2018 publications citing ADF

First author: Adams, RD, The coordination and activation of azobenzene by Ru-5(mu(5)-C) cluster complexes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 878, 77, (2018)
Abstract: The reaction of Ru-5(mu(5)-C)(CO)(15), 1 with azobenzene, PhN = NPh, yielded the pentaruthenium carbido cluster compound Ru5C(CO)(13)(C6H4N=NC6F15)[mu-H], 4 containing a chelating ortho-metalated azobenzene ligand on one of the ruthenium atoms in a opened square-pyramidal Ru5C cluster. Compound 4 is electronically unsaturated and it readily adds one CO ligand at 25 degrees C to yield the electronically saturated complex Ru5(C)(CO)(14)(C6H4N=NC6H5)[mu-H], 5. Ru5C(CO)(13)(mu-eta(2)-Ph)[mu-Au(NHC)], 3 reacts with azobenzene to yield the azobenzene complex Ru5C(CO)(13)(mu-eta(2)-PhN = NPh)(eta(1)-Ph)[mu-Au(NHC)], 6, NHC = 1,3-bis(2,6-diisopropylphenyl-imidazole-2ylidene), which contains a novel bridging di-sigma-eta(2)-N,N-coordinated azobenzene ligand across an open edge of an Ru5C cluster. Compound 6 eliminated benzene and was transformed to the new compound Ru5C(CO)(13)(C6H4N=NC6H5)[mu-Au(NHC)], 7 when heated to 105 degrees C for 3 h. Compound 7 is similar to 4 except that it has an Au(NHC) group in the place of the bridging hydrido ligand in 4. Compound 7 is also formally electronically unsaturated like 4. All of the new compounds were characterized by single-crystal X-ray diffraction analyses. The structures, bonding and reactivity of the complexes are discussed.

First author: Su, J, Energy-Degeneracy-Driven Covalency in Actinide Bonding, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 17977, (2018)
Abstract: Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An-Cl covalency in AnCl(6)(2-)(An(IV) = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and An(IV) 5f- and 6d-orbitals (t(1u)*/t(2u)* and t(2g)*/e(g)*), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals. Moving from Th to U, Np, and Pu markedly changed the amount of M-Cl orbital mixing, such that An(IV) 6d- and Cl 3p-mixing decreased and metal 5f- and Cl 3p-orbital mixing increased across this series.

First author: Cai, WT, Synthesis and Characterization of Non-Isolated-Pentagon-Rule Actinide Endohedral Metallofullerenes U@C-1(17418)-C-76, U@C-1(28324)-C-80, and Th@C-1(28324)-C-80: Low-Symmetry Cage Selection Directed by a Tetravalent Ion, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 18039, (2018)
Abstract: For the first time, actinide endohedral metallofullerenes (EMFs) with non-isolated-pentagon-rule (non-IPR) carbon cages, U@C-80, Th@C-80, and U@C-76, have been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffractometry, UV-vis-NIR and Raman spectroscopy, and cyclic voltammetry. Crystallo-graphic analysis revealed that the U@C-80 and Th@C-80 share the same non-IPR cage of C-1(28324)-C-80, and U@C-76 was assigned to non-IPR U@C-1(17418)-C-76. All of these cages are chiral and have never been reported before. Further structural analyses show that enantiomers of C-1(17418)-C-76 and C-1(28324)-C-80 share a significant continuous portion of the cage and are topologically connected by only two C-2 insertions. DFT calculations show that the stabilization of these unique non-IPR fullerenes originates from a four-electron transfer, a significant degree of covalency, and the resulting strong host-guest interactions between the actinide ions and the fullerene cages. Moreover, because the actinide ion displays high mobility within the fullerene, both the symmetry of the carbon cage and the possibility of forming chiral fullerenes play important roles to determine the isomer abundances at temperatures of fullerene formation. This study provides what is probably one of the most complete examples in which carbon cage selection occurs through thermodynamic control at high temperatures, so the selected cages do not necessarily coincide with the most stable ones at room temperature. This work also demonstrated that the metal-cage interactions in actinide EMFs show remarkable differences from those previously known for lanthanide EMFs. These unique interactions not only could stabilize new carbon cage structures, but more importantly, they lead to a new family of metallofullerenes for which the cage selection pattern is different to that observed so far for nonactinide EMFs. For this new family, the simple ionic A(q+)@C-2n(q-) model makes predictions less reliable, and in general, unambiguously discerning the isolated structures requires the combination of accurate computational and experimental data.

First author: Sawatlon, B, Unraveling Metal/Pincer Ligand Effects in the Catalytic Hydrogenation of Carbon Dioxide to Formate, ORGANOMETALLICS, 37, 4568, (2018)
Abstract: The hydrogenation of carbon dioxide to formate is an intriguing reaction from both an environmental and an energy perspective, primarily due to the prospective uses of the product as a platform chemical in numerous applications such as an organic hydrogen carrier. Although several transition-metal-based catalysts have been shown to facilitate this chemical transformation, few guidelines exist on how best to tune the catalysts in order to achieve maximum activity. Here, we use linear scaling relationships and molecular volcano plots to gauge the potential of different metal-pincer catalysts for the aforementioned reaction. Analysis of combinations of five metals (Ru, Os, Co, Rh, and Ir) and seven tridentate pincer-type ligands reveals several complexes lying near the volcano top, suggesting that these species have nearly ideal energetic profiles for facilitating the hydrogenation reaction. In particular, catalysts bearing group 9 metal centers (Ir, Rh, Co) with pi-acidic ligands provide a clear route to improving catalytic activity. Overall, these findings highlight how linear scaling relationships and molecular volcano plots provide unique insight into the underlying stereoelectronic factors that make specific metal-ligand combinations highly efficient catalysts.

First author: Pigulski, B, Selective synthesis of iridium(iii) end-capped polyynes by oxidative addition of 1-iodopolyynes to Vaska’s complex, DALTON TRANSACTIONS, 47, 17046, (2018)
Abstract: The reaction of bis(triphenylphosphine)iridium(i) carbonyl chloride (Vaska’s complex) with a series of 1-iodopolyynes (1-CnI and 2-CnI) gave sigma-polyynyl iridium(iii) complexes with general formula R(C?C)(n)Ir(PPh3)(2)(Cl)(I)(CO). The use of acetonitrile as a solvent appeared crucial and allowed selectively obtaining only one from a few possible isomers. The X-ray single crystal diffraction experiment for 2-C-4[Ir]I allowed the determination of the exact structure of this complex. Further spectroscopic measurements, especially P-31 NMR, confirmed the formation of the same type of isomers with trans coordinated phosphines in each case. All complexes were fully characterized with the use of NMR (H-1, C-13 and P-31), IR, UV/Vis, cyclic voltammetry and (ESI)HRMS techniques. Moreover, DFT calculations were performed for all the resulting species. The complexes with a linear carbon chain from butadiyne to decapentayne are the longest iridium end-capped polyynes known to date since only compounds with a (C?C)(2) structural motif have been reported so far. Moreover, we confirmed that the synthetic approach, first used for palladium(ii) end-capped polyynes, may be also applied for the synthesis of other structurally new organometallic polyynes.

First author: Martel, L, Insight into the Crystalline Structure of ThF4 with the Combined Use of Neutron Diffraction, F-19 Magic-Angle Spinning-NMR, and Density Functional Theory Calculations, INORGANIC CHEMISTRY, 57, 15350, (2018)
Abstract: Because of its sensitivity to the atomic scale environment, solid-state NMR offers new perspectives in terms of structural characterization, especially when applied jointly with first-principles calculations. Particularly, challenging is the study of actinide-based materials because of the electronic complexity of the actinide cations and to the hazards due to their radioactivity. Consequently, very few studies have been published in this subfield. In the present paper, we report a joint experimental theoretical analysis of thorium tetrafluoride, ThF4, containing a closed-shell actinide (5f(0)) cation. Its crystalline structure has been revisited in the present work using powder neutron diffraction experiments. The F-19 NMR parameters of the seven F crystallographic sites have been modeled using an empirical superposition model, periodic first-principles calculations, and a cluster-based all-electron approach. On the basis of the atomic position optimized structure, a complete and unambiguous assignment of the F-19 NMR resonances to the F sites has been obtained.

First author: Weerawardene, KLDM, Comparison and convergence of optical absorption spectra of noble metal nanoparticles computed using linear-response and real-time time-dependent density functional theories, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1146, 27, (2018)
Abstract: The real-time time-dependent density functional theory (RT-TDDFT) is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems, which warrants the necessity to benchmark the traditional linear response (LR) method and the RT approach. We calculate the absorption spectra of noble metal nanoparticles with a variety of sizes and shapes to demonstrate the consistency of the two methods over a broad range of energy. The RT spectrum obtained using a grid-based basis set with pseudopotentials achieves results in good agreement with the LR spectrum obtained with large QZ4P atom-centered basis sets. Factors that lead to convergence of the spectra are considered. In addition, the real-time variation of the electron density is visualized to show the collective oscillation of electron density for the plasmon modes of noble metal nanoparticles. The RT approach is most useful when calculating wide absorption spectra of larger gold or silver nanoparticles.

First author: Narsaria, AK, Rational design of near-infrared absorbing organic dyes: Controlling the HOMO-LUMO gap using quantitative molecular orbital theory, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 2690, (2018)
Abstract: Principles are presented for the design of functional near-infrared (NIR) organic dye molecules composed of simple donor (D), spacer (pi), and acceptor (A) building blocks in a D-pi-A fashion. Quantitative Kohn-Sham molecular orbital analysis enables accurate fine-tuning of the electronic properties of the pi-conjugated aromatic cores by effecting their size, including silaaromatics, adding donor and acceptor substituents, and manipulating the D-pi-A torsional angle. The trends in HOMO-LUMO gaps of the model dyes correlate with the excitation energies computed with time-dependent density functional theory at CAMY-B3LYP. Design principles could be developed from these analyses, which led to a proof-of-concept linear D-pi-A with a strong excited-state intramolecular charge transfer and a NIR absorption at 879 nm.

First author: Cabral, BJC, Born-Oppenheimer molecular dynamics, hydrogen bond interactions and magnetic properties of liquid hydrogen cyanide, JOURNAL OF MOLECULAR LIQUIDS, 272, 778, (2018)
Abstract: Magnetic properties are a very sensitive probe of hydrogen bond interactions. In this work, the magnetic shielding constants of liquid hydrogen cyanide (HCN) were investigated through a combined approach, where quantum mechanical calculations are carried out by using configurations generated by Born-Oppenheimer molecular dynamics (BOMD). Following the trends observed in small HCN clusters, the results for liquid HCN show that the magnetic shielding constant sigma(N-15) is increased by 10.5 +/- 12 ppm relative to its gas phase value, which is in very good agreement with experiment (10 ppm). The shielding of the N atom in the liquid phase of HCN is in contrast to what is observed in liquid ammonia, where the N atom is deshielded relative to the gas phase. By adopting a natural chemical shielding (NCS) analysis, it is shown that the sigma(d)(N-15) diamagnetic shielding constant of HCN is not changed when we move from the gas to the liquid phase. Moreover, the results strongly indicate that the gas-to-liquid chemical shift of the N-15 atom is essentially determined by the difference between the nitrogen lone-pair (LP) orbital paramagnetic contribution to sigma(p)(N-15). The importance of coupling NCS to BOMD configurations for a better understanding of the relationship between hydrogen bonding and the somewhat anomalous shielding of the N-15 atom in liquid HCN is stressed.

First author: Piotrowski, MJ, Bare versus protected tetrairidium clusters by density functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 29480, (2018)
Abstract: The tetrairidium (Ir-4) clusters are subnanometric systems vastly applied in catalysis, especially, because of the higher activity than mononuclear Ir complexes, intrinsic and controllable stability in relation to supports, and non-coalescence properties. The main catalytic properties of nanoclusters (activity and selectivity) are directly associated with their size, shape, and interactions with the environment, whose understanding requires study at the atomistic level. Here, the Ir-4 clusters are studied considering the energetic stability for different chemical environments, bare versus protected, using density functional theory calculations within the generalized gradient approximation with van der Waals corrections and spin-orbit coupling, employing the all-electron projected augmented wave method. The square planar isomer is confirmed for the bare case as the lowest energy configuration considering semilocal and non-local exchange-correlation functionals, however, for different chemical environments (Ir-4 protected by CO, O-2, PH3, and SH2 ligands) the energy stability scenario is different; for CO, O-2, and PH3 ligands the tetrahedron is the most stable isomer, in agreement with experimental insights, while for SH2 ligands the square motif is the most stable isomer. To improve the understanding of these systems, structural and electronic analysis were performed, in addition to energy decomposition analysis, to explore the bonding situation in Ir-4 compounds. Our results showed an important relationship between the geometrical behavior and the nature and magnitude of Ir2Ir2 interactions, showing how the chemical environment affects the Ir-4 nanoclusters. In general, the compounds with tetrahedron motifs showed a weakening of the sigma and bonds in relation to the square ones.

First author: Teodoro, TQ, Use of Density Functional Based Tight Binding Methods in Vibrational Circular Dichroism, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 9435, (2018)
Abstract: Vibrational circular dichroism (VCD) is a spectroscopic technique used to resolve the absolute configuration of chiral systems. Obtaining a theoretical VCD spectrum requires computing atomic polar and axial tensors on top of the computationally demanding construction of the force constant matrix. In this study we evaluated a VCD model in which all necessary quantities are obtained with density functional based tight binding (DFTB) theory. The analyzed DFTB parametrizations fail at providing accurate vibrational frequencies and electric dipole gradients but yield reasonable normal modes at a fraction of the computational cost of density functional theory (DFT). Thus, by applying DFTB in composite methods along with DFT, we show that it is possible to obtain accurate VCD spectra at a much lower computational demand.

First author: Jana, G, Adsorption of Molecular Hydrogen on Lithium-Phosphorus Double-Helices, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 27941, (2018)
Abstract: The possible interaction of the unprecedented but recently predicted inorganic double-helices made up of lithium and phosphorous (LinPn; n = 7-9) with dihydrogen (H-2) molecules is explored via density functional theory-based computations. Because of the large amount of Li -> P electron transfer, the Li chain carries a high positive charge, which can be utilized to interact with quite less-reactive elements such as H-2. Despite low polarizability of the target species to be bound, these double-helices are found to interact with H-2 molecules, having binding energies within a range of 1.7-3.2 kcal/mol per H-2 molecule. Further, the periodic calculation with the LiP helix reveals that each Li center binds with two H-2 molecules with an average binding energy of 2.5 kcal/mol per H-2, and this leads to a 9.6 wt % of H-2 uptake. The interactions in Li center dot center dot center dot H-2 are mainly originating from both orbital and electrostatic contributions as reflected in the energy decomposition analysis. However, a global minimum search for H2@Li7P7 by a modified kick algorithm reveals that the lowest energy isomer is a significantly distorted structure from a helix, and having two P-H bonds. Therefore, chemisorption should be preferable over the interaction in molecular form. However, for that purpose, the rupture of the H-H bond in the (2) molecule is essential, which needs at least an activation energy barrier of 14.9 kcal/mol to overcome. Given the fact that the H-2 storage in Li-decorated clusters would only be achieved at low temperature, the chemisorption is not likely to take place. Further, their interaction with noble gases (Ar-Rn) is also studied herein. Moreover, an inspection of their band gap structures indicates that the LiP helix could exhibit wide band gap semiconducting properties with a direct band gap value of 2.64 eV.

First author: Bakker, JM, Structural determination of neutral Co-n clusters (n=4-10,13) through IR-UV two- color vibrational spectroscopy and DFT calculations, JOURNAL OF PHYSICS-CONDENSED MATTER, 30, 27941, (2018)
Abstract: We recorded IR spectra for neutral cobalt clusters via two-color IR-UV ionization, using the Free Electron Laser for intracavity experiments (FELICE). Well-resolved IR spectra are presented for Co-n (n = 4-10, 13) and analyzed with the help of Density Functional Theory calculations using two different correlation exchange functionals: the revisited Tao-Perdew-Staroverov-Scuseria (revTPSS) and the frequently used Perdew-Burke-Ernzerhof (PBE) approaches. Although we have not performed an extensive structure search, we tentatively assign the spectra for all cluster sizes except for n = 7, and n = 10. We find that neither of the two functionals chosen clearly outperforms the other in predicting IR spectra, and that relatively low scaling factors of 0.82 (PBE) and 0.8 (revTPSS) are required. In contrast to the magnetic moments, the calculated electric dipole moments fluctuate strongly as a function of cluster size and could therefore be used as an indirect probe to the cluster structure.

First author: Xie, WY, Binding for endohedral-metallofullerene superatoms induced by magnetic coupling, CHEMICAL COMMUNICATIONS, 54, 13383, (2018)
Abstract: To design new materials based on artificial superatoms, clarifying their involved interaction is particularly important. In this study, we discuss first-principle calculations to show that the interaction between endohedral metallofullerenes (EMFs) of U@C-28 can lead to different chemical and physical adsorption structures. Especially, these structures are derived from different magnetic coupling resonances, and they can transform by changing the distance between U@C-28 superatoms. These findings will promote the future development for bottom-up assembling of new functional materials and even devices.

First author: Ahumada, G, Synthesis, structures, electrochemical and quantum chemical investigations of Ni(II) and Cu(II) complexes with a tetradentate Schiff base derived from 1-(2-thienyl)-1,3-butanedione, NEW JOURNAL OF CHEMISTRY, 42, 19294, (2018)
Abstract: Double condensation of the newly prepared 1-(2-thienyl)-1,3-butanedione with ethylenediamine led to the formation of a novel symmetrical Schiff base proligand bearing two potentially electropolymerizable 2-thienyl groups. Both organic species were obtained in 55 and 80% yields, respectively. They exist in their respective keto-enol and enaminone tautomeric forms that were computed to be more stable by 8.6 and 30.3 kcal mol(-1) than their beta-diketone and keto-imine isomers. The corresponding Ni(ii) and Cu(ii) complexes featuring a N2O2-tetradentate Schiff base ligand were readily synthesized upon reaction of the diprotic Schiff base precursor with the appropriate hydrated metal acetates, and isolated as neutral, air and thermally stable solids in excellent yields (84 and 90%). The four compounds were characterized using various analytical and spectroscopic methods, and by an X-ray diffraction study for the two coordination complexes. Both Ni(ii) and Cu(ii) metal ions are four-coordinated and adopt a perfect square planar environment (tau(4) values of 0.036 and 0.025) with two nitrogen and two oxygen atoms as donors. Both complexes were analyzed by cyclic voltammetry experiments showing a decrease of the current response per cycle, indicating the formation of oligomeric units. This was verified using their doping/undoping responses. The optimized geometries of the four compounds as well as the electronic structures of the two Ni(ii) and Cu(ii) complexes and their respective cations were analysed through DFT calculations, allowing the provision of a consistent view of their structure and properties. TDDFT calculations were used to interpret the major features of the UV-vis spectra.

First author: Gao, YJ, Theoretical Studies on Excited-State Properties of Au(III) Emitters with Thermally Activated Delayed Fluorescence, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 27608, (2018)
Abstract: Thermally activated delayed fluorescence (TADF) phenomena have been found in many organometallic complexes, but Au(III) complexes with TADF are rarely reported, possibly due to the existence of efficient nonradiative channels for luminescence states. Recent experiments identified two cyclometalated Au(III) aryl molecules with TADF; however, the underlying photophysical and luminescence mechanisms are elusive. Here, we have employed M06 and TD-M06 methods combined with polarizable continuum model and quantum mechanics/molecular mechanics approaches to comprehensively study the excited-state structures and properties of these two Au(III) complexes in toluene solution and crystal phases, respectively. We have found that both S-1 and T-1 states are of ligand-to-ligand charge transfer character. The significant twisting between C boolean AND N boolean AND C and aryl groups leads to good separation and negligible overlap of the highest occupied molecular orbital and lowest unoccupied molecular orbital. This results in a pretty small S-1-T-1 energy gap, which, in conjunction with strong spin-orbit coupling, facilitates the reverse intersystem crossing (rISC) process. In terms of the results of electronic structure calculations, we have calculated the related radiative and nonradiative rates. The forward intersystem crossing (ISC) and rISC processes are estimated to occur on the timescale of 10(10) s(-1), which is significantly faster than the fluorescence and phosphorescence emission rates (10(6) and 10(3) s-(1)). The faster rISC process relative to the phosphorescence one enables the TADF process. The low-frequency vibrational modes are found to have important contribution to the Huang-Rhys factors and to enhance the ISC and rISC rates. Moreover, environmental effects are found to be important and cannot be completely ignored in realistic simulations. Finally, the substituted -F and -OEt groups have a small influence on geometric structures but visible effects on electronic structures and related radiative and nonradiative rates, which implies that the TADF performance of the Au(III) complexes could be further enhanced through chemical tailoring or tuning these substituting groups.

First author: Teodoro, TQ, Frequency Range Selection Method for Vibrational Spectra, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 9, 6878, (2018)
Abstract: Theoretical calculations of vibrational properties are widely used to explain and predict experimental spectra. However, with standard quantum chemical methods all molecular motions are considered, which is rather time-consuming for large molecules. Because typically only a specific spectral region is of experimental interest, we propose here an efficient method that allows calculation of only a selected frequency interval. After a computationally cheap low-level estimate of the molecular motions, the computational time is proportional to the number of normal modes needed to describe this frequency range. Results for a medium-sized molecule show a reduction in computational time of up to 1 order of magnitude with negligible loss in accuracy. We also show that still larger computational savings are possible by using an additional intensity-selection procedure.

First author: Cabrera-Trujillo, JJ, Influence of the Lewis Acid/Base Pairs on the Reactivity of Geminal E-CH2-E ‘ Frustrated Lewis Pairs, CHEMISTRY-A EUROPEAN JOURNAL, 24, 17823, (2018)
Abstract: The influence of the nature of the acid/base pairs on the reactivity of geminal frustrated Lewis pairs (FLPs) (Me2E-CH2-E ‘ Ph-2) has been computationally explored within the density functional theory framework. To this end, the dihydrogen-activation reaction, one of the most representative processes in the chemistry of FLPs, has been selected. It is found that the activation barrier of this transformation as well as the geometry of the corresponding transition states strongly depend on the nature of the E/E ‘ atoms (E=Group 15 element, E ‘=Group 13 element) in the sense that lower barriers are associated with earlier transition states. Our calculations identify the geminal N/Al FLP as the most active system for the activation of dihydrogen. Moreover, the barrier height can be further reduced by replacing the phenyl group attached to the acidic atom by C6F5 or 3,5-(CF3)(2)C6H3 (Fxyl) groups. The physical factors controlling the computed reactivity trends are quantitatively described in detail by means of the activation strain model of reactivity combined with the energy decomposition analysis method.

First author: Ghorai, S, B-B Coupling and B-B Catenation: Computational Study of the Structure and Reactions of Metal-Bis(borylene) Complexes, CHEMISTRY-A EUROPEAN JOURNAL, 24, 17844, (2018)
Abstract: A detailed molecular orbital analysis of the metal-bis(borylene) complex [Fe(CO)(3){B(Dur)B(N(SiMe3)(2))}] (Dur=2,3,5,6-tetramethylphenyl) (1 a) serves as a focal point of recent developments in this area of chemistry, such as B-B coupling and B-B catenation reactions. There is strong a pi delocalization between the Fe(CO)(3) and (B-Dur)(B-N(SiMe3)(2)) units; the short B-B distance in 1 a is due to this pi delocalization. The pi-donor ligand N(SiMe3)(2) on the boron provides a decisive stability to the complex 1 a. The LUMO of 1 a has B-B sigma-bonding character. Hence B-B coupling is facilitated by filling the LUMO. Strong sigma-donating ligands, such as PMe3 or PCy3, induce B-B coupling. Expulsion of one CO from 1 a followed by dimerization leads to [Fe(CO)(2){B(Dur)B(N(SiMe3)(2))}](2) (3 a) with a short Fe-Fe distance of 2.355 angstrom. A detailed mechanism for the reaction of 3 a with CO to give the B-B catenation product 2 f is presented. The bonding of all intermediates is compared to their isolobal main-group analogues.

First author: Wu, W, Molecular Thorium Compounds with Dichalcogenide Ligands: Synthesis, Structure, Se-77 NMR Study, and Thermolysis, INORGANIC CHEMISTRY, 57, 14821, (2018)
Abstract: A series of dimeric thorium disulfides and diselenides have been prepared with sterically undemanding ancillary ligands. Five complexes, (py)(6)Th2I4(mu(2)-S-2)(2), (py)(6)Th2Br2(SC6F5)2(mu(2)-S-2)(2), (py)(6)Th2I4(mu(2)-Se-2)(2), (py)(6)Th2I2(SC6F5)(2)(mu(2)-Se-2)(2), and (py)(6)Th2Br2(SC6F5)(2)(mu(2)-Se-2)(2), were isolated in high yields by first reducing mixtures of 12, F5C6SSC6F5, PhSeSePh, or PhSSPh, and PhSeBr with elemental Th, followed by in situ ligand-based redox reactions with elemental sulfur or selenium. These are the first examples of thorium compounds with bridging dichalcogenide ligands. Attempts to prepare chloride derivatives gave mixtures of (py)(4)ThCl4 and either (py)(6)Th2Cl2(SC6F5)(2)(mu(2)-S-2)(2) or (py)(8)Th4Se4(SePh)(4)(SC6F5)(4). All products were characterized by single-crystal and powder X-ray diffraction and IR, UV visible, and NMR spectroscopy. A computational analysis of experimental Se-77 NMR chemical shifts reveals that the solvated dimeric structures with two bridging dichalcogenides are maintained in solution. Thermolysis of (py)(6)Th2I4(mu(12)-Se-2)(2) leads to reduction of the bridging Se-2(2-) moieties, oxidation of the 1(-) ligand, and formation of solid-state ThSe2 and I-2.

First author: Kapusta, K, Reconstruction of STO-3G Family Basis Set for the Accurate Calculation of Magnetic Properties, RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A, 92, 2827, (2018)
Abstract: The new approach for the determination of orbital exponents and contracted coefficients for STO-3G family basis sets has been proposed. Calculations of the necessary coefficients have been performed using Mathcad program package with Minerr solving block. This approach has been used to perform the approximation of the Slater-type orbital (STO) by three Gaussian-type orbitals (GTO). The performance of such modified basis sets has been tested for the calculations of atomic energies using STO(0)-3G basis set and for nuclear magnetic shielding tensors using STO(1M)-3G basis set. The obtained atomic energies are characterized by lower values than those calculated using old parameters. The results for H-1 and C-13 chemical shifts calculations demonstrate better agreement with the experimental data compared to the data obtained using standard basis sets, such as 6-311G (2d, p), cc-pVDZ and pcS-1. Required time of calculations using the basic set suggested by us is less than the time spent on the calculation using standard basic sets with a similar number of basis functions. Physically adapted and at the same time small by size basic set STO(1M)-3G is perspective for the calculation of magnetic properties of big molecular systems. Proton and C-13 chemical shifts have been calculated for molecules of adenosine monophosphate (AMP) and flavinadenine dinucleotide (FAD), that play an important role in various biological processes. For both molecules the results of the calculation have shown values close to the experimental data.

First author: Merzoug, M, Molecular models of monometallic-phenazine sandwich complexes M(phz)(2) (M=Ti, Cr, Fe and Ni; phz=C12H8N2): A DFF investigation, JOURNAL OF NEW TECHNOLOGY AND MATERIALS, 8, 44, (2018)
Abstract: This work deals with the calculations of the energy stability of mononuclear sandwiches compounds of transition elements based on a density functional theory DFT In this paper, the structure and electronic properties of a series of organometallic compounds M(C12H8N2)(2) (M= Ti, Cr, Fe and Ni) have been systematically studied by using a functional BP86 based on the density functional theory. Calculations indicate that the phenazine ligand can bind to the metals involving its C6 or C4N2 rings through eta(6), eta(4), eta(3) and eta(2) coordination modes for IM(phz)21 complexes. The calculated spin contamination is comparable to the expected value of 2.00. The energy decomposition analysis was used to characterize the geometry distortion and the steric interaction (electrostatic and Paull) and orbital interaction in the total bonding energy. The results showed that the interactions in the studied compounds are governed by covalent character than ionic.

First author: Nerut, ER, NaRIBaS-A Scripting Framework for Computational Modeling of Nanomaterials and Room Temperature Ionic Liquids in Bulk and Slab, COMPUTATION, 6, 44, (2018)
Abstract: Computational modeling is more and more often used in studies of novel ionic liquids. The inevitable side-effect is the growing number of similar computations that require automation. This article introduces NaRIBaS (Nanomaterials and Room Temperature Ionic Liquids in Bulk and Slab)-a scripting framework that combines bash scripts with computational codes to ease modeling of nanomaterials and ionic liquids in bulk and slab. NaRIBaS helps to organize and document all input and output data, thus, improving the reproducibility of computations. Three examples are given to illustrate the NaRIBaS workflows for density functional theory (DFT) calculations of ionic pairs, molecular dynamics (MD) simulations of bulk ionic liquids (ILs), and MD simulations of ILs at an interface.

First author: Baldovi, JJ, Exploring High-Symmetry Lanthanide-Functionalized Polyoxopalladates as Building Blocks for Quantum Computing, INORGANICS, 6, 44, (2018)
Abstract: The structural, electronic, and magnetochemical properties of the star-shaped polyoxopalladate [Pd15O10(SeO3)(10)](10-) (POPd) and its lanthanide-functionalized derivatives have been investigated on the basis of density functional theory, followed by a ligand field analysis using the Radial Effective Charge (REC) model. Our study predicts that heteroPOPd is a robust cryptand that enforces D-5h symmetry around the encapsulated Ln(3+) centers. This rigid coordination environment favors an interesting potential magnetic behavior in the Er and Ho derivatives, and the presence of a cavity in the structure suggests an effective insulation of the electronic system from the lattice phonons, which may be of interest for molecular spintronics and quantum computing applications.

First author: Turovtsev, VV, Comparison of Standard Functionals to Calculate the Properties of Molecules at the Variational Limit, JOURNAL OF STRUCTURAL CHEMISTRY, 59, 1960, (2018)
Abstract: B1LYP, B1PW91, B3LYP, BHandH, BHandHLYP, BLYP, BP, CAMY-B3LYP, HTBS, KMLYP, LCYBLYP, LCY-BP86, LCY-PBE, LDA, M06, M06-2X, M06-HF, M06L, mPBE, mPW, MPW1K, MPW1PW, O3LYP, OLYP, OPBE, OPBE0, PBE, PBE0, PBEsol, PW91, revPBE, revTPSS, RPBE, TPSS, TPSSH, X3LYP, and HF methods are used to calculate the electron energy E-el of the reference GeO and C2H6 compounds in Slater basis sets QZ4P, aug-TZ2P, and TZ2P, as well as DZ for C2H6. The E-el values are recalculated into the bond breaking enthalpy D-0(Ge-O) and formation enthalpy fH(298)(0) of ethane, and calculation errors for E-el are obtained at the variation limit. The ADF program settings are chosen so that they make it possible to attribute these E-el errors to the structure of DFT functionals. The dependence of the E-el values on the type (size) of the basis set is studied. It is demonstrated that when Eel is calculated for GeO, the optimum combination is DFT/TZ2P, where DFT = LCY-BLYP, LCY-BP86, LCY-PBE, CAMYB3LYP; for C2H6 it is DFT/TZ2P, where DFT = PBE0, M06, mPBE, OLYP. Errors in the calculation of the geometric parameters are studied.

First author: Scorsin, L, Cucurbituril-Mediated Catalytic Hydrolysis: A Kinetic and Computational Study with Neutral and Cationic Dioxolanes in CB7, ACS CATALYSIS, 8, 12067, (2018)
Abstract: Cucurbit[7]uril (CB7) catalyzes the acid hydrolysis of alkoxyphenyldioxolanes bearing both neutral and cationic alkoxy groups. The magnitude of the catalytic effect depends on the dioxolane structure, as reflected by both the CB7 binding constants and the catalysis rate constants. However, there is no clear relationship in such a way that increasing the binding affinity (cationic dioxolanes or large alkoxy groups) does not enhance the catalytic effect. The A-1 mechanism for dioxolane hydrolysis involves the protonation and formation of a carbocation by protonated dioxolane ring opening. Supramolecular catalysis takes place through the formation of the ternary complex dioxolane@CB7@H3O+, where the hydronium ion is stabilized by hydrogen bonding with the carbonyl groups of the CB7 portal. The ternary complex evolves to a binary complex by protonation of dioxolane and release of a water molecule. It is important to note that these structures are only stable in the presence of CB7 and not in bulk water. The carbocation is formed by opening the protonated dioxolane group in the rate-determining step. The distance between the carbonyl portal of CB7 and the dioxolane group in the ternary and binary complexes (protonated and carbocation) increases with the alkyl chain length, resulting in the loss of the CB7 stabilizing effect and decrease in catalytic efficiency. The existence of two recognition motifs with cationic dioxolanes results in the formation of both 1:1 and 2:1 complexes with different catalytic properties.

First author: Yu, S, Factors Controlling the Diels-Alder Reactivity of Hetero-1,3-Butadienes, CHEMISTRYOPEN, 7, 995, (2018)
Abstract: We have quantum chemically explored the Diels-Alder reactivities of a systematic series of hetero-1,3-butadienes with ethylene by using density functional theory at the BP86/TZ2P level. Activation strain analyses provided physical insight into the factors controlling the relative cycloaddition reactivity of aza- and oxa-1,3-butadienes. We find that dienes with a terminal heteroatom, such as 2-propen-1-imine (NCCC) or acrolein (OCCC), are less reactive than the archetypal 1,3-butadiene (CCCC), primarily owing to weaker orbital interactions between the more electronegative heteroatoms with ethylene. Thus, the addition of a second heteroatom at the other terminal position (NCCN and OCCO) further reduces the reactivity. However, the introduction of a nitrogen atom in the backbone (CNCC) leads to enhanced reactivity, owing to less Pauli repulsion resulting from polarization of the diene HOMO in CNCC towards the nitrogen atom and away from the terminal carbon atom. The Diels-Alder reactions of ethenyl-diazene (NNCC) and 1,3-diaza-butadiene (NCNC), which contain heteroatoms at both the terminal and backbone positions, are much more reactive due to less activation strain compared to CCCC.

First author: Visscher, KM, A QM/MM Derived Polarizable Water Model for Molecular Simulation, MOLECULES, 23, 995, (2018)
Abstract: In this work, we propose an improved QM/MM-based strategy to determine condensed-phase polarizabilities and we use this approach to optimize a new and simple polarizable four-site water model for classical molecular simulation. For the determination of the model value for the polarizability from QM/MM, we show that our proposed consensus-fitting strategy significantly reduces the uncertainty in calculated polarizabilities in cases where the size of the local external electric field is small. By fitting electrostatic, polarization and dispersion properties of our water model based on quantum and/or combined QM/MM calculations, only a single model parameter (describing exchange repulsion) is left for empirical calibration. The resulting model performs well in describing relevant pure-liquid thermodynamic and transport properties, which illustrates the merit of our approach to minimize the number of free variables in our model.

First author: Huang, JD, Theoretical study of charge-transport and optical properties of indeno[1,2-b] fluorene-6,12-dione-based semiconducting materials, ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING, 74, 705, (2018)
Abstract: The conducting and optical properties of a series of indeno[1,2-b] fluorene-6,12-dione (IFD)-based molecules have been systematically studied and the influences of butyl, butylthio and dibutylamino substituents on the reorganization energies, intermolecular electronic couplings and charge-injection barriers of IFD have been discussed. The quantum-chemical calculations combined with electron-transfer theory reveal that the incorporation of sulfur-linked side chains decreases reorganization energy associated with hole transfer and optimizes intermolecular pi-pi stacking, which results in excellent ambipolar charge-transport properties (mu(h) = 1.15 cm(2) V-1 s(-1) and mu(e) = 0.08 cm(2) V-1 s(-1)); in comparison, addition of dibutylamino side chains increases intermolecular steric interactions and hinders perfect intermolecular pi-pi stacking, which results in the weak electronic couplings and finally causes the low intrinsic hole mobility (mu(h) = 0.01 cm(2) V-1 s(-1)). Furthermore, electronic spectra of butyl-IFD, butylthio-IFD and dibutylamino-IFD were simulated and compared with the reported experimental data. Calculations demonstrate that IFD-based molecules possess potential for developing novel infrared and near-infrared probe materials via suitable chemical modifications.

First author: Ning, Y, The oxygen sensing mechanism of a trifluoromethyl-substituted cyclometalated platinum(II) complex, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1145, 1, (2018)
Abstract: Trifluoromethyl-substituted cyclometalated platinum(II) (TSCP) is a useful material for oxygen molecule detection and determination. Through quantum chemical computation, we propose a quenching mechanism to explain the nature of oxygen sensing. The luminescence mechanism of TSCP involves phosphorescent emission and the TSCP-O-2 complex internal conversion. By applying the density functional theory (DFT) method, we computed the frontier molecular orbitals and electron configurations of TSCP and the TSCP-O-2 complex. In addition, using the time-dependent density functional theory (TDDFT) method, we computed the excited energies and geometric optimization of the excited state of TSCP and the TSCP-O-2 complex. According to the computation results, the luminescence of TSCP is due to localized excitation, while that of the TSCP-O-2 complex is due to delocalized excitation. We computed the radiative and non-radiative rate constants of TSCP and the TSCP-O-2 complex and elucidated their photophysical processes. For TSCP, after excitation, first the electron jumped from the S-1 to T-1 state by intersystem crossing, and eventually back to the S-0 state by phosphorescence emission. Instead, for the TSCP-O-2 complex without spin flip, the electron jumped directly from the T-1 to T-0 state by internal conversion.

First author: Montisci, F, NO2 center dot center dot center dot NO2 Contacts under Compression: Testing the Forces in Soft Donor-Acceptor Interactions, CRYSTAL GROWTH & DESIGN, 18, 7579, (2018)
Abstract: Intermolecular forces and energies are not directly observable and cannot be retrieved from a crystal structure determination, which simply pictures the resulting equilibrium between forces. In this work, using compression to sample the repulsive part of potentials, we show that high pressure studies may give insight in the nature of intermolecular forces. We focus our attention on controversial pi* <- n interactions between NO2 groups, which exhibit several conformations. Using X-ray diffraction and ab initio calculations, we describe the high pressure behavior and phase transition of 4-amino-4′-nitro biphenyl. To deepen our understanding of the nature of NO2 center dot center dot center dot NO2 interactions, we used several theoretical tools, including pairwise atomic potential energies and forces. The results show that this interaction is associated with a mild stabilization. Since the repulsive forces are experimentally found to be weaker than those of other contacts, we conclude that also the attractive forces are weak, although in excess of the repulsive ones.

First author: Kravtsova, AN, Xanes Specroscopic Diagnostics of the 3D Local Atomic Structure of Nanostructured Materials, JOURNAL OF STRUCTURAL CHEMISTRY, 59, 1691, (2018)
Abstract: A review of current works on XANES spectroscopy applied for the determination of parameters of a threedimensional local atomic structure of nanostructured materials is given. Special attention is paid to a new method based on the theoretical analysis of XANES spectra by means of multivariate interpolation. The uniqueness of the technique consists not only in the highly accurate (up to 0.01 angstrom) determination of interatomic distances in materials without a long-range order in the atomic arrangement but also the estimation of the angular distribution of atoms (i.e. chemical bond angles) in any condensed materials. Several types of nanostructured materials, including coordination compounds, semiconductor quantum dots, nanosized structures in quasicrystals and extraterrestrial materials are given as examples.

First author: Cobeljic, B, Structural diversity of isothiocyanato Cd(II) and Zn(II) Girard’s T hydrazone complexes in solution and solid state: effect of H-bonding on coordination number and supramolecular assembly of Cd(II) complex in solid state, STRUCTURAL CHEMISTRY, 29, 1797, (2018)
Abstract: The isothiocyanato Zn(II) complex (1) and mixed isothiocyanato/thiocyanato Cd(II) complex (2) with the condensation product of 2-acetylpyridine and trimethylammoniumacetohydrazide chloride (Girard’s T reagent) (HLCl) were investigated both experimentally and theoretically. The crystal structures of both complexes showed tridentate N2O coordination of hydrazine ligand. In complex 1 square-pyramidal coordination surrounding of Zn(II) consists of deprotonated hydrazone ligand and two isothiocyanato ligands, while in octahedral Cd(II) complex ligand is coordinated without deprotonation as a positively charged species and coordination geometry is completed with two N-coordinated and one S-coordinated NCS- anions. NMR spectroscopy and molar conductivity results for Cd(II) and Zn(II) complexes indicated their instability in solution. DFT calculations were performed to explain coordination preference and stability of complexes 1 and 2 in solid state and in solution. The obtained Cd(II) complex is the first reported mononuclear pseudohalide/halide Cd(II) complex with quinoline-/pyridine-based hydrazone ligands possessing octahedral geometry in solid state. In this complex, H-bonding has significant impact on coordination number and supramolecular assembly in solid state.

First author: Ferreira, H, Electrochemical properties of a series of Co(II) complexes, containing substituted phenanthrolines, ELECTROCHIMICA ACTA, 292, 489, (2018)
Abstract: Electrochemical studies of a series of substituted phenanthroline-Co(II) complexes all show generally similar behaviour, namely a chemically and electrochemically reversible Co-III/II redox couple, as well as a chemically and electrochemically reversible Co-II/I redox couple, followed by a ligand-based reduction. Electron donating- or -withdrawing substituents on the phenanthroline ligands which are coordinated to the Co metal, directly influence the electron density on the Co metal, due to good communication between these substituents and the Co metal via the aromatic rings of the heterocyclic substituted phenanthroline-Co(II) complexes, leading to either more negative (for electron donating groups) or more positive (for electron withdrawing groups) redox potentials respectively. Linear relationships relating E degrees'(Co-III/II) oxidation and E degrees'(Co-II/I) reduction to various experimental and empirical values, as well as to theoretically calculated energies, show that the electron density on Co is linearly influenced by the electronic properties of the ligands attached to the Co metal. All these established relationships can be used in the design of new substituted phenanthroline-Co(II) complexes with specific customized redox properties as required, for example, for the application of such Co(II) complexes as redox mediator for dye-sensitized solar cells.

First author: Ye, JY, Organic Linker Effect on the Growth and Diffusion of Cu Clusters in a Metal-Organic Framework, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 26987, (2018)
Abstract: One reason that metal nanoparticles encapsulated in metal-organic frameworks are of interest is that confinement effects on the particle size and shape may lead to superior catalytic activity. The interior of a metal-organic framework has the potential to influence nucleation and aggregation of metal nanoparticles and to strongly affect their in situ shape and electronic properties. We apply density functional theory and ab initio molecular dynamics (AIMD) to model the nucleation and diffusion of Cu-n (n = 1-19) clusters on the tetratopic 1,3,6,8-(p-benzoate)pyrene (TBAPy(4-)) linkers of NU-1000 frameworks. We find that Cu atoms and Cu clusters are stabilized by the TBAPy linker, especially by the edge site of aromatic rings. The stabilization increases when the Cu cluster interacts with two linkers. We identified the most favorable site for Cu cluster adsorption as the window site that connects the c pore and the triangular pore. A Pt atom is found to bind much more strongly than a Cu atom on the TBAPy linker, and AIMD simulations show that this promotes Pt atom diffusion from the center of a Cu-15 cluster to the interface between the linker and the cluster. The strong interaction between a Pt atom and a linker is attributed to the greater metal-to-linker charge transfer.

First author: Konecny, L, Resolution-of-identity accelerated relativistic two- and four-component electron dynamics approach to chiroptical spectroscopies, JOURNAL OF CHEMICAL PHYSICS, 149, 26987, (2018)
Abstract: We present an implementation and application of electron dynamics based on real-time time-dependent density functional theory (RT-TDDFT) and relativistic 2-component X2C and 4-component Dirac-Coulomb (4c) Hamiltonians to the calculation of electron circular dichroism and optical rotatory dispersion spectra. In addition, the resolution-of-identity approximation for the Coulomb term (RI-J) is introduced into RT-TDDFT and formulated entirely in terms of complex quaternion algebra. The proposed methodology was assessed on the dimethylchalcogenirane series, C4H8X (X = O, S, Se, Te, Po, Lv), and the spectra obtained by non-relativistic and relativistic methods start to disagree for Se and Te, while dramatic differences are observed for Po and Lv. The X2C approach, even in its simplest one-particle form, reproduces the reference 4c results surprisingly well across the entire series while offering an 8-fold speed-up of the simulations. An overall acceleration of RTTDDFT by means of X2C and RI-J increases with system size and approaches a factor of almost 25 when compared to the full 4c treatment, without compromising the accuracy of the final spectra. These results suggest that one-particle X2C electron dynamics with RI-J acceleration is an attractive method for the calculation of chiroptical spectra in the valence region. Published by AIP Publishing.

First author: Garcia-Rodeja, Y, Influence of the charge on the reactivity of azafullerenes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 28011, (2018)
Abstract: The influence of the charge on the Diels-Alder reactivity of azafullerenes (C59N+ and C59N-) has been computationally explored by means of density functional theory calculations. In addition, the regioselectivity of the process has been investigated and compared to the analogous cycloaddition reaction involving the parent neutral azahydro[60]fullerene C59NH. It is found that the [4+2]-cycloaddition reaction between C59N+ and cyclopentadiene, which occurs concertedly through a synchronous transition state, proceeds with a lower activation barrier and is more exothermic than the analogous process involving C59NH. In contrast, the anionic C59N- counterpart is clearly less reactive. This reactivity trend is quantitatively analyzed in detail by means of the activation strain model of reactivity in combination with the energy decomposition analysis method. It is found that the frontier molecular orbital interactions are not responsible for the observed reactivity trend but the Pauli repulsion between closed-shells mainly governs the transformation.

First author: Long, LY, Highly Fluorescent and Stable Black Phosphorus Quantum Dots in Water, SMALL, 14, 28011, (2018)
Abstract: Although 2D black phosphorus (BP) shows excellent optical and electronic properties, there are few reports on the photoluminescence (PL) properties of BP nanostructures because of the low yield of mechanical exfoliation, instability in water, and relatively weak emission. Herein, liquid exfoliation is combined with surface passivation to produce fluorescent BP quantum dots (BPQDs) with a high yield. The BPQDs exhibit strong PL in both ethanol and water and the absolute fluorescent quantum yield in water reaches 70%. Moreover, the BPQD solution exhibits stable PL for 150 d under ambient conditions and better photostability than conventional organic dyes and heavy-metal semiconducting nanostructures with intense fluorescence. The experiments and theoretical calculation reveal that the intense and stable PL originates from the intrinsic band-to-band excitation states and two surface states related to the P-OH and P-O-CH2CH3 bonding structures introduced by passivation. The polar water molecules remove many nonradiative centers and simultaneously increase the P-related fluorescent groups on the surface of BPQDs. Therefore, PL from the BPQDs in water is enhanced largely. The excellent fluorescent properties of BPQDs in an aqueous solution bode well for bioimaging and the negligible biotoxicity and distinct cell images suggest large potential in the biomedical and display fields.

First author: Bakthavachalam, K, Cyclometallation of a germylene ligand by concerted metalation-deprotonation of a methyl group, DALTON TRANSACTIONS, 47, 15835, (2018)
Abstract: The reaction of [CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)]GeCl with LiN(SiMe3)(2) was previously reported, which led to the formation of a hetero-fulvene type germylene, [CH{(CMe)(C?CH2)(2,6-iPr(2)C(6)H(3)N)}(2)]Ge through the deprotonation of the C-H bond from the methyl substituents. In this paper, we attempted the analogous reaction with (Dipp)NCMeCHCOMeGeCl using LiN(SiMe3)(2) which gave rise to a metathesis product, (Dipp)NCMeCHCOMeGeN(SiMe3)(2) (2). However, the reactions of 2 with [M2Cl2(-Cl)(2)((5)-Cp*)(2)] (M = Rh and Ir) resulted in cyclometallated Rh and Ir complexes through the activation of the C-H bond from the germylene ligand. The complexes were characterized by single crystal X-ray analysis, which authenticated the presence of Ge-Rh and Ge-Ir bonds. DFT studies have been performed to understand the mechanism.

First author: Binh, DH, Entrapment of THF-Stabilized Iridacyclic Ir-III Silylenes from Double H-Si Bond Activation and H-2 Elimination, CHEMISTRY-A EUROPEAN JOURNAL, 24, 17577, (2018)
Abstract: The reaction of H3SiR (R = Ph, nBu) with cationic eta(5)-C3Me5- (Cp*) and benzo[h]quinolinyl-based iridacycle [1b](+) gives rise to new [(IrH)-> SiRH2](+) adducts. In the presence of THF these adducts readily undergo elimination of H-2 gas at subambient temperature to form THF-stabilized metallacyclic Ir-III silylene complexes, which were characterized in situ by NMR spectroscopy, trapped in minute amounts by reactive crystallization, and structurally characterized by XRD. Theoretical investigations (static DFT-D reaction-energy profiling, ETS-NOCV) support the promoting role of THF in the H-2 elimination step and the consolidation of the Ir-to-Si interaction in the spontaneous (Delta G< 0) formation of Ir silylenes in the presence of THF. Mechanistic insights indicate that the Ir silylene species arising from the [1b](+)/phenylsilane system are relevant catalytic species in the hydrode-fluorination of fluoroalkanes.

First author: Bortoli, M, Nature and strength of chalcogen-pi bonds, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 27592, (2018)
Abstract: Chalcogen- interactions occur between a covalently bound chalcogen atom that enters into a non-covalent interaction with an unsaturated moiety, a bonding motif found in various structures, such as, proteins. In this work, we have systematically explored and analyzed chalcogen- interactions in model systems X(2)DA (with D = O, S, Se, Te; X = halogen; A = acetylene, ethylene and 2-butyne), using relativistic density functional theory (DFT). The nature and trends in stability of the chalcogen- bonds are analyzed and interpreted in terms of quantitative MO theory in combination with a matching canonical energy decomposition analysis (EDA) scheme. We find that chalcogen- bonds increase in strength as the X-D electronegativity difference becomes greater. Moreover, 2-butyne was found to participate in the strongest non-covalent interaction due to enhanced orbital interactions.

First author: Wang, JP, Actinide embedded nearly planar gold superatoms: structural properties and applications in surface-enhanced Raman scattering (SERS), PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 27523, (2018)
Abstract: Planarity is a special property of superatoms, different from atoms. In this work, we predicted a series of nearly planar structures, An@Au-6 (An = Ac-1, Th, Pa+1) clusters, using density functional theory (DFT). Calculations of these actinide embedded clusters reveal a 10-electron (1s(2)1p(4)1d(4)) closed-shell singlet configuration. It is found that all An@Au-6 clusters are nearly or purely planar structures with only in-plane two-dimensional occupied superatomic molecular orbitals (SAMOs). In addition, applying them as surface-enhanced Raman scattering (SERS) substrates, the charge-transfer (CT) states at 677 nm (1d(metal)-(1)*(pyridine)) can lead to a SERS signal enhancement of 10(4) for a pyridine-Th@Au-6 complex. Our research indicates that actinide embedded nearly planar superatomic clusters have unique optical properties and potential application value.

First author: Szlag, VM, Isothermal Titration Calorimetry for the Screening of Aflatoxin B1 Surface-Enhanced Raman Scattering Sensor Affinity Agents, ANALYTICAL CHEMISTRY, 90, 13409, (2018)
Abstract: In this work, isothermal titration calorimetry (ITC) is employed as an affinity agent screening method for the surface-enhanced Raman scattering (SERS) detection of aflatoxin B1 (AFB1). AFB1, a potent carcinogen produced by a fungus that infects crops, is an important target due to the monitoring required based on its FDA regulation. Polymer affinity agents, like those studied here, have the potential to enable separation and detection of relevant small molecules such as pesticides, drugs, and biological toxins, like AFB1, especially when paired with a vibrational spectroscopy technique such as SERS. Herein, seven homopolymers were synthesized to be evaluated as AFB1 affinity agents based on hypothetical hydrogen bonding interactions. Nitrogen-inclusive poly(N-(2-aminoethyl) methacrylamide) (pAEMA) polymers and their oxygen analogs, poly(2-hydroxyethyl methacrylate) (pHEMA) were evaluated. ITC was demonstrated as an effective method for rapid screening among the polymer affinity agents. Chain lengths between seven and 39 repeat units were synthesized to study length-based variance in affinity agent performance. An ITC method was optimized and used for the rapid screening of polymer affinity agents. The results were compared to those generated by SERS. Good agreement between the ITC results and follow-up SERS sensing experiments showcased ITC’s screening potential for analytical applications such as separation and detection.

First author: Poater, J, Aromaticity Determines the Relative Stability of Kinked vs. Straight Topologies in Polycyclic Aromatic Hydrocarbons, FRONTIERS IN CHEMISTRY, 6, 13409, (2018)
Abstract: It is well-known that kinked phenacenes are more stable than their isomeric linear acenes, the archetypal example being phenanthrene that is more stable than anthracene by about 4-8 kcal/mol. In previous studies, the origin of the higher stability of kinked polycyclic aromatic hydrocarbons (PAHs) was found to be better pi-bonding interactions, i.e., larger aromaticity, in kinked as compared to linear PAHs. Some years ago, however, Dominikowska and Palusiak (2011) found that dicationic linear anthracene is more stable than the dicationic kinked phenanthrene. Therefore, these authors showed that, in some cases, the linear topology in PAHs can be preferred over the kinked one. Our results using energy decomposition analyses in combination with the turn-upside-down approach show that the origin of the higher stability of dicationic anthracene is the same as in the neutral species, i.e., better pi-bonding interactions. A similar result is found for the kinked and straight pyrano-chromenes. We conclude that the aromaticity is the driving force that determines the relative stability of kinked vs. straight topologies in PAHs.

First author: Reber, AC, The effect of chalcogen and metal on the electronic properties and stability of metal-chalcogenides clusters, TM6Xn(PH3)(6) (TM = Mo, Cr, Re, Co, Ni; X = Se, Te; n=8,5), EUROPEAN PHYSICAL JOURNAL D, 72, 13409, (2018)
Abstract: We have performed a comparative study of the electronic structure, stability, and magnetic properties of a series of metal-chalcogen clusters stabilized by PH3 ligands. Clusters studied include TM6X8(PH3)(6), TM = Cr, Mo, Re, Co, X = Se, Te, and Ni6X(PH3)(6), X = Se, and Te. We find that the phosphine ligands act as charge donors, transferring charge to the metal sites, creating an electrostatic effect that lowers the ionization energy. The electronic structure of the cluster also has a significant effect on its charge donor properties, as the Re cluster has a closed electronic shell with a charge state of +2, making it an alkaline earth superatom. The chromium clusters are found to have a series of close lying magnetic isomers. Selenium is a better charge acceptor than tellurium and this causes the telluride clusters to have lower ionization potentials, while the enhanced charge transfer to selenium increases the binding energy of the phosphine ligand.

First author: Michalczyk, M, Triel-Bonded Complexes between TrR3 (Tr=B, Al, Ga; R=H, F, Cl, Br, CH3) and Pyrazine, CHEMPHYSCHEM, 19, 3122, (2018)
Abstract: Complexes between TrR3 (Tr=B, Al, Ga; R=H, F, Cl, Br, CH3) molecules and pyrazine have been characterized at the MP2 and CCSD(T) levels of theory. The adducts can be grouped according to the type of molecular arrangement. The first situation places the Tr atom in the plane of the pyrazine ring and contains a triel bond to the N lone pair. For the boron complexes the orbital interaction energy is almost equal to the electrostatic component, while the former is only half the latter for Tr=Al and Ga. The two monomers are stacked above one another in the second configuration, which depends to a greater degree upon orbital interaction and dispersion. The former complexes are more strongly bonded than the latter. Interaction energies (E-int) for the stronger complexes vary between -50 and -20 kcal/mol for BBr3 and Ga(CH3)(3) paired respectively with pyrazine. E-int is much smaller for the stacked configurations, ranging from -8 for GaF3 to -1.4 kcal/mol for BF3. The value of the maximum of the electrostatic potential correlates poorly with E-int, attributed in part to monomer distortions upon complexation.

First author: Xu, DX, Altered superatomic properties of U@C-28 by the electron rearrangement via adatom defects, CHEMICAL PHYSICS LETTERS, 712, 20, (2018)
Abstract: First-principles calculations show that when a carbon adatom has been introduced to the surface of U@C-28 superatom, the neutral U@C-29 has (cage)(1)(adatom)(1) electronic state instead of (cage) 2 state in U@C-28. The valence orbitals of U atom keep fully occupied, while the origin of 32-electron principle is changed due to electron rearrangement via introducing the adatom. Furthermore, there exist two transition states when adatom slipping on the surface of U@C-28, indicating that it is a two-step process from [5: 5] to [6: 6] adsorption sites.

First author: Kodikara, MS, Computational studies of the nonlinear optical properties of organometallic complexes, COORDINATION CHEMISTRY REVIEWS, 375, 389, (2018)
Abstract: Computational methods for calculating the molecular nonlinear optical (NLO) properties of molecules are reviewed, with an emphasis on clarifying the strengths and weaknesses of the various approaches. A brief introduction to the theory of NLO effects is provided, and a summary of the key experimental techniques for the determination of molecular first hyperpolarizabilities is included, with discussion of their advantages and disadvantages. Applications of semi-empirical methods and density functional theory in developing structure-quadratic NLO property relationships for organometallic complexes (and particularly metal alkynyl complexes) are reviewed.

First author: Zhang, JX, Aggregation-Induced Enhancement of Molecular Phosphorescence Lifetime: A First-Principle Study, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 25796, (2018)
Abstract: Pure organic phosphorescent molecules are promising compounds for applications of phosphorescence, yet their utilization is restricted because of inefficient intersystem crossing (ISC) between singlet and triplet states. Molecular aggregation has been deemed a viable strategy to modulate molecular luminescence in solution, yet its impact on the phosphorescence is rarely investigated. In this work, we carried out first-principle studies to elucidate how aggregation of selected phosphorescent molecules will affect their phosphorescence behavior. Our calculations show that the overall ISC rate is appreciably enhanced, thanks to a decrease of energy gaps (Delta E) and an increase in the number of ISC channels between singlet and triplet states as the degree of aggregation develops. This facilitates singlet-to-triplet conversion. More importantly, the phosphorescence lifetime increases with the increase of the degree of molecular aggregation. The long-lived phosphorescence associated with aggregation benefits from multiple factors, including small singlet-triplet gaps, enhanced overall ISC rates, and suppression of fluorescence. We believe this aggregation-induced ISC mechanism may be employed as an alternative approach for realizing persistent phosphorescence.

First author: Ponnuchamy, V, Solvent and Salt Effect on Lithium Ion Solvation and Contact Ion Pair Formation in Organic Carbonates: A Quantum Chemical Perspective, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 25930, (2018)
Abstract: Quantum chemical calculations have been employed to investigate the solvation of lithium cations in ethylene carbonate/propylene carbonate and propylene carbonate/dimethyl carbonate mixed electrolytes. The impact of the presence of the counteranion on the solvation of Li+ in pure propylene carbonate and dimethyl carbonate was also studied. The calculations revealed small free-energy changes for the transitions between different preferred structures in mixed solvents. This implies that transitions between distinct local arrangements can take place in the mixtures. The addition of dimethyl carbonate causes a significant increase of the dipole moment of solvation clusters, indicating important molecular-scale modifications when dimethyl carbonate is used as a co-solvent. The presence of an anion in the solvation shell of Li+ modifies the intermolecular structure comprising four carbonate molecules in dilute solutions, allowing only two carbonate molecules to coordinate to Li+. The bidentate complexation of Li+ with the anion’s electron donor atoms, however, maintains the local tetrahedral structure on interatomic length scales. The neutralization of the solvation shell of Li+ due to contact ion pair formation and the consequent implications on the underlying mechanisms provide a rational explanation for the ionic conductivity drop of electrolyte solutions at high salt concentrations.

First author: Soldatov, MA, The insights from X-ray absorption spectroscopy into the local atomic structure and chemical bonding of Metal-organic frameworks, POLYHEDRON, 155, 232, (2018)
Abstract: After a short introduction highlighting the potentialities of metal-organic frameworks (MOFs) and the power of X-ray absorption spectroscopies (XAS), a list of selected examples follows. The first part of this review provides the basic concepts that are behind the most used XAS techniques: Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopies. Moreover, it reports also the basis of an innovative approach to the EXAFS data analysis based on the wavelet transform approach, that allows a more solid attribution to the different paths contributing to the overall signal. The second part is devoted to provide a section of examples where EXAFS and XANES techniques have been determinant in understanding the structural and electronic properties of metal centers in MOFs. The selected examples have been ordered in subsections related to the application foreseen for the investigated MOFs materials: MOFs functionalization for catalytic applications; MOFs as single site catalyst; MOFs as photocatalysts; MOFs for gas sorption and storage; MOFs for energy application. Conclusions and perspectives are provided at the end.

First author: Chu, YH, Computational prediction of cellulose solubilities in ionic liquids based on COSMO-RS, FLUID PHASE EQUILIBRIA, 475, 25, (2018)
Abstract: A computational approach is presented for prediction of cellulose solubilities in ionic liquids (ILs) based on COSMO-RS (Conductor-like Screening Model for Real Solvents). Thermodynamically stable molecular structures were optimized from 2D structures of cellulose and Its following specific force-field based search of conformation lowest in energy and quantum chemical optimizations of molecular geometry. The thermodynamic property of logarithmic activity coefficient (In gamma) and excess enthalpy (H-E) were calculated by COSMO-RS based on the COSMO molecular surfaces of cellulose and ILs to qualitatively predict the ability of ILs for cellulose dissolution. To evaluate the method, four sets of ILs were used to calculate In gamma and H-E based on four different cellulose models. The goodness-of-fit of linear regressions between the experimental cellulose solubilities and the calculated In gamma and H-E shows that ln gamma is more reliable than H-E for prediction of the dissolving power of ILs to dissolve cellulose. However, HE is more suitable for prediction of the dissolution ability of halogen-based ILs. Moreover, all the cellulose models gave comparably good prediction results regarding of the dissolving power of ILs based on the calculated Iny, but the cellobiose model was identified as the optimal model due to the relatively higher prediction ability (R-2) across different IL datasets. The approach is time efficient and robust, which provides a novel method for large-scale screening of ILs for cellulose dissolution.

First author: Gao, YJ, ONIOM studies on thermally activated delayed fluorescence of copper(I) dimers in crystal, CHEMICAL PHYSICS, 515, 692, (2018)
Abstract: Herein we have employed M06 and TD-M06 methods with the ONIOM approach to study the thermally activated delayed fluorescence (TADF) phenomenon of three halide-bridged Cu(I) dimers bearing amino-phosphane ligands in crystal (Cl-, Br-, and I-coordinated ones). On the basis of spectroscopic properties, ground- and excited-state geometric and electronic structures, and photophysical properties, we have found that the S-1 and T-1 states have a very small energy gap Delta Es1-T1, less than 4.0 kcal/mol, which makes the forward and reverse intersystem crossing ISC and rISC processes between S-1 to T-1 very efficient and a population equilibrium can be established. The rISC rates are visibly sensitive to temperature and increasing temperature clearly enhances the rISC rates thus rationalizing experimentally observed TADF phenomenon. Moreover, we have also found that the low-frequency vibrational modes related to the torsional motion of the coordinated ligands have large Huang-Rhys factors, which increase from Cl via Br to I-coordinated Cu(I) dimers. In this varying process, the ISC rates increase visibly whereas the rISC rates change slightly. Our work provides useful microscopic knowledge to understand the TADF emission of the Cu(I) dimers, which could be helpful for the rational design of TADF materials with excellent performance.

First author: Makhoul, R, Redox Properties of Ferrocenyl Ene-diynyl-Bridged Cp*(dppe)M-C C-1,4-(C6H4) Complexes, ORGANOMETALLICS, 37, 4156, (2018)
Abstract: The complexes FcCH=C{1,4-C C-C6H4-C CM(dppe)Cp*}(2) (Fc = ferrocenyl (FeCp(eta-C5H4-); M = Fe (1), Ru (2)) were prepared from FcCH=C{1,4-C C-C6H4-C=C SiMe3}(2) (3) via a desilylation/metalation protocol in good (2; 65%) to excellent (1; 97%) yield. The iron compound 1 could also be prepared in a stepwise fashion by desilylation of 3 to give FcCH=C{1,4-C C-C6H4-C CH}(2) (4), reaction with FeCl(dppe)Cp* to give the vinylidene complex FcCH=C{1,4-C=C-C6H4-CH=C=Fe(dppe)Cp*}(2)] (PF6)(2) (5(PF6)(2); 65%), and deprotonation. The cyclic voltammograms of 1 and 2 are characterized by an initial oxidation wave resulting from the overlap of two closely spaced oxidation processes, the potentials of which are sensitive to the identity of M, and a subsequent, one-electron-oxidation wave. Thus, while the dications I2+ and 2(2+) could be prepared by oxidation with 2 equiv of ferrocenium hexafluorophosphate and isolated as the PF6- salts 1(PF6)(2) and 2(PF6)(2) at low temperature, the monocations 1(+) and 2(+) could only be detected and studied as comproportionated mixtures of 1, 1 (PF6), 1(PF6)(2) and 2, 2(PF6), 2(PF6)(2). A combination of EPR spectroscopy, IR and NIR spectroelectrochemistry, and DFT quantum chemical calculations reveal subtle distinctions in the electronic structures of 1(PF6) and 2(PF6) (n = 0-2). The HOMOs of 1 and 2 are more heavily distributed over the metal-diethynylbenzene arm trans to the ferrocenyl moiety. While one-electron oxidation of 1 gives 1(PF6), in which the spin density is similarly distributed along the branch of the molecule trans to the ferrocenyl group, the spin density in 2(PF6) is more extensively, but not fully, delocalized. Further analysis of the ESR, NIR, and IR spectra reveals that charges are essentially localized in 1(PF6) and 1(PF6)(2) on the IR time scale, but ground-state exchange between the Fe(dppe)Cp* moieties can take place via the ferrocenyl moiety on the slower ESR time scale. For 2(PF6) and 2(PF6)(2), optical charge transfer processes between the ferrocenyl moiety and the organometallic branches can also be observed, consistent with the increased coupling between the Ru(dppe)Cp* and Fc moieties that are linked by a linear conjugation pathway through the bridging-ligand backbone.

First author: Chi, XW, Theoretical Study on Unsupported Uranium-Metal Bonding in Uranium-Group 8 Complexes, ORGANOMETALLICS, 37, 3678, (2018)
Abstract: On the basis of the first structurally authenticated (LU)-U-Ar-FeCp(CO)(2) (L-Ar = deprotonated p-terphenyl bis(aniline) ligand) complex bearing an unsupported U Fe bond, we expanded the structures of complexes (LU)-U-Ar-MCp(CO)(2) (M = Fe, Ru, Os) and systematically investigated the U-M bonding nature by using scalar -relativistic quantum chemical calculations. Theoretical results reveal highly polarized U-M interactions in the three (LU)-U-Ar-MCp(CO)(2) complexes. Moreover, the three U-M bonds are confirmed to show single bond feature. Topology of electron density reveals predominantly “closed shell” U-M interaction with obvious ionic interaction in the three (LU)-U-Ar-MCp(CO)(2) complexes. In addition, the negative binding energy suggests that the three (LU)-U-Ar-MCp(CO)(2) complexes are thermodynamically feasible. This work reveals the bonding nature of the three U-M bonds and expands our knowledge of the unsupported uranium metal bonding in the heterobimetallic complexes.

First author: Toffoli, D, Electronic Structure Characterization of a Thiophene Benzo-Annulated Series of Common Building Blocks for Donor and Acceptor Compounds Studied by Gas Phase Photoelectron and Photoabsorption Synchrotron Spectroscopies, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 8745, (2018)
Abstract: The near-edge x-ray-absorption fine-structure (NEXAFS) and Xray photoelectron spectroscopy (XPS) spectra of benzo[b]thiophene (BBT) and dibenzothiophene (DBT) in the gas phase have been measured at the carbon Kedge and sulfur L-II,L-III-edge regions. The assignment of the spectral features has been provided by theoretical calculations based on density functional theory (DFT) and its time-dependent generalization (TDDFT) in the linear response regime. Observed trends in computed C 1s and S 2p ionization potentials (IPs) have been rationalized in terms of both the inductive effects due to the presence of S and the increased pi-electrons delocalization arising from the benzoannulation process. The analysis of the NEXAFS carbon K-edge and sulfur L-II,L-III-edge regions regions provided information on both low-lying delocalized virtual pi orbitals, and higher-lying localized sigma*(C-S) states. The evolution of the NEXAFS carbon K-edge spectral features along the series thiophene (T) and derivatives, BBT and DBT, is informative of a stabilizing effect due to increased aromaticity. This effect is however more pronounced in going from T to BBT compared to the introduction of a second annulated phenyl ring in DBT. The nature of the most intense sulfur L-II,L-III-edge NEXAFS spectral features is instead conserved along the series reflecting thus the localized nature of the virtual states involved in the S 2p core-excitation process.

First author: Cary, SK, A series of dithiocarbamates for americium, curium, and californium, DALTON TRANSACTIONS, 47, 14452, (2018)
Abstract: Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described herein help to address this issue through isolation of An(S2CNEt2)(3)(N2C12H8) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm-S (mean of 2.86 +/- 0.04 angstrom) and Cf-S (mean of 2.84 +/- 0.04 angstrom) bond distances. Furthermore, they highlight the potential of An(S2CNEt2)(3)(N2C12H8) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.

First author: Shee, A, Equation-of-motion coupled-cluster theory based on the 4-component Dirac-Coulomb(-Gaunt) Hamiltonian. Energies for single electron detachment, attachment, and electronically excited states, JOURNAL OF CHEMICAL PHYSICS, 149, 14452, (2018)
Abstract: We report in this paper an implementation of a 4-component relativistic Hamiltonian based Equation-of-Motion Coupled-Cluster with singles and doubles (EOM-CCSD) theory for the calculation of ionization potential, electron affinity, and excitation energy. In this work, we utilize the previously developed double group symmetry-based generalized tensor contraction scheme and also extend it in order to carry out tensor contractions involving non-totally symmetric and odd-ranked tensors. Several approximated spin-free and two-component Hamiltonians can also be accessed in this implementation. We have applied this method to the halogen monoxide (XO, X = Cl, Br, I, At, Ts) species, in order to assess the quality of a few other recent EOM-CCSD implementations, where spin-orbit coupling contribution has been approximated in different degrees. Besides, we have also studied various excited states of CH2IBr, CH2I2, and I-3(-) (as well as single electron attachment and detachment electronic states of the same species) where comparison has been made with a closely related multi-reference coupled-cluster method, namely, Intermediate Hamiltonian Fock Space Coupled-Cluster singles and doubles theory. Published by AIP Publishing.

First author: Xiao, P, Mechanism of the Visible-Light-Mediated Copper-Catalyzed Coupling Reaction of Phenols and Alkynes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 15099, (2018)
Abstract: A recent experimental study reported a visible-light-mediated aerobic oxidative coupling reaction of phenol with alkynes that produces hydroxyl-functionalized aryl ketones using inexpensive CuCl as catalyst under mild conditions. Here we apply the complete active space self-consistent field (CASSCF) method and multistate second-order perturbation (MS-CASPT2) theory in combination with density functional theory (DFT) to systematically explore the entire photocatalytic reaction between phenol and phenylacetylene in acetonitrile solution in the presence of molecular oxygen and CuCl. Our main findings are as follows: (1) The visible-light-driven conversion of phenyl acetylene to PhCCCu(I) occurs thermally because of efficient excited-state deactivation to the S-0 state. (2) The single electron transfer from PhCCCu(I) to molecular oxygen that leads to the PhCCCu(II) cation takes place in the T-1 state after an efficient S-1 -> T-1 intersystem crossing. (3) During the initial oxidation of phenol, molecular oxygen prefers to attack the para position of the phenol radical intermediate to produce 1,4-benzoquinone, which further reacts with PhCCCu(II) to generate para-hydroxyl-substituted aryl ketones; this is the origin of the experimentally observed regioselectivity. (4) The C C bond of the phenylacetylene moiety is not activated by the triplet state single electron transfer from PhCCCu(I) to molecular oxygen but is cleaved at a later stage, in the [2+2] cycloaddition between PhCCCu(II) and 1,4-benzoquinone. (5) The substrate phenol plays an active role in several hydrogen transfer and decarboxylation reactions; the barriers to these phenol-assisted reactions are lower than those for the corresponding direct or water-assisted reactions, which explains the experimental finding that adding water does not enhance the photocatalytic reaction yield. In summary, while supporting the general features of the experimentally proposed mechanism, our computational study provides detailed mechanistic insights that should be useful for understanding and further improving visible-light-induced copper-catalyzed coupling reactions.

First author: Stein, BW, Vibrational Control of Covalency Effects Related to the Active Sites of Molybdenum Enzymes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 14777, (2018)
Abstract: A multitechnique spectroscopic and theoretical study of the Cp2M-(benzenedithiolato) (M = Ti, V, Mo; Cp = eta(5)-C5H5) series provides deep insight into dithiolene electronic structure contributions to electron transfer reactivity and reduction potential modulation in pyranopterin molybdenum enzymes. This work explains the magnitude of the dithiolene folding distortion and the concomitant changes in metal-ligand covalency that are sensitive to electronic structure changes as a function of d-electron occupancy in the redox orbital. It is shown that the large fold angle differences correlate with covalency, and the fold angle distortion is due to a pseudo-Jahn-Teller (PJT) effect. The PJT effect in these and related transition metal dithiolene systems arises from the small energy differences between metal and sulfur valence molecular orbitals, which uniquely poise these systems for dramatic geometric and electronic structure changes as the oxidation state changes. Herein, we have used a combination of resonance Raman, magnetic circular dichroism, electron paramagnetic resonance, and UV photoelectron spectroscopies to explore the electronic states involved in the vibronic coupling mechanism. Comparison between the UV photoelectron spectroscopy (UPS) of the d(2) M = Mo complex and the resonance Raman spectra of the d(1) M = V complex reveals the power of this combined spectroscopic approach. Here, we observe that the UPS spectrum of Cp2Mo(bdt) contains an intriguing vibronic progession that is dominated by a “missing mode” that is composed of PJT-active distortions. We discuss the relationship of the PJT distortions to facile electron transfer in molybdenum enzymes.

First author: Miralrio, A, C50Cl10, a planar aromatic fullerene. Computational study of C-13-NMR chemical shift anisotropy patterns and aromatic properties, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 26325, (2018)
Abstract: The isolated-pentagon-rule (IPR) is a prime determinant of fullerene stabilization accounting for the difficult isolation of hollow C-n (n < 60) species. In this connection, the isolation and structural characterization of D-5h-C50Cl10 as an IPR-violating fullerene are of interest owing to the study of factors providing further stability. Herein, we use DFT calculations to explore its aromatic behavior. In this connection the C50Cl10 structure is considered as a fullerene displaying a planar-aromatic character provided by the face-to-face disposition of two IPR structural motifs, mediated by ten exobonded sp(3)-carbons. In addition, the D-5h-C50Br10 counterpart appears to be another promising structure as the target for explorative synthesis. Owing to the curvature of its IPR motif, an interesting variation in the C-13-NMR patterns relative to corannulene is described, where the relation between C-I and C-II signals is useful to evaluate the degree of the curvature of the -surface. The charge distribution of C50Cl10 reveals a more electron-deficient IPR dome in comparison to C-60, envisaging an enhanced chemistry related to bare fullerenes. In addition, the -Cl and -Br exobonded atoms provide effective sigma-holes, suggesting such oblate fullerenes as interesting two-dimensional five-fold symmetric synthons useful for the formation of supramolecular species. Hence, an interesting chemistry and supramolecular array derivatives are potential applications to be further explored towards the development of novel nano-devices.

First author: Lamine, W, Unexpected Structure of a Helical N-4-Schiff-Base Zn(II) Complex and Its Demetallation: Experimental and Theoretical Studies, CHEMPHYSCHEM, 19, 2938, (2018)
Abstract: A new Zn-N-4-Schiff base L=((+/-)-trans-N,N’-Bis(2-aminobenzylidene)-1,2-diaminocyclohexane) complex was synthesized and fully characterized, showing an unexpected self-assembled double-stranded helicate structure. The X-ray crystal analysis of the Zn2L2 complex ((C40H44N8Zn2,CH2Cl2, a=14.2375(3) angstrom, b=16.7976(4) angstrom, c=16.1613(4) angstrom, monoclinic, P2(1)/n, Z=4) shows a centrosymmetrical structure in which zinc atoms are in distorted tetrahedral environments, revealing an M- (R, R) left-handed helicity in its asymmetric unit. However, it was observed that this dinuclear complex is thermodynamically unstable in the presence of small water amounts and undergoes demetallation into free N4-Schiff base ligand and ZnO nanoparticles. This hydrolysis process was thoroughly identified and monitored through detailed H-1 NMR, DOSY NMR analysis. The reaction mechanism of this demetallation event was elucidated by using the DFT method, involving an activation energy smaller than 13 kcal/mol. Besides, a theoretical mechanism of the demetallation process is given for the first time.

First author: Chen, LH, Multiscale Simulation of the Interaction and Adsorption of Ions on a Hydrophobic Graphene Surface, CHEMPHYSCHEM, 19, 2954, (2018)
Abstract: The adsorption of ions on a graphene surface is very important to control relevant graphene-based processes. In this work, a multiscale simulation was carried out to study the adsorption of Na+/Cl- ions on graphene by combining quantum mechanics calculations and molecular dynamics (MD) simulations. The interaction energies of the ions with graphene were computed using density functional theory (DFT). It was found that the ions show strong interaction with a graphene cluster and the overwhelming portion of the interaction energy is the ion-pi orbital interaction. The large orbital interaction can be ascribed to the two contributions arising from the ion-induced polarization of graphene and the charge transfer between ion and graphene. Their different contribution degrees reveal that the polarization effect plays a main role on the orbital interaction for ion adsorption. Comparatively, for Na/Cl atom adsorption, the charge transfer shows large part to the orbital interaction with weak atom-induced polarization. The obtained interaction energies were applied to develop new interaction potentials between ion and graphene, and then MD simulations were used to study the interfacial adsorption behavior of Na+/Cl- aqueous solution onto the graphene surface. Due to enhanced ion-pi interactions, Na+/Cl- cooperatively demonstrates a strong ion adsorption layer through direct contact with the hydrophobic graphene surface. Our simulation result presents a new understanding of ion-graphene interactions.

First author: Doppert, MT, Intermolecular pi-hole/n -> pi* interactions with carbon monoxide ligands in crystal structures, CHEMICAL COMMUNICATIONS, 54, 12049, (2018)
Abstract: A thorough analysis of the Cambridge Structure Database reveals that intermolecular -hole/n* interactions with carbon monoxide ligands are abundant in the solid state and somewhat directional, particularly with fac-like M(CO)(3) fragments (P < 4.0). High level DFT calculations suggest interacting energies up to about -10 kcal mol(-1) for adducts of charge neutral complexes.

First author: Kuzniak, E, Molecular Deformation, Charge Flow, and Spongelike Behavior in Anion-pi {[M(CN)(4)](2-);[HAT(CN)(6)]}(infinity) (M=Ni, Pd, Pt) Supramolecular Stacks, CHEMISTRY-A EUROPEAN JOURNAL, 24, 16302, (2018)
Abstract: The synthesis, crystal structures, spectroscopic characterization, and comprehensive quantum-chemical calculations for a novel series of anion-pi hybrid salts (XPh4)(2)[M(CN)(4)][HAT(CN)(6)]center dot 3MeCN (X=P, M=Ni-II (1), Pd-II (3), Pt-II (5); X=As, M=Ni-II (2), Pd-II (4), Pt-II (6); HAT(CN)(6)=1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile) are presented. The systems comprise 1D {[M(CN)(4)](2-);[HAT(CN)(6)]}(infinity) stacks, in which the electron-rich metal complexes adjust their orientation to match the electron-deficient areas of HAT(CN)(6). Electronic charge-transfer interactions along the stacks result in polarization of electron density within HAT(CN)(6) and in perturbations along the {[M(CN)(4)](2-);[HAT(CN)(6)]}(infinity) contacts. Electronic structure analysis suggests, for example, a relocation of 0.1-0.2 e per molecule from [M(CN)(4)](2-) to HAT(CN)(6) and anion-pi interaction energies of around -65 kcal mol(-1). A reversible structural single-crystal-to-single-crystal transformation, through desolvation/resolvation processes in the solid state, is also reported and a scheme for the formation of anion-pi [M(CN)(4)](2-)/HAT(CN)(6) adducts in MeCN is proposed.

First author: Zaccaria, F, RNA versus DNA G-Quadruplex: The Origin of Increased Stability, CHEMISTRY-A EUROPEAN JOURNAL, 24, 16315, (2018)
Abstract: DNA quadruplexes have been the subject of investigation because of their biological relevance and because of their potential application in supramolecular chemistry. Similarly, RNA quadruplexes are now gaining increasing attention. Although DNA and RNA quadruplexes are structurally very similar, the latter show higher stability. In this study we report dispersion-corrected density functional theory (DFT-D) quantum chemical calculations that were undertaken to understand the difference in stabilities of RNA and DNA quadruplexes. The smallest meaningful model of a stack of quartets, interacting with alkali metal cations, was simulated in an aqueous environment. The energy decomposition analysis allows for in-depth examination of the interaction energies, emphasising the role of noncovalent interactions and better electrostatics in determining RNA-GQs higher stabilities, particularly pinpointing the role of the extra 2-OH groups. Furthermore, our computations present new insights on why the cation is required for self-assembly: unexpectedly the cation is not necessary to relieve the repulsion between the oxygen atoms in the central cavity, but it is needed to overcome the entropic penalty.

First author: Dong, DP, Multiscale Modeling of Structure, Transport and Reactivity in Alkaline Fuel Cell Membranes: Combined Coarse-Grained, Atomistic and Reactive Molecular Dynamics Simulations, POLYMERS, 10, 16315, (2018)
Abstract: In this study, molecular dynamics (MD) simulations of hydrated anion-exchange membranes (AEMs), comprised of poly(p-phenylene oxide) (PPO) polymers functionalized with quaternary ammonium cationic groups, were conducted using multiscale coupling between three different models: a high-resolution coarse-grained (CG) model; Atomistic Polarizable Potential for Liquids, Electrolytes and Polymers (APPLE & and ReaxFF. The advantages and disadvantages of each model are summarized and compared. The proposed multiscale coupling utilizes the strength of each model and allows sampling of a broad spectrum of properties, which is not possible to sample using any of the single modeling techniques. Within the proposed combined approach, the equilibrium morphology of hydrated AEM was prepared using the CG model. Then, the morphology was mapped to the APPLE&P model from equilibrated CG configuration of the AEM. Simulations using atomistic non-reactive force field allowed sampling of local hydration structure of ionic groups, vehicular transport mechanism of anion and water, and structure equilibration of water channels in the membrane. Subsequently, atomistic AEM configuration was mapped to ReaxFF reactive model to investigate the Grotthuss mechanism in the hydroxide transport, as well as the AEM chemical stability and degradation mechanisms. The proposed multiscale and multiphysics modeling approach provides valuable input for the materials-by-design of novel polymeric structures for AEMs.

First author: Chen, ZJ, Combustion Mechanisms and Kinetics of Fuel Additives: A ReaxFF Molecular Simulation, ENERGY & FUELS, 32, 11852, (2018)
Abstract: Fuel additives are widely used as octane number improvers, oxygenates, emission depressors, and corrosion inhibitors to promote combustion processes of liquid fuel. In this work, six kinds of fuel additives, including ethanol, butanol, dimethyl carbonate, dibutyl carbonate, methyl tert-butyl ether, and tri-tert amyl glycerol ether, were studied by ReaxFF molecular dynamics simulations. The bond dissociation reactions were found to be more dominant at the early stage than oxidation reactions, which means the unimolecular reactions were the main pathways of primary reactions in hydrocarbon combustion. The rate constants of primary reactions of ethanol combustion were much smaller than those of other systems, which were in good agreement with the product distribution analysis and previous work. The main reaction pathway and relative rate constants for all systems were evaluated. Four kinds of main radicals, including center dot CH3, center dot center dot CH2, center dot OH, and center dot HO2, were detected, and the number variation with time are presented. The number of .OH radicals was the largest among those four radicals, and it was found to gradually increase with time except for ether systems; the number of center dot CH3 and center dot center dot CH2 radicals sharply increased first and then gradually decreased. Hopefully, the results obtained in this work will be helpful to future design and screening of new fuel additives.

First author: Kurczab, R, Salt Bridge in Ligand-Protein Complexes-Systematic Theoretical and Statistical Investigations, JOURNAL OF CHEMICAL INFORMATION AND MODELING, 58, 2224, (2018)
Abstract: Although the salt bridge is the strongest among all known noncovalent molecular interactions, no comprehensive studies have been conducted to date to examine its role and significance in drug design. Thus, a systematic study of the salt bridge in biological systems is reported herein, with a broad analysis of publicly available data from Protein Data Bank, DrugBank, ChEMBL, and GPCRdb. The results revealed the distance and angular preferences as well as privileged molecular motifs of salt bridges in ligand-receptor complexes, which could be used to design the strongest interactions. Moreover, using quantum chemical calculations at the MP2 level, the energetic, directionality, and spatial variabilities of salt bridges were investigated using simple model systems mimicking salt bridges in a biological environment. Additionally, natural orbitals for chemical valence (NOCV) combined with the extended-transition-state (ETS) bond-energy decomposition method (ETS-NOCV) were analyzed and indicated a strong covalent contribution to the salt bridge interaction. The present results could be useful for implementation in rational drug design protocols.

First author: Farradeche, M, Free ion yield of trimethyl bismuth used as sensitive medium for high-energy photon detection, JOURNAL OF INSTRUMENTATION, 13, 2224, (2018)
Abstract: CaLIPSO project is an innovative high-energy photon detector concept using trimethylbismuth as sensitive medium in a liquid ionization chamber. The detector, designed for high precision brain PET imaging, works as a time-projection chamber and detects Cherenkov light and charge signal. We measured the free ion yield of trimethylbismuth, which represents the number of electron-ion pairs released by the incident photon. To do so, we developed a low-noise measuring system to determine the current induced by a Co-60 source in the liquid with an accuracy better than 5 fA for an electric field up to 7 kV/cm. We used tetramethylsilane as benchmark liquid to validate the apparatus and we measured a zero-field free ion yield of 0.53 +/- 0.03 in agreement with measurements in literature. However, we found a zero-field free ion yield of 0.083 +/- 0.003 for trimethylbismuth, which is a factor 7 lower than the typical values for similar dielectric liquids. Quantum chemistry computations on heavy atoms tend to demonstrate a high capacity of trimethylbismuth to capture electrons which could explain the weak value. The consequences of a low free ion yield in terms of high-energy photon detection and brain PET imaging are finally discussed.

First author: Shi, YR, Effects of crystal structures and intermolecular interactions on charge transport properties of organic semiconductors, JOURNAL OF MATERIALS SCIENCE, 53, 15569, (2018)
Abstract: In this study, the effects of the packing configuration and intermolecular interaction on the transport properties are investigated based on density functional theory. Molecular design from the standpoint of a quantum-chemical view is helpful to engender favorable molecular packing motifs. The transfer integral along the orientation with pi-pi overlap is much larger than other directions without pi-pi overlap, and the mobility along this orientation is higher than that along other directions. The intermolecular interaction analyses demonstrate that hydrogen bonds play a crucial role with strong electrostatic interactions in charge transfer. There will be a synergistic relationship when the pi-pi stacking and intermolecular interaction coexist in the same direction. It turns out that intermolecular interactions are responsible for charge transport, while pi-pi stacking interactions dominate donor-acceptor transport. Incorporating the understanding of the molecular packing motifs and intermolecular interactions into the design of organic semiconductors can assist in the development of novel materials.

First author: Tsuchida, Y, Solvation structure for Fe(II), Co(II) and Ni(II) complexes in [P-2225][NTf2] ionic liquids investigated by Raman spectroscopy and DFT calculation, JOURNAL OF MOLECULAR LIQUIDS, 269, 8, (2018)
Abstract: The solvation structures of divalent iron, cobalt and nickel complexes in the ionic liquid, triethyl n pentylphosphonium bis(trifluoromethyl sulfonyl) amide [P-2225][NTf2]) were investigated by Raman spectroscopy. Based on a conventional analysis, the solvation numbers of Fe(II), Co(II), and Ni(II) in [P-2225] [NTf2] were determined to be 3.18, 3.21, and 3.14 at 298 K and 3.24, 332, and 3.37 at 373 K, respectively.

First author: Lakehal, S, Combined QTAIM and ETS-NOCV investigation of the interactions in ClnM[PhB((NBu)-Bu-t)(2)] complexes with M=Si & Ge (n=0), As & Sb (n=1), Te & Po (n=2), JOURNAL OF MOLECULAR MODELING, 24, 8, (2018)
Abstract: In this work, the nature of the chemical interactions between the metalloid atom (M=Si, Ge, As, Sb, Te, Po) and the nitrogen atoms in the bora-amidinate (bam) complexes (ClnM[PhB((NBu)-Bu-t)(2)]) are investigated, mainly via density-based indices. The descriptors used are derived using the quantum theory of atoms in molecules and natural orbitals for chemical valence approaches. It is shown that the strongest interaction is achieved with silicon. Indeed, it is generally the lightest metalloid in a particular group of the periodic table (i.e., Si, As, and Te for groups 14-16, respectively) that exhibits the strongest bond in the bam complex. This suggests that the atomic radius of the metalloid is a useful parameter for predicting the bonding strength. Extended transition state (ETS) decomposition results indicate that the interactions are more electrostatic than due to orbital interactions.

First author: Casella, G, Reaction between Indazole and Pd-Bound Isocyanides-A Theoretical Mechanistic Study, MOLECULES, 23, 8, (2018)
Abstract: The mechanism of the addition of indazole (Ind)-a bifunctional aromatic N,NH-nucleophile-to cyclohexyl isocyanide coordinated to the palladium(II) center in the model complex cis-[PdCl2(CNMe)(CNCy)] (1) to give the corresponding aminocarbene ligand was investigated in detail by theoretical (DFT) methods. The most plausible mechanism of this reaction is that of the associative type involving nucleophilic attack of Ind by its unprotonated N atom at the isocyanide carbon atom followed by the stepwise proton transfer from the nucleophile molecule to the isocyanide N atom via deprotonation/protonation steps. Two reaction channels based on two tautomeric forms of indazole were found. The channel leading to the experimentally isolated aminocarbene product is based on the less stable tautomeric form. Another channel based on the more stable tautomer of Ind is slightly kinetically more favorable but it is endergonic. Thus, the regioselectivity of this reaction is thermodynamically rather than kinetically driven. The bonding situation in key species was analyzed.

First author: Klahr, K, Geometry Optimizations in a Subsystem Density Functional Theory Formalism: A Benchmark Study, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 5631, (2018)
Abstract: We present a benchmark study on equilibrium structures optimized with subsystem density functional theory (sDFT) employing a new analytical gradient implementation in the program SERENITY. Geometry optimizations are performed on all complexes of the S22 [Jureaca et al. Phys. Chem. Chem. Phys. 2006, 8, 1985-1993] and A24 [Rezac and Hobza. J. Chem. Theory Comput. 2013, 9, 2151-2155] test sets. While some combinations of approximate exchange-correlation (XC) and nonadditive kinetic-energy functionals (e.g., LDA/Thomas-Fermi or PW91/PW91k) more or less successfully mimic the effect of medium-range dispersion in these complexes, we also include the combination of BP86/LLP91. This functional reproduces the dispersion problem of the corresponding BP86 Kohn Sham (KS-)DFT calculations and can hence successfully be corrected by empirical dispersion corrections developed for KS-DFT. We propose this as a robust and accurate strategy for sDFT geometry optimizations, which appears to be preferable over the previously used strategy relying on error cancellation between XC and nonadditive kinetic-energy functionals. In fact, the best results in our benchmark are obtained from BP86/LLP91 together with a D3-type dispersion correction. We also discuss the difference between our Gaussian-type orbital implementation in SERENITY and a Slater-type orbital based implementation in the Amsterdam density functional (ADF) program but only find small differences in most cases.

First author: Hu, ZW, A Discrete Interaction Model/Quantum Mechanical Method for Simulating Plasmon-Enhanced Two-Photon Absorption, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 5896, (2018)
Abstract: In this work, we extend the discrete interaction model/quantum mechanical (DIM/QM) method to simulate PUPA plasmon-enhanced two-photon absorption (PETPA). The metal nanoparticle is treated atomistically by means of electrodynamics, while the molecule is described using damped cubic response theory within a time-dependent density functional theory framework. Using DIM/QM, we study the PETPA of para-nitroaniline (p-NA) with a focus on the local and image field effects, the molecular orientation effects, and the molecule nanoparticle distance effects. Our findings show that the enhancement is more complex than the simple vertical bar E vertical bar(4) enhancement mechanism, where vertical bar E vertical bar is the local field at the position of the molecule. Because of specific interactions with the nanoparticle, we find that a TPA dark state of p-NA can be significantly enhanced through a coupling with the plasmon excitation. The results presented in this work illustrate that the coupling between molecular excitations and plasmons can give rise to unusual and complex behavior in nonlinear spectroscopy that cannot simply be understood by considering the optical properties of the individual molecules and nanoparticles separately. The method presented here provides detailed insights into the enhancement of nonlinear optical properties of molecules coupled to plasmonic nanoparticles.

First author: Pan, S, Improvement in hydrogen binding ability of closo-dicarboranes via functionalization and designing of extended frameworks, JOURNAL OF MOLECULAR MODELING, 24, 5896, (2018)
Abstract: Neutral closo-dicarboboranes are reported to have very low H-2 binding ability. Herein, we report an improvement in H-2 binding energy (E-b) of C2B4H6 by substituting H atoms with different functional groups like X=F, Cl, Br, and XY=BO, CN and NC via quantum-chemical density functional theory based computations. In going from B6H62- to C2B4H6, the E-b value is reduced from 14.6kJmol(-1) to 2.7kJmol(-1). C2B4X6 and C2B4(XY)(6) systems, which can bind a total of eight H-2 molecules, with one H-2 molecule occupying at each B-B-C face, possess an E-b value per H-2 in the range of 4.5kJmol(-1) for X=F, 3.9kJmol(-1) for X=Cl, 5.9kJmol(-1) for X=Br, 6.8kJmol(-1) for XY=BO, 5.8kJmol(-1) for XY=CN and 5.2kJmol(-1) for XY=NC. The improvement in E-b value is found to be the highest in case of C2B4(BO)(6), which has the ability to bind 6.6 gravimetric wt% of H-2. The situation can be made more favorable by applying an external electric field. Energy decomposition analysis reveals that although the dispersion interaction (ca. 55-65%) has significant role in binding H-2 with such types of molecules, contribution from electrostatic and orbital interaction is also considerable. Further, we modeled an extended system by linking C2B4(BO)(n) through CC’ units for H-2 storage purpose. The energy difference between the highest occupied and the lowest unoccupied molecular orbitals gradually lessens with the increase in molecular length. Therefore, it can be tuned gradually by controlling the chain length, which may further open up their potency in the field of electronics.

First author: Geri, JB, A systematic examination of ligand basicity effects on bonding in palladium (0)- and palladium(II)-ethylene complexes, INORGANICA CHIMICA ACTA, 483, 191, (2018)
Abstract: The impact of ancillary ligand basicity on the binding and activation of ethylene in a series of [(L)Pd-0(C2H4)] and [(L)Pd-II(C2H4)](2+) complexes (where L = substituted 1,10-phenanthroline ligands) has been studied with density functional theory using natural bond orbital (NBO) analysis, energy decomposition analysis (EDA-NOCV), and molecular orbital (MO) analysis. With palladium(0), metrics of ethylene C=C bond activation are strongly correlated with increasing ligand basicity, including the C=C bond length and vibrational frequency, the magnitude of Pd(0) -> ethylene(pi*) NBO donation, and the Wiberg C=C bond index. In contrast, ethylene(pi) -> Pd(0) donation is not strongly influenced by ligand basicity, which is manifested in strong correlations between Pd(0) -> ethylene(pi*) donation and both C=C bond length and nu(CC). EDA-NOCV results show that the [(L)Pd-0](C2H4) interaction energy is dominated by Coulombic attraction and enhanced slightly with more electron-donating ligands. MO analysis demonstrates that a linear increase in the energy of the filled [(L)Pd-0] HOMO with ligand pK(a) is directly correlated with the enhanced [(L)Pd-0] -> ethylene(pi*) donation. For the [(L)Pd-II(C2H4)](2+) adducts, C=C bond lengthening and weakening is roughly half the amount observed with Pd-0, with ligand substitution having a negligible impact. NBO analysis confirms that ethylene activation is dominated by ethylene (pi) -> Pd-II donation, which is enhanced with electron-withdrawing ligands while Pd-II -> ethylene(pi*) donation decreases with less basic ligands. EDA-NOCV results show that the [(L)Pd-II](2+)-(C2H4) interaction energy is also dominated by Coulombic attraction and is enhanced by more electron-withdrawing ligands, largely as a result of a concurrent increase in ethylene(pi) -> [(L)Pd-II](2+) stabilization and a decrease in Pauli repulsion. Finally, MO analysis indicates an electrophilic ethylene moiety due to substantial stabilization of both the alkene pi- and pi*- orbitals through interaction with the [(L)Pd-II](2+) fragment.

First author: Alkan, F, Spin-orbit effects on the Te-125 magnetic-shielding tensor: A cluster-based ZORA/DFT investigation, SOLID STATE NUCLEAR MAGNETIC RESONANCE, 95, 6, (2018)
Abstract: Cluster-based calculations of Te-125 magnetic-shielding tensors demonstrate that inclusion of spin-orbit effects is necessary to obtain the best agreement of theoretical predictions with experiment. The spin-orbit contribution to shielding depends on the oxidation state and stereochemistry of the Te-125 site. Comparison of the performance of various density functionals indicates that GGA functionals behave similarly to each other in predicting NMR magnetic shielding. The use of hybrid functionals improves the predictive ability on average for a large set of Te-125-containing materials. The amount of Hartree-Fock exchange affects the predicted parameters. Inclusion of larger Hartree-Fock exchange contributions in hybrid functionals results in larger slopes of the correlation between calculated magnetic-shielding and experimental chemical-shift principal components, by 10-15% from the ideal value.

First author: Datsenko, VP, Cyclooctadiene iridium complexes [Cp*Ir(COD)X](+) ( X = Cl, Br, I): Synthesis and application for oxidative coupling of benzoic acid with alkynes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 874, 7, (2018)
Abstract: The cyclooctadiene iridium complexes [Cp* Ir(COD) X] PF6 ([1a-c] PF6; X = Cl, Br, I) were synthesized by reactions of Cp* Ir(COD) with halogens followed by a counterion exchange. The cyclooctadiene in these complexes is a thermally labile ligand. Complex [1b] PF6 reacts with trimethylphosphite to give [Cp* Ir {P(OMe)(3)}(2)Br]PF6([2]PF6) as a result of the cyclooctadiene replacement. The refluxing of [1b] PF6 in 1,2-dichloroethane affords the dimeric iodide [Cp*IrI2](2). The structures of [1b] PF6, [2] PF6 and [Cp* IrI2](2) were determined by X-ray diffraction. The IreCOD bonding in [1a-c] thorn and the related non-methylated complexes was analyzed by energy decomposition analysis. In the presence of silver salts, complexes [1a-c] PF6 (at 2.0 mol % loading) catalyze the oxidative coupling of benzoic acid with 1-phenyl-1-propyne in methanol at 60 degrees C to selectively give 4-methyl-3-phenylisocoumarin (3) or with diphenylacetylene in o-xylene at 160 degrees C to afford 1,2,3,4-tetraphenylnaphthalene (4).

First author: Xemard, M, Lanthanidocenes: Synthesis, Structure, and Bonding of Linear Sandwich Complexes of Lanthanides, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 14433, (2018)
Abstract: The Article presents the synthesis, structure, and bonding of a series of neutral and linear sandwich compounds with the cyclononatetraenyl (Cnt) ligand and divalent lanthanides. These compounds account for the emergence of the lanthanidocene series in reference to the ferrocene and uranocene. The synthetic strategy uses the solubility difference between two conformational isomers of the ligand, as well as the isomerization of the compounds induced by solvent coordination, yielding the isomorphous and isostructural neutral and rigorously linear sandwich complexes. The molecular structures feature a Cnt-Ln-Cnt angle of 180 degrees and a ring size close to the Cnt-Cnt(centroid) distance. A qualitative molecular orbital diagram is provided, in D-9d symmetry, and DFT calculations enforce the bonding model.

First author: Li, JB, Modulating stability of functionalized fullerene cations [R-C-60](+) with the nature of R-group, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 2385, (2018)
Abstract: In this study, the first comprehensive theoretical investigation of the stability of functionalized fullerene-based cations [R-C-60](+) and its relationship with the nature of the attached R-group was performed. C-60-Fullerene core was functionalized with an alkyl group of different length (R = (CH2)(n)CH3, where n = 0-9). This set was further complemented by bulky isopropyl and tert-butyl and conjugated phenyl groups. A detailed study of the relative stability of target cationic species was accompanied by in-depth investigation of their electronic structure and aromaticity using a large set of descriptors of different nature. The stability of target species was considered with respect to two alternative and competing mechanisms of bond breaking, namely, heterolytic ([R-C-60](+) -> R+ + C-60) and homolytic ([R-C-60](+) -> R-center dot + C-60(+center dot)) ones. The transformation of strained sp(2)-carbon atom in unperturbed C-60-fullerene to nonconstrained tetrahedral sp(3)-type in functionalized derivatives was found to be the driving force for the formation of its functionalized cations. In spite of the fact that all systems under consideration were found to be corresponding to local minima on corresponding potential energy surfaces, the functionalization of C-60-core with the smallest and simplest methyl group resulted in most stable compound, as evaluated by bonding energy between R+ and fullerene fragment (in the light of both mechanisms). Subsequent elongation of the alkyl chain or introducing bulky groups led to notable decrease of the bonding energy and, as consequence, of the stability within the framework of heterolytic bond cleavage, whereas homolytic pathway assumes opposite-slight increase of stability along with lengthening of the R-group. The orbital interaction (Delta E-orb) was identified as the main driving force for these trends. In general, the homolytic path was found to be dominating for small-length R-groups such as those with n = 0 and 1. At n = 2, heterolytic and homolytic pathways are equally probable (the difference in corresponding bonding energies is about 1 kcal/mol). However, when the alkyl chain becomes longer (n = 3-9), the cationic bond cleavage appears as the most energetically favorable.

First author: Joy, J, Halogen bond shortens and strengthens the bridge bond of [1.1.1]propellane and the open form of [2.2.2]propellane, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 25792, (2018)
Abstract: Detailed electronic structural analysis of [1.1.1]propellane and the open form of [2.2.2]propellane, especially their highest occupied molecular orbital (HOMO), shows the existence of significant electronic congestion at their bridge bond. The HOMO of [1.1.1]propellane is a spread-out orbital of its inverted tetrahedral bridgehead atoms. The HOMO of the open form of [2.2.2]propellane is an anti-bonding combination of its bridgehead atoms due to the stabilizing through-bond interaction. This unique spatial disposition of the HOMO enables a high electron density at the bridgehead atoms. Herein, we utilize the electron scavenging power of halogen bond donors to extract a fraction of destabilizing electrons from the bridge bond with the aim to alleviate its electronic congestion, which results in shortening and strengthening of the bridge bond with a reduction in the bond order. This result answers the seminal question raised by K. B. Wiberg in 1983, how can one have a relatively strong bond’ without much bonding character?

First author: Wessing, J, The Mackay-Type Cluster [Cu43Al12](Cp*)(12): Open-Shell 67-Electron Superatom with Emerging Metal-Like Electronic Structure, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57, 14630, (2018)
Abstract: The paramagnetic cluster [Cu43Al12](Cp*)(12) was obtained from the reaction of [CuMes](5) and [AlCp*](4) (Cp*-eta(5)-C5Me5; Mes = mesityl). This all-hydrocarbon ligand-stabilized M-55 magic atom-number cluster features a Mackay-type nested icosahedral structure. Its open-shell 67-electron superatom configuration is unique. Three unpaired electrons occupy weakly antibonding jellium states. The situation prefigures the formation of a conduction band, which is in line with the measured temperature-independent magnetism. Steric protection by twelve Cp* ligands suppresses the intrinsic polyradicalar reactivity of the Cu43Al12 core.

First author: Silva, TC, Structure and bonding in NbX5 X = (F, Cl, Br and I) complexes: a molecular orbital perspective in the C-H bond activation, THEORETICAL CHEMISTRY ACCOUNTS, 137, 14630, (2018)
Abstract: In the present work, theoretical studies of the reactivity and stability of the NbX5 complexes (X = F, Cl, Br and I) were carried out in the methane C-H bond activation. To study the chemical bonds formation of these complexes, an energy decomposition analysis was performed together with QTAIM calculations. The main results indicated that the interaction and binding energies are higher for NbF5 in relation to the halogen series. The niobium complexes gaps are influenced by the electron-egativity of the halogens and the Nb-X bonding lengths. According to the energy diagram, the electrons less connected to the bond are sigma Nb-I; on the other hand, the best electron acceptor is sigma*Nb-F. The QTAIM calculations confirmed stronger Nb-X chemical bonds in NbF5 complexes. Regarding the reactivity of the niobium complexes, the overall results indicate better thermodynamic and kinetic conditions for the NbF5 complex.

First author: Lepetit, C, Pentacoordinated, square pyramidal cationic PCP Ni(II) pincer complexes: ELF and QTAIM topological analyses of nickel-triflate interactions, THEORETICAL CHEMISTRY ACCOUNTS, 137, 14630, (2018)
Abstract: A previous report introduced a new series of cationic nickel(II) complexes ligated by PCP-type pincer ligands featuring a charge-bearing imidazoliophosphine binding moiety and described their catalytic reactivities in hydroamination of nitriles into amidines. Solid-state characterization of the cationic acetonitrile adducts [(R-PIMIOCOP+)Ni(NCMe)(triflate)](+) (R-PIMIOCOP+=(P),(C),(P)-{2-(R2PO),6-(R2PC4H5N2)C6H3}; R=i-Pr, [1](+); Ph, [2](+)) carried out in this follow-up study showed a distorted square pyramidal geometry and a Ni-triflate distance that was shorter than the sum of the Ni and O van der Waals radii, features suggestive of an unusual pentacoordination at the Ni(II) center. In contrast, the related aquo adduct [(i-Pr-PIMIOCOP+)Ni(OH2)(triflate)](+), [3](+), displayed a more conventional square planar geometry. Detailed structural comparisons and theoretical analyses conducted on these and related compounds have allowed a thorough examination of the Ni-triflate interactions in this family of complexes. Thus, topological analysis of the electron localization function (ELF) and quantum theory of atoms in molecules (QTAIM) showed that the Ni-triflate interaction is mostly ionic in nature, but has a weak covalence degree. The monosynaptic V(Ni) subvalence basin of nickel is indeed the ELF signature of the covalence degree of the ionic Ni-O bond, which can be quantified by the negative QTAIM energy density at the Ni-O bond critical point and by the absolute value of the ELF covariance . The ionic character of the Ni-O bond is also reflected in an energy decomposition analysis, showing that this interaction is mostly electrostatic in nature. The computational analyses carried out on this family of complexes provide valuable insight into the character and relative strengths of various Ni-ligand interactions, and allow a number of useful conclusions, including the following: (1) significant Ni-anion interactions at the apical site are observed only with pincer-type ligands featuring at least one cationic imidazoliophosphine binding moiety; (2) these primarily electrostatic Ni-O interactions gain increasing covalence degree when different pincer backbone, co-ligand L, or counter-anions are introduced to enhance the electron deficiency of the Ni(II) center.

First author: Alkan, F, TD-DFT and TD-DFTB Investigation of the Optical Properties and Electronic Structure of Silver Nanorods and Nanorod Dimers, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 23639, (2018)
Abstract: Here, we perform theoretical investigation using time-dependent density functional theory (TD-DFT) and time-dependent density functional tight binding (TD-DFTB) for the electronic structure and optical properties of silver nanorods. TD-DFTB generally performs well for the accurate description of optical properties with respect to the – m size and type of dimer assembly of silver nanorods compared to TD-DFT. However, the energies and intensities of the longitudinal and transverse peaks of the nanorods are somewhat underestimated with TD-DFTB compared to the values calculated at the TD-DFT level. By exploiting the computational efficiency of TD-DFTB, we also extend our investigation to longer nanorods and their dimers containing up to similar to 2000 atoms. Our results show that the coupling between nanorods and the resulting optical properties of the dimer assemblies are quite dependent on the length of the monomers. In all cases, the energy shifts in dimers as a function of the gap distance deviate significantly from the dipole-dipole interaction model. Moreover, a comparison of the best-fit curves for the dependence of the fractional shifts (Delta lambda/lambda(0)) on nanorod length indicates that the parameters of the plasmon ruler equation depend on the length of the nanorods and the type of the assembly rather than approaching a universal value. These insights are enabled by the computational efficiency of TD-DFTB and its ability to treat quantum mechanical effects in large nanorod dimer systems.

First author: Foroutan-Nejad, C, Buckyball Difluoride F-2(-)@C-60(+)-A Single-Molecule Crystal, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57, 13931, (2018)
Abstract: We report the F-2@C-60 system as the first example of an endohedral fullerene in which C-60 acts as a cation C-60(+) interacting with endohedral anion, F-2(-). Our state-of-the-art computations reveal that in F-2@C-60, despite of the known high electron affinity of C-60, an electron is transferred from C-60 to F-2 resulting in the F-2(-)@C-60(+) system. The F-F bond length in F-2@C-60 is substantially longer than in free F-2, which is the result of electron-transfer to the antibonding sigma(u) molecular orbital of F-2. Interestingly, although there is a full charge-transfer of one electron between C-60 and F-2, only negligible delocalized covalent interactions are found between F-2(-) and C-60(+) which is a reminiscent of ionic crystals. Therefore, F-2(-)@C-60(+) can be considered as a single-molecule crystal. The other encapsulated halogens in C-60 do not show such behavior.

First author: Hornung, J, Suppressed Phosphine Dissociation by Polarization Effects on the Donor-Acceptor Bonds in [Ni(PEt3)(4-n) (ECp*)(n)] (E = Al, Ga), INORGANIC CHEMISTRY, 57, 12657, (2018)
Abstract: A series of heteroleptic complexes [Ni(PEt3)(4-n)(ECp*)(n)] (E = Al, Ga, Cp* = pentamethylcyclopentadienyl, n = 0-4) was prepared and characterized by experimental as well as computational means. The series of compounds was studied with respect to ligand dissociation processes which are fundamental for reactivity. In contrast to the homoleptic complexes [Ni(PR3)(n)] phosphine dissociation is remarkably suppressed in the heteroleptic title complexes. Single crystal X-ray structures as well as density functional theory calculations reveal a gradual decrease of the Ni-PEt3 distances with increasing number of coordinated group-13 ligands ECp*. Accordingly, variable-temperature UV-vis studies of [Ni(PEt3)(4-n)(AlCp*)(n)] in solution indicate no ligand dissociation equilibrium for n >= 2. Energy decomposition analysis with the natural orbital for chemical valence extension shows higher Ni-P interaction energies for [Ni(PEt3)(4-n)(AlCp*)(n)] than for [Ni(PEt3)(4)] which is mainly a result of an increase in columbic attraction forces induced by Ni-PEt3 bond polarization upon ECp* coordination.

First author: Hayami, M, RAQET: Large-scale two-component relativistic quantum chemistry program package, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 2333, (2018)
Abstract: The Relativistic And Quantum Electronic Theory (RAQET) program is a new software package, which is designed for large-scale two-component relativistic quantum chemical (QC) calculations. The package includes several efficient schemes and algorithms for calculations involving large molecules which contain heavy elements in accurate relativistic formalisms. These calculations can be carried out in terms of the two-component relativistic Hamiltonian, wavefunction theory, density functional theory, core potential scheme, and evaluation of electron repulsion integrals. Furthermore, several techniques, which have frequently been used in non-relativistic QC calculations, have been customized for relativistic calculations. This article introduces the brief theories and capabilities of RAQET with several calculation examples.

First author: Kysliak, O, [PtZn2Ge18(Hyp)(8)] (Hyp = Si(SiMe3)(3)): A Neutral Polynuclear Chain Compound with Ge-9(Hyp)(3) Units, INORGANIC CHEMISTRY, 57, 12603, (2018)
Abstract: The reaction of [ZnGe18(Hyp)(6)] (Hyp = Si(SiMe3)(3)) with Pt(PPh3)(4) gives the neutral polynuclear complex of Ge-9(Hyp)(3) units [HypZn-Ge-9(Hyp)(3)-Pt-Ge-9(Hyp)(3)-ZnHyp], 1. Within 1, the central Pt atom is bound eta(3) to both Ge-9(Hyp)(3) units to which further ZnHyp units are bound again, symmetric eta(3), to the other side of the Ge-9(Hyp)(3) units, leading to the longest chain compound exhibiting Ge-9(Hyp)(3) units that is known to date. Dissolved crystals of 1 give a violet solution, showing an absorption maximum around 543 nm. Further UV-vis investigations on different MxGe(9)(Hyp)(3) compounds show that the absorption maximum depends on the number of transition metal atoms bound to the Ge-9(Hyp)(3) unit, which is supported by TD-DFT calculations.

First author: Gao, YJ, QM and ONIOM studies on thermally activated delayed fluorescence of copper(I) complexes in gas phase, solution, and crystal, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 24955, (2018)
Abstract: Herein, we have employed B3LYP and TD-B3LYP methods with the QM/ MM approach to study the thermally activated delayed fluorescence (TADF) phenomenon of two Cu(I) complexes bearing 5-(2-pyridyl)-tetrazolate (PyrTet) and phosphine (POP) ligands in the gas phase, solution, and crystal form. On the basis of spectroscopic properties, ground-and excited-state geometric and electronic structures, and related radiative and nonradiative rates, we have found that (1) the S1 and T1 excited states have clear metal-to-ligand charge transfer character from the Cu(I) atom to the PyrTet group; (2) the S1 and T1 states have a very small energy gap DES1-T1, less than 0.18 eV, which makes the forward and reverse intersystem crossing ISC and rISC processes between the S1 and T1 states very efficient; and (3) the low-frequency vibrational modes related to the torsional motion of the POP and PyrTet groups are found to have significant Huang-Rhys factors and are responsible for the efficient ISC and rISC rates. However, the corresponding Huang-Rhys factors are remarkably suppressed in the crystal compared with those in the gas phase and in solution due to the rigidity of the crystal surroundings; as a result, the ISC and rISC rates are accordingly reduced slightly in the crystal. This comparison also demonstrates that the surrounding effects are very important for modulating the photophysical properties of the Cu(I) complexes. Finally, our work gives helpful insights into the TADF mechanism of the Cu(I) compounds, which could assist in rationally designing TADF materials with excellent performance.

First author: Cao, GJ, A dinuclear Cu(i)-mediated complex: Theoretical studies of the G(2)Cu(2)(4+) cluster ion, JOURNAL OF CHEMICAL PHYSICS, 149, 24955, (2018)
Abstract: Recently, the T-Hg(ii)(2)-A base pair containing two equivalents of Hg(ii) has been prepared and characterized experimentally, which implies that there might exist considerable stable metal-mediated base pairs holding two neighbouring metal centers. Here we report a quantum chemical study on geometries, electronic structures, and bonding of various G(2)Cu(2)(4+) (G = guanine) isomers including one di-copper(i) unit. Different density functional methods [Becke 3-parameter-Lee-Yang-Parr, Perdew Becke Ernzerhof, Becke Perdew, Density Functional Theory with Dispersion Corrections (DFT-D)] assign ambiguous relative energies to these isomers with the singlet and triplet states. Highlevel ab initio [domain-based local pair natural orbital (DLPNO) coupled-cluster with single and double excitations and DLPNO-coupled-cluster with single, double, and perturbative triple excitations] calculations confirm that the lowest-lying isomer of theG(2)Cu(2)(4+) ion has C2h symmetry with the singlet state and is comparable to the singly and doubly charged homologues (G(2)Cu(2)(+) and G(2)Cu(2)(2+)). The extended transition state (ETS)-natural orbitals for the chemical valence (ETS-NOCV) calculations point out that it has larger instantaneous interaction energy and bond dissociation energy than the corresponding singly and doubly charged complexes due to its relatively stronger attractive energies and weaker Pauli repulsion. The orbital interactions in the quadruply charged cluster chiefly come from Cu-2(4+) <- G…G pi donations. The results may help the understanding of the bonding properties of other potential metal-base pair complexes with the electron transfer. Published by AIP Publishing.

First author: Heshmat, M, Unraveling the Origin of Solvent Induced Enantioselectivity in the Henry Reaction with Cinchona Thiourea as Catalyst, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 7974, (2018)
Abstract: In this work, we report an energy decomposition and electronic structure analysis using DFT calculations for the C-C coupling step in the Henry reaction with cinchona thiourea as catalyst and DMF solvent to unravel the origin of enantioselectivity. We found that the conformation of flexible thiourea moiety is affected by the solvent, and in the preferred conformation of thiourea in strong Lewis basic DMF solvent, the N-H sites are in the opposite direction, i.e., in trans conformation. Hence, the thiourea moiety acts via single hydrogen bonding with substrates. The conformation of the substrates with respect to the forming C-C bond plays critical role to increase orbital interaction between two substrates and enhances hydrogen bond strength between substrates and catalyst, which in turn stabilizes the positive charge developing on the catalyst at the transition state for one of the enantiomers (S). Thus, the enantioselectivity has electronic structure origin. The stronger H-bond formation in the S enantiomer has been confirmed by the calculated IR spectra and is in agreement with thus far experimental and computational results.

First author: Wang, GC, Vinyltrifluoroborate Complexes of Silver Supported by N-Heterocyclic Carbenes, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 122, 4142, (2018)
Abstract: Silver complexes involving vinyltrifluoroborate, (IPr)Ag(CH2=CHBF3) (4), [(IPr)(2)Ag][CH2=CHBF3] (5), (SIPr)Ag(CH2=CHBF3) (6) and (IPr*)Ag(CH2=CHBF3) (7) have been synthesized by using (NHC)AgNO3 [NHC = IPr (1), SIPr (2) and IPr* (3)] and K(CH2=CHBF3) in a metathesis process. NMR spectroscopic details of 1-7 and X-ray crystal structures of compounds 5-7 as well as that of a precursor (IPr)AgNO3 are reported. Compounds 6 and 7 are more stable in solution compared to 4 (which forms 5) indicating a supporting ligand effect in the stability of monomeric (NHC)Ag(CH2=CHBF3). Calculated metal-ligand binding energies show that [CH2=CHBF3](-) is a significantly better ligand for Ag-I than CH2=CH2 or isoelectronic CH2=CHCF3. IPr, SIPr and IPr* carbenes coordinate to Ag(CH2=CHBF3) moiety forming silver adducts 4, 6 and 7, with binding energies of about -72.1, -72.1 and -83.8 kcal/mol, respectively. The C=C bond length of [CH2=CHBF3](-) (calculated value of 1.341 angstrom) increases upon coordination to the silver ion. Experimental data show a similar trend for structurally characterized 6 and 7. Electrostatic attraction dominates the bonding between the alkene ligand [C2H3BF3](-) and the metal fragments [Ag(IPr)](+) and [Ag(SIPr)](+) in 4 and 6. The strongest orbital interaction involves sigma-donation from the occupied -orbital of the [C2H3BF3](-) ligand to the vacant orbital of the metal fragment, while Ag-I[C2H3BF3](-) -backbonding is relatively weak but not insignificant.

First author: Kawano, K, An Ethynylene-Bridged Pentacene Dimer: Two-Step Synthesis and Charge-Transport Properties, CHEMISTRY-A EUROPEAN JOURNAL, 24, 14916, (2018)
Abstract: A rigid and planar ethynylene-bridged pentacene dimer (PenD) was synthesized from pentacenequinone in two steps, skipping the conventional stepwise approach. A brickwork motif in the single crystal shows two-dimensionally extended electronic interaction in the solid state. Highly crystalline dip-coated films exhibited average hole mobility of 0.24 cm(2) V-1 s(-1), comparable to that of the single-crystal organic field-effect transistors. This discovery and understanding of the reaction for the facile synthesis of ethynylene-bridged pi-conjugated systems enables to the synthesis of a wide range of organic semiconducting materials.

First author: Ryu, H, Pitfalls in Computational Modeling of Chemical Reactions and How To Avoid Them, ORGANOMETALLICS, 37, 3228, (2018)
Abstract: Quantum chemical molecular modeling has become a standard tool in organometallic chemistry. In particular, density functional theory calculations are now indispensable for investigating the mechanism of even complex reactions and deliver precise energies of intermediates and transition states. Because software packages have become user-friendly and are widely available, even nonexperts can now produce high-quality computer models. In this tutorial, we highlight nontrivial mistakes, misconceptions, and misinterpretations often encountered when producing models of a chemical reaction that can lead to wrong conclusions. The reasons for these errors are conceptually explained in simple terms, and remedies are offered.

First author: Rodriguez, M, Electrocatalytic performance of different cobalt molybdate structures for water oxidation in alkaline media, CRYSTENGCOMM, 20, 5592, (2018)
Abstract: Cobalt molybdates with different crystalline structures, i.e., alpha, beta, and hydrated (H)-CoMoO4, were synthesized, and their electrocatalytic activities were thoroughly examined for catalyzing the oxygen evolution reaction (OER) in alkaline media. The material characteristics were associated with the electrocatalytic properties by evaluating the CoMoO4 crystal structures (XRD and Raman), morphologies (TEM), and electrochemical features (electrochemically active surface area, roughness factor, electrochemical impedance, Tafel analysis, and controlled -current electrolysis). These combined findings revealed that the electrocatalytic performance is greatly influenced by the crystalline structures of CoMoO4, following the order alpha-CoMoO4 > H-CoMoO4 > beta-CoMoO4. The H-CoMoO4 catalysts crystallized in the triclinic space group, P (1) over bar with Z = 4. On the other hand, the alpha- and beta-CoMoO, catalysts exhibited a monoclinic structure, C2/m (#12), with Z = 8. In the OER experiments, alpha-CoMoO4 showed an overpotential of 0.43 +/- 0.05 V compared to the 0.51 +/- 0.05 V and 0.56 +/- 0.04 V exhibited by the H-CoMoO4 and beta-CoMoO4 catalysts, respectively, to achieve 10 mA cm(-2). All CoMoO4 structures displayed stability for at least 6 h at a controlled current density of 10 mA cm(-2). Finally, computational simulations indicate that the coexistence of Co and Mo ions in edge-shared octahedral sites of alpha-CoMoO4 may favor the interaction between the 0 atom of the water molecule and the metal adsorption sites due to its surface being electronically less dense than beta- and H-CoMoO4 surfaces, thus resulting in its higher performance for OER.

First author: Huynh, W, Solid-state Sc-45 NMR studies of Cp*Sc-2-X and Cp*2ScX(THF), DALTON TRANSACTIONS, 47, 13063, (2018)
Abstract: Cp*Sc-2-X, where X is a halide, were synthesized and studied by solid-state Sc-45 NMR to determine how the Sc-X bond affects quadrupolar NMR parameters. The experimental quadrupolar coupling constants (C-Q) show that the fluoride has the largest coupling constant and that the iodide has the smallest coupling constant. DFT analysis of this data indicates that the C-Q of these compounds is related to core scandium and halide orbitals, which is related to polarizability of the halide and the Sc-X distance. Cp*2ScX(THF) were also investigated by solid-state Sc-45 NMR spectroscopy, and have much smaller C-Q values than the base-free halides. This is related to the change in structure of the THF adduct and occupation of orbitals of -symmetry that reduce C-Q.

First author: Hu, SX, Theoretical studies on the oxidation states and electronic structures of actinide-borides: AnB(12) (An = Th-Cm) clusters, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 23856, (2018)
Abstract: As B-12 clusters exhibit significant structural stability due to double aromaticity, metal doped-B-12 clusters often prefer a half sandwich structure. Herein, we report a systematic theoretical study on the geometric and electronic structures, and chemical bonding of the half sandwich AnB(12) (An = Th to Cm) clusters to explore the stability and extent of covalency of the An-B bonds of these actinide borides. We have shown that in the gas-phase clusters, the significant stability of AnB(12) is determined by electrostatic and orbital interactions between the An 5f6d7s orbitals and pi-type molecular orbitals from B 2p orbitals of the B-12 unit. A change-over of An-B bond length from An = Th to Cm is found at An = Pa as a result of actinide contraction combined with weakening An-B bonding due to an energy decrease and orbital localization of the 5f orbitals. Consistently, the oxidation states of the An atoms at first increase from Th(f(0))(IV) to pa(f(0))(V), and then due to the 5f-AO contraction, they smoothly decline to U(f(2))(IV), Np(f(4))(III) and Pu(f(5))(III), and then eventually to Am(f (7))(II) but Cm(f(7))(III), both with a half-filled 5f shell.

First author: Islam, S, Electronic structure and intramolecular interactions in three methoxyphenol isomers, JOURNAL OF CHEMICAL PHYSICS, 149, 23856, (2018)
Abstract: Electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers have been studied using core X-ray photoelectron spectroscopy and quantum mechanical calculations. The structural calculations are benchmarked against published calculations of enthalpy of formation and rotational constants, and published experimental data. The good agreement obtained confirms the accuracy of the results. A single rotamer of each isomer was then selected and the C 1s photoelectron spectra calculated and compared with experiment. Good agreement is obtained, and the calculations were extended to investigate the effects of conformation. For 3-methoxyphenol, the difference in the C 1s binding energy of the conformers is small, <0.15 eV. For 2-methoxyphenol, whose ground state includes an OH center dot center dot center dot OCH3 hydrogen bond, the higher energy rotamers show the largest shifts for the methyl carbon atom, whereas the ring carbon bonded to OH hardly shifts The theoretical differences in core level energies of the two rotamers of 4-MP are still smaller, <0.05 eV. By comparing calculations neglecting or including final state relaxation upon ionization, the relaxation energy of the phenyl carbons in all isomers is found to be similar to 0.5 eV, while that of the methyl groups is similar to 1.3 eV. Published by AIP Publishing.

First author: Mattock, JD, Boron Centres Allow Design, Control and Systematic Tuning of Neutral Homoaromatics for Functionalization Purposes, CHEMPHYSCHEM, 19, 2525, (2018)
Abstract: Homoaromatic compounds are currently viewed mainly as an interesting novelty with little to no practical application. Based on calculations within density functional theory, we show that the unique charge redirection properties of tricoordinate boron, along with it being isolobal to a carbocation, allow for a larger range of two-electron donors to be utilized, leading to the rational design of homoaromatic compounds better suited to functionalization. Among others, these compounds show a strong dependency on the relative positioning of the hetero-atoms within the ring system, a modulation control rendered possible by the insertion of the boron centres.

First author: Liu, SY, Comprehensive Theoretical Study of Interactions between Ag+ and Polycyclic Aromatic Hydrocarbons, CHEMPHYSCHEM, 19, 2579, (2018)
Abstract: The first comprehensive and systematic theoretical exploration of the bonding nature and energetics of the interactions between Ag(I) cation and a wide set of -ligands was accomplished. This set ranges from simple ethylene and aromatic benzene to planar and curved polyaromatic molecules and to closed-cage C-60-fullerene. Simultaneous application of two energy decomposition schemes based on different ideas, namely, NBO-NEDA and EDA-NOCV, allowed shedding light on the nature of the bonding and its energetics. Importantly, our results unambiguously indicate that reliable results can be obtained only if using more than one theoretical approach. All methods clearly revealed the importance and even domination of the ionic contribution of the bonding in all adducts, except for those of C-60-fullerene, in which the covalent component was found to be the largest. Subsequent decomposition of the orbital term onto components showed that it consists of two major parts: (i) ligand-to-metal ((C=C)s(Ag), LM) and (ii) metal-to-ligand (ML) terms, with significant domination of the former. Interestingly, while the LM component is essentially the same for all systems considered, the nature of the ML one depends on the coordination site of the polycyclic aromatic hydrocarbons (PAH). In most of adducts, the ML can be described as d(xy)(Ag)(*)(C=C) donation, whereas for systems [Ag-spoke-C12H8](+) and [Ag-spoke-C20H10](+) it corresponds to the d(z)(2)(Ag)(*)(C=C) type of interaction. As a result, the coordination mode in such complexes is switched from (2)-type to (1). Thus, the nature of the bonding, its energetics and even coordination mode in adducts of unsaturated hydrocarbons with late transition metal cations should be considered as a function of many components, which primarily includes the topology and aromaticity of the (poly)aromatic molecules.

First author: Stoliaroff, A, PyDEF 2.0: An Easy to Use Post-treatment Software for Publishable Charts Featuring a Graphical User Interface, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 2251, (2018)
Abstract: Herein we present an open-source program automating the post-treatment of solid-state ab initio calculations performed with VASP, the most used solid-state simulation package. The program plots Density of States (DOS) and Band Diagrams, enabling the user to conduct efficiently a detailed study of electronic properties of a material. Our tool includes a complete module dedicated to point defects studies, proposing various corrections which can be activated at will and innovative property calculations such as defect concentrations. This is the first program of its kind to offer a direct plot of the stability domain of the studied matrix with respect to its components’ chemical potentials. We also implemented the retrieval of optical indices (1) and (2), the computation of the refractive and extinction coefficients (n, k) and the reflexivity R of the material. All features of the piece of software are available through a thoroughly designed user-friendly, elegant and efficient Graphical User Interface (GUI) to be accessible to material scientists with various expertises, from both the experimental and theoretical sides. All figures are of publishable quality and can be customized as desired.

First author: Duan, CB, High-Efficiency Blue Dual-Emissive Exciplex Boosts Full-Radiative White Electroluminescence, ADVANCED OPTICAL MATERIALS, 6, 2251, (2018)
Abstract: Regarding lighting application, the main challenges for white organic light-emitting diodes (WOLEDs) include the complicated structure, the high cost, and the low repeatability, which are attributed to the stringent requirement on the exciton allocation and utilization in multiradiation systems. Herein, an effective “full-radiation white emission (FRWE)” strategy for the dynamic exciton allocation is successfully demonstrated by the first dual-emissive blue-emitting exciplex mCP:pTPOTZ. On the basis of an ultrasimple trilayer structure and bimaterial/trimaterial systems, its blue, yellow, and white devices realize state-of-the-art performances. Especially, mCP:pTPOTZ supports its WOLEDs with ultralow driving voltages and extremely high efficiencies beyond 90 lm(-1) and 24%, accompanied by a negligible roll-off less than 10% at 1000 cd m(-2). This work not only establishes a feasible method to construct dual-emissive exciplex systems through the modulation of the donor-acceptor packing modes, but also demonstrates the superiority of FRWE strategy in 100% exciton harvesting and quenching suppression, which makes simple but high-performance WOLED-based lighting sources become a reality.

First author: Burns, CP, Towards understanding of lanthanide-transition metal bonding: investigations of the first Ce-Fe bonded complex, CHEMICAL COMMUNICATIONS, 54, 10893, (2018)
Abstract: The syntheses, structural, and magnetic characterization of three new organometallic Ce complexes stabilized by PyCp22- (PyCp22- = [2,6-(CH2C5H3)(2)C5H3N](2-)) are reported. Complex 1 provides the first example of a crystallographically characterized unsupported Ce-Fe bond in a molecular compound. Results from IR spectroscopy and computational analyses suggest weaker Fe Ce electron-donation than in a previously reported Dy-Fe bonded species.

First author: Yoneya, M, Monolayer Crystal Structure of the Organic Semiconductor 7-Decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 22225, (2018)
Abstract: The monolayer crystal phase structure of the organic semiconductor 7-decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene was theoretically investigated. On the basis of a transition model from the bilayer crystal structure obtained by X-ray diffraction to possible monolayer crystal structures, two model structures for the monolayer crystal, i.e., antiparallel and core-chain nanosegregated structures, were proposed. The carrier mobilities of these two monolayer crystal models were compared through theoretical calculations to obtain insight into the probable monolayer crystal structure model. The results show that the antiparallel monolayer crystal structure model is more probable than the nanosegregated model.

First author: Joshi, M, Counter-Intuitive Stability in Actinide-Encapsulated Metalloid Clusters with Broken Aromaticity, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 22469, (2018)
Abstract: Aromaticity has been traditionally used for decades to explain the exceptional stability of certain conjugated organic compounds. Only in the recent past, this concept has crossed the bounds of organic chemistry and been employed in understanding inorganic ring systems with conjugation. In the present work, actinide element-doped E-12(6-) (E = Sb, Bi) clusters formed from the combination of an actinide ion and aromatic Bi-4(2-) or Sb-4(2-) rings are thoroughly investigated using density functional theory to explore their geometric, electronic and bonding properties in comparison with the bare cluster. The aromatic E-4(2-) rings in the bare clusters lost their aromaticity due to loss in planarity of the E-4(2-) rings on interaction with the central atom/ion. Although the extent of nonplanarity of the three E-4(2-) rings is increased considerably on moving along the valence-isoelectronic series, Th4+-Pa5+-U6+-Np7+ in the doped clusters, the stability of the clusters is increased significantly. Valence-isoelectronic lanthanide ion-doped metalloid clusters, viz., La3+, Ce4+, Pr5+, and Nd6+ have also been investigated for the sake of comparison, among which experimental and theoretical study of [La(eta(4)-Sb-4)(3)](3-) cluster has been reported recently. The highlight of the entire investigation is that the metal atom/ion-doped clusters, nevertheless, displayed higher stability than the bare clusters in spite of losing their valuable aromatic stabilization. The various factors responsible for the stability of the lanthanide- and actinide-doped nonaromatic clusters including electronic shell-closing are elucidated in the present research.

First author: Krivdin, LB, Theoretical calculations of carbon-hydrogen spin-spin coupling constants, PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, 108, 17, (2018)
Abstract: Structural applications of theoretical calculations of carbon-hydrogen spin-spin coupling constants are reviewed covering papers published mainly during the last 10-15 years with a special emphasis on the most notable studies of hybridization, substitution and stereoelectronic effects together with the investigation of hydrogen bonding and intermolecular interactions. The wide scope of different applications of calculated carbon-hydrogen couplings in the structural elucidation of particular classes of organic and bioorganic molecules is reviewed, concentrating mainly on saturated, unsaturated, aromatic and heteroaromatic compounds and their functional derivatives, as well as on natural compounds and carbo-hydrates. The review is dedicated to Professor Emeritus Michael Barfield in view of his invaluable pioneering contribution to this field.

First author: Chen, J, H2O2 Oxidation by Fe-III-OOH Intermediates and Its Effect on Catalytic Efficiency, ACS CATALYSIS, 8, 9665, (2018)
Abstract: The oxidation of the C-H and C=C bonds of hydrocarbons with H2O2 catalyzed by non-heme iron complexes with pentadentate ligands is widely accepted as involving a reactive Fe-IV=O species such as [(N4Py)Fe-IV=O](2+) formed by homolytic cleavage of the O-O bond of an Fe-III-OOH intermediate (where N4Py is 1,1-bis(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine). We show here that at low H2O2 concentrations the Fe-IV=O species formed is detectable in methanol. Furthermore, we show that the decomposition of H2O2 to water and O-2 is an important competing pathway that limits efficiency in the terminal oxidant and indeed dominates reactivity except where only sub-/near-stoichiometric amounts of H2O2 are present. Although independently prepared [(N4Py)Fe-IV=O](2+) oxidizes stoichiometric H2O2 rapidly, the rate of formation of Fe-IV=O from the Fe-III-OOH intermediate is too low to account for the rate of H2O2 decomposition observed under catalytic conditions. Indeed, with excess H2O2, disproportionation to O-2 and H2O is due to reaction with the Fe-III-OOH intermediate and thereby prevents formation of the Fe-IV=O species. These data rationalize that the activity of these catalysts with respect to hydrocarbon/alkene oxidation is maximized by maintaining sub-/near-stoichiometric steady-state concentrations of H2O2, which ensure that the rate of the H2O2 oxidation by the Fe-III-OOH intermediate is less than the rate of the O-O bond homolysis and the subsequent reaction of the Fe-IV=O species with a substrate.

First author: Saielli, G, Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation, ADVANCED THEORY AND SIMULATIONS, 1, 9665, (2018)
Abstract: “Computational spectroscopy” refers to quantum chemistry protocols capable of predicting the electronic and/or magnetic spectra of molecules. The most common techniques used for structural assignment are infrared, electronic, and NMR spectroscopies. Chemists can normally deduce the chemical structure of an unknown substance by using a vast collection of empirical relationships linking the spectral features with the presence or absence of functional groups and, this part mostly by NMR, the connectivity between them and the relative stereochemistry. Computational spectroscopy is a powerful aid for structural elucidation when empirical relationships do not suffice to unambiguously assign the structure. In these cases, the calculated spectrum of a putative structure is compared with the experimental one and the match, or lack thereof, between the two, measured by several statistical parameters, indicates whether or not that structure is the correct one. Is it possible to extend such protocols to bulk phases of complex fluids, such as ionic liquids, rather than covalent molecules, in order to get insights into the average structure of the fluid? It is the aim of this Progress Report to highlight recent advances in this field through the discussion of specific case studies.

First author: Zawadzka, A, Diagnostic and control of linear and nonlinear optical effects in selected self-assembled metallophthalocyanine chlorides nanostructures, DYES AND PIGMENTS, 157, 151, (2018)
Abstract: In this paper we described a new self-assembly phenomenon of the metallophthalocyanine chlorides nanostructures and its influence on the linear optical properties as well as the Second Harmonic Generation process. The self-assembly phenomenon were achieved through an annealing process carried out immediately after the deposition process. The studied nanostructures were subjected to the annealing process for 24 h and the temperature of the process was equal to 525 K. We discussed experimental results and theoretical calculations of structural, linear and nonolinear optical properties for aluminum and gallium phthalocyanine chlorides. The linear and second-order nonlinear optical properties for these compounds were investigated at microscopic and macroscopic levels. The electric dipole moments and dispersion-free first hyperpolarizabilities were determined by quantum chemical calculations based on Density Functional Theory. Ab-initio quantum mechanical calculations (time-dependent Hartree-Fock method) for the studied metallophthalocyanine chlorides were carried out to compute the frequency-dependent first hyperpolarizabilities and second-order susceptibilities at the wavelengths used in SHG measurements. Our results shed light on the linear and nonlinear optical properties of the nanostructures. The results showed that second harmonic signal is strong and polarized, and this polarizing effect was achieved by controlling the arrangement of the molecules inside the formed nanostructures. Our results also reveal potential application of the nanostructures not only for nonlinear optics but also for thermal sensor devices.

First author: Miller, SA, A methodology for the photocatalyzed radical trifluoromethylation of indoles: A combined experimental and computational study, JOURNAL OF FLUORINE CHEMISTRY, 214, 94, (2018)
Abstract: A methodology for the direct introduction of the trifluoromethyl group on to indole scaffolds is presented. The procedure involves the use of sodium trifluoromethylsulfmate (Langlois reagent) as the source of the trifluoromethyl radical, and is performed photochemically with 2-tert-butylanthraquinone as a photocatalyst. The reaction has also been probed computationally. Reaction kinetics and molecular orbital analyses from our quantum chemical computations successfully predict and rationalize the formation of the experimentally observed product and, in the case of 1-methylbenzimidazole, even reproduce the same qualitative trends in regioisomer preference.

First author: Herman, J, Synthesis and properties of chosen 4-butyl-phenyltolane derivatives – On the influence of core substitution on birefringence, mesomorphic and dielectric properties, JOURNAL OF MOLECULAR LIQUIDS, 267, 511, (2018)
Abstract: The synthesis and characterization of new liquid crystal (LC) compounds based on 4-[(4-butyl-2,6-difluorophenyl)ethynyl]biphenyl core are described. New family of dielectrically positive compounds presents alternative molecular approach to the conventional LC design. Correlations between molecular structure and mesomorphic properties for compounds being isothiocyanato, cyano, trifluoromethoxy, chloro and fluoro terminated analogues as well as other known from the literature have been drawn. Additionally, the experimentally determined physical properties (birefringence, dielectric anisotropy) for presented derivatives of phenyl tolane are compared with DFT calculation’s results. Compounds are characterised by H-1 NMR spectroscopy and mass spectrometry (electron ionization) analysis. They show an enantiotropic nematic behavior in broad temperature range, confirmed by a polarizing thermomicroscopy, differential scanning calorimetry and dielectric spectroscopy. Detailed synthetic procedures are attached. Synthesized compounds stand as promising components of medium to highly birefringent liquid crystalline mixtures.

First author: Tahtinen, P, New Sulfur-Containing Polyarsenicals from the New Caledonian Sponge Echinochalina bargibanti, MARINE DRUGS, 16, 511, (2018)
Abstract: Arsenicin A (C3H6As4O3) was isolated from the New Caledonian poecilosclerid sponge Echinochalina bargibanti, and described as the first natural organic polyarsenic compound. Further bioguided fractionation of the extracts of this sponge led us to isolate the first sulfur-containing organic polyarsenicals ever found in Nature. These metabolites, called arsenicin B and arsenicin C, are built on a noradamantane-type framework that is characterized by an unusual As-As bonding. Extensive NMR measurements, in combination with mass spectra, enabled the assignment of the structure for arsenicin B (C3H6As4S2) as 2. The scarcity of arsenicin C and its intrinsic chemical instability only allowed the collection of partial spectral data, which prevented the full structural definition. After the extensive computational testing of several putative structures, structure 3 was inferred for arsenicin C (C3H6As4OS) by comparing the experimental and density functional theory (DFT)-calculated H-1 and C-13 NMR spectra. Finally, the absolute configurations of 2 and 3 were determined with a combined use of experimental and time-dependent (TD)-DFT calculated electronic circular dichroism (ECD) spectra and observed specific rotations. These findings pose great challenges for the investigation of the biosynthesis of these metabolites and the cycle of arsenic in Nature. Arsenicins B and C showed strong antimicrobial activities, especially against S. aureus, which is comparable to the reference compound gentamycin.

First author: Mazalov, LN, Investigation of electronic structure of {Nb2S4}(4+) clusters by XES, XPS and DFT calculations, POLYHEDRON, 153, 268, (2018)
Abstract: For the following compounds [Nb2S4(acac)(4)] (acac = acetylacetonate), K-4[Nb2S4(ox)(4)] (ox = oxalate) and Nb2S4Br4 containing dinuclear cluster core {(Nb4+)(2)(mu-S-2(2-))(2)}(4+) (simply (Nb2S4)(4+)) the electronic structure has been experimentally and theoretically investigated through X-ray emission (XES), X-ray photoelectron (XPS) spectroscopies and Density functional theory (DFT). The bonding and antibonding highest occupied molecular orbitals (HOMOs) observed in the X-ray emission spectra have been characterized by the analysis of overlap populations and the partial atomic composition considering the nature of the electron density distribution. Furthermore, the effective atomic charges have been determined.

First author: Zhang, Y, Insights on decomposition process of c-C4F8 and c-C4F8/N-2 mixture as substitutes for SF6, ROYAL SOCIETY OPEN SCIENCE, 5, 268, (2018)
Abstract: In recent years, many scholars have carried out studies on c-C4F8 and its gas mixture and found it has potential to be used as an environment-friendly insulating medium to replace SF6 in medium-voltage equipment. In this paper, the c-C4F8 and c-C4F6/N-2 gas mixture models were built to study its decomposition process by the combination of reactive molecular dynamics method and density functional theory. The yield of the main decomposition products, the reaction pathways and enthalpy under different temperatures were explored. It was found that the decomposition of c-C4F8/N-2 mainly produces CF2, F, CF3, CF, C, CF4 and C2F4, c-C4F8 can decompose to C2F4 by absorbing 43.28 kcal/mol, which is the main decomposition path and this process easily occurs under high temperature. There is a dynamic equilibrium process among the various produced radicals, which ensures the insulation performance of system to a certain extent. The decomposition performance of c-C4F8/N-2 mixture is better than that of pure c-C4F8 at the same temperature. Relevant results provide guidance for engineering application of the c-C4F8/N-2 gas mixture.

First author: Zaiter, A, Electronic structure and energy decomposition of binuclear transition metal complexes containing beta-diketiminate and imido ligands: spin state and metal’s nature effects, STRUCTURAL CHEMISTRY, 29, 1307, (2018)
Abstract: DFT calculations with full geometry optimization using BP86-D and OPBE functionals have been performed on series of [(BDI)M(NH)](2)(Bz) and [(BDI)M(NH)](2)(Tol) (M = Ti, V, Nb, Cr, Mn, Fe, Co, and Ni; BDI = beta-diketiminate; NH = imido group; Bz = benzene; and Tol = toluene) of various spin states (singlet S = 0, triplet S = 1, quintet S = 2, and singlet S = 0 of broken symmetry method). Depending on the metal nature and its electron count and the spin state, the six-membered ring in [(BDI)M(NH)](2)(Bz) and [(BDI)M(NH)](2)(Tol) adopts various hapticities that involve full or partial coordination, giving rise to a flat or a distorted ring, respectively. The NH2- imido group is linear or bent with respect to its sp or sp(2) hybridization acting as a six- or a four-electron donor, respectively. The (BDI)(-) anion is a bidentate ligand as a six-electron donor. The optimized geometries do not show direct metal-metal bonding and correspond to long separations. The optimized structures for Nb metal are comparable to the available experimental ones. The Ziegler-Rauk energy decomposition analysis scheme was employed to characterize the geometry distortion, the steric interaction (electrostatic and Pauli), and the orbital interaction terms in the total bonding energy. The results showed that the interaction terms in all the studied complexes are governed by one third covalent and two thirds ionic characters, which are in agreement with the Delta E-elstat (electrostatic) and Delta E-orb (orbital) contributions, respectively, into the total attractive interaction (Delta E-elstat + Delta E-orb).

First author: Ali, SM, Role of Ligand Straining in Complexation of Eu3+-Am3+ Ions by TPEN and PPDEN, Scalar Relativistic DFT Exploration in Conjunction with COSMO-RS, ACS OMEGA, 3, 13104, (2018)
Abstract: To search fort new ligands suitable for the separation of minor actinides (MA) from lanthanides (Ln) in nuclear waste reprocessing, theoretical (density functional theory) studies were carried out on the coinplexation (structures, bonding, and therinodynainics) of La3+ Sin(3+) Eu3+, and Am3+ complexes with moderately soft donor ligands TPEN [N,N,N ‘,N ‘-tetrakis(2-pyridylmethyl)ethylenediamine] and PPDEN [N,N,N ‘,N ”,N ”-pentakis(2-pyridylmethyl) diethylenetriamine] in aqueous and nitrobenzene solutions. B3LYP level of theory was used in conjunction with the conductor-like screening model for real systems (COSMO-RS). The metal ions in [M(NO3)(2)(TPEN)]NO3 and [M(NO3)(PPDEN)]-(NO3)(2), complexes were deca-coordinated with both TPEN and PPDEN. The enthalpy of the complexation with TPEN in an aqueous solution was found to be negative, indicating the exothermic nature of the reaction as observed in the experiments. The calculated values of free energy of complexation follow the experimental trend: AM(3+) > SM3+ > La3+ Furthermore, the calculated free energy with PPDEN is reduced compared to that with TPEN, which may be attributed to the ligand straining during complex formation, which is also reflected in greater residua’ charges on both the EU3+ and Am3+ central ions in the complexes of octadentate PPDEN compared to hexadentate TPEN. The experimental complexation selectivity of Am3+ over Eu3+ with TPEN is established by employing COSMO-RS. Furthermore, TPEN is Am3+-selective, whereas PPDEN is Eu3+-selective, which could be exploited for the efficient separation of MA from Ln.

First author: Saha, R, Stabilization of Boron-Boron Triple Bonds by Mesoionic Carbenes, ACS OMEGA, 3, 13720, (2018)
Abstract: Density functional theory-based computations are carried out to analyze the electronic structure and stability of B-2(MIC)(2) complexes, where MIC is a mesoionic carbene, viz., imidazolin-4-ylidenes, pyrazolin-4-ylidene, 1,2,3-triazol-5-ylidene, tetrazol-5-ylidene, and isoxazol-4-ylidene. The structure, stability, and the nature of bonding of these complexes are further compared to those of the previously reported B-2(NHC)(2) and B-2(cAAC)(2). A thorough bonding analysis via natural bond order, molecular orbital, and energy decomposition analyses (EDA) in combination with natural orbital for chemical valence (NOCV) reveals that MICs are suitable ligands to stabilize B-2 species in its (3)(1)Sigma(+)(g) excited state, resulting in an effective B-B bond order of 3. Their high dissociation energy and endergonicity at 298 K for the dissociations L-BB-L -> 2 B-L and L-BB-L -> BB + 2 L (L = Ligand) indicate their viability at ambient condition. The donor property of MICs is comparable to that of NHCMe. The orbital interaction plays a greater role than the coulombic interaction in forming the B-L bonds. The EDA-NOCV results show that the sum of the orbital energies associated with the (+, +) and (+, -) L ->[B-2]-> L sigma-donations is far larger than that of L ->[B-2]-> L pi-back donation. It also reveals that cAAC(Me) possesses the largest sigma-donation and pi-back donation abilities among the studied ligands, and the sigma-donation and pi-back donation abilities of MICs are comparable to those of NHCMe. Therefore, the present study shows that MICs would also be an excellent choice as ligands to experimentally realize new compounds having a strong B-B triple bond.

First author: Hu, SX, Electronic Structure and Chemical Bonding of [AmO2(H2O)(n)](2+/1+), ACS OMEGA, 3, 13902, (2018)
Abstract: Systematic americyl-hydration cations were investigated theoretically to understand the electronic structures and bonding in [(ArnO(2))(H2O)(n)(2+/1+) (n = 1-6) We obtained the binding energy using density functional theory methods with scalar relativistic and spin orbit coupling effects. The geometric structures of these species have been investigated in aqueous solution via an implicit solvation model. Computational results reveal that the complexes of five equatorial water molecules coordinated to americyl ions are the most stable due to the enhanced ionic interactions between the AmO22+/1+ cation and multiple oxygen atoms as electron donors. As expected, Am-O-water bonds in such series are electrostatic in nature and contain a generally decreasing covalent character when hydration number increases.

First author: Chong, DP, Computational study of polarizability anisotropies, CANADIAN JOURNAL OF CHEMISTRY, 96, 934, (2018)
Abstract: The dipole polarizabilities (alpha) and polarizability anisotropies (Delta alpha) of over 20 molecules are calculated to search for negative Delta alpha. The geometry of each molecule is first optimized at the level of CCSD(T)/cc-pVQZ. Then, the alpha tensors are computed both with CCSD(T)/daug-cc-pVTZ in Gaussian 09 and with the exchange-correlation potential V(x)c known as SAOP in the Amsterdam density functional theory program called ADF and a large basis set called QZ3P-3DIFFUSE. In addition to the popular formula of the Delta alpha(Raman) connected with Raman spectroscopy, we also present values of an alternative definition of the polarizability anisotropy Delta alpha(Kerr) connected with Kerr spectroscopy, recently proposed by Kampfrath and colleagues (2018. Chem. Phys. Lett. 692: 319). On one hand, the signs of many Delta alpha(Raman) are undetermined; on the other hand, we obtain negative Delta alpha(Kerr) for more than one-half of the small molecules studied. Of the 24 molecules studied, 18 have negative Delta alpha(Kerr).

First author: Michalczyk, M, Theoretical modeling of argentophilic interactions in [Ag(CN)(2)(-)](3) trimer found in a copper(II) complex of cis-1,2-diaminocyclohexane (Dach), [Cu (Dach)(2)-Ag(CN)(2)-Cu(Dach)(2)][Ag(CN)(2)](3), CHEMICAL PHYSICS LETTERS, 709, 11, (2018)
Abstract: Crystal structure study of a copper(II) complex of cis-1,2-diaminocyclohexane (Dach), [Cu(Dach)(2)-Ag(CN)(2)-Cu (Dach)(2)][Ag(CN)(2)](3) (1) reveals the presence of unsupported Ag center dot center dot center dot Ag center dot center dot center dot Ag interactions with the interatomic Ag center dot center dot center dot Ag distance of 3.230 angstrom. Detailed HF, MP2 and BLYP-D3 theoretical investigations of [Ag(CN)(2)(-)](3) trimer, together with AIM, NCI and EDA analyses verified these interactions as noncovalent Ag-Ag bonds with the magnitude of a weak hydrogen bond, mainly electrostatically and dispersively driven.

First author: Luo, YF, Influence of restricted rotation of small-sized substituent on phosphorescence efficiency for Pt(II) complexes: A theoretical investigation, ORGANIC ELECTRONICS, 61, 25, (2018)
Abstract: Herein, the radiative and non-radiative decay processes of six carborane-based Pt(II) complexes were explored with the help of the density functional theory and time-dependent density functional theory. In order to interpret the influence of non-metal heavy atoms on the phosphorescent quantum yields, the determined factors, i.e., the ZFS (zero-point filed splitting) parameters, radiative decay rate constants and photodeactivation mechanisms, were unveiled. The results indicate that the spin-orbital coupling effects can be slightly regulated via introducing the non-metal heavy atoms into the carborane. Also, the non-metal heavy atoms substituents could cause slightly decrease of the energy barriers between the (ES)-E-3 and (MC)-M-3 excited states, and thus, for Pt-6, a fast non-radiative decay process may occur. Moreover, compared with the Pt-1, the rotation of methyl in Pt-2 similar to 5, can be effectively restricted with the aid of hydrogen bonding and halogen bonding, which is beneficial for obtaining small non-radiative decay rate constants. Accordingly, it provides a strategy for realizing the restriction of small group rotation to achieve the high-efficient phosphorescent emitters.

First author: Wu, QY, Insight into the nature of M-C bonding in the lanthanide/actinide-biscarbene complexes: a theoretical perspective, DALTON TRANSACTIONS, 47, 12718, (2018)
Abstract: We have investigated M-C bonds in lanthanide and actinide complexes ML2 (M = Ce, Th, U, Np and Pu; L = C(PPh2 NMes)(2)) using scalar-relativistic theory. The M-C bonds possess typical sigma and pi bonding character, except for the nearly pi-only Th C bonds. The metal valence electrons significantly reside in the valence d and f orbitals for CeL2, UL2, NpL2 and PuL2, while for ThL2 most electron population is in 6d orbitals. The contribution of 6d orbitals to the An-C bonds decreases and that of 5f orbitals increases across the actinide series. OTAIM (quantum theory of atoms in molecules) and NBO (natural bond orbital) analyses confirm that the M-C bonds possess significant covalent character. This work provides insights into the contributions of d and f valence orbitals to M-C bonding. And inclusion of Np and Pu in this evaluation extends understanding to later actinides.

First author: Moitra, T, Intersystem crossing rate dependent dual emission and phosphorescence from cyclometalated platinum complexes: a second order cumulant expansion based approach, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 23244, (2018)
Abstract: Rates of intersystem crossing (k(ISC)) of two platinum(II) complexes containing acetylacetonate (acac) and extended cyclometalated ppy (Hppy = 2-phenylpyridine) (1) and thpy (Hthpy = 2-(2′ thienyl) pyridine) (2) ligands are calculated using the Condon approximation to the Golden Rule and employing the second-order cumulant expansion method. The emission wavelengths obtained at the RI-CC2 level for the lowest excited singlet (S-1) and triplet (T-1) states of the two complexes are well in agreement with the experimental results. Our analysis based on kISC evinces that the major pathway involved with the phosphorescence process in complex 1 arises from the S-1 -> T-2 intersystem crossing while the S-1 -> T-1 intersystem crossing is the key step towards the commencement of dual emission in complex 2. Furthermore, it is found that the different pathways are mostly guided by two factors namely, the energy gap and the spin-orbit interaction between the concerned states. Interestingly, the calculated k(ISC) for complex 1 is found to be 10(7) times larger than that of complex 2, which suggests a rapid depletion of the S-1 state population vis-a-vis radiative emission only by phosphorescence from the internally converted lowest excited triplet state while for complex 2, the relatively lower k(ISC) is attributed to the dual emission from this complex.

First author: Bennett, JA, Electrochemical Atomic Force Microscopy and First-Principles Calculations of Ferriprotoporphyrin Adsorption and Polymerization, LANGMUIR, 34, 11335, (2018)
Abstract: The adsorption and subsequent electrooxidative polymerization of ferriprotoporphyrin IX chloride (hemin; FePPCl) was investigated on highly ordered pyrolytic graphite, glassy carbon, and polycrystalline Pt electrodes using electrochemical atomic force microscopy, first-principles calculations, and cyclic voltammetry. Hemin was shown to readily adsorb to all three surfaces; however, it was more continuous over the carbon surfaces compared to the Pt surface. This disparity in adsorption appears to be a major contributing factor to differences observed between the electrodes following hemin electropolymerization. Despite differences in roughness and morphology, hemin polymerized as a continuous layer over each electrode surface. Periodic density functional theory calculations were used to model FePP (without Cl) on both the Pt(111) and graphite surfaces using the vdW-DF-optPBE functional to account for the dispersion interactions. Our calculations suggest that the FePP molecule chemisorbs to the Pt surface while at the same time exhibiting intramolecular hydrogen bonding between the carboxylic acid groups, which are extended away from the surface. In contrast to FePP-Pt chemisorption, FePP was found to physisorb to graphite. The preferred spin state upon adsorption was found to be S = 2 on Pt(111), whereas on graphite, the high and intermediate spin states were nearly isoenergetic. Additionally, gas-phase calculations suggest that much of the surface roughness observed microscopically for the polymerized porphyrin layer may originate from the nonparallel stacking of porphyrin molecules, which interact with each other by forming four intermolecular hydrogen bonds and through dispersion interactions between the stacked porphyrin rings. Regardless of polymer thickness, the underlying electrode appears to be able to participate in at least some redox processes. This was observed for the hemin-polymerized Pt electrode using the 2H(+)/H-2 redox couple and was suspected to be due to some Pt surface atoms not being specifically coordinated to the hemin molecules and therefore available to react with H+ that was small enough to diffuse through the polymer layer.

First author: Price, JS, [(dmpe)(2)MnH(C2H4)] as a Source of a Low-Coordinate Ethyl Manganese(I) Species: Reactions with Primary Silanes, H-2, and Isonitriles, ORGANOMETALLICS, 37, 3010, (2018)
Abstract: Wilkinson’s manganese(I) ethylene hydride complex trans-[(dmpe)(2)MnH(C2H4)] (1) reacts as a source of a low-coordinate manganese(I) ethyl complex. This is illustrated in the reactivity of 1 toward a variety of reagents. Reactions of 1 with primary silanes RSiH3 (R = Ph, Bu-n) at 60 degrees C afforded ethane and the disilyl hydride manganese complexes [(dmpe)(2)MnH(SiH2R)(2)] (4a, R = Ph; 4b, R = Bu-n). Additionally, reaction with H-2 at 60 degrees C afforded ethane and the dihydrogen hydride complex [(dmpe)(2)MnH(H-2)] (5), which has previously been prepared by an alternate route. The proposed low-coordinate intermediate, [(dmpe)(2)MnEt], was not observed spectroscopically but could be trapped using isonitrile ligands; reaction of 1 with CNR (R = Bu-t, o-xylyl) afforded the manganese(I) ethyl complexes [(dmpe)(2)MnEt(CNR)] (6a, R = Bu-t; 6b, R = o-xylyl). Ethyl complex 6a did not react further with (CNBu)-Bu-t at 80 degrees C. In contrast, complex 6b reacted with excess o-xylyl isonitrile to form 1,1-insertion products, including the iminoacyl complex [(dmpe)Mn(CNXy1)(3){C(=NXyl)CEt(=NXyl)}] (7, Xyl = o-xylyl). Complexes 4a, 6a,b, and 7, as well as the previously reported 1 and 5, have been crystallographically characterized, and DFT calculations have been employed to probe the accessibility of cis ethylene hydride and ethyl isomers of 1.

First author: Xie, Q, Probing the Strongest Aromatic Cyclopentadiene Ring by Hyperconjugation, ORGANOMETALLICS, 37, 3219, (2018)
Abstract: Hyperconjugation, an interaction of electrons in a sigma orbital or lone pair with an adjacent pi or even sigma antibonding orbital, can have a strong effect on aromaticity. However, most work on hyperconjugative aromaticity has been limited to main-group substituents. Here, we report a thorough density functional theory study to evaluate the aromaticity in various cyclopentadienes that contain both main-group and transition-metal substituents. Our calculations reveal that the strongest aromatic cyclopentadiene ring can be achieved by the synergy of trans influence and hyperconjugation caused by transition-metal substituents. Our findings highlight the great power of transition metals and trans influence in achieving hyperconjugative aromaticity, opening an avenue to the design of other novel aromatic organometallics.

First author: Saraiva, MS, Molybdenum(II) Complexes with -Diimines: Catalytic Activity in Organic and Ionic Liquid Solvents, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 37, 3922, (2018)
Abstract: The new [MoX((3)-C3H5)(CO)(2)(-diimine)] complexes with: (i) X = Br or triflate and -diimine = 1,10-phenanthroline (phen) and dipyridophenazine (dppz); and (ii) X = Br and -diimine = phen and dppz, with several substituents, are synthesized and characterized. The structures of [MoBr((3)-C3H5)(CO)(2)(Cl-phen)] and [Mo(CF3SO3)((3)-C3H5)(CO)(2)(dppz)] are determined by using single-crystal X-ray diffraction. These and three complexes of 2,2-bipyridyl (bpy), and its two derivatives with Me and tBu substituents, are tested in the homogeneous catalytic epoxidation of several olefins in dichloromethane, exhibiting, in general, a good selectivity towards the respective epoxide and relatively low TOFs. For the first time, the oxidation of cis-cyclooctene with some of these catalysts is also conducted in a variety of room-temperature ionic liquids (RTILs). In the presence of [MoBr((3)-C3H5)(CO)(2)(phen)], the conversions, in general, increase, compared with the reactions in organic solvents. Interestingly, different chemoselectivity is found when [C(6)mim][Ntf(2)] and [C(2)mim][FAP] are used with diol (24-26%). On the other hand, [MoBr((3)-C3H5)(CO)(2)(L)] (L = Me-phen or dppz) exhibits much lower conversions in the RTILs tested than in common organic solvents.

First author: Smolentsev, G, Structure of the Co-I Intermediate of a Cobalt Pentapyridyl Catalyst for Hydrogen Evolution Revealed by Time-Resolved X-ray Spectroscopy, CHEMSUSCHEM, 11, 3087, (2018)
Abstract: Cobalt polypyridyls are highly efficient water-stable molecular catalysts for hydrogen evolution. The catalytic mechanism explaining their activity is under debate and the main question is the nature of the involvement of pyridyls in the proton transfer: the pentapyridyl ligand, acting as a pentadentate ligand, can provide stability to the catalyst or one of the pyridines can be involved in the proton transfer. Time-resolved Co K-edge X-ray absorption spectroscopy in the microsecond time range indicates that, for the [Co-II(aPPy)] catalyst (aPPy=di([2,2-bipyridin]-6-yl)(pyridin-2-yl)methanol), the pendant pyridine dissociates from the cobalt in the intermediate Co-I state. This opens the possibility for pyridinium to act as an intramolecular proton donor. In the resting state, the catalyst returns to the original six-coordinate high-spin Co-II state with a pentapyridyl and one water molecule coordinating to the metal center. Such a bifunctional role of the polypyridyl ligands can be exploited during further optimization of the catalyst.

First author: Zhou, YM, Pyrrolopyrrole aza boron dipyrromethene based two-photon fluorescent probes for subcellular imaging, JOURNAL OF MATERIALS CHEMISTRY B, 6, 5570, (2018)
Abstract: A series of pyrrolopyrrole aza boron dipyrromethene derivatives have been designed and synthesised as two-photon fluorescent probes. The bisalkynyl analogues, having a donor–donor quadrupolar skeleton, show a red-shifted Q band at ca. 700 nm in toluene and a two-photon absorption (TPA) cross-section up to 2349 GM at 1040 nm. To enable these dyes to be used for subcellular imaging, a branched oligoethylene glycol unit has been introduced to enhance their hydrophilicity and biocompatibility, and a potential organelle-selective group, namely triphenylphosphonium or morpholine moiety has also been added with a view to targeting the mitochondria or lysosomes respectively. The resulting conjugates are essentially non-aggregated in deionised water, exhibiting an intense Q band at 668 nm and a TPA cross-section up to 384 GM at 1040 nm. These spectral features have been analysed using density functional theory calculations, which suggest that the TPA is mainly due to the S-0 S-2 transition. In the subcellular imaging study, it has been found that the triphenylphosphonium-containing derivative can localise in the lysosomes of HeLa human cervical carcinoma cells, which may be a result of its positive charge and the negative logP value (-2.46, P = partition coefficient), while the morpholine-substituted analogue does not exhibit preferential subcellular localisation.

First author: Zierkiewicz, W, Regium bonds between Mn clusters ( M = Cu, Ag, Au and n=2-6) and nucleophiles NH3 and HCN, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 22498, (2018)
Abstract: The most stable geometries of the coinage metal (or regium) atom (Cu, Ag, Au) clusters M-n for n up to 6 are all planar, and adopt the lowest possible spin multiplicity. Clusters with even numbers of M atoms are thus singlets, while those with odd n are open-shell doublets. Examination of the molecular electrostatic potential (MEP) of each cluster provides strong indications of the most likely site of attack by an approaching nucleophile, generally one of two positions. A nucleophile (NH3 or HCN) most favorably approaches one particular M atom of each cluster, rather than a bond midpoint or face. In the closed-shell clusters, the interaction energies are highly dependent upon the intensity of the MEP, but this correlation fades for the open-shell systems studied in this work. The strength of the interaction is also closely related to the basicity of the nucleophile. Regium bond energies can be more than 30 kcal mol(-1) and tend to follow the Au > Cu > Ag order. These interaction energies are in large part derived from Coulombic attraction, with a smaller orbital interaction contribution.

First author: Ji, LF, Theoretical Study on the Electronic Structures and Charge Transport Properties of a Series of Rubrene Derivatives, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 21226, (2018)
Abstract: The charge transport properties of a series of rubrene derivatives were systematically investigated by density functional theory and molecular dynamics (MD) simulations. It was found that functionalizing electron-withdrawing groups (-CN, -CF3, or fluorination) on the peripheral phenyls not only enhance the chemical stability of materials but also favor electron injection by lowering the energy levels of frontier molecular orbitals and increasing the electron affinities. Derivatives 2-5 and 9, exhibiting packing motifs similar to rubrene but closer pi-stacking distances, possess large hole and electron-transfer integrals, significant bandwidths, and small effective masses, suggesting excellent ambipolar semiconductor behavior. The maximum hole(electron) mobilities in the Marcus hopping mechanism based on kinetic Monte Carlo simulation can reach 14.0-16.5(1.6-3.5) cm(2) V-1 s(-1). Interestingly, the antiparallel 2-D brick stacking and twisted backbones of fluorinated derivatives 11 and 12 result in nearly 1-D percolation network but balanced hole and electron transport property. In contrast, the parallel 2-D brick stacking of 14 leads to 2-D percolation network. Their maximum hole and electron mobilities fall in the range of 0.5-3.6 and 2.0-4.8 cm(2) V-1 s(-1). Furthermore, MD simulations show that dynamic disorder is strongly detrimental to the hole transfer but has a little influence on the electron transfer for 1-5. Moreover, severe twist of backbones of 9 leads to almost 1 order of magnitude lowered mobility. In addition, the influences of different substituents on the molecular structure, packing motif, and intermolecular reorganization energy are discussed.

First author: Jana, G, Noble Gas Inserted Metal Acetylides (Metal = Cu, Ag, Au), JOURNAL OF PHYSICAL CHEMISTRY A, 122, 7391, (2018)
Abstract: Metal acetylides (MCCH, M = Cu, Ag, Au) were already experimentally detected in molecular form. Herein, we investigate the possibility of noble gas (Ng) insertion within the C-H bond of MCCH and their stability is compared with those of the reported MNgCCH and HCCNgH molecules. Our coupled-cluster-level computations show that MCCNgH (Ng = Kr, Xe, Rn) systems are local minima on the corresponding potential energy surfaces, whereas their lighter analogues do not remain in the chemically bound form. Further, their stability is analyzed with respect to all possible dissociation channels. The most favorable dissociation channel leads to the formation of free Ng and MCCH. However, there exists a high free energy barrier (29.3-46.9 kcal/mol) to hinder the dissociation. The other competitive processes against their stability include two-body and three-body neutral dissociation channels, MCCNgH -> MCC + NgH and MCCNgH -> MCC + Ng + H, respectively, which are slightly exergonic in nature at 298 K for Ng = Kr, Xe and M = Cu, Ag, and for AuCCKrH. However, the Xe analogues for Cu and Ag and AuCCKrH would be viable at a lower temperature. AuCCNgH (Ng = Kr-Rn) molecules are the best candidates for experimental realization, since they have higher dissociation energy values and higher kinetic protection in the case of feasible dissociation channels compared to the Cu and Ag systems. A detailed bonding analysis indicates that the Ng-H bonds are genuine covalent bonds and there is also a substantial covalent character in Ng-C contacts of these molecules. Moreover, the possibility of insertion of two Xe atoms in AuCCH resulting in AuXeCCXeH and the stability of XeAuXeCCXeH are also tested herein.

First author: Schneider, FSS, How Do Secondary Phosphine Oxides Interact with Silver Nanoclusters? Insights from Computation, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 21449, (2018)
Abstract: Air-stable nanoparticles stabilized with secondary phosphine oxides (SPOs) can have a remarkable role as catalysts. Since size and activity depend both on the clusterligand interaction and the nature of the employed ligand, the present work provides a fresh perspective on the prospects of bonding analysis, rationalizing for the first time the physical nature of interactions between silver nanoclusters (SNCs) and tp secondary phosphine oxides (SPOs) in the light of energy decomposition (EDA-NOCV) and noncovalent interaction hi (NCI) analyses, using the silver core of the X-ray structure for a highly symmetric, ligand-decorated Ag-44 cluster available in the literature. Our findings reveal that phosphines containing aliphatic substituents are more stabilized when interacting with Ag cluster, in contrast to aromatic groups, and that SPOs containing aromatic moieties become aligned to the silver surface upon adsorption. This alignment of aromatic substituents substantially contribute to dispersion interactions, which is observed by both EDA-NOCV and NCI analyses, showing ligand to metal donations and fragment polarizations, as well as metal to ligand backdonations in some cases. Adsorption conformations bearing hydrogen bonds to the surface were found to be the most favorable ones, and models for SPO-cluster hydrogen transfer are in line with previous experimental findings on gold nanoparticles. The present contribution will help pave the way for the rational development of new SPO-protected nanoparticles and nanoclusters, which may become cheaper and more efficient catalysts in the future.

First author: Ortolan, AO, Helicenes as Molecular Tweezers in the Formation of Cation- Complexes. Bonding and Circular Dichroism Properties from Relativistic DFT Calculations, CHEMPHYSCHEM, 19, 2321, (2018)
Abstract: Helicene ligands possess a unique helicoidal -conjugated framework providing high optical rotation values. This has stimulated a growing interest in helicene derivatives as building blocks, which has triggered the development of simple strategies to tune their properties. In this context, we evaluated the formation of cation- complexes derived from [6]- and [7]helicene, involving Sn2+, Cd2+, and In+ in addition of Ag+, which appears as a plausible modification of such helicoidal structure. The nature of the cation- interaction in the studied helicene complexes exhibits a covalent character, accounting for ligand -donation to 5s and 5p empty orbitals of the involved cations. Furthermore, the evaluation of their optical activity exhibits notorious modification patterns in the circular dichroism spectrum, suggesting that the modifications of the optical activity are dependent on the nature of the cation and its related charge state. Thus, the plausible formation of new cation- complexes derived from helicene ligands, as discussed here, may lead to the characterization of novel species expanding the chemistry of helicene metal complexes to even to larger helicene units. We believe that the present study may open new avenues in the formation of cation- helicene complexes.

First author: Majumder, A, Exohedral complexation of B-39(-) with ECp*+ half-sandwich complexes (E=Si Ge, Sn, Pb): A DFT study, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1140, 49, (2018)
Abstract: The hexagonal and heptagonal holes of B-39(-) allow its complexation with a half sandwich complex ECp*+ (E=Si, Ge, Sn, Pb). Structure and the nature of bonding of (eta(6/7)-B-39)E(eta(5)-Cp-*) are explored through the density functional theory based computation. (eta(6)-B-39)E(eta(5)-Cp-*) isomers are more stable than (eta(7)-B-39)E(eta(5)-Cp*) and the energy difference between these two isomers decreases down the group from Si to Pb. The dissociation path, (eta(6/7)-B-39)E(eta(5)-Cp-*) -> B-39(-)+ ECp*+ is studied. For all E, (eta(6/7)-B-39)E(eta(5)-Cp-*) is formed exergonically at 298 K temperature as given by the Delta G values of dissociation path [60.1(Si) to 68.3(Pb) kcal/mol for (eta(6)-B-39)E(eta(5)-Cp-*) and 58.3(Si) to 67.8(Pb) kcal/mol for (eta(7)-B-39)E(eta(5)-Cp-*)]. The adduct becomes bent around the central E atom when B-39(-) gets attached to ECp*+ and the amount of bending increases gradually down the group from Si to Pb. Bonding analysis of the stable isomer, (eta(6)-B-39)E(eta 5-Cp*) has been done by natural bonding orbital (NBO) and energy decomposition analyses (EDA). The electron density from B-39(-) is transferred to the ECp*+ moiety as revealed by the NBO analysis. All the complexes are mainly stabilized by the electrostatic and orbital interactions between B-39(-) and ECp*+ fragments as highlighted by the EDA results.

First author: Pustula, K, Thermal decomposition of oxetan-2-one molecule in the light of DFT and CASPT2 modelling, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1140, 98, (2018)
Abstract: Only one path of oxetan-2-one pyrolysis, which results in carbon dioxide and ethene, was observed experimentally. Two other paths resulting in ketene and formaldehyde or acetyl aldehyde and carbon monoxide, respectively, were only hypothesized. In this research we use multi-reference quantum chemistry approach to study the possible decomposition pathways. Using a multi-step procedure involving low-cost genetic algorithm based pre-search and subsequent DFT and CASPT2 calculations we found only two low-energetic paths: the experimental one and the second one which leads to the formation of ketene and formaldehyde. Our study confirmed that all the relevant transition states are basically single-reference in terms of electronic structure and have no diradical character. We also showed that using more advanced quantum chemical models give results which are in an excellent agreement with the experiment and allow to benchmark simpler DFT methods.

First author: Sruthi, PK, Pentavalent phosphorus as a unique phosphorus donor in POCl3 homodimer and POCl3-H2O heterodimer: matrix isolation infrared spectroscopic and computational studies, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 22058, (2018)
Abstract: Phosphorus, an important element among the pnicogen group, opens up avenues for experimental and computational explorations of its interaction in a variety of compounds. Although experimental proof of trivalent phosphorus bonding is limited and is growing with time, phosphorus bonding with pentavalent phosphorus has been a long sought after interaction both computationally and experimentally. In the present work, for the first time, we have provided unambiguous experimental evidence for the pentavalent phosphorus bonding interaction by exploiting a phosphoryl chloride (POCl3) prototype under isolated conditions at low temperatures. The POCl3 dimer and higher aggregates can be set as a unique example possessing pentavalent phosphorus bonding with a competing halogen bonding interaction. The POCl3-H2O heterodimer is another interesting system, stabilized through multiple phosphorus and hydrogen bonded interactions. Using matrix isolation infrared spectroscopy, the POCl3 homodimer and POCl3-H2O heterodimer were characterized and the structures were elucidated by employing ab initio and DFT methods. The multifaceted interactions in the POCl3 paradigm were investigated by using Natural Bond Orbital, Energy Decomposition and Electrostatic Potential Mapping analyses.

First author: Heshmat, M, H-2 Cleavage by Frustrated Lewis Pairs Characterized by the Energy Decomposition Analysis of Transition States: An Alternative to the Electron Transfer and Electric Field Models, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 7202, (2018)
Abstract: Knowing that the Papai’s electron transfer (ET) and the Grimme’s electric field (EF) models draw attention to somewhat different physical aspects, we are going to systematically (re)examine interactions in the transition states (TSs) of the heterolytic H-2-cleavage by the Frustrated Lewis Pairs (FLPs). Our main vehicle is the quantitative energy decomposition analysis (EDA), a powerful method for elucidation of interactions, plus the analysis of molecular orbitals (MOs). Herein, the Lewis acid (LA) is B(C6F5)(3) and the Lewis bases (LBs) are tBu(3)P, (o-C6H4Me)(3)P, 2,6-lutidine, 2,4,6-lutidine, MeN=C(Ph)Me imine, MeN(H)-C(H)PhMe amine, THF, 1,4-dioxane, and acetone. For a series of the phosphorus-, nitrogen-, and oxygen-bearing LBs plus B(C6F5)(3), we will show that (i) neither the electrostatic nor the orbital interactions dominate but instead both are essential alongside the Pauli repulsion and (ii) the frontier molecular orbitals (FMOs) of a TS can arise not only from the “push-pull” molecular orbital scheme by Papai et al., which directly involves the occupied sigma and the empty sigma* MOs of H-2, but also from a more intricate but energetically more fitting orbital interactions which have escaped notice thus far.

First author: Bhattacharjee, R, Understanding Thermal and Photochemical Aryl-Aryl Cross-Coupling by the Au-I/Au-III Redox Couple, CHEMISTRY-A EUROPEAN JOURNAL, 24, 13636, (2018)
Abstract: Systematic mechanistic investigations of the gold(I)/gold(III) redox-controlled aryl-aryl cross-coupling reaction have been performed by using both a thermal and photochemical approach. Electron-deficient and electron-rich arenes were considered as the coupling partners of the reaction. Based on transition-state modeling and distortion/interaction analyses, it is shown that Au-I prefers to react with electron-deficient arenes whereas Au-III likes to activate electron-rich arenes. This orthogonal reactivity of gold makes it an efficient catalyst for the aryl-aryl cross-coupling reaction. The crucial role of the carboxylate ligand in the reaction has been elucidated through analysis of the transition states. It is shown that due to the presence of two coordination sites, a carboxylate ligand can stabilize the transition state more efficiently than other monodentate ligands such as chloride (Cl-). Moreover, carbon-boron transmetalation is shown to be favorable over direct C-H metalation, hence reactions initialized by C-B transmetalation are expected to be much faster and selective. Additionally, a dual photoredox/gold catalyst was employed to access the Au-I/Au-III catalytic cycle for the cross-coupling reaction. [Ru(bpy)(3)](2+) was used as the photoredox catalyst for the reaction, which, on excitation, transfers an electron to one of the coupling partners, namely a diazonium salt (ArN2+), and initializes the cycle.

First author: Jash, M, Preparation of gas phase naked silver cluster cations outside a mass spectrometer from ligand protected clusters in solution, NANOSCALE, 10, 15714, (2018)
Abstract: Gas phase clusters of noble metals prepared by laser desorption from the bulk have been investigated extensively in a vacuum using mass spectrometry. However, such clusters have not been known to exist under ambient conditions to date. In our previous work, we have shown that in-source fragmentation of ligands can be achieved starting from hydride and phosphine co-protected silver clusters leading to naked silver clusters inside a mass spectrometer. In a recent series of experiments, we have found that systematic desorption of ligands of the monolayer protected atomically precise silver cluster can also occur in the atmospheric gas phase. Here, we present the results, wherein the [Ag18H16(TPP)(10)](2+) (TPP = triphenylphosphine) cluster results in the formation of the naked cluster, Ag-17(+) along with Ag18H+ without mass selection, outside the mass spectrometer, in air. These cationic naked metal clusters are prepared by passing electrosprayed ligand protected clusters through a heated tube, in the gas phase. Reactions with oxygen suggest Ag-17(+) to be more reactive than Ag18H+, in agreement with their electronic structures. The more common thiolate protected clusters produce fragments of metal thiolates under identical processing conditions and no naked clusters were observed.

First author: Dyduch, K, Exploring the Conformational Space of Cobalt(III)-Salen Catalyst for CO2/Epoxide Copolymerization: Effect of Quaternary Ammonium Salts on Preference of Alternative Isomers, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 1854, (2018)
Abstract: Model catalysts for CO2/epoxide copolymerization based on Co(III) complexes were studied, with focus on the preference of their alternative isomers, cis beta vs. trans. The systems range from model structures without the co-catalyst, as derived from crystallographic data, to complex models with two -(CH2)(4)N+R3 co-catalyst chains (R = Me, Bu) grafted onto a Co(III)-salcy core. To explore the conformational space of the latter complexes, a computational protocol was developed, combining a systematic model-building approach with static and molecular dynamics calculations, and multilevel energy assessment (PM7 and DFT). Results demonstrate an influence of the co-catalyst on the relative stability of the isomers. The cis beta isomer is preferred for complexes without N+-chains and the cis beta <-> trans isomerization is feasible. Five-coordinate species and open-shell electronic configurations are energetically disfavored. The cis beta preference decreases with the introduction and enlargement of -(CH2)(4)N+R3: both isomers can be populated for R=Me, while the trans isomer is visibly preferred for R = Bu.

First author: Luo, YF, Unveiling the Dual Emission Photo-Deactivation Mechanism of a Neutral Heteroleptic Iridium (III) Complex, CHEMPHYSCHEM, 19, 2200, (2018)
Abstract: In this article, the photo-deactivation mechanism of dual emission of a neutral iridium (III) complex is explored by using density function theory (DFT) and time-dependent density function theory (TD-DFT) calculations. To explore the phosphorescence quantum yield of the iridium (III) complex, the radiative decay constant of each emission excited state was computed by TD-DFT calculations, including spin-orbit coupling (SOC). In these calculations, factors such as the transition dipole moments, energy gaps, and SOC elements between the emission states and singlet excited states are taken into account in the evaluation of the radiative decay constants. Additionally, the non-radiative decay is revealed by considering the temperature-independent and the temperature-dependent non-radiative processes. The computational results indicate that the order of the two emission excited states can exert a significant effect on the phosphorescence quantum yield, which is beneficial for understanding the properties of photo-deactivation of phosphorescent emitters.

First author: Rudolph, J, Revisiting the Dependence of Cu K-Edge X-ray Absorption Spectra on Oxidation State and Coordination Environment, INORGANIC CHEMISTRY, 57, 10591, (2018)
Abstract: X-ray absorption spectroscopy (XAS) at the Cu K-edge is an important tool for probing the properties of copper centers in transition-metal chemistry and catalysis. However, the interpretation of experimental XAS spectra requires a detailed understanding of the dependence of spectroscopic features on the local geometric and electronic structure, which can be established by theoretical X-ray spectroscopy. Here, we present a systematic computational study of the Cu K-edge XAS spectra of selected Cu complexes based on time-dependent density-functional theory in combination with a molecular orbital analysis of the relevant transitions. For a series of Cu ammine model complexes as well as a comprehensive test set of 12 Cu(I) and 5 Cu(II) complexes, we revisit the dependence of the pre-edge region in Cu K-edge XAS spectra on oxidation state and coordination geometry. While our calculations confirm earlier experimental assignments, we can also reveal additional signatures of the ligand orbitals and identify the underlying orbital interactions. The comprehensive picture revealed by this study will provide a reliable basis for the interpretation of in situ Cu K-edge XAS spectra of catalytic intermediates.

First author: Yan, X, DFT/TDDFT insight into the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes, APPLIED ORGANOMETALLIC CHEMISTRY, 32, 10591, (2018)
Abstract: Uncovering the photodeactivation mechanisms of unique N-heterocyclic carbene (NHC)-based transition metal complexes is favorable for designing more high-efficiency phosphorescent materials. In this work, four bidentate platinum (II) complexes with NHC-chelate are investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) to probe into how the ring size of NHC-chelate unit influences on electronic structures and the phosphorescent properties. To illustrate the photodeactivation mechanisms clearly, three significant photodeactivation processes (radiative decay process, temperature-independent and temperature-dependent nonradiative decay processes) were taken into consideration. We stated that radiative decay rate constants k(r) slightly increased with declined number of NHC-chelate ring, owing to the gradually larger SOC matrix elements between the T-1 state and S-i, states. Combining the temperature-independent with temperature-dependent nonradiative decay processes, the nonradiative decay rate k(nr) is Pt-4 (five-membered) < Pt-3 (six-membered) < Pt-2 (seven-membered) < Pt-1 (eight-membered). The calculated results testify that the decrease of size of the NHC chelating unit is a reliable insurance to improve the quantum yield. The designed complex Pt-4 with five-membered NHC-ring can serve as a highly efficient phosphorescent material in the future. The results indicated controlling the ring size of NHC-chelate is a feasible method to tune phosphorescence properties of Pt (II) complexes.

First author: Eising, S, Highly Stable and Selective Tetrazines for the Coordination-Assisted Bioorthogonal Ligation with Vinylboronic Acids, BIOCONJUGATE CHEMISTRY, 29, 3054, (2018)
Abstract: Bioorthogonal reactions are selective transformations that are not affected by any biological functional group and are widely used for chemical modification of biomolecules. Recently, we reported that vinylboronic acids (VBAs) gave exceptionally high reaction rates in the bioorthogonal inverse electron-demand Diels-Alder (iEDDA) reaction with tetrazines bearing a boron-coordinating pyridyl moiety compared to tetrazines lacking such a substituent. In this integrated experimental and theoretical study, we show how the reaction rate of the VBA-tetrazine ligation can be accelerated by shifting the equilibrium from boronic acid to the boronate anion in the reaction mixture. Quantum chemical activation strain analyses reveal that this rate enhancement is a direct consequence of the excellent electron-donating capability of the boronate anion in which the pi HOMO is pushed to a higher energy due to the net negative potential of this species. We have explored the second-order rate constants of several tetrazines containing potential VBA-coordinating hydroxyl substituents. We observed an increase in rate constants of several orders of magnitude compared to the tetrazines lacking a hydroxyl substituent. Furthermore, we find the hydroxyl-substituted tetrazines to be more selective toward VBAs than toward the commonly used bioorthogonal reactant norbornene, and more stable in aqueous environment than the previously studied tetrazines containing a pyridyl substituent.

First author: Huang, ZW, Simultaneous elimination of cationic uranium(vi) and anionic rhenium(vii) by graphene oxide-poly(ethyleneimine) macrostructures: a batch, XPS, EXAFS, and DFT combined study, ENVIRONMENTAL SCIENCE-NANO, 5, 2077, (2018)
Abstract: In the field of radioactive wastewater treatment associated with environmental remediation, a big challenge is to achieve the simultaneous elimination of toxic metal cations and metallate anions. Herein, a three-dimensional (3D) graphene oxide-supported ethyleneimine polymer composite (GO-PEI) was synthesized by a self-assembly strategy and used for the simultaneous removal of cationic U(vi) and anionic Re(vii), which acts as a surrogate for Tc(vii), from aqueous solution. The maximum adsorption capacity of GO-PEI composites at pH 5.0 for U(vi) and at pH 3.5 for Re(vii) was determined to be 629.5 and 262.6 mg g(-1), respectively. Based on Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) analyses, and density functional theory (DFT) calculations, the adsorption of U(vi) is predominantly attributed to the coordination with abundant amino and oxygen-containing groups anchored on the hydrogel. In contrast, the removal of Re(vii) is correlated with the anion-exchange mechanism. In addition, GO-PEI has demonstrated a highly extractive adsorption capability toward U(vi) in ultralow concentrations. Our work may pave the way for creating an exciting new category of material with versatile capabilities for the treatment of radioactive effluent from the nuclear fuel cycle.

First author: Altarawneh, M, Introducing Quantum Chemistry in Chemical Engineering Curriculum, JOURNAL OF CHEMICAL EDUCATION, 95, 1562, (2018)
Abstract: Due to the wide and the ever-increasing strategic applications of quantum chemistry in chemical industries, it is important to introduce chemical engineering students to illustrative case studies that deploy molecular modeling in the design of reactors and derivation of thermochemical functions. Herein, we demonstrate how quantum chemical calculations can be implemented within a unit on the chemical reaction engineering to obtain properties that are typically measured in the laboratory classes, namely, reaction rate constants, fractional conversion of reactants, and residence time. A rigorous coupling between quantum chemistry and chemical reaction engineering is expected to encourage students to appreciate the accuracy and the practicality of molecular calculations in process modeling and design of novel materials.

First author: Barrera, M, The role of lithium cations on the photochemistry of ruthenium complexes in dye-sensitized solar cells: A TDDFT study with the BCL model, JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 364, 510, (2018)
Abstract: Lithium cations have been shown to impart an electrostatic Stark effect on molecules bound to mesoporous metal oxides commonly used in dye-sensitized solar cells. Herein, using the Barrera-Crivelli-Loeb theoretical model accompanied by Time Dependent Density Functional Theory calculations, we examined the influence that lithium cations have on the performance of dye-sensitized solar cells that incorporate [Ru(dmb)(2)(dcbH)](2+) sensitizers, where dmb is 4,4′-dimethyl-2,2′-bipyridine and dcbH is 4,4′-dicarboxylic acid-2,2′-bipyridine was examined. Simulations suggest that an enhanced photocurrent occurs in the presence of lithium cations, which is attributed to the photochemical generation of an excited-state dye lithium adduct. In this adduct, a lithium cation is interacting with the carbonyl moieties of the dcbH ligands, which results in a bathochromic shift of the [Ru(dmb)(2)(dcbH)](2+) metal-to-ligand charge-transfer spectral band. This shift in absorption can be canceled by introducing a hypothetical dipolar electric field of 7.3 MV/cm, in good agreement with experimentally reported values for Stark effects observed under solar excitation of TiO2 functionalized with these types of sensitizer molecules. This indicates that lithium cations not only interact with the metal-oxide semiconductor, as shown previously, but also interact directly with the dye upon photoexcitation, something that should be considered when designing and evaluating new sensitizers.

First author: Hakkar, F, Predicted Structures and Electronic Properties of Gallium-Indium Clusters GamInn-m (n=4, 6, 8 and m < n): A Density Functional Study, JOURNAL OF STRUCTURAL CHEMISTRY, 59, 997, (2018)
Abstract: Various structural possibilities for small gallium-indium GamInn-m (n = 4, 6, 8 and m < n) clusters are investigated using the density functional theory (DFT) method at the B3LYP/TZP level. The optimized structures tend to prefer compact structures, wherein the trigonal prism and rhombic prism configurations are favoured for n = 6 and 8, respectively. The bonding energy per atom is calculated according to the cluster size. The HOMO-LUMO gaps, ionization potentials, electron affinities, and chemical hardness () are also computed for the most stable isomers of each cluster and used to predict their relative stabilities. The obtained results indicate that the Ga-rich clusters are more stable than the In-rich ones with the same total number of atoms. The Ga-Ga bond is stronger than the Ga-In bond and the latter is stronger than the In-In one. Therefore, the Ga7In cluster is relatively the most stable structure. The relative reactivity of GamInn-m (n = 4, 6, 8 and m < n) clusters could be predicted based on the chemical hardness. The computed large HOMO-LUMO gap energies could be used as an index of the kinetic stability for the studied clusters.

First author: de Rezende, FMP, Probing long-range spin-spin coupling constants in 2-halo-substituted cyclohexanones and cyclohexanethiones: The role of solvent and stereoelectronic effects, MAGNETIC RESONANCE IN CHEMISTRY, 56, 810, (2018)
Abstract: Earlier studies with 2-bromocyclohexanone demonstrated a measurable long-range coupling constant ((4)J(H2,H6)) for the equatorial conformer, although (4)J(H2,H4) and (4)J(H4,H6) were not observed; as a consequence, it is inferred that the carbonyl group plays an important role particularly due to hyperconjugative interactions sigma(C2H2)*(CO) and sigma(C6H6)*(CO.) In the present study, NBO analysis and coupling constant calculations were performed to cyclohexanone and cyclohexanethione alpha substituted with F, Cl, and Br, aiming to evaluate the halogen effect and acceptor character of the * orbital on the long-range coupling pathway. The sigma(C2H2)*(C1Y) and sigma(C6H6)*(C1Y) (YO and S) hyperconjugative interactions for the equatorial conformer indeed contribute for the (4)J(H2,H6) transmission mechanism(.) Surprisingly, the (4)J(H2,H6) value is higher for the carbonyl compounds, although the interactions sigma(C2H2)*(CY) and sigma(C6H6)*(CY) are more efficient for the thiocarbonyl compounds. Accordingly, the Fermi contact (FC) contribution for the thiocarbonyl compounds decays deeper than in ketones, thus reducing more the (4)J(H2,H6) values. Moreover, both (CS)sigma*(CX) and (CS)sigma*(CH) interactions seem to be stronger in thiocarbonyl than in carbonylic compounds. The implicit solvent effect (DMSO and water) on the coupling constant values was negligible when compared with the gas phase. On the other hand, an explicit solvent effect was found and (4)J(H2,H6) for the thiocarbonyl compounds appeared to be more sensitive than for the cyclohexanones.

First author: Conradie, J, Novel dichloro(bis{2-[1-(4-methylphenyl)-1H-1,2,3-triazol-4-yl-kappa N-3] pyridine-kappa N})metal(II) coordination compounds of seven transition metals (Mn, Fe, Co, Ni, Cu, Zn and Cd), POLYHEDRON, 151, 243, (2018)
Abstract: The synthesis, characterization, DFT and, in two cases, the structure of seven novel dichloro(bis{2-[1-(4methylphenyl)-1H-1,2,3-triazol-4-yl-kappa N-3]pyridine-kappa N})metal(II) coordination compounds (IM(L-2)(2)Cl-2]}, containing transition metals of groups 7-12, are described. Both experimentally measured magnetic moment and DFT calculations showed that d6 Mn(II) (with mu(eff) = 5.62 B.M., S = 5/2), d(6) Fe(II) (with mu(eff) = 5.26 B.M., S = 2), d(7) Co(II) (with mu(eff)= 3.98 B.M., S = 3/2), d(8) Ni(II) (with mu(eff) = 3.00 B.M., S =1) and d(9) Cu(II) (with mu(eff) = 1.70 B.M., S = 1/2) are all paramagnetic, while d(10) Zn(II) and Cd(II) are diamagnetic with S = 0. DFT calculations on the possible isomers of these coordination compounds, showed that the cis-cis trans and the trans-trans-trans isomers, with the pyridyl groups trans to each other, are the lowest in energy. The trans-trans-trans isomers were experimentally characterized by X-ray crystallography for [Ni(L-2)(2)Cl2I and [Zn(L-2)(2)Cl-2]center dot L-2 in this study. In the solid state the coordination compounds are connected by intermolecular hydrogen bonds, mainly involving the chloride atoms, to form 3D supramolecular structures. Computational chemistry calculations, using Natural Bonding Orbital calculations, identified these inter-molecular hydrogen bonds, C-H center dot center dot center dot Cl by a donor-acceptor interaction from a filled lone pair NBO on CI to an empty antibonding NBO on (C-H). The inter-molecular hydrogen bonds were also identified by QTAIM determined bonding paths between CI and the respective hydrogen. The theoretically calculated computational chemistry results thus give an understanding on a molecular level why in the solid state where inter-molecular forces and packing play a role, the trans-trans-trans isomers are mostly obtained.

First author: Demissie, TB, Rare and Nonexistent Nitrosyls: Periodic Trends and Relativistic Effects in Ruthenium and Osmium Porphyrin- Based {MNO}(7) Complexes, ACS OMEGA, 3, 10513, (2018)
Abstract: Relativistic and nonrelativistic density functional theory calculations were used to investigate rare or nonexistent ruthenium and osmium analogues of nitrosylhemes. Strong ligand field effects and, to a lesser degree, relativistic effects were found to destabilize {RuNO}(7) porphyrins relative to their {FeNO}(7) analogues. Substantially stronger relativistic effects account for the even greater instability and/ or nonexistence of {OsNO}(7) porphyrin derivatives.

First author: Schnappinger, T, Intersystem Crossing as a Key Component of the Nonadiabatic Relaxation Dynamics of Bithiophene and Terthiophene, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 4530, (2018)
Abstract: We present a nonadiabatic dynamics study concerning the subpicosecond relaxation of excited states in dimeric and trimeric thiophene chains. The influence of the triplet states in the overall process is, for the first time, taken into account by explicitly including spin-orbit couplings and hence allowing intersystem crossing phenomena. We observe the fundamental role of the triplet state manifold in driving the full relaxation process. In particular we evidence the effect of both, inter-ring rotation and ring-opening, in the process, as compared to the monomer, where the ring-opening process appears as the dominant one. In addition, the evolution of the open structures allows for trans to cis isomerization in the dimer and trimer. The overall relaxation process slows down with chain elongation. The complex decay mechanism characterized by the presence of different competing channels, due to the presence of a quasi degenerate manifold, is explained allowing the rationalization of oligothiophenes photophysics.

First author: Mitoraj, MP, London Dispersion Forces in Crystal Packing of Thiourea Derivatives, CRYSTAL GROWTH & DESIGN, 18, 5385, (2018)
Abstract: Novel thioureas RNHC(S)NHP(S)(OiPr)(2) [R = (HOCH2)(Me)(2) C (1), Me2CH2CH2 (2), 2-CF3C6H4 (3), 2-Pym (4), and bis-thiourea 1,5-C10H6 INHC(S)NHP(S)-(OiPr)(2)} (5)] have been synthesized and characterized by NMR, X-ray diffraction, Hirshfeld surface analysis, and theoretical ETS-NOCV charge and energy decomposition calculations. The monomers contain multiple intramolecular noncovalent interactions including N-H center dot center dot center dot X (X = O, 1-3; F, 3; N, 4; S, 5) and C-H center dot center dot center dot Y (Y = O, 1; N, 2 and 3; S, 4 and 5) augmented further by homopolar C-H center dot center dot center dot H-C contacts in all the structures. It has been determined that the three-dimensional crystal networks are primarily constituted from intermolecular H center dot center dot center dot H and H center dot center dot center dot S contacts due to homopolar C-H center dot center dot center dot H-C as well as X-H center dot center dot center dot S (X = N, C) interactions. They are, depending on the system, augmented further by C-H center dot center dot center dot Y (Y = pi, S, F) as well as by sigma-hole(S)center dot center dot center dot pi interactions. ETS-NOCV allowed us to delineate that in the case of C-H center dot center dot center dot H-C, C-H-Y, and sigma-hole(S)center dot center dot center dot pi intermolecular interactions, except for the electrostatically dominated N-H center dot center dot center dot N in 4, London dispersion forces appeared to be a crucial contributor to the stability with non-negligible factors stemming from electrostatics and charge delocalization terms. Remarkably, the dispersion dominated (similar to 50% of the overall stabilization Delta E-elstat + Delta E-orb + Delta E-dispersion) sigma-hole(S)center dot center dot center dot pi it interactions appeared to be the strongest among all the discovered interactions, including classical hydrogen bonds N-H center dot center dot center dot N. The electrostatic and charge delocalization contributions within the sigma-hole(S)center dot center dot center dot pi interactions amount to similar to 30% and similar to 20%, respectively.

First author: Lam, E, Understanding Trends in Al-27 Chemical Shifts and Quadrupolar Coupling Constants in Chloroalkyl Aluminum [AlClx(Me)(3-x)](n=1 or 2) Compounds, HELVETICA CHIMICA ACTA, 101, 5385, (2018)
Abstract: The usage of alkyl aluminum compounds and related structures as co-catalyst finds a broad range of application in homogeneous and heterogeneous catalysis. While understanding the nature of the aluminum species in solution or in solids can be a challenge, Al-27 solid state NMR is a powerful tool to understand the structures of Al species, but their assignment remains mostly empirical, typically by comparing chemical shifts with known compounds. In this work, the observed trends in Al-27-NMR parameters – chemical shift and quadrupolar coupling constant – of chloroalkyl aluminum compounds, a prototypical class of important Lewis activators, are traced back to their frontier orbitals and electron polarization through a natural localized molecular orbital analysis. This study thus provides guidelines to understand the nature of chemical shift and thereby assignment of possible structure.

First author: Wodrich, MD, Expedited Screening of Active and Regioselective Catalysts for the Hydroformylation Reaction, HELVETICA CHIMICA ACTA, 101, 5385, (2018)
Abstract: The discovery of new homogeneous catalysts that preferentially form one product over another in regio- or enantioselective chemical reactions has traditionally been the province of experimental chemists. Today, computational-based approaches have carved an increasingly important role, which, for computational catalytic designs, often rely on highly inefficient combinatorial-based screening methods. To increase the pace of discovery, tools capable of rapidly assessing large numbers of prospective species and identify those possessing desirable properties, such as activity and selectivity, are vital. Here, through the examination of the hydroformylation of 2-methylpropene, we demonstrate how a new tool built upon molecular volcano plots can be used to quickly predict the activity of molecular catalysts as well as estimate the intrinsic ability of each species to form one regioisomer over the other with striking accuracy. Following training and validation, these regioselective molecular volcanoes are employed to predict catalysts that preferentially form the branched product (2,2-dimethylpropanal) in violation of Keulemans’ 70-year-old law. Eighteen species (out of a total of 68 predicted) were computationally predicted to have regiomeric excess (r.e.) values >90. Overall, these tools can be used to quickly screen the activity and selectivity of potential catalysis based on two easily computed descriptor variables.

First author: Mondal, S, Planar ten-membered 10-pi-electron aromatic (CH)(5)(XH)(5) {X = Ge, Sn} systems, JOURNAL OF MOLECULAR MODELING, 24, 5385, (2018)
Abstract: Being monocyclic planar, benzene retains 6 Huckel aromatic backbone. However, for larger analogues, the repulsion between vicinal C-H bonds makes them nonplanar, as for [10]-annulene. Thus, on this basis, a planar 10–aromatic C10H10 is unreachable. A detailed structural comparison among the C3H3+, C4H42+, C5H5-, C6H6, C7H7+, C8H82+, C9H9-, and C10H10 systems supports that the repulsion between vicinal C-H bonds is the primary reason for the loss of planarity, despite the favorable aromatic electron count. In this respect, here we have discussed ten-membered monocyclic planar 10–aromatic, (CH)(5)(XH)(5) {X=Si, Ge, Sn} systems, modeled by using DFT. From NBO analysis and the overall magnetic behavior it is shown that (CH)(5)(GeH)(5), (CH)(5)(SnH)(5) molecules are promising planar 10–aromatic system. Thus, such species represent plausible Huckel aromatic rings retaining a ten-membered backbone as discussed here, which may lead to the characterization of novel species expanding the chemistry of larger aromatic rings. We believe that the present study may open new avenues in the formation of 10-pi-aromatic species.

First author: Chen, XY, Simultaneous In Situ Monitoring of Trimethoxysilane Hydrolysis Reactions Using Raman, Infrared, and Nuclear Magnetic Resonance (NMR) Spectroscopy Aided by Chemometrics and Ab Initio Calculations, APPLIED SPECTROSCOPY, 72, 1404, (2018)
Abstract: Sol-gels are found in many different scientific fields and have very broad applications. They are often prepared by the hydrolysis and condensation of alkoxysilanes such as trimethoxysilanes, which are commonly used as precursors in the preparation of silsequioxanes via the sol-gel process. The reaction rates of such reactions are influenced by a wide range of experimental factors such as temperature, pH, catalyst, etc. In this study, we combined multiple in situ spectroscopic techniques to monitor the hydrolysis and partial condensation reactions of methyltrimethoxysilane and phenyltrimethoxysilane. A rich set of kinetics information on intermediate species of the hydrolysis reactions were obtained and used for kinetics modeling. Raman and nuclear magnetic resonance (NMR) spectroscopy provided the most information about hydrolysis and NMR provided the most information about condensation. A quantitative method based on Raman spectra to quantify the various transient intermediate hydrolysis products was developed using NMR as the primary method, which can be deployed in the field where it is impractical to carry out NMR measurements.

First author: Ahumada, G, Novel Co(II), Ni(II) and Cu(II) complexes involving a 2-thienyl and trifluoromethyl containing symmetrically-substituted tetradentate Schiff-base ligand: Syntheses, structures, electrochemical and computational studies, POLYHEDRON, 151, 279, (2018)
Abstract: Here, we report three novel metal(II) complexes (M = Co, 3a: Ni, 3b; Cu, 3c) involving a symmetrically substituted N2O2-tetradentate Schiff base ligand bearing trifluoromethyl and 2-thienyl substituents. Complexes 3a-c were readily synthesized upon reaction of the diprotic Schiff base proligand with the appropriate hydrated metal(II) acetates, and isolated as neutral, air and thermally stable solids in good to excellent yields (>65-85%). All the complexes have been well characterized using elemental analysis and different spectroscopic tools (ESI+ HRMS, FT-IR, UV-Vis), and single crystal X-ray diffraction analysis for 3b and 3c. Their crystal structures revealed a four-coordinate square planar geometry at the Ni(II) and Cu(II) metal ions, with two nitrogen and two oxygen atoms as donors. Complexes 3a-c displayed similar cyclic voltammetric behavior, exhibiting one anodic and one cathodic wave, both irreversible and of different intensity. They were tentatively assigned to M(II)/M(III) and M(II)/M(I) redox couples, respectively. No deposits of polymeric films on the electrode surface were observed. Structural, electrochemical and electronic parameters of the complexes have been rationalized on the ground of DFT and TD-DFT computation.

First author: Gayfulin, YM, Electron-rich bioctahedral rhenium chalcohalide clusters [Re12CS14(mu-S)(3)Cl-6](8-) and [Re12CS14(mu-S)(3)Br-6](8-) : Synthesis, structure and properties, POLYHEDRON, 151, 426, (2018)
Abstract: A first method for obtaining of electron-rich bioctahedral rhenium clusters has been developed. Two cluster salts, namely (Et3NH)(4)(Me2NH2)(4)[Re12CS14(mu-S)(3)Cl-6](1) and (Et4N)(4)(Me2NH2)(4)[Re12CS14(mu-S)(3)Br-6] (2), have been synthesized and isolated in the solid state. Single-crystal X-ray diffraction showed that salts 1 and 2 are based on the new cluster anions [Re12CS14(mu-S)(3)Cl-6](8-) and [Re12CS14(mu-S)(3)Br-6](8-) containing 48 cluster valence electrons (CVE). The correlations between geometry and CVE number of the bioctahedral chalcohalide anions have been examined using the DFT calculations. The dissolution of the salts 1 and 2 is accompanied by the oxidation yielding the [Re12CS14(mu-S)(3)Cl-6](6-) and [Re12CS14(mu-S)(3)Br-6](6-) anions. Properties of the new clusters in the DMSO solutions have been investigated by UV-Vis spectroscopy and cyclic voltammetry. The latter revealed the presence of multiple reversible one-electron redox waves in a narrow potential window.

First author: Loginov, DA, (C4Me4)Co-containing triple-decker complexes with bridging heterocyclic ligands, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 870, 130, (2018)
Abstract: (C4Me4) Co-containing triple-decker complexes with bridging boron and phosphorus heterocyclic ligands [(C4Me4) Co(mu-eta:eta-L) MCp*](+) (1: M = Fe, L = C5H5BMe; 2: M = Fe, L = C4Me4P; 3a: M = Fe, L = cyclo-P-5; 3b: M = Ru, L = cyclo-P-5) were synthesized by photochemical reaction of [(C4Me4)Co(C6H6)](+) with sandwich compounds Cp*ML. They were isolated as salts with PF6- anion, and the structures of 1PF(6), 2PF(6), and 3aPF(6) were determined by X-ray diffraction. The m-pentaphospholyl complex 3a was also synthesized by exchange of sandwich compounds in the m-cyclopentadienyl triple-decker complexes [(mu-eta:eta-Cp){Co(C4Me4)}2](+) or [(C4Me4) Co(mu-eta:eta-Cp)FeCp](+). Complexes 1, 2, and 3a undergo nucleophilic degradation by acetone and acetonitrile with selective elimination of the [(C4Me4)Co] thorn fragment giving the starting sandwich compounds. The rate of the nucleophilic degradation depends on the nature of the bridging ligand and decreases in the following order: C4Me4P >= C5H5BMe > cyclo-P-5. The bonding in 1, 2, and 3a was analyzed and compared with that in the cyclopentadienyl analog [(C4Me4) Co(mu-eta:eta-Cp) FeCp*](+) using energy decomposition analysis.

First author: Sures, D, Alkali-Driven Disassembly and Reassembly of Molecular Niobium Oxide in Water, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 10803, (2018)
Abstract: Counterions are deemed “spectators” in aqueous solutions of cationic or anionic molecular metal-oxo clusters. While pH and concentration drive aqueous metal speciation as a first approximation, the important effect of counterions is usually overlooked and never considered in standard Pourbaix databases. Alkali counterions for polyoxometalate (POM) clusters control solubility with distinct periodic trends, but evidence for alkali control over speciation is ambiguous. Here we show that a simple Nb-POM, [Nb10O28](6-) ({Nb-10}), converts to oligomers of (HxNb24O72)((24-x)-)({Nb-24}) upon adding only alkali chloride salts, even in buffered neutral solutions. Raman and X-ray scattering reveal that the rate of {Nb-10} to {Nb-24} conversion increases with alkali cation radius and cation concentration. Cation-bridged oligomers of {Nb-24}(y) (y = 2,4) are defined by comparing experimental to computed small-angle X-ray scattering spectra. Computational studies and mass spectrometry indicate that the alkalis open the compact {Nb-10} cluster in conjunction with protonation of a heptamer {Nb-7} intermediate, in which alkali-{Nb-10} association at key locations on the cluster initiates the reaction. Computation also explains the alkali periodic trend for {Nb-10} to {Nb-24} conversion; larger alkalis more effectively destabilize {Nb-10}. This periodic trend asserts the hypothesis that Nb-cluster speciation near neutral pH is driven by the alkali cations in the absence of added base or acid. The extremely high solubility of these 3.5 nm polyoxoanion assemblies-2 M Nb at near neutral pH-is both surprising and exploitable for aqueous synthesis of niobate thin films or nanomaterials used in energy and microelectronics applications.

First author: Bortoli, M, Oxidation of organic diselenides and ditellurides by H2O2 for bioinspired catalyst design, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 20874, (2018)
Abstract: The reactivity of diselenides and ditellurides of general formula (RX)(2) (X = Se, Te; R = H, CH3, Ph) toward hydrogen peroxide was studied through a computational approach based on accurate Density Functional Theory (DFT) calculations. The aliphatic and aromatic dichalcogenides have been chosen in light of their activity in glutathione peroxidase (GPx)-like catalytic cycles and their promising features as efficient antioxidant compounds. The reaction products, the energetics and the mechanistic details of these oxidations are discussed. Analogous disulfides are included in our analysis for completeness. We find that the barrier for oxidation of dichalcogenides decreases from disulfides to diselenides to ditellurides. On the other hand, variation of the substituents at the chalcogen nucleus has relatively little effect on the reactivity.

First author: Machat, MR, Behind the Scenes of Group 4 Metallocene Catalysis: Examination of the Metal-Carbon Bond, ORGANOMETALLICS, 37, 2690, (2018)
Abstract: This contribution provides the first detailed analysis of the nature of the M-C sigma-bond of three alkylated, isostructural group 4 (M = Ti, Zr, Hf) metallocenes, thereby elucidating individual peculiarities of each metal center in the catalytic conversion of olefins. Therefore, the subtle electronic differences of the individual M-C sigma-bonds, which are considered crucial for several subprocesses in the coordinative polymerization of olefins, were examined by detailed experimental charge density studies. These studies provided measures of the increasing ionic character of the M-C bonds along the group 4 elements (Ti-C < Zr-C < Hf-C). These results are further supported by high-pressure diffraction studies showing that the predominantly ionic Hf-C bond is more compressible than the more covalent Zr-C bond in line with a smaller degree of electron localization in the valence shell of the hafnium relative to the zirconium atom along the M-C bond directions. The Ti-C bond displays the largest degree of electron localization in these group 4 metallocenes as witnessed by a pronounced bonded charge concentration in the valence shell of the titanium atom a rare phenomenon in transition metal alkyls. All findings were then complemented by experimental and theoretical studies of the kinetic aspects of M-C sigma-bond cleavage in group 4 metallocenes. These studies show that the entropy of activation is distinctly more negative for a Zr-C relative to a Hf-C bond dissociation. The combined results of the kinetic and electronic analysis herein shed new light on the different catalytic behavior of group 4 metallocenes with regard to the applied transition metal atom. In this context, deviations between zirconium-and hafnium based catalysts concerning the catalytic activity and the stereoregularities became clearly explainable, just as the well-known “hafnium-effect” in the production of extraordinarily high molecular weight polypropylenes.

First author: Zhang, NX, Theoretical Investigations on Molecular Packing Motifs and Charge Transport Properties of a Family of Trialkylsilylethynyl-Modified Pentacenes/Anthradithiophenes, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 18880, (2018)
Abstract: A family of trialkylsilylethynyl (TAS)-functionalized pentacenes (PENs) and anthradithiophenes (ADTs) are of immense interest due to their good solubility and air stability for uses in optoelectronic devices. Different TAS-substituted PENs and ADTs would result in different crystal packing motifs and carrier transport properties. Quantum nuclear-enabled hopping model combined with molecular dynamics (MD) simulations was used to investigate the effects of the chemical modifications on the carrier transport properties. The disorder-free hole mobilities show that 6,13-bis(trialkylsilylethynyl)anthradithiophenes (TAS-ADTs) own better intrinsic hole transport behaviors than 6,13-bis(trialkylsilylethynyl)pentacenes (TAS-PENs). The MD simulations show that in comparison with TAS-PENs, the thermal disorder effects are less significant for TAS-ADTs; this is probably due to the C-H center dot center dot center dot S hydrogen bonds, which are thought to stabilize the molecules in crystal environments. Furthermore, the syn-TASADTs show more serious nonlocal electron-phonon interactions than the anti-TAS-ADTs, which could be ascribed to the larger S center dot center dot center dot S overlap between neighboring molecules in the syn-TAS-ADTs. Additionally, symmetry-adapted perturbation theory and Hirshfeld surface analyses were performed to characterize the effects of noncovalent interactions on packing motifs. The results indicate that the C-H-center dot center dot center dot pi interaction, the balance relationship between electrostatic, induction, dispersion, and exchange repulsion interactions, and the C-H center dot center dot center dot S hydrogen bonds are responsible for the very different crystal packing motifs between these materials.

First author: Gieseking, RLM, Benchmarking Semiempirical Methods To Compute Electrochemical Formal Potentials, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 6809, (2018)
Abstract: Computational methods to predict and tune electrochemical redox potentials are important for the development of energy technologies. Here, we benchmark several semiempirical models to compute reduction potentials of organic molecules, comparing approaches based on (1) energy differences between the S-0, and one-electron-reduced D-0 states of the isolated molecules and (2) an orbital energy shift approach based on tuning the charge-transfer triplet energy of the Ag-20-molecule complex; the second model enables explicit modeling of electrode-molecule interactions. For molecules in solution, the two models yield nearly identical results. Both PM7 and PM6 predict formal potentials with only a slight loss of accuracy compared to standard density functional theory models, and the results are robust across several choices of geometries and implicit solvent models. PM6 and PM7 show dramatically improved accuracy over older semiempirical Hamiltonians (MNDO, AM1, PM3, and INDO/S). However, our recently developed INDO parameters model the electronic properties of our Ag-20 model electrode much more accurately than does PM7. These results demonstrate the need for further development of semiempirical models to accurately model molecules on surfaces.

First author: Sprague-Klein, EA, Photoinduced Plasmon-Driven Chemistry in trans-1,2-Bis(4-pyridyl)ethylene Gold Nanosphere Oligomers, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 10583, (2018)
Abstract: Continuous wave (CW) pump-probe surface-enhanced Raman spectroscopy (SERS) is used to examine a range of plasmon-driven chemical behavior in the molecular SERS signal of trans-1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on individual Au nanosphere oligomers (viz., dimers, trimers, tetramers, etc.). Well-defined new transient modes are caused by high fluence CW pumping at 532 nm and are monitored on the seconds time scale using a low intensity CW probe field at 785 nm. Comparison of time-dependent density functional theory (TD-DFT) calculations with the experimental data leads to the conclusion that three independent chemical processes are operative: (1) plasmon-driven electron transfer to form the BPE anion radical; (2) BPE hopping between two adsorption sites; and (3) trans-to-cis-BPE isomerization. Resonance Raman and electron paramagnetic resonance (EPR) spectroscopy measurements provide further substantiation for the observation of an anion radical species formed via a plasmon-driven electron transfer reaction. Applications of these findings will greatly impact the design of novel plasmonic devices with the future ability to harness new and efficient energetic pathways for both chemical transformation and photocatalysis at the nanoscale level.

First author: Salomon, W, Bicapped Keggin polyoxomolybdates: discrete species and experimental and theoretical investigations on the electronic delocalization in a chain compound, DALTON TRANSACTIONS, 47, 10636, (2018)
Abstract: Three monomeric polyoxometalates [M(C10H8N2)(3)][-PMoVI9MoV3O(40)Zn(2)(C10H8N2)(2)]2H(2)O (M-PMo12Zn2, M = Fe, Co, Ru) with {Zn(bpy)(2)}(2+) units capped on reduced -Keggin polyanions and [M(bpy)(3)](2+) counter-ions were synthesized under hydrothermal conditions. The 1D polymer [N(C4H9)(4)][Ru(C10H8N2)(3)][-PMoVI8MoV6O(43)] (Ru-PMo14) was prepared by a similar strategy, in the absence of 2,2-bpy ligands. In this chain capped reduced Keggin anions are linked via Mo-O-Mo bridges and are surrounded by both tetrabutylammonium cations and [Ru(bpy)(3)](2+) counter-ions. The compounds were characterized in the solid state by single crystal and powder X-ray diffraction and IR spectroscopy and in solution by P-31 NMR spectroscopy. P-31 diffusion ordered NMR spectroscopy (DOSY) indicates that the diffusion coefficient of the dissolved species of Ru-PMo14 corresponds to a dimeric structure. Magnetic susceptibility measurements performed on Ru-PMo14 show the existence of antiferromagnetic interactions between the d(1) electrons of the six Mo-V centers, with a singlet spin ground state. However, attempts to fit the data in the 2-300 K temperature range with Heisenberg Hamiltonians adapted for 0 or 1D systems suggest that these electrons are delocalized. Density Functional Theory (DFT) and Wave Function Theory (WFT) calculations indicate a migration of the electrons of the capping Mo-V centers into the PMo12 units at high temperature, allowing the rationalization of the experimental observations.

First author: Martinez, JP, Regioselectivity of the Pauson-Khand reaction in single-walled carbon nanotubes, NANOSCALE, 10, 15078, (2018)
Abstract: Chemical functionalization of nanotubes, in which their properties can be combined with those of other classes of materials, is fundamental to improve the physicochemical properties of nanotubes for potential technological applications. In this work, we theoretically and experimentally examine the Pauson-Khand reaction (PKR) on zig-zag, armchair, and chiral single-walled carbon nanotubes (SWCNTs). Our benchmarked density functional theory (DFT) calculations show that an alternative pathway to the widely accepted Magnus reaction pathway has significantly lower energy barriers, thus suggesting the use of this alternative pathway to predict whether a PKR on SWCNTs is favored or hampered. Accessible energy barriers of up to 16 kcal mol(-1) are estimated and our results suggest that semiconducting SWCNTs react faster than metallic ones, although both types can be functionalized. Guided by our theoretical predictions, cyclopentenones are successfully attached to SWCNTs by heating and are, subsequently, characterized in the laboratory.

First author: Aray, Y, Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 20417, (2018)
Abstract: The nature of the electron density localization in two MoS2 nanoclusters containing eight rows of Mo atoms, one with 100% sulphur coverage at the Mo edges (n8_100S) and the other with 50% coverage (n8_50S) was studied using a localized-electron detector function defined in the local moment representation. For n8_100S, pairs of neighboring S-2 dimers cover the edges and the electron density localization function analysis shows the presence of a local triangular-shaped ring zone of highly delocalized electrons along these edges, which corresponds to a good metallic conductor zone. The optimized geometry analysis shows that the Mo-S-2 bond length is much longer than that of the Mo-S bonds inside the cluster. The removal of one S atom from each sulphur dimer to create a cluster with 50% coverage produces a general compressive stress on the cluster optimized geometry, which shortens the Mo-S bond length, particularly at the edge. The electron density location function analysis shows that close to the cluster corners, a zone of highly delocalized electron zones with a characteristic semiconductor pattern and broken one-dimensional metallic ring was generated. These results suggest that the Mo-S-2 bond elongation produced by the sulphur dimers is similar to a MoS2 monolayer under tensile strain and is the origin of the one-dimensional metallic sites at the Mo-edges. In general, the present findings show excellent agreement with the key features of the reported ambient pressure X-ray photoemission spectra and the corresponding simulated scanning tunneling microscopy images.

First author: Alkorta, I, A theoretical study of perovskites related to CH3NH3PbX3 (X = F, Cl, Br, I), NEW JOURNAL OF CHEMISTRY, 42, 13889, (2018)
Abstract: The bond dissociation energies of MAPI (CH3NH3PbI3) and related perovskites (with F, Cl, Br instead of I and with bases other than methylamine) have been calculated using a simplified model consisting of a corner of the perovskite (PbX3-) and the methyl ammonium (CH3NH3+) and other protonated bases. The values obtained show that besides the size (related to the tolerance factor), the energy of the interaction should be considered. Using relativistic corrections (ADF), the H-1, C-13, N-15 and Pb-207 absolute shieldings were calculated and transformed into chemical shifts by empirical equations established here. The C-13 and N-15 light nuclei were well reproduced by the corner model but the Pb-207 chemical shifts need a large correction factor owing to the fact that lead in the perovskites is surrounded by six iodine atoms instead of the corner’s three atoms.

First author: Frances-Monerris, A, Synthesis and Computational Study of a Pyridylcarbene Fe(II) Complex: Unexpected Effects of fac/mer Isomerism in Metal-to-Ligand Triplet Potential Energy Surfaces, INORGANIC CHEMISTRY, 57, 10431, (2018)
Abstract: The synthesis and the steady-state absorption spectrum of a new pyridine-imidazolylidene Fe(II) complex (Fe-NHC) are presented. A detailed mechanism of the triplet metal-to-ligand charge-transfer states decay is provided on the basis of minimum energy path (MEP) calculations used to connect the lowest-lying singlet, triplet, and quintet state minima. The competition between the different decay pathways involved in the photoresponse is assessed by analyzing the shapes of the obtained potential energy surfaces. A qualitative difference between facial (fac) and meridional (mer) isomers’ potential energy surface (PES) topologies is evidenced for the first time in iron-based complexes. Indeed, the mer complex shows a steeper triplet path toward the corresponding (MC)-M-3 minimum, which lies at a lower energy as compared to the fac isomer, thus pointing to a faster triplet decay of the former. Furthermore, while a major role of the metal-centered quintet state population from the triplet (MC)-M-3 region is excluded, we identify the enlargement of iron-nitrogen bonds as the main normal modes driving the excited-state decay.

First author: Bista, D, Electronic and magnetic properties of Fe2Sin (1 <= n <= 12)(+/0/) clusters, CHEMICAL PHYSICS LETTERS, 706, 113, (2018)
Abstract: First principles studies on the geometry, electronic structure and magnetic properties of neutral, cationic, and anionic Fe2Sin (1 <= n <= 12) have been performed to better understand magnetic dopants in silicon. The doubly- Fe doped clusters in the size range 1 <= n <= 12 are marked by finite spin moments at the Fe sites, and Fe2Si3, Fe2Si4, and Fe2Si7 are found to exhibit antiferromagnetic coupling. Fe2Si3 and Fe2Si12 are relatively stable. We find that short Fe-Fe bond distances correlate with ferromagnetic coupling due to the destabilization of antibonding orbitals between the iron sites, while longer Fe-Fe bond distances lead to nonbonding atomic orbitals that favor antiferromagnetic coupling.

First author: Chang, CK, Improved Directional Hydrogen Bonding Interactions for the Prediction of Activity Coefficients with COSMO-SAC, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 57, 11229, (2018)
Abstract: In a recent work, Chen and Lin showed that the consideration of directional hydrogen bonding in the COSMO-SAC model significantly improves the description of solvation properties of the associating fluids. In their method, the direction of a hydrogen bond was determined based on VSEPR theory; however, this geometric approach does not reflect the local electronic environment of the lone pairs and cannot be applied to certain molecules such as DMSO and HF. In this work, we adopt a new scheme that determines the hydrogen bond acceptors of a molecule based on the minima in the molecular electrostatic potential (MESP). The hydrogen bonding directions thus determined result in improvements (about 5-7% for VLE) in the prediction of the COSMO-SAC model for a variety of thermodynamic properties and phase equilibria, such as vapor-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE), the infinite dilution activity coefficient (IDAC), and the octanol-water partition coefficient (K-ow) calculations.

First author: Llancalahuen, FM, New Properties of a Bioinspired Pyridine Benzimidazole Compound as a Novel Differential Staining Agent for Endoplasmic Reticulum and Golgi Apparatus in Fluorescence Live Cell Imaging, FRONTIERS IN CHEMISTRY, 6, 11229, (2018)
Abstract: In this study, we explored new properties of the bioinspired pyridine benzimidazole compound B2 (2,4-di-tert-butyl-6-(3H-imidazo[4,5-c]pyridine-2-yl)phenol) regarding its potential use as a differential biomarker. For that, we performed 1D (HNMR)-H-1 (TOCSY), UV-Vis absorption spectra in different organic solvents, voltammetry profile (including a scan-rate study), and TD-DFT calculations that including NBO analyses, to provide valuable information about B2 structure and luminescence. In our study, we found that the B2 structure is highly stable, where the presence of an intramolecular hydrogen bond (IHB) seems to have a crucial role in the stability of luminescence, and its emission can be assigned as fluorescence. In fact, we found that the relatively large Stokes Shift observed for B2 (around 175 nm) may be attributed to the stability of the B2 geometry and the strength of its IHB. On the other hand, we determined that B2 is biocompatible by cytotoxicity experiments in HeLa cells, an epithelial cell line. Furthermore, in cellular assays we found that B2 could be internalized by passive diffusion in absence of artificial permeabilization at short incubation times (15 min to 30 min). Fluorescence microscopy studies confirmed that B2 accumulates in the endoplasmic reticulum (ER) and Golgi apparatus, two organelles involved in the secretory pathway. Finally, we determined that B2 exhibited no noticeable blinking or bleaching after 1 h of continuous exposure. Thus, B2 provides a biocompatible, rapid, simple, and efficient way to fluorescently label particular organelles, producing similar results to that obtained with other well-established but more complex methods.

First author: Surukonti, N, Mono substituted pyrenes as multifunctional materials for OLED: Analysis of the substituent effects on the charge transport properties using DFT methods, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1138, 48, (2018)
Abstract: In this work, with a general interest to understand the charge transport properties of mono substituted pyrene molecules which can be used as multifunctional materials in Organic Light Emitting Diodes (OLED), we have analyzed the charge transport properties calculated from DFT methods for a number of the mono substituted pyrene molecules whose crystal structures have been obtained from Cambridge structural data base (CSD). The data for the analysis was obtained by optimizing the geometries of the molecules in gas phase and subsequently generating the frontier orbitals and calculation of reorganization energies; transfer integrals in the solid state for various path ways were also calculated. The drift mobilities were then estimated from this data. The reasons for the variation of the drift mobilities in this group are then analyzed and the pattern reported. This work would be useful for generating new efficient pyrene derivatives and for improving existing ones for use in OLED.

First author: Talbi-Ingrachen, F, DFT investigation of methane metathesis with L(2)AnCH(3) actinide complexes catalysts (L = Cl, Cp, Cp*; An = Ac, Th, Pa, U, Np, Pu), COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1138, 123, (2018)
Abstract: In order to understand the catalytic activity of the actinide complexes L(2)AnCH(3) (An = Ac, Th, Pa, U, Np and Pu; L = Cl, Cp and Cp*) towards the activation of the C-H bond of methane, relativistic ZORA/DFT investigations have been carried out. The results obtained from Linear Transit (LT) and Intrinsic Reaction Coordinate (IRC) calculations show that the mechanism involved in these reactions starts with a proton transfer from methane to the methyl group of the complex leading to the formation of a four center transition state characteristic of a bond metathesis process. The U(III) and Np(III) complexes exhibit a high ability to activate the methane C-H bond, the activation energies being respectively equal to 10.5, 17.1 and 21.0 kcal/mol for Cl2NpCH3, Cp2NpCH3 and Cp-2*UCH3 respectively whereas the Th(III) complexes exhibit the highest activation energy, 34.9 kcal/mol for Cp-2*ThCH3. Since the initial step of the reaction is viewed as a proton transfer, the analysis of the charges evolution and frontier molecular orbitals of the complexes and the transition states, shows that a facile polarization of the bonds involved in the reaction has the effect of reducing the activation energy. The role of the metallic 5f orbitals in the reactivity of the L(2)AnCH(3) compounds towards CH4 is analyzed and discussed. More important the 5f actinide orbital contribution, less important is the activation energy.

First author: Montoro-Garcia, C, Impact of Conformational Effects on the Ring-Chain Equilibrium of Hydrogen-Bonded Dinucleosides, CHEMISTRY-A EUROPEAN JOURNAL, 24, 11983, (2018)
Abstract: Supramolecular ring-versus-chain equilibria are ubiquitous in biological and synthetic systems. Understanding the factors that decide whether a system will fall on one side or the other is crucial to the control of molecular self-assembly. This work reports results with two kinds of dinucleoside monomers, in which the balance between closed cycles and open polymers is found to depend on subtle factors that rule conformational equilibria, such as steric hindrance, intramolecular interactions, or pi-conjugation pathways.

First author: Sahoo, S, Graphene Supported Single Atom Transition Metal Catalysts for Methane Activation, CHEMCATCHEM, 10, 3229, (2018)
Abstract: Single-atom catalysis is a relatively new concept to enhance catalytic activity of transition metal atoms through proper choice of support. The interest in such systems is due to the fact that both the quantum size effect and support-catalyst interactions may lead to unique electronic structures that may enhance catalytic properties. This allows for the design of materials systems at the atomic scale, tailored for specific reactions. Utilizing this concept, we investigated theoretically free and graphene supported single transition metal (TM) Cr, Mn, Fe, Co, and Cu atoms for activation of methane and identified catalytically active centers through C-H bond cleavage. We employed here dispersion corrected density functional theory taking into account the generalized gradient approximation and exchange correlations. The results indicate that graphene supported TM systems display relatively low activation barriers for both TM-adsorbed and embedded types of graphene supports compared to that of free TM-methane systems. The reaction pathway for graphene-supported systems is characterized by a single spin state thereby eliminating a multi-state reactivity as observed for free TM-methane systems. Our findings show that the interaction of three d-orbitals (d(xz), d(yz) and d(z)2) with methane, their relative position, and occupancy play a key role in governing the catalytic activity of supported TM systems.

First author: Wang, Y, Strategies on Cyclometalating Ligand Substitution of Several Ir(III) Complexes: Theoretical Investigation of Different Molecular Behaviors, ORGANOMETALLICS, 37, 2491, (2018)
Abstract: A series of Ir(III) light-emitting materials, namely Ir(R-dfpypy)(2)pic (R-dfpypy = 2′,6′-difluoro-4-R-2,3′-bipyridine, pic = picolinate), where R = -H (1), -CN (2), -OMe (3), -NMe2 (4), -N(CF3), (5), is evaluated through a comprehensive theoretical approach in this study. It has been observed in experiments that different kinds of substituent groups on the dfpypy cyclometalating ligands brought about considerable photophysical discrepancies. From a theoretical aspect, these Ir(III) complexes have no obvious differences in the calculation of radiative decay rates (k(r)), which is consistent with experimental results. A convolution method utilized in computation of the non-radiative decay rate (k(nr)) reveals that complex 4 is nonemissive due to its 1 or 2 orders of magnitude larger k(nr) in comparison to the corresponding k(r). Further decomposition of vibration modes that contribute the most to reorganization energies in low- and high-frequency regions into internal coordinates indicates that it is the intense oscillation of bulky substituent groups in complex 4 that leads to its faster k(nr). On the basis of our corroborated theoretical approach, the issue of whether the character or the bulk of the substituent groups influences the quantum efficiency of these similar Ir(III) light-emitting materials is determined. Therefore, complex 5, which replaces hydrogen with fluorine atoms in the substituent groups of complex 4, was investigated further through vibrational analysis. In comparison with the first four compounds, complex 5 has a comparable calculated k(r) value and has an even larger k(nr) than complex 4. Although both compounds 2 and 5 have electron-withdrawing substituent groups, the chemical properties of substituent groups cannot absolutely determine the nonradiative decay process. Moreover, the metal-centered ((MC)-M-3) triplet excited states and other relative temperature-dependent nonradiative photodeactivation

First author: Kharitono, VB, Indenyl Rhodium Complexes with Arene Ligands: Synthesis and Application for Reductive Amination, ORGANOMETALLICS, 37, 2553, (2018)
Abstract: An efficient protocol for synthesis of indenyl rhodium complexes with arene ligands has been developed. The hexafluoroantimonate salts [(eta(5)-indenyl)Rh(arene)]-(SbF6)(2) (arene = benzene (2a), o-xylene (2b), mesitylene (2c), durene (2d), hexamethylbenzene (2e), and [2.2]-paracyclophane (2g)) were obtained by iodide abstraction from [(eta(5)-indenyl)RhI2](n) (1) with AgSbF6 in the presence of benzene and its derivatives. The procedure is also suitable for the synthesis of the dirhodium arene complex [(mu-eta:eta’-1,3-dimesitylpropane){Rh(eta(5)-indenyl)}(2)](SbF6)(4) (3) starting from 1,3-dimesitylpropane. The structures of [2e](SbF6)(2), [2g](SbF6)(2), and [3](SbF6)(4) were determined by X-ray diffraction. The last species has a sterically unfavorable conformation, in which the bridgehead carbon atoms of the indenyl ligand are arranged close to the propane linker between two mesitylene moieties. Experimental and DFT calculation data revealed that the benzene ligand in 2a is more labile than that in the related cyclopentadienyl complexes [(C5R5)Rh(C6H6)](2+). Complex 2c effectively catalyzes the reductive amination reaction between aldehydes and primary (or secondary) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in very high yields (80-99%). This protocol is the most active in water.

First author: Foroutan-Nejad, C, Isocorroles as Homoaromatic NIR-Absorbing Chromophores: A First Quantum Chemical Study, SCIENTIFIC REPORTS, 8, 2553, (2018)
Abstract: Density functional theory calculations of magnetically induced current densities have revealed high diatropic ring currents in unsubstituted isocorrole consistent with homoaromatic character. An examination of the Kohn-Sham molecular orbitals showed clear evidence of homoconjugative interactions in four occupied p-type molecular orbitals as well as in the LUMO. Remarkably, substituents at the saturated meso position were found to exert a dramatic influence on the overall current density pattern. Thus, whereas bis(trimethylsilyl)-substitution strongly enhanced the peripheral diatropic current (consistent with enhanced homoaromaticity), difluoro-substitution engendered a strong, net paratropic current (consistent with antihomoaromaticity). In this respect, isocorroles stand in sharp contrast to benzenoid aromatics, for which substituents typically exert a small influence on the current density distribution.

First author: Poggel, C, Relativistic Effects on Donor-Acceptor Interactions in Coinage Metal Carbonyl Complexes [TM(CO)(n)](+) (TM=Cu, Ag, Au; n=1, 2), CHEMISTRY-A EUROPEAN JOURNAL, 24, 11675, (2018)
Abstract: DFT calculations at the BP86+D3(BJ)/TZ2P level, with and without relativistic contributions, using the ZORA approximation have been carried out for the coinage metal carbonyl complexes [TM(CO)](+) and [TM(CO)(2)](+) with TM = Cu, Ag, Au. The nature of the metal-CO interactions and the relativistic effects on the different energy terms were analyzed with the EDA-NOCV method. The three terms Pauli repulsion, Coulomb attraction, and orbital interactions become stronger when relativistic effects are accounted for; the strengthening exhibits the order Delta E-Pauli > Delta E-elstat > Delta E-orb. The largest change in the calculated energy terms is, as expected, found for gold, followed by silver and copper. The relativistic contributions on the Cu+-CO interactions are significant and thus, relativistic effects should not be neglected in quantum chemical calculations in copper compounds. Breakdown of the orbital term into individual contributions shows that the relativistic effect in [TM(CO)](+) is for the TM+<- CO sigma-donation stronger than for TM+-> CO pi-backdonation, except for TM=Cu. The trend in the dicarbonyls [TM(CO) 2]+ has the order (+,+) sigma-donation > pi-backdonation > (+, -) sigma-donation. The bonding analysis reveals that there is a sizeable contribution from TM+-> CO sigma-backdonation in all carbonyl complexes that further stabilizes the metal-carbonyl bonds. In [Au(CO)(2)](+) it becomes even larger than the (+, -) OC -> TM+<- CO sigma-donation. The trends of the various orbital interactions and the effect of relativity on their strength can be understood when the valence orbitals of the metals and CO are considered.

First author: Kaufmann, C, Discrete pi-Stacks of Perylene Bisimide Dyes within Folda-Dimers: Insight into Long- and Short-Range Exciton Coupling, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 9986, (2018)
Abstract: Four well-defined pi-stacks of perylene bisimide (PBI) dyes were obtained in solution by covalent linkage of two chromophores with spacer units of different length and sterical demand. Structural elucidation of the folda-dimers by in-depth nuclear magnetic resonance studies and geometry optimization at the level of density functional theory suggest different, but highly defined molecular arrangements of the two chromophores in the folded state enforced by the various spacer moieties. Remarkably, the dye stacks exhibit considerably different optical properties as investigated by UV/vis absorption and fluorescence spectroscopy, despite only slightly different chromophore arrangements. The distinct absorption properties can be rationalized by an interplay of long- and short-range exciton coupling resulting in optical signatures ranging from conventional H-type to monomer like absorption features with low and appreciably high fluorescence quantum yields, respectively. To the best of our knowledge, we present the first experimental proof of a PBI-based “null-aggregate”, in which long- and short-range exciton coupling fully compensate each other, giving rise to monomer-like absorption features for a stack of two PBI chromophores. Hence, our insights pinpoint the importance of charge-transfer mediated short-range coupling that can significantly influence the optical properties of PBI pi-stacks.

First author: Zhou, XB, Study on the Shock Sensitivity of the Hydrolysis Products of Hexachlorodisilane, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 57, 10354, (2018)
Abstract: The hydrolysis products of hexachlorodisilane (HCDS) show common heat sensitivity and can become shock sensitive under certain conditions. Study of the shock sensitivity has been difficult due to the unpredictable nature of this phenomenon. We have identified the parameters affecting the shock sensitivity of the materials and developed synthetic methods to consistently prepare the hydrolysis products with a high shock sensitivity. We characterized the composition of the hydrolysis products to be [SiOx (OH)(4-2x)](m)-[Si2Oy(OH)(6-2y)](n)(H2O)(o) where x is 0-2, y is 0-3, m is less than n, and o varies. The hydrogen atoms in the silanol groups or absorbed water are the oxidant and the silicon atoms in the Si-Si bonds are the reductant. When the materials are disturbed by a thermal or mechanical impact, fast redox reactions happen to form molecular hydrogen. A sequence of free radical reactions was proposed to explain the shock sensitivity and shock-induced chemical transformation.

First author: Ramanantoanina, H, A DFT-based theoretical model for the calculation of spectral profiles of lanthanide M-4(,5)-edge x-ray absorption, JOURNAL OF CHEMICAL PHYSICS, 149, 10354, (2018)
Abstract: This presentation reports the theoretical study of 3d core-electron excitation in lanthanide compounds in terms of electronic structure effects and optical properties. The calculations are done at the Density-Functional Theory (DFT) level complemented with an effective Hamiltonian based on ligand-field theory. The strategy consists of obtaining from DFT a totally symmetric density, where an active subspace is set up that forms the basis of the fivefold 3d and sevenfold 4f atomic orbitals of the lanthanide ion. This active subspace is defined with the fractional occupation of electrons, which represents openshell species with the composite configuration 3d(9)4f(n+1). Based on the ligand-field analysis of the DFT results, the multiplet energies and ligand-field effects associated with the configuration 3d(9)4f(n+1) are evaluated; and the X-ray absorption spectra are simulated in terms of the intra-atomic 4f(n) -> 3d(9)4f(n+1) electron transitions within the electric-dipole approximation. Examples for application are proposed taking into consideration the isolated trivalent lanthanides ions and compounds Cs2NaPrX6, with X = F, Cl, and Br. The results are compared with available experimental data, where a good agreement is qualitatively achieved. Also, the screening of the inter-electron repulsion and spin-orbit coupling interaction is numerically obtained that allows one to establish a fully non-empirical treatment of the 3d core-electron excitation, which can be valuable in the characterization and modeling of the spectral profiles of lanthanide M-4,M-5-edge X-ray absorption spectroscopy. The enclosed theoretical model, which is being implemented in the Amsterdam Density Functional (ADF) suite of programs, is computationally economic and can be applied to any lanthanide system without limitations in terms of the size of the matrix elements of the effective Hamiltonian or the coordination symmetry of the lanthanide center. Published by AIP Publishing.

First author: Grabowski, SJ, Coordination of Be and Mg Centres by HCN Ligands – Be…N and Mg…N Interactions, CHEMPHYSCHEM, 19, 1830, (2018)
Abstract: B97XD/aug-cc-pVTZ calculations were performed for clusters of Z(2+) cations (Z=Be and Mg) and HCN molecules (up to six molecules). The clusters of Be(CH3)(2) and Mg(CH3)(2) with HCN species were also calculated to analyse the influence of the Be/Mg-C formally covalent bonds on interactions of Be or Mg centre with ligands. The beryllium and magnesium centres possess different areas of a positive electrostatic potential that depend on a number of HCN ligands in the cluster considered. Numerous correlations between geometrical, energetic and topological parameters of the clusters considered are discussed since various theoretical approaches are applied; Quantum Theory of Atoms in Molecules’, Natural Bond Orbital method and decomposition of the energy of interaction. The Be/Mg…N interactions classified as beryllium and magnesium bonds possess numerous characteristics which are known for the hydrogen bonds. Different types of coordination of Be and Mg centres analysed here exist also in crystal structures.

First author: Chyba, J, Through-Space Paramagnetic NMR Effects in Host-Guest Complexes: Potential Ruthenium(III) Metallodrugs with Macrocyclic Carriers, INORGANIC CHEMISTRY, 57, 8735, (2018)
Abstract: The potential of paramagnetic ruthenium(III) compounds for use as anticancer metallodrugs has been investigated extensively during the past several decades. However, the means by which these ruthenium compounds are transported and distributed in living bodies remain relatively unexplored. In this work, we prepared several novel ruthenium(III) compounds with the general structure Na+[trans-(RuCI4)-C-III(DMSO)(L)](-)undefined (DMSO = dimethyl sulfoxide), where L stands for pyridine or imidazole linked with adamantane, a hydrophobic chemophore. The supramolecular interactions of these compounds with macrocyclic carriers of the cyclodextrin (CD) and cucurbit[n]uril (CB) families were investigated by NMR spectroscopy, X-ray diffraction analysis, isothermal titration calorimetry, and relativistic DFT methods. The long-range hyperfine NMR effects of the paramagnetic guest on the host macrocycle are related to the distance between them and their relative orientation in the host-guest complex. The CD and CB macrocyclic carriers being studied in this account can be attached to a vector that attracts the drug-carrier system to a specific biological target and our investigation thus introduces a new possibility in the field of targeted delivery of anticancer metallodrugs based on ruthenium(III) compounds.

First author: Jeremias, L, Interplay of Through-Bond Hyperfine and Substituent Effects on the NMR Chemical Shifts in Ru(III) Complexes, INORGANIC CHEMISTRY, 57, 8748, (2018)
Abstract: The links between the molecular structure and nuclear magnetic resonance (NMR) parameters of paramagnetic transition-metal complexes are still relatively unexplored. This applies particularly to the contact term of the hyperfine contribution to the NMR chemical shift. We report combining experimental NMR with relativistic density functional theory (DFT) to study a series of Ru(III) complexes with 2-substituted beta-diketones. A series of complexes with systematically varied substituents was synthesized and analyzed using H-1 and C-13 NMR spectroscopy. The NMR spectra recorded at several temperatures were used to construct Curie plots and estimate the temperature-independent (orbital) and temperature-dependent (hyperfine) contributions to the NMR shift. Relativistic DFT calculations of electron paramagnetic resonance and NMR parameters were performed to interpret the experimental observations. The effects of individual factors such as basis set, density functional, exact-exchange admixture, and relativity are analyzed and discussed. Based on the calibration study in this work, the fully relativistic Dirac-Kohn-Sham (DKS) method, the GIAO approach (orbital shift), the PBE0 functional with the triple-zeta valence basis sets, and the polarizable continuum model for describing solvent effects were selected to calculate the NMR parameters. The hyperfine contribution to the total paramagnetic NMR (pNMR) chemical shift is shown to be governed by the Fermi-contact (FC) term, and the substituent effect (H vs Br) on the through-bond FC shifts is analyzed, interpreted, and discussed in terms of spin-density distribution, atomic spin populations, and molecular-orbital theory. In contrast to the closed-shell systems of Rh(III), the presence of a single unpaired electron in the open-shell Ru(III) analogs significantly alters the NMR resonances of the ligand atoms distant from the metal center in synergy with the substituent effect.

First author: Jiang, F, Redox Interconversion between Cobalt(III) Thiolate and Cobalt(II) Disulfide Compounds, INORGANIC CHEMISTRY, 57, 8796, (2018)
Abstract: The redox interconversion between Co(III) thiolate and Co(II) disulfide compounds has been investigated experimentally and computationally. Reactions of cobalt(II) salts with disulfide ligand (LSSL1)-S-1 ((LSSL1)-S-1 = di-2-(bis(2-pyridylmethyl)amino)-ethyl disulfide) result in the formation of either the high-spin cobalt(II) disulfide compound [Co-2(11)((LSSL1)-S-1)Cl-4] or a low-spin, octahedral cobalt(III) thiolate compound, such as [Co-III ((LS)-S- 1)-(MeCN)(2)] (BF4)(2). Addition of thiocyanate anions to a solution containing the latter compound yielded crystals of [Co-III((LS)-S-1)(NCS)(2)]. The addition of chloride ions to a solution of [Co-lll((LS)-S-1)-(MeCN)(2)] (BF4)(2 )in acetonitrile results in conversion of the cobalt(III) thiolate compound to the cobalt(II) disulfide compound [Co-2(11)((LSSL1)-S-1) Cl-4], as monitored with UV-vis spectroscopy; subsequent addition of AgBF4 regenerates the Co(III) compound. Computational studies show that exchange by a chloride anion of the coordinated acetonitrile molecule or thiocyanate anion in compounds [Co-llI ((LS)-S-1)-(MeCN)(2)](2+) and [Co-III ((LS)-S-1) (NCS)(2)] induces a change in the character of the highest occupied molecular orbitals, showing a decrease of the contribution of the p orbital on sulfur and an increase of the d orbital on cobalt. As a comparison, the synthesis of iron compounds was undertaken. X-ray crystallography revealed that structure of the dinuclear iron(II) disulfide compound [F-11((LSSL1)-S-1) Cl-4] is different from that of cobalt(II) compound [Co-2(11)((LSSL1)-S-1) CL4]. In contrast to cobalt, reaction of ligand (LSSL1)-S-1 with [Fe(MeCN)(6)] (BF4)(2) did not yield the expected Fe(III) thiolate compound. This work is an unprecedented example of redox interconversion between a high-spin Co(II) disulfide compound and a low-spin Co(III) thiolate compound triggered by the nature of the anion.

First author: van Niekerk, DME, A DFT Mechanistic Study of the trans-[(OsO2)-O-VI(OH)(4)](2-) and [(OsO4)-O-VIII(OH)(n)](n-) (n = 1, 2 cis) Comproportionation Proton-Coupled Electron Transfer Reaction, INORGANIC CHEMISTRY, 57, 8909, (2018)
Abstract: Herein, we present a DFT computational study of the trans-[(OsO2)-O-VI(OH)(4)](2) and [(OsO4)-O-VIII(OH)(n)](n) (n = 1 2 cis) comproportionation reaction mechanism that occurs in a basic aqueous matrix. The reaction pathway where [(OsO4)-O-VIII(OH)] reacts with trans-[(OsO2)-O-VI(OH)(4)](2) via an intermediate mediated concerted electronproton transfer yielded the best agreement with experiment (Delta H-double dagger degrees Delta S-double dagger degrees and Delta(double dagger)G degrees experimental data for the forward reaction are 10.3 +/- 0.5 kcal mol(1) 2.6 +/- 1.6 cal mol(1) K-1 and 11.1 +/- 0.9 kcal mol(1) and for the reverse reaction are 6.7 +/- 1.0 kcal mol(1) 63.6 +/- 3.4 cal mol(1) K-1 and 12.2 +/- 2.0 kcal mol(1) respectively where at the PBE-D3 level for the forward reaction are 11.3 kcal mol(1) 9.8 cal mol(1) K-1 and 14.2 kcal mol(1) and for the reverse reaction are 11.8 kcal mol(1) 80.7 cal mol(1) K-1 and 12.3 kcal mol(1) respectively) and consists of (i) formation of a (singlet spin state) noncovalent adduct [(OsOH)-O-VIII-Os-VI](3) (ii) spin-forbidden concerted electronproton transfer (i-EPT) from the trans-[(OsO2)-O-VI(OH)(4)](2) donor to the OsVIII acceptor to form a second (triplet spin state) noncovalent adduct [(OsOHOsVII)-O-VII](3-) (iii) separation of the Os-VII monomers and finally (iv) interconversion of the separated species to form trans-[(OsO3)-O-VII(OH)(2)](2-) and mer-[(OsO3)-O-VII(OH)(3)](2-) stereoisomer species. i-EPT from Os-VI to the Os-VIII species was found to be the rate-determining step which corroborated the experimental evidence (kinetic isotope effect) that the rate-determining step involves the transfer of a proton.

First author: Hoseini, SJ, A Bridging Peroxide Complex of Platinum(IV), INORGANIC CHEMISTRY, 57, 8951, (2018)
Abstract: The photolysis of the allylplatinum(IV) complex [PtBr(C3H5)(4-MeC6H4)(2)(bipy)], 1, bipy = 2,2′-bipyridine, in air yielded [{PtBr(4-MeC6H4)(2)(bipy)}(2)(mu-O-2)], 2, the first diplatinum-(IV) complex containing a single bridging peroxide ligand. The PtO-OPt bond distance in 2 is 1.481(3) A. Complex 2 is thought to be formed by homolysis of the allyl-platinum bond of 1, followed by reaction of the platinum(III) intermediate[PtBr(4-MeC6H4)(2)(bipy)] with oxygen.

First author: Szell, PMJ, Comparing the Halogen Bond to the Hydrogen Bond by Solid-State NMR Spectroscopy: Anion Coordinated Dimers from 2-and 3-Iodoethynylpyridine Salts, CHEMISTRY-A EUROPEAN JOURNAL, 24, 11364, (2018)
Abstract: Halogen bonding is an increasingly important tool in crystal engineering, and measuring its influence on the local chemical and electronic environment is necessary to fully understand this interaction. Here, we present a systematic crystallographic and solid-state NMR study of self-complementary halogen-bonded frameworks built from the halide salts (HCl, HBr, HI, HI3) of 2-iodoethynylpyridine and 3-iodoethynylpyridine. A series of single crystal X-ray structures reveals the formation of discrete charged dimers in the solid state, directed by simultaneous X-H-N+ hydrogen bonds and C-IX- halogen bonds (X=Cl, Br, I). Each compound was studied using multinuclear solid-state magnetic resonance spectroscopy, observing H-1 to investigate the hydrogen bonds and C-13, Cl-35, and Br-79/81 to investigate the halogen bonds. A natural localized molecular orbital analysis was employed to help interpret the experimental results. (HSSNMR)-H-1 spectroscopy reveals a decrease in the chemical shift of the proton participating in the hydrogen bond as the halogen increases in size, whereas the (CSSNMR)-C-13 reveals an increased C-13 chemical shift of the C-I carbon for C-IX- relative to C-IN halogen bonds. Additionally, Cl-35 and Br-79/81 SSNMR, along with computational results, have allowed us to compare the C-IX- halogen bond involving each halide in terms of NMR observables. Due to the isostructural nature of these compounds, they are ideal cases for experimentally assessing the impact of different halogen bond acceptors on the solid-state NMR response.

First author: Nagurniak, GR, The ability of Ex(2)Box(4+) to interact with guests containing -electron-rich and -electron-poor moieties, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 118, 11364, (2018)
Abstract: The ability of ExBox(4+) as a host, able to trap guests containing both -electron rich (polycyclic aromatic hydrocarbons-PAHs) and -electron poor (quinoid- and nitro-PAHs) moieties was investigated to shed light on the main factors that control the host-guest (HG) interaction. The nature of the HG interactions was elucidated by energy decomposition (EDA-NOCV), noncovalent interaction (NCI), and magnetic response analyses. EDA-NOCV reveals that dispersion contributions are the most significant to sustain the HG interaction, while electrostatic and orbital contributions are very tiny. In fact, no significant covalent character in the HG interactions was observed. The obtained results point strictly to NCIs, modulated by dispersion contributions. Regardless of whether the guests contain -electron-rich or -electron-poor moieties, and no significant charge-transfer was observed. All in all, HG interactions between guests 3-14 and host 2 are predominantly modulated by – stacking.

First author: Kurimoto, Y, Efficient Synthesis and Properties of [1]Benzothieno[3,2-b]thieno[2,3-d]furans and [1]Benzothieno[3,2-b]thieno[2,3-d]thiophenes, ASIAN JOURNAL OF ORGANIC CHEMISTRY, 7, 1635, (2018)
Abstract: Efficient syntheses of benzodithienofuran (BDTF; [1]benzothieno[3,2-b]thieno[2,3-d]furan) and benzodithienothiophene (BDTT; [1]benzothieno[3,2-b]thieno[2,3-d]thiophene) were achieved by the combination of an addition-elimination reaction, reduction, and Pd-catalyzed dehydrogenative cyclization. We also achieved the synthesis of pi-ex- tended BDTF and BDTT derivatives through the use of coupling reactions. The detailed physical properties of these compounds were investigated. The newly synthesized BDTFs exhibited strong fluorescence compared with BDTTs. 2,2′-Bis([1]benzothieno[3,2-b]thieno[2,3-d]furan) (BBTTF) exhibited p-type organic field-effect transistor (OFET) properties.

First author: Gusarov, S, Coupling methods of quantum chemistry, molecular simulations and dissipative particle dynamics with molecular theory of solvation: Towards a general framework of multiscale methods, JOURNAL OF COUPLED SYSTEMS AND MULTISCALE DYNAMICS, 6, 81, (2018)
Abstract: Multiscale approximations are very frequent in science and in particular in theory. Within this framework, one can achieve improved accuracy, efficiency, and applicability by coupling models and methods on different scales. In this work, we will address different aspects of the combination of computational chemistry methods at different time and length scales in modern material and biomolecular science. This is a rapidly developing field which benefits many areas of research and applications by providing fundamental understanding and predictions. In addition, it could also play a special role in commercialization by guiding new developments and by allowing quick evaluation of prospective research projects. Special attention is given to molecular theory of solvation which allows us to accurately introduce the effect of environment on complex nano-, bio- or macromolecular system. The uniqueness of that approach is that it can be naturally coupled with the full range of computational chemistry approaches (QM, MM, and Coarse Grained).

First author: Fu, B, Photoinduced Anomalous Coulomb Blockade and the Role of Triplet States in Electron Transport through an Irradiated Molecular Transistor, NANO LETTERS, 18, 5015, (2018)
Abstract: In this study, we explore photoinduced electron transport through a molecule weakly coupled to two electrodes by combining first-principles quantum chemistry calculations with a Pauli master equation approach that accounts for many-electron states. In the incoherent limit, we demonstrate that energy-level alignment of triplet and charged states plays a crucial role, even when the rate of intersystem crossing is much smaller than the rate of fluorescence. Furthermore, the field intensity dependence and an upper bound to the photoinduced electric current can be analytically derived in our model. Under an optical field, the conductance spectra (charge stability diagrams) exhibit unusual Coulomb diamonds, which are associated with molecular excited states, and their widths can be expressed in terms of energies of the molecular electronic states. This study offers new directions for exploring optoelectronic response in nanoelectronics.

First author: Zeng, ZQ, Non-flammable electrolytes with high salt-to-solvent ratios for Li-ion and Li-metal batteries, NATURE ENERGY, 3, 674, (2018)
Abstract: Non-flammable electrolytes could intrinsically eliminate fire hazards and improve battery safety, but their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces. Here, we report an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent. At a high Li salt-to-solvent molar ratio (-1:2), the phosphate solvent molecules are mostly coordinated with the Li+ cations, and the undesired reactivity of the solvent molecules toward the graphite anode can be effectively suppressed. High cycling Coulombic efficiency (99.7%), good cycle life and safe operation of commercial 18650 Li-ion cells with these electrolytes are demonstrated. In addition, these non-flammable electrolytes show reduced reactivity toward Li-metal electrodes. Non-dendritic Li-metal plating and stripping in Li-Cu half-cells are demonstrated with high Coulombic efficiency (>99%) and good stability.

First author: Wang, Y, A complete evaluation from theoretical aspect on the phosphorescent efficiency improvement through ancillary ligands modifications of a blue Ir (III) complex, ORGANIC ELECTRONICS, 59, 293, (2018)
Abstract: Five blue-emitting cationic Ir(III) materials with the form [Ir (C<^>N)(2)(N<^>N)](+), where C<^>N = 2-(2,4-difluorophenyl)pyridine (dfppy) cyclometalating ligands, and N<^>N = biimidazole-type ancillary ligands, are investigated through a comprehensive theoretical scheme. Experimental researches concentrating on decorations of ancillary ligand, revealed that complex with 1,1′-CH3-2,2′-biimidazole (dMebiim) ancillary ligand is a non-emissive material due to the detrimental twisting of dMebiim resulting from steric hindrance of the methyl groups. When getting rid of methyl substituents that becomes the complex with a 1,1′-H-2,2′-biimidazole ancillary ligand, the quantum efficiency has been lifted to a large extent. Further rigidifying the biimidazole-type ancillary ligands, complex with an ortho-xylyl-tethered biimidzole ancillary ligand (1) was synthesized and has a higher quantum yield. From experimental aspect, the approaches employed in quantum efficiency enhancement is mainly concentrate on geometrical control through chelate effect. However, from theoretical aspect, we are not confined the strategies to rigidify the biimidazole ligand by divers chelates. In this study, our comprehensive theoretical scheme is firstly employed on the synthesized complex 1. Results show that the calculated radiative (k(r)) and non-radiative (k(nr)) decay rates are consistence with the experimental findings. And further vibrational analysis clarified its nuclear behaviors during electronic transitions. Based on such vibrational analysis, it is found that substituting on the flanks of biimidzole can also effectively avoid detrimental twist. Therefore, in this study, we provide several new designed Ir(III) materials with substituent groups on the flanks of biimidzole, with the consideration of electron-withdrawing or -donating characters of the substituent groups. And Ir(III) materials with better performance are predicted from theoretical aspect.

First author: Murcia, RA, Development of Antibacterial and Antifungal Triazole Chromium(III) and Cobalt(II) Complexes: Synthesis and Biological Activity Evaluations, MOLECULES, 23, 293, (2018)
Abstract: In this work, six complexes (2-7) of Cr(III) and Co(II) transition metals with triazole ligands were synthesized and characterized. In addition, a new ligand, 3,5-bis(1,2,4-triazol-1-ylmethyl)toluene (1), was synthesized and full characterized. The complexes were obtained as air-stable solids and characterized by melting point, electrical conductivity, thermogravimetric analysis, and Raman, infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that complexes 3-7 had 1:1 (M:L) stoichiometries and octahedral geometries, while 2 had a 1:2 (M:L) ratio, which was supported by DFT calculations. The complexes and their respective ligands were evaluated against bacterial and fungal strains with clinical relevance. All the complexes showed higher antibacterial and antifungal activities than the free ligands. The complexes were more active against fungi than against bacteria. The activities of the chromium complexes against Candida tropicalis are of great interest, as they showed minimum inhibitory concentration 50 (MIC50) values between 7.8 and 15.6 mu g mL(-1). Complexes 5 and 6 showed little effect on Vero cells, indicating that they are not cytotoxic. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activities.

First author: Jiang, T, Accurate Quantum Mechanics/Molecular Mechanics Simulation of Aqueous Solutions with Tailored Molecular Mechanics Models, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 3943, (2018)
Abstract: In recent years, quantum mechanical/molecular mechanical (QM/MM) methods have emerged that are designed specifically for chemical reactions in water. Despite the many advances, a remaining problem is that the patchwork of QM and MM descriptions changes the solvent structure. In a solvent as intricately connected as water, such structural changes can alter a chemical process even across large distances. Examples of structural artifacts in QM/MM water include density accumulation at the QM/MM boundary, decreased order, and density differences between regions. These issues are mostly apparent if the difference between the QM and the MM model is very large, which is often the case with water models. Here, we assess the QM/MM performance of simple MM models that are specifically parametrized to match selected data from a QM simulation of bulk water. To this end, we introduce a novel MM model (PM6-(DH+)-EFF) that reproduces PM6-DH+ water properties. We also assess a recent PBE-DFT-based MM model (PBE-EFF) that reproduces structural properties of bulk water simulated with PBE-DFT. Both models consist solely of tabulated potential energy terms for interactions between atom pairs. We compare the matched QM/MM results (PBE-DFT/PBE-EFF and PM6-DH+/PM6(-DH+)-EFF) with those from mismatched QM/MM simulations (PM6-DH+/PBE-EFF). The mismatched simulations reflect issues similar to those reported for other mismatched QM/MM pairs. The matched simulations yield very good results with water structures that barely deviate from the QM reference. In view of these findings, we strongly recommend adoption of specifically parametrized MM models in the QM/MM simulation of chemical processes in water.

First author: Wen, J, Magnetic circular dichroism of an unaromatic planar [8]annulene, JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, 31, 3943, (2018)
Abstract: An overview of magnetic circular dichroism (MCD) spectroscopy of pi-electron systems derived from a 4N-electron perimeter is provided, with emphasis on the hypothetical parent cycloocta-1,3,5,7-tetraene of D-8h symmetry (1) and its D-4h symmetry derivatives. UV-visible absorption and MCD spectra of 2, D-4h, symmetric cycloocta-1,3,5,7-tetraene planarized by the effect of 4 bicyclo[2.1.1]hexeno units fused to its 8-membered ring, are reported and interpreted. The perimeter model is applied to obtain an understanding of the nature of electronic states in 1 and 2 and to predict general trends in the spectra. The electronic excitation patterns are found to be different in the antiaromatic D-8h and unaromatic D-4h species, and their states cannot be unequivocally correlated. The results of time-dependent density functional theory and extended multistate complete active space second-order perturbation theory (XMS-CASPT2) computations agree with the algebraic perimeter model analysis and reproduce the spectra of 2 well, including three of the four observed MCD signs of A and B terms.

First author: Barroso, J, Bonding and Mobility of Alkali Metals in Helicenes, CHEMISTRY-A EUROPEAN JOURNAL, 24, 11227, (2018)
Abstract: In this work, we analyze the interactions of alkali metal cations with [6]- and [14]helicene and the cation mobility of therein. We found that the distortion of the carbon skeleton is the reason that some of the structures which are local minima for the smallest cations are not energetically stable for K+, Rb+, and Cs+. Also, the most favorable complexes are those where the cation is interacting with two rings forming a metallocene-like structure, except for the largest cation Cs+, where the distortion provoked by the size of the cation destabilizes the complex. As far as mobility is concerned, the smallest cations, particularly Na+, are the ones that can move most efficiently. In [6]helicene, the mobility is limited by the capture of the cation forming the metallocene-like structure. In larger helicenes, the energy barriers for the cation to move are similar both inside and outside the helix. However, complexes with the cation between two layers are more energetically favored so that the movement will be preferred in that region. The bonding analysis reveals that interactions with no less than 50% of orbital contribution are taking place for the series of E+-[6]helicene. Particularly, the complexes of Li+ show remarkable orbital character (72.5-81.6%).

First author: Conradie, MM, An experimental and DFT study of the packing and structure of dithenoylmethane monocarbonylphosphine Rhodium(I) complex [Rh((C4H3S)COCHCO(C4H3S))(CO)(PPh3)], JOURNAL OF MOLECULAR GRAPHICS & MODELLING, 83, 33, (2018)
Abstract: [Rh((C4H3S)COCHCO(C4H3S))(CO)(PPh3)] crystals stack in one dimensional linear chains in the solid state, with slightly slipped pi-stacking of the thienyl groups of one molecule and the beta-diketonato backbone of a neighbouring molecule. The observed stacking is possible due to the near planar orientation of the two aromatic thienyl groups and the beta-diketonato backbone. The experimentally observed stacking and close intermolecular contacts are in agreement with theoretical QTAIM calculated intermolecular bond paths and intermolecular hydrogen bonds between neighbouring molecules. NBO calculations revealed donor acceptor NBO interactions between the lone pair on rhodium of one molecule and (i) the empty antibonding orbital on C-H of the nearest thienyl group of a neighbouring molecule, as well as with the (ii) the empty antibonding orbital on two carbons of the nearest thienyl group to rhodium on the neighbouring molecule.

First author: Kumar, J, A Dicobalt Coordination Complex with a Short Cobalt-Cobalt Distance, CHEMISTRYSELECT, 3, 8221, (2018)
Abstract: The existence of a metal-metal bond in organometallic and coordination complexes is a very important aspect. Metal-carbonyl, carbene-metal-carbonyl and metal-carbene complexes were studied for having this feature. Herein, an air stable dark green color dicobalt coordination complex [Co(III)(2)(hep)(3) (N-3)(3)] (1) [hepH = 2-(2-ethylhydroxy)pyridine] with three mu-alkoxide bridges has been synthesized and characterized by Xray single crystal diffraction, NMR and UV/vis spectroscopy. Complex 1 has a short Co center dot center dot center dot Co distance (2.595(6) angstrom) and thus it has been studied by theoretical calculations. QTAIM (quantum theory of atoms in molecules) as well as EDA-NOCV analysis (energy decomposition analysis – natural orbitals for chemical valence) do not indicate any significant metal-metal interaction. The bonding in 1 can be best represented by the interaction of two alkokxy bridged valence electrons fragment Co(III)(hep)(2)N-3 (3d(6)) with Co(III)(hep)(N-3)(2) (3d(6)) where the donation of the lone pair of electrons from three bridging O-hep-atoms stabilizes the dinuclear Co(III) complex. Additionally, thermolysis of 1 at 550 degrees C led to the formation sponge like Co3O4 oxide.

First author: Carreno, A, Two New Fluorinated Phenol Derivatives Pyridine Schiff Bases: Synthesis, Spectral, Theoretical Characterization, Inclusion in Epichlorohydrin-beta-Cyclodextrin Polymer, and Antifungal Effect, FRONTIERS IN CHEMISTRY, 6, 8221, (2018)
Abstract: It has been reported that the structure of the Schiff bases is fundamental for their function in biomedical applications. Pyridine Schiff bases are characterized by the presence of a pyridine and a phenolic ring, connected by an azomethine group. In this case, the nitrogen present in the pyridine is responsible for antifungal effects, where the phenolic ring may be also participating in this bioactivity. In this study, we synthesized two new pyridine Schiff Bases: (E)-2-[(3-Amino-pyridin-4-ylimino)-methyl]-4,6-difluoro-phenol (F1) and (E)-2-[(3-Amino-pyridin-4-ylimino)-methyl]-6-fluoro-phenol (F2), which only differ in the fluorine substitutions in the phenolic ring. We fully characterized both F1 and F2 by FTIR, UV-vis, H-1; C-13; F-19-NMR, DEPT, HHCOSY, TOCSY, and cyclic voltammetry, as well as by computational studies (DFT), and NBO analysis. In addition, we assessed the antifungal activity of both F1 (two fluorine substitution at positions 4 and 6 in the phenolic ring) and F2 (one fluorine substitution at position 6 in the phenolic ring) against yeasts. We found that only F1 exerted a clear antifungal activity, showing that, for these kind of Schiff bases, the phenolic ring substitutions can modulate biological properties. In addition, we included F1 and F2 into in epichlorohydrin-beta-cyclodextrin polymer (beta CD), where the Schiff bases remained inside the beta CD as determined by the k(i), TGA, DSC, and S-BET. We found that the inclusion in beta CD improved the solubility in aqueous media and the antifungal activity of both F1 and F2, revealing antimicrobial effects normally hidden by the presence of common solvents (e.g , DMSO) with some cellular inhibitory activity. The study of structural prerequisites for antimicrobial activity, and the inclusion in polymers to improve solubility, is important for the design of new drugs.

First author: Sproviero, EM, Intramolecular Natural Energy Decomposition Analysis: Applications to the Rational Design of Foldamers, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 1367, (2018)
Abstract: We describe an intramolecular version of the natural energy decomposition analysis (NEDA), with the aim of evaluating interactions between molecular fragments across covalent bonds. The electronic energy in intramolecular natural energy decomposition analysis (INEDA) is divided into electrical, core, and charge transfer components. The INEDA method describes the fragments using the nonfragmented electronic density, and, therefore, there are no limitations in how to choose the boundary orbital. We used INEDA to evaluate the interaction energies that give origin to barriers of rotation around CamideCaromatic (CamCar) and NamideCaromtaic (NamCar) bonds in arylamide-foldamer building blocks. We found that differences of barrier height between models with different ortho-aryl substituents stem from charge transfer and core interactions. In three-center hydrogen-bond (H-bond) models with an NH proton donor H-bound to two electronegative ortho-aryl substituents, the interaction energy of the three-center system is larger than in either of the two-center H-bond subsystem alone, indicating an increase of overall rigidity. The combination of INEDA and NEDA allows the evaluation of intermolecular and intramolecular interactions using a consistent theoretical framework.

First author: Liu, XY, Nonadiabatic dynamics simulations on internal conversion and intersystem crossing processes in gold(i) compounds, JOURNAL OF CHEMICAL PHYSICS, 149, 1367, (2018)
Abstract: The position at which the second gold(i)-phosphine group is attached was experimentally found to play a noticeable role in intersystem crossing rates of gold(i) naphthalene derivatives. However, the physical origin is ambiguous. Herein we have employed generalized trajectory-based surface-hopping dynamics simulations to simulate the excited-state relaxation dynamics of these gold(i) naphthalene compounds including both the intersystem crossing process from the initially populated first excited singlet states S-1 to triplet manifolds and internal conversion processes within these triplet states. Our predicted intersystem crossing rates are consistent with experiments very well. On the basis of the present results, we have found that (1) ultrafast and subpicosecond intersystem crossing processes are mainly caused by small energy gaps and large spin-orbit couplings between S-1 and T-n; (2) adding the second gold(i)-phosphine group does not increase spin-orbit couplings between S-1 and T-n but decrease their values remarkably, which implies that heavy-atom effects are state-specific, not state-universal; (3) the position at which the second gold(i)-phosphine group is attached has a remarkable influence on the electronic structures of S-1 and T-n and their relative energies, which affect energy gaps and spin-orbit couplings between S-1 and T-n and eventually modulate intersystem crossing rates from S-1 to T-n. These new insights are very useful for the design of gold-containing compounds with excellent photoluminescence properties. Finally, this work also exemplifies that different isomers of a compound could have distinct excited-state relaxation dynamics. Published by AIP Publishing.

First author: Qiao, N, The dual-luminescence mechanism of the ESIPT chemosensor tetrasubstituted imidazole core compound: a TDDFT study, NEW JOURNAL OF CHEMISTRY, 42, 11804, (2018)
Abstract: The dual-luminescence mechanism of the tetrasubstituted imidazole core (TIC) compound was theoretically explored by considering the excited-state intramolecular proton transfer (ESIPT) process in the present study. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have been employed to gain the geometrical conformations, electronic transitions, frontier molecular orbitals (FMOs) and various spectra in different electronic states. An intramolecular hydrogen bond O-HN was observed for the TIC in the S-0 state. Upon electronic excitation, the TIC molecule is predominantly excited to the S-1 state as well as to an isosbestic point in the S-2 state. There is a twisted intramolecular charge transfer (TICT) during the S-0 S-1 (-*) transition and an intramolecular charge transfer (ICT) during the S-0 S-2 (-*) transition. The intramolecular hydrogen bond becomes stronger in the S-1 state than in the S-0 state. This leads to a strong fluorescence emission at 461 nm. However, the calculated potential curves showed that the intramolecular hydrogen bond O-HN transforms into OH-N in the S-2 state after the ESIPT reaction. A keto form of TIC is generated which gives rise to the other fluorescence emission at 575 nm through an ultrafast internal conversion (IC) process. This study aims to provide theoretical insights into the development of efficient chemosensors which are switched on through the ESIPT process.

First author: Todisco, S, P-31 and Pt-195 solid-state NMR and DFT studies on platinum(I) and platinum(II) complexes, DALTON TRANSACTIONS, 47, 8884, (2018)
Abstract: P-31 and Pt-195 solid state NMR spectra of anti-[(PHCy)ClPt(mu-PCy2)(2)Pt(PHCy)Cl] (3) and [(PHCy2)Pt(mu-PCy2)(kappa P-2, O-mu-POCy2)Pt(PHCy2)] (Pt-Pt) (4) were recorded under cross polarization/magic-angle spinning conditions (P-31) or with the cross polarization/Carr-Purcell-Meiboom-Gill pulse sequence (Pt-195) and compared to the data obtained by relativistic DFT calculations of P-31 and Pt-195 CS tensors and isotropic shielding at the ZORA spin-orbit level. A good agreement with the experimental results was found and it was possible to rationalize the chemical shift differences of Pt-195 and P-31 nuclei between compounds 3 and 4 as mostly due to a change (in opposite directions for Pt-195 and P-31) of the principal component of the shielding tensor perpendicular to the molecular plane defined by the Pt and P atoms. Paramagnetic and spin-orbit terms were found to be the most important contributions to Pt-195 and P-31 shielding.

First author: Jana, G, Cyanide-isocyanide isomerization: stability and bonding in noble gas inserted metal cyanides (metal = Cu, Ag, Au), PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 18491, (2018)
Abstract: The internal isomerization, MNC <-> MCN (M = Cu, Ag, Au), is investigated through quantum chemical computations. CuNC and AgNC are shown to be neither thermochemically nor kinetically stable against transformation to MCN. The free energy barrier (Delta G(double dagger)) for AuNC is somewhat considerable (7.1 kcal mol(-1)), indicating its viability, particularly at low temperature. Further, the Ng inserted analogues, MNgCN (M = Cu, Ag, Au; Ng = Xe, Rn) turn out to be thermochemically stable with respect to all possible dissociation channels but for two two-body dissociation channels, viz., MNgCN -> Ng + MCN and MNgCN -> Ng + MNC, which are connected to the internal isomerization processes, MNgCN -> NgMCN and MNgCN -> NgMNC, respectively. However, they are kinetically protected by substantial Delta G(double dagger) values (11.8-15.4 kcal mol(-1) for Cu, 9.8-13.6 kcal mol(-1) for Ag, and 19.7-24.7 kcal mol(-1) for Au). The pathways for such internal conversion are explored in detail. A thorough inspection of the bonding situation of the studied molecules, employing natural bond order, electron density, adaptive natural density partitioning, and energy decomposition analyses indicates that the M-Ng bonds in MNgCN and Ng-C bonds in AuNgCN can be represented as an electron-shared covalent bond. For the other Ng-C bonds, although an ionic description is better suited, the degree of covalent character is also substantial therein.

First author: Xue, H, Novel carbon quantum dots for fluorescent detection of phenol and insights into the mechanism, NEW JOURNAL OF CHEMISTRY, 42, 11485, (2018)
Abstract: Phenol is considered as one of the most important pollutants in the water environment, and thus its detection plays a cardinal role in environmental assessment and treatment. In this study, high quality carbon quantum dots (CQDs) were successfully prepared by ozone oxidation, with cheap coal as the carbon material. The as-prepared CQDs exhibited a narrow size distribution between 2 and 9 nm, with an average size of approximately 4.2 nm. The novel CQDs showed high sensitivity and selectivity for phenol detection with a low detection limit of 0.076 M in water due to the fluorescence quenching effect of the CQDs, which is attributed to the hydrogen bonds (C?OH-O) between phenol and the fluorescent CQDs according to the density functional theory (DFT) and time-dependent density functional theory (TDDFT) results. The theoretical calculation matches well with the experimental data, which provides us a new way to investigate the detection mechanism of the CQDs for phenol.

First author: Chauhan, V, Strong Effect of Organic Ligands on the Electronic Structure of Metal-Chalcogenide Clusters, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 6014, (2018)
Abstract: It is shown that multiple ionization energies of metal-chalcogenide clusters can be substantially reduced by adding ligands that form charge transfer complexes. We demonstrate this intriguing phenomenon by considering metal-chalcogenide clusters including cases where a cluster has a filled electronic shell with a large gap between the occupied and unoccupied states reminiscent of stable species. The studies include a Co6Se8 core ligated with tri-ethylphosphine (PEt3) ligands forming a stable Co6Se8(PEt3)(6) species. All of the ligated clusters have a first ionization energy in the range for alkali atoms and multiple ionization energies that are considerably lower than those for the non-ligated clusters. The change in electronic behavior upon ligation can be associated with a shift in the electronic spectrum via a crystal field like effect due to attaching ligands that form charge transfer complexes. We also show that metal-chalcogenide species can be programmed by proper ligand replacement to promote dimerization by first forming the Co6Se8(PEt3)(n)(CO)(6-n) (n = 0-6) clusters where the CO ligands could be replaced by diisocyanide (CNC6H4NC) ligands. The diisocyanide ligand acts as a rigid linker between the metallic cores, enabling the formation of a Co6Se8(PEt3)(5)(CNC6H4NC)-Co6Se8(PEt3)(5) superatomic molecule (SM), and we examine the electronic and magnetic properties of the recently synthesized SM via studies on an analogous SM with smaller ligands.

First author: Sengul, O, Photophysical Properties of Novel Two-Photon Absorbing Dyes: Assessing Their Possible Use for Singlet Oxygen Generation, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 16315, (2018)
Abstract: Herein, we assess the nonlinear absorption properties and the photophysical profile and behavior of two recently synthesized polythiophene-based dyes. In particular, using high level state-of-the-art molecular modeling methodologies, we clearly underline the remarkable two-photon absorption (TPA) cross-section. Furthermore, the possible pathways leading to the So intersystem crossing and triplet manifold population are investigated by considering the energy difference between the relevant triplet and singlet states on the potential energy surfaces as the key critical points. The spin-orbit coupling is also assessed, and the results globally point to a possible, albeit probably slow, intersystem crossing that could allow the use of the two dyes as singlet oxygen photosensitizers, for instance in photodynamic therapy, owing to their high TPA cross-sections.

First author: Senanayake, RD, Theoretical Investigation of Relaxation Dynamics in Au-38(SH)(24) Thiolate-Protected Gold Nanoclusters, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 16380, (2018)
Abstract: A subtle change in the electronic structure of thiolate-protected noble metal nanoparticles can result in distinctive energy relaxation dynamics. Corresponding investigations on different sizes and structures of thiolate-protected gold nanoclusters reveal their physical and chemical properties for further development of catalytic applications. In this work, we performed nonradiative relaxation dynamics simulations of the Au-38(SH)24 nanocluster to describe electron-vibrational energy exchange. The core and higher excited states involving semiring motifs lying in the energy range of 0.00-2.01 eV are investigated using time-dependent density functional theory (TDDFT). The surface hopping method with decoherence correction combined with real-time TDDFT is used to assess the quantum dynamics. The Au-23 core relaxations are found to occur in the range of 2.0-8.2 ps. The higher excited states that consist of core-semiring mixed or semiring states give ultrafast decay time constants in the range of 0.6-4.9 ps. Our calculations predict that the slowest individual state decay of S-11 or the slowest combined S-11-S-52, S-1-S-2-S-6-S-7 and S-4-S-5-S-9-S-10 decay involves intracore relaxations. The analysis of the phonon spectral densities and the ground state vibrational frequencies suggests that the low frequency (25 cm(-1)) coherent phonon emission reported experimentally could be the bending of the bi-icosahedral Au-23 core or the “fan blade twisting” mode of two icosahedral units.

First author: Dalla Tiezza, M, Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses, CHEMPHYSCHEM, 19, 1766, (2018)
Abstract: The intramolecular oxidative coupling converting a bis-acetylene complex of formula CpM (C2H2)(2) (Cp=C5H5-; M=Co, Rh, Ir) into a 16-electron metallacycle is studied in silico. This reaction is paradigmatic in acetylene [2+2+2] cycloaddition to benzene catalyzed by CpM fragments, being the step with the highest activation energy, and thus affecting the whole catalysis. Our activation strain and quantitative molecular orbital (MO) analyses elucidate the mechanistic details and reveal why cobalt performs better than rhodium and iridium catalysts outlining general principles for rational design of catalysts to be used in these processes.

First author: Gaggioli, CA, Theoretical Investigation of Plutonium-Based Single-Molecule Magnets, INORGANIC CHEMISTRY, 57, 8098, (2018)
Abstract: The electronic structure of a plutonium-based single molecule magnet (SMM) was theoretically examined by means of multiconfigurational electronic structure theory calculations, including spin-orbit coupling effects. All Pu 5f to 5f transitions for all possible spin states were computed, as well as ligand to metal charge transfer and Pu 5f to 6d transitions. Spin-orbit coupling effects were included a posteriori to accurately describe the electronic transitions. The spin orbit coupled energies and magnetic moments were then used to compute the magnetic susceptibility curves. The experimental electronic structure and magnetic susceptibility curve were reproduced well by our calculations. A compound with a modified electron-donating ligand (namely a carbene ligand) was also investigated in an attempt to tune the electronic properties of the plutonium SMM, revealing a higher ligand field splitting of the 5f orbitals of Pu, which could in turn enhance the barrier against magnetic relaxation.

First author: Tondreau, AM, A Pseudotetrahedral Uranium(V) Complex, INORGANIC CHEMISTRY, 57, 8106, (2018)
Abstract: A series of uranium amides were synthesized from N,N,N-cyclohexyl(trimethylsilyl)lithium amide [Li][N-(TMS)Cy] and uranium tetrachloride to give U-(NCySiMe3)(x) (Cl)(4-x), where x = 2, 3, or 4. The diamide was isolated as a bimetallic, bridging lithium chloride adduct ((UCl2(NCyTMS)(2))(2)-LiCl(THF)(2)), and the tris(amide) was isolated as the lithium chloride adduct of the monometallic species (UCl(NCyTMS)3-LiCl(THF)(2)). The tetraamide complex was isolated as the four-coordinate pseudotetrahedron. Cyclic voltammetry revealed an easily accessible reversible oxidation wave, and upon chemical oxidation, the U-V amido cation was isolated in near-quantitative yields. The synthesis of this family of compounds allows a direct comparison of the electronic structure and properties of isostructural U-IV and U-V tetraamide complexes. Spectroscopic investigations consisting of UV-vis, NIR, MCD, EPR, and U L-3-edge XANES, along with density functional and wave function calculations, of the four coordinate U-IV and U-V complexes have been used to understand the electronic structure of these pseudotetrahedral complexes.

First author: Tsitovich, PB, Low-Spin Fe(III) Macrocyclic Complexes of Imidazole-Appended 1,4,7-Triazacyclononane as Paramagnetic Probes, INORGANIC CHEMISTRY, 57, 8364, (2018)
Abstract: Two macrocyclic complexes of 1,4,7-triazacyclononane (TACN), one with N-methyl imidazole pendants, [Fe(Mim)](3+), and one with unsubstituted NH imidazole pendants, [Fe(Tim)](3+), were prepared with a view toward biomedical imaging applications. These low-spin Fe3+ complexes produce moderately paramagnetically shifted and relatively sharp H-1 NMR resonances for paraSHIFT and paraCEST applications. The [Fe(Tim)](3+) complex undergoes pH-dependent changes in NMR spectra in solution that are consistent with the consecutive deprotonation of all three imidazole pendant groups at high pH values. N-Methylation of the imidazole pendants in [Fe(Mim)](3+) produces a complex that dissociates more readily at high pH in comparison to [Fe(Tim)](3+), which contains ionizable donor groups. Cyclic voltammetry studies show that the redox potential of [Fe(Mim)](3+) is invariant with pH (E-1/2 = 328 +/- 3 mV vs NHE) between pH 3.2 and 8.4, unlike the Fe(III) complex of Tim which shows a 590 mV change in redox potential over the pH range of 3.3-12.8. Magnetic susceptibility studies in solution give magnetic moments of 0.91-1.3 cm(3) K mol(-1) (mu(eff) value = 2.7-3.2) for both complexes. Solid-state measurements show that the susceptibility is consistent with a S = 1/2 state over the temperature range of 0 to 300 K, with no crossover to a high-spin state under these conditions. The crystal structure of [Fe(Mim)](OTf)(3) shows a six-coordinate all-nitrogen bound Fe(III) in a distorted octahedral environment. Relativistic ab initio wave function and density functional theory (DFT) calculations on [Fe(Mim)](3+), some with spin orbit coupling, were used to predict the ground spin state. Relative energies of the doublet, quartet, and sextet spin states were consistent with the doublet S = 1/2 state being the lowest in energy and suggested that excited states with higher spin multiplicities are not thermally accessible. Calculations were consistent with the magnetic susceptibility determined in the solid state.

First author: Vermeeren, P, Arylic C-X Bond Activation by Palladium Catalysts: Activation Strain Analyses of Reactivity Trends, SCIENTIFIC REPORTS, 8, 8364, (2018)
Abstract: We have quantum chemically explored arylic carbon-substituent bond activation via oxidative insertion of a palladium catalyst in C6H5X + PdLn model systems (X = H, Cl, CH3; L-n = no ligand, PH3, (PH3)(2), PH2C2H4PH2) using relativistic density functional theory at ZORA-BLYP/TZ2P. Besides exploring reactivity trends and comparing them to aliphatic C-X activation, we aim at uncovering the physical factors behind the activity and selectivity. Our results show that barriers for arylic C-X activation are lower than those for the corresponding aliphatic C-X bonds. However, trends along bonds or upon variation of ligands are similar. Thus, bond activation barriers increase along C-Cl < C-H < C-C and along Pd < Pd(PH3) or Pd(PH2C2H4PH2) < Pd(PH3)(2). Activation strain analyses in conjunction with quantitative molecular orbital theory trace these trends to the rigidity and bonding capability of the various C-X bonds, model catalysts, and ligands.

First author: Gladysz-Plaska, A, The use of halloysite functionalized with isothiouronium salts as an organic/inorganic hybrid adsorbent for uranium(VI) ions removal, JOURNAL OF HAZARDOUS MATERIALS, 354, 133, (2018)
Abstract: Elimination of U(VI) from nuclear wastes and from the underground water near the uranium mines is the serious problem. Therefore search for new sorbents for U(VI) is still a big challenge for the scientists. This paper investigates of U(VI) ions sorption on halloysite modified with the isothiouronium salts: S-dodecaneisothiouronium bromide (ligand 1), S,S’-dodecane-1,12-diylbis(isothiouronium bromide) (ligand 2), S-hexadecaneisothiouronium chloride (ligand 3), S,S’-naphthalene-1,4-diyIbis(methylisothiouronium) dichloride (ligand 4), and S,S’-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (ligand 5). It was established that halloysite modified by the ligands with four nitrogen atoms in their structure (ligand-5, 2 and 4) was characterized by higher sorption capacity compared with that modified by the ligands with two donor nitrogens (ligand-1 and 3). The maximum sorption capacity of halloysite-5 toward U(VI) was 157 mg U/g and this places the modified mineral among the most effective sorbents for U(VI) removal from wastes. As follows from ATR, XPS and thermal degradation spectra of the sorption products [R-S-C(=NH)(NH2)](n=1.2)(UO22+) complexes are formed on the external surface of the halloysite whereas oligomeric hydroxy complexes (UO2)(3)(OH)(5)(+) and (UO2)(4)(OH)(7)(+) are present in the interior of halloysite structure and interact predominantly with aluminols.

First author: Diaz-Uribe, CE, Photocatalytic degradation of methylene blue by the Anderson-type polyoxomolybdates/TiO2 thin films, POLYHEDRON, 149, 163, (2018)
Abstract: In the herein work, two Anderson-type polyoxomolybdates (containing Cu and Zn, respectively) were synthesized and deposited on TiO2 thin films. The properties of the films were studied through measurements of inductively coupled plasma optical emission spectrometry (ICP), Fourier transform infrared spectroscopy (FT-IR) and absorption diffuse reflectance.

First author: Gloriozov, IP, 1,6-Methano[10]annulene as prospective organometallic ligand from the annulene family: A DFT study of transition metal pi-complexes and their inter-ring haptotropic rearrangements, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 867, 306, (2018)
Abstract: The structural peculiarities (C1-C6 distances, bending of the ligand, conformation of organometallic group relative to the ligand, etc.), the isomerism and the mechanisms of inter-ring haptotropic rear-rangements (IRHR) in Cr(CO)(3) and CoCp complexes of 1,6-methano[10]annulene were investigated by DFT. An activation barrier of 28.0 kcal/mol, lower than that corresponding to naphthalene, was computed for the eta(6), eta(6)-IRHR in the mononuclear chromium complex. In the case of the mononuclear cobalt species, activations barrier of 33.8 and 31.3 kcal/mol were computed for the eta(4), eta(4)-IRHR in the trans and cis isomers, respectively.

First author: Notario-Estevez, A, Decoding the role of encapsulated ions in the electronic and magnetic properties of mixed-valence polyoxovanadate capsules {X@V22O54} (X = ClO4-, SCN-, VO2F2-): a combined theoretical approach, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 17847, (2018)
Abstract: The electronic structure and magnetism of mixed-valence, host-guest polyoxovanadates {X@VIV/V22O(54)} with diamagnetic (X =) ClO4- (T-d, 1) and SCN- (C-v, 2) template anions are assessed by means of two theoretical methods: density functional theory and effective Hamiltonian calculations. The results are compared to those obtained for another member of this family with X = VO2F2- (C-2v, 3) (see P. Kozowski et al., Phys. Chem. Chem. Phys., 2017, 19, 29767-29771), for which complementary data are also acquired. It is demonstrated that the X guest anions strongly influence the electronic and magnetic properties of the system, leading to various valence states of vanadium and modifying V-O-V exchange interactions. Our findings are concordant with and elucidate the available experimental data (see K. Y. Monakhov et al., Chem. – Eur. J., 2015, 21, 2387-2397).

First author: Bouchouit, M, Synthesis, X-ray structure, in silico calculation, and carbonic anhydrase inhibitory properties of benzylimidazole metal complexes, JOURNAL OF ENZYME INHIBITION AND MEDICINAL CHEMISTRY, 33, 1150, (2018)
Abstract: Three coordination compounds of formula {M(bmim)(2)Cl-2} were synthetised (M=Co, Zn, and Hg) and fully characterised. Each complex incorporates 1-benzyl-2-methylimidazole (bmim) as ligand. The coordination polyhedron around the metal center for all complexes has a quasi-regular tetragonal geometry. Density functional theory calculations were carried out on the title compounds and as well on hypothetical complexes (Cu, Ni), in order to elucidate their electronic and molecular structure. The calculations reproduced the Co, Zn, and Hg experimental structures and could predict stable complexes in the case of Ni(II) and Cu(II) ions. The carbonic anhydrase (CA, EC inhibitory effects of the three complexes were investigated. Only compound {Hg(bmim)(2)Cl-2} (3) exhibited a modest inhibitory effect against hCA I, probably due to the affinity of Hg(II) for His residues at the entrance of the active site cavity.

First author: Zauliczny, M, Bonding in Phosphanylphosphinidene Complexes of Transition Metals and their Correlation with Structures, P-31 NMR Spectra, and Reactivities, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 33, 3131, (2018)
Abstract: Theoretical studies of the bonding interactions and most important properties are carried out for isolable phosphanylphosphinidene complexes of transition metals. Three main types of phosphanylphosphinidene complexes are distinguished, based on the way in which the phosphanylphosphinidene ligand bonds to the metal center: (i) side-on complexes of platinum, where the R2P-P ligand mimics structural features of free singlet phosphanylphosphinidenes with short, polarized, double P-P bonds and two lone electron pairs on the terminal P atom. In this case, interactions between the platinum center and the phosphanylphosphinidene ligand are determined by (PP)s(Pt) donation and d(Pt)*(PP) back-donation; (ii) terminal and bridging complexes of zirconium, where the R2P-P ligand is bonded to the metal center only by the terminal P atom. The metal-ligand interactions are a result of the singly occupied p orbitals of a terminal P atom overlapping with the singly occupied d orbitals of the Zr atom, which leads to multiple bonding; (iii) side-on complexes of early transition metals, where the R2P-P group is bonded to the metal through an R2P-M single bond and a P=M double bond. The observed shortening of the P-P bond in these complexes is explained by a negative hyperconjugation, as a result of the interaction of the (PM) orbital with the sigma*(PC) orbitals.

First author: Reber, AC, Co6Se8(PEt3)(6) superatoms as tunable chemical dopants for two-dimensional semiconductors, NPJ COMPUTATIONAL MATERIALS, 4, 3131, (2018)
Abstract: Electronic, optoelectronic, and other functionalities of semiconductors are controlled by the nature and density of carriers, and the location of the Fermi energy. Developing strategies to tune these parameters holds the key to precise control over semiconductors properties. We propose that ligand exchange on superatoms can offer a systematic strategy to vary these properties. We demonstrate this by considering a WSe2 surface doped with ligated metal chalcogenide Co6Se8(PEt3)(6) clusters. These superatoms are characterized by valence quantum states that can readily donate multiple electrons. We find that the WSe2 support binds more strongly to the Co6Se8 cluster than the PEt3 ligand, so ligand exchange between the phosphine ligand and the WSe2 support is energetically favorable. The metal chalcogenide superatoms serves as a donor that may transform the WSe2 p-type film into an n-type semiconductor. The theoretical findings complement recent experiments where WSe2 films with supported Co6Se8(PEt3)(6) are indeed found to undergo a change in behavior from p-to n-type. We further show that by replacing the PEt3 ligands by CO ligands, one can control the electronic character of the surface and deposited species.

First author: Ortolan, AO, Anion Recognition by Organometallic Calixarenes: Analysis from Relativistic DFT Calculations, ORGANOMETALLICS, 37, 2167, (2018)
Abstract: The physical nature of the noncovalent interactions involved in anion recognition was investigated in the context of metalated calix[4]arene hosts, employing Kohn-Sham molecular orbital (KS-MO) theory, in conjunction with a canonical energy decomposition analysis, at the dispersion-corrected DFT level of theory. Computed data evidence that the most stable host-guest bonding occurs in ruthenium complexed hosts, followed by technetium and molybdenum metalated macrocyclic receptors. Furthermore, the guest’s stenc fit in the host scaffold is a selective and crucial criterion to the anion recognition. Our analyses reveal that coordinated charged metals provide a larger electrostatic stabilization to amon recognition, shifting the calixarenes cavity toward an electron deficient acidic character. I his study contributes to the design and development or new organometallic macrocyclic hosts with increased anion recognition specificity.

First author: Ito, S, Observation of a Metastable P-Heterocyclic Radical by Muonium Addition to a 1,3-Diphosphacyclobutane-2,4-diyl, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57, 8608, (2018)
Abstract: A 1,3-diphosphacyclobutane-2,4-diyl contains a unique unsaturated cyclic unit, and the presence of radical-type centers have been expected as a source of functionality. This study demonstrates that the P-heterocyclic singlet biradical captures muonium (Mu=[mu(+)e(-)]), the light isotope of a hydrogen radical, to generate an observable P-heterocyclic paramagnetic species. Investigation of a powder sample of 2,4-bis(2,4,6-tri-t-butylphenyl)-1-t-butyl-3-benzyl-1,3-diphosphacyclobutane-2,4-diyl using muon (avoided) level-crossing resonance (mu LCR) spectroscopy revealed that muonium adds to the cyclic P2C2 unit. The muon hyperfine coupling constant (A(mu)) indicated that the phosphorus atom bearing the t-butyl group trapped muonium to provide a metastable P-heterocyclic radical involving the ylidic MuP(<)=C moiety. The observed regioselective muonium addition correlates the canonical formula of 1,3-diphosphacyclobutane-2,4-diyl.

First author: Liu, HY, Strategy to modulate the -bridged units in bis(4-methoxyphenyl)amine-based hole-transporting materials for improvement of perovskite solar cell performance, JOURNAL OF MATERIALS CHEMISTRY C, 6, 6816, (2018)
Abstract: We present an effective strategy to modulate the electron-deficiency of the -bridged units in bis(4-methoxyphenyl)amine-based hole-transporting materials (HTMs) for improving hole mobility and the performances of perovskite solar cells (PSC) devices. In order to confirm this strategy, on the basis of the reported bis(4-methoxyphenyl)amine-based pDPA-DBTP, we adjusted the electron-deficiency of -bridge units in pDPA-DBTP, and designed a series of new HTMs (S1-S3). Compared with the parent molecule pDPA-DBTP, the as-designed HTMs S1-S3 exhibit better performance with large Stokes shifts, small exciton binding energy, better stability, good solubility and higher hole mobility. The values of hole mobility for the molecules (S1-S3) are 1.07 x 10(-2), 1.47 x 10(-2) and 1.60 x 10(-1) cm(2) V-1 s(-1), respectively. These results provide useful information and demonstrate that adjusting the electron-deficiency of -bridge units in bis(4-methoxyphenyl)amine-based HTMs is an efficient approach to control the properties for improving the performance of HTMs in PSC applications. Moreover, the designed S1-S3 HTMs can act as promising candidates for providing high efficiency in PSC applications.

First author: Song, YB, Single-ligand exchange on an Au-Cu bimetal nanocluster and mechanism, NANOSCALE, 10, 12093, (2018)
Abstract: An Au-Cu bimetallic nanocluster co-capped by selenolate and phosphine is obtained and its X-ray structure shows an icosahedral Au-13 kernel surrounded by three CuSe2PPh2Py motifs and one CuSe3 motif, formulated as [Au13Cu4(PPh2Py)(3)(SePh)(9)]. Interestingly, a single-ligand exchange process is observed in the growth reaction, in which an [Au13Cu4(PPh2Py)(4)(SePh)(8)](+) intermediate is first formed, but a prolonged reaction leads to one PPh2Py ligand being selectively replaced by a PhSe-ligand. DFT simulations reveal that both steric hindrance and bond dissociation energy have great effects on the single-ligand exchange reaction as well as the thermodynamics, which help to understand the mechanism of the ligand exchange. Temperature-dependent UV-vis absorption and photoluminescence (PL) properties of the Au-Cu nanocluster imply that the optical properties are mainly contributed by the metal core. Femtosecond time-resolved pump-probe analysis maps out further details of the PL process.

First author: Groenewald, F, Ligand-driven formation of halogen bonds involving Au(I) complexes, NEW JOURNAL OF CHEMISTRY, 42, 10529, (2018)
Abstract: In a theoretical investigation at various levels of theory we show that even gold in the oxidation state +1 (i.e. formally positively charged) can behave as a Lewis base and, as a result, a halogen bond acceptor. Depending on the nature of the ligands in the gold complex the resultant halogen bonds are of similar strength to that found in the triiodide ion, but weaker than those involving the auride ion (highest value-59.4 kcal mol(-1) for Au-I2). The strength of the halogen bonds involving I-2 range from -46.3 kcal mol(-1) for the anionic adduct [((Me)(2)N)(2)Au]I–(2) to -5.9 kcal mol(-1) for the cationic [(H3N)(2)Au]I-+(2) adduct (calculated at the MP2/aug-cc-pVTZ-pp level of theory), and still weaker for adducts involving poorer halogen bond donors.

First author: Lee, J, Sigma-hole interactions in the molecular and crystal structures of N-boryl benzo-2,1,3-selenadiazoles, NEW JOURNAL OF CHEMISTRY, 42, 10555, (2018)
Abstract: N-Bonded adducts of benzo-2,1,3-selenadiazole with BX3 (X = Ph, F, Cl, Br) were prepared and crystallographically characterized. The structures of the 1:1 adducts of BF3 and BCl3 demonstrate dimerization through the [Se-N](2) supramolecular synthon and enhancement of the corresponding SeN chalcogen bonding interactions. However, the structures of the BPh3 and BBr3 compounds indicate that other supramolecular interactions can efficiently compete and inhibit [Se-N](2) dimerization. In the case of the BPh3 adduct, dispersion favors a dimer featuring Se center dot center dot center dot C interactions. In the crystal of the BBr3 derivative, the cooperative effect of Se center dot center dot center dot N chalcogen bonding and Br center dot center dot center dot Br halogen bonding interactions lead to a network structure. A 1:2 adduct could be isolated only in the case of BCl3; its structure features short intramolecular Se center dot center dot center dot Cl interactions resulting from the enhanced electrophilic character of the chalcogen atom.

First author: Thompson, S, The intersystem crossing of a cyclic (alkyl)(amino) carbene gold (i) complex, JOURNAL OF CHEMICAL PHYSICS, 149, 10555, (2018)
Abstract: The intersystem crossing (ISC) mechanism of a cyclic (alkyl)(amino) carbene gold (I) complex (CMA1) is studied using quantum dynamics. Amodel spin-vibronic Hamiltonian is developed, which includes 10 excited states and two important nuclear degrees of freedom. The quantum dynamics reveals that ISC from S-1 -> T-1 occurs on the tens of picosecond time scale, consistent with recent experiments. It is driven by motion along the torsional degree of freedom of the carbazole (Cz) ligand, which causes orthogonality between the donor and acceptor groups closing the gap between the initial (S-1) and final (T-1) states. The role of higher triplet states through spin-vibronic interactions is also discussed. Although previous calculations, evaluated in the Condon approximation, yield large ISC rates, our present dynamical treatment, taking into account the large amplitude torsional motion, increases the calculated rate by an order of magnitude improving the agreement with experiments. The model spin-vibronic Hamiltonian developed can also be used to understand the properties of related linear metal carbene compounds, facilitating molecular design. (C) 2018 Author(s).

First author: Martins, FF, Irreversible Magnetic Behaviour Caused by the Thermosalient Phenomenon in an Iron(III) Spin Crossover Complex, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 149, 2976, (2018)
Abstract: The new iron(III) complex [Fe(5-I-salEen)(2)]ClO4 exhibits both spin crossover, with hysteresis, between 304 K and 320 K (16 K hysteresis loop), and thermosalient phenomena. After a symmetry-breaking phase transition between 120 and 130 K, confirmed by single-crystal X-ray diffraction, and the fragmentation of the crystals around 312 K, confirmed by differential scanning calorimetry and hot stage microscopy, the hysteresis loop disappears. This is the first example where the explicitly reported thermosalient effect modifies the magnetic properties of a given spin crossover crystal.

First author: Burns, CP, Structure and Magnetization Dynamics of Dy-Fe and Dy-Ru Bonded Complexes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57, 8144, (2018)
Abstract: We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy3+) and either a first-row (Fe) or a second-row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp22- (PyCp22-=[2,6-(CH2C5H3)(2)C5H3N](2-)) facilitates the isolation and characterization of PyCp2Dy-FeCp(CO)(2) (1; d(Dy-Fe)=2.884(2)angstrom) and PyCp2Dy-RuCp(CO)(2) (2; d(Dy-Ru)=2.9508(5)angstrom). Computational and spectroscopic studies suggest strong TMDy bonding interactions. Both complexes exhibit field-induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy-Fe to Dy-Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin-phonon coupling contributions to magnetic relaxation.

First author: Pan, S, Bonding in Binuclear Carbonyl Complexes M-2(CO)(9) (M = Fe, Ru, Os), INORGANIC CHEMISTRY, 57, 7780, (2018)
Abstract: Quantum-chemical density functional theory calculations using the BP86 functional in conjunction with a triple-zeta basis set and dispersion correction by Grimme with Becke-Johnson damping D3(BJ) were performed for the title molecules. The nature of the bonding was examined with the quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) methods and with the energy decomposition analysis in conjunction with the natural orbital for chemical valence (EDA-NOCV) analysis. The energetically lowest lying form of Fe-2(CO)(9) is the triply bridged D-3h structure, whereas the most stable structures of Ru-2(CO)(9) and Os-2(CO)(9) are singly bridged C-2 species. The calculated reaction energies for the formation of the cyclic trinuclear carbonyls M-3(CO)(12) from the dinuclear carbonyls M-2(CO)(9) are in agreement with experiment, as the iron complex Fe-2(CO)(9) is thermodynamically stable in these reactions, but the heavier homologues Ru-2(CO)(9) and Os-2(CO)(9) are not. The metal CO bond to the bridging CO ligands is stronger than the bonds to the terminal CO ligands. This holds for the triply bridged D-3h structures as well as for the singly bridged C-2 or C-2v species. The analysis of the orbital interactions with the help of the EDA-NOCV method suggests that the overall M -> CO pi backdonation is always stronger than the M <- CO sigma donation. The bridging carbonyls are more strongly bonded than the terminal CO ligands, and they are engaged in stronger a donation and pi backdonation, but the formation of bridging carbonyls requires reorganization energy, which may or may not be compensated by the stronger metal ligand interactions. The lower-lying D-3h form of Fe-2(CO)(9) and C-2 structures of Ru-2(CO)(9) and Os-2(CO)(9) are due to a delicate balance of several forces.

First author: Wang, YP, A 2D covalent organic framework as a sensor for detecting formaldehyde, JOURNAL OF MOLECULAR MODELING, 24, 7780, (2018)
Abstract: Formaldehyde is the main cause of indoor pollution. In this research, we investigated the mechanism that the covalent organic framework (COF) identifies formaldehyde applying density functional theory (DFT) and time-dependent (TD) DFT approaches. On one hand, the calculation results of the geometric parameters, IR spectra, as well as H-1-NMR chemical shifts for protons that associated with the hydrogen bonding formation together with the electronic transition energies verified that the furcate hydrogen bonding formed between the COF and formaldehyde is enhanced in the excited S-1 state and it is not beneficial to luminescence of the COF. On the other hand, excitingly, our further calculation results of the fluorescence rate coefficients also revealed that the strengthened hydrogen bonding behavior in S-1 state caused an efficiently weakened luminescent phenomenon compared with that of the COF. Therefore, this analysis method, which qualitative collaborates with quantitative theoretically, demonstrates the possibility that the COF could be served as a sensor to detect formaldehyde.

First author: Smolentsev, G, Pump-probe XAS investigation of the triplet state of an Ir photosensitizer with chromenopyridinone ligands, PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, 17, 896, (2018)
Abstract: The triplet excited state of a new Ir-based photosensitizer with two chromenopyridinone and one bipyridine- based ligands has been studied by pump-probe X-ray absorption near edge structure (XANES) spectroscopy coupled with DFT calculations. The excited state has a lifetime of 0.5 mu s in acetonitrile and is characterized by very small changes of the local atomic structure with an average metal-ligand bond length change of less than 0.01 angstrom. DFT-based calculations allow the interpretation of the XANES in the energy range of similar to 50 eV around the absorption edge. The observed transient XANES signal arises from an additional metal-centered Ir 5d vacancy in the excited state which appears as a result of electron transfer from the metal to the ligand. The overall energy shift of the excited state spectrum originates from the shift of 2p and unoccupied states induced by screening effects. The approach for the analysis of timeresolved spectra of 5d metal complexes is quite general and can also be used if excited and ground state structures are significantly different.

First author: Stasyuk, OA, Comparison of the DFT-SAPT and Canonical EDA Schemes for the Energy Decomposition of Various Types of Noncovalent Interactions, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 3440, (2018)
Abstract: Interaction energies computed with density functional theory can be divided into physically meaningful components by symmetry-adapted perturbation theory (DFT-SAPT) or the canonical energy decomposition analysis (EDA). In this work, the decomposition results obtained by these schemes were compared for more than 200 hydrogen-, halogen-, and pnicogen-bonded, dispersion-bound, and mixed complexes to investigate their similarity in the evaluation of the nature of noncovalent interactions. BLYP functional with D3(BJ) correction was used for the EDA scheme, whereas asymptotically corrected PBE0 functional for DFT-SAPT provided some of the best combinations for description of noncovalent interactions. Both schemes provide similar results concerning total interaction energies and insight into the individual energy components. For most complexes, the dominant energetic term was identified equally by both decomposition schemes. Because the canonical EDA is computationally less demanding than the DFT-SAPT, the former can be especially used in cases where the systems investigated are very large.

First author: Chirita, P, Inhibitory effect of three phenacyl derivatives on the oxidation of sphalerite (ZnS) in air-equilibrated acidic solution, CORROSION SCIENCE, 138, 154, (2018)
Abstract: Three phenacyl derivatives have been investigated as potential inhibitors for the aqueous oxidation of sphalerite (ZnS) in air-equilibrated solutions of HCl (pH 2.5 and 25 degrees C) using potentyodynamic polarization, aqueous batch experiments, scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, Raman scattering and quantum chemical calculations. Findings show that the studied phenacyl derivatives are inhibitors of sphalerite aqueous oxidation. Quantum chemical calculations indicate that the adsorption of phenacyl derivatives on ZnS is energetically favorable and accounts for the observed inhibiting effects.

First author: Leroy, C, Linear dicoordinate beryllium: a Be-9 solid-state NMR study of a discrete zero-valent s-block beryllium complex, CANADIAN JOURNAL OF CHEMISTRY, 96, 646, (2018)
Abstract: Beryllium-9 (Be-9) quadrupolar coupling and chemical shift tensor data are reported for bis(1-(2,6-dirsopropylphenyl)3,3,5,5-tetramethylpyrrolidine-2-ylidene)beryllium (Be(CAAC) 2). These are the first such data for beryllium in a linear dicoordinate environment. The Be-9 quadrupolar coupling constant, 2.36(0.02) MHz, is the largest recorded in the solid state to date for this isotope. The span of the beryllium chemical shift tensor, 22(2) ppm, covers about half of the known Be-9 chemical shift range, and the isotropic Be-9 chemical shift, 32.0(0.3) ppm, is the largest reported in the solid state to our knowledge. DFT calculations reproduce the experimental data well. A natural localized molecular orbital approach has been used to explain the origins and orientation of the beryllium electric field gradient tensor. The single-crystal X-ray structure of a second polymorph of Be(CAAC)(2) is also reported. Inspection of the powder X-ray diffraction data shows that the new crystal structure is part of the bulk product next to another crystalline phase. Therefore, experimental X-ray powder data for the microcrystalline powder sample and the SSNMR data do not fully match either the originally reported crystal structure (Arrowsmith et al. Nat. Chem. 2016, 8, 890-894) or the new polymorph. The ability of solid-state NMR and powder X-ray diffraction to characterize powdered samples was thus particularly useful in this work.

First author: de Oliveira, AZ, All-electron triple zeta basis sets for the actinides, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1135, 28, (2018)
Abstract: Non-relativistic and Douglas-Kroll-Hess (DKH) segmented all-electron basis sets of valence triple zeta quality plus polarization functions (TZP) for the actinides are developed. To describe accurately the properties that depend on a good description of the electrons far away from the nuclei, the corresponding augmented sets (ATZP and ATZP-DKH) are reported as well. For the actinide monoxides, bond distances, dissociation energies, natural charges and populations of the valence orbitals of the actinides, and bond indices are calculated with the B3LYP/TZP-DKH procedure. For Am and No, the B3LYP/ATZP-DKH static mean dipole polarizabilities are also computed. To assess the performance of these small size all-electron basis sets, comparison with theoretical and experimental data reported previously in the literature is done. These sets must be also helpful on calculations of properties involving simultaneously core and valence electrons.

First author: Baron, M, Di(N-heterocyclic carbene) gold(III) imidate complexes obtained by oxidative addition of N-halosuccinimides, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 866, 144, (2018)
Abstract: The reaction between the gold(I) dicarbene complexes [Au-2(mu(2)-MeIm(CH2)(n)ImMe)(2)](PF6)(2) (Im = imidazol-2-ylidene, n = 1, 2, 3) and N-bromosuccinimide affords the gold(III) complexes [{AuBr(N-suc)}(2)(mu(2)-MeIm(CH2)(n)ImMe)(2)](PF6)(2), in which both gold centres have a bromide and a N-succinimidate anion in the coordination sphere. In the case of the CH2CH2 bridge, two different conformers of the gold(III) complex are formed; the structure of the major species has been clarified by single crystal X-ray diffraction analysis, while the nature and the properties of the minor one have been investigated by means of DFT calculations. Compared to N-bromosuccinimide, oxidative additions are slower with the N-chloro-and faster with the N-iodosuccinimides. In both cases the reactions are scarcely selective and the products distribution markedly depends on halide size and reaction conditions.

First author: Yi, R, Improvement of the extraction ability of bis(2-propyloxy)calix[4]arene-crown-6 toward cesium cation by introducing an intramolecular triple cooperative effect, SEPARATION AND PURIFICATION TECHNOLOGY, 199, 97, (2018)
Abstract: Bis(2-propyloxy)calix[4]arene-crown-6 (L1) is a ligand with high affinity in the extraction of Cs(I). In this work, acrylamido and propionamido groups are decorated at the opposite site of 2-propyloxy on the phenyl ring of L1, giving rise to the derivatives L2 and L3, respectively. Complexation of all the three ligands with Cs(I) is characterized by NMR, spectrophotometric titration, crystal structure and DFT calculation. Both the NMR and spectrophotometric analysis suggest more significant variation of electron density on the phenyl rings in L2 and L3 than that in L1 in complexation with Cs(I). The stability constants (log beta) of the complexes are calculated to be 6.0 +/- 0.1, 6.2 +/- 0.1 and 6.3 +/- 0.1 for Cs-L1, Cs-L2 and Cs-L3, respectively, by fitting of the absorption spectra. As reflected by the crystal structures and DFT calculations, the complexed cesium cation interacts with the crown ether moiety, the two rotated phenyl rings and the acrylamido/propionamido groups in L2/L3, which can be regarded as an intramolecular triple cooperative effect. Extraction of Cs(I) from aqueous solution is performed, and the distribution ratio is in line with the findings in stability constant and interaction energy. This work contributes to further improvement of the extraction of cesium cation by 1,3-alternate calix[4]arene-crown-6.

First author: Kim, P, Coherent Vibrational Wavepacket Dynamics in Platinum(II) Dimers and Their Implications, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 14195, (2018)
Abstract: Vibrational coherence in the metal-metal-toligand-charge transfer (MMLCT) excited state of cyclometalated platinum dimers with a pseudo C-2 symmetry was investigated where two nearly degenerate transitions from the highest occupied molecular orbital (metal-metal sigma* orbital) to higher energy ligand pi* orbitals could be simultaneously induced. We observed oscillatory features in femtosecond degenerate transient absorption (TA) signals from complexes [(ppy)Pt(mu-(t)Bu(2)pz)](2) (1) and anti-[ppy)Pt(mu-pyt)](2) (2), which are attributed to coherent nuclear motions that modulate the HOMO (antibonding sigma* energy level, and hence, the energy for the MMLCT transition. The characteristics of such coherent nuclear motions, such as the oscillatory frequency and the dephasing time, differ between 1 and 2 and are explained by mainly two structural factors that could influence the vibrational coherence: the Pt-Pt distance (2.97 angstrom for 1 vs 2.85 angstrom for 2) and molecular shape (1 in an “A” frame vs 2 in an “H” frame). Because the electronic coupling between the two Pt atoms determines the energy splitting of the bonding sigma and antibonding sigma* orbital, the Pt-Pt stretching mode coupled to the MMLCT transition changes the inter Pt distance from that of the ground state. Interestingly, while 1 shows a single Pt-Pt stretching frequency of 120 cm(-1) in the MMLCT state, 2 exhibits multiple downshifted frequencies (80 and 105 cm(-1)) in the MMLCT state along with a shorter vibrational dephasing time than 1. Based on the ground state optimized structures and Raman calculations, the changes evident in the vibrational wavepacket dynamics in 2 are closely correlated with the “H” framed geometry in 2 compared to the “A” frame in 1, leading to the sharp increase in pi-pi interaction between ppy ligands. Although the TA experiments do not directly reveal the ultrafast intersystem crossing (ISC) because of a strong coherent spike at early time scales, the dependence of the vibrational wavepacket dynamics on molecular geometry can be understood based on previously proposed potential energy surfaces as a function of Pt-Pt distance, suggesting that the interaction between the cyclometalating ligands can be a key factor in determining the Pt-Pt shortening and the related energy relaxation dynamics in the Pt(II) dimers. Further experiments using femtosecond broadband TA and X-ray scattering spectroscopy are planned to investigate directly the ISC and Pt-Pt contraction to support the relationship between ground state molecular geometry and photoinduced structural changes in the Pt(II) dimers.

First author: Liu, XY, Early-Time Excited-State Relaxation Dynamics of Iridium Compounds: Distinct Roles of Electron and Hole Transfer, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 5518, (2018)
Abstract: Excited-state and photophysical properties of Ir-containing complexes have been extensively studied because of their potential applications as organic light-emitting diode emitting materials. However, their early time excited-state relaxation dynamics are less explored computationally. Herein we have employed our recently implemented TDDFT-based generalized surface-hopping dynamics method to simulate excited-state relaxation dynamics of three Ir(III) compounds having distinct ligands. According to our multistate dynamics simulations including five excited singlet states i.e., S-n(n = 1-5) and ten excited triplet states, i.e., T-n(n = 1-10), we have found that the intersystem crossing (ISC) processes from the S-n to T-n are very efficient and ultrafast in these three Ir(III) compounds. The corresponding ISC rates are estimated to be 65, 81, and 140 fs, which are reasonably close to the experimentally measured ca. 80, 80, and 110 fs. In addition, the internal conversion (IC) processes within respective singlet and triplet manifolds are also ultrafast. These ultrafast IC and ISC processes are caused by large nonadiabatic and spin-orbit couplings, respectively, as well as small energy gaps. Importantly, although these Ir(III) complexes share similar macroscopic phenomena, i.e., ultrafast IC and ISC, their microscopic excited-state relaxation mechanism and dynamics are qualitatively distinct. Specifically, the dynamical behaviors of electron and hole and their roles are variational in modulating the excited-state relaxation dynamics of these Ir(III) compounds. In other words, the electronic properties of the ligands that are coordinated with the central Ir(III) atom play important roles in regulating the microscopic excited-state relaxation dynamics. These gained insights could be useful for rationally designing Ir(III) compounds with excellent photoluminescence.

First author: Drideh, S, Electronic structure and structural diversity in indenyl in heterobinuclear transition-metal half-sandwich complexes, THEORETICAL CHEMISTRY ACCOUNTS, 137, 5518, (2018)
Abstract: DFT calculations have been performed on a series of heterobimetallic compounds of the type [MCp][M’Cp](Ind), [M(CO)(3)] [M'(CO)(3)](Ind) and [M(CO)(2)][M'(CO)(3)](Ind) (Ind = Indenyl). The flexibility of the indenyl ligand favors the possibility of the existence of several isomers. The structure and electronic structure of this large family of compounds were analyzed with respect to their total number of electrons (TNE) and the nature of the ancillary ligands. The structures with electron counts lower than 34-TNE adopt the syn configuration to compensate the electronic deficiency.

First author: Rungthanaphatsophon, P, Phosphorano-Stabilized Carbene Complexes with Short Thorium(IV)- and Uranium(IV)-Carbon Bonds, ORGANOMETALLICS, 37, 1884, (2018)
Abstract: While no alkylidene complexes of the f elements are known, the use of phosphorano-stabilized carbene complexes to produce short actinide-carbon bonds has been previously demonstrated. Complexes of the form, (C5Me5)(2)An(X)(CHPPh3), with short thorium(IV)- and uranium(IV)-carbon(carbene) bonds have been synthesized from the reaction of (C5Me5)(2)An(X)(CH3) (An = Th, U; X = Cl, Br, or I) with the ylide, CH2 =PPh3. The resulting uranium complexes feature the shortest uranium(IV)-carbon bonds reported to date. The molecular and electronic structure of the thorium phosphorano-stabilized carbene complexes is detailed using X-ray crystallography, C-13 NMR spectroscopy, and density functional theory calculations, and compared to thorium methandiide complexes.

First author: Gosweiner, C, Tuning Nuclear Quadrupole Resonance: A Novel Approach for the Design of Frequency-Selective MRI Contrast Agents, PHYSICAL REVIEW X, 8, 1884, (2018)
Abstract: The interaction between water protons and suitable quadrupolar nuclei (QN) can lead to quadrupole relaxation enhancement (QRE) of proton spins, provided the resonance condition between both spin transitions is fulfilled. This effect could be utilized as a frequency selective mechanism in novel, responsive T-1 shortening contrast agents (CAs) for magnetic resonance imaging (MRI). In particular, the proposed contrast mechanism depends on the applied external flux density-a property that can be exploited by special field-cycling MRI scanners. For the design of efficient CA molecules, exhibiting narrow and pronounced peaks in the proton T-1 relaxation dispersion, the nuclear quadrupole resonance (NQR) properties, as well as the spin dynamics of the system QN-H-1, have to be well understood and characterized for the compounds in question. In particular, the energy-level structure of the QN is a central determinant for the static flux densities at which the contrast enhancement appears. The energy levels depend both on the QN and the electronic environment, i.e., the chemical bonding structure in the CA molecule. In this work, the NQR properties of a family of promising organometallic compounds containing Bi-209 as QN have been characterized. Important factors like temperature, chemical structure, and chemical environment have been considered by NQR spectroscopy and ab initio quantum chemistry calculations. The investigated Bi-aryl compounds turned out to fulfill several crucial requirements: NQR transition frequency range applicable to clinical 1.5- and 3 T MRI systems, low temperature dependency, low toxicity, and tunability in frequency by chemical modification.

First author: Yepes, D, Hydrogenation of Multiple Bonds by Geminal Aminoborane-Based Frustrated Lewis Pairs, CHEMISTRY-A EUROPEAN JOURNAL, 24, 8833, (2018)
Abstract: The hydrogenation reaction of multiple bonds that is mediated by geminal aminoborane-based frustrated Lewis pairs (FLPs) has been explored by means of density functional theory calculations. It was found that the release of the activated dihydrogen occurred in a concerted, yet highly asynchronous, manner. The physical factors that control the transformation were quantitatively described in detail by using the activation strain model of reactivity in combination with the energy decomposition analysis method. This approach suggested a cooperative double hydrogen-transfer mechanism, which involves the initial migration of the protic (N)H followed by the nucleophilic attack of the (B)H hydride to the carbon atom of the multiple bond. The influence of both the substituents directly attached to the boron atom of the initial FLP and the nature of the multiple bond on the transformation was also investigated.

First author: Li, ZZ, Compounds with Rare Gas-Selenium/Tellurium Bonds: A Theoretical Investigation on FRgLF(n) and FRgLF(n-1)(+)(Rg = Kr-Rn, L = Se and Te, n=1, 3, and 5), JOURNAL OF PHYSICAL CHEMISTRY A, 122, 5445, (2018)
Abstract: A new type of interesting insertion compounds FRgLF(n) (Rg = Kr-Rn, L = Se and Te, n = 1, 3 and 5) and ionic FRgLF(n-1)(+) obtained through the insertion of a rare gas atom into the selenium fluorides and tellurium fluorides have been explored theoretically using MP2, CCSD(T), and PBE0 calculations. These predicted species were examined to present the optimized geometries, vibrational modes, molecular properties, thermodynamic and kinetic stabilities and bond nature. The optimized structures are without imaginary frequencies and metastable. In neutral FRgLF(n), F-Rg bonds should be of ionic character with large dissociation energy ranging from 150-200 kcal mol(-1) that could be best described by F-(RgLF(n))(+). Rg-L bonds have some covalent character with lower interaction energies within the range 25-40 kcal mol(-1). In FRgL(+) and FRgLF(2)(+), the bonding nature of the F-Rg and Rg-L bonds are somewhat similar to that of the neutral compounds. In FRgLF(4)(+), the F-Rg bond could be of partial covalent type but the Rg-L bond could be considered as an ionic bond.

First author: Mu, XL, Theoretical study on the effective dehydrochlorination of 1,2-dichloroethane catalyzed by tetraalkylphosphonium chlorides: electrostatically controlled reactivity, NEW JOURNAL OF CHEMISTRY, 42, 10084, (2018)
Abstract: This work aims at understanding the intriguing experimental observation of the most effective dehydrochlorination of 1,2-dichloroethane (DCE) catalyzed by tetrabutylphosphonium chloride (C4444P+Cl-) vs. other tetraalkylphosphonium chlorides, imidazolium chlorides, and inorganic molten salts. The calculation on the C4444P+Cl–catalyzed DCE dehydrochlorination reaction shows a bimolecular elimination (E2) mechanism, where the ionic liquid (IL) plays an amphiphilic dual activation role, whose component anion and cation act cooperatively to induce the cleavage of the C-H and C-Cl bonds of DCE and the formation of the H-Cl bond. The effective dehydrochlorination of DCE catalyzed by C4444P+Cl- IL is attributed to the strong basicity of the IL, which originates from the weak electrostatic interaction between the anionic and cationic partners in comparison with other tetraalkylphosphonium chlorides, imidazolium chlorides, and inorganic molten salts. The theoretical calculations emphasize the electrostatically controlled character of DCE dehydrochlorination in the ILs as well as the cooperative catalysis of ILs. The present results would provide guidance for understanding the reactivity of the IL-catalyzed dehydrochlorination of DCE.

First author: Foppa, L, Electronic Structure-Reactivity Relationship on Ruthenium Step-Edge Sites from Carbonyl C-13 Chemical Shift Analysis, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 9, 3348, (2018)
Abstract: Ru nanoparticles are highly active catalysts for the Fischer-Tropsch and the Haber-Bosch processes. They show various types of surface sites upon CO adsorption according to NMR spectroscopy. Compared to terminal and bridging ill adsorption modes on terraces or edges, little is known about side-on 172 CO species coordinated to B-5 or B-6 step-edges, the proposed active sites for CO and N-2 cleavage. By using solid-state NMR and DFT calculations, we analyze C-13 chemical shift tensors (CSTs) of carbonyl ligands on the molecular cluster model for Ru nanoparticles, Ru-6(eta(2)-mu(4)-CO)(2)(CO)(13)(eta(6)-C6Me6), and show that, contrary to eta(1) carbonyls, the CST principal components parallel to the C-O bond are extremely deshielded in the eta(2) species due to the population of the C-O pi* antibonding orbital, which weakens the bond prior to dissociation. The carbonyl CST is thus an indicator of the reactivity of both Ru clusters and Ru nanoparticles step-edge sites toward C-O bond cleavage.

First author: Chernyy, V, Direct IR Spectroscopic Detection of a Low-Lying Electronic State in a Metal Carbide Cluster, CHEMPHYSCHEM, 19, 1424, (2018)
Abstract: The electronic structure of metal clusters is notoriously difficult to detect spectroscopically, due to rapid relaxation into the ground state following excitation. We have used IR multiple photon excitation to identify a low-lying electronic state in a tantalum carbide cluster. The electronic excitation is found at 458cm(-1), and is confirmed by experiments on isotopically labeled clusters. Time-dependent density functional theory (TD-DFT) calculations confirm the current assignment, but a second predicted electronic state was not observed.

First author: Poater, J, Covalent and Ionic Capacity of MOFs To Sorb Small Gas Molecules, INORGANIC CHEMISTRY, 57, 6981, (2018)
Abstract: In this work, the aim is to characterize how an Fe-based metal-organic framework (MOF) behaves when gases, like carbon dioxide, are inserted through their channels and to characterize the nature and strength of those interactions. Despite the computational nature of the project, it is based on the experimental results obtained in 2016 by Minguez-Espallargas and coworkers (J. Am. Chem. Soc. 2013, 135, 15986-15989). Those MOFs were found to selectively allocate/adsorb CO2 , having as a drawback that apparently each cavity allocates only one CO2 molecule. Despite truncating the MOF to its unitary cell, the whole cavity of the MOF can be described in detail by precise ab initio calculations. Another computational goal is to unravel why experimentally CO2 was preferred with respect to N-2, and for the sake of consistency, a list of common gases will be further studied, such as H-2, O-2, H2O, CH4, C2H6 , N2O, or NO.

First author: Rungthanaphatsophon, P, Influence of Substituents on the Electronic Structure of Mono- and Bis(phosphido) Thorium(IV) Complexes, INORGANIC CHEMISTRY, 57, 7270, (2018)
Abstract: A series of metallocene thorium complexes with mono- and bis(phosphido) ligands have been investigated with varying hues: (C5Me5)(2)Th(Cl)[P(Mes)(2)] (Mes = mesityl = 2,4,6-(CH3)(3)C6H2; dark red-purple), (C5Me5)(2)Th[P(Mes)(CH3)](2)(dark red-purple), (C5Me5)(2)Th(CH3)[P(Mes)(2)] (dark red-purple), (C5Me5)(2)Th(CH3)[P(Mes)(SiMe3)] (orange), (C5Me5)(2)Th(Cl)-[P(Mes)(SiMe3)] (orange), (C5Me5)(2)Th[P(Mes)(SiMe3)](2)(orange), and (C5Me5)(2)Th[PH(Mes)](2) (pale yellow). While all of these complexes bear a mesityl group on phosphorus, the electronic structure observed differs depending on the other substituent (mesityl, methyl, trimethylsilyl, or hydrogen). This sparked an investigation of the electronic structure of these complexes using( 31)P NMR and electronic absorption spectroscopy in concert with time-dependent density functional theory calculations.

First author: Kobera, L, The Nature of Chemical Bonding in Lewis Adducts as Reflected by Al-27 NMR Quadrupolar Coupling Constant: Combined Solid-State NMR and Quantum Chemical Approach, INORGANIC CHEMISTRY, 57, 7428, (2018)
Abstract: Lewis acids and Lewis adducts are widely used in the chemical industry because of their high catalytic activity. Their precise geometrical description and understanding of their electronic structure are a crucial step for targeted synthesis and specific use. Herein, we present an experimental/computational strategy based on a solidstate NMR crystallographic approach allowing for detailed structural characterization of a wide range of organoaluminum compounds considerably differing in their chemical constitution. In particular, we focus on the precise measurement and subsequent quantumchemical analysis of many different Al-27 NMR resonances in the extremely broad range of quadrupolar coupling constants from 1 to 50 MHz. In this regard, we have optimized an experimental strategy combining a range of static as well as magic angle spinning experiments allowing reliable detection of the entire set of aluminum sites present in trimesitylaluminum (AlMes(3)) reaction products. In this way, we have spectroscopically resolved six different products in the resulting polycrystalline mixture. All Al-27 NMR resonances are precisely recorded and comprehensively analyzed by a quantum-chemical approach. Interestingly, in some cases the recorded Al-27 solid-state NMR spectra show unexpected quadrupolar coupling constant values reaching up to ca. 30 MHz, which are attributed to tetra-coordinated aluminum species (Lewis adducts with trigonal pyramidal geometry). The cause of this unusual behavior is explored by analyzing the natural bond orbitals and complexation energies. The linear correlation between the quadrupolar coupling constant value and the nature of bonds in the Lewis adducts is revealed. Moreover, the Al-27 NMR data are shown to be sensitive to the geometry of the tetra-coordinated organoaluminum species. Our findings thus provide a viable approach for the direct identification of Lewis acids and Lewis adducts, not only in the investigated multicomponent organoaluminum compounds but also in inorganic zeolites featuring catalytically active trigonal (Al-III) and strongly perturbed Al-IV sites.

First author: Ferreira, T, Ba3Fe1.56Ir1.44O9: A Polar Semiconducting Triple Perovskite with Near Room Temperature Magnetic Ordering, INORGANIC CHEMISTRY, 57, 7362, (2018)
Abstract: The crystal chemistry and magnetic properties for two triple perovskites, Ba3Fe1.56Ir1.44O9 and Ba3NiIr2O9, grown as large, highly faceted single crystals from a molten strontium carbonate flux, are reported. Unlike the idealized A(3)MM(2)’O-9 hexagonal symmetry characteristic of most triple perovskites, including Ba3NiIr2O9, Ba3Fe1.56Ir1.44O9 possesses significant site-disorder, resulting in a noncentrosymmetric polar structure with trigonal symmetry. The valence of iron and iridium in the heavily distorted Fe/Ir sites was determined to be Fe(III) and Ir(V) by X-ray absorption near edge spectroscopy (XANES). Density functional theory calculations were conducted to understand the effect of the trigonal distortion on the local Fe(III)O(6 )electronic structure, and the spin state of iron was determined to be S = 5/2 by Mossbauer spectroscopy. Conductivity measurements indicate thermally activated semiconducting behavior in the trigonal perovskite. Magnetic properties were measured and near room temperature magnetic ordering (T-N = 270 K) was observed for Ba3Fe1.56Ir1.44O9.

First author: Venkataramanan, NS, Unravelling the nature of binding of cubane and substituted cubanes within cucurbiturils: A DFT and NCI study, JOURNAL OF MOLECULAR LIQUIDS, 260, 18, (2018)
Abstract: The nature of interactions between the neutral, charged and substituted cubane, within cucurbituril host were analyzed employing the dispersion corrected density functional theory. The structural comparison between the inclusion complexes of CB7 and CB8 shows a best fit for the CB7. The computed Gibbs free energy for the formation of inclusion complexes by the neutral guests were close to the experimental estimate. The dicationic guest within CB has the highest strain energy with least strain on the host. The conceptual DFT based analysis ECT analysis shows a charge transfer from the host to guest in neutral systems, while for the dicationic guest an electron transfer from guest to host has been noticed, which was further conformed from the quantitative MESP values. The computed NICS values on the cubane, are not affected by the introduction of charge/substituents implying that cubane part act as a spacer group while the functional groups present on the cubane dictates the charge transfer. In AIM analysis, the p value is least for the complex cubane@CB7 and highest for the cubane functionalized dicationic complex@CB complexes. The NCI-RDG analysis for the inclusion complex with dicarboxylic guest, the spike at higher density region undergoes a shift, reflecting the increase in repulsive energy. In the inclusion complexes of CB7 the patch escalation in the NCI isosurface occurs evenly in CB7 than on the CB8 inclusion complexes, signifying the fit-induced extra stability of the CB7 inclusion complexes. EDA analysis shows that the Pauli repulsive energy increase with the increase in the size of the guest molecule and among the guest the dicationic has the highest repulsive energy. The presence of higher amount of electrostatic interactions in the dicationic complex has remunerated the dispersion contribution in the dicationic complexes.

First author: Ramakrishnan, S, Origin of beta-agostic interaction in d(0) transition metal alkyl complexes: Influence of ligands, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 865, 37, (2018)
Abstract: Classical picture of agostic interaction involves a three-center two-electron interaction where the metal center has valence electron count less than sixteen. Though unsaturation on metal center is a necessary condition, it is not sufficient to show agostic interaction. For example, TiEtCl3 and its diphosphine adduct TiEtCl3(dmpe) have d(0)-metal center and the electron count is far less from 18 electrons for both. But TiEtCl3 shows no agostic interaction while TiEtCl3(dmpe) has an agostic interaction. An explanation based on negative hyperconjugation is put forward to explain the special case of C-H activation using d(0)-metal centers, which is also not sufficient. On electronic and steric grounds, TiEtCl3, rather than TiEtCl3(dmpe), is expected to exhibit agostic interaction, contrary to the experimental observation. If a molecule possesses vacant orbital in the plane of the M-C-alpha-C-beta-H fragment with appropriate energy, agostic interaction follows. How the nature and arrangement of the ligands around the metal center influence the origin of beta-agostic interaction in d(0) transition metal alkyl complexes is described in this paper. Octahedral type of arrangement of ligands around metal center help TiEtCl3(dmpe) and the pi* orbitals of CN and CF3 group help TiEt(CN)(3) and TiEt(CF3)(3) to be agostic.

First author: Arsenov, MA, (Indenyl)rhodacarboranes. Electronic versus steric effects on the conformation of cyclic ligands, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 865, 45, (2018)
Abstract: (Indenyl) rhodacarboranes 1,2-R-2-3-(eta(5)-indenyl)-3,1,2-RhC2B9H9 (2a: R = H; 2b: R = Me) and 3-(eta(5)-indenyl)-4-SMe-3,1,2-RhC2B9H10 (3) were synthesized by reactions of the iodide complex [(eta(5)-indenyl) RhI2](n) (1b) with Tl[Tl(eta-7,8-R-2-7,8-C2B9H9)] or Tl[9-SMe2-7,8-C2B9H10]. The formation of 3 is accompanied by monodemethylation of the SMe2 substituent. The structures of rhodacarboranes 2b, 3 and the half-sandwich complex (eta(5)-indenyl) RhBr2(dmso) were determined by X-ray diffraction. Rhodacarborane 2b has the sterically unfavorable eclipsed cisoid conformation, in which the bridgehead carbon atoms of the indenyl ligand are arranged close to the carborane cage carbon atoms. The thermal stability of conformers for 2b was analyzed by the DFT calculations.

First author: Lu, MM, F-19 Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors, JOURNAL OF PHYSICAL CHEMISTRY B, 122, 6148, (2018)
Abstract: The F-19 chemical shift is a sensitive NMR probe of structure and electronic environment in organic and biological molecules. In this report, we examine chemical shift parameters of 4F-, 5F-, 6F-, and 7F-substituted crystalline tryptophan by magic angle spinning (MAS) solid-state NMR spectroscopy and density functional theory. Significant narrowing of the 19F lines was observed under fast MAS conditions, at spinning frequencies above 50 kHz. The parameters characterizing the 19F chemical shift tensor are sensitive to the position of the fluorine in the aromatic ring and, to a lesser extent, the chirality of the molecule. Accurate calculations of F-19 magnetic shielding tensors require the PBEO functional with a 50% admixture of a Hartree Fock exchange term, as well as taking account of the local crystal symmetry. The methodology developed will be beneficial for 19F based MAS NMR structural analysis of proteins and protein assemblies.

First author: Joshi, M, Theoretical investigation of M@Pb-12(2-) and M@Sn-12(2-) Zintl clusters (M = Lrn+, Lun+, La3+, Ac3+ and n=0, 1, 2, 3), PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 15253, (2018)
Abstract: The positions of lawrencium (Lr), lutetium (Lu), actinium (Ac) and lanthanum (La) in the periodic table have been a controversial topic for quite some time. According to studies carried out by different groups with their justifications, these elements may potentially be placed in the d-block, p-block or all four in a 15 element f-block. The present work looks into this issue from a new perspective, which involves encapsulation of these four elements into Zintl ion clusters, Pb-12(2-) and Sn-12(2-), followed by the determination of the structural, thermodynamic and electronic properties of these endohedral M@Pb-12(2-) and M@Sn-12(2-) clusters (M = Lrn+, Lun+ with n = 0, 1, 2, 3) using first principles based density functional theory (DFT). These parameters are compared with similar clusters encapsulated La3+ and Ac3+ ions in order to seek out similarities and differences to draw conclusions about their placement in the periodic table. For the first time the structural, energetic, and electronic properties of these metal atom/ion encapsulated Pb-12(2-) and Sn-12(2-) clusters have been investigated thoroughly. Structural parameters such as bond distances, geometry and symmetry, electronic properties viz. the density of states, the molecular orbital ordering, the electron localization function, bond critical point properties and charge distributions have been analyzed. Additionally, the thermodynamic property of the binding energy during the encapsulation process has also been calculated. All M@Pb-12(+) and M@Sn-12(+) (M = Lr and Lu) clusters form stable 18 bonding electron magic number systems with shell closing. They show negative values of binding energy and relatively large HOMO-LUMO energy gaps indicating the stability of such clusters. All the calculated parameters for Lr encapsulated clusters closely match with the corresponding calculated parameters of Lu encapsulated clusters, confirming the similarity between Lr and Lu metal atoms in various oxidation states, though their atomic ground state valence electronic configurations are different. The effect of spin orbit coupling has also been investigated using the ZORA approach. It is interesting to discover that La and Ac showed striking similarities to Lr and Lu with respect to all the properties investigated and have formed a stable 18-electron system.

First author: Racioppi, S, Electron Density Analysis of Metal Clusters with Semi-Interstitial Main Group Atoms. Chemical Bonding in [Co6X(CO)(16)](-) Species, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 5004, (2018)
Abstract: In this work, we propose a careful and thorough analysis of the chemical bond nature in high nuclearity metal carbonyl clusters having semi-interstitial main group atoms. We investigated the species [Co6X(CO)(16)](-) (X = As, P), known for a rather interesting conformational flexibility of the cluster (leading to open or closed cages) and a corresponding polymorphism in the solid state (observed at least for X = As). The factors that trigger the molecular isomerism and the nature of X-Co and Co-Co interactions emerge from theoretical calculations and high resolution X-ray diffraction. Both energy and charge density atomic partitioning (QTAIM, EDA, IQA) are employed for this analysis, with the aim of revealing the stabilizing/destabilizing factors of the interaction between the cage and the semi-interstitial atoms in the various conformations.

First author: Claveria-Cadiz, F, Survey of short and long cuprophilic d(10)-d(10) contacts for tetranuclear copper clusters. Understanding of bonding and ligand role from a planar superatom perspective, NEW JOURNAL OF CHEMISTRY, 42, 8874, (2018)
Abstract: Polynuclear copper(i) complexes involving d(10)-d(10) interactions have been studied to a lesser extent in comparison to their gold counterparts. Here, we attempt to gain a deeper understanding of ligand-protected d(10) copper clusters based on density functional theory calculations, based on the evaluation of several tetranuclear copper arrays offering different cuprophilic interactions, showing short- and long-contact d(10)-d(10) situations. Our results show that the protecting ligands display a fundamental role in the stabilization of the closed-shell central core since there is a direct relationship between ligand charge donation to the ns combinations of multinuclear metallic center and the collateral increasing of the copper-copper stabilizing interactions. Further, quantification of the incoming population of ns shell levels through a selective analysis of coefficients of its corresponding wave functions depicts a useful and novel methodology toward the characterization of the copper-metallophilic phenomena that appears in these closed-shell systems. Thereby, here we use the planar superatom approach to describe the ns valence population in terms of superatomic two-dimensional shell set levels, namely, 1s, 1p(x), 1p(y), and 1d(xy). Thus, the tetranuclear clusters can be viewed as formally 8-valence electron systems, which gives a better understanding of the stable core structures. The formation of different types of cuprophilic interaction in d(10)-d(10) Cu-Cu structures can be used to generate strongly bound closed-shell interactions in lighter counterparts from the coinage metal group, similarly to gold-gold compounds. We expect that this analysis can be extended to linear and polymeric d(10)-d(10) Cu-Cu arrays in order to gain a deeper understanding of the closed-shell bonding situation.

First author: Wu, WC, Thermodynamic and spectroscopic study on the solvation and complexation behavior of Ln( III) in ionic liquids: binding of Ln( III) with CMPO in C4mimNTf2, NEW JOURNAL OF CHEMISTRY, 42, 9098, (2018)
Abstract: Fundamental coordination chemistry of metal ions in ionic liquids (ILs) is of great importance to extend the application of ILs in the area of metal separation. In this work, the solvation of representative trivalent lanthanides (Nd, Eu and La) and their complexation with a functional ligand, octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO, denoted as L), in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C(4)mimNTf(2)) have been probed by spectroscopic, calorimetric and theoretical techniques. Absorption spectrophotometric titrations suggest that four successive Nd/CMPO complexes, NdLj3+ (j = 1-4), form both in dry (water content <250 ppm) and wet (water-saturated) ILs. However, the thermodynamic parameters vary distinctly in the two ILs. In dry IL, the complexation is stronger and overwhelmingly driven by exothermic enthalpies. In contrast, the complexation in wet IL is relatively weak and mainly driven by highly positive entropies. Comparisons between the fitted absorption spectra of Nd/CMPO complexes in wet IL and that of extractive samples from biphasic solvent extraction have clearly identified the extracted species as NdL43+ during the extraction. The formation of a 1:4 Ln/CMPO complex was further supported by DFT calculations and P-31-NMR results (La/CMPO). Additionally, luminescence emission spectra and lifetime of Eu(iii) provide further evidence to illustrate the solvation and complexation behavior of Ln(iii) in ILs. The results from this work shed light on how solvation affects the complexation of metal ions in ILs and how fundamental thermodynamic findings could help reveal the mechanism of biphasic extraction in real applications.

First author: Hamlin, TA, Nucleophilic Substitution (S(N)2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent, CHEMPHYSCHEM, 19, 1315, (2018)
Abstract: The reaction potential energy surface (PES), and thus the mechanism of bimolecular nucleophilic substitution (S(N)2), depends profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the S(N)2 mechanism. One of the most striking effects is the transition from a double-well to a single-well PES when the central atom is changed from a second-period (e.g. carbon) to a higher-period element (e.g, silicon, germanium). Variations in nucleophilicity, leaving group ability, and bulky substituents around a second-row element central atom can then be exploited to change the single-well PES back into a double-well. Reversely, these variations can also be used to produce a single-well PES for second-period elements, for example, a stable pentavalent carbon species.

First author: Wang, Y, Comprehensive Investigation into Luminescent Properties of Ir(III) Complexes: An Integrated Computational Study of Radiative and Nonradiative Decay Processes, INORGANIC CHEMISTRY, 57, 6561, (2018)
Abstract: A comprehensive and concrete exploration into the deactivation mechanisms of luminescent materials is imperative, with the improvement of simulating and computing technology. In this study, an integrated calculation scheme is employed on five Ir(III) complexes for thorough investigation of their photophysical properties, including radiative (kr) and nonradiative (knr) decay rates. As a most famous Ir(III) complex with superior quantum efficiency, facIr(ppy)3 herein serves as a reference relative to the other four /t-diketonate complexes. Both temperature-independent and temperature-dependent knr are taken into account quantitatively for the first time, to unearth the role of different ancillary ligands in the determination of luminescent properties. Since the validated calculations of kr for the five complexes are of the same order of magnitude, the nonemissive peculiarity of 4 is caused by large kr. The newly designed compound 5, which simply has two more CH2 groups than 4 in the ancillary ligand, further manifests that the reason for large knr in molecule 4 should be attributed to the ligand resonance caused by great Jr conjugation.

First author: Ravell, E, Structure and Bonding in CE5- (E=Al-Tl) Clusters: Planar Tetracoordinate Carbon versus Pentacoordinate Carbon, CHEMISTRY-AN ASIAN JOURNAL, 13, 1467, (2018)
Abstract: The structure, bonding, and stability of clusters with the empirical formula CE5- (E=Al-Tl) have been analyzed by means of high-level computations. The results indicate that, whereas aluminum and gallium clusters have C-2v structures with a planar tetracoordinate carbon (ptC), their heavier homologues prefer three-dimensional C-4v forms with a pentacoordinate carbon center over the ptC one. The reason for such a preference is a delicate balance between the interaction energy of the fifth E atom with CE4 and the distortion energy. Moreover, bonding analysis shows that the ptC systems can be better described as CE4-, with 17-valence electrons interacting with E. The ptC core in these systems exhibits double aromatic (both sigma and ) behavior, but the sigma contribution is dominating.

First author: Zhai, SC, Density functional theory study on the stability, electronic structure and absorption spectrum of small size g-C3N4 quantum dots, COMPUTATIONAL MATERIALS SCIENCE, 148, 149, (2018)
Abstract: The geometric stabilities, electronic properties as well as ultraviolet-visible (UV-Vis) absorption spectra of the g-C3N4 quantum dots were systematically investigated by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. Taking the tri-s-triazine as a basic building unit, three types of planar structures of the g-C3N4 quantum dots were designed. The chain-type g-C3N4 quantum dots are the lowest in energy. The growth pattern of the g-C3N4 quantum dots had been speculated. The absorption spectra of the triangular sheet structure are in good agreement with the experimental results, and the absorption spectra of the (g-C3N4)(15) quantum dots with a 3.41 nm lateral size has covered most of the visible light area. These small size g-C3N4 quantum dots are promising to be used as graphitic carbon nitride-based composite materials for energy conversion.

First author: Pinilla-Herrero, I, High Zn/Al ratios enhance dehydrogenation vs hydrogen transfer reactions of Zn-ZSM-5 catalytic systems in methanol conversion to aromatics, JOURNAL OF CATALYSIS, 362, 146, (2018)
Abstract: Two series of Zn-ZSM-5 catalysts were prepared by ion exchanging two commercial zeolites with different Si/Al ratios (40 and 15) with increasing Zn loadings. The nature of the Zn sites in the zeolite was studied by spectroscopy using laboratory and synchrotron techniques. All the evidences suggest that catalytic activity is associated with [Zn(H2O)(n)(OH)](+) species located in the exchange positions of the materials with little or no contribution of ZnO or metallic Zn. The effect of Zn/Al ratio on their catalytic performance in methanol conversion to aromatics has been investigated. In all cases, higher Zn content causes an increase in the yield of aromatics while keeping the production of alkanes low. For similar Zn contents, high densities of Al sites favour the hydrogen transfer reactions and alkane formation whereas in samples with low Al contents, and thus higher Zn/Al ratio, the dehydrogenation reactions in which molecular hydrogen is released are favoured.

First author: Vicha, J, Relativistic Spin-Orbit Heavy Atom on the Light Atom NMR Chemical Shifts: General Trends Across the Periodic Table Explained, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 3025, (2018)
Abstract: The importance of relativistic effects on the NMR parameters in heavy-atom (HA) compounds, particularly the SO-HALA (Spin-Orbit Heavy Atom on the Light Atom) effect on NMR chemical shifts, has been known for about 40 years. Yet, a general correlation between the electronic structure and SO-HALA effect has been missing. By analyzing H-1 NMR chemical shifts of the sixth-period hydrides (Cs-At), we discovered general electronic-structure principles and mechanisms that dictate the size and sign of the SO-HALA NMR chemical shifts. In brief, partially occupied HA valence shells induce relativistic shielding at the light atom (LA) nuclei, while empty HA valence shells induce relativistic deshielding. In particular, the LA nucleus is relativistically shielded in 5d(2)-5d(8) and 6p(4) HA hydrides and deshielded in 4f(0), 5d(0), 6s(0), and 6p(0) HA hydrides. This general and intuitive concept explains periodic trends in the H-1 NMR chemical shifts along the sixth-period hydrides (Cs-At) studied in this work. We present substantial evidence that the introduced principles have a general validity across the periodic table and can be extended to nonhydride LAs. The decades-old question of why compounds with occupied frontier pi molecular orbitals (MOs) cause SO-HALA shielding at the LA nuclei, while the frontier sigma MOs cause deshielding is answered. We further derive connection between the SO-HALA NMR chemical shifts and Spin-Orbit-induced Electron Deformation Density (SO-EDD), a property that can be obtained easily from differential electron densities and can be represented graphically. SO-EDD provides an intuitive understanding of the SO-HALA effect in terms of the depletion/concentration of the electron density at LA nuclei caused by spin-orbit coupling due to HA in the presence of a magnetic field. Using an analogy between the SO-EDD concept and arguments from classic NMR theory, the complex question of the SO-HALA NMR chemical shifts becomes easily understandable for a wide chemical audience.

First author: Wang, Y, Intrinsic quantum efficiency enhancement in well-known Ir(iii) complexes by virtue of a simple and controllable deuteriation strategy, MATERIALS CHEMISTRY FRONTIERS, 2, 1215, (2018)
Abstract: A series of well-known iridium(iii) complex molecular materials are selected for a comprehensive theoretical investigation into their complete or partial ligand deuteriation products. These compounds, respectively, are two homoleptic compounds fac-Ir(ppy)(3) [ppy = 2-phenylpyridinate] (1) and fac-Ir(dfppy)(3) [dfppy = 2-(2,4-difluorophenyl)pyridyl] (2), and two heteroleptic compounds Ir(ppy)(2)acac [acac = acetylacetonate] (3) and Ir(dfpypy)(2)pic [dfpypy = 2,4-difluoro-2,3-bipyridinato-N,C-4, pic = picolinate] (4). Unlike traditional strategies for enhancing the radiative decay process or reducing the non-radiative decay process through cumbersome ligand decorations, our simple and controllable deuteriation strategy, which is insensitive to the radiative decay process, enables us to suppress the non-radiative decay process by almost 50%. It is consistent with previous experimental findings, under our theoretical evaluation, that deuterium has a significant influence on non-radiative deactivation processes due to the reduction in the amplitude and frequency of vibrational modes caused by the increased deuterium mass. The systematic computational approach for the evaluation of the non-radiative decay processes provides us with alterations of every single vibrational mode, from the primitive complexes to the completely or partially deuterated ligand complexes, in detail. The two-averaged modes assessment informs us that deuteriation exerts its main influence on the high-frequency modes, rather than the low-frequency modes. Additionally, partial ligand deuteriation has a correlation with the nature of the electronically excited state decay pathways.

First author: Zierkiewicz, W, Comparison between Tetrel Bonded Complexes Stabilized by sigma and pi Hole Interactions, MOLECULES, 23, 1215, (2018)
Abstract: The sigma-hole tetrel bonds formed by a tetravalent molecule are compared with those involving a pi-hole above the tetrel atom in a trivalent bonding situation. The former are modeled by TH4, TH3F, and TH2F2 (T = Si, Ge, Sn) and the latter by TH2=CH2, THF=CH2, and TF2=CH2, all paired with NH3 as Lewis base. The latter pi-bonded complexes are considerably more strongly bound, despite the near equivalence of the sigma and pi-hole intensities. The larger binding energies of the pi-dimers are attributed to greater electrostatic attraction and orbital interaction. Each progressive replacement of H by F increases the strength of the tetrel bond, whether sigma or pi. The magnitudes of the maxima of the molecular electrostatic potential in the two types of systems are not good indicators of either the interaction energy or even the full Coulombic energy. The geometry of the Lewis acid is significantly distorted by the formation of the dimer, more so in the case of the sigma-bonded complexes, and this deformation intensifies the sigma and pi holes.

First author: Hollas, A, A biomimetic high-capacity phenazine-based anolyte for aqueous organic redox flow batteries, NATURE ENERGY, 3, 508, (2018)
Abstract: Aqueous soluble organic (ASO) redox-active materials have recently attracted significant attention as alternatives to traditional transition metal ions in redox flow batteries (RFB). However, reported reversible capacities of ASO are often substantially lower than their theoretical values based on the reported maximum solubilities. Here, we describe a phenazine-based ASO compound with an exceptionally high reversible capacity that exceeds 90% of its theoretical value. By strategically modifying the phenazine molecular structure, we demonstrate an increased solubility from near-zero with pristine phenazine to as much as 1.8 M while also shifting its redox potential by more than 400 mV. An RFB based on a phenazine derivative (7,8-dihydroxyphenazine-2-sulfonic acid) at its near-saturation concentration exhibits an operating voltage of 1.4 V with a reversible anolyte capacity of 67 Ah l(-1) and a capacity retention of 99.98% per cycle over 500 cycles.

First author: Zuo, K, A potential strategy used for controlling the phosphorescence quantum yield of cyclometalated (CC) platinum(II) NHC complexes: The theoretical insight, ORGANIC ELECTRONICS, 57, 367, (2018)
Abstract: Effectively adjusting the phosphorescent quantum efficiency of transition metal complexes is of great significance for the development of new energy-saving organic light-emitting diodes devices. In this article, density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods are employed to investigate the effects of electronegativity caused by introduction of azole moieties on the phosphorescence properties, radiative and nonradiative decay rate constants and photodeactivation mechanism of cyclometalated (C<^>C*) platinum(II) NHC complexes. According to calculated results, by decreasing the electronegativity of NHC ligand, the maximum wavelength of the complex appears blue shift; the electron transition density of the lowest triplet state is concentrated to the Pt(II) atom, the singlet-triplet splitting energy and the spin-orbital coupling (SOC) matrix elements are obviously increased, leading to a significant increase of radiative decay rate constant. However, the decrease of ligand electronegativity results in a slight decrease in molecular rigidity and the SOC matrix elements between the ground state and the lowest triplet excited state increase, the energy barriers in photodeactivation pathway decrease, which eventually leads to the increase of nonradiative decay rate constant. Considering its prominent effect on the enhancement of the radiative decay rate constant, this method may still effectively improve the phosphorescence quantum yield of the complexes. This work has a certain theoretical reference value for the design of highly efficient phosphorescent complexes.

First author: Lee, J, Microscopy with a single-molecule scanning electrometer, SCIENCE ADVANCES, 4, 367, (2018)
Abstract: The vibrational spectrum of a single carbon monoxide molecule, adsorbed on the tip apex of a scanning tunneling microscope, is used to image electrostatic fields with submolecular spatial resolution. The method takes advantage of the vibrational Stark effect to image local electrostatic fields and the single-molecule sensitivity of tip-enhanced Raman scattering (TERS) to optically relay the signal. We apply the method to single metalloporphyrins adsorbed on Au(111) to image molecular charges, intramolecular polarization, local photoconductivity, atomically resolved hydrogen bonds, and surface electron density waves.

First author: Zouchoune, B, Stability and possible multiple metal-metal bonding in tetranuclear sandwich complexes of cyclooctatetraene ligand, STRUCTURAL CHEMISTRY, 29, 937, (2018)
Abstract: Geometry optimizations have been performed on the M-4(COT)(2) (M = Cr-Ni, Pd and COT = C8H8) complexes by means of DFT method using BP86-D functional combined to the TZP basis set. The M-4 moiety encapsulated between two COT ligands tends to establish M-L and M-M bonding in relationship with the metal nature and the spin state. In accordance with the coordination modes, the COT behaves as neutral or dianionic ligand. The calculations showed that the various complexes are found to have a low, intermediate, or high-spin ground state. The multiple metal-metal bonding is identified by exploring the bond distances, MO plots, and Wiberg bond index, which vary according to the valence electron count of the M-4 core.The Ziegler-Rauk energy decomposition analysis scheme was employed to characterize the geometry distortion and steric interaction (electrostatic and Pauli) and orbital interaction terms in the total bonding energy. The results showed that the interaction terms in all studied complexes are governed by one third covalent and two third ionic characters, in agreement with the Delta E-elstat (electrostatic) and Delta E-orb (orbital) contributions, respectively, into the total attractive interaction (Delta E-elstat + Delta E-orb).

First author: Bircher, MP, Plane-Wave Implementation and Performance of a-la-Carte Coulomb-Attenuated Exchange-Correlation Functionals for Predicting Optical Excitation Energies in Some Notorious Cases, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 3184, (2018)
Abstract: Linear-response time-dependent density functional theory (LR-TD-DFT) has become a valuable tool in the calculation of excited states of molecules of various sizes. However, standard generalized-gradient approximation and hybrid exchange-correlation (xc) functionals often fail to correctly predict charge-transfer (CT) excitations with low orbital overlap, thus limiting the scope of the method. The Coulomb-attenuation method (CAM) in the form of the CAM-B3LYP functional has been shown to reliably remedy this problem in many CT systems, making accurate predictions possible. However, in spite of a rather consistent performance across different orbital overlap regimes, some pitfalls remain. Here, we present a fully flexible and adaptable implementation of the CAM for Gamma-point calculations within the plane-wave pseudopotential molecular dynamics package CPMD and explore how customized xc functionals can improve the optical spectra of some notorious cases. We find that results obtained using plane waves agree well with those from all-electron calculations employing atom-centered bases, and that it is possible to construct a new Coulomb-attenuated xc functional based on simple considerations. We show that such a functional is able to outperform CAM-B3LYP in some cases, while retaining similar accuracy in systems where CAM-B3LYP performs well.

First author: Boulebd, H, New highly fluorescent hybrids (benz)imidazol-2-aminonicotinonitrile and-2-aminoisophthalonitrile: synthesis, characterization, fluorescence study, and theoretical calculations, MONATSHEFTE FUR CHEMIE, 149, 1125, (2018)
Abstract: In this paper, we describe the synthesis of two families of compounds type 2-aminonicotinonitrile and 2-aminoisophthalonitrile bearing a (benz)imidazole moiety. These compounds were prepared via microwave-promoted three-component reaction of 1-(1-methyl-1H-(benz)imidazole-2-yl)ethylidenedicarbonitrile, enolisable ketone, and propanedinitrile under solvent-free conditions. These two classes of compounds were found to be fluorescently active in solution at room temperature showing an intense blue fluorescence with high fluorescent quantum yield, independently of the excitation wavelength. To explore the origin of absorption band in the title compounds, the TD-DFT/B3LYP/TZ2P approach was used to compute electronic excitation energies, and the corresponding oscillator strengths for two compounds. X-ray crystal structures are reported for two compounds.

First author: Naili, N, Structural diversity of homobinuclear transition metal complexes of the phenazine ligand: theoretical investigation, STRUCTURAL CHEMISTRY, 29, 725, (2018)
Abstract: DFT/BP86 calculations have been carried out on a series of hypothetical binuclear compounds of general formula (L3M)(2)(C12N2H8) (M = Sc-Ni, L-3 = (CO)(3), (PH3)(3) and Cp-, and C12N2H8= phenazine ligand-denoted Phn). The various structures with syn and anti configurations have been investigated, in order to determine the phenazine’s coordination to first-row transition metals of various spin states with syn and anti conformations. The lowest energy structures depend on the nature of the metal, the spin state, and the molecular symmetry. This study has shown that the electronic communication between the metal centers depends on their oxidation state and the attached ligands. The tricarbonyl and the triphosphine ligands gave rise to comparable results in terms of stability order of isomers, metal-metal bond distances, and the coordination modes. Metal-metal multiple bonding has been evidenced for Sc, Ti, and V complexes to compensate the electronic deficiency. The Cr, Mn, Fe, Co, and Ni-rich metals prefer the anti conformation due to the enhancement of the metal valence electron count. The spin density values calculated for the triplet and quintet spin structures point out that the unpaired electrons are localized generally on the metal centers. The Wiberg bond indices are used to evaluate the metal-metal bonding. Furthermore, calculations using the BP86-D functional which take into account the attractive part of the van der Waals type interaction potential between atoms and molecules that are not directly connected to each other gave comparable results to those obtained by BP86 functional in terms of coordination modes, HOMO-LUMO gaps, metal-metal bond orders, and the stability order between isomers, but with slight deviation of M-C, M-N. and M-M bond distances not exceeding 3%.

First author: Toor, RA, Synthesis, computational study and characterization of a 3-{[2,3-diphenylquinoxalin-6-yl]diazenyl}-4-hydroxy-2H-chromen-2-one azo dye for dye-sensitized solar cell applications, JOURNAL OF COMPUTATIONAL ELECTRONICS, 17, 821, (2018)
Abstract: A solution-processable 3-{[2,3-diphenylquinoxalin-6-yl]diazenyl}-4-hydroxy-2H-chromen-2-one azo dye was synthesized. Analysis of measured UV-visible absorption spectrum and frontier orbitals computed using simplified time dependent density functional theory (sTDDFT) revealed its suitability for optoelectronic applications. A dye-sensitized solar cell (DSSC) was fabricated using this metal-free organic dye as a sensitizer. The photovoltaic parameters of the cell were studied under simulated AM 1.5 illumination (100 mWcm(-2)). Comparing the photovoltaic data with a DSSC using a different member of the azo family of dyes, open circuit voltage and fill factor of the device studied in this work were found higher by 33 and 104%, respectively. The performance was also compared with the DSSCs fabricated using 49 commercial mordant dyes and open circuit photovoltage of the device studied in this work was found higher. To gain insight into its charge transport, impedance spectroscopy was performed. Impedance spectra were observed both voltage and frequency dependent.

First author: Kubacek, P, Laser ablation synthesis of arsenic-phosphide AsmPn clusters from As-P mixtures. Laser desorption ionisation with quadrupole ion trap time-of-flight mass spectrometry: The mass spectrometer as a synthesizer, RAPID COMMUNICATIONS IN MASS SPECTROMETRY, 32, 789, (2018)
Abstract: RationaleOnly a few arsenic phosphides are known. A high potential for the generation of new compounds is offered by Laser Ablation Synthesis (LAS) and when Laser Desorption Ionization (LDI) is coupled with simultaneous Time-Of-Flight Mass Spectrometry (TOFMS), immediate identification of the clusters can be achieved.

First author: Cerreia Vioglio, P, Br-79/81 nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies, CHEMICAL SCIENCE, 9, 4555, (2018)
Abstract: Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81Br NQR to characterize the electronic changes in the C-Br/N halogen bonding motifs found in supramolecular assemblies constructed from 1,4dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance (dBr/N). Notably, 79/81Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81Br NQR resonances.

First author: Moroz, IB, Discerning gamma-Alumina Surface Sites with Nitrogen-15 Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy of Adsorbed Pyridine, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 10871, (2018)
Abstract: Low-temperature N-15 dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) of adsorbed pyridine in combination with FTIR measurements and DFT calculations was applied to investigate the surface sites of gamma-alumina, which can be divided into four groups: (l) groups 1 and 2, associated with less shielded N-15 chemical shifts and the lowest v(8a) frequencies of adsorbed pyridine, corresponding to weakly adsorbed H-bonding pyridine to hydroxyl group or chemisorbed water on alumina; (2) group 3, with intermediate N-15 chemical shifts and v(8a) frequencies, corresponding to pyridine coordinated to specific Lewis acid sites, namely five-coordinated (Al-v) aluminum atoms of the (100) facet, as well as some H-bonded pyridine; (3) group 4, associated with the most shielded N-15 chemical shift and the highest v(8a) frequency selectively assigned to Lewis acid A1 sites located on the (110) facet and corresponding to both four- and five-coordinated aluminum atoms (A1(IV) and Al-v). Noteworthy, a correlation between the N-15 chemical shift and the adsorption energy of pyridine, that is H-bonded or coordinated to A1 Lewis acid sites, was identified: the stronger the adsorption, the more shielded the N-15 chemical shift. According to Natural Chemical Shielding (NCS) analysis, this behavior is traced back to the bonding interaction of the lone pair of pyridine and the Lewis acid or OH sites, which controls a specific principal component of the chemical shift tensor of pyridine on one hand, and the adsorption energy on the other hand. This correlation between N-15 chemical shift and adsorption energy is likely general since it has a well-defined molecular origin and can thus be extended to other oxides.

First author: Karimova, NV, Chiroptical Activity in BINAP- and DIOP-Stabilized Octa- and Undecagold Clusters, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 11051, (2018)
Abstract: In order to learn more about the origin of chirality in chiral organometallic complexes and to contribute to the understanding of the differences in chiroptical activity of metal clusters stabilized by various phosphine ligands, we examined the optical properties of undecagold (Au-11(3+)) and octagold (Au-8(2+)) clusters protected by two types of bisphosphine ligands [BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) and DIOP (o-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)butane)]. The chirality of pairs of clusters [Au-11(BINAP)(4)Cl-2](+), [Au-11(DIOP)(4)Cl-2] (+) and [Au-8(BINAP)(3)(PPh3)(2)](2+), [Au-8(DIOP)(3)(PPh3)(2)](2+) are investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). The geo- metries of the octa- and undecagold cores in the model clusters are similar to the gold cores of the crystal structures. Theoretical optical absorption and CD spectra of the model clusters are in good agreement with experimental data. Three main hypotheses to explain the different chiroptical activity of the clusters were suggested: (i) the CD activity originates from core deformation due to ligation, (ii) the nature of the chiral ligands can play a crucial role in the optical activity of the core, and (iii) the Cl atom positions can affect the CD intensity. It was shown that the gold core geometry deformation due to ligation and the nature of the ligand play the most important roles in the chiroptical activity of the gold clusters. In addition, the ligands determine the gold core structural deformation and affect the high-energy region of the CD spectra, whereas the gold core itself exhibits a significant effect on the shape and sign of the CD spectra in the low energy region with wavelengths above similar to 350 nm.

First author: Ly, HGT, Superactivity of MOF-808 toward Peptide Bond Hydrolysis, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 6325, (2018)
Abstract: MOF-808, a Zr(IV)-based metal-organic framework, has been proven to be a very effective heterogeneous catalyst for the hydrolysis of the peptide bond in a wide range of peptides and in hen egg white lysozyme protein. The kinetic experiments with a series of Gly-X dipeptides with varying nature of amino acid side chain have shown that MOF-808 exhibits selectivity depending on the size and chemical nature of the X side chain. Dipeptides with smaller or hydrophilic residues were hydrolyzed faster than those with bulky and hydrophobic residues that lack electron rich functionalities which could engage in favorable intermolecular interactions with the btc linkers. Detailed kinetic studies performed by H-1 NMR spectroscopy revealed that the rate of glycylglycine (Gly-Gly) hydrolysis at pD 7.4 and 60 degrees C was 2.69 X 10(-4) s(-1) (t(1/2) = 0.72 h), which is more than 4 orders of magnitude faster compared to the uncatalyzed reaction. Importantly, MOF-808 can be recycled several times without significantly compromising the catalytic activity. A detailed quantum-chemical study combined with experimental data allowed to unravel the role of the {Zr6O8} core of MOF-808 in accelerating Gly-Gly hydrolysis. A mechanism for the hydrolysis of Gly-Gly by MOF-808 is proposed in which Gly-Gly binds to two Zr(IV) centers of the {Zr6O8} core via the oxygen atom of the amide group and the N-terminus. The activity of MOF-808 was also demonstrated toward the hydrolysis of hen egg white lysozyme, a protein consisting of 129 amino acids. Selective fragmentation of the protein was observed with 55% yield after 25 h under physiological pH.

First author: Sorbelli, D, Ligand Effect on Bonding in Gold(III) Carbonyl Complexes, INORGANIC CHEMISTRY, 57, 6161, (2018)
Abstract: We quantitatively assess the Dewar-Chatt-Duncanson (DCD) components of the Au(III)-CO bond and the charge density polarization at the CO, in a series of neutral, cationic, and dicationic bis-and monocyclometalated gold(III) complexes via charge-displacement (CD) analysis. A striking feature concerns the very small net electron charge flux from CO to the metal fragment which is unexpectedly stable toward both the charge of the complex and the oxidation state of gold (I, III). All systems exhibit a similar trend for the sigma charge rearrangement in the region of the carbonyl bond, where, by contrast, the Pi back-donation trend variation is large, which is strictly correlated to the change in CO bond distance and the shift in CO stretching frequencies, in close analogy with the gold(I) carbonyl complexes. In the whole series of gold(III) compounds, a large Au(III) <- CO sigma donation is measured (from 0.19 to 0.31 electrons), as well as a significant Au(III) -> CO Pi back-donation (from-0.09 to-0.22 electrons), which however is not generally able to completely balance the polarization of the CO Pi electrons in the direction from oxygen to carbon (C <- O) induced by the presence of the metal fragment [LAu(III)](0/+1/2). Surprisingly, all the gold(III) complexes in the series are characterized by a very small anisotropy in the Au(III) -> CO in-plane and out-of-plane Pi back-donation components, in sharp contrast with the marked anisotropy found before for the experimentally characterized [((CNC)-N-Lambda-C-Lambda)Au(III)CO](+) complex. A first attempt to figure out a rationale on the bonding/reactivity relationship for Au(III)-CO is made by performing a comparative study with an isostructural [((NNC)-N-Lambda-C-Lambda)Pt(II)CO](+) complex in a model water-gas shift (WGS) reaction.

First author: Buades, B, Dispersive soft x-ray absorption fine- structure spectroscopy in graphite with an attosecond pulse, OPTICA, 5, 502, (2018)
Abstract: Phase transitions of solids and structural transformations of molecules are canonical examples of important photoinduced processes whose underlying mechanisms largely elude our comprehension due to our inability to correlate electronic excitation with atomic position in real time. Here, we present a decisive step towards such new methodology based on water-window covering (284-543 eV) attosecond soft x-ray pulses that can simultaneously access electronic and lattice parameters via dispersive x-ray absorption fine-structure (XAFS) spectroscopy. We validate this approach with an identification of the sigma* and pi* orbital contributions to the density of states in graphite simultaneously with its lattice’s four characteristic bonding distances. This work demonstrates the potential of dispersive XAFS, in combination with attosecond pulses, as a powerful investigative tool that is equally applicable to gas, liquid, and condensed phase.

First author: Li, ZZ, B(4)Rg&ITn&IT2+ (Rg = He similar to Rn, &ITn&IT=1-4): In quest of the potential trapping ability of the aromatic B-4(2+) ring, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 118, 502, (2018)
Abstract: A new series of divalent boron-rare gas cations B(4)Rg(n)(2+)(Rg = He similar to Rn, n = 1-4) have been predicted theoretically at the B3LYP, MP2, and CCSD(T) levels to present the structures, stability, charge distributions, bond natures, and aromaticity. The Rg-B bond energies are quite large for heavy rare gases and increase with the size of the Rg atom. Because of steric hindrance new Rg atoms introduced to the B-4 ring will weaken the Rg-B bond. Thus in B4Rn2+ the Rg-B bond has the largest binding energy 90-100 kcal/mol. p-B(4)Rg(2)(2+) has a slightly shorter Rg-B bond length and a larger bond energy than o-B(4)Rg(2)(2+). NBO and AIM analyses indicate that for the heavy Rg atoms Ar similar to Rn the B-Rg bonds have character of typical covalent bonds. The energy decomposition analysis shows that the sigma-donation from rare gases to the boron ring is the major contribution to the Rg-B bonding. Adaptive natural density partitioning and nuclear-independent chemical shift analyses suggest that both B(4)(2+)and B(4)Rg(n)(2+) have obvious aromaticity.

First author: Unsleber, JP, SERENITY: A Subsystem Quantum Chemistry Program, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 788, (2018)
Abstract: We present the new quantum chemistry program SERENITY. It implements a wide variety of functionalities with a focus on subsystem methodology. The modular code structure in combination with publicly available external tools and particular design concepts ensures extensibility and robustness with a focus on the needs of a subsystem program. Several important features of the program are exemplified with sample calculations with subsystem density-functional theory, potential reconstruction techniques, a projection-based embedding approach and combinations thereof with geometry optimization, semi-numerical frequency calculations and linear-response time-dependent density-functional theory.

First author: Pan, S, Planar pentacoordinate carbon in CGa5+ derivatives, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 12350, (2018)
Abstract: We report a family of systems having a planar pentacoordinate carbon (ppC) based on the next heavier analogue of CAl5+, the ppC system par excellence. Although because of the larger size of Ga, the ppC isomer is not even a local minimum in CGa5+, a single isoelectronic substitution of Ga by smaller sized Be maximizes the bonding in the ppC form. Retaining the 18 valence electron rule, the global minimum structures of CGa4Be, CGa3Be2-, CGa2Be32-, and CGaBe43- clusters and their corresponding lithium salts have a ppC.

First author: Kong, XH, Insight into the Extraction Mechanism of Americium(III) over Europium(III) with Pyridylpyrazole: A Relativistic Quantum Chemistry Study, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 4499, (2018)
Abstract: Separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) is one of the most important steps in spent nuclear fuel reprocessing. However, it is very difficult and challenging to separate them due to their similar chemical properties. Recently the pyridylpyrazole ligand (PypzH) has been identified to show good separation ability toward Am(III) over Eu(III). In this work, to explore the Am(III)/Eu(III) separation mechanism of PypzH at the molecular level, the geometrical structures, bonding nature, and thermodynamic behaviors of the Am(III) and Eu(III) complexes with PypzH ligands modified by alkyl chains (Cn-PypzH, n = 2, 4, 8) have been systematically investigated using scalar relativistic density functional theory (DFT). According to the NBO (natural bonding orbital) and QTAIM (quantum theory of atoms in molecules) analyses, the M-N bonds exhibit a certain degree of covalent character, and more covalency appears in Am-N bonds compared to Eu-N bonds. Thermodynamic analyses suggest that the 1:1 extraction reaction, [M(NO3)(H2O)(6)](2+) + PypzH + 2NO(3)(-) -> M(PypzH)(NO3)(3)(H2O) + 5H(2)O, is the most suitable for Am(III)/Eu(III) separation. Furthermore, the extraction ability and the Am(III)/Eu(III) selectivity of the ligand PypzH is indeed enhanced by adding alkyl-substituted chains in agreement with experimental observations. Besides this, the nitrogen atom of pyrazole ring plays a more significant role in the extraction reactions related to Am(III)/Eu(III) separation compared to that of pyridine ring. This work could identify the mechanism of the Am(III)/Eu(III) selectivity of the ligand PypzH and provide valuable theoretical information for achieving an efficient Am(III)/Eu(III) separation process for spent nuclear fuel reprocessing.

First author: Kikuchi, M, Reactivity of a (Benzene)Ruthenium(II) Cation on a Di-lacunary -Keggin-Type Silicotungstate and Synthesis of a Mono-(Benzene)Ruthenium(II)-Attached -Keggin-Type Silicotungstate, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 122, 1778, (2018)
Abstract: Reaction of a (benzene)Ru2+ complex, [Ru(C6H6)Cl-2](2), with a di-lacunary -Keggin-type silicodecatungstate, K-8[-SiW10O36], at a (C6H6)Ru2+/[-SiW10O36](8-) ratio of 1 produces [-SiW10O36Ru(C6H6)](6-). The cesium salt was characterized using experimental and theoretical methods; one (C6H6)Ru2+ moiety is attached through three bridging oxygen atoms of the non-lacunary site, and the anion is stable in aqueous solution. H-1 NMR spectroscopy and high-resolution electrospray ionization mass spectrometry measurements of the reaction mixture with different (C6H6)Ru2+/[-SiW10O36](8-) ratios indicate that the (C6H6)Ru2+ complex first reacts with the three bridging oxygen atoms to form [-SiW10O36Ru(C6H6)](6-), and then react on the terminal oxygen atoms of the lacunary site to form a [-SiW10O36Ru(C6H6)](6-) complex, which was reported by the Kortz and Nadjo group.

First author: Kelley, MP, Bond Covalency and Oxidation State of Actinide Ions Complexed with Therapeutic Chelating Agent 3,4,3-LI(1,2-HOPO), INORGANIC CHEMISTRY, 57, 5352, (2018)
Abstract: The hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) is a promising agent for biological decorporation of radionuclides, and allows spectroscopic detection of many lanthanide (Ln) and actinide (An) species via sensitized luminescence. Despite the manifest uses of this ligand, the structural and thermodynamic properties of its complexes across the An series remain understudied. Theoretical investigations of the binding of An(III) and An(IV) ions, from actinium to einsteinium, by the 3,4,3-LI(1,2-HOPO) ligand, as well as experimental extended X-ray absorption fine structure (EXAFS) studies on the trivalent americium, curium, and californium complexes were employed to address the resulting structures, thermodynamic parameters, redox properties, and corresponding electronic configurations. An(IV) ions were found to form much stronger complexes than An(III) ions, consistent with experimental measurements. Complexation of both An(III) and An(IV) ions generally becomes more favorable for heavier actinides, reflecting increased energy degeneracy driven covalency and concomitant orbital mixing between the Sf orbitals of the An ions and the Ir orbitals of the ligand. Notably, the ability of this ligand to either accept or donate electron density as needed from its pyridine rings is found to be key to its extraordinary stability across the actinide series.

First author: Allan, M, Dissociative electron attachment and electronic excitation in Fe(CO)(5), PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 11692, (2018)
Abstract: In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)(5). Both are relevant for electron-induced degradation of Fe(CO)(5). The strongest DEA channel is cleavage of one metal-ligand bond that leads to production of Fe(CO)(4)(-). High-resolution spectra of Fe(CO)(4)(-) reveal fine structures at the onset of vibrational excitation channels. Effective range R-matrix theory successfully reproduces these structures as well as the dramatic rise of the cross section at very low energies and reveals that virtual state scattering dominates low-energy DEA in Fe(CO)(5) and that intramolecular vibrational redistribution (IVR) Ways an essential role. The virtual state hypothesis receives further experimental support from the rapid rise of the elastic cross section at very low energies and intense threshold peaks in vibrational excitation cross sections. The IVR hypothesis is confirmed by our measurements of kinetic energy distributions of the fragment ions, which are narrow (similar to 0.06 eV) and peak at low energies (similar to 0.025 eV), indicating substantial vibrational excitation in the Fe(CO)4(-) fragment. Rapid IVR is also revealed by the yield of thermal electrons, observed in two-dimensional (2D) electron energy loss spectroscopy. We further measured mass-resolved DEA spectra at higher energies, up to 12 eV, and compared the bands observed there to resonances revealed by the spectra of vibrational excitation cross sections. Dipole-allowed and dipole/spin forbidden electronic transitions in Fe(CO)(5)-relevant for neutral dissociation by electron impact-are probed using electron energy loss spectroscopy and time-dependent density functional theory calculations. Very good agreement between theory and experiment is obtained, permitting assignment of the observed bands.

First author: Yang, T, Dative versus electron-sharing bonding in N-oxides and phosphane oxides R3EO and relative energies of the R2EOR isomers (E = N, P; R = H, F, Cl, Me, Ph). A theoretical study, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 11856, (2018)
Abstract: Quantum chemical calculations using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory using BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules. The calculated energies suggest that the N-oxides R3NO with R = F, Cl are lower in energy than the amine isomers R2NOR, but the latter form is more stable than the N-oxides when R = H, Me, Ph. In contrast, the phosphane oxides R3PO are always more stable than the phosphanyl isomers R2NOR except for the parent system with R = H, where the two isomers are close in energy. The energy decomposition analysis suggests that the best description of the N-O bond in N-oxides R3NO depends on the nature of the substituent R. The halogen systems F3NO and CI3NO and the triphenyl species Ph3NO possess dative bonds R3N -> O, which are enhanced by R3N <- O pi backdonation. The contribution of the pi backdonation is only 10% of the total orbital interactions Delta E-orb in Ph3NO, but it amounts to similar to 22% of Delta E-orb in F3NO and CI3NO. The N-O bonds H3NO and Me3NO are better described in terms of electron-sharing single bonds between charged fragments R3N+-O, which are supported by modest R3N+<- O- pi backdonation that comprise 13-16% of Delta E-orb. In contrast, all phosphane oxides R3PO are best depicted with electron-sharing single bonds between charged fragments R3P+-O-, which are significantly supported by R3P+<- O- pi backdonation contributing 22-32% of Delta E-orb.

First author: Peuravaara, P, Chemical shift extremum of Xe-129(aq) reveals details of hydrophobic solvation, SCIENTIFIC REPORTS, 8, 11856, (2018)
Abstract: The Xe-129 chemical shift in an aqueous solution exhibits a non-monotonic temperature dependence, featuring a maximum at 311 K. This is in contrast to most liquids, where the monotonic decrease of the shift follows that of liquid density. In particular, the shift maximum in water occurs at a higher temperature than that of the maximum density. We replicate this behaviour qualitatively via a molecular dynamics simulation and computing the Xe-129 chemical shift for snapshots of the simulation trajectory. We also construct a semianalytical model, in which the Xe atom occupies a cavity constituted by a spherical water shell, consisting of an even distribution of solvent molecules. The temperature dependence of the shift is seen to result from a product of the decreasing local water density and an increasing term corresponding to the energetics of the Xe-H2O collisions. The latter moves the chemical shift maximum up in temperature, as compared to the density maximum. In water, the computed temperature of the shift maximum is found to be sensitive to both the details of the binary chemical shift function and the coordination number. This work suggests that, material parameters allowing, the maximum should be exhibited by other liquids, too.

First author: Charistos, ND, Induced Magnetic Field of Fullerenes: Role of sigma- and pi- Contributions to Spherical Aromatic, Nonaromatic, and Antiaromatic Character in C-60(q)(q =+10, 0,-6,-12), and Related Alkali-Metal Decorated Building Blocks, Li12C60 and Na6C60, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 9688, (2018)
Abstract: The induced magnetic field of fullerenes is strongly dependent on the charge state, where C-60 is depicted as a nonaromatic species, in contrast to C-60(10+) which exhibits a strong spherical aromatic character. Here, we account for the response of relevant charged stable building blocks for novel extended networks with variable applications, as observed in A(12)C(60) and A(6)C(60) phases (A = alkali metal), given by, Li12C60 and Na6C60, as well as four different charge states of C-60(q)(q = +10, 0, -6, -12), to an external magnetic field is studied in detail, focusing on the contributions from the pi and sigma systems to the induced magnetic field. C-60, C-60(6-), and C-60(12-) accounts for the variation of their isolated species upon addition of charge, whereas C-60(10+) is a hypothetical highly aromatic counterpart. Our results show that each spherical shell and each canonical molecular orbital exhibit characteristic patterns, revealing the direct dependence of the magnetic response, and therefore of spherical aromatic character, with regard to electron configuration. In particular, low-lying S, P, D, and F pi-type shells exhibit identical strong and long-range shielding character among the four charge states. The G shell exhibits a weak shielding response, precluding the strong deshielding contribution from high-lying H and I shells. A similar analysis is given for sigma-type orbitals. Thus, the aromatic, nonaromatic, and antiaromatic character of C-60 among the different charge states is ruled by the population of the high-lying pi-shells, which is explained in terms of it pi ->pi* excitations of high-lying canonical molecular orbitals. Hence, in spherical aromatic fullerenes, the formation of a shielding cone is given mainly by the pi-type shells, extending characteristic features from planar aromatics to three-dimensional structures, which is useful for further rationalization and characterization of spherical/nonaromatic and antiaromatic spherical structures.

First author: Xu, L, Design of Open-Shell pi-Conjugated Microporous Polymer Film with Super-High Conductivity, MACROMOLECULAR CHEMISTRY AND PHYSICS, 219, 9688, (2018)
Abstract: Polymers with open-shell pi-conjugated structure and thiophene-based building blocks are designed for electropolymerization. These systems are expected to electropolymerize and form solution-processable conjugated microporous polymer films, which can be used for device fabrications. The designed radical structure has a low highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap, high electronic hopping rate for the hole transfer and electron transfer, and ultimately high conductivity. The eclipsed dimer has higher conductivities than that of staggered dimer. The designed monomer with substituted groups has lower conductivities due to steric effect. The open-shell systems designed will be promising materials with various applications. Design principles for open-shell organic materials can be established based on the trends of this paper.

First author: Grabowski, SJ, Tetrel Bonds with -Electrons Acting as Lewis BasesTheoretical Results and Experimental Evidences, MOLECULES, 23, 9688, (2018)
Abstract: MP2/aug-cc-pVTZ calculations were carried out for the ZFH(3)-B complexes (Z = C, Si, Ge, Sn and Pb; B = C2H2, C2H4, C6H6 and C5H5-; relativistic effects were taken into account for Ge, Sn and Pb elements). These calculations are supported by other approaches; the decomposition of the energy of interaction, Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) method. The results show that tetrel bonds with -electrons as Lewis bases are classified as ZC links between single centers (C is an atom of the -electron system) or as Z interactions where FZ bond is directed to the mid-point (or nearly so) of the CC bond of the Lewis base. The analogous systems with ZC/ interactions were found in the Cambridge Structural Database (CSD). It was found that the strength of interaction increases with the increase of the atomic number of the tetrel element and that for heavier tetrel elements the ZFH(3) tetrahedral structure is more deformed towards the structure with the planar ZH(3) fragment. The results of calculations show that the tetrel bond is sometimes accompanied by the Z-HC hydrogen bond or even sometimes the ZFH(3)-B complexes are linked only by the hydrogen bond interaction.

First author: Loan, HTP, Theoretically predicted divalent silicon(0) compounds: Structures and chemical bonding of silylone in molybdenum pentacarbonyl complexes [Mo(CO)(5)-Si(XCp*)(2)] (X = B-Tl), COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1131, 13, (2018)
Abstract: Quantum chemical calculations of structures and bonding in the transition metal complexes with silylone ligands [Mo(CO)(5)-Si(XCp*)(2)] (Mo5-SiX) (X = B-Tl) are reported at the BP86 level of theory with various basis sets SVP, TZVPP, TZ2P +. The calculated equilibrium structures of complexes show that the silylone ligands Si(XCp*)(2) are bonded in a tilted orientation to the metal fragment Mo(CO)(5) in Mo5-SiX. The bond dissociation energies (BDEs) increase from the weakest bonded boron complex, Mo5-SiB, to the strongest bonded thallium adduct, Mo5-SiTl. The bonding analysis suggests that the trend of the Mo-Si bond strength in complexes comes from the increase of (CO)(5) Mo <- Si(XCp*)(2) donation and the increase of the electrostatic interaction Delta E-elstat.

First author: Tsipis, AC, Interaction of Elemental Mercury with a Diverse Series of pi-Organic Substrates Probed by Computational Methods: Is Mercury Fixation Possible?, ACS EARTH AND SPACE CHEMISTRY, 2, 451, (2018)
Abstract: A multitude of electronic structure computational methods has been employed to study the intermolecular adducts formed upon the interaction of elemental mercury, Hg-0, with benzene and substituted benzenes of the general formula [Hg(eta(6)-1,3,5-C3H3R3)], where R is either an electron donor substituent, such as -NH2, -OH, -SH, -NH(COCH3), -C CH, -S(CH3), -C=CH2, -CH3, -N(CH3)(3), and -O(CH3)(3) or an electron acceptor substituent, such as -COOH, -NO2,-CHO, -CO(CH3), -CN, -SO2H, -SO2H, -CF3, -C(CO)(NH2), -Cl, -F, and -C(CO)Cl. In addition, a set of neutral and negatively charged octupolar molecules, with alternating electron donor and electron acceptor groups in the 1,3,5 and 2,4,6 positions of the benzene ring, have been included in this study. The estimated interaction energies of He with these systems range from -2.6 to -13.7 kcal/mol. The interplay of electrostatic, dispersion forces and covalent interaction components constitute the Hg-0 center dot center dot center dot pi-organic substrate interactions. In the [Hg(eta(6)-1,3,5-C3H3R3)] adducts with electron donor R substituents, the electrostatic forces dominate over the dispersion forces, while the opposite is true for the [Hg(eta(6)-1,3,5-C3H3R3)] adducts with electron acceptor R substituents. In both cases, the covalent component of the interactions is estimated to be marginal. In the interactions of Hg-0 with octupolar systems, the electrostatic and dispersion forces are dominant, with the exception of the negatively charged systems, where covalent interactions overwhelm dispersion forces and, along with electrostatic interactions, are the dominant forces. The calculated interaction energies of Hg(0)with the pi-organic substrates are correlated with the eigenvalues of the highest occupied molecular orbital (HOMO) (epsilon(HOMO)) and lowest unoccupied molecular orbital (LUMO) (epsilon(LUMO)) of the substrates as well as their chemical potential (mu). Noteworthy, the orbital interaction components are modulated by epsilon(HOMO)and epsilon(LUMO), while the electrostatic interaction components are modulated by mu. The dispersion force component of the interactions correlates well with the polarizability tensor element in thezaxis, alpha(zz). The computations revealed that mercury fixation by pi-organic substrates is possible, thus helping to design pi-organic linkers in novel MOF sorbents with fast, most efficient, and even reversible Hg(0)fixation.

First author: Senthilnathan, D, Are cucurbiturils better drug carriers for bent metallocenes? Insights from theory, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, 23, 413, (2018)
Abstract: Bent metallocenes (BM) have anti-tumor properties but they face a serious drug efficacy problem due to poor aqueous solubility and rapid hydrolysis under physiological conditions. These two problems can be fixed by encapsulating them in host molecules such as cyclodextrin (CD), cucurbituril (CB) etc. Experimentally, CD-BM, CB-BM host-guest complexes have been investigated to check the efficiency of the drug delivery and efficiency of the encapsulated drug. CB has been reported to be a better host than CD but the reasons for this has not been figured out. This can be done by finding out the mechanism of binding and the nature of the binding forces in both the inclusion complexes. This is exactly done here by performing a DFT study at BP86/TZP level on CB-BM host-guest systems. For comparison CD-BM with beta-cyclodextrin as host have been studied. Four BMs (Cp2MCl2, M=Ti, V, Nb, Mo) and their corresponding cations (Cp2MCl+, Cp2M2+) are chosen as guests and they are encapsulated into cucurbit-[6]-uril (CB[6]) and cucurbit-[7]-uril(CB[7]) host systems. Computations reveal that CB[7] accommodates well the BMs over CB[6] due to their larger cavity size and also CB[7] is found to be a better host than beta-cyclodextrin. BMs enter vertically rather than horizontally into the CB cavity. The reversible binding of BMs within CB[7] is controlled by various non-bonding interactions and mainly by hydrogen bonding between the portal oxygen atoms and Cp protons as revealed by QTAIM analysis. On the other hand, the interaction between the wall nitrogen atoms in CB[7] and chlorine atoms attached to the metal in BM strengthens the M-Cl bonds that prevents rapid hydrolysis of M-Cl and M-Cp bonds saving the drug. Comparatively, BMs experience less electrostatic attraction and more Pauli repulsion within beta-cyclodextrin cavity and this affects the drug binding with CD. This makes beta-cyclodextrin a less suitable drug carrier for BMs than CBs. Among the four BMs, niobocene binds strongly and titanocene binds weakly with CBs. EDA clearly shows that all the interactions between the guest and host are non-covalent in nature and electrostatic interactions outperform high-repulsion resulting in stable complexes. Cations form stronger complexes than neutral BMs. FMO analysis reveals that neutral BMs are less reactive compared to their cations and complexes are more reactive in CB[6] environment due to excess strain. QTAIM analysis helps to bring out the newer insights in these types of host-guest systems.

First author: Cowie, BE, M-H-BR3 and M-Br-BR3 interactions in rhodium and nickel complexes of an ambiphilic phosphine-thioether-borane ligand, CANADIAN JOURNAL OF CHEMISTRY, 96, 484, (2018)
Abstract: Reaction of [Rh(mu-Cl)(CO)(TXPB)] (1; TXPB = 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene) with NaBH4 yielded square planar [Rh(mu-H)(CO)(TXPB)] (2) in which the hydride ligand bridges between rhodium and the borane unit of TXPB. The Rh-H, Rh-B, and Rh-C-ipso distances are short at 1.84(5), 2.456(6), and 2.568(5) angstrom, respectively, whereas the B-H bond, 1.59(6) angstrom, falls at the longer end of the usual range. Compound 2 is compared with the previously reported series of rhodium TXPB complexes: [RhX(CO)(TXPB)] {X = F (3), Cl (1), Br (4), I (5)}. Compound 4 in this series features the only crystallographically characterized example of an M-Br-BR3 interaction, and to expand this area, [NiBr(mu-Br)(TXPB)] (6) was prepared via the reaction of [NiBr2(dme)(2)] (dme = 1,2-dimethoxyethane) with TXPB. An X-ray crystal structure of light purple 6 revealed a square-planar geometry with a strong B-Br interaction {B-Br = 2.311(6) angstrom; Sigma(C-B-C) = 344.5(7)degrees}. An B-11 NMR chemical shift of 23 ppm was observed for 6, indicating that an appreciable B-Br interaction is maintained in solution. No signals were observed in the P-31{H-1} NMR spectrum at room temperature, whereas a broadened 31P signal was observed at -20 degrees C, evolving into a sharp singlet at -67 degrees C. This behaviour suggests that at room temperature, square planar 6 exists in equilibrium with a paramagnetic tetrahedral isomer, present at a level below that detectable through Evans magnetic measurements.

First author: Ouilia, S, Synthesis, crystal structure, magnetic properties and DFT calculations of new dihydroxo-bridged binuclear chromium(III) based on monodentate mixed ligand, INORGANICA CHIMICA ACTA, 476, 54, (2018)
Abstract: A new dihydroxo-bridged binuclear chromium(III) complex [Cr(mu-OH)(Py)(2)(N-3)(2)](2)center dot Py has been synthesized and characterized by elemental analyses, infrared spectroscopy, single crystal X-ray diffraction and magnetic measurements. This metal complex crystallizes in the monoclinic space group P2(1)/c with two binuclear formula units in the crystal cell dimensions a = 10.114(5) angstrom, b = 10.416(5) angstrom, c = 17.341 (5) angstrom and beta = 105.248(5)degrees. The Cr center dot center dot center dot Cr separation is 3.042 (2) angstrom and the bridging Cr-O-Cr angle is 101.83(3)degrees. In addition, moderate O-H center dot center dot center dot N hydrogen bond and weak C-H center dot center dot center dot N and pi-pi stacking interactions, link the components of the structure into a three-dimensional network. The magnetic susceptibility of a powdered sample has been examined in the temperature range 1.8-300 K. The dinuclear complex exhibits an antiferromagnetic exchange interactions between the metal centers, with the best fit to the Van Vleck equation including biquadratic exchange yielding J = -6.762(9) cm(-1) and (g) = 1.9938(2). DFT geometry optimizations using the two B3LYP and PBE0 hybrid functionals were carried out (spin-orbit coupling omitted) on dichromium [Cr-III(mu-OH)(2)Cr-III] complex 1 in high spin (HS) septet ground state with valence electronic 3d(3 alpha)center dot center dot center dot 3d(3 alpha) configuration. The broken symmetry (BS) 3d(3 alpha)center dot center dot center dot 3d(3 beta) state was predicted slightly lower in energy than the HS one, suggesting an occurrence of weak antiferromagnetic coupling between the two Cr(III) metal spin carriers. The computed super-exchange constant J equals to -5.19 cm(-1), in keeping with the experimental value. The DFT/B3LYP/BS results show that the spin density is mostly localized on the two Cr(III) metal centers. The DFT results reveal that the weak exchange coupling exhibited by the complex is due to the small spin density along the dihydroxo-bridged path [Cr-III(mu-OH)(2)Cr-III] linking the two metal spin carriers.

First author: Cui, JY, Effects of thiophene substituents on hole-transporting properties of dipolar chromophores for perovskite solar cells, JOURNAL OF MATERIALS SCIENCE, 53, 6626, (2018)
Abstract: We present a theoretical investigation of thiophene substituent effects on the electrochemical properties of dipolar chromophores (TCNE, TCNE22 and TCNE24) as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). Herein, the material properties in crystalline phases are explored by using the first-principle calculations combined with Marcus theory. The results show that the increased number of thiophene substituents for TCNE, TCNE22 and TCNE24 results in a redshift of the absorption spectrum (27-46 nm). Furthermore, both TCNE22 and TCNE24 have maximum absorption peaks at a wavelength of 400 nm. Most importantly, the molecular planarity is improved effectively, which generates strong intermolecular face-to-face pi-pi packing interaction. The higher hole mobility of TCNE24 (2.069 x 10(-1) cm(2) V-1 s(-1)) with four thiophene substituents is obtained due to the face-to-face pi-pi packing. The new designed TCNE24 not only has excellent spectral property, but also has strong hole mobility. Therefore, TCNE24 is a promising organic small-molecule HTMs. Our work provides theoretical guidance for designing higher-performance HTMs in PSCs.

First author: Viesser, RV, The halogen effect on the C-13 NMR chemical shift in substituted benzenes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 11247, (2018)
Abstract: Recent research [Chem. Sci., 2017, 8, 6570-6576] showed for R-substituted benzenes with R = NH2, NO2 that the substitution effects on the C-13 NMR chemical shifts are correlated with changes in the sigma-bonding framework and do not follow directly the electron-donating or -withdrawing effects on the pi orbitals. In the present work we extend the study to halogen ( X = F, Cl, Br or I) substituted R-benzenes. The effect of X and R groups on C-13 NMR chemical shifts in X-R-benzenes are investigated by density functional calculations and localized molecular orbital analyses. Deshielding effects caused by the X atom on the directly bonded carbon nucleus are observed for F and Cl derivatives due to a paramagnetic coupling between occupied p orbitals and unoccupied sigma*(C-X) antibonding orbitals. The SO coupling plays an important role in the carbon magnetic shielding of Br and I derivatives, as is well known, and the nature of X also modulates the C-13 paramagnetic shielding contributions. Overall, the X and R substituent effects are approximately additive.

First author: Day, PN, Theoretical Analysis of Optical Absorption and Emission in Mixed Noble Metal Nanoclusters, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 4058, (2018)
Abstract: In this work, we studied theoretically two hybrid gold silver clusters, which were reported to have dual-band emission, using density functional theory (DFT) and linear and quadratic response time-dependent DFT (TDDFT). Hybrid functionals were found to successfully predict absorption and emission, although explanation of the NIR emission from the larger cluster (cluster 1) requires significant vibrational excitation in the final state. For the smaller cluster (cluster 2), the Delta H(0-0) value calculated for the T1 -> S0 transition, using the PBE0 functional, is in good agreement with the measured NIR emission, and the calculated T2 -> S0 value is in fair agreement with the measured visible emission. The calculated T1 -> S0 phosphorescence Delta H(0-0) for cluster 1 is close to the measured visible emission energy. In order for the calculated phosphorescence for cluster 1 to agree with the intense NIR emission reported experimentally, the vibrational energy of the final state (S0) is required to be about 0.7 eV greater than the zero-point vibrational energy.

First author: Liu, JC, Heterogeneous Fe-3 single-cluster catalyst for ammonia synthesis via an associative mechanism, NATURE COMMUNICATIONS, 9, 4058, (2018)
Abstract: The current industrial ammonia synthesis relies on Haber-Bosch process that is initiated by the dissociative mechanism, in which the adsorbed N-2 dissociates directly, and thus is limited by Bronsted-Evans-Polanyi (BEP) relation. Here we propose a new strategy that an anchored Fe-3 cluster on the theta-Al2O3(010) surface as a heterogeneous catalyst for ammonia synthesis from first-principles theoretical study and microkinetic analysis. We have studied the whole catalytic mechanism for conversion of N-2 to NH3 on Fe-3/theta-Al2O3(010), and find that an associative mechanism, in which the adsorbed N-2 is first hydrogenated to NNH, dominates over the dissociative mechanism, which we attribute to the large spin polarization, low oxidation state of iron, and multi-step redox capability of Fe-3 cluster. The associative mechanism liberates the turnover frequency (TOF) for ammonia production from the limitation due to the BEP relation, and the calculated TOF on Fe-3/theta-Al2O3(010) is comparable to Ru B5 site.

First author: Zhang, HZ, Electronic structure and luminescence properties of unique complexes: cyclometalated iridium(III) chelated by o-carboranyl-pyridine ligands, NEW JOURNAL OF CHEMISTRY, 42, 5955, (2018)
Abstract: Carboranes are showing promise as phosphorescent materials because of their excellent properties. Until now, very few investigations have been focused on the use of o-carborane itself as a chelating unit. In order to effectively enhance the phosphorescence quantum efficiency of complexes supported by the chelating ligand o-carborane, this work focuses on a series of complexes bearing cyclometalating ligands with pi-conjugation in different positions and of different degrees to explore the properties of the molecules. Density functional theory and time-dependent density functional theory were used to calculate the electronic configurations, emission wavelengths, and the radiative and nonradiative decay processes. The calculated results confirm that the emission peaks of complexes 2 and 3a have a larger blue shift compared with that of complex 1. The introduction of p-conjugation in the cyclometalating ligands gives rise to an increase in the radiative rate constants for the designed complexes 2 and 3. Complex 5 has better structural rigidity, and more difficult to achieve thermally activated nonradiative photodeactivation processes, which is expected to be a better phosphorescent material with a higher phosphorescence quantum efficiency. So far, there has been no theoretical study that systematically focuses on cyclometalating iridium(III) complexes with o-carborane as a chelating ligand. Our research suggests new ideal candidates for the further synthesis of effective blue phosphorescent Ir(III) complexes which are supported by the chelating ligand o-carborane.

First author: Zuo, YN, Mechanism and Origins of Stereoinduction in an Asymmetric Friedel-Crafts Alkylation Reaction of Chalcone Catalyzed by Chiral N,N’-Dioxide-Sc(III) Complex, JOURNAL OF ORGANIC CHEMISTRY, 83, 4628, (2018)
Abstract: The mechanism and selectivity of the asymmetric Friedel Crafts (F-C) alkylation reaction between indole and chalcone catalyzed by chiral N,N’-dioxide -Sc(III) complexes were investigated at the M06/6-311+G(d,p)//M06/ [LANL2DZ,6-31G(d)](SMD,CH2Cl2) level. The reaction occurred via a three step mechanism: (i) the C-3-C-beta bond formation by interacting the most mucleophilic C-3 center of indole with the most electrophilic C-beta center of chalcone; (ii) the abstraction of the proton at the C-3 atom of indole by counterion OTf-; (iii) proton transfer from HOTf to the C-alpha atom of chalcone, generating the F-C alkylation product. The reaction preferred to occur along the favorable reface attack pathway, producing the dominant R-product. The turnover frequency (TOF) of catalysis was predicted to be 1.59 X 10(-7) s(-1), with a rate constant of K(T) = 1.58 X 10(-7) exp(-29057/RT) dm(6).mol(-2).s(-1) over the temperature range of 248-368 K. Activation strain model (ASM) and energy decomposition analysis (EDA), as well as noncovalent interaction (NCI) analysis, for the stereo controlling transition state revealed that the substituent attached to the N atom of the amide subunits as well as the amino acid backbone of ligand played important roles in chiral inductivity. The benzyl group with structural flexibility tended to form strong pi-pi stacking with substrate as well as the terminal phenyl group of chalcone, stabilizing re-face attack transition state.

First author: Fugel, M, A Variety of Bond Analysis Methods, One Answer? An Investigation of the Element-Oxygen Bond of Hydroxides HnXOH, CHEMISTRY-A EUROPEAN JOURNAL, 24, 6248, (2018)
Abstract: There is a great variety of bond analysis tools that aim to extract information on the bonding situation from the molecular wavefunction. Because none of these can fully describe bonding in all of its complexity, it is necessary to regard a balanced selection of complementary analysis methods to obtain a reliable chemical conclusion. This is, however, not a feasible approach in most studies because it is a time-consuming procedure. Therefore, we provide the first comprehensive comparison of modern bonding analysis methods to reveal their informative value. The element-oxygen bond of neutral HnXOH model compounds (X=Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl) is investigated with a selection of different bond analysis tools, which may be assigned into three different categories: i)real space bonding indicators (quantum theory of atoms in molecules (QTAIM), the electron localizability indicator (ELI-D), and the Raub-Jansen index), ii)orbital-based descriptors (natural bond orbitals (NBO), natural resonance theory (NRT), and valence bond (VB) calculations), and iii)energy analysis methods (energy decomposition analysis (EDA) and the Q-analysis). Besides gaining a deep insight into the nature of the element-oxygen bond across the periodic table, this systematic investigation allows us to get an impression on how well these tools complement each other. Ionic, highly polarized, polarized covalent, and charge-shift bonds are discerned from each other.

First author: Hamlin, TA, Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects, CHEMISTRY-A EUROPEAN JOURNAL, 24, 5927, (2018)
Abstract: We have quantum chemically studied the effect of various polar and apolar solvents on the shape of the potential energy surface (PES) of a diverse collection of archetypal nucleophilic substitution reactions at carbon, silicon, phosphorus, and arsenic by using density functional theory at the OLYP/TZ2P level. In the gas phase, all our model S(N)2 reactions have single-well PESs, except for the nucleophilic substitution reaction at carbon (S(N)2@C), which has a double-well energy profile. The presence of the solvent can have a significant effect on the shape of the PES and, thus, on the nature of the S(N)2 process. Solvation energies, charges on the nucleophile or leaving group, and structural features are compared for the various S(N)2 reactions in a spectrum of solvents. We demonstrate how solvation can change the shape of the PES, depending not only on the polarity of the solvent, but also on how the charge is distributed over the interacting molecular moieties during different stages of the reaction. In the case of a nucleophilic substitution at three-coordinate phosphorus, the reaction can be made to proceed through a single-well [no transition state (TS)], bimodal barrier (two TSs), and then through a unimodal transition state (one TS) simply by increasing the polarity of the solvent.

First author: Aldegunde, J, Hyperfine structure of (2)Sigma molecules containing alkaline-earth-metal atoms, PHYSICAL REVIEW A, 97, 5927, (2018)
Abstract: Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

First author: Mahmoudi, G, Quasi-aromatic Mobius Metal Chelates, INORGANIC CHEMISTRY, 57, 4395, (2018)
Abstract: We report the design as well as structural and spectroscopic characterizations of two new coordination compounds obtained from Cd(NO3)(2)-4H(2)O and polydentate ligands, benzilbis(pyridin-2-yl)methylidenehydrazone (L-I) and benzilbis(acetylpyridin-2-yl)methylidenehydrazone (L-II), in a mixture with two equivalents of NH4NCS in MeOH, namely [Cd(SCN)(NCS)(L-1)(MeOH)] (1) and [Cd(NCS)(2)(L-II)- (MeOH)] (2). Both L-I and L-II are bound via two pyridylimine units yielding a tetradentate coordination mode giving rise to the 12 pi electron chelate ring. It has been determined for the first time (qualitatively and quantitatively), using the EDDB electron population-based method, the HOMA index, and the ETS-NOCV charge and energy decomposition scheme, that the chelate ring containing Cd-II can be classified as a quasi-aromatic Mobius motif. Notably, using the methyl-containing ligand L-II controls the exclusive presence of the NCS- connected with the Cd-II atom (structure 2), while applying L-I allows us to simultaneously coordinate NCS- and SCN- ligands (structure 1). Both systems are stabilized mostly by hydrogen bonding, C-H center dot center dot center dot pi interactions, aromatic pi center dot center dot center dot pi stacking, and dihydrogen C-H center dot center dot center dot H-C bonds. The optical properties have been investigated by diffused reflectance spectroscopy as well as molecular and periodic DFT/TD-DFT calculations. The DFT-based ETS-NOCV analysis as well as periodic calculations led us to conclude that the monomers which constitute the obtained chelates are extremely strongly bonded to each other, and the calculated interaction energies are found to be in the regime of strong covalent connections. Intramolecular van der Waals dispersion forces, due to the large size of L-I and L-II, appeared to significantly stabilize these systems as well as amplify the aromaticity phenomenon.

First author: Ai, J, Porous Anionic Uranyl-Organic Networks for Highly Efficient Cs+ Adsorption and Investigation of the Mechanism, INORGANIC CHEMISTRY, 57, 4419, (2018)
Abstract: Exploitation of new materials for the removal of long-lived and highly radioactive actinides and their fission products produced in the nuclear fuel cycle is crucial for radionuclide management. Here, two rare porous anionic uranyl-organic frameworks (UOFs) have been successfully synthesized by a judicious combination of the tetratopic carboxylate ligand 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H(4)TBAPy) and D-3h-symmetrical triangular [UO2(COO)(3)](-). The resulting two compounds exhibit different architectures, albeit with similar coordination modes. Of interest is that they have excellent adsorption performance on Cs+ from aqueous solution. The high removal efficency would make them promising in applications of radioactive waste management. Notably, the framework of compound 2, [(CH3)(2)NH2]4[(UO2)4(TBAPy)3].22DMF.37H(2)O is sufficiently robust to allow the accessibility of intriguing single crystals of a Cs+-adsorbed derivative, which helps to elucidate the adsorption mechanism. The structural, bonding, and spectroscopic properties of the above compounds are examined using relativistic density functional theory (DFT). It is found that the adsorption toward cesium on UOFs is energetically favored, which features largely ionic bonds and is dominated by electrostatic attraction.

First author: Chakraborty, D, Reactions involving some gas molecules through sequestration on Al12Be cluster: An electron density based study, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 535, (2018)
Abstract: The viability of sequestering gas molecules (CO, NO, CO2, NO2, N2O, O-2, O-3, H2O, NH3, H-2, CH3OH, CH3F, C2H5F, C2H2, C2H4, HCN, and SO2) on the Al12Be cluster is investigated by carrying out density functional theory based computations. Thermochemical as well as energetic considerations suggest that Al12Be cluster adsorbs the chosen gas molecules in a favorable fashion. The gas molecules attain an activated state on getting adsorbed on the metal cluster as vindicated by Atoms-in-Molecule analysis. The possibility of CO oxidation, dissociative addition of CH3F and C2H5F, NH bond decomposition in NH3, dissociation of NO, and hydrogenation of C2H2 reactions on Al12Be cluster has been investigated. Results indicate that all the reactions take place in a thermodynamically favorable way at 298.15 K and one atmospheric pressure. The first five reactions aforementioned are kinetically favorable also and therefore are amenable to ambient temperature and pressure conditions.

First author: Vengut-Climent, E, Glucose-nucleobase pairs within DNA: impact of hydrophobicity, alternative linking unit and DNA polymerase nucleotide insertion studies, CHEMICAL SCIENCE, 9, 3544, (2018)
Abstract: Recently, we studied glucose-nucleobase pairs, a binding motif found in aminoglycoside-RNA recognition. DNA duplexes with glucose as a nucleobase were able to hybridize and were selective for purines. They were less stable than natural DNA but still fit well on regular B-DNA. These results opened up the possible use of glucose as a non-aromatic DNA base mimic. Here, we have studied the incorporation and thermal stability of glucose with different types of anchoring units and alternative apolar sugarnucleobase pairs. When we explored butanetriol instead of glycerol as a wider anchoring unit, we did not gain duplex thermal stability. This result confirmed the necessity of a more conformationally restricted linker to increase the overall duplex stability. Permethylated glucose-nucleobase pairs showed similar stability to glucoside-nucleobase pairs but no selectivity for a specific nucleobase, possibly due to the absence of hydrogen bonds between them. The three-dimensional structure of the duplex solved by NMR located both, the hydrophobic permethylated glucose and the nucleobase, inside the DNA helix as in the case of glucose-nucleobase pairs. Quantum chemical calculations on glucose-nucleobase pairs indicate that the attachment of the sugar to the DNA skeleton through the OH1 or OH4 positions yields the highest binding energies. Moreover, glucose was very selective for guanine when attached through OH1 or OH4 to the DNA. Finally, we examined DNA polymerase insertion of nucleotides in front of the saccharide unit. KF- polymerase from E. coli inserted A and G opposite glc and 6dglc with low efficiency but notable selectivity. It is even capable of extending the new pair although its efficiency depended on the DNA sequence. In contrast, Bst 2.0, SIII and BIOTAQ T DNA polymerases seem to display a loop-out mechanism possibly due to the flexible glycerol linker used instead of deoxyribose.

First author: Pandey, IK, Intramolecular stabilization of a catalytic [FeFe]-hydrogenase mimic investigated by experiment and theory, DALTON TRANSACTIONS, 47, 4941, (2018)
Abstract: The mono-substituted complex [Fe-2(CO)(5)(-naphthalene-2-thiolate)(2)(P(PhOMe-p)(3))] was prepared taking after the structural principles from both [NiFe] and [FeFe]-hydrogenase enzymes. Crystal structures are reported for this complex and the all carbonyl analogue. The bridging naphthalene thiolates resemble -bridging cysteine amino acids. One of the naphthyl moieties forms – stacking interactions with the terminal bulky phosphine ligand in the crystal structure and in calculations. This interaction stabilizes the reduced and protonated forms during electrocatalytic proton reduction in the presence of acetic acid and hinders the rotation of the phosphine ligand. The intramolecular – stabilization, the electrochemistry and the mechanism of the hydrogen evolution reaction were investigated using computational approaches.

First author: Zhang, WW, Improvement of the ReaxFF Description for Functionalized Hydrocarbon/Water Weak Interactions in the Condensed Phase, JOURNAL OF PHYSICAL CHEMISTRY B, 122, 4083, (2018)
Abstract: The ReaxFF protein reactive force field (protein-2013) has been successfully employed to simulate the biomolecules and membrane fuel cells, but it inaccurately describes the weak interaction of functionalized hydrocarbon/water molecules in condensed phase, especially for the density. In this article, the development of a ReaxFF force field (CHON-2017_weak) on the basis of protein-2013 is presented that improves the weak interaction description for atom pairs of carbon, hydrogen, oxygen, and nitrogen. To examine the quality of the force field, we performed a series of molecular dynamics simulations with model systems. These simulations, describing density trends for pure and mixture compound systems, demonstrate that CHON-2017_weak force field predictions are in good agreement with experimental data. Furthermore, ReaxFF can also describe the phase separation in hexane-water mixture and dissolution of ethanol or tetramethylammonium (TMA) in liquid water. To validate it in the application of membrane fuel cells, we studied structural property and degradation mechanism of TMA in alkaline aqueous solution, as well as some typical chemical reactions for small compounds. On the basis of our results, an additional reaction pathway is proposed for the degradation of TMA, which seems to be more energetically favorable compared to the main mechanism predicted from quantum mechanics calculations.

First author: van Bochove, MA, How Mg2+ ions lower the S(N)2@P barrier in enzymatic triphosphate hydrolysis, CHEMICAL COMMUNICATIONS, 54, 3448, (2018)
Abstract: Our quantum chemical activation strain analyses demonstrate how Mg2+ lowers the barrier of the enzymatic triphosphate hydrolysis through two distinct mechanisms: (a) weakening of the leaving-group bond, thereby decreasing activation strain; and (b) transition state (TS) stabilization through enhanced electrophilicity of the triphosphate PPP substrate, thereby strengthening the interaction with the nucleophile.

First author: Gottle, AJ, Determinant Role of Electrogenerated Reactive Nucleophilic Species on Selectivity during Reduction of CO2 Catalyzed by Metalloporphyrins, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 4826, (2018)
Abstract: This work provides insights to understand the selectivity during the reduction of CO2 with metalloporphyrin (MP) catalysts. The attack of a nucleophile on the carbon of the CO, appears as an important event that triggers the catalytic reaction, and the nature of this nucleophile determines the selectivity between CO (or further reduced species) and HCOOH/HCOO-. For MP, the possible electrogenerated nucleophiles are the reduced metal-center and the hydride donor species, metal-hydride and phlorin-hydride ligand. The reduced metal-center activates the CO2 with the formation of the metal carbon bond, which then gives rise to the formation of CO. The hydride donor species trigger the CO2 reduction by the attack of the hydride on the carbon of the CO2 (formation of a C-H bond), which results in the formation of HCOOH/HCOO- (formation of the metal-bonded formate intermediate is not involved). The MP with the metals Ni, Cu, Zn, Pd, Ag, Cd, Ga, In, and Sn are predicted to only form the phlorin-hydride intermediate and are thus suitable to produce HCOOH/HCOO-. This agrees well with the available experimental results. The MP with the metals Fe, Co, and Rh can form both the reduced-metal center and the hydride donor species (metal-hydride and phlorin-hydride), and thus are able to form both CO and HCOOH/HCOO-. The production of CO for Fe and Co is indeed observed experimentally, but not for Rh, probably due to the presence of axial ligands that may hinder the formation of the metal-bonded intermediates and thus drive the CO2RR to HCOOH/HCOO- via the phlorin intermediate.

First author: Li, Y, Decomposition Properties of C4F7N/N-2 Gas Mixture: An Environmentally Friendly Gas to Replace SF6, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 57, 5173, (2018)
Abstract: The insulation characteristics and decomposition components of C4F7N/N-2 gas mixture, a potential substitute for SF6, were first explored by breakdown experiments/gas chromatography-mass spectrometer. The structural properties of C4F7N molecule and the decomposition mechanism of C4F7N/N-2 gas mixture were analyzed based on the density functional theory calculation and ReaxFF molecular dynamics simulation. We found that C4F7N/N-2 mixture has great self-recovery performance. The decomposition of C4F7N in a discharge mainly produces CF, C2F6, C3F8, CF3CN, C2F4, C3F6, and C2F5CN, among which the relative content of C2F6, CF, and CF3CN is higher. ReaxFF-MD simulations show that CF3, CN, F, and C3F7 are the four main free radicals produced by C4F7N. The decomposition characteristics of N-2 are better than that of C4F7N. The addition of N-2 has a certain buffering effect to avoid the massive decomposition of C4F7N. The global warming potential value of a gas mixture containing 20% C4F7N decreased by 94.32% compared with SF6. Relevant results not only reveal the decomposition characteristics of C4F7N/N-2 mixture in a discharge comprehensively, but also provide a reference for engineering application and emission of a C4F7N/N-2 gas mixture.

First author: Medina-Ramos, J, Cathodic Corrosion at the Bismuth-Ionic Liquid Electrolyte Interface under Conditions for CO2 Reduction, CHEMISTRY OF MATERIALS, 30, 2362, (2018)
Abstract: Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im])(+))-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi2O3 layer. This oxide layer gets reduced to Bi(0)during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM](+)) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between -1.5 and -1.9 V vs Ag/AgCI due to a similar to 4-10% thinning and a similar to 40% decrease in lateral size of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im](+)cations bind to the metal surface more strongly than tetrabutylammonium (TBA(+)) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im](+)cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi center dot center dot center dot[Im](+)complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between -1.65 and -1.95 V. Bi desorption from a flat terrace requires a potential of approximately -2.25 V. Together, these results suggest the formation of a Bi center dot center dot center dot[Im](+)complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO2 .

First author: Karmakar, A, Mechanochemical Synthesis of Methylammonium Lead Mixed-Halide Perovskites: Unraveling the Solid-Solution Behavior Using Solid-State NMR, CHEMISTRY OF MATERIALS, 30, 2309, (2018)
Abstract: Mixed-halide lead perovskite (MHP) materials are rapidly advancing as next-generation high-efficiency perovskite solar cells due to enhanced stability and bandgap tunability. In this work, we demonstrate the ability to readily and stoichiometrically tune the halide composition in methylammonium-based MHPs using a mechanochemical synthesis approach. Using this solvent-free protocol we are able to prepare domain-free MHP solid solutions with randomly distributed halide ions about the Pb center. Up to seven distinct [PbClxBr6-x](4-) environments are identified, based on the Pb-207 NMR chemical shifts, which are also sensitive to the changes in the unit cell dimensions resulting from the substitution of Br by Cl, obeying Vegard’s law. We demonstrate a straightforward and rapid synthetic approach to forming highly tunable stoichiometric MHP solid solutions while avoiding the traditional solution synthesis method by redirecting the thermodynamically driven compositions. Moreover, we illustrate the importance of complementary characterization methods, obtaining atomic-scale structural information from multinuclear, multifield, and multidimensional solid-state magnetic resonance spectroscopy, as well as from quantum chemical calculations and long-range structural details using powder X-ray diffraction. The solvent-free mechanochemical synthesis approach is also compared to traditional solvent synthesis, revealing identical solid-solution behavior; however, the mechanochemical approach offers superior control over the stoichiometry of the final mixed-halide composition, which is essential for device engineering.

First author: Mahmoudi, G, Extended lead(II) architectures engineered via tetrel bonding interactions, NEW JOURNAL OF CHEMISTRY, 42, 4959, (2018)
Abstract: The evaluation of N’-pyridin-2-ylmethylene) nicotinohydrazide (HLI) and N, N'”-bis(1-(pyridin-2-yl)-thylidene)carbazide (H2LII) as linker precursors in the synthesis of novel PbII extended structures is described. An equimolar one-pot reaction of PbX2 (X = NO3-, H3COO-) salts with HLI and H2LII in MeOH at 60 degrees C in a branched tube apparatus leads to heteroleptic complexes [Pb(HLI)(NO3)(2)](n) (1), [Pb(L-I)(CH3O)](n) (2), [Pb-2(H2LII)(NO3)(4)] (3) and [Pb-2(HLII)(CH3COO)(3)](n) (4), respectively. The nature of the anion in the parent PbII salt also influences the final structure. In all complexes, the PbII center exhibits a hemidirected coordination geometry with all the covalent bonds being concentrated on one hemisphere of the coordination sphere. The sterically available PbII ion participates in Pb center dot center dot center dot O/N tetrel bonding or Pb center dot center dot center dot Cg interaction as evidenced from the detailed structural and topological analysis of the described complexes. As a result of these interactions, the structures of all four compounds can be extended to a higher dimensional framework, which is further stabilized by hydrogen N-H center dot center dot center dot O/C-H center dot center dot center dot O and dihydrogen C-H center dot center dot center dot H-C bonds and/or pi center dot center dot center dot pi stacking interactions. The complementary Hirshfeld surface analysis of the discrete complex 3, considering covalent bonds, showed that the structure is highly dominated by H center dot center dot center dot X (X = O, H and C) and O center dot center dot center dot Y (Y = O, Pb, C and N) contacts, of which the O center dot center dot center dot Pb/H/N/C contacts are highly favoured. DFT based charge and energy decomposition (ETS-NOCV) calculations are performed in order to shed light on the nature of the non-covalent interactions that determine the stability of the obtained structures.

First author: Zierkiewicz, W, Implications of monomer deformation for tetrel and pnicogen bonds, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 8832, (2018)
Abstract: A series of TF4 and ZF(5) molecules (T = Si, Ge, Sn and Z = P, As, Sb) were allowed to engage in tetrel and pnicogen bonds, respectively, with NH3, pyrazine, and HCN. The interaction energies are quite large, approaching 50 kcal mol(-1) in some cases. The formation of each complex is accompanied by substantial geometrical deformation of the Lewis acid to accommodate the approaching base. The energy associated with this monomer rearrangement is the largest for the smaller central atoms Si and P, where it exceeds 20 kcal mol(-1). The total reaction energy of binding, which takes this distortion energy into account, is thus significantly lower than the interaction energy, although remaining quite high, particularly for the larger Sn and Sb central atoms. The tetrel and pnicogen bonds can still form even if the Lewis acid is not permitted to adjust its internal geometry, but they are drastically weakened, dropping by as much as 95%. The monomer rearrangement also aids in the binding by intensifying its sigma-hole by a factor of 1.5-2.9.

First author: Arias-Olivares, D, The role of Cr, Mo and W in the electronic delocalization and the metal-ring interaction in metallocene complexes, NEW JOURNAL OF CHEMISTRY, 42, 5334, (2018)
Abstract: Metal influence over triple-decker, sandwich-like and pyramidal structured benzenes was studied by means of Energy Decomposition Analysis (Morokuma-Ziegler), combined with Extended Transition State Natural Orbitals for Chemical Valence, finding that metal-ring bonding was a covalent contribution of about 60% due to the bonding interaction between d(xz) and d(yz), d(x2-y2) and d(xy) orbitals with p(z) orbitals, respectively, adapted by symmetry in the ring, to form pi and delta bonding interactions. Finally, an important amount of electron density between the ring and the metal was found. This has a key role in the electron delocalization in this zone. This electronic delocalization was analysed via Induced Magnetic Field and Nucleus-Independent Chemical Shift calculations, finding a pattern between metal atomic radii and shielding tensor. Furthermore, similar behaviour for Mo and W, in the enhancement of the diatropic magnetic response, was displayed while Cr had a slightly lower diatropic character.

First author: Gaggioli, CA, Spin-Forbidden Reactions: Adiabatic Transition States Using Spin-Orbit Coupled Density Functional Theory, CHEMISTRY-A EUROPEAN JOURNAL, 24, 5006, (2018)
Abstract: A spin-forbidden chemical reaction involves a change in the total electronic spin state from reactants to products. The mechanistic study is challenging because such a reaction does not occur on a single diabatic potential energy surface (PES), but rather on two (or multiple) spin diabatic PESs. One possible approach is to calculate the so-called “minimum energy crossing point” (MECP) between the diabatic PESs, which however is not a stationary point. Inclusion of spin-orbit coupling between spin states (SOC approach) allows the reaction to occur on a single adiabatic PES, in which a transition state (TS SOC) as well as activation free energy can be calculated. This Concept article summarizes a previously published application in which, for the first time, the SOC effects, using spin-orbit ZORA Hamiltonian within density functional theory (DFT) framework, are included and account for the mechanism of a spin-forbidden reaction in gold chemistry. The merits of the MECP and TS SOC approaches and the accuracy of the results are compared, considering both our recent calculations on molecular oxygen addition to gold(I)-hydride complexes and new calculations for the prototype spin-forbidden N2O and N2Se dissociation reactions.

First author: Halilovic, D, Photochemical Synthesis and Electronic Properties of Extended Corannulenes with Variable Fluorination Pattern, JOURNAL OF ORGANIC CHEMISTRY, 83, 3529, (2018)
Abstract: The first family of extended and fluorinated corannulenes is prepared through a highly efficient and modular synthetic strategy. In this strategy, corannulene aldehyde could be combined with the fluorine-carrying phosphonium ylides to furnish stilbene-like vinylene precursors. A photochemically induced oxidative cyclization process of these precursors gives rise to the fluorinated and curved polycyclic aromatic hydrocarbons. A UV-vis absorption study shows that aromatic extension results in a bathochromic shift of about 12 nm. Fluorination further shifts the absorption spectrum to the red region, and a maximum shift of about 22 nm is detected for a compound carrying two trifluoromethyl groups. A cyclic and square-wave voltammetry investigation reveals that the extension of the corannulene scaffold increases the reduction potential by 0.11 V. Placement of fluorine or trifluoromethyl groups further enhances the electron affinities. In this regard, the presence of one trifluoromethyl group equals the effect of three aromatic fluorine atoms. Molecules with two trifluoromethyl groups, meanwhile, exhibit the highest reduction potentials of -1.93 and -1.83 V. These values are 0.37 and 0.46 V higher than those of the parental corannulene and demonstrate the utility of the present design concept by efficiently accessing effective electron acceptors based on the buckybowl motif.

First author: Vlahovic, F, Rotating Iron and Titanium Sandwich Complexes, CHEMISTRY-A EUROPEAN JOURNAL, 24, 5070, (2018)
Abstract: The origin for the rotational barrier of organometallic versus inorganic sandwich complexes has remained enigmatic for the past decades. Here, we investigate in detail what causes the substantial barrier for titanodecaphosphacene through spin-state consistent density functional theory. Orbital interactions are shown to be the determining factor.

First author: Dourado, DFAR, Why the Flavin Adenine Dinucleotide (FAD) Cofactor Needs To Be Covalently Linked to ComplexII of the Electron-Transport Chain for the Conversion of FADH(2) into FAD, CHEMISTRY-A EUROPEAN JOURNAL, 24, 5246, (2018)
Abstract: A covalently bound flavin cofactor is predominant in the succinate-ubiquinone oxidoreductase (SQR; Complex II), an essential component of aerobic electron transport, and in the menaquinol-fumarate oxidoreductase (QFR), the anaerobic counterpart, although it is only present in approximately 10% of the known flavoenzymes. This work investigates the role of this 8-N3-histidyl linkage between the flavin adenine dinucleotide (FAD) cofactor and the respiratory ComplexII. After parameterization with DFT calculations, classical molecular-dynamics simulations and quantum-mechanics calculations for ComplexII:FAD and ComplexII:FADH(2), with and without the covalent bond, were performed. It was observed that the covalent bond is essential for the active-center arrangement of the FADH(2)/FAD cofactor. Removal of this bond causes a displacement of the isoalloxazine group, which influences interactions with the protein, flavin solvation, and possible proton-transfer pathways. Specifically, for the noncovalently bound FADH(2) cofactor, the N1 atom moves away from the His-A365 and His-A254 residues and the N5 atom moves away from the glutamine-62A residue. Both of the histidine and glutamine residues interact with a chain of water molecules that cross the enzyme, which is most likely involved in proton transfer. Breaking this chain of water molecules could thereby compromise proton transfer across the two active sites of ComplexII.

First author: Obies, M, Redox-Dependent Metal-Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling, CHEMISTRY-A EUROPEAN JOURNAL, 24, 5309, (2018)
Abstract: The synthesis and physical properties of two new cationic tri-metallic chains, [(PEt3)(3)RuCl3MCl3Ru(PEt3)(3)](1+), M=Rh and Ir are reported. These are isostructural with a previously reported 17-electron all-ruthenium analogue, but replacing a d(5) Ru-III ion in the central position with d(6) Rh-III/Ir-III has a significant impact on the nature of the metal-metal interactions. All three materials have been characterized electrochemically at the 18-, 17- and 16-electron levels. X-ray crystallography and spectroelectrochemistry, complemented by electronic structure analysis at the DFT and CASPT2 levels, indicate that whilst the presence of a Ru-III ion in the center of the chain allows multi-center covalent bonding to develop, a closed-shell Rh-III/Ir-III ion pushes the system towards the exchange-coupled limit, where the outer Ru centers are only weakly interacting. This family of three isostructural compounds reveals how changes in metal composition can have subtle effects on physical properties of systems that lie close to the localized/delocalized borderline.

First author: Chen, DD, Adaptive aromaticity in S-o and T-1 states of pentalene incorporating 16 valence electron osmium, COMMUNICATIONS CHEMISTRY, 1, 5309, (2018)
Abstract: Aromaticity is a fundamental chemical concept of ever-increasing diversity. According to Huckel’s and Baird’s rules, cyclic conjugated species with 4n+2 pi-electrons are aromatic in the singlet electronic ground state (S-o) and antiaromatic in the lowest triplet state (T-1), and vice-versa. Thus, species with aromaticity in both states have not yet been reported. Here we carry out density functional theory calculations on recently synthesized organometallics, namely osmapentalyne and osmapentalenes, and demonstrate the first example (16-electron osmapentalene) of aromaticity in both S-o and T-1 states, which we term adaptive aromaticity. Further electronic structure analysis reveals that the excitation pattern for the formation of the T-1 state plays a crucial role in the achievement of adaptive aromaticity. Our findings highlight the role of a transition metal in unorthodox excitation behavior, and may aid the design of adaptive aromatics for photochemical and molecular magnetism applications.

First author: Tran, QT, Spin-Orbit Splittings and Low-Lying Electronic States of AuSi and AuGe: Anion Photoelectron Spectroscopy and ab Initio Calculations, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 3374, (2018)
Abstract: We measured the photoelectron spectra of diatomic AuSi- and AuGe- and conducted calculations on the structures and electronic properties of AuSi-/0 and AuGe-/0. The calculations at the CASSCF/CASPT2 level confirmed that experimentally observed spectra features of AuSi- and AuGe- can be attributed to the transitions from the 3 Sigma(-) anionic ground state to the (2)Pi ((2)Pi(1/2) and (2)Pi(3/2)), (4)Sigma(-), 3(2)Sigma(+), and 4(2)Sigma(+) electronic states of their neutral counterparts. The electron affinities (EAs) of AuSi- and AuGe are determined by the experiments to be 1.54 +/- 0.05 and 1.51 +/- 0.05 eV, respectively. The spin orbit splittings ((2)Pi(1/2)-(2)Pi(3/2)) of AuSi- and AuGe measured in this work are in agreement with the literature values. The energy difference between the (4)Sigma(-) (A) and (2)Pi(1/2) states of AuSi obtained in this work is in reasonable agreement with the literature value, while that of AuGe obtained in this work by anion photoelectron spectroscopy is slightly larger than the literature value by neutral emission spectroscopy. The term energies of the 3(2)Sigma(+) (B) and 4(2)Sigma(+) (C) states of AuSi and AuGe were also determined based on the photoelectron spectra. Because of the different bond lengths between the anionic and neutral states, the electronic state terms energies of AuSi and AuGe estimated from the anion photoelectron spectra might be slightly different from those obtained from the neutral emission spectra.

First author: Grabowski, SJ, Two faces of triel bonds in boron trihalide complexes, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 472, (2018)
Abstract: The NB triel bonds in complexes of boron trihalides, BX3 (X=F, Cl, Br, and I), with species acting as Lewis bases through the nitrogen center, NH3, N-2, and HCN, are analyzed theoretically (MP2/aug-cc-pVTZ calculations). It is confirmed that stronger Lewis acid properties of the boron center are observed for the BCl3 moiety than for the BF3 one in complexes with the strong Lewis base (NH3); while the opposite order is observed for complexes with the weak Lewis base (N-2). The BX3NCH complexes (for X=Cl, Br, and I) are characterized by two tautomeric forms and by two corresponding NB distances, the shorter one possesses characteristics of the covalent bond. In a case of the BF3NCH complex one energetic minimum is observed. Ab initio calculations are supported by an analysis of molecular electrostatic potentials (EPs) and electron density distributions. The quantum theory of atoms in molecules’ and the decomposition of the energy of interaction are applied. The aforementioned acidity orders as well as the existence of two tautomers for some of complexes result partly from the electrostatic interactions’ balance; the EP distribution is different for the BF3 species than for the other BX3 species where X=Cl, Br, and I.

First author: Zheng, M, Electron-Transfer-Enhanced Cation-Cation Interactions in Homo- and Heterobimetallic Actinide Complexes: A Relativistic Density Functional Theory Study, INORGANIC CHEMISTRY, 57, 3893, (2018)
Abstract: To provide deep insight into cation-cation interactions (CCIs) involving hexavalent actinyl species that are major components in spent nuclear fuel and pose important implications for the effective removal of radiotoxic pollutants in the environment, a series of homo- and heterobimetallic actinide complexes supported by cyclopentadienyl (Cp) and polypyrrolic macrocycle (H4L) ligands were systematically investigated using relativistic density functional theory. The metal sort in both parts of (THF)(H2L)(OAn(VI)O) and (An’)Cp-III(3) from U to Np to Pu, as well as the substituent bonding to Cp from electron-donating Me to H to electron-withdrawing Cl, SiH3, and SiMe3, was changed. Over 0.70 electrons are unraveled to transfer from the electron-rich U-III to the electron-deficient An(VI) of the actinyl moiety, leading to a more stable An(V)-U-IV isomer; in contrast, uranylneptunium and uranylplutonium complexes behave as electron-resonance structures between VI-III and V-IV. These were further corroborated by geometrical and electronic structures. The energies of CCIs (i.e., O-exo-An’ bonds) were calculated to be -19.6 to -41.2 kcal/mol, affording those of OUO-Np (-23.9 kcal/mol) and OUO-Pu (-19.6 kcal/mol) with less electron transfer (ET) right at the low limit. Topological analyses of the electron density at the O-exo-An’ bond critical points demonstrate that the CCIs are ET or dative bonds in nature. A positive correlation has been built between the CCIs’ strength and corresponding ET amount. It is concluded that the CCIs of O-exo-An’ are driven by the electrostatic attraction between the actinyl oxo atom (negative) and the actinide ion (positive) and enhanced by their ET. Finally, experimental syntheses of (THF)(H2L)((OUO)-O-VI)(An’)Cp-III(3) (An’ = U and Np) were well reproduced by thermodynamic calculations that yielded negative free energies in a tetrahydrofuran solution but a positive one for their uranylplutonium analogue, which was synthetically inaccessible. So, our thermodynamics would provide implications for the synthetic possibility of other theoretically designed bimetallic actinide complexes.

First author: Dutta, S, Computational Investigation of Carbene-Phosphinidenes: Correlation between P-31 Chemical Shifts and Bonding Features to Estimate the pi-Backdonation of Carbenes, INORGANIC CHEMISTRY, 57, 3993, (2018)
Abstract: Detailed investigations of the electronic structure and bonding scenario in different carbene-phosphinidenes have been presented using state-of-the-art computational methods (BP86/def2-TZVPP//BP86/def2-SVP). We have endeavored to find the correlation of the calculated P-31 chemical shifts with different bonding parameters of compounds to access the relative pi acceptor strengths of the carbenes. P-31 chemical shifts exhibit a weak correlation with sigma-polarizations of Ccarb-P bonds toward phosphorus; however excellent correlations are obtained in the case of pi-polarizations of Ccarb-P bonds toward the carbene carbon (C-carb) and NPA charges on phosphorus atoms. P-31 chemical shifts also show excellent correlations with the electron densities and energy densities of Ccarb-P bonds at BCPs, as suggested by QTAIM calculations. Moreover, EDA-NOCV analysis is implemented to gain brief insight into the bonding scenario in this class of compounds. Good correlation exists between the interaction energies between the carbene and PPh fragments and P-31 chemical shifts. Additionally, we have investigated the correlations of calculated P-31 chemical shifts with different bonding parameters of the corresponding free carbenes. The bonding scenario in different carbene-substituted phosphinidenes is also explored to see how the bonding situation depends on various substituents on phosphinidenes. The other substituted carbene-phosphinidenes show correlations similar to those of carbene-phenylphosphinidenes.

First author: Gao, CL, Double functionalization of a fullerene in drastic arc-discharge conditions: synthesis and formation mechanism of C-2v(2)-C78Cl6(C5Cl6), CARBON, 129, 286, (2018)
Abstract: Arc-discharge of graphite is the most prevalent technique for synthesis of novel fullerenes, but the extreme conditions of the carbon arc prevent any currently available instrument from detecting the reaction species inside. To detour the difficulties for probing the derivatization mechanism in the drastic arc-discharge conditions, C78Cl6(C5Cl6) with prototypical C-2v(2)-C-78 cage has been isolated and characterized in the products of the chlorine-involving carbon arc. The structure of C-2v(2)-C78Cl6(C5Cl6), featuring with fullerene C-2v(2)-C-78 doubly functionalized by chlorine atoms and perchlorinated cyclopentadiene, has been identified by X-ray crystallography. Confirmed by standard Density Functional Theory (DFT) calculations and Car-Parrinello simulations as well as mass spectrometry, the fullerene core has been revealed to form firstly followed then by reaction with chlorine atoms and afterwards with perchlorinated cyclopentadiene, with implication about stepwise reaction temperatures and sequences for the formation of fullerenes and their derivatives in the otherwise inaccessible extreme conditions of the carbon arc.

First author: Krivdin, LB, Carbon-carbon spin-spin coupling constants: Practical applications of theoretical calculations, PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, 105, 54, (2018)
Abstract: Practical applications of theoretical calculations of carbon-carbon spin-spin coupling constants in particular classes of organic and bioorganic molecules are reviewed, concentrating mainly on saturated, unsaturated, aromatic and heteroaromatic compounds and their functional derivatives as well as on carbohydrates and natural compounds.

First author: Yan, B, Thermal Behavior, Specific Heat Capacity and Detonation Characterization of 3,3-Dinitroazetidinium 3,5-Dinitrobenzoate, PROPELLANTS EXPLOSIVES PYROTECHNICS, 43, 398, (2018)
Abstract: 3,3-Dinitroazetidinium 3,5-dinitrobenzoate (DNAZ DNB) was synthesized, its thermal behavior was studied under a non-isothermal condition by DSC and TG/DTG methods. The intense exothermic decomposition process of DSC curves were analyzed to obtain its kinetic parameters. The specific molar heat capacity (C-p,C-m) of DNAZDNB was determined by a continuous C-p mode of micro-calorimeter, and the value was 416.81JK(-1)mol(-1)at 298.15K. Its detonation velocity (D) and detonation pressure (P) were estimated using the nitrogen equivalent equation according to the experimental density. The above results of DNAZDNB were compared with those of 3,3-dinitroazetidinium 3,5-dinitrosalicylate (DNAZDNS) and 3,3-dinitroazetidinium picrate (DNAZPA), and the effect of phenolic hydroxyl, carboxyl, and nitro group on them were discussed.

First author: Manzetti, S, Quantum chemical calculations of the active site of the solute-binding protein PsaA from Streptococcus pneumoniae explain electronic selectivity of metal binding, STRUCTURAL CHEMISTRY, 29, 393, (2018)
Abstract: Streptococcus pneumoniae is the world’s foremost bacterial pathogen. Virulence in the host is dependent on manganese acquisition via the PsaBCA permease. Crystallographic studies of its solute-binding protein component, PsaA, have previously shown that the nature of the metal ion bound by the protein modulates the conformational changes associated with its function. Notably, manganese and cadmium ions can be bound in a reversible manner, facilitating transport via PsaA, whereas zinc binds in an essentially irreversible manner preventing release to the permease. All three ionic species show a similar coordination in the PsaA crystal structures. A set of quantum chemical calculations have here been performed in order to differentiate between the ions in terms of electronic configuration. Based on natural bond orbital (NBO) analysis, the results show that manganese and cadmium bind more strongly to the protein than zinc, in that their coordination to the enzyme involves more shared electrons. Manganese has the highest indirect indicator of bonding strength and provides an unpaired electron that induces the formation of three bonds to the enzyme active site. Cadmium binds more strongly than zinc, though more weakly than manganese, and forms only ionic bonds in its ligand framework. These calculations indicate a concrete differentiation of the bonding states of the three active sites; however, bonding energies which can give more accurate estimates have not been computed presently. The calculations further show that the ionic radii are critical for the bonding state between the enzyme and the metal and that the conformational motions responsible for the PsaA’s functional cycle may depend on the ion binding strongly to the enzyme. Our results add important information of the PsaA-metal ion binding architecture to the existing crystallography data and aid in understanding the function of this protein.

First author: Merlini, ML, Understanding the Catalase-Like Activity of a Bioinspired Manganese(II) Complex with a Pentadentate NSNSN Ligand Framework. A Computational Insight into the Mechanism, ACS CATALYSIS, 8, 2944, (2018)
Abstract: The mechanism of H2O2 dismutation catalyzed by the recently reported 2,6-bis[((2-pyridylmethyl)thio)methyl]pyridine-Mn(II) complex ([MnS2Py3(OTf)(2)]) has been investigated by density functional theory using the S12g functional. The complex has been analyzed in terms of its coordination properties and the reaction of [MnS2Py3](2+) in a distorted square pyramidal coordination geometry with two hydrogen peroxide molecules has been investigated in our calculations. The sextet, quartet, and doublet potential energy profiles of the catalytic reaction have been explored. In the first dismutation process, the rate-determining step (RDS) is found to be the asymmetric O-O bond cleavage, which occurs on the sextet potential energy profile. A subsequent spin crossover from sextet to quartet, associated with a coordination rearrangement around the metal, can take place to generate a stable Mn(IV) dihydroxo intermediate. This could disfavor the ping-pong mechanism commonly considered to describe the H2O2 dismutation reaction, where the binding of the first H2O2 substrate leads to the release of one H2O product and the conversion of the catalyst into a Mn(W) oxo complex. The formation of this stable intermediate, featuring a peculiar trigonal prismatic coordination geometry, paves the way for an alternative reaction pathway for the second dismutation process, termed the dihydroxo mechanism, where two water molecules and dioxygen are easily and simultaneously formed. The competing channels have different spin states: the sextet reaction pathway corresponds to the ping-pong mechanism, whereas the quartet reaction follows preferably the dihydroxo mechanism. The doublet reaction path is energetically disfavored for both channels. For the ping-pong mechanism, the RDS in the second dismutation process is represented by the second hydrogen-abstraction from H2O2, with a calculated energy barrier very close to that of the RDS in the first dismutation reaction. Explicit solvent molecules, counterions, and trace amounts of water are found to further support the preference for the asymmetric O-O bond breaking by favoring the end-on coordination mode of the first H2O2 to the catalyst.

First author: Boereboom, JM, Explicit Solvation Matters: Performance of QM/MM Solvation Models in Nucleophilic Addition, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 1841, (2018)
Abstract: Nucleophilic addition onto a carbonyl moiety is strongly affected by solvent, and correctly simulating this solvent effect is often beyond the capability of single-scale quantum mechanical (QM) models. This work explores multiscale approaches for the description of the reversible and highly solvent-sensitive nucleophilic Nl center dot center dot center dot C=O bond formation in an Me2N (CH2)(3)-CH=O molecule. In the first stage of this work, we rigorously compare and test four recent quantum mechanical/molecular mechanical (QM/MM) explicit solvation models, employing a QM description of water molecules in spherical regions around both the oxygen and the nitrogen atom of the solute. The accuracy of the models is benchmarked against a reference QM simulation, focusing on properties of the solvated Me2N-(CH2)(3)-CH=O molecule in its ring-closed form. In the second stage, we select one of the models (continuous adaptive QM/MM) and use it to obtain a reliable free energy profile for the Nl center dot center dot center dot C bond formation reaction. We find that the dual-sphere approach allows the model to accurately account for solvent reorganization along the entire reaction path. In contrast, a simple microsolvation model cannot adapt to the changing conditions and provides an incorrect description of the reaction process.

First author: Tan, Z, Noble gas supported boron-pentagonal clusters B(5)Ng(n)(3+): exploring the structures and bonding, JOURNAL OF MOLECULAR MODELING, 24, 1841, (2018)
Abstract: A novel type of trivalent BNg five-membered cational species B(5)Ng(n)(3+)(Ng = He similar to Rn, n = 1 similar to 5) has been found and investigated theoretically using the B3LYP and MP2 methods with the def2-QZVPPD and def2-TZVPPD basis sets. The geometry, harmonic vibrational frequencies, bond energies, charge distribution, bond nature, aromaticity, and energy decomposition analysis of these structures were reported. The calculated B-Ng bond energy is quite large (the averaged bond energy is in the range of 209.2 similar to 585.76 kJ mol(-1)) for heavy rare gases and increases with the Ng atomic number. The analyses of the molecular wavefunction show that in the BNg compounds of heavy Ng atoms Ar similar to Rn, the B-Ng bonds are of typical covalent character. Nuclear independent chemical shifts display that both B-5(3+) and B(5)Ng(n)(3+)(n=1 similar to 5) have obvious aromaticity. Energy decomposition analysis shows that these BNg compounds are mainly stabilized by the s-donation from the Ng valence p orbital to the B-5(3+) LUMO. These findings offer valuable clues toward the design and synthesis of new stable Ng-containing compounds.

First author: Zuo, K, Theoretical insight into the photodeactivation pathway of the tetradentate Pt(II) complex: The -conjugation effect, APPLIED ORGANOMETALLIC CHEMISTRY, 32, 1841, (2018)
Abstract: In this work, density functional theory and time-dependent density functional theory were used to investigate the effects of -conjugation of the ligand on the photophysical properties, radiative/nonradiative processes and phosphorescence quantum efficiency of tetradentate cyclometalated Pt (II) complex with carbazolyl-pyridine ligands PtNON. By simulating the absorption spectra and emission wavelengths, increasing the -conjugation of the ligand could cause the absorption and emission wavelengths to red-shift. The results of the computation of key parameters in the radiative decay process, such as singlet-triplet splitting energy, transition dipole moment and spin-coupled matrix element between the lowest triplet and singlet excited states, showed that the expansion of -conjugation on the carbazole ligand of PtNON resulted in reduction of these parameters, thereby reducing the radiation rate constant. The analyses of the PtNON nonradiative pathway also found that the high activation energy of PtNON made it one of the reasons for the high phosphorescence quantum yield. At the same time, enhancing the molecular orbital delocalization of the ligand further enlarged the energy barrier of the nonradiative pathway, and was conducive to the improvement of phosphorescence quantum yield.

First author: Li, Y, Decomposition characteristics of C5F10O/air mixture as substitutes for SF6 to reduce global warming, JOURNAL OF FLUORINE CHEMISTRY, 208, 65, (2018)
Abstract: Sulfur hexafluoride (SF6) is widely used in the power industry but is a serious greenhouse gas. Many researchers committed to achieving sustainable development of the power industry are finding alternatives to SF6 gas. C5F10O performs well in terms of environmental protection, insulation, and safety and is a potential environment-friendly alternative gas. In this paper, the insulation and decomposition characteristics of C5F10O/air gas mixture were examined using gas-insulation performance test platform, and decomposition products were detected by gas chromatography-mass spectrometry. The formation mechanism and distribution of C5F10O decomposition products were analyzed through reactive molecular dynamics method and density functional theory. The influence of air on the decomposition of C5F10O was also evaluated. Results showed that the decomposition of C5F10O/air gas mixture mainly produces CF3 center dot, C3F2 center dot, C4F7O center dot, CO, CF2 center dot, CF center dot, F center dot and CF4. The breakdown voltage of C5F10O/air gas mixture decreased slightly after repeated breakdown tests, and CF4, C2F6, Us, C3F6, C4F10, CF20 were detected. These results can serve as a reference for the systematic comprehension of the decomposition characteristics of C5F10O/air gas mixture and for related engineering applications.

First author: Moreno-Vicente, A, Probing the formation of halogenated endohedral metallofullerenes: Predictions confirmed by experiments, CARBON, 129, 750, (2018)
Abstract: The functionalization of endohedral metallofullerenes by halogenation has not been previously reported and remains a challenging endeavor in carbon nanoscience. In this work, we show that halogenation of endohedral metallofullerenes is predicted to be feasible based on thermodynamic grounds by means of DFT computations, combined with in situ experimental investigations. Computed bond energies for the chlorination, fluorination and hydrogenation of endohedral metallofullerenes that span a range of cage sizes are found to be comparable to those of known halogenated and hydrogenated empty fullerenes. Therefore, we propose that new forms of functionalized metallofullerenes should be synthesized under appropriate experimental conditions, despite many prior unsuccessful attempts. Indeed, we experimentally show for the first time that M@C-2n (M = metal) metallofullerenes and the prototypical Sc3N@C-80 clusterfullerene can be fluorinated by two different routes under the typical ‘harsh’ gas phase conditions of metallofullerene plasma synthesis, and at lower extents that could avoid cage degradation. The combination of halogenation and metal encapsulation offers the potential to create new radical-quenched, functionalized endohedral metallofullerenes that possess stable, large-gap carbon cages. These results open new avenues for the synthesis and stabilization of encapsulated molecular nanocarbons.

First author: Ortolan, AO, Tuning Heterocalixarenes to Improve Their Anion Recognition: A Computational Approach, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 3328, (2018)
Abstract: We have explored and analyzed the physical factors through which noncovalent interactions in anion sensing based on calixarene-type hosts can be tuned, using dispersion corrected DFT and Kohn-Sham molecular orbital (KS-MO) theory in conjunction with a canonical energy decomposition analysis (EDA). We find that the host-guest interaction can be enhanced through the introduction of strongly electron withdrawing groups at particular positions of the arene and triazine units in the host molecule as well as by coordination of a metal complex to the arene and triazine rings. Our analyses reveal that the enhanced anion affinity is caused by increasing the electrostatic potential in the heterocalixarene cavities. This insight can be employed to further tune and improve their selectivity for chloride ions.

First author: Ayuso, D, Chiral dichroism in bi-elliptical high-order harmonic generation, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 51, 3328, (2018)
Abstract: The application of strong bi-elliptically polarized laser fields to the generation of high-order harmonics in organic molecules offers exceptional opportunities for chiral recognition and chiral discrimination. These fields are made by combining an elliptically polarized fundamental, typically in the infrared range, with its counter-rotating second harmonic. Here we present a theoretical study of the harmonic emission from the chiral molecule propylene oxide in bi-elliptical fields. Our calculations include, for the first time in such a complex system, accurate photorecomination matrix elements, evaluated using the static-exchange density functional theory method. We show that bi-elliptical light can induce strong chiral dichroism in the harmonic spectra of chiral molecules in a broad range of harmonic numbers and ellipticities.

First author: Ritschel, B, Double CH Activation of a Masked Cationic Bismuth Amide, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57, 3825, (2018)
Abstract: The transformation of C-H bonds into more reactive C-M bonds amenable to further functionalization is of fundamental importance in synthetic chemistry. We demonstrate here that the transformation of neutral bismuth compounds into their cationic analogues can be used as a strategy to facilitate CH activation reactions. In particular, the double CH activation of bismuth-bound diphenyl amide, (NPh2)(-), is reported along with simple one-pot procedures for the functionalization of the activated positions. The organometallic products of the first and second CH activation steps were isolated in high yields. Analysis by NMR spectroscopy, single-crystal X-ray diffraction, and DFT calculations revealed unusual ground-state properties (e.g., ring strain, moderate heteroaromaticity), and provided mechanistic insight into the formation of these compounds.

First author: Abo-Amer, A, Push-pull ligands to enhance the oxygen activation step in catalytic oxidation with platinum complexes, INORGANICA CHIMICA ACTA, 473, 51, (2018)
Abstract: The ligands RN(CH2-2-C5H4N)(2), L1, R = CH2C6H4-2-OH; L2, R = CH2C6H3-4-Me-2-OH; L3, R = CH2C6H3-5-Cl-2-OH; L4, R = CH2C6H3-5-NO2-2-OH; give dimethylplatinum(II) complexes that activate dioxygen in the absence of a protic solvent. The initial reaction with [Pt2Me4(SMe2)(2)] gives [PtMe2(kappa(2)-N,N’-L)], and these react with oxygen to give [Pt(OH)Me-2(kappa(3)-N,N’,N ”-L-H)], which exist as a mixture of isomers. The factors influencing reactivity and mechanism in these reactions are elucidated, and the presence of both a free pyridyl donor (push group) and a free hydroxyl (pull group) is suggested to give a synergy for dioxygen activation. Some platinum(II) complexes and trimethylplatinum(IV) complexes with these ligands are also reported.

First author: Zouchoune, B, Ligands’ sigma-donation and pi-backdonation effects on metal-metal bonding in trinuclear [M-3(Tr)(2)(L)(3)](2+) (M = Fe, Ni, Pd, Pt, Tr = tropylium and L = CO, HCN and C2H4) sandwich compounds: Theoretical investigation, INORGANICA CHIMICA ACTA, 473, 204, (2018)
Abstract: DFT calculations with full geometry optimization using GGA BP86 and meta-GGA M06L functionals have been performed on the [M-3(Tr)(2)L-3](2+) (M = Fe, Ni, Pd, Pt, Tr+ = C7H7+ and L = CO, HCN and eta(2)-C2H4) sandwich complexes. The M-3 triangular core is encapsulated between two tropylium cations which tends to establish M-L bonding with regards to the metal nature and the spin state. It turned out that each tropylium cation is connected to the M-3 triangular core through an eta(2), eta(2), eta(2) coordination mode engaging six carbon atoms amongst seven. For the Fe singlet structures, the calculated HOMO-LUMO gaps by both BP86 and M06L are small, thus favouring the triplet one. The [Fe-3(Tr)L-3](2+) singlet structures are predicted to have two formal FeAFe single bonds and one formal FeAFe triple one within the Fe-3 triangle based on the bond distances and the Wiberg bond indices (WBIs), while their analogues of triplet state exhibit two formal FeAFe single bonds and one formal FeAFe double bond. For the nickel, palladium and platinum d(10) metal structures, they display large HOMO-LUMO gaps and adopt three formal metal-metal single bonds within the M-3 core, in accordance with the small WBIs. The different binding capabilities of the isoelectronic CO, HCN and C2H4 auxiliary ligands are highlighted by the corresponding MOs’ diagrams and their donation and backdonation amounts.

First author: Zhang, XX, U-2@I-h(7)-C-80: Crystallographic Characterization of a Long-Sought Dimetallic Actinide Endohedral Fullerene, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 3907, (2018)
Abstract: The nature of actinide-actinide bonds has attracted considerable attention for a long time, especially since recent theoretical studies suggest that triple and up to quintuple bonds should be possible, but little is known experimentally. Actinide-actinide bonds inside fullerene cages have also been proposed, but their existence has been debated intensively by theoreticians. Despite all the theoretical arguments, critical experimental data for a dimetallic actinide endohedral fullerene have never been obtained. Herein, we report the synthesis and isolation of a dimetallic actinide endohedral metallofullerene (EMF), U-2@C-80. This compound was fully characterized by mass spectrometry, single crystal X-ray crystallography, UV-vis-NIR spectroscopy, Raman spectroscopy, cyclic voltammetry, and X-ray absorption spectroscopy (XAS). The single crystal X-ray crystallographic analysis unambiguously assigned the molecular structure to U-2@I-h(7)-C-80. In particular, the crystallographic data revealed that the U-U distance is within the range of 3.46-3.79 A, which is shorter than the 3.9 angstrom previously predicted for an elongated weak U-U bond inside the C-80 cage. The XAS results reveal that the formal charge of the U atoms trapped inside the fullerene cage is +3, which agrees with the computational and crystallographic studies that assign a hexaanionic carbon cage, (I-h-C-80)(6-). Theoretical studies confirm the presence of a U-U bonding interaction and suggest that the weak U-U bond in U-2@I-h(7)-C-80 is strengthened upon reduction and weakened upon oxidation. The comprehensive characterization of U-2@I-h(7)-C-80 and the overall agreement between the experimental data and theoretical investigations provide experimental proof and deeper understanding for actinide metal-metal bonding interactions inside a fullerene cage.

First author: Massolle, A, Towards reliable references for electron paramagnetic resonance parameters based on quantum chemistry: the case of verdazyl radicals, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 7661, (2018)
Abstract: We present an efficient and accurate computational procedure to calculate properties measurable by EPR spectroscopy. We simulate a molecular dynamics (MD) trajectory by employing the quantum mechanically derived force field (QMDFF) [S. Grimme, J. Chem. Theory Comput., 2014, 10, 4497] and sample the trajectory at different time steps. For each snapshot EPR properties are calculated with a hybrid density functional theory (DFT) method. EPR spectra are simulated based on the averaged results. We applied the strategy to a number of previously published and novel verdazyl radicals, for which we recorded EPR spectra. The resulting simulated spectra are compatible with experiment already before employing an additional fitting step, in contrast to those from single point electronic-structure calculations. After the refinement, the experimental data are excellently reproduced, and the fitted EPR parameters do not deviate much from the calculated ones. This provides confidence in ascribing a direct physical meaning to the refined data in terms of experimental EPR parameters rather than merely considering them as mathematical fit parameters. We also find that couplings to hydrogen nuclei have a significant influence on the spectra of verdazyl radicals.

First author: Liu, C, Reactivity Studies of [Co@Sn-9](4-) with Transition Metal Reagents: Bottom-Up Synthesis of Ternary Functionalized Zintl Clusters, INORGANIC CHEMISTRY, 57, 3025, (2018)
Abstract: The binary cluster [Co@Sn-9](4-) (1) was extracted directly from ethylenediamine (en) solutions of an intermetallic precursor with nominal composition “K5Co3Sn9”, and its reactions with various organometallic reagents were explored. Reaction with Ni(PPh3)(2)(CO)(2) gives [Co@Sn9Ni(CO)](3-) (2), a Co-centered closo-Sn9Ni bicapped square antiprism. Analogous reactions with Ni(COD)(2), Pt(PPh3)(4), and Au(PPh3)Ph led to the isolation of [Co@Sn9Ni(C2H4)](3-) (3), [CogSn(9)Pt-(PPh3)](3-) (4), and [Co@Sn9AuPh](3-) (5), respectively. 3 is structurally similar to 2 but significantly distorted from a closocluster with one open square face. The coordination of [CoSn9](3-) by PtPPh3 (4) or AuPh (5) induces a structural transformation in the CoSn9 core, from a monocapped square antiprism (C-4v) to a tricapped trigonal prismatic structure (pseudo-C-3v), with the transition metal fragment capping a triangular face. The four trimetallic anions presented here represent a new family of ternary functionalized Zintl clusters incorporating a d(9) transition metal center. All clusters were characterized by single-crystal X-ray diffraction and electrospray ionization mass spectrometry (ESI-MS).

First author: Levandowski, BJ, Origins of the Endo and Exo Selectivities in Cyclopropenone, Iminocyclopropene, and Triafulvene Diels-Alder Cycloadditions, JOURNAL OF ORGANIC CHEMISTRY, 83, 3164, (2018)
Abstract: The endo and exo stereoselectivities of Diels-Alder reactions of cyclopropenone, iminocyclopropene, and substituted triafulvenes with butadiene were rationalized using density functional theory calculations. When cyclopropenone is the dienophile, there is a 1.8 kcal/mol preference for the exo cycloaddition with butadiene, while the reaction of 3-difluoro-methylene triafulvene with butadiene favors the endo cycloaddition by 2.8 kcal/mol. The influence of charge transfer and secondary orbital interactions on the stereoselectivity of Diels-Alder reactions involving triafulvenes and hetero-analogs is discussed. The predicted stereoselectivity correlates with both the charge and highest occupied molecular orbital (HOMO) coefficient at the C-3 carbon of the triafulvene motif.

First author: Zhang, XX, Decomposition mechanism of the C5-PFK/CO2 gas mixture as an alternative gas for SF6, CHEMICAL ENGINEERING JOURNAL, 336, 38, (2018)
Abstract: In recent years, many scholars have been devoted to the search for environmentally friendly gas-insulated medium to gradually replace robust greenhouse gases, such as sulfur hexafluoride (SF6), which are widely used in the power industry at this stage, and thus promote the green development of power industry. In this study, the decomposition characteristics of C5-PFK (C5-perfluoroketone), a potential environmentally friendly alternative gas, were theoretically investigated. First, the bond order and Fukui functions of C5-PFK were calculated based on density functional theory, and the reactivity and stability of C5-PFK were revealed from a molecular viewpoint. Second, the decomposition characteristics of C5-PFK/CO2 gas mixture were examined through reactive molecular dynamics theory. The decomposition mechanism of C5-PFK/CO2 gas mixture and the yield and distribution of the main decomposition products at different temperatures and mixing ratios were obtained. Results show that chemical bonds between carbonyl and its linked carbon atoms in C5-PFK molecule are weak but with robust reactivity. C5-PFK/CO2 gas mixture decomposes mainly above 2600 K, producing CF3 center dot, CO, C3F7CO center dot, CF center dot, CF2 center dot, C3F7 center dot, F-center dot, CF3, and C-center dot, among which the CF3 center dot and CO contents are the highest. The decomposition characteristics of the gas mixture with a larger content of C5-PFK are inferior to those of the smaller content under the same condition. Relevant research results provide guidance for further clarifying the electrical characteristics, such as self-recovery and arc suppression performance of C5-PFK/CO2 gas mixtures and engineering applications.

First author: Munoz-Castro, A, A superatomic molecule under the spin-orbit coupling: Insights from the electronic properties in the thiolate-protected Au-38(SR)(24) cluster, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 118, 38, (2018)
Abstract: The role of the spin-orbit coupling in Au-38(SR)(24), as a representative case for a superatomic molecules is studied to offer a complete view of the relativistic effect in heavy elements clusters. Its Au239+core can be described in as an analog to a diatomic molecule, such as F-2, allowing the electronic structure to be depicted in terms of the D-h point group. First, we showed the electronic structure under the spin-orbit framework using total angular momentum representations (j=+/- s; spinors), which allows us to characterize the expected splitting of certain levels derived from the cluster core. Accordingly, the optical properties are evaluated under spin-orbit coupling regime, revealing differences in the low-energy region of the absorption spectrum. Lastly, the variation of electron affinity (EA) and ionization potential (IP) properties is evaluated. This reveals characteristic consequences of the inclusion of spin-orbit coupling in Au-38(SR)(24), as a bridge to larger thiolate-protected gold clusters.

First author: Pecak, J, Visible light-induced cis/trans isomerization of dicarbonyl Fe(II) PNP pincer complexes, POLYHEDRON, 143, 94, (2018)
Abstract: The synthesis and characterization of dicarbonyl Fe(II) PNP pincer complexes of the type cis-[Fe(PNP-iPr) (Co)(2)(X)](+) (X = Br, CI) is described. These complexes are slowly formed when solutions of complexes trans-[Fe(PNP-iPr)(CO)(2)(X)](+) are kept in the dark for 9 h (X = Br) and 3 days (X = CI). Upon exposure to visible light these complexes isomerize to the respective trans-dicarbonyl complexes within a few hours. The visible-light reaction seems to involve reversible CO dissociation. The isomerization can be repeated serval times. A mechanistic rationale for this isomerization process is established by means of DFT calculations.

First author: Yaghoobi, F, Theoretical Study on the Aza-Diels-Alder Reaction Catalyzed by PHCl2 Lewis Acid via Pnicogen Bonding, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 2781, (2018)
Abstract: The reaction mechanism of the Aza-Diels-Alder (A-D-A) cycloaddition reaction between X2C=NNH2, where X = H, F, Cl, Br, and 1,3-butadiene catalyzed by a PHCl2 Lewis acid was characterized using density functional theory calculations. The influences of various substituents of X on the studied reaction were analyzed using the activation strain model (ASM), which is also termed as the distortion interaction model. Calculations showed that the smallest and largest values of the activation energies belong to the substituents of F and Br, respectively. The activation energy of the studied reactions was decreased within 8.6 kcal.mol(-1) in the presence of PHCl2 catalyst. Investigations showed that the pnicogen bonding is adequately capable I of activating the A-D-A reaction. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were implemented to understand the nature of C4,cbut center dot center dot center dot CxIm and C1,cbut center dot center dot center dot NXIm the energy decomposition analysis (EDA) based on the ETS-NOCV scheme was used to characterize the nature of C4,Cbut center dot center dot center dot CXIm and C1,Cbut center dot center dot center dot NXIm bond. The results of the study mirror the fact that the PHCl2 Lewis acid may be suggested as a simple suitable catalyst for experimental studies on the A-D-A reactions.

First author: Zalaru, C, Synthesis, spectroscopic characterization, DFT study and antimicrobial activity of novel alkylaminopyrazole derivatives, JOURNAL OF MOLECULAR STRUCTURE, 1156, 12, (2018)
Abstract: A new series of substituted N,N-bis-[(1H-pyrazol-1-yl)methyl]-aminohexadecane Mannich bases were synthesized, characterized by IR, H-1 NMR C-13 NMR, UV-Vis, MS and elemental analysis, and tested for their biological activity. All the synthesized compounds were tested for in vitro antimicrobial activity against a panel of selected bacterial and fungal strains using erythromycin and clotrimazole as standards. Most of the synthesized compounds demonstrated very good activity at minimum inhibitory concentrations (MICs). Compound 3b with an halogen atom into the pharmacophore structure exhibited the most significant activity against Bacillus subtilis (MIC = 0.007 mu gmLL(-1)) versus erythromycin as standard. In vitro cytotoxicity of the new compounds was studied using MTT assay. The analysis of the test cells showed that the newly synthesized alkylaminopyrazoles derivatives were biocompatible until a concentration of 5 mu gmL(-1); two compounds presented a high degree of biocompatibility on the studied concentration range.

First author: Behnia, A, Mild and selective Pd-Ar protonolysis and C-H activation promoted by a ligand aryloxide group, DALTON TRANSACTIONS, 47, 3538, (2018)
Abstract: A bidentate nitrogen-donor ligand with an appended phenol group, C5H4NCH=N-2-C6H4OH, H(L1) was treated with a palladium cycloneophyl complex [Pd(CH2CMe2C6H4)(COD)], with both Pd-aryl and Pdalkyl bonds, to give a Pd-alkyl complex, [Pd(CH2CMe2C6H5)(kappa(3)-N, N’, O-OC6H4N=CH(2-C5H4N))], 1. The cleavage of the Pd-aryl bond and the deprotonation of the ligand phenol to afford a bound aryloxide, indicates facile Pd-aryl bond protonolysis. Deuterium labelling experiments confirmed that the ligand phenol promotes protonolysis and that the reverse, aryl C-H activation, occurs under very mild reaction conditions (within 10 min at room temperature). An unusual isomerization of the Pd-alkyl complex 1 to a Pd-aryl complex, [Pd(C6H4(2-t-Bu))(kappa(3)-N, N’, O-OC6H4N=CH(2-C5H4N))], 2, was observed to give an equilibrium with [2]/[1] = 9 after 5 days in methanol. The isomerization requires that both aryl C-H activation and Pd-alkyl protonolysis steps occur. The very large KIE value (k(H)/k(D) = ca. 40) for isomerization of 1 to 2, suggests a concerted S(E)2-type mechanism for the Pd-alkyl protonolysis step.

First author: Muravieva, VK, Mixed-metal clusters with a {Re3Mo3Se8} core: from a polymeric solid to soluble species with multiple redox transitions, DALTON TRANSACTIONS, 47, 3366, (2018)
Abstract: Cluster compounds based on a new {Re3Mo3Se8}(n) core were obtained and studied. The polymeric solid K-6[Re3Mo3Se8( CN)(4)(CN)(2/2)] (1) containing 24 cluster valence electrons (CVE) was isolated as a result of high-temperature reaction. Water-soluble salts K-5[Re3Mo3Se8(CN)(6)]center dot 11H(2)O (2) and Cs-5[Re3Mo3Se8(CN)(6)]center dot H2O (3) were prepared from compound 1. Crystal structures of the diamagnetic compounds 2 and 3 contain a cluster anion [Re3Mo3Se8(CN)(6)](5-) with a 22-electronic core {Re3Mo3Se8}(+). Metathesis reaction followed by recrystallization from CH3CN yielded paramagnetic salt (Ph4P)(4)[Re3Mo3Se8(CN)(6)]center dot 2CH(3)CN (4) containing the {Re3Mo3Se8}(2+) core with 21 CVE. Cyclic voltammetry of the solution of 4 displayed three quasi-reversible waves with E-1/2 = -0.325, -0.818 and -1.410 V vs. Ag/AgCl electrode indicating the presence of [Re3Mo3Se8(CN)(6)](4-/5-/6-/7)-transitions. Electronic structure calculations showed that both mer- and fac-isomers of [Re3Mo3Se8(CN)(6)](n-)clusters undergo great distortion when the number of CVE decreases.

First author: van Hoeve, MD, Computational study of the electronic spectra of the rare gas fluorohydrides HRgF (Rg = Ar, Kr, Xe, Rn), JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 51, 3366, (2018)
Abstract: Simulation of the electronic spectra of HRgF (Rg = Ar, Kr, Xe, Rn) was carried out using the time-dependent density functional method, with the CAMB3LYP functional and several basis sets augmented with even-tempered diffuse functions. A full spectral assignment for the HRgF systems was done. The effect of the rare gas matrix on the HRgF (Rg = Ar and Kr) spectra was investigated and it was found that the matrix blue-shifted the spectra. Scalar relativistic effects on the spectra were also studied and it was found that while the excitation energies of HArF and HKrF were insignificantly affected by relativistic effects, most of the excitation energies of HXeF and HRnF were red-shifted. Spin-orbit coupling was found to significantly affect excitation energies in HRnF. Analysis of performance of the model core potential basis set relative to all-electron (AE) basis sets showed that the former basis set increased computational efficiency and gave results similar to those obtained with the AE basis set.

First author: Pontes, RM, Theoretical perspectives on carbocation chemistry from energy decomposition analysis, THEORETICAL CHEMISTRY ACCOUNTS, 137, 3366, (2018)
Abstract: Understanding carbocation formation is a central concern for all chemical sciences. The widely accepted explanation in terms of inductive/field and delocalization effects is based on quantities that are not straightforwardly computed in popular electronic structure methods. This work reports an alternative approach to the carbocation formation problem based on energy decomposition analysis, more specifically, CMOEDA. The order of stability for carbocations formation was successfully accounted in terms of the energy components. The focus of the analysis shifts from the product of the reaction, i.e., the carbocation itself, to the reactant neutral molecule. Notably, exchange repulsions are the largest energy contribution to increase carbocation stability in the order methyl, primary, secondary and tertiary. Polarization (orbital relaxation) plays a secondary role. Insertion of bulky groups increases the repulsion with the incipient anion (a hydride ion) and decreases the strength of the C-H bond. This pattern is confirmed for several other hydrocarbon cases. Additional systems like halomethanes, amino- and nitro-derivatives are also described.

First author: Gu, LH, Reductive Elimination of C6F5-C6F5 from Pd(II) Complexes: Influence of alpha-Dicationic Chelating Phosphines, ORGANOMETALLICS, 37, 665, (2018)
Abstract: We report the synthesis and characterization through NMR and X-ray techniques of a series of [Pd-(C6F5)(2)((PP)-P-boolean AND’)] complexes constituted by diphosphine chelating ligands of different nature and evaluate the rates for the challenging reductive elimination of C6F5-C6F5. By virtue of their very weak donor properties, dicationic ancillary ligands effectively promote the desired transformation. Density functional theory (DFT) calculations were performed to rationalize these findings. The Pd(0)-complexes formed after the elimination step could not be isolated because the Pd(0) center has a tremendous tendency to insert into one of the P-C+ bonds of the alpha-cationic ligands rendering Pd(II)-phosphinidene complexes. The same behavior was observed for Ni(0) species.

First author: Purushothaman, I, Different Donor-Acceptor Interactions of Carbene Ligands in Heteroleptic Divalent Group 14 Compounds, LEL ‘ (E = C-Sn; L = N-Heterocyclic Carbene; L ‘ = Cyclic Alkyl(Amino) Carbene), CHEMISTRY-A EUROPEAN JOURNAL, 24, 3816, (2018)
Abstract: The electronic structure and reactivity of heteroleptic divalent group 14 compounds, 1E (E = C-Sn) with NHC and cAAC ligands have been studied at the BP86/TZ2P level of theory and compared with homoleptic group 14 compounds. The EDA-NOCV (energy decomposition analysis-natural orbitals for chemical valence) analysis indicates that the interaction between the two carbene ligands and the central C-atom in 1C can be best represented as one 3c-2e electron sharing sigma-bond and one 3c-2e donor-acceptor sigma-bond. There exists an electron sharing interaction between the pi-type orbital on the central C-atom and the C-N pi orbital of cAAC and pi-back-donation from the sigma-type lone pair on the central C-atom to the pi*-MO of NHC. This bonding description is equivalent to the localized bonding representation, where the central C-atom forms two electron sharing bonds and two donor-acceptor bonds with cAAC and NHC ligands. However, the bonding between the carbene ligands and the heavier group 14 element can be best represented as two 2c-2e donor-acceptor sigma-bonds and pi-back-donation from group 14 element to C-N pi* orbital of cAAC. This bonding description is well supported by the geometrical and Natural Bond Orbital (NBO) analyses. Hence, 1C can be best described as a carbene and the heavier analogues can be best described as tetrylones. However, the high first (287.6-274.3 kcal mol(-1)) and second proton affinities (162.0-158.5 kcal mol(-1)) suggest that 1E (E=C-Sn) behave as tetrylones.

First author: Bruce, RC, Contrasting Transport and Electrostatic Properties of Selectively Fluorinated Alkanethiol Monolayers with Embedded Dipoles, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 4881, (2018)
Abstract: Surface dipoles are a powerful tool in interfacial modification for improving device output via energy level matching. Fluorinated alkanethiols show a strong promise for these applications as they can generate large and tunable dipoles based on fluorine location and chain length. Furthermore, these chains can be designed to possess fluorocarbons solely along the backbone, enabling an “embedded” configuration that generates a significant dipole effect from the fluorines while maintaining surface chemistry to prevent deleterious side effects from altered surface interactions. However, fluorine substitution can modify other molecular electronic properties, and it is important to consider the transport properties of these interfacial modifiers so that knowledge can be used to tailor the optimal device performance. In this paper, we report the transport properties of self-assembled monolayers derived from a series of fluorinated alkanethiols, both with and without the embedded dipole structure. Photoelectron spectroscopy and Kelvin probe force microscopy show significant work function modification from all fluorine-containing molecules compared to purely hydrocarbon thiols. However, although embedded fluorocarbons generate a smaller electrostatic effect than terminal fluorocarbons, they yield higher tunneling currents across Au/monolayer/eutectic gallium-indium junctions compared to both terminal fluorocarbon and purely hydrocarbon alkanethiols. Computational studies show that the location of the fluorine constituents modifies not only dipoles and energy levels but also molecular orbitals, enabling the presence of delocalized lowest unoccupied molecular orbital levels within the alkanethiol backbone and, thereby, the appearance of larger tunneling currents compared to other alkanethiols. Ultimately, we show that fluorinated alkanethiols and the embedded dipole architecture are both powerful tools, but they must be thoroughly analyzed for proper utilization in a device setting.

First author: Miranda-Rojas, S, Unraveling the Nature of the Catalytic Power of Fluoroacetate Dehalogenase, CHEMCATCHEM, 10, 1052, (2018)
Abstract: Fluoroacetate dehalogenase is able to cleavage a carbon-fluoride bond, the strongest carbon-halogen bond in nature, in a process initiated by a S(N)2 reaction. The role of the enzyme machinery and particularly of the halogen pocket in the S(N)2 reaction is thoroughly explored by using state-of-the-art computational tools. A comparison between the non-catalyzed versus enzyme-catalyzed reaction, as well as with a mutant of the enzyme (Tyr219Phe), is presented. The energy barrier changes are rationalized by means of reaction force analysis and the activation strain model coupled with energy decomposition analysis. The catalysis is in part caused by the reduction of structural work from bringing the reactant species towards the proper reaction orientation, and the reduction of the electrostatic repulsion between the nucleophile and the substrate, which are both negatively charged. In addition, catalysis is also driven by an important reduction of the electronic reorganization processes during the reaction, where Tyr from the halogen pocket acts as a charge acceptor from the S(N)2 reaction axis therefore reducing the electronic steric repulsion between the reacting parts.

First author: Al Temimi, AHK, Recognition of shorter and longer trimethyllysine analogues by epigenetic reader proteins, CHEMICAL COMMUNICATIONS, 54, 2409, (2018)
Abstract: Histone N-epsilon-lysine methylation is a widespread posttranslational modification that is specifically recognised by a diverse class of N-epsilon-methyllysine binding reader proteins. Combined thermodynamic data, molecular dynamics simulations, and quantum chemical studies reveal that reader proteins efficiently bind trimethylornithine and trimethylhomolysine, the simplest N-epsilon-trimethyllysine analogues that differ in the length of the side chain.

First author: Binder, JF, Assessing the Ligand Properties of NHC-Stabilised Phosphorus(I) Cations, CHEMISTRY-A EUROPEAN JOURNAL, 24, 3556, (2018)
Abstract: The isolation and full characterisation of a series of cationic metal-carbonyl complexes bearing an N-heterocyclic carbene stabilised phosphorus(I) ligand are reported. Specifically, the mononuclear coordination complexes [LM(CO)(5)][BPh4] (M = Cr, Mo, W), [LFe(CO)(4)][BPh4] and the dinuclear complexes [LMn2(CO)(8)][BPh4] and [LCo2(CO)(6)][BPh4], in which L = [bis(1,3,4,5-tetramethylimidazol-2-ylidene)phosphanide](+), have all been isolated in the solid state and structurally confirmed by single-crystal X-ray diffraction. The dicationic platinum complex trans-[L2PtCl2][BPh4](2) is also reported and fully characterised. The donor ability of [L](+) has been assessed by IR spectroscopy of its metal-carbonyl complexes and by using DFT calculations. The results suggest that [L](+) is a weak pi-acceptor with moderate donor strength and thus it bridges the gap that exists between phosphines and amines in terms of ligand properties. Collectively, these molecules represent the first crystallographically characterised cationic metal-carbonyl derivatives of a P-I-centred ligand and are a rare collection of cationic metal-carbonyl complexes.

First author: Schacht, J, Cluster assemblies as superatomic solids: a first principles study of bonding & electronic structure, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 6167, (2018)
Abstract: The synthesis of cluster based materials poses an exciting challenge for experimental chemistry. The main advantage of these materials compared to conventional bulk compounds is the simple tunability of the chemical and physical characteristics of individual clusters. As a consequence, cluster assemblies can theoretically be used for the creation of designer materials exhibiting specifically desired properties. Since superatoms reveal a large intrinsic thermodynamic stability and often very interesting tunable electronic characteristics, they seem to be an excellent choice as building blocks for the bulk. Here, we present a detailed first principles analysis of carefully chosen superatomic cluster binary and bulk assemblies, in order to determine which forces control the attractive interaction in superatomic solids, and how the individual cluster properties affect these assemblies. This study uses the highly tunable and stable Au-13(RS(AuSR)(2))(6) cluster with a variety of dopants as a model system, while the principles are likely transferable to other ligand protected systems with a straightforward superatomic electron count, such as aluminum or sodium clusters. Three different superatomic materials based on doped gold clusters, boranes and C(60)s are constructed and evaluated. Beyond the verification that superatoms can be used to create materials that reveal emergent atom-based solid like properties, various factors influencing superatomic materials, such as the EA, IP and relative sizes of the clusters, have been identified and critically evaluated.

First author: Castrovilli, MC, An experimental and theoretical investigation of XPS and NEXAFS of 5-halouracils, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 6657, (2018)
Abstract: The C, N and O 1s excitation and ionization processes of 5X-uracil (X = F, Cl, Br, and I) were investigated using near edge X-ray absorption fine structure (NEXAFS) and X-ray photoemission (XPS) spectroscopies. This study aims at the fine assessment of the effects of the functionalization of uracil molecules by halogen atoms having different electronegativity and bound to the same molecular site. Two DFT-based approaches, which rely on different paradigms, have been used to simulate the experimental spectra and to assign the corresponding features. The analysis of the screening of the core holes of the different atoms via electronic charge density plots has turned out to be a useful tool to illustrate the competition between the partially aromatic and partially conjugate properties of this class of molecules.

First author: Pan, S, Boron Nanowheels with Axles Containing Noble Gas Atoms: Viable Noble Gas Bound M (c) B-10(-) Clusters (M=Nb, Ta), CHEMISTRY-A EUROPEAN JOURNAL, 24, 3590, (2018)
Abstract: The viability of noble gas axled boron nanowheels Ng(n)M (c) B-10(-) (Ng=Ar-Rn; M=Nb, Ta; n=1, 2) is explored by ab initio computations. In the resulting Ng(2)-M complexes, the Ng-M-Ng nanorod passes through the center of the B-10(-) ring, providing them with an inverse sandwich-like structure. While in the singly Ng bound analogue, the Ng binding enthalpy H-b at 298K ranges from 2.5 to 10.6 kcal mol(-1), in doubly Ng bound cases it becomes very low for the Ng(2)M (c) B-10(-) -> Ng+NgM (c) B-10(-) dissociation channel, except for the case of Rn, for which the corresponding H-b values are 3.4 (Nb) and 4.0kcalmol(-1) (Ta). For a given Ng, Ta has slightly higher Ng-binding ability than Nb. The corresponding free-energy changes indicate that these systems, particularly the Xe and Rn complexes, are good candidates for experimental realization in a low-temperature matrix. The Ng-M bonds were found to be covalent in nature, as reflected in their large Wiberg bond indices, formation of a 2c-2e sigma orbital between Ng and M centers in natural bond orbital and adaptive natural density partitioning (AdNDP) analyses, and the short Ng-M distances. Energy decomposition analysis and a study on the natural orbitals for chemical valence show that the Ng-M contact is supported mainly by the orbital and electrostatic interactions, with almost equal contributions. Although both the NgM sigma donation and NgM backdonation play roles in the origin of orbital interaction, the former is significantly dominant over the latter. Further, AdNDP analysis indicates that the doubly aromatic character (both sigma and ) in MB10- clusters is not perturbed by the interaction with Ng atoms.

First author: Yu, TR, The Dissociation Mechanism of Poly-alpha-methylstyrene (PAMS) Dimers Induced by Spin Polarization, CHEMISTRYSELECT, 3, 2553, (2018)
Abstract: To understand the last step of degradation mechanical of the poly-alpha-methylstyrene (PAMS), we studied the fracture mechanism of PAMS dimers. The calculations show that the PAMS dimer has two different spin-polarized effects dissociation reaction paths. Interestingly, one path is ferromagnetic coupling triplet state, which needed to overcome the energy barrier is about 0.80 eV and corresponding to an endothermic reaction. While, another path is the antiferromagnetic coupling spin-polarized singlet state, which needed to overcome the energy barrier is only about 0.03 eV with an exothermic reaction. Both the electron density difference and the energy decomposition show that the interaction between the two monomers is relatively strong in the transition state (TS) of singlet. This is because, in the TS of singlet state, the distance between the two monomers is closer. Our results highlight that the last dissociation of PAMS and another polymer may be through the antiferromagnetic path and which able to complete spontaneously and quickly. This finding removes a possibility of mass spectrometry experiments that origin of degradation of dimer products, and is helpful to understand the degradation process for materials.

First author: Zhu, QL, Benzimidazobenzothiazole-based highly-efficient thermally activated delayed fluorescence emitters for organic light-emitting diodes: A quantum-chemical TD-DFT study, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 192, 297, (2018)
Abstract: Based upon two thermally activated delayed fluorescence (TADF) emitters 1 and 2, compounds 3-6 have been designed by replacing the carbazol group with the bis(4-biphenyl)amine one (3 and 4) and introducing the electron-withdrawing CF3 group into the acceptor unit of 3 and 4 (5 and 6). It is found that the present calculations predict comparable but relatively large energy differences (approximate 0.5 eV) between the lowest singlet S-1 and triplet T-1 states (Delta E-ST) for the six targeted compounds. In order to explain the highly-efficient TADF behavior observed in compounds 1 and 2, the “triplet reservoir” mechanism has been proposed. In addition, the fluorescence rates of all six compounds are very large, in 10(7)-10(8) orders of magnitude. According to the present calculations, it is a reasonable assumption that the newly designed compounds 3-6 could be considered as the potential TADF emitters, which needs to be further verified by experimental techniques.

First author: Xia, YY, Regional Susceptibility in VCD Spectra to Dynamic Molecular Motions: The Case of a Benzyl -Hydroxysilane, CHEMPHYSCHEM, 19, 561, (2018)
Abstract: Experimental and theoretical studies of the vibrational circular dichroism (VCD) spectrum of 3-methyl-1-(methyldiphenlsilyl)-1-phenylbutan-1-ol, whose absolute configuration is key to elucidating the Brook rearrangement of tertiary benzylic -hydroxylsilanes, are presented. It is found that the entire OH-bending region in this spectruma region that provides important marker bandscannot be reproduced at all by standard theoretical approaches even though other regions are well described. Using a novel approach to disentangle contributions to the rotational strength of these bands, internal coordinates are identified that critically influence the appearance of this part of the spectrum. We show that the agreement between experiment and theory is greatly improved when structural dynamics along these coordinates are explicitly taken into account. The general applicability of the approach underlines its usefulness for structurally flexible chiral systems, a situation that is more the rule rather than the exception.

First author: Tuscher, L, A General Route to Metal-Substituted Dipnictenes of the Type [L(X)M](2)E-2, CHEMISTRY-A EUROPEAN JOURNAL, 24, 3241, (2018)
Abstract: Two equivalents of LGa (L=HC[C(Me)N(2,6-iPr(2)C(6)H(3))](2)) reacted with PX3 (X=Cl, Br) with insertion into two P-X bonds and formation of [L(X)Ga](2)PX (X= Cl 1, Br 2), whereas the analogous reaction with AsCl3 occurred with twofold insertion and subsequent elimination of LGaCl2 and formation of the Ga-substituted diarsene [L(Cl)Ga](2)As-2 (3). Analogous findings were observed in the reactions with Me2NAsCl2, yielding the unsymmetrically-substituted diarsene [L(Cl)Ga]As=As[Ga(NMe2)L] (4). The reaction of As(NMe2)(3) with LGa gave [L(Me2N)Ga](2)As-2 (5) after heating at 165 degrees C for five days, whereas the reaction with LAl gave [L(Me2N)Al](2)As-2 (6) after heating at only 80 degrees C for one day. Finally, two equivalents of LGa reacted with Bi(NEt2)(3) to give [L(Et2N)Ga](2)Bi-2 (7). Complexes 1-7 were characterized by NMR spectroscopy (H-1, C-13, P-31), elemental analysis, and single-crystal X-ray diffraction (except for 1 and 5). The bonding situations in 4, 6, and 7 were analyzed by quantum chemical calculations.

First author: Nowak, PM, Thermodynamics of acid-base dissociation of several cathinones and 1-phenylethylamine, studied by an accurate capillary electrophoresis method free from the Joule heating impact, JOURNAL OF CHROMATOGRAPHY A, 1539, 78, (2018)
Abstract: Capillary electrophoresis is often used to the determination of the acid-base dissociation/deprotonation constant (pK(a)), and the more advanced thermodynamic quantities describing this process (Delta H degrees, -T Delta S degrees). Remarkably, it is commonly overlooked that due to insufficient dissipation of Joule heating the accuracy of parameters determined using a standard approach may be questionable. In this work we show an effective method allowing to enhance reliability of these parameters, and to estimate the magnitude of errors. It relies on finding a relationship between electrophoretic mobility and actual temperature, and performing pK(a) determination with the corrected mobility values. It has been employed to accurately examine the thermodynamics of acid-base dissociation of several amine compounds – known for their strong dependency of pK(a) on temperature: six cathinones (2-methylmethcathinone, 3-methylmethcathinone, 4-methylmethcathinone, alpha-pyrrolidinovalerophenone, methylenedioxypyrovalerone, and ephedrone); and structurally similar 1-phenylethylamine. The average pK(a) error caused by Joule heating noted at 25 degrees C was relatively small – 0.04-0.05 pH unit, however, a more significant inaccuracy was observed in the enthalpic and, in particular, entropic terms. An alternative correction method has also been proposed, simpler and faster, but not such effective in correcting Delta H degrees/-T Delta S degrees terms. The corrected thermodynamic data have been interpreted with the aid of theoretical calculations, on a ground of the enthalpy-entropy relationships and the most probable structural effects accounting for them. Finally, we have demonstrated that the thermal dependencies of electrophoretic mobility, modelled during the correction procedure, may be directly used to find optimal temperature providing a maximal separation efficiency.

First author: Pecher, L, Bond Insertion at Distorted Si(001) Subsurface Atoms, INORGANICS, 6, 78, (2018)
Abstract: Using density functional theory (DFT) methods, we analyze the adsorption of acetylene and ethylene on the Si(001) surface in an unusual bond insertion mode. The insertion takes place at a saturated tetravalent silicon atom and the insight gained can thus be transferred to other saturated silicon compounds in molecular and surface chemistry. Molecular orbital analysis reveals that the distorted and symmetry-reduced coordination of the silicon atoms involved due to surface reconstruction raises the electrophilicity and, additionally, makes certain sigma bond orbitals more accessible. The affinity towards bond insertion is, therefore, caused by the structural constraints of the surface. Additionally, periodic energy decomposition analysis (pEDA) is used to explain why the bond insertion structure is much more stable for acetylene than for ethylene. The increased acceptor abilities of acetylene due to the presence of two pi*-orbitals (instead of one pi*-orbital and a set of pi*(C-H) orbitals for ethylene), as well as the lower number of hydrogen atoms, which leads to reduced Pauli repulsion with the surface, are identified as the main causes. While our findings imply that this structure might be an intermediate in the adsorption of acetylene on Si(001), the predicted product distributions are in contradiction to the experimental findings. This is critically discussed and suggestions to resolve this issue are given.

First author: Ohmori, M, Fabrication of field-effect transistor utilizing oriented thin film of octahexyl-substituted phthalocyanine and its electrical anisotropy based on columnar structure, JAPANESE JOURNAL OF APPLIED PHYSICS, 57, 78, (2018)
Abstract: Field-effect transistors with molecularly oriented thin films of metal-free non-peripherally octahexyl-substituted phthalocyanine (C6PcH(2)), which characteristically form a columnar structure, have been fabricated, and the electrical anisotropy of C6PcH(2) has been investigated. The molecularly oriented thin films of C6PcH(2) were prepared by the bar-coating technique, and the uniform orientation in a large area and the surface roughness at a molecular level were observed by polarized spectroscopy and atomic force microscopy, respectively. The field effect mobilities parallel and perpendicular to the column axis of C6PcH(2) were estimated to be (1.54 +/- 0.24) x 10(-2) and (2.10 +/- 0.23) x 10(-3)cm(2)V(-1) s(-1), respectively. The electrical anisotropy based on the columnar structure has been discussed by taking the simulated results obtained by density functional theory calculation into consideration.

First author: Zhao, ZY, A recognition mechanism study: Luminescent metal-organic framework for the detection of nitro-explosives, JOURNAL OF MOLECULAR GRAPHICS & MODELLING, 80, 132, (2018)
Abstract: This article presents a recognition mechanism for nitro-explosives by the luminescent metal-organic framework 1 (LMOF-1) with the aid of density functional theory (DFT) and time-dependent density functional theory (TDDFT). The behavior of hydrogen bonding between the LMOF-1 and nitro-explosives in the S-1 state is closely associated with the fluorescence properties of the LMOF-1. In our research, we calculated the geometric configuration, H-1 NMR and IR spectra of the Complex 2 formed by LMOF-1 and nitrobenzene in the So and S-1 states. The results showed that the hydrogen bond in the S-1 state was increased, which was unfavorable for the luminescence of LMOF-1. Furthermore, the fluorescence rate of LMOF-1 decreased after encapsulating nitrobenzene into it. These calculated results collectively suggest that LMOF-1 is a potential fluorescence sensor for the detection of nitro-explosives. This research was aiming to provide a better understanding of the recognition mechanism by LMOFs for nitro-explosives.

First author: Chaudhuri, RG, Visible light active 2D C3N4-CdS hetero-junction photocatalyst for effective removal of azo dye by photodegradation, MATERIALS RESEARCH EXPRESS, 5, 132, (2018)
Abstract: Ahetero-junction two dimensional photocatalyst that consists of organic semiconductor carbon nitride (C3N4) and inorganic semiconductor CdS, which acts as the light harvesting units and heterogeneous catalyst, was developed for the degradation of azo dye methyl orange (MO). Both materials are visible light active semiconductor. So the effective band gap of this heterojunction materials does not significantly change the visible light activity, but the injection of electrons from excited C3N4 to CdS increases the stability of hole-electron pair and that ultimately enhances the photocatalytic activity. This heterojunction catalyst finally can remove 97% of dyes and that is comparatively higher than individual pure materials. Finally, by using DFT analysis the band structure and the level diagrams of this photocatalyst are also analyzed.

First author: Klumpp, S, Photoabsorption of the molecular IH cation at the iodine 3d absorption edge, PHYSICAL REVIEW A, 97, 132, (2018)
Abstract: Yields of atomic iodine Iq+ (q >= 2) fragments resulting from photoexcitation and photoionization of the target ions IH+ and I+ have been measured in the photon-energy range 610-680 eV, which comprises the thresholds for iodine 3d ionization. The measured ion-yield spectra show two strong and broad resonance features due to the excitation of the 3d(3/2,5/2) electrons into epsilon f states rather similar for both parent ions. In the 3d pre-edge range, excitations into (np pi)-like orbitals and into an additional sigma* orbital are found for IH+, which have been identified by comparison of the atomic I+ and molecular IH+ data and with the help of (time-dependent) density functional theory (DFT) and atomic Hartree-Fock calculations. The (5p pi) orbital is almost atomlike, whereas all other resonances of the IH+ primary ion show a more pronounced molecular character, which is deduced from the chemical shifts of the resonances and the theoretical analysis.

First author: Martinez, JP, Acylation of dimethyl maleate photocatalyzed by decatungstate anion: insights into the hydrogen atom transfer reaction mechanism, RESEARCH ON CHEMICAL INTERMEDIATES, 44, 2061, (2018)
Abstract: Polyoxometalates arise as significant catalysts in the field of organic chemistry due to their diverse properties and functions. Recent progress based on experimental evidence and density functional theory (DFT) calculations provides valuable information to demystify the chemistry of decatungstate anion, W10O32 (4-). Particularly, functionalization of aldehydes by homolytic C-H bond cleavage can be efficiently achieved when it is catalyzed by this polyoxometalate. Two reaction mechanisms have been formulated to account for the role of W10O32 (4-) in organic chemical reactions: the single electron transfer and the hydrogen atom transfer (HAT) mechanisms. In this contribution, the HAT pathway for the acylation of dimethyl maleate is experimentally and quantum-chemically explored in detail. Results based on DFT calculations under the unrestricted formalism suggest that the acylation occurs in a barrierless process upon the formation of the lowest-in-energy triplet excited state of W10O32 (4-). These outcomes agree well with the experimental evidence since the acylated adduct was produced at a 90% yield; in this regard, side reactions like radical couplings and decarbonylation resulted in less competitiveness. The current work may therefore help in the comprehension of the mechanistic details leading to the synthesis of organic compounds photocatalyzed by polyoxometalates, even under solar radiation.

First author: He, MH, Metal-to-Ligand Charge-Transfer-based Visual Detection of Alkaline Phosphatase Activity, ANALYTICAL SCIENCES, 34, 341, (2018)
Abstract: The ability to directly detect alkaline phosphatase (ALP) activity in undiluted serum samples is of great importance for clinical diagnosis. In this work, we report the use of the distinctive metal-to-ligand charge-transfer (MLCT) absorption properties of the Cu(BCA)(2)(+) (BCA = bicinchoninic acid) reporter for the visual detection of ALP activity. In the presence of ALP, the substrate ascorbic acid 2-phosphate (AAP) can be enzymatically hydrolyzed to release ascorbic acid (AA), which in turn reduces Cu2+ to Cu+. Subsequently, the complexation of Cu+ with the BCA ligand generates the chromogenic Cu(BCA)(2)(+) reporter, accompanied by a color change of colorless-to-purple of the solution with a sharp absorption band at 562 nm. The underlying MLCT-based mechanism has been demonstrated on the basis of density functional theory (DFT) calculations. Needless of any sequential multistep operations and elaborately designed colorimetric probe, the proposed MLCT-based method allows for a fast and sensitive visual detection of ALP activity within a broad linear range of 20 – 200 mU mL(-1) (R-2 = 0.999), with a detection limit of 1.25 mU mL(-1). The results also indicate that it is highly selective and has great potential for the screening of ALP inhibitors in drug discovery. More importantly, it shows a good analytical performance for the direct detection of the endogenous ALP levels of undiluted human serum samples. Owing to the prominent simplicity and practicability, it is reasonable to conclude that the proposed MLCT-based method has a high application prospect in clinical diagnosis.

First author: Zhao, RD, Interlocking Mechanism between Molecular Gears Attached to Surfaces, ACS NANO, 12, 3020, (2018)
Abstract: While molecular machines play an increasingly significant role in nanoscience research and applications, there remains a shortage of investigations and understanding of the molecular gear (cogwheel), which is an indispensable and fundamental component to drive a larger correlated molecular machine system. Employing ab initio calculations, we investigate model systems consisting of molecules adsorbed on metal or graphene surfaces, ranging from very simple triple arm gears such as PF3 and NH3 to larger multiarm gears based on carbon rings. We explore in detail the transmission of slow rotational motion from one gear to the next by these relatively simple molecules, so as to isolate and reveal the mechanisms of the relevant intermolecular interactions. Several characteristics of molecular gears are discussed, in particular the flexibility of the arms and the slipping and skipping between interlocking arms of adjacent gears, which differ from familiar macroscopic rigid gears. The underlying theoretical concepts suggest strongly that other analogous structures may also exhibit similar behavior which may inspire future exploration in designing large correlated molecular machines.

First author: Zink, JR, Electrochemical Investigation of the Kinetics of Chloride Substitution upon Reduction of [Ru(porphyrin)(NO)Cl] Complexes in Tetrahydrofuran, CHEMELECTROCHEM, 5, 861, (2018)
Abstract: The electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran (THF). The complexes undergo one-electron irreversible reductions, which result in diffusion-limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron-donating porphyrin ligands favoring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR, and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates >0.40Vs(-1). The [Ru(por) (NO)(THF)](+/0) couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One-electron reductions of the [Ru(por)(NO)Cl] complexes result in approximately 10(18) enhancement of the rates of chloride loss.

First author: Bogdanovic, GA, Short Intramolecular O center dot center dot center dot O Contact in Some o-Dialkoxybenzene Derivatives Generates Efficient Hydrogen Bonding Acceptor Area, CRYSTAL GROWTH & DESIGN, 18, 1303, (2018)
Abstract: Statistical analysis of data extracted from the Cambridge Structural Database (CSD) has been used to investigate the crystal structure properties of odialkoxybenzene derivatives, compounds containing two ether oxygen acceptors in ortho positions of benzene ring. It has been shown that in more than 90% of cases, the fragment has predictable geometrical characteristics where the two ether oxygens form short interatomic O center dot center dot center dot O contact (2.57 A in average), while O-substitutents take trans position, both approximately coplanar with the benzene ring. Such arrangement of oxygen acceptors produces a large and uniform area of the negative electrostatic potential suitable for multiple hydrogen bonding. The acceptor abilities of the O center dot center dot center dot O system have been investigated by the statistical CSD analysis. The ab initio estimation of the interaction energy in the dimer of o-dimethoxybenzene (DMB) and H2O, employed as a model system, is achieved via high-level electron correlation CCSD(T) calculation with the complete basis set extrapolation. The interaction energy is estimated to be 6.5 kcal/mol. The results indicate the existence of a very flat potential the region between methoxy oxygens and that DMB water is a highly flexible system. The structural role of the O center dot center dot center dot O acceptor system is particularly interesting considering its ability to form multiple hydrogen bonding

First author: Zhu, HC, Adsorption orientation effects of porphyrin dyes on the performance of DSSC: Comparison of benzoic acid and tropolone anchoring groups binding onto the TiO2 anatase (101) surface, APPLIED SURFACE SCIENCE, 433, 1137, (2018)
Abstract: A new porphyrin dye with tropolone anchoring group showing superior stability but lower efficiency versus the promising dye YD2-o-C8 with benzoic acid anchoring group was theoretically investigated for the first time. A series of important parameters related to the efficiency of DSSC were calculated to explore the nature of the experimentally observed lower efficiency and superior stability of tropolone-based solar cells. We found these two dyes with different anchoring groups show comparable electron injection and dye regeneration process. Interestingly, the red-shifted absorption spectrum, relatively weaker ability of releasing protons, and the larger conduction band energy shift of tropolone-based dyes all demonstrated it should show better performance than the benzoic acid dyes, which contradicts with the experimental results. However, through investigating the interaction between the porphyrin dye and the semiconductor by analyzing the electron localization function of the porphyrin dye and preforming energy decomposition analysis, we found that the direction of lone-pair electrons of carbonyl oxygen in the tropolone-based dye makes the dye prefer to adsorb on the surface in an inclined way, in contrary to the benzoic acid-based dye that favored a vertical adsorption. The inclined adsorption could significantly accelerate the charge recombination process between the injected electrons and the oxidized dye, leading to a decreased efficiency of DSSC.

First author: Chong, DP, MP2 or B3LYP: computed bond distances compared with CCSD(T)/cc-pVQZ, CANADIAN JOURNAL OF CHEMISTRY, 96, 336, (2018)
Abstract: The equilibrium bond lengths of 41 small molecules are calculated by Gaussian09 and ADF2013 programs. We use five different basis sets: 6-31G*, cc-pVDZ, 6-311G+(2d, p), cc-pVTZ, and cc-pVQZ, for six different methods: Hartree-Fock, MP2, MP3, CCSD, CCSD(T), and B3LYP. The reliability of each level of theory on 89 bond lengths compared with CCSD(T)/cc-pVQZ is examined in terms of the mean absolute deviation. In particular, basis set dependence of the relative reliability of the two popular methods MP2 versus B3LYP is important to computational chemists. In addition, the efficient even-tempered basis set of Slater-type orbital called et-pVQZ, available in the ADF2013 program, is tested with the popular density functional B3LYP.

First author: Wilkin, OM, How Inert, Perturbing, or Interacting Are Cryogenic Matrices? A Combined Spectroscopic (Infrared, Electronic, and X-ray Absorption) and DFT Investigation of Matrix-Isolated Iron, Cobalt, Nickel, and Zinc Dibromides, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 1994, (2018)
Abstract: The interactions of FeBr2, CoBr2, NiBr2, and ZnBr2 with Ne, Ar, Kr, Xe, CH4, and N-2 matrices have been investigated using IR, electronic absorption, and X-ray absorption spectroscopies as well as DFT calculations. ZnBr2 is linear in all of the matrices. NiBr2 is linear in all but N-2 matrices, where it is severely bent. For FeBr2 and CoBr2 there is a more gradual change, with evidence of nonlinearity in Xe and CH4 matrices as well as N-2. In the N-2 matrices, the presence of nu(NN) modes blue-shifted from the “free” N-2 values indicates the presence of physisorbed species, and the magnitude of the blue shift correlates with the shift in the nu(3) mode of the metal dibromide. In the case of NiCl2 and NiBr2, chemisorbed species are formed after photolysis, but only if deposition takes place below 10 K. There was no evidence for chemisorbed species for NiF2 and FeBr2, and in the case of CoBr2 the evidence was not strong.

First author: Hernandez, E, Catalytic Reduction of Nitrous Oxide by the Low-Symmetry Pt-8 Cluster, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 2209, (2018)
Abstract: The search for a catalyst for the reduction of nitrous oxide (N2O) is now imperative, as this molecule is a very dangerous pollutant. We found that the low-symmetry Pt-8 cluster presents multiple reaction pathways for N2O rupture, which are regioselective. This result was revealed by means of density functional theory calculations within the zero-order-regular approximation, ZORA, explicitly including relativistic effects. It is further proved that Pt-8 is a competitive N2O catalyst compared to sub-nanometric rhodium clusters, obtaining similar reaction barriers. The hot adsorption site, a tip atom of Pt-8, and the rotation of the N2O molecule over the metallic cluster promote the formation of a frustrated bridge activated transition state, Pt-8-N2O. This transition structure yields to spontaneous dissociation of N2O without bridge formation. Along this catalytic process, rearrangements within the metal cluster take place, preserving its stability. Moreover, in addition to being important attributes of the Pt-8 particle in the N2O reduction, fluxionality and multiple reaction pathways may also prevent poisoning effects. Overall, this differs from reported results for more symmetric metal particles also used as catalysts.

First author: Moreno-Vicente, A, Formation of C-2v-C-72(11188)Cl-4: A Particularly Stable Non-IPR Fullerene, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 2288, (2018)
Abstract: Halogenation has been one of the most used strategies to explore the reactivity of empty carbon cages. In particular, the higher reactivity of non-IPR fullerenes, i.e., those fullerenes that do not satisfy the isolated pentagon rule (IPR), has been used to functionalize and capture these less stable fullerenes. Here, we have explored the stability of the non-IPR isomer C-72(11188) with C-2v symmetry, which is topologically linked to the only IPR isomer of C-70, as well as its reactivity to chlorination. DFT calculations and Car-Parrinello molecular dynamics simulations suggest that chlorination takes places initially in nonspecific sites, once carbon cages are formed. When the temperature in the arc reactor decreases sufficiently, Cl atoms are trapped on the fullerene surface, migrating from not-so-favored positions to reach the most favored sites in the pentalene. We have also discussed why cage C-2v-C-72(11188) is found to take four chlorines, whereas cage C-1-C-74(14049) is observed to capture 10 of them, even though these two fullerenes are closely related by a simple C-2 insertion.

First author: Zhang, J, Promising heterocyclic anchoring groups with superior adsorption stability and improved IPCE for high-efficiency noncarboxyl dye sensitized solar cells: A theoretical study, ORGANIC ELECTRONICS, 54, 104, (2018)
Abstract: The strong adsorption stability and significantly improved incident photon-to-current conversion efficiency (IPCE) of the new anchoring group hydantoin moiety (HY) introduced into D-A-pi-A dyes for dye sensitized solar cells (DSSCs), compared with the commonly used anchoring group cyanoacrylic acid (CA), were investigated through DFT/TD-DFT calculations on the dye@(TiO2)(48) interfacial electron dynamics for the first time. It is found that the dissociative bidentate bridging mode with a hydrogen bond is the most stable adsorption configuration on the TiO2 anatase (101) surface for HY-based dyes and could produce a dramatic increase in adsorption energy compared with that of CA-based dye. Energy decomposition analysis (EDA) was performed to elucidate the different adsorption energies for the different anchoring groups with different adsorption configurations. A simplified Tamm-Dancoff density functional theory approach (sTDA-DFT), proposed by Grimme, was used to calculate the excitation energy and oscillator strength of the sensitizers after adsorption. The calculated results indicate that the adsorption mode has significant effects on the absorption spectrum. In contrast to CA-based dye, HY-based dye exhibits comparable light harvesting ability after adsorption due to the combined effects of different adsorption configurations, although the isolated dye exhibits a blue-shifted absorption spectrum. It shows a similar electron injection and dye regeneration driving force, but the significantly larger coupling between the sensitizer and the semiconductor for HY-based dye is the main reason for its improved IPCE. Moreover, to further improve the light-harvesting ability of the dyes, two other heterocyclic groups, rhodanine (RD) and 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (MT), were introduced into the dyes as anchoring groups. The results show that dyes with the RD anchoring group exhibited significantly enhanced light harvesting ability with the red-shifted absorption spectrum, higher electron injection efficiency with larger electronic coupling and strong adsorption ability; thus, it is worthy of experimental synthesis for use in high-performance dye sensitized solar cells.

First author: Zouchoune, B, Why is bis-indenylchromium a dimer? A DFT investigation, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 858, 47, (2018)
Abstract: Unsubstituted bis-indenylchromium has been shown to be a dimer, Cr-2(Ind)(4), whereas the monomeric sandwich-type structure, Cr(Ind)(2), has been only observed for substituted relatives. DFT calculations indicate that dimerization allows the building of a quadruple Cr-Cr bond whereas it can still participate in five formal 2-electron metal-ligand bonds. Despite of this apparently favorable situation with respect to dimer stability, the energetic balance in favor of the dimer is computed not to be very large. Calculations on a series of related Cr, Mn, Fe and Co relatives indicate that Cr-2(Ind)(4) appears unique in terms of its stability relatively to its monomer. However, dimeric species such as Cr-2(Cp)(2)(Ind)(2), Cr-2(Cp)(4) or Mn-2(Ind)(4) appear to be not that much unstable relatively to their monomer for being observed under some specific circumstances.

First author: Nasser, N, Oxygen atom transfer to platinum(II): A 2-pyridyloxaziridine and a 2-pyridylnitrone as potential oxygen atom donors, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 858, 67, (2018)
Abstract: The oxygen atom transfer reactions of 2-pyridyl-N-t-butyloxaziridine, pyox, with the dimethylplatinum(II) complex [Pt2Me4(mu-SMe2)(2)], 1, have been studied. In the presence of methanol or water, proton coupled oxygen atom transfer occurs, with displacement of dimethylsulfide ligands by the product ligand 2-pyridyl-N-t-butylmethanimine, pyim, to give initially the complexes [Pt(OH)(OR)Me-2(pyim)], R = Me or H, respectively, which were slowly oxidized further to give the binuclear picolinate complexes [Pt-2(mu-OR)(2)Me-4(2-pyCO(2))(2)], R = Me or H, respectively, and t-butylamine. The complex [Pt(OH)(2)Me-2(pyim)] is also formed by oxidative addition of H2O2 to [PtMe2(pyim)], and the complex [Pt-2(mu-OMe)(2)Me-4(2-pyCO(2))(2)] is also formed by reaction of 2-pyridyl-N-t-butylnitrone, pyNO, with complex 1 in methanol solution. The structures of several of the above complexes, as well as model complexes [PtXRMe2(pyim)], X = R = Cl; X = Cl or I, R = Me; X = Cl, R = CH2Cl, [PtMe(2-pyCO(2))(dmso)] and [PtCl2(SMe2)(pyNO)], were determined to aid in characterization of new compounds. In the absence of a protic solvent, the oxa-ziridine group is still activated on reaction of pyox with complex 1 but a more complex mixture of products is formed.

First author: Artem’ev, AV, Bright green-to-yellow emitting Cu(I) complexes based on bis(2-pyridyl)phosphine oxides: synthesis, structure and effective thermally activated-delayed fluorescence, DALTON TRANSACTIONS, 47, 2701, (2018)
Abstract: A family of brightly luminescent dinuclear complexes of [Cu(mu(2)-X)((NN)-N-boolean AND)](2) type (X = I or SCN) has been synthesized in 76-90% yields by the reaction of bis(2-pyridyl)phosphine oxides ((NN)-N-boolean AND) with the corresponding Cu(I) salts. The X-ray diffraction study reveals that the Cu2I2 core of the [Cu(mu(2)-I)((NN)-N-boolean AND)](2) complexes has either a butterfly-or rhomboid-shaped structure, while the eighth-membered [Cu((SCN)(NCS))Cu] ring in the [Cu-2(SCN)(2)((NN)-N-boolean AND)](2) complexes is nearly planar. In the solid state, these compounds exhibit a strong green-to-yellow emission (lambda(em)(max) = 536-592 nm) with high PLQYs (up to 63%) and short lifetimes (1.9-10.0 mu s). The combined photophysical and DFT study indicates that the ambient-temperature emission of the complexes obtained can be assigned to the thermally activated-delayed fluorescence (TADF) from the (1)(M + X)LCT excited state, while at 77 K, phosphorescence from the (3)(M + X) LCT state is likely observed.

First author: Liu, YD, Recognition of Melamine by Chromium Tricarbonyl (Thio)barbituric Acid Derivatives: Theoretical Insight into Multiple Hydrogen-Bond Modes, CHEMISTRYSELECT, 3, 2404, (2018)
Abstract: Melamine-contaminated milk products continually emerge in recent years and cause disease. Therefore, how to swiftly and efficiently differentiate melamine from protein becomes an urgent issue. In this work, three neutral receptors p-dimethylaminobenzaldehyde-barbituric acid chromium tricarbonyl (PBC), p-dimethylaminobenzaldehyde-2-thiobarbituric acid chromium tricarbonyl (2-PTC), and p-dimethylaminobenzaldehyde-4-thiobarbituric acid chromium tricarbonyl (4-PTC) were constructed for recognition of melamine, and their non-covalent interactions were systematically studied using density functional theory and several theoretical analysis methods. Our results suggest that melamine can be theoretically recognized by receptors PBC and 2-/4-PTC due to the formation of multiple hydrogen bonds upon complexation, indicating the good detecting capability of the Cr(CO)(3)-based (thio)barbituric acid moiety. Nevertheless, the IR analysis results show the receptors 2-/4-PTC cannot distinctly detect melamine by evident frequency shift of metal carbonyl. Therefore, we further proposed a structural modification strategy by introducing the cyano group into the (thio)barbituric acid moiety, and the corresponding IR analysis exhibits large frequency shift of metal carbonyl, indicating the potential of modified receptors in the infrared neutral molecular recognition of melamine. The results reported herein will be very useful in the design of potent receptors distinguishing melamine from protein.

First author: Dalgleish, S, Controlling the crystallinity and crystalline orientation of “shuttlecock” naphthalocyanine films for near-infrared optoelectronic applications, JOURNAL OF MATERIALS CHEMISTRY C, 6, 1959, (2018)
Abstract: The thin film properties of tin(ii) 2,3-naphthalocyanine (SnNPc) were interrogated and various strategies for controlling the crystallinity and crystalline orientation within the films were assessed. SnNPc is shown to crystallize in the space group P2(1)/c (Z = 4), where the molecular arrangement consists of alternating layers of concave and convex overlap, induced by the out-of-plane Sn atoms, resulting in a 3D slipped–stack network structure analogous to that reported for Phase I of titanyl phthalocyanine. The thin films were studied by X-ray diffraction, atomic force microscopy and absorption spectroscopy and are highly sensitive not just to the conditions during growth, but also to substrate pre- and post-deposition treatment. While the films grown at room temperature were largely amorphous, the crystallinity was enhanced with substrate temperature, with the molecules orienting in a standing molecular geometry. A thin layer of 3,4:9,10-perlenetetracarboxylic dianhydride induces a lying molecular geometry of the same polymorph as that of the single crystal, while different polymorphs are accessible through solvent vapor annealing of amorphous films. Transient photocurrent measurements showed a dramatic improvement in photodetector device bandwidth for the lying molecular geometry, which was attributed to enhanced photoconductivity along the -stacking axis, while solvent vapor annealing could be used to tune the photosensitivity across the near-infrared region.

First author: Schneider, FSS, Bond Analysis in Dihalogen-Halide and Dihalogen-Dimethylchalcogenide Systems, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 6, 1007, (2018)
Abstract: The bonding in mixed chalcogen/halogen three-body systems of general formula XIY (X = Cl, Br, I; Y = I-, EMe2; E = S, Se, Te) is theoretically examined by using different methodologies, namely: charge-displacement (CD) analysis, which quantifies the electronic flux throughout the whole adduct; the energy decomposition analysis combined with natural orbital for chemical valence (EDA-NOCV) method; and zeroth order symmetry adapted perturbation theory (SAPT0), where the latter two methods decompose the contributions of the interaction energy between XI and Y into physically meaningful terms. In the solid state, the distribution of the relative elongations of the two bonds ((XI) and (IY)) in the three-body systems examined here can be rationalized in terms of only one common equation derived from the bond-valence model. According to CD and EDA-NOCV, the charge transfer between the two fragments does not depend on the exact nature of the atoms involved, but only on the values of (XI) and (IY), with a variability of 0.05 e, and on the total charge of the system. On the other hand, using the SAPT0 method and computing the polarization-free value of the charge transfer between the two fragments, the results are the same for all of the systems with the same (XI) and (IY), irrespectively not only of the nature of the atoms, but also of the total charge of the system (anionic and neutral).

First author: Pan, S, Stable NCNgNSi (Ng= Kr, Xe, Rn) Compounds with Covalently Bound C-Ng-N Unit: Possible Isomerization of NCNSi through the Release of the Noble Gas Atom, CHEMISTRY-A EUROPEAN JOURNAL, 24, 2879, (2018)
Abstract: Although the noble gas (Ng) compounds with either Ng-C or Ng-N bonds have been reported in the literature, compounds containing both bonds are not known. The first set of systems having a C-Ng-N bonding unit is predicted herein through the analysis of stability and bonding in the NCNgNSi (Ng= Kr-Rn) family. While the Xe and Rn inserted analogues are thermochemically stable with respect to all dissociation channels, but for the one producing CNSiN and free Ng, NCKrNSi has another additional three-body dissociation channel, NCKrNSi -> CN+ Kr+ NSi, which is exergonic by-9.8 kcal mol(-1) at 298 K. This latter dissociation can be hindered by lowering the temperature. Moreover, the NCNgNSi -> Ng+ CNSiN dissociation is also kinetically prohibited by a quite high free energy barrier ranging from 25.2 to 39.3 kcal mol(-1), with a gradual increase in going from Kr to Rn. Therefore, these compounds are appropriate candidates for experimental realization. A detailed bonding analysis by employing natural bond orbital, electron density, energy decomposition, and adaptive natural density partitioning analyses indicates that both Ng-N and C-Ng bonds in the title compounds are covalent in nature. In fact, the latter analysis indicates the presence of delocalized 3c-3e s-bond within the C-Ng-N moiety and a totally delocalized 5c-2e s-bond in these compounds. This is an unprecedented bonding characteristic in the sense that the bonding pattern in Ng inserted compounds is generally represented as the presence of covalent bond in one side of Ng, and the ionic interaction in the other side. Further, the dissociation of Ng from NCNgNSi facilitates the formation of a higher energy isomer of NCNSi, CNSiN, which cannot be formed from bare NCNSi as such, because of the very high free energy barrier associated with the isomeric transformation. Therefore, in the presence of Ng atoms it might be possible to detect the high energy isomer.

First author: Ardizzoia, GA, Homoleptic complexes of divalent metals bearing N,O-bidentate imidazo [1,5-a] pyridine ligands: Synthesis, X-ray characterization and catalytic activity in the Heck reaction, INORGANICA CHIMICA ACTA, 471, 384, (2018)
Abstract: Two imidazo[1,5-a] pyridine-based ligands, namely 2-(1-phenylimidazo[1,5-a] pyridin-3-yl) phenol (N, OH-L-Ph) and 2-(1-methylimidazo[1,5-a] pyridin-3-yl) phenol (N, OH-L-Me) have been reacted with different divalent metals (M = Co, Cu, Ni, Pd) to obtain the following complexes [Co(N, O-L-Ph)(2)] (1), [Cu(N, O-L-Ph)(2)] (2), [Ni(N, O-L-Ph)(2)] (3), [Pd(N, O-L-Ph)(2)] (4), [Co(N, O-L-Me)(2)] (5), [Cu(N, O-L-Me)(2)] (6), [Ni(N, O-L-Me)(2)] (7) and [Pd (N, O-LMe)(2)] (8). These homoleptic complexes showed the monoanionic ligands to be coordinated in a N, Obidentate mode via the pyridine-like nitrogen of the imidazo[1,5-a] pyridine skeleton and the phenolic oxygen. The coordination mode of the ligands was confirmed by the single-crystal X-ray structure analysis of [Co(N, O-L-Ph)(2)] (1) and [Pd(N, O-L-Me)(2)] (8). The palladium compounds [Pd(N, O-LPh)(2)] (4) and [Pd(N, O-LMe)(2)] (8) proved to be good catalysts in the Heck reaction between iodobenzene and different olefins.

First author: von Eschwege, KG, Iron phenanthrolines: A density functional theory study, INORGANICA CHIMICA ACTA, 471, 391, (2018)
Abstract: A comprehensive DFT study on the most extensive series of 1,10-phenanthroline iron complexes, to date, is reported here. Results have relevance to fields of active research; amongst others that of metal-to-ligand charge transfer complexes and of redox indicators. ADF geometry optimizations at the BP86/TZP level for a series of twenty-four iron complexes with substituted phenanthrolines for which electrochemical data is available, were obtained. Visible light excitations in these MLCT complexes involve transitions from the upper three metal based HOMO’s to the lower five ligand based LUMO’s. With high accuracy calculated HOMO energies, ionization potentials and Mulliken electronegativities are linearly correlated with experimentally obtained redox data from different studies. Molecular orbital renderings and TDDFT computed oscillators are illustrated to closely predict and explain experimental data. As part of the establishment of a larger data base, also for iron phenanthrolines an experimentally vindicated basis is now presented by which its chemical properties may theoretically be ascertained before embarking on more demanding experimental procedures.

First author: Alvarez, JR, Mapping Base Modifications in DNA by Transverse-Current Sequencing, PHYSICAL REVIEW APPLIED, 9, 391, (2018)
Abstract: Sequencing DNA modifications and lesions, such as methylation of cytosine and oxidation of guanine, is even more important and challenging than sequencing the genome itself. The traditional methods for detecting DNA modifications are either insensitive to these modifications or require additional processing steps to identify a particular type of modification. Transverse-current sequencing in nanopores can potentially identify the canonical bases and base modifications in the same run. In this work, we demonstrate that the most common DNA epigenetic modifications and lesions can be detected with any predefined accuracy based on their tunneling current signature. Our results are based on simulations of the nanopore tunneling current through DNA molecules, calculated using nonequilibrium electron-transport methodology within an effective multiorbital model derived from first-principles calculations, followed by a base-calling algorithm accounting for neighbor current-current correlations. This methodology can be integrated with existing experimental techniques to improve base-calling fidelity.

First author: Szatylowicz, H, Dependence of the Substituent Effect on Solvent Properties, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 1896, (2018)
Abstract: The influence of a solvent on the substituent effect (SE) in 1,4-disubstituted derivatives of benzene (BEN), cyclohexa-1,3-diene (CHD), and bicyclo[2.2,2]octane (BCO) is studied by the use of polarizable continuum model method. In all X-R-Y systems for the functional group Y (NO2, COOH, OH, and NH2), the following substituents X have been chosen: NO2, CHO, H, OH, and NH2. The substituent effect is characterized by the charge of the substituent active region (cSAR(X)), substituent effect stabilization energy (SESE), and substituent constants sigma or F descriptors, the functional groups by cSAR(Y), whereas pi-electron delocalization of transmitting moieties (BEN and CHD) is characterized by a geometry based index, harmonic oscillator model of aromaticity. All computations were carried out by means of B3LYP/6-311++G(d,p) method. An application of quantum chemistry SE models (cSAR and SESE) allows to compare the SE in water solutions and in the gas phase. Results of performed analyses indicate an enhancement of the SE by water. The obtained Hammett-type relationships document different nature of interactions between Y and X in aromatic and olefinic systems (a coexistence of resonance and inductive effects) than in saturated ones (only the inductive effect). An increase of electric permittivity dearly enhances communications between X and Y for BEN and CHD systems.

First author: Knoppe, S, Role of Donor and Acceptor Substituents on the Nonlinear Optical Properties of Gold Nanoclusters, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 4019, (2018)
Abstract: In recent years, a large number of monolayer-protected clusters (MPCs) have been studied by means of single crystal structure characterization. A central aspect of research on MPCs is the correlation of their interesting optical properties with structural features and the formulation of a theoretical framework that allows interpretation of their unique properties. For this, superatom and jellium models have been proven successful. Little attention, however, has been paid to the influence of the protecting ligands. Here, we investigate the effect of changes in [Au-25(SR)(18-x)(SR’)(x)](-), where SR’ represents a para-substituted thiophenolate derivative (SPh-4-X). We computed the first hyperpolarizabilities, screening a broad range of substituents X. For [Au-25(SR)(17)(SR’)(1)](-) clusters, significant first hyperpolarizabilities were calculated, spanning 2 orders of magnitude depending on X. A strong dependence on the electron-donating/withdrawing properties of the substituent was found for para-substituted thiophenol ligands. Protonation of amine substituents leads to a change from donor to acceptor substitution, leading to a record setting contrast for nonlinear optical proton sensing. Furthermore, “push/pull” systems were considered where both an acceptor and a donor ligand were positioned at opposite ends of the cluster. This induces significant increase of the first hyperpolarizability through charge transfer. Overall, our results indicate that the right choice of ligand can significantly impact the (nonlinear) optical properties of MPCs. This adds a new component to the cluster chemist’s toolbox.

First author: Zierkiewicz, W, Aerogen bonds formed between AeOF(2) (Ae = Kr, Xe) and diazines: comparisons between sigma-hole and pi-hole complexes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 4676, (2018)
Abstract: The interaction between KrOF2 or XeOF2 and the 1,2, 1,3, and 1,4 diazines is characterized chiefly by a Kr/Xe center dot center dot center dot N aerogen bond, as deduced from ab initio calculations. The most stable dimers take advantage of the sigma-hole on the aerogen atom, wherein the two molecules lie in the same plane. The interaction is quite strong, as much as 18 kcal mol(-1). A second class of dimer geometry utilizes the pi-hole above the aerogen atom in an approximate perpendicular arrangement of the two monomers; these structures are not as strongly bound: 6-8 kcal mol(-1). Both sorts of dimers contain auxiliary CH center dot center dot center dot F H-bonds which contribute to their stability, but even with their removal, the aerogen bond energy remains as high as 14 kcal mol(-1). The nature and strength of each specific interaction is confirmed and quantified by AIM, NCI, NBO, and electron density shift patterns. There is not a great deal of sensitivity to the identity of either the aerogen atom or the position of the two N atoms in the diazine.

First author: Novakova Lachmanova, S, Correlation of electrochemical properties of expanded pyridinium compounds with their single molecule conductance, ELECTROCHIMICA ACTA, 264, 301, (2018)
Abstract: A series of four expanded pyridinium molecules were used to investigate the correlation between a single molecule conductance (electron transport) and redox (electron transfer) properties at the electrode vertical bar electrolyte interface. Quantum chemical calculations of the transmission functions using DFT and non-equilibrium Green’s function approach confirmed LUMO. mediated electron transport in the break junction experiment. Single molecule conductance data can be rationalized within the framework of the non. resonant tunneling mechanism. More interestingly, a linear correlation was found between the conductance values and the apparent electron transfer rate constants for three molecules of this series.

First author: Riesco-Dominguez, A, Trifluoromethyl Vinyl Sulfide: A Building Block for the Synthesis of CF3S-Containing Isoxazolidines, JOURNAL OF ORGANIC CHEMISTRY, 83, 1779, (2018)
Abstract: Trifluoromethyl vinyl sulfide, a potential building block for pharmaceutically and agrochemically relevant products, is prepared and used for the first time in high-pressure-mediated 1,3-dipolar cycloaddition reactions with nitrones to synthesize (trifluoromethyl)sulfanyl isoxazolidines.

First author: Pershina, V, Electronic structure and properties of MAu and MOH, where M = Tl and Nh: New data, CHEMICAL PHYSICS LETTERS, 694, 107, (2018)
Abstract: Properties of the MAu and MOH (M = Tl and element 113, Nh) molecules were calculated using the 2c-DFT method. The obtained data are needed for evaluation of reactivity of Nh studied by gas-phase chromatography experiments. Results show that Nh should be less reactive (or more volatile) than Tl, both with respect to gold and the hydroxyl group. The reason for that are strong relativistic effects on the valence 7s and 7p electron shells. In difference to the atoms, NhOH may be less volatile than TlOH due to its larger both dipole moment and anisotropic polarizability.

First author: Reta, D, The performance of density functional theory for the description of ground and excited state properties of inorganic and organometallic uranium compounds, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 857, 58, (2018)
Abstract: Molecular uranium complexes are the most widely studied in actinide chemistry, and make a significant and growing contribution to inorganic and organometallic chemistry. However, reliable computational procedures to accurately describe the properties of such systems are not yet available. In this contribution, 18 experimentally characterized molecular uranium compounds, in oxidation states ranging from III to VI and with a variety of ligand environments, are studied computationally using density functional theory. The computed geometries and vibrational frequencies are compared with X-ray crystallographic, and infra-red and Raman spectroscopic data to establish which computational approach yields the closest agreement with experiment. NMR parameters and UV-vis spectra are studied for three and five closed-shell U(VI) compounds respectively. Overall, the most robust methodology for obtaining accurate geometries is the PBE functional with Grimme’s D3 dispersion corrections. For IR spectra, different approaches yield almost identical results, which makes the PBE functional with Grimme’s D3 dispersion corrections the best choice. However, for Raman spectra the dependence on functional is more pronounced and no clear recommendation can be made. Similarly, for H-1 and C-13 NMR chemical shifts, no unequivocal recommendation emerges as to the best choice of density functional, although for spin-spin couplings, the LC-uPBE functional with solvent corrections is the best approach. No form of time-dependent density functional theory can be recommended for the simulation of the electronic absorption spectra of uranyl (VI) compounds; the orbitals involved in the transitions are not calculated correctly, and the energies are also typically unreliable. Two main approaches are adopted for the description of relativistic effects on the uranium centres: either a relativistic pseudopotential and associated valence basis set, or an all-electron basis set with the ZORA Hamiltonian. The former provides equal, if not better, agreement with experiment vs all-electron basis set calculations, for all properties investigated.

First author: Grosch, AA, Nature of Intramolecular Resonance Assisted Hydrogen Bonding in Malonaldehyde and Its Saturated Analogue, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 1813, (2018)
Abstract: The nature of resonance-assisted hydrogen bonds (RAHB) is still subject of an ongoing debate. We therefore analyzed the sigma and pi charge redistributions associated with the formation of intramolecular hydrogen bonds in malonaldehyde (MA) and its saturated analogue 3-hydroxypropanal (3-OH) and addressed the question whether there is a resonance assistance phenomenon in the sense of a synergistic interplay between the sigma and pi electron systems. Our quantum chemical calculations at the BP86/TZ2P level of theory show that the pi charge flow is indeed in line with the Lewis structure as proposed by the RAHB model. This typical rearrangement of charge is only present in the unsaturated system, and not in its saturated analogue. Resonance in the pi electron system assists the intramolecular hydrogen bond by reducing the hydrogen bond distance, and by providing an additional stabilizing component to the net bonding energy. The sigma orbital interaction plays an important role in the enhanced hydrogen bond strength in MA as well. However, there is no resonance assistance in the sense of an interplay between sigma charge transfer and pi polarization; sigma and pi contribute independently from each other.

First author: Bernard, GM, Methylammonium Cation Dynamics in Methylammonium Lead Halide Perovskites: A Solid-State NMR Perspective, JOURNAL OF PHYSICAL CHEMISTRY A, 122, 1560, (2018)
Abstract: In light of the intense recent interest in the methylammonium lead halides, CH3NH3PbX3 (X = Cl, Br, and I) as sensitizers for photovoltaic cells, the dynamics of the A methylammonium (MA) cation in these perovskite salts has been reinvestigated as a function of temperature via H-2, N-14 and Pb-207 NMR spectroscopy. In the cubic phase of all three salts, the MA cation undergoes pseudoisotropic tumbling (picosecond time scale). For example, the correlation time, tau(2), for the C-N axis of the iodide salt is 0.85 +/- 0.30 ps at 330 K. The dynamics of the MA cation are essentially continuous across the cubic H tetragonal phase transition; however, H-2 and N-14 NMR line shapes indicate that subtle ordering of the MA cation occurs in the tetragonal phase. The temperature dependence of the cation ordering is rationalized using a six-site model, with two equivalent sites along the c-axis and four equivalent sites either perpendicular or approximately perpendicular to this axis. As the cubic 4-tetragonal phase transition temperature is approached, the six sites are nearly equally populated. Below the tetragonal H orthorhombic phase transition, H-2 NMR line shapes indicate that the C-N axis is essentially frozen.

First author: Boussebbat, W, Theoretical aspect of the bonding in bis-chelate thiosemicarbazones nickel (II) complexes: A DFT study, JOURNAL OF MOLECULAR STRUCTURE, 1154, 19, (2018)
Abstract: The theoretical study was carried out on the nickel (II) complexes with the bidentatethiosemicarbazone ligands; aromatic and aliphatic presented in square planar geometries.

First author: Yang, B, Transition states of spin-forbidden reactions, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 4129, (2018)
Abstract: Spin-orbit coupling plays an important role in determining the mechanisms and kinetics of spin-forbidden reactions and many reactions exhibiting two-state reactivity. Spin-orbit coupling can allow the system to change its spin state, especially when potential energy surfaces (PESs) of two spin states approach each other. Here, we introduce a convenient new approximation method for locating stationary points on the lowest mixed-spin potential energy surface along a reaction pathway by using density functional calculations. The mixing of different spin states is achieved by introducing the spin-orbit coupling into the electronic Hamiltonian using a pre-defined coupling constant. Two examples are given using the new methodology: (a) a CO association reaction with the coordinatively unsaturated Fe(CO)(4) complex and (b) an alpha-H elimination reaction of a model complex containing W. We computed a Gibbs free energy of activation of 2.8 kcal mol(-1) for the CO association reaction, which is reasonably consistent with the experimentally measured reaction rate. For the H elimination reaction, the spin change occurs at a relatively low energy, and the present treatment allows one conclude that kinetics of the reaction can be reasonably well described without spin-orbit coupling.

First author: Andrella, NO, Metal Heptafluoroisopropyl (M-hfip) Complexes for Use as hfip Transfer Agents, ORGANOMETALLICS, 37, 422, (2018)
Abstract: New coinage-metal heptafluoroisopropyl (LnM-hfip) complexes are synthesized from the metal fluoride and inexpensive hexafluoropropene (M = Ag, Cu; L = PPh3, 2,2,6,6-tetramethylpiperidine (Htmp)). Reaction of the silver Htmp complex with a Ni dibromide complex led to efficient hfip transfer to afford L2NiBr(hfip) (L = 2-ethylpyridine). Treatment of the Ni-hfip complex with ZnPh2 gave the corresponding L2NiPh(hfip) complexes, which were investigated for reductive elimination of PhCF(CF3)(2). Although the desired reductive elimination proved unsuccessful, addition of carbon monoxide to L2NiPh(hfip) effected an efficient heptafluoroisopropyl carbonylative cross-coupling. Further, while the silver complex does not undergo hfip transfer to organic electrophiles, the copper complex (phen)(PPh3)Cu(hfip) (3b) effectively transfers the hfip unit to various substrates. We investigated the scope of 3b with acid chlorides toward the synthesis of perfluoroisopropyl aryl ketones. Additionally, reaction conditions for hfip transfer to p-fluorobenzyl bromide and p-fluorobenzaldehyde were identified. As a bonus, 3b was easily generated on a gram scale using commercially available copper hydride by taking advantage of a rapid hydrodefluorination to generate “Cu-F” in situ. Aspects of the observed reactivity are supported by DFT calculations.

First author: Zarifi, N, Crystal Structures and Electronic Properties of Xe-CI Compounds at High Pressure, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 2941, (2018)
Abstract: Crystal structure prediction techniques coupled with enthalpies obtained at 0 K from density functional theory calculations suggest that pressure can be used to stabilize the chlorides of xenon. In particular, XeCl and XeCl2 were calculated to become metastable by 10 GPa and thermodynamically stable with respect to the elemental phases by 60 GPa. Whereas at low pressures Cl-2 dimers were found in the stable phases, zigzag Cl chains were present in Cmcm XeCl at 60 GPa and atomistic chlorine comprised P6(3)/mmc XeCl and Ed (3) over barm XeCl2 at 100 GPa. A XeCl4 phase that was metastable at 100 GPa contained monomers, dimers, and trimers of chlorine. XeCl, XeCl2 and XeCl4, were metallic at 100 GPa, and at this pressure they were predicted to be superconducting below 9.0, 4.3, and 0.3 K, respectively. Spectroscopic properties of the predicted phases are presented to aid in their eventual characterization, should they ever be synthesized.

First author: Soulis, K, New luminescent copper(I) complexes with extended pi-conjugation, POLYHEDRON, 140, 42, (2018)
Abstract: While copper(I)-bis(diimine) complexes [Cu-I(L)(2)](+) are considered as potent substitutes for [Ru-II(bpy)(3)](2+), they exhibit low molar extinction coefficients with respect to ruthenium parent analogues. One interesting possibility to improve the light collection ability of [Cu-I(L)(2)](+) consists in increasing the length of the Cu-L dipole. In order to achieve this goal, we propose in this contribution to fuse aromatic rings onto the 2,9-di-nbutyl-1,10-phenanthroline core and examine how the properties of the corresponding copper(I) complexes are impacted. Electrochemical, absorption and emission properties are assessed; rewardingly, the envisioned approach was successful since extinction coefficients above 10,000 M-1.cm(-1) were measured. All copper(I) complexes remain photoluminescent, with emission maxima greatly varying from 725 to 815 nm, strongly affected by the molecular structures. A rationale to explain the variations of the emission quantum yields is proposed.

First author: Ji, LF, Theoretical study on the charge transport in single crystals of TCNQ, F-2-TCNQ and F-4-TCNQ, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 3784, (2018)
Abstract: 2,5-Difluoro-7,7,8,8-tetracyanoquinodimethane (F-2-TCNQ) was recently reported to display excellent electron transport properties in single crystal field-effect transistors (FETs). Its carrier mobility can reach 25 cm(2) V-1 s(-1) in devices. However, its counterparts TCNQ and F-4-TCNQ (tetrafluoro-7,7,8,8-tetracyanoquinodimethane) do not exhibit the same highly efficient behavior. To better understand this significant difference in charge carrier mobility, a multiscale approach combining semiclassical Marcus hopping theory, a quantum nuclear enabled hopping model and molecular dynamics simulations was performed to assess the electron mobilities of the F-n-TCNQ (n = 0, 2, 4) systems in this work. The results indicated that the outstanding electron transport behavior of F2-TCNQ arises from its effective 3D charge carrier percolation network due to its special packing motif and the nuclear tunneling effect. Moreover, the poor transport properties of TCNQ and F-4-TCNQ stem from their invalid packing and strong thermal disorder. It was found that Marcus theory underestimated the mobilities for all the systems, while the quantum model with the nuclear tunneling effect provided reasonable results compared to experiments. Moreover, the band-like transport behavior of F-2-TCNQ was well described by the quantum nuclear enabled hopping model. In addition, quantum theory of atoms in molecules (QTAIM) analysis and symmetry-adapted perturbation theory (SAPT) were used to characterize the intermolecular interactions in TCNQ, F-2-TCNQ and F-4-TCNQ crystals. A primary understanding of various noncovalent interaction responses for crystal formation is crucial to understand the structure-property relationships in organic molecular materials.

First author: Liu, W, Highly Sensitive Detection of UV Radiation Using a Uranium Coordination Polymer, ACS APPLIED MATERIALS & INTERFACES, 10, 4844, (2018)
Abstract: The accurate detection of UV radiation is required in a wide range of chemical industries and environmental or biological related applications. Conventional methods taking advantage of semiconductor photodetectors suffer from several drawbacks such as sophisticated synthesis and manufacturing procedure, not being able to measure the accumulated UV dosage as well as high defect density in the material. Searching for new strategies or materials serving as precise UV dosage sensor with extremely low detection limit is still highly desirable. In this work, a radiation resistant uranium coordination polymer [UO2(L)(DMF)] (L = 5-nitroisophthalic acid, DMF = N,N-dimethylformamide, denoted as compound 1) was successfully synthesized through mild solvothermal method and investigated as a unique UV probe with the detection limit of 2.4 x 10(-7) J. On the basis of the UV dosage dependent luminescence spectra, EPR analysis, single crystal structure investigation, and the DFT calculation, the UV-induced radical quenching mechanism was confirmed. Importantly, the generated radicals are of significant stability which offers the opportunity for measuring the accumulated UV radiation dosage. Furthermore, the powder material of compound 1 was further upgraded into membrane material without loss in luminescence intensity to investigate the real application potentials. To the best of our knowledge, compound 1 represents the most sensitive coordination polymer based UV dosage probe reported to date.

First author: Kovalenko, A, Multiscale methods framework: self-consistent coupling of molecular theory of solvation with quantum chemistry, molecular simulations, and dissipative particle dynamics, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 2947, (2018)
Abstract: In this work, we will address different aspects of self-consistent field coupling of computational chemistry methods at different time and length scales in modern materials and biomolecular science. Multiscale methods framework yields dramatically improved accuracy, efficiency, and applicability by coupling models and methods on different scales. This field benefits many areas of research and applications by providing fundamental understanding and predictions. It could also play a particular role in commercialization by guiding new developments and by allowing quick evaluation of prospective research projects. We employ molecular theory of solvation which allows us to accurately introduce the effect of the environment on complex nano-, macro-, and biomolecular systems. The uniqueness of this method is that it can be naturally coupled with the whole range of computational chemistry approaches, including QM, MM, and coarse graining.

First author: Berezin, AS, Temperature- and excitation wavelength-dependent emission in a manganese(II) complex, DALTON TRANSACTIONS, 47, 1657, (2018)
Abstract: A mononuclear manganese(II) complex with a chelating 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine ligand (L), [MnL2Cl2]center dot H2O, shows intriguing excitation wavelength-dependent emission. Depending on the excitation wavelength, the complex demonstrates three emission bands with the maxima at 380 nm, 440 nm and 495 nm. The 380 nm and 440 nm emissions originate from the pi ->pi* and n ->pi* ligand-centered transitions. The long-wave 495 nm emission with microsecond lifetimes is related to the d-d transitions and/or metal-to-ligand and halogen-to-ligand charge transfer. The emission behavior of this complex is strongly temperature-dependent: upon cooling from 300K down to 77K, the intensity of emission considerably increases. The enhancement of the luminescence upon cooling is accompanied by the appearance of the vibrational structure. This complex is the first example of manganese(II) complexes demonstrating excitation wavelength-dependent emission.

First author: Du, WGH, A Water Dimer Shift Activates a Proton Pumping Pathway in the P-R -> F Transition of ba(3) Cytochrome c Oxidase, INORGANIC CHEMISTRY, 57, 1048, (2018)
Abstract: Broken-symmetry density functional calculations have been performed on the [Fe-a3(4+),Cu-B(2+)] state of the dinuclear center (DNC) for the P-R -> F part of the catalytic cycle of ba(3) cytochrome c oxidase (CcO) from Thermus thermophilus (Tt), using the OLYP-D3-BJ functional. The calculations show that the movement of the H2O molecules in the DNC affects the pK(a) values of the residue side chains of Tyr237 and His376(+), which are crucial for proton transfer/pumping in ba(3) CcO from Tt. The calculated lowest energy structure of the DNC in the [Fe-a3(4+),Cu-B(2+)] state (state F) is of the form Fe-a3(4+)=O2-center dot center dot center dot Cu-B(2+), in which the H2O ligand that resulted from protonation of the OH- ligand in the P-R state is dissociated from the Cu-B(2+) site. The calculated Fe-a3(4+)=O2- distance in F (1.68 angstrom) is 0.03 angstrom longer than that in PR (1.65 angstrom), which can explain the different Fe-a3(4+)=O2- stretching modes in P (804 cm(-1)) and F (785 cm(-1)) identified by resonance Raman experiments. In this F state, the Cu-B(2+)center dot center dot center dot O2- (ferryl-oxygen) distance is only around 2.4 angstrom. Hence, the subsequent O-H state [Fe-a3(3+)-OH–Cu-B(2+)] with a mu-hydroxo bridge can be easily formed, as shown by our calculations.

First author: Aguio, E, Reversible Self-Assembly of Water-Soluble Gold(I) Complexes, INORGANIC CHEMISTRY, 57, 1017, (2018)
Abstract: The reaction of the gold polymers containing bipyridyl and terpyridyl units, [Au(C CC15H10N3)](n) and [Au(C CC10H7N2)](n), with the water-soluble phosphines 1,3,5-triaza-7-phosphatricyclo[]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane gives rise to the formation of four gold(I) alkynyl complexes that self-assemble in water (H2O) and dimethyl sulfoxide (DMSO), through different intermolecular interactions, with an impact on the observed luminescence displayed by the supramolecular assemblies. A detailed analysis carried out by NMR studies performed in different DMSO/deuterated H2O mixtures indicates the presence of two different assembly modes in the aggregates: (i) chain assemblies, which are based mainly on aurophilic interactions, and (ii) stacked assemblies, which are based on Au…pi and pi…pi interactions. These different supramolecular environments can also be detected by their intrinsic optical properties (differences in absorption and emission spectra) and are predicted by the changes in the relative binding energy from density functional theory calculations carried out in DMSO and H2O. Small-angle X-ray scattering (SAXS) experiments performed in the same mixture of solvents are in agreement with the formation of aggregates in all cases. The aromatic units chosen, bipyridine and terpyridine, allow the use of external stimuli to reversibly change the aggregation state of the supramolecular assemblies. Interaction with the Zn2+ cation is observed to disassemble the aggregates, while encapsulating agents competing for Zn2+ complexation revert the process to the aggregation stage, as verified by SAXS and NMR. The adaptive nature of the supramolecular assemblies to the metal-ion content is accompanied by significant changes in the absorption and emission spectra, signaling the aggregation state and also the content on Zn2+.

First author: Bendjabeur, S, DFT and TD-DFT insights, photolysis and photocatalysis investigation of three dyes with similar structure under UV irradiation with and without TiO2 as a catalyst: Effect of adsorption, pH and light intensity, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 190, 494, (2018)
Abstract: TiO2-mediated photocatalytic degradation of three triphenylmethane dyes (basic fuchsin, acid fuchsin and Gentian violet), was investigated in aqueous suspensions in the presence and the absence of titanium dioxide P25 Degussa as photocatalyst. The photodegradation process was investigated using UV-A (365 nm) and UV-C (254 nm) light alone and UV-A in the presence of TiO2. The effects of various operational parameters were investigated such as: the effect of adsorption in the dark, the influence of pH, the influence of irradiation wavelength and the effect of light intensity. The study of the effect of various parameters reveals that the photolysis of dyes increases with the increase of light intensity, the degradation rate under UV-C (254 nm) was found better than under UV-A 365 nm. The photocatalytic degradation was found to follow the same order of adsorption. The decolorization and the degradation kinetics were found to follow the pseudo-first-order kinetics. The mineralization of dye was found to follow the same order of disappearance as the photocatalytic degradation and depended directly to its functional groups and its number of carbons. Additionally, density functional theory (DFr) was applied for calculations of both electronic structure and spectroscopic properties of the studied compounds, where the obtained results of the three dyes show that the theoretical electronic spectra and the experimental UV-visible ones are similar in shapes, positions and intensities.

First author: Hayashi, A, Preparation of Preyssler-type Phosphotungstate with One Central Potassium Cation and Potassium Cation Migration into the Preyssler Molecule to form Di-Potassium-Encapsulated Derivative, ACS OMEGA, 3, 2363, (2018)
Abstract: A mono-potassium cation-encapsulated Preyssler-type phosphotungstate, [P5W30O110K](14-) (1), was prepared as a potassium salt, K-14[P5W30O110K] (1a), by heating mono-bismuth-or monocalcium-encapsulated Preyssler-type phosphotungstates (K-12[P5W30O110Bi(H2O)] or K-13[P5W30O110Ca(H2O)]) in acetate buffer. Characterization of the potassium salt 1a by single-crystal X-ray structure analysis, P-31 and W-183 nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectroscopy, and elemental analysis revealed that one potassium cation is encapsulated in the central cavity of the Preyssler-type phosphotungstate molecule with a formal D-5h symmetry. Density functional theory calculations have confirmed that the potassium cation prefers the central position of the cavity over a side position, in which no water molecules are coordinated to the encapsulated potassium cation. P-31 NMR and cyclic voltammetry analyses revealed the rapid protonation-deprotonation of the oxygens in the cavity compared to that of other Preyssler-type compounds. Heating of 1a in the solid state afforded a di-K(+)encapsulated compound, K-13[P5W30O110K2] (2a), indicating that a potassium counter-cation is introduced in one of the side cavities, concomitantly displacing the internal potassium ion from the center to a second side cavity, thus providing a new method to encapsulate an additional cation in Preyssler compounds.

First author: Ashley, MJ, Shape and Size Control of Substrate-Grown Gold Nanoparticles for Surface-Enhanced Raman Spectroscopy Detection of Chemical Analytes, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 2307, (2018)
Abstract: Anisotropic gold nanoparticles often exhibit superior optical properties compared to spherical ones, in part due to intense electric field localization near sharp geometric features and a broadly tunable localized surface plasmon resonance. As a result, anisotropic nanoparticles are attractive building blocks for surface-enhanced Raman spectroscopy (SERS) substrates. To unlock the full potential of such substrates, one should be able to (1) generate a sufficient number of SERS hotspots with structures of controlled shape and size and (2) remove ligands so that analytes can easily access nanoparticle surface sites. Here, we develop a synthetic strategy for the shape- and size-controlled anisotropic growth of gold nanoparticles (concave rhombic dodecahedra and concave cubes, 70-135 nm characteristic length) from spherical seeds structurally complex surface (common filter paper) and subsequently combine electrodynamics and electronic structure calculations with experiment to systematically characterize these substrates using SERS. Furthermore, we explore the generalizable functionality of these substrate-stabilized nanoparticles by using a continuous extraction method to partially remove surface ligands that were necessary for anisotropic growth, enabling the specific SERS detection of serotonin, a molecular neurotransmitter with a weak affinity for gold.

First author: Chu, TS, A theoretical approach for simulations of anisotropic charge carrier mobility in organic single crystal semiconductors, ORGANIC ELECTRONICS, 53, 165, (2018)
Abstract: Charge carrier mobility is important for organic semiconductor materials and mainly determines their device performance. Thereby how to improve carrier mobility lies at the heart of the development of organic electronics. Theoretical predictions and simulations can provide guidelines towards the possible realization of high mobility and the design of highly functional semiconductor materials and thus can help to achieve further discoveries in the field. In this paper, we review a recently proposed theoretical method (an effective one-dimensional diffusion equation model) which presents the first analytical expression for angular resolution anisotropic mobility of organic single crystal semiconductors. The method encompasses the hopping mechanism, Marcus-Hush theory and first-principles calculations and is suitable to characterizing the anisotropic transport behaviors in organic single crystal semiconductors as well as to studying the property-structure relationship in semiconductor materials. Illustration of applications of the method demonstrated its capabilities in description and understanding of the transport of charges, correct prediction of angular resolution anisotropic mobility, and assist in the design of n-type and p-type organic electronic materials.

First author: Dimuthu, KL, Origin of Photoluminescence of Ag-25(SR)(18)(-) Nanoparticles: Ligand and Doping Effect, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 2440, (2018)
Abstract: Recent theoretical insights into the origin of photo-luminescence of thiolate-protected gold nanoclusters raise the question of whether the observed luminescence mechanism is valid for related silver nanoparticles. To this end, we perform density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations on the Ag-25(SR)(18)(-) (R = H, PhMe2) nanocluster, which is currently the only thiolate-protected silver cluster that has a matching analogue in gold. The geometric and electronic structural modifications of Ag-25(SH)(18)(-) upon photo excitation are found to be similar but less pronounced than those of Au-25(SH)(18)(-) at the same level of theory. The Stokes shift is calculated to be 0.37 eV and the replacement of R = H model ligands by R = PhMe2 decreases the Stokes shift in contrast to the increase in Stokes shift for aliphatic ligands previously observed in the Au-25 system. The calculated emission energy agrees well with the experimental photoluminescence energy when the typical underestimation of DFT calculations is considered. Similar to Au-25, luminescence of Ag-25 arises from a HOMO-LUMO transition where core-based superatomic P and D orbitals are involved. Heteroatom doping of Au-25 and Ag-25 clusters with Ag/Au does not affect the origin of the photoemission of these systems. However, the radiative lifetimes of the lowest singlet excited states (S-1) and emission energies are slightly affected.

First author: Morales-Bayuelo, A, Theoretical study of B-11 NMR chemical shifts of prototypical boranes: The case of closo-[B12H12](2-), nest-B11H15, and arachno-B10H16, INDIAN JOURNAL OF CHEMISTRY SECTION A-INORGANIC BIO-INORGANIC PHYSICAL, 57, 143, (2018)
Abstract: The structural and electronic dependence of the (11B) chemical shifts for a series of borane structures, namely, closo-[B12H21](2-), nest-[B11H15], and arachno-[B10H16] are investigated using density functional theory calculations. Three types of environments are identified for the borane systems, in increasing order of chemical shielding as: B-H < B-H-B < B-B-B. The obtained chemical shifts are in good agreement with the available experimental results and reflect the extent of heterogeneity of the electronic environments present in these chemical systems in terms of symmetry and the number of boron cores. In addition, results of molecular quantum similarity studies using similarity descriptors such as overlap and coulomb indices and Euclidean distances are also reported.

First author: Moradi, F, Remediation of phenol-contaminated water by pristine and functionalized SWCNTs: Ab initio van der Waals DFT investigation, DIAMOND AND RELATED MATERIALS, 82, 7, (2018)
Abstract: Despite known toxic properties of phenol and its derivatives, their man-caused release into nature continues. Their importance as building blocks in polymers, pesticides, pharmaceuticals and other industrial chemicals remains a barrier for reducing their introduction into ecosystems. Hence, a considerable effort has been devoted to these organic contaminates removal from water sources. In the present work, we have employed functionalized (5, 5) carbon nanotubes (f-CNTs) for adsorption and remidiation of phenol pollutant from water. Several binding sites (incloding hydroxyl and phenyl groups) were considered due to their ability in pi-pi stacking and H-bonding interactions with phenol. The adsorption modes and energies of both water and phenol to these sites are evaluated using a general dispersion-corrected density functional (DFT-D3) method. We showed that both water and phenol molecules are weakly bound (weak physisorption) to the outer surface of pristine CNT while they can be adsorbed stronger on the functionalized CNTs. It was found that phenol bound stronger to the CNT-OH than water molecule which was due to the existence of simultaneous pi-pi stacking and H-bonding in the system. Also, we have prepared a brief report about the solvent effect in the adsorption nature of the more stable systems. The results show that the absorption energy sequence for the absorbing/carbon nanotube complexes in the aqueous phase is similar to the calculated absorption energy for in the gas phase, but adsorption decreased in the aqueous phase. We have also provided a succinct report about the reactivity, energy gap and polarity of the considered systems for all systems. For comparison, we evaluated the adsorption behavior for zigzag OH-CNT (8, 0). The calculation reveal that difference of the binding energy of phenol and water molecules on a zigzag is alike to the armchair CNT system. The phenol adsorption properties onto CNT-OH system in periodic and cluster SWCNT have compared and we were found that the results predicted by the CNT saturated with hydrogen can be comparable to periodic SWCNT. Furthermore, our first-principles calctilations demonstrated the importance of dispersion corrections based on weak intermolecular interactions in designing absorbents. Our study offers molecular level understanding of the interactions between water/phenol molecule and CNTs surface and may be informative for toxicity agent adsorption and remediation from environment.

First author: Meng, GH, Theoretical insight into the carrier mobility anisotropy of organic-inorganic perovskite CH3NH3PbI3, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 810, 11, (2018)
Abstract: High mobility, which is highly relevant to crystal structures, is one of the predominant superiorities of organic inorganic halide perovskites. However, the anisotropy of carrier mobility for this photoelectric material on different crystal planes is still unclear. Based on Marcus theory and Density Functional Theory, we investigated the anisotropy of carrier mobility by calculating the intramolecular vibration (namely, internal recombination energy lambda) and intermolecular electronic coupling integral V along a representative crystal plane. Results show that the electrons and holes exhibit consistency in the transport orientations that are parallel to the (010), (101), and (110) crystal planes. However, inconsistency was observed in those parallel to the (111) and (001) crystal planes (with an angle of approximately 60 degrees) between the electron and hole transport directions This condition is unfavorable to the balancing of the transport and collection of photoinduced carriers. Our work reveals the theoretical significance of control-oriented growth of perovskites.

First author: Baituti, B, Computational studies of the Mn-4/Ca cluster in photosystem II, JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY, 17, 11, (2018)
Abstract: Computational chemistry with the data from more detailed X-ray diffraction (XRD) oxygen evolving complex (OEC) structure has been used extensively of late in exploring the mechanisms of water oxidation in the OEC. The study reported in this paper involves density functional theory (DFT) calculations to investigate whether the data are in agreement with the four manganese ions in the OEC, being organized as a ‘3+1’ (trimer plus one) model [Gatt et al. Angewandte Chemie International Edition, 51, 12025-12028, 2012; Petrie et al. Chemistry – A European Journal, 21, 6780-6792, 2015; Terrett et al. Chemical Communications, 50, 3187-3190, 2014] or ‘dimer of dimers’ model. [Terrett et al. Journal of Inorganic Biochemistry, 162, 178-189, 2016]. The data analysis method used involves quantum chemical DFT calculations on relevant models of the OEC cluster. DFT calculations were performed using both the so-called ‘open’ and ‘closed’ forms [Terrett et al. Journal of Inorganic Biochemistry, 162, 178-189, 2016] of the S-2 OEC structure models with total spin (S-T) 1/2, 7/2, 9/2 and 15/2 within the Mn-III Mn-IV Mn-III Mn-III ‘low’ oxidation paradigm to examine exchange coupling within the OEC cluster. The results show that the J-coupling in the ‘closed’ form: J(23) = -23.4 cm(-1), J(13) = 43.66 cm(-1), J(12) = 126.1 cm(-1) and J(34) = 70-81.67 cm(-1). In the ‘closed’ form, J(12) and J(34) represent the two largest exchange interactions within the manganese cluster, whereas J(23) and J(13) are small and almost net cancel. The magnetic coupling between the four Mn ions is close to ‘dimer of dimers’, with both dimers anti-ferromagnetically coupled internally and with weak inter-dimer net coupling.

First author: Poltev, V, Biologically important conformational features of DNA as interpreted by quantum mechanics and molecular mechanics computations of its simple fragments, JOURNAL OF MOLECULAR MODELING, 24, 11, (2018)
Abstract: Deciphering the mechanism of functioning of DNA as the carrier of genetic information requires identifying inherent factors determining its structure and function. Following this path, our previous DFT studies attributed the origin of unique conformational characteristics of right-handed Watson-Crick duplexes (WCDs) to the conformational profile of deoxydinucleoside monophosphates (dDMPs) serving as the minimal repeating units of DNA strand. According to those findings, the directionality of the sugar-phosphate chain and the characteristic ranges of dihedral angles of energy minima combined with the geometric differences between purines and pyrimidines determine the dependence on base sequence of the three-dimensional (3D) structure of WCDs. This work extends our computational study to complementary deoxydinucleotide-monophosphates (cdDMPs) of nonstandard conformation, including those of Z-family, Hoogsteen duplexes, parallel-stranded structures, and duplexes with mispaired bases. For most of these systems, except Z-conformation, computations closely reproduce experimental data within the tolerance of characteristic limits of dihedral parameters for each conformation family. Computation of cdDMPs with Z-conformation reveals that their experimental structures do not correspond to the internal energy minimum. This finding establishes the leading role of external factors in formation of the Z-conformation. Energy minima of cdDMPs of non-Watson-Crick duplexes demonstrate different sequence-dependence features than those known for WCDs. The obtained results provide evidence that the biologically important regularities of 3D structure distinguish WCDs from duplexes having non-Watson-Crick nucleotide pairing.

First author: Atesci, H, Humidity-controlled rectification switching in ruthenium-complex molecular junctions, NATURE NANOTECHNOLOGY, 13, 117, (2018)
Abstract: Although molecular rectifiers were proposed over four decades ago(1,2), until recently reported rectification ratios (RR) were rather moderate(2-11) (RR similar to 10(1)). This ceiling was convincingly broken using a eutectic GaIn top contact(12) to probe molecular monolayers of coupled ferrocene groups (RR similar to 10(5)), as well as using scanning tunnelling microscopy-break junctions(13-16) and mechanically controlled break junctions(17) to probe single molecules (RR similar to 10(2)-10(3)). Here, we demonstrate a device based on a molecular monolayer in which the RR can be switched by more than three orders of magnitude (between RR similar to 10(0) and RR >= 10(3)) in response to humidity. As the relative humidity is toggled between 5% and 60%, the current-voltage (I-V) characteristics of a monolayer of di-nuclear Ru-complex molecules reversibly change from symmetric to strongly asymmetric (diode-like). Key to this behaviour is the presence of two localized molecular orbitals in series, which are nearly degenerate in dry circumstances but become misaligned under high humidity conditions, due to the displacement of counter ions (PF6-). This asymmetric gating of the two relevant localized molecular orbital levels results in humidity-controlled diode-like behaviour.

First author: Majid, A, A Computational Study of Ferromagnetic Exchange Interactions and Charge Transfer in Codoped Gallium Nitride, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 31, 475, (2018)
Abstract: This study reports a systematic density functional theory-based analysis on electronic properties of individual doping and codoping of Ti and Ce into GaN. In the case of codoped GaN, the placement of Ti and Ce at nearest neighbour sites appeared as the most stable configuration. The unoccupied states in the case of individual doped material are observed to become occupied after codoping, and a metal-to-metal charge transfer of the Ti-N-Ce character is observed in the material. The interaction between dopants suggests 4f-5d-CB hybridization that opens the way to the exploitation of novel luminescence phenomena. A model showing charge transfer and interaction between the dopants is proposed.

First author: Chakraborty, D, Confinement induced thermodynamic and kinetic facilitation of some Diels-Alder reactions inside a CB[7] cavitand, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 151, (2018)
Abstract: The effect of geometrical confinement on the Diels-Alder reactions between some model dienes viz. furan, thiophene, cyclopentadiene, benzene, and a classic dienophile, ethylene has been explored by performing density functional theory-based calculations. The effect of confinement has been imposed by a rigid macrocyclic molecule cucurbit[7]uril (CB[7]). Results indicate that all the reactions become thermodynamically more favorable at 298.15 K temperature and one atmospheric pressure inside CB[7] as compared to the corresponding free gaseous state reactions. Moreover, the rate constants associated with the reactions experience manifold enhancement inside CB[7] as compared to the unconfined reactions. Suitable contribution from the entropy factor makes the concerned reactions more facile inside CB[7]. The energy gap between the frontier molecular orbitals of the dienes and dienophiles decrease inside CB[7] as compared to that in the free state reactions thereby allowing facile orbital interactions. The nature of interaction as well as bonding has been analyzed with the help of atoms-in-molecules, noncovalent interaction, natural bond orbital as well as energy decomposition analyses. Results suggest that all the guests bind with CB[7] in an attractive fashion. Primarily, noncovalent interactions stabilize the host-guest systems.

First author: Chakraborty, D, Host-guest interactions between octa acid and cations/nucleobases, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 161, (2018)
Abstract: The nature of host-guest interaction in between octa acid cavitand (OA) and some representative cationic guests (Li+, Na+, K+, Be+2, Mg+2, Ca+2, Li3O+, Na3O+, K3O+) as well as heterocyclic moieties like [adenine (A), guanine (G), cytosine (C), thymine (T), uracil (U), and tetrathiafulvalene (TTF)] has been examined with the aid of density functional theory (DFT)-based computations. Thermochemical results indicate that all the guests bind with OA in a thermodynamically favorable fashion at 298.15 K temperature and one atmospheric pressure. OA exhibits high selectivity in binding the lighter cations/metal cluster cations as compared to the heavier congeners along each given series. Moreover, OA exhibits enhanced affinity as well as selectivity in binding A/G/TTF molecules as compared to C/T/U. Noncovalent interaction and energy decomposition analyses reveal that in addition to the van der Waals interaction, significant contribution from electrostatic as well as orbital interactions dictate the outcome in all the host-guest complexes. Time dependent DFT calculations have been carried out to assess the role of the guests in tuning the electronic properties as well as absorption spectrum of OA.

First author: Ahumada, G, Octahedral bis(2-thenoyltrifluoroacetonato)-ethylenediamine Co(II), Ni(II) and Cu(II) complexes: Synthetic, structural, electrochemical, and theoretical studies, INORGANICA CHIMICA ACTA, 470, 221, (2018)
Abstract: We report the synthesis of three new octahedral bis(2-thenoyltrifluoroacetonato)-ethylenediamine metal (II) complexes [M(TTA)(2)(en)] (M = Co, 2a; Ni, 2b; Cu, 2c) resulting from the coordination of the diamine onto the bis(beta-diketonate) precursors [Co(TTA)(2)(CH3OH)(2)] (1a), [Ni(TTA)(2)(H2O)(2)] (1b) and [Cu(TTA)(2)] (1c), respectively. The six-coordinate paramagnetic complexes 2a-c have been isolated as neutral, air and thermally stable solids in high yields (>80%) and have been fully characterized by elemental analysis, ESI+ HRMS, FT-IR and UV-vis spectroscopy. Single-crystal X-ray diffraction studies indicate that the metal (II) ion sits in a pseudo-octahedral environment; the copper derivative 2c showing a significant elongation along the O-Cu-O axis due to Jahn-Teller distorsion associated with the “eg” electron occupation of the d(z2)-type MO. The three complexes 2a-c display similar cyclic voltammetric behavior exhibiting two irreversible anodic waves, tentatively assigned to the M(II)/M(III) redox couples and to the oxidation of soluble short oligomeric species generated during the first redox process, respectively. No deposits of polymeric species on the electrode surface occured. The electronic structures of 2a-c and their cations have been analysed through DFT calculations, allowing providing a consistent view of their structure and properties. TDDFT calculations have been used to interpret the major features of their UV-vis spectra.

First author: Daigre, G, Stabilization of Ni2+ dimers in hexacyano Mo-6 cluster-based Prussian blue derivatives: experimental and theoretical investigations of magnetic properties, DALTON TRANSACTIONS, 47, 1122, (2018)
Abstract: Herein, two new octahedral molybdenum cyanide cluster compounds, namely [{Ni(NH3)(6)}(4){Ni-2(NH3)(8)}(1)] [Mo(6)Br(6)Q(2)(CN)(6)](3)center dot 12H(2)O, Q = S (1) and Se (2), have been synthesized as single crystals by slow diffusion of a solution of nickel chloride into aqueous ammonia solutions of a K2Cs2[Mo(6)Br(6)Q(2)(CN)(6)] molybdenum cyanide cluster-based compound. Both 1 and 2 were structurally characterized by single-crystal X-ray diffraction. They are isostructural and crystallize in the cubic system (Im (3) over barm (no. 229); Z = 2, a = 18.147(1) angstrom, and V = 5976(1) angstrom(3) and a = 18.188(2) angstrom and V = 6016(2) angstrom(3) for 1 and 2, respectively). 1 and 2 are based on the association of [Mo(6)Br(6)(i)Q(2)(i)(CN)(6)(a)](4-) (Q = S, Se) cluster anions with Ni2+ dimer-based cubic [Ni-2(NH3)(8)](4+) and octahedral [Ni(NH3)(6)](2+) cations. The structure is based on 2-fold interpenetrated [{Ni(NH3)(6)}(4){Ni-2(NH3)(8)}(1)][Mo(6)Br(6)Q(2)(CN)(6)](3) frameworks related to each other by [12, 12, 12] translation. The unit cell is based on a body-centered cubic framework of cubic [Ni-2(NH3)(8)](4+). The [Mo(6)Br(6)(i)Q(2)(i)(CN)(6)(a)](4-) (Q = S, Se) cluster units are located in the middle of the edges and at the center of the faces of the cell. The [{Ni(NH3)(6)}](2+) cations are located at the center of the cubes of the a/2 edge. The dimers [Ni-2(NH3)(8)](4+) are stabilized by hydrogen bonds between the cyanide ligands of the cluster unit and the hydrogen atoms of the ammonia molecules. Both compounds exhibit a weak antiferromagnetic coupling within the [Ni-2(NH3)(8)](4+) dimer entities at low temperatures together with a paramagnetic behavior originating from the cations of the octahedral [{Ni(NH3)(6)}](2+) complexes.

First author: Pan, S, Noble gas encapsulated B-40 cage, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 1953, (2018)
Abstract: The efficacy of B-40 borospherene to act as a host for noble gas atoms is explored via density functional theory based computations. Although the Ng@B-40 complexes are thermochemically unstable with respect to dissociation into free Ng and B-40, it does not rule out their viability as all the systems possess a high activation free energy barrier (84.7-206.3 kcal mol(-1)). Therefore, once they are formed, it is hard to take out the Ng atom. Two Ng atoms can also be incorporated within B-40 for the lighter Ng atoms (He and Ne). In fact, the destabilization offered by the encapsulation of one and two He atoms and one Ne atom inside B-40 is significantly less than that in experimentally synthesized He@C20H20, highlighting their greater possibility for synthesis. Although Ar-2 and Kr-2 encapsulated B-40 systems are very much destabilized by the repulsive interaction between Ng(2) and B-40, an inspection of the bonding situation reveals that the confinement can even induce some degree of covalent interaction between two otherwise non-bonded Ng atoms. Ng atoms transfer electrons towards B-40 which is smaller for lighter Ng atoms and gradually increases along He to Rn. Even if the electrostatic interaction between Ng and B-40 is the most predominant term in these systems, the extent of the orbital interaction is also considerable. However, the very large Pauli repulsion counterbalances the attractive interaction, eventually turning the interaction repulsive in nature. Ng@B-40 also shows dynamical behaviour involving continuous exchange between hexagonal and heptagonal holes, similar to the host cage, as understood from the very little variation in the activation barrier because of the Ng encapsulation. Furthermore, sandwich complexes like [(eta(5)-C5Me5)-Fe(eta(6)-B-40)](+) and [(eta(5)-C5Me5) Fe(eta(7)-B-40)](+) are noted to be viable with the latter being slightly more stable than the former. The encapsulation of Xe slightly improves the dissociation energy associated with the decomposition into Xe@B-40 and [Fe(eta(5)-C5Me5)](+) compared to that in the bare one.

First author: Baron, M, A square planar gold(III) bis-(1,1 ‘-dimethyl-3,3 ‘-methylene-diimidazol-2,2 ‘-diylidene) trication as an efficient and selective receptor towards halogen anions: the cooperative effect of Au center dot center dot center dot X and X center dot center dot center dot HC interactions, DALTON TRANSACTIONS, 47, 935, (2018)
Abstract: Treatment of the tricationic gold(III) [Au(MeImCH(2)]mMe)(2)](PF6)(3) complex 1-3PF(6) (Im = imidazol-2-ylidene) with excess halides affords complexes 1-3X (X = Cl, Br, and I), resulting from counter anion PF6 (-)/ X- exchange. The H-1 chemical shift of the CH3 groups and particularly that of the CH2 linker in DMSO-d6 are different in the three complexes, thus suggesting selective X center dot center dot center dot HC interactions. Complex 1(3+) can therefore be used as a halide sensor in DMSO and water. The host-guest interaction between the tricationic gold(III) complex and the halides C-l-, Br- and I- in solution and in the solid state has been investigated by means of NMR titration experiments, DFT calculations and X-ray structure analysis. The electrostatic interaction between the halides and the triple formal positive charge on the metal centre, together with the CH center dot center dot center dot X hydrogen bonding between the NHC ligand and halides, contributes to the formation of stable supramolecular aggregates in solution and in the solid state. The complexing properties of 1(3+) are strongly influenced by the nature of the solvent. Formation of the 1 : 1 and 1 : 2 species (1X(2+) and 1X(2+)) is observed in DMSO-d(6), while that of only the 1 : 1 aggregates (1X(2+)) is observed in D2O (X = Cl, Br, and I). Moreover, the selectivity towards the various halides is reversed in the two solvents, being in the order Cl-> Br-> Iin DMSO-d(6) and I-> Br-> Cl- in D2O. The formation constants of the species 1X2+ and 1X2 + in DMSO and 1X(2+) in water have been determined by fitting the NMR titration curves.

First author: Burgess, KMN, Structural Insights from Co-59 Solid-State NMR Experiments on Organocobalt(I) Catalysts, CHEMPHYSCHEM, 19, 227, (2018)
Abstract: A series of fumarate-based organocobalt(I) [CoCp(CO)(fumarate)] catalysts is synthesized and characterized by X-ray crystallography, multinuclear (C-13 and Co-59) solid-state NMR spectroscopy, and Co-59 NQR spectroscopy. Given the dearth of Co-59 solid-state NMR studies on Co-I compounds, the present work constitutes the first systematic characterization of the Co-59 electric field gradient and chemical shift tensors for a series of cobalt complexes in this oxidation state. Using X-ray crystallography, the molecular geometry about the Co-I centre is found to be nearly identical in all compounds studied herein. Owing to the Co-59 nucleus’ large chemical shift range, solid-state NMR experiments are found to be able to detect small structural differences between the individual organocobalt(I) compounds. With the aid of density functional theory calculations on these complexes, it is shown that the Co-59 chemical shift anisotropy and the Co-59 quadrupolar coupling constant are both extremely sensitive gauges of the Fu-Co-Cp bond angle, providing a link between these Co-59 NMR observables and the catalysts’ structures.

First author: Chung, H, Rotator side chains trigger cooperative transition for shape and function memory effect in organic semiconductors, NATURE COMMUNICATIONS, 9, 227, (2018)
Abstract: Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition. Cooperativity enables shape memory effect in single crystals and function memory effect in thin film transistors. We establish a molecular design rule to trigger martensitic transition in organic semiconductors, showing promise for designing next-generation smart multifunctional materials.

First author: Dehnhardt, N, Ternary Iodido Bismuthates and the Special Role of Copper, INORGANIC CHEMISTRY, 57, 633, (2018)
Abstract: Two new, isostructural members of the title material class, [PPh4](4)[Cu2Bi2I12] (1) and [PPh4](4)[Ag2Bi2I12] (2), have been prepared via a facile solution route. The crystal structure of both compounds features a tetranuclear [M2Bi2I12](4-) (M = Cu, Ag) anion that displays an unprecedented face-sharing mode of connection between BiI6 octahedra and MI4 tetrahedra, enabling close Bi center dot center dot center dot M contacts. The two compounds allow for a direct experimental and quantum chemical investigation of the influence of group 11 metal cations on the optical and electronic properties of ternary iodido bismuthate anions, indicating that: Cu+ is a better electronic match than Ag+, resulting in a Significantly lower optical band gap of the copper compound.

First author: Novotny, J, Hyperfine Effects in Ligand NMR: Paramagnetic Ru(III) Complexes with 3-Substituted Pyridines, INORGANIC CHEMISTRY, 57, 641, (2018)
Abstract: NMR spectroscopy is an indispensable tool in characterizing molecular systems, including transition-metal complexes. However, paramagnetic transition-metal complexes such as those with ruthenium in the +3 oxidation state are troublemakers because their unpaired electrons induce a fast nuclear spin relaxation that significantly broadens their NMR resonances. We recently demonstrated that the electronic and spin structures of paramagnetic Ru(III) systems can be characterized in unprecedented details by combining experimental NMR results with relativistic density-functional theory (Novotny et al. J. Am. Chem. Soc. 2016, 138, 8432). In this study we focus on paramagnetic analogs of NAMI with the general structure [3-R-pyH](+)trans-[(RuCl4)-Cl-III(DMSO)(3-R-py)](-), where 3-R-py stands for a 3-substituted pyridine. The experimental NMR data are interpreted in terms of the contributions of hyperfine (HF) NMR shielding and the distribution of spin density calculated using relativistic DFT. The DFT computational methodology is evaluated, and the effects of substituents, environment, and relativity on the hyperfine shielding are discussed. Particular attention is paid to the analysis of the fundamental Fermi-contact (FC), spin-dipole (SD), and paramagnetic spin-orbit (PSO) terms that contribute to the hyperfine H-1 and C-13 NMR shifts of the individual atoms in the pyridine ligands and the spin-polarization effects in the ligand system that are linked to the character of the metal-ligand bond. The individual HF shielding terms are systematically discussed as they relate to the traditional, but somewhat mixed, contact and pseudocontact NMR contributions, used extensively by experimental spectroscopists in biomolecular NMR and the development of PARACEST magnetic-resonance contrast agents.

First author: Steenbock, T, Toward an Automated Analysis of Exchange Pathways in Spin-Coupled Systems, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 81, (2018)
Abstract: Understanding (super-)exchange coupling between local spins is an important task in theoretical chemistry and solid-state physics. We show that a Green’s-function approach introduced earlier (Liechtenstein et al., J. Phys. F 1984, 14, L125; Steenbock et al., J. Chem. Theory Comput. 2015, 11, 5651) can be used for analyzing exchange coupling pathways in an automated fashion rather than by visual inspection of molecular orbitals. We demonstrate the capabilities of this approach by comparing it to previously published pathway analyses for hydroxy-bridged dinuclear copper complexes and an oxo-bridged dinuclear manganese complex, and employ it for discriminating between through-space and through-bond pathways in a naphthalene-bridged bisnickelocene complex.

First author: Calborean, A, Combined Molecular and Periodic DFT Analysis of the Adsorption of Co Macrocycles on Graphene, JOURNAL OF COMPUTATIONAL CHEMISTRY, 39, 130, (2018)
Abstract: The molecular doping of graphene with pi-stacked conjugated molecules has been widely studied during the last 10 years, both experimentally or using first-principle calculations, mainly with strongly acceptor or donor molecules. Macrocyclic metal complexes have been far less studied and their behavior on graphene is less clear-cut. The present density functional theory study of cobalt porphyrin and phthalocyanine adsorbed on monolayer or bilayer graphene allows to compare the outcomes of two models, either a finite-sized flake of graphene or an infinite 2D material using periodic calculations. The electronic structures yielded by both models are compared, with a focus on the density of states around the Fermi level. Apart from the crucial choice of calculation conditions, this investigation also shows that unlike strongly donating or accepting organic dopants, these macrocycles do not induce a significant doping of the graphene sheet and that a finite size model of graphene flake may be confidently used for most modeling purposes.

First author: Oung, SW, Uncertainty quantification in theoretical spectroscopy: The structural sensitivity of X-ray emission spectra, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 118, 130, (2018)
Abstract: We present a methodology for analyzing the dependence of molecular spectra calculated with quantum-chemical methods on the underlying molecular structure. This analysis is applied to investigate the structural sensitivity of calculated valence-to-core X-ray emission (VtC-XES) spectra for the test case of three iron carbonyl complexes, Fe(CO)(5), [FeCp(CO)(2)(THF)](+) (Cp=cyclopentadienyl, THF=tetrahydrofuran), and Fe(CO)(3)(cod) (cod=cyclooctadienyl). Based on this analysis, we discuss how the VtC-XES spectra depend on changes of metal-ligand bond distances and bond angles as well as on the structure of the ligands. The benefits of such an analysis of the structural sensitivity are discussed. Our methodology can serve as a first step toward quantifying and accounting for uncertainties due to the underlying model structure in theoretical spectroscopy.

First author: Heerdt, G, Photoisomerization induced scission of rod-like micelles unravelled with multiscale modeling, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 510, 357, (2018)
Abstract: Hypothesis: In photorheological fluids, subtle molecular changes caused by light lead to abrupt macroscopic alterations. Upon UV irradiation of an aqueous cetyltrimethylammonium bromide (CTAB) and trans-ortho-methoxycinnamic acid (trans-OMCA) solution, for instance, the viscosity drops over orders of magnitude. Multiscale modeling allows to elucidate the mechanisms behind these photorheological effects.

First author: Rao, B, X-ray crystal structure and doping mechanism of bimetallic nanocluster Au36-xCux(m-MBT)(24) (x=1-3), DALTON TRANSACTIONS, 47, 475, (2018)
Abstract: A novel Au36-xCux(m-MBT)(24) (x = 1-3, m-MBT = 3-methylbenzenethiolate) nanocluster has been prepared. According to the X-ray single crystal diffractometer, the structure of Au36-xCux(m-MBT)(24) is similar to that of Au-36(SPhtBu)(24). The Au36-xCux(m-MBT)(24) nanocluster contains a face-centered cubic (FCC) M-28 core, which is protected by 4 M2S3 (M = Au/Cu) staple motifs and 12 bridging SR ligands. The Cu dopants could possibly occupy 14 sites (six in the sub-surface and eight in the staple motifs). Spectral monitoring indicates that the number of Cu dopants sequentially increased on increasing the amount of Cu precursors (relative to a Au control). Meanwhile, DFT calculations imply that the maximum doping number of Cu is 3, and doping occurs preferentially at the staple sites and sub-surface sites (instead of the centre of the core). Because the atomic orbital of the peripheral locations hardly contributes to the frontier molecular orbitals, the UV-vis of the AuCu alloy is almost the same as that of its homometallic Au counterpart.

First author: Miralrio, A, Intermediates for Larger Endohedral Metallofullerenes: Theoretical Characterization of M@C-44 Species, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 798, (2018)
Abstract: Endohedral metallofullerenes M@C-44 containing several different endohedral species have been considered as intermediates in the path to form larger species. Such compounds containing interstitial atoms of groups 3 and 4, recently detected in experiments, are studied theoretically for the first time. Calculations carried out at a dispersion-corrected density functional theory level agree admirably well with experimental data for C-44 and its endohedral compounds. The most suitable C-44 isomer to form endohedral compounds is the D-2 (89) isomer. The binding energy between the endohedral atom and the cage is a good indicator of the abundance found in synthesis. The properties of the endohedral compounds of C-44-D-2 (89) can be compared directly with those of the tri- and tetraanions of empty C-44. In addition, the electron-richest regions in all of them are the four triple sequentially fused pentagon units. The centroids of the central pentagons of each such unit are approximately disposed in a seesaw structure around the endohedral atom. This structural feature of C-44-D-2 (89) accounts for the preferential bonding in almost all cases of these to the endohedral atom. A detailed study of the metal cage bonding highlights the partially ionic and covalent character of their interaction. The ionic nature of the metal cage bonding increases for the heavier endohedral atoms. Endohedral species containing group 3 metals are expected to be more reactive than those containing group 4 metals according to their highest occupied molecular orbital lowest unoccupied molecular orbital gaps. The cage aromaticity evaluated by the NICS(0)(iso) indices indicates that this property does not play a crucial role in the stabilization of the endohedral species. The evaluated behavior and properties of intermediate M@C-44 species can be useful to extend and understand the encapsulation processes of elements as the size of the cage increases toward larger fullerenes.

First author: Kruithof, A, Integrative Theory/Experiment-Driven Exploration of a Multicomponent Reaction towards Imidazoline-2-(thi)ones, EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, 2018, 104, (2018)
Abstract: Predicting reactivity in multicomponent reactions (MCRs) is extremely difficult. These reactions proceed by multiple pathways and are inherently associated with a potentially large variation of reactants and functional groups. To date, theoretical chemistry has been used in hindsight to verify experimental observations. However, its use in the early stages of the development of a (multicomponent) reaction process can prevent laborious and time-consuming optimization studies by pinpointing the most relevant parameter(s) in the reactivity, thus focusing experimental efforts. Herein, we discuss a study that truly integrates theoretical and synthetic chemistry to unravel in full detail the complex and intricate reaction characteristics of the novel versatile MCR of -acidic iso(thio)cyanates, amines and aldehydes to access densely functionalized imidazoline-2-(thi)ones.

First author: Durini, S, H-bonding dependent phosphorescence in a mixed ligand copper(I) complex, POLYHEDRON, 139, 189, (2018)
Abstract: The mixed ligand copper(I) derivative [Cu(PPh3)(2)(kappa(2)-O,O ”-lact)] (1) (lact = L-(+)-lactate) has been prepared and fully characterized. NMR studies indicated the occurrence of a fluxional behavior involving the lactate anion, in solution. The alpha-hydroxycarboxylate ligand is responsible for the generation of a catemeric O-H center dot center dot center dot O(CO) H-bonding network that strongly influences the photophysical properties of 1, in the solid state. Indeed, when irradiated with UV light the title compound shows a bright phosphorescence, which as suggested by DFT calculations is strictly related to the abovementioned H-bonding network.

First author: Leone, VO, Adsorption of diclofenac on a magnetic adsorbent based on maghemite: experimental and theoretical studies, NEW JOURNAL OF CHEMISTRY, 42, 437, (2018)
Abstract: In the present study, a magnetic adsorbent for diclofenac formed by maghemite (gamma-Fe2O3) nanoparticles with high saturation magnetization (19.8 emu g(-1)) and specific area (79 m(2) g(-1)) was synthesized by a one-pot method through the precipitation of Fe2+ ions with NaOH solution followed by rapid oxidation with hydrogen peroxide. The X-ray diffraction and Mossbauer spectroscopy data confirmed that the adsorbent is formed solely by maghemite. The adsorption equilibrium time for diclofenac (C-0 = 500 mg L-1) was reached after 120 min, and the kinetic data were best fitted to the pseudo-first-order model. The adsorption isotherms acquired at five different temperatures showed an increase in the maximum adsorption capacity (261 mg g(-1)) until 298 K, but at higher temperatures, the maximum adsorption capacity was not increased. The isotherm data were best fitted to the Langmuir and Sips models. Adsorption tests as a function of solution pH showed a decrease in the diclofenac adsorption capacity with increasing solution pH, suggesting that the hydroxyl anions compete with diclofenac molecules for the adsorption sites. Diclofenac adsorption on maghemite was endothermic (67.31 kJ mol(-1)) and entropically driven (T Delta S-ads degrees = 96.33 kJ mol(-1)). Finally, theoretical calculations and infrared spectroscopy data suggest a physisorption mechanism of diclofenac on the maghemite surface.

First author: Kuhn, A, Orbital control over the metal vs. ligand reduction in a series of neutral and cationic bis(cyclopentadienyl) Ti(IV) complexes, NEW JOURNAL OF CHEMISTRY, 42, 662, (2018)
Abstract: Quantum chemistry calculations showed that the first reduction, as experimentally observed by cyclic voltammetry for a series of neutral and cationic functionalised bis(cyclopentadienyl) titanium(IV) derivatives, is metal based, involving the chemically and electrochemically reversible Ti-IV/Ti-III redox couple. The second reduction peak observed is chemically and electrochemically irreversible. For the neutral [Cp2TiIV(ligand)(n)] (n = 1 or 2) complexes (Cp = cyclopentadienyl), the second irreversible reduction peak is metal-based, while for the cationic [Cp2TiIV(ligand)](+) complexes, the second irreversible reduction peak involves ligand reduction, leading to a Ti-III species coupled to a ligand radical. The electronic properties of the substituents directly influence electron density at the reduction centre when p-interactions between the electro-active centre and the substituent groups exist in the lowest unoccupied molecular orbital (LUMO) of the complexes. In this case, a number of relationships between the electronic properties of the substituents and the reduction potentials have been affirmed, yielding linear relationship between experimentally measured reduction potentials and DFT calculated energies (energy of the LUMO, electron affinity, Mulliken electronegativity and global electrophilicity index). However, the substituent effect is ill defined when the LUMO is highly localised without pi-interaction between the electro-active centre and the substituents.

First author: Jahiruddin, S, Structure and Electronic Properties of Unnatural Base Pairs: The Role of Dispersion Interactions, CHEMPHYSCHEM, 19, 67, (2018)
Abstract: Recent reports of the successful incorporation of unnatural base pairs (UBPs), such as d5SICS-dNaM, in the gene sequence and replication with DNA is an important milestone in synthetic biology. Followed by this, several other UBPs, such as dTPT3-dNaM, dTPT3-dFIMO, dTPT3-IMO, dTPT3-FEMO, FTPT3-NaM, FTPT3-FIMO, FTPT3-IMO, and FTPT3-FEMO, have demonstrated similar or better retention and fidelity inside cells. Of these base pairs, dNaM-dTPT3 has been optimized to be a better fit inside a pAIO plasmid. Based on both implicit and explicit dispersion-corrected density functional theory (DFT) calculations, we show that although this set of UBPs is significantly diverse in elemental and structural configuration, the members do share a common trait of favoring a slipped parallel stacked dimer arrangement. Unlike the natural bases (A, T, G, C, and U), this set of UBPs has a negligible affinity for a Watson-Crick (WC)-type planar structure because they are invariably more stable within slipped parallel stacked orientations. We also observed that all the UBPs have either similar or higher binding energies with the natural bases in similar stacked orientations. When arranged between two natural base pairs, the UBPs exhibited a binding energy similar to that of three-base sequences of natural bases. Our computational data show that the most promising base pairs are 5SICS-NaM, TPT3-NaM, and TPT3-FEMO. These results are consistent with recent progress on experimental research into UBPs along with our previous calculations on the d5SICS-dNaM pair and, therefore, strengthen the hypothesis that hydrogen bonding might not be absolutely essential and that interbase stacking dispersion interactions play a key role in the stabilization of genetic materials.

First author: Behzadi, H, Application of calculated NMR parameters, aromaticity indices and wavefunction properties for evaluation of corrosion inhibition efficiency of pyrazine inhibitors, JOURNAL OF MOLECULAR STRUCTURE, 1151, 34, (2018)
Abstract: In light of the importance of developing novel corrosion inhibitors, a series of quantum chemical calculations were carried out to evaluate N-15 chemical shielding CS tensors as well as aromaticity indexes including NICS, HOMA, FLU, and PDI of three pyrazine derivatives, 2-methylpyrazine (MP), 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP). The NICS parameters have been shown in previous studies to be,paramount to the prediction of anti-corrosion properties, and have been combined here with HOMA, FLU and PDI and detailed wavefunction analysis to determine the effects from bromination and methylation on pyrazine. The results show that the electron density around the nitrogens, represented by CS tensors, can be good indicators of anti-corrosion efficiency. Additionally, the NICS, FLU and PDI, as aromaticity indicators of molecule, are well correlated with experimental corrosion inhibition efficiencies of the studied inhibitors. Bader sampling and detailed wavefunction analysis shows that the major effects from bromination on the pyrazine derivatives affect the Laplacian of the electron density of the ring, delocalizing the aromatic electrons of the carbon atoms into lone pairs and increasing polarization of the Laplacian values. This feature is well agreement with empirical studies, which show that ABP is the most efficient anti-corrosion compound followed by AP and MP, a property which can be attributed and predicted by derivation of the Laplacian of the electron density of the ring nuclei. This study shows the importance of devising DFT methods for development of new corrosion inhibitors, and the strength of electronic and nuclear analysis, and depicts most importantly how corrosion inhibitors composed of aromatic moieties may be modified to increase anti-corrosive properties.

First author: Lehtola, S, Recent developments in LIBXC – A comprehensive library of functionals for density functional theory, SOFTWAREX, 7, 1, (2018)
Abstract: LIBXC is a library of exchange-correlation functionals for density-functional theory. We are concerned with semi-local functionals (or the semi-local part of hybrid functionals), namely local-density approximations, generalized-gradient approximations, and meta-generalized-gradient approximations. Currently we include around 400 functionals for the exchange, correlation, and the kinetic energy, spanning more than 50 years of research. Moreover, LIBXC is by now used by more than 20 codes, not only from the atomic, molecular, and solid-state physics, but also from the quantum chemistry communities.

First author: Ohlin, CA, O-17 NMR as a Tool in Discrete Metal Oxide Cluster Chemistry, ANNUAL REPORTS ON NMR SPECTROSCOPY, VOL 94, 94, 187, (2018)
Abstract: This chapter covers recent developments in O-17 NMR spectroscopy as applied to discrete metal oxide clusters, particularly in the context of their use as models in geochemistry and catalysis. Dynamic O-17 NMR methods based on the McConnell-Bloch equations are explored in depth, and recent advances are reviewed. High-pressure NMR methods are also discussed and reviewed, as are recent developments in the use of density functional theory in the computation of O-17 NMR shifts in polyoxometalates. The emphasis of the chapter is on the new developments that promise to reinvigorate O-17 NMR as a central tool in the study of aqueous chemical kinetics, with the most urgent challenges being understanding the rates of isotopic substitution into bridging oxygens in clusters.

First author: Manzetti, S, Bonding of Butylparaben, Bis(2-ethylhexyl)-phthalate, and Perfluorooctanesulfonic Acid to DNA: Comparison with Benzo[a]pyrene Shows Low Probability for Strong Noncovalent DNA Intercalation, CHEMICAL RESEARCH IN TOXICOLOGY, 31, 22, (2018)
Abstract: Parabens, phthalates, and perfluorinated compounds are pollutant compounds used A in cosmetics, plastics, and fire-fighting foams. All three compounds have been studied over several years for toxicity mechanism; however, a clear view of their ability to bind to DNA has not been supplied empirically. In this work, a simulation study is done to reveal the interaction of three of these pollutants, bis(2-ethylhexyl)-phthalate (DEHP), butylparaben (BPRB), and the protonated form of perfluorooctanesulfonic acid (PFOS(H)), with DNA. The results show that the DEHP, PFOS(H), and BPRB bind with a probability of 1/5 to DNA, with respective bonding energies -23.96 kJ/mol (PFOS(H)), -94.92 kJ/mol (BPRB), and -216.52 kJ/mol (DEHP). The positive control, benzo[a]pyrene diol epoxide (BAP), which is known for its notorious DNA intercalation, binds at a rate of 3/5 simulations, with bonding energies of -6544.52, -7034.66, and -7578.67 kJ/mol. The results are compared to empirical studies and conclusively show that all these pollutants can interfere with transcription and DNA related mechanisms by forming noncovalent interactions with DNA. The results show also that these pollutants are unlikely to undergo strong noncovalent intercalation to DNA, such as BAP, and do not possess the frontier orbital profiles to undergo adduct formation. After many years of research and several unanswered questions on the action of these pollutants on DNA, a calculation on their properties hence to the DNA confirms that there is a low probability for these to undergo a strong intercalation with DNA. Literature shows however that the pollutants are strongly interfering with the protein machinery and receptors on the cell surface and are therefore still priority pollutants for ecotoxicity research.

First author: Yu, VWZ, ELSI: A unified software interface for Kohn-Sham electronic structure solvers, COMPUTER PHYSICS COMMUNICATIONS, 222, 267, (2018)
Abstract: Solving the electronic structure from a generalized or standard eigenproblem is often the bottleneck in large scale calculations based on Kohn-Sham density-functional theory. This problem must be addressed by essentially all current electronic structure codes, based on similar matrix expressions, and by high-performance computation. We here present a unified software interface, ELSI, to access different strategies that address the Kohn-Sham eigenvalue problem. Currently supported algorithms include the dense generalized eigensolver library ELPA, the orbital minimization method implemented in libOMM, and the pole expansion and selected inversion (PEXSI) approach with lower computational complexity for semilocal density functionals. The ELSI interface aims to simplify the implementation and optimal use of the different strategies, by offering (a) a unified software framework designed for the electronic structure solvers in Kohn-Sham density-functional theory; (b) reasonable default parameters for a chosen solver; (c) automatic conversion between input and internal working matrix formats, and in the future (d) recommendation of the optimal solver depending on the specific problem. Comparative benchmarks are shown for system sizes up to 11,520 atoms (172,800 basis functions) on distributed memory supercomputing architectures.

First author: Megger, DA, Mixed guanine, adenine base quartets: possible roles of protons and metal ions in their stabilization, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, 23, 41, (2018)
Abstract: Structural variations of the well-known guanine quartet (G(4)) motif in nucleic acid structures, namely substitution of two guanine bases (G) by two adenine (A) nucleobases in mutual trans positions, are discussed and studied by density functional theory (DFT) methods. This work was initiated by three findings, namely (1) that GA mismatches are compatible with complementary pairing patterns in duplex-DNA structures and can, in principle, be extended to quartet structures, (2) that GA pairs can come in several variations, including with a N1 protonated adeninium moiety (AH), and (3) that cross-linking of the major donor sites of purine nucleobases (N1 and N7) by transition metal ions of linear coordination geometries produces planar purine quartets, as demonstrated by some of us in the past. Here, possible structures of mixed AGAG quartets both in the presence of protons and alkali metal ions are discussed, and in particular, the existence of a putative four-purine, two-metal motif.

First author: Kremennaya, MA, The Atomic Structure of Cu(II) Acetate-Bipyridine Under Thermal Decomposition: An X-Ray Spectroscopy Study, JOURNAL OF STRUCTURAL CHEMISTRY, 59, 64, (2018)
Abstract: A number of experimental techniques were used to study the changes in the atomic structure of copper(II) acetate-bipyridine under thermal decomposition between 25A degrees C and 700A degrees C to form copper-containing nanoparticles. The dynamics of structural changes during decomposition in a thermogravimetric chamber is compared with X-ray absorption spectra, IR spectra, and diffraction patterns for a sequence of annealing temperatures. The experimental results were used to construct theoretical structural models of the complex under thermal decomposition.

First author: Zhao, RD, Intermolecular orbital interaction in systems, MOLECULAR PHYSICS, 116, 978, (2018)
Abstract: Intermolecular interactions, in regard to which people tend to emphasise the noncovalent van der Waals (vdW) forces when conducting investigations throughout chemistry, can influence the structure, stability and function of molecules and materials. Despite the ubiquitous nature of vdW interactions, a simplified electrostatic model has been popularly adopted to explain common intermolecular interactions, especially those existing in -involved systems. However, this classical model has come under fire in revealing specific issues such as substituent effects, due to its roughness; and it has been followed in past decades by sundry explanations which sometimes bring in nebulous descriptions. In this account, we try to summarise and present a unified model for describing and analysing the binding mechanism of such systems from the viewpoint of energy decomposition. We also emphasise a commonly ignored factor-orbital interaction, pointing out that the noncovalent intermolecular orbital interactions actually exhibit similar bonding and antibonding phenomena as those in covalent bonds.

First author: Navamani, K, Theoretical modeling of charge transport in triphenylamine-benzimidazole based organic solids for their application as host-materials in phosphorescent OLEDs, RSC ADVANCES, 8, 30021, (2018)
Abstract: The dynamic disorder and electric field effects on charge transport in triphenylamine-benzimidazole based molecular solids have been investigated using electronic structure calculations, molecular dynamics and Monte-Carlo simulations. During the charge propagation, the energy loss of the carrier in each hopping step is monitored by Monte-Carlo simulation. We derive a survival probability correlated momentum-energy distribution for drift-diffusion analysis and we demonstrate the dispersion initiated charge trapping mechanism which is indeed ideal for light emission efficiency via recombination. In the present model, the proposed carrier drift energy-current density expression and Shockley diode current density equation are used to study the current density-voltage characteristics; accordingly the ideality factor (approximate to 1.8-2.0) dictates the deviation of Einstein’s classical diffusion-mobility relation (where the ideality factor is unity). The dual mechanism of electric field assisted site energy gap on coherent-like transport and the electric field stretched dispersion on recombination are observed in tris(3-(1-phenyl-1H-benzimidazole-2-yl)biphenyl-4-yl)amine (TBBI) and tris(4-(1-phenyl-1H-benzimidazole-2-yl)biphenyl-4-yl)amine (TIBN) molecular systems, which can be used as host materials in organic light emitting diodes (OLEDs). We find the transport going from coherent to incoherent, due to the conversion mechanism of dynamic to static disorder. This can also be a controlled by applied electric field. By adjusting the applied electric field, film thickness and changing the -stacked molecular aggregation via substitutions, one can fix the dispersive parameter and accordingly calculate the charge transport properties to design efficient host-materials for photovoltaic and light emitting diode devices.

First author: Lein, M, Structure and Bonding in Hexa-tert-butyl-hexa-perihexabenzocoronene Sandwich Complexes of Ruthenium, AUSTRALIAN JOURNAL OF CHEMISTRY, 71, 222, (2018)
Abstract: We evaluate the balance of steric and electronic effects in the site selectivity of the binding of [Rh(Me5Cp)] thorn ([RhCp.](+)) to the three possible coordination sites of the polyaromatic hydrocarbon (PAH) hexa-tert-butyl-hexa-peri-hexabenzocoronene (HBBC). We find that despite the close proximity of sterically demanding tert-butyl groups to the methyl groups of the Cp* ligand, the extent of steric repulsion is minor compared to electronic interaction from bond formation and that the site selectivity is best explained in terms of the electronics of the (poly) aromatic system. This is in contrast to previous investigations on similar systems with a COD ligand where steric influence has been shown to dominate selectivity.

First author: Vinodha, M, Counter anion effect on structural, opto-electronic and charge transport properties of fused pi-conjugated imidazolium compound, MOLECULAR PHYSICS, 116, 1145, (2018)
Abstract: The structure-activity relationship of fused pi-conjugated imidazolium cation with three counter anion molecules, BF4-, CF3SO3- and (CF3SO2)(2)N-, was studied using electronic structure calculations. The structural, opto-electronic and charge transport properties of these complexes were studied. The charge transfer from pi-conjugated imidazolium(I) to counter anion was confirmed in all the studied complexes. Interaction energy varies significantly depending on the counter anion and the stability was found higher for I-BF4 complex than both I-CF3SO3 and I-(CF3SO2)(2)N complexes. The strong (C-H)(+)center dot center dot center dot F- hydrogen bond of length 1.95 angstrom between fused pi-conjugated imidazolium and BF4- anion is the driving force for the strongest interaction energy in I-BF4 complex. The energy decomposition analysis confirms that the interaction between imidazolium and counter anion is mainly driven by electrostatic and orbital interaction. It has been observed that the absorption spectra of the complex are independent of anion nature but the influence of anion character is observed on frontier molecular orbital pattern. The charge transport property of I-BF4 complex was studied by using tight-binding Hamiltonian approach and found that the hole mobility in I-BF4 is 1.13 x 10(-4) cm(2) V-1 s(-1).

First author: Rusakova, IL, Relativistic effects in the NMR spectra of compounds containing heavy chalcogens, MENDELEEV COMMUNICATIONS, 28, 1, (2018)
Abstract: An accurate and efficient prediction of the NMR spectra of organoelement compounds containing heavy elements is on the cutting edge of the modern chemistry. Reviewed herewith are the relativistic effects provided by heavy chalcogens on light and heavy nuclei (accordingly, HALA and HAHA effects), which play a major role in the interpretation of the NMR spectra of vitally important chalcogen-containing compounds and should certainly be taken into account for practical purposes.

First author: Zhang, ZY, Spin polarization and dispersion effects in emergence of roaming transition state for nitrobenzene isomerization, CHINESE PHYSICS B, 27, 1, (2018)
Abstract: Since roaming was found as a new but common reaction path of isomerization, many of its properties, especially those of roaming transition state (TSR), have been studied on many systems. However, the mechanism of roaming is still not clear at an atomic level. In this work, we use first-principles calculations to illustrate the detailed structure of TSR in an internal isomerization process of nitrobenzene. The calculations distinctively show its nature of antiferromagnetic coupling between two roaming fragments. Moreover, the effect of dispersion is also revealed as an important issue for the stability of the TSR. Our work provides a new insight into the TSR from the view of electronic structure and contributes to the basic understanding of the roaming systems.

First author: Solovyev, IV, Synthesis, photophysical properties and cationbinding studies of bipyridine-functionalized gold(I) complexes, INORGANIC CHEMISTRY FRONTIERS, 5, 160, (2018)
Abstract: Gold(I) has been used as an interlocking center to design five phenyl-bipyridine based complexes [LAu(L1)] and [RAu(L2)] where L1 = 5-(4-ethynylphenyl)-2,2′-bipyridine and L2 = 5-(4-(diphenylphosphino) phenyl)-2,2′-bipyridine (L = P(C6H11)(3), 1; C6H3(CH3)(2)NC, 2; R = Ph2OHCC2, 3; PhC2, 4; C(6)F(5)d, 5). The obtained compounds have been characterized by polynuclear NMR spectroscopy and X-ray crystallography. Investigation of their UV-Vis absorption and emission characteristics has been supported by density functional theory (DFT) calculations that rationalize the tunable electronic properties of these compounds. Complexation of the metal cations and the corresponding optical responses of [LAu(L1)], in particular for Cd(II) and Pb(II), indicate the important role of gold(I) ions in modulating the luminescence characteristics of these species upon binding the analyte cations.

First author: Talaga, P, ETS-NOCV decomposition of the reaction force for double-proton transfer in formamide-derived systems, JOURNAL OF MOLECULAR MODELING, 24, 160, (2018)
Abstract: The analysis of the electronic-structure changes along IRC paths for double-proton-transfer reactions in the formamide dimer (R1), formamide-thioformamide system (R2), and the thioformamide dimer (R3) was performed based on the extendedtransition- state natural orbitals for chemical valence (ETS-NOCV) partitioning of the reaction force, considering the intra-fragments strain and the inter-fragments interaction terms, and further-the electrostatic, Pauli-repulsion and orbital interaction components, with the latter being decomposed into the NOCV components. Two methods of the system partitioning into the fragments were considered (‘reactant perspective’ / bond-formation, ‘product perspective’ / bond-breaking). In agreement with previous studies, the results indicate that the major changes in the electronic structure occur in the transition state region; the bond-breaking processes are, however, initiated already in the reactant region, prior to entering the TS region. The electrostatic contributions were identified as the main factor responsible for the increase in the activation barrier in the order R1 < R2 < R3.

First author: Rabanal-Leon, WA, Exploring the potential energy surface of small lead clusters using the gradient embedded genetic algorithm and an adequate treatment of relativistic effects, RSC ADVANCES, 8, 145, (2018)
Abstract: It is a well-known fact that theoretical methodologies play a crucial role to assure an adequate structural assignment of gas-phase clusters. Particularly, in heavy-element containing clusters the inclusion of relativistic effects (scalar and spin-orbit coupling) can significantly affect their chemistry. Therefore, these effects become the keystone on their structural determination. In our work, the way in which relativistic effects were treated, as well as their influence in the process of an adequate identification of lowest-energy isomer (the global minima – “GM” – energy structure), were evaluated in small lead clusters. The potential energy surfaces of small Pb-n (n = 3-10) clusters was explored by means of the gradient embedded genetic algorithm program (GEGA). Subsequently, the most stable isomers were re-optimized incorporating relativistic effects through two different approximations: (i) using relativistic effective core potentials (RECPs) or pseudopotentials, which mimics the scalar and spin-orbit coupling relativistic effects (SR and SO) of the core electrons; and (ii) using relativistic Hamiltonians (with proper all-electron basis sets), like, the zeroth-order regular approximation (ZORA) to the Dirac equation, in which the scalar (SR) and spin-orbit coupling (SOC) relativistic effects were also included. The results evidence that methodologies including SOC effect allow to identify the GM energy structure correctly in all the studied cases. Besides, the GEGA algorithm, using a modest RECP, provides good initial structures that become GM after re-optimization at the SOC level.

First author: Yu, TR, Actinide endohedral boron clusters: A closed-shell electronic structure of U@B-40, NANO RESEARCH, 11, 354, (2018)
Abstract: The distinctive electronic bonding properties of actinide-containing clusters have made them the subject of increased attention. Herein, we use density functional theory calculations to examine a unique actinide-encapsulated U@B-40 cage structure, revealing that it exhibits a 32-electron (1S(21)P(61)D(101)F(14)) closed-shell singlet configuration in which all s, p, d, and f shells of the U atom are filled. Furthermore, the binding energy of 8.22 eV calculated for this cluster implies considerable stability, and the simulated infrared and Raman spectra feature U-B-40 stretching and pure B-40 breathing vibration modes, respectively. These spectral characteristics may aid future experimental investigations. Thus, this work not only describes a new member of the superatomic family, but also provides a method of encapsulating radioactive actinides.

First author: Lu, SI, Application of discrete solvent reaction field model with self-consistent atomic charges and atomic polarizabilities to calculate the chi((1)) and chi((2)) of organic molecular crystals, CHEMICAL PHYSICS LETTERS, 691, 8, (2018)
Abstract: We use the discrete solvent reaction field model to evaluate the linear and second-order nonlinear optical susceptibilities of 3-methyl-4-nitropyridine-1-oxyde crystal. In this approach, crystal environment is created by supercell architecture. A self-consistent procedure is used to obtain charges and polarizabilities for environmental atoms. Impact of atomic polarizabilities on the properties of interest is highlighted. This approach is shown to give the second-order nonlinear optical susceptibilities within error bar of experiment as well as the linear optical susceptibilities in the same order as experiment. Similar quality of calculations are also applied to both 4-N, N-dimethylamino-3-acetamidonitrobenzene and 2-methyl-4-nitroaniline crystals.

First author: Mondal, S, A possible reason behind the initial formation of pentagonal dodecahedron cavities in sI-methane hydrate nucleation: A DFT study, CHEMICAL PHYSICS LETTERS, 691, 415, (2018)
Abstract: this letter, a possible reason behind selective host-guest organization in the initial stage of sI methane hydrate nucleation is provided, through density functional theory based calculations. In doing so, we have connected earlier experimental and theoretical observations on the structure and energetics of sI methane hydrate to our findings. Geometry and relative stability of small (H2O)(5) and (H2O)(6) clusters, presence of CH4 guest, integrity and cavity radius of (H2O)(20) and (H2O)(24), as well as the weak van der Waals type of forces, particularly dispersion interaction, are major factors responsible for initial formation of methane encapsulated dodecahedron cavity over tetrakaidecahedron.

First author: Zhang, HM, Photophysical and photochemical insights into the photodegradation of sulfapyridine in water: A joint experimental and theoretical study, CHEMOSPHERE, 191, 1021, (2018)
Abstract: For organic pollutants, photodegradation, as a major abiotic elimination process and of great importance to the environmental fate and risk, involves rather complicated physical and chemical processes of excited molecules. Herein, we systematically studied the photophysical and photochemical processes of a widely used antibiotic, namely sulfapyridine. By means of density functional theory (NT) computations, we examined the rate constants and the competition of both photophysical and photochemical processes, elucidated the photochemical reaction mechanism, calculated reaction quantum yield (Phi) based on both photophysical and photochemical processes, and subsequently estimated the photodegradation rate constant. We further conducted photolysis experiments to measure the photodegradation rate constant of sulfapyridine. Our computations showed that sulfapyridine at the lowest excited singlet state (Si) mainly undergoes internal conversion to its ground state, and is difficult to transfer to the lowest excited triplet states (T-1) via intersystem crossing (ISC) and emit fluorescence. In T-1 state, compared with phosphorescence emission and ISC, chemical reaction is much easier to initiate. Encouragingly, the theoretically predicted photodegradation rate constant is close to the experimentally observed value, indicating that quantum chemistry computation is powerful enough to study photodegradation involving ultra-fast photophysical and photochemical processes.