2017 publications citing ADF

First author: Vinogradov, MM, Cluster [Co-3(CO)(3)(mu(2)-CO)(3)(mu(3)-C8H8)](-) as a Ligand: Experimental and Theoretical Study,
Abstract: The cluster anion [Co-3(CO)(3)(mu(2)-CO)(3)(mu(3)-C8H8)](-) (2) reacts with fragments [(ring)M](+) and [(cod)M](+) to give the Co3M clusters (ring)MCo3(CO)(3)(mu(3)-CO)(3)(mu(3)-C8H8) {(ring)M = CpFe (3a), Cp*Fe (3b), CpRu (4a), (C4Me4)Co (5)} and (cod)MCo3(CO)(3)(mu(3)-CO)(3)(mu(3)-C8H8) {M = Rh (6), Ir (7)}, respectively. However, 2 does not form stable complexes with [(Ph3P)M](+) species (M = Cu, Ag, Au), which was explained on the basis of DFT calculations by the inefficient overlap between the cluster and fragment orbitals. The structures of 3b and 5 were determined by X-ray diffraction.

First author: Baseggio, O, S2p core level spectroscopy of short chain oligothiophenes,
Abstract: The Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) of short-chain oligothiophenes (thiophene, 2,2′-bithiophene, and 2,2′:5′,2 ”-terthiophene) in the gas phase have been measured in the sulfur L-2,L-3-edge region. The assignment of the spectral features is based on the relativistic two-component zeroth-order regular approximation time dependent density functional theory approach. The calculations allow us to estimate both the contribution of the spin-orbit splitting and of the molecular-field splitting to the sulfur binding energies and give results in good agreement with the experimental measurements. The deconvolution of the calculated S2p NEXAFS spectra into the two manifolds of excited states converging to the L-III and L-II edges facilitates the attribution of the spectral structures. The main S2p NEXAFS features are preserved along the series both as concerns the energy positions and the nature of the transitions. This behaviour suggests that the electronic and geometrical environment of the sulfur atom in the three oligomers is relatively unaffected by the increasing chain length. This trend is also observed in the XPS spectra. The relatively simple structure of S2p NEXAFS spectra along the series reflects the localized nature of the virtual states involved in the core excitation process. Published by AIP Publishing.

First author: Dervaux, J, Probing the interaction between 2,2 ‘-bithiophene-5-carboxylic acid and TiO2 by photoelectron spectroscopy: A joint experimental and theoretical study,
Abstract: The interaction between 2,2′-bithiophene-5-carboxylic acid (PT2) sublimed under ultra-high vacuum conditions and anatase (101) and rutile (110) TiO2 single crystal surfaces is investigated by studying the electronic spectral density near the Fermi level with synchrotron-based spectroscopy. The experimental results are compared to density functional theory calculations of the isolated PT2 molecule and of the molecule adsorbed on an anatase TiO2 (101) cluster. The relative concentrations of Ti, C, and S atoms indicate that the adsorbed molecule remains intact upon deposition, which is typical of a Stranski-Krastanov growth mode. The analysis of the O1s spectrum suggests a predominant bidentate geometry of the adsorption with both rutile and anatase surfaces, as supported by previous theoretical simulations. It is also theoretically and experimentally demonstrated that the PT2 adsorption causes the appearance of new electronic states in the gap near the TiO2 valence band. A pinning effect of the LUMO level of the dye is also theoretically predicted. Published by AIP Publishing.

First author: Ramanantoanina, H, On the calculation of multiplet energies of three-open-shell 4f(13)5f(n)6d(1) electron configuration by LFDFT: modeling the optical spectra of 4f core-electron excitation in actinide compounds,
Abstract: Methodological concepts are reported for the calculation, without empirical parameters, of multiplet energy levels and ligand-field effects associated with three-open-shell 4f(13)5f(n)6d(1) electron configurations, and for the modeling of X-ray absorption spectra in relation to intra-atomic 5f(n) -> 4f(13)5f(n)6d(1) electron transitions. A density functional theory (DFT) method is used for the determination of the electronic structure. An effective ligand-field Hamiltonian is also used to incorporate many body effects and corrections via the configuration interaction algorithm within the active space of Kohn-Sham orbitals with dominant actinide 4f, 5f and 6d characters. The theoretical method ensures a parameter-free ligand-field model, which will be implemented in the Amsterdam density functional (ADF) program package as part of the available and automated ligand-field density functional theory (LFDFT) routine. The theoretical method is illustrated with examples for applications: U4+ in the free ion and U4+ in bulk UO2 by means of the molecular (UO8)(12-) cluster. The DFT calculations are performed at different levels of the DFT functional, from which the LFDFT parameters such as Slater-Condon integrals, spin-orbit coupling constants and ligand-field potential (represented within the Wybourne formalism) are emulated. The comparison with available experimental data is good. Therefore, a non-empirical ligand-field treatment of the 4f(13)5f(n)6d(1) configuration is established illustrating the spectroscopic details of the 4f core-electron excitation, which can be valuable for further understanding and prediction of the spectral profiles of actinide N-6,N-7-edge X-ray absorption spectroscopy.

First author: Kowalska, P, Detection of a weak ring current in a nonaromatic porphyrin nanoring using magnetic circular dichroism,
Abstract: We compare the absorption and magnetic circular dichroism (MCD) spectra of a series of porphyrin oligomers – dimer, tetramer, and hexamer – bound in a linear or cyclic fashion. The MCD signal is extremely weak for low energy transitions in the linear oligomers, but it is amplified when the cyclic porphyrin hexamer binds a template, restricting rotational freedom. The appearance of Faraday A terms in the MCD spectra demonstrates the presence of a magnetic moment, and thus, uncompensated electronic current. The value of the excited state magnetic moment estimated from the A term is very low compared with those of monomeric porphyrins, which confirms the nonaromatic character of the cyclic array and the lack of a global ring current in the ground state of the neutral nanoring. DFT calculations predict the absorption and MCD patterns reasonably well, but fail to reproduce the MCD sign inversion observed in substituted monomeric zinc porphyrins (“soft” chromophores). Interestingly, a correct sign pattern is predicted by INDO/S calculations. Analysis of the MCD spectra of the monomeric porphyrin unit allowed us to distinguish between two close-lying lowest energy transitions, which some previous assignments placed further apart. The present results prove the usefulness of MCD not only for deconvolution and assignment of electronic transitions, but also as a sensitive tool for detecting electronic ring currents.

First author: Stoyanov, ES, Protonation of N2O and NO2 in a solid phase,
Abstract: Adsorption of gaseous N2O on the acidic surface Bronsted centers of the strongest known solid acid, H(CHB11F11), results in formation of the N N-OH+ cation. Its positive charge is localized mainly to the H-atom, which is H-bonded to the CHB11F11- anion forming an asymmetric proton disolvate of the L-1-H+center dot center dot center dot L-2 type, where L-1 = N2O and L-2 = CHB11F11-. NO2 protonation under the same conditions leads to the formation of the highly reactive cation radical NO2H center dot+, which reacts rapidly with an NO2 molecule according to the equation N2OH+ + NO2 –> [N2O4H+] –> N2OH+ + O-2 resulting in the formation of two types of N2OH+ cations: (i) a typical Bronsted superacid, N N-OH+, with a strongly acidic OH group involved in a rather strong H-bond with the anion, and (ii) a typical strong Lewis acid, N N+-OH, with a positive charge localized to the central N atom and ionic interactions with the surrounding anions via the charged central N atom.

First author: Chiang, NH, Probing Intermolecular Vibrational Symmetry Breaking in Self-Assembled Monolayers with Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy,
Abstract: Ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) combines the atomic-scale imaging capability of scanning probe microscopy with the single-molecule chemical sensitivity and structural specificity of surface-enhanced Raman spectroscopy. Here, we use these techniques in combination with theory to reveal insights into the influence of intermolecular interactions on the vibrational spectra of a N-N’-bis(2,6-diisopropylphenyl)-perylene-3,4: 9,10-bis ( dicarboximide) (PDI) self-assembled monolayer adsorbed on single-crystal Ag substrates at room temperature. In particular, we have revealed the lifting of a vibrational degeneracy of a mode of PDI on Ag(111) and Ag(100) surfaces, with the most strongly perturbed mode being that associated with the largest vibrational amplitude on the periphery of the molecule. This work demonstrates that UHV-TERS enables direct measurement of molecule molecule interaction at nanoscale. We anticipate that this information will advance the fundamental understanding of the most important effect of intermolecular interactions on the vibrational modes of surface-bound molecules.

First author: Behnia, A, Reactivity of a Palladacyclic Complex: A Monodentate Carbonate Complex and the Remarkable Selectivity and Mechanism of a Neophyl Rearrangement,
ORGANOMETALLICS, 36, 4759, (2017)
Abstract: The ligand N(CH2-2-C5H4N)(2)(CH2CH2CH2OH), L1, reacted with [Pd(CH2CMe2C6H4)(COD)] to give a new fluxional “cycloneophyl” organopalladium complex [Pd(CH2CMe2C6H4)(kappa(2)-L1)], 1, which on attempted recrystallization from THF gave the monodentate carbonate complex [Pd(CO3)(kappa(3)-L1)], 2. Complex 2 was prepared in designed syntheses by reaction of [PdCl(kappa(3)-L1)]+ with silver carbonate or by reaction of [Pd(OH)(kappa(3)-L1)]+ with CO2. Complex 1 reacted with aqueous CO2 to give the cationic neophylpalladium complex [Pd(CH2CMe2C6H5)(kappa 3-L1)]+(HCO3)-, 6. Complex 6 reacts with hydrogen peroxide to give complex 2 with release of a mixture of organic products, the major one being 2-phenyl-2-butanol, PB. The formation of PB involves a neophyl rearrangement with the unprecedented preference for methyl over phenyl migration. A mechanistic basis for this unexpected reaction is proposed, involving beta-carbon elimination at a palladium(IV) center.

First author: Paenurk, E, Trends in Metallophilic Bonding in Pd-Zn and Pd-Cu Complexes,
ORGANOMETALLICS, 36, 4854, (2017)
Abstract: Metallophilic interactions stabilize the bond between closed-shell metal centers, which electrostatically repel one another. Since their introduction, the origin of these interactions has been argued to be either London dispersion forces or dative bonding, but as yet, there is no definitive answer. Insight into the nature of metallophilic bonding would provide the key for rational tuning of the stabilizing interaction, for example, in specific transmetalation transition states. We now report on a computational study focused on the metallophilic d(8)-d(10) bond in recendy published families of Pd(II)-Cu(I) and Pd(II)-Zn(n) heterobimetallic compexes. We show that dative bonding outweighs dispersion interaction in controlling the metallophilic bonding energy in the studied heterobimetallic complexes, and elucidate the governing orbital interactions.

First author: Hamdaoui, M, Iridacycles as Catalysts for the Autotandem Conversion of Nitriles into Amines by Hydrosilylation: Experimental Investigation and Scope,
ORGANOMETALLICS, 36, 4864, (2017)
Abstract: The set of iridacycles [{C,N}Cp*Ir-III-Cl] ({C,N} = benzo[h]quinoline, dibenzo[f,h]quinoline) containing the (pentamethylcyclopentadienyl)iridium(III) unit were synthesized and derivatized into cations [{C,N}Cp*Ir-NCMe](+) associated with BArF-type anions. The latter salts were benchmarked for their potential catalytic properties toward HSiEt3 in a H-2-releasing test reaction. The best-performing BArF-type salts demonstrated the capability to promote with a low catalytic load of ca. 0.5-1 mol % the autotandem hydrosilylation of acetonitrile, propionitrile, and a series of arylnitrile substrates. Mechanistic investigations confirmed the preliminary formation of a silane-iridacycle adduct by electrophilic and heterolytic activation of the Si-H bond. The molecular structure of a new example of such an adduct was resolved by X-ray diffraction analysis. Theoretical considerations support a donor-acceptor [{C,N}Cp*Ir-III-H]->[SiEt3](+)({C,N} = benzo[h]quinolinyl) formulation where the cationic silyl moiety acting as a Z ligand binds both Ir and H centers. Under the conditions of the catalysis, the latter adduct is assumed to transfer readily the electrophilic [SiEt3](+) moiety to the nucleophilic nitrile substrate to form a

First author: Heshmat, M, Theory-Based Extension of the Catalyst Scope in the Base-Catalyzed Hydrogenation of Ketones: RCOOH-Catalyzed Hydrogenation of Carbonyl Compounds with H-2 Involving a Proton Shuttle,
Abstract: As an extension of the reaction mechanism describing the base-catalyzed hydrogenation of ketones according to Berkessel et al., we use a standard methodology for transition-state (TS) calculations in order to check the possibility of heterolytic cleavage of H-2 at the ketone’s carbonyl carbon atom, yielding one-step hydrogenation path with involvement of carboxylic acid as a catalyst. As an extension of the catalyst scope in the base-catalyzed hydrogenation of ketones, our mechanism involves a molecule with a labile proton and a Lewis basic oxygen atom as a catalyst-for example, R-C(=O) OH carboxylic acids-so that the heterolytic cleavage of H-2 could take place between the Lewis basic oxygen atom of a carboxylic acid and the electrophilic (Lewis acidic) carbonyl carbon of a ketone/aldehyde. According to our TS calculations, protonation of a ketone/aldehyde by a proton shuttle (hydrogen bond) facilitates the hydride-type attack on the ketone’s carbonyl carbon atom in the process of the heterolytic cleavage of H-2. Ketones with electron-rich and electron-withdrawing sub-stituents in combination with a few carboxylic and amino acids-in total, 41 substrate-catalyst couples-have been computationally evaluated in this article and the calculated reaction barriers are encouragingly moderate for many of the considered substrate-catalyst couples.

First author: Ganguly, S, Electronic Structure of Cobalt-Corrole-Pyridine Complexes: Noninnocent Five-Coordinate Co(II) Corrole-Radical States,
Abstract: Two sets of complexes of Co-triarylcorrole-bispyridine complexes, Co[TpXPC](py)(2) and Co[Br(8)TpXPC](py)(2) have been synthesized, where TpXPC refers to a meso-tris(para-X-phenyl)corrole ligand with X = CF3, H, Me, and OMe and Br8TpXPC to the corresponding beta-octabrominated ligand. The axial pyridines in these complexes were found to be labile and, in dilute solutions in dichloromethane, the complexes dissociate almost completely to the five-coordinate monopyridine complexes. Upon addition of a small quantity of pyridine, the complexes revert back to the six coordinate forms. These transformations are accompanied by dramatic changes in color and optical spectra. H-1 NMR spectroscopy and X-ray crystallography have confirmed that the bispyridine complexes are authentic low-spin Co(III) species. Strong substituent effects on the Soret maxima and broken-symmetry DFT calculations, however, indicate a Co-II-corrole(center dot 2-) formulation for the five-coordinate Co[TpXPC]-(py) series. The calculations implicate a Co(d(z)(2))-corrole(“a(2u)”) orbital interaction as responsible for the metal-ligand antiferromagnetic coupling that leads to the open-shell singlet ground state of these species. Furthermore, the calculations predict two low-energy S = 1 intermediate-spin Co(III) states, a scenario that we have been able to experimentally corroborate with temperature-dependent EPR studies. Our findings add to the growing body of evidence for noninnocent electronic structures among first-row transition metal corrole derivatives.

First author: Chauhan, V, CO ligands stabilize metal chalcogenide Co6Se8(CO)(n) clusters via demagnetization,
Abstract: The role of carbon monoxide ligands on the magnetic moment of Co6Se8(CO)(n) clusters, n = 0-6 was investigated to better understand the interplay between the electronic structure of metal chalcogenide clusters and their ligands. We find that the addition of CO ligands to Co6Se8 results in the gradual demagnetization of the cluster. Generally, the addition of a CO ligand effectively adds two electrons to the cluster that occupy deeper states and further pushes up an antibonding orbital out of the valence manifold of cluster states. Through such processes, the fully ligated Co6Se8(CO)(6) cluster attains a closed electronic shell with a large gap between occupied and unoccupied states. Each removal of a CO ligand from the cluster then stabilizes an antibonding state that adds unoccupied states to the valence manifold. Such a cluster with partially filled states may either deform as in a Jahn-Teller distortion to quench the spin, or maintain its core structure and be stabilized in a high spin state as in Hund’s rules. As these clusters generally maintain their octahedral core, the high spin state prevails and the removal of the ligands results in an increase in spin multiplicity.

First author: Sebechlebska, T, Investigation of the geometrical arrangement and single molecule charge transport in self-assembled monolayers of molecular towers based on tetraphenylmethane tripod,
ELECTROCHIMICA ACTA, 258, 1191, (2017)
Abstract: Multipodal molecular platforms were designed recently to establish a well-defined contact between molecular electronic components and metallic electrodes to manufacture working devices based on molecular electronics. In this work, we use electrochemical techniques, scanning tunneling microscopy break junction technique and theoretical approaches combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF) formalism to investigate the geometrical arrangement and single molecule charge transport in self-assembled monolayers (SAMs) of molecular towers anchored by tetraphenylmethane tripod on Au (111) surface. The effect of the molecular length as well as the role of the position of anchoring groups was addressed. Electrochemical double-layer capacitance measurements and reductive desorption studies combined with theoretical modeling clearly demonstrated that the molecular towers form densely packed SAMs, in which the individual molecules are attached to the Au (111) surface by the tripodal base and the principal molecular axis is directed away from the electrode surface, providing thus desired orientation. Temperature resolved single molecule conductance measurements combined with DFT/NEGF calculations showed that the electric charge is transported by tunneling via highly conductive molecular junctions formed by the tripodal base. Our combined experimental and theoretical work demonstrates that tetraphenylmethane tripods are suitable platforms to bear functional groups serving as molecular electronic components.

First author: Hu, KQ, Novel Viologen Derivative Based Uranyl Coordination Polymers Featuring Photochromic Behaviors,
Abstract: A series of novel uranyl coordination polymers have been synthesized by hydrothermal reactions. Both complexes 1 and 2 prosess two ipbp(-) ligands (H(2)ipbpCl=1-(3,5-dicarboxyphenyl)-4,4-bipyridinium chloride), one uranyl cation, and two coordination water molecules, which can further extend to 2D networks through hydrogen bonding. In complex 1, two sets of equivalent nets are entangled together, resulting in a 2D + 2D 3D polycatenated framework. In complex 2, the neighbouring equivalent nets interpenetrate each other, forming a twofold interpenetrated network. Complexes 3 and 4 are isomers, and both of them are constructed from (UO2)(2)(OH)(2) dinuclear units, which are connected with four ipbp(-) ligands. The 3D structures of complexes 3 and 4 are similar along the b axis. Similar to other viologen-based coordination polymers, complexes 3 and 4 exhibit photochromic and thermochromic properties, which are rarely observed in actinide coordination polymers. Unlike the monotonous coordination mode in complexes 1-4, the ipbp(-) ligands feature a (3)-bridge through two kinds of coordination modes in complex 5. Notably, complex 5 presents a unique example in which terminal pyridine nitrogen atom is involved in the coordination.

First author: Smith, JS, ANI-1, A data set of 20 million calculated off-equilibrium conformations for organic molecules,
SCIENTIFIC DATA, 4, 18074, (2017)
Abstract: One of the grand challenges in modern theoretical chemistry is designing and implementing approximations that expedite ab initio methods without loss of accuracy. Machine learning (ML) methods are emerging as a powerful approach to constructing various forms of transferable atomistic potentials. They have been successfully applied in a variety of applications in chemistry, biology, catalysis, and solid-state physics. However, these models are heavily dependent on the quality and quantity of data used in their fitting. Fitting highly flexible ML potentials, such as neural networks, comes at a cost: a vast amount of reference data is required to properly train these models. We address this need by providing access to a large computational DFT database, which consists of more than 20M off equilibrium conformations for 57,462 small organic molecules. We believe it will become a new standard benchmark for comparison of current and future methods in the ML potential community.

First author: Ganguly, S, Cobalt- and Rhodium-Corrole-Triphenylphosphine Complexes Revisited: The Question of a Noninnocent Corrole,
INORGANIC CHEMISTRY, 56, 14788, (2017)
Abstract: A reinvestigation of cobalt-corrole-triphenylphosphine complexes has yielded an unexpectedly subtle picture of their electronic structures. UV-vis absorption spectroscopy, skeletal bond length alternations observed in X-ray structures, and broken-symmetry DFT (B3LYP) calculations suggest partial Co-II-corrole(center dot 2-) character for these complexes. The same probes applied to the analogous rhodium corroles evince no evidence of a noninnocent corrole. X-ray absorption spectroscopic studies showed that the Co K rising edge of Co[TPC]-(PPh3) (TPC = triphenylcorrole) is red-shifted by similar to 1.8 eV relative to the bona fide Co(III) complexes Co[TPC](py)(2) and Co[TPP](py)Cl (TPP = tetraphenylporphyrin, py = pyridine), consistent with a partial Co-II-corrole(center dot 2-) description for Co[TPC](PPh3). Electrochemical measurements have shown that both the Co and Rh complexes undergo two reversible oxidations and one to two irreversible reductions. In particular, the first reduction of the Rh corroles occurs at significantly more negative potentials than that of the Co corroles, reflecting significantly higher stability of the Rh(III) state relative to Co(III). Together, the results presented herein suggest that cobalt-corrole-triphenylphosphine complexes are significantly noninnocent with moderate Co-II-corrole(center dot 2-) character, underscoring-yet again-the ubiquity of ligand noninnocence among first-row transition metal corroles.

First author: Vallet, V, Structure and Bonding in Uranyl(VI) Peroxide and Crown Ether Complexes; Comparison of Quantum Chemical and Experimental Data,
INORGANIC CHEMISTRY, 56, 15231, (2017)
Abstract: The structure, chemical bonding, and thermodynamics of alkali ions in M[12-crown-4](+), M[15-crown-5](+), and M[18-crown-6](+), M[UO2(O-2)(OH2)(2)](4,5)(+), and M[UO2(O-2)(OH)(OH2)]n(1)n (n = 4, 5) complexes have been explored by using quantum chemical (QC) calculations at the ab initio level. The chemical bonding has been studied in the gas phase in order to eliminate solvent effects. QTAIM analysis demonstrates features that are very similar in all complexes and typical for electrostatic M-O bonds, but with the M-O bonds in the uranyl peroxide systems about 20 kJ mol(-1) stronger than in the corresponding crown ether complexes. The regular decrease in bond strength with increasing M-O bond distance is consistent with predominantly electrostatic contributions. Energy decomposition of the reaction energies in the gas phase and solvent demonstrates that the predominant component of the total attractive (Delta E-elec + Delta E-orb) energy contribution is the electrostatic component. There are no steric constraints for coordination of large cations to small rings, because the M+ ions are located outside the ring plane, [O-n], formed by the oxygen donors in the ligands; coordination of ions smaller than the ligand cavity results in longer than normal MO distances or in a change in the number of bonds, both resulting in weaker complexes. The Gibbs energies, enthalpies, and entropies of reaction calculated using the conductor-like screening model, COSMO, to account for solvent effects deviate significantly from experimental values in water, while those in acetonitrile are in much better agreement. Factors that might affect the selectivity are discussed, but our conclusion is that present QC methods are not accurate enough to describe the rather small differences in selectivity, which only amount to 510 kJ mol(-1). We can, however, conclude on the basis of QC and experimental data that M[crown ether](+) complexes in the strongly coordinating water solvent are of outer-sphere type, [M(OH2)n(+)][crown ether], while those in weakly coordinating acetonitrile are of inner-sphere type, [M-crown ether](+). The observation that the M[UO2(O-2)(OH)(OH2)]n(+)n complexes are more stable in solution than those of M[crown ether](+) is an effect of the different charges of the rings.

First author: Ahumada, G, Spectroscopic, structural, electrochemical and computational studies of some new 2-thienyl-containing beta-diketonate complexes of cobalt(II), nickel(II) and copper(II),
Abstract: In this work, we present the synthesis of the unsymmetrical beta-diketone 1-(2-thienyl)-3-(4-fluorophenyl)-propane-1,3-dione (HL) and its corresponding Co(II), Ni(II) and Cu(II) bis(beta-diketonato) complexes 1-3, respectively. The four new compounds were isolated in good yields (65-70%), and characterized by mass spectrometry, elemental analysis, FF-IR and UV-Vis spectroscopy and, in the case of HL, by H-1: C-13 and F-19 NMR spectroscopy. In addition, the molecular identities and the geometries of the beta-diketone HL and complex 3 were confirmed by X-ray diffraction analysis. The dicarbonyl derivative HL does exist as the diketo tautomeric form in DMSO solution and as its keto-enol tautomer in the solid-state with the OH group adjacent to the 4-fluorophenyl unit. The keto-enol isomer was computed to be more stable by 8.2 kcal/mol in free energy at room temperature. In 3, the Cu(II) center adopts a perfect square-planar geometry. Two reduction processes were observed in the cyclovoltammogram of 3 at -1.30 and -1.80 V vs. Fc/Fc(+), with copper deposit on the surface of the electrode. DFT and TD-DFT calculations on HL and complex 3 allow rationalizing their stability, bonding and properties.

First author: Jia, XB, Theoretical studies on the effect of benzene and thiophene groups on the charge transport properties of Isoindigo and its derivatives,
Abstract: In this work, the charge transport properties of Isoindigo (II) and its derivatives which have the same hexyl chain were theoretically investigated by the Marcus-Hush theory combined with density functional theory (DFT). Here we demonstrate that the changes of benzene and thiophene groups in molecular structure have an important influence on the charge transport properties of organic semiconductor. The benzene rings of II are replaced by thiophenes to form the thienoisoindigo (TII), and the addition of benzene rings to the TII form the benzothienoisoindigo (BTII). The results show that benzene rings and thiophenes change the chemical structure of crystal molecules, which lead to different molecule stacking, thus, the length of hydrogen bond was changed. A shorter intermolecular hydrogen bond lead to tighter molecular stacking, which reduces the center-to-center distance and enhances the ability of charge transfer. At the same time, we theoretically demonstrated that II and BTII are the ambipolar organic semiconductor. BTII has better carrier mobility. The hole mobility far greater than electron mobility in TII, which is p-type organic semiconductor. Among all hopping path, we find that the distance of face-to-face stacking in II is the shortest and the electron-transport electronic coupling V-e is the largest, but II has not a largest anisotropic mobility, because the reorganization energy has a greater influence on the mobility than the electronic coupling. This work is helpful for designing ambipolar organic semiconductor materials with higher charge transport properties by introducing benzene ring and thiophene.

First author: Palinkas, N, Viable pathways for the oxidative addition of iodobenzene to palladium(0)-triphenylphosphine-carbonyl complexes: a theoretical study,
DALTON TRANSACTIONS, 46, 15789, (2017)
Abstract: The oxidative addition of 4-substituted iodobenzenes on Pd(0) catalysts under CO atmosphere was investigated by means of density functional calculations employing the M06//B97-D3 level of theory. The 18-electron triphenylphosphine-tricarbonyl complex was found to be the global minimum. Several co-ordinatively unsaturated species are predicted to be present both in N,N-dimethylformamide and toluene solution. In terms of activating iodobenzene, bis(triphenylphosphine)palladium(0) was proved to be the most active. However, due to its lower thermodynamic stability, it is slightly inferior to the Pd-triphenylphosphine-carbonyl complex, which is predicted to react with a free energy of activation of 23.2 kcal mol(-1) with respect to the initial resting state tetrakis(triphenylphosphine) palladium(0). The effect of 4-substituents of iodobenzene on reaction energetics is also discussed. The activity of the Pd(0) catalyst was found to be governed by the donor-acceptor strength of the ancillary ligands: the barrier decreases with increasing basicity and decreasing back-donating capability.

First author: Lalitha, M, Gas adsorption efficacy of graphene sheets functionalised with carboxyl, hydroxyl and epoxy groups in conjunction with Stone-Thrower-Wales (STW) and inverse Stone-Thrower-Wales (ISTW) defects,
Abstract: The complete reduction of graphene oxide is difficult to achieve, and hence oxygen-containing functional groups do exist in graphene, along with structural defects. On the other hand, efficient gas sensor materials have been a subject of relentless interest. This instigates the need to explore the gas adsorption on STW and ISTW defective graphene sheets functionalised by -COOH, -OH and C-O-C groups, using density functional theory calculations. Both defects are experimentally feasible as evident through their formation energies. Furthermore mono-functionalisation induces significant buckling of the sheet; in contrast, bi-functionalisation of the sheet restores the planarity of the sheet. We found that the ISTW defective sheet is more reactive than the STW defective sheet to all the functional groups considered, and in particular -COOH is the most adsorptive group to both the defects, while epoxy has consistent adsorptivity towards the defects. Gas molecules such as CO2, H-2, N-2, CH4 and O-2 are physisorbed, whereas HF and H2O are chemisorbed on the functionalised sheets. The sensitivity of the gas molecules towards the functionalised sheets is obtained by Lambda E-g, which is pronounced for pristine + OH and STW + epoxy and bare ISTW defective sheets. However, the functionalised sheets exhibit improved sensing properties for O-2; specifically, mono-epoxy functionalised and bi-carboxylated defective sheets show high sensitivity towards O-2. Furthermore, the surface functionalisation enhances the selectivity of the sensor. From the TDOS plot, the functionalised sheet exhibits p-type behaviour. Thus, the results of this study reveal that the functionalised defective sheets can be utilized as O-2 sensors.

First author: Dau, PD, Remarkably High Stability of Late Actinide Dioxide Cations: Extending Chemistry to Pentavalent Berkelium and Californium,
Abstract: Actinyl chemistry is extended beyond Cm to BkO2+ and CfO2+ through transfer of an O atom from NO2 to BkO+ or CfO+, establishing a surprisingly high lower limit of 73kcalmol(-1) for the dissociation energies, D[O-(BkO+)] and D[O-(CfO+)]. CCSD(T) computations are in accord with the observed reactions, and characterize the newly observed dioxide ions as linear pentavalent actinyls; these being the first Bk and Cf species with oxidation states above IV. Computations of actinide dioxide cations AnO(2)(+) for An=Pa to Lr reveal an unexpected minimum for D[O-(CmO+)]. For CmO2+, and AnO(2)(+) beyond EsO2+, the most stable structure has side-on bonded (2)-(O-2), as An(III) peroxides for An=Cm and Lr, and as An(II) superoxides for An=Fm, Md, and No. It is predicted that the most stable structure of EsO2+ is linear [O=Es-V=O](+), einsteinyl, and that FmO2+ and MdO2+, like CmO2+, also have actinyl(V) structures as local energy minima. The results expand actinide oxidation state chemistry, the realm of the distinctive actinyl moiety, and the non-periodic character towards the end of the periodic table.

First author: Liu, CM, Probing the Impact of Solvation on Photoexcited Spin Crossover Complexes with High-Precision X-ray Transient Absorption Spectroscopy,
Abstract: Investigating the photoinduced electronic and structural response of bistable molecular building blocks incorporating transition metals in solution phase constitutes a necessary stepping stone for steering their properties toward applications and performance optimizations. This work presents a detailed X-ray transient absorption (XTA) spectroscopy study of a prototypical spin crossover (SCO) complex [Fe-II(mbpy)3](2+) (where mbpy = 4,4′-dimethyl-2,2′-bipyridine) with an [(FeN6)-N-II] first coordination shell in water (H2O) and acetonitrile (CH3CN). The unprecedented data quality of the XTA spectra together with the direct fitting of the difference spectra in k space using a large number of scattering paths enables resolving the subtle difference in the photoexcited structures of an Fe-II complex in two solvents for the first time. Compared to the low spin (LS) (1)A(1) state, the average Fe-N bond elongations for the photoinduced high spin (HS) T-5(2) state are found to be 0.181 +/- 0.003 angstrom in H2O and 0.199 +/- 0.003 angstrom in CH3CN. This difference in structural response is attributed to ligand-solvent interactions that are stronger in H2O than in CH3CN for the HS excited state. Our studies demonstrate that, although the metal center of [Fe-II(mbpy)(3)](2+) could have been expected to be rather shielded by the three bidentate ligands with quasi-octahedral coordination, the ligand field strength in the HS excited state is nevertheless indirectly affected by solvation effects that modifies the charge distribution within the Fe-N covalent bonds. More generally, this work highlights the importance of including solvation dynamics in order to develop a generalized understanding of the spin-state switching at the atomic level.

First author: Sebesta, F, The Influence of the Metal Cations and Microhydration on the Reaction Trajectory of the N3 <-> O2 Thymine Proton Transfer: Quantum Mechanical Study,
Abstract: This study involves the intramolecular proton transfer (PT) process on a thymine nucleobase between N3 and O2 atoms. We explore a mechanism for the PT assisted by hexacoordinated divalent metals cations, namely Mg2+, Zn2+, and Hg2+. Our results point out that this reaction corresponds to a two-stage process. The first involves the PT from one of the aqua ligands toward O2. The implications of this stage are the formation of a hydroxo anion bound to the metal center and a positively charged thymine. To proceed to the second stage, a structural change is needed to allow the negatively charged hydroxo ligand to abstract the N3 proton, which represents the final product of the PT reaction. In the presence of the selected hexaaqua cations, the activation barrier is at most 8 kcal/mol.

First author: Sarkar, S, Pyrrole multimers and pyrrole-acetylene hydrogen bonded complexes studied in N-2 and para-H-2 matrixes using matrix isolation infrared spectroscopy and ab initio computations,
Abstract: Hydrogen bonded interaction of pyrrole multimer and acetylene-pyrrole complexes were studied in N-2 and p-H-2 matrixes. OFT computations showed T-shaped geometry for the pyrrole dimer and cyclic complex for the trimer and tetramer were the most stable structures, stabilized by N-H center dot center dot center dot pi interactions. The experimental vibrational wavenumbers observed in N-2 and p-H-2 matrixes for the pyrrole multimers were correlated with the computed wavenumbers. Computations performed at MP2/aug-cc-pVDZ level of theory showed that C2H2 and C4H5N forms 1:1 hydrogen-bonded complexes stabilized by C-H center dot center dot center dot pi interaction (Complex A), N-H center dot center dot center dot pi interaction (Complex B) and pi center dot center dot center dot pi interaction (Complex C), where the former complex is the global minimum and latter two complexes were the first and second local minima, respectively. Experimentally, 1:1 C2H2-C4H5N complexes A (global minimum) and B (first local minimum) were identified from the shifts in the N-H stretching, N-H bending, C-H bending region of pyrrole and C-H asymmetric stretching and bending region of C2H2 in N-2 and p-H-2 matrixes. Computations were also performed for the higher complexes and found two minima corresponding to the 1:2 C2H2-C4H5N and three minima for the 2:1 C2H2-C4H5N complexes. Experimentally the global minimum 1:2 and 2:1 C2H2-C4H5N complexes were identified in N-2 and p-H-2 matrixes.

First author: Mazalov, LN, X-ray emission study of the electronic structure of binuclear niobium complexes with (S-2)(2)-disulfide bridging ligands,
Abstract: The electronic structure of binuclear niobium complexes [Nb2S4(acac)(4)] and K-4[Nb2S4(ox)4] is studied by X-ray emission fluorescent spectroscopy and quantum chemistry techniques. Data on the partial atomic composition of highest occupied molecular orbitals of the complexes are obtained. The energy positions of bonding and antibonding frontier molecular orbitals observed in the X-ray emission spectra of binuclear [Nb-2((S-2)(2-))(2)](4+) clusters are determined by the analysis of overlap populations.

First author: Grabowski, SJ, New Type of Halogen Bond: Multivalent Halogen Interacting with – and sigma-Electrons,
MOLECULES, 22, 1625, (2017)
Abstract: MP2/aug-cc-pVTZ calculations were performed for complexes of BrF3 and BrF5 acting as Lewis acids through the bromine centre, with species playing a role of Lewis base: dihydrogen, acetylene, ethylene, and benzene. The molecular hydrogen donates electrons by its sigma-bond, while in remaining moietiesin complexes of hydrocarbons; such an electron transfer follows from -electrons. The complexes are linked by a kind of the halogen bond that is analyzed for the first time in this study, i.e., it is the link between the multivalent halogen and or sigma-electrons. The nature of such a halogen bond is discussed, as well as various dependencies and correlations are presented. Different approaches are applied here, the Quantum Theory of Atoms in Molecules, Natural Bond Orbital method, the decomposition of the energy of interaction, the analysis of electrostatic potentials, etc.

First author: Binh, DH, Is the R3Si Moiety in Metal-Silyl Complexes a Z ligand? AnAnswer from the Interaction Energy,
Abstract: The computation of metal-silyl interaction energies indicates the existence of situations in which the silyl group behaves as a Z-type ligand according to the Green method of covalent-bond classification. There is a scale of relative intrinsic silylicity , defined as the ratio of the intrinsic silyl-to-triflate interaction energy of a silyltriflate as a reference compound relative to the silyl-to-metal interaction of given complex, that can reveal in a straightforward manner the propensity of SiR3 groups to behave chemically as metal-bound silylium ions, namely, [SiR3](+). Emblematic cases, either taken from the Cambridge Structural Database (CSD) or constructed for the purpose of this study, were also investigated from the viewpoints of extended transition-state natural orbitals for chemical valence (ETS-NOCV) and quantum theory of atoms in molecules (QTAIM) analyses. It is shown in the case of POBMUPwhich is the iridium 1,3-bis[(di-tert-butylphosphino)oxy]benzene (POCOP) complex isolated by Brookhart etal.how slight variations of molecular charge and structure can drastically affect the relative intrinsic silylicity of the SiEt3 group that is weakly bonded to the hydrido-iridium motif.

First author: Andrada, DM, Understanding the Heteroatom Effect on the Ullmann Copper-Catalyzed Cross-Coupling of X-Arylation (X = NH, O, S) Mechanism,
CATALYSTS, 7, 17058, (2017)
Abstract: Density Functional Theory (DFT) calculations have been carried out in order to unravel the governing reaction mechanism in copper-catalyzed cross-coupling Ullmann type reactions between iodobenzene (1, PhI) and aniline (2-NH, PhNH2), phenol (2-O, PhOH) and thiophenol (2-S, PhSH) with phenanthroline (phen) as the ancillary ligand. Four different pathways for the mechanism were considered namely Oxidative Addition-Reductive Elimination (OA-RE), sigma-bond Metathesis (MET), Single Electron Transfer (SET), and Halogen Atom Transfer (HAT). Our results suggest that the OA-RE route, involving Cu-III intermediates, is the energetically most favorable pathway for all the systems considered. Interestingly, the rate-determining step is the oxidative addition of the phenyl iodide to the metal center regardless of the nature of the heteroatom. The computed energy barriers in OA increase in the order O < S < NH. Using the Activation Strain Model (ASM) of chemical reactivity, it was found that the strain energy associated with the bending of the copper(I) complex controls the observed reactivity.

First author: Arokiyanathan, AL, Molecular properties of metal difluorides and their interactions with CO2 and H2O molecules: a DFT investigation,
Abstract: A computational study of metal difluorides (MF2; M = Ca to Zn) and their interactions with carbon dioxide and water molecules was performed. The structural parameter values obtained and the results of AIM analysis and energy decomposition analysis indicated that the Ca-F bond is weaker and less ionic than the bonds in the transition metal difluorides. A deformation density plot revealed the stablizing influence of the Jahn-Teller effect in nonlinear MF2 molecules (e.g., where M= Sc, Ti, Cr). An anaysis of the metal K-edge peaks of the difluorides showed that shifts in the edge energy were due to the combined effects of the ionicity, effective nuclear charge, and the spin state of the metal. The interactions of CO2 with ScF2 (Scc3 geometry) and TiF2 (Tic2 geometry) caused CO2 to shift from its usual linear geometry to a bent geometry (eta(2)(C=O) binding mode), while it retained its linear geometry (eta(1)(O) binding mode) when it interacted with the other metal difluorides. Energy decomposition analysis showed that, among the various geometries considered, the Scc3 and Tic2 geometries possessed the highest interaction energies and orbital interaction energies. Heavier transition metal difluorides showed stronger affinities for H2O, whereas the lighter transition metal (Sc and Ti) difluorides preferred CO2. Overall, the results of this study suggest that fluorides of lighter transition metals with partially filled d orbitals (e.g., Sc and Ti) could be used for CO2 capture under moist conditions.

First author: Menacer, R, Electronic structure and bonding of the dinuclear metal M-2(CO)(10) decacarbonyls: applications of natural orbitals for chemical valence,
Abstract: The nature of the chemical metal-metal bond in M-2(CO)(10) (M = Mn, Re, Tc) dinuclear decacarbonyls complexes was investigated for the first time using the natural orbital chemical valence (NOCV) approach combined with the extended transition state (ETS) for energy decomposition analysis (EDA). The optimized geometries carried out at different levels of theory BP86, BLYP, BLYPD and BP86D, showed that the latter method, i.e., BP86D, led to the best agreement with X-ray experimental measurements. The BP86D/TZP results revealed that the computed covalent contribution to the metal-metal bond are 60.5%, 54.1% and 52.0% for Mn-Mn, Re-Re and Tc-Tc, respectively. The computed total interaction energies resulting from attractive terms (Delta E-orb and Delta E-eles), correspond well to experimental predictions, based on bond lengths and energy interaction analysis for the studied complexes.

First author: Chaudhuri, S, Electron Transfer Assisted by Vibronic Coupling from Multiple Modes,
Abstract: Understanding the effect of vibronic coupling on electron transfer (ET) rates is a challenge common to a wide range of applications, from electrochemical synthesis and catalysis to biochemical reactions and solar energy conversion. The Marcus-Jortner-Levich (MJL) theory offers a model of ET rates based on a simple analytic expression with a few adjustable parameters. However, the MJL equation in conjunction with density functional theory (DFT) has yet to be established as a predictive first-principles methodology. A framework is presented for calculating transfer rates modulated by molecular vibrations, that circumvents the steep computational cost which has previously necessitated approximations such as condensing the vibrational manifold into a single empirical frequency. Our DFT MJL approach provides robust and accurate predictions of ET rates spanning over 4 orders of magnitude in the 10(6)-10(10) s(-1) range. We evaluate the full MJL equation with a Monte Carlo sampling of the entire active space of thermally accessible vibrational modes, while using no empirical parameters. The contribution to the rate of individual modes is illustrated, providing insight into the interplay between vibrational degrees of freedom and changes in electronic state. The reported findings are valuable for understanding ET rates modulated by multiple vibrational modes, relevant to a broad range of systems within the chemical sciences.

First author: Fu, WY, Ultrasensitive Ethene Detector Based on a Graphene-Copper(I) Hybrid Material,
NANO LETTERS, 17, 7980, (2017)
Abstract: Ethene is a highly diffusive and relatively unreactive gas that induces aging responses in plants in concentrations as low as parts per billion. Monitoring concentrations of ethene is critically important for transport and storage of food crops, necessitating the development of a new generation of ultrasensitive detectors. Here we show that by functionalizing graphene with copper complexes biologically relevant concentrations of ethene and of the spoilage marker ethanol can be detected. Importantly, in addition these sensors provide us with important insights into the interactions between molecules, a key concept in chemistry. Chemically induced dipole fluctuations in molecules as they undergo a chemical reaction are harvested in an elegant way through subtle field effects in graphene. By exploiting changes in the dipole moments of molecules that occur upon a chemical reaction we are able to track the reaction and provide mechanistic insight that was, until now, out of reach.

First author: Sanhueza, L, Nonlinear optical response of octupolar Zn(II) complexes incorporating highly aromatic polypyridinic ligands: Insights into the role of the metal center,
SYNTHETIC METALS, 234, 9, (2017)
Abstract: In this work, the linear and nonlinear optical properties of a series of octupolar Zn(II) complexes with highly aromatic polypyridine ligands are investigated. The effect of the metal center on the spectroscopic properties of octupolar Zn (II) complexes are explored and compared to its respective free ligands. DFT and TD-DFT calculations were performed to gain more insights about the electronic and structural properties of these compounds. The aromaticity index of ligands and its modulation by Zn(II) in complexes was also theoretically studied. Quadratic hyperpolarizabilities (beta) were determined by using the Hyper-Light Scattering (HIS) technique at 1.06 mu m.

First author: Kozelka, J, Lone pair-pi interactions in biological systems: occurrence, function, and physical origin,
Abstract: Lone pair-pi interactions are now recognized as a supramolecular bond whose existence in biological systems is documented by a growing number of examples. They are commonly attributed to electrostatic forces. This review attempts to highlight some recent discoveries evidencing the important role which lone pair-pi interactions, and anion-pi interactions in particular, play in stabilizing the structure and affecting the function of biomolecules. Special attention is paid to studies exploring the physical origin of these at first glance counterintuitive interactions between a lone pair of electrons of one residue and the pi-cloud of another. Recent theoretical work went beyond the popular electrostatic model and inquired the extent to which orbital interactions have to be taken into account. In at least one biologically relevant case-that of anion-flavin interactions-a substantial charge-transfer component has been shown to operate.

First author: Szatylowicz, H, Olefinic vs aromatic way of substituent effects: The case of 3-and 4-substituted cyclohexa-1,3-dienamine derivatives,
Abstract: Quantum chemical modeling was used to confront substituent effects in olefinic systems with an analogous situation in benzene. The B3LYP/6-311++G(d,p) method was applied to examine electron-donating properties of the amino group in a series of 3- (meta-like) and 4- (para-like) X-substituted cyclohexa-1,3-dienamines (X=NMe2, NH2, OH, OMe, Me, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO). As in the case of substituted anilines (PCCP, 2016, 18, 11711), the substituent properties were described by sigma, charge of the substituent active region(X), and substituent effect stabilization energy descriptors; the amino group was characterized by structural and electronic parameters, whereas a transmitting moietyby aromaticity index harmonic oscillator model of aromaticity. All applied substituent properties parameters were found to be mutually interrelated, with much better correlations for the para-derivatives than the meta-derivatives. Electron-donating ability of the amino group is stronger affected (circa 1.4 times) by substituent acting from position 4 in cyclohexa-1,3-dienamines than in aniline derivatives. It was also numerically confirmed that the reverse substituent effect acting to para-position is stronger (circa 1.14 times) in olefinic systems than in aromatic ones. Moreover, for 1-4 interactions, an increase of the electron-attracting power of the substituent increases -electron delocalization in the olefinic series, whereas decreases it in the aromatic ones.

First author: Huang, YH, Hexagonal boron-noble gas compounds B(6)Ng(n)(4+): Structures and bonding,
Abstract: The hexagonal boron-noble gas compounds B(6)Ng(n)(4+) (n = 1-6, Ng = He-Rn) have been studied theoretically. The geometry, bond energies and thermodynamics properties are reported. For Ar-Rn, the B-Ng bond length is close to the sum of the covalent radii of B and Ng, the B-Ng average bond energy is large up to 59.61-169.43 kcal/mol. There is large charge transfer from Ng to the boron ring, the Ng -> boron sigma-donation originating from the interaction between the valence p orbital of Ng and the LUMO of the boron ring is the predominant contribution towards the Ng-B bond stabilization. The NICS analysis shows that B(6)Ng(n)(4+) have aromaticity.

First author: Murashov, A, Effect of X-ray irradiation and thermal treatment on luminescent properties of barium-phosphate glasses doped with silver and copper,
Abstract: It is shown experimentally that in silver- and copper-containing barium-phosphate glasses metal subnanosized luminescent molecular clusters are formed during the glass synthesis. X-ray irradiation and the subsequent thermal treatment of these glasses result in the considerable change of their luminescence spectra in visible spectral region. This effect is caused by the transformation of the charge state of molecular clusters. In the luminescence spectra of the glass doped with silver and copper simultaneously new luminescence bands appear in comparison with the spectra of glasses doped only with one metal. The reason of this can be the formation of hybrid Agr,Cum molecular clusters. The computer simulation of the structure and optical properties of such stable clusters by TDDFT method is presented.

First author: Abroushan, E, Pnicogen bond interaction between PF2Y (Y = -Cay degrees N, -Nay degrees C) with NH3, CH3OH, H2O, and HF molecules,
STRUCTURAL CHEMISTRY, 28, 1843, (2017)
Abstract: Ab initio calculations have been carried out at MP2/aug-cc-pVDZ level to investigate the XaEuro broken vertical bar PF2Y pnicogen bond interactions (Y = -Cay degrees N, -Nay degrees C; X = NH3, CH3OH, H2O, and HF molecules). Characteristics of XaEuro broken vertical bar PF2CN complexes have been compared with XaEuro broken vertical bar PF2NC complexes for a specific X molecule. Results are dealing with stronger pnicogen bond interaction in the XaEuro broken vertical bar PF2CN systems. For all XaEuro broken vertical bar PF2Y complexes, strength of pnicogen bond interaction increased with basicity of X molecules. NBO and AIM methodologies were used to analyze the pnicogen bond interactions in XaEuro broken vertical bar PF2Y adducts. Also, energy decomposition analysis (EDA) was carried out on the intermolecular interactions in the XaEuro broken vertical bar PF2Y complexes.

First author: Abubekerov, M, Ferrocene-bis(phosphinimine) Nickel(II) and Palladium(II) Alkyl Complexes: Influence of the Fe-M (M = Ni and Pd) Interaction on Redox Activity and Olefin Coordination,
ORGANOMETALLICS, 36, 4394, (2017)
Abstract: The synthesis of several novel nickel(II) and palladium(II) ferrocene-bis(phosphinimine) alkyl complexes containing iron-nickel and iron-palladium interactions is reported. The redox behavior of all complexes was evaluated electrochemically and chemically; in addition, reactions with weak nucleophiles, such as acetonitrile and olefins, were also investigated. DFT calculations were performed to understand the electronic structure of the alkyl metal complexes.

First author: Caise, A, A Gallium Hydride as an Oxidizing Agent: Direct Synthesis of Ir-V Complexes via Ga-H Bond Activation,
Abstract: Reactions of the beta-diketiminate-stabilized gallium dihydride (Nacnac)(GaH2)-Ga-Dipp with chelating Ir-I bis(phosphine) precursors under an H-2 atmosphere are shown to provide a simple route to IrV complexes stabilized by strongly sigma-donating hydrides and the carbene-like (Nacnac)Ga-Dipp donor. Characterization of these systems as seven-coordinate Ir-V tetrahydride species is supported by single crystal X-ray and neutron diffraction, and by T-1 NMR measurements. By contrast related systems featuring more sterically demanding (non-chelating) ancillary ligands are better described in terms of a bis(hydride) dihydrogen [L3Ir(H)(2)(H-2)](+) formulation and a formal Ir-III oxidation state.

First author: Li, QJ, SERRS and absorption spectra of pyridine on AumAgn (m plus n=6) bimetallic nanoclusters: substrate composition and applied electric field effects,
NANOTECHNOLOGY, 28, 16906, (2017)
Abstract: Surface-enhanced Raman scattering (SERS) and absorption spectra of the pyridine molecule adsorbed on AumAgn (m + n = 6) bimetallic clusters are theoretically investigated by time-dependent density functional theory. The contributions of static chemical enhancement to the ground-state system are analyzed, and the static Raman intensity of Py-AumAgn complexes are enhanced by an order of 10. A method of visualization on charge transfer is used to distinguish the contributions of charge-transfer enhancement and electromagnetic enhancement. The intensity of surface-enhanced resonance Raman scattering (SERRS) spectroscopy of Py-AumAgn is strongly enhanced by an order of 10(3)-10(5), compared to the static Raman intensity of pyridine. The influence of the static external electric field on SERS is investigated by calculating the optical properties of the Py-Au3Ag3 complex. The intensity of SERRS spectra and normal Raman spectra can be significantly enhanced by the positive electric fields, and the intensities of specific Raman vibrational modes could be selectively enhanced or weakened by tuning the direction and strength of the static electric field applied on Py-Au3Ag3.

First author: Ponikiewski, L, Reactions of lithiated diphosphanes R2P-P(SiMe3)Li.nTHF (R = tBu, iPr) with [(PNP)TiCl2]. Two different coordination types of phosphanylphosphido ligand to the metal center,
POLYHEDRON, 137, 182, (2017)
Abstract: [(PNP)TiCl2] (PNP = N[2-PiPr(2)-4-methylphenyl](2)) reacts with one equivalent of lithium derivative of diphosphane R2P-P(SiMe3)Li center dot nTHF (R = tBu, iPr) in toluene and forms the first complex with eta(1)-coordination [(PNP)Ti(Cl){eta(1)-P(SiMe3)-PtBu2)] (1) and complex with eta(2)-coordination [(PNP)Ti(Cl){eta(2)-P(SiMe3)-PiPr(2))] (2) of phosphanylphosphido ligands to the titanium center. The similar reaction with two equivalents of tBu(2)P-P(SiMe3)Li center dot nTHF in toluene leads to solid 3 which contains 1 and excess of tBu(2)P-P(SiMe3) Li in the unit cell. In complex 2 disorder of the phosphanylphosphido ligand was observed. The disorder model shows that the phosphanylphosphido ligand coordinates to the metal center alternately as a bidentate and as a monodentate ligand.

First author: Wang, P, Nonconventional Hydrogen Bonds between Silver Anion and Nucleobases: Size-Selected Anion Photoelectron Spectroscopy and Density Functional Calculations,
Abstract: We conducted combined gas-phase anion photoelectron spectroscopy and density functional theory studies on nucleobase-silver complexes. The most probable structures of the nucleobase-Ag- complexes were determined by comparing the theoretical calculations with the experimental measurements. The vertical detachment energies (VDEs) of uracil-Ag-, thymine-Ag-, cytosine-Ag-, and guanine-Ag- were estimated to be 2.18 +/- 0.08, 2.11 +/- 0.08, 2.04 +/- 0.08, and 2.20 +/- 0.08 eV, respectively, based on their photoelectron spectra. Adenine-Ag- has two isomers coexisting in the experiment; the experimental VDEs of the two isomers are 2.18 and 2.53 eV, respectively. In the most probable isomers of nucleobases-Ag-, uracil, thymine, and cytosine interact with Ag- anion via N-H center dot center dot center dot Ag and C-H center dot center dot center dot Ag hydrogen bonds, while adenine and guanine interact with Ag anion through two N-H center dot center dot center dot Ag hydrogen bonds. The N-H center dot center dot center dot Ag hydrogen bonds hydrogen bonds. It is found that binding sites of the Ag anion to the nucleobases are affected by the deprotonation energies and the steric effects of two adjacent X-H groups.

First author: Turan, HT, Understanding the Impact of Thiophene/Furan Substitution on Intrinsic Charge-Carrier Mobility,
Abstract: One of the major challenges in rationalizing the intrinsic influences of molecular fine tuning on charge transport in organic semiconductors is due to changes in molecular packing. Thus, it is, to a limited extent, desirable to elaborate materials to exhibit similar packing arrangements that slightly differ in their molecular structures. A molecular system, consisting of a heterocyclic core flanked by phthalimide end-capping units, is promising to overcome this issue. Previous XRD measurements have revealed that, when the bithiophene (bi-T) core was replaced by bifuran (biF), the molecular packing was largely maintained, while the resulting difference in charge transport was substantial, substituting bi-T with bi-F results in more than 1 order of magnitude increase in hole mobility (i.e., 1.7 X 10(-3) vs 2.6 x 10(-2) cm(2)/(V s)) with a loss in electron mobility (i.e., 0.21 vs 0.0 cm(2)/(V s)). The calculated hole mobilities with the MPW1K/TZ2P methodology are found to be lower for bi-T, as the reorganization energies of bi-T are noticeably higher than those of bi-F due to the nonplanarity of bi-T. MD simulations have shown that the disordered hole mobility predictions are in good agreement with the experimental measurements, for which T -> F substitution results in an increase in hole mobility. In contrast, the difference in electron mobilities with T -> F substitution is predicted to be insignificant, most likely due to the lower average electronic coupling of bi-F. The discrepancy between calculated and experimental electron mobility may originate from macroscopic effects, such as the organic field effect transistor (OFET) device configuration which was not taken into consideration in this study.

First author: Skara, G, Heterolytic Splitting of Molecular Hydrogen by Frustrated and Classical Lewis Pairs: A Unified Reactivity Concept,
SCIENTIFIC REPORTS, 7, 25682, (2017)
Abstract: Using a set of state-of-the-art quantum chemical techniques we scrutinized the characteristically different reactivity of frustrated and classical Lewis pairs towards molecular hydrogen. The mechanisms and reaction profiles computed for the H-2 splitting reaction of various Lewis pairs are in good agreement with the experimentally observed feasibility of H-2 activation. More importantly, the analysis of activation parameters unambiguously revealed the existence of two reaction pathways through a low-energy and a high-energy transition state. An exhaustive scrutiny of these transition states, including their stability, geometry and electronic structure, reflects that the electronic rearrangement in low-energy transition states is fundamentally different from that of high-energy transition states. Our findings reveal that the widespread consensus mechanism of H-2 splitting characterizes activation processes corresponding to high-energy transition states and, accordingly, is not operative for H-2-activating systems. One of the criteria of H-2-activation, actually, is the availability of a low-energy transition state that represents a different H-2 splitting mechanism, in which the electrostatic field generated in the cavity of Lewis pair plays a critical role: to induce a strong polarization of H-2 that facilities an efficient end-on acid-H-2 interaction and to stabilize the charge separated “H+-H-” moiety in the transition state.

First author: Wu, Z, Parent Thioketene S-Oxide H2CCSO: Gas-Phase Generation, Structure, and Bonding Analysis,
Abstract: The parent thioketene S-oxide H2CCSO has been generated in the gas phase through flash vacuum pyrolysis (ca. 1000 K) of vinyl sulfoxide H2CC(Br)-S(O)CF3 via the intermediacy of a novel vinyl sulfinyl radical H2C=C(Br)-SO (syn and anti conformers). Upon irradiation at 266 nm, H2CCSO decomposes into HCCH/SO and H2CS/CO in cryogenic Ar matrix. Whereas, visible-light irradiations result in syn <-> anti conformational interconversion in H2C=C(Br)-SO. The molecular structures of H2CCSO and isomers are computationally studied at the CCSD(T)-F12/VTZ-F12 level of theory, and the bonding properties of H2CCSO are analyzed with the EDA-NOCV method at the M06-2X/TZ2P level.

First author: Perrin, ML, Design of an efficient coherent multi-site single-molecule rectifier,
Abstract: We propose the design of a single-molecule diode with a rectification ratio exceeding a million. The employed mechanism is based on coherent resonant charge transport across a molecule that consists of four conjugated sites coupled by non-conjugated bridges. Using density functional theory calculations, we rationalize the design of the molecule and demonstrate the crucial role of aligning the sites at a specific voltage. Rectification ratios are calculated for a series of chemical substituents and demonstrate that with careful molecular design, high rectification ratios can be achieved. Finally, we comment on the shortcomings of our approach, how further improvements can be obtained and discuss some of the experimental challenges.

First author: Arbouch, I, Influence of the nature of the anchoring group on electron injection processes at dye-titania interfaces,
Abstract: We report (time-dependent) density functional theory calculations characterizing the changes in the electronic and optical properties of oligothiophene dyes when grafted on a titania surface via a carboxylic acid or catechol moiety as anchoring group, in relation to their use in dye-sensitized solar cells. The broadening of the LUMO level of the compounds upon adsorption has been extracted from the computed electronic structures and used to estimate electron injection times into the conduction band of the oxide. The strongly coupled carboxylic-containing dyes lead to faster electron injection times compared to catechol-substituted dyes. This difference is ascribed to the electron-donating character of the catechol moiety that polarizes the dye LUMO away from the dyetitania interface. The absorption spectra simulated at the TD-DFT level indicate that the grafted carboxylic-thiophene dyes undergo an indirect injection mechanism (type I) in which an intramolecular excitation is created before the charge is transferred to titania. In contrast, catechol dyes with a short conjugation length for the thiophene backbone are type II sensitizers exhibiting a direct injection mechanism leading to a direct photoexcitation from the dye HOMO to the titania conduction band. A mixed character prevails for the injection in the case of catechol dyes containing a longer oligothiophene chain.

First author: Groh, MF, Ionothermal Syntheses, Crystal Structures, and Chemical Bonding of the Rhodium-Centered Clusters [RhBi9](4+) and [(RhBi7)I-8],
Abstract: The first filled Bi-9(5+) polycation was isolated in the form of [RhBi9](AlCl4)(4) crystals by dissolution of the solid precursor Bi12-xRhX13-x in the Lewis-acidic ionic liquid [BMIm]Cl center dot 3.6AlCl(3) (BMIm = 1-butyl-3-methylimidazolium) at 140 center dot C. In the monoclinic crystal structure [P2(1)/n, a = 1217.5(2) pm, b = 1741.6(3) pm, c = 5085.7(7) pm, beta = 90.117(8)degrees], the almost spherical [RhBi9](4+) polycations (approximate D-3h symmetry; Rh-Bi 276 +/- 3 pm) show pro-nounced orientational disorder. Shiny black needles of Bi7RhI8 were obtained from the reaction of rhodium, bismuth, and BiI3 in the ionic liquid [BMIm]Cl center dot 1.3AlCl(3) at 200 degrees C. Bi7RhI8 [P2(1)/n, a = 943.10(1) pm, b = 1582.40(1) pm, c = 1645.40(1) pm, beta = 95.48(1)degrees] is iso-structural to Bi7RhBr8 and consists of molecular clusters [(RhBi7)I-8]. The rhodium atom centers a pentagonal bipyramid of bismuth atoms, and the two apical bismuth atoms are in square-planar coordination of iodide ions. DFT-based calculations indicate strong bismuth-rhodium bonding with predominantly covalent character for both clusters. The electronic structure of the Bi-9(5+) cage is notably modified by this interaction, but the characteristic bonding features of the host cluster with the D-3h configuration are still maintained. In Bi7RhI8, on the other hand, bonding is dictated by the spatial distribution of mutually repelling iodine atoms, and the Bi-Rh bonding is highly polar.

First author: Gao, FW, Intra- and Intermolecular Charge Transfer in a Novel Dimer: Cooperatively Enhancing Second-Order Optical Nonlinearity,
Abstract: Based on s-indaceno[1,2,3-cd;5,6,7-c’d’]diphenalene (1) consisting of two phenalenyl moieties, the monomer 2 and its dimer 2(2) are designed by boron and nitrogen atoms substituting the central carbon atoms of phenalenyl moieties. Calculated energy decompose analysis (EDA) shows that the orbital interaction for 2(2) possesses a large attractive contribution of-18.31 kcal mol(-1), which is dominated by the pi-pi stacking interaction between the upper and the lower pi-conjugated units. Interestingly, the natural population analysis (NPA) charge and the transition density matrix (TDM) show that both intramolecular charge transfer and intermolecular charge transfer (CT) exist in 2(2). Further, the first hyperpolarizability (beta(tot) = 4.56 X 10(4) au) of 2 with intramolecular CT is greatly larger than that of reported molecule 3 (5.45 X 10(3) au) with intermolecular CT. Significantly, 2(2) exhibits the largest beta(tot) value to be 1.42 x 10(5) au, which is caused by combining the intra- and intermolecular CT transitions (beta(x) = 1.40 x 10(5) au and fix = 2.27 x 10(4) au). Correspondingly, highest occupied molecular orbital (HOMO) -> lowest unoccupied molecular orbital (LUMO) (intramolecular CT) in the low-energy electronic transition of 2(2) is 68%, while HOMO -> LUMO + 1 (intermolecular CT) is 18%, which demonstrates that the intramolecular CT effect on the beta(tot) value is stronger than the case of the intermolecular CT effect. The present work might provide rich insight into designing and developing potential second-order optical nonlinearity materials with inter- and intramolecular CT characters.

First author: Charistos, ND, Canonical Orbital Contributions to the Magnetic Fields Induced by Global and Local Diatropic and Paratropic Ring Currents,
Abstract: The induced magnetic field (IMF) of naphthalene, biphenyl, biphenylene, benzocyclobutadiene, and pentalene is dissected to contributions from the total pi system, canonical pi-molecular orbitals (CMO), and HOMO ->pi* excitations, to evaluate and interpret relative global and local diatropicity and paratropicity. Maps of the IMF of the total pi system reveal its relative strength and topology that corresponds to global and local diatropic and paratropic ring currents. The total pi magnetic response is determined by this of canonical HOMOs and particularly by paratropic contributions of rotational excitations from HOMOs to unoccupied pi* orbitals. Low energy excitations and similar nodal structure of HOMO and pi* induce strong paratropic fields that dominate on antiaromatic rings. High energy excitations and different nodal structures lead to weak paratropic contributions of canonical HOMOs, which are overwhelmed by diatropic response of lower energy canonical orbitals in aromatic rings. CMO-IMF analysis is found in agreement with ring current analysis.

First author: Greene, C, Binding and electrophilic activation of ethylene by zinc(II), cadmium(II), and mercury(II) complexes: A theoretical investigation,
Abstract: Density functional theory has been used to investigate binding and activation of ethylene by the group12 metal ions Zn2+, Cd2+, and Hg2+ in a series of [M(L)(eta(2)-C2H4)](n+) complexes (where L = 2,2′-bipyridine, N, N, N’, N’-tetramethylethylenediamine, tris(3,5-dimethyl-1-pyrazolyl) methane, 1,4,7-trimethyl-1,4,7-triazacyclononane, hyrdotris(3,5-dimethyl-1-pyrazolyl) borate, the bis(2,6-dimethylphenyl)-substituted beta-diketiminate, and the iminophosphanamide (tBu) 2P(NSiMe3) 2). Structural and vibrational analyses predict an activated ethylene C=C bond in all complexes, with activation maximized by the use of neutral bidentate ligands and the Hg2+ ion. Bond energy decomposition analysis (EDA-NOCV) shows that [M(L)](n+)-ethylene interaction energies are favorable for all complexes studied, and even more favorable than those for many of the analogous and experimentally-isolated [Cu(L)(eta(2)-C2H4)](n+) complexes. Electrostatic and orbital stabilization provide roughly equal contributions to the metaleethylene bond, while both EDA-NOCV and natural bond orbital (NBO) analysis indicate that ethylene(p)/[M(L)](n+) electron donation and orbital stabilization dominates Dewar-Chatt-Duncanson bonding in these complexes, yielding a significant positive charge on the ethylene moiety. Molecular orbital analysis confirms these findings and indicates that the electrophilic reactivity of the metal-bound ethylene moiety would be further enhanced due to substantial stabilization of the alkene p*-and p-orbitals. Finally, addition of ammonia to the bound ethylene moiety to form the metaleammonioalkyl species is generally predicted to be thermodynamically favorable, with less bulky, neutral ligands enhancing the favorability of the reaction and yielding a lower activation barrier.

First author: Ferreira, H, Packing polymorphism of dicarbonyl-[2-(phenylamino)pent-3-en-4-onato]rhodium(I),
Abstract: Depending on the crystallization conditions, the interaction between the rhodium metal centres of the separate [Rh(CH3COCHCN(Ph)CH3)(CO)(2)] molecular units, as described by the interplanar separation and lateral shift of two of the units, leads to packing polymorphism of [Rh(CH3COCHCN(Ph)CH3)(CO)(2)], which means the same molecule crystallises in different fashions, resulting in different polymorphs (a and b), with a difference in crystal packing. Six different sets of solid state single crystal data of [Rh(CH3COCHCN(Ph)CH3)(CO)(2)], show that this complex is polymorphic, forming dinuclear units that either stack in wire-like chains with weak metallophilic rhodium-rhodium interactions (beta-polymorph), or with packing of the dinuclear units that does not result in rhodium-rhodium chains (alpha-polymorph). A DFT study on the inter-molecular interactions in different dinuclear [Rh(CH3COCHCN(Ph)CH3)(CO)(2)](2) models, using different DFT methods, provides an understanding on a molecular level of the rhodiumrhodium and other inter-molecular interactions between the two separate [Rh(CH3COCHCN(Ph)CH3)(CO)(2)] molecules in the dinuclear unit.

First author: Chashmniam, S, NMR investigation and theoretical calculations of the solvent effect on the conformation of valsartan,
Abstract: Structure and conformational properties of valsartan were studied by advanced NMR techniques and quantum calculation methods. Potential energy scanning using B3LYP/6-311++g** and B3LYP-D3/6-311++g** methods were performed and four conformers (V1-V4) at minimum points of PES diagram were observed. According to the NMR spectra in acetone-d(6), there are two conformers (M and m) with m/M = 0.52 ratio simultaneously and energy barriers of the two conformers were predicted from chemical shifts and multiplicities. While, intramolecular hydrogen bond at tetrazole ring and carboxylic groups prevent the free rotation on N-6-C-11 bond in M-conformer, this bond rotates freely in m-conformer. On the other hand, intramolecular hydrogen bond at carbonyl and carboxylic acid can be observed at m conformer. So, different intramolecular hydrogen bond is the reason for the stability of both M and m structures. Quite interestingly, H-1 NMR spectra in CDCl3 show two distinct conformers (N and n) with unequal ratio which are differ from M-m conformers. Also, intramolecular hydrogen bond seven member ring involving five-membered tetrazole ring and carboxylic acid group observed in both N and n-conformers Solvent effect, by using a set of polar and non-polar solvents including DMSO-d(6), methanol-d(4), benzene-d(6), THE-d(8), nitromethane-d(3), methylene chloride-d(2) and acetonitrile-d(3) were investigated. NMR parameters include chemical shifts and spin-spin coupling constants were obtained from a set of 2D NMR spectra (H-H COSY, HMQC and HMBC). For this purpose, several DFT functionals from LDA, GGA and hybrid categories were used which the hybrid method showed better agreement with experiment values.

First author: Fias, S, Extension of the source-sink potential approach to Hartree-Fock and density functional theory: A new tool to visualize the ballistic current through molecules,
Abstract: The recent source and sink potential approach by Pickup et al. [J. Chem. Phys. 143, 194105 (2015)] is extended to Hartree-Fock and density functional theory, allowing the calculation of the transmission and the visualization of ballistic currents through molecules at these levels of theory. This visualization allows the study of the transmission process in real-space, providing an important tool to better understand the conduction process. Published by AIP Publishing.

First author: Mahmoodinia, M, Geometrical flexibility of platinum nanoclusters: impacts on catalytic decomposition of ethylene glycol,
Abstract: Catalytic decomposition of ethylene glycol on the Pt-13 cluster was studied as a model system for hydrogen production from a lignocellulosic material. Ethylene glycol was chosen as a starting material because of two reasons, it is the smallest oxygenate with a 1 : 1 carbon to oxygen ratio and it contains the C-H, O-H, C-C, and C-O bonds also present in biomass. Density functional theory calculations were employed for predictions of reaction pathways for C-H, O-H, C-C and C-O cleavages, and Bronsted-Evans-Polanyi relationships were established between the final state and the transition state for all mechanisms. The results show that Pt-13 catalyzes the cleavage reactions of ethylene glycol more favourably than a Pt surface. The flexibility of Pt-13 clusters during the reactions is the key factor in reducing the activation barrier. Overall, the results demonstrate that ethylene glycol and thus biomass can be efficiently converted into hydrogen using platinum nanoclusters as catalysts.

First author: Castro, E, Unusual C-2h-Symmetric trans-1-(Bis-pyrrolidine)-tetra-malonate Hexa-Adducts of C-60: The Unexpected Regio- and Stereocontrol Mediated by Malonate-Pyrrolidine Interaction,
Abstract: A totally unanticipated regio- and stereoisomerically pure C-2h-symmetric trans-1-(bis-pyrrolidine)-tetra-malonate hexa-adduct of C-60 was obtained via a topologically controlled method, followed by a 1,3-dipolar cycloaddition reaction. The structures of the products were elucidated by H-1 and (CNMR)-C-13 and by X-ray crystallography. The unexpected regio- and stereoselectivity observed, supported by theoretical calculations, was found to be a consequence of malonate-pyrrolidine interactions.

First author: Fan, JX, Theoretical Study on Charge Transport Properties of Copolymers of Diketopyrrolopyrrole and Oligo-thiophene,
Abstract: The electronic structures and charge transport properties of the oligomers of diketopyrrolopyrrole (DPP) with the thiophene were investigated with ab initio density functional theory and classical Marcus charge transport theory. The results show that with the increase of the DPP concentration (or decrease of the thiophene numbers) in the polymer unit both the HOMO and LUMO energy levels of the polymers decrease, and the band gaps narrow. As the DPP concentration increased, the intrachain overlap of the electron wave functions of the DPP acceptor units was improved, that facilitates the intrachain electron transport. Moreover, the increase of DPP concentration strengthens the rigidity of the molecular backbone and enhances the interchain overlap of LUMO orbitals, which strengthens the electron transfer integrals and the system is conver. ted from p-type into ambipolar materials.

First author: Alkan, F, Relativistic DFT investigation of electronic structure effects arising from doping the Au-25 nanocluster with transition metals,
NANOSCALE, 9, 15825, (2017)
Abstract: We perform a theoretical investigation using density functional theory (DFT) and time-dependent DFT (TDDFT) on the doping of the Au-25(SR)(18)(-1) nanocluster with group IX transition metals (M = cobalt, rhodium and iridium). Different doping motifs, charge states and spin multiplicities were considered for the single-atom doped nanoclusters. Our results show that the interaction (or the lack of interaction) between the d-type energy levels that mainly originate from the dopant atom and the super-atomic levels plays an important role in the energetics, the electronic structure and the optical properties of the doped systems. The evaluated MAu24(SR)(18)(q) (q = -1, -3) systems favor an endohedral disposition of the doping atom typically in a singlet ground state, with either a 6- or 8-valence electron icosahedral core. For the sake of comparison, the role of the d energy levels in the electronic structure of a variety of doped Au-25(SR)(18)(-1) nanoclusters was investigated for dopant atoms from other families such as Cd, Ag and Pd. Finally, the effect of spin-orbit coupling (SOC) on the electronic structure and absorption spectra was determined. The information in this study regarding the relative energetics of the d-based and super-atom energy levels can be useful to extend our understanding of the preferred doping modes of different transition metals in protected gold nanoclusters.

First author: Zheng, DY, The promotion effects of thionation and isomerization on charge carrier mobility in naphthalene diimide crystals,
Abstract: Herein, the promotion effects of thionation and isomerization on the carrier mobility properties of naphthalene diimide and thionated naphthalene diimide crystals were investigated in detail based on the Marcus-Hush theory and quantum-chemical calculations. The thionation of NDIs will improve the charge mobility of both electrons and holes, which is similar to the thionation of PDIs. The compound P only behaves as an n-type organic semiconductor (OSC), whereas the three other thionation structures have higher mobility values and can behave as p-type OSCs. For the cis/trans isomers of the two double-thionation structures, trans-S2 has a larger hole and electron carrier mobility than cis-S2; this is consistent with the experimental results obtained for cis-trans-isomers. A potential strategy for the development of high performance ambipolar OSCs is the substitution of O atoms by S atoms. These results will provide a guide for the design and optimization of OSCs via analysis of the relationship between carrier mobility and molecular crystal structures.

First author: Bortoli, M, Role of the Chalcogen (S, Se, Te) in the Oxidation Mechanism of the Glutathione Peroxidase Active Site,
CHEMPHYSCHEM, 18, 2990, (2017)
Abstract: The oxidation by H2O2 of the human phospholipid hydroperoxide glutathione peroxidase (GPx4), used as a model peroxidase selenoenzyme, as well as that of its cysteine (Cys) and tellurocysteine (Tec) mutants, was investigated insilico through a combined classic and quantum mechanics approach to assess the role of the different chalcogens. To perform this analysis, new parameters for selenocysteine (Sec) and tellurocysteine (Tec) were accurately derived for the AMBER ff14SB force field. The oxidation represents the initial step of the antioxidant activity of GPx, which catalyzes the reduction of H2O2 and organic hydroperoxides by glutathione (GSH). A mechanism involving a charge-separation intermediate is feasible for the Cys and Sec enzymes, leading from the initial thiol/selenol form to sulfenic/selenenic acid, whereas for the Tec mutant a direct oxidation pathway is proposed. Activation strain analyses, performed for Cys-GPx and Sec-GPx, provided insight into the rate-accelerating effect of selenium as compared to sulfur and the role of specific amino acids other than Cys/Sec that are typically conserved in the catalytic pocket.

First author: Rossi, S, Benzodithiophene and Benzotrithiophene as pi Cores for Two- and Three-Blade Propeller-Shaped Ferrocenyl-Based Conjugated Systems,
Abstract: The syntheses of linear and star-shaped bis- and tris(ferrocenyl) derivatives of benzo[1,2-b:4,5-b’]dithiophene and benzo[1,2-b:3,4-b’:5,6-b ”]trithiophene are achieved through one-pot CuI/TMEDA-catalyzed (TMEDA = tetramethylethylenediamine) multiple annulations of bromoethynylbenzenes with sodium sulfide. In addition, the preparation of the parent benzotrithiophene in a good yield with a short reaction time is achieved through the threefold annulation of 1,3,5-trifluoro-2,4,6-tris(trimethylsilyl)ethynylbenzene. The computed structural and electronic features of these ferrocenyl derivatives as well as their UV/Vis spectra and electrochemistry are discussed, and the results provide insights into the effect of the presence of three rather than two ferrocenyl units. To the best of our knowledge, 2,5,8-tris(ferrocenyl)benzo[1,2-b;3,4-b’;5,6-b ”]trithiophene is the first organometallic complex containing benzotrithiophene.

First author: Cao, GJ, Dinuclear Metal-Mediated Homo Base Pairs with Metallophilic Interactions: Theoretical Studies of G(2)M(2)(2+) (M = Cu, Ag, and Au) Ions,
SCIENTIFIC REPORTS, 7, 5966, (2017)
Abstract: Dinuclear metal-mediated homo base pairs are interesting clusters with highly symmetric structures and significant stabilities. The geometric and electronic structures of G(2)M(2)(2+) (G = Guanine, M = Cu, Ag or Au) cluster ions were studied with quantum chemical calculations. The lowest-energy isomers of G(2)M(2)(2+) cluster ions have C-2h symmetries with an approximately antiparallel alignment of two sets of N-M center dot center dot center dot O groups being formed in the planar structures. The M-M distances are shorter than the sum of van der Waals radii of corresponding two homo coinage metal atoms, showing that metallophilic interactions significantly exist in these complexes. They have the large HOMO-LUMO gaps of about 5.80 eV at the DFT level and the bond dissociation energies of more than 5.60 eV at the DFT/B3LYP level, indicating that these cluster dications are highly stable. The second lowest-energy isomers stabilized by an approximately parallel alignment of one set of O-M-O group and one set of N-M-N group are found to be close to the lowest-energy isomers in energy. The barrier between the two isomers of G(2)M(2)(2+) cluster ions is significantly large, also showing that these lowest-energy isomers are very stable.

First author: Krivdin, LB, Calculation of N-15 NMR chemical shifts: Recent advances and perspectives,
Abstract: Recent advances in computation of N-15 NMR chemical shifts are reviewed, concentrating mainly on practical aspects of computational protocols and accuracy factors. The review includes the discussion of the level of theory, the choice of density functionals and basis sets together with taking into account solvent effects, rovibrational corrections and relativistic effects. Computational aspects of N-15 NMR are illustrated for the series of neutral and protonated open-chain nitrogen-containing compounds and nitrogen heterocycles, coordination and intermolecular complexes.

First author: Iron, MA, Evaluation of the Factors Impacting the Accuracy of C-13 NMR Chemical Shift Predictions using Density Functional Theory-The Advantage of Long-Range Corrected Functionals,
Abstract: The various factors influencing the accuracy of C-13 NMR calculations using density functional theory (DFT), including the basis set, exchange-correlation (XC) functional, and isotropic shielding calculation method, are evaluated. A wide selection of XC functionals (over 70) were considered, and it was found that long-range corrected functionals offer a significant improvement over the other classes of functionals. Based on a thorough study, it is recommended that for calculating NMR chemical shifts (5) one should use the CSGT method, the COSMO solvation model, and the LC-TPSSTPSS exchange-correlation functional in conjunction with the cc-pVTZ basis set. A selection of problems in natural product identification are considered in light of the newly recommended level of theory.

First author: Bombarda, E, Continuum Electrostatic Calculation on Bovine Rhodopsin: Protonation and the Effect of the Membrane Potential,
Abstract: In this work, we calculate the protonation probabilities of titratable residues of bovine rhodopsin using the Poisson-Boltzmann equation. We also consider the influence of the membrane potential. Our results indicate that at physiological pH, the titratable groups directly involved in photosensing, namely Glu113, Glu181 and the retinal Schiff base, are charged. In contrast, the residues Asp83, Glu122 and His211, which are buried in the membrane, are uncharged. However, as these later residues are localized in the middle of the membrane, they are exposed to the membrane potential more strongly, which may have important functional implications. Despite of their large distance, Asp83 and Glu122 interact relatively strongly. As these two residues are in contact with opposite sides of the membrane, the membrane potential has different effects on them, which allows an enhancement of the membrane potential signal. An analysis of the different contributions to the protonation energy indicates that conformational changes that reduce the desolvation penalty of Asp83, Glu122 and His211 may lead to a complex protonation pattern change that allows an influence of the membrane potential on the function of rhodopsin. The high degree of evolutionary conservation of these three buried residues supports the idea of their functional importance. Our results are in-line with many experimental findings and lead to new ideas that can be experimentally tested.

First author: Buda, F, A Quantum-mechanical Study of the Binding Pocket of Proteorhodopsin: Absorption and Vibrational Spectra Modulated by Analogue Chromophores,
Abstract: Proteorhodopsin is a light-driven proton pumping membrane protein related to bacteriorhodopsin. It contains an all-trans retinal A1 chromophore covalently bound to a lysine residue via a protonated Schiff base. In this study, we exploited density functional theory (DFT) calculations to investigate the retinal binding pocket in the dark state and after mimicking photoisomerization. The model of the binding pocket is constructed incrementally by adding the residues near the retinal that are necessary to ensure a stable protonated Schiff base. The presence of a few water molecules near the Schiff base turns out to be an essential feature of the model. The absorption properties are then studied using time-dependent DFT (TDDFT) and compared to experimental data to further validate the structural model and to assess the accuracy of the computational setting. It is shown that TDDFT is able to reproduce the main absorption peak accurately and to quantitatively determine the spectral shift induced by substituting the native all-trans retinal A1 chromophore with different retinal analogues. Moreover, ab initio molecular dynamics simulations are performed to investigate the vibrational spectra of our models before and after isomerization. Specific differences in the vibrational spectra are identified that provide further insight into experimental FTIR difference spectra.

First author: Yen, TW, Studying the varied shapes of gold clusters by an elegant optimization algorithm that hybridizes the density functional tight-binding theory and the density functional theory,
Abstract: We combined a new parametrized density functional tight-binding (DFTB) theory (Fihey et al. 2015) with an unbiased modified basin hopping (MBH) optimization algorithm (Yen and Lai 2015) and applied it to calculate the lowest energy structures of Au clusters. From the calculated topologies and their conformational changes, we find that this DFTB/MBH method is a necessary procedure for a systematic study of the structural development of Au clusters but is somewhat insufficient for a quantitative study. As a result, we propose an extended hybridized algorithm. This improved algorithm proceeds in two steps. In the first step, the DFTB theory is employed to calculate the total energy of the cluster and this step (through running DFTB/MBH optimization for given Monte-Carlo steps) is meant to efficiently bring the Au cluster near to the region of the lowest energy minimum since the cluster as a whole has explicitly considered the interactions of valence electrons with ions, albeit semi-quantitatively. Then, in the second succeeding step, the energy-minimum searching process will continue with a skilledly replacement of the energy function calculated by the DFTB theory in the first step by one calculated in the full density functional theory (DFT). In these subsequent calculations, we couple the DFT energy also with the MBH strategy and proceed with the DFT/MBH optimization until the lowest energy value is found. We checked that this extended hybridized algorithm successfully predicts the twisted pyramidal structure for the Au-40 cluster and correctly confirms also the linear shape of C-8 which our previous DFTB/MBH method failed to do so. Perhaps more remarkable is the topological growth of Au-n: it changes from a planar (n = 3-11) -> an oblate-like cage (n = 12-15) -> a hollow-shape cage (n = 16-18) and finally a pyramidal-like cage (n = 19, 20). These varied forms of the clusters shapes are consistent with those reported in the literature.

First author: Abella, L, Current status of oxide clusterfullerenes,
Abstract: The field of endohedral metallofullerenes has developed extraordinarily since the synthesis and characterization of Sc3N@I-h-C-80 in 1999, the third most abundant fullerene after C-60 and C-70. During these almost two decades other clusterfullerenes have been trapped inside different IPR and non-IPR fullerenes. Sc2O has demonstrated to be a good template for middle size fullerenes, between C-70 and C-82, permitting to characterize many structures and determining different physical properties. This mini-review will allow the reader to gain insight into the field of endohedral metallofullerenes and in particular into the richness of the fullerenes containing scandium oxide clusters as well as into experimental and theoretical techniques used to characterize them.

First author: Duinea, MI, Aqueous oxidation of iron monosulfide (FeS) in the presence of glycine,
Abstract: The effect of glycine on the aqueous oxidation of FeS was evaluated in the range of 0.1-1.0 mM at pH 2.5 and 25 degrees C by electrochemical techniques (potentiodynamic polarization and Electrochemical Impedance Spectroscopy) and Density Functional Theory (DFT) computations. Our findings show that the inhibition efficiency of glycine in controlling the oxidative dissolution of FeS increases when the glycine concentration increases up to 0.5 mM. Further increase of glycine concentration up to 1 mM produces the decrease of the corresponding inhibition efficiency. The results of our study indicate that the inhibiting effect of glycine on the oxidative dissolution of FeS is produced by the glycine adsorption on the ferric iron formed by the oxidation of the FeS surface.

First author: Fanfrlik, J, Pnictogen bonding in pyrazine center dot PnX(5) (Pn = P, As, Sb and X = F, Cl, Br) complexes,
Abstract: This paper presents a study of pnictogen bonding in a series of pyrazinea center dot PnX(5) (Pn = P, As, Sb and X = F, Cl, Br) complexes. The whole series was studied computationally. Moreover, the pyrazine complexes with PCl5 and SbCl5 were prepared and characterized experimentally. It was found that the Pn-N distances are only slightly elongated when compared to the sum of covalent radii. The conformation of PnX(5) changed considerably upon the complex formation, which resulted in a significant change of the dipole moment of the PnX(5) fragment and a considerably more positive sigma-hole on the pnictogen atom. Finally, interaction energies were decomposed in order to provide a deeper insight into the nature of the studied pnictogen-bonded complexes.

First author: Rogachev, AY, Exploring energetics of dirhodium paddlewheel complexes with pi-ligands of different topologies,
Abstract: The first comprehensive theoretical exploration of the energetics of the interaction between pi-ligands with isolated multiple carbon-carbon bonds (acetylene and ethylene), aromatic (benzene), planar polyaromatic (naphthalene, acenaphthalene, pyrene), curved polyaromatic (corannulene) and closed-cage C-60-fullerene systems and Lewis acidic [Rh-2(O2CCF3)(4)] complex has been carried out. Importantly, two energy decomposition schemes (EDA-NOCV and NBO-NEDA) that are based on very different approaches and algorithms were utilized in order to shed light on the energy and nature of bonding. The total bonding energy was sequentially represented as a combination of attractive covalent (Delta E-orb and E-CT in EDA and NBO approaches, respectively) and ionic (Delta E-elstat and E-EL), as well as repulsive (Delta E-Pauli and E-CO) terms. This approach provides a balanced and complete picture of bonding between two (or more) interacting molecular fragments. All computational methods applied unambiguously indicate that the actual stability of adducts formed by unsaturated hydrocarbons with the selected Lewis acidic dirhodium complex is indeed a multifaceted phenomenon. Important contributions come from a different interplay between attractive (Delta E-orb vs. Delta E-elstat or E-CT vs. E-EL) and repulsive (Delta E-Pauli or E-CO) components of the bonding and from variations in aromatic behavior of the selected pi-systems.

First author: Mulet-Gas, M, Transformation of doped graphite into cluster-encapsulated fullerene cages,
Abstract: An ultimate goal in carbon nanoscience is to decipher formation mechanisms of highly ordered systems. Here, we disclose chemical processes that result in formation of high-symmetry clusterfullerenes, which attract interest for use in applications that span biomedicine to molecular electronics. The conversion of doped graphite into a C-80 cage is shown to occur through bottom-up self-assembly reactions. Unlike conventional forms of fullerene, the iconic Buckminsterfullerene cage, I-h-C-60, is entirely avoided in the bottom-up formation mechanism to afford synthesis of group 3-based metallic nitride clusterfullerenes. The effects of structural motifs and cluster-cage interactions on formation of compounds in the solvent-extractable C-70-C-100 region are determined by in situ studies of defined clusterfullerenes under typical synthetic conditions. This work establishes the molecular origin and mechanism that underlie formation of unique carbon cage materials, which may be used as a benchmark to guide future nanocarbon explorations.

First author: Shi, YR, Theoretical study of the charge transport mechanism in pi-stacked systems of organic semiconductor crystals,
CRYSTENGCOMM, 19, 6008, (2017)
Abstract: In this study, the orientational dependence of the charge transport mechanism and some important factors related to crystal structure are systematically investigated by quantum chemical methods. Organic semiconductors with small reorganization energies and large transfer integrals originating from their p-stacking crystal structures show excellent charge transport properties. The reorganization energy from the geometrical relaxation occurs during the charge transfer process. The transfer integral of a molecular crystal should be attributed to multiple stacking parameters. A semi-classical simulation model to calculate the anisotropic mobility of a crystalline molecule is extended from one to three dimensions. As we predicted, the anisotropic mobility calculated from our model is improved by considering the contribution from every direction in space, rather than just one plane. This theoretical study determines the importance of tuning the molecular geometry and calculation accuracy for high-performance organic semiconductor materials.

First author: Mai, S, Excited-states of a rhenium carbonyl diimine complex: solvation models, spin-orbit coupling, and vibrational sampling effects,
Abstract: We present a quantum-chemical investigation of the excited states of the complex [Re(CO)(3)(lm)(Phen)](+) (Im = imidazole: Phen = 1,10-phenanthroline) in solution including spin-orbit couplings and vibrational sampling. To this aim, we implemented electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) in the Amsterdam Density Functional program suite, suitable for time-dependent density functional calculations including spin-orbit couplings. The new implementation is employed to simulate the absorption spectrum of the complex, which is compared to the results of implicit continuum solvation and frozen-density embedding. Molecular dynamics simulations are used to sample the ground state conformations in solution. The results demonstrate that any study of the excited states of [Re(CO)(3)(lm)(Phen)](+) in solution and their dynamics should include extensive sampling of vibrational motion and spin-orbit couplings.

First author: Aldegunde, J, Hyperfine structure of alkali-metal diatomic molecules,
PHYSICAL REVIEW A, 96, 27240, (2017)
Abstract: We present calculations of the hyperfine coupling constants for all the heteronuclear alkali-metal diatomic molecules at the equilibrium geometry of the electronic ground state. These constants are important in developing methods to control ultracold polar molecules. The results are based on electronic structure calculations using density-functional theory, and are in good agreement with experiment for the limited set of molecules for which experiments are so far available.

First author: Vinogradov, MM, Thioether Iron Complexes [(X-SMe-7,8-C2B9H10)Fe(C6H6)] (X=9 or 10) as Synthons of Neutral Ferracarborane Fragments,
Abstract: The demethylation reactions of the cyclohexadienyl complexes [(eta-X-SMe2-7,8-C2B9H10)Fe(eta(5)-C6H7)] {X = 9 (1a), 10 (1b); X is the number of the substituent position} with PhCH2SNa in N,N-dimethylformamide (DMF) and subsequent protonation by acetic acid lead to the iron-benzene complexes [(eta-X-SMe-7,8-C2B9H10)Fe(eta-C6H6)] (2a and 2b). The visible-light irradiation of 2a in the presence of tBuNC or [Cp*Fe(eta-cyclo-P-5)] (Cp* = pentamethylcyclopentadienyl) affords the neutral half-sandwich complex [(eta-9-SMe-7,8-C2B9H10)Fe(tBuNC)(3)] (3) or the triple-decker complex [(eta-9-SMe-7,8-C2B9H10)Fe(mu-eta:eta cyclo-P-5)FeCp*] (4). The reaction of 2b with (THF)W(CO)(5) (THF = tetrahydrofuran) selectively gives the iron-tungsten dinuclear complex [(eta-10-SMe{W(CO)(5)}-7,8-C2B9H10)Fe(eta-C6H6)] (5). The structures of 2a, 4, and 5 were determined by X-ray diffraction. Electrochemistry revealed that the redox processes of the SMe-substituted ferracarboranes are cathodically shifted (by ca. 350 mV) with respect to the corresponding redox changes of the SMe2 analogs. The Fe-C6H6 bonding in 2a and the related benzene complexes [(eta-9-SMe2-7,8-C2B9H10)Fe(eta-C6H6)](+) and [(eta-7,8-C2B9H11)Fe(eta-C6H6)] was analyzed by energy-decomposition analysis.

First author: Molotkov, AP, Iridium Halide Complexes [1,1-X-2-8-SMe2-1,2,8-IrC2B9H10](2) (X = Cl, Br, I): Synthesis, Reactivity and Catalytic Activity,
Abstract: The reactions of thallium salt Tl[7-SMe2-7,8-C2B9H10] with [(cod)RhCl](2) and [Cp*RuCl](4) are accompanied by room-temperature polyhedral rearrangement, giving rhoda- and ruthenacarboranes 1-cod-8-SMe2-1,2,8-RhC2B9H10 (2) and 1-Cp*-8-SMe2-1,2,8-RuC2B9H10 (3), respectively. According to DFT calculations, the rearrangement could be attributed to the triangular face rotation mechanism. The reaction of iridium derivative 1-cod-8-SMe2-1,2,8-IrC2B9H10 (1) with anhydrous hydrohalic acids HX (X = Cl, Br, I) results in the dimeric halide iridacarboranes [1,1-X-2-8-SMe2-1,2,8-IrC2B9H10](2) [4a-c; X = Cl (a), Br (b), I (c)]. Bromide 4b reacts with Tl[Tl(eta-7,8-C2B9H11)] and TlCp giving iridacarboranes 8 ‘-SMe2-1,1 ‘-Ir(2,3-C2B9H11)(2 ‘,8 ‘-C2B9H10) (5) and 1-Cp-8-SMe-1,2,8-IrC2B9H10 (6). The formation of the latter compound is accompanied by demethylation of the SMe2 substituent. The structures of 2, 3, 5 and 6 were determined by single-crystal X-ray diffraction. Iridacarboranes 4b and [1,1-Br-2-4-SMe2-1,2,3-IrC2B9H10](2) (7) catalyze the dimerization of diphenylacetylene, giving 1,2,3-triphenylnaphthalene in 20-24% yields. Compounds 4b and 7 also effectively catalyze the reductive amination reaction between aldehydes (or ketones) and primary (or secondary) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in high yields (60-85%).

First author: Chakraborty, D, Effect of functionalization of boron nitride flakes by main group metal clusters on their optoelectronic properties,
Abstract: The possibility of functionalizing boron nitride flakes (BNFs) with some selected main group metal clusters, viz. OLi4, NLi5, CLi6, BLI7 and Al12Be, has been analyzed with the aid of density functional theory (DFT) based computations. Thermochemical as well as energetic considerations suggest that all the metal clusters interact with the BNF moiety in a favorable fashion. As a result of functionalization, the static (first) hyperpolarizability (beta) values of the metal cluster supported BNF moieties increase quite significantly as compared to that in the case of pristine BNF. Time dependent DFT analysis reveals that the metal clusters can lower the transition energies associated with the dominant electronic transitions quite significantly thereby enabling the metal cluster supported BNF moieties to exhibit significant non-linear optical activity. Moreover, the studied systems demonstrate broad band absorption capability spanning the UV-visible as well as infra-red domains. Energy decomposition analysis reveals that the electrostatic interactions principally stabilize the metal cluster supported BNF moieties.

First author: Harris, JW, Molecular Structure and Confining Environment of Sn Sites in Single-Site Chabazite Zeolites,
CHEMISTRY OF MATERIALS, 29, 8824, (2017)
Abstract: Chabazite (CHA) molecular sieves, which are industrial catalysts for the selective reduction of nitrogen oxides and the conversion of methanol into olefins, are also ideal materials in catalysis research because their crystalline frameworks contain one unique tetrahedral site. The presence of a single lattice site allows for more accurate descriptions of experimental data using theoretical models and consequently for precise structure-function relationships of active sites incorporated into framework positions. A direct hydrothermal synthesis route to prepare pure-silica chabazite molecular sieves substituted with framework Sn atoms (Sn-CHA) was developed, which is required to predominantly incorporate Sn within the crystalline lattice. Quantitative titration with Lewis bases (NH3, CD3CN, and pyridine) demonstrates that framework Sn atoms behave as Lewis acid sites which catalyze intermolecular propionaldehyde reduction and ethanol oxidation as well as glucose-fructose isomerization. Aqueous-phase glucose isomerization turnover rates (per accessible Sn, 398 K) on Sn-CHA are four orders of magnitude lower than on Sn-Beta zeolites, but similar to those on amorphous Sn-silicates. Further analysis of Sn-CHA by dynamic nuclear polarization enhanced solid-state nuclear magnetic resonance (DNP NMR) spectroscopy enables measurement of Sn-119 NMR chemical shift anisotropy (CSA) of Sn sites. Comparison of experimentally determined CSA parameters to those computed on cluster models using density functional theory supports the presence of closed sites (Sn-(OSi equivalent to)(4)) and defect sites ((HO)-Sn-(OSi equivalent to)(3)) adjacent to a framework Si vacancy), which respectively become hydrated hydrolyzed-open sites and hydrated defect sites when Sn-CHA is exposed to ambient conditions or aqueous solution. Kinetic and spectroscopic data show that large substrates (e.g., glucose) are converted only on Sn sites located within disordered mesoporous voids of Sn-CHA, which are selectively detected and quantified in IR and N-15 and Sn-119 DNP NMR spectra using pyridine titrants. This integrated experimental and theoretical approach allows precise description of the primary coordination and secondary confining environments of Sn active sites isolated in crystalline silica frameworks and establishes the role of confinement within microporous voids of Beta zeolites for aqueous-phase glucose isomerization catalysis.

First author: Wu, QY, Theoretically unraveling the separation of Am(III)/Eu(III): insights from mixed N,O-donor ligands with variations of central heterocyclic moieties,
Abstract: With the fast development of nuclear energy, the issue related to spent nuclear fuel reprocessing has been regarded as an imperative task, especially for the separation of minor actinides. In fact, it still remains a worldwide challenge to separate trivalent An(III) from Ln(III) because of their similar chemical properties. Therefore, understanding the origin of extractant selectivity for the separation of An(III)/Ln(III) by using theoretical methods is quite necessary. In this work, three ligands with similar structures but different bridging frameworks, Et-Tol-DAPhen (L-a), Et-Tol-BPyDA (L-b) and Et-Tol-PyDA (L-c), have been investigated and compared using relativistic density functional theory. The electrostatic potential and molecular orbitals of the ligands indicate that ligand L-a is a better electron donor compared to ligands L-b and L-c. The results of QTAIM, NOCV and NBO suggest that the Am-N bonds in the studied complexes have more covalent character compared to the Eu-N bonds. Based on the thermodynamic analysis, [M(NO3)(H2O)(8)](2+) + L + 2NO(3)(-) = [ML(NO3)(3)] + 8H(2)O should be the most probable reaction in the solvent extraction system. Our results clearly verify that the relatively harder oxygen atoms offer these ligands higher coordination affinities toward both of the An(III) and Ln(III) ions compared to the relatively softer nitrogen atoms. However, the latter possess stronger affinities toward An(III) over Ln(III), which partly results in the selectivity of these ligands. This work can afford useful information on achieving efficient An(III)/Ln(III) separation through tuning the structural rigidity and hardness or softness of the functional moieties of the ligands.

First author: Novak, M, Anti-Electrostatic CH-Ion Bonding in Decorated Graphanes,
Abstract: State-of-the-art computations combined with Ziegler-Rauk energy decomposition analyses are employed to introduce a new class of anti-electrostatic ion-sigma bonds with considerable stability and a substantial contribution from charge transfer and dispersion between ions and finite-size functionalized graphane flakes, G-XYs. G-XYs have diverse electric multipolar moments that are comparable with those of newly synthesized all-cis-hexa-halocyclohexanes. The strong, long-range electrostatic and Pauli repulsions between some G-XYs and certain ions induce a gas-phase energy barrier to the physisorption of ions on the surface of G-XYs. However, the repulsive interactions can be overbalanced by the strong orbital interactions operating in the formation of ion-sigma complexes at short range, leading to covalent-type intermolecular bonds as strong as -34 kcal mol(-1).

First author: Kumar, PS, Cooperation and Environment Characterize the Low-Lying Optical Spectrum of Liquid Water,
Abstract: The optical spectrum of liquid water is analyzed by subsystem time-dependent density functional theory. We provide simple explanations for several important (and so far elusive) features. Due to the disordered environment surrounding each water molecule, the joint density of states of the liquid is much broader than that of the vapor, thus explaining the red-shifted Urbach tail of the liquid compared to the gas phase. Confinement effects provided by the first solvation shell are responsible for the blue shift of the first absorption peak compared to the vapor. In addition, we also characterize many-body excitonic effects. These dramatically affect the spectral weights at low frequencies, contributing to the refractive index by a small but significant amount.

First author: Gayfulin, YM, Facile Substitution of Bridging SO22- Ligands in Re-12 Bioctahedral Cluster Complexes,
INORGANIC CHEMISTRY, 56, 12389, (2017)
Abstract: Selective substitution of mu-SO22- groups by either O2- or Se2- ions occurs upon heating the bioctahedral rhenium cluster complex K-6[Re12CS14(mu-SO2)(3)(CN)(6)] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO22- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re12CS14(mu-O)(3)(CN)(6)](6-), [Re12CS14(mu-Se)(3)(CN)(6)](6-), and [Re12CS14(mu-O)(3)(OH)(6)](6-), were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported mu-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re12CS14(mu-Q)(3)L-6](5-) (Q = O, S, Se, L = CN-; Q = O, S, L = OH-), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the subStitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

First author: Kias, F, C-F bond breaking by bare actinide monocations in the gas phase: a relativistic DFT study,
Abstract: Investigations of the C-F bond activation by actinide monocation An(+) (An = Ac, Th, Pa, U, Np, Pu and Am) are carried out using relativistic density functional theory (OFF) computations. Originally, the aim of the study is to compare the ability of different actinide ions to break strong bonds particularly in the context of accidental radioactive dissemination. The An(+) reaction with the fluorinated hydrocarbon CH3F was selected as a representative system in this context. Unexpectedly, the considered An+ were found to react differently. Via linear transit (LT) and intrinsic reaction coordinate (IRC) calculations, three reaction mechanisms for the C-F bond activation, leading to the An-F+ formation, were revealed; the first one, i.e. ‘harpoon’ mechanism which was observed in the case of Pu+, Am+, while the second called ‘inser tion-elimination’ mechanism concerned the case of Th+, Pa+, U+ and Np+. OFT computations highlight the particular case of the Ac+ system which presents two different mechanisms according to its spin state: a mechanism qualified as ‘harpoon-like’ for the triplet state and an ‘insertion-elimination’ mechanism for the singlet state. The activation barrier for the fluorine elimination from CH3F is weak for all the studied systems, from 0.9 kcal/mol for Th+ to 8.2 kcal/mol for Am+. Th+ is found as the most effective ion to activate the C-F bond and a considerable exergonic character (-81.5 kcal/mol) for this reaction is expected. The performed orbital, population and charge analyses permitted to reveal the role of the actinide 7s, 6d and 5f orbitals and of electron transfers during the reaction.

First author: Goszczycki, P, Synthesis, crystal structures, and optical properties of the pi-pi interacting pyrrolo[2,3-b] quinoxaline derivatives containing 2-thienyl substituent,
Abstract: Three (E/Z)-diastereoisomers, based on pyrrolo[2,3-b]quinoxaline system as fluorophore and containing: 2-thienylmethyl (1), bis(2-thienylmethyl)-2-aminoethyl (3a), bis(2-thienylmethyl)-3-aminopropyl (3b) groups as substituents, were synthesized and characterized by X-ray structural analysis, PXRD, NMR, UV Vis as well as fluorescence. These compounds are non-fluorescent in acetonitrile solution, however, they exhibit aggregation induced emission enhancement (AIEE) upon water addition and in solid state. X-ray structural analysis revealed that molecules with 2-thienylmethyl and bis(2-thienylmethyl)-2-aminoethyl groups form dimers and pi-stacks through pi-pi interactions between anitiparallel oriented pyrroloquinoxaline cores with interplanar distances 3.45 angstrom and 3.20 angstrom, respectively. Conformation of bis(2-thienylmethyl)-3-aminopropyl group is imposed by incorporated DMSO-d(6) solvent molecule and weak intermolecular S-pi and CH-pi interactions, that prevents pi-pi interaction between fluorophore cores. The correlation between crystal structure and fluorescent properties of synthesized molecules was discussed. The DFT calculations were performed to rationalize the differences between considered systems.

First author: Hurtado, J, Synthesis, crystal structure, catalytic and anti-Trypanosoma cruzi activity of a new chromium(III) complex containing bis(3,5-dimethylpyrazol-1-yl)methane,
Abstract: The reaction of CrCl(3)6H(2)O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H2O)(2)Cl-2](+), which crystallized as the chloride trihydrate [(Cr(L)(H2O)(2)Cl-2]Cl.3H(2)O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by O-H…(O,Cl) hydrogen bonds and weak C-H…O interactions to build a monoclinic P2(1)/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of epsilon-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 degrees C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC50) of 1.08 mu g/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.

First author: Gong, LF, The effects of halogen elements on the opening of an icosahedral B-12 framework,
Abstract: The fully halogenated or hydrogenated B12X122- (X = H, F, Cl, Br and I) clusters are confirmed to be icosahedral. On the other hand, the bare B-12 cluster is shown to have a planar structure. A previous study showed that a transformation from an icosahedron to a plane happens when 5 to 7 iodine atoms are remained [P. Farras et al., Chem. -Eur. J. 18, 13208-13212 (2012)]. Later, the transition was confirmed to be seven iodine atoms based on an infrared spectroscopy study [M. R. Fagiania et al., Chem. Phys. Lett. 625, 48-52 (2015)]. In this study, we investigated the effects of different halogen atoms on the opening of the B-12 icosahedral cage by means of density functional theory calculations. We found that the halogen elements do not have significant effects on the geometries of the clusters. The computed infrared (IR) spectra show similar representative peaks for all halogen doped clusters. Interestingly, we found a blue-shift in the IR spectra with the increase in the mass of the halogen atoms. Further, we compared the Gibbs free energies at different temperatures for different halogen atoms. The results show that the Gibbs free energy differences between open and close structures of B12X7- become larger when heavier halogen atoms are presented. This interesting finding was subsequently investigated by the energy decomposition analysis. Published by AIP Publishing.

First author: Georgopoulou, AN, Site preferences in hetero-metallic [Fe9-xNix] clusters: a combined crystallographic, spectroscopic and theoretical analysis,
DALTON TRANSACTIONS, 46, 12835, (2017)
Abstract: The reaction of mixtures of Fe(O2CMe) (2)center dot 2H(2)O and Ni(O2CMe)(2)center dot 4H(2)O of various compositions with di-2-pyridyl ketone (py(2)CO, dpk) in MeCN under an inert atmosphere afforded a family of hetero-metallic enneanuclear clusters with general formula [Fe9-xNix(mu(4)-OH)(2)(O2CMe)(8)(py(2)CO(2))(4)](2, x = 1.00; 3: x = 6.02; 4, x = 7.46; 5, x = 7.81). Clusters 2-5 are isomorphous to the homo-metallic [Fe-9] cluster (1) previously reported by some of us, and also isostructural to the known homo-metallic [Ni-9] cluster. All four clusters contain a central M-II ion in an unusual 8-coordinate site and eight peripheral M-II ions in distorted octahedral environments. The distribution of Fe-II and Ni-II ions over these two distinct coordination sites in 2-5 can be established through a combination of X-ray fluorescence and Mossbauer spectroscopies, which show that Fe-II preferentially occupies the unique 8-coordinate metal site while Ni-II accumulates in the octahedral holes. Density functional theory indicates that the distribution of ions across the two sites arises not from any intrinsic preference of the Fe-II ions for the 8-coordinate sites, but rather because of the large ligand field stabilization energy available to Ni-II in octahedral coordination.

First author: Chi, WJ, Optimizing thienothiophene chain lengths of D-pi-D hole transport materials in perovskite solar cells for improving energy levels and hole mobility,
Abstract: Although perovskite solar cells (PSCs) have recently achieved power conversion efficiencies (PCE) of over 23.6%, one major bottleneck for further improving the PCE is the lack of suitable hole transport materials. To further understand the structure-property relationship of hole transport materials and design new materials, we calculated the energy levels and optical properties of a series of thienothiophene derivatives by using density functional theory, and their hole transfer behaviors were also described by the Marcus charge transfer theory. It is found that the HOMO energies gradually decrease as the number of thiophene rings (n) increases when n is less than 4. However, when n is more than 4, the HOMO energy is a constant value of -5.23 eV. As for the LUMO energy and energy gaps, they show a similar change trend, that is, a gradual decrease with growing n. Optical calculations showed that thienothiophene extension cannot affect the Stokes shifts of thienothiophene derivatives. Importantly, it is found that the hole mobility of thienothiophene molecules is co-determined by the molecular size and odd or even number of thiophthene units, and all investigated thienothiophene molecules show higher hole mobility than Sprio-OMeTAD due to the face-to-face packing model. These results provide useful information to further develop suitable HTMs used in PSCs.

First author: Rezabal, E, The trans Effect in Palladium Phosphine Sulfonate Complexes,
Abstract: Palladium phosphine sulfonate complexes constitute an efficient family of catalysts for both homo-polymerization of ethylene and copolymerization of ethylene with a number of polar monomers. Their catalytic mechanisms have been extensively studied but not fully understood at the electronic structure level. The energy decomposition analysis, complemented with the inspection of the natural orbitals for chemical valence, reveals that their catalytic activity can be rationalized in terms of the so-called trans effect. Furthermore, our analysis shows that the competition for the sigma donation of the two ligands PMe3 and L, of the palladium phosphine sulfonate complexes, to the same orbital of Pd in the trans isomer and to different orbitals in the cis isomer is the origin of the trans effect. Although the dominance of the phosphine group prevents an efficient interaction of the ligand L with the Pd atom, the large stabilization gained by the phosphine group renders a very stable trans complex.

First author: Lorenzoni, A, Morphology and Electronic Properties of N,N’-Ditridecylperylene-3,4,9,10-tetracarboxylic Diimide Layered Aggregates: From Structural Predictions to Charge Transport,
Abstract: The morphology of layered aggregates of N,N ‘-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13), a prototypical n-type semiconductor for organic electronic devices, was investigated by molecular dynamics and corroborated by metadynamics simulations. Calculations were targeted to ordered 3D aggregates, differing in the relative orientation of the perylene pi-cores and on the degree of interdigitation among contiguous planar layers. Our simulations indicated the noninterdigitated cofacial structure as the thermodynamically most stable form of ordered PTCDI-C13 aggregates, in both bulk crystals and bilayers. Other structures, however, may occur in the growth of PTCDI-C13 under kinetic conditions. Density functional theory calculations were also performed to evaluate the relative total electronic energy of 3D crystals of PTCDI-C13 and related transfer integrals, correlating structure with potential charge-transport properties in devices. The most stable ordered aggregated form of PTCDI-C13 exhibits significant transfer integrals for electrons and accounts for the remarkable n-type charge-transport properties observed in thin films grown under thermodynamic conditions. The effect of structural disorder on charge-transport properties was also assessed by computing transfer integrals in PTCDI-C13 layers at the interface with a model surface. Targeting a strategic material for organic electronics, this work also highlights an integrated computational approach to simulate the structure and energetics of competing 3D morphologies in thin films and to shed light on the details of ordered structures that are responsible for the charge transport in small-molecule organic semiconductors.

First author: Kubicki, DJ, Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)(x)(FA)(1-x)Pbl(3) Hybrid Perovskites from Solid-State NMR,
Abstract: Hybrid (organic-inorganic) multication lead halide perovskites hold promise for a new generation of easily processable solar cells. Best performing compositions to date are multiple-cation solid alloys of formamidinium (FA), methylammonium (MA), cesium, and rubidium lead halides which provide power conversion efficiencies up to around 22%. Here, we elucidate the atomic-level nature of Cs and Rb incorporation into the perovskite lattice of FA-based materials. We use Cs-23, Rb-87, K-89, C-13, and N-14 solid-state MAS NMR to probe microscopic composition of Cs-, Rb-, K-, MA-, and FA-containing phases in double-, triple-, and quadruple-cation lead halides in bulk and in a thin film. Contrary to previous reports, we have found no proof of Rb or K incorporation into the 3D perovskite lattice in these systems. We also show that the structure of bulk mechanochemical perovskites bears close resemblance to that of thin films, making them a good benchmark for structural studies. These findings provide fundamental understanding of previously reported excellent photovoltaic parameters in these systems and their superior stability.

First author: Kias, F, Redox Properties of Monocyclooctatetraenyl Uranium(IV) and (V) Complexes: Experimental and Relativistic DFT Studies,
ORGANOMETALLICS, 36, 3841, (2017)
Abstract: The redox properties of a series of mono(cyclooctatetraenyl) uranium(IV) and (V) complexes [(Cot)(Cp)U-(NEt2)(2)] (1) (Cot = eta-C8H8, Cp = eta-C5H5) [(Cot)U((OPr)-Pr-i)(3)] (2), [(Cot)U(NMe2)(3)] (3), [(Cot)U(N{SiMe3}(2))(2)] (4), [(Cot)U(NEt2)(3)](-) (5), and the cyclopentadienyl compound [(C5Me5)U(NEt2)(3)] (6) have been investigated using cyclic voltammetry and relativistic density functional theory (DFT). Electrochemical measurements of half-wave potentials in tetrahydrofuran were carried out under strictly anaerobic conditions. The calculations of ionization energies (IE) and electron affinities (EA) of these compounds, related to the U-III/U-IV, U-IV/U-V and U-V/U-VI redox systems, revealed a very good linear correlation (r(2) = 0.99) between calculated ionization energies at the ZORA/BP86/TZP level and the measured E-1/2 half-wave oxidation potentials. A similar good linear correlation between the computed electron affinities and the electrochemical reduction potentials (r(2) = 0.98) was obtained. It was found to be crucial to take into account the solvent effect as well as the spin-orbit coupling. The DFT computations permitted the estimation of the oxidation potential of 3 as well as the reduction potential of 5 for which the electrochemical measurement failed. An explanation of the different redox behaviors of the complexes has been given, considering the donating ability of the ligands and the nature of their frontier molecular orbitals (MOs). The molecular orbital analysis underlines the determining role of the metal 5f orbitals, whereas a good correlation is observed between the Nalewajski-Mrozek bond indices and the structural variations related to the redox processes.

First author: Patra, R, Rational design of Fe catalysts for olefin aziridination through DFT-based mechanistic analysis,
Abstract: Nitrene transfer reactions are increasingly used to access various kinds of amine derivatives but the underlying mechanisms have not been unraveled in most cases. Fe-catalyzed aziridination of alkenes has appeared as a promising route to aziridines which are important derivatives both per se and as intermediates in many synthetic procedures. We report the strong activity and the mechanism of di-iron catalysts for aziridination of styrenes using phenyltosyliodinane (PhI=NTs). In addition, we have developed a similar mono-iron catalyst which operates under the same mechanism albeit with a reduced activity. DFT calculations were performed to investigate the structure and electronic structure of the (FeNTs)-N-IV species of the latter catalyst. They suggest that the reaction pathway leading to the nitrene transfer to the olefin involves a transient charge transfer on the way to a radical intermediate, which is totally consistent with the experimental results. Moreover, these calculations identify the electron affinity (EA) of the active species as one key parameter allowing rationalization of the observations, which opens the way to improving the catalyst efficiency on a rational basis.

First author: Stepanovic, S, The role of spin states in the catalytic mechanism of the intra- and extradiol cleavage of catechols by O-2,
Abstract: Iron-dependent enzymes and biomimetic iron complexes can catalyze the ring cleavage of very inert, aromatic compounds. The mechanisms of these transformations and the factors that lead either to extradiol cleavage or intradiol cleavage have not been fully understood. By using density functional theory we have elucidated the mechanism of the catalytic cycle for two biomimetic complexes, and explained the difference in the experimentally obtained products.

First author: Jaoul, A, Assessment of Density Functionals for Computing Thermodynamic Properties of Lanthanide Complexes,
CHEMPHYSCHEM, 18, 2688, (2017)
Abstract: The equilibrium between the radical phenanthroline complex Cp*Sm-2(phen) and the coupling product (Cp*Sm-2(phen))(2) has been investigated based on quantum chemistry calculations. Topological analyses pointed out that the C-C bond created has a partial covalent character, explaining why both the monomeric and the dimeric forms exist in equilibrium. A large variety of density functionals have been tested to reproduce experimental thermodynamic data for this equilibrium. Finally, the PBE0-D3 and M06-2X functionals lead to a good evaluation of the energies and enable a correct description of the ligand to metal charge transfer, both in the 4f and 5d metal orbitals.

First author: Boughlala, Z, Alkali Metal Cation Affinities of Anionic Main Group-Element Hydrides Across the Periodic Table,
Abstract: We have carried out an extensive exploration of gas-phase alkali metal cation affinities (AMCA) of archetypal anionic bases across the periodic system using relativistic density functional theory at ZORA-BP86/QZ4P//ZORA-BP86/TZ2P. AMCA values of all bases were computed for the lithium, sodium, potassium, rubidium and cesium cations and compared with the corresponding proton affinities (PA). One purpose of this work is to provide an intrinsically consistent set of values of the 298K AMCAs of all anionic (XHn-1-) constituted by main group-element hydrides of groups14-17 along the periods2-6. In particular, we wish to establish the trend in affinity for a cation as the latter varies from proton to, and along, the alkali cations. Our main purpose is to understand these trends in terms of the underlying bonding mechanism using Kohn-Sham molecular orbital theory together with a quantitative bond energy decomposition analyses (EDA).

First author: Rutledge, KM, Macrocycles All Aflutter: Substitution at an Allylic Center Reveals the Conformational Dynamics of [13]-Macrodilactones,
Abstract: The shapes adopted by large-ring macrocyclic compounds play a role in their reactivity and their ability to be bound by biomolecules. We investigated the synthesis, conformational analysis, and properties of a specific family of [13]-macrodilactones as models of natural-product macrocycles. The features of our macrodilactones enabled us to study the relationship between stereogenic centers and planar chirality through the modular synthesis of new members of this family of macrocycles. Here we report on insights gained from a new [13]-macrodilactone that is substituted at a position adjacent to the alkene in the molecule. Analysis of the compound, in comparison to an -substituted regioisomer, by using X-ray crystallography, NMR coupling constants, and reaction-product characterization in concert with computational chemistry, revealed that the alkene unit is dynamic. That is, the data support a model in which the alkene in our [13]-macrodilactones oscillates between two conformations. A difference in reactivity of one conformation compared to the other leads to manifestation of this dynamic behavior. The results underscore the local conformational dynamics observed in some natural-product macrocycles, which could have implications for biomolecule binding.

First author: Chai, JS, X-ray Crystal Structure and Optical Properties of Au38-x,Cu-x(2,4(CH3)(2)C6H3S)(24) (x=0-6) Alloy Nanocluster,
Abstract: In this work, we report the synthesis and crystal structure of Au38-xCux(2,4-DMBT)(24) (x = 0-6, 2,4-DMBTH = 2,4-dimethylbenzenethiol) alloy nanocluster for the first time. A variety of characterizations including ESIMS, TGA, and XPS reveal the composition as Au(38-x)Cux(2,4-DMBT)(24) (x = 0-6). The single crystal structure has been determined by an X-ray single crystal diffractometer. From the anatomy of the structure, a bi-icosahedral Au23 core is protected by Or dimeric [SR M SR M SR] units (M = Cu/Au) and three monomeric.[SR Au SR] units. It is interesting that all the Cu atoms are selectively doped in the motifs of the Au38-xCux(2,4-DMBT)(24) nanocluster. This phenomenon. is distinct from the exclusive core doping of the Ag atoms in the previously reported Au38-xAgx alloy. Both the experimental results and DFT calculations -of UV vis spectra Imply that the optical property of the Au(38-x)cu(x)(2,4-DMBT)(24) nanocluster is consistent with that of the Au-38(2,4-DMBT)(24) make little contribution to the frontier orbitals of the alloy NC.

First author: Szatylowiciz, H, Toward the Physical Interpretation of Inductive and Resonance Substituent Effects and Reexamination Based on Quantum Chemical Modeling,
ACS OMEGA, 2, 7163, (2017)
Abstract: An application of a charge of the substituent active region concept to 1-Y,4-X-disubstituted derivatives of bicyclo[2.2.2] octane (BCO) [where Y = NO2, COOH, OH, and NH2 and X = NMe2, NH2, OH, OMe, Me, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, and NO] provides a quantitative information on the inductive component of the substituent effect (SE). It is shown that the effect is highly additive but dependent on the kind of substituents. An application of the SE stabilization energy characteristics to 1,4disubstituted derivatives of BCO and benzene allows the definition of inductive and resonance contributions to the overall SE. Good agreements with empirical approaches are found. All calculations have been carried out by means of the B3LYP/6-311++G(d,p) method.

First author: Song, Y, Influence of beta-octabromination on free-base triarylcorroles: Electrochemistry and protonation-deprotonation reactions in nonaqueous media,
Abstract: Electrochemical and acid-base properties of four free-base triarylcorroles were examined in nonaqueous media. These compounds are represented here as (tdcc)H-3, (tpfc)H-3, (Br(8)tdcc)H-3 and (Br(8)tpfc)H-3, where tdcc and tpfc are the trianions of tris(2,6-dichlorophenyl) corrole and tris(pentafluorophenyl) corrole, respectively. Different spectroscopic and electrochemical properties were observed for the beta-brominated corroles as compared to the non-brominated derivatives, due in part to the corrole ring distortion and in part to the strong electron-withdrawing properties of the Br groups. The brominated free-base corroles are easier to deprotonate than the non-brominated corroles in solution, which was confirmed by electrochemistry and spectroelectrochemistry as well as protonation/deprotonation reactions of the compounds with acid or base in PhCN. The electrochemistry of the protonated and deprotonated corroles is presented and comparisons made with previously published data for other protonated and deprotonated free-base corroles under the same solution conditions.

First author: Li, YX, Isomeric Effects of Solution Processed Ladder-Type Non-Fullerene Electron Acceptors,
SOLAR RRL, 1, 633, (2017)
Abstract: The role of electronic structure and thin film morphology is investigated in determining charge transfer and electron coupling due to orbital interactions in two isomeric non-fullerene acceptors with the structure of acceptor-donoracceptor. Differences are found in the distribution of electron density of the highest occupied molecular and lowest unoccupied molecular orbitals, whose bonding interactions result in improved intermolecular interactions and hence, molecular stacking. When combined with a large band gap polymer donor, solution-processed organic photovoltaic cells are demonstrated with power conversion efficiencies as high as 10.5 +/- 0.4%, and with absorption extending to wavelengths of 800 nm. Due to strong internal organization driven by the planar molecular structure and strong intermolecular interactions, no post-deposition processing such as solvent vapor or thermal annealing is required. To our knowledge, these are the highest efficiencies for as-cast solution-based devices employing non-fullerene acceptors.

First author: Pawlak, R, Design and Characterization of an Electrically Powered Single Molecule on Gold,
ACS NANO, 11, 9930, (2017)
Abstract: The surface diffusion of individual molecules is of paramount importance in self-assembly processes and catalytic processes. However, the fundamental understanding of molecule diffusion peculiarities considering conformations and adsorption sites remain poorly known at the atomic scale. Here, we probe the 4′-(4-tolyl)-2,2′:6′,2 ”-terpyridine adsorbed on the Au(111) herringbone structure combining scanning tunneling microscopy and atomic force microscopy. Molecules are controllably translated by electrons excitations over the reconstruction, except at elbows acting as pinning centers. Experimental data supported by theoretical calculations show the formation of coordination bonds between the molecule and Au atoms of the surface. Using force spectroscopy, we quantify local variation of the surface potential and the lateral force required to move the molecule. We found an elevation of the diffusion barrier at elbows of the reconstruction of similar to 100 meV compared to the rest of the surface.

First author: Southern, SA, Prospects for Pb-207 solid-state NMR studies of lead tetrel bonds,
FARADAY DISCUSSIONS, 203, 165, (2017)
Abstract: The feasibility and value of Pb-207 solid-state NMR experiments on compounds featuring lead tetrel bonds is explored. Although the definition remains to be formalized, lead tetrel bonds may be qualitatively described as existing when there is evidence of a net attractive interaction between an electrophilic region associated with lead in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Unambiguous identification of lead tetrel bonds can be challenging due to the hypervalent tendency of lead. We report here a series of Pb-207 solid-state NMR experiments on five metal-organic frameworks featuring lead coordinated to hydrazone-based ligands. Such frameworks may be held together in part by lead tetrel bonds. The acquisition of Pb-207 solid-state NMR spectra for such materials is feasible and is readily accomplished using a combination of magic-angle spinning and Carr-Purcell-Meiboom-Gill methods in moderate to low applied magnetic fields. The lead centres are characterized by Pb-207 isotropic chemical shifts ranging from -426 to -2591 ppm and chemical shift tensor spans ranging from 910 to 2681 ppm. Careful inspection of the structures of the compounds and the literature Pb-207 NMR data may suggest that a tetrel bond to lead results in chemical shift parameters which are intermediate between those which are characteristic of holodirected and hemidirected lead coordination geometries. Challenges associated with DFT computations of the Pb-207 NMR parameters are discussed. In summary, the Pb-207 data for the compounds studied herein show a marked response to the presence of non-coordinating electron-rich moieties in close contact with the electrophilic surface of formally hemidirectionally coordinated lead compounds.

First author: Ho, PC, Building new discrete supramolecular assemblies through the interaction of iso-tellurazole N-oxides with Lewis acids and bases,
FARADAY DISCUSSIONS, 203, 187, (2017)
Abstract: The supramolecular macrocycles spontaneously assembled by iso-tellurazole N-oxides are stable towards Lewis bases as strong as N-heterocyclic carbenes (NHC) but readily react with Lewis acids such as BR3 (R = Ph, F). The electron acceptor ability of the tellurium atom is greatly enhanced in the resulting O-bonded adducts, which consequently enables binding to a variety of Lewis bases that includes acetonitrile, 4-dimethylaminopyridine, 4,4 ‘-bipyridine, triphenyl phosphine, a N-heterocyclic carbene and a second molecule of iso-tellurazole N-oxide.

First author: Zhang, LJ, Water as a proton mediator for dioxygen-selective oxidation of alcohols by a planar dinuclear butterfly-like Cu-Cu bonding complex: A combined experimental and computational study,
JOURNAL OF CATALYSIS, 354, 78, (2017)
Abstract: The selective catalytic oxidation of alcohols is important both in laboratory and industrial production, and traditional oxidants cause environmentally lethal wastes. The development of dioxygen selective oxidation efficient has been pursued from atom-efficient, economic and environmental view of points. Using DFT calculation and ESI-MS experiments, we studied the activation of the Cu-Cu bonded planar complex Cu-2(ophen)(2) to dioxygen and the application of the dioxygen-copper system for the selective oxidation of alcohols. For practical application and green chemistry, this catalytic system avoided the use of a large excess of base and expensive nitroxyl derivatives. In the cycle of oxidation, two oxidative dehydrogenation processes featuring superoxide/peroxide (I) and hydroperoxide (II) occurred along with a series of conformational changes of the butterfly-like Cu-complex from stretched to folded to stretched. Additionally, we characterized the role of the water molecule as a proton mediator in the dioxygencopper system.

First author: Alkan, F, Role of Exact Exchange and Relativistic Approximations in Calculating F-19 Magnetic Shielding in Solids Using a Cluster Ansatz,
Abstract: Calculations of F-19 magnetic shielding in various materials are presented. In calculations on gas-phase molecules, the variation of magnetic shielding with the amount of Hartree-Fock exchange (HFX) in the functional demonstrates that excellent agreement with experiment is obtained with an admixture of 50%, here denoted PBE0 (50%). Calculations at the PBE, PBE0 (25%), and PBE0 (50%) levels on 10 crystalline organofluorines and 15 crystalline inorganic fluorides, in which a cluster ansatz is used to model the lattice environment, were performed. For fluorine-containing aromatics, increasing the admixture of HFX results in the prediction of larger magnetic-shielding spans, whereas increasing the admixture of HFX in calculations for CFCl3 decreases the span. In calculations of F-19 magnetic shielding of the inorganic fluorides, the use of sufficiently large clusters of inorganic fluorides results in accuracies similar to those calculated for the organofluorines. Relativistic effects on the magnetic shielding of inorganic fluorides, modeled with ZORA at both the scalar and spin-orbit levels, are dominated by the scalar terms that increase the shielding of most F-19 sites over the non-relativistic results. These effects appear to scale with the atomic number of the cation. For most elements of the sixth row (Cs, Ba, La, and Pb), the scalar relativistic contribution to the magnetic shielding is in the range of 20-77 ppm. For elements of group XII (Zn, Cd, and Hg) bonded to fluorine, the scalar relativistic contribution results in deshielding of the F-19 site.

First author: Shunmugam, L, Road Map for the Structure-Based Design of Selective Covalent HCV NS3/4A Protease Inhibitors,
PROTEIN JOURNAL, 36, 397, (2017)
Abstract: Over the last 2 decades, covalent inhibitors have gained much popularity and is living up to its reputation as a powerful tool in drug discovery. Covalent inhibitors possess many significant advantages including increased biochemical efficiency, prolonged duration and the ability to target shallow, solvent exposed substrate-binding domains. However, rapidly mounting concerns over the potential toxicity, highly reactive nature and general lack of selectivity have negatively impacted covalent inhibitor development. Recently, a great deal of emphasis by the pharmaceutical industry has been placed toward the development of novel approaches to alleviate the major challenges experienced through covalent inhibition. This has unexpectedly led to the emergence of “selective” covalent inhibitors. The purpose of this review is not only to provide an overview from literature but to introduce a technical guidance as to how to initiate a systematic “road map” for the design of selective covalent inhibitors which we believe may assist in the design and development of optimized potential selective covalent HCV NS3/4A viral protease inhibitors.

First author: Aissaoui, T, Computational investigation of the microstructural characteristics and physical properties of glycerol-based deep eutectic solvents,
Abstract: Recently, there has been significant interest in the possibility of using deep eutectic solvents (DESs) as novel green media and alternatives to conventional solvents and ionic liquids (ILs) in many applications. Due to their attractive properties, such as their biodegradability, low cost, easy preparation, and nontoxicity, DESs appear to be very promising solvents for use in the field of green chemistry. This computational study investigated six glycerol-based DESs: DES1 (glycerol: methyl triphenyl phosphonium bromide), DES2 (glycerol: benzyl triphenyl phosphonium chloride), DES3 (glycerol: allyl triphenyl phosphonium bromide), DES4 (glycerol: choline chloride), DES5 (glycerol: N, N-diethylethanolammonium chloride), and DES6 (glycerol: tetra-n-butylammonium bromide). The chemical structures and combination mechanisms as well as the sigma profiles and sigma potentials of the studied DESs were explored in detail. Moreover, density, viscosity, vapor pressure, and IR analytical data were predicted and compared with the corresponding experimental values reported in the literature for these DESs. To achieve these goals, the conductor-like screening model for realistic solvents (COSMO-RS) and the Amsterdam Density Functional (ADF) software package were used. The predicted results were found to be in good agreement with the corresponding experimental values reported in the literature. Further theoretical investigations are needed to confirm the experimental results-regarding both properties and applications-reported for these DESs.

First author: Bouzidi, Y, Cyanide linkage isomerism in cerium(III) and uranium(III) complexes. A relativistic DFT study,
Abstract: The chemistry of cyanide complexes of the f-elements has witnessed significant recent advances, showing in particular the remarkable ability of the cyanide ligand to stabilize uranium compounds in their +3 to +6 oxidation states and its capacity to adopt two distinct ligation modes, namely cyanide M-CN or isocyanide M-NC, towards trivalent f-ions. Here, we have theoretically investigated the tris(cyanide) complexes[ML2X3](2-) (M = Ce3+, U3+; L = C5H4Me, N(SiMe3)(2); X = CN, NC), using relativistic DFT computations, focusing on cyanide (CN-) and isocyanide (NC-) coordination competition and differences between their electronic structures. X-ray crystal data reveal distinct coordination modes of the CN ligand towards uranium and cerium metal centers. Interestingly, in the case of the cerium complexes, and contrarily to the uranium ones, the coordination mode of the cyanide ligand depends on the coligand L attached to the metal. The observed coordination in these tris(cyanide) complexes is driven by the binding energies of the CN-/NC- ligands to the metals. The solvent is shown to play a determining role for the chosen coordination. The developed methodology can help to confirm the cyanide or isocyanide coordination mode when X-ray crystal data are not conclusive or to predict the configuration of a complex to be synthesized. Another application is in the field of lanthanide (III)/actinide (III) differentiation.

First author: Zhao, YF, TGMin: A global-minimum structure search program based on a constrained basin-hopping algorithm,
NANO RESEARCH, 10, 3407, (2017)
Abstract: In this article, we introduce Tsinghua Global Minimum (TGMin) as a new program for the global minimum searching of geometric structures of gas-phase or surface-supported atomic clusters, and the constrained basin-hopping (BH) algorithm implemented in this program. To improve the efficiency of the BH algorithm, several types of constraints are introduced to reduce the vast search space, including constraints on the random displacement step size, displacement of low-coordination atoms, and geometrical structure adjustment after displacement. The ultrafast shape-recognition (USR) algorithm and its variants are implemented to identify duplicate structures during the global minimum search. In addition to the Metropolis acceptance criterion, we also implemented a morphology-based constraint that confines the global minimum search to a specific type of morphology, such as planar or non-planar structures, which offers a strict divide-and-conquer strategy for the BH algorithm. These improvements are implemented in the TGMin program, which was developed over the past decade and has been used in a number of publications. We tested our TGMin program on global minimum structural searches for a number of metal and main-group clusters including C-60, Au-20 and B-20 clusters. Over the past five years, the TGMin program has been used to determine the global minimum structures of a series of boron atomic clusters (such as [B-26](-), [B-28](-), [B-30](-), [B-35](-), [B-36](-), [B-39](-), [B-40](-), [MnB16](-), [CoB18](-), [RhB18](-), and [TaB20](-)), metal-containing clusters Li (n) (n = 3-20), Au-9(CO)(8) (+) and [Cr6O19](2-), and the oxide-supported metal catalyst Au-7/gamma-Al2O3, as well as other isolated and surface-supported atomic clusters. In this article we present the major features of TGMin program and show that it is highly efficient at searching for global-minimum structures of atomic clusters in the gas phase and on various surface supports.

First author: Zhang, LS, Theoretical studies on the switching behavior of dithienylethene-containing platinum(II) complexes,
Abstract: Stepwise ring closing processes of platinum(II) alkynyl arkynyl bridged DTEs (OO/OC/CC) were studied theoretically with density functional theory method in this work for better understanding the Pt(II) alkynyl coordination effect on the photophysical and photochemical properties of dithienylethene (DTE). It is observed that the absorption spectrum of OO complex is red-shifted compared with that of ring-opened DTE monomer because of the decreased HOMO-LUMO gap energy. The first S-0 -> S-1 absorption of OC is red shifted than that of OO and is blue shifted than that of CC complex because of the increased conjugation of the ring-closed DTE moiety. In addition, potential energy surface (PSE) studies show that the energy barrier for the ring-closing process in the ground state of Pt(II) complex is smaller than that of the isolated DTE monomer and the isomerization process is changed from endothermic to exothermic reaction. Moreover, the energy barrier for the first ring-closing process is a little larger than the second ring-closing process involved in the DTE moieties. More important, similar with that in the DTE monomers, the ring closing processes in the ionic and triplet states of Pt(II) complexes is easier than that in the neutral case.

First author: Gruden, M, Benchmarking density functional tight binding models for barrier heights and reaction energetics of organic molecules,
Abstract: Density Functional Tight Binding (DFTB) models are two to three orders of magnitude faster than ab initio and Density Functional Theory (DFT) methods and therefore are particularly attractive in applications to large molecules and condensed phase systems. To establish the applicability of DFTB models to general chemical reactions, we conduct benchmark calculations for barrier heights and reaction energetics of organic molecules using existing databases and several new ones compiled in this study. Structures for the transition states and stable species have been fully optimized at the DFTB level, making it possible to characterize the reliability of DFTB models in a more thorough fashion compared to conducting single point energy calculations as done in previous benchmark studies. The encouraging results for the diverse sets of reactions studied here suggest that DFTB models, especially the most recent third-order version (DFTB3/3OB augmented with dispersion correction), in most cases provide satisfactory description of organic chemical reactions with accuracy almost comparable to popular DFT methods with large basis sets, although larger errors are also seen for certain cases. Therefore, DFTB models can be effective for mechanistic analysis (e.g., transition state search) of large (bio)molecules, especially when coupled with single point energy calculations at higher levels of theory.

First author: Meixmer, P, J(Si,H) Coupling Constants of Activated Si-H Bonds,
Abstract: We outline in this combined experimental and theoretical NMR study that sign and magnitude of J(Si,H) coupling constants provide reliable indicators to evaluate the extent of the oxidative addition of Si-H bonds in hydrosilane complexes. In combination with experimental electron density studies and MO analyses a simple structure-property relationship emerges: positive J(Si,H) coupling constants are observed in cases where M -> L pi-back-donation (M = transition metal; L = hydrosilane ligand) dominates. The corresponding complexes are located close to the terminus of the respective oxidative addition trajectory. In contrast negative J(Si,H) values signal the predominance of significant covalent Si-H interactions and the according complexes reside at an earlier stage of the oxidative addition reaction pathway. Hence, in nonclassical hydrosilane complexes such as Cp2Ti(PMe3)(HSiMe3-nCln) (with n = 1-3) the sign of J(Si,H) changes from minus to plus with increasing number of chloro substituents n and maps the rising degree of oxidative addition. Accordingly, the sign and magnitude of J(Si,H) coupling constants can be employed to identify and characterize nonclassical hydrosilane species also in solution. These NMR studies might therefore help to reveal the salient control parameters of the Si-H bond activation process in transition-metal hydrosilane complexes which represent key intermediates for numerous metal-catalyzed Si-H bond activation processes. Furthermore, experimental high-resolution and high-pressure X-ray diffraction studies were undertaken to explore the close relationship between the topology of the electron density displayed by the eta(2)(Si-H)M units and their respective J(Si,H) couplings.

First author: Pathak, AD, First-Principles Study of Chemical Mixtures of CaCl2 and MgCl2 Hydrates for Optimized Seasonal Heat Storage,
Abstract: Chloride-based salt hydrates form a promising class of thermochemical materials (TCMs), having high storage capacity and fast kinetics. In the charging cycles of these hydrates however hydrolysis might appear along with dehydration. The HCl produced during the hydrolysis degrades and corrodes the storage system. Our GGA-DFT results show that the enthalpy charge during proton formation (an important step in hydrolysis) is much higher for CaCl2 center dot 2H(2)O (33.75 kcal/mol) than for MgCl2 center dot 2H(2)O (19.55 kcal/mol). This is a strong indicator that hydrolysis can be minimized by appropriate chemical mixing of CaCl2 and MgCl2 hydrates, which is also confirmed by recent experimental studies. GGA-DFT calculations were performed to obtain and analyze the optimized structures, charge distributions, bonding indicators and harmonic frequencies of various chemical mixtures hydrates and compared them to their elementary salts hydrates. We have further assessed the equilibrium products concentration of dehydration/hydrolysis of the chemical mixtures under a wide range of operating conditions. We observed that chemical mixing leads to an increase of the onset hydrolysis temperature with a maximum value of 79 K, thus increasing the resistance against hydrolysis with respect to the elementary salt hydrates. We also found that the chemical mixing of CaCl2 and MgCl2 hydrates widens the operating dehydration temperature range by a maximum value of 182 K (CaMg2Cl6 center dot 2H(2)O) and lowers the binding enthalpy with respect to the physical mixture by approximate to 65 kcal/mol for TCM based heat storage systems.

First author: Mahmoodinia, M, Tuning the Electronic Properties of Single-Atom Pt Catalysts by Functionalization of the Carbon Support Material,
Abstract: When using support materials in heterogeneous catalysis, a fundamental understanding of the interactions between the catalyst and the support material is of critical importance. In this work, the stability, electronic structure, and catalytic activity of single-atom Pt catalysts on oxidized carbon support materials are investigated using first-principles calculations. The results are discussed based on both frontier-orbital hybridization and on a charge-transfer scheme. It is found that the strengthening of the Pt/C interactions by the carbon support with different oxygen concentrations is more due to charge transfer than frontier-orbital hybridization. In general, the larger the concentration of oxygen containg groups (OCGs) is and the closer they are to the Pt adatom, the stronger is the Pt binding energy to the carbon support. The dependence of the CO adsorption energy and CO vibrational stretching frequency on the concentration and the proximity of the OCGs to the Pt adatoms enables us to gauge quantitatively the effects of surface functionalization on the stability and catalytic activity of Pt catalysts. The change in the chemisorption energy of the CO molecule to the Pt adatom is discussed based on the position of the Pt d-band center, where it is found that it is shifted toward lower energy by increasing the concentration of OCGs. This downshift suppresses the coupling between the Pt d-band and the CO 2 pi* state, and consequently both the catalytic activity and the CO adsorption energy are reduced. Our results suggest that tailoring the carbon support by oxygen-containing groups could provide a route for improving the tolerance of Pt/C catalysts to CO poisoning.

First author: Gozzi, M, Antiproliferative activity of (eta(6)-arene)-ruthenacarborane sandwich complexes against HCT116 and MCF7 cell lines,
DALTON TRANSACTIONS, 46, 12067, (2017)
Abstract: Three [(eta(6)-arene) RuC2B9H11] complexes (arene = p-cymene (2), biphenyl (3) and 1-Me-4-COOEt-C6H4 (4)) were synthesised according to modified literature procedures and fully characterised. 2-4 were found to be moderately active against two types of tumour cell lines (HCT116 and MCF7), with IC50 values in the low micromolar range. However, viability of normal, healthy cells (MRC-5 cell line, MLEC and mouse macrophages) was not affected by treatment with 2-4, indicating high selectivity of the metallacarborane complexes towards tumour cell lines, compared to the unselective antitumour agent cisplatin and other potential Ru-II drugs. Moreover, flow cytometric analysis suggested that 4 induces cell death via a caspase-dependent apoptotic mechanism. DFT calculations of the frontier molecular orbitals showed that the HOMO-LUMO gap in 2-4 is smaller than in the corresponding cyclopentadienyl complexes 2-Cp-4-Cp (e.g. 5.47 (2) vs. 6.31 eV (2-Cp)). In order to assess the stability of 2-4, particularly the ruthenium-dicarbollide bond, energy decomposition analysis (EDA) of 2-4, together with the respective cyclopentadienyl analogues 2-Cp-4-Cp, was performed. EDA suggests that the ruthenium(II)-dicarbollide bond in the three complexes is mostly ionic and far stronger than the ruthenium(II)-arene bond.

First author: Pan, S, Endohedral gas adsorption by cucurbit[7] uril: a theoretical study,
Abstract: The selectivity of cucurbit[7] uril (CB[7]) towards adsorbing a series of 14 molecules encompassing four hydrocarbons (C2H2, C2H4, C2H6, and CH4), diatomic molecules of halogens (F-2 and Cl-2), nitrogen oxides (NO2 and NO), carbon oxides (CO2 and CO), SO2, H2S, N-2, and H-2 is explored via a density functional theory based study. CB[7] is noted to have high selectivity towards adsorbing SO2 over the other considered molecules, highlighting its probable utility to separate SO2 fromflue gas or other gas mixtures containing these molecules. The nature of bonding is deciphered via the computations of non-covalent interaction indices and energy decomposition analysis. Although in all cases the dispersion interaction turns out to be the most dominating contributor in stabilizing these complexes, the electrostatic contribution is also considerable. In fact, the combined effect of these two energy terms in SO2@CB[7] is responsible for the obtained selectivity.

First author: Ortolan, AO, How the electron-deficient cavity of heterocalixarenes recognizes anions: insights from computation,
Abstract: We have quantum chemically analyzed the bonding mechanism behind the affinity of various heterocalixarenes for anions with a range of geometries and net charges, using modern dispersioncorrected density functional theory (DFT-D3BJ). The purpose is to better understand the physical factors that are responsible for the computed affinities and thus to develop principles for a more rational design of anion receptors. Our model systems comprise heterocalixarenes 1-4 as hosts, which are characterized by different bridging heteroatoms (O, N, S) as well as the anionic guests Cl-, Br-, I-, BF4-, CH3 CO2-, H2PO4-, HSO4-, NCS-, NO3-, PF6-, and SO42-. We use various analysis schemes (EDA, NCI, and NBO) to elucidate the interactions between the calixarene cavity and the anions to probe the importance of the different bonding modes (anion-pi, lone-pair electron-pi, s-complexes, hydrogen bonds, and others) of the interactions. Electrostatic interactions appear to be dominant for heterocalixarenes with oxygen bridges whereas orbital interactions prevail in the case of nitrogen and sulfur bridges. Dispersion interactions are however in all cases non-negligible.

First author: Sokolov, MN, Complexes of {W6I8}(4+) Clusters with Carboxylates: Preparation, Electrochemistry, and Luminescence,
Abstract: The reactions between (Bu4N)(2)[{W6I8}I-6] (1) and silver carboxylates RCOOAg in CH2Cl2 afforded new luminescent carboxylate complexes (Bu4N)(2)[{W6I8}(RCOO)(6)] [R = CH3 (2), C6H5 (3), C2F5 (4), C3F7 (5), C6F5 (6)]. The complexes were characterized by single-crystal X-ray diffraction, elemental analysis, cyclic voltammetry, and IR and NMR spectroscopy. Complexes 1-6 all exhibit intense and long-lived photoluminescence. The carboxylate complexes undergo reversible electrochemical oxidation in two consecutive one-electron steps.

First author: Zhang, YH, Charge-transfer mobility and electrical conductivity of PANI as conjugated organic semiconductors,
Abstract: The intramolecular charge transfer properties of a phenyl-end-capped aniline tetramer (ANIH) and a chloro-substituted derivative (ANICl) as organic semiconductors were theoretically studied through the first-principles calculation based on the Marcus-Hush theory. The reorganization energies, intermolecular electronic couplings, angular resolution anisotropic mobilities, and density of states of the two crystals were evaluated. The calculated results demonstrate that both ANIH and ANICl crystals show the higher electron transfer mobilities than the hole-transfer mobilities, which means that the two crystals should prefer to function as n-type organic semiconductors. Furthermore, the angle dependence mobilities of the two crystals show remarkable anisotropic character. The maximum mobility mu(max) of ANIH and ANICl crystals is 1.3893 and 0.0272 cm(2) V-1 s(-1), which appear at the orientation angles near 176 degrees/356 degrees and 119 degrees/299 degrees of a conducting channel on the a-b reference plane. It is synthetically evaluated that the ANIH crystal possesses relatively lower reorganization energy, higher electronic coupling, and electron transfer mobility, which means that the ANIH crystal may be the more ideal candidate as a high performance n-type organic semiconductor material. The systematic theoretical studies on organic crystals should be conducive to evaluating the charge-transport properties and designing higher performance organic semiconductor materials. Published by AIP Publishing.

First author: Martinez, JP, Effects of Dispersion Forces on Structure and Photoinduced Charge Separation in Organic Photovoltaics,
Abstract: We present a theoretical study on the role of van der Waals (vdW) interactions on the structure and, as a consequence, the photoinduced charge separation (CS) of a series of dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. CS rate constants for P3HT/PCBM dimer structures in which vdW interactions are taken into account agree well with experimental data. Without proper treatment of vdW interactions during geometry optimizations, the predicted CS rates can be too low by up to 3 orders of magnitude. These variations in computed CS rates are not due to changes in the Gibbs energy for CS. Instead, the electronic coupling increases by up to 2 orders of magnitude for structures obtained with dispersion-corrected density functionals that lead to deformations in the P3HT oligomer with pronounced pi-pi stacking interactions with PCBM.

First author: Tsunoyama, H, Development of Integrated Dry-Wet Synthesis Method for Metal Encapsulating Silicon Cage Superatoms of M@Si-16 (M = Ti and Ta),
Abstract: Nanoclusters (NCs) of several to hundreds of atoms in size are prospective functional units for future nanomaterials originating in their unique, size-specific properties. To explore the field of NC-based materials science, the development of large-scale, size-exclusive synthesis methods is in high demand, as one can see from the successful evolution of fullerene science. We have developed a large-scale synthesis method for main group-based NC compounds by scaling up the clean dry-process with a high-power impulse magnetron sputtering. The 100 mg scale synthesis of binary NCs of M@Si-16 (M = Ti and Ta) stabilized by poly(ethylene glycol) dimethyl ether enables us to characterize their structures by an array of methods, for example, mass spectroscopy, X-ray photoemission spectroscopy, Raman spectroscopy, and Si-29 nuclear magnetic resonance. Spectroscopic evidence indicates that the M@Si-16 NCs are the metal-encapsulating tetrahedral silicon-cage structure satisfying the 68 electrons, closed-electronic-shell superatom.

First author: Procopio, EQ, A family of solution-processable macrocyclic and open-chain oligothiophenes with atropoisomeric scaffolds: structural and electronic features for potential energy applications,
NEW JOURNAL OF CHEMISTRY, 41, 10009, (2017)
Abstract: FeCl3 oxidation of the racemate of C-2 symmetric, inherently chiral, sexithiophene monomer 1 (2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene) affords a mixture of cyclic oligomers, from the prevailing dimer to traces of the pentamer. The oligomers are constituted by mixtures of stereoisomers which are two for dimer 2, four for trimer 3 and six for tetramer 4. Cyclooligomers 2 and 3 could be separated by chromatography, while 4 was synthesized by ring closure of open chain dimer 2a, prepared in turn by controlled coupling of the anion of racemic 1. The optical properties of open-chain stereoisomer 2a and tetramer 4 have been compared with those of 2 and 3 respectively. The macrocyclic oligomers have been tested as donor materials in bulk heterojunction solar cell prototypes both as a crude mixture resulting from oxidation of 1 and as a single oligomer. Theoretical calculations support the photophysical properties of these new materials.

First author: Shi, YT, A theoretical study on the electronic properties of two ring-fused derivatives of 9,10-diphenylanthracene,
NEW JOURNAL OF CHEMISTRY, 41, 10251, (2017)
Abstract: Two new contorted polycyclic aromatic hydrocarbons (PAHs) 1 and 2 have been synthesized by Perepichka and coworkers (Org. Lett., 2015, 17, 4224). In this work, we aim to clarify the effect of packings of the isomers on the charge-transfer mobility of PAHs by quantum chemistry calculations combined with the Marcus-Hush electron transfer theory. The isomers reveal dissimilar properties with PAH2 having a much smaller energy gap than PAH1. Significantly, the maximum hole mobility of PAH2 is nearly 3.5 times larger than that of PAH1, while the adiabatic ionization potential (IP) value of PAH2 is smaller than that of PAH1. In the solid state, PAH2 packs in a unique two-dimensional herringbone motif with high intrinsic hole mobility and suitable adiabatic ionization potential (IP) values making it a good p-type material.

First author: Jin, X, The structural landscape in 14-vertex clusters of silicon, M@Si-14: when two bonding paradigms collide,
DALTON TRANSACTIONS, 46, 11636, (2017)
Abstract: The structural chemistry of the title clusters has been the source of controversy in the computational literature because the identity of the most stable structure appears to be pathologically dependent on the chosen theoretical model. The candidate structures include a D-3h-symmetric ‘fullerene-like’ isomer with 3-connected vertices (A), an ‘arachno’ architecture (B) and an octahedral isomer with high vertex connectivities typical of ‘closo’ electron-deficient clusters (C). The key to understanding these apparently very different structures is the fact that they make use of the limited electron density available from the endo-hedral metal in very different ways. Early in the transition series the favoured structure is the one that maximises transfer of electron density from the electropositive metal to the cage whereas for later metals it is the one that minimises repulsions with the increasingly core-like d electrons. The varying role of the d electrons across the transition series leads directly to strong functional dependency, and hence to the controversy in the literature.

First author: Gaggioli, CA, The ligand effect on the oxidative addition of dioxygen to gold(I)-hydride complexes,
DALTON TRANSACTIONS, 46, 11679, (2017)
Abstract: The ligand effect on the recently uncovered feasible oxidative addition reaction of O-2 on [LAuH] complexes has been investigated for a series of fifteen ligands. The activation barriers of this spin-forbidden reaction have been estimated at the minimum energy crossing points (MECP, relativistic scalar level) between the adiabatic triplet (reactants spin state) and singlet (product spin state) potential energy surfaces (PES) and calculated at the transition states by including Spin-Orbit Coupling (SOC) effects, as applied for the mechanistic study of this reaction in a previous study by us [Chem. Sci., 2016, 7, 7034-7039]. We find a sizeable effect of the ligand on the activation barriers, and some of the stronger electron donating phosphines are predicted to induce the highest catalyst efficiency. The inclusion of SOC effects lowers the activation barriers by about 3 kcal mol(-1) systematically with respect to the MECP values independently of the ligand type. We used the Charge-Displacement (CD) analysis to quantify the net electron charge donation from the ligand L towards the metallic fragment AuH in the [LAuH] series, and surprisingly only a poor correlation was found between the net electron donor character of L and the activation barriers. Application of the CD-NOCV (Natural Orbitals for Chemical Valence) approach, which allows the quantification of the Dewar-Chatt-Duncanson (DCD) L-AuH bond components, suggests that the ligand effect on the activation barriers is not easily predictable on the basis of solely the electronic properties of the ligand and depends significantly on the ligand nature or carbene or phosphine type. We show that for both phosphine and carbene ligand subsets, however, the sigma donation component of the L-AuH bond quantitatively accounts for the ligand effect on the activation energy barriers (a larger sigma-donor capability of L correlates with a smaller activation barrier), whereas the pi back-donation, strongly affected by geometrical rearrangement, is a poor reactivity descriptor (pi acceptor properties of the ligand L in the linear [LAuH] complexes are not transferable to the trigonal [LAuH(O-2)] transition state structures).

First author: Singh, SK, Key role of higher order symmetry and electrostatic ligand field design in the magnetic relaxation of low-coordinate Er(III) complexes,
DALTON TRANSACTIONS, 46, 11913, (2017)
Abstract: The conceptual framework of electrostatic ligand field modulation based on oblate/prolate type electron density of lanthanide ions is one of the most successful approaches to enhance barrier height in lanth-anide- based single-ion magnets. Recently, a tetra coordinated [Er{N(SiMe3)(2)}s(3)Cl]. 2THF (1) complex with an unfavourable ligand field showed slow relaxation of magnetization in zero field and challenges the concept of electrostatic ligand field modulation. To unravel the magnetic relaxation in this complex, we carried out a detailed theoretical investigation on three Er(III) complexes belonging to the same family of single-ion magnets. The CASSCF/PT2 + RASSI-SO approach highlights that the concept of electrostatic ligand field modulation based on oblate/prolate type is still valid in these complexes, and the relaxation dynamics observed can be rationalized by accounting for both the symmetry and geometrical distortions around the Er(III) ion. Using ab initio computed blockade barriers and crystal field analysis, we analysed the key components of the magnetic relaxation. Our study suggests that in these structures, the Er(III) ion shifted out of the triangular plane formed by the three nitrogen donor atoms and this out-of-plane shift (tau) significantly influences the slow-relaxation of magnetization. In order to gain deeper insights into the nature of metal-ligand bonding, and to predict quantitatively the strength of the axial and equatorial ligand field, ELF, QTAIM, and EDA analysis were carried out in these complexes. Our findings highlight that the molecules possessing large barrier height for magnetic relaxation are due to the combined effect of a favourable ligand field and the symmetry around the Er(III) ion. To understand the intricate role of both effects, several robust magneto-structural correlations were developed. Besides, the lanthanide-halogen covalency was also found to play a vital role in controlling the magnetic anisotropy and thus the magnetic relaxation. A near linear trend was observed between the calculated barrier height and the increase in the Er-X covalency as we move from -F to -I. This offers a de novo approach to increase barrier height in mononuclear lanthanide based complexes.

First author: Hu, WX, Influence of pi-bridge conjugation on the electrochemical properties within hole transporting materials for perovskite solar cells,
NANOSCALE, 9, 12916, (2017)
Abstract: Hole transporting materials (HTMs) play an important role in most efficient perovskite solar cells (PSCs). In particular, donor-pi-bridge-donor type oligomers (D-pi-D) have been explored extensively as alternative and economical HTMs. In the present work, a series of triphenylamine-based derivatives as alternatives to the expensive Spiro-OMeTAD were explored by using first-principles calculations combined with the Marcus theory. The electronic structures, optical properties and hole mobilities of all the molecules were investigated to reveal the relationship between their charge-transport properties and the pi-bridge conjugation. The HOMO levels decrease with the extension of the pi-bridge conjugation length, which may lead to higher open-circuit voltages. Moreover, we employed a quantum mechanical (QM) methodology to estimate the carrier mobility for organic crystals. Specifically, an orientation function mu(Phi) (V, lambda, r, theta, gamma; Phi) is first applied to quantitatively evaluate the overall carrier mobility of HTMs in PSCs. The theoretically calculated results validate that this model predicts the hole mobility of HTMs correctly. More importantly, it is revealed that enhancing the pi-bridge conjugation in HTMs can improve the hole mobility, which will definitely improve the performance of PSCs. We hope that our theoretical investigation will offer a reliable calculation method to estimate the charge-transport properties of novel HTMs applied in perovskite solar cells.

First author: Zhai, SC, First principle study of electronic structures and optical absorption properties of O and S doped graphite phase carbon nitride (g-C3N4)(6) quantum dots,
ACTA PHYSICA SINICA, 66, 12916, (2017)
Abstract: Graphite phase carbon nitride (g-C3N4) quantum dots have received much attention due to its good stability, water solubility, biological compatibility, non-toxicity as well as strong fluorescence characteristics. In order to enhance the light absorption and improve photocatalytic activities of the g-C3N4 quantum dots, theoretical studies are carried out on the O and S atoms doped (g-C3N4)(6) quantum dots. First-principles calculations based on the density functional theory and time dependent density functional theory are performed to investigate the geometries, electronic structures and ultraviolet visible absorption spectra of O and S atoms doped (g-C3N4)(6) quantum dots. The results show that the highest electron occupied molecular orbital-the lowest electron unoccupied molecular orbital (HOMO-LUMO) energy gap of doped (g-C3N4)(6) quantum dots is significantly reduced though the C-N bond lengths closely related to the impurities only change slightly. The calculated formation energies indicate that the O-doped (g-C3N4)(6) quantum dots are more stable, and the O atom tends to substitute for N atom at the N3-site, while the S atoms prefer to substitute for N atom at the N8-site. The simulated spectra indicate that the doping of O and S in (g-C3N4)(6) could improve the light absorption. Not only the absorption peaks are extended from the UV to the infrared region (e.g. 200-1600 nm), but also the corresponding absorption intensities are enhanced significantly by doping the O or S atoms with the appropriate concentration. The increase of proper impurity concentration will lead to a pronounced red shift in light absorption. The effect of doping site on the optical absorption property of (g-C3N4)(6) quantum dots shows that the absorption intensity is mainly affected in the visible range, however, besides the influence on the absorption intensity, the light absorptions of some structures are also affected beyond 800 nm. Overall, the O atoms and S atoms have a substantially similar effect on the light absorption of the (g-C3N4)(6) quantum dots, while the effects of these impurity atoms are different in the long wavelength region. Oxygen doping is better than sulfur doping in the absorption of (g-C3N4)(6) quantum dots by comparing the doping of O and S. These first-principles studies give us a method to effectively improve the light absorption of g-C3N4 quantum dots, and could provide a theoretical reference for tuning its electronic optical properties and applications.

First author: Hayashi, S, Relativistic Effect on (1)J(M,C) in Me4M, Me3M-, Ph4M, and Ph3M- (M=Pb, Sn, Ge, Si, and/or C): Role of s-Type Lone Pair Orbitals in the Distinct Effect for the Anionic Species,
CHEMPHYSCHEM, 18, 2466, (2017)
Abstract: Indirect one-bond nuclear spin-spin couplings between M and C [(1)J(M,C)] in Me4M, Me3M-, Ph4M, and Ph3M- (M=Pb, Sn, Ge, Si, C) are analyzed with consideration of the relativistic effect and by employing Slater-type basis sets. The evaluated total values (1)J(TL)(M,C) reproduced the observed values with some systematic calculation errors. Fermi contact terms (1)J(FC)(M,C) contribute predominantly to (1)J(TL)(M,C) (approximate to 99%). A distinct relativistic effect on (1)J(Pb,C) is predicted for Me3Pb- and Ph3Pb-. The mechanisms for the distinct effect are elucidated by using the comparison between Me3Pb- and Me4Pb as an example. The contributions to (1)J(FC)(M,C) [or (1)J(SD+FC)(M,C), where SD denotes the spin-dipolar term] are decomposed into those of occupied orbitals and occupied-to-unoccupied transitions. The s-type lone-pair orbitals are demonstrated to contribute to the distinct relativistic effect on (1)J(Pb,C) of Me3Pb- (and Ph3Pb-). The results are in sharp contrast to the cases of (1)J(M,C) for M atoms lighter than Pb, such as Si, and are explained by the s character of the M-C bonds. This treatment enables visualization and clear recognition the origin of the nuclear couplings for the species exhibiting a relativistic effect.

First author: Padial, JS, Stabilization of 2,6-Diarylanilinum Cation by Through-Space Cation-pi Interactions,
Abstract: Energetically favorable cation-pi interactions play important roles in numerous molecular recognition processes in chemistry and biology. Herein, we present synergistic experimental and computational physical organic chemistry studies on 2,6-diarylanilines that contain flanking meta/parasubstituted aromatic rings adjacent to the central anilinium ion. A combination of measurements of pK(a) values, structural analyses of 2,6-diarylanilinium cations, and quantum chemical analyses based on the quantitative molecular orbital theory and a canonical energy decomposition analysis (EDA) scheme reveal that through-space cation-pi interactions essentially contribute to observed trends in proton affinities and pK(a) values of 2,6-diarylanilines.

First author: Baranac-Stojanovic, M, 4-Electron B-N Monocycles: Stability and (Anti)aromaticity,
Abstract: This is a theoretical (DFT) study of the impact of electronic structural changes, induced by B-N/C-C isosterism, on two basic properties of 4-electron antiaromatic system, that is, stability and antiaromaticity. The main driving force for the nonplanarity of B2N2 rings is electrostatic energy, and that for a ring with one B-N unit is the relief of Pauli repulsion. The charge-separation instability, inherent for a 1,3-B,N relationship, turns the ground state of the BCNC system to an aromatic triplet, which is less stable than the isomeric BNCC system, mostly because of larger Pauli interactions. The alternating BNBN connectivity is favoured primarily by orbital interaction energy and, secondarily, by better electrostatic attraction. The C-C B-N substitution weakens the antiaromatic character, except that for a 1,3-B,N relationship, which results in increased antiaromaticity in the closed-shell state relative to that of cyclobutadiene.q

First author: Manzetti, S, Quantum chemical study of regular and irregular geometries of MgO nanoclusters: Effects on magnetizability, electronic properties and physical characteristics,
Abstract: Advanced materials and surfaces are key components in nanotechnology and are applied by their magnetizable and spintronic properties, high-frequency scattering, and properties attributing to nano electronics and nanomagnetic components. Earth oxides are a group of materials with catalytic effects in nanocrystalline forms, and strong magnetic field effects with promising applications in nanomagnetics as well as potential key parts in memory processing units. Their electronic properties in nanocrystalline forms are however not fully understood, and as nanocrystal species behave differently from bulk material, the electronic properties of a set of MgO clusters in small, large, regular and irregular geometries and forms are here studied using the B3LYP and M06-2X levels of quantum theory. The analysis show that particularly the thin sheet MgO clusters exert high diamagnetic properties. Furthermore, vacancies of MgO induce interesting effects at the orbital gap-level and on the electronic populations of the clusters. A NBO analysis shows furthermore that the electronic population in irregular clusters missing MgO units, is quite different from regular structures which highlights that material deficiencies may induce different chemical reactivities and physical effects. The results supplied here show that computational quantum mechanical approaches are of significant value for studying and engineering nano particles and nanoclusters, with particular relevance to the emerging methods of nanoscaling by nanophotonic processes, for synthesis and industrial application of nanoparticle MgO in nanoelectronics.

First author: Diaz, S, ETS-NOCV Decomposition of the Reaction Force: The HCN/CNH Isomerization Reaction Assisted by Water,
Abstract: The partitioning of the reaction force based on the extendedtransition- state natural orbital for chemical valence (ETS-NOCV) scheme has been proposed. This approach, together with the analysis of reaction electronic flux (REF), has been applied in a description of the changes in the electronic structure along the IRC pathway for the HCN/CNH isomerization reaction assisted by water. Two complementary ways of partitioning the system into molecular fragments have been considered (“reactant perspective” and ” product perspective”). The results show that the ETS-NOCV picture is fully consistent with REF and bondorder changes. In addition, proposed ETS-NOCV decomposition of the reaction force allows for the quantitative assessment of the influence of the observed bond-breaking and bondformation processes, providing detailed information about the reaction-driving and reaction-retarding force components within the assumed partitioning scheme.

First author: Conradie, MM, Rhodium-rhodium interactions in [Rh(beta-diketonato)(CO)(2)] complexes,
Abstract: The solid state single crystal structures of [Rh((3-diketonato)(CO)(2)], where beta-diketonato = (R1COCHCOR2)(-), with R-1, R-2 = CF3, C4H3S (1), C4H3S, C4H3S (2), Ph, C4H3S (3) and CF3, Ph (4), show that these compleXes in some cases form dinuclear units, which stack in chains with weak metallophilic rhodium-rhodium interactions, while in other cases they produce continuous polymeric units, with equal intermolecular Rh. Rh distances. Different solid state structural data is reported herein for these four complexes, including a low temperature comparison with ambient data for (4). In the latter case, weak intermolecular halogen bonding has also been identified, which additionally contributes to the stability of (4) in the solid state. Computational evaluation of the frontier molecular orbitals of both dinuclear and tetranuclear models of complexes (1) (4), show Rh(d(z)(2))-Rh(d(z)(2)) a bonding and sigma* anti bonding orbitals. An NBO analysis of the dinuclear units, revealed a donor -acceptor interaction between the two rhodium atoms in such a unit, while a QTAIM study identified a bonding path between the two rhodium atoms therein.

First author: Lam, E, Role of Coordination Number, Geometry, and Local Disorder on Al-27 NMR Chemical Shifts and Quadrupolar Coupling Constants: Case Study with Aluminosilicates,
Abstract: Al-27 solid-state NMR is a powerful tool for elucidating local geometries at Al sites in molecular and solid-state systems because they are typically associated with specific NMR signatures, namely, isotropic chemical shift (delta(iso)) and quadrupolar coupling constant (CQ). Assignment is however mostly empirical; hence, obtaining a detailed understanding of the origins of the NMR parameters would be a valuable step toward a structure property/reactivity relationship. Here, we investigate the origin of the Al-27 NMR signatures in aluminosilicates using DFT calculations on cluster models complemented by natural chemical shift (NCS) analysis. In particular, NCS analysis shows that the chemical shift of Al is mostly associated with the coupling Al-O a and sigma* orbitals for sigma(11) leading to deshielding as the coordination number of Al decreases, allowing the distinction between tri-, tetra-, penta-, and hexacoordinated sites. In contrast, C-Q can take a broad range of values (between 8.0 and 23.6 MHz) independently of the coordination number because it is greatly affected by slight variation of the bond distance of siloxane bonds coordinated to aluminum, which perturbs the electrostatic interaction with aluminum and thereby the C-Q.

First author: Gattuso, H, Deciphering the photosensitization mechanisms of hypericin towards biological membranes,
Abstract: Resorting to state-of-the art molecular modeling and simulation techniques we provide full characterization of the photophysical properties of the naturally occurring hypericin chromophore, currently used in photodynamic therapy. In particular, we reveal the different photophysical pathways leading to intersystem-crossing and hence, triplet manifold population that is necessary for the subsequent production of singlet oxygen. In particular we identify an extended region of quasi-degeneracy between the first singlet excited state and three triplet state surfaces. This energetic factor allows the occurrence of intersystem-crossing even in the presence of a relatively small spin-orbit coupling. Furthermore, thanks to extended all-atom molecular dynamics simulations we provide insight into the interaction of hypericin with lipid bilayers. We demonstrate the formation of stable interactions with the membrane and, in particular, the penetration of hypericin into its hydrophobic core. This organization allows a spatial overlap between hypericin and the lipid oxidizable double bond pointing towards the production of singlet oxygen in close spatial proximity to its reactant, hence favoring photosensitization.

First author: Gryn’ova, G, Guidelines and diagnostics for charge carrier tuning in thiophene-based wires,
Abstract: Reported experimental trends in charge carrier tuning in single molecule junctions of oligothiophene-based wires are rationalized by means of frontier molecular orbital theory. The length and substituent effects on the energy levels of the frontier orbitals have been shown to translate to the computed transmission spectra – with a caveat of the role of the linker group. The resulting transport (charge carrier) type – n- (electrons) or p- (holes) – is easily identifiable from the in silico charge transfer trends.

First author: Chakraborty, D, Change in optoelectronic properties of ExBox(+4) on functionalization and guest encapsulation,
Abstract: The impact of functionalization as well as guest encapsulation on the optoelectronic properties of the ExBox+ 4 moiety has been investigated with the aid of density functional theory (DFT) based calculations. To this end, three functionalized variants of the ExBox+ 4 moiety have been modelled in silico, viz. NH2-ExBox(+4)-F, CN-ExBox(+4)-NH2 and NO2-ExBox(+4)-NH2, whereas coronene (Cor), B-doped coronene (BCor), N-doped coronene (NCor), tetrathiafulvalene (TTF), biphenyl (BiPh), tetracyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ) molecules have been employed as guests. The results indicate that as a result of functionalization, the ExBox(+4) moiety can exhibit tangible non-linear optical (NLO) response properties as vindicated by the first static hyperpolarizability (beta). As a result of guest encapsulation, significant variation in the optoelectronic properties of the chosen hosts takes place. BCor/TCNQ/NCor molecules enhance the NLO activity of the hosts while TTF/TCNE suppresses the same. In particular, NCor@ host moieties demonstrate very high beta values at the static field limit. Time dependent DFT results suggest that in general, the ability of the guest in tuning the transition energy associated with the pivotal electronic transitions of the host plays the dominant role in the observed variation in beta. In addition, BCor/NCor@ host moieties demonstrate broadband optical absorption capability thereby elucidating the possibility of deriving multi-purpose optoelectronic features such as NLO activity as well as utility in photovoltaic systems. Thermochemical results suggest that all the guest@ host systems are stable at 298.15 K. Non-covalent and electrostatic binding forces stabilize the studied systems.

First author: Shen, W, Theoretical study of the substituent effect controlling the radiative and non-radiative decay processes of platinum(II) complexes,
Abstract: Six platinum complexes bearing different electron-withdrawing groups (-CN, -NO2, -o-carborane, -SF5 and -CF2CF2CF3) have been designed to explore the electron-withdrawing capability and the conjugative effect of the substituents, and density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been performed to determine their electronic structures and phosphorescent properties. Three factors, including the oscillator strength mu(S-n) for S-0-S-n excitations, the energy gap between the triplet and singlet states DE(Sn-T1) and the spin-orbital coupling < T-1|(H) over cap (SOC)| S-n >, have been calculated to analyze the radiative processes. In addition, temperature-independent, temperature-dependent and triplet-triplet annihilation (TTA) have been analyzed to determine the non-radiative decay processes. Introducing strong electron-withdrawing groups into phosphorescent transition-metal complexes has a significant impact on the phosphorescent properties and some regularity besides the inductive effect (the electron-withdrawing capability) and the conjugative effect of the substituents. The stronger electron-withdrawing capability and smaller conjugative effect can give rise to blue-shifted emission behavior and give larger radiative decay rate constants. The results demonstrate that complex 4 (-NO2 substituted) and complex 2 (-o-carborane) are possible candidates for blue-emitting materials.

First author: Wei, W, Theoretical Investigation on the Interactions of Isoamethyrins and AnO(2)(+/2+) (An=U, Pu),
CHEMISTRYSELECT, 2, 8008, (2017)
Abstract: By using density functional theory, this article selected isoamethyrin and its derivatives as ligands to study interactions between ligandsand uranyl, as well as plutonyl. The result shows that isoamethyrin has a strong affinity to uranyl than to plutonyl, which is derived from the bond formation between the f orbitals in two metal atoms and the ligands. Pu atom provides the less number of f orbitals but the more number of p orbitals than U atom, which leads to the weak interaction between Pu atom and the ligands. The calculation of TBE (Bonding Energy Total) shows that the isoamethyrin ligands have large deformation after coordination.

First author: Couzijn, EPA, Intuitive Quantifiers of Charge Flows in Coordinate Bonding,
ORGANOMETALLICS, 36, 3205, (2017)
Abstract: ETS-NOCV charge and bond energy analyses have been carried out for a broad range of transition-metal carbonyl complexes L-[M], comprising different ligand classes, transition metals, and coordination geometries. The resulting electronic redistributions are visually assigned to sigma donation, pi backbonding, and related interactions. We propose a Hirshfeld partitioning of these electronic redistributions to afford the corresponding charge flow contributions Delta(go), Delta(g pi), etc. Taken together, a detailed picture of the dative bonding arises, in terms of both energetics and the extent of sigma-electron donation and pi-rcelectron backbonding. The charge flows Delta(q sigma), and Delta(q pi); appropriately quantify trends in the ligand sigma-donor and pi-acceptor abilities and are transferable across the transition-metal complexes studied and thus promise to be suitable descriptors for ligand knowledge bases. As a case in point, the TEP is well reproduced: by the calculated nu(CO)(A(1)) frequencies and is 3 times more strongly affected by Delta(q sigma), than by Delta(q pi), with an additional modest steric influence. Further, empirical relationships are derived among the charge flows Delta(g pi) and Agit, the (L)W(CO)5 carbonyl stretching frequencies, and the ligand’s steric volume %V-bur which allow estimating the a-donor and pi-acceptor abilities of phosphines from experimental observables. On the other hand, direct Cl: -> L-sigma* interactions are identified in several cis-(L)Ir(CO)(2)Cl complexes, which compromises the use of these species as experimental probes for ligand parameters.

First author: Tuscher, L, Synthesis, Structure, and Reactivity of Ga-Substituted Distibenes and Sb-Analogues of Bicyclo[1.1.0]butane,
Abstract: Monovalent gallanediyl LGa {L= HC[C(Me) N(2,6-iPr(2)C(6)H(3))](2)} reacts with SbX3 to form the Ga-substituted distibenes [(LGaX)(2)Sb-2] (X= NMeEt 1, Cl 2). Upon heating, 2 reacts to the bicyclo[1.1.0]butane analogue [(LGaCl)(2)(mu,eta(1:1)-Sb-4)](3) containing a [Sb-4](2-) dianion. Moreover, 2 reacts with Li amides LiNR2 in salt elimination reactions that form the corresponding amido-substituted compounds 1 and [(LGaN-Me-2)(2)Sb-2] 4, whereas reactions of 4 and [(LGaNMe2)(2)(mu,eta(1:1)-Sb-4)] 5 with two equivalents of GaCl3 resulted in the formation of 2 and 3, respectively. 1, 2 and 3 were characterized by H-1 and C-13 NMR spectroscopy, elemental analysis, and single crystal X-ray diffraction. In addition, their bonding situation was analyzed by quantum chemical calculations.

First author: Ciborska, A, Silver complexes stabilized by large silanethiolate ligands – crystal structures and luminescence properties,
DALTON TRANSACTIONS, 46, 11097, (2017)
Abstract: Bulky silanethiolate and disiladithiolate ligands were applied to synthesize one mononuclear and three tri-nuclear silver complexes including two cyclic “microclusters” and a linear tri-nuclear silanethiolate complex. All obtained compounds are characterized by X-ray diffraction and FT-IR. NMR and emission spectroscopies were used where possible. The first trinuclear anionic silver thiolate is structurally characterized. The influence of the different charge of cyclic silver complexes as well as the overall ligand environment on the structural properties is demonstrated. The impact of the different synthetic routes on the final structures of the obtained clusters – cyclic or linear – is discussed.

First author: Karimova, NV, Optical Properties of Small Gold Clusters Au8L82+ (L = PH3, PPh3): Magnetic Circular Dichroism Spectra,
Abstract: A theoretical study of the optical and electronic properties of small phosphine-protected centered gold clusters with gold core symmetry C-3v was performed using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. It is well-known that magnetic circular dichroism (MCD) spectroscopy yields more detailed information about electronic structure and optical properties with respect to optical absorption spectroscopy. In this work, we combine electronic absorption and MCD spectroscopy for gold nanoclusters to gain a better understanding of their electronic states. These results can be used to help with interpretation of the experimentally measured MCD spectra, which is a very complicated process, especially for low-symmetry systems. In the present paper, absorption and MCD spectra were calculated for ligand-protected gold clusters Au-8(PPh3)(8)(2+) and Au-8(PH3)(8)(2+), in addition to bare Au-8(2+). The influence of the nature of the ligands on the optical properties of gold cluster was investigated. Geometrical changes and changes in optical properties that occur in the Au-8 gold core during the ligation process were also determined. A comparative analysis of the obtained theoretical and experimental results was performed. The results show that the theoretically simulated optical absorption and MCD spectra for Au-8(PPh3)(8)(2+) exhibit a very good agreement with empirical spectra for [Au-8(PPh3)(8)](NO3)(2) in acetonitrile.

First author: Soleymani, E, Enantioseparation performance of CNTs as chiral selectors for the separation of ibuprofen isomers: a dispersion corrected DFT study,
Abstract: The enantioseparation of chiral drugs has been of great interest in the modern pharmaceutical industry since the majority of bioorganic compounds are chiral. In this work, we have investigated the ability of pristine and defected (10, 5) chiral carbon nanotubes (CNTs) in enantioseparation of chiral R-IS-ibuprofen isomers. The interactions between the two enantiomers of ibuprofen and the outer surface and inner side wall of the chiral CNTs have been evaluated. We utilized dispersion-corrected density functional theory (DFT) calculations within the framework of the GGA-PBE scheme for the systems under study. The results indicated that the inner side walls of the defected (10, 5) CNTs exhibited the highest energy difference (Delta U-0) between the pairs of considered enantiomers with the energy difference of about 1.4 kcal mol(-1), indicating that these nanotubes are a promising candidate in enantioseparation processes. The effect of solvation has also been considered in the calculations and it was found that changing the dielectric properties of the medium cannot affect the overall interactions between the drug and CNT. The electronic properties of the considered systems did not change upon the interaction between the incorporated molecules and the type of interaction was found to be dispersion-governed physisorption.

First author: Grabowski, SJ, H+ Hydrogen Bonds and Their Lithium and Gold Analogues: MP2 and CASPT2 Calculations,
CHEMPHYSCHEM, 18, 2409, (2017)
Abstract: Molecular systems in which two simple -electron species, acetylene and ethylene, are linked by a cation located between them are analyzed in this study. In particular, the C2H2M+C2H2, C2H4M+C2H2, and C2H4M+C2H4 complexes (M+=H+, Li+, Au+) are calculated with the use of MP2 and CASPT2 methods. The Quantum Theory of Atoms in Molecules (QTAIM), energy decomposition analysis (EDA), and Natural Bond Orbital (NBO) approaches are applied to deepen the understanding of the nature of M+ interactions in these complexes. It is found that the interactions in gold and proton complexes are characterized by at least partial covalency, whereas interactions in lithium complexes are rather electrostatic in nature.

First author: Liang, YZ, Quantum Chemically Estimated Abraham Solute Parameters Using Multiple Solvent-Water Partition Coefficients and Molecular Polarizability,
Abstract: Polyparameter Linear Free Energy Relationships (pp-LFERs), also called Linear Solvation Energy Relationships (LSERs), are used to predict many environmentally significant properties of chemicals. A method is presented for computing the necessary chemical parameters, the Abraham parameters (AP), used by many pp-LFERs. It employs quantum chemical calculations and uses only the chemicals molecular structure. The method computes the Abraham E parameter using density functional theory computed molecular polarizability and the Clausius-Mossotti equation relating the index refraction to the molecular polarizability, estimates the Abraham V as the COSMO calculated molecular volume, and computes the remaining AP S, A, and B jointly with a multiple linear regression using sixty-five solventwater partition coefficients computed using the quantum mechanical COSMO-SAC solvation model. These solute parameters, referred to as Quantum Chemically estimated Abraham Parameters (QCAP), are further adjusted by fitting to experimentally based APs using QCAP parameters as the independent variables so that they are compatible with existing Abraham pp-LFERs. QCAP and adjusted QCAP for 1827 neutral chemicals are included. For 24 solvent-water systems including octanolwater, predicted log solventwater partition coefficients using adjusted QCAP have the smallest root-mean-square errors (RMSEs, 0.314-0.602) compared to predictions made using APs estimated using the molecular fragment based method ABSOLV (0.45-0.716). For munition and munition-like compounds, adjusted QCAP has much lower RMSE (0.860) than does ABSOLV (4.45) which essentially fails for these compounds.

First author: van Rensburg, AJ, Structural and electronic features of triphenylstibine-functionalized Fischer carbene complexes of molybdenum(0),
POLYHEDRON, 133, 307, (2017)
Abstract: The synthesis and characterization of the first triphenylstibine-containing Fischer carbene complexes of Mo(0) with general formula [(SbPh3)(CO)(4)MoC(OEt)(Ar)] with Ar = 2-thienyl (1), 2-furyl (2), 2 -(N-methyl) pyrrolyl (3), and 2,2′-bithienyl (4) are reported. The solid state crystal structures of these complexes show a syn conformation of the 2-thienyl and 2,2′-bithienyl groups relative to the ethoxy group, and an anti conformation of the 2-furyl group relative to the ethoxy group. Density functional theory calculations using natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations gave insight into the electronic structure and preferred conformations of these novel complexes. X-ray photoelectron spectroscopy measurements show that the binding energy of the Mo 3d(5/2) photoelectron line for the 2-(N-methyl)pyrrolyl-containing Fischer carbene complex, 3, is the smallest; followed by 2 and then 1. This implies that the Mo metal centre is more electron rich in 3, relative to the 2-furyl or 2-thienyl containing Fischer carbene complexes, 2 and 1, respectively.

First author: Chashmniam, S, Conformation of repaglinide: A solvent dependent structure,
Abstract: Experimental and theoretical conformational study of repaglinide in chloroform and dimethyl sulfoxide was investigated. By applying potential energy scanning (PES) at B3LY13/6-311++g** and B3LYP-D3/6-311++g** level of theory on rotatable single bonds, four stable conformers (R1-R4) were identified. Spin-spin coupling constant values were obtained from a set of 2D NMR spectra (H-H COSY, H-C HMQC and H-C HMBC) and compared to its calculated values. Interestingly, from (HNMR)-H-1 and 2D-NOESY NMR, it has been found that repaglinide structure is folded in CDCl3 and cause all single bonds to rotate at an extremely slow rate. On the other hand, in DMSO-d(6), with strong solvent-solute intermolecular interactions, the single bonds rotate freely. Also, energy barrier and thermodynamic parameters for chair to chair interconversion was measured (13.04 kcal mol(-1)) in CDCl3 solvent by using temperature dynamic NMR.

First author: Al-Yasari, A, Organoimido-Polyoxometalate Nonlinear Optical Chromophores: A Structural, Spectroscopic, and Computational Study,
INORGANIC CHEMISTRY, 56, 10181, (2017)
Abstract: Ten organoimido polyoxometalate (POM)-based chromophores have been synthesized and studied by hyper-Rayleigh scattering (HRS), Stark and Resonance Raman spectroscopies, and density functional theory (DFT) calculations. HRS beta(0) values for chromophores with resonance electron donors are significant (up to 139 x 10(-3) esu, similar to 5 times greater than that of the DAS(+) cation), but systems with no donor, or the -NO2 acceptor show no activity, in some cases, despite large DFT-predicted beta-values. In active systems with short (phenyl) pi-bridges, beta(0) values comfortably exceed that of the purely organic structural analogue N,N-dimethyl-4-nitroaniline (DMPNA), and intrinsic beta-values, beta(0)/N-3/2 (where N is the number of bridge pi-electrons) thus appear to break empirical performance limits (beta(0)/N-3/2 vs lambda(max)) for planar organic systems. However, beta(0) values obtained for extended systems with a diphenylacetylene bridge are comparable to or lower than that of their nitro analogue, N,N-dimethyl-4-[(4-nitrophenyl)ethynyl]-aniline (DMNPEA). Resonance Raman spectroscopy confirms the involvement of the POM in the electronic transitions, whether donor groups are present or not, but Stark spectroscopy indicates that, in their absence, the transitions have little dipolar character (hence, NLO inactive), consistent with DFT-calculated frontier orbitals, which extend over both POM and organic group. Stark and DFT also suggest that beta is enhanced in the short compounds because the extension of charge transfer (CT) onto the POM increases changes in the excited-state dipole moment. With extended pi-systems, this effect does not increase CT distances, relative to a -NO2 acceptor, so beta(0) values do not exceed that of DMNPEA. Overall, our results show that (i) the organoimido-POM unit is an efficient acceptor for second-order NLO, but an ineffective donor; (ii) the nature of electronic transitions in arylimido-POMs is strongly influenced by the substituents of the aryl group; and (iii) organoimido-POMs outperform organic acceptors with short pi-bridges, but lose their advantage with extended pi-conjugation.

First author: Mondal, T, DFT Study on C-F Bond Activation by Group 14 Dialkylamino Metalylenes: A Competition between Oxidative Additions versus Substitution Reactions,
INORGANIC CHEMISTRY, 56, 10633, (2017)
Abstract: The C-F bond activation of pentafluoropyridine (PFP) by group 14 dialkylamino metalylenes has been studied employing DFT calculations. Emphasis is placed on the group 14 central atom (M = Si-II, Ge-II, and Sn-II) and substituents (-NMe2, -(NPr2)-Pr-i, -Cl, -NH2, and -PH2) dependent switching of oxidative addition to the metathesis/substitution reaction route, using state-of-the-art theoretical methods (M062X/def2-QZVP(SMD)//M062X/def2-TZVP) to provide a systematic classification of the individual mode of reactions. Moreover, an energy decomposition analysis (EDA) is implemented to get a brief insight into the physical factors that control the activation barriers originating via the different mode of reactions, viz., oxidative addition and metathesis routes. The key finding is that the distortion of PFP is the principal guiding factor in the oxidative addition reaction, while distortions imposed on both the PFP and metalylenes are inevitable toward the origin of the metathesis reaction barrier. The preferable oxidative addition reaction over metathesis of substituted silylenes can be explained on the basis of electron concentration and the HOMO-LUMO gap between the reacting substrates. However, the dramatic switch between oxidative addition and metathesis reaction in substituted germylenes depends on both the electronic and steric nature of the substituents. Similar observations are also noted for the reactivity of substituted stannylenes.

First author: Shapovalov, VV, Formation of adhesive bonds under contact rotaprint lubrication,
Abstract: The mechanism of the formation of adhesive bonds of a friction modifier (a lubricant based on bitumen) with a wheel of railway transport is considered. Calculations performed using quantum chemical methods allow us to draw a conclusion on the existence of the physical adsorption of this lubricant on a wheel surface. The lubrication’s effectiveness can be improved using fatty acids whose introduction into the lubricating material leads to the formation of chemical bonds in the system; this is experimentally confirmed for the contact rotaprint lubrication technology.

First author: Ryzhikov, MR, Induced currents and an H-1 NMR chemical shifts in transition metal clusters (mu-H)(2)Fe-3(mu(3)-Q)(CO)(9) (Q = S, Se, Te),
Abstract: The quantum chemical calculations of induced electric currents in (mu-H)(2)Fe-3(mu(3)-Q)(CO)(9) complexes, where Q = S, Se, Te, are carried out. It is demonstrated that the appearance of anomalous (1)De NMR chemical shifts on bridging hydrogen atoms is, first of all, due to the effect of induced currents on iron atoms.

First author: Mazalov, LN, Electronic structure of functionalized thia- and calix[4]arenes,
Abstract: The electronic structure of calix[4]arene phosphine oxides (CPO) and thiacalix[4]arene phosphine oxides (TCPO) is studied by X-ray photoelectron and emission spectroscopy and quantum chemical methods. The electron density distribution over atoms contained in CPO and TCPO is analyzed. The structure of higher occupied molecular orbitals (HOMO) is examined. It is shown that HOMOs of these compounds mainly consist of contributions of oxygen 2p atomic orbitals (AOs) of phosphoryl and hydroxyl moieties and also bridging sulfur 3p AOs, which indicates the bifunctionality of the considered extractant molecules. The mutual effect of the lower and upper rims of CPOs and TCPOs as well as the effect of their structures on the electron density distribution over calixarene molecules is investigated.

Abstract: Single crystal X-ray diffraction is used to study the nitrosoruthenium mer-trinitrato complex [RuNO(NH3)(2)(NO3)(3)]. The crystallographic data for H6N6O10 Ru are as follows: a = 7.6477(1) angstrom, b = 10.8404(2) angstrom, c = 24.0168(6) angstrom, alpha = beta = gamma = 90 degrees, V = 1991.09(7) angstrom(3), Z = 8, d(calc) = 2/338 g/cm(3), space group P2(1)2(1)2(1). The structure is formed of two structurally non-equivalent uncharged mer-[RuNO(NH3)(2)(NO3)(3)] complexes. The complex crystallizes as yellow needles or orange powder belonging to the orthorhombic system. The substance is poorly soluble in water, ethanol, and acetone, stable in dark storage. The comparisons with the EXAFS data for this complex and the theoretical DFT calculations with different functionals are performed.

First author: Atkins, AJ, Assessing Excited State Energy Gaps with Time-Dependent Density Functional Theory on Ru(II) Complexes,
Abstract: A set of density functionals coming from different rungs on Jacob’s ladder is employed to evaluate the electronic excited states of three Ru(II) complexes. While most studies on the performance of density functionals compare the vertical excitation energies, in this work we focus on the energy gaps between the electronic excited states, of the same and different multiplicity. Excited state energy gaps are important for example to determine radiationless transition probabilities. Besides energies, a functional should deliver the correct state character and state ordering. Therefore, wave function overlaps are introduced to systematically evaluate the effect of different functionals on the character of the excited states. As a reference, the energies and state characters from multistate second-order perturbation theory complete active space (MS-CASPT2) are used. In comparison to MS-CASPT2, it is found that while hybrid functionals provide better vertical excitation energies, pure functionals typically give more accurate excited state energy gaps. Pure functionals are also found to reproduce the state character and ordering in closer agreement to MS-CASPT2 than the hybrid functionals.

First author: Philips, A, Quadrupolar NMR Relaxation from ab Initio Molecular Dynamics: Improved Sampling and Cluster Models versus Periodic Calculations,
Abstract: Quadrupolar NMR relaxation rates are computed for 170 and H-2 nuclei of liquid water, and of Na-23(+), and Cl-35(-) in aqueous solution via Kohn-Sham (KS) density functional theory ab initio molecular dynamics (aiMD) and subsequent KS electric field gradient (EFG) calculations along the trajectories. The calculated relaxation rates are within about a factor of 2 of experimental results and improved over previous aiMD simulations. The relaxation rates are assessed with regard to the lengths of the simulations as well as configurational sampling. The latter is found to be the more limiting factor in obtaining good statistical sampling and is improved by averaging over many equivalent nuclei of a system or over several independent trajectories. Further, full periodic plane-wave basis calculations of the EFGs are compared with molecular cluster atomic-orbital basis calculations. The two methods deliver comparable results with nonhybrid functionals. With the molecular cluster approach, a larger variety of electronic structure methods is available. For chloride, the EFG computations benefit from using a hybrid KS functional.

First author: Haroon, M, An Interesting Behavior and Nonlinear Optical (NLO) Response of Hexamolybdate Metal Cluster: Theoretical Insight into Electro-Optic Modulation of Hybrid Composites,
Abstract: Hexamolybdate is a Lindqvist polyoxometalate cluster. Conjugated polymer is covalently bonded with hexamolybdate cluster via side chain. The conjugated polymer containing metal cluster as side-chain pendant has already been investigated for synthesis and optical properties. Herein, the TDDFT calculation were used to investigate the second-order nonlinear optical (NLO) response of a crystal system. A robust wide range of charge-transfer has been observed via donor (metal cluster) towards the acceptor (end organic ring), consequently responsible for the large NLO response of the studied system. This type of charge transfer containing material is considered to be an efficient candidate for NLO applications. However, polymer shows not only efficient charge transfer but also better charge transporting characteristics. The answer whether cluster is donor or acceptor has been explained through DFT calculations.

First author: Poater, J, Kekulene: Structure, stability and nature of H center dot center dot center dot H interactions in large PAHs,
Abstract: We have quantum chemically analyzed how the stability of small and larger polycyclic aromatic hydrocarbons (PAHs) is determined by characteristic patterns in their structure using density functional theory at the BLYP/TZ2P level. In particular, we focus on the effect of the nonbonded H center dot center dot center dot H interactions that occur in the bay region of kinked (or armchair) PAHs, but not in straight (or zigzag) PAHs. Model systems comprise anthracene, phenanthrene, and kekulene as well as derivatives thereof. Our main goals are: (1) to explore how nonbonded H center dot center dot center dot H interactions in armchair configurations of kinked PAHs affect the geometry and stability of PAHs and how their effect changes as the number of such interactions in a PAH increases; (2) to understand the extent of stabilization upon the substitution of a bay C-H fragment by either C-center dot or N; and (3) to examine the origin of such stabilizing/destabilizing interactions.

First author: Wei, ZX, The synthesis and electrical transport of ligand-protected Au-13 clusters,
Abstract: The ligand-protected Au-13 clusters have been synthesized by using meso-2,3-dimercaptosuccinic acid as the reducing and stabilizing agent. Transmission electron microscopic analysis shows a size distribution of 1.4 +/- 0.6 nm. Optical spectrum shows an absorbance peak at 390 nm. The electrical transport measurement devices are fabricated using the electro-migration method. Coulomb blockade is observed at the temperature of 1.6 K, revealing the formation of the tunneling junction. The Coulomb oscillation’s on/off ratio is nearly 5. Three peaks are extracted in the dI/dV data and attributed to the energy levels of Au13 clusters, gapped by about 60 meV. First principle calculations are carried out to interpret the energy diagram.

First author: Buyens, DMS, Solvent-directed Regioselective Benzylation of Adenine: Characterization of N9-benzyladenine and N3-benzyladenine,
Abstract: The preferred sites for the benzylation of adenine under basic conditions were proven to be the N9 and N3 positions. Formation of the N9-benzyladenine product is favored in polar aprotic solvents, such as DMSO, whereas the proportion of N3-benzyladenine formed increases as the proportion of polar protic solvents, such as water, increases. X-ray crystal structures were obtained for both N9-benzyladenine and N3-benzyladenine. H-1-C-13 HMBC NMR spectroscopy revealed diagnostic correlations used to assign the H-1 and C-13 NMR chemical shifts confirming that the solution structures in three different solvents were the same as the isolated crystals. C-13 NMR assignment for N9-benzyladenine, N3-benzyladenine, and N7-benzyladenine was confirmed by computation using ADF.

First author: Nguyen, TAN, Bonding Situation of Bis-gold Chloride Complexes with N-heterocyclic CarbeneAnalogues [(AuCl)(2)-NHEMe] (E = C – Pb) based on DFT Calculations,
Abstract: We computationally investigated the structure and bonding situation of bis-gold chloride complexes, (AuCl)(2), containing N-heterocyclic carbenes and analogues, called tetrylenes [(AuCl)(2) -NHEMe] (Au2-NHE) with E = C to Pb, using density functional theory (DFT) at the BP86 level with the basis sets def2-SVP, def2-TZVPP, and TZ2P +. The nature of the (AuCl) 2 -NHEMe bond in the Au2-NHE complexes was analyzed using charge and energy decomposition methods. The calculated equilibrium structures of the Au2-NHE complexes showed that the tetrylene ligands, NHEMe (E = C to Ge), are bonded in a head-on fashion to the bis-gold chloride fragment, (AuCl)(2), and that the structure of Au2-NHSn contains a distorted head-on NHSn ligand, and the NHPb ligand is bonded in a side-on mode to the bis-gold chloride fragment, (AuCl) 2. The theoretical calculation of bond dissociation energy (BDE) suggests that the bisgold chloride-NHEMe bond strength increases from Au2-NHC to Au2-NHSi and then significantly decreases from Au2-NHSi to Au2-NHSn, and the strongest bond is exhibited for Au2-NHPb. The EDA-NOCV results and NOCV pairs indicate that the NHE Me ligand in the Au2-NHE complexes is a strong s-donor and a weak pi-acceptor, as well as a very weak pi-donor (AuCl)(2) <- {NHEMe}. The trend in the Au-E bond strength resulted from the increase in (AuCl)(2) <- NHEMe donation. The results of this study may establish an interesting class of compounds worthy of further study.

First author: Zhao, MF, Relativistic and distorted wave effects on Xe 4d electron momentum distributions,
CHINESE PHYSICS B, 26, 1467, (2017)
Abstract: The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons. The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.

First author: Braglia, L, Tuning Pt and Cu sites population inside functionalized UiO-67 MOF by controlling activation conditions,
FARADAY DISCUSSIONS, 201, 265, (2017)
Abstract: The exceptional thermal and chemical stability of the UiO-66, -67 and -68 classes of isostructural MOFs [J. Am. Chem. Soc., 2008, 130, 13850] makes them ideal materials for functionalization purposes aimed at introducing active centres for potential application in heterogeneous catalysis. We previously demonstrated that a small fraction (up to 10%) of the linkers in the UiO-67 MOF can be replaced by bipyridinedicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the grafting of Pt(II) and Pt(IV) ions in the MOF framework [Chem. Mater., 2015, 27, 1042] upon interaction with PtCl2 or PtCl4 precursors. Herein we extend this functionalization approach in two directions. First, we show that by controlling the activation of the UiO-67-Pt we can move from a material hosting isolated Pt(II) sites anchored to the MOF framework with Pt(II) exhibiting two coordination vacancies (potentially interesting for C-H bond activation) to the formation of very small Pt nanoparticles hosted inside the MOF cavities (potentially interesting for hydrogenation reactions). The second direction consists of the extension of the approach to the insertion of Cu(II), obtained via interaction with CuCl2, and exhibiting interesting redox properties. All materials have been characterized by in situ X-ray absorption spectroscopy at the Pt L3-and Cu K-edges.

First author: Ma, HP, Charge-transport properties of 4-(1,2,2-triphenylvinyl) aniline salicylaldehyde hydrazone: tightpacking induced molecular ‘hardening’,
IUCRJ, 4, 695, (2017)
Abstract: Based on first-principles calculations, the relationship between molecular packing and charge-transport parameters has been investigated and analysed in detail. It is found that the crystal packing forces in the flexible organic molecule 4-(1,2,2-triphenylvinyl) aniline salicylaldehyde hydrazone (A) can apparently overcome the dynamic intramolecular rotations and the intramolecular steric repulsion, effectively enhancing the molecular rigidity and decreasing the internal reorganization energy. The conducting properties of A have also been simulated within the framework of hopping models, and the calculation results show that the intrinsic electron mobility in A is much higher than the corresponding intrinsic hole mobility. These theoretical investigations provide guidance for the efficient and targeted control of the molecular packing and charge-transport properties of organic small-molecule semiconductors and conjugated polymeric materials.

First author: Fieser, ME, Evaluating the electronic structure of formal Ln(II) ions in Ln(II)(C5H4SiMe3)(3)(1-) using XANES spectroscopy and DFT calculations,
CHEMICAL SCIENCE, 8, 6076, (2017)
Abstract: The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)(3)], formally containing Ln(II), for aLL Lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment caLcuLations are used to investigate the possibility that Ln(C5H4SiMe3)(3)(1-) (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular Ln(II) compLexes. Results from the ground-state DFT caLcuLations were supported by additional caLcuLations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)(3)(1-) (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f(6) 5d(0) (Sm-II), 4f(13) 5d(0) (Tm-II), 4f(14) 5d(0) 4f(14) 5d(1)) and 4d(1) (Y-II) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)(3)(1-) (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain Ln(II) ions, but with 4f(n) 5d(1) configurations (not 4f(n+1) 5d(0)). In these 4f(n) 5d(1) complexes, the C-3h-symmetric Ligand environment provides a highly shielded 5d-orbital of a’ symmetry that made the 4f(n) 5d(1) eLectronic configurations Lower in energy than the more typical 4f(n+1) 5d configuration.

First author: Viesser, RV, The unexpected roles of sigma and pi orbitals in electron donor and acceptor group effects on the C-13 NMR chemical shifts in substituted benzenest,
CHEMICAL SCIENCE, 8, 6570, (2017)
Abstract: Effects of electron-donating (R = NH2) and electron-withdrawing (R = NO2) groups on C-13 NMR chemical shifts in R-substituted benzene are investigated by molecular orbital analyses. The C-13 shift substituent effect in ortho, meta, and para position is determined by the a bonding orbitals in the aryl ring. The pi orbitals do not explain the substituent effects in the NMR spectrum as conventionally suggested in textbooks. The familiar electron donating and withdrawing effects on the pi system by NH2 and NO2 substituents induce changes in the sigma orbital framework, and the C-13 chemical shifts follow the trends induced in the sigma orbitals. There is an implicit dependence of the a orbital NMR shift contributions on the pi framework, via unoccupied pi* orbitals, due to the fact that the nuclear shielding is a response property.

First author: Jin, JY, Preparation and characterization of chemically bonded argon-boroxol ring cation complexes,
CHEMICAL SCIENCE, 8, 6594, (2017)
Abstract: The cation complexes [ArB3O4](+), [ArB3O5](+), [ArB4O6](+) and [ArB5O7](+) were prepared via a laser vaporization supersonic ion source in the gas phase. Their vibrational spectra were measured via mass-selected infrared photodissociation spectroscopy. Spectroscopy combined with quantum chemical calculations revealed that the [ArB3O5](+), [ArB4O6](+) and [ArB5O7](+) cation complexes have planar structures each involving an aromatic boroxol ring and an argon -boron covalent bond. In contrast, the [ArB3O4](+) cation is characterized to be a weakly bound complex with a B3O4+ chain structure.

First author: Sowmiya, M, Opto-electronic and interfacial charge transfer properties of azobenzene dyes on anatase TiO2 (001) surface – The effect of anchoring group,
Abstract: The opto-electronic and interfacial charge transfer properties of azobenzene dye with different anchoring groups, carboxylic acid, alkoxysilyl and tropolone were studied for dye sensitized solar cell applications. Frontier molecular orbital analysis shows that the lowest unoccupied molecular orbital of azobenzene dye with tropolone anchoring group is delocalized on the anchoring group and azobenzene chromophore, which indicates the possibility of efficient electron transfer from dye molecule to TiO2 conduction band. The azobenzene dye with tropolone anchoring group is having maximum absorption wavelength of 458 nm and light harvesting efficiency of 0.94. The driving force for electron injection (Delta G(inject)) and dye regeneration (Delta G(reg)), excited state life time (tau) and open-circuit voltage (eV(OC)) of designed dye molecules were calculated. The calculated adsorption energies of dye/TiO2 interface indicates that the azobenzene dye with topolone anchoring group possess strong interaction with anatase TiO2 (001) surface. The analysis of density of states shows the electrostatic interaction between dye molecule and TiO2 surface and feasible channel for photo-induced electron transfer from dye to TiO2. It is observed that the tropolone anchoring group is suitable for the dye sensitized solar cell applications than the carboxylic acid and alkoxysilyl anchoring groups for azobenzene dye with anatase TiO2 semiconductor.

First author: Chaudhuri, S, Ultrafast photo-induced charge transfer of 1-naphthol and 2-naphthol to halocarbon solvents,
Abstract: We explore the fluorescence quenching of 1-naphthol and 2-naphthol in halocarbon solvents by using time-correlated single-photon-counting, femtosecond IR-spectroscopy and quantum chemistry computations. We find that halocarbon solvents facilitate a de-excitation mechanism via solute-solvent electron transfer. Decay rates are modulated by close contact interactions between the p-electronic structure of naphthols and halocarbon molecules in their first solvation shell. 1-naphthol exhibits faster decay rates than 2-naphthol due to closer interactions with the solvent.

First author: Lara-Astiaso, M, Role of electron-nuclear coupled dynamics on charge migration induced by attosecond pulses in glycine,
Abstract: We present a theoretical study of charge dynamics initiated by an attosecond XUV pulse in the glycine molecule, which consists in delocalized charge fluctuations all over the molecular skeleton. For this, we have explicitly used the actual electron wave packet created by such a broadband pulse. We show that, for the chosen pulse, charge dynamics in glycine is barely affected by nuclear motion or non adiabatic effects during the first 8 fs, and that the initial electronic coherences do not dissipate during the first 20 fs. In contrast, small variations in the initial nuclear positions, compatible with the geometries expected in the Franck-Condon region, lead to noticeable changes in this dynamics.

First author: Alonso-Lanza, T, Interaction of Cobalt Atoms, Dimers, and Coo Clusters with Circumcoronene: A Theoretical Study,
Abstract: We study the interaction of circumcoronene molecule C54H18 with cobalt in the form of atoms, dimers, and clusters of four atoms. We find that the cobalt atom prefers to be on a hollow site in the edge zone. The cobalt dimer is bonded perpendicularly to another different hollow site in the edge zone. The Co-4 cluster adopts a tetrahedral shape with a face parallel to circumcoronene, placing each of the three atoms over contiguous hollow sites, starting from the edge. Cobalt remains bonded to circumcoronene as Co-2 molecules or Co-4 clusters, rather than spread as isolated atoms, because the cobalt cobalt interaction is stronger than the cobalt carbon bond. The interaction with cobalt clusters induces a small magnetic moment on circumcoronene. The magnetic moment of cobalt is reduced when bonding to circumcoronene. There is charge transfer between those systems and its direction depends on the relative position of the cluster with respect to circumcoronene. We then propose that the presence of cobalt over circumcoronene or similar polycyclic-aromatic hydrocarbons can be detected in experiments, looking at the carbon isomer shift which arises due to the contact charge densities at the nuclei.

First author: Jana, G, MNgCCH (M = Cu, Ag, Au; Ng = Xe, Rn): The First Set of Compounds with M-Ng-C Bonding Motif,
Abstract: Although Ng-M (M = Cu, Ag, Au; Ng = noble gas) and Ng-C bonds are known to exist in different viable species, we report here a series of systems with formula MNgCCH (Ng = Xe, Rn) in which both bonds coexist. These compounds possess reasonably high kinetic stability (free energy barrier, Delta G(double dagger) of 14.0-34.8 kcal/mol) along an exergonic isomerization channel, MNgCCH -> NgMCCH. For a given M, the Delta G(double dagger) associated with this channel increases from Xe to Rn, whereas for a given Ng, it increases along Ag < Cu < Au. No other possible dissociation channel is feasible at standard condition, except for the Ag-Xe analogue, where one three-body neutral dissociation channel, AgXeCCH -> Ag + Xe + CCH, is slightly exergonic by 2.4 kcal/mol. Examination Of the thermochemical stability of the Ng-M bonds in noninserted compounds against the dissociation, NgMCCH -> Ng + MCCH reveals that Kr-Rn bound Cu and Au analogues, and Xe and Rn bound Ag analogues would be viable at 298 K. The natural bond order analysis indicates the formation of M-Ng covalent bond and Ng-C ionic bonds in these compounds having an ionic representation of (MNg)(+)(CCH)(-). Energy decomposition analysis reveals a significant contribution of the electrostatic term in the M-Ng covalent bonds.

First author: Huhn, WP, One-hundred-three compound band-structure benchmark of post-self-consistent spin-orbit coupling treatments in density functional theory,
Abstract: We quantify the accuracy of different non-self-consistent and self-consistent spin-orbit coupling (SOC) treatments inKohn-Sham and hybrid density functional theory by providing a band-structure benchmark set for the valence and low-lying conduction energy bands of 103 inorganic compounds, covering chemical elements up to polonium. Reference energy band structures for the PBE density functional are obtained using the full-potential (linearized) augmented plane wave code WIEN2K, employing its self-consistent treatment of SOC including Dirac-type p(1/2) orbitals in the basis set. We use this benchmark set to benchmark a computationally simpler, non-self-consistent all-electron treatment of SOC based on scalar-relativistic orbitals and numeric atom-centered orbital basis functions. For elements up to Z approximate to 50, both treatments agree virtually exactly. For the heaviest elements considered (Tl, Pb, Bi, Po), the band-structure changes due to SOC are captured with a relative deviation of 11% or less. For different density functionals (PBE versus the hybrid HSE06), we show that the effect of spin-orbit coupling is usually similar but can be dissimilar if the qualitative features of the predicted underlying scalar-relativistic band structures do not agree. All band structures considered in this work are available online via the NOMAD repository to aid in future benchmark studies and methods development.

First author: Yang, J, Multiscale molecular simulations on interfacial adsorption and permeation of nanoporous graphynes,
Abstract: Graphyne has been proposed as a distinctive molecular sieving membrane due to its intrinsic nanoscale pores and single-atom thickness. However, this novel application requires a precise quantification and understanding of the molecular interaction at graphyne interfaces, which can modulate molecular transport across graphyne. Herein, interfacial adsorption and permeation of ethanol-water mixtures on graphynes are studied by a multiscale simulation strategy, in which dispersion-corrected density functional theory (DFT-D) and classical molecular dynamics (MD) are combined. Our results show that graphyne possesses differential surface affinities with ethanol and water, provoking a preferential adsorption layer of ethanol. The adsorption on the graphyne surface is dominated by attractive dispersion force, even for polar water molecules. As a joint function of ethanol-rich segregation adsorption on graphyne and preferred pore occupation of ethanol, polyporous graphyne with a suitable pore size is envisioned to act as an alcohol-permselective membrane. Our simulation results present new insights into interfacial interaction and have an impact on the promising application of two-dimensional graphyne membranes.

First author: Zhang, YH, Influence of the Halogenated Substituent on Charge Transfer Mobility of Aniline Tetramer and Derivatives: Remarkable Anisotropic Mobilities,
Abstract: The halogen-substituted derivatives and the parent aniline tetramer as organic semiconductors have been theoretically investigated with a focus on the electronic properties and charge transport properties through density functional theory and Marcus Hush theory methods. The study on the transport properties of holes and electrons can obtain insight into the effect of halogenation substitution on injection of charge carriers and transport character. The equilibrium geometries, reorganization energies, frontier molecular orbitals, intermolecular electronic couplings, electrostatic potential isosurfaces, and angular resolution anisotropic mobilities were calculated. The calculated results revealed that perfluorination and perchlorination can induce stronger structure relaxation and effectively lower the highest occupied molecular orbital and lowest unoccupied molecular orbital levels. The angle dependence mobilities of the three crystals show remarkable anisotropic character. The carrier mobility curves for both electron and hole transport of the parent aniline tetramer and halogen-substituted derivatives all show a remarkable anisotropic feature. Furthermore, the ANIH and ANIC1 crystals show higher electron-transfer mobilities than hole-transfer mobilities and, hence perform better as an n-type organic semiconductor. The ANIH crystal possesses a low reorganization energy combined with a high electronic coupling and electron-transfer mobility, which indicates that the ANIH crystal might be a more ideal candidate as an n-type organic semiconductor material.

First author: Kittikhunnatham, P, Fluorescence Polarization Measurements to Probe Alignment of a Bithiophene Dye in One-Dimensional Channels of Self-Assembled Phenylethynylene Bis-Urea Macrocycle Crystals,
Abstract: This paper describes the use of polarized fluorescence microscopy to directly probe guest molecule orientation in bis-urea macrocycle crystals. These macrocydes assemble to afford one-dimensional (1D) microchannels similar to 9 angstrom in diameter that have previously been shown to exhibit normal Fickian diffusion and induce selective reactivity among the confined guest molecules. In the present work, we take advantage of the quasi-1D morphology of fiber-like micro crystals with the extended dimension corresponding to the channel axis to measure excitation and emission polarization values for a bithiophene guest. Guest fluorescence is shown to be polarized along the fiber axis with emission polarization values up to 0.729, indicating a high degree of orientational order within the 1D channels. The observed behavior is consistent with calculated results for the guest orientation and electronic transition dipole moment. The results indicate the value of functional fluorescent probes as a measure of guest confinement in low-dimensional environments.

First author: Wu, J, Isohexide Dinitriles: A Versatile Family of Renewable Platform Chemicals,
CHEMSUSCHEM, 10, 3202, (2017)
Abstract: Building blocks of isohexides extended by one carbon atom at the 2- or 5-positions are now synthetically accessible by a convenient, selective, base-catalyzed epimerization of the corresponding dinitriles. Kinetic experiments using the strong organic base 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU) show that all three possible isohexide dinitrile isomers exist within a dynamic equilibrium. An epimerization mechanism based on density functional theory (DFT) calculations is proposed. Structural identification of all three possible isomers is based on NMR analysis and single crystal x-ray crystallography. DFT calculations confirm that the observed crystal structures are indeed the lowest energy conformers of these isohexide derivatives.

First author: Kang, X, Synthesis and Structure of Self-Assembled Pd2Au23(PPh3)(10)Br-7 Nanocluster: Exploiting Factors That Promote Assembly of Icosahedral Nano-Building-Blocks,
CHEMISTRY OF MATERIALS, 29, 6856, (2017)
Abstract: The essential force of self-assembly in the nanocluster range is not intrinsically understood to date. In this work, the synergistic effect between metals was exploited to render the self-assembly from the icosahedral M-13 (M = Pd, Au) nano-building-blocks. Single-crystal X-ray diffraction analysis revealed that the two Pd1Au12 icosahedrons were linked by five halogen linkages, and the assembled structure was determined to be Pd2Au23(PPh3)(10)Br-7. The finding of Au-halogen linkages in the rod-like M-25 nanoclusters has not been previously reported. Furthermore, the calculations on Hirshfeld charge analysis were performed, which implied that the reduced electronic repulsion (induced by the synergistic effect of Pd and Au metals) between two icosahedral units promoted the assembly. This study sheds light on the deep understanding of the essential force of self-assembly from icosahedral nano-building-blocks.

First author: Ferbinteanu, M, On The Density Functional Theory Treatment of Lanthanide Coordination Compounds: A Comparative Study in a Series of Cu-Ln (Ln = Gd, Tb, Lu) Binuclear Complexes,
INORGANIC CHEMISTRY, 56, 9474, (2017)
Abstract: The nontrivial aspects of electron structure in lanthanide complexes, considering ligand field (LF) and exchange coupling effects, have been investigated by means of density functional theory (DFT) calculations, taking as a prototypic case study a series of binuclear complexes [LCu(O2COMe)Ln(thd)(2)], where L2- = N,N’-2,2-dimethyl-propylene-di(3-methoxy-salicylidene-iminato) and Ln = Tb, Lu, and Gd. Particular attention has been devoted to the Cu-Tb complex, which shows a quasi-degenerate nonrelativistic ground state. Challenging the limits of density functional theory (DFT), we devised a practical route to obtain different convergent solutions, permuting the starting guess orbitals in a manner resembling the run of the beta electron formally originating from the f(8) configuration of the Tb(III) over seven molecular orbitals (MOs) with predominant f-type character. Although the obtained states cannot be claimed as the DFT computed split of the F-7 multiplet, the results are yet interesting numeric experiments, relevant for the ligand field effects. We also performed broken symmetry (BS) DFT estimation of exchange coupling in the Cu-Gd system, using different settings, with Gaussian-type and plane-wave bases, finding a good match with the coupling parameter from experimental data. We also caught BS-type states for each of the mentioned series of different states emulated for the Cu-Tb complex, finding almost equal exchange coupling parameters throughout the seven LF-like configurations, the magnitude of the J parameter being comparable with those of the Cu-Gd system.

First author: Mahmoudi, G, Ligand-Driven Coordination Sphere-Induced Engineering of Hybride Materials Constructed from PbCl2 and Bis-Pyridyl Organic Linkers for Single-Component Light-Emitting Phosphors,
INORGANIC CHEMISTRY, 56, 9698, (2017)
Abstract: We report design and structural characterization of six new coordination polymers fabricated from PbCl2 and a series of closely related bis-pyridyl ligands L-I and HLII-HLVI, namely, [Pb-2(L-I)Cl-4], [Pb(HLII)-Cl-2](n)center dot nMeOH, [Pb(HLIII)Cl-2](n)center dot 0.5 nMeOH, [Pb-2(L-IV)Cl-3](n), [Pb(HLV)Cl-2](n), and [Pb-3(L-VI)(2)Cl-4](n)center dot nMeOH. The topology of the obtained networks is dictated by the geometry of the organic ligand. The structure of [Pb-2(L-I)Cl-4](n) is constructed from the [PbCl2](n) two-dimensional (2D) sheets, linked through organic linkers into a three-dimensional framework, which exhibits a unique binodal 4,7-connected three-periodic topology named by us as sdal. Topological analysis of the 2D metal-organic sheet in [Pb(HLII)Cl-2](n)center dot nMeOH discloses a binodal 3,4-connected layer topology, regardless of the presence of tetrel bonds. A one-dimensional (1D) coordination polymer [Pb(HLIII)Cl-2](n)center dot 0.5 nMeOH is considered as a uninodal 2-connected chain. The overall structure of [Pb-2(L-IV)Cl-3](n) is constructed from dimeric tetranuclear [Pb-4(mu(3)-L-IV-kappa N-6:N’:N”:mu(3)-O)(2)(mu(4)-Cl)(mu(2)-Cl)(2)](3+) cationic blocks linked in a zigzag manner through bridging mu(2)-Cl- ligands, yielding a 1D polymeric chain. Topological analysis of this chain reveals a unique pentanodal 3,4,4,5,6-connected chain topology named by us as sda2. The structure of [Pb(HLV)Cl-2](n) exhibits a ID zigzaglike polymeric chain. Two chains are further linked into a 1D gridlike ribbon through the dimeric [Pb-2(mu(2)-Cl)(2)Cl-2] blocks as bridging nodes. With the bulkiest ligand HLVI, a 2D layered coordination polymer [Pb-3(L-VI)(2)Cl-4](n)center dot nMeOH is formed, which network, considering all tetrel bonds, reveals a unique heptanodal 3,3,3,3,4,5,5-connected layer topology named by us as sda3. Compounds [Pb-2(L-I)Cl-4](n), [Pb-2(L-IV)Cl-3](n), and [Pb(HLV)Cl-2] were found to be emissive in the solid state at ambient temperature. While blue emission of [Pb-2(L-I)Cl-4] is due to the ligand-centered transitions, bluish-green and white luminescence of [Pb-2(L-IV)Cl-3] and [Pb(HLV)Cl-2], respectively, was assigned to ligand-to-metal charge transfer mixed with metal-centered excited states. Molecular as well as periodic calculations were additionally applied to characterize the obtained polymers.

First author: Werhun, P, Structural and Crystallographic Information from Ni-61 Solid-State NMR Spectroscopy: Diamagnetic Nickel Compounds,
INORGANIC CHEMISTRY, 56, 9996, (2017)
Abstract: Despite the significance of nickel compounds, NMR spectroscopy of the active nickel isotope Ni-61 remains a largely unexplored field. While nickel(0) compounds have been studied by Ni-61 NMR in solution, solid-state experiments have been limited to Knight shift studies of nickel metal and nickel intermetallics. In conjunction with an NMR study of their ligands and Ni-61 relativistic computations, the first Ni-61 solid-state NMR (SSNMR) spectra of diamagnetic compounds are reported here. Specifically, bis(1,5-cyclooctadiene)nickel(0) [Ni(cod)(2)], tetrakis(triphenylphosphite)nickel(0) [Ni[P(OPh)(3)](4)], and tetrakis(triphenylphosphine)nickel(0) [Ni(PPh3)(4)] were studied. Ni-61 SSNMR spectra of Ni(cod)(2) were used to determine its isotropic chemical shift (delta(iso) = 965 +/- 10 ppm), span (Omega = 1700 +/- 50 ppm), skew (kappa = -0.15 +/- 0.05), quadrupolar coupling constant (C-Q = 2.0 +/- 0.3 MHz), quadrupolar asymmetry parameter (eta = 0.5 +/- 0.2), and the relative orientation of the chemical shift and electric field gradient tensors. A solution study of Ni(cod)(2) in C6D6 yielded a narrow Ni-61 signal, and the temperature dependence of delta(iso)(Ni-61) was assessed (delta(iso) being 936.5 ppm at 295 K). The solution is proposed as a secondary chemical shift reference for Ni-61 NMR in lieu of the extremely toxic Ni(CO)(4) primary reference. For Ni[P(OPh)(3)](4), Ni-61 SSNMR was used to infer the presence of two distinct crystallographic sites and establish ranges for diso in the solid state, as well as an upper bound for C-Q (3.5 MHz for both sites). For Ni(PPh3)(4), line shape fitting provided a diso value of 515 +/- 10 ppm, Omega of 50 +/- 50 ppm, kappa of 0.5 +/- 0.5, C-Q of 0.05 +/- 0.01 MHz, and eta of 0.0 +/- 0.2. The study of Ni(PPh3)(4), in particular, demonstrates the utility of Ni-61 SSNMR given the lack of a previously reported crystal structure and transient nature of Ni(PPh3)(4) in solution.

First author: Ramanantoanina, H, A non-empirical calculation of 2p core-electron excitation in compounds with 3d transition metal ions using ligand-field and density functional theory (LFDFT),
Abstract: Methodological advents for the calculation of the multiplet energy levels arising from multiple-open-shell 2p(5)3d(n+1) electron configurations, with n = 0, 1, 2,… and 9, are presented. We use the Ligand-Field Density Functional Theory (LFDFT) program, which has been recently implemented in the Amsterdam Density Functional (ADF) program package. The methodology consists of calculating the electronic structure of a central metal ion together with its ligand coordination by means of the Density Functional Theory code. Besides, the core-hole effects are treated by incorporating many body effects and corrections via the configuration interaction algorithm within the active space of Kohn-Sham orbitals with dominant 2p and 3d characters of the transition metal ions, using an effective ligand-field Hamiltonian. The Slater-Condon integrals (F-2(3d, 3d), F-4(3d, 3d), G(1)(2p, 3d), G(3)(2p, 3d) and F-2(2p, 3d)), spin-orbit coupling constants (zeta(2p) and zeta(3d)) and parameters of the ligand-field potential (represented within the Wybourne formalism) are therefore determined giving rise to the multiplet structures of systems with 3d(n) and 2p(5)3d(n+1) 1 configurations. The oscillator strengths of the electric-dipole allowed 3d(n) -> 2p(5)3d(n+1) transitions are also calculated allowing the theoretical simulation of the absorption spectra of the 2p core-electron excitation. This methodology is applied to transition metal ions in the series Sc2+, Ti2+,…, Ni2+ and Cu2+ but also to selective compounds, namely SrTiO3 and MnF2. The comparison with available experimental data is good. Therefore, a non-empirical ligand-field treatment of the 2p(5)3d(n+1) configurations is established and available in the ADF program package illustrating the spectroscopic details of the 2p core-electron excitation that can be valuable in the further understanding and interpretation of the transition metal L-2,L-3-edge X-ray absorption spectra.

First author: Chakraborty, D, Does Confinement Always Lead to Thermodynamically and/or Kinetically Favorable Reactions? A Case Study using Diels-Alder Reactions within ExBox(+4) and CB[7],
CHEMPHYSCHEM, 18, 2162, (2017)
Abstract: The impact of geometrical confinement on the thermodynamic as well as kinetic aspects of a model cycloaddition reaction between 1,3-butadiene and ethylene have been investigated based on density functional theory calculations. To this end, organic hosts ExBox(+4) and cucurbit[7]uril (CB[7]) were used to impose confinement effects on the reactants, transition state (TS), and product involved in the reaction. The results suggest that the shape of the host and thereby the nature of the confining regime dictates the thermodynamic outcome of the reaction. The reaction becomes thermodynamically more spontaneous inside CB[7] as compared with that in either ExBox(+4) or in the “unconfined” gaseous state. Furthermore, the rate constant associated with the reaction increases manifold inside CB[7]. Atoms-in a-molecule, noncovalent interaction, natural bond orbital, as well as energy decomposition analyses suggest that the close geometrical proximity of the reactants inside CB[7] as well as extra stabilization of the TS in the encapsulated state may dictate the outcome.

First author: Levandowski, BJ, Role of Orbital Interactions and Activation Strain (Distortion Energies) on Reactivities in the Normal and Inverse Electron-Demand Cycloadditions of Strained and Unstrained Cycloalkenes,
Abstract: The Diels-Alder reactivities of a series of cycloalkenes, from the highly strained cydopropene to the unstrained cydohexene, have been studied with density functional theory using the M06-2X functional. The normal electron-demand Diels-Alder reactions with cyclopentadiene and the inverse electron-demand Diels-Alder reactions with 3,6-bis(trifluoromethyl)tetrazine were analyzed using the distortion/ interaction-activation strain model. Previous studies showed that activation strain computed from the distorted reactants in the transition structures are larger for unstrained than strained cycloalkenes, and that most of the activation energy differences are accounted for by this difference. We have now analyzed the strain and interaction energy curves for the series of cycloalkenes along the reaction coordinate. Our analyses reveal that the strain curves associated with the distortion of the reactants in the Diels-Alder reactions are nearly identical and that the reactivity differences originate from differences in interaction energies. Analysis of the diene-dienophile interactions reveal that the reactivity trends result from differences in the strength of the primary and secondary orbital interactions.

First author: Pushkarevsky, NA, Nature of Bonding in Donor-Acceptor Interactions Exemplified by Complexes of N-Heterocyclic Carbenes with 1,2,5-Telluradiazoles,
Abstract: Comprehensive structural, spectroscopic, and quantum chemical analyses of new donor-acceptor complexes between N-heterocyclic carbenes and 1,2,5-telluradiazoles and a comparison with previously known complexes involving tellurenyl cations showed that the dative C-Te bonds cannot be solitarily described with only one Lewis formula. Canonical Lewis formulas that denote covalency and arrows emphasizing ionicity complement each other in varying extents. Evaluation of the relative weights of these resonance forms requires proper bonding description with a well-balanced toolbox of analytical methods. If for conciseness only, one resonance form is used, it must be the most significant one according to the analytical evaluation. If unclear, all significant resonance forms should be displayed.

First author: Genova, A, eQE: An open-source density functional embedding theory code for the condensed phase,
Abstract: In this work, we present the main features and algorithmic details of a novel implementation of the frozen density embedding (FDE) formulation of subsystem density functional theory (DFT) that is specifically designed to enable ab initio molecular dynamics (AIMD) simulations of large-scale condensed-phase systems containing 1000s of atoms. This code (available at http://eqe. rutgers.edu) has been given the moniker of embedded Quantum ESPRESSO (eQE) as it is a generalization of the open-source Quantum ESPRESSO (QE) suite of programs. The strengths of eQE reside in a hierarchical parallelization scheme that allows for an efficient and fully self-consistent treatment of the electronic structure (via the addition of an additional DIIS extrapolation layer) while simultaneously exploiting the inherent symmetries and periodicities in the system (via sampling of subsystem-specific first Brillouin zones and utilization of subsystem-specific basis sets). While bulk liquids and molecular crystals are two classes of systems that exemplify the utility of the FDE approach (as these systems can be partitioned into weakly interacting subunits), we show that eQE has significantly extended this regime of applicability by outperforming standard semilocal Kohn-Sham DFT (KS-DFT) for large-scale heterogeneous catalysts with quite different layer-specific electronic structure and intrinsic periodicities. eQE features very favorable strong parallel scaling for a model system of bulk liquid water composed of 256 water molecules, which allows for a significant decrease in the overall time to solution when compared to KS-DFT. We show that eQE achieves speedups greater than one order of magnitude (>10x) when performing AIMD simulations of such large-scale condensed-phase systems as: (1) molecular liquids via bulk liquid water represented by 1024 independent water molecules (3072 atoms with a 25.3x speedup over KS-DFT), (2) polypeptide/biomolecule solvation via (GLY)(6) solvated in (H2O)(395) (1230 atoms with a 38.6x speedup over KS-DFT), and (3) molecular crystals via a 3 x 3 x 3 periodic supercell of pentacene (1940 atoms with a 12.0x speedup over KS-DFT). These results represent a significant improvement over the current state-of-the-art and now enable subsystem DFT-based AIMD simulations of realistically sized condensed-phase systems of interest throughout chemistry, physics, and materials science.

First author: Gray, HB, Electronic structures and photophysics of d(8)-d(8) complexes,
Abstract: Research on d(8)-d(8) complexes is being actively pursued, owing, in part, to newly developed time-resolved optical, IR, and X-ray methods that directly interrogate bonding changes upon excitation. Our review covers work on the ground-and electronic excited states, as well as the oxidized and reduced forms, of these complexes. Recent experimental and theoretical results add a new chapter to the rich history of d(8)-d(8) spectroscopic and chemical behavior.

First author: Natarajan, M, A mononuclear iron carbonyl complex [Fe(mu-bdt) (CO)(2)(PTA)(2)] with bulky phosphine ligands: a model for the [FeFe] hydrogenase enzyme active site with an inverted redox potential,
DALTON TRANSACTIONS, 46, 10050, (2017)
Abstract: A mononuclear hexa-coordinated iron carbonyl complex [Fe(mu-bdt)(CO)(2)(PTA)(2)](1) (bdt = 1,2-benzenedithiolate; PTA = 1,3,5-triaza-7-phosphaadamantane) with two bulky phosphine ligands in the trans position was synthesized and characterized by X-ray structural analysis coulometry data, FTIR, electrochemistry and electronic structure calculations. The complex undergoes a facilitated two-electron reduction 1/1(2-) and shows an inverted one-electron reduction for 1/1(-) at higher potentials. Electrochemical investigations of 1 are compared to the closely related [Fe(bdt)(CO)(2)(PMe3)(2)] compound. A mechanistic suggestion for the hydrogen evolution reaction upon proton reduction from acid media is derived. The stability of 1 in both weak and strong acids is monitored by cyclic voltammetry.

First author: Ramaraj, A, Approaches to Sigma Complexes via Displacement of Agostic Interactions: An Experimental and Theoretical Investigation,
ORGANOMETALLICS, 36, 2736, (2017)
Abstract: A series of coordinatively unsaturated, 16-electron, cationic ruthenium complexes bearing PNP pincer ligands of the type [RuH(L)((PNP)-P-R)](+) (L = PPh3, R = PhCH2 (3), Ph (4); L = CO, R = PhCH2 (5); (PNP)-P-R = RN(CH2CH2PPh2)(2)) has been prepared and characterized. These complexes exhibit agostic interaction in the sixth coordination site. The binding of various X-H (X = H, Si, B, and C) bonds in small molecules such as H-2, silanes, tetracoordinate boranes, and CH4 to the ruthenium center via displacement of the relatively weak agostic interaction in these complexes has been studied. Structures of [RuH(L)((PNP)-P-R)](+) (L = PPh3, R = PhCH2 (3), Ph (4); L = CO, R = PhCH2 (5); (PNP)-P-R = RN(CH2CH2PPh2)(2)) complexes and the sigma-borane complex trans-[RuH(CO)(eta(1)-H-BH2 center dot NMe3)((PNP)-P-R)](+) (R = PhCH2 (15)) have been established by X-ray crystallography. The relative binding strengths of the X-H bonds to ruthenium center in these complexes has been studied using computational methods.

First author: Thomas, KE, Stabilization and Structure of the cis Tautomer of a Free-Base Porphyrin,
Abstract: Single-crystal X-ray analysis of the beta-heptakis(trifluoromethyl)-meso-tetrakis(p-fluorophenyl) porphyrin, H-2[(CF3)(7)TpFPP], has revealed the first example of a stable cis tautomer of a free-base porphyrin, the long-postulated intermediate of porphyrin tautomerism. The stability of the unique molecule appears to reflect a dual origin: a strongly saddled porphyrin skeleton, which alleviates electrostatic repulsion between the two NH protons, and two polarization-enhanced, transannular N-H center dot center dot center dot O-H center dot center dot center dot N hydrogen bond chains, each involving a molecule of water. DFT calculations suggest that the observed tautomer has a lower energy than the alternative, doubly hydrated trans tautomer by some 8.3 kcalmol(-1). A fascinating prospect thus exists that H-2[(CF3)(7)TpFPP]center dot 2H(2)O and cognate structures may act as supramolecular synthons, which, given their chirality, may even be amenable to resolution into optically pure enantiomers.

First author: Ayuso, D, Ultrafast charge dynamics in glycine induced by attosecond pulses,
Abstract: The combination of attosecond pump-probe techniques with mass spectrometry methods has recently led to the first experimental demonstration of ultrafast charge dynamics in a biomolecule, the amino acid phenylalanine [Calegari et al., Science, 2014, 346, 336]. Using an extension of the static-exchange density functional theory (DFT) method, the observed dynamics was explained as resulting from the coherent superposition of ionic states produced by the broadband attosecond pulse. Here, we have used the static-exchange DFT method to investigate charge migration induced by attosecond pulses in the glycine molecule. We show that the observed dynamics follows patterns similar to those previously found in phenylalanine, namely that charge fluctuations occur all over the molecule and that they can be explained in terms of a few typical frequencies of the system. We have checked the validity of our approach by explicitly comparing with the photoelectron spectra obtained in synchrotron radiation experiments and with the charge dynamics that follows the removal of an electron from a given molecular orbital, for which fully correlated ab initio results are available in the literature. From this comparison, we conclude that our method provides an accurate description of both the coherent superposition of cationic states generated by the attosecond pulse and its subsequent time evolution. Hence, we expect that the static-exchange DFT method should perform equally well for other medium-size and large molecules, for which the use of fully correlated ab initio methods is not possible.

First author: Campbell, JE, Predicted energy-structure-function maps for the evaluation of small molecule organic semiconductors,
Abstract: The computational assessment of materials through the prediction of molecular and crystal properties could accelerate the discovery of novel materials. Here, we present calculated energy-structure-function maps based on crystal structure prediction for a series of hypothetical organic molecular semiconductors, to demonstrate their utility in evaluating molecules prior to their synthesis. Charge transfer in organic semiconductors relies on the degree of p-conjugation and overlap of the p-systems of neighbouring molecules in the solid state. We explore the effects of varying levels of nitrogen substitution on the crystal packing and charge transport properties of aza-substituted pentacenes, in which C-H…N hydrogen bonding is predicted to favour co-planar molecular packing in preference to the edge-to-face herringbone packing seen for pentacene. The charge mobilities of predicted structures in the energy range of expected polymorphism were calculated, highlighting the important balance between intra- and intermolecular properties when designing novel organic semiconductors. The use of predicted landscapes to rank molecules according to their likely properties is discussed.

First author: Aramburu, JA, Large Differences in the Optical Spectrum Associated with the Same Complex: The Effect of the Anisotropy of the Embedding Lattice,
INORGANIC CHEMISTRY, 56, 8944, (2017)
Abstract: Transition-metal complexes with a well-defined geometry are usually considered to display almost the same properties independently of the system where they are embedded. Here we show that the above statement is not true depending on the anisotropy of the host lattice, which is revealed in the form of the electric field created by the rest of lattice ions over the complex. To illustrate this concept we analyze the origin of the surprisingly large differences in the d-d optical transitions of two systems containing square-planar CuF42- complexes, CaCuF4, and center II in Cu2+-doped Ba2ZnF6, even though the Cu2+-F- distance difference is just found to be 1%. Using a minimalist first-principles model we show that the different morphology of the host lattices creates an anisotropic field that red-shifts the in vacuo complex transitions to the 1.25-1.70 eV range in CaCuF4, while it blue-shifts them to the 1.70-3.0 eV region in Ba2ZnF6:Cu2+. This particular example shows how the lattice anisotropy strongly alters the optical properties of a given transition-metal complex. This knowledge opens a new path to tune the spectra of this large family of systems.

First author: Li, ZZ, Monocyclic aromatic compounds B(n)Rg(n)((n-2)+) of boron and rare gasest,
Abstract: The monocyclic compounds (BRg)(3)(+)(D3h), (BRg)(4)(2+) (D-4h), (BRg)(5)(3+) (D-5h) and (BRg)(6)(4+) (D-6h) formed between boron and rare gases Rg (He-Rn) are theoretically predicted to be stable structures and have pi-aromaticity with a delocalized nc-2e pi-system. For heavier rare gases Ar-Rn, the B-Rg bond energy is quite high and ranges from 15 to 96 kcal moL(-1), increasing with the ring size and the atomic number of rare gases; the B-Rg bond Length is dose to the sum of covalent radii of B and Rg atoms; NBO and AIM analyses show that the B-Rg bonds for Ar-Rn have a typical covalent character. The B-Rg bond is stabilized mainly by sigma donation from the valence p orbital of Rg to the vacant valence orbital of the boron ring. We searched for a Large number of isomers for the systems of Ar and found that the titled monocyclic compounds (BAr)(3)(+)(D-3h), (BAr)(4)(2+) (D-4h) and (BAr)(5)(3+) (D-5h) should be global energy minima. For (BAr)(6)(4+) the global energy minimum is an octahedral caged structure, but the titled monocyclic compound is the secondary stable local energy minimum. The energy and thermodynamic stability of the ring B(n)Rg(n)((n-2)+) cations indicate that these rare gas compounds may be viable species in experiments.

First author: Yuan, HJ, A quantum-chemical insight into the tunable fluorescence color and distinct photoisomerization mechanisms between a novel ESIPT fluorophore and its protonated form,
Abstract: Enol-keto proton tautomerization and cis-trans isomerization reactions of a novel excited-state intramolecular proton transfer (ESIPT) fluorophore of BTImP and its protonated form (BTImP(+)) were explored using density functional theory/time-dependent density functional theory (DFT/TD-DFT) computational methods with a B3LYP hybrid functional and the 6-31 + G(d,p) basis set. In addition, the absorption and fluorescence spectra were calculated at the TD-B3LYP/6-31 + G(d,p) level of theory. Our results reveal that both BTImP and BTImP(+) can undergo an ultrafast ESIPT reaction, giving rise to the single fluorescence emission with different fluorescence colors, which are nicely consistent with the experimental findings. Calculations also show that following the ultrafast ESIPT, BTImP and BTImP+ can experience the distinctly different cis-trans isomerization processes. The intersystem crossing between the first excited singlet S-1 state and triplet T-1 state is found to play an important role in the photoisomerization process of BTImP(+). In addition, the energy barrier of the trans-keto -> cis-keto isomerization in the ground state of BTImP(+) is calculated to be 10.49 kcal mol(-1), which implies that there may exist a long-lived trans-keto species in the ground state for BTImP(+).

First author: Tong, H, TDDFT study on recognition mechanism for the oxygen sensing of the cyclometalated platinum (II) complex,
Abstract: The influence of oxygen molecule on the luminescent properties of a cyclometalated Pt(II) complex Lxp1, was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Analysis of frontier molecular orbitals and electronic configuration indicated that the highest-occupied molecular orbital of the Lxp1 has a significant mixture of metal Pt (d) as well as 2-phenylpyridine and acetyl acetone(pi). The lowest-unoccupied orbital of the Lxp1 primarily locates on pi* of 2-phenylpyridineligands. The emission mechanism of the cyclometalated Pt(II) complex Lxp1 is assigned to the mixing of ligand-to-metal charge transfer and ligand-to-ligand charge transfer. The emission mechanism of the Lxp1-O-2 complex can be attributed to the charge transfer from the oxygen molecule to the luminescent material Lxp1. Our study showed that intermolecular hydrogen bonding between the Lxp1 and oxygen molecule was strengthened by the calculation of electronic excitation, leading to a luminescence-decreasing phenomenon. The calculation of the radiative and non-radiative decay rate constants of the Lxp1 and the Lxpl-O-2 complex demonstrates that the phosphorescence from T-1-S-0 of the Lxp1 would alter to the internal conversion from T-1-T-0 of the Lxp1-O-2 Complex. This alteration further explains the luminescence quenching phenomenon of the cyclometalated Pt(II) complex Lxp1 after interacting with oxygen molecule.

First author: Gao, Y, Solid-State N-15 and O-17 NMR Studies of S-Nitrosothiols,
Abstract: We report a solid-state N-15 and O-17 NMR study of two representative S-nitrosothiols (RSNO): S-nitroso N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO). The N-15 and O-17 NMR tensors are experimentally determined for the first time for this important class of nitric-oxide (NO)-related compounds. The observed NMR characteristics for RSNO include large N-15 and O-17 chemical shift anisotropies and large O-17 quadrupole coupling constants. Quantum chemical calculations are also performed for the N-15 and O-17 NMR tensors in two simple RSNO models: t-BuSNO and MeSNO. On the basis of computational results, we have identified the molecular orbitals that are responsible for the observed large chemical shift anisotropies in RSNO compounds.

First author: Engwerda, AHJ, Deracemization of a Racemic Allylic Sulfoxide Using Viedma Ripening,
CRYSTAL GROWTH & DESIGN, 17, 4454, (2017)
Abstract: Despite the importance of enantiopure chiral sulfoxides, few methods exist that allow for their deracemization. Here, we show that an enantiopure sulfoxide can be produced from the corresponding racemate using Viedma ripening involving rearrangement-induced racemization. The suitable candidate for Viedma ripening was identified from a library of 24 chiral sulfoxides through X-ray structure determination. Starting from the racemic sulfoxide, an unprecedented application of a 2,3-sigmatropic rearrangement type racemization in a Viedma ripening process allowed for complete deracemization.

First author: Pigulski, B, Polyynes as Precursors of Photoluminescent Solvent Polarity Probes,
Abstract: A simple and convenient synthesis of substituted thiophenes from pyrrole end-capped polyynes is being reported. The method allows one to obtain a variety of different fluorescent oligo(hetero)aryles from polyyne precursors. The resulting thiophenes exhibit strong emission solvatochromism in a wide scope of different solvents which makes them promising candidates for fluorescent solvent polarity probes.

First author: Ramanantoanina, H, Electronic fine structure calculation of metal complexes with three-open-shell s, d, and p configurations,
Abstract: The ligand field density functional theory (LFDFT) algorithm is extended to treat the electronic structure and properties of systems with three-open-shell electron configurations, exemplified in this work by the calculation of the core and semi-core 1s, 2s, and 3s one-electron excitations in compounds containing transition metal ions. The work presents a model to non-empirically resolve the multiplet energy levels arising from the three-open-shell systems of non-equivalent ns, 3d, and 4p electrons and to calculate the oscillator strengths corresponding to the electric-dipole 3d(m) -> ns(1)3d-(m)4p(1) transitions, with n = 1, 2, 3 and m = 0, 1, 2,., 10 involved in the s electron excitation process. Using the concept of ligand field, the Slater-Condon integrals, the spin-orbit coupling constants, and the parameters of the ligand field potential are determined from density functional theory (DFT). Therefore, a theoretical procedure using LFDFT is established illustrating the spectroscopic details at the atomic scale that can be valuable in the analysis and characterization of the electronic spectra obtained from X-ray absorption fine structure or electron energy loss spectroscopies.

First author: Novotny, J, Linking the Character of the Metal-Ligand Bond to the Ligand NMR Shielding in Transition-Metal Complexes: NMR Contributions from Spin-Orbit Coupling,
Abstract: Relativistic effects significantly affect various spectroscopic properties of compounds containing heavy elements. Particularly in Nuclear Magnetic Resonance (NMR) spectroscopy, the heavy atoms strongly influence the NMR shielding constants of neighboring light atoms. In this account we analyze paramagnetic contributions to NMR shielding constants and their modulation by relativistic spin-orbit effects in a series of transition-metal complexes of Pt(II), Au(I), and Hg(II). We show how the paramagnetic NMR shielding and spin orbit effects relate to the character of the metal ligand (M-L) bond. A correlation between the (back)-donation character of the M-L bond in d(10) Au(I) complexes and the propagation of the spin orbit (SO) effects from M to L through the M-L bond influencing the ligand NMR shielding via the Fermi-contact mechanism is found and rationalized by using third-order perturbation theory. The SO effects on the ligand NMR shielding are demonstrated to be driven by both the electronic structure of M and the nature of the trans ligand, sharing the a-bonding metal orbital with the NMR spectator atom L. The deshielding paramagnetic contribution is linked to the sigma-type M-L bonding orbitals, which are notably affected by the trans ligand. The SO deshielding role of a-type orbitals is enhanced in d(10) Hg(II) complexes with the Hg 6p atomic orbital involved in the M-L bonding. In contrast, in d8 Pt(II) complexes, occupied pi-type orbitals play a dominant role in the SO-altered magnetic couplings due to the accessibility of vacant antibonding sigma-type MOs in formally open 5d-shell (d(8)). This results in a significant SO shielding at the light atom. The energy- and composition-modulation of sigma- vs pi-type orbitals by spin-orbit coupling is rationalized and supported by visualizing the SO-induced changes in the electron density around the metal and light atoms (spin-orbit electron deformation density, SO-EDD).

First author: Grabias, E, A DFT study of uranyl hydroxyl complexes: structure and stability of trimers and tetramers,
Abstract: A DFT study of U(VI) hydroxy complexes was performed with special attention paid to the [(UO2)(3)(OH)(5)(H2O)(4-7)](+) and [(UO2)(4)(OH)(7)(H2O)(5-8)](+) species. It was established that the ionicity of the U=O bond increased when moving from [(UO2)(H2O)(5)](2+), [(UO2)(2)(OH)(H2O)(8)](3+), [(UO2)(2)(OH)(2)(H2O)(6)](2+), [(UO2)(3)(OH)(5)(H2O)(4-6)](+) to [(UO2)(4)(OH)(7)(H2O)(5-8)](+) species. In both [(UO2)(3)(OH)(5)(H2O)(4-6)](+) and [(UO2)(4)(OH)(7)(H2O)(5-8)](+) complexes, the U=O bond was observed to have a range of different lengths which depended on the composition of the first coordination sphere of UO22+. The cyclic structures of trimeric complexes were somewhat more stable than their linear structures, which was probably due to the steric effect.

First author: Cai, WT, Single crystal structures and theoretical calculations of uranium endohedral metallofullerenes (U@C-2n, 2n=74, 82) show cage isomer dependent oxidation states for U,
CHEMICAL SCIENCE, 8, 5282, (2017)
Abstract: Charge transfer is a general phenomenon observed for all endohedral mono-metallofullerenes. Since the detection of the first endohedral metallofullerene (EMF), La@C-82, in 1991, it has always been observed that the oxidation state of a given encapsulated metal is always the same, regardless of the cage size. No crystallographic data exist for any early actinide endohedrals and little is known about the oxidation states for the few compounds that have been reported. Here we report the X-ray structures of three uranium metallofullerenes, U@D-3h-C-74, U@C-2(5)-C-82 and U@C-2v(9)-C-82, and provide theoretical evidence for cage isomer dependent charge transfer states for U. Results from DFT calculations show that U@D3h-C74 and U@C2(5)-C82 have tetravalent electronic configurations corresponding to U4+@D-3h-C-74(4-) and U4+@C-2(5)-C-82(4-). Surprisingly, the isomeric U@C2v(9)-C82 has a trivalent electronic configuration corresponding to U-3+@C-2v(9)-C-82(3-). These are the first X-ray crystallographic structures of uranium EMFs and this is first observation of metal oxidation state dependence on carbon cage isomerism for mono-EMFs.

First author: Yoneya, M, Characterization of crystal polymorphs of the organic semiconductor non-peripheral octa-hexyl phthalocyanine,
Abstract: The carrier-transport and thermodynamic properties of two crystal polymorphs, i.e., bulk and needle polymorphs, of non-peripheral octa-hexyl substituted phthalocyanine were investigated using density functional theory calculations and molecular dynamics simulations. The calculated results show that the bulk and needle polymorphs have hole mobilities of the same order of magnitude and that the hole mobility of the bulk polymorph was approximately twice that of the needle polymorph. For ideal one-dimensional transport along Pi stacking columns, the difference in mobility between the two polymorphs was larger by a factor of approximately 8. Therefore, we can expect the bulk polymorph to have 2 (or 8) times higher mobility than the values for the needle polymorph. These results predict that the bulk polymorph has the potential to show higher device performance than the needle polymorph. We also obtained the results that imply that a needle-polymorph-like phase with uniform (monoclinic) phthalocyanine-core tilting (instead of the alternative tilting of the needle polymorph) could be a new polymorph in this crystal system.

First author: Liu, L, 3D fluorescent cucurbit[7]uril framework linked by anion fluorophore,
Abstract: By linkage of 1,5-naphthalenedisulfonate (1,5-NDS) anion fluorophore, 3D cucurbit[7]uril (CB[7]) framework has been constructed. The maximum solid-state fluorescence wavelength of the CB[7] framework exhibits blue-shift from 406 to 340 nm in comparison with that of 1,5-NDS, which was ascribed to increased excited energy from 0.10 to 0.13 eV according to theoretical calculations.

First author: Bol, M, Differences in the complexation of sodium with methyl esterified carboxymethyl/methoxyacetyl-O-glucans in electrospray ionization-mass spectrometry,
Abstract: Methoxyacetates and (methoxycarbonyl)methyl ethers of alcohols are isomers where only the positions of C=0 and CH2 are interchanged. Therefore, methoxyacetates of methyl esterified carboxymethyl derivatives of glucans were expected to give equal response in electrospray ionization mass spectrometry which is a prerequisite for the quantitative analysis of substitution patterns in carboxymethyl celluloses (CMC). In order to fad out why this is not the case, corresponding derivatives of 1,2-ethanediol and trans-1,2-cyclohexanediol, resembling the 2,3-diol feature of glucose, where studied in ESI-MS. At high total concentration (10(-3) M) in pure acetonitrile, the methoxyacetates of the model compounds were strongly discriminated. With dilution, the relative intensities (RI) of the isomeric analytes progressively dropped to achieve similar to 2 at a total concentration of 10(-10) M. Similar retention in chromatography and surface activity and polarity parameters do not indicate to different surface chemistry of the constitutional isomers as predominant reason for this strong suppression. Quantum-chemical calculations (DFT) showed a difference of binding energies for Na+ between the two diol derivatives of about 50 kJ/mol. While the CM-ethers can involve the more basic carbonyls into the tetra-coordinated sodium complex, this is sterically not possible for the methoxyacetates. At addition of 10% water RI drastically decreased’ probably due to change of conditional stability constants of the competing sodium complexes. Adjusting sodium molarities to 10(-4) M up to 10(-2) M caused typical salt effects, but will also influence the formation of sodium adducts. In case of mono- and substantially in di- and oligosaccharides, the number of conformations that can coordinate Na+ are more complex, and the discrepancy between the various substituent patterns decreases, but does not fully disappear.

First author: Fadli, S, Coordination chemistry and bonding analysis of tetranuclear transition metal pyrene sandwich complexes,
Abstract: Geometry optimizations have been performed on the M-4(Pyr)(2) (M = Ti-Ni, Pd and Pt, Pyr = C16H10) complexes by means of DFT method using BP86 and mPW1PW91 functionals combined to the TZP basis set. The M-4 moiety encapsulated between two pyrene ligands tends to establish M-L bonding with various hapticies from eta(2) to eta(6). In accordance with the coordination modes, the pyrene behaves as neutral, dianionic, or tetraanionic ligand. For the Ti, V, and Fe, the low-spin (S = 0) and the high-spin (S = 1) structures are isoenergetic, while the Cr, Mn, and Co structures prefer the high-spin states. The Ni, Pd, and Pt structures are more favorable in low-spin state. The zigzag metallic chain is predicted to be more stable than that of the two-dimensional sheet for the Pd complexes. The spin state changes of the studied complexes in their ground states could be characterized in some cases by different molecular structure modifications (structural isomerisation, where structural modifications accompany the spin state modification like as bonds and angles), electronic configurations (low-spin or high-spin), or oxidation states with respect to the metal charges, in agreement with the metal nature. The optimized structures obtained by both BP86 and mPW1PW91 methods are consistent to each other, where the energetic parameters follow similar tendencies regarding the stability order between isomers.

First author: Valaboju, A, DFT study of host-dopant systems of DPVBi with organophosphorus pi-conjugated materials,
Abstract: A detailed computational analysis of intermolecular interactions and optoelectronic properties is carried out using DFT/TD-DFT methods for the emissive materials namely 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl, DPVBi., phospholes 2-thienyl 5-fluorenyl thioxophosphole, A and 2-(5-methyl) thienyl 5-fluorenyl thioxophosphole, B and the two host-dopant systems, DPVBi-A(DA) and DPVBi-B(DB). DPVBi is a classical blue emitter and, phosphole-based compounds A and B are the complementary orange emitters for generation of white light emission in Organic Light Emitting Diodes (OLEDs). The intermolecular interactions are analyzed at B2PLYPD/6-31G(d,p) level for homodimers using the data from CSD and heterodimers with possible structures as predicted at B971)/6-31G(d) level of theory. Drift mobilities, based on Marcus theory for both hole and electron transfers are estimated for DPVBi and compounds A and B in solid state. Vertical and adiabatic excitation energies are calculated for DPVBi and phospholes A and B using TD-DFT. To determine the emission energies, excited state geometry optimizations are carried out using B3LYP, CAM-B3LYP, PBE0, M06-2X functionals with 6-31+G(d,p) basis set.

First author: Calhorda, MJ, Structure, bonding and reactivity of seven-coordinate allylic Mo(II) and W(II) complexes,
Abstract: The family of Mo(II) and W(II) complexes [M(eta(3) allyl)X(CO)(2)(L)(2)] fragment (X = anion, (L)(2) = two monodentate or one bidentate ligand, allyl = C3H5 or substituted allyl) was revisited. A structural search in the CSD afforded 441 molybdenum and 68 tungsten complexes with a pseudo-octahedral geometry (the allyl centroid is taken as one ligand for these purposes) and 18 electrons. Almost all the complexes have the allyl and carbonyls arranged in a facial way, the two carbonyls being cis and lying exo relative to the allyl, but with a fairer distribution between the A (X trans to the allyl) and B isomers (X cis to the allyl). Both A and B, as well as endo and exo species, are fluxional in solution. They may coexist in the solid state and there are examples of exceptions to everything: mer arrangement, trans carbonyls, endo allyl/CO. The A/B conversion is not easy to rationalize, as even an energy decomposition analysis reveals a competition between almost balancing effects. Still a strong pi-acceptor as X favors B. This structural fluxionality may contribute to the limited number of applications in catalysis, though many complexes exhibit promising biological activity.

First author: Dognon, JP, Electronic structure theory to decipher the chemical bonding in actinide systems,
Abstract: The chemical bonding in actinide compounds is usually analysed by inspecting the shape and the occupation of the orbitals or by calculating bond orders which are based on orbital overlap and occupation numbers. However, this may not give a definite answer because the choice of the partitioning method may strongly influence the result possibly leading to qualitatively different answers. In this review, we summarized the state-of-the-art of methods dedicated to the theoretical characterisation of bonding including charge, orbital, quantum chemical topology and energy decomposition analyses. This review is not exhaustive but aims to highlight some of the ways opened up by recent methodological developments. Various examples have been chosen to illustrate this progress.

First author: Lopez-Tarifa, P, Coulomb couplings in solubilised light harvesting complex II (LHCII): challenging the ideal dipole approximation from TDDFT calculations,
Abstract: The light harvesting complex II (LHCII), is a pigment-protein complex responsible for most of the light harvesting in plants. LHCII harvests sunlight and transfers excitation energy to the reaction centre of the photo-system, where the water oxidation process takes place. The energetics of LHCII can be modulated by means of conformational changes allowing a switch from a harvesting to a quenched state. In this state, the excitation energy is no longer transferred but converted into thermal energy to prevent photooxidation. Based on molecular dynamics simulations at the microsecond time scale, we have recently proposed that the switch between different fluorescent states can be probed by correlating shifts in the chromophore-chromophore Coulomb interactions to particular protein movements. However, these findings are based upon calculations in the ideal point dipole approximation (IDA) where the Coulomb couplings are simplified as first order dipole-dipole interactions, also assuming that the chromophore transition dipole moments lay in particular directions of space with constant moduli (FIX-IDA). In this work, we challenge this approximation using the time-dependent density functional theory (TDDFT) combined with the frozen density embedding (FDE) approach. Our aim is to establish up to which limit FIX-IDA can be applied and which chromophore types are better described under this approximation. For that purpose, we use the classical trajectories of solubilised light harvesting complex II (LHCII) we have recently reported [Liguori et al., Sci. Rep., 2015, 5, 15661] and selected three pairs of chromophores containing chlorophyll and carotenoids (Chl and Car): Chla611-Chla612, Chlb606-Chlb607 and Chla612-Lut620. Using the FDE in the Tamm-Dancoff approximation (FDEc-TDA), we show that IDA is accurate enough for predicting Chl-Chl Coulomb couplings. However, the FIX-IDA largely overestimates Chl-Car interactions mainly because the transition dipole for the Cars is not trivially oriented on the polyene chain.

First author: Kelley, MP, On the Origin of Covalent Bonding in Heavy Actinides,
Abstract: Recent reports have suggested the late actinides participate in more covalent interactions than the earlier actinides, yet the origin of this shift in chemistry is not understood. This report considers the chemistry of actinide dipicolinate complexes to identify why covalent interactions become more prominent for heavy actinides. A modest increase in measured actinide:dipicolinate stability constants is coincident with a significant increase in An 5f energy degeneracy with the dipicolinate molecular orbitals for Bk and Cf relative to Am and Cm. While the interactions in the actinide dipicolinate complex are largely ionic, the decrease in 5f orbital energy across the series manifests in orbital-mixing and, hence, covalency driven by energy degeneracy. This observation suggests the origin of covalency in heavy actinide interactions stems from the degeneracy of 5f orbitals with ligand molecular orbitals rather than spatial orbital overlap. These findings suggest that the limiting radial extension of the 5f orbitals later in the actinide series could make the heavy actinides ideal elements to probe and tune effects of energy degeneracy driven covalency.

First author: Kubicki, DJ, Cation Dynamics in Mixed-Cation (MA)(x)(FA)(1-x)PbI3 Hybrid Perovskites from Solid-State NMR,
Abstract: Mixed-cation organic lead halide perovskites attract unfaltering attention owing to their excellent photovoltaic properties. Currently, the best performing perovskite materials contain multiple cations and provide power conversion efficiencies up to around 22%. Here, we report the first quantitative, cation-specific data on cation reorientation dynamics in hybrid mixed-cation formamidinium (FA)/methylammonium (MA) lead halide perovskites. We use N-14, H-2, C-13, and H-1 solid-state MAS NMR to elucidate cation reorientation dynamics, microscopic phase composition, and the MA/FA ratio, in (MA)(x)(FA)(1-x)PbI3 between 100 and 330 K. The reorientation rates correlate in a striking manner with the carrier lifetimes previously reported for these materials and provide evidence of the polaronic nature of charge carriers in PV perovskites.

First author: Min, H, Modified Random Sequential Adsorption Model for Understanding Kinetics of Proteins Adsorption at a Liquid-Solid Interface,
LANGMUIR, 33, 7215, (2017)
Abstract: In this Article, we experimentally measure the adsorption kinetics of human serum albumin (HSA) on a hydrophobic hexadecanethiolated gold surface. We use micromachined quartz crystal resonators with fundamental frequency of 83 MHz to accomplish these measurements in real time. In this work, we focus on two key results: (i) asymptotic behavior of the sensor responses upon HSA adsorption and (ii) the jamming limit of adsorbed layer formed by both single-injection and multi-injection experiments with the same value of final concentration. We develop a new interface-depletion modified random sequential adsorption (RSA) model to elucidate the adsorption kinetics and the transport properties of the protein molecules. Analysis of the experimentally measured data shows that the results can be explained on the basis of the exponentially depleting interfacial layer RSA model. To better understand the origin of the formation of the interfacial depletion region where the supply of protein molecules is dramatically reduced, we performed a series of molecular dynamics (MD) simulations using the ReaxFF method. These simulations predict that the resulting adsorption of the protein molecules on the thiolated surface results in a specific orientation at the interface and the diffusion constant of the protein molecules in this layer is significantly reduced. This interplay between the surface adsorption rate and the reduced diffusion coefficient leads to the depletion of the protein molecules in the interfacial layer where the concentration of the protein molecules is much less than the bulk concentration and explains the observed slowdown of the HSA adsorption characteristics on a hydrophobic surface.

First author: Joy, J, A halogen bond route to shorten the ultrashort sextuple bonds in Cr-2 and Mo-2,
Abstract: Sextuple bonded group 6 diatomics Cr-2 and Mo-2 possess ultrashort metal-metal bonds. Yet their bond dissociation energy is very low. The destabilising nature of sigma-bonds is responsible for this. Selective extraction of these sigma-electrons via a sigma-hole on a halogen bond donor shortens and strengthens the metal-metal bond. This study constitutes a hitherto unexplored application of halogen bonding and an example for the true violation of bond order-bond strength relation.

First author: Nakatsuka, S, 5,9-Dioxa-13b-Oxophosphanaphtho[3,2,1-de]anthracenes Prepared by Tandem Phospha-Friedel Crafts Reaction as Hole-/Exciton-Blocking Materials for OLEDs,
ORGANOMETALLICS, 36, 2622, (2017)
Abstract: We report a short synthesis of phosphorus-fused triarylphosphine oxides, 5,9-dioxa-13b-oxophosphanaphtho[3,2,1-de]anthracenes (DOPNAs), based on a tandem phospha-Friedel Crafts reaction. Phosphorescence, UV-visible absorption, and photoelectron yield spectroscopy of vacuum deposited thin films revealed that the triplet energies, optical band gaps, and ionization potentials of these materials were sufficiently large for them to be utilized in organic light-emitting diodes (OLEDs). Therefore, we fabricated a set of phosphorescent OLEDs based on the above phosphine oxides, confirming that the utilization of these compounds as hole-/exciton-blocking materials significantly improved OLED efficiencies and lifetimes.

First author: Cortes-Arriagada, D, Oxidized and Si-doped graphene: emerging adsorbents for removal of dioxane,
Abstract: Graphene-based materials have emerged as new potential adsorbents for the adsorption and removal of persistent pollutants, and they could play a key role in the remediation of 1,4-dioxane. In this framework, a quantum chemistry study was carried out to rationalize the sorption properties of oxidized graphene (GO) and Si-doped graphene (SiG) nanosheets for use in 1,4-dioxane removal, taking into account that these adsorbents are experimentally available. Dispersion corrected PBE-D3/SVP calculations show that GO and SiG adsorbs dioxane through non-covalent and covalent interactions, respectively, with adsorption energies of up to similar to 0.9 eV, which represents an important improvement with respect to the adsorption onto intrinsic graphene. The adsorption strength was also rationalized in terms of natural bond orbitals, atoms-in-molecules and energy decomposition analyses. In the case of GO, a high content of hydroxyl and carboxyl functional groups enhances the removal efficiency, and they are responsible for the high adsorption stability in aqueous environments and at room temperature (300 K). In addition, explicit/implicit solvent calculations and molecular dynamics trajectories show that the SiG-dioxane interaction is highly stable at 300 K, without pollutant diffusion; besides, the SiG-dioxane interaction is stabilized in the presence of H2O molecules. All the analyses suggest that GO and SiG should be considered as new remarkable candidates for sorption technologies related to the removal, control and remediation of 1,4-dioxane, where the sorption efficiency is sorted as SiG > GO >> G.

First author: Safin, DA, Complexes and salts of the nitrogen-rich triazole-tetrazole hybrid ligand with alkali and alkaline earth metal cations: experimental and theoretical findings,
NEW JOURNAL OF CHEMISTRY, 41, 6210, (2017)
Abstract: Reaction of the nitrogen-rich triazole-tetrazole hybrid ligand 5-(4H-1,2,4-triazol-yl)-2H-tetrazole (trz-tetH) with Li+, Na+, K+ and Ba2+ in water leads to the coordination polymers [Li(trz-tet)H2O](n), [Na(trz-tet)(H2O)(2)](n), [K(trz-tetH)(trz-tet)(H2O)(2)](n) and [Ba-2(trz-tet)(4)(H2O)(9)](n), exhibiting different topologies and coordination modes. Salt-like structures with anionic triazole-tetrazole building blocks [Mg(H2O)(6)](trz-tet)(2) and [Ca(H2O)(8)](trz-tet)(2) were also obtained. All structures were simplified by topological analysis, which showed that the structures of [Mg(H2O)(6)](trz-tet)(2) and [Ca(H2O)(8)](trz-tet)(2) can be considered as underlying networks, constructed from the hydrogen bonded [Mg(H2O)(6)](2+) or [Ca(H2O)(8)](2+) cations and trz-tet ligands, with the rare binodal 5,10-connected topology alb-5,10, P21/c-1 and a unique binodal 5,12-connected topology, respectively. According to TGA/DTA analysis, all compounds show endothermic mass losses below 200 degrees C due to dehydration processes. The dehydrated residues are stable up to 300 degrees C. It was also established that the anionic form of the coordinated ligand trz-tet decomposes with an abrupt mass loss accompanied by a sharp and intense exothermic effect, while the non-coordinated trz-tet, as in the structures of the Mg- and Ca-based compounds, decomposes with a more gradual mass loss and significantly broad exothermic effect. Static DFT, ab initio molecular dynamics simulations as well as charge and energy decomposition (ETS-NOCV) based studies are performed in order to shed light on the stability of the newly obtained crystals.

First author: Biltek, SR, Complete Ag4M2(DMSA)(4) (M = Ni, Pd, Pt, DMSA = Dimercaptosuccinic Acid) Cluster Series: Optical Properties, Stability, and Structural Characterization,
Abstract: The cluster series Ag4M2(DMSA)(4) (M = Ni, Pd, Pt) has been synthesized and the optical spectra and stability have been examined as a function of the metal, M. We have also obtained the structure of Ag4Ni2(DMSA)(4) using X-ray crystallography, confirming the previously calculated structure. In the optical spectrum, there is a significant blue shift as the substituted metal M progresses down the periodic table. Theoretical calculations suggest that the blue shift is due to the lowering in energy of the d orbitals of the transition metal, M; however the expected metal metal excitations are optically weak, and the spectra are dominated by metal ligand excitations. The Ag(4)Pcd(2)(DMSA)(4) species has exceptionally high stability relative to the previously reported Ni and Pt analogues.

First author: Weerawardene, KLDM, Photoluminescence Origin of Au-38(SR)(24) and Au-22(SR)(18) Nanoparticles: A Theoretical Perspective,
Abstract: Photoluminescence of metal nanoparticles has drawn considerable research interest due to their potential fundamental and industrial applications in optoelectronics and biomedicine. However, the origin and underlying mechanism of photoluminescence in these clusters still need to be explored. Herein, the geometrical and electronic structural changes upon photoexcitation in the Au-38(SH)(24) and Au-22(SH)(18) nanoclusters are discussed using time-dependent density functional theory (TD-DFT) methods. Geometric relaxations in the Au-23 core of Au-38(SH)(24) up to a maximum of 0.05 angstrom lead to slight electronic structure changes in the optimized singlet excited states with different state symmetries. The observed geometric and electronic structure variations upon photoexcitation are minor compared to the previously studied Au-25(SH)(18) nanoparticle. These small distortions can be correlated with small Stokes shifts calculated in the range of 0.06-0.09 eV in comparison to 0.49 eV for the Au-25(SH)(18)(-) nanoparticle. Compared to Au-38(SH)(24), the optimized first singlet and triplet excited states of Au-22(SH)(18) nanoparticle show larger structural flexibility in the Au7 core, which leads to significant electronic structure modifications and large Stokes shifts. These states are predicted to have microsecond-scale or longer lifetimes, in agreement with available experimental data.

First author: Nguyen, TAN, Can Tetrylone Act in a Similar Fashion to Tetrylene in Ni(CO)(2) Complexes? A Theoretical Study based on a Comparison using DFT Calculations,
Abstract: A comparison was made to investigate the structures and bonding of nickel complex that carry tetrylone and tetrylene ligands [(CO)(2)Ni-{E(PH3)(2)}] (Ni1E) and [(CO)(2)Ni-{NHEMe}] (Ni2E) (E = C to Pb) using quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+). The nature of the Ni-E bonds was analyzed with charge-and energy decomposition methods. The structures of tetrylone complexes Ni1E exhibit an interesting trend with the ligands E(PH3)(2) are bonded in a tilted orientation relative to the fragment Ni(CO)(2). In contrast, the calculated equilibrium structures of complexes Ni2E exhibit the NHEMe ligands (E = C to Sn) bonded in a head-on way to the Ni(CO)(2) fragment, while the bending angle gives the strongest side-on bonded ligand NHPbMe when E = Pb. The interesting trend of the bond dissociation energy (BDE) is observed for the tetrylone, which has the same trend BDEs compared with tetrylene complexes. The EDA-NOCV results indicate that the tetrylone ligands {E(PH3)(2)} in complexes are similar to the tetrylene ligands NHEMe as strong sigma-donors and weak pi-acceptors. The BDEs calculated for the Ni-E bonds in Ni1E and Ni2E show that the effect of bulky ligands may obscure the intrinsic Ni-E bond strength. The bonding analysis shows that the tetrylone ligands in Ni1E may act in a similar fashion to the tetrylene ligands in Ni2E. All complexes Ni1E and Ni2E are suitable targets for synthesis.

First author: Munoz-Castro, A, On the formation of smaller p-block endohedral fullerenes: Bonding analysis in the E@C-20 (E=Si, Ge, Sn, Pb) series from relativistic DFT calculations,
Abstract: Experimentally characterized endohedral metallofullerenes are of current interest in expanding the range of viable fullerenic structures and their applications. Smaller metallofullerenes, such as M@C-28, show that several d- and f-block elements can be efficiently confined in relatively small carbon cages. This article explores the potential capabilities of the smallest fullerene cage, that is, C-20, to encapsulate p-block elements from group 14, that is, E=Si, Ge, Sn, and Pb. Our interest relates to the bonding features and optical properties related to E@C-20. The results indicate both s- and p-type concentric bonds, in contrast to the well explored endohedral structures encapsulating f-block elements. Our results suggest the E@C-20 series to be a new family of viable endohedral fullerenes. In addition spectroscopic properties related to electron affinity, optical, and vibrational were modeled to gain further information useful for characterization. Characteristic optical patterns were studied predicting a distinctive first peak located between 400 and 250 nm, which is red-shifted going to the heavier encapsulated Group 14 atoms. Electron affinity properties expose different patterns useful to differentiate the hollow C-20 fullerene to the proposed p-block endohedral counterparts.

First author: Papp, T, Theoretical insights into the nature of PtSn bond: Reevaluating the bonding/back-bonding properties of trichlorostannate with comparison to the cyano ligand,
Abstract: The coordinating properties of the trichlorostannate ligand in hydrido platinum trichlorostannato and platinum bis-trichlorostannato complexes, containing various phosphine ligands, have been elucidated by means of charge decomposition analysis, the Ziegler-Rauk Energy Decomposition with the Natural Orbitals for Chemical Valence, Domain-Averaged Fermi Hole, and natural bond orbital methods. Trichlorostannate has been found to be a strong sigma-donor and a weak -acceptor ligand with coordination properties not far from those of the cyano ligand. For back-bonding, the tin-chlorine sigma orbitals are mostly responsible. In contrast to previous assumptions, the 5d orbitals of tin play no role at all in the interaction with the platinum center. QTAIM calculations suggest, that the platinum-tin interaction should be interpreted as donor-acceptor, rather than covalent type. Trichlorostannate has been found to have weaker trans influence in comparison to the cyano ligand.

First author: Shah, JK, Cassandra: An open source Monte Carlo package for molecular simulation,
Abstract: Cassandra is an open source atomistic Monte Carlo software package that is effective in simulating the thermodynamic properties of fluids and solids. The different features and algorithms used in Cassandra are described, along with implementation details and theoretical underpinnings to various methods used. Benchmark and example calculations are shown, and information on how users can obtain the package and contribute to it are provided.

First author: Hamlin, TA, B-DNA model systems in non-terran bio-solvents: implications for structure, stability and replication,
Abstract: We have computationally analyzed a comprehensive series of Watson-Crick and mismatched B-DNA base pairs, in the gas phase and in several solvents, including toluene, chloroform, ammonia, methanol and water, using dispersion-corrected density functional theory and implicit solvation. Our analyses shed light on how the molecular-recognition machinery behind life’s genetic code depends on the medium, in order to contribute to our understanding of the possibility or impossibility for life to exist on exoplanetary bodies. Calculations show how a common non-terran environment like ammonia, less polar than water, exhibits stronger hydrogen-bonding affinities, although showing reduced selectivities towards the correct incorporation of Watson-Crick base pairs into the backbone. Thus, we prove the viability of DNA replication in a non-terran environment.

First author: Moustafa, ME, Photoswitchable and pH responsive organoplatinum(II) complexes with azopyridine ligands,
DALTON TRANSACTIONS, 46, 8405, (2017)
Abstract: Several platinum(II) complexes with ligands containing azo groups have been prepared and structurally characterised, and their photoswitching between trans and cis azo group isomers has been studied. The azo groups in the cationic complexes [PtMe(bipy)(4-NC5H4-N=N-4-C6H4X)][PF6], X = H, OH or NMe2, and in the dicationic complex [Pt(bipy)(4-H2NC6H4-N=N-C6H5)(2)][OTf](2) undergo trans to cis photoswitching on irradiation at 365 nm. The complex [PtMe(bipy)(4-NC5H4-N=N-4-C6H4NMe)(2)][PF6] also exhibits a reversible halochromic effect on protonation to give the dicationic complex [PtMe(bipy) (4-NC5H4-NH=N-4-C6H4NMe2](2+). The nature of the frontier orbitals in the platinum(II) complexes depends on the charge on the complex and on the degree of metal-ligand pi-bonding.

First author: Majid, A, Computational study of titania-ceria hybrid clusters for electrochemical applications,
Abstract: First principles calculations were carried out to investigate the electronic and optical properties with spotlight on excitation spectra and circular dichroism (CD) spectra of Ce2O4, Ti2O4 and the hybrid cluster CeTiO4. The calculated UV/Vis spectrum and CD spectrum for Ce2O4 and Ti2O4 clusters found in respective IR and UV regions is shifted to visible region in case of the hybrid cluster. The major singlet-singlet-allowed transitions for the structures are discussed in detail. The hybrid cluster is optically active in the visible region and simultaneously contains titania’s appealing catalytic properties as well as ceria’s attractive properties for solid state electrolytes. The results point to possibility of adjustable band edges for potential applications in water splitting, coupling semiconductors applicable in dye-sensitized solar cells and other electrochemical devices.

First author: Nasiri, R, Specificity Switching Pathways in Thermal and Mass Evaporation of Multicomponent Hydrocarbon Droplets: A Mesoscopic Observation,
SCIENTIFIC REPORTS, 7, 8405, (2017)
Abstract: For well over one century, the Hertz-Knudsen equation has established the relationship between thermal – mass transfer coefficients through a liquid – vapour interface and evaporation rate. These coefficients, however, have been often separately estimated for one-component equilibrium systems and their simultaneous influences on evaporation rate of fuel droplets in multicomponent systems have yet to be investigated at the atomic level. Here we first apply atomistic simulation techniques and quantum/statistical mechanics methods to understand how thermal and mass evaporation effects are controlled kinetically/thermodynamically. We then present a new development of a hybrid method of quantum transition state theory/improved kinetic gas theory, for multicomponent hydrocarbon systems to investigate how concerted-distinct conformational changes of hydrocarbons at the interface affect the evaporation rate. The results of this work provide an important physical concept in fundamental understanding of atomistic pathways in topological interface transitions of chain molecules, resolving an open problem in kinetics of fuel droplets evaporation.

First author: Georgiou, DC, A Strong cis-Effect in an Imidazole-Imidazolium-Substituted Alkene,
Abstract: We report the first example of an alkene with two carbon-bound substituents (imidazole and imidazolium rings) where the Z-isomer has a greater thermodynamic stability than the E-isomer which persists in both the gas phase and in solution. Theoretical calculations, solution fluorescence spectroscopy and gas-phase ion mobility mass spectrometry studies confirm the preference for the Z-isomer, the stability of which is traced to a non-covalent interaction between the imidazole lone pair and the imidazolium ring.

First author: Pu, MP, Liberation of H-2 from (o-C6H4Me)(3)P-H(+) + H(-)-B(p-C6F4H)(3) ion-pair: A transition-state in the minimum energy path versus the transient species in Born-Oppenheimer molecular dynamics,
Abstract: Using Born-Oppenheimer molecular dynamics (BOMD) with density functional theory, transition-state (TS) calculations, and the quantitative energy decomposition analysis (EDA), we examined the mechanism of H-2-liberation from LB-H(+) + H(-)-LA ion-pair, 1, in which the Lewis base (LB) is (o-C6H4Me)(3)P and the Lewis acid (LA) is B(p-C6F4H)(3). BOMD simulations indicate that the path of H-2 liberation from the ion-pair 1 goes via the short-lived transient species, LB center dot center dot center dot H(2 center dot center dot center dot)LA, which are structurally reminiscent of the TS-structure in the minimum-energy-path describing the reversible reaction between H-2 and (o-C6H4Me)(3)P/B(p-C6F4H)(3) frustrated Lewis pair (FLP). With electronic structure calculations performed on graphics processing units, our BOMD data-set covers more than 1 ns of evolution of the ion-pair 1 at temperature T approximate to 400 K. BOMD simulations produced H-2-recombination events with various durations of H-2 remaining fully recombined as a molecule within a LB/LA attractive “pocket”-from very short vibrational-time scale to time scales in the range of a few hundred femtoseconds. With the help of perturbational approach to trajectory-propagation over a saddle-area, we directly examined dynamics of H-2-liberation. Using EDA, we elucidated interactions between the cationic and anionic fragments in the ion-pair 1 and between the molecular fragments in the TS-structure. We have also considered a model that qualitatively takes into account the potential energy characteristics of H-H recombination and H-2-release plus inertia of molecular motion of the (o-C6H4Me)(3)P/B(p-C6F4H)(3) FLP.

First author: Xiao, P, Mechanistic insights into the light-driven hydrogen evolution reaction from formic acid mediated by an iridium photocatalyst,
Abstract: A novel light-triggered hydrogen evolution reaction from formic acid mediated by an Ir(III) photocatalyst has been experimentally reported recently. However, its reaction mechanism remains elusive. Herein, we have employed the density functional theory (DFT) method to explore this photocatalytic reaction in detail. On the basis of the results, we have proposed a possible photocatalytic reaction mechanism. In the formation of the metal hydride [Cp*Ir.bpy)(H)](+) (5), formic acid acts as a bridge assisting proton shuttling. Upon irradiation, two nonadiabatic excited-state decay pathways quickly populate the lowest triplet T-1 state of the metal hydride from its initially populated excited singlet S-1 state. In the T-1 state, water and formic acid facilitate excited-state hydride/proton transfers from the Ir center to Cp* and bpy ligands producing several energetically lower triplet-state isomers demonstrating that the triplet-state metal hydride 5* could not be the only precursor for the photocatalysis. Adiabatic H-2 evolution in the T-1 state is energetically unfavorable. These T-1 isomers hop, through radiationless T-1 -> S-0 intersystem crossings via T-1/S-0 crossing points, to the S-0 state in which H-2 evolution takes place. In these reactions, solvents acting as assistants and catalysts reduce reaction barriers, thereby accelerating H-2 release and enhancing the overall photocatalytic performance. Our current work provides significant mechanistic insights into light-induced hydrogen-evolution reactions of iridium-containing photocatalysts.

First author: Galliot, A, Effects of oxygenation on the intercalation of 1,10-phenanthroline-5,6/4,7-dione between DNA base pairs: a computational study,
Abstract: The effects of oxygen in positions 4,7 and 5,6 of phenanthroline when this ligand intercalates between guanine-cytosine and adenine-thymine DNA base pairs (GC/CG and AT/TA) have been studied at the M06-2X/6-31+G(d,p) level of calculation. We focused on the changes in the structure, stabilization and energy contributions in the analysis of the interaction. The obtained trends in stabilization are explained by a model including repulsive Pauli (Delta E-Pauli) contributions, and attractive dispersion (Delta E-disp), orbital (Delta E-orb) and electrostatic (Delta E-elstat) contributions to energy. When no solvation is considered, the intrinsic DEelstat contribution results are crucial for the stabilization of the system. However, the inclusion of the solvation energy Delta E-solv can reverse the final stability trend of the systems becoming, thus, the driving force of the process. Therefore, the solvent will have a relevant influence in the potential cytotoxicity of the intercalation drugs.

First author: Wu, Z, The hypothiocyanite radical OSCN and its isomers,
Abstract: A biologically relevant reactive sulfur species (RSS), the hypothiocyanite radical OSCN, is generated in the gas phase through flash vacuum pyrolysis (FVP) of trifluoromethyl sulfinyl cyanide CF3S(O)CN at ca. 1000 K. Upon UV light irradiation (365 nm), OSCN rearranges to novel isomers OSNC and SOCN, and further visible light irradiation (400 +/- 20 nm) leads to reverse isomerization. The identification of OSCN, OSNC, and SOCN in cryogenic matrices (Ar and N-2, 2.8 K) with IR spectroscopy is supported by quantum chemical calculations up to the CCSD(T)-F12/VTZ-F12 level. The potential energy surface for the interconversion of OSCN isomers and their bonding properties are computationally explored by using the CCSD(T)-F12/VTZ-F12 and EDA-NOCV methods, respectively.

First author: Pogany, L, Series of high spin mononuclear iron(III) complexes with Schiff base ligands derived from 2-hydroxybenzophenones,
NEW JOURNAL OF CHEMISTRY, 41, 5904, (2017)
Abstract: The reaction of various phenols with benzoyl chloride afforded the derivatives of phenyl benzoate that subsequently underwent Fries rearrangement. The obtained 2-hydroxybenzophenone analogues were combined with linear aliphatic triamines, which afforded pentadentate Schiff base ligands. Moreover, nine new iron(III) complexes with the general formula [Fe(L-n)X] (where, L-n is the dianion of the pentadentate Schiff base ligand, N,N’-bis((2-hydroxy-5-methylphenyl)phenyl)methylidene-1,5-diamino-3-azapentane = H2L1, N,N’-bis((2-hydroxy-3,5-dimethylphenyl)phenyl)methylidene-1,5-diamino-3-azapentane = H2L2, N,N’-bis((2-hydroxy-5-chlorophenyl)phenyl)methylidene-1,5-diamino-3-azapentane = H2L3, N, N’-bis(( 2-hydroxy-4-methylphenyl)phenyl)methylidene-1,5-diamino-3-azapentane = H2L4, N,N’-bis((2-hydroxy-5- bromophenyl) phenyl)methylidene-1,7-diamino-4-azaheptane = H2L5, N,N’-bis((2-hydroxy-5-bromophenyl)phenyl)methylidene-1,7-diamino-4-methyl-4-azaheptane = H2L6 and X is the chlorido, azido or isocyanato terminal ligand) were synthesized and characterized via elemental analysis, and IR and UV-VIS spectroscopy; in addition, the crystal structures of all the complexes were determined by X-ray diffraction. Magnetic investigation reveals high spin state behaviour in all the reported compounds. DFT calculations and analysis of the magnetic functions allowed to extract absolute values of the zero field splitting parameters and exchange coupling constants.

First author: Lo, WKC, [Pt(bipy)(ONO2)(2)] and [{(bipy)Pt(mu-O2NO)(2)Pt(bipy)}(2)](NO3)(4): Empirically identical but structurally distinct complexes obtained from a basic aqueous solution of [Pt(bipy)(2)](NO3)(2),
POLYHEDRON, 130, 145, (2017)
Abstract: Vapour diffusion of acetonitrile into a basic aqueous solution of [Pt(bipy)(2)](NO3)(2)center dot H2O results in slow crystallisation of a mixture of the monomeric complex [Pt(bipy)(ONO2)(2)]center dot 5.25H(2)O and the tetrameric complex {[(bipy)Pt(mu-O2NO)(2)Pt(bipy)}(2)](NO3)(4)center dot 8.5H(2)O, the structures of which were confirmed by X-ray crystallography. Calculations on the tetrameric complex show that the central Pt-Pt bond is weak, as evidenced by the fact that inclusion of dispersion forces is required to prevent the cation from dissociating into two [(bipy)Pt(mu-O2NO)(2)Pt(bipy)](2+) dimers. Isolation of the monomeric and tetrameric complexes shows that one of the bipy ligands in the [Pt(bipy)(2)](2+) cation is easily displaced in basic aqueous solution. This displacement may be a consequence of OH- attack at the Pt ion.

First author: Heshmat, M, Carbonyl Activation by Borane Lewis Acid Complexation: Transition States of H-2 Splitting at the Activated Carbonyl Carbon Atom in a Lewis Basic Solvent and the Proton-Transfer Dynamics of the Boroalkoxide Intermediate,
Abstract: By using transition-state (TS) calculations, we examined how Lewis acid (LA) complexation activates carbonyl compounds in the context of hydrogenation of carbonyl compounds by H-2 in Lewis basic (ethereal) solvents containing borane LAs of the type (C6F5)(3)B. According to our calculations, LA complexation does not activate a ketone sufficiently enough for the direct addition of H-2 to the O = C unsaturated bond; but, calculations indicate a possibly facile heterolytic cleavage of H-2 at the activated and thus sufficiently Lewis acidic carbonyl carbon atom with the assistance of the Lewis basic solvent (i.e., 1,4-dioxane or THF). For the solvent-assisted H-2 splitting at the carbonyl carbon atom of (C6F5)(3)B adducts with different ketones, a number of TSs are computed and the obtained results are related to insights from experiment. By using the Born-Oppenheimer molecular dynamics with the DFT for electronic structure calculations, the evolution of the (C6F5)(3)B-alkoxide ionic intermediate and the proton transfer to the alkoxide oxygen atom were investigated. The results indicate a plausible hydrogenation mechanism with a LA, that is, (C6F5)(3)B, as a catalyst, namely, 1) the step of H-2 cleavage that involves a Lewis basic solvent molecule plus the carbonyl carbon atom of thermodynamically stable and experimentally identifiable (C6F5)(3)B-ketone adducts in which (C6F5)(3)B is the “Lewis acid promoter”, 2) the transfer of the solvent-bound proton to the oxygen atom of the (C6F5)(3)B-alkoxide intermediate giving the (C6F5)(3)B-alcohol adduct, and 3) the S(N)2-style displacement of the alcohol by a ketone or a Lewis basic solvent molecule.

First author: Chapellet, LL, Experimental and Theoretical Study of the Complexation of Cesium and Thallium Cations by a Water-Soluble Cryptophane,
CHEMISTRYSELECT, 2, 5292, (2017)
Abstract: Cs (cesium) and Tl (thallium) are known to be very toxic for the environment and human health. Thus, the synthesis of molecular receptors aimed at extracting these two elements from the environment is strongly desired. In this article, we report the synthesis of the two enantiomers of a water-soluble cryptophane-223 (1) and the study of their interaction with cesium and thallium cations in basic aqueous solutions. These two complexes have been studied by Cs-133 and Tl-205 NMR spectroscopy to reveal the complexation of the two metallic cations and by chiroptical techniques (electronic and vibrational circular dichroism) to provide valuable information about the conformational changes occurring during the binding process. The thermodynamic parameters of complexation K, Delta H-0 and Delta S-0 obtained from titration experiments reveal a strong interaction between 1 and the two cations under a large range of experimental conditions. A decomposition of the total binding energy, performed by DFT calculations, allows us to characterize the nature of the interactions existing between the cage-molecule and these two cations. These calculations also reveal the importance of the spin-orbit coupling for predicting correctly the large frequency difference between the free Tl+ and Tl+@1 NMR signals and to understand its origin. In addition to the development of a methodology enabling detailed understanding of the host-guest interaction, this study indicates a very pronounced selectivity of this cage-molecule towards both Cs+ and Tl+ cations in various experimental conditions.

First author: Marchenko, A, Uranyl Carbonate Complexes in Aqueous Solution and Their Ligand NMR Chemical Shifts and O-17 Quadrupolar Relaxation Studied by ab Initio Molecular Dynamics,
INORGANIC CHEMISTRY, 56, 7384, (2017)
Abstract: Dynamic structural effects, NMR ligand chemical shifts, and O-17 NMR quadrupolar relaxation rates are investigated in the series of complexes UO22+, UO2(CO3)(3)(4-), and (UO2)(3)(CO3)(6)(6-). Car-Parrinello molecular dynamics (CPMD) is used to simulate the dynamics of the complexes in water. NMR properties are computed on clusters extracted from the CPMD trajectories. In the UO22+ complex, coordination at the uranium center by water molecules causes a decrease of around 300 ppm for the uranyl O-17 chemical shift. The final value of this chemical shift is within 40 ppm of the experimental range. The UO2(CO3)(3)(4-) and (UO2)(3)(CO3)(6)(6-) complexes show a solvent dependence of the terminal carbonate O-17 and C-13 chemical shifts that is less pronounced than that for the uranyl oxygen atom. Corrections to the chemical shift from hybrid functionals and spin-orbit coupling improve the accuracy of chemical shifts if the sensitivity of the uranyl chemical shift to the uranyl bond length (estimated at 140 ppm per 0.1 (A) over circle from trajectory data) is taken into consideration. The experimentally reported trend in the two unique C-13 chemical shifts is correctly reproduced for (UO2)(3)(CO3)(6)(6-). NMR relaxation rate data support large O-17 peak widths, but remain below those noted in the experimental literature. Comparison of relaxation data for solvent-including versus solvent-free models suggest that carbonate ligand motion overshadows explicit solvent effects.

First author: Chong, DP, Computational Study of the Electron Spectra of Acetamide and N-methylformamide,
Abstract: The molecular structures of the three conformers of acetamide are first studied by ab initio method of CCSD/cc-pVTZ. Using the optimized geometry of each species, we apply established and/or developing methods to compute several physical properties of acetamide and compare them with available experimental data. The properties include dipole moments, polarizabilities, ionization energies of both valence and core electrons, and absorption spectra of both valence and core electrons. Similar results for N-methylformamide are included for comparison.

First author: Kobera, L, Multinuclear solid-state magnetic resonance study of oxo-bridged diniobium and quadruply-bonded dimolybdenum carboxylate clusters,
Abstract: Carboxylate paddlewheels and their oxo-bridged analogues constitute ideal building blocks for the assembly of two- and three-dimensional framework materials. Here, we present a multinuclear (H-1, C-15, Nb-93, Mo-95) magnetic resonance study of solid samples of Nb2OCl6(O-2 PH)(2) (1), Mo-2(O2CMe)(4) (2), and Mo-2(O2CCHF2)(4) (3). High-resolution proton and C-13 CP/MAS NMR spectra provide valuable information on structure and crystal symmetry and on cocrystallized solvent. Nb-93 solid-state NMR spectra of 1 provide quadrupolar coupling constants and chemical shift tensors which are characteristic of the axially asymmetric Nb-O-Nb bridging environment. Mo-95 solid-state NMR spectra of 2 and 3 provide quadrupolar coupling constants and chemical shift tensors which are directly characteristic of the molybdenum-molybdenum quadruple bonds in these compounds. The quadruple bonds are characterized by particularly large Mo-95 chemical shift tensor spans on the order of 5500 ppm. Density functional theoretical computations provide good agreement with the Nb-93 and Mo-95 experimental data, with some exceptions noted. This work demonstrates possible NMR approaches to characterize more complex framework materials and provides key insight into the Mo-Mo quadruple bond.

First author: Kong, XQ, Solid-state O-17 NMR study of 2-acylbenzoic acids and warfarin,
Abstract: We report synthesis and solid-state O-17 NMR characterization of four site-specifically O-17-labeled 2-acylbenzoic acids (2-RC(O)C6H4COOH) where R=H and CH3): 2-[3(17)O]formylbenzoic acid, 2-[1,2-O-17(2)]formylbenzoic acid, 2-[3-O-17]acetylbenzoic acid, and 2-[1,2,3-O-17(3)]acetylbenzoic acid. In the solid state, both 2-formyl- and 2 acetyl -benzoic acids exist as the cyclic phthalide form each containing a five-membered lactone ring and a cyclic hemiacetal/hemiketal group. Static and magic-angle-spinning O-17 NMR spectra were recorded at 14.1 and 21.1 T for these compounds, from which the O-17 chemical shift and nuclear quadrupolar coupling tensors were determined for each oxygen site. These results represent the first time that O-17 NMR tensors are fully characterized for lactone, cyclic hemiacetal, and cyclic hemiketal functional groups. We also report solid-state O-17 NMR data for the cyclic hemiketal group an anticoagulant drug, warfarin. Experimental O-17 NMR tensors in these compounds were compared with computational results obtained with a periodic DFT code BAND.

First author: Yepes, D, Effect of Lewis acid bulkiness on the stereoselectivity of Diels-Alder reactions between acyclic dienes and alpha,beta-enals,
Abstract: The factors controlling the reactivity and endo/exo selectivity of Lewis acid-catalysed Diels-Alder reactions between highly substituted open-chain 1,3-dienes and alpha, beta-enals have been explored computationally by means of density functional theory calculations. In agreement with previous experimental observations, it is found that the B(C6F5) (3)-catalysed cycloaddition reaction leads almost exclusively to the corresponding exo-cycloadduct, whereas the analogous AlCl3-mediated process is highly endo-selective. The effect of Lewis acid bulkiness on stereoselectivity has been quantitatively analysed by means of a combination of the activation strain model of reactivity and the energy decomposition analysis methods. In contrast to the current view, the exo-selectivity promoted by the bulky B(C6F5) (3) catalyst does not result from the steric destabilization of the corresponding endo-transition state but from the interplay between the less destabilizing strain energy and the stronger interaction between the deformed reactants along the entire reaction coordinate. In addition, non-covalent interactions are found to play a crucial role in stabilizing the exo-approach. These results allow us to not only quantitatively understand the effect of the Lewis acids in the process, but also predict new catalysts leading to highly exo-selective Diels-Alder reactions.

First author: Laloo, JZA, ExcelAutomat: a tool for systematic processing of files as applied to quantum chemical calculations,
Abstract: The processing of the input and output files of quantum chemical calculations often necessitates a spreadsheet as a key component of the workflow. Spreadsheet packages with a built-in programming language editor can automate the steps involved and thus provide a direct link between processing files and the spreadsheet. This helps to reduce user-interventions as well as the need to switch between different programs to carry out each step. The ExcelAutomat tool is the implementation of this method in Microsoft Excel (MS Excel) using the default Visual Basic for Application (VBA) programming language. The code in ExcelAutomat was adapted to work with the platform-independent open-source LibreOffice Calc, which also supports VBA. ExcelAutomat provides an interface through the spreadsheet to automate repetitive tasks such as merging input files, splitting, parsing and compiling data from output files, and generation of unique filenames. Selected extracted parameters can be retrieved as variables which can be included in custom codes for a tailored approach. ExcelAutomat works with Gaussian files and is adapted for use with other computational packages including the non-commercial GAMESS. ExcelAutomat is available as a downloadable MS Excel workbook or as a LibreOffice workbook.

First author: Gieseking, RL, Semiempirical modeling of electrochemical charge transfer,
FARADAY DISCUSSIONS, 199, 547, (2017)
Abstract: Nanoelectrochemical experiments using detection based on tip enhanced Raman spectroscopy (TERS) show a broad distribution of single-molecule formal potentials E degrees’ for large p-conjugated molecules; theoretical studies are needed to understand the origins of this distribution. In this paper, we present a theoretical approach to determine E degrees’ for electrochemical reactions involving a single molecule interacting with an electrode represented as a metal nanocluster and apply this method to the Ag-20-pyridine system. The theory is based on the semiempirical INDO electronic structure approach, together with the COSMO solvation model and an approach for tuning the Fermi energy, in which the silver atomic orbital energies are varied until the ground singlet state of Ag-20-pyridine matches the lowest triplet energy, corresponding to electron transfer from the metal cluster to pyridine. Based on this theory, we find that the variation of E degrees’ with the structure of the Ag-20-pyridine system is only weakly correlated with changes in either the ground-state interaction energy or the charge-transfer excited-state energies at zero applied potential, which shows the importance of calculations that include an applied potential in determining the variation of formal potential with geometry. Factors which determine E degrees’ include wavefunction overlap for geometries when pyridine is close to the surface, and electrostatics when the molecule-cluster separation is large.

First author: Pan, S, Modeling of 1-D Nanowires and analyzing their Hydrogen and Noble Gas Binding Ability,
Abstract: The theoretical calculation at the M05-2X/6-311+G(d,p) level reveals that the B-B bond length in [N-4-B-2-N-4](2-) system (1.506 ) is slightly smaller than that of typical B=B bond in B2H2 (1.518 ). These systems interact with each M+ (M = Li, Na, K) ion very strongly with a binding energy of 213.5 (Li), 195.2 (Na) and 180.3 (K) kcal/mol. Additionally, the relief of the Coulomb repulsion due to the presence of counter-ion, M+, the B-B bond contracts to 1.484-1.488 in [N-4-B-2-N-4]M-2. We have further extended our study to [N-4-B-2-N-4-B-2-N-4](4-) and [N-4-B-2-N-4-B-2-N-4-B-2-N-4](6-) systems. The B-B bond length is found to be 1.496 in the former case, whereas the same is found to be 1.493 and 1.508 , respectively, for the two B-B bonds present in the latter one. The M (+) counter-ions stabilize such negatively charged systems and thus, create a possibility to design a long 1-D nanowire. Their utilities as probable hydrogen and noble gas (Ng) binding templates are explored taking [N-4-B-2-N-4-B-2-N-4]Li-4 system as a reference. It is found that each Li center binds with three H-2 molecules with an average binding energy of 2.1 kcal/mol, whereas each Ng (Ar-Rn) atom interacts with Li center having a binding energy of 1.8-2.1 kcal/mol. The H-2 molecules interact with Li centers mainly through equal contribution from orbital and electrostatic interaction, whereas the orbital interaction is found to be major term (ca. 51-58%) in Ng-Li interaction followed by dispersion (ca. 24-27%) and electrostatic interaction (ca. 17-24%).

First author: Morgenstern, A, Quantified electrostatic preorganization in enzymes using the geometry of the electron charge density,
CHEMICAL SCIENCE, 8, 5010, (2017)
Abstract: Electrostatic preorganization is thought to be a principle factor responsible for the impressive catalytic capabilities of enzymes. The full protein structure is believed to facilitate catalysis by exerting a highly specific electrostatic field on the active site. Computationally determining the extent of electrostatic preorganization is a challenging process. We propose using the topology and geometry of the electron charge density in the enzyme’s active site to asses the effects of electrostatic preorganization. In support of this approach we study the convergence of features of the charge density as the size of the active site model increases in Histone Deacetylase 8. The magnitude of charge density at critical points and most Bader atomic charges are found to converge quickly as more of the protein is included in the simulation. The exact position of critical points however, is found to converge more slowly and be strongly influenced by the protein residues that are further away from the active site. We conjecture that the positions of critical points are affected through perturbations to the wavefunctions in the active site caused by dipole moments from amino acid residues throughout the protein. We further hypothesize that electrostatic preorganization, from the point of view of charge density, can not be easily understood through the charges on atoms or the nature of the bonding interactions, but through the relative positions of critical points that are known to correlate with reactivity and reaction barriers.

First author: Pathak, AD, Diffusive transport of water in magnesium chloride dihydrate under various external conditions for long term heat storage: A ReaxFF-MD study,
Abstract: Pure Magnesium chloride hydrates are exceptional materials for long term thermochemical heat storage. In a heat storage cycle, the material is charged by dehydration, taking up heat, and discharged by hydration, generating heat. On charging, the H2O molecules released by the dehydration reaction have to diffuse through the solid material. Gas-solid interactions play an important role in mass and heat transport throughout the volume of the storage materials. Under certain experimental conditions, the mass transport may become a rate-determining step. In order to simulate the complex reaction coupled diffusion process, a reliable MgCl2-H2O reactive forcefield (ReaxFF) is parameterized using a single parameter search algorithm. The parameters of ReaxFF are trained against a set of data obtained from density functional theory (DFT). ReaxFF-MD simulations are carried out on a 2D periodic slab of MgCl2 center dot 2H(2)O to simulate various possible operating conditions of temperature, external water vapor pressure, incomplete dehydration layers and various vacancy defects during a charging-discharging cycle. The diffusion coefficient of H2O through the 2D periodic slab of dihydrate is observed as 1.24 +/- 0.37 x 10(-10) m(2)/sec at 300 K. The diffusivity increases with temperature and follows the Arrhenius equation. External water molecules impede the dehydration and promote the diffusion of water. The vacancies of MgCl2 center dot 2H(2)O molecules are characterized using vibrational density of states obtained from ReaxFF-MD simulations. The vacancy concentrations for MgCl2 center dot 2H(2)O molecules have been varied from 1.38% to 4.16%, which result in a diffusivity enhancement from 32.9% to 107.7% when compared with perfect slab. The incomplete hydration at the surface and the mid-layer increases diffusivity by 76.7% and 75.0%.

First author: Braun, M, Multi-domain muffin tin finite element density functional calculations for small molecules,
Abstract: In this contribution a multi domain finite element density functional code for molecules is presented. The method makes use of higher order elements to enforce the continuity of the orbitals between the spherical domains and the interstitial domain. The salient computational details of the algorithm are described in some detail. Results of calculations for the orbital energies of methane, ethane, water, ammonia and benzene are given and compared with those obtained using GPAW.

First author: Gao, Y, Ce@Au-14: A Bimetallic Superatom Cluster with 18-Electron Rule,
Abstract: Doping of gold clusters and nanoparticles has received substantial attention due to their ability to encapsulate atoms and molecules. Here, the geometric and electronic properties of the cerium-encapsulated nanocage Ce@Au-14 are reported using density functional theory. Calculated results show that its ground electronic state is a singlet state and conforms to the superatomic 18-electron configuration of 1S (2)1P (6)1D (10) jellium state, both primarily involving the bonding interaction between s- and d-shell atomic orbitals of the Ce atom and superatomic orbitals of the hollow polyhedral Au-14 cage. In addition, it should be noted that f electrons in rare earth atoms trend to retain their localized state, and their doping in gold clusters could easily lead to clusters with large magnetic moments. However, in the case of superatom clusters, the f-shell electrons will be the preferential arrangement at the unfilled d-shell to satisfy the superatomic electron structure. Further analysis of the electronic structure also proves that the unoccupied 1F superatomic orbitals mainly originate from the contribution of the 4f-shell. As a consequence, this work provides a theoretical basis for the future design and synthesis of f-elements-encapsulated gold nanoclusters.

First author: Grabowski, K, Multiscale electro-mechanical modeling of carbon nanotube composites,
Abstract: This paper presents the development of a numerical framework for modeling of composite materials based on carbon nanotubes that are used in strain sensors. The proposed model allows for multiscale analysis of electro-mechanical properties of such systems. The model is composed of three scales, namely nano-, meso- and macro-scale. The nano-scale model bases on Molecular Dynamics simulations and provides information about elastic properties and density of the polymeric material and carbon nanotubes. Furthermore, the meso-scale model employs the Finite Element discretization and utilizes information from nano-scale for its constituents. At the meso-scale, electro-mechanical behavior of the CNT/polymer composite is investigated. Finally, stresses and conductivity from the meso-scale model are coupled to the macro-scale using the Hill-Mandel principle. Numerical framework is then validated and compared to experimental results.

First author: Liu, ZL, Observation of promoted C-O bond weakening on the heterometallic nickel-silver: Photoelectron velocity-map imaging spectroscopy of AgNi(CO)n(-),
Abstract: We report a joint experimental and theoretical study on heterodinuclear silver-nickel carbonyl clusters: AgNi(CO)n- and AgNi(CO)(n)(-) (n = 2, 3). The photoelectron spectra and photoelectron angular distribution provide information on the electronic structures and geometries of these complexes. Electron affinities of AgNi(CO)(2) and AgNi(CO)(3) are measured from the photoelectron velocity-map imaging spectra to be 2.29 +/- 0.03 and 2.32 +/- 0.03 eV, respectively. The complementary theoretical calculations at the B3LYP level and Franck- Condon simulations are performed to establish their geometrical structures. The C- O stretching modes are activated upon photodetachment and determined to be 2024 and 2028 cm(-1) for AgNi(CO)(2) and AgNi(CO)(3), respectively, which are notably red- shifted with respect to those of corresponding unsaturated binary nickel carbonyls. These findings will shed light on the promoted C-O bond weakening by the introduction of a foreign atom to binary unsaturated TM carbonyl complexes. Published by AIP Publishing.

First author: Baron, M, Gold(III) Bis(di-N-heterocyclic carbene) Square Planar Trication with Axial Ligand Interactions with Bromides from Ag/Br Counteranion Assemblies,
ORGANOMETALLICS, 36, 2285, (2017)
Abstract: The mononuclear tricationic bis(di-N-heterocyclic carbene) gold(III) complex 1(3+) of formula [Au-(MeImCH(2)ImMe)(2)](3+) (Im = imidazol-2-ylidene) was successfully synthesized by transmetalation of the di(N-heterocyclic carbene) ligand from the corresponding silver(I) complex to KAuBr4. The counteranion of the gold(III) cationic complex depends on the synthetic procedure. The crude product, isolated by the transmetalation reaction, consists of infinite (Ag4Br73-)(n) ribbons. By adding a stoichiometric amount of AgPF6, the complete precipitation of AgBr is achieved, and the counteranions are PF6-. If substoichiometric amounts of silver salts are added, then the (Ag4Br73-)(n) ribbon breaks, and silverbromides anionic aggregates of lower nuclearity are obtained, for example, Ag2Br64-. The X-ray crystal structures of 1-Ag4Br7, 1-PF6, and 1-Br,(Ag2Br6)(0.5) were determined. The complexes with any type of bromide present interactions between the Au center and two bromides of the counteranions so that the geometry around gold is pseudo-octahedral. The gold-bromide interaction has been investigated via DFT calculations and is mainly electrostatic.

First author: D’Amore, L, Unraveling the Anion/Ligand Interplay in the Reaction Mechanism of Gold(I)-Catalyzed Alkoxylation of Alkynes,
ORGANOMETALLICS, 36, 2364, (2017)
Abstract: In this work DFT calculations have been performed to investigate the anion/ligand interplay in the reaction mechanism of alkoxylation of alkynes promoted by gold(I) catalysts of general formula [L-Au-X] (L = NHC, P(Bu-t)(3) and X = OTs-, OTf-, BF4-, TFA(-)) on the basis of available experimental data. The observed catalytic efficiency trend in this series of compounds strictly depends on the specific anion/ligand combination used, thus suggesting that it cannot be estimated by evaluating the properties of L and X separately. Similarly to [NHC-Au-X], for the [P((t)3u)(3)-Au-X] catalyst series, we demonstrate that the anion effect in the reaction mechanism can be predicted on the basis of its coordinating/proton acceptor properties. A comparison between the P(Bu-t)(3)/OTs- and NHC/OTs- settings shows that the anion/ligand interplay has a crucial role in the nucleophilic attack step of the reaction mechanism. A charge-displacement (CD) analysis reveals that the activation of the unsaturated hydrocarbon multiple bond (alkyne) by the [L-Au](+) fragment depends both on the ligand-withdrawing ability at the outer region of the CC bond and on the counterion affinity for the, cationic fragment, both affecting in the opposite way the electrophilic character of the alkyne at the transition state.

First author: Zhang, WW, Second-Generation ReaxFF Water Force Field: Improvements in the Description of Water Density and OH-Anion Diffusion,
Abstract: Hydronium (H3O+) and hydroxide (OH-) ions have anomalously large diffusion constants in aqueous solutions due to their combination of vehicular and Grotthuss hopping diffusion mechanisms. An improvement of the ReaxFF reactive water force field on the basis of our first-generation water force field (water-2010) is presented to describe the proton transfer (PT) mechanisms of H3O+ and OH- in water. Molecular dynamics simulation studies with the water-2017 force field support the Eigen-Zundel-Eigen mechanism for PT in acidic aqueous solution and reproduce the hypercoordinated solvation structure of the OH- in a basic environment. In particular, it predicts the correct order of the diffusion constants of H2O, H3O+, and OH- and their values are in agreement with the experimental data. Another interesting observation is that the diffusion constants of H3O+ and OH- are close to each other at high concentration due to the strong correlation between OH- ions in basic aqueous solution. On the basis of our results, it is shown that ReaxFF provides a novel approach to study the complex acid-base chemical reactions in aqueous solution with any pH value.

First author: Lee, D, Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor-Acceptor Molecular Dyads,
Abstract: We simulate subpicosecond charge separation in two donor acceptor molecular dyads. Charge separation dynamics is described using a quantum master equation, with parameters of the dyad Hamiltonian obtained from density functional theory (DET)rand time dependent density functional theory (TDDFT) calculations and the rate of energy dissipation estimated from Ehrenfest-TDDFT molecular dynamics simulations. We find that higher-energy charge transfer states must be included in the dyad Hamiltonian in order to obtain agreement of charge separation rates with the experimental values. Our results show that efficient and irreversible charge separation involves both coherent election transfer from the donor excited state to higher-energy unoccupied states on the acceptor and incoherent energy dissipation that relaxes the dyad to the lowest,energy charge transfer state. The role of coherence depends on the initial excited state, with electron delocalization within Hamiltonian eigenstates found to be mote important than coherence between eigenstates. We conclude that ultrafast charge separation is most likely to occur in donor acceptor dyads possessing dense manifolds of charge transfer states at energies close to those of Frenkel excitons on the donor, with strong couplings to these states enabling partial delocalization of eigenstates over acceptor and donor.

First author: Wong, YTA, Dynamic Disorder and Electronic Structures of Electron-Precise Dianionic Diboranes: Insights from Solid-State Multinuclear Magnetic Resonance Spectroscopy,
Abstract: The J(B-11,B-11) coupling constants of various salts of the electron-precise hexacyanodiborane(6) dianion, [B-2(CN)(6)](2-), were obtained using B-11 double-quantum filtered (DQF) J-resolved solid-state nuclear magnetic resonance (SSNMR) spectroscopy. Our results show that the magnitude of the DQF J splitting is influenced by both the crystallographic symmetry of the system and the presence of dynamics. The :splittings are amplified by a factor of 3 as compared to the corresponding theoretical J coupling constants for cases where (1) there is an absence of dynamics but the boron pairs are crystallographically equivalent or (2) the boron pairs are crystallographically inequivalent but are rendered magnetically equivalent on the time scale of the experiment due to dynamic disorder, which was identified by B-11 and C-13 SSNMR experiments. Consequently, molecular motions-need to-be taken into consideration when interpreting the results of DQF J-resolved experiments, and conversely, these experiments maybe used to identify dynamic disorder. Variable-temperature NMR data support the notion of three different motional processes with correlation times ranging from 10(2) to 10(6) s(-1) over the temperature range of 248-306 K. When molecular motion and crystallographic symmetry are both accounted for, the J(B-11,B-11) coupling constants for various [B-2(CN)(6)](2-) salts were measured to range from 29.4 to 35.8 Hz, and their electronic origins were determined using natural localized molecular orbital and natural bond orbital analyses. The coupling constants were found to strongly correlate to the hybridization states of the boron orbitals that form the B-B bonds and to the strength of the B-B bonds. This study provides a novel tool to study dynamics in ordered and disordered solids and provides new perspectives on electron-precise dianionic diboranes featuring two-center-two-electron bonds in the context of related compounds featuring multiply and singly bonded boron spin pairs.

First author: Xu, DX, Unusual spin-polarized electron state in fullerene induced by carbon adatom defect,
NANOSCALE, 9, 7875, (2017)
Abstract: First-principles calculations show that a carbon adatom defect at the Def[5, 6] site on the surface of C-60 can produce a more stable spin-polarized singlet electronic state instead of a magnetic triplet state. This is clearly different from the cases of graphene and nanotubes. The mechanism results from the electron population of the adatom, which produces antiferromagnetic coupling around the C-60 cage and the adatom itself. Our calculations show the same phenomenon occurs in other IPR fullerenes, such as C-70 and C-80. These findings extend the understanding of the magnetic origin of pure carbon structures and are valuable for research related to the spin polarization of carbon systems.

First author: Sebera, J, Tuning Charge Transport Properties of Asymmetric Molecular Junctions,
Abstract: Charge transport characteristics of asymmetric :molecules containing a 9,9 ‘-spirobitluorene platform coupled covalently to a phenylene ethynylene linker capped with either a thiol or a nitrile end group are investigated by break junction techniques. It is shown that the platform provides very good electronic coupling with metallic leads and the differences in the charge transport depend solely on the type of the anchoring group at the opposite end of the molecule. The SH-terminated molecule has 1 order of magnitude higher conductance compared to the CN-terminated one, and the charge transport path depends on the end,group utilized. By a combined :experimental break junction techniques and theoretical DFT calculations, it was demonstrated that in molecules containing SH- terminated phenylene ethynylene Wire attached to the 9,9 ‘-spirobifluorerie platform the charge is transported through fluorene unit and covalently coupled :phenylene ethynylene linker.’ For CN-terminated molecules charge is transported through the thiolate termini olthe 9,9 ‘-spirobifluorene tripod. These :studies demonstrate the potential of spinbifluorene platform for the bottom-up approach to Molecular architectures by its immobilization with all three thiol groups to one of the electrodes without compromising,charge transport via the conjugated backbone.

First author: Gopi, R, Experimental evidence for the blue-shifted hydrogen-bonded complexes of CHF3 with pi-electron donors,
Abstract: Blue-shifted hydrogen-bonded complexes of fluoroform (CHF3) with benzene (C6H6) and acetylene (C2H2) have been investigated using matrix isolation infrared spectroscopy and ab initio computations. For CHF3-C6H6 complex, calculations performed at the B3LYP and MP2 levels of theory using 6-311 ++G (d,p) and aug-cc-pVDZ basis sets discerned two minima corresponding to a 1:1 hydrogen-bonded complex. The global minimum correlated to a structure, where the interaction is between the hydrogen of CHF3 and the pi-electrons of C6H6 and a weak local minimum was stabilized through H center dot center dot center dot F interaction. For the CHF3-C2H2 complex, computation performed at MP2/aug-cc-pVDZ level of theory yielded two minima, corresponding to the cyclic C-H center dot center dot center dot pi complex A (global) and a linear C-H center dot center dot center dot F (n-sigma) complex B (local). Experimentally a blue-shift of 32.3 cm(-1) and 7.7 cm(-1) was observed in the nu(1) C-H stretching mode of CHF3 sub-molecule in Ar matrix for the 1:1 C-H center dot center dot center dot pi complexes of CHF3 with C6H6 and C2H2 respectively. Natural bond orbital (NBO), Atoms-in-molecule (AIM) and energy decomposition (EDA) analyses were carried out to explain the blue-shifting and the nature of the interaction in these complexes.

First author: Grover, CJ, Ionic versus metallic bonding in AlnNam and AlnMgm (m <= 3, n + m <= 15) clusters,
Abstract: First principles electronic structure studies on the ground state geometries, stability, and the electronic structure of AlnNam and AlnMgm (m <= 3, n + m <= 15) clusters have been carried out to examine the nature of bonding between Na or Mg and Al. Identifying whether the bonding is ionic or metallic in bulk materials is typically straightforward; however, in small clusters where quantum confinement is important, the nature of bonding may become unclear. We have performed a critical analysis of the bonding in these bimetallic clusters using charge analysis, electrical dipole moments, hybridization of the atomic orbitals, the Laplacian of the charge density at the bond critical points, and the change in the bonding energy between neutral and anionic forms of the cluster. For NanAlm clusters, we find that the Na binding is primarily ionic, while the bonding in AlnMgm is primarily metallic. We find that the Mulliken population of the 3p orbital of Na and Mg can provide a rapid assessment of the nature of bonding. We also find that the Hirshfeld charge and dipole moments are effective indicators, when placed in context. We found that the Laplacian of the charge density at the bond critical points can be misleading in identifying whether the bonding is ionic or metallic in small clusters. Published by AIP Publishing.

First author: Mahmoudi, G, Polar protic solvent-trapping polymorphism of the Hg-II-hydrazone coordination polymer: experimental and theoretical findings,
CRYSTENGCOMM, 19, 3017, (2017)
Abstract: A novel series of Hg-II coordination polymers with a general formula [HgL(N)(3)](n)center dot n(solv) (HL = 2-pyridinecarbaldehyde isonicotinoylhydrazone; n(solv) = 0.5H(2)O (1), 2MeOH (2), EtOH (3), PrOH (4) and 0.5BuOH (5)) was prepared and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The crystal structure of HL, elucidated by X-ray diffraction, comprises two independent molecules in the asymmetric unit cell, each of which is stabilized by an intramolecular hydrogen bond formed between the carbohydrazide hydrogen atom and the 2-pyridyl nitrogen atom. Crystal structures of 1-5 each reveal a similar 1D zigzag metal-organic chain [HgL(N)(3)] n, where the organic ligands bridge metal centers. These chains are extended into distinct 2D supramolecular nets by strong hydrogen bonds with the solvent molecules and/or short Hg center dot center dot center dot N supramolecular contacts. These networks were topologically classified as the hcb in 1 and fes in 2-5 underlying nets. On comparing the H-bonding patterns, it can be concluded that the lattice water molecules in 1 and methanol molecules in 2 form H-bonding interactions with the O and amide N atoms of L in the former structure and the O atom of L in the latter structure. In the remaining coordination compounds, the lattice solvent prefers the azide N atom for H-bonding. Furthermore, the existence of Hg center dot center dot center dot N interactions in 2-5 and their absence in 1 clearly highlights the importance of the size and polarity of the solvents on the self-assembly generation of Hg-II coordination polymers. A broad network of intermolecular pi center dot center dot center dot pi stacking interactions, formed between the pyridyl fragments, provide further reinforcement of crystal packing patterns in the structures of HL and 2-5. DFT based charge and energy decomposition scheme (ETS-NOCV) was applied to characterize the obtained polymers.

First author: Morgenstern, A, Predicting Chemical Reactivity from the Charge Density through Gradient Bundle Analysis: Moving beyond Fukui Functions,
Abstract: Predicting chemical reactivity is a major goal of chemistry. Toward this end, atom condensed Fukui functions of conceptual density functional theory have been used to predict which atom is most likely to undergo electrophilic or nucleophilic attack, providing regioselectivity information. We show that the most probable regions for electrophilic attack within each atom can be predicted through analysis of gradient bundle volumes, a property that depends only on the charge density of the neutral molecules. We also introduce gradient bundle condensed Fukui functions to compare the stereoselectivity information obtained from gradient bundle volume analysis. We demonstrate this method using the test set of molecular fluorine, oxygen, nitrogen, carbon monoxide, and hydrogen cyanide.

First author: Baranac-Stojanovic, M, Theoretical study of azido gauche effect and its origin,
NEW JOURNAL OF CHEMISTRY, 41, 4644, (2017)
Abstract: The strength of the azido gauche effect in 1,2-diazidoethane, N-(2-azidoethyl)ethanamide, (protonated) 2-azidoethanamine and (protonated) 2-azidoethanol and its origin were theoretically studied at the MP2/6-311++G(d,p) level of theory. The results show that the azido gauche effect in the amine and alcohol can exert a control over the molecular conformation to a similar extent as the fluorine gauche effect, but to a greater extent in the charged species, amide and vicinal diazido fragment. A quantitative partitioning of isomerization energy into contributions from electrostatic, orbital, dispersion and Pauli interactions and energy consumed in structural changes revealed that electrostatic forces play an important role in the stabilization of the gauche isomer in the two charged species and alcohol. Electrostatic and dispersion interactions are the main contributors to the gauche effect in the amide, whereas dispersion and orbital interactions can be considered to be the two most important stabilizing factors of the gauche form in the vicinal diazido fragment. The interplay of all three stabilizing interactions determines the gauche preference in the amine. Stereoelectronic effects, which are involved in orbital interactions, contribute to the gauche effect in all the molecules except the 2-azidoethylammonium ion and protonated 2-azidoethanol. Hydrogen-bonding interactions were found only in the protonated alcohol.

First author: Castro, AC, The influence of substituents and the environment on the NMR shielding constants of supramolecular complexes based on A-T and A-U base pairs,
Abstract: In the present study, we have theoretically analyzed supramolecular complexes based on the Watson-Crick A-T and A-U base pairs using dispersion-corrected density functional theory (DFT). Hydrogen atoms H8 and/or H6 in the natural adenine and thymine/uracil bases were replaced, respectively, by substituents X8, Y6 = NH-, NH2, NH3+ (N series), O-, OH, OH2+ (O series), F, Cl or Br (halogen series). We examined the effect of the substituents on the hydrogen-bond lengths, strength and bonding mechanism, and the NMR shielding constants of the C2-adenine and C2-thymine/uracil atoms in the base pairs. The general belief in the literature that there is a direct connection between changes in the hydrogen-bond strength and the C2-adenine shielding constant is conclusively rejected by our computations.

First author: Ji, LF, Theoretical investigations into the charge transfer properties of thiophene alpha-substituted naphthodithiophene diimides: excellent n-channel and ambipolar organic semiconductors,
Abstract: A theoretical study was carried out to investigate the electronic structures and the charge transport properties of a series of naphthodithiophene diimide (NDTI) thiophene alpha-substituted derivatives NDTI-X using density functional theory and classical Marcus charge transfer theory. This study deeply revealed the structure-property relationships by analyzing the intermolecular interactions in crystal structures of C8-NDTI and C8-NDTI-Cl thoroughly by using the Hirshfeld surface, QTAIM theories and symmetry-adapted perturbation theory (SAPT). Our results suggested that a 2-D brick-like pi-stacking structure makes C8-NDTI-Cl a more excellent n-type semiconducting material with mu(max-e) of 2.554 cm(2) V-1 s(-1) than C8-NDTI with a herringbone-like slipped pi-stacking motif. In addition, the calculated results showed that by modifying the thiophene alpha-positions of NDTI with electron-withdrawing substituents, -F, -Cl and -CN, low-lying LUMO energy levels and a high adiabatic electron affinity EA(a) can be obtained; while introducing electron-donating groups, benzene (-B), thiophene (-T), benzo[b]thiophene (-BT) and naphtha[2,3-b]thiophene (-NT), expanded the molecular pi-conjugated backbone, and narrow band gaps, high EA(a) and small reorganization energies can be obtained. Theoretical simulations predict that NDTI-CN is an excellent air-stable n-type organic semiconducting material with an average electron mobility mu(e) of up to 1.743 cm(2) V-1 s(-1). Owing to their high EA(a), moderate adiabatic ionization potential IP(a) as well as small hole and electron reorganization energies, NDTI-BT and NDTI-NT are two well-balanced air-stable ambipolar semiconducting materials. The theoretical average hole/electron mobilities are as high as 2.708/3.739 cm(2) V-1 s(-1) for C8-NDTI-NT and 1.597/2.350 cm(2) V-1 s(-1) for C8-NDTI-BT, respectively.

First author: Arshad, S, Synthesis, XRD crystal structure, spectroscopic characterization, local reactive properties using DFT and molecular dynamics simulations and molecular docking study of (E)-1-(4-bromophenyl)-3-(4-(trifluoromethoxy)phenyl)prop-2-en-1-one,
Abstract: In the present study, the title compound named as (E)-1-(4-bromophenyl)-3-(4-(trifluoromethoxy)phenyl) prop-2-en-l-one was synthesized and structurally characterized by single-crystal X-ray diffraction. The FT-IR spectrum was recorded and interpreted in details with the aid of Density Functional Theory (DFT) calculations and Potential Energy Distribution (PED) analysis. Average local ionization energies (ALIE) and Fukui functions have been used as quantum-molecular descriptors to locate the molecule sites that could be of importance from the aspect of reactivity. Degradation properties have been assessed by calculations of bond dissociation energies (BDE) for hydrogen abstraction and the rest of the single acyclic bonds, while molecular dynamics (MD) simulations were used in order to calculate radial distribution functions and determine the atoms with significant interactions with water. In order to understand how the title molecule inhibits and hence increases the catalytic efficiency of MOA-B enzyme, molecular docking study was performed to fit the title compound into the binding site of MOA-B enzyme.

First author: Varaksin, KS, Towards a physical interpretation of substituent effect: Quantum chemical interpretation of Hammett substituent constants,
Abstract: Quantitative description of substituent effects is of a great importance especially in organic chemistry and QSAR-type treatments. The proposed approaches: substituent effect stabilization energy (SESE) and charge of the substituent active region (cSAR) provide substituent effect characteristics, physically independent of the Hammett’s substituent constants, sigma. To document abilities of these descriptors the B3LYP/6-311++G(d,p) method is employed to examine changes in properties of a reaction center Y (Y = COOH or COO- groups) and a transmitting moiety (benzene ring) due to substituent effects in a series of meta- and para-X-substituted benzoic acid and benzoate anion derivatives (X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO). The transmitting moiety is described by aromaticity indices HOMA and NICS(1). Furthermore, an advantage of the cSAR characteristic is the ability to use it to describe both electron donating/accepting properties of a substituent as well as a reaction center. It allows demonstration of the reverse substituent effects of COOH and COO- groups on substituent X.

First author: Manzetti, S, State-of-the-art developments in metal and carbon-based semiconducting nanomaterials: applications and functions in spintronics, nanophotonics, and nanomagnetics,
Abstract: Nanomaterials composed of metals and metal alloys are the most valuable components in emerging micro-and nano-electronic devices and innovations to date. The composition of these nanomaterials, their quantum chemical and physical properties, and their production methods are in critical need of summarization, so that a complete state of the art of the present and future of nanotechnologies can be presented. In this review, we report on the most recent activities and results in the fields of spintronics, nanophotonics, and nanomagnetics, with particular emphasis on metallic nanoparticles in alloys and pure metals, as well as in organic combinations and in relation to carbon-based nanostructures. This review shows that the combinatory synthesis of alloys with rare metals, such as scandium, yttrium, and rare earths imparts valuable qualities to high-magnetic-field compounds, and provides unique properties with emphasis on nanoelectronic and computational components. In this review, we also shed light on the methods of synthesis and the background of spintronic, nanomagnetic, and nanophotonic materials, with applications in optics, diagnostics, nanoelectronics, and computational nanotechnology. The review is important for the industrial development of novel materials, and for summarizing both fabrication and manufacturing methods, as well as principles and functions of metallic nanoparticles.

First author: Li, SHL, Franck-Condon Models for Simulating the Band Shape of Electronic Absorption Spectra,
Abstract: Band shape is an essential ingredient in the simulation of electronic absorption spectra. The excitation of multiple series of vibrational levels during an electronic excitation is a main contributor to band shapes. Here we present two simple models based on the Franck-Condon displaced-harmonic-oscillator model. The models are both derived from the time-dependent formulation of electronic spectroscopy. They assume that the transition dipoles do not depend on geometry and that the potential energy surfaces are locally quadratic; one model is second order in time and is called LQ2, and the other is third order in time and is called LQ3. These models are suitable for simulating the unresolved vibronic band shapes of electronic spectra that involve many vibrational modes. The models are straightforward and can be easily applied to simulate absorption spectra that are composed of many electronic transitions. As compared to carrying out molecular dynamics simulations, they require relatively few electronic structure calculations, and the additional cost for constructing the spectra is negligible. Therefore, the models are suitable for simulating the spectra of complex systems such as transition-metal complexes.

First author: Orenha, RP, Nature of the Ru-NO Coordination Bond: Kohn-Sham Molecular Orbital and Energy Decomposition Analysis,
CHEMISTRYOPEN, 6, 410, (2017)
Abstract: We have analyzed structure, stability, and Ru-NO bonding of the trans-[RuCl(NO)(NH3)(4)](2+) complex by using relativistic density functional theory. First, we focus on the bond dissociation energies associated with the three canonical dissociation modes leading to [RuCl(NH3)(4)](+)+NO+, [RuCl(NH3)(4)](2+)+NO, and [RuCl(NH3)(4)](3+)+NO-. The main objective is to understand the Ru-NO+ bonding mechanism in the conceptual framework of Kohn-Sham molecular orbital theory in combination with a quantitative energy decomposition analysis. In our analyses, we have addressed the importance of the synergism between Ru-NO+ sigma-donation and pi-backdonation as well as the so-called negative trans influence of the Cl- ligand on the Ru-NO bond. For completeness, the Ru-NO+ bonding mechanism is compared with that of the corresponding Ru-CO bond.

First author: Molina, V, Aromaticity introduced by antiferromagnetic ligand mediated metal-metal interactions. Insights from the induced magnetic response in [Cu-6(dmPz)(6)(OH)(6)],
Abstract: [trans-Cu(mu-OH)(mu-dmpz)](6) (1) exhibits six Cu(II) centers effectively coupled through a ligand mediated mechanism leading to a diamagnetic ground state over a wide temperature range. Here we investigate further magneto-structural correlations based on the possible free electron precession along such a copper-based ring-like nanocoil mediated by bridging ligands. We find that in 1, mediated antiferro-magnetic coupling leads to characteristics that induce aromatic ring behavior through evaluation of both induced currents and shielding of cones from a relativistic density functional theory level. According to our gauge calculations including magnetically induced current densities and an induced magnetic field, a sizable ring current strength susceptibility is obtained for the cyclic Cu-N-N-Cu and Cu-O-Cu pathways, allowing a magnetic exchange between the copper centers. Our study suggests that [Cu-6(dmPz)(6)(OH)(6)] consisting of an aromatic ring structure displays aromaticity and superexchange along the Cu-O-Cu and Cu-N-N-Cu backbones, which accounts for 80% and 20% of the overall ring current strength susceptibility, respectively. This reveals the presence of particular aromatic ring characteristics in coordination compounds without a direct metal-metal bond, where several formally paramagnetic centers are antiferromagnetically-coupled through supporting ligands. We envisage that our findings can be extended to other examples depicting ligand-mediated interaction between metal centers.

First author: Lalitha, M, Interface energetics of [Emim](+)[X](-) and [Bmim](+)[X](-) (X = BF4, Cl, PF6, TfO, Tf2N) based ionic liquids on graphene, defective graphene, and graphyne surfaces,
Abstract: The interfacial interaction between the ionic liquids (ILs) and the 2d surfaces is of primary importance for the better outcome of the energy storage devices. The interaction of ILs such as [Emim](+)[X](-) and [Bmim](+)[X](-) (X = BF4, Cl, PF6, TfO, Tf2N) on graphene, STW defective graphene, and graphyne surfaces are studied using Density Functional Theory (DFT) methodology. The adsorption of IL on the surface is mainly via the cationic imidazolium ring driven through van der Waals interaction and in particular, Cl- containing IL exhibits pi-pi stacking with the surface. ILs containing the Cl- anion exhibits stronger interaction with the considered surfaces. The effect of the increase in the alkyl chain length on adsorption is trivial except for Cl- based ILs. The effect of intrinsic pores on the surface has a significant impact on the IL adsorption rather than the in-plane defects, evident through the adsorption characteristics of IL on graphyne. The interaction between anion-cation in ILs reduces in the range 0.8%-10% in the vicinity of the surface. Minimal change in the anion-cation interaction in the vicinity of the surface strengthens adsorption. Thermochemical parameters indicate possible desorption of ionic liquids. NPA charge analysis indicates that ILs donate charges to the carbon surfaces.

First author: Pan, S, Ligand-Supported E-3 Clusters (E = Si-Sn),
Abstract: The interaction among E-3 (E = Si, Ge, Sn) clusters and different ligands (L) encompassing five carbon-based donors (cyclic (alkyl)(amino)carbene (cAAC), N-heterocyclic carbene (NHC), saturated NHC (SNHC), mesoionic carbenes (MIC1, and MIC2)), two nitrogen-based donors (trimethylamine and pyridine), and two phosphorous-based donors (phosphinine and trimethylphosphine) in E-3(L)(3) complexes is explored through DFT computations. Although all carbenes form very strong bonds with E-3 clusters, cAAC makes the strongest bond with Si-3 and Ge-3 clusters, and MIC1 with the Sn-3 cluster. Nevertheless, other ligand-bound complexes are also viable at room temperature. This finding indicates that experimentalists may make use of them to synthesize the desired clusters based on precursor availability. The nature of the interaction in E-L bonds is analyzed through natural bond orbital analysis; energy decomposition analysis, in combination with the natural orbital for chemical valence; and adaptive natural density partitioning analysis. The L -> E sigma-donation and L <- E pi-back-donation play important roles in making contacts between L and E-3 clusters favorable; where the former is significantly more dominant over the latter.

First author: Gaggioli, CA, Modulating the Bonding Properties of N-Heterocyclic Carbenes (NHCs): A Systematic Charge-Displacement Analysis,
Abstract: In view of their intensive use as ligands in many reactions catalyzed by transition-metal complexes, modulation of the bonding properties of N-heterocyclic carbenes (NHCs) on a rational basis is highly desirable, which should enable optimization of current applications or even promote new functions. In this paper, we provide a quantitative analysis of the chemical bond between a metal fragment AuCl and a series of 29 different NHCs in [(NHC) AuCl] complexes. NHCs electronic properties are modified through: i) variation of the groups attached to the NHC nitrogen atoms or backbone; ii) change of unsaturation/ size of the NHC ring; iii) inclusion of paracyclophane moieties; or iv) heteroatom substitution on the NHC ring. For evaluating the donation and back-donation components of the Dewar-Chatt-Duncanson (DCD) model in the NHC-AuCl bond, we apply the charge-displacement (CD) analysis within the NOCV (natural orbitals for chemical valence) framework, a methodology that avoids the constraint of using symmetrized structures. We show that modulation of the NHC bonding properties requires substantial modification of their structure, such as, for instance, insertion of two ketone groups into the NHC backbone (which enhances the pi back-donation bond component and introduces an effective electronic communication within the NHC ring) or replacement of a nitrogen atom in the ring with an sp(3) or sp(2) carbon atom (which increases and decreases the p back-donation bond component, respectively). We extend our investigation by quantitatively comparing the NHC electronic structures for a subset of 13 NHCs in [(NHC)PPh] adducts, the P-31 NMR chemical shift values of which are experimentally available. The latter have been considered as a suitable tool for measuring the NHCs p acceptor properties [Bertrand et al., Angew. Chem. Int. Ed. 2013, 52, 2939-2943]. We show that information obtained using the metal fragment can be transferred to the PPh moiety and vice versa. However, the 31P NMR chemical shift values only qualitatively correlate with the p acceptor properties of the NHCs, with the stronger p acidic carbenes as the most outliners.

First author: Hu, ZW, Importance of double-resonance effects in two-photon absorption properties of Au-25(SR)(18)(-),
CHEMICAL SCIENCE, 8, 4595, (2017)
Abstract: The two-photon absorption (TPA) cross-sections of small thiolate-protected gold clusters have been shown to be much larger than typical small organic molecules. In comparison with larger nanoparticles, their TPA cross-sections per gold atom are also found to be larger. Theoretical simulations have suggested that the large enhancement of these TPA cross-sections comes from a one-photon double-resonance mechanism. However, it remains difficult to simulate TPA cross-sections of thiolate-protected gold clusters due to their large system size and a high density of states. In this work, we report a time-dependent density functional theory (TDDFT) study of the TPA spectra of the Au-25(SR)(18)(-) cluster based on a damped response theory formalism. Damped response theory enables a consistent treatment of on-and off-resonance molecular properties even for molecules with a high density of states, and thus is well-suited for studying the TPA properties of gold clusters. Our results indicate that the one-and two-photon double-resonance effect is much smaller than previously found, and thus is unlikely to be the main cause of the large TPA cross-sections found experimentally. The effect of symmetry breaking of the Au-25(SR)(18)(-) cluster due to the ligands on the TPA cross-sections has been studied and was found to only slightly increase the cross-section. Furthermore, by comparing with larger nanoparticles we find that the TPA cross-section per gold atom scales linearly with the diameter of the particles, and that the Kerr non-linear response of the Au-25(SR)(18)(-) cluster is on the same order as that of bulk gold films.

First author: Zheng, XJ, Infrared vibrational spectra, electronic structures, and formation reactions of polypyrrolic mono- and bis-actinyl complexes: A relativistic DFT study,
Abstract: The development of synthetic techniques has enabled synthesis and characterization of a series of mono and bis-uranyl complexes of octadentate polypyrrolic macrocycles such as aryl-lined H4LAr and anthracenyl-linked H4L, which is complemented by theoretical investigation via extending to more toxic and radioactive transuranics. The relativistic density functional theory (DFT) study has been dedicated to twelve actinyl complexes supported by the H4L ligand. The actinides include U, Np, and Pu elements, and either one or two is rendered in complexes with oxidation states of V or VI. Calculated symmetric/asymmetric An = O stretching vibrational frequencies show the decreasing trend along U, Np, and Pu, which is consistent with calculated bond orders. The hydrogen bonds between -yl endo-oxo and remaining hydrogen atoms of pyrrolides in mononuclear complexes cause pronounced redshift of An = O vibrational frequencies compared to those in binuclear complexes, so does the reduction from hexa-to pentavalent complexes. The electronic structures of actinyl complexes were calculated. For example, B-pyU(VI) possesses low-lying U(5f)-character virtual orbitals, where f(delta) and f(phi) orbitals occur in low-energy region and pi-type ones are residing further high; the sigma*(U = O) and sigma(U = O) orbitals are significantly split over 7 eV. The previous experimental observation that the 1: 1 reactions between uranyl salts and the macrocycle tend to give a mixture of bis- and mono-uranyl complexes, with bis- the major product, has been corroborated by computational studies of the thermodynamics of the reactions.

First author: Cisterna, J, Nickel(II) and copper(II) complexes of new unsymmetrically-substituted tetradentate Schiff base ligands: Spectral, structural, electrochemical and computational studies,
Abstract: The synthesis, spectroscopic and structural characterization, electrochemical properties and theoretical studies of a series of eight robust neutral Nickel(II) and Copper(II) complexes (4-11) supported by unsymmetrically-substituted N2O2-tetradentate Schiff base ligands are reported. The M(salophen)-type compounds are substituted by either a pair of donor (anisyl, ferrocenyl, methoxy) or acceptor (fluoro, nitro) groups, forming D-pi-D and A-pi-A systems, respectively. The compounds were prepared in good yields by condensation of the free amino group of the desired ONN-tridentate half-unit with the appropriate substituted salicylaldehyde in the presence of hydrated Nickel(II) or Copper(II) acetate salts. They were characterized by elemental analysis, FT-IR, UV-vis, and for diamagnetic species by multinuclear NMR spectroscopy, mass spectrometry and cyclic voltammetry. The crystal structures of one Ni(II) (4) and four Cu(II) complexes (5, 7, 9 and 11) revealed a four-coordinate square-planar environment for the nickel and copper metal ions, with two nitrogen and two oxygen atoms as donors. In 4, 5, 7 and 9, the crystallization solvent interacts through hydrogen bonding with the phenolato oxygen atoms of the Schiff base pocket, while 11 packs as centrosymmetric dimers with an apical CuAO short contact interaction (2.63 angstrom). the cyclovoltammograms of the nickel complexes present an irreversible monoelectronic Ni(II)/Ni(I) reduction wave while those of their copper counterparts exhibit a reversible or quasi-reversible one-electron Cu(II)/Cu(I) redox process. The electronic structures of the eight complexes were analyzed by DFT and TD-DFT calculations.

First author: Zabardasti, A, The S center dot center dot center dot P noncovalent interaction: diverse chalcogen bonds,
Abstract: The S center dot center dot center dot P interactions in the complexes of HSX (X=F, Cl, Br, I) with PHnMe3-n(n=0-3) have been investigated with ab initio calculations at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ//MP2/aug-cc-pVDZ level of theory. The interaction energies and structural properties of intermolecular complexes have been analyzed. Results of QTAIM analysis are dealing with expand of interactions, including pure closed-shell interactions (van der Waals interactions and chalcogen bonding, YB), partially covalent closed-shell (CS; Charge Transfer) and shared-shell interactions (SS; weak covalent bond and very strong YB) for these complexes. The energy decomposition analysis (EDA) showed that electrostatic interactions are an important contributing factor for these complexes. In considering second-order contributions, the donor-acceptor pair charge transfer (CT) is most important. These findings are consistent with the Electron Localization Function (ELF) isosurface of the complexes. In each series of HXS:PHnMe3-n-chalcogen bond complexes with increasing basicity of phosphines, the stability and S center dot center dot center dot P bond strength of adducts were increased so that the HXS:PMe3 (X=F, Cl, Br) complexes had very strong S center dot center dot center dot P chalcogen interactions with nearly covalent characters.

First author: Bora, PL, Supramolecular Covalence in Bifurcated Chalcogen Bonding,
Abstract: Supramolecular interactions are generally classified as noncovalent. However, recent studies have demonstrated that many of these interactions are stabilized by a significant covalent component. Herein, for systems of the general structure [MX6](2-): YX2 (M= Se or Pt; Y= S, Se, or Te; X= F, Cl, Br, I), featuring bifurcated chalcogen bonding, it is shown that, although electrostatic parameters are useful for estimating the long-range electrostatic component of the interaction, they fail to predict the correct order of binding energies in a series of compounds. Instead, the Lewis basicity of the individual substituents X on the chalcogen atom governs the trends in the binding energies through fine-tuning the covalent character of the chalcogen bond. The effects of substituents on the binding energy and supramolecular electron sharing are consistently identified by an arsenal of theoretical methods, ranging from approaches based on the quantum chemical topology to analytical tools based on the localized molecular orbitals. The chalcogen bonding investigated herein is driven by orbital interactions with significant electron sharing; this can be designated as supramolecular covalence.

First author: Michael, JR, On the error in the nucleus-centered multipolar expansion of molecular electron density and its topology: A direct-space computational study,
Abstract: The convergence of nucleus-centered multipolar expansion of the quantum-chemical electron density (QC-ED), gradient, and Laplacian is investigated in terms of numerical radial functions derived by projecting stockholder atoms onto real spherical harmonics at each center. The partial sums of this exact one-center expansion are compared with the corresponding Hansen-Coppens pseudoatom (HC-PA) formalism [Hansen, N. K. and Coppens, P., “Testing aspherical atom refinements on smallmolecule data sets,”Acta Crystallogr., Sect. A34, 909-921 (1978)] commonly utilized in experimental electron density studies. It is found that the latter model, due to its inadequate radial part, lacks pointwise convergence and fails to reproduce the local topology of the target QC-ED even at a highorder expansion. The significance of the quantitative agreement often found between HC-PA-based (quadrupolar-level) experimental and extended-basis QC-EDs can thus be challenged. Published by AIP Publishing.

First author: Ho, PC, Synthesis and structural characterisation of the aggregates of benzo-1,2-chalcogenazole 2-oxides,
DALTON TRANSACTIONS, 46, 6570, (2017)
Abstract: Iodine oxidation of bis[2-(hydroxyiminomethyl) phenyl] dichalcogenides yields benzo-1,2-chalcogenazole 2-oxides. Annulated derivatives of iso-tellurazole N-oxides spontaneously aggregate into cyclic tetra-and hexamersthrough Te…O chalcogen bonding; the structures of the co-crystals with benzene and CH2Cl2 illustrate the ability of these macrocycles to interact with small guest molecules. The selenium congener crystallizes forming a supramolecular polymer. VT NMR indicates that both compounds aggregate in solution but only at low temperature in the selenium case. The different abilities of these molecules to engage in supramolecular interactions are interpreted on the basis of their electronic properties evaluated with DFT-D3 calculations.

First author: Alemayehu, AB, Relativistic effects in metallocorroles: comparison of molybdenum and tungsten biscorroles,
Abstract: The homoleptic sandwich compounds – Mo and W biscorroles – have afforded a novel platform for experimental studies of relativistic effects. A 200 mV difference in reduction potential and a remarkable 130 nm shift of a near-IR spectral feature have been identified as manifestations of relativistic effects on the properties of these complexes.

First author: Senanayake, RD, Theoretical Investigation of Electron and Nuclear Dynamics in the [Au-25(SH)(18)](-1) Thiolate-Protected Gold Nanocluster,
Abstract: Clear mechanistic insights into excited state dynamics in thiolate-protected gold nanoclusters are vital for understanding the Origin of the photocatalytic enhancement via metal nanoparticles in the visible region. Extensive experimental studies on the [Au-25(SR)(18)](-1) thiolate-protected gold nanocluster nonradiative relaxation dynamics reported very distinct time constants which span from the femtosecond to nanosecond scale. In this work, the rionradiative excited state relaxations of the [Au-25(SH)(18)](-1) cluster are investigated theoretically to characterize the electron relaxation dynamics. The core and higher excited states lying in the energy range 0.00-2.20 eV are investigated using time-dependent density functional theory (TD-DFT). The quantum dynamics of these states is studied using a surface hopping method with decoherence correction, augmented with a realtime approach to DFT. Population transfer from the Si state to the ground state occurs on the several hundred picoseconds time scale. Relaxation between excited states that arise from core-to-core transitions is found to occur on a much shorter time scale (2-18 ps). No seruiring or other states are observed, at an energy lower than the core-based S-1 state. This observation suggests that the several picosecond time constants observed. by Moran and co-workers could arise from core-to-core transitions rather than from a core-to-semiring transition. A large energy gap between the. S-7 and S-6 states is found to be responsible for a relatively slow decay time for S-7. The S-1 state population decrease demonstrates the slowest decay time due to the large energy gap to the ground state. The spectral densities are calculated to understand the electron-phonon interactions that lead to electronic relaxations.

First author: Xu, CQ, Manipulating Stabilities and Catalytic Properties of Trinuclear Metal Clusters through Tuning the Chemical Bonding: H-2 Adsorption and Activation,
Abstract: Chemical bonding involving metal-metal (M-M) and metal-ligand (M-L) interactions provides an opportunity to tune the stabilities and catalytic properties of metal clusters. We report here the electronic and bonding properties of a series of trinuclear clusters [M3X3(PR3)(3)](+) (M = Ni, Pd, Pt; X = F, Cl, Br, I; R = H) to explore the electronic effect on the adsorption and activation of H-2 and other small molecules. The chemical bonding model of M-3 is discussed in detail, and the formal +4/3 oxidation state of the metal element in the M-3 cluster is proposed. Metallic sigma-aromaticity is also found in the trinuclear clusters. We have shown that the stability and the catalytic activity of the trinuclear clusters can be tuned by altering the energies and compositions of M-M and M-L chemical bonding orbitals. The performance of H-2 dissociative adsorption on these clusters can be explained by the orbital interactions. Relativistic effects also play a significant role in determining the activity of H-2 adsorption. This finding provides an example for controlling catalytic properties through tuning chemical bonding of metal clusters.

First author: Izgorodina, EI, Quantum Chemical Methods for the Prediction of Energetic, Physical, and Spectroscopic Properties of Ionic Liquids,
CHEMICAL REVIEWS, 117, 6696, (2017)
Abstract: The accurate prediction of physicochemical properties of condensed systems is a longstanding goal of theoretical (quantum) chemistry. Ionic liquids comprising entirely of ions provide a unique challenge in this respect due to the diverse chemical nature of available ions and the complex interplay of intermolecular interactions among them, thus resulting in the wide variability of physicochemical properties, such as thermodynamic, transport, and spectroscopic properties. It is well understood that intermolecular forces are directly linked to physicochemical properties of condensed systems, and therefore, an understanding of this relationship would greatly aid in the design and synthesis of functionalized materials with tailored properties for an application at hand. This review aims to give an overview of how electronic structure properties obtained from quantum chemical methods such as interaction/binding energy and its fundamental components, dipole moment, polarizability, and orbital energies, can help shed light on the energetic, physical, and spectroscopic properties of semi-Coulomb systems such as ionic liquids. Particular emphasis is given to the prediction of their thermodynamic, transport, spectroscopic, and solubilizing properties.

First author: Jana, G, Binding of Small Gas Molecules by Metal-Bipyridyl Monocationic Complexes (Metal = Cu, Ag, Au) and Possible Bond Activations Therein,
Abstract: The viability of a series of small gas molecules (H-2, N-2, CO, CO2, H2O, H2S, C2H2, CH4, CH3C1, C2H4, and C2H6) bound [M-(bipy)](+) (bipy = bipyridyl; M = Cu, Ag, Au) complexes is investigated at the PBEO/cc-pVTZ/cc-pVTZ-PP level with a special emphasis on the possible bond activation within the bound ligands. While the bond dissociation energy, enthalpy change, and free energy change are computed to show the stability of the complexes with respect to the dissociation into [M-(bipy)](+) and free gas molecule (L), natural bond orbital, electron density, and energy decomposition analyses in conjunction with natural orbitals for chemical valence are carried out to characterize the nature of L M bonds. For a given L, the L binding ability is the highest for Au followed by Cu and Ag complexes, except for quite loosely bound CO2. For all ligand cases, the dissociation processes from the respective bound complexes are endergonic in nature at room temperature, except for the H-2-, CH4-, and C2H6-bound Ag complexes and CO2-bound Ag and Au complexes. The interaction between L and M centers is supported by orbital and ionic interactions with latter being more dominant over the former. The delocalization index and local energy density values support the covalent character in L M bonds in most of the cases. These M centers can act as a mild bond activation agent for L, Au being the best candidate in this series for this purpose. Particularly, the H-H bond in H-2, C=C bond in C2H4 C C bond in C2H2, and C-H bonds in CH4 and C2H6 (the last two are for Au) are elongated along with a significant red-shift in the corresponding stretching frequency, compared to those in free molecules. These can be explained by the significant pi-back donation populating the lowest unoccupied antibonding molecular orbital of L in these complexes.

First author: Miller, CE, Modeling Singlet Fission in Rylene and Diketopyrrolopyrrole Derivatives: The Role of the Charge Transfer State in Superexchange and Excimer Formation,
Abstract: Singlet fission (SF) is being explored as a way to improve the efficiency of organic photovoltaics beyond the Shockley-Queisser limit; however, many aspects of the SF mechanism remain unresolved. The generally accepted mechanisms provide simplified models of SF that equivocate over whether a charge transfer (CT) state is involved in SF. A one-step superexchange model allows the CT state to act as a virtual state, reducing the effect of large Gibbs free energy values from SF rate calculations. Also, extending superexchange to an excimer-mediated process allows for further refinement of the triplet formation model. Application of the superexchange and excimer-mediated models to a variety of rylene and diketopyrrolopyrrole derivatives provides new insights into the role of the CT and excimer states, providing a semiquantitative description of SF that is dictated by the CT state energy.

First author: Qu, N, Metal-metal multiple bond in low-valent diuranium porphyrazines and its correlation with metal oxidation state: A relativistic DFT study,
Abstract: To explore the uranium-uranium bonding nature, a ligated diuranium complex that could be experimentally possible would show features with no bridging ligand constraints (i.e. discrete or unsupported ligand), rigid ligand skeleton and suitable U-ligand bond. In this respect, we have designed and examined a series of diuranium diporphyrazines (U(2)(m)Pz(2), m = II, III and IV) using relativistic density functional theory. Optimizations on all possible electron-spin isomers find that the triplet, quintet and quintet states are energetically lowest for Um(2)Pz(2) (m = II, III and IV), respectively. They possess bond lengths of U-U at 2.37, 2.46 and 2.91 angstrom, bond orders of 3.48, 3.33 and 2.11, and stretching vibrational frequencies of 239, 172 and 108 cm(-1). Associated with the electronic-structure and QTAIM (quantum theory of atoms in molecules) analyses, a weak quadruple bond is suggested for the triplet state of U(2)(II)Pz(2), and the triple and double bonds for U(2)(III)Pz(2), and U(2)(IV)Pz2, respectively. It shows that the uranium oxidation state approximately correlates with the number of multiple bonds.

First author: Zhang, WT, Fine tuning phosphorescent properties of platinum complexes via different N-heterocyclic- based CNN ligands,
Abstract: In this article, series of platinum(II) complexes with different [C<^>N<^>N] cyclometalated ligand scaffolds was elaborated via density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods to mainly explore how the N atomic number, the atomic number of cyclization and the position of N atom influence phosphorescent processes (radiative and nonradiative decay processes). Thereinto, the factors which determine the radiative processes, including mu(S-n) for S-0-S-n transitions, Delta E(S-n-T-1) and SOC matrix elements < T-1 | H-SOC| S-n > were calculated. In addition, according to the energy gap law, the absorption-emission Stokes shifts as well as energy gaps between T-1 and S-0 states were also computed to describe the nonradiative decay processes qualitatively. As revealed, compared with six-membered Nheterocyclic compounds, five-membered N-heterocyclic compounds exhibit obvious blue-shifted behaviors, smaller nonradiative decay rate constants and similar radiative decay rate constant, especially complex 2b with the other N atom at the 4-position of five-membered N-heterocyclic ligand, which leads to a maximum hypsochromic shift of phosphorescence band and relatively larger radiative decay rate constant and smaller nonradiative decay rate constant among these complexes. These findings successfully illustrated the structure-property relationship and provide valuable information to design highly efficient phosphorescent material.

First author: Servis, MJ, Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate,
Abstract: Extraction of polar molecules by amphiphilic species results in a complex variety of clusters whose topologies and energetics control phase behavior and efficiency of liquid-liquid separations. A computational approach including quantum mechanical vibrational frequency calculations and molecular dynamics simulation with intermolecular network theory is used to provide a robust assessment of extractant and polar solute association through hydrogen bonding in the tributyl phosphate (TBP)/HNO3/H2O/dodecane system for the first time. The distribution of local topologies of the TBP/HNO3/H2O hydrogen bonded clusters is shown to be consistent with an equilibrium binding model. Mixed TBP/HNO3/H2O clusters are predicted that have not been previously observable in experiment due to limitations in scattering and spectroscopic resolution. Vibrational frequency calculations are compared with experimental data to validate the experimentally observed TBP-HNO3-HNO3 Chain structure. At high nitric acid and water loading, large hydrogen-bonded clusters of 20 to 80 polar solutes formed. The cluster sizes were found to be exponentially distributed, consistent with a constant average solute association free energy in that size range. Due to the deficit of hydrogen bond donors in the predominantly TBP/HNO3 organic phase, increased water concentrations lower the association free energy and enable growth of larger cluster sizes. For sufficiently high water concentrations, changes in the cluster size distribution are found to be consistent with the formation of a percolating cluster rather than reverse micelles, as has been commonly assumed for the occurrence of an extractant-rich third phase in metal-free solvent extraction systems. Moreover, the compositions of the large clusters leading to percolation agrees with the 1 : 3 TBP : HNO3 ratio reported in the experimental literature for TBP/HNO3/H2O third phases. More generally, the network analysis of cluster formation from atomic level interactions could allow for control of phase behavior in multi-component solutions of species with a variety of hydrogen bond types.

First author: Venkataramanan, NS, Theoretical Investigation of the Binding of Nucleobases to Cucurbiturils by Dispersion Corrected DFT Approaches,
Abstract: The encapsulation of nucleobases inside CB7 has gained prominence due to its use as anticancer and antiviral drugs. With this respect, the nonconvalent interactions existing in the nucleobases encapsulated inside the CB7 cavity have been analyzed employing the dispersion corrected density functional theory. The CBn cavity has the ability to encapsulate two guest nucleobases molecules when they are aligned in parallel configuration. The computed association energy using the two- and three-body correction method computed at B3LYP-D3 level is close to the experimental estimate. The use of dispersion corrected DFs is essential to identify the correct binding energies. The solvation energy plays a vital role in the estimation of association energy. QTAIM analysis shows that the Laplacian of the charge density (del(2)rho) is negative and the presence of covalent interaction between the guest and host molecule. The NCI-RDG isosurface shows the presence of noncovalent intermolecular interactions such as van der Waals and hydrogen bonding. The existence of splattering of charges in guanine@CB7 molecule is responsible for its higher stability. From the AIM, NCI-RDG, and EDA results, we conclude that noncovalent and electrostatic interaction with partial covalent character exists in the intermolecular bonding between the host and the guest nucleobases. The ramification of such intermolecular bonds is reflected in the H-1 NMR and (NMR)-N-13 spectra.

First author: Wang, F, Dominant Carbons in trans- and cis-Resveratrol isomerization,
Abstract: A comprehensive analysis for isomerization of geometric isomers in the case of resveratrol (R) has been presented. As an important red wine molecule, only one geometric isomer of resveratrol, i.e., trans-R rather than cis-R, is primarily associated with health benefit. In the present study, density function theory (DFT) provides accurate descriptions of isomerization of resveratrol. The nearly planar trans-R forms a relatively rigid and less flexible conjugate network, but the nonplanar cis-R favors a more flexible structure with steric through space interaction. The calculated carbon nuclear magnetic resonance (NMR) chemical shift indicates that all carbons are different in the isomers; it further reveals that four carbon sites, i.e., C-(6), C((8))=C-(9), and C-(11), have a significant response to the geometric isomerization. Here C-(6) is related to the steric effect in cis-R, whereas C-(11) may indicate the isomerization proton transfer on C-(9) linking with the resorcinol ring. The excess orbital energy spectrum (EOES) confirms the NMR bridge of interest carbons and reveals that five valence orbitals of 34a, 35a, 46a, 55a, and 60a respond to the isomerization most significantly. The highest occupied molecular orbital (HOMO), 60a, of the isomer pair is further studied using dual space analysis (DSA) for its orbital momentum distributions, which exhibit p-electron dominance for trans-R but hybridized sp-electron dominance for cis-R. Finally, energy decomposition analysis (EDA) highlights that trans-R is preferred over cis-R by -4.35 kcal mol(-1), due to small electrostatic energy enhancement of the attractive orbital energy with respect to the Pauli repulsive energy.

First author: Lesiuk, M, Combining Slater-type orbitals and effective core potentials,
PHYSICAL REVIEW A, 95, 4745, (2017)
Abstract: We present a general methodology to evaluate matrix elements of the effective core potentials (ECPs) within a one-electron basis set of Slater-type orbitals (STOs). The scheme is based on translation of individual STO distributions in the framework of the Barnett-Coulson method. We discuss different types of integrals which naturally appear and reduce them to a few basic quantities which can be calculated recursively or purely numerically. Additionally, we consider evaluation of the STOs matrix elements involving the core polarization potentials and effective spin-orbit potentials. Construction of the STOs basis sets designed specifically for use with ECPs is discussed and differences in comparison with all-electron basis sets are briefly summarized. We verify the validity of the present approach by calculating excitation energies, static dipole polarizabilities, and valence orbital energies for the alkaline-earth metals (Ca, Sr, and Ba). Finally, we evaluate interaction energies, permanent dipole moments, and ionization energies for barium and strontium hydrides, and compare them with the best available experimental and theoretical data.

First author: Phan, H, A Simple Approach for Predicting the Spin State of Homoleptic Fe(II) Tris-diimine Complexes,
Abstract: We propose a simple method for predicting the spin state of homoleptic complexes of the Fe(II) d(6) ion with chelating diimine ligands. The approach is based on the analysis of a single metric parameter within a free (non-coordinated) ligand: the interatomic separation between the N-donor metal-binding sites. An extensive analysis of existing complexes allows the determination of critical N center dot center dot center dot N distances that dictate the regions of stability for the high-spin and low spin complexes, as well as the intermediate range in which the magnetic bistability (spin crossover) can be observed. The prediction has been tested on several complexes that demonstrate the validity of our method.

First author: Jacobsen, H, Its Environment Engraves the Geometry of a Molecular Entity: Allyl Coordination within a Dicationic Ruthenium(IV) Complex,
ORGANOMETALLICS, 36, 1770, (2017)
Abstract: The best molecular arrangements for [Ru(eta C-5(5)(CH5)(5))(eta(3)-CH2CHCHC6H5)(CH3CN)(2)](2+) (1) in various environments are determined. The isolated compound la serves as a point of reference. On the basis of crystal structure data, solid-state environments are modeled by first placing the cationic compound into the appropriate anionic environment 2a and then completing the unit cell contents by addition of the solvent molecule 3a. Density functional calculations (BP86) augmented by various dispersion corrections (BP86-D2, BP86-D3, BP86-D3(BJ), BP86-dDsC) establish the computational approach for electronic structure and geometry optimization. According to the models considered, intermolecular electrostatic interactions are to a major part responsible for substantial changes in intramolecular arrangements.

First author: Cabrera, KD, Monodentate phosphine substitution in [Pd(kappa(3)-dppf)(PR3)][BF4](2) (dppf=1,1 ‘-bis(diphenyl-phosphino)ferrocene) compounds,
DALTON TRANSACTIONS, 46, 5702, (2017)
Abstract: The ligand 1,1′-bis(diphenylphosphino) ferrocene (dppf) is commonly employed in a variety of catalytic systems. There are a variety of coordination modes known for dppf, the least studied being the kappa(3) coordination mode, in which both phosphorus atoms and the iron atom of dppf interact with another metal center. One such compound is the previously reported [Pd(kappa(3)-dppf)(PPh3)](2+). A series of related compounds, [Pd(kappa(3)-dppf)(P(p-C6H4R)(3))](2+) (R = OCH3, CH3, F and CF3), has been synthesized and characterized. The X-ray crystal structure of [Pd(dppf)(P(p-C6H4F)(3))][BF4](2) was determined. Electrochemical and computational studies indicate that the electron donor ability of the P(p-C6H4R)(3) ligands influences the properties of these compounds. Substitution reactions of the P(p-C6H4R)(3) ligands have been examined, and, in general, the more electron donating P(p-C6H4R)(3) ligands completely replace the less electron donating ones. The kinetics of the reaction of [Pd(kappa(3)-dppf)P(p-C6H4R)(3)](2+) with P(p-C6H4OCH3)(3) indicate that the reaction proceeds through a dissociative mechanism, contrary to the associative substitutions prevalent in square planar palladium(II) chemistry.

First author: Wang, Y, Carbanion Translocations via Intramolecular Proton Transfers: A Quantum Chemical Study,
Abstract: Intramolecular proton transfers are important processes in chemical reactions and biological transformations. In particular, the translocation of reactive carbanion centers can be achieved through 1,n-proton transfer in either a direct or an assisted manner (via the protonation/deprotonation mechanism). Despite some mechanistic investigations on proton transfers within zwitterionic species, no guiding principles have been summarized for carbanion-induced intramolecular proton transfers. Herein, we report our quantum chemical study on the carbanion translocations via intramolecular proton transfers. Our calculations indicated that the reaction barriers generally decrease with longer tether lengths and more ?-withdrawing substituents. The physical bases behind these effects were revealed according to the charge and bond energy decomposition analysis, showing that the destabilizing closed-shell Pauli repulsions play important roles in determining the relative ease of intramolecular proton transfers. We also found that the thermodynamic driving force may affect the regiochemistry. This study may help chemists to understand whether a carbanion translocation occurs via an intramolecular proton transfer or with the assistance of proton shuttles, such as water and alcohols.

First author: Nowak, PM, Origin of Remarkably Different Acidity of Hydroxycoumarins-Joint Experimental and Theoretical Studies,
Abstract: In the present work the origin of highly varied acidity of hydroxycoumarins (pK(a) values) has been for the first time investigated by joint experimental and computational studies. The structurally simple regio-isomers differing in the location of hydroxyl group, 3-hydroxycoumarin (3-HC), 4-hydroxycoumarin (4-HC), 6-hydroxycoumarin (6-HC), 7-hydroxycoumarin (7 -HC), as well as 4,7-dihydroxycoumarin (4,7-HC) and the larger 4-hydroxycoumarin-based derivatives: warfarin (WAR), 7-hydroxywarfarin (W7), coumatetralyl (CT), and 10-hydroxywarfarin (W10), have been compared in terms of enthalpy-entropy relationships accounting for the observed pK(a), values. We have revealed that in the case of large molecules the acidic proton is stabilized by the following noncovalent interactions OH center dot center dot center dot O (WAR and W7), OH center dot center dot center dot pi (CT), and OH center dot center dot center dot OH center dot center dot center dot O (W10), this effect leads to a compensatory enthalpy-entropy relation and yields a moderate pKa increase. On the other hand, different location of the hydroxyl group in the regio-isomers (3 -HC, 4 -HC, 6 -HC, and 7 -HC) leads to the massive changes in acidity due to a lack of enthalpy-entropy compensation. Our results suggest that the solvent-solute interactions and electron delocalization degree in anions contribute to the observed behaviors. Such knowledge can be useful in the future to design novel systems exhibiting desired acid-base properties, and to elucidate enthalpy-entropy compensation phenomena.

First author: Arnold, N, Formation of a Trifluorophosphane Platinum(II) Complex by P-F Bond Activation of Phosphorus Pentafluoride with a Pt-0 Complex,
Abstract: The reaction of PF5 with [(Cy3P)(2)Pt] gave the PF3 complex trans-[(Cy3P)(2)PtF(PF3)][PF6], which was characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy, and elemental analysis. To the best of our knowledge, this reaction is the first example of the oxidative addition of a P-F bond to a transition metal and is a rare example of an activation of a main-group-element-fluorine bond by a metal. Relativistic DFT calculations showed that the formation of the Lewis pair [(Cy3P)(2)PtPF5], which was not observed even at low temperatures, represents the initial step of the reaction. From this key intermediate, the cation trans-[(Cy3P)(2)PtF(PF3)](+) was furnished by a two-step mechanism involving, successively, a second and a third PF5 molecule.

First author: Kolesnikov, VI, Mechanism of lubricating action of polyphosphate and heteropolyphosphate additives in tribosystems,
Abstract: The phase diagrams of the Zn(PO3)(2)-Ca(PO3)(2) and Zn(PO3)(2)-Ni(PO3)(2) systems were studied, and the double phosphates CaZn(PO3)(4) and NiZn(PO3)(4) were allocated. The anions of these compounds are chain polyphosphates with PO4 tetrahedra in the period of identity. The structures and mechanism of the action of these compounds as additives to lubricants were described using quantum-chemical analysis. Improvement of the physicochemical and tribotechnical characteristics of lubricating materials containing these phosphates compared to the traditionally used lubricating materials was confirmed in tribotechnical tests.

First author: Szatylowicz, H, Inductive or Field Substituent Effect? Quantum Chemical Modeling of Interactions in 1-Monosubstituted Bicyclooctane Derivatives,
ACS OMEGA, 2, 1746, (2017)
Abstract: Inductive substituent constants were obtained for systems lacking the resonance effect. The application of the charge of the substituent active region concept to study the substituent effect in 1-X-substituted bicyclooctane derivatives (B3LYP/6-311++G** calculations, X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO) has revealed inductive interactions, which are through bonds.

First author: Chen, X, DFT Study of the Oxygen Reduction Reaction Activity on Fe-N-4-Patched Carbon Nanotubes: The Influence of the Diameter and Length,
MATERIALS, 10, 1746, (2017)
Abstract: The influences of diameter and length of the Fe-N-4-patched carbon nanotubes (Fe-N-4/CNTs) on oxygen reduction reaction (ORR) activity were investigated by density functional theory method using the BLYP/DZP basis set. The results indicate that the stability of the Fe-N-4 catalytic site in Fe-N-4/CNTs will be enhanced with a larger tube diameter, but reduced with shorter tube length. A tube with too small a diameter makes a Fe-N-4 site unstable in acid medium since Fe-N and C-N bonds must be significantly bent at smaller diameters due to hoop strain. The adsorption energy of the ORR intermediates, especially of the OH group, becomes weaker with the increase of the tube diameter. The OH adsorption energy of Fe-N-4/CNT with the largest tube diameter is close to that on Pt(111) surface, indicating that its catalytic property is similar to Pt. Electronic structure analysis shows that the OH adsorption energy is mainly controlled by the energy levels of Fe 3d orbital. The calculation results uncover that Fe-N-4/CNTs with larger tube diameters and shorter lengths will exhibit better ORR activity and stability.

First author: Liu, PC, Single-Molecule Imaging Using Atomistic Near-Field Tip-Enhanced Raman Spectroscopy,
ACS NANO, 11, 5094, (2017)
Abstract: Advances in tip-enhanced Raman spectroscopy (TERS) have demonstrated ultrahigh spatial resolution so that the vibrational modes of individual molecules can be visualized. The spatial resolution of TERS is determined by the confinement of the plasmon-induced field in the junction; however, the conditions necessary for achieving the high spatial confinement required for imaging individual molecules are not fully understood. Here, we present a systematic theoretical study of TERS imaging of single molecules, using a hybrid atomistic electrodynamics quantum mechanical method. This approach provides a consistent treatment of the molecule and the plasmonic near field under conditions where they cannot be treated separately. In our simulations, we demonstrate that TERS is capable of resolving intricate molecule vibrations with atomic resolution, although we find that TERS images are extremely sensitive to the near field in the junction. Achieving the atomic resolution requires the near field to be confined within a few angstroms in diameter and the near-field focal plane to be in the molecule plane. Furthermore, we demonstrate that the traditional surface selection rule of Raman spectroscopy is altered due to the significant field confinement that leads to significant field-gradient effects in the Raman scattering. This work provides insights into single-molecule imaging based on TERS and Raman scattering of molecules in nanojunctions with atomic dimensions.

First author: Soares, ACF, Study of Anti-Tuberculosis Activity Behaviour of Natural Kaurane and Trachylobane Diterpenes Compared with Structural Properties Obtained by Theoretical Calculations,
Abstract: A set of seven diterpenes, three kauranes and four trachylobanes, isolated from the African plant Psiadia punctulata were assayed against Mycobacterium tuberculosis and reached activity comparable with cycloserine, a second line drug used to treat tuberculosis (TB). Several structural properties of those diterpenes, such as lipophilicity, HOMO and LUMO energies, charge density, and intramolecular hydrogen bond (IHB) formation, were obtained by theoretical calculations and compared with their activities. Peculiar correlations were observed, especially between activity, lipophilicity and IHB formation.

First author: Dale, BB, Research Update: Density functional theory investigation of the interactions of silver nanoclusters with guanine,
APL MATERIALS, 5, 763, (2017)
Abstract: Bare and guanine-complexed silver clusters Ag-n(z) (n = 2-6; z = 0-2) are examined using density functional theory to elucidate the geometries and binding motifs that are present experimentally. Whereas the neutral systems remain planar in this size range, a 2D-3D transition occurs at Ag-5 (+) for the cationic system and at Ag-4 (2+) for the dicationic system. Neutral silver clusters can bind with nitrogen 3 or with the pi system of the base. However, positively charged clusters interact with nitrogen 7 and the neighboring carbonyl group. Thus, the cationic silver-DNA clusters present experimentally may preferentially interact at these sites. (C) 2017 Author(s).

First author: Wang, X, A Computational Way To Achieve More Effective Candidates for Photodynamic Therapy,
Abstract: The purpose of the work described herein is to design highly efficient photosensitizers (PS) for photodynamic therapy (PDT) in theory. A series of expanded Zn porphyrins have been studied as light activated PS. Their main photophysical properties are systematically calculated by using density functional theory and its time-dependent extension. The mechanisms of PDT are discussed. All the considered candidates exhibit intense absorption in the therapeutic window (600-800 nm), efficient intersystem crossing, and sufficient energy for singlet molecular oxygen production. Accordingly, the designed Zn pentaphyrins and sapphyrins would be proposed as potential PS for PDT. Moreover, the therapeutic effects of Zn pentaphyrins and sapphyrins are better than those of the referenced Zn iso-pentaphyrin. It is expected that the results could provide a new way to design and develop PS for PDT application.

First author: Alemayehu, AB, Stepwise Deoxygenation of Nitrite as a Route to Two Families of Ruthenium Corroles: Group 8 Periodic Trends and Relativistic Effects,
INORGANIC CHEMISTRY, 56, 5285, (2017)
Abstract: ‘Given the many-applications of ruthenium porphyrins, the rarity of ruthenium corroles and the underdeveloped state of their chemistry;are clearly indicative of an area ripe for significant breakthroughs. The tendency of ruthenium corroles to form unreactive metal-rnetal-bonded dimers has been recognized as a key impediment in this area. Herein, by exposing, free-base meso-tris(p-X-phenyl)corroles, H-3[TpXPC] (X = CF3, H, Me and OMe), and [Ru(COD)Cl-2](x), in refluxing 2-methoXyethanol to nitrate, we have been able to reliably intercept the series Ru[TpXPC](NO) in a matter :of seconds to minutes and subseqnently Ru-VI[TpXPC](N), the products of a second deoxygenation, over some 16 h. Two of the (RuN)-N-VI complexes and one ruthenium corrole dimer could be crystaltographically analyzed; the Ru-N-nitrido distance was found to be similar to 1.61 angstrom, consistent with the triple-bonded Charecter of the (RuN)-N-VI units and essentially identical with the Os-N-nitrido distance, in analogous osmium correles Spectrostopic and, density functional theory (DFT) calculations suggest hat the RuNO corroles are best viewed as innocent {RuNO}(6) complexes, whereas the analogous FeNO corroles are noninnocent, i.e, best viewed as {FeNO}(7)-corrole(center dot 2-). Both (RuN)-N-VI and (OsN)-N-VI corroles exhibit sharp Soret bands, suggestive, of an innocent inacrocycle. A key difference between the two rnetals is that the Sotet maxima of the (OsN)-N-VI corroles are red-shifted some 25 non relative to those of the (RuN)-N-VI complexes. Carefal time-dependent DFT studies indicate that this difference is largely. attributable to relativistic effects in (OsN)-N-VI corroles. The availability, of two new classes Of mononuclear ruthenium corroles potentially opens the door to new application’s, in such areas as catalysis and cancer therapy.

First author: Grimme, S, A Robust and Accurate Tight-Binding Quantum Chemical Method for Structures, Vibrational Frequencies, and Noncovalent Interactions of Large Molecular Systems Parametrized for All spd-Block Elements (Z=1-86),
Abstract: We propose a novel, special purpose semiempirical tight binding (TB) method for the calculation of structures, vibrational frequencies, and noncovalent interactions of large molecular systems with 1000 or more atoms. The functional form of the method is related to the self-consistent density functional TB scheme and mostly avoids element-pair-specific parameters. The parametrization covers all spd-block elements and the lanthanides up to Z = 86 using reference data at the hybrid density functional theory level. Key features of the Hamiltonian are the use of partially polarized Gaussian-type orbitals, a double-zeta orbital basis for hydrogen, atomic-shell charges, diagonal third order charge fluctuations, coordination number-dependent energy levels, a noncovalent halogen-bond potential, and the well established D3 dispersion correction. The accuracy of the method, called Geometry, Frequency, Noncovalent, eXtended TB (GFN-xTB), is extensively benchmarked for various systems comparison with existing semiempirical approaches, and the method is applied to a few representative structural problems chemistry.

First author: Golze, D, Local Fitting of the Kohn-Sham Density in a Gaussian and Plane Waves Scheme for Large-Scale Density Functional Theory Simulations,
Abstract: A local resolution-of-the-identity (LRI) approach is introduced in combination with the Gaussian and plane waves (GPW) scheme to enable large-scale Kohn-Sham density functional theory calculations. In GPW, the computational bottleneck is typically the description of the total charge density on real-space grids. Introducing the LRI approximation, the linear scaling of the GPW approach with respect to system size is retained, while the prefactor for the grid operations is reduced. The density fitting is an O(N) scaling process implemented by approximating the atomic pair densities by an expansion in one-center fit functions. The computational cost for the grid-based operations becomes negligible in LRIGPW. The self-consistent field iteration is up to 30 times faster for periodic systems dependent on the symmetry of the simulation cell and on the density of grid points. However, due to the overhead introduced by the local density fitting, single point calculations and complete molecular dynamics steps, including the calculation of the forces, are effectively accelerated by up to a factor of similar to 10. The accuracy of LRIGPW is assessed for different systems and properties, showing that total energies, reaction energies, intramolecular and intermolecular structure parameters are well reproduced. LRIGPW yields also high quality results for extended condensed phase systems such as liquid water, ice XV, and molecular crystals.

First author: Campos, CT, Segmented all-electron Gaussian basis sets of double and triple zeta qualities for Fr, Ra, and Ac,
Abstract: Segmented all-electron basis sets of valence double and triple zeta qualities plus polarization functions for the elements Fr, Ra, and Ac are generated using non-relativistic and Douglas-Kroll-Hess (DKH) Hamiltonians. The sets are augmented with diffuse functions with the purpose to describe appropriately the electrons far from the nuclei. At the DKH-B3LYP level, first atomic ionization energies and bond lengths, dissociation energies, and polarizabilities of a sample of diatomics are calculated. Comparison with theoretical and experimental data available in the literature is carried out. It is verified that despite the small sizes of the basis sets, they are yet reliable.

First author: Chen, X, Recent progresses of global minimum searches of nanoclusters with a constrained Basin-Hopping algorithm in the TGMin program,
Abstract: Finding the global minima of nanoclusters is of great importance in cluster science and nanoscience. We have developed an efficient global minimum search program, named Tsinghua Global Minimum (TGMin, first released in 2012), based on the Basin-Hopping algorithm to find the global minima of nanoclusters, as well as periodic systems. We have recently made several improvements to the original Basin-Hopping algorithm, including a constrained perturbation function, a covalent-radius-based relaxation algorithm, an improved ultrafast shape recognition algorithm, and a planeness-check mechanism. The TGMin program has been successfully applied to search the global minima of a number of nanoclusters and periodic structures, including B-30, B-35, B-36, B-30, B-40, CoBm, RhBjs, MnBm, and Au-7 on the alpha-Al2O3(0001) surface. An overview of the TGMin code and several of its recent applications are presented here.

First author: Medved’ko, AV, The design and synthesis of thiophene-based ruthenium(II) complexes as promising sensitizers for dye-sensitized solar cells,
DYES AND PIGMENTS, 140, 169, (2017)
Abstract: A new series of promising synthetically facile cycloruthenated thiophene-based sensitizers have been developed and fully characterized by UV-vis spectroscopy, NMR and cyclic voltammetric studies. The synthesized dyes have broad MLCT bands spanning the visible spectrum, with high extinction coefficients. The energies of the molecular orbitals for the isolated moletules of the complexes and densities of occupied states were determined. The cycloruthenated compounds contains ortho-metallated thiophene moiety substituted by N-(methyliden)aniline or pyridine-2-y1 at the ortho-position. Having 4,4′-dicarboxy-2,2′-bipyridine as the linker and auxiliary ligands and anchored to nanocrystalline TiO2 films, they achieve efficient sensitization in the visible range and display an overall conversion efficiency of 5.3% under standard AM 1.5 sunlight.

First author: Krishnamoorthy, P, Violet-blue emitting 2-(N-alkylimino)pyrrolyl organoboranes: Synthesis, structure and luminescent properties,
DYES AND PIGMENTS, 140, 520, (2017)
Abstract: The condensation reactions of 2-formylpyrrole (1) or 2-formylphenanthro[9,10-c]pyrrole (2) with various aliphatic amines afforded the corresponding 2-iminopyrrole ligand precursors 3-10, which, upon stoichiometric reaction with BPh3, led to the new mononuclear boron chelate compounds Ph2B[NC4H3C(H)=N-R] (R = Me 11; iPr 12; tBu 13; nOct 14; Cy 15; Adam 16), and Ph2B(NC16H9C(H)=N-R) (R = Me 17; Adam 18), respectively. Boron complexes 11-16, containing a simple 2-(N-allcylformimino)pyrrolyl ligand, are violet emitters and showed relatively modest fluorescence quantum efficiencies in solution (10%-16%), whereas complexes 17 and 18, bearing the pi-extended 2-(N-allcylformimino)phenanthro [9,10-c]pyrrolyl ligand, are blue emitters presenting enhanced quantum efficiencies of 35% and 43%, respectively, in THE solution. DFT and TDDFT calculations were in good agreement with experimental results, showing that it systems (pyrrolyl and phenanthropyrrolyl in this case) have a strong influence on the observed optical properties by changing the nature of the low energy transitions. Non-doped single layer light-emitting diodes (OLEDs) were fabricated with complexes 11-18, deposited essentially by spin coating, those of complexes 17 and 18 revealing maximum luminances of 69 and 88 cd m(-2), respectively.

First author: Kaminsky, J, Properties of the Only Thorium Fullerene, Th@C-84, Uncovered,
Abstract: Only a single thorium fullerene, Th@C-84, has been reported to date (Akiyama, K.; et al. J. Nucl. Radiochem. Sci. 2002, 3, 151-154). Although the system was characterized by UV-vis and XANES (X-ray absorption near edge structure) spectra, its structure and properties remain unknown. In this work we used the density functional calculations to identify molecular and electronic structure of the Th@C-84. Series of molecular structures satisfying the ThC84 stoichiometric formula were studied comprising 24 IPR and 110 non-IPR Th@C-84 isomers as well as 9 ThC2@C-82 IPR isomers. The lowest energy structure is Th@C-84-C-s(10) with the singlet ground state. Its predicted electronic absorption spectra are in agreement with the experimentally observed ones. The bonding between the cage and Th was characterized as polar covalent with Th in formal oxidation state IV. The NMR chemical shifts of Th@C-84-C-s(10) were predicted to guide the future experimental efforts in identification of this compound.

First author: Bahramian, A, Molecular interactions insights underlying temperature-dependent structure of water molecules on TiO2 nanostructured film: A computational study using reactive and non-reactive force fields,
Abstract: Understanding the interaction of water molecules with TiO2 surface is vitally important in practical purposes. Hence, this study is focused on studying the temperature-dependent effect of water on the 5 nm-thick TiO2 film by molecular dynamics (MD) approach. A non-reactive force field proposed by Matsui Akaogi is applied to simulate the bulk and surface properties of TiO2 anatase, while a developed ReaxFF reactive force field is used to predict the molecular and dissociative adsorption configurations of water molecules on the anatase (001) and (101) surfaces. The density profiles of the mentioned system provided molecular insights into the multilayer-adsorbed water on the TiO2 surfaces at different temperatures, T. The structural properties of water, TiO2 (anatase) and their interface were studied through the radial distribution functions of the related atomic pairs over the range 273 <= T <= 373 K. At T <= 313 K, strong hydrogen bonds (HBs) are found in the near-surface water molecUles because of the strong liquid surface integrations. At T >= 353 K, strong HBs are formed in the neat-surface water molecules, while weak HBs are created on the upper layers of water because of liquid-gas interface. The reactive MD simulations showed dissociative adsorption of water molecules on the (101) surface are higher than that on the (001). This property is in good agreement with the literature data.

First author: Yurenko, YP, Weak Supramolecular Interactions Governing Parallel and Antiparallel DNA Quadruplexes: Insights from Large-Scale Quantum Mechanics Analysis of Experimentally Derived Models,
Abstract: The topology and energetics of guanine (G) quadruplexes is governed by supramolecular interactions within their strands. In this work, an extensive quantum mechanical (QM) study has been performed to analyze supramolecular interactions that shape the stems of (4+0) parallel (P) and (2+2) antiparallel (AP) quadruplex systems. The large-scale (approximate to 400atoms) models of P and AP were constructed from high-quality experimental structures. The results provide evidence that each of the P and AP structures is shaped by a distinct network of supramolecular interactions. Analysis of electron topological characteristics of hydrogen bonds in P and AP systems indicates that the P model benefits from stronger intratetrad hydrogen bonding. For intertetrad stacking interactions, both noncovalent interaction plot and energy decomposition analysis approaches suggest that the stem of the P quadruplex benefits more from stacking than that of the AP stem; the difference in energetic stabilization for the two topologies is about 10%. Stronger hydrogen-bonding and stacking interactions in the stem of the P quadruplex, relative to those in the AP system, can be an important indicator to explain the experimental observations that guanine-rich oligonucleotides tend to form all-parallel stems with an all-anti orientation of nucleobases. However, in addition to intrinsic stabilization, partial desolvation effects, which affect the energetics and dynamics of the G-quadruplex folding process, call for further investigations.

First author: Durini, S, Tuning the fluorescence emission in mononuclear heteroleptic trigonal silver(I) complexes,
NEW JOURNAL OF CHEMISTRY, 41, 3006, (2017)
Abstract: Seven mononuclear heteroleptic silver(I) complexes, [Ag(N boolean AND N)(PR3)](NO3) (N boolean AND N = 2-(1-(pyridin-2-yl)imidazo[1,5-a]pyridin-3-yl)phenol; P = PPh3 (1), PMe2Ph (2), PMePh2 (3), P(p-tolyl)(3) (4), P(Bu-n)(3) (5), P(OPh)(3) (6), and P(OEt)(3) (7)), have been prepared and characterized. In these ompounds, N boolean AND N acts as a bidentate ligand with the pyridine ring and the pyridine-like nitrogen of the imidazo[1,5-a]pyridine group. The coordination around silver is completed by the monodentate phosphine, the nitrate anion being not bound to the metal, which then displays a trigonal planar geometry as confirmed by the X-ray crystal structure of compounds 1, 2, 5 and 6. P-31{H-1} NMR and conductivity measurements were performed to settle on the behavior of these complexes in solution. The photophysical properties of these species have been investigated, both in solution and in the solid state: they showed intense fluorescence when excited with UV light, with lambda(max) of emission comprised between 440-460 nm (in solution) and 460-498 nm (solid state) and lifetime decay of a few nanoseconds. In the solid state, a reasonable tuning of the emission is observed according to the electronic features of the coordinated phosphine.

First author: Polo, A, Tuning diastereoisomerism in platinum(II) phosphino- and aminothiolato hydrido complexes,
NEW JOURNAL OF CHEMISTRY, 41, 3015, (2017)
Abstract: Chelate assisted oxidative addition of one equivalent of 2-phosphinothiols (2-(diphenylphosphino)ethanethiol 1, 1-(benzyloxy)-2-(diphenylphosphino) ethanethiol 2 and 2-(diphenylphosphino)-cyclohexanethiol 3) to tetrakis(triphenylphosphine) platinum(0) gives the corresponding hydrido[2-(phosphino-kappa P)thiolato-kappa S]triphenylphosphineplatinum(II) complexes 8-10. Temperature variable NMR studies show that these complexes display a chemical equilibrium between the cis-P,P and trans-P,P geometries, strongly displaced toward the trans-P,P configuration (70-90%). XRD studies carried out on crystals of 8 indicate that although the two geometric isomers are present in solution, only the trans-P,P is obtained in the solid state. These results differ from the cis-P,N geometry observed for the related hydrido[2-(amino-kappa N)thiolato-kappa S] triphenylphosphineplatinum(II) complexes 5-7 in solution. The crystal structures obtained for these aminothiolate hydrides show that the cis-P, N configuration is the only one observed in the solid state. Chelate assisted oxidative addition of one equivalent of 3-(diphenylphosphino) propanethiol 4 to tetrakis(triphenylphosphine) platinum(0) gives the resultant hydrido[3-(phosphino-kappa P)thiolato-kappa S]triphenylphosphineplatinum(II) complex 11. This 3-phosphinothiolate hydride shows in solution only a trans-P, P geometry but presents two chelate ring conformational isomers. Density functional theory calculations have been used to explore the ligand-based stereoelectronic effects that are determinant in the different diastereoisomerism observed in these platinum(II) hydrides (5-11).

First author: Trepte, K, The origin of the measured chemical shift of Xe-129 in UiO-66 and UiO-67 revealed by DFT investigations,
Abstract: The NMR chemical shift of the xenon isotope Xe-129 inside the metal-organic frameworks (MOFs) UiO-66 and UiO-67 (UiO – University of Oslo) has been investigated both with density functional theory (DFT) and in situ high-pressure Xe-129 NMR measurements. The experiments reveal a decrease of the total chemical shift comparing the larger isoreticular MOF (UiO-67) with the smaller one (UiO-66), even though one may expect an increase due to the higher amount of adsorbed Xe atoms. We are able to calculate contributions to the chemical shift individually. This allows us to evaluate the shift inside the different pores independently. To compare the theoretical results with the experimental ones, we performed molecular dynamics simulations of Xe in the MOFs. For this purpose, the pores were completely filled with Xe to gain insight into the distribution of Xe at high pressures. The resulting trend of the total shift agrees well between the theoretical predictions and the experiments. Moreover, we are able to describe specific contributions to the total shift per pore, explaining the experimental behavior at an atomistic level.

First author: Groenewald, F, Gold setting the “gold standard” among transition metals as a hydrogen bond acceptor a theoretical investigation,
DALTON TRANSACTIONS, 46, 4960, (2017)
Abstract: The Au(I) atom of dimethylaurate (DMA) is shown to behave as a hydrogen-bond acceptor, providing theoretical evidence that it can act as a Lewis base. Calculations at the MP2/aug-cc-pVTZ-pp level of theory confirm that DMA forms hydrogen bonds decreasing in strength from -16.2 kcal mol(-1) to -2.4 kcal mol(-1) in the order HCN approximate to HF > H2O > HCCH > NH3 > CH4, i.e. following the trend of decreasing proton acidity of the hydrogen-bond donor. The geometrical and Atoms in Molecules (AIM) parameters of the hydrogen-bonded adducts compare well to those obtained with the auride anion, a known hydrogen-bond acceptor. Relativistic effects are shown to play a dominant role in the formation of the hydrogen bonds with DMA: omission of these effects (confirmed using two different approaches) results in the loss of the hydrogen bond. Instead, the hydrogen-bond donor interacts with the carbon atom on one of the methyl ligands, yielding an adduct that is closely comparable to those found with the Cu and Ag analogues of DMA.

First author: Gopi, R, Probing C-H center dot center dot center dot N interaction in acetylene-benzonitrile complex using matrix isolation infrared spectroscopy and DFT computations,
CHEMICAL PHYSICS, 487, 67, (2017)
Abstract: Hydrogen-bonded complexes of acetylene (C2H2) and the benzonitrile (C6H5CN) have been investigated using matrix isolation infrared spectroscopy and DFF computations. The structure of the complexes and the energies were computed at B3LYP and B3LYP+D3 levels of theory using 6-311++G (d, p) and aug-cc-pVDZ basis sets. DFT computations indicated two minima corresponding to the C-H center dot center dot center dot N (global) and C-H center dot center dot center dot pi interactions (local) of 1:1 C2H2-C6H5CN complexes, where C2H2 is the proton donor in both complexes. Experimentally, the 1:1 C-H center dot center dot center dot N complex identified from the shifts in the C-H and C equivalent to N stretching modes corresponding to the C2H2 and C6H5CN sub-molecules in N-2 and Ar matrices. Atoms in Molecules and Natural Bond Orbital analyses were performed to understand the nature of interaction and to unravel the reasons for red-shifting of the C-H stretching frequency in these complexes. Energy decomposition analysis was carried out to discern the various stabilizing and destabilizing components as a result of hydrogen bonding in the C2H2-C6H5CN complexes.

First author: Selent, M, Clathrate Structure Determination by Combining Crystal Structure Prediction with Computational and Experimental Xe-129 NMR Spectroscopy,
Abstract: An approach is presented for the structure determination of clathrates using NMR spectroscopy of enclathrated xenon to select from a set of predicted crystal structures. Crystal structure prediction methods have been used to generate an ensemble of putative structures of o- and m-fluorophenol, whose previously unknown clathrate structures have been studied by Xe-129 NMR spectroscopy. The high sensitivity of the Xe-129 chemical shift tensor to the chemical environment and shape of the crystalline cavity makes it ideal as a probe for porous materials. The experimental powder NMR spectra can be used to directly confirm or reject hypothetical crystal structures generated by computational prediction, whose chemical shift tensors have been simulated using density functional theory. For each fluorophenol isomer one predicted crystal structure was found, whose measured and computed chemical shift tensors agree within experimental and computational error margins and these are thus proposed as the true fluorophenol xenon clathrate structures.

First author: Melgar, D, Electronic Structure Studies on the Whole Keplerate Family: Predicting New Members,
Abstract: A comprehensive study of the electronic structure of nanoscale molecular oxide capsules of the type [{M-VI(M-VI)(5)O-21}(12){M’V2O2(mu-X)(mu-Y)(Ln-)}(30)]((12+n)-) is presented, where M, M’=Mo, W, and the bridging ligands X, Y=O, S, carried out by means of density functional theory. Discussion of the electronic structure of these derivatives is focused on the thermodynamic stability of each of the structures, the one having the highest HOMO-LUMO gap being M=W, M’=Mo, X=Y=S. For the most well-known structure M=M’=M’, X=Y=O, [Mo132O372](12-) the chemical bonding of several ligands to the {(Mo2O2)-O-V(mu-O)(2)} linker moiety produces negligible effects on its stability, which is evidence of a strong ionic component in these bonds. The existence of a hitherto unknown species, namely W-132 with both bridging alternatives, is discussed and put into context.

First author: Azarkish, M, Heteroleptic complexes of Zn(II) based on 1-(5-bromo-2-hydroxybenzylidene)-4-phenylthiosemicarbazide: Synthesis, structural characterization, theoretical studies and antibacterial activity,
Abstract: Four new ternary complexes, [ZnL (2,2′-bipy)] (1), Zn2L2(4,4′-bipy)] (2), [ZnL(Imd)].H(2)0 (3) and [ZnL3(MeImd)] (4), have been synthesized from the reaction of Zn(II) acetate with 1-(5-bromo-2hydroxybenzylidene)-4-phenylthiosemicarbazide (H2L) in the presence of a heterocyclic base, 2,2′-bipyridine, 4,4′-bipyridine, imidazole or 2-methylimidazole, as an auxiliary ligand. The complexes have been investigated by elemental analysis and FT-IR, UV-Vis and (HNMR)-H-1 spectroscopy. These data show that the thiosemicarbazone acts as a tridentate dianionic ligand and coordinates via the thiol group, imine nitrogen, and phenolic oxygen. The coordination sphere was completed by the nitrogen atom(s) of the secondary ligand. The structure of 1 was also confirmed by X-ray crystallography and shown to be a five coordinate complex with coordination geometry between the square-pyramidal and trigonal-bipyramidal. Density functional theory (DFT) calculations including geometry optimization, vibrational frequencies and electronic absorptions have been performed for 1 with the B3LYP functional at the TZP(6-311G(*)) basis set using the Gaussian 03 or ADF 2009 packages. The optimization calculation showed that the crystallographically determined geometry parameters can be reproduced with that basis set. Experimental IR frequencies and calculated vibration frequencies also support each other. The in vitro antibacterial activities of the ligand and complexes have been evaluated against Gram-positive (B. subtilis and S. aureus) and Gram-negative (P. aeruginosa) bacteria and compared with the standard antibacterial drugs. The results reveal that all of the complexes show much better activity in comparison to the individual thiosemoicarbazone ligand (H2L), against all bacterial strains used, with complex 3 showing the most promising results.

First author: Vujovic, M, in/out Isomerism of cyclophanes: a theoretical account of 2,6,15-trithia-[3(4,10)][7]metacyclophane and [3(4,10)][7]metacyclophane as well as their halogen substituted analogues,
Abstract: A detailed theoretical investigation of cyclophanes with a divergent set of methods ranging from molecular mechanics through semiempirical to ab initio is presented. Cyclophanes have attracted interest over the years due to their unusual chemistry and increasing applications. There has been previous debate over the effects contributing to the greater stability of more-crowded in isomers of certain cyclophanes, and a higher strain in the out isomer was the prevailing explanation. Application of EDA-NOCV and SAPT analysis has enabled us to distinguish between different effects controlling isomer stability and determine the significance of all effects involved. Our results show that, although strain has a large significance, orbital stabilization within the molecule from the aromatic electron density is crucial. Furthermore, we analysed halogen-substituted cyclophanes in order to further understand these subtle effects.

First author: Pushkarevsky, NA, Different Reductive Reactivities of SmCp2x(THF)(n) (Cp-x = C5Me5 and (C5H3Bu2)-Bu-t) Samarocenes toward P2Ph4: THF Ring-Opening and Ligand-Exchange Pathways,
ORGANOMETALLICS, 36, 1287, (2017)
Abstract: The reduction of tetraphenyldiphosphine with two differently substituted samarocenes(II) proceeds via different pathways. With [SmCp*(2)(THF)(2)] (Cp* = eta(5)-C5Me5), the reaction had been known to result in the THF ring-opening product, [SmCp*(2)(O(CH2)(4)PPh2)], 3, owing to the instability of phosphido complex [SmCp*(2)(PPh2)] in the presence of THF. Complex 3 crystallizes from apolar solvents as dimeric or polymeric polymorph with butoxo-phosphine bridging ligands in both cases. In contrast, the phosphide [SmCp ”(2)(PPh2)] (Cp ” = eta(5)-1,3-(C5H3Bu2)-Bu-t), 5, is not prone to ring-opening owing to insufficient space in the Sm coordination sphere for a THF ligand. Product 5 is inevitably accompanied by homoleptic complex [SmCp ”(3)] 6 and dinuclear mixed-valent complex [(SmCp)-Cp-III ”(2)(mu-PPh2)(2)(SmCp)-Cp-II ”] 7 as the further products of redox transformations and ligand exchange The formation of 5-7 is rationalized by a sequence of initial coordination of one or two {(SmCp)-Cp-II ”(2)} fragments by P atoms and reductive elimination of PPh2 center dot or Cp ”center dot radicals. Further reaction with another equivalent of [SmCp ”(2)] results in the trapping the radicals and formation of all three products.

First author: Kutateladze, AG, High-Throughput in Silico Structure Validation and Revision of Halogenated Natural Products Is Enabled by Parametric Corrections to DFT-Computed C-13 NMR Chemical Shifts and Spin-Spin Coupling Constants,
Abstract: Halogenated natural products constitute diverse and promising feedstock for molecular pharmaceuticals. However, their solution-structure elucidation by NMR presents several challenges, including the lack of fast methods to compute C-13 chemical shifts for carbons bearing heavy atoms. We show that parametric corrections to DFT-computed chemical shifts in conjunction with rff-computed spin spin coupling constants allow for fast and reliable screening of a large number of reported halogenated natural products, resulting in expedient structure validation or revision. In this paper, we examine more than 100 structures of halogenated terpenoids and other natural products with the new parametric approach and demonstrate that the accuracy of the combined method is sufficient to identify misassignments and suggest revisions in most cases (16 structures are revised). As the 1D H-1 and C-13 NMR data are ubiquitous and most routinely used in solution structure elucidation, this fast and efficient two-criterion method (nuclear spin spin coupling and C-13 chemical shifts) which we term DU8+ is recommended as the first essential step in structure assignment and validation.

First author: Sures, DJ, Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems,
Abstract: Ion pairs and solubility related to ion-pairing in water influence many processes in nature and in synthesis including efficient drug delivery, contaminant transport in the environment, and self-assembly of materials in water. Ion pairs are difficult to observe spectroscopically because they generally do not persist unless extreme solution conditions are applied. Here we demonstrate two advanced techniques coupled with computational studies that quantify the persistence of ion pairs in simple solutions and offer explanations for observed solubility trends. The system of study, ([(CH3)(4)N](+), Cs)(8)[M6O19] (M = Nb, Ta), is a set of unique polyoxometalate salts whose water solubility increases with increasing ion-pairing, contrary to most ionic salts. The techniques employed to characterize Cs+ association with [M6O19](8-) and related clusters in simple aqueous media are Cs-133 NMR (nuclear magnetic resonance) quadrupolar relaxation rate and PDF (pair distribution function) from X-ray scattering. The NMR measurements consistently showed more extensive ion-pairing of Cs+ with the Ta-analogue than the Nb-analogue, although the electrostatics of the ions should be identical. Computational studies also ascertained more persistent Cs+-[Ta6O19] ion pairs than Cs+-[Nb6O19] ion pairs, and bond energy decomposition analyses determined relativistic effects to be the differentiating factor between the two. These distinctions are likely responsible for many of the unexplained differences between aqueous Nb and Ta chemistry, while they are so similar in the solid state. The X-ray scattering studies show atomic level detail of this ion association that has not been prior observed, enabling confidence in our structures for calculations of Cs-cluster association energies. Moreover, detailed NMR studies allow quantification of the number of Cs+ associated with a single [Nb6O19](8-) or [Ta6O19](8-) anion which agrees with the PDF analyses.

First author: Huang, CH, Room-temperature phosphorescence from small organic systems containing a thiocarbonyl moiety,
Abstract: Small organic molecules based on the unnatural DNA base pair dTPT3 are designed and synthesized, among which compounds bearing the thiocarbonyl group, compared with their carbonyl counterparts, show a much larger SOC integral between S-1((1)n pi*) and T-1((3)pi pi*) states due to the appropriate energy level alignment and the heavy sulfur atom effect, resulting in the appearance of both fluorescence and phosphorescence in solution and solid state at room temperature.

First author: Gao, XJJ, Computational Study on the Mechanisms of Multiple Complexation of CO and Isonitrile Ligands to Boron,
Abstract: The recent experimental realization of compound Tripp-B(CO)(2) (denoted as 2a), where Tripp is 2,6-di(2,4,6-triisopropylpheny1)-phenyl), breaks through conventional knowledge that only transition metals can bind more than one CO to form multicarbonyl adducts. Compound 2a is stable in air but liberates CO under light. The B CO bonds of 2a are considered to be similar to donor acceptor bonds of transition metal complexes. To address the formation mechanism and chemical bonding of this novel type of boron compounds, we present a density functional theory study on the formation and photolysis of 2a and similar compounds. The results suggest that the formation of 2a is facile by three consecutive additions of CO to the terminal borylene metal complex, that is, the boron source of the synthesis. These CO additions can be practically accomplished via two different paths: CO direct addition and CO migration followed by addition. Such mechanisms can be excellently rationalized by the donor acceptor bonding model of the terminal borylene complex, which in turn suggests that using donor acceptor bonds for 2a is natural for understanding the mechanisms. Liberation of CO from 2a and its similar compounds has higher energy barriers at the ground states than that at the triplet states by 40 kcal/mol. These energy barriers explain the experimentally observed air stability and photolysis of these compounds. The results for the first time provide mechanistic insights for the unprecedented chemical processes; they allow evaluation of the applicability of donor acceptor bonding in main-group compounds from the new perspective of chemical reactions.

First author: Munoz-Castro, A, Computational Study of C-13 NMR Chemical Shift Anisotropy Patterns in C20H10 and [C20H10](4-). Insights into Their Variation upon Planarization and Formation of Concentric Aromatic Species in the Smaller Isolated-Pentagon Structural Motif,
Abstract: Corannulene, C20H10, exhibits a concave surface in the ground state that is able to experience a bowl-to-bowl inversion through a planar conformation. Such a structure is the smaller example resembling an isolated-pentagon motif, as a relevant fragment in fullerene chemistry. Here, we explored the differences between bowl and planar conformations involving both energetic and C-13 NMR properties, for the neutral and tetraanionic species by using density functional theory (DFT) methods. This allows us to understand the variation of the chemical environment at the carbon atoms upon planarization of this representive motif. Our results reveal that the variation of the chemical shift comes about from the variation of different main components of the shielding tensor, according to the relative position of the carbon atoms in the structure (i.e., rim, hub, and protonated), which is more relevant for both hub and protonated sites, in contrast to the rim carbon remaining almost unshifted. Interestingly, the planar transition state exhibits a more favorable bonding situation than the bowl-shaped conformation; however, the higher strain is enough to overcome this extra stabilization. Upon reduction to the tetraanionic counterpart C20H104- a lesser strain in the planar conformation is observed, decreasing the inversion barrier. In addition, the formation of the concentric aromatic ring systems in C20H104-, results in a more axially symmetric chemical shift anisotropy (CSA) tensor for the hub carbons, accounting in a local manner, for the concentric aromatic behavior in such structure in contrast to the neutral parent. These observations can be useful to evaluate the aromatic behavior of teh isolated -pentagon rule (IPR) motif in fullerene cages.

First author: Jensen, SR, The Elephant in the Room of Density Functional Theory Calculations,
Abstract: Using multiwavelets, we have obtained total energies and corresponding atomization energies for the GGA-PBE and hybrid-PBE0 density functionals for a test set of 211 molecules with an unprecedented and guaranteed mu Hartree accuracy. These quasi exact references allow us to quantify the accuracy of standard all-electron basis sets that are believed to be highly accurate for molecules, such as Gaussian-type orbitals (GTOs), all electron numeric atom-centered orbitals (NAOs), and full-potential augmented plane wave (APW) methods. We show that NAOs are able to achieve the so-called chemical accuracy (1 kcal/mol) for the typical basis set sizes used in applications, for both total and atomization energies. For GTOs, a triple-zeta quality basis has mean errors of similar to 10 kcal/mol in total energies, while chemical accuracy is almost reached for a quintuple -zeta basis. Due to systematic error cancellations, atomization energy errors are reduced by almost an order of magnitude, placing chemical accuracy within reach also for medium to large GTO bases, albeit with significant outliers. In order to check the accuracy of the computed densities, we have also investigated the dipole moments, where in general only the largest NAO and GTO bases are able to yield errors below 0.01 D. The observed errors are similar across the different functionals considered here.

First author: Yoshimura, T, Synthesis, Structures, and Proton Self-Exchange Reaction of mu(3)-Oxido/Hydroxido Bridged Trinuclear Uranyl(VI) Complexes with Tridentate Schiff-Base Ligands,
INORGANIC CHEMISTRY, 56, 4057, (2017)
Abstract: New mu(3)-hydroxido/oxido bridged trinuclear uranyl-(VI) complexes with 3,5-di-t-butyl-N-salicylidene-2-aminophenolato (dbusap(2-)) ligands, Et3NH[(UO2)(3)(mu(3)-OH)(dbusap)(3)] (Et3NH[1]) and (Et3NH)(2)[(UO2)(3)(mu(3)-O) (dbusap)(3)] ((Et3NH)(2)[2]) were synthesized and characterized. Single-crystal X-ray structures of both complexes were determined. The oxygen atom on mu(3)-hydroxido center in [1](-) is sp(3) hybridized with an average U-(mu(3)-O)-U bond angle of 109.7(5)degrees; the mu(3)-oxido atom in [2](2-) is sp(2) hybridized with an average U-(mu(3)-O)-U bond angle of 118.0(10)degrees. U-(mu(3)-O) distances in [1](-) are long (average of 2.43(1) angstrom) compared with those in [2](2-) (average of 2.23(2) angstrom). The optimized geometries of the [(UO2)(3)(mu(3)-OH)](5+) core in [(UO2)(3)(mu(3)-OH)(sap)(3)](-) and the [(UO2)(3)(mu(3)-O)](4+) core in [(UO2)(3)(mu(3)-O)(sap)(3)](2-) (where sap = N-salicylidene-2-aminophenolato) from, density functional theory (DFT) calculations resemble those in [1](-) and [2](2-), respectively. The U-(mu(3)-O) bond in [2](2-) is significantly shorter than that in [1](-), because of the greater negative charge on the central mu(3)-oxido. A reversible structural conversion between [2](2-) and [1](-) was conducted by protonation and deprotonation of the mu(3)-oxid/hydroxido group. The activation enthalpy and entropy of the proton self-exchange reaction between [1](-) and [2](2-) determined from the temperature dependence of H-1 NMR coalescence are Delta H++ = 23 +/- 2 kJ mol(-1) and Delta S++ = 77 +/- 5 J K-1 mol(-1).

First author: Guascito, MR, Nickel-macrocycle interaction in nickel(II) porphyrins and porphyrazines bearing alkylthio beta-substituents: A combined DFT and XPS study,
Abstract: An electronic structure analysis of two nickel(II) tetrapyrrole complexes bearing beta-alkylthio substituents, NiOMTP and NiOETPz, has been carried out through a combination of high-resolution XPS experiments and DFT calculations. The Ni 2p XPS spectra show a 0.5 eV shift to higher energy of the Ni 2p(3/2) and Ni 2p(1/2) binding energies on going from the porphyrin to the porphyrazine complex. This shift, which is well-reproduced by relativistic spin-orbit ZORA calculations, is indicative of a depletion of electron density on the central metal. Such a depletion of electron density is related to the macrocycle-induced changes in the metal-ligand interactions. In the porphyrazine complex both the ligand to metal sigma donation and the metal to ligand p-back donation increase. The latter increases slightly more than the former, however, leading to a decrease of electron density on the central metal.

First author: Zhao, LL, Synthesis and bonding model of chelate stabilized [Ph2P (CH2) PPh2CF2](2+) (n=2, 3) dications,
Abstract: The difluorine dications [Ph2P(CH2)(n)PPh2CF2](2+)(Br-)(2) with n=2, 3 have been synthesized by reacting Br2CF2 with the chelating ligands Ph2P(CH2)(n)PPh2 (dppe, n=2; dppp, n=3). The dications [Ph2P(CH2)(n),Ph2CF2](2+) were structurally characterized by x-ray analysis and NMR spectroscopy. The doubly charged species are formally derived from the cyclic carbones [Ph2P(CH2)(n)PPh2C] where two r ions are attached to the divalent C(0) atom. The transient mono addition cations [Ph2P(CH2)(n)PPh2CF2Br](+) were observed but could not be isolated. The bonding analyses of [Ph2P(CH2)(n)PPh2CF2](2+) and [Ph2P(CH2)(n),Ph2CF2](+) suggest that the P-C-P bonds should be considered as classical electron-sharing bonds.

First author: Khlebopros, RG, Possible mantle phase transitions by the formation of SiO2 peroxides: Implications for mantle convection,
DOKLADY EARTH SCIENCES, 473, 416, (2017)
Abstract: On the basis of quantum-chemical calculations of the linear to isomeric bent transition of the SiO2 molecule, it is suggested that the bent to linear transition of SiO2 forms can occur in melted mantle minerals of the lower mantle. This may be important for the formation of the peculiarities of mantle convection and origination of plumes.

First author: Jin, JY, Dicarbonyls of Carbon and Methylidyne Cations,
Abstract: The carbon suboxide cation C3O2+ and the protonated carbon suboxide HC3O2+/DC3O2+ were produced in the gas phase. The vibrational spectra were measured via infrared photodissociation spectroscopy of their argon or CO tagged complexes. Spectroscopic evidence combined with state-of-the-art quantum chemical calculations indicate that both cations have a bent C-2v symmetry and can be designated as dicarbonyls of a carbon cation and methylidyne cation, respectively.

First author: Blades, WH, Evolution of the Spin Magnetic Moments and Atomic Valence of Vanadium in VCux+, VAgx+, and VAux+ Clusters (x=3-14),
Abstract: The atomic structures, bonding characteristics, spin magnetic moments, and stability of VCUx+, VAgx+, and VAux+ (x = 3-14) clusters were examined using density functional theory. Our studies indicate that the effective valence of vanadium is size-dependent and that at small sizes some of the valence electrons of vanadium are localized on vanadium, while at larger sizes the 3d orbitals of the vanadium participate in metallic bonding eventually quenching the spin magnetic moment. The electronic stability of the clusters may be understood through a split-shell model that partitions the valence electrons in either a delocalized shell or localized on the vanadium atom. A molecular orbital analysis reveals that in planar clusters the delocalizatibn of the 3d orbital of vanadium is enhanced when surrounded by gold due to enhanced 6s-5d hybridization. Once the clusters become three-dimensional, this hybridization is reduced, and copper most readily delocalizes the vanadium’s valence electrons. By understanding these unique features, greater insight is offered into the role of a host material’s electronic structure in determining the bonding characteristics and stability of localized spin magnetic moments in quantum confined systems.

First author: Sedlak, R, Empirical D3 Dispersion as a Replacement for ab lnitio Dispersion Terms in Density Functional Theory-Based Symmetry-Adapted Perturbation Theory,
Abstract: In density functional theory-based symmetry-adapted perturbation theory (DFT-SAPT) interaction energy calculations, the most demanding step is the calculation of the London dispersion term. For this bottleneck to be avoided and DFT-SAPT to be made applicable to larger systems, the ab initio dispersion terms can be replaced by one calculated empirically at an almost negligible cost (J Phys. Chem. A 2011; 115, 11321-11330). We present an update of this approach that improves accuracy and makes the method applicable to a wider range of systems. It is based on Grimme’s D3 dispersion correction for DFT, where the damping function is changed to one suitable for the calculation of the complete dispersion energy. The best results have been achieved with the Tang-Toennies damping function. It has been parametrized on the S66X8 data set for which we report density fitting DFT-SAPT/aug-cc-pVTZ interaction energy decomposition. The method has been validated on a diverse set of noncovalent systems including difficult cases such as very compact noncovalent complexes of charge-transfer type. The root-mean-square errors in the complete test set are 0.73 and 0.42 kcal mol(-1) when charge-transfer complexes are excluded. The proposed empirical dispersion terms can also be used outside the DFT-SAPT framework, e.g., for the estimation of the amount of dispersion in a calculation where only the total interaction energy is known.

First author: Wang, X, Theoretical insights into the phosphorescent process of a series of 2-(2-trifluoromethyl) pyrimidine-pyridine based heteroleptic iridium(III) compounds: The influence of the ancillary ligand,
Abstract: The structure-property relationship is theoretically elucidated for four heteroleptic Ir(III) complexes with different ancillary ligand (see Fig. 1). Besides the ground state geometric parameters, the different triplet states are finally determined by both the density functional theory (DFT) and time-dependent DFT (TDDFT) methods. On the basis of the respective optimized triplet geometry, the emissive wavelength is determined by the Delta SCF-DFT method. For all the experimental reported complexes, the Kasha rule is broken. The emission from the non-Kasha state is possible. To determine the quantum yield, the radiative rate constant (k(r)) is calculated by two different methods. Moreover, the items related with the k(r), such as, Zero-field splitting (ZFS), transition dipole moments mu(S-n,), singlet-triplet splitting energies Delta E (S-n- T-1), and spin-orbit coupling (SOC) matrix elements < T1 vertical bar Hso vertical bar Sn > are also calculated to further confirm the k(r). The nonradiative rate constant (k(nr)) is qualitatively evaluated by the popularity of the (MC)-M-3 d-d state by the energy difference between (MLCT)-M-3/pi-pi* and 3MC d-d state, the barrier height between (MLCT)-M-3/pi-pi* and 3MC d-d state, and the required energy from 3MC d-d state decay to the S-1(0) state. The barrier height between (MLCT)-M-3/pi-pi* and 3MC d-d state plays an important role to determine the knr. Finally, a novel Will) complex is designed bearing 2-(2-trifluoromethyl) pyrimidine-pyridine (TPP) as primary ligand and amidinate as ancillary ligand. The phosphorescent emissive wavelength is obviously blue-shifted. Moreover, the quantum yield is comparable with that of complex 1.

First author: Safin, DA, Azide-rich complexes of cobalt(III) with the rare 5-phenyl-2,2 ‘-bipyridine ligand,
Abstract: Reaction of one or two equivalents of 5-phenyl-2,2 ‘-bipyridine (L) with a mixture of one equivalent of CoCl2 and two equivalents of NaN3 leads to mononuclear heteroleptic cobalt(III) complexes [CoL2(N-3)(2)] (N-3)(0.55)Cl-0.45.EtOH (1) and [CoL2(N-3)(2)]N-3.2.5EtOH (2), respectively. Both structures reveal that cobalt (III) atom is linked to the six nitrogen atoms of two L and two Ni anions. Both structures are stabilized by intermolecular C-H…N and pi…pi stacking interactions. TG and DSC analyses reveal 1 being stable up to 63 degrees C and decomposing in three steps, 2 on the other hand decomposes at 84 degrees C in two steps. Both decomposition pathways start with an endothermic loss of the lattice ethanol molecules. The second step in 1 (177 degrees C) and 2 (196 degrees C) is related to the “jet” effect, seen as an abrupt weight loss due to a drastic energy release upon heating. In 2 this is the result of a release of N-2 gas from the azides and decomposition of the ligands L followed by the full reduction of cobalt(III) to cobalt(0). In 1 there is a loss of one azide accompanied by the reduction of cobalt(III) to cobalt(II). The final decomposition step of 1 at 215 degrees C is attributed to the exothermic decomposition of L and remaining azide with the formation of a mixture of CoCl2 and Co2N. DFT calculations are performed in order to shed additional light on possible spin states of cobalt complexes as well as to rationalize the stability of the synthesized materials.

First author: Liu, XR, Rational design of bis(4-methoxyphenyl)amine-based molecules with different pi-bridges as hole-transporting materials for efficient perovskite solar cells,
DYES AND PIGMENTS, 139, 283, (2017)
Abstract: Exploration on alternative organic hole -transporting materials (HTMs) especially for high-efficiency perovskite solar cells (PSCs) has attracted great attention recently. In this work, a strategy to tune it bridged units of the small molecular HTM which consists of bis(4-methoxyphenyl)amine as arm and spiro[fluorene-9,9′-xanthenej as it-bridge were theoretically presented for improvement of the PSC efficiency. The pi-bridged tunings could promote the contribution of the highest occupied molecular orbital (HOMO) to delocalize throughout whole molecules in order to be favorable for enhancing the hole transfer integral and hole mobility. Compared with the parent HTM, the neW designed HTMs in PSC applications exhibit better performance with higher HOMO energy levels, larger Stokes shifts, little exciton binding energy, better stability and higher hole mobility. Therefore, the strategy on basis of modulating the it-bridge units of small molecules can effectively change the performance of HTMs and thereby provide a useful guideline of 7c-bridge screening for the design of excellent HTMs in PSC applications. In view of the excellent properties, the designed molecules as HTMs can act as a promising candidates for providing a large efficiency in PSC applications.

First author: Borthakur, B, Nature of transannular interaction in heavier group 13 (In, Tl) atranes: A theoretical study,
POLYHEDRON, 125, 113, (2017)
Abstract: Quantum chemical calculations have been carried out to investigate the nature and extent of transannular M…N interaction in heavier group 13 (M = In, Tl) atranes. Substituents at the equatorial as well as apical positions were found to have a profound effect on the extent of this transannular M…N interaction. Introduction of the apical substituents tends to decrease the extent of this interaction owing to the competition for the vacant p orbital at the group 13 elemerits. The extent of decrease of this interaction was found to be the highest with stronger a donating apical substituents such as NHC (N-heterocyclic carbene). Energy decomposition analysis (EDA) reveal that the extent of M…N interaction is influenced by both axial and equatorial substituents. Quantum theory of atoms in molecules (QTAIM) indicate the presence of covalent character in the transannular M…N bonds while source function (SF) analysis provided the contribution of the constituent atoms towards the electron density at the M…N bond critical point.

First author: Scharf, LT, The Bonding Situation in Metalated Ylides,
Abstract: Quantum chemical calculations have been carried out to study the electronic structure of metalated ylides particularly in comparison to their neutral analogues, the bisylides. A series of compounds of the general composition Ph3P-C-L with L being either a neutral or an anionic ligand were analyzed and the impact of the nature of the substituent L and the total charge on the electronics and bonding situation was studied. The charge at the carbon atom as well as the dissociation energies, bond lengths, and Wiberg bond indices strongly depend on the nature of L. Here, not only the charge of the ligand but also the position of the charge within the ligand backbone plays an important role. Independent of the substitution pattern, the NBO analysis reveals the preference of unsymmetrical bonding situations (P=C-L or P-C=L) for almost all compounds. However, Lewis structures with two lone-pair orbitals at the central carbon atom are equally valid for the description of the bonding situation. This is confirmed by the pronounced lone-pair character of the frontier orbitals. Energy decomposition analysis mostly reveals the preference of several bonding situations, mostly with dative and ylidic electron-sharing bonds (e.g., P -> C–L). In general, the anionic systems show a higher preference of the ylidic bonding situations compared to the neutral analogues. However, in most of the cases different resonance structures have to be considered for the description of the “real” bonding situation.

First author: Pu, Z, Insights into the enhanced Ce equivalent to N triple bond in the HCe equivalent to N molecule,
Abstract: Herein, an experimental study of the vibrational spectra of HCeN was carried out in solid argon, followed by theoretical investigations of molecular structures and the nature of CeR equivalent to N bond. The absorption band at 937.7 cm(-1) with the 1.0311 N-14/N-15 isotopic shift ratio is characteristic of Ce equivalent to N stretching band for HCeN, showing a 94 cm(-1) higher shift relative to that of the diatomic CeN molecule. This large frequency shift indicates a much stronger Ce equivalent to N bond in HCeN, which is confirmed by DFT calculations. Qualitative orbital interaction and orbital composition analyses suggest that the addition of the H ligand to the Ce center will activate the 4f valence shell and strengthen the covalent bond between Ce and N, which may contribute to enhance the Ce equivalent to N triple bond in the HCeN molecule.

First author: Majid, A, First principles study of vibrational dynamics of ceria-titania hybrid clusters,
Abstract: Density functional theory based calculations were performed to study vibrational properties of ceria, titania, and ceria-titania hybrid clusters. The findings revealed the dominance of vibrations related to oxygen when compared to those of metallic atoms in the clusters. In case of hybrid cluster, the softening of normal modes related to exterior oxygen atoms in ceria and softening/hardening of high/low frequency modes related to titania dimmers are observed. The results calculated for monomers conform to symmetry predictions according to which three IR and three Raman active modes were detected for TiO2, whereas two IR active and one Raman active modes were observed for CeO2. The comparative analysis indicates that the hybrid cluster CeTiO4 contains simultaneous vibrational fingerprints of the component dimmers. The symmetry, nature of vibrations, IR and Raman activity, intensities, and atomic involvement in different modes of the clusters are described in detail. The study points to engineering of CeTiO4 to tailor its properties for technological visible region applications in photocatalytic and electrochemical devices.

First author: Birchall, C, A monomeric, heterobimetallic complex with an unsupported Mg-Fe bond,
Abstract: The phosphinimine, trimethylsilyl-substituted BIPM ligand [BIPM = bis(iminophosphorano)methanide] has been used to stabilise CH(Ph2PNSiMe3)(2)MgFe(eta(5)-C5H5)(CO)(2) (1), which is a structurally authenticated complex exhibiting a direct, unsupported bond between an alkaline earth metal and a transition metal. The FTIR-measured carbonyl stretching frequencies for this complex suggest that there is a polarisation of charge from the transition metal fragment to the magnesium centre. The presence of a polar metal-metal bond in 1 is confirmed by DFT calculations, which suggest that the Mg-Fe bond is predominantly ionic in nature.

First author: Jaegers, NR, Investigation of Silica-Supported Vanadium Oxide Catalysts by High Field V-51 Magic-Angle Spinning NMR,
Abstract: Supported V2O5/SiO2 catalysts were studied using solidstate V-51 magic-angle spinning NMR at a sample spinning rate of 36 kHz and at a magnetic field of 19.975 T to provide a better understanding of the coordination of the vanadium oxide as a function of environmental conditions. Structural transformations of the supported vanadium oxide species between the catalyst in the dehydrated state and hydrated state under an ambient environment were revisited to examine the degree of oligomerization and the effect of water. The experimental results indicate the existence of a single dehydrated surface vanadium oxide species that resonates at-67S ppm and two vanadium oxide species under ambient conditions that resonate at 566 and 610 ppm. No detectable structural difference was found as a function of vanadium oxide loading on SiO2 (3% V2O5/SiO2 and 8% V2O5/SiO2). Quantum chemistry simulations of the 51V NMR chemical shifts on predicted surface structures were used as an aid in understanding potential surface vanadium oxide species on the silica support. The results suggest the formation of isolated surface VO4 units for the dehydrated catalysts with the possibility of dimer and cyclic trimer presence. The absence of bridging V-O-V vibrations (similar to 200-300 cm(-1)) in previous Raman spectra, however, indicates that the isolated surface VO4 sites are the dominant dehydrated surface vanadia species on silica. Upon exposure to water, hydrolysis of the bridging V-O-Si bonds is most likely responsible for the decreased electron shielding experienced by vanadium. No indicators for the presence of hydrated decavanadate clusters or hydrated vanadia gels previously proposed in the literature were detected in this study.

First author: Ma, HP, A DFT Study on the Electronic Structures and Conducting Properties of Rubrene and its Derivatives in Organic Field-Effect Transistors,
SCIENTIFIC REPORTS, 7, 6246, (2017)
Abstract: We systematically studied the electronic structures and conducting properties of rubrene and its derivatives reported recently, and disscussed the influences of electron-withdrawing groups and chemical oxidation on the reorganization energies, crystal packing, electronic couplings, and charge injection barrier of rubrene. Hirshfeld surface analysis and quantum-chemical calculations revealed that the introduction of CF3 groups into rubrene decreases the H… H repulsive interaction and increases intermolecular F… H/H… F attractive interactions, which resulted in the tight packing arrangement and the increase of the electronic couplings, and finally cause the higer intrinsic holemobility in bis(trifluoromethyl)-dimethyl-rubrene crystal (mu(h) = 19.2 cm(2) V-1 s(-1)) than in rubrene crystal (mu(h) = 15.8 cm(2) V-1 s(-1)). In comparison, chemical oxidation reduces charge-carrier mobility of rubrene crystal by 2 similar to 4 orders of magnitude and increased the hole and electron injection barrier, which partly explains the rubrene-based field-effect transistor performance degrades upon exposure to air. Furthermore, we also discussed the influence of structural parameters of carbon nanotube (CNT) electrode on charge injection process, which suggests that the regulation of CNT diameters and increasing in thickness is an effective strategy to optimize CNT work functions and improve n-type OFET performances based on these organic materials.

First author: Kobylarczyk, J, Anion-pi recognition between [M(CN)(6)](3-) complexes and HAT(CN)(6): structural matching and electronic charge density modification,
DALTON TRANSACTIONS, 46, 3482, (2017)
Abstract: Hexacyanidometalates (M = Fe-III, Co-III) and multisite anion receptor HAT(CN)(6) (1,4,5,8,9,11-hexaazatri-phenylenehexacarbonitrile) recognize each other in acetonitrile solution and self-assemble into the novel molecular networks (PPh4)(3)[M(CN)(6)][HAT(CN)(6)] (M= Fe, 1; Co, 2) and (AsPh4) (3)[M(CN)(6)][HAT(CN)(6)].2MeCN.H2O (M = Fe, 3; Co, 4). 1-4 contain the stacked columns {[M(CN)(6)](3-);[HAT(CN)(6)]}(infinity) separated by the organic cations. All of the M-Cu equivalent to N vectors point collectively towards the centroids of pyrazine rings on neighboring HAT(CN)(6) molecules, with N-cyanide. ..centroid(pyrazine) distances that are under 3 angstrom. The directional character and structural parameters of the new supramolecular synthons correspond to collective triple anion-p interactions between the CN- ligands of the metal complexes and the p-deficient areas of HAT (CN)(6). Physicochemical characterisation (IR spectroscopy, UV-Vis spectroscopy, cyclic voltammetry) and dispersion-corrected DFT studies reveal the dominating charge-transfer (CT) and polarisation characters of the interactions. The electronic density flow occurs from the CN- ligands of [M(CN)(6)](3-) to the HAT(CN)(6) orbital systems and further, toward the peripheral -CN groups of HAT(CN)(6). Solid-state DFT calculations determined the total interaction energy of HAT(CN)(6) to be ca. -125 kcal mol(-1), which gives ca. -15 kcal mol-1 per one CN-…HAT(CN)(6) contact after subtraction of the interaction with organic cations. The UV-Vis electronic absorption measurements prove that the intermolecular interactions persist in solution and suggest a 1 : 1 composition of the anion-pi {[M(CN)(6)](3-);[HAT(CN)(6)]} chromophore, with the formation constant K-add = (5.8 +/- 6) x 10(2) dm(3) mol(-1) and the molar absorption coefficient epsilon(add) = 180 +/- 9 cm(-1) dm(3) mol(-1) at 600 nm, as estimated from concentration-dependent studies.

First author: Fard, MA, Coordination chemistry of mercury(II) with 2-pyridylnitrones: monomers to polymers,
DALTON TRANSACTIONS, 46, 3579, (2017)
Abstract: The coordination chemistry of mercury(II) halides, HgX2, X = Cl, Br, I, with N-methyl-alpha-(2-pyridyl) nitrone, L1, and N-t-butyl-alpha-(2-pyridyl) nitrone, L2, is reported. The structures of 1:1 complexes [HgX2L], X = Cl, L = L1; X = Br, L = L2, 2:1 complexes [(HgX2)(2)L], X = Br or I, L = L1; X = Cl or I, L = L2, and a unique compound [(HgBr2)(5)(L2)(3)] have been determined. In the 1:1 and 1:2 complexes, the ligand L1 adopts the anti conformation, and is either monodentate or bridging, while the ligand L2 adopts the syn conformation and acts as a chelate ligand. In the compound [(HgBr2)(5)(L2)(3)] the ligand L2 is present in both syn-chelate and anti-bridging bonding modes. Secondary intermolecular bonding, involving O…Hg or X…Hg interactions, can lead to association of the molecular compounds to form polymers of several kinds. In solution, the complexes are labile and the crystalline products do not necessarily reflect the reaction stoichiometry.

First author: Toman, P, Modelling of the charge carrier mobility in disordered linear polymer materials,
Abstract: We introduced a molecular-scale description of disordered on-chain charge carrier states into a theoretical model of the charge carrier transport in polymer semiconductors. The presented model combines the quantum mechanical approach with a semi-classical solution of the inter-chain charge hopping. Our model takes into account the significant local anisotropy of the charge carrier mobility present in linear conjugated polymers. Contrary to the models based on the effective medium approximation, our approach allowed avoiding artefacts in the calculated concentration dependence of the mobility originated in its problematic configurational averaging. Monte Carlo numerical calculations show that, depending on the degree of the energetic and structural disorder, the charge carrier mobility increases significantly with increasing charge concentration due to trap filling. At high charge carrier concentrations, the effect of the energetic disorder disappears and the mobility decreases slightly due to the lower density of unoccupied states available for the hopping transport. It could explain the experimentally observed mobility degradation in organic field-effect transistors at high gate voltage.

First author: Qi, ZX, Theoretical Study of the Dehydration Process of MgCl2 center dot 4H(2)O to MgCl2 center dot 2H(2)O,
Abstract: Density functional theory was employed to study the dehydration mechanism of MgCl2 center dot 4H(2)O. Analysis of potential energy surface (PES) of possible pathways indicated that the most possible way was one of the water molecules halfly dissociated with an elongated bond distance with Mg2+, where electrostatic interaction played a leading role; another water molecule dissociated sequentially. It was in agreement with the result from differencial thermal analysis. The dehydration process of MgCl2 center dot 4H(2)O was clarified theoretically, promoting the theoretical study of dehydration of MgCl2 center dot 2H(2)O.

First author: Conradie, J, A comparative DFT study of stacking interactions between adjacent metal atoms in linear chains of Ir and Rh acetylacetonato complexes,
Abstract: A computational chemistry study using DFT explains why the electrical conductivity along the metal axis in adjacent [Rh(acetylacetonato)(CO)(2)] molecules was found to be four to five orders of magnitude smaller than along the metal axis of adjacent [Ir(acetylacetonato)(CO)(2)] molecules. Computational chemistry results, obtained by a variety of different techniques, showed that strong interaction exists between iridium atoms in neighbouring [Ir(acetylacetonato)(CO)(2)] molecules. Bonds between the neighbouring iridium atoms were identified by quantum theory of atoms in molecules (QTAIM) calculations. A natural bond orbital (NBO) analysis showed that LP(Ir) donor – LP*(Ir) acceptor interactions between the two adjacent iridium centres in [Ir(acetylacetonato)((CO)(2)](2), are more than twice the value the LP(Rh) donor – LP*(Rh) acceptor interactions obtained for adjacent rhodium centres in [Rh(acetylacetonato)(CO)(2)](2). The stacking of [Ir(acetylacetonato)((CO)(2)] molecules in the solid state is stabilised by additional four weak BD(COcarbonyl) donor – BD*(CHmethyl) acceptor interactions, as well as four weak BD(COcarbonyl) donor – BD*(COacac) acceptor interactions between adjacent [Ir(acetylacetonato)(CO)(2)] molecules, which were not obtained by the NBO analysis of [Rh(acetylacetonato)(CO)(2)](2). A fragment analysis of the frontier molecular orbitals of [Ir(acetylacetonato)(CO)(2)](2) showed that the intermolecular iridium-iridium bonding energy in dimolecular [Ir(acetylacetonato)(CO)(2)](2) is about times higher than the intermolecular rhodium-rhodium bonding energy in [Rh(acetylacetonato)(CO)(2)](2).

First author: Stoyanov, ES, Stabilization of carbocations CH3+, C2H5+, i-C3H7+, tert-Bu+, and cyclo-pentyl(+) in solid phases: experimental data versus calculations,
Abstract: Comparison of experimental infrared (IR) spectra of the simplest carbocations (with the weakest carborane counterions in terms of basicity, CHB(11)Hal(11)(-), Hal = F, Cl) with their calculated IR spectra revealed that they are completely inconsistent, as previously reported for the t-Bu+ cation [Stoyanov E. S., et al. J. Phys. Chem. A, 2015, 119, 8619]. This means that the generally accepted explanation of hyperconjugative stabilization of the carbocations should be revised. According to the theory, one CH bond (denoted as) from each CH3/CH2 group transfers its s-electron density to the empty 2p(z) orbital of the sp(2) C atom, whereas the s-electron density on the other CH bonds of the CH3/CH2 group slightly increases. From experimental IR spectra it follows that donation of the s-electrons from the bond to the 2p(z) C-orbital is accompanied by equal withdrawal of the electron density from other CH bonds, that is, the electrons are supplied from each CH bond of the CH3/CH2 group. As a result, all CH stretches of the group are red shifted, and IR spectra show typical CH3/CH2 group vibrations. Experimental findings provided another clue to the electron distribution in the hydrocarbon cations and showed that the standard computational techniques do not allow researchers to explain a number of recently established features of the molecular state of hydrocarbon cations.

First author: Paragi, G, The evaluation of 5-amino- and 5-hydroxyuracil derivatives as potential quadruplex-forming agents,
Abstract: 5-Substituted uracils (NH2 or OH groups in position 5) have been examined theoretically and experimentally as potential building blocks in quadruplex structures. Our high level Density Functional Theory (DFT) calculations showed that the tetramer formation and stacking energies for 5-substituted uracils are similar to the energies of purine-based xanthine (X) or guanine (G) structures. As tetrads of 5-substituted uracils cover almost exactly the same area as purine tetrads, mixed tetrads or quadruplex structures based on X or G and 5-substituted uracil motifs are possible. According to the calculations, 5-hydroxyuracil-based structures are the best candidates for experimental implementation which was corroborated by the existence of higher complexes in the mass spectra of 1-benzyl-5-hydroxyuracil. These pyrimidine-based molecules can be used as efficient building blocks in different applications including aptamers, biosensors or – taking into account the larger cavity in the central region of 5-hydroxyuracil structures – as an artificial ion channel.

First author: Kang, X, Au15Ag3(SPhMe2)(14) Nanoclusters – Crystal Structure and Insights into Ligand-Induced Variation,
Abstract: Understanding the ligand effects in the nanocluster (NC) range is crucial for tailoring the properties. We herein report on the crystal structure of the Au15Ag3(SPhMe2)(14) nanocluster. Compared with the previously reported Au15Au3(SC6H11)(14) nanocluster, Au15Ag3(SPhMe2)(14) exhibits a different crystal and electronic structure, which further affects the optical spectra because of the ligand effect. In combination with density functional theory (DFT) calculations, the differences in the UV/Vis spectra were found to be caused by the distinct electronic components of the frontier orbitals. In addition, accompanied by many recrystallization steps on Au15Ag3(SPhMe2)(14), mass spectrometry analysis revealed that the by-products (i.e. Au14Ag4 and Ag13Ag5 nanoclusters) gradually decompose, and finally only the Au15Ag3 nanocluster exists. Our findings offer an extended insight into the ligand-induced variation on a nanocluster level.

First author: Aramburu, JA, Jahn-Teller and Non-Jahn-Teller Systems Involving CuF64- Units: Role of the Internal Electric Field in Ba2ZnF6:Cu2+ and Other Insulating Systems,
Abstract: The applicability of the Jahn-Teller (JT) framework to 6-fold coordinated d(9) ions whose local symmetry is not strictly octahedral is explored by means of first principle calculations. Our results contradict much of the existing literature where these systems are analyzed within the quasi-JT regime which assumes the usual JT description with a small splitting between b(1g)(similar to x(2)-y(2)) and a(1g)(similar to 3z(2)-r(2)) orbitals and also the existence of three nearly equivalent distortions. To clarify this issue we investigate the equilibrium geometry (equatorial, R-eq, and axial, R-ax., Cu2+-F- distances) and optical transitions for CuF64- units formed in Cu2+-doped the tetragonal Ba2ZnF6 host lattice. While the experimental d-d transitions cannot be reproduced through the isolated CuF64- unit at the equilibrium geometry, a reasonable agreement is reached adding in the calculation the internal electric field, ER(r), created by the rest of lattice ions on the electrons confined in the complex. It is shown that this tetragonal field, ER(r), already produces a gap Delta(0) similar to 0.35 eV between b(1g)(similar to x(2)-y(2)) and a(1g)(,similar to 3z(2)-r(2)) orbitals of Ba2ZnF6:Cu2+ when R-ax,, = R-eq. Nevertheless, as this internal field leads to a Delta(0) value higher than typical JT barriers it drastically modifies the characteristic pattern of a JT effect. In particular, it prevents the existence of three equivalent distortions as confirmed by experimental EPR data. Furthermore, ER(r) is shown to be the main physical reason behind an unusual compressed ground state with the hole in the a(1g)(similar to 3z(2)-r(2)) level while it is always placed in the b(1g)(similar to x(2)-y(2)) level for MX6 complexes (M = Cu2+, Ag2+, Nit; X = F–,F- Cl-) in cubic lattices displaying a static JT effect. While the experimental results of CuF64- in Ba2ZnF6 cannot be understood within the JT framework it is pointed out that a quasi-JT situation can however happen for a d9 ion in a cubic lattice under a strain of -10(-3) in agreement with experimental data. The present results stress the key role played by the internal electric fields for a quantitative understanding of compounds with transition metal cations. Moreover, they also demonstrate that in the interpretation of experimental data the use of a simple model should be avoided unless all its assumptions are well justified.

First author: Sevcik, R, New condensed nitrogen-phosphorus heterocycles,
POLYHEDRON, 124, 96, (2017)
Abstract: To extend our previous study aimed at the reactions of chlorodithiophosphoric acid pyridiniumbetaine (py.PS2Cl) with thiosemicarbazide derivatives, we performed the reactions of chlorodithiophosphoric acid pyridiniumbetaine with a new group of polyfunctional nucleophiles – symmetrical and nonsymmetrical derivatives of hydrazine-1,2-bis(thiocarboamide) of general formula R(H)N-C(S)N(H)N(H)C(S)-N(H) R (R = methyl, i-propyl, ethyl, t-butyl, phenyl). In analogy to heterocyclic anions obtained with the thiosemicarbazide derivatives, the hydrazine derivatives were expected to form heterobicyclic dianions from the reactions with py.PS2CI. All the reactions were carried out in acetonitrile in the presence of pyridine to keep the same reaction conditions as with the previous experiments. Four new compounds were prepared and characterized by P-31 NMR, FTIR, Raman spectroscopy, and single crystal X-ray diffraction. Molecular structures of the products are based on heterobicyclic dianion consisting of two condensed five membered P-N-N-C-N rings, each of them bearing an organic group. Both of the organic groups in heterobicyclic dianion are either identical (Me, (i)pr) or different (Et/Bu-t, Et/Ph). The molecular structure of the heterobicyclic dianion with unusual structural features was further examined by quantum chemistry calculations.

First author: Cendic, M, Chelating properties of EDTA-type ligands containing six-membered backbone ring toward copper ion: Structure, EPR and TD-DFT evaluation,
POLYHEDRON, 124, 215, (2017)
Abstract: The P-APC ligands (EDTA-like aminopolycarboxylate ligands comprising 1,3-propanediamine backbone) H(4)pdta, H(4)pd(3)ap, H(4)pddadp and H(4)pdtp (H(4)pdta = 1,3-propanediamine-N,N,N’,N’-tetraacetatic acid; H(4)pd(3)ap = 1,3-propanediamine-N,N,N’-triacetic-N’-3-propionic acid; H4pddadp = 1,3-propanediamine-N,N’-diacetatic-N,N’-di-3-propionic acid; H(4)pdtp = 1,3-propanediaminetetra-3-propionic acid) were investigated. The chelating ligands coordinate to copper(II) via five or six donor atoms affording distorted trigonal-bipyramid and octahedral structures that were verified by X-ray analysis for Ba[Cu(pd(3)ap)]center dot 6H(2)O (1) and trans(O-6)-Ba[Cu(pddadp)]center dot 8H(2)O (2) complexes respectively. The impact of counter-ions on the P-APC complexes is shown in detail together with the analysis of another strain parameters. EPR spectral results confirm the penta-coordination of 1 and hexa-coordination of 2 in aqueous solution, even if several Cu(II) species with different protonation degree exist as a function of pH, and indicate that a hexa-coordinated structure is favored when the two axial COO- donors close five-membered chelate rings. We also present here the results of molecular mechanics (LFMM) calculations based on our previously-developed force field along with results of DFT (Density Functional Theory). On the basis of extensive DFT and TD-DFT calculations the B1LYP/6-311++G(d,p) level has been seen as an accurate theory for calculating and predicting the UVVis spectra in case of copperP-APC compounds.

First author: Takahashi, K, Engineering Thin Films of a Tetrabenzoporphyrin toward Efficient Charge-Carrier Transport: Selective Formation of a Brickwork Motif,
Abstract: Tetrabenzoporphyrin (BP) is a p-type organic semiconductor characterized by the large, rigid yr-framework, excellent stability, and good photoabsorption capability. These characteristics make BP and its derivatives prominent active layer components in organic electronic and optoelectronic devices. However, the control of the solid-state arrangement of BP frameworks, especially in solution-processed thin films, has not been intensively explored, and charge-carrier mobilities observed in BP-based materials have stayed relatively low as compared to those in the best organic molecular semiconductors. This work concentrates on engineering the solidstate packing of a BP derivative, 5,15-bis(triisopropylsilyl)ethynyltetrabenzoporphyrin (TIPS-BP), toward achieving efficient charge-carrier transport in its solution-processed thin films. The effort leads to the selective formation of a brickwork packing that has two dimensionally extended 7c-staking. The maximum field-effect hole mobility in the resulting films reaches 1.1 cm(2) s(-1), which is approximately 14 times higher than the record value for pristine free-base BP (0.070 cm(2) V-1 s(-1)). This achievement is enabled mainly through the optimization of three factors; namely, deposition process, cast solvent, and self-assembled monolayer that constitutes the dielectric surface. On the other hand, polarized-light microscopy and grazing-incident wide-angle X-ray diffraction analyses show that there remains some room for improvement in the in-plane homogeneity of molecular alignment, suggesting even higher charge-carrier mobilities can be obtained upon further optimization. These results will provide a useful basis for the polymorph engineering and morphology optimization in solution-processed organic molecular semiconductors.

First author: Terrett, R, Vibrational intensities in the mobile block Hessian approximation,
Abstract: Herein we present a proof of concept for the recovery of vibrational intensities from density functional theory vibrational calculations performed in the Mobile Block Hessian (MBH) approximation, which constrains the internal degrees of freedom of designated subsets of a molecule. We compare and contrast the behaviour of this methodology with respect to conventional vibrational calculations, and characterise the performance and accuracy of our method with respect to the size of MBH constrained regions within a variety of species. We demonstrate the viability of this method as a means by which to obtain vibrational intensities for regions of interest within a molecule whilst potentially dramatically reducing computational expense with respect to conventional all-atom vibrational calculations, and discuss caveats for application.

First author: Haller, LJL, Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)(4)-( L)H](0/+) species (NHC = N-heterocyclic carbene; L = vacant, H-2, N-2, CO, MeCN, O-2, P-4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)(2)(L)H](+) congeners,
DALTON TRANSACTIONS, 46, 2861, (2017)
Abstract: Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC)(4)(L)H](0/+) species (NHC = N-heterocyclic carbene; L = vacant, H-2, N-2, CO, MeCN, O-2, P-4, SO2, H-, F- and Cl-), as well as selected phosphine analogues [Ru(R2PCH2CH2PR2)(2)(L) H](+) (R = Pr-i, Cy; L = vacant, O-2). Inclusion of spinorbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl-, F-) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru d(pi) orbitals and the unoccupied sigma(star)(Ru-H) orbital. In [Ru(NHC)(4)(eta(2)-O-2) H](+) a delta-interaction with the O-2 ligand results in a low-lying LUMO of d(pi) character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) dp orbital under the L-z angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru((i)Pr(2)PCH(2)CH(2)PiPr(2))(2)(eta(2)-O-2) H]+ (delta = -6.2 ppm) and [Ru(R2PCH2CH2PR2)(2)H](+) (ca. -32 ppm, R = Pr-i, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC)(4)H](+) analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily readily detected experimentally) can aid in the interpretation of hydride chemical shift data for nominally unsaturated hydride-containing species. The synthesis and crystallographic characterization of the BArF(4)(-)salts of [Ru(IMe4)(4)(L) H](+) (IMe4 = 1,3,4,5-tetramethy-limidazol- 2-ylidene; L = P-4, SO2; Ar-F = 3,5-(CF3)(2)C6H3) and [Ru(IMe4)(4)(Cl) H] are also reported.

First author: Zhao, HB, Interfacial Interaction of Titania Nanoparticles and Ligated Uranyl Species: A Relativistic DFT Investigation,
INORGANIC CHEMISTRY, 56, 2763, (2017)
Abstract: To understand interfacial behavior of actinides adsorbed onto mineral surfaces and unravel their structure-property relationship, the structures, electronic properties, and energetics of various ligated uranyl species adsorbed onto TiO2 surface nanoparticle clusters (SNCs) were examined using relativistic density functional theory. Rutile (110) and anatase (101) titania surfaces, experimentally known to be stable, were fully optimized. For the former, models studied include clean and water-free Ti27O64H2O (dry), partially hydrated (Ti27O64H20) (H2O)(8) (Sol) and proton-saturated [(Ti27O64H20)(H2O)(8)(H)(2)](2+) (sat), while defect-free and defected anatase SNCs involving more than 38 TiO2 units were considered. The aquouranyl sorption onto rutile SNCs is energetically preferred, with interaction energies of -8.54, -10.36, and -2.39 eV, respectively. Energy decomposition demonstrates that the sorption is dominated by orbital attractive interactions and modified by steric effects. Greater hydrogen-bonding involvement leads to increased orbital interactions (i.e., more negative energy) from dry to sol/sat complexes, while much larger steric interaction in the sat complex significantly reduces the sorption interaction (i.e., more positive energy). For dry SNC, adsorbates were varied from aquo to aquo-carbonato, to carbonato, to hydroxo uranyl species. Longer U-O-surf/U-Ti distances and more positive sorption energies were calculated upon introducing carbonato and hydroxo ligands, indicative of weaker uranyl sorption onto the substrate. This is consistent with experimental observations that the uranyl sorption rate decreases upon raising solution pH value or adding carbon dioxide. Anatase SNCs adsorbing aquouranyl are even more exothermic,, because more bonds are formed than in the case of rutile. Moreover, the anatase sorption can be tuned by surface defects as well as its Ti and O stoichiometry. All the aquouranyl-SNC complexes show similar character of molecular orbitals and energetic order although differing in highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and orbital energy levels, but changes can be accomplished by adding carbonato and hydroxo ligands.

First author: Nickolaus, J, Phosphenium Hydride Reduction of [(cod)MX2] (M = Pd, Pt; X = CI, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles,
INORGANIC CHEMISTRY, 56, 3071, (2017)
Abstract: The outcome of the reduction of [(cod)PtX2] (X = Cl, Br; cod = 1,S-cyclooctadiene) with N -heterocyclic phosphenium hydrides (NHP)-N-R-H depends strongly on the steric demand of the N -aryl group R and the nature of X. Reaction of [(cod)PtCl2] with (NHP)-N-DiPP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [((NHP)-N-DiPP) ((NHP)-N-DIPP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z -type ligand. In contrast, reaction of [(cod)PtBr2] with the sterically less protected (NHP)-N-Mes-H afforded a mixture of donor-ligand free oligonuclear complexes [{((NHP)-N-Mes,)PtBr}(n)] (n = 2, 3), which are structural analogues of known palladium complexes with mu(2)-bridging phosphenium units. All reductions studied proceed via spectroscopically detectable intermediates, several of which could be unambiguously identified by means of multinuclear (H-1, P-31, Pt-195) NMR spectroscopy and computational studies. The experimental findings reveal that the phosphenium hydrides in these multistep processes adopt a dual function as ligands and hydride transfer reagents. The preference for the observed intricate pathways over seemingly simpler ligand exchange processes is presumably due to kinetic reasons. The attempt to exchange the bulky phosphine ligand in [((NHP)-N-DiPP)((NHP)-N-DiPP-H)PtC1] by Me3P resulted in an unexpected isomerization to a platinum(0) chlorophosphine complex via a formal chloride migration from platinum to phosphorus, which accentuates the electrophilic nature of the phosphenium ligand. Phosphenium metal(0) halides of platinum further show a surprising thermal stability, whereas the palladium complexes easily disintegrate upon gentle heating in dimethyl sulfoxide to yield metal nanoparticles, which were characterized by TEM and XRD studies.

First author: Khosla, AL, Spin-orbit coupling and strong electronic correlations in cyclic molecules,
PHYSICAL REVIEW B, 95, 3071, (2017)
Abstract: In atoms spin-orbit coupling (SOC) cannot raise the angular momentum above a maximum value or lower it below a minimum. Here we show that this need not be the case in materials built from nanoscale structures including multinuclear coordination complexes, materials with decorated lattices, or atoms on surfaces. In such cyclic molecules the electronic spin couples to currents running around the molecule. For odd-fold symmetric molecules (e.g., odd-membered rings) the SOC is highly analogous to the atomic case; but for even-fold symmetric molecules every angular momentum state can be both raised and lowered. These differences arise because for odd-fold symmetric molecules the maximum and minimum molecular orbital angular momentum states are time-reversal conjugates, whereas for even-fold symmetric molecules they are aliases of the same single state. We show, from first-principles calculations, that in suitable molecules this molecular SOC is large, compared to the energy differences between frontier molecular orbitals. Finally, we show that, when electronic correlations are strong, molecular SOC can cause highly anisotropic exchange interactions and discuss how this can lead to effective spin models with compass Hamiltonians.

First author: Orian, L, In Silico Stark Effect: Determination of Excited-State Polarizabilities of Squaraine Dyes,
Abstract: The static electric polarizabilities (alpha) of a quadrupolar squaraine dye are investigated in silico, either as the excess polarizability, i.e., the change from the ground to the lowest excited state, Delta alpha, or as those of the two states separately, depending on the approach. The polarizabilities are worked out by making use of the energy and dipole moment Taylor expansions as a function of the electric field (E), in which alpha is represented by the quadratic and linear terms, respectively, and also by means of the linear response approach. Dipoles and energies are computed at a few values of the electric field, with different strategies that consider the geometry of the molecule either frozen in the ground state or relaxed at each E value. From a physical standpoint, the most appropriate approach to describing the molecular polarizability depends on the processes in which the molecule is involved: for example, fluorescence methods provide information about relaxed excited states, and absorption methods are used to determine the polarizability changes of excited states frozen in the ground-state conformation. We show that the excited-state polarizability does not strongly differ from the ground-state polarizability when the field is applied along the main axis of the squaraine. In contrast, remarkable differences are found when the field is applied perpendicular to the molecular plane due to a large geometrical distortion of the molecular backbone.

First author: Qu, H, Infrared Photodissociation Spectroscopy of Heterodinuclear Iron-Zinc and Cobalt-Zinc Carbonyl Cation Complexes,
Abstract: Fe-Zn and Co-Zn heteronuclear carbonyl cation complexes are produced via a laser vaporization supersonic cluster source in the gas phase. The dinuclear FeZn(CO)(5)(+) and CoZn(CO)(7)(+) cation complexes are observed to be the most intense heterodinuclear carbonyl cation species in the mass spectra. The infrared spectra are obtained via mass selection and infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are assigned with the support of density functional calculations. The FeZn(CO)(5)(+) complex is determined to have a (OC)(5)Fe-Zn structure with a Fe-Zn half bond. The CoZn(CO)(7)(+) ion is established to have a staggered (OC)(4)Co-Zn(CO)(3) structure involving a Co-Zn sigma single bond.

First author: Spivak, M, Quantum Chemical Characterization of Single Molecule Magnets Based on Uranium,
Abstract: Multiconfigurational electronic structure theory calculations including spin-orbit coupling effects were performed on four uranium-based single-molecule-magnets. Several quartet and doublet states were computed and the energy gaps between spin-orbit states were then used to determine magnetic susceptibility curves. Trends in experimental magnetic susceptibility curves were well reproduced by the calculations, and key factors affecting performance were identified.

First author: Becker, TM, Polarizable Force Fields for CO2 and CH4 Adsorption in M-MOF-74,
Abstract: The family of M-MOF-74, with M = Co, Cr, Cu, Fe, Mg, Mn, Ni, Ti, V, and Zn, provides opportunities for numerous energy related gas separation applications. The pore structure of M-MOF-74 exhibits a high internal surface area and an exceptionally large adsorption capacity. The chemical environment of the adsorbate molecule in M-MOF-74 can be tuned by exchanging the metal ion incorporated in the structure. To optimize materials for a given separation process, insights into how the choice of the metal ion affects the interaction strength with adsorbate molecules and how to model these interactions are essential. Here, we quantitatively highlight the importance of polarization by comparing the proposed polarizable force field to orbital interaction energies from DFT calculations. Adsorption isotherms and heats of adsorption are computed for CO2, CH4, and their mixtures in M-MOF-74 with all 10 metal ions. The results are compared to experimental data, and to previous simulation results using nonpolarizable force fields derived from quantum mechanics. To the best of our knowledge, the developed polarizable force field is the only one so far trying to cover such a large set of possible metal ions. For the majority of metal ions, our simulations are in good agreement with experiments, demonstrating the effectiveness of our polarizable potential and the transferability of the adopted approach.

First author: Paragi, G, Cooperativity in the Self-Assembly of the Guanine Nucleobase into Quartet and Ribbon Structures on Surfaces,
Abstract: The guanine nucleobase can self-assemble into tetrameric or ribbon structures on surfaces or in solution. The origin for the occurrence of different aggregation patterns has not yet been investigated. Herein, a quantum chemical study on the different self-assembled structures of guanine and xanthine by using dispersion-corrected DFT is presented. Theoretical investigations can be used to explain, from an electronic point of view, the differences between the experimental findings. With quantitative Kohn-Sham molecular orbital theory and the accompanying energy decomposition analysis, the hydrogen-bonding mechanism within the guanine ribbons can be disclosed and the preferred self-assembled structures under different experimental conditions can be explained. An important role of the sigma-electronic system in the guanine self-assembled structures is revealed as the main factor for the switch between different arrangements on surfaces and in crystals.

First author: Yurenko, YP, Anion-pi Interactions in Flavoproteins Involve a Substantial Charge-Transfer Component,
Abstract: Anion-pi interactions have been shown to stabilize flavoproteins and to regulate the redox potential of the flavin cofactor. They are commonly attributed to electrostatic forces. Herein we show that anion-flavin interactions can have a substantial charge-transfer component. Our conclusion emanates from a multi-approach theoretical analysis and is backed by previously reported observations of absorption bands, originating from charge transfer between oxidized flavin and proximate cysteine thiolate groups. This partial covalency of anion-flavin contacts renders classical simulations of flavoproteins questionable.

First author: Hermann, M, Carbones as Ligands in Novel Main-Group Compounds E[C(NHC)(2)](2) (E=Be, B+, C2+, N3+, Mg, Al+, Si2+, P3+): A Theoretical Study,
Abstract: Quantum chemical calculations of the main-group compounds E[C(NHCMe)(2)](2) ( E= Be, B+, C2+, N3+, Mg, Al+, Si2+, P3+) have been carried out using density functional theory at the BP86/ def2-TZVPP and BP86-D3( BJ)/def2-TZVPP levels of theory. The geometry optimization at BP86/def2TZVPP gives equilibrium structures with two-coordinated species E and bending angles C-E-C between 152.5 degrees (E= Be) and 110.5 degrees ( E= Al). Inclusion of dispersion forces at BP86D3( BJ)/ def2-TZVPP yields a three- coordinated beryllium compound Be[ C( NHCMe)(2)](2) as the only energy minimum form. Three- coordinated isomers are found besides the two- coordinated energy minima for the boron and carbon cations B[C(NHCMe)(2)](2) + and C[ C( NHCMe)(2)](2) (2+). The three- coordinated form of the boron compound is energetically lower lying than the two- coordinated form, while the opposite trend is calculated for the carbon species. The theoretically predicted bond dissociation energies suggest that all compounds are viable species for experimental studies. The X-ray structure of the benzoannelated homologue of P[C(NHCMe)(2)](2) (3)+ that was recently reported by Dordevic et al. agrees quite well with the calculated geometry of the molecule. A detailed bonding analysis using charge and energy decomposition methods shows that the two- coordinated neutral compounds Be[C( NHCMe)(2)](2) and Mg[ C(NHCMe)(2)](2) possess strongly positively charged atoms Be and Mg. The carbodicarbene groups C( NHCMe)(2) serve as acceptor ligands in the compounds and may be sketched with dative bonds ( NHCMe)(2)C <- E <- C( NHCMe)(2) ( E= Be, Mg). Dative bonds in which the carbones C( NHCMe)(2) are donor ligands are suggested for the cations ( NHCMe)(2)C -> E -> C(NHCMe)(2) ( E= B+, Al+). The dications and trications possess electron- sharing bonds in which the bonding situation is best described with the formula [( NHCMe)(2)C]+- E-[ C( NHCMe)(2)]+ ( E= C, Si, N+, P+).

First author: Le Vaillant, F, Room temperature decarboxylative cyanation of carboxylic acids using photoredox catalysis and cyanobenziodoxolones: a divergent mechanism compared to alkynylation,
CHEMICAL SCIENCE, 8, 1790, (2017)
Abstract: The one-step conversion of aliphatic carboxylic acids to the corresponding nitriles has been accomplished via the merger of visible light mediated photoredox and cyanobenziodoxolones (CBX) reagents. The reaction proceeded in high yields with natural and non-natural alpha-amino and alpha-oxy acids, affording a broad scope of nitriles with excellent tolerance of the substituents in the alpha position. The direct cyanation of dipeptides and drug precursors was also achieved. The mechanism of the decarboxylative cyanation was investigated both computationally and experimentally and compared with the previously developed alkynylation reaction. Alkynylation was found to favor direct radical addition, whereas further oxidation by CBX to a carbocation and cyanide addition appeared more favorable for cyanation. A concerted mechanism is proposed for the reaction of radicals with EBX reagents, in contrast to the usually assumed addition elimination process.

First author: Akkerman, QA, Nearly Monodisperse Insulator Cs4PbX6 (X = Cl, Br, I) Nanocrystals, Their Mixed Halide Compositions, and Their Transformation into CsPbX3 Nanocrystals,
NANO LETTERS, 17, 1924, (2017)
Abstract: We have developed a colloidal synthesis of nearly monodisperse nanocrystals of pure Cs4PbX6 (X = Cl, Br, I) and their mixed halide compositions with sizes ranging from 9 to 37 nm. The optical absorption spectra of these nanocrystals display a sharp, high energy peak due to transitions between states localized in individual PbX64- octahedra. These spectral features are insensitive to the size of the particles and in agreement with the features of the corresponding bulk materials. Samples with mixed halide composition exhibit absorption bands that are intermediate in spectral position between those of the pure halide compounds. Furthermore, the absorption bands of intermediate compositions broaden due to the different possible combinations of halide coordination around the Pb2+ ions. Both observations electronically decoupled in these systems. Because of the large are supportive of the fact are band gap of Cs4PbX6 (>3.2 the that the [PbX6](4-) octahedra eV), no excitonic emission in visible range was observed. The Cs4PbBr6 nanocrystals can be converted into green fluorescent CsPbBr3 nanocrystals by their reaction with an excess of PbBr2 with preservation of size and size distributions. The insertion of PbX2 into Cs4PbX6 provides a means of accessing CsPbX3 nanocrystals in a wide variety of sizes, shapes, and compositions, an important aspect for the development of precisely tuned perovskite nanocrystal inks.

First author: Munoz-Castro, A, Au-10(2+) and Au6X42+ clusters: Superatomic molecules bearing an SP3-hybrid Au-6 core,
Abstract: The octahedral Au-6 core is explored for the formation of novel SP3-hybrid superatomic molecules by considering and Au6X42+ clusters (X= F, Cl, Br, I). The bonding between the four capping atoms and the Au-6 core requires a combination of 1S and 1P shells of the core leading to a set of four equivalent hybrid orbitals. Thus, combining the superatom concept with both the Lewis structure model and VSEPR theory contributes to the rationalization of structure and bonding in metal clusters. For example, our results consider the Au6X42+ clusters as analogues of the simplest perhalogenated hydrocarbon, CX4.

First author: Ardizzoia, GA, Interpretation of Tolman electronic parameters in the light of natural orbitals for chemical valence,
Abstract: Understanding the nature and the strength of metal-ligand interactions in d-and f-block metal complexes has always been a central issue for both synthetic and theoretical chemists. These interactions are usually described according to the well accepted Dewar-Chatt-Duncanson model, and thus over the years numerous research groups directed their efforts to shed light on the role of s-and p-contributions. Among others, the electronic parameter introduced by Tolman in the 1970s represents a milestone in this field. Herein we present a quantitative description of the nickel-phosphine bond in Tolman’s nickel(0) carbonyl complexes. The combination of Natural Orbitals for Chemical Valence with Energy Decomposition Analysis resulted in the definition of a new parameter (T phos) which comprises all the energetic contributions needed to describe the nickel-phosphine bond and thus stands as a reliable descriptor of the electronic properties of phosphines. Moreover, steric effects of phosphines (i.e. Tolman’s cone angles) have been considered too, and a linear relation including Ni-P bond distances, T phos and cone angle has been found.

First author: Melgar, D, Anions coordinating anions: analysis of the interaction between anionic Keplerate nanocapsules and their anionic ligands,
Abstract: Keplerates are a family of anionic metal oxide spherical capsules containing up to 132 metal atoms and some hundreds of oxygen atoms. These capsules holding a high negative charge of -12 coordinate both mono-anionic and di-anionic ligands thus increasing their charge up to -42, even up to -72, which is compensated by the corresponding counter-cations in the X-ray structures. We present an analysis of the relative importance of several energy terms of the coordinate bond between the capsule and ligands like carbonate, sulphate, sulphite, phosphinate, selenate, and a variety of carboxylates, of which the overriding component is contributed by solvation/de-solvation effects.

First author: Conradie, J, Mechanistic investigation of cis and trans oxidative addition to acetylacetonato-1,5-cyclooctadieneiridium(I),
POLYHEDRON, 123, 252, (2017)
Abstract: Density functional theory (DFf) calculations of the oxidative addition of CH3I, as well as Hg(CN)(2), to [Ir(acac)(cod)] are described (acac acetylacetone). Both cis and trans oxidative addition mechanisms are considered and compared to experimental data. The DFT calculated thermodynamically most stable oxidative addition products are trans-Ur(acac)(cod)(CH3)(I)] and cis-[Ir(acac)(cod)(HgCN)(CN)]. The steric demand of the cod ligand leads to a distorted octahedral trans-[Ir(acac)(cod)(CH3)(I)] complex, with the C-CH3-Ir-I angle deviating by more than 20 degrees from 180 degrees, as expected for real octahedral geometry. However, the steric demand of the cod ligand does not lead to any cis transition state for the [Ir(acac)(cod)] + CH3I reaction, rather the trans transition state is energetically favoured, as is generally found for oxidative addition of CH3I to square planar complexes. On the other hand, oxidative addition of lig(CN)(2) to [Ir(acac)(cod)], occurs via a concerted three-centre cis transition state structure. The concerted three centre cis transition state structure is confirmed by the existence of a ring critical point, as obtained by the Bader’s quantum theory of atoms in molecules analysis of the cis transition state structure. Both trans addition of CH3I to [Ir(acac)(cod)] as well as cis addition of Hg(CN)(2) to [Ir(acac)(cod)], are in agreement with experimental observation.

First author: Chen, X, Germanium Nanotube as the Catalyst for Oxygen Reduction Reaction: Performance and Mechanism,
ACTA CHIMICA SINICA, 75, 189, (2017)
Abstract: One of the major technical barriers to the commercialization of proton exchange membrane fuel cells is the high cost of Pt-based oxygen reduction reaction (ORR) electrocatalysts. In this paper, the ORR catalytic performance and the possible mechanism on (5,5) germanium nanotube (GeNT) were studied by density functional theory methods using DZP basis set. The results indicate that the ORR on the GeNT may undergo three mechanisms including O-2 dissociation, OOH dissociation and H2O2 dissociation. For any of the above mechanism, the whole process could easily take place on the GeNT with a complete 4e(-) ORR pathway. The adsorption properties of the ORR intermediates, especially for O and OH, are also very important for evaluating the catalytic performance. The calculated adsorption energies of the above species are -4.33 and -2.21 eV respectively, much close to those on the Pt. Furthermore, the adsorption energy of H2O on the GeNT is only -0.05 eV, much weaker than the O-2 binding, indicating the catalytic cycle of ORR could repeat most easily on the GeNT. Therefore, both the reaction energies of the ORR steps and the adsorption energies of ORR intermediates show that the current GeNT model has the catalytic performance similar to that of precious Pt catalyst. Furthermore, the solvent effect was also studied by using three-water-molecule clusters as the real solvent. The obtained results indicate that the solvent effect could affect the geometrical structure of some adsorbed ORR intermediates, such as atomic O. This would lead to the decrease of the heat loss during the O-2 dissociation mechanism. The decreased heat loss would accelerate the following electron transfer steps, due to the fact that an effective electrocatalyst must make the energy loss as small as possible for non-electron-transfer step, in which case the cathode electrocatalyst would deliver all the Gibbs energy of the ORR as electrical work. With solvation, the heat loss is slightly increased from *O-2 to *OOH, and decreased from *OOH to *OH in the H2O2 dissociation mechanism, which are also more favorable for ORR.

First author: Aazaad, B, Reaction of NO3 radical with benzyl alcohol – A DFT study,
Abstract: Volatile primary aromatic benzyl alcohol (BzOH) reacts with strong atmospheric oxidants like OH, CI, NO3 radicals. The present study elucidates detailed investigation of gas phase reaction mechanisms of benzyl alcohol with NO3 radicals using density functional theory at M06-2X/6-311+G(d,p) and MPW1K/6-311+G (d,p) levels. The results show that the H-abstraction from methyl group is more energetically favorable with small barrier height. Single-point energy calculations were also performed at the CCSD(T)/6-311+G(d,p) level of theory. The spin state analysis (singlet, triplet) concludes ground state (singlet) reactions are feasible. The reaction force profile along the reaction path is rationalized in terms of structural and electronic rearrangements that take place during the chemical transformation. From the reaction force analysis, it is evident that structural rearrangement plays more dominant role than electronic reordering in this reaction. The calculated rate constant of H-atom abstraction from methyl group of benzyl alcohol with NO3 radical is 16.72 x 10(-15) cm3 molecule(-1) s(-1), which is in good agreement with experimental study. Overall, NO3 will replace OH and play a major role in reaction with BzOH during night time.

First author: Ortolan, AO, Metal-ligand bonding situation in ruthenophanes containing ij-xylylene-linked bis(NHC)cyclophane ligands,
Abstract: The electronic structure of a isomeric series of ruthenophanes containing NHC-cyclophanes derived from imidazolium-linked cyclophanes was studied in the light of energy decomposition analysis and natural bond orbitals. The relative stability, bridge tensions and the metal-ligand bonding situation in a set complexes (1-9) formed by isomers of the ij-xylylene-linked bis(NHC)cyclophane ligand were determined. Isomers containing aromatic moieties in both anti and syn conformations were evaluated. The relative stability of the isomeric series was evaluate by means of electronic structure calculations at DFT level, including the already synthesized and characterized Baker’s complex 1, which was identified as the most stable, followed by complex 4. Our calculations reveal that by using as starting material a imidazolium-linked-m,o-cyclophane salt under similar conditions as used by Baker [1], the complex 4 can be likewise obtained. The calculated strain energies imposed on the ligand tether revealed that the strain in NHC-cyclophanes bridges is considerably high. The EDA-NOCV results concerning metal-ligand bonding situation reveal that the stabilization between the cyclophanes and the {RuCl}(+) fragments is mainly due to the orbital term, followed by the electrostatic interaction. The orbital stabilization is comprised mainly of sigma-donation from carbenes to ruthenium(II) ion, which is the most significant contribution, followed by the metal -> ligand pi-backdonation.

First author: Fetisov, EO, Thermally induced inter-ring haptotropic rearrangements in pi-complexes of molybdenum with nitrogen containing polyaromatic heterocycles: A DFT study,
Abstract: Inter-ring haptotropic rearrangements (IRHRs) are well-known phenomena in fluxional ogranometallic chemistry. They are mainly observed for transition metal complexes with polyaromatic ligands (PALs), but are usually limited to PALs without heteroatoms. Here, we report DFT studies of recent experimentally observed IRHRs in heterocyclic complexes of Mo. Four different ligands (quinoline, isoquinoline, quinoxaline, and indolyl) have been investigated. Overall, structural and energetic trends agree well with available experimental data. In addition, mechanistic trends and heteroatom participation are discussed and elucidated to further understanding of IRHRs in heterocyclic polyaromatic complexes in particular, and haptotropic processes in general.

First author: Karpov, Y, Molecular Doping of a High Mobility Diketopyrrolopyrrole- Dithienylthieno[3,2-b]thiophene Donor-Acceptor Copolymer with F6TCNNQ,
MACROMOLECULES, 50, 914, (2017)
Abstract: Herein we present a molecular doping of a high mobility diketopyrrolopyrrole dithienylthieno[3,2-b]thiophene donor-acceptor copolymer poly[3,6-(dithiophene-2-yl)-2,5-di(6-dodecyloctadecyl)-pyrrolo [3,4-c]pyrrole-1,4-dione-alt-thien o [3,2-b)] thioph en e], PDPP (6-DO)(2)TT, with the electron-deficient compound hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ). Despite a slightly negative HOMOdonor-LUMOacceptor offset of -0.12 eV which may suggest a reduced driving force for the charge transfer (CT), a partial charge CT was experimentally observed in PDPP(6-DO)(2)TT:F6TCNNQ by absorption, vibrational, and electron paramagnetic resonance spectroscopies and predicted by density functional theory calculations. Despite the modest CT, PDPP(6-DO)(2)TT:F6TCNNQ films possess unexpectedly high conductivities up to 2 S/cm (comparable with the conductivities of the benchmark doped polymer system P3HT:F4TCNQhaving a large positive offset). The observation of the high conductivity in doped PDPP(6-DO)(2)TT films can be explained by a high hole mobility in PDPP(6-DO)(2)TT blends which compensates a lowered (relatively to P3HT:F4TCNQ) concentration of free charge carriers. We also show that F6TCNNQ-doped P3HT, the system which has not been reported so far to the best of our knowledge, exhibits a conductivity up to 7 S/cm, which exceeds the conductivity of the benchmark P3HT:F4TCNQ system.

First author: Cortes-Arriagada, D, Adsorption/desorption process of formaldehyde onto iron doped graphene: a theoretical exploration from density functional theory calculations,
Abstract: The interaction of formaldehyde (H2CO) onto Fe-doped graphene (FeG) was studied in detail from density functional theory calculations and electronic structure analyses. Our aim was to obtain insights into the adsorption, desorption and sensing properties of FeG towards H2CO, a hazardous organic compound. The adsorption of H2CO was shown to be energetically stable onto FeG, with adsorption energies of up to 1.45 eV and favored in different conformations. This interaction was determined to be mostly electrostatic in nature, where the oxygen plays an important role in this contribution; besides, our quantum molecular dynamics results showed the high stability of the FeG-H2CO interaction at ambient temperature (300 K). All the interactions were determined to be accompanied by an increase in the HOMO-LUMO energy gap with respect to the isolated adsorbent, indicating that FeG is highly sensitive to H2CO with respect to pristine graphene. Finally, it was found that external electric fields of 0.04-0.05 a. u. were able to induce the pollutant desorption from the adsorbent, allowing the adsorbent reactivation for repetitive applications. These results indicate that FeG could be a promising candidate for adsorption/sensing platforms of H2CO.

First author: de Ruiter, JM, Introducing a closed system approach for the investigation of chemical steps involving proton and electron transfer; as illustrated by a copper-based water oxidation catalyst,
Abstract: The investigation of the catalytic mechanism of homogeneous water oxidation catalysts remains an active field of research. When examining catalytic steps theoretically, it is often difficult to account for the transfer of protons and electrons from step to step. To this end, a closed system approach is proposed which includes both proton and electron acceptors in the simulation box to allow for the description of proton-coupled electron transfer processes. Using Car-Parrinello Molecular Dynamics, a mononuclear copper water oxidation catalyst Cu(bpy)(OH)(2) was used as a model system to explore this closed system approach. The exploration of this model system shows that, compared to traditional methods, this approach offers extra insight into proposed catalytic steps and allows for the clear identification of preferred reaction paths.

First author: Shakourian-Fard, M, The effect of defect types on the electronic and optical properties of graphene nanoflakes physisorbed by ionic liquids,
Abstract: Defect engineering and non-covalent interaction strategies allow for dramatically tuning the optoelectronic properties of graphene. Using ab initio density functional theory (M06-2X/cc-pVDZ), we find that the nature of defects on the graphene nanoflakes (GNFs) and the size of defective GNF (DGNF) surfaces affect the binding energy (Delta E-b) of ionic liquids (ILs) and the UV-Vis absorption spectra of DGNF. . .IL complexes. Further, our results indicate that increasing the size of DGNFs affects the geometrical structure of the surfaces and increases the binding energy of ILs by about 10%. Analysis based on AIM and EDA shows that the interactions between ILs and DGNFs are non-covalent in nature (dispersion energy being dominant) and associated with charge transfer between the IL and nanoflakes. A comparison between the DEb values of ILs on DGNFs, GNFs, and h-BN nanoflakes (h-BNNF) shows that the presence of defects on the GNF surfaces increases the binding energy values as follows: DGNF . . . IL 4 pristine GNF . . . IL 4 h-BNNF . . . IL. Our calculations indicate that increasing the size of DGNF surfaces leads to a decrease in the HOMOLUMO energy gap (E-g) of the DGNF surfaces. Orbital energy and density of state calculations show that the Eg of DV(SW)-GNFs decreases upon IL adsorption and their Fermi energy level is shifted depending on the type of IL, thus enabling better conductivity. Reactivity descriptors generally indicate that the chemical potential (mu) and chemical hardness (eta) of nanoflakes decrease upon IL adsorption, whereas the electrophilicity index (omega) increases. The UV-Vis absorption spectrum of DV-GNF and SW-GNF shows four bands in the visible spectrum which correspond to pi -> pi* transitions with the absorption bands of SW-GNF appearing at higher wavelengths than those of DV-GNF. The most intense absorption bands in DV-GNF (lambda = 348 nm) and SW-GNF (lambda = 375 nm) are associated with electronic transitions HOMO-1 -> LUMO+2 and HOMO -> LUMO+1, respectively. In addition, these absorption bands undergo a red-shift by both increasing the size of the DV(SW)-GNF surfaces and IL adsorption. We also observe that the energy gaps and absorption spectra can be altered by varying the defect types and the type of IL adsorbate, where the defect types affect the spectral shapes of the bands and adsorbates at the first absorption peak, thus having potential application for light-emitting devices.

First author: Feng, RL, Acidity of M(VI)O-2(OH)(2) for M = Group 6, 16, and U as Central Atoms,
Abstract: Gas-phase acidities and aqueous solution pK(a)'(s) are predicted for MO,(OH)2, where the center, atom M is a main Group 6, 16, and U atom using the Feller Peterson Dixon approach based on coupled cluster CCSD(T) calculations with additional corrections. The gas-phase acidities of the MO,(OH)(2) compounds are essentially the same for elements (M) of the same group, 304-310 kcal/mol at 298 K. All of the Group 6 compounds are 5-6 kcal/mol less acidic in the gas phase than H2SO4. The gas phase acidity of UO2(OH)2 is calculated to be up to 338.0 kcal/mol,,similar to 10% less acidic in the gas phase than the other MO2(OH)2 acids. The most acidic molecule in aqueous solution is predicted to be H2SO4. Overall, for the Group 16 compounds, the pKa’s increase going down the group, with H2PoO4 predicted to be slightly more acidic than nitric acid. H2CrO4 is the most acidic of the Group 6 transition metal compounds. The aqueous acidities of H2MoO4 and H2WO4 are comparable and about 3 pK(a) units less acidic than H2CrO4 and comparable in acidity to HNO3. H2UO4 is not acidic at all in aqueous solution with a plc near 20 plc units and is also not predicted to readily undergo hydrolysis reactions.

First author: Liu, YX, Intersystem Crossing Rates of Isolated Fullerenes: Theoretical Calculations,
Abstract: Although the triplet states of fullerenes have prosperous applications, it remains unclear how the structural parameters of singlet and triplet states control the intersystem crossing (ISC) rates. Here, electronic structure calculations (reorganization energy, driving force, and spin-orbit coupling) and a rate theory (Marcus formula) are employed to quantitatively predict the ISC rates of isolated fullerenes C-n (n = 60-110). The results demonstrate that the driving force is not the only factor to predict the ISC rates. For instance, although C-80, C-82, and C-110 have the favorable driving force, the ISC rates are close to zero because of small spin obit couplings, whereas small ISC rates of C-96 and C-100 result from quite small reorganization energies. Meanwhile, in addition to well-known C-60 and C-70, C-92 possesses good ISC property with obviously large ISC rate. C-92 also has a higher triplet-state energy than singlet-state oxygen energy; it may thus have a good photoactive property.

First author: Chauhan, V, Metal Chalcogenide Clusters with Closed Electronic Shells and the Electronic Properties of Alkalis and Halogens,
Abstract: Clusters with filled electronic shells and a large gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are generally energetically and chemically stable. Enabling clusters to become electron donors with low ionization energies or electron acceptors with high electron affinities usually requires changing the valence electron count. Here we demonstrate that a metal cluster may be transformed from an electron donor to an acceptor by exchanging ligands while the neutral form of the clusters has closed electronic shells. Our studies on Co6Te8(PEt3),(CO) (m + n = 6) clusters show that Co6Te8(PEt3)(6) has a closed electronic shell and a low ionization energy of 4.74 eV, and the successive replacement of PEt3 by CO ligands ends with Co6Te8(CO)(6) exhibiting halogen-like behavior. Both the low ionization energy Co6Te8(PEt3)(6) and high electron affinity Co6Te8(CO)(6) have closed electronic shells marked by high HOMO-LUMO gaps of 1.24 and 1.39 eV, respectively. Further, the clusters with an even number of ligands favor a symmetrical placement of ligands around the metal core.

First author: Grazioli, C, Study of the electronic structure of short chain oligothiophenes,
Abstract: The electronic structure of short-chain thiophenes (thiophene, 2,2 ‘-bithiophene, and 2,2 ‘: 5 ‘,2 ”-terthiophene) in the gas phase has been investigated by combining the outcomes of Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the C K-edge with those of density functional theory (DFT) calculations. The calculated NEXAFS spectra provide a comprehensive description of the main experimental features and allow their attribution. The evolution of the C1s NEXAFS spectral features is analyzed as a function of the number of thiophene rings; a tendency to stabilization for increasing chain length is found. The computation of the binding energy allows to assign the experimental XPS peaks to the different carbon sites on the basis of both the inductive effects generated by the presence of the S atom as well as of the differential aromaticity effects. Published by AIP Publishing.

First author: Ponikiewski, L, Reactions of Lithiated Diphosphanes R2P-P(SiMe3)Li (R = tBu and iPr) with [(Me)NacnacTiCl(2)center dot THF] and [(Me)NacnacTiCl(3)]. Formation and Structure of Titanium(III) and Titanium(IV) beta-Diketiminato Complexes Bearing the Side-on Phosphanylphosphido and Phosphanylphosphinidene Functionalities,
INORGANIC CHEMISTRY, 56, 1094, (2017)
Abstract: beta-Diketiminate complexes of Ti-III-containing phosphanylphosphido ligands [(Me)NacnacTi(Cl){eta(2)-P(SiMe3)-PR2}] ((Me)Nacnac- = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr(2)C(6)H(3)) were prepared by reactions of [(Me)NacnacTiCl(2)center dot THF] with lithium derivatives of diphosphanes R2P-P(SiMe3)Li (R = tBu, iPr) in toluene solutions. Surprisingly, reactions of [(Me)NacnacTiCl2 center dot THF] with R2P-P(SiMe3)Li in THF solutions led to Ti-IV complexes containing phosphanylphosphinidene ligands [(Me)NacnacTi(Cl)(eta(2)-P-PtBu2)] via an autoredox path involving a migration of a nitrene NAr from the Nacnac skeleton to the Ti centers. Solid-state structures of [(Me)NacnacTi(Cl){eta(2)-P(SiMe3)-PtBu2}] (1a) and [(Me)NacnacTi(Cl)(eta(2)-P-PtBu2)] (two isomers 2a1, 2a2) together with [(Me)NacnacTi(Cl){eta(2)-P(SiMe3)-PiPr(2)}] (1b) and [(Me)NacnacTi(Cl)(eta(2)-P-PiPr(2))] (2b) were established by the single-crystal X-ray diffraction and display clearly side-on geometry of the (Me3Si)P-PR2 and P-PR2 moieties in the solid state. Phosphanylphosphinidene complexes [(Me)NacnacTi(Cl)(eta(2)-P-PR2)] indicate that the P-31 NMR resonances of phosphinidene P atoms appear at a very low field in solution and in the solid state.

First author: Joy, J, Contrasting Behavior of the Z Bonds in X-Z … Y Weak Interactions: Z = Main Group Elements Versus the Transition Metals,
INORGANIC CHEMISTRY, 56, 1132, (2017)
Abstract: In contrast to the increasing family of weak intermolecular interactions in main-group compounds (X-Z…Y, Z = main-group elements), an analysis of the Cambridge Structural Database indicates that electron-saturated (18-electron) transition-metal complexes show reluctance toward weak M bond formation (X-M…Y, M = transition metal). In particular, weak M bonds involving electron-saturated (18-electron) complexes of transition metals with partially filled d-orbitals are not found. We propose that the nature of valence electron density distribution in transition-metal complexes is the primary reason for this reluctance. A survey of the interaction of selected electron-saturated transition-metal complexes with electron-rich molecules (Y) demonstrates the following: shielding the possible sigma-hole on the metal center by the core electron density in 3d series, and enhanced electronegativity and relativistic effects in 4d and 5d series, hinders the formation of the M bond. A balance in all the destabilizing effects has been found in the 4d series due to its moderate polarizability and primogenic repulsion from inner core d-electrons. A changeover in the donor-acceptor nature of the metal center toward different types of incoming molecules is also unveiled here. The present study confirms the possibility of M bond as a new supramolecular force in designing the crystal structures of electron-saturated transition-metal complexes by invoking extreme ligand conditions.

First author: Kahlal, S, Ag-13-Centered Cuboctahedral Architecture in Inorganic Cluster Chemistry: A DFT Investigation,
INORGANIC CHEMISTRY, 56, 1209, (2017)
Abstract: The bonding in the [Ag-13{mu(3)-Fe(CO)(4)}(8)](3-/5-) clusters, which exhibit an Ag-13-centered cuboctahedral core, has been analyzed and rationalized by DFT calculations. Not considering the interaction with its encapsulated atom, the empty [Ag-12{mu(3)-Fe(CO)(4)}(8)](4-) cage can be considered as the assembly of 12 linearly coordinated 14-electron AgI metal centers. Adding a supplementary Ag+ at the center allows some covalent delocalized bonding which to some extent tends to reduce the electron deficiency of the 14-electron centers. Adding now two electrons strengthens the delocalized bonding between the encapsulated atom and its host, making [Ag-13{mu(3)-Fe(CO)(4)}(8)](5-) a superatom with two jellium (5s-type) electrons. TDDFT calculations predict near-IR absorption for this penta-anion, because of the presence of an a1g HOMO in the middle of an energy gap. Luminescence in the same optical range is also suggested. Other related cubococtahedral species, such as [Ag-23(SH)(16)](-), a model for the known 8-electron [Au-23(SR)(16)](-) species which exhibits a bicapped centered dodecahedral kernel structure, have also been investigated.

First author: Kremer, AB, A Comparison of Gallium and Indium Alkoxide Complexes as Catalysts for Ring-Opening Polymerization of Lactide,
INORGANIC CHEMISTRY, 56, 1375, (2017)
Abstract: The impact of the metal size and Lewis acidity on the polymerization activity of group 13 metal complexes was studied, and it was shown that, within the same ligand family, indium complexes are far more reactive and selective than their gallium analogues. To this end, gallium and aluminum complexes supported by a tridentate diaminophenolate ligand, as well as gallium complexes supported by N,N’-ethylenebis(salicylimine)(salen) ligands, were synthesized and compared to their indium analogues. Using the tridentate ligand set, it was possible to isolate the gallium chloride complexes 3 and (+/-)-4 and the aluminum analogues 5 and (+/-)-6. The alkoxygallium complex (+/-)-2, supported by a salen ligand, was also prepared and characterized and, along with the three-component system GaCl3/BnOH/NEt3, was tested for the ring-opening polymerization of lactide and e-caprolactone. The polymerization rates and selectivities of both systems were significantly lower than those for the indium analogues. The reaction of (+/-)-2 with 1 equiv of lactide forms the first insertion product, which is stable in solution and can be characterized at room temperature. In order to understand the differences of the reactivity within the group 13 metal complexes, a Lewis acidity study using triethylphosphine oxide (the Gutmann-Beckett method) was undertaken for a series of aluminum, gallium, and indium halide complexes; this study shows that indium halide complexes are less Lewis acidic than their aluminum and gallium analogues. Density functional theory calculations show that the Mulliken charges for the indium complexes are higher than those for the gallium analogues. These data suggest that the impact of ligands on the reactivity is more significant than that of the metal Lewis acidity.

First author: Vorobyev, V, Triammine fac and mer Coordination for Ruthenium-Nitrosyl Complexes: Synthesis and Characterization of [RuNO(NH3)(3)Cl-2]Cl,
Abstract: New high-yielding methods for two [RuNO(NH3)(3)Cl-2]Cl complexes are suggested. First, the ammine ligands are arranged facially through the reaction of a concentrated ammonia solution with the ruthenium-hexanitro complex. In the next step, the treatment of the previously unknown fac-Na[Ru(NO2)(3)(NH3)(3)]center dot 3H(2)O with hydrochloric acid leads to the nitrosyl complex. The mer-[RuNO(NH3)(3)Cl-2]Cl center dot H2O complex is formed from the corresponding aqua complex under reflux in 6 M HCl. The complexes were studied by various methods [FTIR spectroscopy, N-14 NMR spectroscopy, extended X-ray absorption fine structure (EXAFS), thermogravimetric analysis (TGA), and X-ray diffraction studies]. Metastable states (Ru-O-N) were observed in mer-[RuNO(NH3)(3)Cl(H2O)]Cl-2, mer-[RuNO(NH3)(3)Cl-2]Cl center dot H2O, and fac-[RuNO(NH3)(3)Cl-2]Cl under illumination at lambda = 443 nm at liquid-nitrogen temperatures.

First author: Safin, DA, Alternative Route Toward Nitrones: Experimental and Theoretical Findings,
Abstract: Nitrones are important building blocks for natural and biologically active compounds, used as spin-trap reagents and therapeutic agents. All this makes nitrones intriguing and valuable compounds for fundamental studies and as useful chemicals in various synthetic strategies. Therefore, nitrones are still of great interest and in the limelight of researches. With our initial goal to solve synthetic problems toward 5-phenyl-2,2′-bipyridine (Phbpy), we found that this reaction can proceed through the formation of 6-phenyl-3-(pyridin-2-yl)-1,2,4-triazin-4(3H)-ol (4-OH), which rapidly isomerizes to a 3,4-dihydro-1,2,4-triazine-based nitrone, namely 6-phenyl-3-pyridin-2-y1-2,3-dihydro-1,2,4-triazin-4-oxide (4′), This encouraged us to study condensation of hydrazonophenylacetaldehyde oxime (2), obtained from 2-isonitrosoacetophenone (1), with other aldehydes. The reaction with both salicylaldehyde and p-tolualdehyde leads to the open-chain isomers, namely (2-hydroxybenzylidene)hydrazono-2phenylacetaldehyde oxime (5) and (4-methylbenzylidene)hydrazono-2-phenylacetaldehyde oxime (6), respectively. The latter product exists in solution in equilibrium with its cyclic isomer 6-phenyl-3-(4-methylphenyl)-2,3-dihydro-1,2,4-triazin-4-oxide (6′), while the former one exists in solution exclusively in the open-chain form. It was also found that 2 reacts with acetone with the formation of 3,3-dimethyl-6-phenyl-2,3-dihydro-1,2,4-triazin-4-oxide (7′), which also exists in solution in equilibrium with its open-chain isomer 2-phenyl-2-(propan-2-ylidenehydrazono)acetaldehyde oxime (7). The static DFT as well as ab initio molecular dynamics simulations have corroborated the experimental findings.

First author: Mandal, N, Exploring Ultrashort Hydrogen-Hydrogen Nonbonded Contacts in Constrained Molecular Cavities,
Abstract: Confined molecular chambers such as macrocycle bridged E-1-H…H-E-2 (E-1(E-2) = Si(Si), 1) exhibit rare ultrashort HH nonbonded contacts (d(H…H) = 1.56 angstrom). In this article, on the basis of density functional theory and ab initio molecular dynamics simulations, we propose new molecular motifs where d(H…H) can be reduced to 1.44 angstrom (E-1(E-2) = Si(Ge), 3). Further tuning the structure of the macrocycle by replacing the bulky phenyl groups by ethylenic spacers and substitution of the H-atoms by -CN groups makes the cavity more compact and furnishes even shorter d(HH) = 1.38 angstrom (E-1(E-2) = Ge(Ge), 8). These unusually close HH nonbonded contacts originate from the strong attractive noncovalent interactions between them, which are evident from various computational indicators, namely, NCI, Wiberg bond index, relaxed force constant, quantum theory of atoms in molecules, and natural orbitals for chemical valence combined with the extended transition state method analyses. Substantial stabilization of the in,in-configuration (exhibiting short HH contacts) compared with the out,out-configuration (by similar to 5.7 kcal/mol) and statistically insignificant fluctuations in < d(H….H)> and <theta(av)>

(theta(E-1(E-2)-H….H = 152 degrees) at room temperature confirm that the ultrashort HH distances in these molecules are thermodynamically stable and would be persistent under ambient experimental conditions.

First author: Kubelka, J, Activation Strain Analysis of S(N)2 Reactions at C, N, O, and F Centers,
Abstract: Fundamental principles that determine chemical reactivity and reaction mechanisms are the very foundation of chemistry and many related fields of science. Bimolecular nucleophilic substitutions (S(N)2) are among the most common and therefore most important reaction types. In this report, we examine the trends in the SN2 reactions with respect to increasing electronegativity of the reaction center by comparing the well studied backside S(N)2 Cl- + CH3Cl with similar Cl substitutions on the isoelectronic series with the second period elements N, O, and F in place of C. Relativistic (ZORA) DFT calculations are used to construct the gas phase reaction potential energy surfaces (PES), and activation strain analysis, which allows decomposition of the PES into the geometrical strain and interaction energy, is employed to analyze the observed trends. We find that S(N)2@N and S(N)2@O have similar PES to the prototypical S(N)2@C, with the well-defined reaction complex (RC) local minima and a central barrier, but all stationary points are, respectively, increasingly stable in energy. The S(N)2@F, by contrast, exhibits only a single-well PES with no barrier. Using the activation strain model, we show that the trends are due to the interaction energy and originate mainly from the decreasing energy of the empty acceptor orbital (sigma*(A-Cl)) on the reaction center A in the order of C, N, 0, and F. The decreasing steric congestion around the central atom is also a likely contributor to this trend. Additional decomposition of the interaction energy using Kohn-Sham molecular orbital (KS-MO) theory provides further support for this explanation, as well as suggesting electrostatic energy as the primary reason for the distinct single-well PES profile for the FCl reaction.

First author: Rocha, MVJ, Asymmetric identity S(N)2 transition states: Nucleophilic substitution at alpha-substituted carbon and silicon centers,
Abstract: We have quantum chemically investigated the archetypal nucleophilic substitution reactions at carbon (SN2@C) and at silicon (SN2@Si) in the model reaction systems Cl- +A(CH3)2(CH2X)CI (A= C, Si; X= H, F, Cl, Br, I) using relativistic density functional theory (DFT) at ZORA-OLYNTZ2P. Our purpose is twofold. We wish to understand: (i) how the alpha-substituent X affects S(N)2 reactivity; and (ii) how methyl substituents at the central electrophilic atom A exactly participate in the transition vector of the Walden inversion. Interestingly, despite the fact that our SN2 model reactions are symmetric, i.e., constitute identity reactions, they proceed via slightly asymmetric transition states. We have also explored competing E2 pathways. i3/4

First author: Vorobyev, V, Nitrosyl cis-dichlorodiammine ruthenium complex with bridging H3O2- ligand,
Abstract: The ruthenium complex with bridging H3O2 ligand was obtained and the crystal structure was determined. The compound cis-l(RuNO(NH3)2C1(2)h( (2)-H3O2)]Cl crystallizes in the monoclinic space group P21/n with cell parameters a = 15.0651(5), b = 63624(2), c = 153813(6) A, = 94.9690(10), Z = 4 and R = 0.0185. The hydroxide hydrate anion is coordinated to the ruthenium atoms of the identical cis-{RuNO(NH3)(2)C1(2)) fragments. The protonation of the starting cis-[RuNO(NH3)(2)(NO2)(2)OH complex leads to the required coordinated aqua/hydroxide ratio if the specific amount of hydrochloric add is used. The DFT calculations confirm the formation of the dimer structure in the gas phase. However, the presence of water molecules dramatically reduces the dimerization efficiency.

First author: Conradie, J, The Blue-Violet Color of Pentamethylbismuth: A Visible Spin-Orbit Effect,
CHEMISTRYOPEN, 6, 15, (2017)
Abstract: Two component relativistic time dependent density functional theory calculations with spin-orbit coupling predict yellow and orange-red absorption for BiPh5 and BiMe5, respectively, providing an excellent explanation for their respective violet and blue-violet colors. According to the calculations, the visible absorption is clearly attributable to a single transition from a ligand-based HOMO to a low-energy LUMO with a significant contribution from a relativistically stabilized Bi 6s orbital. Surprisingly, scalar releativistic calculations completely fail to reproduce the observed visible absorption and place it at the violet/near-UV borderline instead.

First author: de Oliveira, PMC, Benchmark, DFT assessments, cooperativity, and energy decomposition analysis of the hydrogen bonds in HCN/HNC oligomeric complexes,
Abstract: Hydrogen cyanide (HCN) and its tautomer hydrogen isocyanide (HNC) are relevant for extraterrestrial chemistry and possible relation to the origin of biomolecules. Several processes and reactions involving these molecules depend on their intermolecular interactions that can lead to aggregates and liquids especially due to the hydrogen bonds. It is thus important to comprehend, to describe, and to quantify their hydrogen bonds, mainly their nature and the cooperativity effects. A systematic study of all linear complexes up to pentamers of HCN and HNC is presented. CCSD(T)/CBS energy calculations, with and without basis set superposition error (BSSE) corrections for energies and geometries, provided a suitable set of benchmarks. Approximated methods based on the density functional theory (DFT) such as BP86, PBE, TPSS, B3LYP, CAM-B3LYP with and without dispersion corrections and long-range corrections, were assessed to describe the interaction energies and cooperativity effects. These assessments are relevant to select DFT functionals for liquid simulations. Energy decomposition analysis was performed at the PBE/STO-TZ2P level and provided insights into the nature of the hydrogen bonds, which are dominated by the electrostatic component. In addition, several linear relationships between the various energy components and the interaction energy were obtained. The cooperativity energy was also found to be practically linear with respect to the interaction energy, which may be relevant for designing and/or correcting empirical force fields.

First author: Thompson, KA, Reactivity of organoplatinum complexes containing appended alcohol functional groups: Activation of dioxygen and hydrogen peroxide,
Abstract: The oxidative addition reactions of platinum(II) complexes [PtMe2(RN=CH-2-C5H4N)], especially when R = CH2CH2OH or CH2CH2CH2OH, have been studied. Both complexes react with R’X (Mel or PhCH2Br) by trans oxidative addition to give [PtXMe2R'(RN=CH-2-C5H4N)]. They also react with oxygen in methanol solution or with hydrogen peroxide to give [Pt(OH)(OMe)Me-2(RN=CH-2-C5H4N)] or [Pt(OH)(2)Me-2(RN=CH-2-C5H4N)], respectively, but the reactions are complicated in the case with R = (CH2)(3)OH by partial cyclization of the imine ligand to give the corresponding oxazine complex. When R = CH2CH2OH, the complex [PtMe2(RN=CH-2-C5H4N)] reacts with oxygen in acetone solution to give the platinum(IV) complex [Pt(OH)Me-2{kappa(3)-N,N,O-RNH-CH(2-C5H4N)(CH=CMeO)}], but no reaction occurs when R = CH2CH2CH2OH or CH2CH2NMe2. It is suggested that the hydroxyethyl substituent plays a key role in the dioxygen activation and subsequent reactions of a coordinated acetone molecule.

First author: Georgiou, DC, NHC-Stabilised Acetylene-How Far Can the Analogy Be Pushed?,
Abstract: Experimental studies suggest that the compound (NHCbz)(2)C2H2 can be considered as a complex of a distorted acetylene fragment which is stabilised by benzoannelated N-heterocyclic carbene ligands (NHCbz)->(C2H2)<-(NHCbz). A quantum chemical analysis of the electronic structures shows that the description with dative bonds is more favourable than with electron-sharing double bonds (NHCbz)=(C2H2)=(NHCbz).

First author: Jash, B, A metal-mediated base pair that discriminates between the canonical pyrimidine nucleobases,
CHEMICAL SCIENCE, 8, 1337, (2017)
Abstract: A nucleoside analogue comprising the ligand 1H-imidazo[ 4,5-f][1,10] phenanthroline (P) was applied to develop a molecular beacon capable of discriminating the canonical nucleobases cytosine and thymine. The beacon is based on the formation of a stable Ag+- mediated base pair between P and cytosine, whereas the presence of Ag+ strongly destabilizes nucleic acids comprising an artificial base pair between P and thymine. Metal-mediated base pair formation was investigated by temperature-dependent UV spectroscopy and CD spectroscopy and complemented by extensive DFT calculations. The molecular beacon significantly extends the application spectrum of nucleic acids with metal-mediated base pairs. It is of potential use in the detection of single-nucleotide polymorphisms.

First author: Ribaudo, G, Mechanistic Insight into the Oxidation of Organic Phenylselenides by H2O2,
Abstract: The oxidation of organic phenylselenides by H2O2 is investigated in model compounds, namely, n-butyl phenyl selenide (PhSe(nBu)), bis(phenylselanyl)methane (PhSeMeSePh), diphenyl diselenide (PhSeSePh), and 1,2-bis(phenylselanyl)ethane (PhSeEtSePh). Through a combined experimental (H-1 and Se-77 NMR) and computational approach, we characterize the direct oxidation of monoselenide to selenoxide, the stepwise double oxidation of PhSeMeSePh that leads to different diastereomeric diselenoxides, the complete oxidation of the diphenyldiselenide that leads to selenium-selenium bond cleavage, and the subsequent formation of the phenylseleninic product. The oxidation of PhSeEtSePh also results in the formation of phenylseleninic acid along with 1-(vinylseleninyl)benzene, which is derived from a side elimination reaction. The evidence of a direct mechanism, in addition to an autocatalytic mechanism that emerges from kinetic studies, is discussed. By considering our observations of diselenides with chalcogen atoms that are separated by alkyl spacers of different length, a rationale for the advantage of diselenide versus monoselenide catalysts is presented.

First author: Ganesamoorthy, C, Reduction of [Cp*Sb](4) with Subvalent Main-Group Metal Reductants: Syntheses and Structures of [((LMg)-Mg-1)(4)(Sb-4)] and [((LGa)-Ga-2)(2)(Sb-4)] Containing Edge-Missing Sb-4 Units,
Abstract: [Cp*Sb](4) (Cp*=C5Me5) reacts with [(LMg)-Mg-1](2) and (LGa)-Ga-2 with formation of [((LMg)-Mg-1)(4)(mu(4),eta(1:2:2:2)-Sb-4)] (L-1=iPr(2)NC[N(2,6-iPr(2)C(6)H(3))](2), 1) and [((LGa)-Ga-2)(2)(mu,eta(2:2)-Sb-4)] (L-2=HC[C(Me)N(2,6-iPr(2)C(6)H(3))](2), 2). The cleavage of the Sb-Sb and Sb-C bonds in [Cp*Sb](4) are the crucial steps in both reactions. The formation of 1 occurred by elimination of the Cp* anion and formation of Cp*MgL1, while 2 was formed by reductive elimination of Cp*(2) and oxidative addition of (LGa)-Ga-2 to the Sb-4 unit. 1 and 2 were characterized by heteronuclear NMR spectroscopy and single-crystal X-ray diffraction, and their bonding situation was studied by quantum chemical calculations.

First author: Silva, TC, Theoretical structural and electronic analyses with emphasis on the reactivity of iron oxide prototypes in methane C-H bond activation,
Abstract: In the present work, a detailed theoretical investigation using B3LYP, CCSD(T) and ZORA-B3LYP calculations has been performed in order to investigate activation processes of methane C-H bond by iron oxide prototype series: FeOmn+ (m = 1, 2; n = 0, 1, 2). The main results indicate that, in accordance with previous experimental findings, only FeO+ monoxide is kinetically and thermodynamically feasible through the hydrogen abstraction mechanism, with an already known pathway described as “oxidative hydrogen migration”. The overall results indicate better thermodynamic and kinetic conditions for all iron monoxides, in relation to iron dioxides. Based on the energy values and the structural parameters, the 4-center abstraction mechanism should be thermodynamically more favorable in relation to the direct abstraction mechanism, due to the lack of Fe-C interaction for the direct abstraction mechanism. The AIM calculations indicate a larger ionic character for the Fe-O+ chemical bond, whereas a mixed participation, relative to ionic and covalent character, was found in chemical bonds of the remaining iron oxides.

First author: Cho, H, Anion conducting methylated aliphatic PBI and its calculated properties,
Abstract: A methylated polybenzimidazole with an aliphatic chain in the backbone (Me-PBI-C10) was synthesized and formed into membranes. Literature suggests that alkyl chains on C2 of imidazolium ions increase their alkaline stability. While this may be true for model compounds or ions attached as a side chain, both our DFT calculations and experimental results show that Me-PBI-C10 does not withstand alkaline conditions. To increase the alkaline stability, blend membranes with PBI-OO were fabricated. A blend membrane with 50% PBI-OO showed a chloride conductivity of up to 6 mS/cm, indicating that these membranes could find use in non-alkaline applications like vanadium redox flow batteries (VRFB). The high mechanical stability (tensile strength: 70.25 +/- 14.85 MPa, Young modulus: 1.65 +/- 0.16 GPa) would be an advantage over currently used Nafion membranes. Finally, three different models were successfully applied to qualitatively predict the water uptake of Me-PBI-C10 exchanged with different anions. The results match with experimental data.

First author: Yuan, LY, Large-Pore 3D Cubic Mesoporous (KIT-6) Hybrid Bearing a Hard-Soft Donor Combined Ligand for Enhancing U(VI) Capture: An Experimental and Theoretical Investigation,
Abstract: A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N-2 adsorption/desorption, X-ray diffraction, FT-IR, C-13 cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization. Subsequently, the effects of contact time, solution pH, initial U(VI) concentration, and the presence of competing metal ions on the U(VI) sorption onto KIT-6-DAPhen sorbent were investigated in detail. It was found that KIT-6-DAPhen showed largely enhanced sorption capacity and excellent selectivity toward U(VI). The maximum sorption capacity of KIT-6-DAPhen at pH 5.0 reaches 328 mg of U/g of sorbent, which is superior to most of functionalized mesoporous silica materials. Density functional theory coupled with quasi-relativistic small-core pseudopotentials was used to explore the sorption interaction between U(VI) and KIT-6-DAPhen, which gives a sorption reaction of KIT-6-DAPhen + [UO2(H2O)(5)](2+) + NO3- reversible arrow [UO2(KIT-6-DAPhen)(NO3)](+) + 5H(2)O. The findings of the present work provide new clues for developing new actinide sorbents by combining new ligands with various mesoporous matrixes.

First author: Conradie, J, Stacking of dicarbonylacetylacetonatorhodium(I) molecules,
Abstract: Density functional theory calculations was used to understand the stabilisation of intermolecular rhodium-rhodium interactions as observed in [Rh(acac)(CO)(2)] crystals. Quantum theory of atoms in molecules calculations confirm that bonding paths, consistent with weak bonds stronger than hydrogen bonds, between the rhodium centres in different [Rh(acac)(CO)(2)] molecules, exist. The linear array of [Rh (acac)(CO)(2)] molecules were further stabilised by intermolecular hydrogen bonds. The weak interaction between the rhodium centres were further confirmed by natural bond orbital (NBO) calculations that showed donor-acceptor interaction between the a filled and an empty NBO on the rhodium atoms in adjacent [Rh(acac)(CO)(2)] molecules. A visualisation of the molecular orbitals of linear units of [Rh (acac)(CO)(2)] molecules showed sigma bonding and anti-bonding interactions between the d(z2), as well as between the p(z) orbitals, on rhodium of different [Rh(acac)(CO)(2)] molecules.

First author: Ogden, WA, Partial Fluorination as a Strategy for Crystal Engineering of Rubrene Derivatives,
CRYSTAL GROWTH & DESIGN, 17, 643, (2017)
Abstract: Through a close examination of the intermolecular interactions of rubrene (1a) and select derivatives (1b-1p), a clearer understanding of why certain fluorinated rubrene derivatives pack with planar tetracene backbones has been achieved. In this study we synthesized, crystallized, and determined the packing structure of new rubrene derivatives (1h-p). Previously, we proposed that introducing electron withdrawing CF3 substituents induced planarity by reducing intramolecular repulsion between the peripheral aryl groups (1e-g). However, we found that in most cases, further increasing the fluorine content of rubrene lead to twisted tetracene backbones in the solid state. To understand how rubrene (1a) and its derivatives (1b-p) pack in the solid state, we (re)examined the crystal structures through a systematic study of the close contacts. We found that planar tetracene cores occur when close contacts organize to produce an S symmetry element about a given rubrene molecule. We report the first instance of rubrene derivatives (1l and 1n) that pack in a two-dimensional brick motif. The prospects for new rubrene derivatives in semiconductors were estimated by calculating the reorganization energies of the monomers and transfer integrals of the dimers we observed. Our work allows for the rational design and improved crystal engineering of new rubrene derivatives.

First author: Schluns, D, Analytical gradients for subsystem density functional theory within the slater-function-based amsterdam density functional program,
Abstract: We present a new implementation of analytical gradients for subsystem density-functional theory (sDFT) and frozen-density embedding (FDE) into the Amsterdam Density Functional program (ADF). The underlying theory and necessary expressions for the implementation are derived and discussed in detail for various FDE and sDFT setups. The parallel implementation is numerically verified and geometry optimizations with different functional combinations (LDA/TF and PW91/PW91K) are conducted and compared to reference data. Our results confirm that sDFT-LDA/TF yields good equilibrium distances for the systems studied here (mean absolute deviation: 0.09 angstrom) compared to reference wave-function theory results. However, sDFT-PW91/PW91k quite consistently yields smaller equilibrium distances (mean absolute deviation: 0.23 angstrom). The flexibility of our new implementation is demonstrated for an HCN-trimer test system, for which several different setups are applied.

First author: Mawale, RM, Laser Desorption Ionization Quadrupole Ion Trap Time-of-Flight Mass Spectrometry of Au (m) Fe (n) (+/-) Clusters Generated from Gold-Iron Nanoparticles and their Giant Nanoflowers. Electrochemical and/or Plasma Assisted Synthesis,
Abstract: Gold nanoparticles (NP) with average diameter similar to 100 nm synthesized from tetrachloroauric acid solution using stainless steel as a reducing agent were found to contain iron. Applying simultaneously high frequency (HF) plasma discharge in solution during the electrochemical reduction, giant gold-iron nanoflowers with average size similar to 1000-5000 nm were formed. Scanning electron microscopy (SEM) shows the morphology of the nanopowders produced as polygonal yet nearly spherical, whereas iron content in both products determined by energy dispersive X-ray analysis (EDX) was found to be at similar to 2.5 at. %. Laser desorption ionization (LDI) of both nanomaterials and mass spectrometric analysis show the formation of Au (m) Fe (n) (+/-) (m = 1-35; n = 1-3) clusters. Structure of few selected clusters in neutral or monocharged forms were computed by density functional theory (DFT) calculations and it was found that typical distances of an iron nucleus from adjacent gold nuclei lie in the interval 2.5 to 2.7 . Synthetized Au-Fe nanoparticles were found stable for at least 2 mo at room temperature (even in aqueous solution) without any stabilizing agent. Produced Au-Fe nanoparticles in combination with standard MALDI matrices enhance ionization of peptides and might find use in nanomedicine.

First author: Goesten, MG, Eight-coordinate fluoride in a silicate double-four-ring,
Abstract: Fluoride, nature’s smallest anion, is capable of covalently coordinating to eight silicon atoms. The setting is a simple and common motif in zeolite chemistry: the box-shaped silicate double-four-ring (D4R). Fluoride seeks its center. It is the strain of box deformation that keeps fluoride in the middle of the box, and freezes what would be a transition state in its absence. Hypervalent bonding ensues. Fluoride’s compactness works to its advantage in stabilizing the cage; chloride, bromide, and iodide do not bring about stabilization due to greater steric repulsion with the box frame. The combination of strain and hypervalent bonding, and the way they work in concert to yield this unusual case of multiple hypervalence, has potential for extension to a broader range of solidstate compounds.

First author: Bertani, R, Pt(II) nitrile complexes: New insights on old complexes from a combined experimental and theoretical study,
Abstract: The spectroscopic characterization of cis- and trans-[PtCl2(NCR)(2)] (R = CH3, Ph, CH2Ph) was reported in solid state and solution phase. Moreover, the X-ray structures of cis-[PtCl2(NCCH3)(2)], cis- and trans[PtCl2(NCPh)(2)] were redetermined at low temperature. FT-IR and NMR showed a blue-shift and a slight shielding of the vCN and delta(C-13(CN)) values, respectively, in a counterintuitive way with respect to the well known improved reactivity towards nucleophiles of nitriles ligands coordinated to platinum(II), when compared to their free forms. These spectroscopic behaviors were also confirmed by theoretical experiments at DFT level. Moreover, DFT approach showed that the increased reactivity of the nitrile ligands, after coordination to Pt(II), can be explained by the energy decreasing of the ligands’ LUMOs, instead of an increased polarization of the CN bond, accordingly with the orbital control model previously proposed for trans-[PtCl2(MeCN)(2)]. Finally, bond analysis also discarded the occurrence of Pt -> N back-donation.

First author: van Niekerk, DME, A spectroscopic (stopped-flow UV-Vis and H-1 NMR Evans method) and DFT thermodynamic study of the comproportionation reaction of [(OsO4)-O-VIII(OH)(n)](n-) (n=1, 2) and [(OsO2)-O-VI(OH)(4)](2-),
Abstract: From a mole ratio H-1 NMR Evans method experiment it is found that, in a 2.0 M NaOH aqueous matrix, diamagnetic [(OsO4)-O-VIII(OH)(n)](n-) (n = 1, 2) (of d(0) electron configuration) and trans-[(OsO2)-O-VI(OH)(4)](2-) species (d(2)) react in a 1:1 mol ratio to form two paramagnetic Os-VII oxido/hydroxido product species (d(1)). This result is further validated as the chemical reaction model that best fitted stopped-flow UVVis spectroscopy kinetic data is given by [Os-VIII]+[Os-VI]

First author: Zhao, L, Effects of a highly lipophilic substituent on the environmental stability of naphthalene tetracarboxylic diimide-based n-channel thin-film transistors,
Abstract: N, N’-Bis(4-trifluoromethylthiobenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NTCDI-BSCF3) is synthesized. It shows a similar molecular packing structure and intermolecular transfer integral to N, N’-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NTCDI-BOCF3), but demonstrates different behaviors in terms of electron mobility and air stability. NTCDI-BSCF3 based organic thin-film transistors (OTFTs) exhibit much better environmental stability when compared with NTCDI-BOCF3 due to their high hydrophobicity which prevents the diffusion of moisture and oxygen into the devices. In addition, the electron mobility of NTCDI-BSCF3 shows good thermal stability in relation to the deposition temperature, and achieves a value as high as 0.17 cm(2) (V s)(-1) in air, although it is lower than that of NTCDI-BOCF3. The lower mobility may be attributed to the unexpected crystal growth mode after the deposition of the second monolayer and an insufficient quality of the thin films of NTCDI-BSCF3, especially their inadequate crystallinity. This contrasts with the Stranski-Krastanov (SK) (layer-plus-island) growth mode with the expected crystal growth direction and good crystallinity of NTCDI-BOCF3. Nevertheless, it can be concluded that the introduction of the trifluoromethanesulfenyl (SCF3) group at the N-group of naphthalene tetracarboxylic diimide (NTCDI) is an effective approach for enhancing the environmental stability of NTCDI based n-channel OTFTs.

First author: Ferreira, H, Electrochemical and DFT study of the reduction of substituted phenanthrolines,
POLYHEDRON, 122, 147, (2017)
Abstract: The irreversible electrochemical reduction data of a series of free uncoordinated differently substituted phenanthrolines is presented. Electron withdrawing chloride substituents in the 4,7 ring positions increase the reduction potential by 0.3 V, while electron donating methyl substituents lead to a lowering of reduction potential relative to unsubstituted 1,10-phenanthroline. Linear relationships are obtained between the reduction potential of free uncoordinated differently substituted phenanthrolibes and density functional theory (DFT) calculated LUMO (lowest unoccupied molecular orbital) energies, electron affinities, global electrophilicity indexes and Mulliken electronegativities. The reduction potential of 4,7-diphenyl-1,10-phenanthroline deviates slightly from the linear trend, since the phenyl groups donate electron density to the phenanthroline ring system through both pi-resonance and sigma-inductive effects. This enables the phenanthroline ring system to more readily accept an electron at a higher, less negative potential than is otherwise the case. On the contrary, the non-aromatic substituents (e.g. Me, NH2 and Cl) withdraw donate electron density from/to the phenanthroline ring system through sigma-inductive effects only. Linear relationships are also obtained between the reduction potential of the series of phenanthroline free ligands and the formal reduction potential of corresponding metal-phenanthroline complexes.

First author: Bhattacharyya, K, Polymorphism Controlled Singlet Fission in TIPS-Anthracene: Role of Stacking Orientation,
Abstract: Generation of multiple triplet excitons from one singlet exciton (singlet fission, SF) has been reported in several organic molecules recently. The overall SF yield in such molecular materials, however, is controlled by polymorphism in organic semiconductors through non covalent interactions like van der Waals and weak electrostatic interactions. In this article, we demonstrate how SF is strongly perturbed by even small variations in molecular packing for polymorphic crystals of triisopropylsilyethnyl-anthracene derivatives, TIPS-Ant (PI and PII). Based on quantum chemical calculations, SF dynamics have been computed for both PI and PII polymorphs. PI and PII differ in their intermolecular pi…pi stacking patterns, which eventually control their electronic properties. Using the incoherent hopping model for the crystals, we computed SF rate through the Marcus electron transfer theory. For both PI and PII, the direct two-electron pathway predominates over the charge-transfer (CT) mediated mechanism. PII has higher triplet yield (similar to 196%) compared to PI (similar to 178%). Both time-dependent DFT as well as Weller equation reveal that the charge transfer (CT) state is a high energy state, and hence, CT mediated SF barely influences triplet yield. Interplay of the local excitation (LE), multiple excitation (ME), and correlated triplet (T1T1) energy levels controlled the overall exciton dynamics/diffusion in TIPS-Ant polymorphs. Polymorphism is shown to be a key factor for the rational design of optimal SF in polyaromatic hydrocarbons (PAH).

First author: Pratik, SM, Design of van der Waals Two-Dimensional Heterostructures from Facially Polarized Janus All-Cis 1,2,3,4,5,6-Hexafluorocyclohexane (C6H6F6),
Abstract: The recently synthesized all-cis 1,2,3,4,5,6-hexafluorocyclohexane (1) has a large dipole moment (6.2 D) and uniaxial facial polarization. Based on density functional theory (DFT) calculations, it is shown that both the “positive” and “negative” surfaces of 1 can recognize flat aromatic molecules (X, X = benzene, pyrene, and coronene), 2D materials (graphene), and their fully hydrogenated analogues through attractive noncovalent interactions. 1 can be sandwiched between graphene and graphane layers, where the enhanced polarity of the axial C-H and C-F bonds leads to the formation of an unusual “triple-decker” complex. Upon adsorption with 1, the band gap of graphane reduces from 3.40 to 2.05 eV, which might be useful for visible-light energy-conversion applications. We demonstrate the controlled tuning of the structural and electronic properties in 1-benzene, 1-cyclohexane, and benzene-1-cyclohexane complexes by the application of an external electric field along the polarization axis. The extended analogue of 1, hydrofluorinated graphene (HFG), which has semiconducting properties (band gap approximate to 3.0 eV), can form strong C-H center dot center dot center dot F-C interlayer interactions with graphane to form a stable, metallic bilayer. Our calculations show that the two-dimensional HFG can be realized through the high-pressure topochemical condensation of monofluoroacetylene (C2HF) for which the barrier of activation is 18.7 kcal/mol.

First author: Munoz-Castro, A, Toward Two-Dimensional Superatomic Honeycomb Structures. Evaluation of [Ge-9(Si(SiMe3))(3)](-) as Source of Ge-9-Cluster Building Blocks for Extended Materials,
Abstract: Inspired by recent experimental realizations of two-dimensional (2D) metals and alloys, we theoretically investigate plausible formation of new germanium frameworks based on the aggregation of ligand-decorated Ge-9 clusters. Here, we explore the formation of single-, double-, and triply connected arrays of species with Zintl-ion core of Ge9 leading to the formation of dimers ([Ge9R2](2)(2)), hexamers ([Ge9R](6)(6)), and two-dimensional arrays ([M-3{Ge-9}(3)](infinity); M = Li, Cs). This can be potentially addressed by the controlled removal of ligands from the [Ge-9{Si(SiMe3)(3)}(3)](-) monoanion acting as the source of Ge-9 building blocks. Our results reveal that the bonding between different Ge-9 cores is favorable and covalent in nature as a localized 2c2e GeGe exobond. The extended two-dimensional {Ge9}(infinity) array designed as [M3{Ge9}3](infinity) with M = Li, Cs in periodic boundary conditions is energetically stable. The resulting layered Ge-structure has similar stability as that of germanene. It exhibits large pores with radius of 5.23 angstrom between the three-connected Ge9 clusters. Hence, it can be considered as a the first superatomic honeycomb structure proposed to date. This 2D material exhibit a small band gap in contrast to the 2D germanene which has no such gap. Hence, the two-dimensional Ge9 cluster-based compound would have potential for a tunable bandgap material. The use of Ge-clusters is suggested as an interesting approach to obtain nanomaterials accessing to novel alleotropes.

First author: Zhang, FY, Theoretical Studies of Photodeactivation Pathways of NHC-Chelate Pt(II) Compounds with Different Numbers of Triarylboron Units: Radiative and Nonradiative Decay Processes,
Abstract: The radiative and nonradiative decay processes of four platinum(II) complexes chelated with triarylboron (TAB)-functionalized N-heterocyclic carbenes (NHC) are investigated by using density functional theory (DFT) and time dependent DFT (TD-DFT) calculation, for probing into the influence of different numbers of TAB on the phosphorescent emission properties. For the radiative decay processes, zero-field splitting energies, radiative rates, and lifetimes are explored, and corresponding factors including transition dipole moments, singlet triplet splitting energies as well as spin orbit coupling matrix elements are also analyzed in detail. Additionally, energy-gap law is considered in the temperature-independent nonradiative decay processes; meanwhile, potential energy profiles are obtained to elaborate the temperature-dependent nonradiative decay processes. As a result, radiative rates declined slightly with the increased numbers of TAB. The minimum temperature-independent nonradiative decay may occur in BC-3 due to its smallest structural distortion between S-0 and T-1 states. According to the potential energy, profiles of the deactivation pathways, four investigated phosphors have the similar temperature-dependent nonradiative decay processes because of the incredibly analogous energy barriers. We speculate that it does not mean greater phosphorescent emission and higher phosphorescent quantum yield with more TAB units, which would provide extraordinary assistance for further research in potential phosphors of organic light emitting diodes.

First author: Barroso, J, Structure and Bonding of Alkali-Metal Pentalenides,
ORGANOMETALLICS, 36, 310, (2017)
Abstract: The lowest energy isomers of alkali-metal pentalenides, E2C8H6 (E = Li, Na, K, Rb, Cs), are inverted sandwiches. Along Li to Cs, the location of the E atoms shifts toward the points over the center of the pentalene moiety even in the presence of solvent molecules such as dimethoxyethane. Adaptive natural density partitioning analysis reveals the equivalent 10 z bonding frameworks in the C8H62- and E2C8H6 systems. The stability of these complexes practically originates from the electrostatic interaction (84-92%) between C8H62- and [E…E](2+). While the sharp drop in interaction energy in Na complex, in comparison to that in the Li analogue, is due to the lower contribution from both electrostatic (by 31.6 kcal mol(-1)) and orbitalic (by 48.1 kcal mol(-1)) terms, for the rest of the complexes the obtained trend of interaction energy originates from the reduced ionic contacts. Although the orbital interaction is less important in these complexes, it plays an important role in deciding their geometries. The obtained geometrical change along Li to Cs is a consequence of the participation of the d orbitals in the heavier analogues.

First author: Saha, R, The strongest CO binding and the highest C-O stretching frequency,
Abstract: A coupled-cluster study is performed on CO bound BeY complexes (Y = O, CO3, SO4, NH, NCN, and NBO) to understand the effect of attached ligands (Y) on the CO binding ability and C-O stretching frequency (nu(CO)). Herein, we report that BeNCN has the highest CO binding ability (via both C-and O-side binding) among the studied neutral Be-based clusters, whereas OCBeSO4 has the highest nu(CO) among the neutral carbonyls. The nature and extent of shift in nu(CO) compared to free CO are explained in terms of change in polarization in the bonding orbitals of CO and relative contribution from OC-BeY or CO <- BeY s-donation, and OC <- BeY or CO <- BeY p-back-donation. The largest blue-shift in OCBeSO4 and the largest red-shift in COBeNH are consequences of the smallest OC <- BeSO4 pi-backdonation and the largest CO <- BeNH p-back-donation, respectively.

First author: Munoz-Castro, A, Doping the cage. Re@Au11Pt and Ta@Au11Hg, as novel 18-ve trimetallic superatoms displaying a doped icosahedral golden cage,
Abstract: Expanding the versatility of well defined clusters is a major concern in the design of building blocks towards functional nanostructures. W@Au-12 is a prototypical binary bare superatomic cluster involving an icosahedral symmetry, which has been discussed in the literature, precluding the proposal of several endohedral d-block and f-block element structures within a golden cage. Here we pursue the construction of related trimetallic clusters, which has been explored to a lesser extent. Our results expose the great advantages of involving heterocages in the superatom approach, unraveling Re@Au11Pt and Ta@Au11Hg as novel trimetallic candidates. Re@Au11Pt exhibits an electron-deficient element in the cage, and an endohedral atom with an extra electron. In contrast, Ta@Au11Hg is conceived as having an icosahedral cage with an extra electron, and an electron-deficient endohedral element. These new clusters follow the eighteen valence electron principle, with similar characteristics to their W@Au-12 parent. This leads to stable clusters with an electronic structure formally described by the 1s(2)1p(6)1d(10) closing shell order, showing an interesting approach to design ternary superatoms, where the variation of valence electrons occurs in both cage and endohedral sites. Moreover, the cage doping appears as a useful approach to further evaluate the formation of magnetic superatoms, and also the construction of larger clusters by fusing different icosahedral structures.

First author: O’Brien, KTP, Computational study of An-X bonding (An = Th, U; X = p-block-based ligands) in pyrrolic macrocyclesupported complexes from the quantum theory of atoms in molecules and bond energy decomposition analysis,
DALTON TRANSACTIONS, 46, 760, (2017)
Abstract: A systematic computational study of organoactinide complexes of the form [LAnX](n+) has been carried out using density functional theory, the quantum theory of atoms in molecules (QTAIM) and Ziegler-Rauk energy decomposition analysis (EDA) methods. The systems studied feature L = trans-calix[2] benzene[2] pyrrolide, An = Th(IV), Th(III), U(III) and X = BH4, BO2C2H4, Me, N(SiH3)(2), OPh, CH3, NH2, OH, F, SiH3, PH2, SH, Cl, CH2Ph, NHPh, OPh, SiH2Ph, PHPh2, SPh, CPh3, NPh2, OPh, SiPh3 PPh2, SPh. The PBE0 hybrid functional proved most suitable for geometry optimisations based on comparisons with available experimental data. An-X bond critical point electron densities, energy densities and An-X delocalisation indices, calculated with the PBE functional at the PBE0 geometries, are correlated with An-X bond energies, enthalpies and with the terms in the EDA. Good correlations are found between energies and QTAIM metrics, particularly for the orbital interaction term, provided the X ligand is part of an isoelectronic series and the number of open shell electrons is low (i. e. for the present Th(IV) and Th(III) systems).

First author: Wu, MM, Aryl-NHC-group 13 trimethyl complexes: structural, stability and bonding insights,
DALTON TRANSACTIONS, 46, 854, (2017)
Abstract: Treatment of aromatic N-substituted N-heterocyclic carbenes (NHCs) with trimethyl-gallium and -indium yielded the new Lewis acid-base adducts, IMes center dot GaMe3 (1), SIMes center dot GaMe3 (2), IPr center dot GaMe3 (3), SIPr center dot GaMe3 (4), IMes center dot InMe3 (5), SIMes center dot InMe3 (6), IPr center dot InMe3 (7), and SIPr center dot InMe3 (8), with all complexes being identified by X-ray diffraction, IR, and multinuclear NMR analyses. Complex stability was found to be largely dependent on the nature of the constituent NHC ligands. Percent buried volume (%V-Bur) and topographic steric map analyses were employed to quantify and elucidate the observed trends. Additionally, a detailed bond snapping energy (BSE) decomposition analysis focusing on both steric and orbital interactions of the M-NHC bond (M = Al, Ga and In) has been performed.

First author: Golze, D, Fast evaluation of solid harmonic Gaussian integrals for local resolution-of-the-identity methods and range-separated hybrid functionals,
Abstract: An integral scheme for the efficient evaluation of two-center integrals over contracted solid harmonic Gaussian functions is presented. Integral expressions are derived for local operators that depend on the position vector of one of the two Gaussian centers. These expressions are then used to derive the formula for three-index overlap integrals where two of the three Gaussians are located at the same center. The efficient evaluation of the latter is essential for local resolution-of-the-identity techniques that employ an overlap metric. We compare the performance of our integral scheme to the widely used Cartesian Gaussian-based method of Obara and Saika (OS). Non-local interaction potentials such as standard Coulomb, modified Coulomb, and Gaussian-type operators, which occur in range-separated hybrid functionals, are also included in the performance tests. The speed-up with respect to the OS scheme is up to three orders of magnitude for both integrals and their derivatives. In particular, our method is increasingly efficient for large angular momenta and highly contracted basis sets. Published by AIP Publishing.

First author: Papovic, S, Investigation of 1,2,3-trialkylimidazolium ionic liquids: experiment and density functional theory calculations,
Abstract: Physico-chemical properties, thermal stability and bonding in 1,2,3-trialkylimidazolium based ionic liquids (ILs) were investigated by viscosity and density measurements together with thermogravimetric analysis (TGA) and IR spectroscopy. The obtained results were compared to those obtained for the corresponding 1,3-dialkylimidazolium based ILs. To obtain more insight into the influence of the methylation at position C-2 of the imidazolium ion, IR spectra were calculated with the help of density functional theory (DFT) calculations. The reduction in bonding intensity between ions was confirmed as a consequence of chain reduction and methylation. In this regard, DFT calculations indicated a much higher influence of methylation and these results were explained through the analysis of inter-molecular non-covalent interactions (NCIs). Intra-molecular NCIs together with quantum molecular descriptors were also applied for the explanation of thermal stability of the investigated ILs.

First author: Yau, SH, Optical Properties and Structural Relationships of the Silver Nanoclusters Ag-32(SG)(19) and Ag-15(SG)(11),
Abstract: The recent discovery of stable Ag nanoclusters presents new opportunities to understand the detailed electronic and optical properties of the metal core and the ligands using ultrafast spectroscopy. This paper focuses on Ag-32 and Ag-15 (with thiolate ligands), which are stable in solution. The steady state absorption spectra of Ag nanoclusters show interesting quantum size effects, expected for this size regime. Using a simple structural model for Ag-32, TDDFT calculations show absorption at 480 nm and 680 nm that are in reasonable correspondence with experiments. Ag-32(SG)(19) and Ag-15(SG)(11) have quantum yields up to 2 orders of magnitude higher than Au nanoclusters of similar sizes, with an emission maximum at 650 nm, identified as the metalligand state. The emission from both Ag nanoclusters has a common lifetime of about 130 ps and a common energy transfer rate of KEET (3) 9.7 X 10(9) s(1). A dark state competing with the emission process was also observed and was found to be directly related to the difference in quantum yield (QY) for the two Ag clusters. Two-photon excited emission was observed for Ag-15(SG)(11), with a cross-section of 34 GM under 800 nm excitation. Femtosecond transient absorption measurements for Ag-32 recorded a possible metal core state at 530 nm, a metalligand state at 651 nm, and ground state bleaches at 485 and 600 nm. The ground state bleach signals in the transient spectrum for Ag-32 are 100 nm blue-shifted in comparison to Au-25. The transient spectrum for Ag-15 shows a weak ground state bleach at similar to 480 nm and a broad excited state centered at 610 nm. TDDFT calculations indicate that the electronic and optical properties of Ag nanoclusters can be divided into core states and metalligand states, and photoexcitation generally involves a ligand to metal core transition. Subsequent relaxation leaves the electron in a core state, but the hole can be either ligand or core-localized. This leads to emission/relaxation that is consistent with the observed photophysics.

First author: Margulies, EA, Direct Observation of a Charge-Transfer State Preceding High-Yield Singlet Fission in Terrylenediimide Thin Films,
Abstract: Singlet exciton fission (SF) in organic chromophore assemblies results in the conversion of one singlet exciton (S-1) into two triplet excitons (T-1), provided that the overall process is exoergic, i.e., E(S-1) > 2E(T-1). We report on SF in thin polycrystalline films of two terrylene-3,4:11,12-bis(dicarboximide) (TDI) derivatives 1 and 2, which crystallize into two distinct pi-stacked structures. Femtosecond transient absorption spectroscopy (fsTA) reveals a charge-transfer state preceding a 190% T-1 yield in films of 1, where the pi-stacked TDI molecules are rotated by 23 degrees along an axis perpendicular to their pi systems. In contrast, when the TDI molecules are slip-stacked along their N-N axes in films of 2, fsTA shows excimer formation, followed by a 50% T-1 yield.

First author: Berruyer, P, Three-Dimensional Structure Determination of Surface Sites,
Abstract: The spatial arrangement of atoms is directly linked to chemical function. A fundamental challenge in surface chemistry and catalysis relates to the determination of three-dimensional structures with atomic-level precision. Here we determine the three-dimensional structure of an organometallic complex on an amorphous silica surface using solid-state NMR measurements, enabled through a dynamic nuclear polarization surface enhanced NMR spectroscopy approach that induces a 200-fold increase in the NMR sensitivity for the surface species. The result, in combination with EXAFS, is a detailed structure for the surface complex determined with a precision of 0.7 angstrom. We observe a single well-defined conformation that is folded toward the surface in such a way as to include an interaction between the platinum metal center and the surface oxygen atoms.

First author: Stibr, B, Unusual Cage Rearrangements in 10-Vertex nido-5,6-Dicarbaborane Derivatives: An Interplay between Theory and Experiment,
INORGANIC CHEMISTRY, 56, 852, (2017)
Abstract: The reaction between selected X-nido-5,6-C2B8H11, compounds (where X = Cl, Br, I) and “Proton Sponge” [PS; 1,8-bis(dimethylamino)naphthalene], followed by acidification, results in extensive rearrangement of all cage vertices. Specifically, deprotonation of 7-X-5,6-C2B8H11,compounds with one equivalent of PS in hexane or CH2Cl2 at ambient temperature led to a 7 -> 10 halogen rearrangement, forming a series of PSH+[10-X-5,6-C2B8H,0](-) salts. Reprotonation using concentrated H2SO4 in CH2Cl2 generates a series of neutral carbaboranes 10-X-5,6-C2B8H11, with the overall 7 -> 10 conversion being 75%, 95%, and 100% for X = Cl, Br, and I, respectively. Under similar conditions, 4-Cl-5,6-C2B8H11 gave similar to 66% conversion to 3-Cl-5,6-C2B8H11. Since these rearrangements could not be rationalized using the B vertex swing mechanism, new cage rearrangement mechanisms, which are substantiated using DFT calculations, have been proposed. Experimental B-11 NMR chemical shifts are well reproduced by the computations; as expected delta(B-11) for B(10) atoms in derivatives with X = Br and I are heavily affected by spin-orbit coupling.

First author: Calborean, A, Combined molecular and periodic DFT analysis of the adsorption of co macrocycles on graphene,
Abstract: The molecular doping of graphene with -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: Anderson, JSM, Relativistic (SR-ZORA) Quantum Theory of Atoms in Molecules Properties,
Abstract: The Quantum Theory of Atoms in Molecules (QTAIM) is used to elucidate the effects of relativity on chemical systems. To do this, molecules are studied using density-functional theory at both the nonrelativistic level and using the scalar relativistic zeroth-order regular approximation. Relativistic effects on the QTAIM properties and topology of the electron density can be significant for chemical systems with heavy atoms. It is important, therefore, to use the appropriate relativistic treatment of QTAIM (Anderson and Ayers, J. Phys. Chem. 2009, 115, 13001) when treating systems with heavy atoms.

First author: Reber, AC, Symmetry and magnetism in Ni9Te6 clusters ligated by CO or phosphine ligands,
Abstract: The removal of a single ligand from the magnetic Ni9Te6(L)(8) (L = P(CH3)(3), CO) clusters is found to quench the magnetic moment. The reduction in magnetic moment is caused by a geometric deformation of the Ni9Te6 core that breaks the octahedral symmetry of the cluster. This effect is observed in both the CO and phosphine based ligands. The octahedral symmetry bare cluster is also found to have a large magnetic moment. These results highlight the dilemma faced by magnetic ligand protected clusters whose symmetry has been broken: whether to break the spin symmetry as in Hund’s rules or to break the spatial symmetry as in the Jahn-Teller effect. The spatial symmetry breaking is found to be an oblate distortion that forms additional Ni-Te bonds resulting in the enhanced stability of the cluster. Published by AIP Publishing.

First author: Zhao, RD, Beyond the electrostatic model: the significant roles of orbital interaction and the dispersion effect in aqueous-pi systems,
Abstract: The electrostatic model, which is widely used to explain pi-involved interactions, gives an intuitive picture of these intermolecular interactions and has successfully predicted many phenomena in recent decades. Still, this simple model faces problems in certain cases and it has come under fire in previous studies on pi-pi stacking interactions. Here, employing ab initio calculations, we have identified several counter examples in aqueous-pi systems which cannot be explained adequately using the classical electrostatic model, and revealed the underlying reason. We find strong intermolecular orbital interactions in both aqueous-pi hydrogen bond and lone-pair-pi interactions, and thus extend the previously proposed new model for pi-pi stacking to aqueous-pi systems: while the electrostatic attraction and dispersion effects are the main driving forces pulling the monomers together, Pauli repulsion plays a role in keeping them apart. Interestingly, the molecular orbitals on the concerned monomers exhibit a weak bonding nature at the equilibrium distance.

First author: Nitsch, J, Enhanced pi-Back-Donation as a Way to Higher Coordination Numbers in d(10) [M(NHC)(n)] Complexes: A DFT Study,
Abstract: We aim to understand the electronic factors determining the stability and coordination number of d(10) transition-metal complexes bearing N-heterocyclic carbene (NHC) ligands, with a particular emphasis on higher coordinated species. In this DFT study on the formation and bonding of Group 9-12 d(10) [M(NHC)(n)] (n = 1-4) complexes, we found that all metals form very stable [M(NHC)(2)] complexes, but further coordination depends on the specific interplay of 1) the interaction energy (Delta E-int) between the [M(NHC)(n-1)] (n = 2-4) fragment and the incoming NHC ligand, and 2) the strain energy (Delta E-strain) associated with bending of the linear NHC-M-NHC arrangement. The key observation is that DEstrain, which is an antagonist for higher coordination numbers, can significantly be lowered by M -> NHC pi*-back-donation. This leads to favorable thermodynamics for n = 3-4 for highly electrophilic metals in our study, and thus presents a general design motif to achieve coordination numbers beyond two. The scope of our findings extends beyond the NHC model systems and has wider implications for the synthesis of d(10) [MLn] complexes and their catalytic activity.

First author: Maity, B, Computational Investigation on the Role of Disilene Substituents Toward N2O Activation,
Abstract: The effect of substituents in disilene mediated N2O activation was studied at the M06-2X/QZVP//omega B97xD/TZVP level of theory. The relationship between structural diversity and the corresponding reactivity of six disilenes (I-A-F(t)) in the presence of four different substituents (-NMe2, -Cl, -Me, -SiMe3) is addressed in this investigation. We primarily propose two plausible mechanistic routes: Pathway I featuring disilene -> silylene decomposition followed by N2O coordination and Pathway II constituting the N2O attack without Si-Si bond cleavage. Depending on the fashion of N2O approach the latter route was further differentiated into Pathway IIa and Pathway IIb detailing the “end-on” and “side-on” attack to the disilene scaffold. Interestingly, the lone pair containing substituents (-NMe2, -Cl,) facilitates disilene -> silylene dissociation; on the contrary it reduces the electrophilicity at Si center in silylene, a feature manifested with higher activation barrier during N2O attack. In the absence of any lone-pair influence from substituents (-Me, -SiMe3), the decomposition of disilenes is considerably endothermic. Therefore, Pathway I appears to be the less preferred route for both types of substituents. In Pathway IIa, the N2O moiety uniformly approaches via O-end to both the silicon centers in disilenes. However, the calculations reveal that Pathway IIa, although not operational for all disilenes, is unlikely to be a viable route due to the predominantly higher transition barrier (ca. 36 kcal/mol). The most feasible route in this current study accompanying moderately low activation barriers (similar to 1926 kcal/mol) is Pathway IIb, which involves successive addition of two N2O units proceeding via terminal N,O toward the Si centers and is applicable for all disilenes. The reactivity of substituted disilenes can be estimated in terms of the first activation barrier of N2O attack. Surprisingly, in Pathway IIb, the initial activation barrier and hence the reactivity shows negligible correlation with Si-Si bond strength, indicating toward the versatility of the reaction route.

First author: Abul-Futouh, H, [FeFe]-Hydrogenase H-Cluster Mimics with Unique Planar mu-(SCH2)(2)ER2 Linkers (E = Ge and Sn),
Abstract: Analogues of the [2Fe-2S] subcluster of hydrogenase enzymes in which the central group of the three-atom chain linker between the sulfur atoms is replaced by GeR2 and SnR2 groups are studied. The six-membered FeSCECS rings in these complexes (E=Ge or Sn) adopt an unusual conformation with nearly co-planar SCECS atoms perpendicular to the Fe-Fe core. Computational modelling traces this result to the steric interaction of the Me groups with the axial carbonyls of the Fe-2(CO)(6) cluster and low torsional strain for GeMe2 and SnMe2 moieties owing to the long C-Ge and C-Sn bonds. Gas-phase photoelectron spectroscopy of these complexes shows a shift of ionization potentials to lower energies with substantial sulfur orbital character and, as supported by the computations, an increase in sulfur character in the predominantly metal-metal bonding HOMO. Cyclic voltammetry reveals that the complexes follow an ECE-type reduction mechanism (E = electron transfer and C = chemical process) in the absence of acid and catalysis of proton reduction in the presence of acid. Two cyclic tetranuclear complexes featuring the sulfur atoms of two Fe2S2(CO)(6) cores bridged by CH2SnR2CH2, R = Me, Ph, linkers were also obtained and characterized.

First author: Niu, XH, Photoabsorption Tolerance of Intrinsic Point Defects and Oxidation in Black Phosphorus Quantum Dots,
Abstract: Black phosphorus quantum dots (BPQDs) exhibit excellent optical and photothermal properties and promising applications in optoelectronics and biomedicine. However, various intrinsic structural defects and oxidation are nearly unavoidable in preparation of BPQDs and how they affect the electronic and optical properties remains unclear. Here, by employing time-dependent density functional theory, we reveal that there are two types of photoabsorption in BPQDs for both point defects and oxidation. A close structure-absorption relation is unraveled: BPQDs are defect-tolerant and show excellent photoabsorption as long as the coordination number (CN) of defective P atoms is 3. By contrast, the unsaturated or oversaturated P atoms with CN not equal 3 create in-gap-states (IGSs) and completely quench the optical absorption. An effective way to eliminate the IGSs and repair the photoabsorption of defective BPQDs via sufficient hydrogen passivation is further proposed.

First author: Yildirim, AO, Keto-enol tautomerism of (E)-2-[(3,4-dimethylphenylimino)methyl]-4-nitrophenol: Synthesis, X-ray, FT-IR, UV-Vis, NMR and quantum chemical characterizations,
Abstract: (E)-2-((3,4-dimethylphenylimino)methyl)-4-nitrophenol, which is a new Schiff base compound, was synthesized and characterized by experimental and computational methods. Molecular geometry, harmonic oscillator model of aromaticity (HOMA) indices, intra- and inter-molecular interactions in the crystal structure were determined by using single crystal X-ray diffraction technique. The optimized structures, which are obtained by Gaussian and Slater type orbitals, were compared to experimental structures to determine how much correlation is found between the experimental and the calculated properties. Intramolecular and hyperconjugative interactions of bonds have been found by Natural Bond Orbital analysis. The experimental infrared spectrum of the compound has been analyzed in detail by the calculated infrared spectra and Potential Energy Distribution analysis. To find out about the correlation between the solvent polarity and the enol-keto equilibrium, experimental UV-Visible spectra of the compound were obtained in benzene, CHCl3, EtOH and DMSO solvents. In these solvents, the UV-Vis spectra and relaxed potential energy surface scan (PES) calculations have been performed to get more insight into the equilibrium dynamics. Solvent effects in UV-Vis and PES calculations have been taken into account by using Polarizable Continuum Modelling method. H-1 and C-13 NMR spectra of the compound (in DMSO) were analyzed. The computational study of nonlinear optical properties shows that the compound can be used for the development of nonlinear optical materials.

First author: Kundu, S, An unprecedented 1,4-diphospha-2,3-disila butadiene (-P=Si-Si=P-) derivative and a 1,3-diphospha-2-silaallyl anion, each stabilized by the amidinate ligand,
Abstract: The first acyclic 4 pi-electron -P=Si-Si=P- motif with two four coordinate silicon substituents supported by the amidinate ligand and two coordinate phosphorus has been synthesized from the reaction of heteroleptic chlorosilylene LSiCl ( 1), TripPCl(2) Trip = 2,4,6-(Pr3C6H2)-Pr-i) and KC8 in a 1 : 1 : 3 ratio. The same reaction in a 1 : 2 : 6 ratio in the presence of one equivalent of 18-crown-6 ether affords the 1,3-diphospha-2-silaallyl anion.

First author: Baddour, FG, Pt-Mg, Pt-Ca, and Pt-Zn Lantern Complexes and Metal-Only Donor-Acceptor Interactions,
INORGANIC CHEMISTRY, 56, 452, (2017)
Abstract: Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR)(4)(L)] have been shown previously to form intermolecular metallophilic interactions and engage in anti-ferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal-metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc)(4)(OH2)] (1), [PtMg(tba)(4)(OH2)] (2), [PtCa(tba)(4)(OH2)] (3), [Pan(tba)(4)(OH2)] (4), and a mononuclear control (Ph4P)(2)[Pt(SAc)(4)] (5) have been synthesized. Crystallographic data show dose Pt-M contacts enforced by the lantern structure in each dinudear case. 19813t-NMR spectroscopy of 1-4, (Ph4P)(2)[Pt(SAc)(4)] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH3 (thioacetate, SAc), C6H5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt center dot center dot center dot Zn metallophilic interaction in [PtZn(SAc)(4)(OH2)], and computational studies demonstrate significant dative character. In all of 1-4, the short Pt M distances suggest that metal-only Lewis donor (Pt)-Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.

Abstract: The influence of aza-substitution on sumanene and C-52 fullerene was investigated. Various substitution patterns, derived for the structures of pyrrole, indolizine and pyridine have been proposed and aromaticity indices like HOMA, NICS, delocalization indices PDI and FLU were considered, at B3LYP/6-311+G(d) level of theory. The results outlined an enhanced aromatic character for the sumanene derivatives where similar aza-substitution patterns as encountered in pyrrole and indolizine have been considered.

First author: Magana-Vergara, NE, Synthesis of Frechet-type poly(aryl ether) dendrimers with allyl end groups: comparative convergent and divergent approaches,
ARKIVOC, 62, 117, (2017)
Abstract: The high versatility of allyl groups at the dendrimer periphery makes it important to improve the methodologies to obtain them. Frechet-type poly(aryl ether) first and second generation dendrimers bearing a conjugated phloroglucinol core with 6 or 12 peripheral allyl groups have been synthesized by convergent and divergent approaches. By the divergent approach the dendrimers were obtained in higher yields and product purification was easier. Steric hindrance proved not to be the key factor in achieving higher yields in the divergent approach; MM and DFT analysis corroborate that electronic effects on the alkoxide play a key role.

First author: Rusakov, YY, On the significant relativistic heavy atom effect on C-13 NMR chemical shifts of beta- and gamma-carbons in seleno- and telluroketones,
MOLECULAR PHYSICS, 115, 3117, (2017)
Abstract: Unexpectedly large ‘Heavy Atomon Light Atom’ (HALA) effects have been found in C-13 NMR (Nuclear Magnetic Resonance) chemical shifts of beta- and gamma-carbons of seleno-and telluroketones established by means of the high-accuracy calculations of C-13 NMR chemical shifts in three representative real-life compounds, 2,2,5,5-tetramethyl-3-cyclopentene-1-selone, selenofenchone and 1,1,3,3-tetramethyl-1,3-dihydro-2H-indene-2-tellurone. The proposed computational scheme consists of the combination of accurately correlated coupled-cluster singles and doubles model approach for the non-relativistic calculations of shielding constants taking into account the solvent, vibrational and relativistic corrections, the latter obtained within the 4-component fully relativistic gauge-including atomic orbitals KT2 approach resulting in a very good agreement of the performed calculations with the experiment. The stereochemical dependence of the ‘long-range’ gamma-HALA effect on the dihedral angle has been established in the model seleno-and telluroketones providing the largest shielding effect in the orthogonal orientation of the X=C-alpha-C-beta-C-gamma (X=Se, Te) moiety.

First author: Holzer, C, Quasi-relativistic two-component computations of intermolecular dispersion energies,
MOLECULAR PHYSICS, 115, 2775, (2017)
Abstract: A method for computing quasi-relativistic two-component dispersion energies is developed and implemented in the TURBOMOLE program package. The method is based on the Casimir-Polder formula for dispersion energies, which occurs in symmetry-adapted perturbation theory. The method is applied to evaluate the dispersion energies of a small set of van der Waals complexes involving heavy elements such as gold, mercury and bismuth.

Abstract: A method for computing quasi-relativistic two-component dispersion energies is developed and implemented in the TURBOMOLE program package. The method is based on the Casimir-Polder formula for dispersion energies, which occurs in symmetry-adapted perturbation theory. The method is applied to evaluate the dispersion energies of a small set of van der Waals complexes involving heavy elements such as gold, mercury and bismuth.

First author: Zhang, XX, Reactive molecular dynamics study of the decomposition mechanism of the environmentally friendly insulating medium C3F7CN,
RSC ADVANCES, 7, 50663, (2017)
Abstract: The extensive use of sulfur hexafluoride (SF6) gas in the power industry has a strong greenhouse effect. Hence, many scholars are committed to studying SF6 alternative gases to achieve green power development. In the past two years, C3F7CN (heptafluoroisobutyronitrile) has attracted the attention of many scholars due to its excellent insulation and environmental protection characteristics as a potential alternative gas. This study theoretically explores the decomposition characteristics of C3F7CN and the C3F7CN/CO2 gas mixture based on the reactive molecular dynamics method and density functional theory. The main decomposition pathways of C3F7CN and the enthalpy of each path at different temperatures were analyzed. The yield of the main decomposition products was obtained under several temperature conditions. The decomposition of C3F7CN mainly produced CF3, C3F7, CN, CNF, CF2, CF, F, and other free radicals and a few molecular products, such as CF4 and C3F8. The C3F7CN/CO2 gas mixture has more excellent decomposition characteristics than that of the pure C3F7CN. The addition of CO2 effectively ensures that the gas mixture has a low liquefaction temperature, which is considerably suitable for use as a gas insulation medium. The relevant research results provide guidance for the further exploration on the electrical properties and practical engineering application of the C3F7CN gas mixture.

First author: Lv, Y, Theoretical investigations on the structure-property relationships of Au-13 and AuxM13-x nanoclusters,
RSC ADVANCES, 7, 51538, (2017)
Abstract: As a fundamental building block in ultrasmall, noble metal nanoclusters, icosahedral AuxM13-x structures have recently attracted extensive research interest. In this study, density functional theory (DFT) and time-dependant DFT calculations have been carried out to investigate the structure-property (optical and electronic) relationships of a series of Au-13 and AuxM13-x (M = Au, Ag, Cu, and Pd) nanoclusters co-protected by phosphine and chloride ligands. It was found that the size of the peripheral ligands significantly affects the geometric structure: the larger exterior ligands (with a larger cone angle) result in relatively longer Au-M bond distances and weaker metallic interactions within the AuxM13-x core. Therefore, the optical peak (in the UV-vis spectrum) corresponding to the HOMO -> LUMO transition red-shifts accordingly. When different foreign atom(s) are incorporated, the preferential doping site is different, and the electronic and optical structures alter accordingly.

First author: Ashwell, AP, A Time-Dependent Density Functional Theory Study of the Impact of Ligand Passivation on the Plasmonic Behavior of Ag Nanoclusters,
Abstract: We present a detailed study of the impact of ligand passivation on the electronic structures and optical properties of plasmonic Ag nanoclusters using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The clusters studied are Ag-13(5+), Ag-25(SH)(18)(-), Ag-25(NH2)(18)(-), Ag-32(14+), and Ag-44 (SH)(30)(4-). We find that the highest occupied ligand orbitals from S (3p) and N (2p) appear just above the conduction band, and this leads to significant ligand-to-metal charge transfer transitions at high energies. Dielectric screening associated with ligand passivation results in reduced HOMO-LUMO gaps and in an increased gap between the HOMO and the valence band associated with the Ag 4d orbitals. Ligand field effects result in splitting of plasmonic peaks, leading to reduced mixing between nearby single-particle excitations. The magnitude of these effects is found to decrease when thiolate ligands are replaced with amine ligands. We also find that, in the case of the Ag-44(SH)(30)(4-) cluster, the ligands localize plasmonic excitations into the core of the cluster.

First author: Dabrowski, R, Nematic compounds and mixtures with high negative dielectric anisotropy,
LIQUID CRYSTALS, 44, 1534, (2017)
Abstract: Syntheses, mesogenic and dielectric properties of three-ring alkylcyclohexyl, alkoxy and alkylphenyl benzoates substituted with four fluorine atoms or with two fluorine atoms and simultaneously a cyano group or two cyano groups are described. Their properties are compared with analogous three-ring phenyl tolanes. Conformation analysis and the calculation of dipole moments with the quantum chemistry method are performed to explain the experimental results. Several four fluorine-substituted two-ring tolanes and biphenyls are also prepared, which are used as a solvent decreasing viscosity, melting point and clearing point of the formulated mixtures. Examples of mixtures prepared from the esters and tolanes with high dielectric anisotropy are given. Curiosity is observed that 4′-(4-ethoxyphenyl)-4-pentyloxy-2,2′,3,3′-tetrafluorotolane is not the mesogenic compound, while analogous ester 4′-ethoxy-2,3-difluorobiphenyl-4-yl 2,3-difluoro-4-pentyloxybenzoate exhibits a broad temperature range of the nematic phase.

First author: Gostynski, R, Significance of the electron-density of molecular fragments on the properties of manganese(III) beta-diketonato complexes: an XPS and DFT study,
RSC ADVANCES, 7, 27718, (2017)
Abstract: DFT and XPS studies were conducted on a series of nine manganese(III) complexes of the general formula [Mn(beta-diketonato) 3], with the ligand beta-diketonato = dipivaloylmethanato (1), acetylacetonato (2), benzoylacetonato (3), dibenzoylmethanato (4), trifluoroacetylacetonato (5), trifluorothenoylacetonato (6), trifluorofuroylacetonato (7), trifluorobenzoylacetonato (8) and hexafluoroacetylacetonato (9). The binding energy position of the main and satellite structures of the Mn 2p(3/2) photoelectron line, as well as the spin-orbit splitting, gave insight into the electronic structure of these manganese(III) complexes. DFT calculations showed that an experimental sample of the d(4) [Mn(beta-diketonato) 3] complex can contain a mixture of different bond stretch isomers and different electronic states, in dynamic equilibrium with one other. The presence of more than one isomer in the experimental sample, as well as interaction between an unpaired 2p electron (originating after photoemission) and an unpaired 3d electron, which aligned anti-parallel to the unpaired 2p electron, caused broadening of the Mn 2p photoelectron lines. Multiplet splitting simulations of these photoelectron lines, similar to those calculated by Gupta and Sen for the free Mn(III) ion, gave good fits with the observed Mn 2p(3/2) photoelectron lines. The XPS spectra of complexes with unsymmetrical beta-diketonato ligands were simulated with two sets of multiplet splitting peaks, representing both the mer and fac isomers. The satellite structures obtained in both the Mn 2p(3/2) photoelectron line (shake-up peaks) and the ligand F 1s photoelectron line (shake-down peaks), are representative of the ligand-to-metal charge transfer during photoionisation. The binding energies of the Mn 2p, F 1s and S 2p electrons, as well as the amount of charge transfer from ligand-to-metal, are both dependent on the electronegativity of the different groups attached to the beta-diketonato ligand.

First author: Fan, HW, Theoretical investigation on the effect of ancillary ligand modification for highly efficient phosphorescent platinum(II) complex design,
RSC ADVANCES, 7, 17368, (2017)
Abstract: In this study, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were employed to investigate the geometries, electronic structures, reorganization energy (lambda) and photophysical properties of four cyclometalated Pt(II) complexes (bzq)Pt(dpm) (1), (bzq)Pt(ppy) (2), (bzq)Pt(Ncaz) (3) and (bzq)Pt(Ndbt) (4) (where bzq = benzo[h] quinoline, dpm = dipivolylmethanoate, ppy = 2-phenylpyridine, Ncaz = N-substituted carbazole and Ndbt = N-substituted dibenzothiophene). In addition, the radiative decay processes and zero-field splitting were calculated based on the spin-orbit coupling (SOC) effect, and nonradiative decay pathways were discussed to evaluate the phosphorescence efficiency qualitatively. All the complexes retain the bzq as a cyclometalated ligand and our research focuses on the role recognition of another ancillary ligand modification theoretically. According to the results, in complexes 2-4 replacing the dpm with different ligands shows better rigidity which may weaken the nonradiative decay pathways and enhance the capability of charge transfer. Furthermore, complexes 1-4 tend to be bluish-green luminescent materials, and the emission wavelengths of 1, 2 and 4 are close to each other due to the similar excited state energy levels and electronic density distribution. Compared with complex 1, the radiative decay rate constants (k(r)) of 2-4 are greatly increased. Therefore, the designed complexes would be potential phosphorescence materials because of their high phosphorescence quantum efficiency and complex 3 can also serve as a promising bipolar transporting material due to its better charge transfer balance character.

First author: Goez, A, Including protein density relaxation effects in first-principles embedding calculations of cofactor excitation energies,
MOLECULAR PHYSICS, 115, 526, (2017)
Abstract: The Three-Partition Frozen Density Embedding (3-FDE) method is applied to the photosynthetic Fenna-Matthews-Olson (FMO) complex of green sulphur bacteria in order to determine cofactor excitation energies. We present a sophisticated multi-layer embedding protocol, which allows to choose fragments of arbitrary size. This is useful in order to limit the total number of calculations, which can create a significant overhead. The approach allows to determine fully polarised densities for realistic proteins in this framework for the first time. A solvent shell around the total system is described in terms of the LoCOSMO algorithm, which tremendously simplifies the computational effort of a continuum description around a system of this size. The solvent response to the excitation is incorporated by a new extension of the LoCOSMO scheme to time-dependent density functional theory. Excitation energies for the chromophores are calculated under the influence of density-based embedding potentials obtained with different technical settings. It is found that protein density relaxation in this particular example hardly influences the transitions, indicating that embedding of the pigments in the initial protein density is sufficient to determine site energy modulations with our approach.

First author: Priya, AM, Atmospheric fate of diketones and OH radical-kinetics, reaction force, ETS-NOCV analysis,
MOLECULAR PHYSICS, 115, 839, (2017)
Abstract: In this work, we have focused on the atmospheric reaction chemistry of two a-diketones 2,3Pentanedione (2,3-PTD) and 2,3-hexanedione (2,3-HEX) withOH radical. The full reaction pathway was studied theoretically under H-atom abstraction reaction using density functional theory and wavefunction- based MP2 calculations. Single-point energy calculations were performed at CCSD(T) level of theory with 6-31+ G(d, p) basis set. The H-atom abstraction from -CH 2 group is the most dominant channel in both 2,3-PTD and 2,3-HEX with OH radical. The fate of secondary reactions of peroxy and alkoxy radical is studied in detail. The reaction force analysis shows that abstraction process is dominated by structural rearrangement than electronic reordering. The ETS-NOCV-based reaction scheme is studied in order to find out the pair wise interaction energy of the chemical bonding. The ETSNOCV method for all the transition states shows p-bonding nature for the bond breaking (C-H) and bond formation (O-H) due to the presence of hydrogen bond. The theoretical rate constant value matches well with the experimental rate constant value for both a-diketones. Normal linear Arrhenius behaviour for all the pathways is found in the range of 278-350 K. The short atmospheric lifetime indicates the removal process of diketones with OH radical.

First author: Chub, DS, On the Dynamics of the Spin Crossover in Cobalt Octaethylporphyrin Molecular Magnets in a Terahertz Pulsed Magnetic,
Abstract: The results of theoretical study of the spin crossover dynamics in the cobalt octaethylporphyrin molecule under the action of an external pulsed magnetic field with an induction of 36.8 T are presented. It is shown that, in the case of the high-spin state, under the action of a pulsed magnetic field, spin switching occurs in the system, and the system is characterized by a large relaxation time. In the case of the low-spin state, the system relaxes rapidly to the ground state. The temperature dependence of the product of the magnetic susceptibility and the temperature has a feature in the vicinity of 40 K related to the transition between spin states.

First author: Kuwajima, S, A Bowl-Type Dodecavanadate as a Halide Receptor,
ACS OMEGA, 2, 268, (2017)
Abstract: The dodecavanadate framework, [V12O32](4-), exhibits a unique bowl-type structure with an open molecular oxide cage having a cavity diameter of 4.4 angstrom, and different synthetic paths were required to construct the bowl-type structure with a different guest. A new dodecavanadate, {(n-C4H9)(4)N} 4[V12O32(CH3NO2)] (1), is synthesized with a nitromethane guest, which is stacked above the entrance of the hemisphere rather than fully occupying the cavity, and it enables a guest-capturing reaction, while retaining the anionic cage structure. Compound 1 is a good precursor for halide-centered dodecavanadates, {(C2H5)(4)N}(5)[V12O32(X)] (X = Cl- (2), Br- (3), and I- (4)). The position of the halide inside the cavity correlates with the ionic radius of the guest; the small chloride ion sat at the far bottom, and the large iodide floated at the entrance. The inclusion reaction rates were estimated through V-51 NMR time-course measurements in nitromethane. The reaction rates increase in the order I- < Br- < Cl-.

First author: Li, QJ, Surface-enhanced Raman scattering of pyrazine on Au5Al5 bimetallic nanoclusters,
RSC ADVANCES, 7, 12170, (2017)
Abstract: In this study, we theoretically investigated the Raman and absorption spectra of pyrazine adsorbed on Au5Al5 bimetallic nanoclusters by a time-dependent density functional theory (TD-DFT) method. The surface-enhanced resonance Raman scattering (SERRS) spectra of pyrazine absorbed on different isomers and sites of the Au5Al5 cluster were simulated. The visualization of orbital transitions in electronic transitions was used to analyze the enhancement mechanism of SERRS spectroscopy. Compared with those of isolated pyrazine excited at 598 nm, the SERRS of pyrazine-Au-Au(4)Al(5-)a excited at the same incident light can be enhanced on the order of 10(4), which is a typical charge transfer (CT) resonance excitation and charge transfer from substrate to pyrazine. Due to the fact that the intensity of ultraviolet SERRS can be significantly enhanced to 1.2 x 106 A(4) per amu for pyrazine-Au- Au4Al5-a model at 280 nm, the Au5Al5 cluster may be a good candidate for research of the ultraviolet SERRS materials. Other key factors that can change the intensity of SERRS include the resonance excitation wavelength, oscillator strength of the electronic excited state, metal-molecule binding site and structure of the substrate cluster. Hence, the optical properties of complexes can be tuned by varying these factors.

First author: Mahmoudi, G, Anion-driven tetrel bond-induced engineering of lead(II) architectures with N’-(1-(2-pyridyl) ethylidene) nicotinohydrazide: experimental and theoretical findings,
Abstract: The evaluation of N’-(1-(2-pyridyl)ethylidene)nicotinohydrazide (HL) as a linker for the Pb-II tagged extended structures is described. The reaction of Pb(ClO4)(2) or Pb(OAc)(2) with HL in MeOH at 60 degrees C and room temperature, respectively, leads to heteroleptic complexes {[PbL] ClO4}(n)center dot nH(2)O and [PbL(OAc)](2), while the same reaction of Pb(ClO4)(2) with HL at 60 degrees C in the presence of two equivalents of NaOAc or NaNO2 leads to heteroleptic complexes {[Pb(HL)(OAc)] ClO4}(n) and [PbL(NO2)](n), respectively. Using Pb(NO3)(2) as a source of PbII in the same reaction with HL and two equivalents of NaN3 or NaNCS at room temperature yields [PbLN3](n) and [Pb-2(HL)(2)(NO3)(2)(NCS)(2)], respectively. The room temperature reaction of Pb(NO3)(2) with HL in the presence of two equivalents of NaClO4 leads to the transformation of the parent ligand to its perchlorate salt [H2L] ClO4. In all the obtained Pb-II structures, HL or its deprotonated form L acts both as a chelating and a bridging ligand. The nature of the inorganic anion 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 with the closest approach of two atoms on the other side varying from 151 degrees to 232 degrees. The sterically available PbII ion participates in tetrel bonding as evidenced from the detailed structural analysis of the described complexes. As a result of tetrel bonding, the structures of all the six compounds can be extended to a higher dimensional framework, which is further stabilized by pi center dot center dot center dot pi stacking interactions between the aromatic rings. The DFT based charge and energy decomposition (ETS-NOCV) calculations are performed in order to shed light on the nature of non-covalent interactions that determine the stability of the obtained structures.

First author: Munoz-Castro, A, Evaluation of Hollow Golden Icosahedrons: Bonding and Spherical Aromatic Properties of [Au11E](3-) Superatoms (E=Se and Te) from Relativistic DFT calculations, Persistent Structures?,
CHEMPHYSCHEM, 18, 87, (2017)
Abstract: Two novel clusters were proposed according to the superatom model involving a favorable inclusion of Se and Te into a Au-12 cage leading to [Au11E](3+) clusters. Such structures retain a hollow gold-based icosahedron with spherical aromatic character, according to the 18-valence electron rule. Interestingly, it is shown that despite the favorable electronic structure and aromatic behavior, the titled structure is further found to be a local minimum in the potential surface, which exhibits a planar isomer as a plausible candidate for the lowest-energy structure. The proposed strategy employed to vary the electron count of the cage is useful for the further design of novel spherical aromatic superatoms and ligand-protected clusters, for which the main variation is generated directly in the surface of the cluster, in addition to the extensive formation of endohedral clusters with different heteroatoms.

First author: Baus, JA, Silylene-Induced Reduction of [Mn-2(CO)(10)]: Formation of a Five-Coordinate Silicon(IV) Complex with an O-Bound [(OC)(4)Mn=Mn(CO)(4)](2-)Ligand,
Abstract: Treatment of the donor-stabilized silylene [iPrNC(NiPr2)NiPr](2)Si (1) with [Mn-2(CO)(10)] leads to the five-coordinate silicon(IV) complex 6, accompanied by elimination of two CO molecules. In this redox reaction, the dimanganese fragment is reduced to form an [(OC)(4)Mn=Mn(CO)(4)](2-) moiety that is coordinated to the silicon(IV) species {[iPrNC(NiPr2)NiPr](2)Si}(2+).

First author: Neyts, EC, Molecular Dynamics Simulations for Plasma-Surface Interactions,
Abstract: Plasma-surface interactions are in general highly complex due to the interplay of many concurrent processes. Molecular dynamics simulations provide insight in some of these processes, subject to the accessible time and length scales, and the availability of suitable force fields. In this introductory tutorial-style review, we aim to describe the current capabilities and limitations of molecular dynamics simulations in this field, restricting ourselves to low-temperature non-thermal plasmas. Attention is paid to the simulation of the various fundamental processes occurring, including sputtering, etching, implantation, and deposition, as well as to what extent the basic plasma components can be accounted for, including ground state and excited species, electric fields, ions, photons, and electrons. A number of examples is provided, giving an bird’s eye overview of the current state of the field.

First author: Gendron, D, A thiocarbonyl-containing small molecule for optoelectronics,
RSC ADVANCES, 7, 10316, (2017)
Abstract: We report the synthesis and characterization of a novel thiocarbonyl iso-DPP derivative, namely 1,3,4,6-tetraphenylpyrrolo[3,2-b]pyrrole-2,5(1H, 4H)-dithione. Even without solubilising alkyl chains, the small molecule could be processed from organic solvents such as dichloromethane, chloroform or dichlorobenzene, and it was found that the optical properties of neat thin films were strongly dependent on the solvent used. Field effect hole mobilities were of the order 10(-4) cm(2) V-1 s(-1), with mobilities measured in a diode configuration solvent dependent and at least an order of magnitude lower. Importantly, blends of the iso-DPP derivative with PC70BM, a typically used electron acceptor in bulk heterojunction solar cells, were found to possess hole mobilities of up to 10(-3) cm(2) V-1 s(-1) in a diode configuration, which was an order of magnitude larger than the electron mobility. Finally, simple bulk heterojunction solar cells were fabricated with maximum power conversion efficiencies of 2.3%.

First author: Calborean, A, DFT study of Zn2+ and Ni2+ BCP8 bridled porphyrins: Theoretical correlations,
Abstract: DFT investigations on M-BCP8 (M = Zn, Ni) bridled chiral porphyrins were performed. The conformational flexibility depending on the metal ion, the environment, or the electronic redox state was analysed in the framework of Kohn-Sham formalism, within a Generalized Gradient functional, namely GGA-PBE, corroborated with triple-zeta Slater basis sets. Correlations between the metal ion size and the deformation of the porphyrinic core highlight a more pronounced deformation for Ni2+-BCP8 than for Zn2+-BCP8, suggesting that the short distances in Ni-N porphyrins are responsible for the ruffling of the porphyrinic core, whereas the Zn2+ ion being larger, fits better in the cavity and does not impose any strong deformation. Description of the most stable atropoisomer was proved in agreement with experimental NMR and X-ray measurements. The free base and the Zn2+ complex exhibit a preferential alpha alpha alpha alpha conformation in solution, while for Ni2+ analogue, the atropisomer was 100% alpha beta alpha beta. In the case of ZnBCP-8 the main atropoisomer is changing in comparison with the crystal data, obtaining in dichloromethane and nitrobenzene a more stable Zn open conformation but in equilibrium with the closed conformation. Stabilization due to solvation was investigated, explaining the difference of behaviour observed for ZnBCP-8. The effect of supramolecular aggregation observed experimentally was theoretically investigated in terms of dimer formation. We also calculated the BSSE errors and even the thermodynamic entropy and ZPE parameters that can eventually influence the alpha beta alpha beta/alpha alpha alpha alpha equilibriums.

First author: Purcell, W, Characterization and oxidative addition reactions for iridium cod complexes,
Abstract: Three different [Ir(LL)(cod)] complexes (LL=N-aryl-N-nitrosohydroxylaminato) (cupf), trifluoroacetylacetonato (tfaa), and (methyl 2-(methylamino)-1-cyclopentene-1-dithiocarboxylato-N,S) (macsm)) were synthesized, characterized, and their rates of oxidative addition with methyl iodide were determined. Formation of an isosbestic point during the oxidative addition of methyl iodide with the complexes containing tfaa and cupf as bidentate ligands indicated formation of only one product, while an increase in absorbance maximum observed for macsm confirms that the same reaction between the complex and methyl iodide occurs. Kinetic results for all complexes, except [Ir(tfaa)(cod)], showed simple second-order kinetics with a zero intercept (within experimental error). Rates of oxidative addition for bidentate ligands in acetonitrile showed an increase of an order of magnitude with a change in the type of bidentate ligands. Computational chemistry using density functional theory calculations showed that the oxidative addition reaction proceeds through a linear transition state with the methyl iodide unit tilted towards the LL-bidentate ligand.

First author: Realista, S, Electrochemical studies and potential anticancer activity in ferrocene derivatives,
Abstract: Several ferrocene derivatives (five mononuclear and two binuclear), including the new N-(p-chlorophenyl)-carboxamidoferrocene (1), were synthesized and their anticancer activity investigated. Two of them, 3 and 7, bearing a benzimidazole backbone were the most active against HeLa cells achieving IC50 values of similar to 5 mu M along with 4 with a dipyridylamine ligand (similar to 6 mu M). Complex 6, also with a benzimidazole backbone, displayed slightly higher values (similar to 11 mu M). Cyclic voltammetry studies show that while the non-cytotoxic ferrocene derivatives 1, 2, and 5 follow a ferrocene-based redox behavior, derivatives 3, 4, 6, and 7 exhibit a more complex mechanism. These complex mechanisms are consistent with a more effective cytotoxic activity. Mossbauer spectroscopy parameters reflect a very small influence of the substituents

First author: Miorelli, J, Using Computational Visualizations of the Charge Density To Guide First-Year Chemistry Students through the Chemical Bond,
Abstract: The chemical bond concept is the foundation of the molecular sciences. Therefore, helping students gain a clear physical representation of chemical bonding is necessary for progress in chemistry. Bond Explorer, an activity that utilizes the three-dimensional (3D) plotting functionality of Mathematica, is intended to provide a clear physical picture of electron sharing among atoms i.e., a physical picture of the chemical bond. The app takes advantage of Mathematica’s free-to-use CDF Player, removing the high cost often associated with implementing computational activities in the classroom. Through the course of the activity, students visualize the 3D charge density using both fog and contour plots. Students then go on to describe the density differences that characterize various bonding types, i.e., covalent, polar covalent, and ionic. The activity involves both independent and group work and was designed to guide students as they identify key similarities and differences among the charge densities corresponding to various bond types. Preliminary assessment suggests that students who participated in the activity understand bonding and electronegativity more fully than students who did not complete the activity.

First author: Chong, DP, Computational study of the anticancer drug cisplatin,
Abstract: Systems containing platinum (Pt) are more challenging for reliable computations, because Pt has 78 electrons and requires relativistic treatment. However, to reduce computational demands, most previous researchers used effective core potentials. In this investigation, we perform numerous computations on the cisplatin molecule with ab initio methods and density functional theory, some of which involve all electron and zero-order relativistic approximation. Tentative conclusions on the reliability of various methods are drawn from comparison of our results with previous calculations and available experimental data. Vibrational and electronic spectra are calculated and compared with previous studies and available experimental data.

First author: Armakovic, S, Optoelectronic properties of curved carbon systems,
CARBON, 111, 371, (2017)
Abstract: Systematic investigation of optoelectronic properties of curved carbon systems has been performed and the results have been compared with the representatives of flat carbon systems. Moreover, the application of third order dispersion corrected density functional tight binding method (with third order corrections of self-consistent charges) including Becke-Johnson dumping (DFT133-03(BJ)) has been validated in order to obtain reliable dimer structures for the calculations of charge transfer rates. Optoelectronic properties encompassed calculations of reorganization energies, energy difference between the singlet and triplet state, first hyperpolarizabilities, whereas the charge transfer rates have been calculated according to the equation of Marcus semi-empiric approach. The obtained results indicate that a wide list of outstanding features of buckybowls could be expanded for optoelectronic properties as well. Furthermore, it has also been shown that correlation in the form of the second order exponential decay between electron transfer rates and the specific structural property of buckybowls exists. This allows for computationally inexpensive assessment of electron hopping rates.

First author: Munoz-Castro, A, Evaluation of Bonding, Electron Affinity, and Optical Properties of M@C-28 (M=Zr, Hf, Th, and U): Role of d- and f-Orbitals in Endohedral Fullerenes from Relativistic DFT Calculations,
Abstract: The experimentally characterized endohedral metallic fullerenes involving the small C-28 cage, has shown to be able to encapsulate zirconium, hafnium, and uranium atoms, among other elements. Here, we explore the formation and nature of concentric bonds from purely d- to f-block elements, given by Zr, Hf, and uranium, along a borderline metal between such blocks, thorium. We explore the interplay of d- and f-orbitals in the chemistry of the early actinides, where the features of a d- or f-block metal can be mixed. Our results indicate that the bonding of Th@C-28 involves contributions from both d- and f-type bonds, as characteristic of this early actinide element. Even uranium in U@C-28, also exhibits a contribution from d-type bonds in addition to its relevant f-block character. Electron affinity and optical properties were evaluated to gain more insights into the variation of these molecular properties in this small endohedral fullerene, along Zr, Hf, Th, and U. The current results, allows to unravel the role of (n=1)d and (n=2)f orbitals in confined elements ranging from d- to f-blocks, which can be useful to gain a deeper understanding of the bonding situation in other endohedral species.

First author: Lalitha, M, Improved lithium adsorption in boron- and nitrogen-substituted graphene derivatives,
Abstract: We present the results from density functional theory calculations of the lithium adsorption on various forms of boron- and nitrogen-doped graphene derivatives. Encouraging results are noticed for the lithium adsorption on the boron-doped graphyne model. The acetylenic linkage increases the lithium adsorption affinity but decreases the gravimetric densities marginally in bare, boron/nitrogen-doped graphene derivatives. From lithiation potential, gravimetric density, and specific capacity values, we notice boronated graphyne as a highly suitable anode material for Li-ion batteries.