGANIC CHEMISTRY, 60, 4646, (2021)
Abstract: Methylmercury (CH3Hg+) binding to catalytically fundamental cysteine and selenocysteine of peroxide-reducing enzymes has long been postulated as the origin of its toxicological activity. Only very recently, CH3Hg+ binding to the selenocysteine of thioredoxin reductase has been directly observed [Pickering, I. J. et al. Inorg. Chem., 2020, 59, 2711-2718], but the precise influence of the toxicant on the peroxide-reducing potential of such a residue has never been investigated. In this work, we employ state-of-the-art density functional theory calculations to study the reactivity of molecular models of the free and toxified enzymes. Trends in activation energies are discussed with attention to the biological consequences and are rationalized within the chemically intuitive framework provided by the activation strain model. With respect to the free, protonated amino acids, CH3Hg+ binding promotes oxidation of the S or Se nucleus, suggesting that chalcogenoxide formation might occur in the toxified enzyme, even if the actual rate of peroxide reduction is almost certainly lowered as suggested by comparison with fully deprotonated amino acids models.

First author: Fomenko, IS, Solution and solid-state light-induced transformations in heterometallic vanadium-ruthenium nitrosyl complex,
Abstract: The work is devoted to the preparation and photochemical investigations of the novel binuclear heterometallic complex [Ru(NO)(NO2)(2)(mu-NO2)(mu-CH3COO)(mu-O)VO(dbbpy)]center dot CH3CN (dbbpy – 4,4′-di-tert-butyl-2,2′-bipyridyl), which is obtained with quantitative yield. The structure of the complex is determined by single crystal Xray diffraction and by DFT calculations. On the one hand, irradiation at 445 nm of an acetonitrile solution of the complex leads to a NO photo-release reaction. The light excitation induces the charge transfer from NO2 and dbbpy ligands to the antibonding orbitals of ON-Ru-O-V chain, leading to the NO release, which is confirmed by the DFT. The quantum yield of the Ru-NO photo-cleavage is 0.57 +/- 0.05 %. The products of the photolysis (NO and paramagnetic Ru m complex) are confirmed by the Griess test and EPR-spectroscopy. On the other hand, the irradiation of the complex in the solid phase at 10 K results in the formation of the metastable bond isomer RuON (MS1), which is detected by the infrared spectroscopy. The stretching vibration of the u(NO) band of MS1 (1750 cm(-1)) is shifted by 150 cm(-1) to lower energy with respect to the u(NO) band of the ground state GS (1900 cm(-1)). The population of the MS1 is about 5%. MS1 thermally decays at 120-140 K back to the GS. Hence, this complex represents a bifunctional platform, which can release nitric oxide in solution and reversibly switch the NO ligand coordination in the solid state. It is shown, that the presence of vanadium strongly influences the photochemical properties of ruthenium nitrosyl both in the solid phase and in solution.

First author: Marri, AR, Record power conversion efficiencies for iron(ii)-NHC-sensitized DSSCs from rational molecular engineering and electrolyte optimization,
Abstract: Three Fe(ii) pyridylNHC-carboxylic heteroleptic complexes with (ARM7 and ARM11) or without spacers (ARM13) between the pyridine and the COOH anchoring group have been designed and characterized with the aim to increase the metal to surface charge separation and avoid undesired recombination processes in iron-sensitized DSCCs. The ARM13-sensitized DSSC scored the highest efficiency ever reported for an iron-sensitized solar cell (1.44%) providing that Mg2+ cations and NBu4I were present in the electrolyte, thus substantially boosting the photocurrent. The gain in efficiency derived from the use of MgI2-based electrolytes was rationalized by employing DFT calculations for the isolated dye sensitizers and dye/TiO2 interface models.

First author: Svatunek, D, How the Lewis Base F- Catalyzes the 1,3-Dipolar Cycloaddition between Carbon Dioxide and Nitrilimines,
Abstract: The mechanism of the Lewis base F- catalyzed 1,3-dipolar cycloaddition between CO2 and nitrilimines is interrogated using DFT calculations. F(- )activates the nitrilimine, not CO2 as proposed in the literature, and imparts a significant rate enhancement for the cycloaddition. The origin of this catalysis is in the strength of the primary orbital interactions between the reactants. The Lewis base activated nitrilimine-F(- )has high-lying filled FMOs. The smaller FMO-LUMO gap promotes a rapid nucleophilic attack and overall cycloaddition with CO2.

First author: Zouchoune, B, Theoretical investigation on the biological activities of ginger and some of its combinations: an overview of the antioxidant activity,
STRUCTURAL CHEMISTRY, 32, 1659, (2021)
Abstract: This theoretical investigation using DFT/B3LYP calculations is dealing with the molecular structures and biological activities of ginger and some of its combinations containing menthol, ascorbic acid, hesperidin, allicin, hydoxycoumarin, or cinnamic aldehyde. The main goal of this theoretical investigation is the prediction of the biological activities of different combinations based on the evaluation of the occurred interactions which are of X-HMIDLINE HORIZONTAL ELLIPSISY hydrogen bonding types evidenced by the energy decomposition analysis (EDA) and natural bond analysis (NBO) within the natural energy decomposition analysis (NEDA). The antioxidant potency is based on the BDEs (bonding dissociation enthalpies), spin densities, and the stability order between the formed radicals. The O-H bond breaking is related to the H-abstraction. The HOMO-LUMO gaps explain that the possible charge transfer interactions that take place within the molecules are responsible for the molecular reactivity of the studied molecules in the resulting combinations. The chemical hardness, the chemical potential, and the electrophilicity indexes show clearly the improvement of the biological activities of 6-gingerol in different combinations except in the presence of menthol. The spin density distribution for the radicals formed after H-abstraction on each OH of the 6-gingerol displays large value on O(2) of OH(2) group, contrary to that of O(1) showing a delocalization over the C6 ring leading to a significant antioxidant potency, in agreement with low BDE values favoring the H(2)-abstraction in all cases excluding only the H(4′)-abstraction from ascorbic acid of the combination (3) giving rise to the most stable formed radical. The calculated dipole moments of 6-gingerol increase in the combinations with allicin and hydroxycoumarin, thus increasing their polarities giving rise to blood thinner combinations. The combination (6) has the highest polarity, so it dissolves in blood more than the others.

First author: Bella, G, Do Secondary Electrostatic Interactions Influence Multiple Dihydrogen Bonds? AA-DD Array on an Amine-Borane Aza-Coronand: Theoretical Studies and Synthesis,
CHEMPHYSCHEM, 22, 593, (2021)
Abstract: Hydrogen bond plays a key role in a wide range of inorganic, organic, as well as biological systems. The understanding on how the chemical environment can affect this kind of interaction is crucial to predict its binding strength and consequently the robustness and the dynamic properties of many supramolecular systems. In this paper a new donor-acceptor complex was synthesized and characterized by SCXRD, showing for the first time in an organic system an AA-DD pattern of a particular hydrogen interaction, called dihydrogen bond. Over 250 functionals were computationally evaluated to select the best method to reproduce the binding interaction geometry of this new pattern. Moreover, a new vector force model was used to split the contribution of primary and secondary electrostatic interactions (SEIs), in order to evaluate how the latter one can modify the binding strength of this unusual hydrogen-hydrogen interaction.

First author: Kieser, JM, Synthesis and Characterization of Tellurium Catecholates and Their N-Oxide Adducts,
INORGANIC CHEMISTRY, 60, 3460, (2021)
Abstract: Tellurium catecholate complexes were investigated to probe the redox chemistry of tellurium, whose oxidation state can span from -2 to +6. Treating TeO2 with catechols resulted in tellurium coordination complexes in high yields within minutes to hours at room temperature or with extended heating, depending on the ligand substituents, giving Te(IV) complexes of the form Te(C)(2), where C = 3,5-di-tert-butylcatecholate, o-catecholate, or tetrachlorocatecholate. The redox behavior of these complexes was investigated through addition of organic oxidants, giving nearly quantitative adducts of pyridine N-oxide or N-methylmorpholine N-oxide with each tellurium complex, the latter set leading to ligand oxidation upon heating. Each compound was characterized crystallographically and computationally, providing data consistent with a mostly electrostatic interaction and very little covalent character between the N-oxide and Te complex. The Te N-oxide bond orders are consistently lower than those with the catechol derivatives, as characterized with the Mayer, Gopinathan-Jug (G-J), and first Nalewajski-Mrozek (N-M1) bond indices. The tellurium lone pair is energetically buried by 1.93-2.81 eV, correlating with the observation that the ligands are more reactive than the tellurium center toward oxidation. This combined experimental and theoretical study finds structure-property relationships between ligand design and reactivity that will aid in future efforts for the recovery of tellurium.

First author: Timmer, BJJ, Intermolecular pi-pi Stacking Interactions Made Visible,
Abstract: Mixing the liquids hexafluorobenzene (1) and 1,3,5-trimethylbenzene (mesitylene, 2) results in a crystalline solid with a melting point of 34 degrees C. The solid consists of alternating pi-pi stacked pillars of both aromatics. This simple experiment can be used to visually demonstrate the existence and the effect of noncovalent intermolecular pi-pi stacking interactions. Both benzene derivatives are relatively benign and widely available, and the experiment can be performed within minutes for less than $15 when done on a 22 mL scale (total volume). The demonstration is very robust, as 1:2 mixtures in volume ratios between 2/3 and 3/2 all give a visually similar result (molar ratios of 1.8-0.8). Substituting 2 with the liquid aromatics o-xylene, p-xylene, and aniline also resulted in the formation of a crystalline solid, while using many other liquid aromatics did not.

First author: Senjean, B, Generalization of Intrinsic Orbitals to Kramers-Paired Quaternion Spinors, Molecular Fragments, and Valence Virtual Spinors,
Abstract: Localization of molecular orbitals finds its importance in the representation of chemical bonding (and antibonding) and in the local correlation treatments beyond mean-field approximation. In this paper, we generalize the intrinsic atomic and bonding orbitals [G. Knizia, J. Chem. Theory Comput. 2013, 9, 11, 4834-4843] to relativistic applications using complex and quaternion spinors, as well as to molecular fragments instead of atomic fragments only. By performing a singular value decomposition, we show how localized valence virtual orbitals can be expressed on this intrinsic minimal basis. We demonstrate our method on systems of increasing complexity, starting from simple cases such as benzene, acrylic acid, and ferrocene molecules, and then demonstrate the use of molecular fragments and inclusion of relativistic effects for complexes containing heavy elements such as tellurium, iridium, and astatine. The aforementioned scheme is implemented into a standalone program interfaced with several different quantum chemistry packages.

First author: Havenith, RWA, The electronic structure of carbones revealed: insights from valence bond theory,
Abstract: In this contribution, we studied the OC-C bond in carbon suboxide and related allene compounds using the valence bond method. The nature of this bond has been the subject of debate, whether it is a regular, electron sharing bond or a dative bond. We compared the nature of this bond in carbon suboxide with the gold-CO bond in Au(CO)(2)(+), which is a typical dative bond, and we studied its charge-shift bond character. We found that the C-CO bond in carbon suboxide is unique in the sense that it cannot be assigned as either a dative or electron sharing bond, but it is an admixture of electron sharing and dative components, together with a high contribution of ionic character. These findings provide a clear basis for distinguishing the commonly found dative bonds between ligands and transition metals and the present case of what may be described as coordinative bonding to carbon.

First author: Chen, WC, Charge transport properties of open-shell graphene fragments: a computational study of the phenalenyl tilings,
Abstract: Thinking outside the box of the phenalenyl radical: a systematic structure design strategy, phenalenyl tiling, is found to benefit the electron transport properties of open-shell graphene fragments with one free radical. Compared with the closed-shell species, phenalenyl-based pi-radicals exhibit smaller intramolecular reorganization energies and larger intermolecular electronic couplings. However, the on-site Coulomb repulsion can be too strong and impedes the charge transport efficiency of such materials. The repulsion can be weakened in radical species by spin delocalization. In this paper, the extended pi-radicals we studied are categorized into three types of open-shell structures: the zigzag, the armchair and the discotic odd alternant hydrocarbons. The latter two belong to phenalenyl tilings. We found that the phenalenyl tilings fully inherit the desirable features of the singly occupied molecular orbital of the phenalenyl radical in a predictable and delocalized fashion, and their on-site Coulomb repulsion is effectively reduced. The zigzag pi-radicals are less satisfactory. Therefore, the phenalenyl tilings are favorable candidates for charge transporting materials.

First author: Santos, LD, Chalcogen bonds: Hierarchical ab initio benchmark and density functional theory performance study,
Abstract: We have performed a hierarchical ab initio benchmark and DFT performance study of D(2)Ch center dot center dot center dot A(-) chalcogen bonds (Ch = S, Se; D, A = F, Cl). The ab initio benchmark study is based on a series of ZORA-relativistic quantum chemical methods [HF, MP2, CCSD, CCSD(T)], and all-electron relativistically contracted variants of Karlsruhe basis sets (ZORA-def2-SVP, ZORA-def2-TZVPP, ZORA-def2-QZVPP) with and without diffuse functions. The highest-level ZORA-CCSD(T)/ma-ZORA-def2-QZVPP counterpoise-corrected complexation energies (Delta E-CPC) are converged within 1.1-3.4 kcal mol(-1) and 1.5-3.1 kcal mol(-1) with respect to the method and basis set, respectively. Next, we used the ZORA-CCSD(T)/ma-ZORA-def2-QZVPP (Delta E-CPC) as reference data for analyzing the performance of 13 different ZORA-relativistic DFT approaches in combination with the Slater-type QZ4P basis set. We find that the three-best performing functionals are M06-2X, B3LYP, and M06, with mean absolute errors (MAE) of 4.1, 4.2, and 4.3 kcal mol(-1), respectively. The MAE for BLYP-D3(BJ) and PBE amount to 8.5 and 9.3 kcal mol(-1), respectively.

First author: Hansen, T, How Lewis Acids Catalyze Ring-Openings of Cyclohexene Oxide,
Abstract: We have quantum chemically studied the Lewis acid-catalyzed epoxide ring-opening reaction of cyclohexene epoxide by MeZH (Z = O, S, and NH) using relativistic dispersion-corrected density functional theory. We found that the reaction barrier of the Lewis acid-catalyzed epoxide ring-opening reactions decreases upon ascending in group 1 along the series Cs+ > Rb+ > K+ > Na+ > Li+ > H+. Our activation strain and Kohn-Sham molecular orbital analyses reveal that the enhanced reactivity of the Lewis acid-catalyzed ring-opening reaction is caused by the reduced steric (Pauli) repulsion between the filled orbitals of the epoxide and the nucleophile, as the Lewis acid polarizes the filled orbitals of the epoxide more efficiently away from the incoming nucleophile. Furthermore, we established that the regioselectivity of these ring-opening reactions is, aside from the “classical” strain control, also dictated by a hitherto unknown mechanism, namely, the steric (Pauli) repulsion between the nucleophile and the substrate, which could be traced back to the asymmetric orbital density on the epoxide. In all, this work again demonstrates that the concept of Pauli-lowering catalysis is a general phenomenon.

First author: Maudrich, JJ, Tetryl-Tetrylene Addition to Phenylacetylene,
Abstract: Phenylacetylene adds [Ar*GeH2-SnAr’], [Ar*GeH2-PbAr’] and [Ar’SnH2-PbAr*] at rt in a regioselective and stereoselective reaction. The highest reactivity was found for the stannylene, which reacts immediately upon addition of one equivalent of alkyne. However, the plumbylenes exhibit addition to the alkyne only in reaction with an excess of phenylacetylene. The product of the germylplumbylene addition reacts with a second equivalent of alkyne and the product of a CH-activation, a dimeric lead acetylide, were isolated. In the case of the stannylplumbylene the trans-addition product was characterized as the kinetically controlled product which isomerizes at rt to yield the cis-addition product, which is stabilized by an intramolecular Sn-H-Pb interaction. NMR chemical shifts of the olefins were investigated using two- and four-component relativistic DFT calculations, as spin-orbit effects can be large. Hydride abstraction was carried out by treating [Ar’SnPhC=CHGeH2Ar*] with the trityl salt [Ph3C][Al(OC{CF3})(4)] to yield a four membered ring cation.

First author: Onawole, AT, Theoretical studies of methane adsorption on Silica-Kaolinite interface for shale reservoir application,
APPLIED SURFACE SCIENCE, 546, 4691, (2021)
Abstract: Shale gas is mostly made up of methane and is currently being exploited in fulfilling the world’s energy demands. Density Functional Theory (DFT) and Molecular Dynamics (MD) techniques are employed for understanding methane transport in the pores at typical reservoir conditions. Shale, which is made up of clay and quartz-like material, is represented in this study by a combined silica-kaolinite surface. The simulations revealed that the interface is formed by a chemical bond between silicon to two oxygen atoms from the kaolinite surface. Physisorption is the mode of adsorption of methane irrespective of the position of the gas on the interface. However, methane has stronger adsorption on the kaolinite region than the silica region.

First author: Pandey, IK, Switching Site Reactivity in Hydrogenase Model Systems by Introducing a Pendant Amine Ligand,
ACS OMEGA, 6, 4192, (2021)
Abstract: Hydrogenases are versatile enzymatic catalysts with an unmet hydrogen evolution reactivity (HER) from synthetic bio-inspired systems. The binuclear active site only has one-site reactivity of the distal Fe-d atom. Here, binuclear complexes [Fe-2(CO)(5)(mu-Mebdt)(P(4-C6H4OCH3)(3))] 1 and [Fe-2(CO)(5)(mu-Mebdt)(PPh2Py)] 2 are presented, which show electrocatalytic activity in the presence of weak acids as a proton source for the HER. Despite almost identical structural and spectroscopic properties (bond distances and angles from single-crystal X-ray; IR, UV/vis, and NMR), introduction of a nitrogen base atom in the phosphine ligand in 2 markedly changes site reactivity. The bridging benzenedithiolate ligand Mebdt interacts with the terminal ligand’s phenyl aromatic rings and stabilizes the reduced states of the catalysts. Although 1 with monodentate phosphine terminal ligands only shows a distal iron atom HER activity by a sequence of electrochemical and protonation steps, the lone pair of pyridine nitrogen in 2 acts as the primary site of protonation. This swaps the iron atom catalytic activity toward the proximal iron for complex 2. Density-functional theory (DFT) calculations reveal the role of terminal phosphines ligands without/with pendant amines by directing the proton transfer steps. The reactivity of 1 is a thiol-based protonation of a dangling bond in 1(-) and distal iron hydride mechanism, which may follow either an ECEC or EECC sequence, depending on the choice of acid. The pendant amine in 2 enables a terminal ligand protonation and an ECEC reactivity. The introduction of a terminal nitrogen atom enables the control of site reactivity in a binuclear system.

First author: Ray, D, Tuning the Conductivity of Hexa-Zirconium(IV) Metal-Organic Frameworks by Encapsulating Heterofullerenes,
CHEMISTRY OF MATERIALS, 33, 1182, (2021)
Abstract: Electrical conductivity in metal-organic frameworks (MOFs) has a great potential for energy storage applications and electrocatalysis. Zirconium-based MOFs such as NU-901 and NU-1000 have a low electrical conductivity due to the redox innocence of Zr-oxo bonds. Recently, it has been shown that the electrical conductivity of NU-901 can be increased by 11 orders of magnitude by physically encapsulating fullerene (C-60) in its diamond pore. This effect is due to the host-guest interaction between the electron-rich 1,3,6,8-tetrakis(p-benzoate) pyrene (TBAPy(4-)) organic linkers of NU-901 (host) and the electron-poor fullerene (guest). Herein, we used density functional theory to study heterofullerene (C59X; X = B, Al, Ga, In, Si, Ge, and Sn) encapsulation in NU-901. Our study suggests that encapsulated heterofullerenes enhance the electrical conductivity of the NU-901 MOF even further than C-60.

First author: Gourlaouen, C, Substituent effects on the photophysical properties of 2,9-substituted phenanthroline copper(I) complexes: a theoretical investigation,
CHEMPHYSCHEM, 22, 509, (2021)
Abstract: The electronic and nuclear structures of a series of [Cu(2,9-(X)(2)-phen)(2)](+) copper(I) complexes (phen=1,10-phenanthroline; X=H, F, Cl, Br, I, Me, CN) in their ground and excited states are investigated by means of density functional theory (DFT) and time-dependent (TD-DFT) methods. Subsequent Born-Oppenheimer molecular dynamics is used for exploring the T-1 potential energy surface (PES). The T-1 and S-1 energy profiles, which connect the degenerate minima induced by ligand flattening and Cu-N bond symmetry breaking when exciting the molecule are calculated as well as transition state (TS) structures and related energy barriers. Three nuclear motions drive the photophysics, namely the coordination sphere asymmetric breathing, the well-documented pseudo Jahn-Teller (PJT) distortion and the bending of the phen ligands. This theoretical study reveals the limit of the static picture based on potential energy surfaces minima and transition states for interpreting the luminescent and TADF properties of this class of molecules. Whereas minor asymmetric Cu-N bonds breathing accompanies the metal-to-ligand-charge-transfer re-localization over one or the other phen ligand, the three nuclear movements participate to the flattening of the electronically excited complexes. This leads to negligible energy barriers whatever the ligand X for the first process and significant ligand dependent energy barriers for the formation of the flattened conformers. Born-Oppenheimer (BO) dynamics simulation of the structural evolution on the T-1 PES over 11 ps at 300 K confirms the fast backwards and forwards motion of the phenanthroline within 200-300 fs period and corroborates the presence of metastable C-2 structures.

First author: Ciaffaglione, V, Structural Investigations, Cellular Imaging, and Radiolabeling of Neutral, Polycationic, and Polyanionic Functional Metalloporphyrin Conjugates,
Abstract: Over the past decade, porphyrin derivatives have emerged as invaluable synthetic building blocks and theranostic kits for the delivery of cellular fluorescence imaging and photodynamic therapy. Tetraphenylporphyrin (TPP), its metal complexes, and related derivatives have been investigated for their use as dyes in histology and as components of multimodal imaging probes. The photophysical properties of porphyrin-metal complexes featuring radiometals have been a focus of our attention for the realization of fluorescence imaging probes coupled with radio-imaging capabilities and therapeutic potential having “true” theranostic promise. We report hereby on the synthesis, radiochemistry, structural investigations, and preliminary in vitro and in vivo uptake studies on a range of functionalized porphyrin-based derivatives. In pursuit of developing new porphyrin-based probes for multimodality imaging applications, we report new functionalized neutral, polycationic, and polyanionic porphyrins incorporating nitroimidazole and sulfonamide moieties, which were used as targeting groups to improve the notoriously poor pharmacokinetics of porphyrin tags. The resulting functional metalloporphyrin species were stable under serum challenges and the nitroimidazole and sulfonamide derivatives remained fluorescent, allowing in vitro confocal studies and visualization of the lysosomal uptake in a gallium(III) sulfonamide derivative. The molecular structures of selected porphyrin derivatives were determined by single crystal X-ray diffraction using synchrotron radiation. We also investigated the nature of the emission/excitation behavior of model functional porphyrins using in silico approaches such as TD DFT in simple solvation models. The conjugation of porphyrins with the [7-13] and [7-14] fragments of bombesin was also achieved, to provide targeting of the gastrin releasing peptide receptor (GRPR). Depending on the metal, probe conjugates of relevance for single photon emission computed tomography (SPECT) or positron emission tomography (PET) probes have been designed and tested hereby, using TPP and related functional free base porphyrins as the bifunctional chelator synthetic scaffold and In-111[In] or Ga-68[Ga], respectively, as the central metal ions. Interestingly, for simple porphyrin conjugates good radiochemical incorporation was obtained for both radiometals, but the presence of peptides significantly diminished the radio-incorporation yields. Although the gallium-68 radiochemistry of the bombesin conjugates did not show radiochemical incorporation suitable for in vivo studies, likely because the presence of the peptide changed the behavior of the TPP-NH2 synthon taken alone, the optical imaging assays indicated that the conjugated peptide tags do mediate uptake of the porphyrin units into cells.

First author: Wang, F, Density functional theory study of single-molecule ferroelectricity in Preyssler-type polyoxometalates,
APL MATERIALS, 9, 1374, (2021)
Abstract: A detailed study on the single-molecule ferroelectric property of Preyssler-type polyoxometalates (POMs), [M3+P5W30O110](12-) (M = La, Gd, and Lu), is performed by density functional theory calculations. Linked to one H2O molecule, the cation (M3+) encapsulated in the cavity of the Preyssler framework is off-centered, and it generates a permanent dipole, which is essential for a ferroelectric ground state. Accompanied with a 180 degrees rotation of H2O, the switching of M3+ between two isoenergetic sites on both sides of the cavity results in a calculated barrier of 1.15 eV for Gd3+, leading to the inversion of electric polarization. The height of the barrier is in good agreement with the experimentally measured barrier for the Tb3+ ion, whose ionic radius is similar to Gd3+. The total polarization value of the crystal is estimated to be 4.7 mu C/cm(2) as calculated by the modern theory of polarization, which is quite close to the experimental value. Considering that the order of contributions to the polarization is M3+-H2O > counter-cations (K+) > [P5W30O110](15-), the interconversion of M3+-H2O between the two isoenergetic sites is predicted to be the main origin of ferroelectricity with a polarization contribution of 3.4 mu C/cm(2); the K+ counter-cations contribute by 1.2 mu C/cm(2) and it cannot be disregarded, while the framework appears to contribute negligibly to the total polarization. Our study suggests that a suitable choice of M3+-H2O could be used to tune the single-molecule ferroelectricity in Preyssler-type polyoxometalates.

Abstract: The [RuNO(3-CNPy)(2)Cl-3] complex is obtained in the reaction of K-2[RuNOCl5] with 3-cyanopyridine. The compound is characterized by the elemental analysis and IR spectroscopy; its crystal structure is investigated by single crystal X-ray diffraction. Crystallographic data are: P2(1)/c, a = 8.1487(3) angstrom, b = 14.8118(6) angstrom, c = 13.0364(5) angstrom, alpha = 90 degrees, beta = 101.966(1)degrees, gamma = 90 degrees, V = 1539.26(10) angstrom(3), Z = 4, R = 0.0256. The complex is obtained as a facial isomer where chlorine atoms occupy one of the faces of a distorted {RuN3Cl3} octahedron. Photochemical isomerization (lambda = 445 nm, 100 mW) at 80 K leads to the formation of a bond isomer with occupancy of 17% and coordination of the nitrosyl group through an oxygen atom. At temperatures above 170 K in the absence of radiation a reverse reaction occurs with the formation of a main isomer with coordination of the nitrosyl group through the nitrogen atom. Activation parameters of this process are determined by IR spectroscopy: E-a= 46.5(1.7) kJ/mol and lgk(0) = 10.8(1.0).

First author: Ozawa, Y, A Cuboidal Cu4S4 Cluster Supported by Bulky Iminothiolate Ligands: Synthesis, Solid-State Structure, and Solution Study,
Abstract: A new tetracopper(I) complex containing a cuboidal Cu4S4 core, [Cu-4(dap)(4)], where dap(-) is dibenzodiazepinethiolate(1-), has been synthesized and structurally characterized by singlecrystal X-ray diffraction analysis. The monoanionic iminothiolate ligand dap(-) renders the cluster framework exceptionally stable to retain the tetranuclear structure in solution, which allows us to examine for the first time the solution properties of this class of clusters, including UV-vis and NMR spectroscopy and cyclic voltammetry.

First author: Tang, JW, Uncovering the unusual effect of halogenation on crystal packing in an azzaacee-based electron transporting material,
Abstract: Due to strong interaction with perovskite, azzaacee-based derivative TDTP is promising electron-transporting material (ETM) in the inverted perovskite solar cell. However, the low electron mobility of TDTP seriously limits the photoelectric conversion efficiency (PCE) of the device. Herein, three TDTP-type material molecules, FT, ClT and BrT, are designed based on the paternal TDTP to boost the electron mobility. The results demonstrate that the introduction of halogen (electron-withdrawing group) improves the electron mobility of the materials due to the enhanced intermolecular pi-pi stacking. Unexpectedly, ClT with chlorine substitution violates the electronegative order and shows the highest electron mobility, which results from the head-to-head stacking manner only in ClT crystal. This special stacking produces stronger electron coupling between molecules, thus facilitating carrier transport. This work provides theoretical guidance for the design of ETMs with excellent electron mobility by deeply understanding the relationship between the charge transporting properties of ETMs and their molecular/crystal structures.

First author: Muhammad, IK, Computational study of 4d transition metals doped bismuthene for spintronics,
Abstract: The new spintronic materials has earned extensive research attention due to their properties including faster data transfer, processing and storage. Espcially, antiferromagnets have fascinated due to their utilization in ultrafast spintronic devices. It has motivated us to explore the electronic and magnetic properties of buckled bismuthene doped with 4 d transition metals (TM) including Y, Zr, Nb, Mo, Tc, and Ru. The first principles calculations predicted the formation of covalent bond between dopant and host atoms. The doping of single 4 d-TM atom revealed that the magnetic moments show oscillating character due to hybridization of host-p and TM-d orbitals. The doping of Zr, Nb, Tc and the Ru in Bi appeared to produce spin polarized states with half metallic properties whereas Mo shown magnetic semiconductor. The doping of Nb in the matrix exhibited half mettalic behavior when dopant was placed at different sites. The single (S) and double (B) Mo-doped-Bi shown diluted magnetic semiconductor character except 2Mo-B-AFM. Remarkably, our calculations shown that 2Tc-S-Bi and 2Mo-S-Bi system appears ferromagnetic (FM) state, but 2Tc-B-Bi and 2Mo-B-Bi shows anti-ferromagnetism (AFM) state. A model presenting charge transfer and interaction between the impurities is proposed. Critical temperature investigation presents the probability of room temperature ferromagnetism from the structures. This study discloses that 4 d-doped Bi can be favorable applicant for potential applications in spintronic devices.

First author: Jeon, S, Reversible disorder-order transitions in atomic crystal nucleation,
SCIENCE, 371, 498, (2021)
Abstract: Nucleation in atomic crystallization remains poorly understood, despite advances in classical nucleation theory. The nucleation process has been described to involve a nonclassical mechanism that includes a spontaneous transition from disordered to crystalline states, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporal resolution shows that the early stage of atomic crystallization proceeds through dynamic structural fluctuations between disordered and crystalline states, rather than through a single irreversible transition. Our experimental and theoretical analyses support the idea that structural fluctuations originate from size-dependent thermodynamic stability of the two states in atomic dusters. These findings, based on dynamics in a real atomic system, reshape and improve our understanding of nucleation mechanisms in atomic crystallization.

First author: Kovacs, A, H2O coordination in macropa complexes of f elements (Ac, La, Lu): feasibility of the 11th coordination site,
Abstract: The feasibility of an additional ligand coordination at the 11th coordination site of actinium, lanthanum, and lutetium ions in 10-fold coordinated macropa complexes has been studied by means of density functional theory calculations. The study covered the two main macropa conformers, Delta(delta lambda delta)(delta lambda delta) and Delta(lambda delta lambda)(lambda delta lambda), favoured by larger (Ac3+, La3+) and smaller (Lu3+) ions, respectively. At the molecular level, the coordination of H2O is the most favourable to the largest Ac3+ while only slightly less to La3+. Protonation of the picoline arms enhances the coordination by shifting the metal ion closer to the open site of the ligand. The choice of macropa conformer has only a slight influence on the strength and bonding properties of the H2O coordination. Aqueous solution environment decreases considerably the energy gain of H2O coordination at the 11th coordination site.

First author: Giret, Y, A quantum dynamics study of the hyperfluorescence mechanism,
Abstract: Triplet state harvesting using thermally-activated delayed fluorescence (TADF) combined with efficient Forster resonant energy transfer (FRET) to a narrow fluorescent emitter is seen as a promising approach to achieve high efficiency and colour-purity in organic light-emitting diodes (OLEDs). In this work, we perform quantum chemistry and quantum dynamics simulations to model the so-called hyperfluorescence (HF) process between a carbene-metal-amide (CMA) molecule with a Au bridging metal (Au-Cz) and a narrow blue fluorescent emitter, 2,5,8,11-tetra-tert-butylperylene (TBPe). Our quantum dynamics simulations illustrate a FRET rate of similar to 10(10) s(-1) indicating that it occurs on the picosecond timescale comparable with the ISC crossing rate of Au-Cz. This high FRET rate, which is most strongly dependent on the energy difference between the S-1 states of the donor and acceptor molecules, is advantageous for devices as it encourages rapid triplet harvesting. In addition, the comparable FRET and intersystem crossing (ISC) rates, in contrast to most organic only systems, would facilitate studying this mechanism using photoexcitation. Besides the FRET rate, Forster radii are also estimated from the quantum dynamics simulations for different energy differences between the donor and acceptor molecules and are in quantitative agreement with the experimental estimations for different systems, showing that quantum nuclear dynamics simulation could be an important tool for enhancing our understanding of hyperfluorescence-based emitters.

First author: Karaush-Karmazin, NN, Impact of molecular and packing structure on the charge-transport properties of hetero[8]circulenes,
Abstract: Hetero[8]circulenes have been shown to be potential charge transport materials in the field-effect devices. In particular, the hole mobility of the octathia[8]circulene thin-film can reach as much as 9 x 10(-3) cm(2) V-1 s(-1) with on/off current ratio of 10(6) (E. S. Balenkova, R. M. Osuna, F. Rosei, V. G. Nenajdenko and D. F. Perepichka, Chem. Commun., 2008, 5354-5356). In the present paper we carry out a detailed computational study for sixteen crystals of hetero[8]circulenes to gain insight into the design principles of organic semiconductors based on relationships between the crystal packing and charge transport properties. The charge transport parameters and carrier mobilities for the hetero[8]circulenes are systematically explored using the Marcus-Hush electron transfer theory and the Einstein relation. The results show that the O/NH replacement and benzoannelation decreases the reorganization energy during the charge hopping process and increases the electronic coupling within the charge transport pathways, and that sequential replacements of the peripheral sulfur atoms by selenium atoms improve the charge transfer properties. Interestingly, the S/Se substitution induces a conduction inversion; i.e. octathia[8]circulene shows dominating hole transfer and is more suitable as a p-type material, while tetrathiatetraselena[8]circulene and octaselena[8]circulene demonstrate electron-dominated mobility and represent n-type materials. The transfer integrals are sensitive to the stacking organization of the molecules in the crystal, something that is especially clear for regioisomers of tetra-tert-butyl-substituted tetraoxa[8]circulene and azaoxa[8]circulenes. A general trend is that the charge transport within the pi-pi stacks plays a dominant role for the carrier mobility in the heterocirculene crystals due to the large transfer integrals within such stacking dimer models.

First author: Viesser, RV, Inverse halogen dependence in anion C-13 NMR,
Abstract: Halogens cause pronounced and systematic effects on the C-13 NMR chemical shift (delta C-13) of an adjacent carbon nucleus, usually leading to a decrease in the values across the halogen series. Although this normal halogen dependence (NHD) is known in organic and inorganic compounds containing the carbon atom in its neutral and cationic forms, information about carbanions is scarce. To understand how delta C-13 changes in molecules with different charges, the shielding mechanisms of CHX3, CX3+, and CX3- (X = Cl, Br, or I) systems are investigated via density functional theory calculations and further analyzed by decomposition into contributions of natural localized molecular orbitals. An inverse halogen dependence (IHD) is determined for the anion series as a result of the negative spin-orbit contribution instead of scalar paramagnetic effects. The presence of a carbon nonbonding orbital in anions allows magnetic couplings that generate a deshielding effect on the nucleus and contradicts the classical association between delta C-13 and atomic charge.

First author: Li, ZW, Chemical Bonding as a New Avenue for Controlling Excited-State Properties and Excitation Energy-Transfer Processes in Zinc Phthalocyanine-Fullerene Dyads,
Abstract: Whether chemical bonding can regulate the excited-state and optoelectronic properties of donor-acceptor dyads has been largely elusive. In this work, we used electronic structure and nonadiabatic dynamics methods to explore the excited-state properties of covalently bonded zinc phthalocyanine (ZnPc)-fullerene (C-60) dyads with a 6-6 (or 5-6) bonding configuration in which ZnPc is bonded to two carbon atoms shared by the two hexagonal rings (or a pentagonal and a hexagonal ring) in C-60. In both cases, the locally excited (LE) states on ZnPc are spectroscopically bright. However, their different chemical bonding differentiates the electronic interactions between ZnPc and C-60. In the 5-6 bonding configuration, the LE states on ZnPc are much higher in energy than the LE states on C-60. Thus, the excitation energy transfer from ZnPc to C-60 is thermodynamically favorable. On the other hand, in the 6-6 bonding configuration, such a process is inhibited because the LE states on ZnPc are the lowest ones. More detailed mechanisms are elucidated from nonadiabatic dynamics simulations. In the 6-6 bonding configuration, no excitation energy transfer was observed. In contrast, in the 5-6 bonding configuration, several LE and charge-transfer (CT) excitons were shown to participate in the energy-transfer process. Further analysis reveals that the photoinduced energy transfer is mediated by a CT exciton, such that electron- and hole-transfer processes take place in a concerted but asynchronous manner in the excitation energy transfer. It is also found that high-level electronic structure methods including exciton effects are indispensable to accurately describe photoinduced energy- and electron-transfer processes. Furthermore, this work opens up new avenues for regulating the excited-state properties of molecular donor-acceptor dyads by means of chemical bonding.

First author: Nadolinny, VA, Effect of the spin-orbit interaction of ligands on the parameters of EPR spectra for a series of niobium(IV) complexes of trans-[NbX4(OPPh3)(2)] (X = Cl, Br, I),
INORGANICA CHIMICA ACTA, 515, 4159, (2021)
Abstract: Two crystal modifications of new molecular niobium(IV) complex trans-NbI4(OPPh3)(2) were obtained by ampoule synthesis, and their X-ray crystal structures were solved (P-1, a = 9.5795 angstrom, b = 9.7287 angstrom, c = 11.2337 angstrom, alpha = 107.984 degrees, beta = 104.061 degrees, gamma = 95.500 degrees, V = 949.24 angstrom(3); P2(1), a = 10.204 angstrom, b = 16.039 angstrom, c = 11.857 angstrom, beta = 102.663 degrees, V = 1893.3 angstrom(3)). For the series of molecular complexes trans-NbX4(OPPh3)(2) (X = Cl, Br, I) magnetic properties were studied and systematized using EPR, magnetic susceptibility measurements, and theory calculations with DFT approximation. Theory calculations of EPR parameters have shown good accordance with experimental data and allowed to establish a negative sign of the principal hyperfine tensor values.

First author: Yassia, KT, How the Ancillary Ligand X Drives the Redox Properties of Biscyclopentadienyl Pentavalent Uranium Cp2U(=N-Ar)X Complexes,
INORGANIC CHEMISTRY, 60, 2203, (2021)
Abstract: Relativistic zero order regular approximation (ZORA) density functional theory computations, coupled with the conductor-like screening model for solvation effects, are used to investigate the redox properties of a series of biscyclopentadienyl pentavalent uranium(V) complexes Cp2U(=N-Ar)X (Ar = 2,6-Me-2-C6H3; X = OTf, C6F5, SPh, C=CPh, NPh2, Ph, Me, OPh, N(TMS)(2), N=CPh2). Regarding the U-V/U-IV and U-VI/U-V couple systems, a linear correlation (R-2 similar to 0.99) is obtained at the ZORA/BP86/TZP level, between the calculated ionization energies and the measured experimental E-1/2 half-wave oxidation potentials (U-VI/U-V) and between the electron affinities and the reduction potentials E-1(/2) (U-V/U-IV). The study brings to light the importance of solvation effects that are needed in order to achieve a good agreement between the theory and experiment. Introducing spin-orbit coupling corrections slightly improves this agreement. Both the singly occupied molecular orbital and the lowest unoccupied molecular orbital of the neutral U-V complexes exhibit a majority 5f orbital character. The frontier molecular orbitals show a substantial ancillary ligand X sigma and/or pi character that drives the redox properties. Moreover, our investigations allow estimating the redox potentials of the X = Ph, X = C6F5, and N(TMS)(2) U-V complexes for which no experimental electrochemical data exist.

First author: Miller, DP, Seeking Out Heterogeneous Hydrogen Bonding in a Self-Assembled 2D Cocrystal of Croconic Acid and Benzimidazole on Au(111),
Abstract: A two-dimensional (2D) hydrogen-bonded cocrystal was synthesized from croconic acid (CA) and benzimidazole (BI) on a gold surface under ultrahigh vacuum conditions. The network domains have a 1:1 CA/BI stoichiometry, can be synthesized over a range of temperatures, and contain one-dimensional chains of molecules connected by heterogeneous hydrogen bonds. Density functional theory (DFT) computations suggest that a tautomeric salt-like structure, with deprotonated CA and protonated BI, is the most stable model, which creates heterogeneous N-H center dot center dot center dot O contacts instead of N-H center dot center dot center dot O ones. The homogeneity of the network’s appearance in scanning tunneling microscopy (STM) and a habitual change in the STM features under certain tip conditions indicate that there is an equilibrium of tautomeric molecular states that may be influenced to some degree by STM stimuli. Overall, this study demonstrates how careful consideration of the precursor molecules can tune the architecture within a family of cocrystal networks and introduce desired bonding motifs that haven’t been achieved by solution-based synthesis for these species, such as the heterogeneous hydrogen bonds herein.

First author: Morad, R, First principle simulation of coated hydroxychloroquine on Ag, Au and Pt nanoparticles,
SCIENTIFIC REPORTS, 11, 2403, (2021)
Abstract: From the first month of the COVID-19 pandemic, the potential antiviral properties of hydroxychloroquine (HCQ) and chloroquine (CQ) against SARS-CoV-2 suggested that these drugs could be the appropriate therapeutic candidates. However, their side effects directed clinical tests towards optimizing safe utilization strategies. The noble metal nanoparticles (NP) are promising materials with antiviral and antibacterial properties that can deliver the drug to the target agent, thereby reducing the side effects. In this work, we applied both the quantum mechanical and classical atomistic molecular dynamics approaches to demonstrate the adsorption properties of HCQ/CQ on Ag, Au, AgAu, and Pt nanoparticles. We found the adsorption energies of HCQ/CQ towards nanoparticles have the following trend: PtNP>AuNP>AuAgNP>AgNP. This shows that PtNP has the highest affinity in comparison to the other types of nanoparticles. The (non)perturbative effects of this drug on the plasmonic absorption spectra of AgNP and AuNP with the time-dependent density functional theory. The effect of size and composition of NPs on the coating with HCQ and CQ were obtained to propose the appropriate candidate for drug delivery. This kind of modeling could help experimental groups to find efficient and safe therapies.

First author: Varathan, E, Computational Study of Actinyl Ion Complexation with Dipyriamethyrin Macrocyclic Ligands,
Abstract: Relativistic density functional theory has been employed to characterize [AnO(2)(L)](0/-1) complexes, where An = U, Np, Pu, and Am, and L is the recently reported hexa-aza porphyrin analogue, termed dipyriamethyrin, which contains six nitrogen donor atoms (four pyrrolic and two pyridine rings). Shorter axial (An=O) and longer equatorial (An-N) bond lengths are observed when going from An(VI) to An(V). The actinide to pyrrole nitrogen bonds are shorter as compared to the bonds to the pyridine nitrogens; the former also play a dominant role in the formation of the actinyl (VI and V) complexes. Natural population analysis shows that the pyrrole nitrogen atoms in all the complexes carry higher negative charges than the pyridine nitrogens. Upon binding actinyl ions with the ligand a significant ligand-to-metal charge transfer takes place in all the actinyl (VI and V) complexes. The formation energy of the actinyl(VI,V) complexes in the gas-phase is found to decrease in the order of UO2L > PuO2L > NpO2 L > AmO2 L. This trend is consistent with results for the formation of complexes in dichloromethane solution. The calculated Delta G and Delta H values are negative for all the complexes. Energy decomposition analysis (EDA) indicates that the interactions between actinyl(V/VI) and ligand are mainly controlled by electrostatic components over covalent orbital interactions, and the covalent character gradually decreases from U to Am for both pentavalent and hexavalent actinyl complexes.

First author: Li, TL, Reactivity of dicationic N-heterocyclic chalcogen carbene analogues with methane and ethene: a theoretical investigation,
Abstract: The reactions of chalcogen N-heterocyclic carbenic (NHC) dications [(Dipp(2)DAB)M2+, M = O, S, Se, and Te, and Dipp(2)DAB = 1,4-(2,6-diisopropyl)phenyl-1,4-diaza-1,3-butadiene] with methane and ethene are investigated by the density functional theory. The activation energies and reaction enthalpies are analyzed by the energy decomposition analysis (EDA) to understand the reactivity of the reactions. Calculations show that the oxide carbenic dication (Dipp(2)DAB)O2+ reactant has a pair of rather unbalanced O-N bonds due to the combined effects of the smallness of the central O atom and the bulkiness of the two Dipp ligands surrounding the DAB ring, suggesting the oxide reactant is much less stable than the chalcogenide ones. Because of its unique characteristics, the oxide carbenic dication distinguishes itself from the rest of the chalcogen family. The differences between oxides and chalcogenides of the chalcogen family complexes well known in inorganic chemistry are also observed in this theoretical investigation. This work further reveals that the reasons for the distinctive characteristics between oxide and chalcogenide complexes are due to the fundamental fact that the 2s and 2p atomic orbitals are more amenable to hybridization than those of higher valences, and the mixing of the former valence orbitals results in much smaller atoms than the latter.

First author: Orenha, RP, Can the relative positions (cis-trans) of ligands really modulate the coordination of NO in ruthenium nitrosyl complexes?,
NEW JOURNAL OF CHEMISTRY, 45, 1658, (2021)
Abstract: Nitric oxide is involved in a series of biological processes. Ruthenium tetraammine complexes are model structures to control the NO availability. The influence of ligands is critical to determine the Ru-NO bond stability. Herein, the ligands of different natures and charges, namely, sigma-donors (NH3 and H-), (ii) pi-donors (H2O and NH2-), and (iii) sigma-donors/pi-acceptors (CO and CN-) were evaluated relative to the effect promoted by same ligands not only in the cis position to the NO group, but also in the trans position to NO. The energy decomposition analysis shows linear Ru-NO+ and bent Ru-NO0 bonds in ruthenium tetraammine complexes independent of ligands in cis or trans positions with regard to the NO group. Overall, the substitution of one sigma-donor ligand with one pi-donor ligand in the cis position to the NO group not stabilized the Ru-NO bond. These substitutions involving ligands in the trans position to NO stabilized the Ru-NO bond. Complexes with sigma-donor/pi-acceptor ligands compared to compounds with pi-donor ligands in the cis or trans position to the NO group destabilized the Ru-NO bond. Charge distribution investigation realized from the Voronoi deformation density (VDD) method presents the Ru-NO bond more stabilized by negatively charged sigma-donor, pi-donor and sigma-donor/pi-acceptor ligands, in the cis or trans position to NO. These findings provide crucial information to the rational design of new NO storage-release systems with potential to deliver NO to desired targets in a controlled manner.

First author: Yu, S, How Oriented External Electric Fields Modulate Reactivity,
Abstract: A judiciously oriented external electric field (OEEF) can catalyze a wide range of reactions and can even induce endo/exo stereoselectivity of cycloaddition reactions. The Diels-Alder reaction between cyclopentadiene and maleic anhydride is studied by using quantitative activation strain and Kohn-Sham molecular orbital theory to pinpoint the origin of these catalytic and stereoselective effects. Our quantitative model reveals that an OEEF along the reaction axis induces an enhanced electrostatic and orbital interaction between the reactants, which in turn lowers the reaction barrier. The stronger electrostatic interaction originates from an increased electron density difference between the reactants at the reactive center, and the enhanced orbital interaction arises from the promoted normal electron demand donor-acceptor interaction driven by the OEEF. An OEEF perpendicular to the plane of the reaction axis solely stabilizes the exo pathway of this reaction, whereas the endo pathway remains unaltered and efficiently steers the endo/exo stereoselectivity. The influence of the OEEF on the inverse electron demand Diels-Alder reaction is also investigated; unexpectedly, it inhibits the reaction, as the electric field now suppresses the critical inverse electron demand donor-acceptor interaction.

First author: Cabrera-Trujillo, JJ, Understanding the C-F Bond Activation Mediated by Frustrated Lewis Pairs: Crucial Role of Non-covalent Interactions,
Abstract: The activation of a single C-F bond in di- and trifluoromethyl groups by frustrated Lewis pairs (FLPs) has been computationally explored by means of Density Functional Theory calculations. It is found that in this activation reaction the FLP partners exhibit a peculiar cooperative action, which is markedly different from related FLP-mediated processes, and where non-covalent interactions established between the Lewis base and the substrate play a decisive role. In addition, the process proceeds through the intermediacy of a hypervalent species featuring a pentacoordinate carbon atom, which is rare in the chemistry of FLPs. The physical factors controlling this process as well as the bonding situation of these hypervalent intermediates have been quantitatively analyzed in detail by using state-of-the-art computational methods to not only rationalize the mechanism of the transformation but also to guide experimentalists towards the realization of these so far elusive hypervalent systems.

First author: Khan, MI, A DFT study of bismuthene as anode material for alkali-metal (Li/Na/K)-ion batteries,
Abstract: The buckled Bismuthene (b-Bi) has attracted the researchers owing to its exceptional properties. The first-principles calculations were utilized to investigate application of b-Bi in lithium-, sodium- and potassium-ion batteries. The respective values of adsorption energies of Li, Na and K atoms were found as 2.70 eV, 2.94 eV and -3.45 eV for b-Bi which point to good stability in the lithiation, sodiation and potassiation processes. The fully lithiated, sodiated and potassiated structures exhibited theoretical capacity of 2276 mAh g(-1), 2149 mAh g(-1), and 1896 mAh g(-1) for Li, Na and K respectively which are higher than that of commercially available graphite anode. The value of diffusion barrier calculated using CI-NEB is reasonably lower than that of contemporary materials. Our findings such as storage capacity, low open circuit voltage (OCV) and diffusion energies are better than the commonly studied 2D materials which makes b-Bi a favorable candidate as an anode material for said rechargeable batteries.

First author: Xu, S, Stabilities, Electronic Structures, and Bonding Properties of 20-Electron Transition Metal Complexes (Cp)(2)TMO and their One-Dimensional Sandwich Molecular Wires (Cp = C5H5, C-5(CH3)H-4, C-5(CH3)(5); TM = Cr, Mo, W),
Abstract: First-principles calculations have been carried out for the 20-electron transition metal complexes (Cp)(2)TMO and their molecular wires (Cp = C5H5, C-5(CH3)H-4, C-5(CH3)(5); TM = Cr, Mo, W). The calculation results at the BP86/def2-TZVPP level reveal that the ground state is singlet and the optimized geometries are in good agreement with the experimental values. The analysis of frontier molecular orbitals shows that two electrons in the highest occupied molecular orbital HOMO-1 are mainly localized on cyclopentadienyl and oxygen ligands. Furthermore, the nature of the TM-O bond was investigated with the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV). The attraction term in the intrinsic interaction energies Delta E-int is mainly composed of two important parts, including electrostatic interaction (about 52% of the total attractive interactions Delta E-elstat + Delta E-orb) and orbital interaction, which might be the major determinant of the stability of these (Cp)(2)TMO complexes. All of the TM-O bonds should be described as electron-sharing 6 single bonds [(Cp)(2)TM](+)-[O](-) with the contribution of 53-57% of AE orb and two pi backdonations from the occupied p orbitals of oxygen ligands into vacant pi* MOs of the [(Cp)(2)TM](+) fragments, which are 35-40% of Delta E-orb. The results of bond order and interaction energy from EDA-NOCV calculations suggest the influence of the radius of TM and methyl in the interactions between TM and O in (Cp)(2)TMO. Additionally, the relativistic effects slightly amplify the strength of bonding with increasing Delta E-orb for the EDA-NOCV calculations on three metal complexes (C5H5)(2)TMO. Finally, the geometries, electronic structures, and magnetics of infinitely extended systems, [(C5H5)TMO](infinity), have also been explored. The results of the density of states (DOS) and band structure revealed that [(C5H5)CrO](infinity) and [(C5H5)WO](infinity) are semiconductors with the narrow bands, whereas [(C5H5)MoO](infinity) behaves as metal.

First author: Morgenstern, A, Computer-Assisted Design of Macrocyclic Chelators for Actinium-225 Radiotherapeutics,
INORGANIC CHEMISTRY, 60, 624, (2021)
Abstract: Actinium-225 (Ac-225) is an excellent candidate for targeted radiotherapeutic applications for treating cancer, because of its 10-day half-life and emission of four high-energy alpha(2+) particles. To harness and direct the energetic potential of actinium, strongly binding chelators that remain stable in vivo during biological targeting must be developed. Unfortunately, controlling chelation for actinium remains challenging. Actinium is the largest +3 cation on the periodic table and has a 6d05f0 electronic configuration, and its chemistry is relatively unexplored. Herein, we present theoretical work focused on improving the understanding of actinium bonding with macrocyclic chelating agents as a function of (1) macrocycle ring size, (2) the number and identity of metal binding functional groups, and (3) the length of the tether linking the metal binding functional group to the macrocyclic backbone. Actinium binding by these chelators is presented within the context of complexation with DOTA(4-), the most relevant Ac3+ binding agent for contemporary radiopharmaceutical applications. The results enabled us to develop a new strategy for actinium chelator design. The approach is rooted in our identification that Ac3+-chelation chemistry is dominated by ionic bonding interactions and relies on (1) maximizing electrostatic interactions between the metal binding functional group and the Ac3+ cation and (2) minimizing electronic repulsion between negatively charged actinium binding functional groups. This insight will provide a foundation for future innovation in developing the next generation of multifunctional actinium chelators.

First author: Hanada, T, Synergistic Deep Eutectic Solvents for Lithium Extraction,
Abstract: Hydrophobic deep eutectic solvents (DESs) have attracted much attention as sustainable extraction media for various metals. However, in previously developed DESs, only one DES component is involved in metal complex formation, which has limited their extraction performance and selectivity. Here, we propose a novel synergistic DES concept for improving the performance of environmentally benign liquid-liquid extraction of lithium (Li). Two different conventional extractants, a beta-diketone and a neutral extractant, were effective for creating the synergistic DESs. When the two extractants were mixed, they formed a liquid DES. DESs have much lower viscosity than conventional hydrophobic ionic liquids. The Conductor-like Screening Model for Real Solvents method was used to estimate the formation of DESs with the melting point depressed by the intermolecular interaction between their components. The extraction performance of Li was greatly enhanced with the synergistic DESs. The extraction capacity of Li reached 4.4 g/L using the optimum DES combination because it was solvent-free and highly concentrated. Using the optimum DES, highly selective recovery of Li over Na and K was demonstrated with a model brine solution. This is the first report of efficient and selective extraction of Li with DES-based liquid-liquid extraction.

First author: Dwivedi, S, Atomistic Mechanisms of Thermal Transformation in a Zr-Metal Organic Framework, MIL-140C,
Abstract: To understand the mechanisms responsible for thermal decomposition of a Zr-MOF (MIL-140C), we perform atomistic-scale molecular dynamics (MD) simulations and discuss the simulation data in comparison with the TEM images obtained for the decomposed Zr-MOF. First, we introduce the ReaxFF parameters suitable for the Zr/C/H/O chemistry and then apply them to investigate the thermal stability and morphological changes in the MIL-140C during heating. Based on the performed simulations we propose an atomic mechanism for the collapse of the MIL-140C and the molecular pathways for carbon monoxide formation, the main product of die MIL-140C thermal degradation. We also determine that the oxidation state of the ZrOx clusters, evolved due to the thermal degradation, approximates the tetragonal phase of ZrO2. Both simulations and experiments show a distribution of very small ZrOx clusters embedded in the disrupted organic sheet that could contribute to the unusual high catalytic activity of the decomposed MIL-140C.

First author: Ghidinelli, S, Characterization of “Free Base” and Metal Complex Thioalkyl Porphyrazines by Magnetic Circular Dichroism and TDDFT Calculations,
Abstract: UV-vis absorption and magnetic circular dichroism (MCD) spectra of octakis thioethyl “free base”porphyrazine H(2)OESPz and its metal complexes MOESPz (M = Mg, Zn, Ni, Pd, Cu), as well as of [MnOESPz(SH)] were recorded. In the last case, MCD proved to have quite good sensitivity to the coordination of this complex with 1-methylimidazole (1-mim) in benzene. Time-dependent density functional theory (TDDFT) calculations were carried out for the considered porphyrazine complexes and showed good performance on comparing with MCD and UV-vis experimental spectra, even in the open-shell Cu and Mn cases. Calculations accounted for the red shift observed in the thioalkyl compounds and allowed us to reveal the role of sulfur atoms in spectroscopically relevant molecular orbitals and to highlight the importance of the conformations of the thioethyl external groups. Calculated MCD spectra of [MnOESPz(SH)] confirm the Mn(III) -> Mn(II) redox process, which leads to the [Mn(OESPz)(1-mim)(2)] species, and the relevance of the spin state for MCD is revealed.

First author: Gorantla, SMNVT, Revisiting the Bonding Scenario of Two Donor Ligand Stabilized C-2 Species,
Abstract: Quantum chemical calculations using density functional methods were performed for complexes of type L2C2 with L = NHCMe (1), SNHCMe (2) (S = saturated), cAAC(Me) (3), and diamidocarbene (DAC(Me)) (4). The equilibrium structures of 1-4 possess almost linear C-4 cores. A high thermochemical stability of the complexes with respect to dissociation, L2C2 -> C-2 + 2L, is indicated by the large bond dissociation energy following the order 3 > 4 > 2 > 1. The results show that the use of SNHCMe and DAC(Me) as ligands is preferable over NHCMe. The bonding analysis using charge and energy decomposition methods reveals that (cAAC(Me))(2)C-2 and (DAC(Me))(2)C-2 possess genuine cumulene C-4 moieties, which results from the electron-sharing bonding between quintet L-2 and quintet C-2 fragments. In contrast, the bonding in (NHCMe)(2)C-2 and (SNHCMe)(2)C-2 comes from a combination of dative and electron-sharing interactions between doublet L-2(+) and doublet C-2(-) fragments.

First author: Gloriozov, IP, DFT Investigation of the eta(6) reversible arrow eta(6)-Inter-ring Haptotropic Rearrangement of the Group 8 Metals Complexes [(graphene)MCp](+) (M = Fe, Ru, Os),
Abstract: Metalcyclopentadienyl complexes (MCp)(+) (M = Fe, Ru, Os) bound to the large polyaromatic hydrogenated hydrocarbon (PAH) C96H24 used as a model for pristine graphene have been studied using a density functional theory (DFT) generalized gradient approximation (PBE functional) to reveal their structural features and dynamic behavior. The inter-ring haptotropic rearrangements (IRHRs) for these complexes were shown to occur via two transition states and one intermediate. The energy barriers of the eta(6) reversible arrow eta(6) IRHRs of the (MCp)(+) unit were found to be 30, 27, and 29 kcal/mol for M = Fe, Ru, and Os, respectively. These values are significantly lower than the values found previously for smaller PAHs. Both polar and nonpolar solvents were found not to affect significantly the energy barrier heights. Investigated transition metal complexes could be used in general as catalysts in the design of novel derivatives or materials with promising properties. Metalcyclopentadienyl complexes (MCp)(+) of PAHs show catalytic properties mainly due to their structural details as well as their important characteristic of inter-ring haptotropic rearrangement. IRHRs take place usually by intramolecular mechanisms. During IRHRs, the MLn organometallic groups (OMGs) undergo shifting along the PAH plane and could coordinate additional reagents, which is important for catalysis. Large PAHs such as graphene, fullerenes, and nanotubes possess intrinsic anticancer activity, and numerous arene complexes of Ru and Os have been proven to have anticancer properties as well. We suppose that coordinating Ru or Os to very large PAHs could synergistically increase the anticancer activity of resulting complexes.

First author: Sameera, WMC, CH3O Radical Binding on Hexagonal Water Ice and Amorphous Solid Water,
Abstract: Binding energies of the CH3O radical on hexagonal water ice (I-h) and amorphous solid water (ASW) were calculated using the ONIOM(QM:MM) method. A range of binding energies is found (0.10-0.50 eV), and the average binding energy is 0.32 eV. The CH3O radical binding on the ASW surfaces is stronger than on the I-h surfaces. The computed binding energies from the ONIOM(wB97X-D/def2-TZVP:AMBER) and wB97X-D/def2-TZVP methods agree quite well. Therefore, the ONIOM(QM:MM) method is expected to give accurate binding energies at a low computational cost. Binding energies from the ONIOM(wB97X-D/def2-TZVP:AMBER) and ONIOM(wB97X-D/def2-TZVP:AMOE-BA09) methods differ noticeably, indicating that the choice of force field matters. According to the energy decomposition analysis, the electrostatic interactions and Pauli repulsions between the CH3O radical and ice play a crucial role in the binding energy. This study gives quantitative insights into the CH3O radical binding on interstellar ices.

First author: Bista, D, A Magnetic Superatomic Dimer with an Intense Internal Electric Dipole Moment,
Abstract: The electronic and magnetic properties of the ligand-decorated Fe6S8 cluster and fused superatomic dimer are investigated using first-principles density functional theory. It is shown that the redox properties of the Fe6S8 cluster can be effectively controlled by altering the nature of the attached ligands. Donor ligands such as phosphines reduce the ionization energy of the Fe(6)S(8 )cluster, whereas the acceptor ligands such as CO increase the electron affinity. Such variation in the redox properties of the Fe6S8 cluster is the result of the ligand-induced shift in the cluster’s electronic levels, so the occupation number remains mostly unaffected, leading to a marginal change in the spin magnetic moment of the cluster. A combination of two identical Fe6S8 clusters decorated by unbalanced ligands results in a superatomic dimer with a massive dipole moment and a large spin magnetic moment. Donor ligands on one side of the superatomic dimer with acceptor ligands on the other cause significant intercluster charge transfer. The resulting superatomic dimer offers an interesting motif for spintronics-related applications.

First author: Stoppa, V, Mononuclear and dinuclear gold(i) complexes with a caffeine-based di(N-heterocyclic carbene) ligand: synthesis, reactivity and structural DFT analysis,
Abstract: Two new gold(i) complexes with a di(N-heterocyclic carbene) ligand (diNHC) derived from caffeine have been synthesised by a base-assisted metalation of the appropriate di(azolium) salt in the presence of the gold precursor AuCl(SMe2). Under kinetically controlled conditions, the reaction affords a mononuclear cationic complex with the diNHC ligand chelating the gold centre, while the thermodynamically more stable complex is a dinuclear species with two bridging diNHC ligands. The two complexes have been characterised in solution by mass spectrometry, and H-1, C-13 and DOSY NMR spectroscopies; the mononuclear-dinuclear transformation has been also followed with kinetic experiments giving a second-order rate constant k = (1.46 +/- 0.01) x 10(-2) dm(3) mol(-1) s(-1) in CD3CN, at 313 K. Density functional theory (DFT) calculations have been performed to support these findings. The reactivity of the gold(i) complexes has been evaluated in the oxidative addition of halogens. The reaction allows accessing the corresponding mono- and dinuclear gold(iii) complexes, which are stable and do not interconvert. With the mononuclear complex, species of general formula [AuX2(diNHC)](BF4) (X = Cl and I) have been isolated and a systematic structural investigation of the possible isomers has been performed through DFT calculations.

First author: Li, HF, Enhanced 1.54 mu m luminescence of a perfluorinated erbium complex sensitized by perfluorinated Pt(ii) and Zn(ii) phthalocyanines with 980 nm emission,
Abstract: By the sensitization effect of metallophthalocyanines showing similar to 980 nm emission to an erbium complex, a remarkably long average lifetime of 1.05 ms and an optimal PLQY of 13% with a sensitization efficiency of 81 for the Er3+ 1.54 mu m emission are obtained in a perfluorinated organic erbium co-doped system.

First author: Sanchez-Gonzalez, A, Elucidating the intercalation of methylated 1,10-phenanthroline with DNA: the important weight of the CH/H interactions and the selectivity of CH/pi and CH/n interactions,
RSC ADVANCES, 11, 1553, (2021)
Abstract: Flat molecules like phenanthroline derivatives intercalate between base pairs of deoxyribonucleic acid and produce cytotoxic effects against tumoral cells. Elucidating the way of intercalation and its modulation on their efficiency by substitution still remains a challenging topic of research. In this work we analysed the intercalation via the major groove of methylated derivatives of phenanthroline, in different number and position, between guanine-cytosine base pairs. We studied our systems by using semi-empirical methods and density functional theory including dispersion corrections with the PM6-DH2 Hamiltonian and the B3LYP-D3 functional. We explored the geometry and electronic structure by means of the quantum theory of atoms in molecules and non-covalent interactions index analyses, whereas the interaction energy was estimated by means of two different approaches: one taking into account the results from the quantum theory of atoms in molecules analysis and the other based on the so-called energy decomposition analysis. The effect of solvation was also taken into consideration. Our studies show that CH/pi and CH/n interactions by means of the -CH3 groups of methylated phen follow a clear pattern for any number of -CH3 groups and their position in the methylated phen ligand. That is, they try to produce the CH/pi and CH/n interactions with the O and N heteroatoms of the base pairs and with the O atoms of the sugar and phosphate backbone. These findings suggest that the modulation of the intercalation of ligands that are able to form CH/pi and CH/n weak interactions with the deoxyribonucleic acid is ruled not only by the number and position of the substitutions of the ligands but also by some key sites, which are the O and N atoms of the deoxyribonucleic acid in our analysed systems. It suggests some key and lock mechanism in which the interacting fragments fit like puzzle pieces in order to achieve the optimal interaction for the stabilization of the system. Interaction energies were calculated by using different approaches which converged to similar trends about the number and position of the -CH3 groups. The important weight of the CH/H interactions in the total interaction energy must be highlighted.

First author: Li, ZW, The interaction of M-BZ, M(H2O)-BZ, M-2BZ and M(H2O)-2BZ (M = Li+, Na+, K+, Mg2+, Ca2+): EDA and ETS-NOCV approaches,
Abstract: Cation-pi or cation-2 pi interactions generally exist between one cation and one or two electron-rich pi-ring, which play an important role in many areas (such as benzene, borazine, aromatic rings, graphene and carbon nanotubes). Here, we report the interaction of M-BZ, M(H2O)-BZ, M-2BZ and M(H2O)-2BZ (BZ=borazine, M=Li+, Na+, K+, Mg2+, Ca2+) at the B3LYP-D3/TZ2P levels of theory. We found that the interaction energy decreases as the radii of the cations increase. The total interaction energy was decomposed into the dispersion correction, Pauli repulsion, electrostatic interaction and orbital interaction by using energy decomposition analysis. In addition, the binding energy of M-BZ (2BZ) is similar to that of M-benzene (2benzene), indicating the special importance of M-BZ (2BZ) interaction in biological system. From the extended transition state scheme with the theory of natural orbitals for chemical valence, the first dominant deformation densities plot shown the flow of charge between the fragments, which mean the BZ is pi donation and cation (M(H2O)) is sigma or pi acceptor.

First author: Heijmans, K, Gibbs Ensemble Monte Carlo for Reactive Force Fields to Determine the Vapor-Liquid Equilibrium of CO2 and H2O,
Abstract: Absorption and reactive properties of fluids in porous media are key to the design and improvement of numerous energy related applications. Molecular simulations of these systems require accurate force fields that capture the involved chemical reactions and have the ability to describe the vapor-liquid equilibrium VLE). Two new reactive force fields (ReaxFF) for CO2 and H2O are developed, which are capable of not only modeling bond breaking and formation in reactive environments but also predicting their VLEs at saturation conditions. These new force fields include extra terms (ReaxFF-Ig) to improve the long-range interactions between the molecules. For validation, we have developed a new Gibbs ensemble Monte Carlo (GEMC-ReaxFF) approach to predict the VLE. Computed VLE data show good agreement with National Institute of Standards and Technology reference data as well as existing nonreactive force fields. This validation proves the applicability of the GEMC-ReaxFF method to test new reactive force fields, and simultaneously it proves the applicability to extend newly developed ReaxFF force fields to other more complex reactive systems.

First author: Vermeeren, P, Bifunctional Hydrogen Bond Donor-Catalyzed Diels-Alder Reactions: Origin of Stereoselectivity and Rate Enhancement,
Abstract: The selectivity and rate enhancement of bifunctional hydrogen bond donor-catalyzed Diels-Alder reactions between cyclopentadiene and acrolein were quantum chemically studied using density functional theory in combination with coupled-cluster theory. (Thio)ureas render the studied Diels-Alder cycloaddition reactions exo selective and induce a significant acceleration of this process by lowering the reaction barrier by up to 7 kcal mol(-1). Our activation strain and Kohn-Sham molecular orbital analyses uncover that these organocatalysts enhance the Diels-Alder reactivity by reducing the Pauli repulsion between the closed-shell filled pi-orbitals of the diene and dienophile, by polarizing the pi-orbitals away from the reactive center and not by making the orbital interactions between the reactants stronger. In addition, we establish that the unprecedented exo selectivity of the hydrogen bond donor-catalyzed Diels-Alder reactions is directly related to the larger degree of asynchronicity along this reaction pathway, which is manifested in a relief of destabilizing activation strain and Pauli repulsion.

First author: Dumpala, RMR, Characterization of Thorium-Pyrazinoic acid complexation and its decorporation efficacy in human cells and blood,
CHEMOSPHERE, 271, 5180, (2021)
Abstract: Thorium (Th) exposure to the human beings is a radiochemical hazard and the chelation therapy by suitable drugs is the major prevention approach to deal with. The present studies aimed at usage of pyrazinoic acid (PCA), which is a prodrug to treat tuberculosis, for its usage as decorporating agent for thorium from human body. The present studies provide a comprehensive knowledge on the chemical interaction and biological efficacy of pyrazinoic acid (PCA) for decorporation of Thorium from the human body. The thermodynamic parameters for Th-PCA speciation are determined by both experiment and theory. The potentiometric data analysis and Electro-Spray Ionization Mass Spectrometry (ESI-MS) studies revealed the formation of MLi (i = 1-4) species with the decrease in stepwise stability constants. All the species formations are endothermic reactions and are predominantly entropy-driven. Biological experiments using human erythrocytes, whole blood and normal human lung cells showed cytocompatibility and decorporation ability of PCA for Thorium. Density functional calculations have been carried out to get insights on interaction process at molecular level. The experimental results and theoretical predictions found to be in line with each other. Present findings on complexation of Th by PCA and its evaluation in human cells and blood would further motivate determination of its safety levels and decorporation efficacy in animal models.

First author: Wang, SP, Computational Studies on the Materials Combining Graphene Quantum Dots and Pt Complexes with Adjustable Luminescence Characteristics,
INORGANIC CHEMISTRY, 60, 1480, (2021)
Abstract: Graphene materials with particular properties are proved to be beneficial to photoelectric devices, but there are rare reports on a positive effect by graphene on emissive layer materials of organic light-emitting diodes (OLEDs) previously. On the basis of the latest important experiments, an OLED device with the aid of graphene quantum dots shows the dawn of their application for luminescent materials. The luminescence performance has been improved, but the understanding of the internal excited-state radiation mechanism of the material needs further study. In this work, the Pt(II)-coordinated graphene quantum dot coplanar structures with different shapes are studied theoretically in detail, and the results present the improvement in phosphorescence under the promoted radiative decay and suppressed nonradiative decay. This composite combines the advantages of transition metal complexes and graphene quantum dots and also exhibits excellent properties in the light absorption region and carrier transportation for the OLED. This comprehensive theoretical calculation research can provide a comprehensive basis of the material design in the future.

First author: Rojisha, VC, Nature of C-N bond in N-heterocyclic carbene,
Abstract: The electronic structure and bonding in five-membered N-heterocyclic carbene (NHC) have been explored by EDA-NOCV analysis, which indicates that the C-N bonds in NHC are different from conventional electron sharing covalent bonds. The interaction between the carbene carbon atom and the adjacent nitrogen atoms in NHC can be best represented as one sigma-type 3c-2e electron sharing bond and one sigma-type 3c-2e donor-acceptor bond. It can be considered equivalent to two localized representations viz., one electron sharing N-C sigma bond and one donor-acceptor N -> C sigma bond between the two nitrogen atoms and the carbene carbon atom.

First author: Michalczyk, M, Experimental and Theoretical Studies of Dimers Stabilized by Two Chalcogen Bonds in the Presence of a N center dot center dot center dot N Pnicogen Bond,
Abstract: The structure of the 5,6-dichloro-2,1,3-benzoselenadiazole homo-dimer, obtained by adding the ligand, 4,5-dichloro-o-phenylenediamine, to the methanolic solution of SeCl4, was determined by X-ray crystallography, augmented by Fourier transform infrared, Raman, and NMR spectroscopy. The binding motif involves a pair of Se center dot center dot center dot N chalcogen bonds, with a supplementary N center dot center dot center dot N pnicogen bond. Quantum calculations provide assessments of the strengths of the individual interactions as well as their contributing factors. All together, these three bonds compose a total interaction energy between 5.4 and 16.8 kcal/mol, with the larger chalcogen atom associated with the strongest interactions. Replacement of the Se atoms by S and Te analogues allows analysis of the dependence of these forces on the nature of the chalcogen atom. Calculations also measure the importance to the binding of the presence of a second N atom on each diazole unit as well as the substituted phenyl ring to which it is fused.

First author: Fan, XW, Computational insight into newly anomalous delayed fluorescence emitters based on D-A-A structures,
Abstract: In variety of skeleton structures of delayed fluorescence molecular materials, the D-A-A type has been widely concerned recently for its improved double efficiency of reverse intersystem crossing process (RISC). Based on the D-A-A structure, eight new D-TRZ-nPO molecules (D = dihydrophenazine (DHPZ), phenothiazine (PTZ), phenoxazine (PXZ) and 9,9-dimethyl-9,10-dihydroacridan (DMAC), TRZ = triphenyl triazine, n = 1 or 2) with potential performance improvement have been deeply investigated by theoretical calculations. Interestingly, these molecules with the closing energy levels of high-lying excited states and charge transfer characters may perform rare high-lying excited state delayed fluorescence. Meanwhile, the changes of RISC and the corresponding effects caused by D-A-A structure from low energy level to high energy level are analyzed in detail. Furthermore, DHPZ-TRZ-2PO with blue emission (452 nm) is expected to be a potential high-lying excited state delayed fluorescence material candidate.

First author: Rao, CV, Anion assisted extraction of U(VI) in alkylammonium ionic liquid: Experimental and DFT studies,
Abstract: The extraordinary extraction of metal ions in imidazolium ionic liquid phase containing neutral extractants was most often attributed to the cation exchange mechanism in addition to the usual solvation-type mechanism. The cation exchange mechanism results in an irreversible loss of the ionic liquid cation, which eventually leads to the pollution of aqueous phase also. To minimize the limitations of imidazolium based ionic liquid, strongly hydrophobic ionic liquids containing tetra-alkyl ammonium ion have been introduced and studied for actinide separation. Even though these tetra-alkyl ammonium ionic liquids did not undergo cation exchange, but showed exceptional extraction of actinides for the reason, which was not established so far. To unravel the unique role of these hydrophobic ionic liquids, the extraction behavior of U(VI) was studied in a solution of tri-n-octylmethylammonium nitrate ([N-1888][NO3]) in conjunction with a neutral ligand, 2-hydroxy-N,N-dioctyl acetamide (DOHyA). The extraction of U(VI) was studied as a function of various extraction parameters and the organic phase obtained after extraction was probed by FTIR and Raman spectroscopy to elucidate the mechanism of U (VI) extraction in ionic liquid phase. The result revealed that U(VI) was extracted into ionic liquid phase by a couple of extraction modes, namely through metal-ligand coordination and by loss-less anion exchange mode and these pathways did not cause any undue burden to the organic and aqueous phases, unlike the traditional imidazolium ionic liquids. Further, DFT studies were performed to elucidate the underlying mechanism of U(VI) complexation in ionic liquid phase. The calculated values of binding energy (Delta E) and Gibbs free energy (Delta G) for the complexation of U(VI) with DOHyA in dodecane and tetra-alkyl ammonium ionic liquids medium were found in good agreement with the experimentally determined complexation trends of U(VI) ion with DoHyA. The DFT calculations further established that the cation exchange mechanism by both the ionic liquids, [N-1888][NO3] and [N-1888][NTf2] was not feasible, but anion exchange mechanism could be possible as observed in the experimental studies.

First author: van Niekerk, DME, Kinetic UV-Vis Spectroscopic and DFT Mechanistic Study of the Redox Reaction of [(OsO4)-O-VIII(OH)(n)](n-) (n=1, 2) and Methanol in a Basic Aqueous Matrix,
INORGANIC CHEMISTRY, 60, 783, (2021)
Abstract: This combined experimental and computational study builds on our previous studies to elucidate the reaction mechanism of methanol oxidation by OsVIII oxido/hydroxido species (in basic aqueous media) while accounting for the simultaneous formation of OsVII species via a comproportionation reaction between OsVIII and OsVI. UV-Vis spectroscopy kinetic analyses with either CH3OH or the deuterated analogue CD3OH as a reducing agent revealed that transfer of a-carbon-hydrogen of methanol is the partial rate-limiting step. The resulting relatively large KIE value of approximately 11.82 is a combination of primary and secondary isotope effects. The Eyring plots for the oxidation of these isotopologues of methanol under the same reaction conditions are parallel to each other and hence have the same activation enthalpy [Delta H degrees = 14.4 +/- 1.2 kcal mol(-1) (CH3OH) and 14.5 +/- 1.3 kcal mol(-1) (CD3OH)] but lowered activation entropy (Delta S degrees) from -12.5 +/- 4.1 cal mol(-1) K-1 (CH3OH) to -17.1 +/- 4.4 cal mol(-1) K-1 (CD3OH). DFT computational studies at the PBE-D3 level with QZ4P (Os) and pVQZ (O and H) basis sets provide clear evidence to support the data and interpretations derived from the experimental kinetic work. Comparative DFT mechanistic investigations in a simulated aqueous phase (COSMO) indicate that methanol and OsVIII first associate to form a noncovalent adduct bound together by intermolecular H-bonding interactions. This is followed by spin-forbidden a-carbon-hydrogen transfer (not O-H transfer) from methanol to OsVIII by means of HAT, which is found to be the partial rate-limiting step. Without the organic and inorganic fragments dissociating from each other during the entire stepwise redox reaction (in order to avoid formation of highly energetically unfavorable monomer species), the HAT step is followed by PT and then ET before the final product monomers formaldehyde and OsVI dissociate from each other. DFT-calculated..H degrees is within 5 kcal mol-1 of the experimentally obtained value, while the DFT..S degrees is three times larger than that found from the experiment.

First author: Moitra, T, Behind the scenes of spin-forbidden decay pathways in transition metal complexes,
Abstract: The interpretation of the ultrafast photophysics of transition metal complexes following photo-absorption is quite involved as the heavy metal center leads to a complicated and entangled singlet-triplet manifold. This opens up multiple pathways for deactivation, often with competitive rates. As a result, intersystem crossing (ISC) and phosphorescence are commonly observed in transition metal complexes. A detailed understanding of such an excited-state structure and dynamics calls for state-of-the-art experimental and theoretical methodologies. In this review, we delve into the inability of non-relativistic quantum theory to describe spin-forbidden transitions, which can be overcome by taking into account spin-orbit coupling, whose importance grows with increasing atomic number. We present the quantum chemical theory of phosphorescence and ISC together with illustrative examples. Finally, a few applications are highlighted, bridging the gap between theoretical studies and experimental applications, such as photofunctional materials.

First author: Li, XM, U2N@I-h(7)-C-80: fullerene cage encapsulating an unsymmetrical U(IV)=N=U(v) cluster,
CHEMICAL SCIENCE, 12, 282, (2021)
Abstract: For the first time, an actinide nitride clusterfullerene, U2N@I-h(7)-C-80, is synthesized and fully characterized by X-ray single crystallography and multiple spectroscopic methods. U2N@I-h(7)-C-80 is by far the first endohedral fullerene that violates the well-established tri-metallic nitride template for nitride clusterfullerenes. The novel U=N=U cluster features two U=N bonds with uneven bond distances of 2.058(3) angstrom and 1.943(3) angstrom, leading to a rare unsymmetrical structure for the dinuclear nitride motif. The combined experimental and theoretical investigations suggest that the two uranium ions show different oxidation states of +4 and +5. Quantum-chemical investigation further reveals that the f(1)/f(2) population dominantly induces a distortion of the U=N=U cluster, which leads to the unsymmetrical structure. A comparative study of U2X@C-80 (X = C, N and O) reveals that the U-X interaction in U=X=U clusters can hardly be seen as being formed by classical multiple bonds, but is more like an anionic central ion Xq- with biased overlaps with the two metal ions, which decrease as the electronegativity of X increases. This study not only demonstrates the unique bonding variety of actinide clusters stabilized by fullerene cages, showing different bonding from that observed for the lanthanide analogs, it also reveals the electronic structure of the U=X=U clusters (X = C, N and O), which are of fundamental significance to understanding these actinide bonding motifs.

First author: da Silva, EH, Theoretical study of chloride complexes with hybrid macrocycles,
Abstract: Anions show relevant roles in biological routes. The supramolecular chemistry investigates the chemical bonding between two or more molecules and/or ions. Herein, the nature of the bond between chloride anions and macrocycle receptors elaborated from (i) pyridines, (ii) pyrroles, (iii) borazines, (iv) triazines, and (v) 1,2,3-triazole rings are studied. The energy decomposition analysis (EDA) shows that the receptors that predominantly establish non-covalent interactions with the Cl- anions proportionate a preferable bond than the macrocycles that mostly form a covalent interaction with the Cl- anions. The substitution of pyridine by borazine rings in the macrocycles or the protonation of the receptors increases the interaction with the Cl- anions since there is an increase in the number of -BH or -NH groups available to establish hydrogen bonds with the Cl- anions. In addition, the pyridine -> borazine substitution decreases the number of repulsive interactions. The substitution of pyrrole by 1,2,3-triazole rings does not relevantly favor the interaction with the Cl- anions. The substitution of pyridine by the triazine rings or the addition of electron-withdrawing groups (-OH, -F and -NO2) in the receptor structures increases the acidity of the cavity of the macrocycles and, therefore, favors the interaction with the Cl- anions. The addition of electron-donating groups (-NH2) to the receptor structure promotes the opposite effect. Accordingly, the present investigation brings relevant information for the design of new hybrid macrocycles with the potential for anionic recognition.

First author: Wan, IC, On the Origin of Regioselectivity in Palladium-Catalyzed Oxidation of Glucosides,
Abstract: The palladium-catalyzed oxidation of glucopyranosides has been investigated using relativistic density functional theory (DFT) at ZORA-BLYP-D3(BJ)/TZ2P. The complete Gibbs free energy profiles for the oxidation of secondary hydroxy groups at C2, C3, and C4 were computed for methyl beta-glucoside and methyl carba-beta-glucoside. Both computations and oxidation experiments on carba-glucosides demonstrate the crucial role of the ring oxygen in the C3 regioselectivity observed during the oxidation of glucosides. Analysis of the model systems for oxidized methyl beta-glucoside shows that the C3 oxidation product is intrinsically favored in the presence of the ring oxygen. Subsequent energy decomposition analysis (EDA) and Hirschfeld charge analysis reveal the role of the ring oxygen: it positively polarizes C1/C5 by inductive effects and disfavors any subsequent buildup of positive charge at neighboring carbon atoms, rendering C3 the most favored site for the beta-hydride elimination.

First author: Selvakumar, J, An electrochemically controlled release of NHCs using iron bis(dithiolene) N-heterocyclic carbene complexes,
Abstract: A series of five coordinated iron bis(dithiolene) complexes [Fe(NHC)(S2C2R2)(2)] (R = C6H5 or C6H4-p-OCH3) containing N-heterocyclic carbene (NHC) (NHC = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene or 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) were isolated in high yield (84-92%). The iron complexes were characterized by NMR spectroscopy and confirmed by single crystal X-ray diffraction studies. The combination of cyclic voltammetry and spectroelectrochemical analysis revealed that iron complexes undergo Fe-C-NHC bond cleavage and release NHC upon subjection to electrochemical reduction. The electrochemically released NHC was trapped using 1-naphthylisothiocyanate and the adduct was isolated in nearly quantitative yield (similar to 99%). As a proof of concept, the electrochemically released NHC was subsequently used as a catalyst for synthesis of gamma-butyrolactones from commercially available cinnamaldehydes.

First author: Dominikowska, J, Lack of Cooperativity in the Triangular X-3 Halogen-Bonded Synthon?,
CRYSTAL GROWTH & DESIGN, 21, 597, (2021)
Abstract: We have investigated 44 crystal structures, found in the Cambridge Structural Database, containing the X-3 synthon (where X = Cl, Br, I) in order to verify whether three type II halogen-halogen contacts forming the synthon exhibit cooperativity. A hypothesis that this triangular halogen-bonded motif is stabilized by cooperative effects is postulated on the basis of structural data. However, theoretical investigations of simplified model systems in which the X-3 motif is present demonstrate that weak synergy occurs only in the case of the 13 motif. In the present paper we computationally investigate crystal structures in which the X-3 synthon is present, including halomesitylene structures, that are usually described as being additionally stabilized by a synergic interaction. Our computations find no cooperativity for halomesitylene trimers containing the X-3 motif. Only in the case of two other structures containing the 13 synthon a very weak or weak synergy, i.e. the cooperative effect being stronger than-0.40 kcal mol(-1), is found. The crystal structure of iodoform has the most pronounced cooperativity of all investigated systems, amounting to about 10% of the total interaction energy.

First author: Kitajima, K, Delivery of Electrons by Proton-Hole Transfer in Ice at 10 K: Role of Surface OH Radicals,
Abstract: Although water ice has been widely accepted to carry a positive charge via the transfer of excess protons through a hydrogen-bonded system, ice was recently found to be a negative charge conductor upon simultaneous exposure to electrons and ultraviolet photons at temperatures below 50 K. In this work, the mechanism of electron delivery was confirmed experimentally by both measuring currents through ice and monitoring photodissociated OH radicals on ice by using a novel method. The surface OH radicals significantly decrease upon the appearance of negative current flow, indicating that the electrons are delivered by proton-hole (OH-) transfer in ice triggered by OH- production on the surface. The mechanism of proton-hole transfer was rationalized by density functional theory calculations.

First author: Wan, QY, Strong metal-metal Pauli repulsion leads to repulsive metallophilicity in closed-shell d(8) and d(10 )organometallic complexes,
Abstract: Metallophilicity is defined as the interaction among closed-shell metal centers, the origin of which remains controversial, particularly for the roles of spd orbital hybridization (mixing of the spd atomic orbitals of the metal atom in the molecular orbitals of metal complex) and the relativistic effect. Our studies reveal that at close M-M’ distances in the X-ray crystal structures of d(8) and d(10) organometallic complexes, M-M’ closed-shell interactions are repulsive in nature due to strong M-M’ Pauli repulsion. The relativistic effect facilitates (n + 1)s-nd and (n + 1)p-nd orbital hybridization of the metal atom, where (n + 1)s-nd hybridization induces strong M-M’ Pauli repulsion and repulsive M-M’ orbital interaction, and (n + 1)p-nd hybridization suppresses M-M’ Pauli repulsion. This model is validated by both DFT (density functional theory) and high-level coupled-cluster singles and doubles with perturbative triples computations and is used to account for the fact that the intermolecular or intramolecular Ag-Ag’ distance is shorter than the Au-Au’ distance, where a weaker Ag-Ag’ Pauli repulsion plays an important role. The experimental studies verify the importance of ligands in intermolecular interactions. Although the M-M’ interaction is repulsive in nature, the linear coordination geometry of the d(10) metal complex suppresses the L-L’ (ligand-ligand) Pauli repulsion while retaining the strength of the attractive L-L’ dispersion, leading to a close unsupported M-M’ distance that is shorter than the sum of the van der Waals radius (r(vdw)) of the metal atoms.

First author: Negri, C, In situ X-ray absorption study of Cu species in Cu-CHA catalysts for NH3-SCR during temperature-programmed reduction in NO/NH3,
Abstract: Ammonia-mediated selective catalytic reduction (NH3-SCR) using Cu-exchanged chabazite zeolites as catalysts is one of the leading technologies for NOx removal from exhaust gases, with Cu-II/Cu-I redox cycles being the basis of the catalytic reaction. The amount of Cu-II ions reduced by NO/NH3 can be quantified by the consumption of NO during temperature-programmed reduction experiments (NO-TPR). In this article, we show the capabilities of in situ X-ray absorption near-edge spectroscopy (XANES), coupled with multivariate curve resolution (MCR) and principal component analysis (PCA) methods, in following Cu-II/Cu-I speciation during reduction in NO/NH3 after oxidation in NO/O-2 at 50 degrees C on samples with different copper loading and pretreatment conditions. Our XANES results show that during the NO/NH3 ramp Cu-II ions are fully reduced to Cu-I in the 50-290 degrees C range. The number of species involved in the process, their XANES spectra and their concentration profiles as a function of the temperature were obtained by MCR and PCA. Mixed ligand ammonia solvated complexes [Cu-II(NH3)(3)(X)](+) (X = OH-/O- or NO3-) are present at the beginning of the experiment, and are transformed into mobile [Cu-I(NH3)(2)](+) complexes: these complexes lose an NH3 ligand and become framework-coordinated above 200 degrees C. In the process, multiple Cu-II/Cu-I reduction events are observed: the first one around 130 degrees C is identified with the reduction of [Cu-II(NH3)(3)(OH/O)](+) moieties, while the second one occurs around 220-240 degrees C and is associated with the reduction of the ammonia-solvated Cu-NO3- species. The nitrate concentration in the catalysts is found to be dependent on the zeolite Cu loading and on the applied pretreatment conditions. Ammonia solvation increases the number of Cu-II sites available for the formation of nitrates, as confirmed by infrared spectroscopy.

First author: Aquino, LED, Seven-Coordinate Tb3+ Complexes with 90% Quantum Yields: High-Performance Examples of Combined Singlet- and Triplet-to-Tb3+ Energy-Transfer Pathways,
INORGANIC CHEMISTRY, 60, 893, (2021)
Abstract: Seven-coordinate, pentagonal-bipyramidal (PBP) complexes [Ln(bbpen)Cl] and [Ln(bbppn) Cl], in which Ln = Tb3+ (products I and II), Eu3+ (III and IV), and Gd3+ (V and VI), with bbpen(2-) = N,N’-bis(2-oxidobenzyl)-N,N’-bis(pyridin-2-ylmethyl)-ethylenediamine and bbppn(2-) = N,N’-bis(2-oxidobenzyl)-N,N’-bis(pyridin-2-ylmethyl)-1,2-propanediamine, were synthesized and characterized by single-crystal X-ray diffraction analysis, alternating-current magnetic susceptibility measurements, and photoluminescence (steady-state and time-resolved) spectroscopy. Under a static magnetic field of 0.1 T, the Tb3+ complexes I and II revealed single-ion-magnet behavior. Also, upon excitation at 320 nm at 300 K, I and II presented very high absolute emission quantum yields (0.90 +/- 0.09 and 0.92 +/- 0.09, respectively), while the corresponding Eu3+ complexes III and IV showed no photoluminescence. Detailed theoretical calculations on the intramolecular energy-transfer rates for the Tb3+ products indicated that both singlet and triplet ligand excited states contribute efficiently to the overall emission performance. The expressive quantum yields, Q(Ln)(L), measured for I and II in the solid state and a dichloromethane solution depend on the excitation wavelength, being higher at 320 nm. Such a dependence was rationalized by computing the intersystem crossing rates (W-ISC) and singlet fluorescence lifetimes (tau(S)) related to the population dynamics of the S-1 and T-1 levels. Thin films of product II showed high air stability and photostability upon continuous UV illumination, which allowed their use as downshifting layers in a green light-emitting device (LED). The prototypes presented a luminous efficacy comparable with those found in commercial LED coatings, without requiring encapsulation or dispersion of II in host matrixes. The results indicate that the PBP environment determined by the ethylenediamine (en)-based ligands investigated in this work favors the outstanding optical properties in Tb3+ complexes. This work presents a comprehensive structural, chemical, and spectroscopic characterization of two Tb3+ complexes of mixed-donor, en-based ligands, focusing on their outstanding optical properties. They constitute good molecular examples in which both triplet and singlet excited states provide energy to the Tb3+ ion and lead to high values of Q(Ln)(L).

First author: Kennedy, SJO, Coordination and Precipitation of Calcium Oxalate: Computation to Kinetics,
CRYSTAL GROWTH & DESIGN, 21, 1249, (2021)
Abstract: The precipitation kinetics of calcium oxalate was investigated using a novel acidic reaction rate control and pH-monitoring method and a sequence of acid-base, coordination, nucleation, and growth differential equations. The results indicate that the complex formation is remarkably favorable and is diffusion rate-limited. The nucleation reaction is shown to initiate via the molecular assembly of near-zwitterionically polarized complexes. From experimental results, growth and formation of the crystal phase leads to an enthalpically less stabilized state.

First author: Bursch, M, Comprehensive Benchmark Study on the Calculation of Si-29 NMR Chemical Shifts,
INORGANIC CHEMISTRY, 60, 272, (2021)
Abstract: A comprehensive and diverse benchmark set for the calculation of Si-29 NMR chemical shifts is presented. The SiS146 set includes 100 silicon containing compounds with 146 experimentally determined reference Si-29 NMR chemical shifts measured in nine different solvents in a range from -400 to +828 ppm. Silicon atoms bound to main group elements as well as transition metals with coordination numbers of 2-6 in various bonding patterns including multiple bonds and coordinative and aromatic bonding are represented. The performance of various common and specialized density functional approximations including (meta-)GGA, hybrid, and double-hybrid functionals in combination with different AO basis sets and for differently optimized geometries is evaluated. The role of scalar-relativistic effects is further investigated by inclusion of the zeroth order regular approximation (ZORA) method into the calculations. GGA density functional approximations (DFAs) are found to outperform hybrid DFAs with B97-D3 performing best with an MAD of 7.2 ppm for the subset including only light atoms (Z < 18), while TPSSh is the best tested hybrid functional with an MAD of 10.3 ppm. For Si-29 cores in the vicinity of heavier atoms, the application of ZORA proved indispensable. Inclusion of spin-orbit effects into the Si-29 NMR chemical shift calculation decreases the mean absolute deviations by up to 74% compared to calculations applying effective core potentials.

First author: Babetto, L, Multireference Ab Initio Investigation on Ground and Low-Lying Excited States: Systematic Evaluation of J-J Mixing in a Eu3+ Luminescent Complex,
INORGANIC CHEMISTRY, 60, 315, (2021)
Abstract: A theoretical protocol combining density functional theory (DFT) and multireference (CAS) calculations is proposed for a Eu3+ complex. In the complex, electronic levels of the central Eu3+ ion are correctly calculated at the CASPT2 level of theory, and the effect of introducing different numbers of states in the configuration interaction matrices is highlighted as well as the shortcomings of DFT methods in the treatment of systems with high spin multiplicity and strong spin-orbit coupling effects. For the D-5(0) state energy calculation, the inclusion of states with different multiplicity and the number of states considered for each multiplicity are crucial parameters, even if their relative weight is different. Indeed, the addition of triplet and singlets is important, while the number of states is relevant only for the quintets. The herein proposed protocol enables a rigorous, full ab initio treatment of Eu3+ complex, which can be easily extended to other Ln(3+) ions.

First author: Majid, A, A first-principles study on improvement of photoinjection in organic dyes,
Abstract: First principles methods are implemented in order to design new metal free organic dyes with motivation to improve photoinjection in dye sensitized solar cell (DSSC). The simulated structures obey general D-pi-A structure and various structural modifications are made in pi-bridge as well as donor assembly of the dyes. The addition of benzothiadiazole and pyridine in pi-bridge caused shifting of absorption spectrum of dyes shifted toward lower energies. The analysis of structural and photoelectric properties of the dyes revealed that the dyes containing triarylamine in donor assembly show largest light harvesting efficiencies. The process of photoinjection was modeled by adsorbing the series of dyes on surface of (TiO2)(n) particles to investigate the injection and recombination kinetics. The dyes having benzothiadiazole in pi-bridge exhibited smallest injection energies while the dyes having pyridine in the in pi-bridge shown highest recombination energies. The detailed investigation of UV-visible spectra of dye-semiconductor complex was carried out to explore suitability of the dyes for practical applications in DSSC.

First author: Geng, LJ, Co13O8-metalloxocubes: a new class of perovskite-like neutral clusters with cubic aromaticity,
Abstract: Exploring stable clusters to understand structural evolution from atoms to macroscopic matter and to construct new materials is interesting yet challenging in chemistry. Utilizing our newly developed deep-ultraviolet laser ionization mass spectrometry technique, here we observe the reactions of neutral cobalt clusters with oxygen and find a very stable cluster species of Co13O8 that dominates the mass distribution in the presence of a large flow rate of oxygen gas. The results of global-minimum structural search reveal a unique cubic structure and distinctive stability of the neutral Co13O8 cluster that forms a new class of metal oxides that we named as `metalloxo cubes’. Thermodynamics and kinetics calculations illustrate the structural evolution from icosahedral Co-13 to the metalloxocube Co13O8 with decreased energy, enhanced stability and aromaticity. This class of neutral oxygen-passivated metal clusters may be an ideal candidate for genetic materials because of the cubic nature of the building blocks and the stability due to cubic aromaticity.

First author: Southern, SA, Recent advances in NMR crystallography and polymorphism,
Abstract: This chapter covers some recent developments in NMR crystallography with a focus on its application towards the identification and characterization of crystal structures and their polymorphs. NMR crystallography is a discipline that uses insights or constraints obtained from solid-state NMR spectroscopy and first-principles calculations to predict, identify, validate, or refine crystal structures. In recent years, there have been plenty of developments in the area of NMR crystallography as it applies to study polymorphism in organic and inorganic systems, the understanding of noncovalent bonding networks directing crystal growth, and the study of dynamic processes present within solids. We discuss these topics through the lens of solid-state NMR and consider some of the more innovative or unusual strategies being applied to these problems, such as dynamic nuclear polarization (DNP) or nuclear quadrupole resonance (NQR) spectroscopy. The focus is on literature reports from 2016 to mid-2020.

First author: Cantu, DC, Predicting lanthanide coordination structures in solution with molecular simulation,
Abstract: The chemical and physical properties of lanthanide coordination complexes can significantly change with small variations in their molecular structure. Further, in solution, coordination structures (e.g., lanthanide-ligand complexes) are dynamic. Resolving solution structures, computationally or experimentally, is challenging because structures in solution have limited spatial restrictions and are responsive to chemical or physical changes in their surroundings. To determine structures of lanthanide-ligand complexes in solution, a molecular simulation approach is presented in this chapter, which concurrently considers chemical reactions and molecular dynamics. Lanthanide ion, ligand, solvent, and anion molecules are explicitly included to identify, in atomic resolution, lanthanide coordination structures in solution. The computational protocol described is applicable to determining the molecular structure of lanthanide-ligand complexes, particularly with ligands known to bind lanthanides but whose structures have not been resolved, as well as with ligands not previously known to bind lanthanide ions. The approach in this chapter is also relevant to elucidating lanthanide coordination in more intricate structures, such as in the active site of enzymes.

First author: de Luzuriaga, IO, Learning to Model G-Quadruplexes: Current Methods and Perspectives,
ANNUAL REVIEW OF BIOPHYSICS, VOL 50, 2021, 50, 209, (2021)
Abstract: G-quadruplexes have raised considerable interest during the past years for the development of therapies against cancer. These noncanonical structures of DNA may be found in telomeres and/or oncogene promoters, and it has been observed that the stabilization of such G-quadruplexes may disturb tumor cell growth. Nevertheless, the mechanisms leading to folding and stabilization of these G-quadruplexes are still not well established, and they are the focus of much current work in this field. In seminal works, stabilization was observed to be produced by cations. However, subsequent studies showed that different kinds of small molecules, from planar and non-planar organic molecules to square-planar and octahedral metal complexes, may also lead to the stabilization of G-quadruplexes. Thus, the comprehension and rationalization of the interaction of these small molecules with G-quadruplexes are also important topics of current interest in medical applications. To shed light on the questions arising from the literature on the formation of G-quadruplexes, their stabilization, and their interaction with small molecules, synergies between experimental studies and computational works are needed. In this review, we mainly focus on in silico approaches and provide a broad compilation of different leading studies carried out to date by different computational methods. We divide these methods into two main categories: (a) classical methods, which allow for long-timescale molecular dynamics simulations and the corresponding analysis of dynamical information, and (b) quantum methods (semiempirical, quantum mechanics/molecular mechanics, and density functional theory methods), which allow for the explicit simulation of the electronic structure of the system but, in general, are not capable of being used in long-timescale molecular dynamics simulations and, therefore, give a more static picture of the relevant processes.

First author: Ishida, K, Thiophene-Fused Naphthodiphospholes: Modulation of the Structural and Electronic Properties of Polycyclic Aromatics by Precise Fusion of Heteroles,
CHEMPLUSCHEM, 86, 130, (2021)
Abstract: For polycyclic aromatics with heterole-fused structures, the orientation of fused heterole rings as well as the geometry of their fused structures has a large impact on the physicochemical properties. In this study, a series of isomers of thiophene-fused naphthodiphospholes was designed and synthesized. Systematic investigation unveiled the explicit impact of heterole-fused structures on their structural and electronic properties. The isomers with 1,2/5,6-fused structure display phosphorescence due to enhanced spin-orbit coupling, whereas the isomers with 2,3/6,7-fused structure exhibit intense fluorescence. The trans isomers exhibited 1D slip pi-stacked arrangement. In contrast, the cis isomers displayed 2D herringbone structure or columnar structure with a cavity. Therefore, the precisely controlled fusion of heterole rings is a universal approach to uncover their intrinsic properties for versatile applications as organic functional materials.

Abstract: Heterometallic coordination compounds based on copper(II) and palladium(II) beta-diketonates 2 2[CuL2 center dot PdL2] (L = 2-methoxy-2,6,6-trimethylheptane-3,5-dionato) and [Cu(hfa)(2)center dot PdL2′] (hfa = hexafluoroacetylacetonate, L’ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionato) with a polymeric chain-like crystal structure can be used to prepare Cu-Pd films by MOCVD. It was previously suggested that the Pd:Cu ratio in the films is related to the stability of binuclear complexes CuL2 center dot PdL2 and Cu(hfa)(2)center dot PdL2′ (the forms these compound adopt in the gas phase). In the present work, the most probable structure of such binuclear complexes at 0 K is determined, their stability is studied, and interatomic interactions are analyzed by density functional theory calculations. The monometallic fragments of the complexes are connected by a network of weak non-covalent interactions, the Cu center dot center dot center dot O contact being the strongest one. When modeling such systems, empirical corrections are shown to be essential for the account of dispersion interactions.

First author: Bortoli, M, Chalcogen-Nitrogen Bond: Insights into a Key Chemical Motif,
CATALYSTS, 11, 9, (2021)
Abstract: Chalcogen-nitrogen chemistry deals with systems in which sulfur, selenium, or tellurium is linked to a nitrogen nucleus. This chemical motif is a key component of different functional structures, ranging from inorganic materials and polymers, to rationally designed catalysts, to bioinspired molecules and enzymes. The formation of a selenium-nitrogen bond, typically occurring upon condensation of an amine and the unstable selenenic acid, often leading to intramolecular cyclizations, and its disruption, mainly promoted by thiols, are rather common events in organic Se-catalyzed processes. In this work, focusing on examples taken from selenium organic chemistry and biochemistry, the selenium-nitrogen bond is described, and its strength and reactivity are quantified using accurate computational methods applied to model molecular systems. The intermediate strength of the Se-N bond, which can be tuned to necessity, gives rise to significant trends when comparing it to the stronger S- and weaker Te-N bonds, reaffirming also in this context the peculiar and valuable role of selenium in chemistry and life.

First author: Zhao, ZW, Superiority of Iridium Photocatalyst and Role of Quinuclidine in Selective alpha-C(sp(3))-H Alkylation: Theoretical Insights,
Abstract: Recent experimental work reported that visible-light photoredox catalysis coupled with primary sulfonamides and electron-deficient alkenes could efficiently construct C-C bonds at the a-position of primary amine derivatives under mild conditions. Here, a systematic study was conducted to explore the non-negligible excited-state single-electron-transfer (SET) processes and the catalytic cycle. Hydrogen atom transfer (HAT) catalysis containing different site-selective functionalization, involved as a critical process during the reaction, was computationally characterized. The superiorities of iridium-based photoredox catalysts in terms of photoabsorption properties, phosphorescence rates, and electron-transfer rates for SET processes were focused on. In addition, the function of quinuclidine in the entire photocatalytic reaction was also probed. These intrinsic properties and detailed insights into the mechanism are supposed to be helpful to the understanding of the C-C bond functionalization reaction and the future application of the iridiumbased photoredox catalyst.

First author: Grabowski, SJ, Intramolecular Hydrogen Bond Energy and Its Decomposition-O-H center dot center dot center dot O Interactions,
CRYSTALS, 11, 484, (2021)
Abstract: The method to calculate the energy of intramolecular hydrogen bond is proposed and tested for a sample of malonaldehyde and its fluorine derivatives; the corresponding calculations were performed at the omega B97XD/aug-cc-pVTZ level. This method based on relationships found for related intermolecular hydrogen bonds is compared with other approaches which may be applied to estimate the intramolecular hydrogen bond energy. Particularly, methods based on the comparison of the system that contains the intramolecular hydrogen bond compared with corresponding conformations where such interaction does not occur are discussed. The function-based energy decomposition analysis, FB-EDA, of the intramolecular hydrogen bonds is also proposed here.

First author: Su, DM, Theoretical design and exploration of low-valent uranium metallocenes via manipulating cyclopentadienyl substituent,
Abstract: Over a century of investigations on uranium complexes resulted in great progress in establishing their fundamental properties and developing applications. However, the in-depth understanding of uranium chemistry, particularly in record low + II valence, is still challenging due to rare crystallographically-identified U(II) complexes, extremely low stability and rigid synthetic conditions. Herein, to further expand experimental findings, various substituted-cyclopentadienyl uranium complexes, [U(Cp-X)(3)](n) (X = Me, H, Cl, SiMe3 and 2SiMe(3); n = -1 and 0), have been explored using relativistic density functional theory. It is shown that the reduction from [U(Cp-X)(3)] to [U(Cp-X)(3)](-) slightly strengthens the U-Cp bonding, while the great enhancement is found in previously reported uranium arene analogues. The + III oxidation state is assigned to the metal of [U (Cp-X)(3)]; in contrast, it is approximately + II valence for [U(Cp-X)(3)](-) because of non-negligible electron density residing on the Cp-X ligands, whose amount positively correlates with the electron-withdrawing ability of X substituent. Calculated reduction potentials range from -3.02 to -2.74 V while considering solvation and spin-orbit coupling effects. The largest value of the chloride complex couples is attributed to the better balance of electronic and steric effects.

First author: Liu, Y, Oil-water separation performance of aligned single walled carbon nanotubes membrane: A reactive molecular dynamics simulation study,
Abstract: Carbon nanotubes (CNTs) have played pivoting role in water remediation owing to peculiar features such as high porosity and desirable chemical and mechanical properties. This research is dedicated to separation of oil-water systems by using aligned armchair SWCNTs-based membrane via reactive molecular dynamic (MD) simulation and density functional theory (DFT) calculations. It was found that no water molecules transmitted through CNT with 5.7 angstrom diameter, but CNTs with diameters of 7 angstrom and 8.5 angstrom were both able to transfer water molecules, although CNT with diameter of 7 angstrom was more efficient for water permeation. The incorporation of hexane was observed into CNTs with diameters of 7 angstrom and 85 angstrom and also toluene into latter one. Moreover, the determination of interaction energy, electronic structures and barrier energy with DFT-D3 calculation for hexane molecule incorporating into the nanotube cavity confirms our reactive MD simulation outcomes. It was revealed that armchair CNTs membrane with diameter of 7 angstrom has more efficacy for the separation of oil-water mixture compared to other counterparts though it could not avoid the perrneance of small oil components such as linear hydrocarbons. Our reactive MD simulations findings provided a novel strategy for the application of aligned CNTs membranes in water treatments with voluntarily viable motivations, high efficiency and stability as well as long lifetime.

First author: Carreno, A, Exploring rhenium (I) complexes as potential fluorophores for walled-cells (yeasts and bacteria): Photophysics, biocompatibility, and confocal microscopy,
DYES AND PIGMENTS, 184, 484, (2021)
Abstract: In the present work, we synthesized and characterized two complexes: fac-Re(CO)(3)(4,5-diazafluoren-9-one)Br (ReL1) and fac-Re(CO)(3)(5,6-epoxy-5,6-dihydro-1,10-phenanthroline)Br (ReL2), where ReL2 has not been reported at present. In this study, we show a complete structural characterization of both ReLl and ReL2 by elemental analysis, FTIR, H-1 and C-13 NMR, DEPT, and HHCOSY. Moreover, we carried out UV-Vis and luminescence experiments in organic solvents showing different polarities. In addition, we performed relativistic theoretical calculations to better understand electronic transitions and optical properties. We also assessed the cytotoxicity of ReL1, ReL2, and their respective N,N ligands (i.e., 4,5-diazafluoren-9-one and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline) against walled-cells, including Gram-negative bacteria (Salmonella enterica semvar Typhimurium), non-sporulated Gram-positive bacteria (Staphylococcus aureus), sporulated Gram-positive bacteria (Bacillus cereus), and yeasts (Candida albicans and Cryptococcus spp.). We observed that these complexes exhibited very low or no cytotoxicity. We also found that only ReL2, and not ReL1, exhibited good properties as a luminescent probe for this kind of cells. Accordingly, we found that ReL2 showed good potential to be directly used as a luminescent probe for walled cells, including yeasts (e.g., Candida albicans) and bacteria (e.g., Salmonella enterica), which can be observed by confocal microscopy.

First author: Carey, DM, Evaluation of C-60 and C-70 analogs bearing Cyclo-meta-Phenylene faces as improved devices for Polymer:Fullerene solar cells from DFT calculations,
DYES AND PIGMENTS, 184, 484, (2021)
Abstract: A new structure for spherical fullerene is evaluated involving sixty phenylene rings, replacing every C-vertex from C-60, which is based on the isolated-pentagon-rule (IPR) motif based on a cyclo-meta-phenylene derivatives reported by Isobe group, resulting in superstructures mimicking C-60 (1). Density functional theory calculation shows its stability and properties, also predicting a related C-70 counterpart (2), and nano-onions incorporating C-60 and C-70 inside 1 and 2. These species are attractive targets of 0D-covalent organic frameworks (0D-COF) related to hollow fullerenes, which can be extended to other sp (Taylor et al., 1990) [2]-based species. The obtained structures show increased redox potentials in a larger pi-surface area in comparison to C-60 and C-70, which are of relevance for photovoltaic applications.