2013 publications citing ADF

First author: Li, Wei-Li, Probing the electronic structures of low oxidation-state uranium fluoride molecules UFx- (x=2-4),JOURNAL OF CHEMICAL PHYSICS, 139, , (2013)
Abstract: We report the experimental observation of gaseous UFx- (x = 2-4) anions, which are investigated using photoelectron spectroscopy and relativistic quantum chemistry. Vibrationally resolved photoelectron spectra are obtained for all three species and the electron affinities of UFx (x = 2-4) are measured to be 1.16(3), 1.09(3), and 1.58(3) eV, respectively. Significant multi-electron transitions are observed in the photoelectron spectra of U(5f(3)7s(2)) F-2(-), as a result of strong electron correlation effects of the two 7s electrons. The U-F symmetric stretching vibrational modes are resolved for the ground states of all UFx (x = 2-4) neutrals. Theoretical calculations are performed to qualitatively understand the photoelectron spectra. The entire UFx- and UFx (x = 1-6) series are considered theoretically to examine the trends of U-F bonding and the electron affinities as a function of fluorine coordination. The increased U-F bond lengths and decreased bond orders from UF2- to UF4- indicate that the U-F bonding becomes weaker as the oxidation state of U increases from I to III.

First author: Hua, Weijie, Fe L-Edge X-ray Absorption Spectra of Fe(II) Polypyridyl Spin Crossover Complexes from Time-Dependent Density Functional Theory, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 14075, (2013)
Abstract: L-edge near-edge X-ray fine structure spectroscopy (NEXAFS) has become a powerful tool to study the electronic structure and dynamics of metallo-organic and biological compounds in solution. Here, we present a series of density functional theory calculations of Fe L-edge NEXAFS for spin crossover (SCO) complexes within the time-dependent framework. Several key factors that control the L-edge excitations have been carefully examined using an Fe(II) polypyridyl complex [Fe(tren(py)(3))](2+) (where tren(py)(3) = tris(2-pyridylmethyliminoethyl)amine) as a model system. It is found that the electronic spectra of the low-spin (LS, singlet), intermediate-spin (IS, triplet), and high-spin (HS, quintet) states have distinct profiles. The relative energy positions, but not the spectral profiles, of different spin states are sensitive to the choice of the functionals. The inclusion of the vibronic coupling leads to almost no visible change in the resulting NEXAFS spectra because it is governed only by low-frequency modes of less than 500 cm(-1). With the help of the molecular dynamics sampling in acetonitrile at 300 K, our calculations reveal that the thermal motion can lead to a noticeable broadening of the spectra. The main peak position is strongly associated with the length of the Fe-N bond.

First author: Jablonska, Agnieszka, Syntheses, spectroscopic and structural properties of phenoxysilyl compounds: X-ray structures, FT-IR and DFT calculations, JOURNAL OF MOLECULAR STRUCTURE, 1054, 359, (2013)
Abstract: The reaction of silicon disulfide with alkylphenols yields tetraphenoxysilane, cyclodisilthiane and silanethiol. The outcome of the reaction depends on the presence of the steric hindrance in the ortho position on the reacting phenol. New products of the reaction of silicon disulfide with phenols are characterized by FT-IR, NMR, X-ray diffraction and DFT calculations. The intramolecular interactions in the compounds are mainly XH-pi (X = C, S) whereas the intermolecular interactions are either very weak CH-pi/CH-O contacts found in aryloxysilane or electrostatic dipole-dipole attraction in cyclodisilthiane and silanethiol. The S-H-pi interactions in the obtained silanethiol are analyzed with the use of DFT/GGA BLYP-D XC potentials. The energy of intramolecular S-H-pi interaction is estimated.

First author: Zhang, Igor Ying, Numeric atom-centered-orbital basis sets with valence-correlation consistency from H to Ar,NEW JOURNAL OF PHYSICS, 15, 359, (2013)
Abstract: We present a series of numerically tabulated atom-centered orbital (NAO) basis sets with valence-correlation consistency (VCC), termed NAO-VCC-nZ. Here the index ‘nZ’ refers to the number of basis functions used for the valence shell with n = 2, 3, 4, 5. These basis sets are constructed analogous to Dunning’s cc-pVnZ, but utilize the more flexible shape of NAOs. Moreover, an additional group of (sp) basis functions, called enhanced minimal basis, is established in NAO-VCC-nZ, increasing the contribution of the s and p functions to achieve the valence-correlation consistency. NAO-VCC-nZ basis sets are generated by minimizing frozen-core random-phase approximation (RPA) total energies of individual atoms from H to Ar. We demonstrate that NAO-VCC-nZ basis sets are suitable for converging electronic total-energy calculations based on valence-only (frozen-core) correlation methods which contain explicit sums over unoccupied states (e.g. the RPA or second-order Moller-Plesset perturbation theory). The basis set incompleteness error, including the basis set superposition error, can be gradually reduced with the increase of the index ‘n’, and can be removed using two-point extrapolation schemes.

First author: Carreras, Javier, Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely pi-Acidic Catalysts, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 18815, (2013)
Abstract: Very often ligands are anionic or neutral species. Cationic ones are rare, and, when used, the positively charged groups are normally appended to the periphery of the ligand. Here, we describe a dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups. This structural feature makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF3 or P(CF3)(3). By exploiting these properties, a new Au catalyst has been developed displaying a dramatically enhanced capacity to activate pi-systems. This has been used to synthesize very sterically hindered and naturally occurring 4,5-disubstituted phenanthrenes. The present approach is expected to be applicable to the development and improvement of many other transition metal catalyzed transformations that benefit from extremely strong pi-acceptor ligands. The mechanism of selected catalytic transformations has been explored by density functional calculations.

First author: Du, Wen-Ge Han, Density Functional Study for the Bridged Dinuclear Center Based on a High-Resolution X-ray Crystal Structure of ba(3) Cytochrome c Oxidase from Thermus thermophilus, INORGANIC CHEMISTRY, 52, 14072, (2013)
Abstract: Strong electron density for a peroxide type dioxygen species bridging the Fe-a3 and CUB dinuclear center (DNC) was observed in the high-resolution (1.8 angstrom) X-ray crystal structures (PDB entries 3S8G and 3S8F) of ba(3) cytochrome c oxidase (CcO) from Thermus thermophilus. The crystals represent the as-isolated X-ray photoreduced CcO structures. The bridging peroxide was proposed to arise from the recombination of two radiation-produced HO center dot radicals formed either very near to or even in the space between the two metals of the DNC. It is unclear whether this peroxide species is in the O-2(2-), O-2(center dot-), HO2-, or the H2O2 form and what is the detailed electronic structure and binding geometry including the DNC. In order to answer what form of this dioxygen species was observed in the DNC of the 1.8 angstrom X-ray CcO crystal structure (3S8G), we have applied broken-symmetry density functional theory (BS-DFT) geometric and energetic calculations (using OLYP potential) on large DNC cluster models with different Fe-a3-Cu-B oxidation and spin states and with O-2(2-), O-2(center dot-), HO2-, or H2O2 in the bridging position. By comparing the DFT optimized geometries with the X-ray crystal structure (3S8G), we propose that the bridging peroxide is HO2-. The X-ray crystal structure is likely to represent the superposition of the Fe-a3(2+)-(HO2-)-Cu-B(+) DNC’s in different states (Fe2+ in low spin (LS), intermediate spin (IS), or high spin (HS)) with the majority species having the proton of the HO2- residing on the oxygen atom (O1) which is closer to the Fe-a3(2+) site in the Fe-a3(2+)-(HO-O)(-)-Cu-B(+) conformation. Our calculations show that the side chain of Tyr237 is likely trapped in the deprotonated Tyr237(-) anion form in the 3S8G X-ray crystal structure.

First author: Thellamurege, Nandun M., QuanPol: A Full Spectrum and Seamless QM/MM Program, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 2816, (2013)
Abstract: The quantum chemistry polarizable force field program (QuanPol) is implemented to perform combined quantum mechanical and molecular mechanical (QM/MM) calculations with induced dipole polarizable force fields and induced surface charge continuum solvation models. The QM methods include Hartree-Fock method, density functional theory method (DFT), generalized valence bond theory method, multiconfiguration self-consistent field method, MOller-Plesset perturbation theory method, and time-dependent DFT method. The induced dipoles of the MM atoms and the induced surface charges of the continuum solvation model are self-consistently and variationally determined together with the QM wavefunction. The MM force field methods can be user specified, or a standard force field such as MMFF94, Chemistry at Harvard Molecular Mechanics (CHARMM), Assisted Model Building with Energy Refinement (AMBER), and Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA). Analytic gradients for all of these methods are implemented so geometry optimization and molecular dynamics (MD) simulation can be performed. MD free energy perturbation and umbrella sampling methods are also implemented.

First author: Mousavi, Masoumeh, Bonding analysis of trimethylenemethane (TMM) complexes [(CO)(3)M-TMM] (M = Fe, Ru, Os, Rh+). Absence of expected bond paths, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 748, 2, (2013)
Abstract: Quantum chemical calculations using gradient-corrected DFT methods (BP86) using effective core potentials and TZP quality basis sets have been carried out for the complexes (CO)(3)M-TMM (M = Fe, Ru, Os, Rh+; TMM = trimethylenemethane). The calculated equilibrium geometries give trigonal pyramidal structures which are in good agreement with experimental results for the iron and ruthenium species. The TMM ligand adopts a pyramidal coordination of the central carbon atom which has a shorter distance to the metal atom than the terminal carbon atoms. The theoretically predicted bond dissociation energies of the TMM ligand are between 108.0 kcal/mol for the iron complex and 155.1 kcal/mol for the rhodium complex. The trend of the calculated TMM-M bond strength is Fe < Ru < Os < Rh+. The investigation of the electronic structure of the complexes (CO)(3)M-TMM using MO correlation diagrams and energy partitioning methods clearly shows that the metal atom is mainly bonded to the terminal carbon atoms of the TMM ligand while the bonding to the closer central carbon atom is much weaker. This is further supported by the AIM analysis which shows that the Laplacian distribution del(2)rho(r) at the terminal carbon atoms possesses local area of charge concentration which points toward the metal atom while the Laplacian distribution at the central carbon atoms is nearly undistorted. In spite of the shape of the Laplacian distribution, there are bond paths between the metal atom and the central carbon atom but not to the terminal carbon atom which comes from the different interatomic distances. This clearly shows that the absence and the existence of a bond path are not reliable criteria for chemical bonding.

First author: Kulasekera, Erandi, DFT/TD-DFT analysis of structural, electrochemical and optical data from mononuclear osmium and heterobinuclear osmium-ruthenium alkynyl complexes, JOURNAL OF ORGANOMETALLIC CHEMISTRY,748, 21, (2013)
Abstract: Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations of the molecular structures, optical absorption spectra, and spectroelectrochemical behavior of the complexes trans-[Os(C CC6H4-4-C CH)Cl(dppe)(2)] (1), trans, trans-[(dppe)(2)ClOs(C CC6H4-4-C C)RuCl(dppe)(2)] (2), trans, trans-[(dppe)(2)ClOs(C CC6H4-4-C C)Ru(C CC6H4-4-C CH)(dppe)(2)] (3), trans-[Os(C CC6H4-4-C CC6H4-4-C CH)Cl(dppe)(2)] (4), and trans, trans-[(dppe)(2)ClOs(C CC6H4-4-C CC6H4-4-C C)RuCl(dppe)(2)] (5) were undertaken. The calculated structures for the mononuclear osmium complexes 1 and 4 are in good agreement with the X-ray data, a 0.3 angstrom lengthening of the Os-Cl bond in proceeding from the theoretical model for 4 to the experimental structure being rationalized on the basis of intermolecular H-bonding effects for the latter. For the non-oxidized forms of these five complexes, the lowest-energy bands are assigned to MLCT transitions along the main molecular axis from orbitals with mostly Os d, Cl p and alkynyl character to orbitals on the alkynyl backbone. The calculations indicate that the heterobimetallic complexes 2, 3 and 5 do not undergo metal-centred oxidation. Instead, the electron is lost from an orbital that is delocalized across the bridge and both metal centres. The mono-oxidized and di-oxidized species show new bands in the low-energy region arising from LMCT transitions, primarily corresponding to transitions from the dppe ligands to metal- and alkynyl-based orbitals. For structures involving two or more phenylethynyl units along the main axis of the molecule, the TD-DFT calculations are in significantly better agreement with the observed spectra when the phenyl groups adopt a non-coplanar conformation.

First author: Giorgi, Giacomo, On the dual deuterium/deuteron nature of D charge distribution in the Ti host matrix: A DFT analysis, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 38, 16477, (2013)
Abstract: In the present work we have investigated the charge distribution on deuterium atom inside a titanium host matrix and their interaction energy. This analysis is motivated by the role that Ti-D alloys play in nuclear processes, i.e. the reported neutron generation as a consequence of the pressure exerted on such hybrid systems. A two-fold DFT procedure has been employed in order to carry out our analysis, namely a periodic and a cluster approach. Both show that the D atom, at variance with the prediction by T. Asami et al. (T. Asami, Journal of Condensed Matter Nuclear Science 2011; 5:7-16; T Asami, N. Sano, Journal of Condensed Matter Nuclear Science 2012; 9:1-9), tends to avoid the deuteron form when entering the Ti tetrahedral site. In particular, according to the cluster approach results, both the Voronoi Deformation Density atomic charge analysis and the interaction energy decomposition analysis indicate that the deuterium enters the tetrahedron cage retaining its electron, provided that a high energy barrier could be overcome. The largest contribution to the interaction energy is the charge-transfer orbital interaction term but the sizeable energy barrier is mainly due to the electrostatic repulsive interaction between Ti cluster and D+. We thus conclude that the experimental conditions (i.e., the combination of pressure and temperature) could be responsible for the hypothesized “switching on” of the deuterium-to-deuteron charge oxidation.

First author: Kociper, Birgit, Spatial Extension of Excitons in Triphenylene-Based Polymers Given by Range-Separated Functionals, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 26213, (2013)
Abstract: Motivated by an experiment in which the singlet triplet gap in triphenylene-based copolymers was effectively tuned, we used time-dependent density functional theory (TDDFT) to reproduce the main results. By means of conventional and long-range corrected exchange correlation functionals, the luminescence energies and the exciton localization were calculated for a triphenylene homopolymer and several different copolymers. The phosphorescence energy of the pure triphenylene chain is predicted accurately by means of the optimally tuned long-range corrected LC-PBE functional and slightly less accurate by the global hybrid B3LYP. However, the experimentally observed fixed phosphorescence energy could not be reproduced because the localization pattern is different from the expectations: instead of localizing on the triphenylene moiety-which is present in all types of polymers-the triplet state localizes on the different bridging units in the TDDFT calculations. This leads to different triplet emission energies for each type of polymer. Yet, there are clear indications that long-range corrected TDDFT has the potential to predict the triplet emission energies as well as the localization behavior more accurately than conventional local or semilocal functionals.

First author: Conradie, Marrigje M., Crystal and electronic structures of tris[4,4,4-Trifluoro-1-(2-X)-1,3-butanedionato]iron(III) isomers (X = thienyl or furyl): An X-ray and computational study, JOURNAL OF MOLECULAR STRUCTURE, 1053, 134, (2013)
Abstract: DFT calculations showed that [Fe(acac)(3)] (where acac = acetylacetonato) is high-spin, with a negative D-3 distortion from the octahedral ligand field. Calculations further showed that, although both the fac and met isomers of complexes [Fe(CF3COCHCOR)(3)], where R = C4H3S or C4H3O, can exist, the mer isomers are energetically favoured in both complexes. The structure of the major mer isomer of [Fe(CF3COCH-COC4H3S)(3)] has been published previously, while the crystal structure of the minor fac isomer of [Fe(CF3-COCHCOC4H3S)(3)] is presented in this study. The structure of the mer isomer of [Fe(CF3COCHCOC4H3O)(3)], in agreement with DFT calculations, showed that the furyl substituent pointed towards the CF3 group in a syn orientation.

First author: Younker, Jarod M., Correlating Experimental Photophysical Properties of Iridium(III) Complexes to Spin Orbit Coupled TDDFT Predictions, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 25714, (2013)
Abstract: Ir(III) complexes are efficient phosphorescent emitters. The transition dipole moment between the triplet and singlet manifolds is formally spin forbidden. However, spin-orbit coupling (SOC), induced by the high angular momentum orbitals in Ir, efficiently mixes the triplet manifold with higher-energy singlets, increasing the transition probability. Spin-orbit coupled time-dependent density functional (TDDFT) calculations within the zero-order relativistic approximation (ZORA) are used to study nine complexes that have a range of emissions from 450 to 630 nm and quantum efficiencies of 0.1-0.9. We find that using the singlet ground-state geometry to calculate radiative rates produces the best correlation with experiment. We also show that the equal thermal population of the three sublevels in the triplet manifold is sufficient to understand rates at 300 K. We find that emission energies and radiative rates are best reproduced at the TD-B3LYP/TZP/DZP//BP86/TZ2P/TZP level of theory, where the larger basis set is supplied for Ir.

First author: Cendic, Marina, Molecular Modeling for Cu(II)-Aminopolycarboxylate Complexes: Structures, Conformational Energies, and Ligand Binding Affinities, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 2687, (2013)
Abstract: A ligand field molecular mechanics (LFMM) force field (FF) has been developed for d(9) copper(II) complexes of aminopolycarboxylate ligands. Training data were derived from density functional theory (DFT) geometry optimizations of 14 complexes comprising potentially hexadentate N2O4, tetrasubstituted ethylenediamine (ed), and propylenediamine cores with various combinations of acetate and propionate side arms. The FF was validated against 13 experimental structures from X-ray crystallography including hexadentate N2O4 donors where the nitrogens donors are forced to be cis and bis-tridentate ONO ligands which generate complexes with trans nitrogen donors. Stochastic conformational searches for [Cu{ed(acetate)(n) (propionate)(4-n)}](2-), n=0-4, were carried out and the lowest conformers for each system reoptimized with DFT. In each case, both DFT and LFMM predict the same lowest-energy conformer and the structures and energies of the higher-energy conformers are also in satisfactory agreement. The relative interaction energies for n=0, 2, and 4 computed by molecular mechanics correlate with the experimental log binding affinities. Adding in the predicted log values for n=1 and 3 suggest for this set of complexes a monotonic decrease in log as the number of propionate arms increases.

First author: Johns, James E., Metal Oxide Nanoparticle Growth on Graphene via Chemical Activation with Atomic,Oxygen, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 18121, (2013)
Abstract: Chemically interfacing the inert basal plane of graphene with other materials has limited the development of graphene-based catalysts, composite materials, and devices. Here, we overcome this limitation by chemically activating epitaxial graphene on SiC(0001) using atomic oxygen. Atomic oxygen produces epoxide groups on graphene, which act as reactive nucleation sites for zinc oxide nanoparticle growth using the atomic layer deposition precursor diethyl zinc. In particular, exposure of epoxidized graphene to diethyl zinc abstracts oxygen, creating mobile species,that diffuse on the surface to form metal oxide clusters. This mechanism is corroborated with a combination of scanning probe microscopy, Raman spectroscopy, and density functional theory and can likely be generalized to a wide variety of related surface reactions on graphene.

First author: Vila-Nadal, Laia, Towards Polyoxometalate-Cluster-Based Nano-Electronics, CHEMISTRY-A EUROPEAN JOURNAL, 19, 16502, (2013)
Abstract: We explore the concept that the incorporation of polyoxometalates (POMs) into complementary metal oxide semiconductor (CMOS) technologies could offer a fundamentally better way to design and engineer new types of data storage devices, due to the enhanced electronic complementarity with SiO2, high redox potentials, and multiple redox states accessible to polyoxometalate clusters. To explore this we constructed a custom-built simulation domain bridge. Connecting DFT, for the quantum mechanical modelling part, and mesoscopic device modelling, confirms the theoretical basis for the proposed advantages of POMs in non-volatile molecular memories (NVMM) or flash-RAM.

First author: Stepanovic, Stepan, Role of Spin State and Ligand Charge in Coordination Patterns in Complexes of 2,6-Diacetylpyridinebis(semioxamazide) with 3d-Block Metal Ions: A Density Functional Theory Study, INORGANIC CHEMISTRY, 52, 13415, (2013)
Abstract: We report here a systematic computational study on the effect of the spin state and ligand charge on coordination preferences for a number of 3d-block metal complexes with the 2,6-diacetylpyridinebis(semioxamazide) ligand and its mono- and dianionic analogues. Our calculations show excellent agreement for the geometries compared with the available X-ray structures and clarify some intriguing experimental observations. The absence of a nickel complex in seven-coordination is confirmed here, which is easily explained by inspection of the molecular orbitals that involve the central metal ion. Moreover, we find here that changes in the spin state lead to completely different coordination modes, in contrast to the usual situation that different spin states mainly result in changes in the metal ligand bond lengths. Both effects result from different occupations of a combination of pi- and sigma-antibonding and nonbonding orbitals.

Abstract: In this study we evaluated the importance of the relativistic effects (scalar and spin-orbit) on the description of the electronic structure, bonding and the energetic of the [ReF8](-) and [UF8](2-) ions. We described the bonding interaction between ligands and metal center using the energy decomposition analysis (EDA) proposed by Morokuma and Ziegler, in which it can be appreciated a strong ionic behavior for both ions since the electrostatic interaction energy (Delta E-Elestat) is greater than the orbitalic interaction energy (Delta E-Orb). Furthermore, a qualitative analysis using the mapping of the electrostatic potential over the total electronic density evidence an increase of the ionic character, as well as, the polarization of the electronic density as U > Re. The electron localization function (ELF) corroborates the bonding analysis because of the lack of di-synaptic basins on the metal-ligand bonding region.

Abstract: We have investigated the molecular, electronic and optical properties of the [Os(tpy-py)(2)](2+) complex (tpy-py = 4′-(4-pyridyl)-2,2′:6′, 2”-terpyridine) and its protonated derivative [Os(tpy-pyH)(2)](4+) through Density Functional Relativistic calculations including Scalar and Spin Orbit corrections. The molecular geometry of the parent complex is not strongly modified by the protonation at the basic nitrogen atoms of the pyridine moieties of the terpyridine ligands in the complex. On the other hand, the optical properties of these complexes can be controlled by a change in the chemical acid-base environment, converting them into suitable materials to act as molecular switches or pH sensor devices.

First author: Hirao, Hajime, Importance of H-Abstraction in the Final Step of Nitrosoalkane Formation in the Mechanism-Based Inactivation of Cytochrome P450 by Amine-Containing Drugs, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 14, 24692, (2013)
Abstract: The metabolism of amine-containing drugs by cytochrome P450 enzymes (P450s) is prone to form a nitrosoalkane metabolic intermediate (MI), which subsequently coordinates to the heme iron of a P450, to produce a metabolic-intermediate complex (MIC). This type of P450 inhibition, referred to as mechanism-based inactivation (MBI), presents a serious concern in drug discovery processes. We applied density functional theory (DFT) to the reaction between N-methylhydroxylamine (NMH) and the compound I reactive species of P450, in an effort to elucidate the mechanism of the putative final step of the MI formation in the alkylamine metabolism. Our DFT calculations show that H-abstraction from the hydroxyl group of NMH is the most favorable pathway via which the nitrosoalkane intermediate is produced spontaneously. H-abstraction from the N-H bond was slightly less favorable. In contrast, N-oxidation and H-abstraction from the C-H bond of the methyl group had much higher energy barriers. Hence, if the conversion of NMH to nitrosoalkane is catalyzed by a P450, the reaction should proceed preferentially via H-abstraction, either from the O-H bond or from the N-H bond. Our theoretical analysis of the interaction between the MI and pentacoordinate heme moieties provided further insights into the coordination bond in the MIC.

First author: Ren, Li, Facile Synthesis of the Naturally Cytotoxic Triterpenoid Saponin Patrinia-Glycoside B-II and Its Conformer, MOLECULES, 18, 15193, (2013)
Abstract: The first chemical synthesis of the natural triterpenoid saponin Patrinia-glycoside B-II, namely oleanolic acid 3-O-alpha-L-rhamnopyranosyl-(1 -> 2)-[beta-D-gluco-pyranosyl( 1 -> 3)]-alpha-L-arabinopyranoside, has been accomplished in a linear 11-step sequence 11 with 9.4% overall yield. The abnormal C-1(4) conformation of the arabinose residue was found to occur via conformational fluctuation during preparation of the intermediates. Molecular mechanism and quantum chemistry calculations showed that Patrinia-glycoside B-II and its conformer 1 cannot interconvert under normal conditions. Preliminary structure-activity relationships studies indicated that the C-4(1) chair conformation of the arabinose residue in the unique alpha-L-rhamnopyranosyl-(1 -> 2)-alpha-L-arabinopyranosyl disaccharide moiety is one of the chief positive factors responsible for its cytotoxic activity against tumors.

First author: Freitag, Roxanne, Understanding the Jahn-Teller Effect in Octahedral Transition-Metal Complexes: A Molecular Orbital View of the Mn(beta-diketonato)(3) Complex, JOURNAL OF CHEMICAL EDUCATION, 90, 1692, (2013)
Abstract: Density functional theory calculations are utilized to calculate and visualize the compression and elongation Jahn-Teller distortion in selected Mn(beta-diketonato)(3) complexes. Students often struggle to understand this effect, due to the lack of visualization of the repulsion effect between charges on the metal and the axial ligands. Here, a visualization of the molecular orbitals involved in the elongation and compression Jahn-Teller distortion provides a great understanding of the effect.

First author: Barone, Giampaolo, B-DNA Structure and Stability as Function of Nucleic Acid Composition: Dispersion-Corrected DFT Study of Dinucleoside Monophosphate Single and Double Strands, CHEMISTRYOPEN, 2, 186, (2013)
Abstract: We have computationally investigated the structure and stability of all 16 combinations of two out of the four natural DNA bases A, T, G and C in a di-2′-deoxyribonucleoside-monophosphate model DNA strand as well as in 10 double-strand model complexes thereof, using dispersion-corrected density functional theory (DFT-D). Optimized geometries with B-DNA conformation were obtained through the inclusion of implicit water solvent and, in the DNA models, of sodium counterions, to neutralize the negative charge of the phosphate groups. The results obtained allowed us to compare the relative stability of isomeric single and double strands. Moreover, the energy of the Watson-Crick pairing of complementary single strands to form double-helical structures was calculated. The latter furnished the following increasing stability trend of the doublehelix formation energy: d(TpA)(2) < d(CpA)(2) < d(ApT)(2) < d(ApA)(2) < d(GpT)(2) < d(GpA)(2) < d(ApG)(2) < d(CpG)(2) < d(GpG)(2) < d(GpC)(2), where the energy differences between the last four dimers, d(ApG)(2), d(CpG)(2), d(GpG)(2) and d(GpC)(2), is within 4.0 kcalmol(-1), and the energy between the most and the least stable isomers is 13.4 kcalmol(-1). This trend shows that the formation energy essentially increases with the number of hydrogen bonds per base pair, that is two between A and T and three between G and C. Superimposed on this main trend are more subtle effects that depend on the order in which bases occur within a strand from the 5′-to the 3′-end.

First author: Storchi, Loriano, Efficient Parallel All-Electron Four-Component Dirac-Kohn Sham Program Using a Distributed Matrix Approach II, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 5356, (2013)
Abstract: We propose a new complete memory-distributed algorithm, which significantly improves the parallel implementation of the all-electron four-component Dirac-Kohn-Sham (DKS) module of BERTHA (J. Chem. Theory Comput. 2010, 6, 384). We devised an original procedure for mapping the DKS matrix between an efficient integral-driven distribution, guided by the structure of specific G-spinor basis sets and by density fitting algorithms, and the two-dimensional block-cyclic distribution scheme required by the ScaLAPACK library employed for the linear algebra operations. This implementation, because of the efficiency in the memory distribution, represents a leap forward in the applicability of the DKS procedure to arbitrarily large molecular systems and its porting on last-generation massively parallel systems. The performance of the code is illustrated by some test calculations on several gold clusters of increasing size. The DKS self-consistent procedure has been explicitly converged for two representative clusters, namely Au-20 and Au-34, for which the density of electronic states is reported and discussed. The largest gold cluster uses more than 39k basis functions and DKS matrices of the order of 23 GB.

First author: Bulo, Rosa E., Multiscale Modeling of Chemistry in Water: Are We There Yet?, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 5567, (2013)
Abstract: This paper critically evaluates the state of the art in combined quantum mechanical/molecular mechanical (QM/MM) approaches to the computational description of chemistry in water and supplies guidelines for the setup of customized multiscale simulations of aqueous processes. We differentiate between structural and dynamic performance, since some tasks, e.g., the reproduction of NMR or UV-vis spectra, require only structural accuracy, while others, i.e., reaction mechanisms, require accurate dynamic data as well. As a model system for aqueous solutions in general, the approaches were tested on a QM water cluster in an environment of MM water molecules. The key difficulty is the description of the possible diffusion of QM molecules into the MM region and vice versa. The flexible inner region ensemble separator (FIRES) approach constrains QM solvent molecules within an active (QM) region. Sorted adaptive partitioning (SAP), difference-based adaptive solvation (DAS), and buffered-force (BF) are all adaptive approaches that use a buffer zone in which solvent molecules gradually adapt from QM to MM (or vice versa). The costs of SAP and DAS are relatively high, while BF is fast but sacrifices conservation of both energy and momentum. Simulations in the limit of an infinitely small buffer zone, where DAS and SAP become equivalent, are discussed as well and referred to as ABRUPT. The best structural accuracy is obtained with DAS, BF, and ABRUPT, all three of similar quality. FIRES performs very well for dynamic properties localized deep within the QM region. By means of elimination DAS emerges as the best overall compromise between structural and dynamic performance. Eliminating the buffer zone (ABRUPT) improves efficiency and still leads to surprisingly good results. While none of the many new flavors are perfect, all together this new field already allows accurate description of a wide range of structural and dynamic properties of aqueous solutions.

First author: Liu, Chun-Guang, Electronic and bonding properties of mono-ruthenium-substituted Keggin-type polyoxometalates: a theoretical study of [{PW11O39}Ru-II/III(L)](n-) (L = dimethyl sulfoxide (DMSO), water, pyridine, and ammonia) and [{GeW11O39}Ru-II(DMSO)(3)(H2O)](6-), MOLECULAR PHYSICS, 111, 3733, (2013)
Abstract: The electronic structure and bonding feature of a series of mono-ruthenium-substituted Keggin-type polyoxometalates (POMs) have been investigated by using density functional theory (DFT) calculation, natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). A comparison of the electronic properties of two known dimethyl sulfoxide (DMSO)-supported mono-ruthenium-substituted Keggin-type POMs shows that both complexes have the analogous frontier-molecular orbital feature. One of them possesses a relatively small HOMO-LUMO gap because of the high HOMO energy level. This difference comes from a high composition of POM ligand with antibonding feature in HOMO. In addition, three typical Keggin-type POM complexes [{PW11O39}Ru-II/III(L)](n-) (L = H2O, C5H5N, NH3) have also been explored according to our computational studies. The NBO analysis shows that the Ru-II/III-L bond comes from donor-acceptor interactions between the end ligand and the ruthenium (II/III) centre. The EDA shows that the POM complex [{PW11O39}Ru-II(C5H5N)](5-) has much stronger Ru-II-L bond than ammonia-supported Keggin-type POM [{PW11O39}Ru-II(NH3)](5-). And the enhancement of the Ru-II-L bonding interaction in [{PW11O39}Ru-II(C5H5N)](5-) is mainly due to the large orbital interaction energy E-orb. The ammonia-supported Keggin-type POM [{PW11O39}Ru-II(NH3)](5-) and the aqua-ruthenium derivative [{PW11O39}Ru-II(H2O)](5-) have an analogous magnitude of the total bond energy. This result supports a non-aqueous environment for synthesis of an ammonia-supported Keggin-type POM [{PW11O39}Ru-II(NH3)](5-).

First author: Sampson, Matthew D., Direct observation of the reduction of carbon dioxide by rhenium bipyridine catalysts,ENERGY & ENVIRONMENTAL SCIENCE, 6, 3748, (2013)
Abstract: In order to further efforts in synthesis and catalysis, the mechanisms of catalysts must be completely understood. The Re(bpy)(CO)(3)Cl molecular catalysts are some of the most robust and well-characterized CO2 reduction catalysts known to date. Stopped-flow infrared spectroscopy is reported as a technique for studying the kinetics and mechanisms of the reactions of catalytically-relevant [Re(bpy-R)(CO)(3)](-) anions (R = tBu or H) with CO2/H+. [Re(bpy-tBu)(CO)(3)](-) reacts approximately ten times faster with CO2 than does [Re(bpy)(CO)(3)](-). These reactions occur via a direct two-electron oxidative addition of CO2 to the metal center and result in the formation of an intermediate CO2 reduction product, Re(bpy-R)(CO)(3)(CO2H). This is the first in situ identification of this key intermediate. Evidence for this Re-CO2H species includes isotopic labeling studies, stopped-flow experiments of the kinetics of its formation in the presence of proton sources, comparison with genuine Re(bpy)(CO)(3)(CO2H), and DFT calculations.

First author: Loginov, Dmitry A., (Cyclopentadienyl)metalladicarbollides 3-(eta-C5R5)-3,1,2-MC2B9H11(M = Co, Rh, Ir): Synthesis, electrochemistry, and bonding, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 747, 69, (2013)
Abstract: Metallacarboranes 3-(eta-C5R5)-3,1,2-MC2B9H11 (1a: M = Co, R = H; 1b: M = Co, R = Me; 2a: M = Rh, R = H; 2b: M = Rh, R = Me; 3a: M = Ir, R = H; 3b: M = Ir, R = Me) were obtained by reactions of Tl[Tl(eta-7,8-C2B9H11)] with [(eta-C5R5)MX2](2) (X = Cl, I) or [CpM(MeCN)(3)](2+). The structures of 2a and 3a were determined by X-ray diffraction. The electrochemical investigation of complexes 2a,b and 3a, b shows that they undergo the partially reversible M(III)/M(II) electron addition followed by the irreversible M(II)/M(I) reduction. Such a path is quite reminiscent of that occurring for the isolobal and isoelectronic monocations [(eta-C5R5)MCp](+) (M = Rh, Ir; R = H, Me). An electrochemical comparison is made also with respect to the cobalt derivatives 1a, b. DFT calculations of the redox potentials and the respective geometrical changes were performed. Metal-ligand bonding in 1a, 2a and 3a was analyzed by energy decomposition analysis.

First author: Aramburu, J. A., Transition Metal Complexes Coupled to Vacancies in Oxides: Origin of Different Properties of Cr3+ in MgO Bounded to a < 100 > or < 110 > Mg2+ Vacancy, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 12642, (2013)
Abstract: Despite the importance of vacancies over the properties of insulating oxides its influence on neighboring transition metal ions is far from being understood. This work is devoted to find the origin of various up to now unexplained properties of chromium bounded either to a < 100 > or a < 110 > Mg2+ vacancy in MgO. In these model systems particular attention is paid to understand, by means of ab initio calculations, why the cubic field splitting parameter, 10Dq, is surprisingly 1600 cm(-1) higher for a < 100 > than for a < 110 > vacancy, a fact behind the suppression of the sharp E-2 -> (4)A(2) luminescence in the latter case. Our calculations, which reproduce the main experimental facts, prove that the average Cr3+-O2- distance is the same within 0.8% for both systems, and thus, the low 10Dq value for a < 110 > vacancy is shown to be due mainly to the electrostatic potential from the missing Mg2+ ion, which increases the energy of antibonding t(2g) (similar to xy, xz, yz) levels. By contrast, for a < 100 > Mg2+ vacancy that potential provides a supplementary increase of the e(g) (similar to x(2) – y(2), 3z(2) – r(2)) level energy and thus of 10Dq. The existence of the E-2 -> (4)A(2) luminescence for Cr3+-doped MgO under perfect cubic symmetry or with a < 100 > vacancy is shown to be greatly helped by the internal electric field created by the rest of the lattice ions on the CrO69- unit, whose importance is usually ignored. The present results underline the role of ab initio calculations for unveiling the subtle effects induced by a close vacancy on the properties of transition metal ions in oxides. At the same time they stress the failure of the empirical superposition model for deriving the equilibrium geometry of C-4, and C-2, centers in MgO:Cr3+.

First author: Schott, Eduardo, Effect over the electronic structure by changing the core metals from Mo to W in a family of [Mo6-nWnCl8F6](2-) (n=0-6) clusters, POLYHEDRON, 65, 98, (2013)
Abstract: A complete theoretical characterization of a family of [Mo6-nWnCl8F6](2-) clusters where n = 0-6, was performed. The calculated geometrical parameters show a very good agreement with the previously reported experimental data. The assessed reactivity indexes indicate that the less reactive cluster would be [W6Cl8F6](2-) which is in concordance with the fact that is the most energetically stable cluster. Relativistic time-dependent density functional (TDDFT) calculations including spin-orbit interactions via the zeroth order regular approximation (ZORA) Hamiltonian and solvent effects were carried out for the cluster families. These calculations showed that the frontier molecular orbitals involved in the transitions are largely centered on the cubic [Mo6-nWnCl8](4+) core and all the molecular orbitals involved in the calculated transitions of each cluster are very much alike. More interestingly, the UV-Vis transitions are tuned and displaced to higher wavelength by the mixture of Mo and W atoms. Furthermore, our calculations and the electronic similarities with previously reported clusters, suggest that the clusters family [Mo6-nWnCl8F6](2-) might show similar properties to those previously reported.

First author: Chiarella, Gina M., Solubilizing the Most Easily Ionized Molecules and Generating Powerful Reducing Agents, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 17889, (2013)
Abstract: Two very soluble compounds having W-2(bicyclic guanidinate)(4) paddlewheel structures show record low ionization energies (onsets at 3.4 to 3.5 eV) and very negative oxidation potentials in THF (-1.84 to -1.90 V vs Ag/AgCl). DFT computations show the correlation from the gas-phase ionization energies to the solution redox potentials and chemical behavior. These compounds are thermally stable and easy to synthesize in high yields and good purity. They are very reactive and potentially useful stoichiometric reducing agents in nonpolar, nonprotonated solvents.

First author: Freitag, Sarah, Stannylene-Based Lewis Pairs, ORGANOMETALLICS, 32, 6785, (2013)
Abstract: Intramolecular stannylene-based Lewis pairs with phosphine Lewis bases were synthesized at the ortho position in benzene or the peri position in acenaphthene. The spectroscopic data of the Lewis pairs are discussed, and the reactivity toward unsaturated hydrocarbons and organic azides is presented.

First author: Li, Yongyao, Matter-wave solitons supported by field-induced dipole-dipole repulsion with spatially modulated strength, PHYSICAL REVIEW A, 88, 6785, (2013)
Abstract: We demonstrate the existence of one- and two-dimensional (1D and 2D, respectively) bright solitons in the Bose-Einstein condensate with repulsive dipole-dipole interactions induced by a combination of dc and ac polarizing fields, oriented perpendicular to the plane in which the BEC is trapped, assuming that the strength of the fields grows in the radial (r) direction faster than r(3). Stable tightly confined 1D and 2D fundamental solitons, twisted solitons in 1D, and solitary vortices in 2D are found in a numerical form. The fundamental solitons remain robust under the action of an expulsive potential, which is induced by the interaction of the dipoles with the polarizing field. The confinement and scaling properties of the soliton families are explained analytically. The Thomas-Fermi approximation is elaborated for fundamental solitons. The mobility of the fundamental solitons is limited to the central area. Stable 1D even and odd solitons are also found in the setting with a double-well modulation function, along with a regime of Josephson oscillations.

First author: Olszewska, Teresa, Helicity discrimination in N,N ‘-dibenzoyl-1,2,3,4,7,8,9,10-octahydro-1,10-phenanthrolines and their thiono- and selenocarbonyl analogues by inclusion complexation with chiral diols, ORGANIC & BIOMOLECULAR CHEMISTRY, 11, 7522, (2013)
Abstract: X-ray crystallographic analysis of the title compounds revealed that they assume a folded helical conformation of an approximate C-2 symmetry in the solid state. Dithioamide 5b, diselenoamide 5c and monoselenoamide 5d were resolved to enantiomers by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest molecules in the complexes 5b.6a, 5c.6a and 5d.6a was assigned as P. The optical activity of the resolved compounds is manifested by their CD spectra showing relatively strong Cotton effects in the region of thionoamide and selenoamide n-pi* transition. The optically active thiono- and selenoamides are configurationally labile compounds and gradually racemize in solution but they are stable in the form of the inclusion complexes. The first-order kinetics of the racemization in solution allowed us to assign the racemization barriers by the spectropolarimetric measurements.

First author: Ramanantoanina, Harry, Calculation of the 4f(1) -> 4f(0)5d(1) transitions in Ce3+-doped systems by Ligand Field Density Functional Theory, CHEMICAL PHYSICS LETTERS, 588, 260, (2013)
Abstract: We present a recipe for the calculation of the optical properties of Ce3+-doped systems. The model implies the use of ligand field phenomenology in conjunction with Density Functional Theory (DFT). The particular procedures enable the reliable prediction of the 4f(1) -> 4f(0)5d(1) transitions in Cs-2 NaYCl6:Ce3+. The analysis of the doping of Ce3+ into the host is accomplished by band structure calculations. The calculated multiplet energy levels are in agreement with the experimental observation, the outlined treatment being, to the best of our knowledge, unprecedented clear and conclusive application of DFT for the rather complex problems of structure and spectroscopy of cerium-doped systems.

First author: Takahata, Yuji, Substituent effect in 1-X-decanes and 3-X-gonanes based on core-electron binding energies calculated with density-functional theory, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1024, 9, (2013)
Abstract: The substituent effect in substituted n-decanes (1-X-decan), chain sigma-systems of saturated hydrocarbon, and C-3 substituted gonanes (3-X-gonane), fused ring sigma-systems, where X = H, NO2, CHO, F, CH3, Bu-t (tertiary butyl), was investigated using calculated core electron binding energies. The energies were calculated using the density-functional theory (DFT) with the Perdew-Wang 1986 exchange and the Perdew-Wang 1991 correlation functionals. A triple-zeta polarized Slater type basis set was employed. The effect of the electron withdrawing substituents, NO2, F, and CHO, is felt all the way to the end of the 10-carbon chain in 1-X-decane. Similarly, the effect of the electron withdrawing substituents is felt to the D ring carbons in 3-X-gonane. A possible explanation of the long-range effect is given. It was shown that the substituent effect was very similar, but not identical, in 1-X-decane and 3-X-gonane in quality and quantity.

First author: Purcell, Walter, Characterization and oxidative addition reactions of rhodium(I) carbonyl cupferrate diphenyl-2-pyridylphoshine complexes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 745, 439, (2013)
Abstract: The oxidative addition of CH3I to the [Rh(cupf)(CO)(DPP)] complex (DPP = diphenyl-2-pyridylphoshine and cupf = N-nitroso-N-phenylhydroxylaminen) was kinetically investigated using UV/vis and infrared spectroscopy. The kinetics followed in chloroform, acetonitrile and acetone as solvents, indicated three different consecutive reactions. Firstly, a very fast reaction (intermediate formation, IM), secondly, a slower reaction with the formation of the Rh(III) alkyl complex (5.0(1) x 10(-3) M-1 s(-1) for acetonitrile at 20 degrees C) and thirdly a very slow formation of the Rh(III) acyl complex as final product with a rate constant of 2.9(6) x 10(-4) s(-1). The same oxidative addition reaction in ethyl acetate as solvent exhibited only two reactions. Firstly the Rh(III) alkyl formation (1.03(3) x 10(-3) M-1 s(-1)), which was five times slower than in the other solvents. Secondly, the Rh(III) acyl formation, which was masked by solvent IR stretching frequencies in the detection area. Rh(III) acyl, however, was isolated from ethyl acetate. There was no indication of intermediate formation with ethyl acetate. This apparent discrepancy between the rate and the mechanism for the same reaction prompted a DFT study to gain more insight into the reactants and products of the reaction, as well as to try and determine the geometry of the transition state. The DFT study predicted the formation of a linear transition state (TS), followed by the formation of the cationic five-coordinate [Rh(cupf)(CO)(DPP)(CH3)](+) intermediate with the CH3 group in the apical position and with the iodide ion drifting away into the solvent sphere. This was in agreement with the experimental very fast first reaction. The experimentally observed difference in the rates and mechanisms of the [Rh(cupf)(CO)(DPP)] + CH3I reaction in ethyl acetate relative to the other solvents can be attributed to the rate of the formation and/or the build-up and conversion of the I.M.

First author: Tao, Jingcong, Titanocene-catalyzed dehydrocoupling of the adduct Me2NH center dot BH3 via competitive pathways: A DFT study, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 745, 479, (2013)
Abstract: The molecular mechanism of the dehydrocoupling of Me2NH center dot BH3 to form the cyclic diborazane [Me2N-BH2](2) catalyzed by the [Cp2Ti] fragment has been investigated using density functional theory calculations. The reaction is likely to proceed via competitive pathways: the intermolecular and the intramolecular mechanism. For the intermolecular mechanism, firstly, the linear dimer Me2NH-BH2-NMe2-BH3 is obtained by the catalytic dehydrogenation of two Me2NH center dot BH3 adducts. Then, the species [Me2N-BH2](2) is generated by the Ti-catalyzed dehydrogenative cyclization of Me2NH-BH2-NMe2-BH3. The rate-determining step is the nucleophilic substitution (S(N)2) step from the hydride intermediate to the dihydride complex in both gas phase and the solution phase, with the free energies of 26.0 (gas phase) and 33.6 kcal/mol (solvent), respectively. In the intramolecular process, the aminoborane Me2N=BH2 is formed by the interaction of Me2NH center dot BH3 with [Cp2Ti] and then undergoes an uncatalyzed dimerization cyclization reaction to form [Me2N-BH2](2). The highest point on the reaction pathway of intramolecular process is the dimerization step with the free energies of 29.8 (gas phase) and 30.2 kcal/mol (solvent), respectively.

First author: Addy, David A., Substituent effects on iron boryl and borylene systems: Unusual reactivity and spectroscopic properties, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 745, 487, (2013)
Abstract: Synthetic studies illustrate the crucial roles played by the steric and electronic properties of both the metal-bound ancillary ligands, L, and the boron-bound substituents, X, in the structural and reaction chemistry of boryl (LnMBX2) and borylene systems (LnMBX). Thus, the strong sigma donor properties of trialkyl phosphine ligands are reflected in the fact that [CpFe(dmpe)(BOMes)](+) is shown to be a tractable, room-temperature stable species, whereas [CpFe(CO)(2)(BOMes)](+) is not. Moreover the enhanced steric profile of dmpe (compared to a dicarbonyl ancillary ligand set) is shown to influence the propensity for electrophilic alkylation at boryl amino substituents, for example in CpFe(dmpe){B(NMe2)Cl} vs. CpFe(-CO)(2){B(NMe2)Cl}. Steric factors within the X substituent itself are also of key importance, and provide, for example, a rationale for the differing lability of NMe2 and NCy2 substituents in the presence of [Me3O] [BF4]. In addition, relatively subtle electronic factors within the B-X linkage have been shown to have a profound effect on spectroscopic properties, with the unusual chemical shift measured for [CpFe(dmpe)(BOMes)](+) being influenced by the presence of a heteroatom substituent featuring two lone pairs.

First author: Batke, Kilian, Topology of the Electron Density of d(0) Transition Metal Compounds at Subatomic Resolution,JOURNAL OF PHYSICAL CHEMISTRY A, 117, 11566, (2013)
Abstract: Accurate X-ray diffraction experiments allow for a reconstruction of the electron density distribution of solids and molecules in a crystal. The basis for the reconstruction of the electron density is in many cases a multipolar expansion of the X-ray scattering factors in terms of spherical harmonics, a so-called multipolar model. This commonly used ansatz splits the total electron density of each pseudoatom in the crystal into (i) a spherical core, (ii) a spherical valence, and (iii) a nonspherical valence contribution. Previous studies, for example, on diamond and a-silicon have already shown that this approximation is no longer valid when ultrahigh-resolution diffraction data is taken into account. We report here the results of an analysis of the calculated electron density distribution in the d(0) transition metal compounds [TMCH3](2+) (TM = Sc, Y, and La) at subatomic resolution. By a detailed molecular orbital analysis, it is demonstrated that due to the radial nodal structure of the 3d, 4d, and 5d orbitals involved in the TM-C bond formation a significant polarization of the electron density in the inner electronic shells of the TM atoms is observed. We further show that these polarizations have to be taken into account by an extended multipolar model in order to recover accurate electron density distributions from high-resolution structure factors calculated for the title compounds.

First author: Kevorkyants, Ruslan, Calculating Hyperfine Couplings in Large Ionic Crystals Containing Hundreds of QM Atoms: Subsystem DFT Is the Key, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 13967, (2013)
Abstract: We present an application of the linear scaling frozen density embedding (FDE) formulation of subsystem DFT to the calculation of isotropic hyperfine coupling constants (hfcc’s) of atoms belonging to a guanine radical cation embedded in a guanine hydrochloride monohydrate crystal. The model systems range from an isolated guanine to a 15 000 atom QM/MM cluster where the QM region is comprised of 36 protonated guanine cations, 36 chlorine anions, and 42 water molecules. Our calculations show that the embedding effects of the surrounding crystal cannot be reproduced by small model systems nor by a pure QM/MM procedure. Instead, a large QM region is needed to fully capture the complicated nature of the embedding effects in this system. The unprecedented system size for a relativistic all-electron isotropic hfcc calculation can be approached in this work because the local nature of the electronic structure of the organic crystals considered is fully captured by the FDE approach.

First author: Barman, Sanmitra, Helical Oxidovanadium(IV) Salen-Type Complexes: Synthesis, Characterisation and Catalytic Behaviour, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2013, 5708, (2013)
Abstract: Chiral [VO(salen)] complexes (R,R)-7 and (R,R)-8 were synthesised by ligand replacement from [VO(acac)(2)] with the resolved (1R,2R)-cyclohexyl ligands 3,3-[(1R,2R)-1,2-cyclohexane-diylbis(nitrilomethylidyne)]bis-4-phenanthr enol [(R,R)-3] and 3,3-[(1R,2R)-1,2-cyclohexanediylbis(nitrilomethylidyne)]bisbenz[a]anthra cen-1-ol [(R,R)-4], respectively. Similarly, complexes (R)-9 and (R)-10 were synthesised using the (R)-binaphthyl ligands 3,3-[(1R)-(1,1-binaphthalene)-2,2-diylbis(nitrilomethylidyne)]bis-4-phen anthrenol [(R)-5] and 3,3-[(1R)-(1,1-binaphthalene)-2,2-diylbis(nitrilomethylidyne)]bis-benz[a ]anthracen-1-ol [(R)-6], respectively. These complexes were characterised by IR spectroscopy, ESI-TOF-MS, electronic absorption spectroscopy and circular dichroism (CD). Single crystal X-ray analysis of (R,R)-7 and (R,R)-8 revealed distorted square pyramidal geometries and a 1:1 ratio of diastereomeric M and P helical conformers. Solution CD studies in THF combined with DFT calculations indicate that the M conformer dominates in solution for (R,R)-7. Preliminary catalytic oxidation of thioanisole with H2O2 and 1% [VO(salen)] showed good selectivity for sulfoxides over sulfones but low enantioselectivities (8 to 33%) which are solvent dependent but insensitive to the catalyst used.

First author: Cavigliasso, German, The nature of species derived from [Pt(bipy)(2)](2+) in aqueous solution: X-ray structural, mass spectral, NMR, and computational studies, POLYHEDRON, 64, 238, (2013)
Abstract: The reaction of [Pt(bipy)(2)](2+) with a variety of organic and inorganic ligands in aqueous solution has been studied by Pt-195, H-1 and C-13 NMR, X-ray crystallography, UV-Vis spectroscopy and high-resolution mass spectrometry. Pt-195 NMR spectra of D2O solutions containing equimolar amounts of [Pt(bipy)(2)](2+) and the heterocyclic N donor ligands pyridine, 3-methylpyridine and 4-methylpyridine give evidence for the formation of at least one species, while quinoline appears to give only a single product under the same conditions. These results are supported by H-1 and C-13 NMR data. The complex [Pt(bipy)(py)(2)](ClO4)(2) was isolated from a reaction mixture containing equimolar amounts of [Pt(bipy)(2)](2+) and pyridine, and was characterised by X-ray crystallography. The Pt-195 NMR chemical shift of this material suggested the presence of [Pt(bipy)(R-py)(2)](2+) species in aqueous solutions containing equimolar amounts of [Pt(bipy)(2)](2+) and R-py (R-py = py, 3-Mepy, 4-Mepy). High-resolution mass spectral analysis of aqueous solutions containing [Pt(bipy)(2)](2+) and inorganic ligands L (L = OH-, S2O32-, N-3(-), SCN-, CN-, Cl- and SO42-) gives strong evidence for the formation of pseudo five-coordinate complexes of the type [Pt(bipy-kappa N-2,N’)(bipy-kappa N)(L)(n+) in the cases of OH-, S2O32-, N-3(-) and SCN-. The results of calculations aimed at determining the Pt-195 NMR chemical shifts of the possible species resulting from the reaction of [Pt(bipy)(2)](2+) with OH- in aqueous solution are consistent with the formation of pseudo five-coordinate [Pt(bipy-kappa N-2,N’)(bipy-kappa N)(OH)](+), but are not absolutely conclusive. However, the bonding energy of this complex is calculated to be significantly lower than that of any species resulting from OH- attack at a bipy ligand of [Pt(bipy)(2)](2+).

First author: Hall, Gabriel B., Redox Chemistry of Noninnocent Quinones Annulated to 2Fe2S Cores,ORGANOMETALLICS, 32, 6605, (2013)
Abstract: Noninnocent ligands that are electronically coupled to active catalytic sites can influence the redox behavior of the catalysts. A series of (mu-dithiolato)Fe-2(CO)6 complexes, in which the sulfur atoms of the mu-dithiolato ligand are bridged by 5-substituted (Me, OMe, Cl, t-Bu)-1,4-benzoquinones, 1,4-naphthoquinone, or 1,4-anthraquinone, have been synthesized and characterized. In addition, the bisphosphine complex derived from the 1,4-naphthoquinone-bridged complex has also been prepared and characterized. Cyclic voltammetry of these complexes shows two reversible one-electron reductions at potentials 0.2 to 0.5 V less negative than their corresponding parent quinones. In the presence of acetic acid two-electron reductions of the complexes result in conversion of the quinones to hydroquinone moieties. EPR spectroscopic and computational studies of the one-electron-reduced complexes show electron delocalization from the semiquinones to the 2Fe2S moieties, thereby revealing the “noninnocent” behavior of these ligands with these catalysts.

First author: Garcia-Fernandez, Pablo, A simple monomer-based model-Hamiltonian approach to combine excitonic coupling and Jahn-Teller theory, JOURNAL OF CHEMICAL PHYSICS, 139, 6605, (2013)
Abstract: The interplay of excitonic and vibronic coupling in coupled chromophores determines the efficiency of exciton localization vs delocalization, or in other words, coherent excitation energy transfer vs exciton hopping. For the investigation of exciton localization in large coupled dimers, a model Hamiltonian approach is derived, the ingredients of which can all be obtained from monomer ab initio calculations alone avoiding costly ab initio computation of the full dimer. The accuracy and applicability of this model are exemplified for the benzene dimer by rigorous comparison to ab initio results.

First author: Frisenda, Riccardo, Statistical analysis of single-molecule breaking traces, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 2431, (2013)
Abstract: We present an experimental study of charge transport through single oligo(phenylene-ethynylene) (OPE3) molecules and anthracene substituted OPE3 (OPE3-AC) contacted with a mechanically controlled break junction. Both molecules are measured using two different methods. In the first approach, we measure the low-bias conductance, while the junction is repeatedly broken and fused. In the second approach, instead of applying a fixed bias, we record current-voltage characteristics. For both approaches the data is fitted to a model describing transport through a single level, and information about the level alignment and the electronic coupling to the electrodes is extracted. We find that the electronic coupling is similar for both molecules, but that the level alignment differs. The observed trends are confirmed by quantum chemistry calculations.

First author: Gamez, Jose A., Structures and Bonding Situation of the Allyl Systems and Cyclic Isomers [H2E-E(H)-EH2](-,center dot,+) (E = C, Si, Ge, Sn), ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 639, 2493, (2013)
Abstract: Quantum chemical calculations using DFT and ab initio methods were carried out on the structures of the title compounds. The nature of the bonding was investigated with an energy decomposition analysis. The calculations predict that the planar C-2v allyl structures of the neutral and charged heavier group-14 homologues [H2E-E(H)-EH2](-,center dot,+) (E = Si – Sn) are no minima on the potential energy surface. Energy minima for allyl-type structures of the latter systems possess C-s symmetry and pyramidal EH2 groups. The energetically lowest lying form of [H2E-E(H)-EH2](,center dot,+) (E = Si – Sn) has a cyclic structure for the neutral molecules and the anion and a quasi-cyclic equilibrium arrangement for the cations. In contrast, the cyclic isomers of the carbon molecules [H2C-C(H)-CH2](,center dot,+) are significantly higher in energy than the allyl structures. Energy decomposition analyses show that the lower stability of the planar C-2v allyl structures of [H2E-E(H)-EH2](,center dot,+) (E = Si – Sn) does not come from weak pi conjugation. The relative contribution of pi conjugation in the latter species is even higher than in the allyl system of carbon. The cyclic form of [H2E-E(H)-EH2](,center dot,+) (E = Si – Sn) is lower in energy than the allyl form, because the sigma bonding in the former structures is much stronger than in the latter. This overcompensates the higher Pauli repulsion in the cyclic form. In the carbon systems, the Pauli repulsion of the cyclic structures is very strong, because the bonds are much shorter than in the heavier homologues. Consequently, the stronger Pauli repulsion in the cyclic isomers is not compensated by the stronger attraction compared with the allyl system.

First author: Guerard, Jennifer J., Critical Evaluation of Implicit Solvent Models for Predicting Aqueous Oxidation Potentials of Neutral Organic Compounds, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 5046, (2013)
Abstract: Quantum chemical implicit solvent models are used widely to estimate aqueous redox potentials. We compared the accuracy of several popular implicit solvent models (SM8, SMD, C-PCM, IEF-PCM, and COSMO-RS) for the prediction of aqueous single electron oxidation potentials of a diverse test set of neutral organic compounds for which accurate experimental oxidation potential and gas-phase ionization energy data are available. Using a thermodynamic cycle, we decomposed the free energy of oxidation into contributions arising from the gas-phase adiabatic ionization energy, the solvation free energy of the closed-shell neutral species, and the solvation free energy of the radical cation species. For aqueous oxidation potentials, implicit solvent models exhibited mean unsigned errors (MUEs) ranging from 0.27 to 0.50 V, depending on the model. The principal source of error was attributed to the computed solvation free energy of the oxidized radical cation. Based on these results, a recommended implicit solvation approach is the SMD model for the solvation free energy combined with CBS-QB3 for the gas-phase ionization energy. With this approach, the MUE in computed oxidation potentials was 0.27 V, and the MUE in solvation free energy of the charged open-shell species was 0.32 eV. This baseline assessment provides a compiled benchmark test set of vetted experimental data that may be used to judge newly developed solvation models for their ability to produce improved predictions for aqueous oxidation potentials and related properties.

First author: Karakas, A., Quantum chemical calculations and experimental studies of third-order nonlinear optical properties of conjugated TTF-quinones, OPTICAL MATERIALS, 36, 22, (2013)
Abstract: To investigate microscopic third-order nonlinear optical (NLO) behaviour of two tetrathiafulvalene (TTF) derivatives, TTF-diquinone triad (1) and TTF-monoquinone dyad (2), we have computed both dispersion-free and also dispersion of dipole polarizabilities (alpha) and third-order hyperpolarizabilities (gamma) at 532 nm wavelength using time-dependent Hartree-Fock (TDHF) method. The one-photon absorption (OPA) characterizations of the title molecules have been theoretically obtained by means of configuration interaction (CI) method with all doubly occupied molecular orbitals. We have also calculated the dynamic third-order susceptibilities (chi((3))) using the TDHF method. Our theoretical results on the maximum OPA wavelengths, third-order susceptibilities and corresponding microscopic NLO responses are in good agreement with the previous experimental observations of the examined TTF-based molecules. The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO-LUMO band gaps for I and 2 have been evaluated by density functional theory (DFT) quantum mechanical calculations at B3LYP/6-31 G(d,p) level.

First author: Barolo, Claudia, A Simple Synthetic Route to Obtain Pure Trans-Ruthenium(II) Complexes for Dye-Sensitized Solar Cell Applications, CHEMSUSCHEM, 6, 2170, (2013)
Abstract: We report a facile synthetic route to obtain functionalized quaterpyridine ligand and its trans-dithiocyanato ruthenium complex, based on a microwave-assisted procedure. The ruthenium complex has been purified using a silica chromatographic column by protecting carboxylic acid groups as iso-butyl ester, which are subsequently hydrolyzed. The highly pure complex exhibits panchromatic response throughout the visible region. DFT/time-dependent DFT calculations have been performed on the ruthenium complex in solution and adsorbed onto TiO2 to analyze relative electronic and optical properties. The ruthenium complex endowed with the functionalized quaterpyridine ligand was used as a sensitizer in dye-sensitized solar cell yielding a short-circuit photocurrent density of more than 19mAcm(-2) with a broad incident photon to current conversion efficiency spectra ranging from 400 to 900nm, exceeding 80% at 700nm.

First author: Yan, Biao, Thermodynamic Properties and Detonation Characterization of 3,3-Dinitroazetidinium Hydrochloride, JOURNAL OF CHEMICAL AND ENGINEERING DATA, 58, 3033, (2013)
Abstract: The thermal behavior of 3,3-dinitroazetidinium hydrochloride (DNAZ center dot HCl) was studied at a nonisothermal condition by differential scanning calorimetric and thermogravimetric/differential thermogravimetric methods. The results show that there is only one intense exothermic decomposition process. Its kinetic parameters of the intense exothermic decomposition process are obtained from analysis of the DSC curves. The apparent activation energy (E-a), pre-exponential factor (A), and the mechanism function (f(alpha)) are 155.72 kimol(-1), 10(15.84) s(-1) and 3 alpha(2/3), respectively. The specific heat capacity (C-p) of DNAZ center dot HCl was determined with a continuous C-p mode of microcalorimeter. The specific molar heat capacity (C-p,C-m) of DNAZ center dot HCl was 205.10 J.mol(-1).K-1 at 298.15 K. The self-accelerating decomposition temperature (T-SADT), thermal ignition temperature (T-TTT), and critical temperatures of thermal explosion (T-b) were obtained to evaluate the thermal stability and safety of DNAZ center dot HCl. The detonation velocity (D) and detonation pressure (P) of DNAZ center dot HCl were estimated using the nitrogen equivalent equation according to the experimental density. The stability, safety, and detonation performance of DNAZ center dot HCl were compared with that of 3,3-dinitroazetidinium 3,5-dinitrosalicylate (DNAZ center dot HClO4).

First author: Xu ChaoFei, Theoretical studies on the complexation of uranyl with typical carboxylate and amidoximate ligands, SCIENCE CHINA-CHEMISTRY, 56, 1525, (2013)
Abstract: Understanding of the bonding nature of uranyl and various ligands is the key for designing robust sequestering agents for uranium extraction from seawater. In this paper thermodynamic properties related to the complexation reaction of uranyl(VI) in aqueous solution (i.e. existing in the form of UO2(H2O)(5) (2+)) by several typical ligands (L) including acetate (CH3CO2 (-)), bicarbonate (HOCO2 (-)), carbonate (CO3 (2-)), CH3(NH2)CNO- (acetamidoximate, AO(-)) and glutarimidedioximate (denoted as GDO(2-)) have been investigated by using relativistic density functional theory (DFT). The geometries, vibrational frequencies, natural net charges, and bond orders of the formed uranyl-L complexes in aqueous solution are studied. Based on the DFT analysis we show that the binding interaction between uranyl and amidoximate ligand is the strongest among the selected complexes. The thermodynamics of the complexation reaction are examined, and the calculated results show that complexation of uranyl with amidoximate ligands is most preferred thermodynamically. Besides, reaction paths of the substitution complexation of solvated uranyl by acetate and AO(-) have been studied, respectively. We have obtained two minima along the reaction path of solvated uranyl with acetate, the monodentate-acetate complex and the bidentate-acetate one, while only one minimum involving monodentate-AO complex has been located for AO(-) ligand. Comparing the energy barriers of the two reaction paths, we find that complexation of uranyl with AO(-) is more difficult in kinetics, though it is more preferable in thermodynamics. These results show that theoretical studies can help to select efficient ligands with fine-tuned thermodynamic and kinetic properties for binding uranyl in seawater.

First author: Mitoraj, Mariusz P., Theoretical description of halogen bonding – an insight based on the natural orbitals for chemical valence combined with the extended-transition-state method (ETS-NOCV), JOURNAL OF MOLECULAR MODELING, 19, 4681, (2013)
Abstract: In the present study we have characterized the halogen bonding in selected molecules H3N-ICF3 (1-NH (3) ), (PH3)(2)C-ICF3 (1-CPH (3) ), C3H7Br-(IN2H2C3)(2)C6H4 (2-Br), H-2-(IN2H2C3)(2)C6H4 (2-H (2) ) and Cl-(IC6F5)(2)C7H10N2O5 (3-Cl), containing from one halogen bond (1-NH (3) , 1-CPH (3) ) up to four connections in 3-Cl (the two Cl-HN and two Cl-I), based on recently proposed ETS-NOCV analysis. It was found based on the NOCV-deformation density components that the halogen bonding C-X (aEuro broken vertical bar) B (X-halogen atom, B-Lewis base), contains a large degree of covalent contribution (the charge transfer to X (aEuro broken vertical bar) B inter-atomic region) supported further by the electron donation from base atom B to the empty sigma*(C-X) orbital. Such charge transfers can be of similar importance compared to the electrostatic stabilization. Further, the covalent part of halogen bonding is due to the presence of sigma-hole at outer part of halogen atom (X). ETS-NOCV approach allowed to visualize formation of the sigma-hole at iodine atom of CF3I molecule. It has also been demonstrated that strongly electrophilic halogen bond donor, [C6H4(C3H2N2I)(2)][OTf](2), can activate chemically inert isopropyl bromide (2-Br) moiety via formation of Br-I bonding and bind the hydrogen molecule (2-H (2) ). Finally, ETS-NOCV analysis performed for 3-Cl leads to the conclusion that, in terms of the orbital-interaction component, the strength of halogen (Cl-I) bond is roughly three times more important than the hydrogen bonding (Cl-HN).

First author: Tehrani, Zahra Aliakbar, Do coinage metal anions interact with substituted benzene derivatives?, JOURNAL OF MOLECULAR MODELING, 19, 4763, (2013)
Abstract: The nature of the anion-pi interaction has been investigated by carrying out ab initio calculations of the complexes of coinage metal anions (Au-, Ag-, and Cu-) with different kinds of pi-systems. The binding energies indicate that gold anion has the highest and copper anion has the lowest affinity for interactions with pi-systems. Different aspects of the anion-pi interaction in these systems have been investigated, including charge-transfer effects (using the Merz-Kollman method), “atoms-in-molecules” (AIM) topological parameters, and interaction energies (using energy decomposition analysis, EDA). Our results indicated that, for most M-center dot center dot center dot pi interactions, the electrostatic term provides the dominant contribution, whereas polarization, charge transfer, and dispersion effects contribute less than 25 % of the interaction. We believe that the present results should lead to a greater understanding of the basis for anion-pi interactions of coinage metal anions.

First author: Aguilar, Charles M., The nature of the M-NO bond in [M(Imidazole)(PPIX)(L)](q) complexes (M = Fe2+, Ru2+; L = NO+, NO center dot and NO-; PPIX = Protoporphyrin IX), INORGANICA CHIMICA ACTA, 408, 18, (2013)
Abstract: Aiming at understanding the effect of the replacement of iron by ruthenium in the Protoporphyrin IX (PPIX) system of the heme group, in this work density functional theory calculations were performed to investigate the structures, nature of the M-NO bond and electronic spectra of the complexes [M(Im)(PPIX)(L)](q), where M = Fe2+ and Ru2+, Im = Imidazole ring, PPIX = Protoporphyrin IX of the heme group and L = NO+, NO and NO-. Energetic and structural results obtained at the B3LYP/SBKJC/6-31G(d) level of theory indicates that the NO coordinates preferentially through the nitrogen atom and its oxidized form NO+ produces more stable complexes. Charge and energy decomposition analysis revealed that, independent of the coordination mode, the interaction of NO species with the ruthenium fragment is stronger than with iron. TD-DFT calculations predict that the transition that can lead to photodissociation of the Ru-NO bond occurs at 419 nm and if the NO coordinates to ruthenium in its oxidized form this transition is blue-shifted to 384 nm. The results obtained in this work also gives support to conclude that ruthenium complexes with the protoporphyrin IX (PPIX) system can strongly bind NO, which can be used to capture NO species, and releasing it upon irradiation with visible light.

First author: Majid, Abdul, A density functional theory study of electronic properties of Ce:GaN, COMPUTATIONAL MATERIALS SCIENCE, 79, 929, (2013)
Abstract: First principle calculations for Ce:GaN using mBJ, GGA, LDA (+U) are presented to demonstrate the electronic, optical and magnetic properties of the system. The effect of variation of U on Ce 4f levels and forbidden gap are discussed in detail and an optimized value of U-eff (5.3 eV) is obtained. The 4f levels were observed shifted away from Fermi level with increase in value of U-eff. Our results revealed that dopant introduces localized level near conduction band whose width increases with increase in doping concentration. It is noted that for large Ce concentration, the impurity band is found merged with bottom of the conduction band and form a new conduction band edge. It predicts the band gap narrowing in the material which is expected to facilitate the optical transitions.

First author: Vijayakumar, M., Elucidating the higher stability of vanadium(V) cations in mixed acid based redox flow battery electrolytes, JOURNAL OF POWER SOURCES, 241, 173, (2013)
Abstract: The vanadium(V) cation structures in mixed acid based electrolyte solution were analyzed by density functional theory (DFT) based computational modeling and V-51 and Cl-35 nuclear magnetic resonance (NMR) spectroscopy. The vanadium(V) cation exists as di-nuclear [V2O3Cl2 center dot 6H(2)O](2+) compound at higher vanadium concentrations (>= 1.75 M). In particular, at high temperatures (>295 K) this di-nuclear compound undergoes ligand exchange process with nearby solvent chlorine molecule and forms chlorine bonded [V2O3Cl center dot 6H(2)O](2+) compound. This chlorine bonded [V2O3Cl2 center dot 6H(2)O]2+ compound might be resistant to the de-protonation reaction which is the initial step in the precipitation reaction in vanadium based electrolyte solutions. The combined theoretical and experimental approach reveals that formation of chlorine bonded [V2O3Cl2 center dot 6H(2)O](2+) compound might be central to the observed higher thermal stability of mixed acid based vanadium(V) electrolyte solutions.

First author: Wang, Jing, Theoretical studies on organoimido-substituted hexamolybdates dyes for dye-sensitized solar cells (DSSC), DYES AND PIGMENTS, 99, 440, (2013)
Abstract: A series of POM-based organic-inorganic hybrids with different pi-conjugated bridges are investigated as sensitizers for application in dye-sensitized solar cells (DSSCs). A combination of density functional theory (DFT) and time-dependent DFT (TDDFT) approaches is employed. The effects of pi-conjugated spacer size and pi-conjugation length on the spectra of designed systems are demonstrated. The results show that the absorption spectra are systematically broadened and red-shifted with increasing sizes of the pi-conjugated spacer and the length of pi-conjugation. The theoretical examination was performed on the key parameters of incident photon-to-electron conversion efficiency (IPCE), light harvesting efficiency (LHE) and electron injection efficiency (Phi(inj)). The result suggests that system 2 with thieno[3,2-b] thiophene demonstrates a balance of the two crucial factors and may result in the highest IPCE of DSSCs. This study is expected to deepen our understanding of POM-based organic-inorganic hybrid dyes and assist the molecular design of new dyes for the further optimization of DSSCs.

First author: Ramaniah, Lavanya M., How universal are hydrogen bond correlations? A density functional study of intramolecular hydrogen bonding in low-energy conformers of alpha-amino acids, MOLECULAR PHYSICS, 111, 3067, (2013)
Abstract: Hydrogen bonding is one of the most important and ubiquitous interactions present in Nature. Several studies have attempted to characterise and understand the nature of this very basic interaction. These include both experimental and theoretical investigations of different types of chemical compounds, as well as systems subjected to high pressure. The O-H center dot center dot center dot O bond is of course the best studied hydrogen bond, and most studies have concentrated on intermolecular hydrogen bonding in solids and liquids. In this paper, we analyse and characterise normal hydrogen bonding of the general type, D-H center dot center dot center dot A, in intramolecular hydrogen bonding interactions. Using a first-principles density functional theory approach, we investigate low energy conformers of the twenty -amino acids. Within these conformers, several different types of intramolecular hydrogen bonds are identified. The hydrogen bond within a given conformer occurs between two molecular groups, either both within the backbone itself, or one in the backbone and one in the side chain. In a few conformers, more than one (type of) hydrogen bond is seen to occur.Interestingly, the strength of the hydrogen bonds in the amino acids spans quite a large range, from weak to strong. The signature of hydrogen bonding in these molecules, as reflected in their theoretical vibrational spectra, is analysed. With the new first-principles data from 51 hydrogen bonds, various parameters relating to the hydrogen bond, such as hydrogen bond length, hydrogen bond angle, bond length and vibrational frequencies are studied. Interestingly, the correlation between these parameters in these bonds is found to be in consonance with those obtained in earlier experimental studies of normal hydrogen bonds on vastly different systems. Our study provides some of the most detailed first-principles support, and the first involving vibrational frequencies, for the universality of hydrogen bond correlations in materials.

First author: Zhu, Yu-Lan, A new D-A derivative with a 1,3-dithiol-2-ylidene unit: Structural, spectroscopic and theoretical studies, POLYHEDRON, 63, 36, (2013)
Abstract: A novel D-A compound, [Cu(L)(2)Cl-2]center dot 2CH(2)Cl(2) ML, has been synthesized based on 4′,5′-diaza-9′-(4,5-bis(benzylthio)-1,3-dithiole-2-ylidene)-fluorene ((C11N2H6)(C3S2)(SCH2C6H5)(2), L). Both ML and L are further characterized by elemental analysis, IR, H-1 and C-13 NMR. Single-crystal X-ray diffraction shows ML displays a 3-D supramolecular network built by the neutral mononuclear unit [Cu(L)(2)Cl-2] via hydrogen bonds, pi-pi stacking and S center dot center dot center dot S interactions. The UV-Vis spectra show the lowest-energy absorption band (431 nm) of ML is red-shifted compared to that of L (415 nm). The electrochemistry behavior shows that while the HOMO level of the ML is lowered by L coordinating with the Cu2+ ion, the oxidative potentials are increased (1.19 to 1.37 V). Photocurrent measurements show the intramolecular charge transfer (ICT) of L should be easier than that of ML The results of the reorganization energy obtained from DFT calculations (lambda(i): 0.25 eV for L, 0.82 eV for ML) reveal the lower reorganization energy is of great benefit to carrier transport within L. These results are in good agreement with those experimentally obtained by CV, UV-Vis, fluorescence and photocurrent measurements.

First author: Priyakumari, Chakkingal P., P3F92-: An All-Pseudo-pi* 2 pi-Aromatic, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 16026, (2013)
Abstract: A qualitative MO analysis suggests (PH3)(3)(2-) as a candidate for an all-pseudo-pi* 2 pi-aromatic; however computational studies rule out its existence. Fluorine substitution which increases the contribution of p orbitals on P in the pseudo-pi* MO makes (PF3)(3)(2-) a minimum and an aromatic. The 2 pi aromaticity arising from the bonding combination of the three pseudo-pi* fragment MOs is comparable to that in C3O32- and is another example for the analogy between CO and PF3. The dianion (PF3)(3)(2-) forms the first example of a three-membered ring with all the vertices constituted by pentacoordinate phosphorus. The ability of PF3 to form the all-pseudo-pi* 2 pi-aromatic system is not shared by the heavier analogues, AsF3 and SbF3.

First author: Gramigna, Kathryn M., Palladium(II) and Platinum(II) Compounds of 1,1 ‘-Bis(phosphino)metallocene (M = Fe, Ru) Ligands with Metal-Metal Interactions, ORGANOMETALLICS, 32, 5966, (2013)
Abstract: The reaction of [Pd(dtbpf)Cl-2] (dtbpf = 1,1′-bis(di-tert-butylphosphino)ferrocene) with a chemical oxidant led unexpectedly to the formation of [Pd(dtbpf)Cl](+). Further study found that a variety of reagents could be used to abstract a chloride ligand from [Pd(dtbpf)Cl-2] to yield [Pd(dtbpf)Cl](+). The solid-state structure suggests the formation of an Fe-Pd interaction. The presence of the bulky tert-butyl groups is essential, as similar reactions with [Pd(PP)Cl-2] (PP = other 1,1′-bis(phosphino)ferrocene ligands) results in the formation of [Pd(PP)(mu-Cl)](2)(2+). The analogous platinum compounds have also been investigated and appear to behave in a similar manner. Similar compounds of the type [M'(PP)(PR3)](2+) (M’ = Pd, Pt, R = Ph, Me) have been prepared, and a metal-metal interaction has also been observed. Steric and electronic effects dictate the formation of these compounds. X-ray crystal structures were obtained for eight of these compounds and were used as the basis for a computational analysis of the metal-metal interaction. DFT analysis indicates the presence of a weak, noncovalent interaction between the two metal centers. The electrochemical properties of these compounds were examined by cyclic voltammetry and typically show one oxidative wave and either one two-electron or two one-electron reductive waves.

First author: Pedicini, Anthony F., The effect of sulfur covalent bonding on the electronic shells of silver clusters,JOURNAL OF CHEMICAL PHYSICS, 139, 5966, (2013)
Abstract: The nature of the bonding in AgnSm0/- clusters, n = 1-7; m = 1-4, has been analyzed to understand its effect on the electronic shell structure of silver clusters. First-principle investigations reveal that the sulfur atoms prefer 2 or 3-coordinate sites around a silver core, and that the addition of sulfur makes the planar structures compact. Molecular orbital analysis finds that the 3p orbitals of sulfur form a bonding orbital and two weakly bonding lone pairs with silver. We examine the electronic shell structures of Ag6Sm, which are two electrons deficient of a spherical closed electronic shell prior to the addition of sulfur, and Ag7Sm- clusters that contain closed electronic shells prior to the addition of sulfur. The Ag6S4 cluster has a distorted octahedral silver core and an open shell with a multiplicity of 3, while the Ag7Sn- clusters have compact geometries with enhanced stability, confirming that the clusters maintain their electronic shell structure after bonding with sulfur.

First author: Duhovic, Selma, Investigation of the Electronic Structure of Mono(1,1 ‘-Diamidoferrocene) Uranium(IV) Complexes, ORGANOMETALLICS, 32, 6012, (2013)
Abstract: The electronic structure of several mono(1,1′-diamidoferrocene) uranium complexes (NNR)UX2 (NNR = fc(NR)(2), fc = 1,1′-ferrocenediyl, R = SiMe3, (SiBuMe2)-Bu-t, SiMe2Ph, X = I, CH2Ph), (NNTBS)UI(OAr) (OAr = 2,6-di-tert-butylphenoxide), and (NNTBS)U(CH2Ph)(OAr) was investigated by electrochemistry, electronic absorption and vibrational spectroscopy, and DFT calculations. Similar metrical parameters were observed for (NNTBS)U(CH2Ph)(2) and (NNDMP)U(CH2Ph)(2) (and also for the previously reported (NNTBS)UI2(THF), (NNTBS)UI2(THF), and (NNTBS)U(CH2Ph)(OAr)) that translate in similar DFT parameters (bond orders, metal charges) despite some small differences observed by electrochemistry and IR or electronic absorption spectroscopy.

First author: Sanz, Xavier, Metal-free borylative ring-opening of vinyl epoxides and aziridines, ORGANIC & BIOMOLECULAR CHEMISTRY, 11, 7004, (2013)
Abstract: A rational approach towards the borylative ring-opening of vinylepoxides and vinylaziridines, by the in situ formed MeO–> bis(pinacolato)diboron adduct, has been developed. The enhanced nucleophilic character of the Bpin (sp(2)) moiety from the reagent favours the S(N)2′ conjugated B addition with the concomitant opening of the epoxide and aziridine rings. The reaction proceeds with total chemoselectivity towards the polyfunctionalised (-OH or -NHTs) allyl boronate. Theoretical calculations have determined the transition states that come from the reaction of the vinylic substrates with the activated MeO–> bis-(pinacolato)diboron adduct, and a plausible mechanism for the organocatalytic borylative ring opening reaction has been suggested.

First author: Yang, Yang, Computational Modeling of Octahedral Iron Oxide Clusters: Hexaaquairon(III) and Its Dimers,JOURNAL OF PHYSICAL CHEMISTRY C, 117, 21706, (2013)
Abstract: Octahedral monomeric and dimeric iron oxide clusters represent the basic units in many iron oxide and oxide-hydroxide minerals. In this paper, we provide a detailed theoretical analysis of the structural and optical properties of the most important of these clusters in a vacuum and in an aqueous environment. An evaluation of various computational methods was performed on the experimentally well-known monomer [Fe(H2O)(6)](3+), and it is found that all methods provide similar and reliable structures. Most density functional theory (DFT) methods reasonably reproduce the spin-forbidden sextet-quartet d-d transition energy, which also resembles the lowest transition energies in many infinite octahedral iron oxide systems. On the other hand, Hartree-Fock (HF) and MP2 methods significantly overestimate this energy. The ligand-to-metal charge transfer (LMCT) energy is highly sensitive to the method employed, with the closest agreement with experiment provided by the BHandHLYP functional. Thermodynamic property calculations suggest that dimerization reactions starting from [Fe(H2O)(6)](3+) are highly exothermic in a vacuum. In contrast, these reactions have insignificant energy changes in solution, though the singly mu-oxo bridged dimer is slightly favored. The electrostatic repulsion between two charged monomers hinders their close contact. The singly mu-oxo bridged dimer suffers less from this because of its maximal Fe-Fe distance, which is consistent with the existence of stable crystal structures for this dimer. A comparison between the calculated structures and experimental results suggests that several dimer species coexist in solution. The calculated ferromagnetic and antiferromagnetic states of the dimers are found to have comparable energies and structures. While the singly mu-oxo and doubly mu-hydroxo bridged dimers have spin states that are well separated in energy, the spin states in the triply mu-hydroxo bridged dimer pack closely. The single excitation d-d transition in the dimer structure is comparable in energy to the d-d transition in the monomer, while the double excitation d-d transition, i.e., simultaneous excitation of two iron centers, has a higher excitation energy that is 1.6-2.6 times the single excitation energy but below the LMCT energy. This means that doubly excited states can be populated during the non-radiative relaxation of iron oxide clusters following initial photoexcitation of the LMCT state.

First author: Hossain, Washim, SERS and DFT study of silver nano particle induced dark isomerisation in 1H-2(Phenylazo) imidazole, CHEMICAL PHYSICS LETTERS, 586, 132, (2013)
Abstract: Raman spectra and SERS of 1H-2(Phenylazo) imidazole (PaiH) adsorbed on silver nano particles are reported. Monomolecular layer is formed at a concentration of 5 x 10(-6) M. A trans-to-cis isomerisation of PaiH is suggested by the cis-signature peak at 570 cm(-1). In absorption spectra a single pi-pi* band at 358 nm is observed at higher concentrations whereas the pi-pi*/and the n-pi* bands appear at 370 nm and 456 nm, respectively, at a concentration of 5 x 10(-6) M. This is in support of the hypothesis of trans-to-cis-isomerisation with lowering of concentration. DFT calculations are shown.

First author: Lopez, Rafael, Multipole moments from the partition-expansion method, THEORETICAL CHEMISTRY ACCOUNTS, 132, 132, (2013)
Abstract: Analytical expressions for the atomic multipole moments defined from the partition-expansion method are reported for both Gaussian and Slater basis sets. In case of Gaussian functions, two algorithms are presented and examined. The first one gives expressions in terms of generalized overlap integrals whose master formulas are derived here with the aid of the shift-operator technique. The second uses translation methods, which lead to integrals involving Gaussian and Bessel functions, which are also known. For Slater basis sets, an algorithm based on translation methods is reported. In this algorithm, atomic multipoles are expressed in terms of integrals involving Macdonald functions, which have been solved in previous works. The accuracy of these procedures is tested and their efficiency illustrated with practical applications, including the computation of the full molecular electrostatic potential (not only the long-range) in large systems.

First author: Mino, Lorenzo, Low-dimensional systems investigated by x-ray absorption spectroscopy: a selection of 2D, 1D and 0D cases, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 46, 132, (2013)
Abstract: Over the last three decades low-dimensional systems have attracted increasing interest both from the fundamental and technological points of view due to their unique physical and chemical properties. X-ray absorption spectroscopy (XAS) is a powerful tool for the characterization of such kinds of systems, owing to its chemical selectivity and high sensitivity in interatomic distance determination. Moreover, XAS does not require long-range ordering, that is usually absent in low-dimensional systems. Finally, this technique can simultaneously provide information on electronic and local structural properties of the nanomaterials, significantly contributing to clarify the relation between their atomic structure and their peculiar physical properties. This review provides a general introduction to XAS, discussing the basic theory of the technique, the most used detection modes, the related experimental setups and some complementary relevant characterization techniques (diffraction anomalous fine structure, extended energy-loss fine structure, pair distribution function, x-ray emission spectroscopy, high-energy resolution fluorescence detected XAS and x-ray Raman scattering). Subsequently, a selection of significant applications of XAS to two-, one-and zero-dimensional systems will be presented. The selected low-dimensional systems include IV and III-V semiconductor films, quantum wells, quantum wires and quantum dots; carbon-based nanomaterials (epitaxial graphene and carbon nanotubes); metal oxide films, nanowires, nanorods and nanocrystals; metal nanoparticles. Finally, the future perspectives for the application of XAS to nanostructures are discussed.

First author: Jacobsen, Heiko, More on Diphosphadithiatetrazocines and the Importance of Being Bonded, INORGANIC CHEMISTRY, 52, 11843, (2013)
Abstract: The cross-ring sulfur-sulfur bond for seven R’RP(NSN)(2)PRR’ molecules 1a (R = R’ = Me), 1b (R = R’ = Ph), 1c (R = R’ = Et), 1d (R = Cl, R’ = CCl3), 1e (R = R’= Cl), 1f (R = R’ = F), and 1g (R = R’ = H) has been scrutinized by a topology analysis for a bond descriptor based on the kinetic energy density, supported by a fragment-based bond energy analysis. Contrary to a regular disulfide bond, the cross-ring connection is only a secondary electron-sharing bond, about half as strong as a common S-S linkage. The regular disulfide bond itself is best described as a charge-shift bond. These analyses are based on results obtained from B3PW91/def2-TZVP density functional calculations.

First author: Erdem, Oezlen F., Effect of Cyanide Ligands on the Electronic Structure of [FeFe] Hydrogenase Active-Site Model Complexes with an Azadithiolate Cofactor, CHEMISTRY-A EUROPEAN JOURNAL, 19, 14566, (2013)
Abstract: A detailed characterization of a close synthetic model of the [2Fe](H) subcluster in the [FeFe] hydrogenase active site is presented. It contains the full primary coordination sphere of the CO-inhibited oxidized state of the enzyme including the CN ligands and the azadithiolate (adt) bridge, [((mu-S-CH2)(2)NR)Fe-2(CO)(4)(CN)(2)](2-), R=CH2CH2SCH3. The electronic structure of the model complex in its (FeFeII)-Fe-I state was investigated by means of density functional theory (DFT) calculations and Fourier transform infrared (FTIR) spectroscopy. By using a combination of continuous-wave (CW) electron paramagnetic resonance (EPR) and hyperfine sublevel correlation (HYSCORE) experiments as well as DFT calculations, it is shown that, for this complex, the spin density is delocalized over both iron atoms. Interestingly, we found that the nitrogen hyperfine coupling, which represents the interaction between the unpaired electron and the nitrogen at the dithio-late bridge, is slightly larger than that in the analogous complex in which the CN- ligands are replaced with PMe3 ligands. This reveals, first, that the CN-/PMe3 ligands coordinated to the iron core are electronically coupled to the amine in the adt bridge. Second, the CN- ligands in this complex are somewhat stronger sigma-donor ligands than the PMe3 ligand, and thereby enable more spin density to be transferred from the Fe core to the adt unit, which might in turn affect the reactivity of the bridging amine.

First author: Lopchuk, Justin M., What Controls Regiochemistry in 1,3-Dipolar Cycloadditions of Munchnones with Nitrostyrenes?, ORGANIC LETTERS, 15, 5218, (2013)
Abstract: The distinct experimentally observed regiochemistries of the reactions between mesoionic munchnones and beta-nitrostyrenes or phenylacetylene are shown by DFT/BDA/ETS-NOCV analyses of the transition states to be dominated by steric and reactant reorganization factors, rather than the orbital overlap considerations predicted by Frontier Molecular Orbital (FMO) Theory.

First author: Balamurugan, K., Adsorption of Chlorobenzene onto (5,5) Armchair Single-Walled Carbon Nanotube and Graphene Sheet: Toxicity versus Adsorption Strength, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 21217, (2013)
Abstract: Adsorption of the homologues series of chlorobenzenes (CBs) onto the surface of the (5,5) armchair single-walled carbon nanotube (SWCNT) and graphene (Graph) sheet has been investigated using density functional theory-based calculations, and the concomitant interaction between the CBs and SWCNT/Graph has also been characterized with the help of the Bader’s theory of atoms in molecules. Results reveal that interaction of CBs with the SWCNT and Graph enhances with the increase in the chlorine content. The adsorption of CBs on Graph is more favorable when compared with SWCNT. Evidence shows that the planar surface of the graphene facilitates the direct through-space interaction of the chlorine atoms of CBs with the aromatic surface. The pi character of CBs governs the interaction process in the case of SWCNT. Findings from this study clearly demonstrate the importance of geometry (curved or planar) of the nanomaterial in the adsorption of aromatic pollutants. In addition, the inter-relationship between the electrophilicity index (a powerful conceptual DFT descriptor of toxicity of CBs) and the interaction energy (adsorption capacity) has also been derived.

First author: Guidez, Emilie B., Origin and TDDFT Benchmarking of the Plasmon Resonance in Acenes, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 21466, (2013)
Abstract: The origin of plasmon resonance in acenes is described by analyzing the excitation spectrum of naphthalene in terms of configuration interaction. The strong longitudinal beta-peak in the UV region of the spectrum results from a constructive interaction of the transition dipole moments of two degenerate configurations V-1 and V-2. V-1 corresponds to the excitation of an electron from the HOMO to the LUMO+1. V-2 corresponds to the excitation of an electron from the HOMO-1 to the LUMO. The weak longitudinal a-peak in the visible results from a destructive interaction of the dipole moments of the same two configurations. Previous time-dependent density functional theory (TDDFT) calculations showed a similar behavior for silver and gold nanoparticles but often with more than two interacting configurations. The plasmon occurs at the frequency where all configurations interact constructively. The beta-peak of acenes can therefore be identified as the plasmon peak. The natural transition orbitals involved in the alpha- and beta-peaks of naphthalene have identical shapes, which reflects the fact that the transitions involved in these two peaks are similar, but they may have opposite phases. An analysis of the transition density of the beta-peak of naphthalene reveals that the electron density moves from one side of the molecule to the other upon excitation, as expected for a dipolar plasmon. The plasmonic character of the beta-peak is compared to the single-particle transition character of the transverse p-band. Several exchange-correlation functionals have been benchmarked. Hybrid functionals give the best description of the beta-peak and the alpha-peak. The couplings between the two interacting configurations at all levels of theory are similar to experimental values. On the other hand, long-range corrected functionals give the most accurate energies for the transverse p-band.

First author: Pietrzyk, Piotr, Intimate Binding Mechanism and Structure of Trigonal Nickel(I) Monocarbonyl Adducts in ZSM-5 Zeolite-Spectroscopic Continuous Wave EPR, HYSCORE, and IR Studies Refined with DFT Quantification of Disentangled Electron and Spin Density Redistributions along sigma and pi Channels, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 15467, (2013)
Abstract: Interaction of tetracoordinated nickel(I) centers generated inside the channels of ZSM-5 zeolite with carbon monoxide ((CO)-C-12,13, p(CO) < 1 Torr) led to the formation of T-shaped, top-on monocarbonyl adducts with a unique trigonal nickel core, supported by two oxygen donor ligands. The mechanism of the formation of the {Ni-I-CO}ZSM-5 species was accounted for by a quantitative molecular orbital correlation diagram of CO ligation. Detailed electronic and magnetic structure of this adduct was obtained from comprehensive DFT calculations, validated by quantitative reproduction of its continuous wave electron paramagnetic resonance (CW-EPR), hyperfine sublevel correlation (HYSCORE), and IR fingerprints, using relativistic Pauli and ZORA-SOMF/B3LYP methods. Molecular analysis of the stretching frequency, nu(CO) = 2109 cm(-1), g and A(C-13) tensors (g(xx) = 2.018, g(yy) = 2.380, g(zz) = 2.436, A(xx) = +1.0 +/- 0.3 MHz, A(yy) = -3.6 +/- 0.9 MHz, A(zz) = -1.6 +/- 0.3 MHz) and Q(Al-27) parameters (e(2)Qq/h = -13 MHz and eta = 0.8) supported by quantum chemical modeling revealed that the Ni-CO bond results from the pi overlap between the low-laying pi(2p) CO states with the 3d(zz) and 3d(yz) orbitals, with a small sigma contribution due to the overlap of sigma(2p+2s) orbital and a protruding lobe of the in-plane 3d(xz) orbital. Two types of orbital channels (associated with the sigma and pi overlap) of the electron and spin density flows within the {Ni-I-CO} unit were identified. A bathochromic shift of the nu(CO) stretching vibration was accounted for by resolving quantitatively the separate contributions due to the sigma donation and pi back-donation, whereas the C-13 hyperfine coupling was rationalized by incongruent alpha and beta spin flows via the sigma and nu channels. As a result the very nature of the carbon-metal bond in the Ni-I-CO adduct and the molecular backbone of the corresponding spectroscopic parameters were revealed with unprecedented accuracy.

First author: Zamani, Mehdi, Gas storage of simple molecules in boron oxide nanocapsules, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 2319, (2013)
Abstract: The capability of the B20O30 nanocapsule to store H-2, N-2, CO, CO2, NH3, CH4, and Cl-2 molecules on the outer surface and inside of the cage was investigated using Monte Carlo simulations, long-range and dispersion corrected density functional theory, and MOller-Plesset second-order perturbation theory. Also, Monte Carlo simulations were employed to investigate the adsorption behavior of larger number of guest molecules inserted into and onto the larger B80O120 and B20O30@B80O120 cages. Absolute localized molecular orbitals energy decomposition analysis was used to describe the nature of intermolecular interactions in these endohedral and exohedral complexes. It is found that the hydrogen and ammonia gases are diffused to the inside of spherical B20O30 capsule, while other guest molecules prefer to interact with the outer surface of spherical and pyramidal capsules. For B80O120, up to 26 H-2 and 11-14 N-2, CO, CO2, NH3, and CH4 molecules are stored inside the capsule. The residual molecules are adsorbed on the outer surface of nanocapsule.

First author: Green, Katy, Covalent Immobilization of Redox-Active Fe(kappa(2)-dppe)(eta(5)-C5Me5)-Based pi-Conjugated Wires on Oxide-Free Hydrogen-Terminated Silicon Surfaces, ORGANOMETALLICS, 32, 5333, (2013)
Abstract: Several redox-active Fe(kappa(2)-dppe)(eta(5)-C5Me5) arylacetylide complexes (dppe = 1,2-bis(diphenylphosphino)ethane) featuring a pendant ethynyl (1b-d and 2) or ethenyl (3) group have been grafted on oxide-free hydrogen-terminated silicon (Si-H) surfaces through a covalent interfacial Si-C bond. They form densely packed redox-active monolayers. The charge-transfer process between the terminal redox center and the underlying silicon interface was subsequently studied by cyclic voltammetry. The latter turned out to be strongly dependent on the nature of the spacer linking the organometaflic end groups to the silicon surface, the highest charge-transfer rates being obtained for monolayers anchored through conjugated and unsaturated spacers. Although the rates measured were among the highest values obtained for redox-active systems grafted to Si H surfaces, this study nevertheless suggests that the electron tunnelling is not entirely controlling the interfacial charge-transfer process for the shorter linkers tested. In this respect, strategies to improve further the charge-transfer kinetics of the produced redox-active films are briefly discussed.

First author: Thirumoorthi, Ramalingam, CH-NH Tautomerism in the Products of the Reactions of the Methanide [HC(PPh2NSiMe3)(2)](-) with Pnictogen and Tellurium Iodides, ORGANOMETALLICS, 32, 5360, (2013)
Abstract: The reactions of K[HC(PPh2NSiMe3)(2)] (K[1]) and MI3 (M = As, Sb) or TeI4 gave as the major products the complexes [{MIn}{C(PPh2NSiMe3)(PPh2NHSiMe3)}] (MIn = trans-AsI2, trans- or cis-SbI2, TeI3), which feature the ligand [C(PPh2NSiMe3)(PPh2NHSiMe3)](-) (2). This anion, the NH tautomer of [HC(PPh2NSiMe3)(2)](-), is formally generated by a 1,3-hydrogen shift to give complexes in which the ligand is N,C-chelated to the main-group-metalloid center. The M-C distances are slightly longer than the sum of the covalent radii for M and C in the case of the group IS metalloids but significantly shorter for M = Te. The arsenic derivative [{t-AsI2}2] is monomeric in the solid state, with As I distances that differ by ca. 0.55 angstrom, whereas the antimony analogues [{t-SbI2}2] and [{c-SbI2}2] are dimeric through bridging iodide ligands and the disparity in Sb-I distances of the SbI2 units is 0.10 and 0.33 angstrom, respectively. The tellurium derivative [{TeI3}2] is monomeric with a distorted-square-pyramidal geometry at the Te center and Te-I distances in the narrow range 2.9142(4)-3.0337(4) angstrom. In contrast to the lighter pnictogens, the bismuth complex [{t-BiI2}1] is comprised of the methanide 1 coordinated in a tridentate (N,C,N) mode to a BiI2+ cation. In the case of arsenic triiodide, the metathesis is accompanied by Si-N bond cleavage to give [{AsI2}{CH2(PPh2N)(PPh2NSiMe3)}] (3), which was characterized by P-31 NMR spectroscopy, and conversion to the corresponding salt [{AsI}{CH2(PPh2N)(PPh2NSiMe3)}][SbF6] (3A) by treatment with AgSbF6. The As-N distances in the six-membered CP2N2As ring in 3A differ by 0.20 angstrom due to the different coordination numbers (2 and 3) of the two N atoms in the novel N,N’-chelated [CH2(PPh2N)(PPh2NSiMe3)](-) anion. In contrast, reaction of [{t-SbI2}2] with AgSbF6 gives the expected salt as the dimer {[{SbI}2][SbF6]}(2). The two hydrolysis products [CH2(PPh2NSiMe3)(PPh2NHSiMe3)][SbF6] (4A) and [CH2(PPh2NSiMe3) (PPh2NHSiMe3)](2)[Te2I6] (4B) were also structurally characterized and shown to contain the same cation. DFT calculations indicate that the N-H tautomer 2 is stabilized by strong M-N and M-C bonding interactions which include a small degree of pi character. Weaker bonds, as in the Bi complex, favor the C-H tautomer 1 as the ligand.

First author: Nasser, Nasser, Organoplatinum Chemistry with a Dicarboxamide-Diphosphine Ligand: Hydrogen Bonding, Cyclometalation, and a Complex with Two Metal-Metal Donor-Acceptor Bonds, ORGANOMETALLICS, 32, 5504, (2013)
Abstract: The chemistry of the ligand bis(2-diphenylphosphinoethyl)phthalamide, dpppa, with platinum(II) is described. The reaction of dpppa with I [Pt2Me4(mu-SMe2)(2)], 1, in a 2:1 ratio gave a mixture of [PtMe2(dpppa)] and [Pt2Me4(mu-dpppa)(2)], both of which contain Pt center dot center dot center dot H-N hydrogen bonds. However, reaction in a 1:1 ratio gave a remarkable tetraplatinum complex, [Pt4Me6(mu-dpppa-H)(2)], which is shown to contain two Pt-Pt donor-acceptor bonds and in which one arm of the dpppa ligand has been cyclometalated. The reaction of [PtCl2(dpppa)] with silver trifluoroacetate, to abstract chloride, and triethylamine as base has given the bis(cyclometalated) complex [Pt(dpppa-2H)], and this has been crystallized in three different forms, in which one or both of the carbonyl groups act as donors to a proton or to silver(I). The complex [Pt(dpppa-2H)]center dot AgO2CCF3 center dot dmso forms a dimer and [Pt(dpppa-2H)]center dot(AgO2CCF3)(2) forms a coordination polymer in the solid state.

First author: Wagler, Joerg, Disilicon Complexes with Two Hexacoordinate Si Atoms: Paddlewheel-Shaped Isomers with (ClN4)Si-Si(S4Cl) and (ClN2S2)Si-Si(S2N2Cl) Skeletons, CHEMISTRY-A EUROPEAN JOURNAL, 19, 14296, (2013)
Abstract: The reaction of 1-methyl-3-trimethylsilylimidazoline-2-thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N,S-bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel-shaped complexes of the type ClSi(-mt)(4)SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN4)SiSi(S4Cl), (ClN3S)SiSi(S3NCl), and (ClN2S2)SiSi(S2N2Cl) skeletons as so-called (4,0), (3,1), and cis-(2,2) paddlewheels) were detected in solution by using (SiNMR)-Si-29 spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X-ray diffraction studies. In accord with time-dependent NMR spectroscopy, computational analyses proved the cis-(2,2) isomer with a (ClN2S2)SiSi(S2N2Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two SiSi-bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms.

First author: Bae, Gyun-Tack, Improved ReaxFF Force Field Parameters for Au-S-C-H Systems, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 10438, (2013)
Abstract: Evaluation and reparameterization of previously reported ReaxFF parameters (Jarvi, T. T.; et al. J. Phys. Chem. A 2011, 115, 10315-10322) is carried out for Au-S-C-H systems. Changes in Au-S and Au-Au bond parameters and S-Au-S angle bending parameters yield improvements for bond bending potential energy surfaces. The new ReaxFF parameters lead to good agreement with density functional theory geometries of small clusters and gold-thiolate nanoparticles. The energies of Au-38(SCH3)(24) clusters are compared, and the new ReaxFF calculations are also in good agreement with PBE calculations for the isomer orderings. In addition, the relative energies of Au-40(SCH3)(24) nanoparticles and Au-thiolate SAMs are calculated using the updated parameters. These new ReaxFF parameters will enable the study of the geometries and reactivity of larger gold-thiolate nanoparticles.

First author: Diaz-Cervantes, Erik, Unraveling the Origin of the Relative Stabilities of Group 14 M2N22+ (M, N = C, Si, Ge, Sn, and Pb) Isomer Clusters, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 10462, (2013)
Abstract: We analyze the molecular structure, relative stability, and aromaticity of the lowest-lying isomers of group 14 M2N22+ (M and N = C, Si, and Ge) clusters. We use the gradient embedded genetic algorithm to make an exhaustive search for all possible isomers. Group 14 M2N22+ clusters are isoelectronic with the previously studied group 13 M2N22- (M and N = B, Al, and Ga) clusters that includes Al-4(2-), the archetypal all-metal aromatic molecule. In the two groups of clusters, the cyclic isomers present both sigma- and pi-aromaticity. However, at variance with group 13 M2N22- clusters, the linear isomer of group 14 M2N22+ is the most stable for two of the clusters (C2Si22+ and C2Ge22+), and it is isoenergetic with the cyclic D-4h isomer in the case of C-4(2+). Energy decomposition analyses of the lowest-lying isomers and the calculated magnetic- and electronic-based aromaticity criteria of the cyclic isomers help to understand the nature of the bonding and the origin of the stability of the global minima. Finally, for completeness, we have also analyzed the structure and stability of the heavier Sn and Pb group 14 M2N22+ analogues.

First author: Gong, Yu, Experimental and Theoretical Studies on the Fragmentation of Gas-Phase Uranyl-, Neptunyl-, and Plutonyl-Diglycolamide Complexes, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 10544, (2013)
Abstract: Fragmentation of actinyl(VI) complexes (UO2)-O-VI(L)(2)(2+), (NpO2)-O-VI(L)(2)(2+), and (PuO2)-O-VI(L)(2)(2+) (L = tetramethyl-3-oxa-glutaramide, TMOGA) produced by electrospray ionization was examined in the gas phase by collision induced dissociation (CID) in a quadrupole ion trap mass spectrometer. Cleavage of the C-O-ether bond was observed for all three complexes, with dominant products being (UO2)-O-VI(L)(L-86)(+) with charge reduction, and NPv102(L)(1–101)2+ and (PuO2)-O-VI(L)(L-101)(2+) with charge conservation. The neptunyl and plutonyl complexes also exhibited substantial L+ loss to give pentavalent complexes (NpO2)-O-V(L)(+) and (PuO2)-O-V(L)(+), whereas the uranyl complex did not, consistent with the comparative An 5f-orbital energies and the An(VI)O(2)(2+)/An(V)O(2)(+) (An = U, Np, Pu) reduction potentials. CID of (NpO2)-O-V(L)(2)(+) and (PuO2)-O-V(L)(2)(+) was dominated by neutral ligand loss to form (NpO2)-O-V(L)(+) and (PuO2)-O-V(L)(+), which hydrated by addition of residual water in the ion trap; (UO2)-O-V(L)(2)(+) was not observed. Theoretical calculations of the structures and bonding of the An(VI)O(2)(L)(2)(2+) complexes using density functional, theory reveal that the metal centers are coordinated by six oxygen atoms from two TMOGA ligands.

First author: Silverstein, Daniel W., Investigation of Linear and Nonlinear Raman Scattering for Isotopologues of Ru(bpy)(3)(2+), JOURNAL OF PHYSICAL CHEMISTRY C, 117, 20855, (2013)
Abstract: Tris(2,2′-bipyridine)ruthenium(II), Rubpy, an important transition metal complex for its robust photochemistry, is studied using simulated resonance Raman scattering (RRS) and resonance hyper-Raman scattering (RHRS) in comparison to measured surface-enhanced Raman scattering (SERS) and surface-enhanced hyper-Raman scattering (SEHRS). Detailed examination of the simulated data shows that many of the observed features in the experiments are captured by the theory. For the metal-to-ligand charge transfer (MLCT) absorption band at 452 nm, it is demonstrated that the shoulder on the absorption band at 425 nm is not a vibronic feature and that the line shape should be considered as coming from two separate MLCT states. We find that good agreement can be obtained by comparing simulated spectra to the SERS and SEHRS spectra on resonance with the absorption band. However, the simulations do not capture the high sensitivity of relative peak intensities Observed during wavelength scanned SERS and SEHRS experiments. This result is interpreted on the basis of discussion of the literature and the approximations made in the vibronic model, where it is concluded that the simulations underestimate interference effects. These results demonstrate the complexity of using theoretical methods for accurately describing the electronic structure of large molecules, and that commonly used exchange-correlation functionals like B3LYP and LC-PBE cannot completely describe all of the vibronic features in the Raman scattering of Rubpy.

First author: Sundararajan, K., Complexes of acetylene-fluoroform: A matrix isolation and computational study, JOURNAL OF MOLECULAR STRUCTURE, 1049, 69, (2013)
Abstract: Hydrogen-bonded complexes of C2H2 and CHF3 have been investigated using matrix isolation infrared spectroscopy and ab initio computations. The complexes were trapped in both solid argon and nitrogen matrices at 12 K. The structure of the complexes and the energies were computed at the B3LYP and MP2 levels of theory using a 6-311++G(d,p) basis set and at the MP2/aug-cc-pvdz level. Our computations indicated two minima for the 1:1 C2H2-CHF3 complex, with the C-H center dot center dot center dot pi complex being the global minimum, where CHF3 is the proton donor. The second minimum corresponded to a relatively less exothermic C-H center dot center dot center dot F complex, in which C2H2 is the proton donor. Experimentally, we observed only the C-H center dot center dot center dot pi complex in our matrix, which was evidenced by the shifts in the vibrational frequencies of the modes involving the C2H2 and CHF3 sub-molecules. The increase in the blue shift of the C-H stretching frequency in going from CHCl3-acetylene complex to CHF3-acetylene complex with corresponding increase in the interaction energy helps to place these two complexes on the left hand end of the qualitative diagram (Fig. 1). We also performed computations to study the higher complexes of C2H2 and CHF3. One minimum was found for the 1:2 C2H2-CHF3 complexes and two minima for the 2:1 C2H2-CHF3 complexes, at all levels of theory. Experimentally we observed the features corresponding to the 1:2 and 2:1 C2H2-CHF3 complexes in the N-2 matrix. The computed vibrational frequencies of C2H2-CHF3 complexes at B3LYP and MP2/6-311++G(d,p) level corroborated well with the experimental frequencies. Interestingly, no experimental evidence for the formation of higher complexes was observed in the Ar matrix.

First author: Randles, Michael D., Syntheses of Pentanuclear Group 6 Iridium Clusters by Core Expansion of Tetranuclear Clusters with Ir(CO)(2)(eta(5)-C5Me4R) (R = H, Me), INORGANIC CHEMISTRY, 52, 11256, (2013)
Abstract: Metal cluster core expansion at tetrahedral group 6-group 9 mixed-metal clusters MIr3(mu-CO)(3)(CO)(8)(eta(5))-L) (M = W, Mo, L = C5H5; M = Mo, L = C5Me5) with the iridium capping reagents Ir(CO)(2)(eta(5))-L’) (L’ = C5Me5, C5Me4H) in refluxing toluene afforded the trigonal-bipyramidal clusters MIr4(mu-CO)(3)(CO)(7)(eta(5))-C5H5)(eta(5))-L’) (M = Mo, L’ = C5Me5, 1a; M = W, L’ = C5Me5, 1b; M = Mo, L’ = C5Me4H, 1c; M = W, L’ = C5Me4H, 1d) and MoIr4(mu(3)-H)(mu-CO)(2)(mu-eta(1):eta(5))-CH2C5Me4)(CO)(7)(eta(5))-C5Me 5) (2). Related reactions with M2Ir2(mu-CO)(3)(CO)7(eta(5))-L)(2) (M = W, Mo, L = C5H5; M = Mo, L = C5Me5) afforded M2Ir3(mu-CO)(3)(CO)(6)(eta(5))-C5H5)(2)(eta(5))-L’) (M = Mo, L’ = C5Me5, 3a; M = W, L’ = C5Me5, 3b; M = Mo, L’ = C5Me4H, 3c; M = W, L’ = C5Me4H, 3d), W2Ir3(mu-CO)(4)(CO)(5)(eta(5))-C5H5)(2)(eta(5))-C5Me4H) (4), and Mo2Ir3(mu-CO)(3)(CO)(6)(eta(5))-C5Me5)(3) (5). Single-crystal X-ray diffraction studies of 1a-1d, 2, 3a-3d, and 4 confirmed their molecular structures, including the mu-eta(1)):eta(5)-CH2C5Me4 ligand at hydrido cluster 2, derived from a C-H bond activation of one of the methyl groups. Density functional theory (DFT) studies were employed to suggest the structure of 5. The redox behavior of the new clusters was examined through cyclic voltammetry; all clusters exhibit oxidation and reduction processes (with respect to the resting state), with the oxidation processes being the more reversible, and increasingly so on decreasing Ir content of the clusters, replacing W by Mo, and increasing alkylation of the cyclopentadienyl ligands. In situ IR and UV-vis-near-IR spectroelectrochemical studies of the reversible oxidation processes in 1a and 3a were undertaken, with the spectra of the former suggesting progression to an all-terminal CO geometry concomitant with the first oxidation and a significant structural change upon the second oxidation step. DFT studies of 1a revealed that its crystallographically-confirmed Mo-equatorial core geometry is essentially isoenergetic with a possible Mo-apical isomer, and identified several bridging CO structures for the charged states.

First author: Dube, Jonathan W., Synthesis of Zwitterionic Triphosphenium Transition Metal Complexes: A Boron Atom Makes The Difference, INORGANIC CHEMISTRY, 52, 11438, (2013)
Abstract: A collection of zwitterionic phosphanide metal carbonyl coordination complexes has been synthesized and fully characterized, representing the first isolated series of metal complexes for the triphosphenium family of compounds. The dicoordinate phosphorus atom of the zwitterion is formally in the +1 oxidation state and can coordinate to one metal, 2M (M = Cr, Mo, W) and 2Fe, or two metals, a Co-2(CO)(6) fragment 4, depending on the starting reagents. All complexes have been isolated in greater than 80% yield, and structures were confirmed crystallographically. Metrical parameters are consistent with 1 being a weak donor and results in long metal phosphorus bonds being observed in all cases. Unique bimetallic structures, 3M (M = Cr, Mo, W), consisting of a M(CO)(5) fragment on phosphorus and a piano-stool M(CO)(3) fragment on a boron phenyl group have been identified in the P-31){H-1} NMR spectra and confirmed using X-ray diffraction studies. Use of the borate backbone in 1, which renders the molecule zwitterionic, proves to be a determining factor in whether these metal complexes will form; the halide salt of a cationic triphosphenium ion, 6[Br], shows no evidence for formation of the analogous metal complexes by P-31){H-1} NMR spectroscopy, and tetraphenylborate salts, 6{BPh4} and 7{BPH4}, produce complexes that are unstable.

First author: Broeckaert, Lies, Reactivity of Dicoordinated Stannylones (Sn-0) versus Stannylenes (Sn-II): An Investigation Using DFT-Based Reactivity Indices, CHEMPHYSCHEM, 14, 3233, (2013)
Abstract: The reactivity of dicoordinated Sn-0 compounds, stannylones, is probed using density functional theory (DFT)-based reactivity indices and compared with the reactivity of dicoordinated Sn-II compounds, stannylenes. For the former compounds, the influence of different types of electron-donating ligands, such as cyclic and acyclic carbenes, stannylenes and phosphines, on the reactivity of the central Sn atom is analyzed in detail. Sn-0 compounds are found to be relatively soft systems with a high nucleophilicity, and the plots of the Fukui function f(-) for an electrophilic attack consistently predict the highest reactivity on the Sn atom. Next, complexes of dicoordinated Sn compounds with different Lewis acids of variable hardness are computed. In a first part, the double-base character of stannylones is demonstrated in interactions with the hardest Lewis acid H+. Both the first and second proton affinities (PAs) are high and are well correlated with the atomic charge on the Sn atom, probing its local hardness. These observations are also in line with electrostatic potential plots that demonstrate that the tin atom in Sn-0 compounds bears a higher negative charge in comparison to Sn-II compounds. Stannylones and stannylenes can be distinguished from each other by the partial charges at Sn and by various reactivity indices. It also becomes clear that there is a smooth transition between the two classes of compounds. We furthermore demonstrate both from DFT-based reactivity indices and from energy decomposition analysis, combined with natural orbitals for chemical valence (EDA-NOCV), that the monocomplexed stannylones are still nucleophilic and as reactive towards a second Lewis acid as towards the first one. The dominating interaction is a strong sigma-type interaction from the Sn atom towards the Lewis acid. The interaction energy is higher for complexes with the cation Ag+ than with the non-charged electrophiles BH3, BF3, and AlCl3.

First author: Malecki, Jan G., Ruthenium(II) complexes with quinoline carboxylate as a co-ligand, POLYHEDRON, 62, 188, (2013)
Abstract: Ruthenium(II) complexes with the general formulas [Ru(H/Cl)(CO)(PPh3)(2)(L)] and cis/trans-[Ru(PPh3)(2)(-L)(2)] (L = isoquinoline-1-carboxylate or quinoline-2-carboxylate) were synthesized and characterized by IR, H-1, C-13 and P-31 NMR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies were completed by quantum chemical calculations, which were used to describe the nature of the interactions between the ligands and the central ion, and the orbital compositions in the frontier electronic structures. Based on a molecular orbital scheme, the calculated results allowed the interpretation of the UV-Vis spectra obtained at an experimental level. The luminescence properties of the complexes were determined.

First author: Alegret, Nuria, Bingel-Hirsch Addition on Non-Isolated-Pentagon-Rule Gd3N@C-2n, (2n=82 and 84) Metallofullerenes: Products under Kinetic Control, JOURNAL OF ORGANIC CHEMISTRY, 78, 9986, (2013)
Abstract: Bingel-Hirsch reactions on, fullerenes take place under kinetic control. We here predict, by means of DFT methodology, the products of the Bingel-Hirsch addition on non-isofated-pentagon-rule (non-IPR) metallofullerenes Gd3N@C-2n (2n = 82, 84), as modeled by closed-shell Y3N@C-2n systems. Adducts on [6,6] B-type bonds placed near the pentalene unit are predicted for the two cages, as found for other non-IPR endohedral fullerenes such as Sc3N@C-68.

First author: Duarte, Helio Anderson, Chemical Speciation of Metal Complexes from Chemical Shift Calculations: The Interaction of 2-Amino-N-hydroxypropanamide with V(V) in Aqueous Solution, JOURNAL OF PHYSICAL CHEMISTRY B,117, 11670, (2013)
Abstract: The chemical speciation of 2-amino-N-hydroxypropanamide (beta-alaninohydroxamic acid, HL) and vanadium (V) in aqueous solution has been investigated through calculations of the thermodynamic properties and the V-51 nuclear magnetic resonance (NMR) chemical shifts of the species formed at equilibrium. The results have been compared directly with the experimental V-51 NMR data The V-51 NMR chemical shifts have been calculated by using a density functional theory (DFT) approach accounting for relativistic corrections and solvent effects. All tautomers of the 1:1 and 1:2 VO2+/beta-ala complexes with different degrees of protonation have been calculated and thermodynamic and structural properties are presented for the most stable species. The system is better modeled as tautomeric equilibria, and species lying down in the range of 10 kcal.mol(-1) cannot be neglected at the BP/TZ2P/COSMO approach. In fact, the metal complex speciation in aqueous solution should not be investigated based solely on the thermodynamic analysis, but together with spectroscopic calculations such as NMR

First author: Stein, Matthias, Microbial hydrogen splitting in the presence of oxygen, BIOCHEMICAL SOCIETY TRANSACTIONS, 41, 1317, (2013)
Abstract: The origin of the tolerance of a subclass of [NiFe]-hydrogenases to the presence of oxygen was unclear for a long time. Recent spectroscopic studies showed a conserved active site between oxygen-sensitive and oxygen-tolerant hydrogenases, and modifications in the vicinity of the active site in the large subunit could be excluded as the origin of catalytic activity even in the presence of molecular oxygen. A combination of bioinformatics and protein structural modelling revealed an unusual co-ordination motif in the vicinity of the proximal Fe-S cluster in the small subunit. Mutational experiments confirmed the relevance of two additional cysteine residues for the oxygen-tolerance. This new binding motif can be used to classify sequences from [NiFe]-hydrogenases according to their potential oxygen-tolerance. The X-ray structural analysis of the reduced form of the enzyme displayed a new type of [4Fe-3S] cluster co-ordinated by six surrounding cysteine residues in a distorted cubanoid geometry. The unusual electronic structure of the proximal Fe-S cluster can be analysed using the broken-symmetry approach and gave results in agreement with experimental Mossbauer studies. An electronic effect of the proximal Fe-S cluster on the remote active site can be detected and quantified. In the oxygen-tolerant hydrogenases, the hydride occupies an asymmetric binding position in the Ni-C state. This may rationalize the more facile activation and catalytic turnover in this subclass of enzymes.

First author: Su, Jing, A Joint Photoelectron Spectroscopy and Theoretical Study on the Electronic Structure of UCl5- and UCl5, CHEMISTRY-AN ASIAN JOURNAL, 8, 2489, (2013)
Abstract: We report a combined photoelectron spectroscopic and relativistic quantum chemistry study on gaseous UCl5- and UCl5. The UCl5- anion is produced using electrospray ionization and found to be highly electronically stable with an adiabatic electron binding energy of 4.76 +/- 0.03eV, which also represents the electron affinity of the neutral UCl5 molecule. Theoretical investigations reveal that the ground state of UCl5- has an open shell with two unpaired electrons occupying two primarily U 5f(z3) and 5f(xyz) based molecular orbitals. The structures of both UCl5- and UCl5 are theoretically optimized and confirmed to have C-4v symmetry. The computational results are in good agreement with the photoelectron spectra, providing insights into the electronic structures and valence molecular orbitals of UCl5- and UCl5. We also performed systematic theoretical studies on all the uranium pentahalide complexes UX5- (X=F, Cl, Br, I). Chemical bonding analyses indicate that the UX interactions in UX5- are dominated by ionic bonding, with increasing covalent contributions for the heavier halogen complexes.

First author: Sheikhshoaie, Iran, Quantum chemical calculations and X-ray crystallographic studies of cis-dioxomolybdenum(VI) Schiff base complex, ARABIAN JOURNAL OF CHEMISTRY, 6, 407, (2013)
Abstract: Treatment of the Schiff base 2-((E)-(2-hydroxy propylimino)methyl)phenol with MoO2(acac)(2) in dry methanol gave the mononuclear complex (methanol{6-[(2-oxidopropyl)iminometh-yl]phenolato}dioxidomolybdenum(VI) , which was characterized by X-ray crystal analysis, and it has monoclinic space group p2(1)/c, and a = 10.330(17) angstrom, b = 9.397(15) angstrom, c = 13.695(2) angstrom, V = 1252.1(3) angstrom(3), and Z = 4. B3LYP theoretical method with DZP basis sets calculations nicely reproduces the X-ray experimental geometry, molecular orbital levels and the other structural properties for this complex.

First author: Zheng, Wei, The dynamic motion of a M (M = Ca, Yb) atom inside the C-74 (D (3h)) cage: a relativistic DFT study, JOURNAL OF MOLECULAR MODELING, 19, 4521, (2013)
Abstract: The interaction between M (M = Ca, Yb) atom and C-74 (D (3h)) has been investigated by all electron relativistic density function theory. With the aid of the representative patch of C-74 (D (3h)), we studied the interaction between C-74 (D (3h)) and M (M = Ca, Yb) atom and obtained the interaction potential. Optimized structures show that there are three equivalent stable isomers and there is one transition state between every two stable isomers. According to the minimum energy pathway, the possible movement trajectory of M (M = Ca, Yb) atom in the C-74 (D (3h)) cage is explored. The calculated energy barrier for Yb atoms moving from the stable isomer to the transition state is 10.4 kcal mol(-1) and the energy barrier for Ca atoms is 6.1 kcal mol(-1). The calculated NMR spectra of M@C-74 (M = Ca, Yb) are in good agreement with the experimental data. There are nine lines in the spectra: one 1/6 intensity signal, four half intensity signals and four full intensity signals.

First author: Zamani, Mehdi, Quantitative analysis of intermolecular forces for hydrogen bond driven self-assembly of resorcinol and bis(pyridine) substituted ethylene cocrystals, before and after [2+2] dimerization, STRUCTURAL CHEMISTRY, 24, 1597, (2013)
Abstract: The long-range and dispersion corrected density functional theory (DFT + Disp), and Moller-Plesset second-order perturbation theory (MP2) were used for describing the intermolecular interactions between hydrogen bond driven self-assembly of 2(5-CN-res) aEuro broken vertical bar 2(4,4′-bpe) and 2(4,6-diCl-res) aEuro broken vertical bar 2(4,4′-bpe) cocrystals [where 5-CN-res = 5-cyanoresorcinol, 4,6-diCl-res = 4,6-dichlororesorcinol, and 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene], before and after [2 + 2] dimerization to 2(5-CN-res) aEuro broken vertical bar (4,4′-tpcb) and 2(4,6-diCl-res) aEuro broken vertical bar (4,4′-tpcb), respectively [where 4,4′-tpcb = 1,2,3,4-tetra(4-pyridyl)cyclobutane]. The nature and strength of intermolecular forces were studied using the absolutely localized molecular orbitals energy decomposition analysis, and the plot of reduced density gradient versus the electron density multiplied by the sign of the second Hessian eigenvalue [sign(lambda(2))rho]. The results show that the interaction of 2(4,4′-bpe) is basically dispersive nature, while all of the electrostatic, dispersion, polarization and charge-transfer interactions are largely contributed to the interaction energy of 2(4,4′-bpe) with 5-CN-res and 4,6-diCl-res molecules. The total interaction energy of complexes before dimerization is greater than that after dimerization. Since the contribution of polarization and charge-transfer interactions after dimerization are nearly unchanged, the main difference in the interaction energy of complexes is due to the weaker contribution of van der Waals and electrostatic forces in the products.

First author: Sherman, David M., Equilibrium isotopic fractionation of copper during oxidation/reduction, aqueous complexation and ore-forming processes: Predictions from hybrid density functional theory, GEOCHIMICA ET COSMOCHIMICA ACTA, 118, 85, (2013)
Abstract: Copper exists as two isotopes: Cu-65 (similar to 30.85%) and Cu-63 (similar to 69.15%). The isotopic composition of copper in secondary minerals, surface waters and oxic groundwaters is 1-12 parts per thousand heavier than that of copper in primary sulfides. Changes in oxidation state and complexation should yield substantial isotopic fractionation between copper species but it is unclear to what extent the observed Cu isotopic variations reflect equilibrium fractionation. Here, I calculate the reduced partition function ratios for chalcopyrite (CuFeS2), cuprite (Cu2O), tenorite (CuO) and aqueous Cu+, Cu+2 complexes using periodic and molecular hybrid density functional theory to predict the equilibrium isotopic fractionation of Cu resulting from oxidation of Cu+ to Cu+2 and by complexation of dissolved Cu. Among the various copper(II)complexes in aqueous environments, there is a significant (1.3 parts per thousand) range in the reduced partition function ratios. Oxidation and congruent dissolution of chalcopyrite (CuFeS2) to dissolved Cu+2 (as Cu(H2O)(5)(+2)) yields (65-63)delta(Cu+2-CuFeS2) = 3.1 parts per thousand at 25 degrees C; however, chalcopyrite oxidation/dissolution is incongruent so that the observed isotopic fractionation will be less. Secondary precipitation of cuprite (Cu2O) would yield further enrichment of dissolved Cu-65 since (65-63)(delta)(Cu+2-Cu2O) is 1.2 parts per thousand at 25 degrees C. However, precipitation of tenorite (CuO) will favor the heavy isotope by +1.0 parts per thousand making dissolved Cu isotopically lighter. These are upper-limit estimates for equilibrium fractionation. Therefore, the extremely large (9 parts per thousand) fractionations between dissolved Cu+2 (or Cu+2 minerals) and primary Cu+ sulfides observed in supergene environments must reflect Rayleigh (open-system) or kinetic fractionation. Finally the previously proposed (Asael et al., 2009) use of delta Cu-65 in chalcopyrite to estimate the oxidation state of fluids that transported Cu in stratiform sediment-hosted copper deposits is refined.

First author: Paul, Satadal, Concurrent loss of aromaticity and onset of superexchange in Mg3Na2 with an increasing Na-Mg-3 distance, THEORETICAL CHEMISTRY ACCOUNTS, 132, 85, (2013)
Abstract: Gradual migration of Na+ from Mg-3(2-) brings about fascinating change in aromatic and magnetic behavior of inorganic Mg3Na2 cluster, which is addressed at the B3LYP and QCISD levels. During this process, Na+ takes away the electron density from Mg-3(2-) causing a net decrease in aromaticity. A tug-of-war between the Pauli repulsion and the aromaticity is shown to be responsible for the observed stability and aromaticity trends in singlet and triplet states. Implications of a spin crossover vis-a-vis a possible superexchange are also explored.

First author: Dar, Amna, Electronic structure analysis of rare earth ions Ce and Nd doped gallium nitride, JOURNAL OF APPLIED PHYSICS, 114, 85, (2013)
Abstract: First principle calculations on electronic structure of Rare Earth ions Ce and Nd doped GaN are presented. Band gap narrowing, optical transitions, and hybridization of impurity states with the host are discussed. The dopants introduced 4f states in the band gap of the doped material in such a way that REGa isoelectronic traps facilitate the optical transitions in RE:GaN. The observed formation of intermediate bands and impurity levels in band gap of host material predicted it to be excellent candidate for the future solar cell generation and other optoelectronic devices.

First author: Orian, Laura, In Silico Design of Heteroaromatic Half-Sandwich Rh-I Catalysts for Acetylene [2+2+2] Cyclotrimerization: Evidence of a Reverse Indenyl Effect, CHEMISTRY-A EUROPEAN JOURNAL, 19, 13337, (2013)
Abstract: A mechanistic density functional theory study of acetylene [2+2+2] cyclotrimerization to benzene catalyzed by Rh-I half metallocenes is presented. The catalyst fragment contains a heteroaromatic ligand, that is, the 1,2-azaborolyl (Ab) or the 3a,7a-azaborindenyl (Abi) anions, which are isostructural and isoelectronic to the hydrocarbon cyclopentadienyl (Cp) and indenyl (Ind) anions, respectively, but differ from the last ones on having two adjacent carbon atoms replaced with a boron and a nitrogen atom. The better performance of either the classic hydrocarbon or the heteroaromatic catalysts is found to depend on the different mechanistic paths that can be envisioned for the process. The present analyses uncover and explain general structure-reactivity relationships that may serve as rational design principles. In particular, we provide evidence of a reverse indenyl effect.

First author: Chulhai, Dhabih V., Determining Molecular Orientation With Surface-Enhanced Raman Scattering Using Inhomogenous Electric Fields, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 19622, (2013)
Abstract: The inhomogenous electric field near the metal surface of plasmonic nanoparticles allows molecular orientation to be determined from surface-enhanced Raman scattering (SERS). We illustrate this by simulating the effects of the field-gradient on the SERS spectrum of benzene and pyridine. To do this, we present an origin-independent formalism describing the effects of the local electric-field gradient in SERS. Using this formalism, we found that the field-gradient led to observation of Raman-inactive modes in benzene and allowed for extraction of orientation information from the SERS spectra of both benzene and pyridine. It was also observed that the SERS electromagnetic enhancement factor, when considering field-gradient effects, depends on the field-gradient magnitudes and is only approximately described by |E|(4) for certain modes. The field-gradient mechanism may also lead to a weakening of intensities as compared to a homogeneous local field. Thus, inclusion of field-gradient effects are crucial in understanding relative intensity changes in SERS.

First author: van der Eide, Edwin F., Isolation of Two Agostic Isomers of an Organometallic Cation: Different Structures and Colors, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 10190, (2013)
Abstract: The inhomogenous electric field near the metal surface of plasmonic nanoparticles allows molecular orientation to be determined from surface-enhanced Raman scattering (SERS). We illustrate this by simulating the effects of the field-gradient on the SERS spectrum of benzene and pyridine. To do this, we present an origin-independent formalism describing the effects of the local electric-field gradient in SERS. Using this formalism, we found that the field-gradient led to observation of Raman-inactive modes in benzene and allowed for extraction of orientation information from the SERS spectra of both benzene and pyridine. It was also observed that the SERS electromagnetic enhancement factor, when considering field-gradient effects, depends on the field-gradient magnitudes and is only approximately described by |E|(4) for certain modes. The field-gradient mechanism may also lead to a weakening of intensities as compared to a homogeneous local field. Thus, inclusion of field-gradient effects are crucial in understanding relative intensity changes in SERS.

First author: Burgun, Alexandre, Straightforward Access to Tetrametallic Complexes with a Square Array by Oxidative Dimerization of Organometallic Wires, ORGANOMETALLICS, 32, 5015, (2013)
Abstract: The bimetallic ruthenium complex {Cp(dppe)Ru}(2)(mu-C CC CC C) (3; Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane) has been prepared and the molecular structure determined. The cyclic voltammogram of 3 is characterized by three reversible one-electron events with a large potential difference between the two first waves (Delta E degrees = 0.44 V), indicating the large thermodynamic stability of the MV (mixed-valence) 3(PF6), which can be considered as a class III MV complex. The complex 3(PF6) was quantitatively prepared by treatment of 3 with 1 equiv of [FeCp2](PF6) at -78 degrees C and characterized by EPR spectroscopy. Above -10 degrees C, solutions of 3(PF6) provide the asymmetric tetranuclear complex {cyclo-C([Ru])C(CCCC[Ru])C(CC[Ru])C-(CC[Ru])}(PF6)(2) (4(PF6)(2).; [Ru] = Cp(dppe)Ru) which was formed regiospecifically and isolated in 92% yield. Thus, despite the thermodynamic stability of the monocation radical 3(PF6) as evidenced by the electrochemical data, and the extensively delocalized electronic structure, a slow dimerization reaction takes place, affording a stable, tetranuclear complex. The new compound was characterized by a single-crystal X-ray diffraction study, cyclic voltammetry, and multinuclear NMR, IR, UV-vis, and near-IR spectroscopy, and the data were analyzed with the support of quantum chemical investigations at the DFT level of theory. The regiospecificity of the dimerization reaction is controlled by a balance of steric and electronic factors, which favors intermolecular (C-alpha + C-gamma) radical coupling.

First author: Dai, Wei, Synthesis and Properties of NHC-Supported Palladium(I) Dimers with Bridging Allyl, Cyclopentadienyl, and Indenyl Ligands, ORGANOMETALLICS, 32, 5114, (2013)
Abstract: The synthesis of a family of new Pd(I) dimers, (mu-All)(mu-Cp){Pd(IPr)}(2) (All = C3H5, Cp = C5H5, IPr = 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-yli-dene), (mu-All)(mu-Ind){Pd(IPr)}(2) (Ind = C7H9), (mu-Cp)(mu-Cp){Pd(IPr)}(2), (mu-Cp)(mu-Ind){Pd(IPr)}(2), and (mu-Ind)(mu-Ind){Pd(IPr)}(2), which contain a combination of bridging ally!, Cp, and indenyl ligands and are all supported by IPr as the ancillary ligand, is reported. All of these compounds are thermally stable at room temperature, and the solid-state geometries, electronic structures, reactivity, and redox chemistry of these new compounds have been compared with those of the dimer (mu-All)(2){Pd(IPr)}(2), which was previously reported. This work provides further evidence that bridging allyl, Cp, and indenyl ligands bind in a similar manner to Pd(I). However, it is demonstrated that there are notable differences between the IPr-supported species and related Pd(I) diners with triethylphosphine ancillary ligands, which have been previously described.

First author: Waters, Jordan B., Group 12 Metal Complexes of N-Heterocyclic Ditopic Carbanionic Carbenes,ORGANOMETALLICS, 32, 5190, (2013)
Abstract: Reaction of the N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) with M(mes)(2) (M = Zn, Cd) in diethyl ether afforded the Lewis acid base adducts [M(IPr)(mes)(2)] (M = Zn (1), Cd (2)) in quantitative yields. An analogous reaction between Hg(mes)(2) and IPr failed to form the desired 1:1 adduct, [Hg(IPr)-(mes)(2)], as evidenced by NMR spectroscopy. Reduction of 1 and 2 with KC8 afforded K+ salts of the anionic complexes [{1:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}(2)M(mes)](-) (M = Zn (3), Cd (4)). By contrast, reduction of a THF solution of a mixture of Hg(mes)(2) and IPr gave rise to the homoleptic anionic species [{:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}(3)Hg](-) (5). Species 3-5 display abnormally bonded anionic N-heterocyclic “dicarbene” ligands (or ditopic carbanionic carbenes) in which IPr has been deprotonated at the C4/C5 position. The vacant C2 atoms retain carbenic character, allowing for further coordination to Lewis acids. This was demonstrated by reaction of 3 with H3B:SMe2, AlEt3, and CO2 (in the presence of the appropriate cation-sequestering agents), which afforded salts of the [{LA:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}(2)Zn(mes)](-) anions (LA = BH3 (6), AlEt3 (7), and CO2 (8)).

First author: Alperovich, Igor, Electronic Structure Assessment: Combined Density Functional Theory Calculations and Ru L-2,L-3-Edge X-ray Absorption Near-Edge Spectroscopy of Water Oxidation Catalyst, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 18994, (2013)
Abstract: Density functional theory (DFT) is now widely used for analysis of the electronic structure and reactivities of transition metal complexes. However, large variability in how well different combinations of exchange-correlation potentials/basis sets reproduce real molecular geometries and electronic configurations remains a problem. Experimental X-ray absorption near-edge structure (XANES) spectra directly reflect the electronic structure of transition metal complexes. Combined analysis of theoretical calculations and experimental data is highly beneficial for DFT validation as well as for understanding limitations of the DFT. Ruthenium-based molecular water oxidation catalyst cis,cis-[(bbpy)(2)(H2O)(RuORuO)-O-III-O-IV(OH)(bpy)(2)](4+) is a complex coordination compound with two Ru centers in different oxidation states bound by mu-oxo bridge. Multiple DFT calculations of this catalyst in different oxidation states have been reported previously but it was never clear whether DFT is truly capable of describing its. geometry and electronic structure. We tested a variety of DFT potentials with two relativistic models for electronic structure calculations and simulated experimental Ru L-2,L-3-edges ?CANES spectra. We found that the local density approximation (LDA) exchange-correlation potential reproduces the experimental geometry and ?CANES spectra, while more advanced potentials fail. We also report combined DFT calculations/Ru L2,3-edges ?CANES spectra for three protonation forms: cis,cis-[(bpy)(2)(H2O)(RuORuO)-O-III-O-IV(OH)(H2O)(bpy)(2)](5+), cis,cis-[(bpy)(2)(H2O)(RuORuO)-O-III-O-IV(OH)(bpy)(2)](4+), and cis,cis-[(bpy)(2)(OH)(RuORuO)-O-III-O-IV(OH)(bpy)(2)](3+). We found that selected DFT technique captures well small modifications of the electronic structure caused by changes in the protonation state of the ligand. Small differences in the Ru L-edges}CANES for various protonation states are reflected in the corresponding theoretical spectra. We also observed that overall DFT-based XANES modeling is sensitive to various subtle changes in molecular geometries of Ru complex.

First author: Kobylianskii, Ilia J., Co-C Bond Energies in Adenosylcobinamide and Methylcobinamide in the Gas Phase and in Silico, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 13648, (2013)
Abstract: Essential to biological activity of adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl) is the Co-C bond cleavage step. Hence, we report an accurate determination of the homolytic gas-phase Co-C bond dissociation energies in the related adenosyl- and methylcobinamides (41.5 +/- 1.2 and 44.6 +/- 0.8 kcal/mol, respectively) utilizing an energy-resolved threshold collision-induced dissociation technique. This approach allows for benchmarking of electronic structure methods separate from (often ill-defined) solvent effects. Adequacy of various density functional theory methods has been tested with respect to the experimentally obtained values.

First author: Wach, Amanda, Determination of the Structures of Molecularly Imprinted Polymers and Xerogels Using an Automated Stochastic Approach, ANALYTICAL CHEMISTRY, 85, 8577, (2013)
Abstract: An automated stochastic docking program with a graphical user interface, RANDOMDOCK (RD), has been developed to aid the development of molecularly imprinted polymers and xerogels. RD supports computations with ab initio and semiempirical quantum chemistry programs. The RD algorithms have been tested by searching for the most stable geometries of a varying number of methacrylic acid molecules interacting with nicotinamide. The optimal structures found are either as stable or more stable than those previously proposed for this molecularly imprinted polymer, illustrating that RD is capable of identifying the lowest-energy structures out of a potentially vast number of possible configurations. RD was subsequently applied to determine the most favorable binding sites between silane molecules and tetracycline (TC) as well as TC analogues. Hydrogen bonding between the templates and a silane is an important determinant of stability. Dispersion interactions are also sizable, sometimes dominant, especially between the largest slime and TC analogues not possessing a site readily available for hydrogen bonding. We highlight the importance of exploring the full intermolecular potential energy landscape when studying systems which may not afford highly specific interactions.

First author: Wang, Xuefeng, Infrared Spectra of H2ThS and H2US in Noble Gas Matrixes: Enhanced H-An-S Covalent Bonding, INORGANIC CHEMISTRY, 52, 10275, (2013)
Abstract: Laser-ablated thorium and uranium atoms have been co-deposited at 4 K with hydrogen sulfide in excess noble gas matrixes. The major dihydride sulfide reaction products were observed for each actinide and identified on the basis of S-34 and D isotopic substitution. These assignments were confirmed by frequency and structure calculations using density functional theory with the B3LYP and PW91 exchange-correlation functionals and the CCSD(T) method for the pyramidal H2ThS ((1)A’) and H2US ((3)A ”) molecules. The lowest three spin states of triplet H2US are calculated to be within 3 kcal/mol using all three methods, just as in H2UO. The major products are compared with the oxygen analogues H2ThO and H2UO, and the sulfides have 71-85 cm(-1) higher hydrogen-actinide stretching frequencies. The actinide-hydrogen bonding appears to be enhanced in the actinide sulfides through back-bonding of a S 3p electron pair to a vacant 6d orbital, which is delocalized over the H atoms. This unique covalent bond is favored by the inductive effect of the hydride substituents, the pyramidal structures, and the lower electronegativity of sulfur. Sulfur back-bonding gives polarized triple bond character to the US and ThS bonds and enhanced metal hydride bonding in H2ThS and H2US.

First author: Baus, Johannes A., Neutral Six-Coordinate and Cationic Five-Coordinate Silicon(IV) Complexes with Two Bidentate Monoanionic N,S-Pyridine-2-thiolato(-) Ligands, INORGANIC CHEMISTRY, 52, 10664, (2013)
Abstract: A series of neutral six-coordinate silicon(IV) complexes (4-11) with two bidentate monoanionic N,S-pyridine-2-thiolato ligands and two monodentate ligands and R-2 was synthesized (4, RI = R-2 = Cl; 5, RI = Ph, R-2 = Cl; 6, RI = Ph, R-2 = F; 7, RI = Ph, R-2 = Br; 8, R-I = Ph, R-2 = N-3; 9, RI = Ph, R-2 = NCO; 10, RI = Ph, R-2 = NCS; 11, R (I) = Me, R-2 = Cl). In addition, the related ionic compound 12 was synthesized, which contains a cationic five-coordinate silicon(IV) complex with two bidentate monoanionic N,S-pyridine-2-thiolato ligands and one phenyl group (counterion: Compounds 4-12 were characterized by elemental analyses, NMR spectroscopic studies in the solid state and in solution, and crystal structure analyses (except 7). These structural investigations were performed with a special emphasis on the sophisticated stereochemistry of these compounds. These experimental investigations were complemented by computational studies, including bonding analyses based on relativistic density functional theory.

First author: Moreno, Diego, Re-examination of the C6Li6 Structure: To Be, or not To Be Symmetric, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12668, (2013)
Abstract: The potential energy surface of C6Li6 was re-examined and a new non-symmetric global minimum was found. The new structure can be described as three C-2(2-) fragments strongly aggregated through lithium bridges. At high temperatures, fluxionality is perceived instead of dissociation. At 600 and 900K, the BOMD simulations show that the lithium mobility is high, indicating that the cluster behaves in a liquid-like manner (BOMD=Born-Oppenheimer molecular dynamics).

First author: Demont, Antoine, Unprecedented Electron-Poor Octahedral Ta-6 Clusters in a Solid-State Compound: Synthesis, Characterisations and Theoretical Investigations of Cs2BaTa6Br15O3, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12711, (2013)
Abstract: The crystal structure of Cs2BaTa6Br15O3 has been elucidated by using synchrotron X-ray powder diffraction and absorption experiments. It is built from edge-bridged octahedral [((Ta6Br9O3i)-O-i)Br-6(a)](4-) cluster units with a singular poor metallic electron (ME) count equal to thirteen. This leads to a paramagnetic behaviour related to one unpaired electron. The arrangement of the Ta-6 clusters is similar to that of Cs2LaTa6Br15O3 exhibiting 14-MEs per [((Ta6Br9O3i)-O-i)Br-6(a)](5-) motif. The poorer electron-count cluster presents longer metal-metal distances as foreseen according to the electronic structure of edge-bridged hexanuclear cluster. Density functional theory (DFT) calculations on molecular models were used to rationalise the structural properties of 13- and 14-ME clusters. Periodic DFT calculations demonstrate that the electronic structure of these solid-state compounds is related to those of the discrete octahedral units. Oxygen-barium interactions seem to prevent the geometry of the octahedral cluster to strongly distort, allowing stabilisation of this unprecedented electron-poor Ta-6 cluster in the solid state.

First author: Bernhammer, Jan C., Electronic Structure Trends in N-Heterocyclic Carbenes (NHCs) with Varying Number of Nitrogen Atoms and NHC-Transition-Metal Bond Properties, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12892, (2013)
Abstract: Carbenes derived from five-membered heterocycles with different numbers of nitrogen atoms ranging from two to four lead formally either to normal N-heterocyclic or mesoionic carbenes with, in some cases, the same skeletal structure. The electronic structures of fourteen of these compounds were examined by means of DFT calculations at the B3LYP/aug-cc-pVTZ level. The examined parameters include the energies of the sigma-lone pair at C-carbene and the -HOMO of the protonated form, which are correlated to the first and second proton affinities. The singlet-triplet energy gap was used as a measure of the stability of the N-heterocyclic carbene (NHC) towards dimerisation. Natural population analysis provided insight into the variation of the p population and the natural charge at C-carbene with NHC structure. Additionally, the transition metalNHC bond in L-AuCl and L-TiCl4 and the nature of the orbital interactions between the NHC and the transition-metal fragment were analysed in detail by the extended transition state-natural orbitals for chemical valence (ETS-NOCV) approach at the BP86/TZ2P level. Similarities and differences between the NHCgold and the NHCtitanium bond are discussed, and trends in key bonding properties can be traced back to the variation of the electronic parameters of the NHC.

First author: Tian, Dongxu, A relativistic DFT study on the structure and property of M(M = Ba, Sr) @ C-74 (D-3h),COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1020, 57, (2013)
Abstract: The interaction between M (M = Ba, Sr) and C-74 (D-3h) was investigated by the relativistic DFT. With the representative patch of C-74 (D-3h), all the possible isomers, transition states, and energy barriers were studied. Optimized structures show that there are three equivalent isomers, with Ba or Sr located about 1.7 angstrom off-center. According to the minimum energy pathway, the possible movement trajectory of Ba or Sr in the C-74 (D-3h) cage was predicted. The energy barriers for Ba and Sr hopping from one stable site to another are 8.30 and 7.88 kcal mol(-1), respectively. According to the trajectory, the NMR spectra of M@C-74 (M = Ba, Sr) was predicted. When the Ba or Sr was encapsulated into the C-74 cage, the symmetry of M@C-74 (M = Ba, Sr) changes from D-3h to C-2v, and the blue shift of the Raman vibrational mode within 100-200 cm(-1) of M@C-74 was found.

First author: Pandey, Krishna K., Bonding analysis of the neutral electrophilic phosphinidene complexes of vanadium and niobium [(eta(5)-C5H5)(CO)(3)M(PNR2)] (R = Me, Pr-i, Bu-t): A DFT study, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 740, 135, (2013)
Abstract: Density functional theory (DFT) calculations have been performed on the neutral electrophilic phosphinidene complexes [(eta(5)-C5H5)(CO)(3)M(PNR2)] (M = V, Nb; R = Me, Pr-i, Bu-t) at BP86/TZ2P/ZORA level of theory. The calculated geometry parameters of the complex [(eta(5)-C5H5)(CO)(3)V(PNR2)] are in good agreement with their available experimental values. On the basis of Mayer bond order analysis, the M-P bonds in all the studied complexes are found to be shorter than the M-P single bonds. On going from R = methyl to R = tertiary butyl, the optimized M-P bond distances increase. The observed geometry parameters are well supported by the results of energy decomposition analysis. The M-PNR2 bonds of the niobium complexes are slightly stronger than that of the vanadium complexes due to d-orbital extent. The orbital interactions between metal and PNR2 fragments in all complexes arise mainly from M <- PNR2 sigma-donation; however, the M -> PNR2 pi back-donation also contributes significantly (24.1% -28.5%) to the total orbital contribution. The pi back bonding contribution to the M-PNR2 bonds increases on going from M = V to M = Nb. The pi back bonding increases going from R = Me < iPr < tBu. The sigma-bonding orbitals in all studied complexes are well occupied.

First author: Hofener, Sebastian, Solvatochromic shifts from coupled-cluster theory embedded in density functional theory,JOURNAL OF CHEMICAL PHYSICS, 139, 135, (2013)
Abstract: Building on the framework recently reported for determining general response properties for frozen-density embedding [S. Hofener, A. S. P. Gomes, and L. Visscher, J. Chem. Phys. 136, 044104 (2012)], in this work we report a first implementation of an embedded coupled-cluster in density-functional theory (CC-in-DFT) scheme for electronic excitations, where only the response of the active subsystem is taken into account. The formalism is applied to the calculation of coupled-cluster excitation energies of water and uracil in aqueous solution. We find that the CC-in-DFT results are in good agreement with reference calculations and experimental results. The accuracy of calculations is mainly sensitive to factors influencing the correlation treatment (basis set quality, truncation of the cluster operator) and to the embedding treatment of the ground-state (choice of density functionals). This allows for efficient approximations at the excited state calculation step without compromising the accuracy. This approximate scheme makes it possible to use a first principles approach to investigate environment effects with specific interactions at coupled-cluster level of theory at a cost comparable to that of calculations of the individual subsystems in vacuum.

First author: Lasoroski, Aurelie, Hyperfine interactions in a gadolinium-based MRI contrast agent: High-frequency modulations from ab initio simulations, JOURNAL OF CHEMICAL PHYSICS, 139, 135, (2013)
Abstract: Hyperfine coupling tensors of the water molecule coordinated to the Prohance contrast agent in liquid water were calculated within and beyond the point dipole approximation along an ab initio molecular dynamics trajectory. We observe the non-equivalence at short time scales on structural as well as magnetodynamical properties of inner sphere water protons due to hydrogen bonds formation with the solvent. In addition, the influence of ultrafast internal motions on the anisotropic, dipolar, contribution to hyperfine couplings was probed thanks to a decomposition of its fluctuations in terms of a small set of meaningful collective variables.

First author: Filidou, Vasileia, Probing the C-60 triplet state coupling to nuclear spins inside and out, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 371, 135, (2013)
Abstract: The photoexcitation of functionalized fullerenes to their paramagnetic triplet electronic state can be studied by pulsed electron paramagnetic resonance (EPR) spectroscopy, whereas the interactions of this state with the surrounding nuclear spins can be observed by a related technique: electron nuclear double resonance (ENDOR). In this study, we present EPR and ENDOR studies on a functionalized exohedral fullerene system, dimethyl[9-hydro (C60-Ih)[5,6]fulleren-1(9H)-yl]phosphonate (DMHFP), where the triplet electron spin has been used to hyperpolarize, couple and measure two nuclear spins. We go on to discuss the extension of these methods to study a new class of endohedral fullerenes filled with small molecules, such as H-2@C-60, and we relate the results to density functional calculations.

First author: Rastrelli, Federico, Predicting the paramagnet-enhanced NMR relaxation of H-2 encapsulated in endofullerene nitroxides by density-functional theory calculations, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 371, 135, (2013)
Abstract: We have investigated the structure and nuclear magnetic resonance (NMR) spectroscopic properties of some dihydrogen endofullerene nitroxides by means of density-functional theory (DFT) calculations. Quantum versus classical roto-translational dynamics of H-2 have been characterized and compared. Geometrical parameters and hyperfine couplings calculated by DFT have been input to the Solomon-Bloembergen equations to predict the enhancement of the NMR longitudinal relaxation of H-2 due to coupling with the unpaired electron. Estimating the rotational correlation time via computed molecular volumes leads to a fair agreement with experiment for the simplest derivative; the estimate is considerably improved by recourse to the calculation of the diffusion tensor. For the othermore flexible congeners, the agreement is less good, which may be due to an insufficient sampling of the conformational space. In all cases, relaxation by Fermi contact and Curie mechanisms is predicted to be negligible.

First author: Day, Benjamin M., Normal-to-Abnormal Rearrangement and NHC Activation in Three-Coordinate Iron(II) Carbene Complexes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 13338, (2013)
Abstract: The ‘normal’ three-coordinate iron-NHC complex [(IPr)Fe(N”)(2)] (N ” = N(SiMe3)(2)) rearranges to its abnormal NHC analogue [(aIPr)Fe(N ”)(2)] (6) on heating, providing a rare abnormal iron-aNHC complex, and the first such three-coordinate complex. The tert-butyl-substituted complex [((IBu)-Bu-t)Fe(N”)(2)] (4) undergoes a thermal decomposition that has not previously been observed in iron-NHC chemistry, resulting in the bis(imidazole) complex [((t)BuIm)(2)Fe(N ”)(2)] (7). A mechanism that involves consecutive C-H and C-N activation is proposed to account for the formation of 7.

First author: El-Hamdi, Majid, Analysis of the Relative Stabilities of Ortho, Meta, and Para MClY(XC4H4)(PH3)(2) Heterometallabenzenes (M = Rh, Ir; X = N, P; Y = Cl and M = Ru, Os; X = N, P; Y = CO), ORGANOMETALLICS, 32, 4892, (2013)
Abstract: Density functional theory calculations of the relative stabilities of the ortho, meta, and para MClY(XC4H4)(PH3)(2) heterometallabenzenes (M = Rh, Ir; X = N, P; Y = Cl and M = Ru, Os; X = N, P; Y = CO) have been carried out. The ortho isomer is the most stable for X = P, irrespective of the metal M. For X = N and M = Ir, Rh the meta is the lowest-lying isomer, whereas for M = Ru, Os the ortho and meta isomers are almost degenerate. The electronic structure and chemical bonding have been investigated with energy decomposition analyses of the interaction energy between various fragments, to discuss the origin of the differences observed. The values of the multicenter index of aromaticity and nucleus-independent chemical shifts indicate that the heterometallabenzenes studied should be classified as aromatic or slightly aromatic.

First author: Vila-Nadal, Laia, Polyoxometalate {W18O56XO6} Clusters with Embedded Redox-Active Main-Group Templates as Localized Inner-Cluster Radicals, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 9695, (2013)
Abstract: Density functional theory calculations of the relative stabilities of the ortho, meta, and para MClY(XC4H4)(PH3)(2) heterometallabenzenes (M = Rh, Ir; X = N, P; Y = Cl and M = Ru, Os; X = N, P; Y = CO) have been carried out. The ortho isomer is the most stable for X = P, irrespective of the metal M. For X = N and M = Ir, Rh the meta is the lowest-lying isomer, whereas for M = Ru, Os the ortho and meta isomers are almost degenerate. The electronic structure and chemical bonding have been investigated with energy decomposition analyses of the interaction energy between various fragments, to discuss the origin of the differences observed. The values of the multicenter index of aromaticity and nucleus-independent chemical shifts indicate that the heterometallabenzenes studied should be classified as aromatic or slightly aromatic.

First author: Johnston, Karen E., A Study of Transition-Metal Organometallic Complexes Combining Cl-35 Solid-State NMR Spectroscopy and (35)ClNQR Spectroscopy and First-Principles DFT Calculations, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12396, (2013)
Abstract: A series of transition-metal organometallic complexes with commonly occurring metalchlorine bonding motifs were characterized using Cl-35 solid-state NMR (SSNMR) spectroscopy, Cl-35 nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static Cl-35 ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4T) and high (21.1T) magnetic field strengths using the WURST-QCPMG pulse sequence. The Cl-35 electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. (35)ClNQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of (ClSSNMR)-Cl-35 spectra. (35)ClEFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a (ClSSNMR)-Cl-35 spectrum of a transition-metal species (TiCl4) diluted and supported on non-porous silica is presented. The combination of (ClSSNMR)-Cl-35 and (35)ClNQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms.

First author: Munusamy, Elango, Endohedral and exohedral complexes of substituted benzenes with carbon nanotubes and graphene, JOURNAL OF CHEMICAL PHYSICS, 139, 12396, (2013)
Abstract: Non-covalent complexes of cyclohexane and a series of substituted benzenes with short carbon nanotube (CNT) models are investigated primarily at the B97-D3/TZV(2d,2p) level of theory. Understanding non-covalent interactions of arenes with CNTs is vital for the development of next-generation organic electronic materials and for harnessing CNTs as nano-reactors and vehicles for drug delivery. The interaction of benzene and cyclohexane with the interior and exterior of CNTs depends on the nanotube diameter, particularly for endohedral complexes. Both benzene and cyclohexane interact more strongly with the interior of CNTs than the outside, with benzene exhibiting stronger interactions than cyclohexane for CNTs larger than (8,8). Studies of two benzenes inside of CNTs predict the formation of one-dimensional sandwich and parallel-displaced stacks of benzenes within certain sized CNTs, which could have interesting optoelectronic properties. Concerning the impact of substituents on the interaction of benzene with CNTs, we find that electrostatic interactions do not control substituent effects. That is, the electron-donating or -withdrawing character of the substituents is not correlated with the predicted interaction energies. Moreover, substituent effects are the same for both endohedral and exohedral complexes, despite the different electronic character of the interior and exterior CNT walls. Ultimately, substituent effects in pi-stacking interactions with CNTs and graphene are explained by differences in dispersion interactions between the substituents and CNT walls or graphene surface.

First author: Zeng, Qun, Structures and optical absorptions of PbSe clusters from ab initio calculations, JOURNAL OF CHEMICAL PHYSICS, 139, 12396, (2013)
Abstract: Based on the low-lying structures of (PbSe)(n) (n = 1-10) clusters identified with a first-principles molecular dynamics approach, two growth patterns with distinct structure and energy evolutions were predicted for the even-n and odd-n clusters, respectively. Moreover, the clusters favor a simple cubic and bulk-like growth pattern, unlike the extensively studied II-VI clusters whose structural diversity has been well established. The overlap between 6p of Pb and 4p of Se makes not only the ordered and bulk-like structures but also a stable building block of (PbSe)(4). The high stability of (PbSe)(4) is recognized in terms of its binding energy, HOMO-LUMO gap, appearance in the structures of larger-size clusters, as well as its appearance in the fragmentation products of PbSe clusters. The geometrical and electronic structures of the PbSe clusters were further studied within the density functional theory framework including spin-orbital (SO) coupling. We found that SO coupling does not change the relative stability of the clusters but reduces their binding energy significantly. Particularly, the SO effect has a great impact on the UV-vis spectra of the clusters, which were simulated with time-dependent density functional theory at SO level of zeroth-order regular approximation.

First author: Fernandez, Israel, Reactivity in Nucleophilic Vinylic Substitution (SNV): SNV pi versus SNV sigma Mechanistic Dichotomy, JOURNAL OF ORGANIC CHEMISTRY, 78, 8574, (2013)
Abstract: The intrinsic electronic factors that determine reactivity in prototypical identity nucleophilic vinylic substitution reactions, X- + ViX -> XVi + X- (Vi = vinyl), have been studied by performing quantum chemical calculations (OPBE/6-311++G(d,p)). Of the two limiting reaction types envisaged-the SNV pi. and SNV sigma mechanisms-the former is preferred for most combinations of nucleophiles and substrates, except for the combination of unactivated substrates and poor nucleophiles, as seen for the much studied reactions Cl- + CH2CHCl and Br- + CH2CHBr. It was found that periodic trends for SNV pi are essentially the same as those previously reported for nucleophilic aromatic substitution, SNAr, while intrinsic SNV sigma. nucleophilicity parallels aliphatic S(N)2. It is therefore concluded that SNV reactivity in general can be understood in terms of this mechanistic dichotomy. Furthermore, a few representative reactions were analyzed applying two complementary schemes for energy decomposition analysis.

First author: Liao, Meng-Sheng, Binding of O-2 and NO to Heme in Heme-Nitric Oxide/Oxygen-Binding (H-NOX) Proteins. A Theoretical Study, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 10103, (2013)
Abstract: The binding of O-2 and NO to heme in heme-nitric oxide/oxygen-binding (H-NOX) proteins has been investigated with DFT as well as dispersion-corrected DFT methods. The local protein environment was accounted for by including the six nearest surrounding residues in the studied systems. Attention was also paid to the effects of the protein environment, particularly the distal Tyr140, on the proximal iron-histidine (Fe-His) binding. The Heme-AB (AB = O-2, NO) and Fe-His binding energies in iron porphyrin FeP(His)(AB), myoglobin Mb(AB), H-NOX(AB), and Tyr140 -> Phe mutated H-NOX[Y140F(AB)] were determined for comparison. The calculated stabilization of bound O-2 is even higher in H-NOX than that in a myoglobin (Mb), consistent with the observation that the H-NOX domain of T. tengcongensis has a very high affinity for its oxygen molecule. Among the two different X-ray crystal structures for the Tt H-NOX protein, the calculated results for both AB = O-2 and NO appear to support the crystal structure with the PDB code 1XBN, where the Trp9 and Asn74 residues do not form a hydrogen-bonding network with Tyr140. A hydrogen bond interaction from the polar residue does not have obvious effects on the Fe-His binding strength, but a dispersion contributions to E-bind(Fe-His) may be significant, depending on the crystal structure used. We speculate that the Fe-His binding strength in the deoxy form of a native protein could be an important factor in determining whether the bond of His to Fe is broken or maintained upon binding of NO to Fe.

First author: Han Vinh Huynh, A Pd-II Complex Bearing a Benzimidazole-Derived Ligand with Potentially “Mesoionic and Remote” Character and Its Catalytic Activity, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2013, 4654, (2013)
Abstract: The oxidative addition of palladium(0) to the C2-protected 5-bromo-2-methylbenzimidazolium tetrafluoroborate 3 affords the complex trans-[PdBr(bimy)(PPh3)(2)]BF4 (4), which is the first complex of an unprecedented benzimidazole-derived ligand (bimy) with a potentially mesoionic and remote character. DFT calculations revealed that the bimy ligand bridges the gap between the mesoionic pyrazolin-4-ylidene and the anionic phenyl ligand. A preliminary catalytic study revealed the promising activity of 4 in the Sonogashira coupling of aryl bromides with phenylacetylene.

First author: Su, Jing, Theoretical Studies on the Photoelectron and Absorption Spectra of MnO4- and TcO4-,INORGANIC CHEMISTRY, 52, 9867, (2013)
Abstract: The tetraoxo pertechnetate anion (TcO4-) is of great interest, for nuclear waste management and radiopharmceuticals. To elucidate its electronic structure and to compare with that of its lighter congener MnO4-, the photoelectron and electronic absorption spectra of MnO4- and TcO4- are investigated with density functional theory (DFT) and ab initio wave theory.(WFT). The vertical electron detachment energies (VDEs) of MnO4- obtained with the CR-EOM-CCSD(T) method are, in good agreement with the lowest two experimental VDEs;. the differences are less,, than 0.1 eV, representing a significant improvement over the IP-EOM-CCSD(T) result in the literature. Combining our CCSD(T) and CR-EOM-CCSD(T) results, the first five,VDEs of TeO4- are estimated between 5 and 3 PES spectra expt 10 eV with an estimated accuracy of about +0.2 eV. The vertical excitation Binding Energy (eV) energies are determined by using TD-DFT, CR-EOM-CCSD(T), and AS-PT2 methods. The excitation energies and the assignments of the spectra are analyzed and partly improved. They are compared with reported SAC-CI results and available experimental data. Both dynamic and nondynamic electron correlations are important in the ground and excited states of MnO4- and TcO4-. Nondynamical correlations are particularly relevant in TcO4- for reliable prediction of excitation energies. In TcO4- one Rydberg state interlaces but does not mix with the valence excited states, and it disappears in the condensed phase.

First author: Barry, Brian M., Metal Complexes (M = Zn, Sn, and Pb) of 2-Phosphinobenzenethiolates: Insights into Ligand Folding and Hemilability, INORGANIC CHEMISTRY, 52, 9875, (2013)
Abstract: The divalent metal complexes M-II{(SC6H4-2-PR2)-kappa S-2,P}(2) (3-7, and 9-11) (M= Zn, Sn, or Pb; R = Pr-i, Bu-t, or. Ph); the Sn(W) complexes :Sn{(SC6H4-2-PR2)-kappa(2)-S,P}Ph2Cl (12 and 13) (R = Pr-i and Bu-t), and the ionic Sn(IV) complexes [Sn{(SC6H4-2-PR2)-kappa(2)-S,P}Ph-2[BPh4] (14 and 15) (R = Pr-i and Bu-t) have been prepared and characterized by multinuclear NMR spectroscopy and single. crystal X.-ray diffraction when suitable crystals were afforded The Sn(II) and Pb(II) complexes with R = Ph, Pr-i, or Bu-t (5, 6, 9, and 10) demonstrated ligand “folding” hinging on the P,S vector-a behavior driven by the repulsions of the metal/phosphorus and:metal/sulfur lone Pairs and increased M-S sigma bonding strength. This phenomenon Was examined by density functional theory (DFT) calculations for the compounds in both folded and unfolded states. The Sn(IV) compound 13 (R = Bu-t) crystallized with the phosphine in an axial position of the pseudotrigonal bipyramidal complex and also exhibited hemilability in the Sn P dative bond, while compound 12 (R = Pr-i), interestingly, crystallized with phosphine in an equatorial position and did not show hemilability. Finally, the crystal structure of 15 (R = Bu-t) revealed the presence of an uncommon, 4-coordinate, stable Sn(IV) cation.

First author: Widdifield, Cory M., Multinuclear Solid-State Magnetic Resonance as a Sensitive Probe of Structural Changes upon the Occurrence of Halogen Bonding in Co-crystals, CHEMISTRY-A EUROPEAN JOURNAL, 19, 11949, (2013)
Abstract: Although the understanding of intermolecular interactions, such as hydrogen bonding, is relatively well-developed, many additional weak interactions work both in tandem and competitively to stabilize a given crystal structure. Due to a wide array of potential applications, a substantial effort has been invested in understanding the halogen bond. Here, we explore the utility of multinuclear (C-13, N-14/15, F-19, and I-127) solid-state magnetic resonance experiments in characterizing the electronic and structural changes which take place upon the formation of five halogen-bonded co-crystalline product materials. Single-crystal X-ray diffraction (XRD) structures of three novel co-crystals which exhibit a 1:1 stoichiometry between decamethonium diiodide (i.e., [(CH3)(3)N+(CH2)(10)N+(CH3)(3)][2I(-)]) and different para-dihalogen-substituted benzene moieties (i.e., p-C6X2Y4, X=Br, I; Y=H, F) are presented. C-13 and (NNMR)-N-15 experiments carried out on these and related systems validate sample purity, but also serve as indirect probes of the formation of a halogen bond in the co-crystal complexes in the solid state. Long-range changes in the electronic environment, which manifest through changes in the electric field gradient (EFG) tensor, are quantitatively measured using (NNMR)-N-14 spectroscopy, with a systematic decrease in the N-14 quadrupolar coupling constant (C-Q) observed upon halogen bond formation. Attempts at I-127 solid-state NMR spectroscopy experiments are presented and variable-temperature (FNMR)-F-19 experiments are used to distinguish between dynamic and static disorder in selected product materials, which could not be conclusively established using solely XRD. Quantum chemical calculations using the gauge-including projector augmented-wave (GIPAW) or relativistic zeroth-order regular approximation (ZORA) density functional theory (DFT) approaches complement the experimental NMR measurements and provide theoretical corroboration for the changes in NMR parameters observed upon the formation of a halogen bond.

First author: Srebro, Monika, Computational Analysis of Ti-47/49 NMR Shifts and Electric Field Gradient Tensors of Half-Titanocene Complexes: Structure-Bonding-Property Relationships, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12018, (2013)
Abstract: Metal NMR shielding and electric-field gradient (EFG) tensors are examined by quantum-chemical calculations for a set of 14 titanium(IV) complexes. Benchmarks are performed for titanocene chlorides that have been characterized recently by solid-state NMR experiments, focusing on the dependence of Ti-IV NMR parameters on the computational model in terms of the choice of the density functional, and considering molecular clusters versus infinite-periodic solid. Nearest-neighbor and long-range effects in the solid state are found to influence NMR parameters in systems without spatially extended ligands. Bulky ligands increase the fraction of local structure and bonding information encoded in the EFG tensors by reducing intermolecular interactions. Next, Ti shielding constants and EFG tensors for a variety of olefin (co)polymerization catalysts are analyzed in terms of contributions from localized molecular orbitals representing Lewis bonds and lone pairs. Direct links between the observed theoretical trends and the local bonding environment around the Ti metal center are found. A specific dependence of the Ti EFG tensors on the exact arrangement and type of surrounding bonds is demonstrated, providing a basis for further studies on solid-supported titanium catalytic systems.

First author: Yang, Zhiwei, Mechanistic Study on Ligand-Controlled Cobalt-Catalyzed Regioselectivity-Switchable Hydroarylation of Styrenes, CHEMISTRY-A EUROPEAN JOURNAL, 19, 12093, (2013)
Abstract: Density functional theory (DFT) calculations have been performed to study the mechanism of the recently reported Co-catalyzed ligand-controlled hydroarylation of styrenes as a means of preparing 1,1- or 1,2-diarylalkanes. The present study corroborates the previously proposed three-step mechanism, comprising CH activation (CH oxidative addition), styrene insertion, and reductive elimination. In the CH activation and reductive elimination steps, our calculations suggest that styrene does not coordinate to the Co center. In the insertion step, styrene is inserted into the CoH bond rather than the CoC bond. Furthermore, the rate- and regiodetermining step is found to be CC reductive elimination. It is significant that the regioselectivity observed experimentally has been successfully reproduced by our calculations. More importantly, in analyzing the origin of the ligand-controlled regioselectivity, we have found that the steric effects of different ligands mainly determine the observed regioselectivity. Both the shape (i.e., umbrella-up or umbrella-down) and bulkiness of the ligand contribute to the steric effect.

First author: Badu, Shyam, Quadrupolar NMR Spin Relaxation Calculated Using Ab Initio Molecular Dynamics: Group 1 and Group 17 Ions in Aqueous Solution, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 4074, (2013)
Abstract: Electric field gradient (EFG) fluctuations for the monoatomic ions Li-7(+), Na-23(+), Cl-35(-), Br-81(-), and I-127(-) in aqueous solution are studied using Car-Parrinello ab initio molecular dynamics (aiMD) simulations based on density functional theory. EFG calculations are typically performed with 1024 ion-solvent configurations from the aiMD simulation, using the Zeroth Order Regular Approximation (ZORA) relativistic Hamiltonian. Autocorrelation functions for the spherical EFG tensor elements are computed, transformed into the corresponding spectral densities (under the extreme narrowing condition), and subsequently converted into NMR quadrupolar relaxation rates for the ions. The relaxation rates are compared with experimental data. The order of magnitude is correctly predicted by the simulations. The computational protocol is tested in detail for Br-81(-).

First author: Baldes, Alexander, Efficient two-component self-consistent field procedures and gradients: implementation in TURBOMOLE and application to Au-20(-), MOLECULAR PHYSICS, 111, 2617, (2013)
Abstract: The implementation of gradients of two-component density functional (DFT) and hybrid-DFT energies is presented as well as several improvements with respect to our previous version in the self-consistent field (SCF) procedure: Calculation of the Hartree-Fock (HF) exchange with four-centre integrals, use of difference density formalism and partial exploitation of symmetry. Efficiency is demonstrated by comparison to recently reported data and by calculation of energy and gradient of Au-147. As an example of use, structure parameters of Au- (20) were optimised and subsequently vibration frequencies were calculated numerically from the analytical gradients at two-component level. For this example, spin-orbit coupling leads to higher degeneracy of vibrational levels by lifting degeneracy of electronic levels, as the latter prevents Jahn-Teller distortion.

First author: Thi Ai Nhung Nguyen, Structure and bonding of tetrylone complexes [(CO)(4)W{E(PPh3)(2)}] (E = C-Pb),MOLECULAR PHYSICS, 111, 2640, (2013)
Abstract: Quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+) have been carried out for transition metal complexes of carbodiphosphorane analogues E(PPh3)(2) with E = C-Pb. The nature of the W(CO)(4)-E(PPh3) bonds was analysed with charge and energy decomposition methods. The equilibrium structures of the tetrylone complexes W(CO)(4)-E(PPh3)(2) possess for E = C, Si, Ge a trigonal bipyramidal coordination at tungsten with the tetrylone ligand occupying an equatorial position. The heavier homologues with E = Sn, Pb exhibit a square pyramidal coordination at tungsten where the tetrylone ligand is at a basal position, while one phenyl group is found trans to the apical CO group which yields a hexacoordinated tungsten complex. The bond dissociation energies for the W(CO)(4)-E(PPh3)(2) bonds are higher than for the W(CO)(5)-E(PPh3)(2) homologues. The bonding analyses of the complexes show that the W-E bonds have a significant contribution from (CO)(4)WE(PPh3)(2)-donation. All complexes W(CO)(4)-E(PPh3)(2) are suitable targets for synthesis.

First author: Hauf, Christoph, Remanent Si-H Interactions in Late Transition Metal Silane Complexes, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 639, 1996, (2013)
Abstract: In general, it is assumed that the reaction between silanes and late transition metal fragments yields silyl hydride species as oxidative addition products. However, the silane complex Ni(iPr(2)Im)(2)(SiHMePh2) (iPr(2)Im = 1, 3-diisopropylimidazolin-2-ylidene) (3a), might represent one of the rare systems where a stable (2)-(Si-H)Ni intermediate of the oxidative addition process has been isolated. Indeed, 3a is characterized by an acute [ang]Si-Ni-H angle of 62.0(2)degrees, a rather short Si-H bond length of 1.992(6) angstrom and displays a silicon-hydride cross peak in Si-H-HMQC 2D-NMR studies. We therefore selected the latter system for a combined experimental and theoretical charge density study to explore the electronic prerequisites which hinder the full completion of the oxidative addition step in transition metal silane complexes and cause the presence of remanent Si-H interactions in these species.

First author: Zhekova, Hristina, Density functional theory studies on the structure and electron distribution in the peroxide intermediate of the catalytic cycle of multicopper oxidases, CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 91, 847, (2013)
Abstract: The peroxide intermediate (PI) is obtained in the first step of the reduction of O-2 by multicopper oxidases. Earlier density functional theory (DFT) studies as well as spectral and structural comparison to a fully oxidized structural analogue of the PI known as the peroxide adduct (PA) reveal that O-2 bridges all three copper atoms of the trinuclear cluster in the PI. This orientation of the oxygen moiety has been discussed as a result of the influence from the second coordination sphere. In the present study, we investigate by DFT and quantum mechanics/molecular mechanics (QM/MM) the potential energy surface (PES) of the PI as a function of the orientation of O-2 within the copper cluster to examine the influence of the second coordination sphere on the structure of the PI. We use the second order spin-flip constricted variational DFT method to probe a possible multideterminantal nature of the PI and to devise a computational strategy for its treatment. Our results suggest that the PI can be approximated to a closed shell singlet. Additionally, for the determination of the oxidation states of the three copper atoms in the PI, the electron redistribution upon the formation of the PI has been investigated with the extended transition state-natural orbitals for chemical valence method. We observe a flat PES on which oxygen can easily rotate between the copper atoms. The fully bridged PI structure emerges in the absence of atoms from the second coordination sphere and has been attributed to the coordination unsaturation of the copper atoms in the cluster. The good Cu-O overlap leads to the participation of all copper atoms in the reduction of O-2.

First author: Conradie, Jeanet, P(OPh)(3) substitution at [Rh(beta-diketonato)(cod)] complexes: The relationship between kinetics and frontier orbitals, INORGANICA CHIMICA ACTA, 406, 211, (2013)
Abstract: The energy of the highest occupied molecular orbital of [Rh(beta-diketonato)(cod)] relates to the experimental second order substitution rate constant (k(2)) for a series of [Rh(beta-diketonato)(cod)] complexes in the [Rh(beta-diketonato)(cod)] + 2P(OPh)(3) -> [Rh(beta-diketonato)(P(OPh)(3))(2)] + cod reaction: E-HOMO (eV) = -0.125 ln k(2) (dm(3) mol(-1) s(-1)) – 3.73. ln k(2) also relates to the sum of the DFT calculated charges (Mulliken, NPA, Hirshfeld, Voronoi and Bader) on the Rh(cod) fragment of [Rh(beta-diketonato)(cod)]. Linear equations obtained for this [Rh(beta-diketonato)(cod)] series of compounds may be used for theoretical estimation of substitution rates for similar complexes.

First author: Celik, Mehmet Ali, Exploiting the Twofold Donor Ability of Carbodiphosphoranes: Theoretical Studies of [(PPh3)(2)C -> EH2](q) (E-q=Be, B+, C2+, N3+, O4+) and Synthesis of the Dication [(Ph3P)(2)C = CH2](2+),CHEMPLUSCHEM, 78, 1024, (2013)
Abstract: Quantum chemical calculations at the BP86/TZVPP//BP86/SVP level of theory have been performed for the isoelectronic series of compounds [(PPh3)(2)CEH2](q) (E-q=Be, B+, C2+, N3+, O4+). The equilibrium geometries and bond dissociation energies were calculated and the nature of the CE bond was investigated with charge and energy decomposition methods. The dication [(PPh3)(2)CCH2](2+) could become isolated as a salt compound with two counter ions [AlBr4](-). The X-ray structure analysis of [(PPh3)(2)CCH2](2+) gave bond lengths and angles that are in good agreement with the calculated data. The geometry optimization of [(PPh3)(2)COH2](4+) gave [(PPh3)(2)COH](3+) as the equilibrium structure. Bonding analysis of [(PPh3)(2)CEH2](q) shows that [(PPh3)(2)CBeH2] and [(PPh3)(2)CBH2](+) possess donor-acceptor bonds in which the sigma and lone-pair electrons of (PPh3)(2)C donate into the vacant orbitals of the acceptor fragment. The multiply charged compounds are better described as substituted olefins [(PPh3)(2)CCH2](2+), [(PPh3)(2)CNH2](3+), and [(PPh3)(2)COH](3+), which possess electron-sharing sigma and bonds that arise from the interaction between the triplet states of [(PPh3)(2)C](2+) and the respective fragment CH2, (NH2)(+), and (OH)(+). The multiply charged cations [(PPh3)(2)CCH2](2+), [(PPh3)(2)CNH2](3+), and [(PPh3)(2)COH](3+) are calculated to be stable toward dissociation.

First author: Shakourian-Fard, Mehdi, Structural and electronic properties of alkyl-trifluoroborate based ionic liquids: A theoretical study, JOURNAL OF FLUORINE CHEMISTRY, 153, 96, (2013)
Abstract: In this study, ionic liquids formed between 1-ethyl-3-methylimidazolium cation ([emim](+)) and alkyltrifluoroborate ([RBF3](-), R = n-CmH2m+1 (m = 1-5)) anions have been investigated theoretically. The interactions between the cation and anions have also been calculated at the MP2/6-311++G(d,p)//B3LYP/6-311++G(d,p) level of theory. The calculated interaction energies were found to decrease in magnitude with the increase of side-chain length in anions. The results of energy decomposition analysis (EDA) show that the interaction of these anions with [emim](+) cation is electrostatic in the nature and the side chain length in the anions has an important effect on the contribution of Delta E-elect elect term. The H-bonds in the most stable ion pairs occur between fluorine atoms of anion and hydrogen atoms of methyl, ethyl groups and the hydrogen atom on the imidazolium ring (C2-H). These H-bonds were also considered by quantum theory of atoms in molecules (QTAIM).

First author: Yang, Shuang-Yang, The influence of molecular solid packings on the photoluminescence and carrier transport properties for two bow-shaped thiophene compounds: a theoretical study, THEORETICAL CHEMISTRY ACCOUNTS, 132, 96, (2013)
Abstract: The quantum mechanical and quantum mechanical/molecular mechanical methods were employed to investigate the photoluminescence and carrier transport properties of two bow-shaped thiophene compounds, whose optimized geometries were proved to have large deviation between the single-molecule and the solid-phase models. The results show that the molecular packings have large influence on the geometrical structures for both systems, but barely affect their energy levels of the frontier molecular orbitals and the reorganization energies, thus indicating little effect on the charge transport properties. While the obvious blue shifts of absorption and emission spectra in solid phase compared with single molecule are considered to relate with the intermolecular interactions, the difference in center thiophene units between two bow-shaped compounds induces the decided differences in optoelectronic properties, especially in carrier transport abilities.

First author: Aviles, R., The spin significance in the capture and activation of N2O by small Rh nanoparticles, JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 376, 22, (2013)
Abstract: This work presents many possible theoretical reaction pathways of N2O reduction to N-2 and O on Rh-n nanoparticles (n = 1-4) using density functional theory (DFT) method and the zero order regular approximation (ZORA), which explicitly considers the scalar relativistic corrections. The Rh spin multiplicity is an essential condition to dissociate N2O, because can promote or inhibit the electron back donation from the metal. Rh activates N2O by exothermic and spontaneous reactions. For each case presented, the optimized geometry adsorption site, reaction energy, spin multiplicity and Voronoi charges are calculated. On a single Rh atom in the ground and low-lying excited states, the N2O is captured only. On the Rh-2 quintet ground state, N2O is also chemisorbed and dissociation occurs for the next two excited states (triplet and septet). In the Rh-3 case, there are N2O adsorption and dissociation for Rh-3 quartet ground state and for most excited states. Several dissociation cases take place when N2O is parallel to the plane and parallel to a Rh-3 bond. On the Rh-4, however, there are two optimal geometries: tetrahedral and square; for both cases there are N2O adsorption and dissociation.

First author: Dorovskikh, S. I., Deposition of Ni thin films from Ni(II) beta-diketonates derivatives with 1,3-diaminopropane,JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 74, 1204, (2013)
Abstract: Two octahedral nickel complexes namely Ni(pda)(hfac)(2) and Ni(pda)(thd)(2) (pda-1,3-diaminopropane, hfac-1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (-), thd-2,2,6,6-tetramethyl-3,5-heptanedionato (-)) were tested in a Metal-Organic Chemical Vapor Deposition (MOCVD) process. Based on density functional theory (DFT) calculations, the thermodynamic stability of molecules in the gas phase was estimated. The intramolecular bond was found in case of complex Ni(pda)(hfac)(2). The different fragmentation mechanisms of complexes in the gas phase were examined by double focusing sector (DFS) mass spectrometry. According to TG/DTA analyses and P/T measurements compounds have good volatility. Deposition conditions resulting in one phase Ni films were established. Films compositions and structures were confirmed by XRD, EXAFS, XPS, and SEM. According to XRD and SEM, the average crystallite sizes and thicknesses of films deposited from Ni(pda)(hfac)(2) were 12-34 nm and 135-320 nm, whereas from Ni(pda)(thd)(2) they were 10-24 nm and 100-380 nm, respectively. The dependences of films thicknesses as a function of substrate temperatures have shown that complex Ni(pda)(hfac)(2) is more stable in the gas phase than Ni(pda)(thd)(2).

First author: Manna, Debashree, Enhancement in the Stability of 36-Atom Fullerene through Encapsulation of a Uranium Atom, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 17859, (2013)
Abstract: With an objective to rationalize the experimentally observed intense U@C-36 peak in the mass spectrum of U@C-2n metallofullerene, structural, stability, and spectroscopic aspects of the uranium doped C-36 fullerene have been studied in a unified and systematic way using density functional theory (DFT) and its time-dependent variant. Relativistic effects have been taken into account within the framework of zeroth-order regular approximation using scalar and spin-orbit-based approaches. Among all of the 15 possible classical isomers reported for the C-36 fullerene cage system, singlet D-2d and triplet D-6h structures are found to be isoenergetic and most stable. Encapsulation of uranium atom into various C-36 cages leads to 15 distinct isomers with considerable energy differences. It has also been shown that this encapsulation process results in significant gain in thermodynamic stability. The most stable U@C-36 isomer is found to be associated with C-6v symmetry and closed-shell electronic configuration, derived from the open-shell D-6h structure of C-36. The next stable isomer is associated with C-s symmetry and obtained from the corresponding singlet D-2d structure of the C-36 cage. Distinct changes have also been found in the calculated vibrational and UV-visible spectra of the U@C-36 cluster as compared to the corresponding bare C-36 cage. All of the calculated quantities reported here suggest that the stability of the U@C-36 duster is high enough for possible formation of cluster-assembled material leading to synthesis of this metallofullerene experimentally.

First author: Shandilya, Ashutosh, A plausible mechanism for the antimalarial activity of artemisinin: A computational approach, SCIENTIFIC REPORTS, 3, 17859, (2013)
Abstract: Artemisinin constitutes the frontline treatment to aid rapid clearance of parasitaemia and quick resolution of malarial symptoms. However, the widespread promiscuity about its mechanism of action is baffling. There is no consensus about the biochemical target of artemisinin but recent studies implicate haem and PfATP6 (a calcium pump). We investigated the role of iron and artemisinin on PfATP6, in search of a plausible mechanism of action, via density functional theory calculations, docking and molecular dynamics simulations. Results suggest that artemisinin gets activated by iron which in turn inhibits PfATP6 by closing the phosphorylation, nucleotide binding and actuator domains leading to loss of function of PfATP6 of the parasite and its death. The mechanism elucidated here should help in the design of novel antimalarials.

First author: Pal, Rajat, Characterization of citrate capped gold nanoparticle-quercetin complex: Experimental and quantum chemical approach, JOURNAL OF MOLECULAR STRUCTURE, 1046, 153, (2013)
Abstract: Quercetin and several other bioflavonoids possess antioxidant property. These biomolecules can reduce the diabetic complications, but metabolize very easily in the body. Nanoparticle-mediated delivery of a flavonoid may further increase its efficacy. Gold nanoparticle is used by different groups as vehicle for drug delivery, as it is least toxic to human body. Prior to search for the enhanced efficacy, the gold nanoparticle-flavonoid complex should be prepared and well characterized. In this article, we report the interaction of gold nanoparticle with quercetin. The interaction is confirmed by different biophysical techniques, such as Scanning Electron Microscope (SEM), Circular Dichroism (CD), Fourier-Transform InfraRed (FT-IR) spectroscopy and Thermal Gravimetric Analysis (TGA) and cross checked by quantum chemical calculations. These studies indicate that gold clusters are covered by citrate groups, which are hydrogen bonded to the quercetin molecules in the complex. We have also provided evidences how capping is important in stabilizing the gold nanoparticle and further enhances its interaction with other molecules, such as drugs. Our finding also suggests that gold nanoparticle-quercetin complex can pass through the membranes of human red blood cells.

First author: El-Hamdi, Majid, Comparison between Alkalimetal and Group 11 Transition Metal Halide and Hydride Tetramers: Molecular Structure and Bonding, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 8026, (2013)
Abstract: A comparison between alkalimetal (M = Li, Na, K, and Rb) and group 11 transition metal (M = Cu, Ag, and Au) (MX)(4) tetramers with X = H, F, Cl, Br, and I has been carried out by means of the Amsterdam Density Functional software using density functional theory at the BP86/QZ4P level of theory and induding relativistic effects through the ZORA approximation. We have obtained that, in the case of alkalimetals, the cubic isomer of T-d geometry is more stable than the ring structure with D-4h symmetry, whereas in the case of group 11 transition metal tetramers, the isomer with D-4h symmetry (or D-2d symmetry) is more stable than the T-d form. To better understand the results obtained we have made energy decomposition analyses of the tetramerization energies. The results show that in alkalimetal halide and hydride tetramers, the cubic geometry is the most stable because the larger Pauli repulsion energies are compensated by the attractive electrostatic and orbital interaction terms. In the case of group 11 transition metal tetramers, the D-4h/D-2d geometry is more stable than the Td one due to the reduction of electrostatic stabilization and the dominant effect of the Pauli repulsion.

First author: Barriuso, M. T., Origin of Small Barriers in Jahn-Teller Systems: Quantifying the Role of 3d-4s Hybridization in the Model System NaCl:Ni+, INORGANIC CHEMISTRY, 52, 9338, (2013)
Abstract: Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn-Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out both periodic and cluster ab initio calculations on the model system NaCl:Ni+. This system is particularly puzzling because, according to experimental data, its barrier is much smaller than that for other d(9) and d(7) ions in similar lattices. All calculations performed on the model system lead, in fact, to values vertical bar B vertical bar <= 160 cm(-1), which are certainly smaller than B = 500 cm(-1) derived for NaCl:M2+ (M = Ag, Rh) or B = 1024 cm(-1) obtained for KCl:Ag2+. As a salient feature, analysis of calculations carried out as a function of the Q(theta) (similar to 3z(2) – r(2)) coordinate unveils the microscopic origin of the barrier. It is quantitatively proven that the elongated geometry observed for NaCl:Ni+ is due to the 3d-4s vibronic admixture, which is slightly larger than the anharmonicity in the e(g) JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system, contrary to cases where the complex formed by d9 or d7 ions is elastically decoupled from the host lattice. Although the magnitude of B for NaCl:Ni+ is particularly small, the tunneling splitting, 3 Gamma, is estimated to be below 9 cm(-1), thus explaining why the coherence is easily destroyed by random strains and thus a static JT effect is observed experimentally. As a main conclusion, the barrier in JT systems cannot be understood neglecting the tiny changes of the electronic density involved in small distortions. The present calculations reasonably explain the experimental g tensor of NaCl:Ni+, pointing out that the d-d transitions in NiCl65- are much smaller than those for CuCl64- and the optical electronegativity of Ni+ is only around 1.

First author: Weinberger, David S., Isolation of Neutral Mono- and Dinuclear Gold Complexes of Cyclic (Alkyl)(amino)carbenes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 8964, (2013)
Abstract: Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn-Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out both periodic and cluster ab initio calculations on the model system NaCl:Ni+. This system is particularly puzzling because, according to experimental data, its barrier is much smaller than that for other d(9) and d(7) ions in similar lattices. All calculations performed on the model system lead, in fact, to values vertical bar B vertical bar <= 160 cm(-1), which are certainly smaller than B = 500 cm(-1) derived for NaCl:M2+ (M = Ag, Rh) or B = 1024 cm(-1) obtained for KCl:Ag2+. As a salient feature, analysis of calculations carried out as a function of the Q(theta) (similar to 3z(2) – r(2)) coordinate unveils the microscopic origin of the barrier. It is quantitatively proven that the elongated geometry observed for NaCl:Ni+ is due to the 3d-4s vibronic admixture, which is slightly larger than the anharmonicity in the e(g) JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system, contrary to cases where the complex formed by d9 or d7 ions is elastically decoupled from the host lattice. Although the magnitude of B for NaCl:Ni+ is particularly small, the tunneling splitting, 3 Gamma, is estimated to be below 9 cm(-1), thus explaining why the coherence is easily destroyed by random strains and thus a static JT effect is observed experimentally. As a main conclusion, the barrier in JT systems cannot be understood neglecting the tiny changes of the electronic density involved in small distortions. The present calculations reasonably explain the experimental g tensor of NaCl:Ni+, pointing out that the d-d transitions in NiCl65- are much smaller than those for CuCl64- and the optical electronegativity of Ni+ is only around 1.

First author: Jamshidi, Zahra, Nature of closed- and open-shell interactions between noble metals and rare gas atoms,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 1981, (2013)
Abstract: Interactions between noble metals and rare gases have become an interesting topic over the last few years. In this work, a computational study of the open-shell (d10s1) and closed-shell (d10s and d10s2) noble metals (M = Cu, Ag, and Au) with three heaviest rare gas atoms (Rg = Kr, Xe, and Rn) has been performed. Potential energy curves based on ab initio [MP2, MP4, QCISD, and CCSD(T)] and DFT functionals (M06-2X and CAM-B3LYP) were obtained for ionic and neutral AuXe complexes. Dissociation energies indicate that neutral metals have the lowest and cationic metals have the highest affinities for interaction with rare gas atoms. For the same metals, there is a continuous increase in dissociation energies (De) from Kr to Rn. The nature of bonding and the trend of De and equilibrium bond lengths (Re) have been interpreted by means of quantum theory of atoms in molecules, natural bond orbital, and energy decomposition analysis.

First author: Duignan, Timothy T., A Continuum Solvent Model of the Multipolar Dispersion Solvation Energy, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 9412, (2013)
Abstract: The dispersion energy is an important contribution to the total solvation energies of ions and neutral molecules. Here, we present a new continuum model calculation of these energies, based on macroscopic quantum electrodynamics. The model uses the frequency dependent multipole polanzabilities of molecules in order to accurately calculate the dispersion interaction of a solute particle with surrounding water molecules. It includes the dipole, quadrupole, and octupole moment contributions. The water is modeled via a bulk dielectric susceptibility with a spherical cavity occupied by the solute. The model invokes damping functions to account for solute-solvent wave function overlap. The assumptions made are very similar to those used in the Born model. This provides consistency and additivity of electrostatic and dispersion (quantum mechanical) interactions. The energy increases in magnitude with cation size, but decreases slightly with size for the highly polarizable anions. The higher order multipole moments are essential, making up more than 50% of the dispersion solvation energy of the fluoride ion. This method provides an accurate and simple way of calculating the notoriously problematic dispersion contribution to the solvation energy. The result establishes the importance of using accurate calculations of the dispersion energy for the modeling of solvation.

First author: Nizovtsev, A. S., Activation of C-H bond in methane by Pd atom from the bonding evolution theory perspective, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 1917, (2013)
Abstract: We report detailed study focused on the electron density redistribution during the simple oxidative addition reaction being the crucial stage of various catalytic processes. The bonding evolution theory based on the electron localization function and Thom’s catastrophe theory shows that activation of methane’s CH bond by Pd atom consist of six elementary steps. The important feature revealed is the pronounced reorganization of Pd’s outer core maxima corresponding to N-shell electrons of metal. Electronic rearrangements identified in this model reaction are likely to be the case in the more complex reactions of the same type involving transition metal compounds and, in principle, can be observed by modern ultrafast spectroscopy and diffraction techniques.

First author: Hayes, Paul G., The Osmium-Silicon Triple Bond: Synthesis, Characterization, and Reactivity of an Osmium Silylyne Complex, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 11780, (2013)
Abstract: The first silylyne complex of a metal beyond group 6, [Cp*((Pr3P)-Pr-i)(H)Os Si(Trip)][HB(C6F5)(3)], was prepared by a new synthetic route involving hydride abstraction from silicon. NMR and DFT computations support the presence of a silylyne ligand, and NBO and ETS-NOCV analysis revealed the nature of this Os-Si interaction as a triple bond consisting of a covalent sigma bond and two strong pi back-donations. The discovery of this complex allowed observations of the first cycloadditions involving a silylyne complex, and terminal alkynes are shown to react via C-H bond additions across the Os Si bond.

First author: Parafiniuk, Monika, Origin of Binding of Ammonia-Borane to Transition-Metal-Based Catalysts: An Insight from the Charge and Energy Decomposition Method ETS-NOCV, ORGANOMETALLICS, 32, 4103, (2013)
Abstract: In the present study the bonding of ammonia borane (AB) to selected transition-metal-based catalysts was studied on the basis of the charge and energy decomposition scheme ETS-NOCV. The following complexes of AB with mono- and bifunctional catalysts were considered: [Cp2Ti](2+) (I), [Pd(allyl)(2,4-hexadiene)](+) (II), [Pd(allyl)](+) (III), Ir(P2CH6)(2)](+) (IV), [Pd(PH3)(2)] (V), [Ni(NHC)(2)] (VI), [(POCOP)-IrH2] (VII), [FeC8N2P2H22] [RuC8N2P2H24] (IX), and [RuC19N5F3BO2H20](+) (X). ETS-NOCV allowed us to conclude that activation of X-H bonds (X = B, N) in AB occurs through different bonding mechanisms, starting from strong bonds based on typical sigma donation from the occupied sigma(B-H) orbital(s) to the metal (AB complexes I-IV) and sigma-back-donation from the metal to the empty sigma*(N-H) orbital of AB (complexes V and VI), going through hydrogen bonding, (AB)NH center dot center dot center dot N (VIII and IX), and ending up on untypical, weak pi center dot center dot center dot HB(AB) and dihydrogen CH center dot center dot center dot HB(AB) interactions (X). Quantitative estimation of sigma/pi charge transfer contributions to the AB-catalyst bond explains the variation in the activation of B-H and N-H connections. Apart from the major components of the AB-catalyst bond, ETS-NOCV also revealed an important role of the secondary interactions XH-pi (X = B, N) and BH center dot center dot center dot HN. The orbital interaction term Delta E-orb associated with the overall charge reorganization upon formation of AB-catalyst bonds, is less important than the electrostatic stabilization Delta E-elstat. Furthermore, electrostatic stabilization appeared to be the major factor that controls the course of the reaction of AB with the catalysts; this term predominantly makes this reaction barrierless. Finally, the molecular electrostatic potential (MEP) contours allowed us to envisage that “electrophilic” catalysts will activate solely B-H bonds of AB, whereas complexes containing nucleophilic sites/areas should bind AB through the NH3 group. Finally, catalysts containing both electrophilic metal centers and, in dose proximity, nucleophilic sites can simultaneously activate both the B-H and N-H bonds of AB.

First author: Chalkley, Matthew J., Synthesis, Electronic Structure, and Reactivity of Palladium(I) Dimers with Bridging Allyl, Cyclopentadienyl, and Indenyl Ligands, ORGANOMETALLICS, 32, 4223, (2013)
Abstract: The synthesis of three new Pd(I) dimers, (mu-All)(mu-Cp){Pd(PEt3)}(2) (All = C3H5, Cp = C5H5), (mu-All)(mu-Ind){Pd(PEt3)}(2) (Ind = C7H9), and (mu-Cp)(mu-Ind){Pd-(PEt3)}(2), which contain a combination of bridging allyl, Cp, or indenyl ligands and are all supported by triethylphosphine as the ancillary ligand, is reported. The solid-state geometries, electronic structures, and reactivity of these new compounds have been compared with those of the dimers (mu-All)(2){Pd-(PEt3)}(2) and (mu-Cp)(2){Pd(PEt3)}(2), which have previously been reported. This work establishes that there are many similarities in the solid-state and electronic structures of complexes containing bridging allyl, Cp, or indenyl ligands. For example, in all cases the bridging ligands bind through three carbon atoms to the two Pd atoms, with only the central carbon atom of the bridging group bound to both metal centers. However, there are also important differences based on the identity of the bridging ligand. As a result of different overlap between the metal centers and the pi orbitals of the bridging allyl, Cp, or indenyl ligand, Cp ligands are more likely to result in an anti relationship between the two bridging ligands, while allyl and indenyl ligands are more likely to give a syn relationship. The solid-state structures indicate that bridging allyl ligands bind the most tightly to the metal center and bridging Cp ligands bind the least tightly. DFT calculations reveal that the nature of the bridging ligand alters the HOMO of the Pd(I) dimers. As a result, in some cases it is possible to selectively protonate one of the bridging ligands using the electrophile 2,6-lutidinium chloride.

First author: Green, Katy, Synthesis and Characterization of Redox-Active Mononuclear Fe(kappa(2)-dppe)(eta(5)-C5Me5)-Terminated pi-Conjugated Wires, ORGANOMETALLICS, 32, 4366, (2013)
Abstract: Several new redox-active Fe(kappa(2)-dppe)(eta(5)-C5Me5) arylacetylide complexes featuring pendant ethynyl (Fe(kappa(2)-dppe)(eta(5)-C5Me5)-[{C equivalent to C(1,4-C6H4)}(n)C equivalent to CH] (1b-d; n = 1-3), Fe(kappa(2)-dppe)(eta(5)-C5Me5)[C equivalent to C(1,3-C6H4)C equivalent to CH] (2)) or ethenyl (Fe(kappa(2)-dppe)(eta(5)-C5Me5)[CE equivalent to C(1,4-C6H4)CH equivalent to CH2] (3)) groups have been synthesized and characterized under their Fe(II) and Fe(III) states. In contrast to the known ethynyl Fe(III) complex [Fe(kappa(2)-dppe)(eta(5)-C5Me5)(C7 equivalent to CH)][PF6] (1a[PF6]), most of the new Fe(III) derivatives turned out to be kinetically stable in solution. A consistent picture of the electronic structure of the latter complexes in both redox states emerged from experimental data and DFT calculations. This study revealed that beyond the first 1,4-phenylene ring, modification or extension of the carbon-rich linker using (4-phenylene)ethynylene spacers will have only a minor influence on their electronic properties in their ground state, while still maintaining some (weak) electronic interaction along the carbon-rich backbone.

First author: Ruiz-Serrano, Alvaro, A variational method for density functional theory calculations on metallic systems with thousands of atoms, JOURNAL OF CHEMICAL PHYSICS, 139, 4366, (2013)
Abstract: A new method for finite-temperature density functional theory calculations which significantly increases the number of atoms that can be simulated in metallic systems is presented. A self-consistent, direct minimization technique is used to obtain the Helmholtz free energy of the electronic system, described in terms of a set of non-orthogonal, localized functions which are optimized in situ using a periodic-sinc basis set, equivalent to plane waves. Most parts of the calculation, including the demanding operation of building the Hamiltonian matrix, have a computational cost that scales linearly with the number of atoms in the system. Also, this approach ensures that the Hamiltonian matrix has a minimal size, which reduces the computational overhead due to diagonalization, a cubic-scaling operation that is still required. Large basis set accuracy is retained via the optimization of the localized functions. This method allows accurate simulations of entire metallic nanostructures, demonstrated with calculations on a supercell of bulk copper with 500 atoms and on gold nanoparticles with up to 2057 atoms.

First author: Wodrich, Matthew D., Electronic Elements Governing the Binding of Small Molecules to a [Fe]-Hydrogenase Mimic, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2013, 3993, (2013)
Abstract: [Fe]-hydrogenase, one of three types of hydrogenases, activates molecular hydrogen. Here, using DFT computations, we examine the electronic elements governing the binding of small ligands to a recently synthesized [Fe]-hydrogenase biomimic. Computed reaction free energies indicate that anionic species, such as CN- and H-, and acceptors, such as CO, bind favourably with the Fe centre. Ligands such as H2O, CH3CN, and H-2, however, do not bind iron. Protonation of an adjacent thiolate ligand on the mimic significantly increases the energies of ligand binding. Additional computational analysis reveals that the degree of electron donation from the ligand to the mimic correlates strongly with overall binding ability. The results give insights into the electronic elements of iron-small-molecule interaction in these model complexes.

First author: Sarkar, Uttam K., Concentration dependent conformation of inosine on colloidal silver nanoparticles: A study by Raman, SERS and DFT calculation, JOURNAL OF MOLECULAR STRUCTURE, 1045, 42, (2013)
Abstract: Surface enhanced Raman spectroscopic (SERS) study of biologically important inosine molecules adsorbed in Ag-sol is reported for the first time. Possible adsorption mechanism is discussed. The enhancement is significantly influenced by the concentration of inosine in Ag-sols. The in plane base ring breathing mode appears at 715 cm(-1) in solid phase and is shifted to 724 cm(-1) in aqueous solution. Appearance of this band at 736 cm(-1) in the adsorbed state suggests C(2′) endo-anti conformation at concentrations up to 5 x 10(-7) M at which monomolecular layer is formed on the silver surface. However, C(3′) endo-syn conformation is suggested at a concentration of 5 x 10(-11) M. Inosine molecule, possibly, interact with the silver nano-particles through C5′ atom at higher concentration. The pi system of electrons of the hypoxanthine ring may be involved in the adsorption process at lower concentration. Mono-molecular layer is formed at concentrations of 5 x 10(-7) M and 5 x 10(-11) M indicating perpendicular and parallel adsorption respectively. Density functional calculations are performed for the explanation of the experimental results.

First author: Yousef, T. A., Structural, spectral analysis and DNA studies of heterocyclic thiosemicarbazone ligand and its Cr(III), Fe(III), Co(II) Hg(II), and U(VI) complexes, JOURNAL OF MOLECULAR STRUCTURE, 1045, 145, (2013)
Abstract: The paper presents a combined experimental and computational study of novel Cr(III), Fe(III), Co(II), Hg(II) and U(VI) complexes of (E)-2-((3-hydroxynaphthalen-2-yl)methylene)-N-(pyridin-2-yl)hydrazinecar bothioamide (H2L). The ligand and its complexes have been characterized by elemental analyses, spectral (IR, UV-vis, H-1 NMR and C-13 NMR), magnetic and thermal studies. IR spectra show that H2L is coordinated to the metal ions in a mononegative bi or tri manner. The structures are suggested to be octahedral for all complexes except Hg(II) complex is tetrahedral. Theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, MM, Zindo/1, MM+ and PM3, methods. Satisfactory theoretical-experimental agreements were achieved by MM method for the ligand and PM3 for its complexes. DOS calculations carried out by MM (ADF) method for ligand Hg complex from which we concluded that the thiol form of the ligand is more active than thione form and this explains that the most complexation take place in that form. The calculated IR vibrations of the metal complexes, using the PM3 method was the nearest method for the experimental data, and it could be used for all complexes. Also, valuable information are obtained from calculation of molecular parameters for all compounds carried out by the previous methods of calculation (electronegativity of the coordination sites, net dipole moment of the metal complexes, values of heat of formation and binding energy) which approved that the complexes are more stable than ligand. The low value of Delta E could be expected to indicate H2L molecule has high inclination to bind with the metal ions. Furthermore, the kinetic and thermodynamic parameters for the different decomposition steps were calculated using the Coats-Redfern and Horowitz-Metzger methods. Finally, the biochemical studies showed that, complex 2, 4 have powerful and complete degradation effect on DNA. For the foremost majority of cases the activity of the ligand is greatly enhanced by the presence of a metal ion. Thus presented results may be useful in design new more active or specific structures.

First author: Lopez, Rafael, Improved Partition-Expansion of Two-Center Distributions Involving Slater Functions,JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 1800, (2013)
Abstract: The calculation of the electronic structure of large systems is facilitated by the substitution of the two-center distributions by their projections on auxiliary basis sets of one-center functions. An alternative is the partition-expansion method in which one first decides what part of the distribution is assigned to each center, and next expands each part in spherical harmonics times radial factors. The method is exact, requires neither auxiliary basis sets nor projections, and can be applied to Gaussian and Slater basis sets. Two improvements in the partition-expansion method for Slater functions are reported: general expressions valid for arbitrary quantum numbers are derived and the efficiency of the procedure is increased giving analytical solutions to integrals previously computed by numerical quadrature. The efficiency of the new version is assessed in several molecules and the advantages over the projection methods are pointed out.

First author: Franchini, Mirko, The Becke Fuzzy Cells Integration Scheme in the Amsterdam Density Functional Program Suite, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 1819, (2013)
Abstract: In this article, we document a new implementation of the fuzzy cells scheme for numerical integration in polyatomic systems [Becke, J. Chem. Phys. 1998, 88, 2547] and compare its efficiency and accuracy with respect to an integration scheme based on the Voronoi space partitioning. We show that the accuracy of both methods is comparable, but that the fuzzy cells scheme is better suited for geometry optimization. For this method, we also introduce the locally dense grid concept and present a proof-of-concept application.

First author: Seidu, Issaka, Role Played by Isopropyl Substituents in Stabilizing the Putative Triple Bond in Ar ‘ EEAr ‘ [E = Si, Ge, Sn; Ar ‘ = C6H3-2,6-(C6H3-2,6-Pr-2(i))(2)] and Ar*PbPbAr* [Ar* = C6H3-2,6-(C6H2-2,4,6-Pr-3(i))(2)], INORGANIC CHEMISTRY, 52, 8378, (2013)
Abstract: A theoretical study of the bonding in ArEEAr (where E = Si, Ge, Sn, Pb; Ar = terphenyl ligand) revealed for the first time why bulky isopropyl substituents electronically are required in order to isolate stable ArEEAr species. This was accomplished by combining the natural orbitals for chemical valence (NOCV) method with the extended transition state (ETS) scheme. The NOCV-ETS analysis was based on two ArE fragments in their doublet ground state with the configuration sigma(2)pi(1). For E = Si, Ge, and Sn, it revealed one pi-bond perpendicular to the CEEC plane and two sigma/pi-type bonds in the plane, whereas the ArPbPbAr system was found to have a single a bond with a C Pb Pb trans-bent angle close to 90 degrees. While similar bonding pictures have been obtained in previous model studies with AT = H and CH3, the NOCV ETS scheme was able to obtain quantitative estimates for the strength of various sigma/pi components without artificial truncations or twisting of the system. More importantly, NOCV ETS analysis was able to show that the electronic influence of the isopropyl substituents on the sigma/pi components differs little from that found in a system where they are replaced by hydrogen. Instead, the favorable role of the isopropyl substituents is due to dispersive van der Waals attractions between Pr-i groups on aryl rings attached to different E atoms as well as hyperconjugation involving donation into sigma* orbitals on Pr-i. Dispersive interaction amounts to -27.5 kcal/mol (Si), -29.1 kcal/mol (Ge), -26.2 kcal/mol (Sn), and -44.0 kcal/mol (Pb). The larger dispersive stabilization for Pb reflects the fact that the longer Pb-Pb and Pb-C bonds sterically allow for more isopropyl groups with Ar = C6H3-2,6-(C6H2-2,4,6-Pr-3(i))(2). This is compared to the other elements where Ar = C6H3-2,6-(C6H3-2,6-Pr-2(i))(2). It is finally concluded from the analysis that real ArEEAr systems reveal little character of the EE bond in contrast to the findings of previous studies on model systems.

First author: Sharga, Olena V., Unprecedented Trapping of Difluorooctamolybdate Anions within an alpha-Polonium Type Coordination Network, INORGANIC CHEMISTRY, 52, 8784, (2013)
Abstract: New fluorinated hybrid solids [MO2F2O5(tr(2)Pr)] (1), [Co-3(tr(2)pr)(2)(MoO4)(2)F-2]center dot 7H(2)O (2), and [Co-3(H2O)(2)(tr(2)pr)(3)(Mo8O26F2)]center dot 3H(2)O (3) (tr(2)pr = 1,3-bis(1,2,4-triazol-4-yl)propane) were prepared from the reaction systems consisting of Co(OAc)(2)/CoF2 and MoO3/ (NH4)(6)Mo7O24, as Co-II and Mo-VI sources, in water (2) or in aqueous HF (1, 3) employing mild hydrothermal conditions. The tr(2)pr ligand serves as a conformationally flexible tetradentate donor. In complex 1, the octahedrally coordinated Mo atoms are linked in the discrete corner-sharing {Mo-2(mu(2)-O)F2P4N4) unit in which a pair of tr-heterocycles (tr = 1,2,4triazole) is arranged in cis positions opposite to “molybdenyl” oxygen atoms. The anti anti conformation type of tr2pr facilitates the tight zigzag chain packing motif The crystal structure of the mixed anion complex salt 2 consists of trinuclear [Co-3(mu 3MoO4)(2)(mu(2)-F)(2)] units self assembling in Coll-undulating chains (Co…Co 3.0709(15) and 3.3596(7) angstrom), which are cross linked by tr2pr in layers. In 3, containing condensed oxyfluoromolybdate species, linear centrosymmetric {Co-3(mu(2)-tr)(6)](6+) SBUs are organized at distances of 10.72-12.45 angstrom in an a-Po-like network using bitopic tr-linkers. The octahedral {N-6} and {N3O3} environments of the central and peripheral cobalt atoms, respectively, are filled by triazole N atoms, water molecules, and coordinating [Mo8O26F2](6-) anions. Acting as a tetradentate O-donor, each difluorooctamolybdate anion anchors four [Co-3(p(2)tr)(6)](6-) units through their peripheral Co sites, which consequently leads to a novel type of a two nodal 4,10-c net with the Schlafli symbol {3(2).4(3).5}{3(4).4(20).5(16).6(5)}. The 2D and 3D coordination networks of 2 and 3, respectively, are characterized by significant overall antiferroznagnetic exchange interactions (J/k) between the Co-II spin centers on the order of -8 and -4 K The [Mo8O26F2](6-) anion is investigated in detail by quantum chemical calculations.

First author: Guo, Yuan-Ru, Theoretical Study of Structural, Spectroscopic and Reaction Properties of trans-bis(imido) Uranium(VI) Complexes, INORGANIC CHEMISTRY, 52, 9143, (2013)
Abstract: To advance the understanding of the chemical behavior of actinides, a series of trans-bis(imido) uranium(VI) complexes, U(NR)(2)(THF)(2)(cis-I-2) (2R; R = H, Me, Bu-t, Cy, and Ph), U(NR)(2)(THF)(3)(trans-I-2) (3R; R = H, Me, Bu-t Cy, and Ph) and U((NBu)-Bu-t)(2)(THF)(3)(cis-I-2) (3(t)Bu’), were investigated using relativistic density functional theory. The axial U=N bonds in these complexes have partial triple bonding character. The calculated bond lengths, bond orders, and stretching vibrational frequencies reveal that the U=N bonds of the bis-imido complexes can be tuned by the variation of their axial substituents. This has been evidenced by the analysis of electronic structures. 2H, for instance, was calculated to show iodine based high lying occupied orbitals and U(f)-type low-lying unoccupied orbitals. Its U=N bonding orbitals, formed by U(f) and N(p), occur in a region of the relatively low energy. Upon varying the axial substituent from H to Bu-t and Ph, the U=N bonding orbitals of 2(t)Bu and 2Ph are greatly destabilized. We further compared the U=E (E = N and 0) bonds of 2H with 3H and their uranyl analogues, to address effects of the equatorial tetrahydrofuran (THF) ligand and the E group. It is found that the U=N bonds are slightly weaker than the U=O bonds of their uranyl analogues. This is in line with the finding that cis-UNR2 isomers, although energetically unfavorable, are more accessible than cis-UO2 would be It is also evident that 2H and 3H display lower U=(NH) stretching vibrations at 740 cm(-1) than the U=O at 820 cm(-1) of uranyl complexes. With the inclusion of both solvation and spin-orbit coupling, the free energies of the formation reactions of the bis-imido uranium complexes were calculated. The formation of the experimentally synthesized 3Me, 3Ph, and 2tBu are found to be thermodynamically favorable. Finally, the absorption bands previously obtained from experimental studies were well reproduced by time dependent density functional theory calculations.

First author: Huang, Jin-Dou, First-Principles Investigation of Anisotropic Electron and Hole Mobility in Heterocyclic Oligomer Crystals, CHEMPHYSCHEM, 14, 2579, (2013)
Abstract: Based on quantum chemistry calculations combined with the Marcus-Hush electron transfer theory, we investigated the charge-transport properties of oligothiophenes (nTs) and oligopyrroles (nPs) (n= 6, 7, 8) as potential p-or n-type organic semiconductor materials. The results of our calculations indicate that 1) the nPs show intrinsic hole mobilities as high as or even higher than those of nTs, and 2) the vertical ionization potentials (VIPs) of the nPs are about 0.6-0.7 eV smaller than the corresponding VIPs of the nTs. Based on their charge-trans-port ability and hole-injection efficiency, the nPs have potential as p-type organic semiconducting materials. Furthermore, it was also found that the maximum values of the electron-transfer mobility for the nTs are larger by one-to-two orders of magnitude than the corresponding maximum values of hole-transfer mobility, which suggests that the nTs have the potential to be developed as promising n-type organic semiconducting materials owing to their electron mobility.

First author: Baramov, Todor, Synthesis and Structural Characterization of Hexacoordinate Silicon, Germanium, and Titanium Complexes of the E-coli Siderophore Enterobactin, CHEMISTRY-A EUROPEAN JOURNAL, 19, 10536, (2013)
Abstract: The E. coli siderophore enterobactin, one of the strongest Fe-III chelators known to date, is also capable of binding Si-IV under physiological conditions. We report on the synthesis and structural characterization of the tris(catecholate) Si-IV-enterobactin complex and its Ge-IV and Ti-IV analogues. Comparative structural analysis, supported by quantum-chemical calculations, reveals the correlation between the ionic radius and the structural changes in enterobactin upon complexation.

First author: Di Carlo, Gabriele, Tetraaryl Zn-II Porphyrinates Substituted at -Pyrrolic Positions as Sensitizers in Dye-Sensitized Solar Cells: A Comparison with meso-Disubstituted Push-Pull Zn-II Porphyrinates, CHEMISTRY-A EUROPEAN JOURNAL, 19, 10723, (2013)
Abstract: A facile and fast approach, based on microwave-enhanced Sonogashira coupling, has been employed to obtain in good yields both mono-and, for the first time, disubstituted pushpull ZnII porphyrinates bearing a variety of ethynylphenyl moieties at the bpyrrolic position(s). Furthermore, a comparative experimental, electrochemical, and theoretical investigation has been carried out on these b-monoor disubstituted ZnII porphyrinates and meso-disubstituted push-pull ZnII porphyrinates. We have obtained evidence that, although the HOMO-LUMO energy gap of the meso-substituted push-pull dyes is lower, so that charge transfer along the push-pull system therein is easier, the b-mono-or disubstituted push-pull porphyrinic dyes show comparable or better efficiencies when acting as sensitizers in DSSCs. This behavior is apparently not attributable to more intense B and Q bands, but rather to more facile charge injection. This is suggested by the DFT electron distribution in a model of a bmonosubstituted porphyrinic dye interacting with a TiO2 surface and by the positive effect of the b substitution on the incident photon-to-current conversion efficiency (IPCE) spectra, which show a significant intensity over a broad wavelength range (350-650 nm). In contrast, meso-substitution produces IPCE spectra with two less intense and well-separated peaks. The positive effect exerted by a cyanoacrylic acid group attached to the ethynylphenyl substituent has been analyzed by a photophysical and theoretical approach. This provided supporting evidence of a contribution from chargetransfer transitions to both the B and Q bands, thus producing, through conjugation, excited electrons close to the carboxylic anchoring group. Finally, the straightforward and effective synthetic procedures developed, as well as the efficiencies observed by photoelectrochemical measurements, make the described b-monosubstituted ZnII porphyrinates extremely promising sensitizers for use in DSSCs.

First author: Gandubert, Aurore, Synthesis and Crystal Structure of the Azide K-4[Re6Se8i(N-3)(6)(a)]center dot 4H(2)O; Luminescence, Redox, and DFT Investigations of the [Re6Se8i(N-3)(6)(a)](4-) Cluster Unit, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 639, 1756, (2013)
Abstract: The reaction of K-4[Re6Se8i(OH)(a)(6)]8H(2)O with NaN3 in water results in the formation of [Re6Se8i(N-3)(a)](4-) units that crystallize with K+ and H2O to form K-4[Re6Se8i(N-3)(a)(6)]4H(2)O [P2(1)/c (N degrees 14), a = 9.0595(3) angstrom, b = 13.2457(4) angstrom, c = 13.2040(5) angstrom, = 94.472(1)degrees]. In the solid state, the unit is characterized by N-3 linear groups forming bond angles of roughly 120 degrees with the Re-6 cluster. (as) and (sy) bands as well as N-N-N deformation modes of the N-3 groups are discussed. Luminescence properties of the [Re6Se8i(N-3)(a)](4-) unit were measured in the solid state and in an acetonitrile solution. The redox potential of the [Re6Se8i(N-3)(a)](4-)/[Re6Se8i(N-3)(a)](3-) system was measured in acetonitrile. Experimental results were analyzed in the light of density functional theory calculations.

First author: Moussa, Mehdi El Sayed, Chiroptical Properties of Carbo[6]Helicene Derivatives Bearing Extended -Conjugated Cyano Substituents, CHIRALITY, 25, 455, (2013)
Abstract: New carbo[6]helicene derivatives grafted with -conjugated cyano-phenyl arms were synthesized in enantiopure forms and their -conjugation examined by UV-vis spectroscopy. The influence of the -conjugation on the circular dichroism spectra and molar rotations is discussed based on comparing experimental data with results from quantum-chemical calculations. The results highlight the fact that increasing the spatial extension of the -system in a helicene molecule is an efficient way of increasing its molar rotation. Chirality 25:455-465, 2013.

First author: Patel, Dipti, Reductive assembly of cyclobutadienyl and diphosphacyclobutadienyl rings at uranium, NATURE COMMUNICATIONS, 4, 455, (2013)
Abstract: Despite the abundance of f-block-cyclopentadienyl, arene, cycloheptatrienyl and cyclo-octatetraenide complexes, cyclobutadienyl derivatives are unknown in spite of their prevalence in the d-block. Here we report that reductive [2 + 2]-cycloaddition reactions of diphenylacetylene and (2,2-dimethylpropylidyne) phosphine with uranium(V)-inverted sandwich 10 pi-toluene tetra-anion complexes results in the isolation of inverted sandwich cyclobutadienyl and diphosphacyclobutadienyl dianion uranium(IV) complexes. Computational analysis suggests that the bonding is predominantly electrostatic. Although the psi(4) molecular orbital in the cyclobutadienyl and diphosphacyclobutadienyl ligands exhibits the correct symmetry for delta-bonding to uranium, the dominant covalent contributions arise from pi-bonding involving psi(2) and psi(3) orbital combinations. This contrasts with uranium complexes of larger arenes and cyclo-octatetraenide, where delta-bonding dominates. This suggests that the angular requirements for uranium to bond to a small four-membered ring favours pi-bonding, utilizing 5f- instead of 6d-orbitals, over delta-bonding that is favoured with larger ligands, where 6d-orbitals can become involved in the bonding.

First author: Antoniotti, Paola, (HNg(+))(OH2) complexes (Ng = He-Xe): An ab initio and DFT theoretical investigation,COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1017, 117, (2013)
Abstract: The HNgOH(2)(+) cations (Ng = He-Xe), formally arising from the insertion of a Ng atom into the O-H bond of H3O+, were characterized by MP2, CCSD(T), B3LYP, and BP86 calculations as ion-dipole complexes, best described by the resonance form (HNg(+))(OH2). While the MP2, CCSD(T), and B3LYP methods predict planar structures of C-2v symmetry, the BP86 predicts non-planar structures of Cs symmetry. The structural differences are however only minor, and do not affect the bonding situation, as described by the atomic charges, and the AIM bond topologies. The energy decomposition analysis performed by the ETS method at the BP86 level of theory revealed that the interaction between NgH(+) and H2O is prevailingly electrostatic for Ng = Ne, Ar, Kr, and Xe, while the electrostatic and the orbital contributions become comparable for Ng = He. The NOCV analysis unraveled also that, for any Ng, the dominant orbital contribution is the donor-acceptor interaction between the sigma(O-H) orbital of H2O (3 A(1)) and the empty sigma orbital of NgH(+). All the (HNg(+))(OH2) are however largely unstable with respect to dissociation into H3O+ and Ng, and only the heaviest (HAr+)(OH2), (HKr+)(OH2), and (HXe+)(OH2) are predicted to be metastable, and conceivably observable at low temperature. The structure and stability of the Ng-H3O+ intermediates involved in the decomposition of the (HNg(+))(OH2) were also briefly examined.

First author: Liao, Meng-Sheng, Effects of local protein environment on the binding of diatomic molecules to heme in myoglobins. DFT and dispersion-corrected DFT studies, JOURNAL OF MOLECULAR MODELING, 19, 3307, (2013)
Abstract: The heme-AB binding energies (AB = CO, O-2) in a wild-type myoglobin (Mb) and two mutants (H64L, V68N) of Mb have been investigated in detail with both DFT and dispersion-corrected DFT methods, where H64L and V68N represent two different, opposite situations. Several dispersion correction approaches were tested in the calculations. The effects of the local protein environment were accounted for by including the five nearest surrounding residues in the calculated systems. The specific role of histidine-64 in the distal pocket was examined in more detail in this study than in other studies in the literature. Although the present calculated results do not change the previous conclusion that the hydrogen bonding by the distal histidine-64 residue plays a major role in the O-2/CO discrimination by Mb, more details about the interaction between the protein environment and the bound ligand have been revealed in this study by comparing the binding energies of AB to a porphyrin and the various myoglobins. The changes in the experimental binding energies from one system to another are well reproduced by the calculations. Without constraints on the residues in geometry optimization, the dispersion correction is necessary, since it improves the calculated structures and energetic results significantly.

First author: Guo, Yuan-Ru, Relativistic theoretical studies on hydrogen bonds and the electronic structure of aqueous solvated bis(uranyl) complex: an insight into explicit and/or implicit solvent effects, JOURNAL OF MOLECULAR MODELING, 19, 3325, (2013)
Abstract: To understand the chemical behavior of uranyl complexes in water, a bis-uranyl [(phen)(UO2)(mu(2)-F)(F)](2) (A; phen = phenanthroline, mu(2) = doubly bridged) and its hydrated form A center dot (H2O)(n) (n = 2, 4 and 6) were examined using scalar relativistic density functional theory. The addition of water caused the phen ligands to deviate slightly from the U-2(mu(2)-F)(2) plane, and red-shifts the U-F-terminal and U = O stretching vibrations. Four types of hydrogen bonds are present in the optimized hydrated A center dot (H2O)(n) complexes; their energies were calculated to fall within the range 4.37-6.77 kcal mol(-1), comparable to the typical values of 5.0 kcal mol(-1) reported for hydrogen bonds. An aqueous environment simulated by explicit and/or implicit models lowers and re-arranges the orbitals of the bis-uranyl complex.

First author: Li, Ping, Theoretical studies on the interaction mechanisms between tetrachloro-p-benzoquinone and hydrogen peroxide, STRUCTURAL CHEMISTRY, 24, 1253, (2013)
Abstract: A detailed knowledge of the initial complexes is crucial for the better understanding of the reaction mechanisms between tetrachloro-p-benzoquinone (TCBQ) and hydrogen peroxide (H2O2). In the present study, the interaction modes and interaction mechanisms between TCBQ and H2O2 in the absence and presence of one, two, and three water molecules have been systematically investigated employing the B3LYP/6-311++G** level of theory in combination with the atoms in molecules theory and natural bond orbital (NBO) method. It was found that the introduction of water molecules can influence the original interaction modes between TCBQ and H2O2 through the formation of the intermolecular H-bonds. The interaction energies between TCBQ and H2O2 range from -0.37 to -2.75 kcal/mol for four stable complexes, which are smaller than that of the interaction between H2O2 and water molecule. Further energy decomposition analyses suggest that the coupling interactions between TCBQ and H2O2 are predominated by the electrostatic interactions regardless of the presence or absence of water molecules. In addition, the significant heat released from the interaction process in the presence of water molecules is expected to be favorable for the following reactions involving the production of the hydroxyl radical.

First author: Cobeljic, Bozidar, Synthesis, characterization, DFT calculations and biological activity of derivatives of 3-acetylpyridine and the zinc(II) complex with the condensation product of 3-acetylpyridine and semicarbazide,INORGANICA CHIMICA ACTA, 404, 5, (2013)
Abstract: A Schiff base of 3-acetylpyridine with semicarbazide as well as the corresponding tetrahedral Zn(II) complex were synthesized and characterized by X-ray crystal structure analysis and spectroscopic methods. It is interesting to note that the ligand coordinated as a monodentate although there are several donor atoms in it. Computational studies showed that such structure is more stable than the hypothetical structure with one ligand bound as a bidentate. The complex exibited moderate antibacterial, antifungal and cytotoxic activities while the ligand was mostly inactive. The complex strongly induced formation of reactive oxygen species in tumor cell lines. It also influenced cell cycle progression in tumor cell lines, and induced autophagy. The latter effect is, at least in part, a protective one.

First author: Renaud, Nicolas, Quantum Interferences and Electron Transfer in Photosystem I, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 5899, (2013)
Abstract: We have studied the electron transfer occurring in the photosystem I (PSI) reaction center from the special pair to the first iron-sulfur cluster. Electronic structure calculations performed at the DFT level were employed to determine the on-site energies of the fragments comprising PSI, as well as the charge transfer integrals between neighboring pairs. This electronic Hamiltonian was then used to compute the charge transfer dynamics, using the stochastic surrogate Hamiltonian approach to account for the coherent propagation of the electronic density but also for its energy relaxation and decoherence. These simulations give reasonable transfer time ranging from subpicoseconds to nanoseconds and predict coherent oscillations for several picoseconds. Due to these long-lasting coherences, the propagation of the electronic density can be enhanced or inhibited by quantum interferences. The impact of random fluctuations and asymmetries on these interferences is then discussed. Random fluctuations lead to a classical transport where both constructive and destructive quantum interferences are suppressed. Finally it is shown that an energy difference of 0.15 eV between the on-site energies of the phylloquinones leads to a highly efficient electron transfer even in presence of strong random fluctuations.

First author: Goeltl, Florian, What Makes Copper-Exchanged SSZ-13 Zeolite Efficient at Cleaning Car Exhaust Gases?,JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 4, 2244, (2013)
Abstract: Recently, the outstanding properties of Cu-SSZ-13 (a zeolite in the chabazite structure) for the selective catalytic reduction of nitrous oxides were discovered. However, the true nature of the active site is still not answered satisfactorily. In this work, we identify the active site for the given reaction from first-principles simulations of the total energy of Cu(II) ions in various positions in combination with previously published catalytic activity as a function of the copper exchange level. This attribution is confirmed by the simulation of vibrational properties of CO adsorbed to the reduced Cu(I) species. The relation between energetic considerations, vibrational calculations, and experiment allows a clear statement about the distribution of active sites in the catalyst. We furthermore discuss the structural properties of the active site leading to the high stability under reaction conditions over a large temperature range. The insights from this work allow a more targeted catalyst design and represent a step toward an industrial application of copper-exchanged zeolites in cleaning car exhaust gases.

First author: Garcia-Fernandez, Pablo, Compounds Containing Tetragonal Cu2+ Complexes: Is the d(x2-y2)-d(3z2-r2) Gap a Direct Reflection of the Distortion?, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 4, 2385, (2013)
Abstract: It is widely assumed that the gap, A, between d(x2)-(y2) and d(3×2-r2) orbitals in fluorides and oxides containing tetragonal Cu2+ or Ag2+ complexes directly reflects the tetragonal distortion in the MX6 complex (M = d9 ion; X = F-, O2-). This assumption on that relevant quantity is shown to be not correct through the study of pure K2CuF4-, KCuF3-, and Cu2+-doped KZnF3 and K2ZnF4 model compounds. Indeed, ab initio calculations prove that A in these insulating materials also depends on the internal electric field created by the rest of lattice ions on active electrons confined in a given CuF64- complex. This internal field, especially important for layered compounds, is shown to explain all puzzling experimental facts on the d-d transitions of the studied systems and is of interest in the search of new Cu2+ and Ag2+ superconducting materials where a strong correlation between Delta and the transition temperature, T been conjectured.

First author: Murata, Kei, Revelation of the Photoactive Species in the Photocatalytic Dimerization of alpha-Methylstyrene by a Dinuclear Ruthenium-Palladium Complex, INORGANIC CHEMISTRY, 52, 8030, (2013)
Abstract: A quantum chemical study of the photocatalytic dimerization of alpha-methylstyrene catalyzed by a dinuclear ruthenium-palladium complex was performed at the DFT/TD-DFT level in order to find the key steps of the catalytic reaction. This study reveals that the second insertion of alpha-methylstyrene is the rate-determining step and that it proceeds via triplet excited states of an intermediate complex. These excited states have geometries significantly different from that of the reactant, especially within the coordination sphere of the Pd unit. Indeed, one Pd-carbon bond is considerably lengthened, favoring the insertion process. These results open up the possibilities to optimize the process by fine modulation of the catalyst structure.

First author: Jawiczuk, Magdalena, Dimolybdenum Tetracarboxylates as Auxiliary Chromophores in Chiroptical Studies of vic-Diols, INORGANIC CHEMISTRY, 52, 8250, (2013)
Abstract: The aim of the present work was to check the suitability of dimolybdenum carboxylates, other than commonly used [Mo-2(OAc)(4)], as auxiliary chromophores for determining the absolute configuration of optically active vic-diols by means of electronic circular dichroism (ECD). To this end, a set of dimolybdenum tetracarboxylates was synthesized, and subsequently, the two most promising compounds were selected, namely dimolybdenum tetrakis(mu-pivalate) and tetrakis(mu-isovalerate). The selection was based on their solubility in commonly used solvents, their stability in solution, their tolerance to air exposure, as well as their utility for dichroic studies. The stability of the obtained in situ chiral complexes was verified by measuring the dependence of ECD, UV-vis, and NMR spectra on time, temperature, and concentration. We have shown that the ECD spectra of diverse vic-diols with these complexes are suitable for configurational assignment based on the correlation between signs of Cotton effects (CEs) arising in the spectra and the stereostructure of the ligand. Furthermore, to aid in the interpretation of experimental results, a separate set of DFT calculations has been incorporated to provide additional insight into the structure of the chiral complexes involved. In contrast to the earlier assumptions, experiments showed that the chelating mode of ligation is preferred for the studied complexes.

First author: Benson, Eric E., Structural and spectroscopic studies of reduced [Re(bpy-R)(CO)(3)](-1) species relevant to CO2 reduction, POLYHEDRON, 58, 229, (2013)
Abstract: Spectroscopic and structural comparisons are made between the rhenium anions with bpy-R ligands spanning a wide range of electron-withdrawing and donating abilities (R = CF3, H, Me, tBu, OMe). The synthesis and characterization of the rhenium anions [Re(bpy-R)(CO)(3)](-1) (bpy-R = 4,4′-disubstitued-2,2′-bipyridine; R = CF3, Me, OMe) are reported. The anions [Re(bpy-R)(CO)(3)](-1) (R = Me and OMe) were structurally characterized. X-ray characterization of [Re(bpy-CF3)(CO)(3)](-1) was unsuccessful. However, the structure of a mono-reduced complex, [Re(bpy-CF3)(CO)3Cl][K(18-crown-6)] was obtained. This compound is a rare example of a structurally characterized “19e(-)” intermediate formed in the chemical and electrochemical reduction of a Re(bpy-R)(CO)(3)Cl species.

First author: Pellarin, Kyle R., Oxidation of a Dimethylplatinum(II) Complex with Oxaziridines: A Hemiaminal Intermediate but No Oxo Complex, ORGANOMETALLICS, 32, 3604, (2013)
Abstract: The complex [PtMe2(bipy)] (1; bipy = 2,2′-bipyridine) fails to react with the oxaziridine derivatives RCHON-t-Bu (R = H, Ph, 2-Pyridyl) in acetone at room temperature, but an easy reaction occurs in methanol solution to give the platinum(IV) complex [Pt(OH)(OMe)Me-2(bipy)] and the corresponding imine RCH=N-t-Bu. In the case with R = Ph, the hemiaminal intermediate [Pt(OMe)-(OCHPhNH-t-Bu)Me-2(bipy)] was formed and then reacted only slowly to form [Pt(OH)(OMe)Me-2(bipy)] and PhCH=N-t-Bu. Computational studies indicate that the reaction of 1 with oxaziridines occurs to give a charge transfer complex but that further reaction requires assistance from hydrogen bonding and coordination with specific methanol molecules. The work provides strong support for the theory that oxygen atom transfer to 1 from either dioxiranes or oxaziridines must be coupled to proton transfer and does not involve oxoplatinum(IV) intermediates.

First author: Zabula, Alexander V., Silicon in a Negatively Charged Shell: Anions of Spirosilabifluorene,ORGANOMETALLICS, 32, 3760, (2013)
Abstract: Mono- and dianions of a polycyclic compound with a central sp(3)-hybridized silicon atom, spirosilabifluorene (C24H16Si, 1), were prepared by reduction with alkali metals. The salts containing 1(center dot-) and 1(2-) anions were isolated and studied by single-crystal X-ray diffraction. The lithium salt of the C24H16Si center dot- radical monoanion ([Li(THF)(4)(+)][1(center dot-)], 2) exists as a solvent-separated ion pair in the solid state. Substantially different geometrical parameters were found for each of the fluorene groups within the C24H16Si center dot- anion of 2 due to asymmetric charge distribution. The C24H16Si2- dianion was isolated in the form of its sodium ([{Na(THF)(3)(+)}{Na(THF)(+)(1(2-))], 3) or potassium ([{K(THF)(+)}(2)(1(2-))], 4) salt. The environment at the central silicon go:U.1i in the dianion is flattened in comparison to the monOanion and neutral compound, with the angle between the two fluorene planes measured at 55 degrees in 1(2-) vs 89 degrees in 1(center dot-) and 83 degrees in 1(0). The aggregation of dianions and alkali-metal counterions leads to the formation of dimeric units and 1D polymeric chains in the solid Sodium and potassium salts, respectively. The structure of the cesium salt 5, containing both mono- and dianions in the crystal lattice, was also studied by X, ray diffraction. Complexes 2-5 were investigated by ESR and variable-temperature rnultinuclear NMR spectroscopy. Theoretical investigations at the PBE0, MP2, and multireference NEVPT2 levels of theory for the C24H16Sin- (n = 0-2) species revealed the conjugation of two fluorene units over the central silicon atom and a singlet ground state for the dianion.

First author: Choi, Seung-Hoon, Amorphous Zinc Stannate (Zn2SnO4) Nanofibers Networks as Photoelectrodes for Organic Dye-Sensitized Solar Cells, ADVANCED FUNCTIONAL MATERIALS, 23, 3146, (2013)
Abstract: A new strategy for developing dye-sensitised solar cells (DSSCs) by combining thin porous zinc tin oxide (Zn2SnO4) fiber-based photoelectrodes with purely organic sensitizers is presented. The preparation of highly porous Zn2SnO4 electrodes, which show high specific surface area up to 124 m(2)/g using electrospinning techniques, is reported. The synthesis of a new organic donor-conjugate-acceptor (D–A) structured orange organic dye with molar extinction coefficient of 44 600 M-1 cm(-1) is also presented. This dye and two other reference dyes, one organic and a ruthenium complex, are employed for the fabrication of Zn2SnO4 fiber-based DSSCs. Remarkably, organic dye-sensitized DSSCs displayed significantly improved performance compared to the ruthenium complex sensitized DSSCs. The devices based on a 3 m-thick Zn2SnO4 electrode using the new sensitizer in conjunction with a liquid electrolyte show promising photovoltaic conversion up to 3.7% under standard AM 1.5G sunlight (100 mW cm(-2)). This result ranks among the highest reported for devices using ternary metal oxide electrodes.

First author: Hjertenaes, Eirik, Assessment of density functionals for van der Waals complexes of sodium and benzene,MOLECULAR PHYSICS, 111, 1211, (2013)
Abstract: We present a detailed assessment of state-of-the-art exchange-correlation functionals. The assessment is carried out by comparing potential energy curves of van der Waals complexes of sodium and benzene calculated with density functional theory to extrapolated CCSD(T)/aug-cc-pVQZ values. According to the presented results, the Perdew-Burke-Ernzerhof functional (PBE) displays the best performance among the tested density functionals. PBE is the most accurate functional for the complexes studied, both in terms of absolute and relative accuracy.

First author: Rinaldi, John Michael, A discrete interaction model/quantum mechanical method for simulating nonlinear optical properties of molecules near metal surfaces, MOLECULAR PHYSICS, 111, 1322, (2013)
Abstract: In this work, we extend the discrete interaction model/quantum mechanics (DIM/QM) method to calculate the frequency-dependent hyperpolarisabilities of molecules near metal surfaces. The DIM/QM method is a polarisable quantum mechanics/molecular mechanics method, which represents the metal surface atomistically and thus allows for explicitly modelling the influence of the local environment on the optical properties of a molecule. The interactions between the metal surface and the molecules include both the image field and local field effects. The image field effects arise from the response induced in the metal surface due to the molecule’s electronic charge distributions whereas the local field effects arise from interactions between the metal surface and the external light. The frequency-dependent first-hyperpolarisability is obtained in an efficient way based on time-dependent density functional theory and the (2n+1) rule. The method was tested for calculating the first-hyperpolarisability responsible for the second-harmonic generation of a fumaramide[2]rotaxane interacting with a sliver surface. The first-hyperpolarisability of the fumaramide[2]rotaxane is very small in the gas phase due to near inversion symmetry. We find that the breaking of the symmetry due to interactions with the metal surface leads to a significant induced first-hyperpolarisability. The image field effects are found to be modest and short-range. In contrast, we find that the local field effects are large and rather long-range, illustrating the importance of including these effects directly in the simulations. Comparison with experimental results shows good qualitative agreement.

First author: Smalo, Hans S., Combined nonmetallic electronegativity equalisation and point-dipole interaction model for the frequency-dependent polarisability, MOLECULAR PHYSICS, 111, 1470, (2013)
Abstract: A molecular mechanics model for the frequency-dependent polarisability is presented. It is a combination of a recent model for the frequency dependence in a charge-dipole model [Nanotechnology 19, 025203, 2008] and a nonmetallic modification of the electronegativity equalisation model rephrased as atom-atom charge-transfer terms [J. Chem. Phys. 131, 044101, 2009]. An accurate model for the frequency-dependent polarisability requires a more accurate partitioning into charge and dipole contributions than the static polarisability, which has resulted in several modifications of the charge-transfer model. Results are presented for hydrocarbons, including among others, alkanes, polyenes and aromatic systems. Although their responses to an electric field are quite different in terms of the importance of charge-transfer contributions, it is demonstrated that their frequency-dependent polarisabilities can be described with the same model and the same set of atom-type parameters.

First author: Gross, Lynn, The angular dependence of spin-state energy splittings in the Fe2O22+ core, MOLECULAR PHYSICS, 111, 1482, (2013)
Abstract: Spin-state energy splittings are highly relevant for catalysis, molecular magnetism, and materials science, yet continue to pose a challenge for electronic structure methods. For a Fe2O2+ (2) core, we evaluate the bridging angle dependence of energy splittings between ferromagnetically and antiferromagnetically coupled states for different exchange-correlation functionals, and compare with complete active space self-consistent field (CASSCF) values, also including second-order perturbative corrections (CASPT2). CASSCF and CASPT2 yield strong antiferromagnetic coupling, with the smallest coupling at 100 degrees, and a smooth dependence on the angle for Fe-O-Fe angles of 70 degrees to 120 degrees. Interestingly, this is qualitatively the same behaviour as often found for stable dinuclear transition metal complexes. While all functionals show the same angular dependence as CASPT2, they favour the antiferromagnetic state less strongly. Pure functionals such as BP86, BLYP, SSB-D, and TPSS come closer to the CASPT2 results (with energy splittings by about 60 kJ/mol smaller than the CASPT2 ones) than hybrid functionals. The hybrid functionals B3LYP, B3LYP, and PBE0 favour the antiferromagnetic state even less strongly, resulting in ferromagnetic coupling for angles around 100 degrees. The good qualitative agreement between CASPT2 and CASSCF on the one hand and CASPT2 and density functional theory on the other hand for angles between 70 degrees and 110 degrees suggests that the chosen active space of 18 electrons in 14 orbitals may be adequate for spin-state energy splitting of Fe2O22+ in that region (possibly due to error cancellation), while angles of 60 degrees or 120 degrees may require larger active spaces. This study is complemented by an analysis of local spins, local charges, and CASSCF natural orbitals.

First author: Chong, Delano P., Density functional theory study of allopurinol, CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 91, 637, (2013)
Abstract: Allopurinol vapour is studied with density functional theory. Using the best method from past experience for each property, we predict the equilibrium geometry, vibrational spectrum, dipole moment, average dipole polarizability, UV absorption spectrum, vertical ionization energies of valence electrons, and core-electron binding energies.

First author: Foerster, Daniela, Donor-Free Phosphenium-Metal(0)-Halides with Unsymmetrically Bridging Phosphenium Ligands, INORGANIC CHEMISTRY, 52, 7699, (2013)
Abstract: Reactions of (cod)MCl2 (cod = 1,5 cyclooctadiene, M = Pd, Pt) with N-heterocyclic secondary phosphines or diphosphines produced complexes [(NHP)-MCl](2) (NHP = N-heterocyclic phosphenium). The Pd complex was also accessible from a chlorophosphine precursor and Pd-2(dba)(3 center dot) Single-crystal X-ray diffraction studies established the presence of dinuclear complexes that contain mu-bridging NHP ligands in an unsymmetrical binding mode and display a surprising change in metal coordination geometry from distorted trigonal (M = Pd) to T-shaped (M = Pt). DFT calculations on model compounds reproduced these structural features for the Pt complex but predicted an unusual C-2v-symmetric molecular structure with two different metal coordination environments for the Pd species. The deviation between this structure and the actual centrosymmetric geometry is accounted for by the prediction of a flat energy hypersurface, which permits large distortions in the orientation of the NHP ligands at very low energetic cost. The DFT results and spectroscopic studies suggest that the title compounds should be described as phosphenium-metal(0)-halides rather than conventional phosphido complexes of divalent metal cations and indicate that the NHP ligands receive net charge donation from the metals but retain a distinct cationic character. The unsymmetric NHP binding mode is associated with an unequal distribution of sigma-donor/pi-acceptor contributions in the two M-P bonds. Preliminary studies indicate that reactions of the Pd complex with phosphine donors provide a viable source of ligand-stabilized, zerovalent metal atoms and metal(0)-halide fragments.

First author: Elder, Philip J. W., Chalcogenation of the 1,4-C2P4 Ring: Oxidation, Isomerization, Insertion, and Ring Contraction, INORGANIC CHEMISTRY, 52, 7791, (2013)
Abstract: The reaction of H2C(PCl2)(2) with 4 equiv of (BuMgCl)-Bu-t in tetrahydrofuran (THF) produces 1,4-(CH2)(2)((PBu)-Bu-t)(4), 1, in about 65% yield. This six-membered ring reacts directly with elemental sulfur or selenium in toluene at low temperatures to give the mono- and dichalcogenides 1,4-(CH2)(2)((PBuE)-Bu-t)((PBu)-Bu-t)(3) (E = S, 2a, E = Se, 2b) and 1,4-(CH2)(2)-2,5-((PBuE)-Bu-t)(2)((PBu)-Bu-t)(2) (E = S, 3a, E = Se, 3h). X-ray structural determinations showed that 3a and 3b are isostructural in the solid state. the six-membered C2P4 ring exhibits a twist-boat geometry with chalcogen substituents in syn positions in each case. Density functional theory (DFT) calculations for the three possible isomers of disubstitution were performed to elucidate the factors that favor the 2,5-isomer. Thermal isomerism was observed in solutions of 3b or 3a in toluene at 60 and 95 degrees C, respectively, to give the corresponding 2,6-isomers. With an excess of chalcogen in toluene at reflux, the four-membered rings (H2C)((PBuE)-Bu-t)(2)E (E = S, 4a, E = Se, 4b) were obtained and identified by Multinuclear NMR spectroscopy and single crystal X-ray crystallography, which showed the Bu-t groups in a trans orientation with respect to the CP2E ring. With a large excess of chalcogen, the five-membered rings (H2C)((PBuE)-Bu-t)(2)E-2 (E = S, 5a, E = Se, 5b) were also observed; the X-ray structure of 5b revealed a half-envelope conformation for the CP2Se2 ring. The direct reaction of 4a with sulfur in boiling toluene does not produce 5a, whereas 5b is formed slowly and in low yields from 4b and selenium under similar conditions. On the basis of DFT calculations of the relative energies of likely intermediates, chalcogen insertion into the P P bonds of 3a and 3b to give eight-membered C2P4E2 rings, followed by monomerization, is proposed as a feasible pathway for the formation of the four-membered CP2E heterocycles 4a and 4b.

First author: Bauer, Tobias, Ternary Rare-Earth Transition-Metal Polyhydride Cluster Compounds, CHEMISTRY-A EUROPEAN JOURNAL, 19, 8732, (2013)
Abstract: The reaction of H2C(PCl2)(2) with 4 equiv of (BuMgCl)-Bu-t in tetrahydrofuran (THF) produces 1,4-(CH2)(2)((PBu)-Bu-t)(4), 1, in about 65% yield. This six-membered ring reacts directly with elemental sulfur or selenium in toluene at low temperatures to give the mono- and dichalcogenides 1,4-(CH2)(2)((PBuE)-Bu-t)((PBu)-Bu-t)(3) (E = S, 2a, E = Se, 2b) and 1,4-(CH2)(2)-2,5-((PBuE)-Bu-t)(2)((PBu)-Bu-t)(2) (E = S, 3a, E = Se, 3h). X-ray structural determinations showed that 3a and 3b are isostructural in the solid state. the six-membered C2P4 ring exhibits a twist-boat geometry with chalcogen substituents in syn positions in each case. Density functional theory (DFT) calculations for the three possible isomers of disubstitution were performed to elucidate the factors that favor the 2,5-isomer. Thermal isomerism was observed in solutions of 3b or 3a in toluene at 60 and 95 degrees C, respectively, to give the corresponding 2,6-isomers. With an excess of chalcogen in toluene at reflux, the four-membered rings (H2C)((PBuE)-Bu-t)(2)E (E = S, 4a, E = Se, 4b) were obtained and identified by Multinuclear NMR spectroscopy and single crystal X-ray crystallography, which showed the Bu-t groups in a trans orientation with respect to the CP2E ring. With a large excess of chalcogen, the five-membered rings (H2C)((PBuE)-Bu-t)(2)E-2 (E = S, 5a, E = Se, 5b) were also observed; the X-ray structure of 5b revealed a half-envelope conformation for the CP2Se2 ring. The direct reaction of 4a with sulfur in boiling toluene does not produce 5a, whereas 5b is formed slowly and in low yields from 4b and selenium under similar conditions. On the basis of DFT calculations of the relative energies of likely intermediates, chalcogen insertion into the P P bonds of 3a and 3b to give eight-membered C2P4E2 rings, followed by monomerization, is proposed as a feasible pathway for the formation of the four-membered CP2E heterocycles 4a and 4b.

First author: Hamilton, Alex, Mechanisms of Catalysis in Confined Spaces: Hydrogenation of Norbornadiene with a Rhodium Complex included in a Self-Folding Cavitand, CURRENT ORGANIC CHEMISTRY, 17, 1499, (2013)
Abstract: The reaction mechanism for the hydrogenation of norbornadiene (nbd) catalysed by bis-norbornadiene rhodium(I) [Rh(nbd)(2)](+) complex has been studied by means of DFT based methods, in the absence and in the presence of a self-folding octaamide cavitand. Formation of three products, norbornene, nortricyclene and a dimer is discussed. When the metal complex is encapsulated inside the cavitand, the steric crowding prevents formation of the dimer, while in the absence of the cavity, the dimer is the major product. Although energy differences between the studied reaction pathways are small, the present study explains the changes in regioselectivity when the hydrogenation reaction is carried out in a confined space.

First author: Zhu, Hongjuan, The effects of the ligand, central metal, and solvent on the O-2 binding of non-precious metal catalyst model systems: An ab initio study, ELECTROCHIMICA ACTA, 101, 293, (2013)
Abstract: Non-precious metal (NPM) catalysts are currently under development to replace the expensive platinum-based materials currently utilized for oxygen reduction in PEM fuel cells. In this work, systematic studies were carried out to examine the effect of central metal, chelating ligand, and solvent on the O-2 binding activity of a series of M-N-2 and M-N-4 NPM catalysts (Im)MLn where M=Cu2+, Fe2+, Fe3+, Ni2+ and Co2+, L= diaminotriazole or porphyrin, and a support ligand imidazole (Im). O-2 and H2O binding energies were calculated for all the catalysts. Cu2+-based catalysts exhibit no activity toward O-2 regardless of the ligand, Fe2+- and Co2+-based catalysts show the strongest O-2 binding, and the rest fall in between. This is in alignment with the energy gap between the metal 3d(z2) and the in-plane anti-bonding pi* orbital on the O-2 with the larger the energy gap, the weaker the interaction. Porphyrin-based catalysts bind weakly with H2O compared to their diaminotriazole counterparts, which is attributed to the larger energy gap between the HOMO of H2O and the higher lying LUMO of Porphyrin-based catalysts resulted from a stronger anti-bonding interaction between their metal d orbitals and the sigma(N) orbitals of porphyrin. We propose that the initial O-2 absorption activity of M-N-4 or M-N-2 catalysts in the oxygen reduction reaction be considered on the basis of the relative binding of O-2 to H2O.

First author: Dyduch, Karol, ETS-NOCV description of sigma-hole bonding, JOURNAL OF MOLECULAR MODELING, 19, 2747, (2013)
Abstract: The ETS-NOCV analysis was applied to describe the sigma-hole in a systematic way in a series of halogen compounds, CF3-X (X = I, Br, Cl, F), CH3I, and C(CH3)(n)H3-n-I (n = 1,2,3), as well as for the example germanium-based systems. GeXH3, X = F, Cl, H. Further, the ETS-NOCV analysis was used to characterize bonding with ammonia for these systems. The results show that the dominating contribution to the deformation density, Delta rho (1) , exhibits the negative-value area with a minimum, corresponding to sigma-hole. The “size” (spatial extension of negative value) and “depth” (minium value) of the sigma-hole varies for different X in CF3-X, and is influenced by the carbon substituents (fluorine atoms, hydrogen atoms, methyl groups). The size and depth of sigma-hole decreases in the order: I, Br, Cl, F in CF3-X. In CH3-I and C(CH3)(n)H3-n-I, compared to CF3-I, introduction of hydrogen atoms and their subsequent replacements by methyl groups lead to the systematic decrease in the sigma-hole size and depth. The ETS-NOCV sigma-hole picture is consistent with the existence the positive MEP area at the extension of sigma-hole generating bond. Finally, the NOCV deformation density contours as well as by the ETS orbital-interaction energy indicate that the sigma-hole-based bond with ammonia contains a degree of covalent contribution. In all analyzed systems, it was found that the electrostatic energy is approximately two times larger than the orbital-interaction term, confirming the indisputable role of the electrostatic stabilization in halogen bonding and sigma-hole bonding.

First author: Barngrover, Brian M., Oxidation of Gold Clusters by Thiols, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 5377, (2013)
Abstract: The formation of gold-thiolate nanoparticles via oxidation of gold clusters by thiols is examined in this work. Using the BP86 density functional with a triple zeta basis set, the adsorption of methylthiol onto various gold clusters Au-n(Z) (n = 1-8, 12, 13, 20; Z = 0, -1, +1) and Au-38(4+) is investigated. The rate-limiting step for the reaction of one thiol with the gold cluster is the dissociation of the thiol proton; the resulting hydrogen atom can move around the gold cluster relatively freely. The addition of a second thiol can lead to H-2 formation and the generation of a gold-thiolate staple motif.

First author: Manna, Arun K., Computational Studies on Non-covalent Interactions of Carbon and Boron Fullerenes with Graphene, CHEMPHYSCHEM, 14, 1844, (2013)
Abstract: First-principles DFT calculations are carried out to study the changes in structures and electronic properties of two-dimensional single-layer graphene in the presence of non-covalent interactions induced by carbon and boron fullerenes (C60, C70, C80 and B80). Our study shows that larger carbon fullerene interacts more strongly than the smaller fullerene, and boron fullerene interacts more strongly than that of its carbon analogue with the same nuclearity. We find that van der Waals interactions play a major role in governing non-covalent interactions between the adsorbed fullerenes and graphene. Moreover, a greater extent of van der Waals interactions found for the larger fullerenes, C80 and B80, relative to smaller C60, and consequently, results in higher stabilisation. We find a small amount of electron transfer from graphene to fullerene, which gives rise to a hole-doped material. We also find changes in the graphene electronic band structures in the presence of these surface-decorated fullerenes. The Dirac cone picture, such as that found in pristine graphene, is significantly modified due to the re-hybridisation of graphene carbon orbitals with fullerenes orbitals near the Fermi energy. However, all of the composites exhibit perfect conducting behaviour. The simulated absorption spectra for all of the graphene-fullerene hybrids do not exhibit a significant change in the absorption peak positions with respect to the pristine graphene absorption spectrum. Additionally, we find that the hole-transfer integral between graphene and C60 is larger than the electron-transfer integrals and the extent of these transfer integrals can be significantly tuned by graphene edge functionalisation with carboxylic acid groups. Our understanding of the non-covalent functionalisation of graphene with various fullerenes would promote experimentalists to explore these systems, for their possible applications in electronic and opto-electronic devices.

First author: Cheng, Hong-Ye, Adsorption of a single Pt atom on polyaromatic hydrocarbons from first-principle calculations, CHEMICAL PHYSICS LETTERS, 575, 76, (2013)
Abstract: Adsorption of a single Pt atom on polyaromatic hydrocarbons has been investigated systematically using density functional theory calculations. The bond length between the Pt and the nearest C atom increases with the coordination of the Pt atom and the Pt charge increases with shorter Pt-C bond distances, indicating that the catalytic activity of the Pt atom can be tuned by modifying its chemical bonding. A computational approach in line with the SSB-D functional, with the ZORA model for relativistic effects and basis sets like TZ2P or QZ4P is required for accurate results for the Pt/C interaction.

First author: Albrecht, Florian, Formation and Characterization of a Molecule-Metal-Molecule Bridge in Real Space,JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 9200, (2013)
Abstract: Metal-organic complexes were formed by means of inelastic excitations in a scanning tunneling microscope (STM). The electronic structure of the complex was characterized using STM imaging and spectroscopy. By exploiting the symmetry of the complex, its electronic structure can be rationalized from linear combinations of molecular orbitals. The actual bonding geometry, which cannot be inferred from STM alone, was determined from atomic force microscopy images with atomic resolution. Our study demonstrates that the combination of these techniques enables a direct quantification of the interplay of geometry and electronic coupling in metal-organic complexes in real space.

First author: Ciesielski, Artur, Self-Assembly of N-3-Substituted Xanthines in the Solid State and at the Solid-Liquid Interface, LANGMUIR, 29, 7283, (2013)
Abstract: The self-assembly of small molecular modules interacting through noncovalent forces is increasingly being used to generate functional. structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H-bond supramolecular architectures, especially in H-bonded supramolecular polymers, can be achieved by exploiting the rich programmability of artificial nucleobases undergoing self-assembly through strong H bonds. Here N-3-functionalized xanthine modules are described, which are capable of self-associating through self-complementary H-bonding patterns to form H-bonded supramolecular ribbons. The self-association of xanthines through directional H bonding between neighboring molecules allows the controlled generation of highly compact ID supramolecular polymeric ribbons on graphite. These architectures have been characterized by scanning tunneling microscopy at the solid liquid interface, corroborated by dispersion-corrected density functional theory (DFT) studies and X-ray diffraction.

First author: Ivanova, Maria V., Synthesis and Lewis Acid Properties of (ReO3F)(infinity) and the X-ray Crystal Structures of (HF)(2)ReO3F center dot HF and [N(CH3)(4)](2)[{ReO3(mu-F)}(3)(mu(3)-O)]center dot CH3CN, INORGANIC CHEMISTRY, 52, 6806, (2013)
Abstract: A high-yield, high-purity synthesis of (ReO3F)(infinity) has been achieved by solvolysis of Re2O7 in anhydrous HF (aHF) followed by reaction of the water formed with dissolved F-2 at room temperature. The improved synthesis has allowed the Lewis acid and fluoride ion acceptor properties of (ReO3F)(infinity) to be further investigated. The complex, (HF)(2)ReO3F center dot HF, was obtained by dissolution of (ReO3F)(infinity) in aHF at room temperature and was characterized by vibrational spectroscopy and single-crystal X-ray diffraction at -173 degrees C. The HF molecules are F-coordinated to rhenium, representing the only known example of a HF complex with rhenium. The trirhenium dianion, [{ReO3(mu-F)}(3)(mu(3)-O)](2-), was obtained as the [N(CH3)(4)](+) salt by the reaction of stoichiometric amounts of (ReO3F)(infinity) and [N(CH3)(4)]F in CH3CN solvent at -40 to -20 degrees C. The anion was structurally characterized in CH3CN solution by F-19 NMR spectroscopy and in the solid state by Raman spectroscopy and a single-crystal X-ray structure determination of [N(CH3)(4)](2)[{ReO3(mu-F)}(3)(mu(3)-O)]center dot CH3CN at -173 degrees C. The structural parameters and vibrational frequencies of the [{MO3(mu-F)}(3)(mu(3)-O)](2-) and [{MO3(mu-F)}(3)(mu(3)-F)](-) anions (M = Re, Tc) were calculated using density functional theory. The calculated geometries of [{ReO3(mu-F)}(3)(mu(3)-O)](2-) and [{TcO3(mu-F)}(3)(mu(3)-F)](-), are in very good agreement with their experimental geometries. Calculated vibrational frequencies and Raman intensities have been used to assign the Raman spectra of (HF)(2)ReO3F center dot HF and [N(CH3)(4)](2) [{ReO3(mu-F)}(3)(mu(3)-O)]center dot CH3CN. The X-ray crystal structures of the byproducts, [N(CH3)(4)][ReO4] and KF center dot 4HF, were also determined in the course of this work.

First author: Aramburu, J. A., Cu2+ in Layered Compounds: Origin of the Compressed Geometry in the Model System K2ZnF4:Cu2+, INORGANIC CHEMISTRY, 52, 6923, (2013)
Abstract: Many relevant properties (including superconductivity and colossal magnetoresistance) of layered materials containing Cu2+, Ag2+, or Mn3+ ions are commonly related to the Jahn-Teller instability. Along this line, the properties of the CuF64- complex in the K2ZnF4 layered perovskite have recently been analyzed using a parametrized Jahn-Teller model with an imposed strain [Reinen, D. Inorg. Chem. 2012, 51, 4458]. Here, we present results of ab initio periodic supercell and cluster calculations on K2ZnF4:Cu2+, showing unequivocally that the actual origin of the unusual compressed geometry of the CuF64- complex along the crystal c axis in that tetragonal lattice is due to the presence of an electric field due to the crystal surrounding the impurity. Our calculations closely reproduce the experimental optical spectrum. The calculated values of the equilibrium equatorial and axial Cu2+-F- distances are, respectively, R-ax = 193 pm and R-eq = 204 pm, and so the calculated distortion R-ax – R-eq = 11 pm is three times smaller than the estimated through the parametrized Jahn-Teller model. As a salient feature, we find that if the CuF64- complex would assume a perfect octahedral geometry (R-ax – R-eq = 203 pm) the antibonding a(1g)*(similar to 3z(2) – r(2)) orbital is placed above b(1g)*(similar to x(2) – y(2)) with a transition energy E((2)A(1g) –> B-2(1g)) = 0.34 eV. This surprising fact stresses that about half the experimental value E((2)A(1g) –> B-2(1g)) = 0.70 eV is not due to the small shortening of the axial Cu2+ – F- distance, but it comes from the electric field, E-R(r), created by the rest of the lattice ions on the CuF64- complex. This internal field, displaying tetragonal symmetry, is thus responsible for the compressed geometry in K2ZnF4:Cu2+ and the lack of symmetry breaking behind the ligand relaxation. Moreover, we show that the electronic energy gain in this process comes from bonding orbitals and not from antibonding ones. The present results underline the key role played by ab initio calculations for unveiling all the complexity behind the properties of the model system K2ZnF4:Cu2+, opening at the same time a window for improving our knowledge on d(9), d(7), or d(4) ions in other layered compounds.

First author: Rogachev, Andrey Yu., Hypervalent Compounds as Ligands: I-3-Anion Adducts with Transition Metal Pentacarbonyls, INORGANIC CHEMISTRY, 52, 7161, (2013)
Abstract: Just a couple of transition metal complexes of the familiar triiodide anion are known. To investigate the bonding in these, as well as isomeric possibilities, we examined theoretically adducts of I-3(-) with model organometallic fragments, [Cr(CO)(5)] and [Mn(CO)(5)](+). Bonding energy computations were augmented by a Natural Bond Orbital (NBO) perturbation theory analysis and Energy Decomposition Analysis (EDA). The bonding between I-3(-) and the organometallic fragment is substantial, especially for the electrostatically driven anion cation case. “End-on” coordination is favored by 5-13 kcal/mol over “side-on” (to the central I of I-3(-)), with a similar to 10 kcal/mol barrier for isomerization. A developing asymmetry in the I-I bonding of “end-on” coordinated I-3(-) led us to consider in some detail the obvious fragmentation to a coordinated I- and free I-2. While the signs of incipient fragmentation in that direction are there, these is a definite advantage to maintaining some I- to I-2 bonding in triiodide complexes.

First author: Laidlaw, W. Michael, 140 H/D Isotopomers Identified by Long-Range NMR Hyperfine Shifts in Ruthenium(III) Ammine Complexes. Hyperconjugation in Ru-NH3 Bonding, INORGANIC CHEMISTRY, 52, 7280, (2013)
Abstract: H-1 NMR spectra of the paramagnetic cyanide-bridged mixed-valence compound [(eta(5)-C5H5)Fe(CO)(2)(mu-CN)Ru(NH3)(5)](CF3SO3)(3) (I) have been obtained in several solvents. When traces of partially deuterated water are present, instead of a single cyclopentadienyl (Cp) resonance shifted by the hyperfine interaction, numerous well-resolved resonances are observed. The spectra were simulated satisfactorily by giving the appropriate statistical weight to 140 possible H/D isotopomers formed by deuteration in the five ruthenium(III) ammine ligands. The proliferation of distinct resonances occurs because (a) the hyperfine shifts (HSs) due to each sequential deuteration in a single ammine are different and (b) while deuteration in an ammine cis to the cyanide bridge causes a downfield shift, in the trans ammine it causes an upfield shift that is nearly twice as large. All of these shifts exhibit a 1/T dependence, but temperature-independent components, due to large second-order Zeeman effects at the Ru-III center, are also present. Combining the results of density functional theory calculations with data from metal-metal charge-transfer optical transitions and with the effect of solvent-induced NMR HSs, it is argued that Fermi contact shifts at the Cp protons are insignificant compared to those due to the dipolar (pseudocontact) mechanism. Analytical expressions are presented for the dependence of the HS on the tetragonal component of the ligand field at the Rum ion. The tetragonal field parameter, defined as the energy by which the 4d(xy) orbital exceeds the mean t(2g) orbital energy, was found to be 147, 52, and 76 cm(-1), in dimethylformamide, acetone, and nitromethane, respectively. The effects of deuteration show that there is a significant component of hyperconjugation in the Ru-ammine interaction and that ND3 is a weaker pi donor than NH3. A single deuteration in an axial ammine increases the tetragonal field parameter (nu) by +2.8 cm(-1), resulting in a HS of -37 ppb in the Cp proton resonance, whereas a single deuteration in an equatorial ammine decreases the field by -1.5 cm(-1) with a HS of +20 ppb, despite a nominal separation of seven chemical bonds. We analyze the origin of this remarkable sensitivity, which relies on the favorable characteristics of the Ru-III low-spin t(2g)(5) configuration, having a spin-orbit coupling constant zeta approximate to 950 cm(-1).

First author: Guidez, Emilie B., Diameter Dependence of the Excitation Spectra of Silver and Gold Nanorods, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 12325, (2013)
Abstract: An analysis of the excitation spectra of silver and gold nanorods with different cross sections, lengths, and diameters was performed using time-dependent density functional theory at the LB94/DZ level. Silver nanorods show a strong longitudinal peak, corresponding to excitations along the main axis (z axis) of the nanorods, and a smaller transverse peak, corresponding to excitations in the xy plane of the nanorods. For systems with a large cross-section (star-shaped and large pentagonal nanorods), the single transverse peak is split into a wide band. The orbitals involved in these transitions are delocalized cylindrical orbitals. Constructive addition of the dipole moments of these transitions is observed for the strong longitudinal and transverse peaks, which is likely at the origin of the surface plasmon resonance phenomenon. The wavelength of the longitudinal peak increases linearly with increasing length, crossing over the transverse peak or transverse band, which remains at nearly constant energy and intensity. The intensity of the longitudinal peak increases with increasing system length due to the increasing number of electrons being collectively excited. The energy of the longitudinal peak for systems of identical length also tends to increase as the diameter of the system increases, which can be correlated to a decreasing aspect ratio. Gold nanorods display more complex excitation spectra due to the presence of transitions originating from the d-band. Such transitions may also mix with cylindrical orbital-based transitions, especially for systems with low aspect ratios, splitting the longitudinal peak into several peaks of lower intensity. As the aspect ratio increases, the energy of the longitudinal peak decreases, and its intensity increases. It then becomes separated from the d-band transitions which remain approximately constant in intensity and energy. Consequently, the amount of d-band coupling to the main cylindrical orbital-based excitations decreases, which leads to a strong isolated longitudinal peak similar to the silver case. No strong transverse peak is observed for gold nanorods at this level of theory. Instead, the transverse excitations are hidden by the d-band transitions.

First author: Wang Guang-Yu, Theoretical Study on the Carrier Transport Properties of Indolo[3,2-b]carbazole Derivatives,CHEMICAL JOURNAL OF CHINESE UNIVERSITIES-CHINESE, 34, 1490, (2013)
Abstract: The influence of introduction of chlorine and long alkyl side chains on the hole transport properties of indolo[3,2-b]carbazole derivatives was investigated by combining density functional theory (DFT) with Marcus theory in hopping regime. The results show that the introduction of chlorine atoms induces more delocalized HOMO of 2,8-dichloro-indolo[3,2-b]carbazole(2) and 2,8-dichloro-5,11-dihexyl-indole[3,2-b]carbazole(3) than indolo[3,2-b]carbazole(1), while the LUMO is just the opposite. Besides, both the HOMO/LUMO energy levels and the reorganization energies of compounds 2 and 3 are lower than those of compound 1, and the former is ascribed to chlorine exerting conjugate effect to HOMO but electron-withdrawing effect to LUMO. With the introduction of both chlorine and long alkyl side chains on indolo[3,2-b]carbazole derivatives, compound 3 has higher mobility, which is the result of denser intermolecular packing of dimer A in compound 3 than compounds 1 and 2, thus larger electronic coupling and higher the mobility are measured for compound 3. The results obtained from the band model are consistent with those calculated by hopping regime. Finally, our calculation clarify again in theory that rational chemical modification can improve the carrier transport property of indolo[3,2-b]carbazole derivatives.

First author: Das, Animesh, Tris(alkyne) and Bis(alkyne) Complexes of Coinage Metals: Synthesis and Characterization of (cyclooctyne)(3)M+ (M = Cu, Ag) and (cyclooctyne)(2)Au+ and Coinage Metal (M = Cu, Ag, Au) Family Group Trends,ORGANOMETALLICS, 32, 3135, (2013)
Abstract: The tris(alkyne) copper complex [(cyclooctyne)(3)Cu][SbF6] has been synthesized using cyclooctyne and in situ generated CuSbF6. Tris(alkyne) silver complexes [(cyclooctyne)(3)Ag](+) involving weakly coordinating counterions such as [SbF6](-) and [PF6](-) have also been isolated in good yield using cyclooctyne and commercially available AgSbF6 and AgPF6. These coinage metal tris(alkyne) adducts have trigonal-planar metal sites. The alkyne carbon atoms and the metal site form distorted spoke-wheel (rather than upright trigonal-prismatic) structures in the solid state. In [(cyclooctyne)(3)Cu][SbF6], these distortions result in a propeller-like arrangement of alkynes. A cationic gold(I) complex having two alkynes has been prepared by a reaction of equimolar amounts of Au(cyclooctyne)(2)Cl and AgSbF6 in dichloromethane. The gold atom of [(cyclooctyne)(2)Au](+) coordinates to the cyclooctynes in a linear fashion, while the carbon atoms of the alkyne groups form a tetrahedron around gold(I). Optimized geometries of cationic [(cyclooctyne)(3)M](+), [(cyclooctyne)(2)M](+), and [(cyclooctyne)M](+) and neutral [(cyclooctyne)(2)MCl] and [(cyclooctyne)MCl] adducts (M = Cu, Ag, Au) using density functional theory (DFT) at the BP86/def2-TZVPP level of theory and a detailed analysis of metal-alkyne bonding interactions are also presented.

First author: Jones, Gavin O., Computational Investigations on Base-Catalyzed Diaryl Ether Formation, JOURNAL OF ORGANIC CHEMISTRY, 78, 5436, (2013)
Abstract: We report investigations with the dispersion-corrected B3LYP density functional method on mechanisms and energetics for reactions of group I metal phenoxides with halobenzenes as models for polyether formation. Calculated barriers for ether formation from para-substituted fluorobenzenes are well correlated with the electron-donating or -withdrawing properties of the substituent at the para position. These trends have also been explained with the distortion/interaction energy theory model which show that the major component of the activation energy is the energy required to distort the arylfluoride reactant into the geometry that it adopts at the transition state. Resonance-stabilized aryl anion intermediates (Meisenheimer complexes) are predicted to be energetically disfavored in reactions involving fluorobenzenes with a single electron-withdrawing group at the para position of the arene, but are formed when the fluorobenzenes are very electron-deficient, or when chelating substituents at the ortho position of the aryl ring are capable of binding with the metal cation, or both. Our results suggest that the presence of the metal cation does not increase the rate of reaction, but plays an important role in these reactions by binding the fluoride or nitrite leaving group and facilitating displacement. We have found that the barrier to reaction decreases as the size of the metal cation increases among a series of group I metal phenoxides due to the fact that the phenoxide becomes less distorted in the transition state as the size of the metal increases.

First author: Mei, Yuan, Complexation of gold in S-3(-)-rich hydrothermal fluids: Evidence from ab-initio molecular dynamics simulations, CHEMICAL GEOLOGY, 347, 34, (2013)
Abstract: Recent Raman spectroscopic studies suggest that S(3)(-)is an important sulfur species in magmatic hydrothermal and metamorphic fluids at P> 0.5 GPa and T> 250 degrees C, and may be an important ligand for metal transport (Pokrovski and Dubrovinsky, 2011). Based on static Density Functional Theory calculations, Tossell (2012) confirmed the stability of the S-3(-) ion, and suggested some possible Cu-S-3 complexes in the ideal gas phase and in aqueous solution. We investigated the complexation of Au and Si in aqueous fluids by ab-initio molecular dynamics (MD) simulations. We performed ab-initio MD simulations in aqueous solution at 300 degrees C, 0.5 and 2 GPa to investigate the competition among theS(3)(-), HS-, H2S(aq), OH- and H2O ligands for Au, aiming at evaluating the significance of the ‘exotic’ S-3(-) ligand for Au metallogenesis. The results indicate that, in contrast to results of static calculations that show a symmetric Au-S-3 complex with bidentate structure, Au+ forms linear complexes with S-3(-)-. The stoichiometry of these complexes depends on pH and fluid composition (e.g., Au(H2O)S-3(aq); Au(HS)S-3(-) Au(OH)S-3(-) Au(S-3)2(-). The S-3(-) and bisulfide (HS-) ions are ligands of similar strength for Au; this confirms Pokrovski and Dubrovinsky’s (2011) assumption that such ‘exotic’ ligands may play a major role in promoting Au mobility in magmatic and metamorphic environments.

First author: Wolters, Lando P., Nonlinear d(10)-ML2 Transition-Metal Complexes, CHEMISTRYOPEN, 2, 106, (2013)
Abstract: We have investigated the molecular geometries of a series of dicoordinated d(10)-transition-metal complexes ML2 (M=Co-, Rh-, Ir-, Ni, Pd, Pt, Cu+, Ag+, Au+; L=NH3, PH3, CO) using relativistic density functional theory (DFT) at ZORA-BLYP/TZ2P. Not all complexes have the expected linear ligand-metal-ligand (L-M-L) angle: this angle varies from 180 degrees to 128.6 degrees as a function of the metal as well as the ligands. Our main objective is to present a detailed explanation why ML2 complexes can become bent. To this end, we have analyzed the bonding mechanism in ML2 as a function of the L-M-L angle using quantitative Kohn-Sham molecular orbital (MO) theory in combination with an energy decomposition analysis (EDA) scheme. The origin of bent L-M-L structures is pi backdonation. In situations of strong pi backdonation, smaller angles increase the overlap of the ligand’s acceptor orbital with a higher-energy donor orbital on the metal-ligand fragment, and therefore favor pi backdonation, resulting in additional stabilization. The angle of the complexes thus depends on the balance between this additional stabilization and increased steric repulsion that occurs as the complexes are bent.

First author: Ji, Min, The Electronically Excited-State of the MFU-4 [Zn5Cl4(BBTA)(3)] Metal-Organic Frameworks: Time-Dependent Density Functional Theory Study, JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE,10, 1477, (2013)
Abstract: The density functional theory (DFT) and time-dependent density functional theory (TDDFT) have been carried out to investigate luminescent property of [Zn5Cl4(BBTA)(3)]. The frontier molecular orbitals and electronic configuration of the MOF [Zn5Cl4(BBTA)(3)] have been calculated using DFT. The results shown that the luminescent mechanism in the nature of the [Zn5Cl4(BBTA)(3)] should be the ligand-to-ligand charge transfer (LL’CT) and the transition from HOMO to LUMO be delocalized excitation. The geometric structures of the electronically excited state of the [Zn5Cl4(BBTA)(3)] was optimized using the TDDFT method. The Zn1-N1 and Zn2-N2 coordination bonds were strengthened in the electronically excited state which is confirmed by the bond length, bond order and the stretching vibration frequency of the Zn1-N1 and Zn2-N2 bonds. Combined with luminescent mechanism, we further explained that the Zn1-N1 and Zn2-N2 bonds strengthening in the electronically excited state can promote the luminescent of the [Zn5Cl4(BBTA)(3)].

First author: Rodriguez, Juan I., Molecular (global) and atom-in-cluster (local) polarizabilities of medium-size gold nanoclusters: isomer structure effects, EUROPEAN PHYSICAL JOURNAL D, 67, 1477, (2013)
Abstract: In this work, we extend our recent study [J.I. Rodriguez, J. Autschbach, F. L. Castillo-Alvarado, M. I. Baltazar-Mendez, J. Chem. Phys. 135, 034109 (2011)] to quantify the isomer structure effects on the atom-in-cluster polarizabilities of medium size gold clusters Au (n = 6, 12, 20, 34, 54). For three isomers for each cluster size, a density functional perturbation theory calculation was performed to compute the cluster polarizability and the polarizability of each atom in the cluster using Bader’s “quantum theory of atoms in molecules” formalism. The cluster polarizability tensor is expressed as a sum of the atom-in-cluster atomic tensors. We found that the strong quadratic correlation (R-2 = 0.98) in the isotropic polarizability of atoms in the cluster and their distance to the cluster center of mass reported before holds independently of the cluster structure.

First author: Thellamurege, Nandun, Water Complexes of Cytochrome P450: Insights from Energy Decomposition Analysis, MOLECULES, 18, 6782, (2013)
Abstract: Water is a small molecule that nevertheless perturbs, sometimes significantly, the electronic properties of an enzyme’s active site. In this study, interactions of a water molecule with the ferric heme and the compound I (Cpd I) intermediate of cytochrome P450 are studied. Energy decomposition analysis (EDA) schemes are used to investigate the physical origins of these interactions. Localized molecular orbital EDA (LMOEDA) implemented in the quantum chemistry software GAMESS and the EDA method implemented in the ADF quantum chemistry program are used. EDA reveals that the electrostatic and polarization effects act as the major driving force in both of these interactions. The hydrogen bonding in the Cpd I center dot center dot center dot H2O complex is similar to that in the water dimer; however, the relative importance of the electrostatic effect is somewhat larger in the water dimer.

First author: Krykunov, Mykhaylo, Self-consistent Formulation of Constricted Variational Density Functional Theory with Orbital Relaxation. Implementation and Applications, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 2761, (2013)
Abstract: We introduce here a new version of the constricted nth order variational density functional method (CV(n)-DFT) in which the occupied excited state orbitals are allowed to relax in response to the change of both the Coulomb and exchange-correlation potential in going from the ground state to the excited state. The new scheme is termed the relaxed self-consistent field nth order constricted variational density functional (RSCF-CV(n)-DFT) method. We have applied the RSCF-CV(n)-DFT scheme to the n(sigma)->pi* transitions in which an electron is moved from an occupied lone pair orbital n(sigma) to a virtual pi* orbital. A total of 34 transitions involving 16 different compounds were considered using the LDA, B3LYP, and BHLYP functionals. The DFT-based results were compared to the “best estimates” (BE) from high level ab initio calculations With energy terms included to second order in the variational parameters (CV(2)-DFT), our theory is equivalent to the adiabatic version of time dependent DFT. We find that calculated excitation energies for CV(2)-DFT using LDA and BHLYP differ substantially from BE with root-mean-square-deviations (RMSD) of 0.87 and 0.65 eV, respectively, whereas B3LYP affords an excellent fit with BE at RMSD = 033 eV. Resorting next to CV(infinity)-DFT where energy terms to all orders in the variational parameters are included results for all three functionals in too high excitation energies with RMSD = 1.62, 1.14, and 1.48 eV for LDA, B3LYP, and BHLYP, respectively. Allowing next for a relaxation of the orbitals (n(sigma),pi*) that participate directly in the transition (SCF-CV(n)-DFT) leads to an improvement with RMSD = 0.49 eV (LDA), 0.50 eV (B3LYP), and 1.12 eV (BHLYP). The best results are obtained with full relaxation of all orbitals (RSCF-CV(n)) where now RMSD = 0.61 eV (LDA), 0.32 eV (B3LYP), and 0.52 eV (BHLYP). We discuss finally the relation between RSCF-CV(n) and Slater ‘s ASCF method and demonstrate that the two schemes affords quite similar results in those cases where the excitation can be described by a single orbital displacement (n(sigma)->pi*).

First author: Kaszuba, Karol, Parameterization of the prosthetic redox centers of the bacterial cytochrome bc(1) complex for atomistic molecular dynamics simulations, THEORETICAL CHEMISTRY ACCOUNTS, 132, 2761, (2013)
Abstract: Cytochrome (cyt) bc(1) is a multi-subunit membrane protein complex that is a vital component of the respiratory and photosynthetic electron transfer chains both in bacteria and eukaryotes. Although the complex’s dimer structure has been solved using X-ray crystallography, it has not yet been studied in large-scale classical molecular dynamics (MD) simulations. In part, this is due to lack of suitable force field parameters, centered atomic point charges in particular, for the complex’s prosthetic redox centers. Accurate redox center charges are needed to depict realistically the inter-molecular interactions at different redox stages of the cyt bc(1) complex. Accordingly, here we present high-precision atomic point charges for the metal centers of the cyt bc(1) complex of Rhodobacter capsulatus derived from extensive density functional theory calculations, fitted using the restrained electrostatic potential methodology and combined with the CHARMM force field parameters. We also provide the Hartree-Fock charges for all substrate forms (quinol, quinone, and semiquinone) and the inhibitors antimycin and stigmatellin of the bacterial bc(1) complex. The accuracy of the parameterization scheme was verified by running a 200-ns MD simulation encompassing the entire cyt bc(1) complex embedded in a lipid bilayer and solvated with explicit water. The results indicate that these meticulously derived parameters are ready for running extensive MD simulations encompassing all biologically relevant stages of the cyt bc(1) complex reaction cycle.

First author: Elder, Philip J. W., Experimental and Computational Investigations of Tautomerism and Fluxionality in PCP- and PNP-Bridged Heavy Chalcogenides, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 132, 2867, (2013)
Abstract: The reaction of H2C(PCl2)2 with four equivalents of iPrMgCl produces H2C(PiPr2)2, which was treated with tellurium in boiling toluene, or selenium in toluene at room temperature, to give the monochalcogenides EPiPr2CH2PiPr2 (E = Te, 4a; E = Se, 4b) in high yields. X-ray structural determinations show that 4a and 4b exist as the CH2 tautomers in the solid state with EPCP dihedral angles of 56.1(2)degrees and 56.7(1)degrees, respectively. DFT calculations were carried out for the isolectronic series EPR2CH2PR2 and EPR2NHPR2 (E = Se, Te; R = Me, iPr, tBu, Ph) and for their non-chalcogenated precursors in order to elucidate the factors that determine the preference for PH tautomers in some PNP-bridged systems. Compounds 4a and 4b were also characterized by multinuclear (1H, 13C, 31P, 77Se, 125Te) NMR spectroscopy. In solution, 4a exhibits fluxional behavior, which has been investigated by variable-temperature and variable-concentration multinuclear NMR spectroscopy. The observed behavior is consistent with an intermolecular tellurium transfer with an activation energy of 21.9 +/- 3.2 kJmol1; consideration of selenium exchange in 4b indicates a much higher energetic barrier. DFT calculations provide insights into the pathway for the chalcogen exchange process in 4a (E = 20.4 kJmol1). The outcome of reactions of 4a with selenium and nBuLi reflects the lability of the P-Te functionality.

First author: Lee, Choongkeun, Effects of Mn doping on (TiO2)(n) (n=2-5) complexes, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1013, 32, (2013)
Abstract: Mn-doped TiO2 systems are of interest for low cost and high efficiency photocatalysts. However, little is known about the effects of doping on their structure. In this work, Mn is doped into (TiO2)(n) (n = 2-5) complexes. In the most stable structures of Mn doped TiO2 complexes, the overall appearance of the cluster does not change much from that of the associated parent complex. Mn-O bonds are usually shorter, and nearby Ti-O bonds lengthen slightly. However, the angle centered on Mn significantly increases. Structures exhibit trigonal planar arrangements around Mn with 3 O ligands and tetrahedral arrangements with four ligands. The most stable structures typically have Mn at lower coordinated positions. Relative to the parent TiO2 systems, occasionally a Mn-O bond breaks in order to maintain a low coordination number of Mn. The HOMO-LUMO gap decreases significantly by Mn doping, but this decrease is not proportional to the number of doped Mn.

First author: Wiegand, Thomas, Solid state NMR studies and chemical shift calculations of a gold(I) complex with a diphosphacyclobutadiene cobaltate sandwich anion, SOLID STATE NUCLEAR MAGNETIC RESONANCE, 53, 13, (2013)
Abstract: The P-31 and C-13 solid state nuclear magnetic resonance spectra of a neutral gold(I) complex with bis(diphosphacyclobutadiene) cobaltate anions, [Au{Co(P(2)C(2)tPent(2))(2)}(2)(PMe3)(2)], are reported. Complete P-31 resonance assignments have been derived from saturation transfer, radio-frequency driven recoupling (RFDR) and RTOBSY experiments and confirmed further by ab-initio calculations of magnetic shielding tensors by density functional theory, with consideration of relativistic effects. Coordination of the diphosphacyclobutadiene ring with gold(I) results in a high-frequency shift of the P-31 signal of the directly coordinated P atom, whereas a low-frequency shift is observed for the P atom at the opposite end of that ring. Based on these results, a previous assignment made for the complex salts [Au(PMe3)(4)][Au{Co(P(2)C(2)Ad(2))(2)}(2)] and [K(18-crown-6)(thf)(2)][Au{Co(P(2)C(2)Ad(2))(2)}(2)] (Ad=adamantyl) must be corrected.

First author: Peric, Marko, Spherical aromaticity of Jahn-Teller active fullerene ions, MONATSHEFTE FUR CHEMIE, 144, 817, (2013)
Abstract: Density functional theory was applied to compute the nucleus-independent chemical shifts of fullerene (C-60), the fullerene ion C-60 (10+), and the Jahn-Teller active fullerene anion C-60 (-) and cation C-60 (+). Positioning a He-3 nucleus inside the cage of each of these fullerene species facilitates investigations of the substantial differences among them, He-3 NMR chemical shifts can provide important data on the aromatic behavior of these molecular cages. Thus, we also calculated the NMR chemical shift of a He-3 atom positioned at the center of each fullerene species investigated (C-60, C-60 (10+), C-60 (-), and C-60 (+)). The data obtained revealed significant differences in the aromatic behavior of the C-60 (moderately aromatic) and C-60 (10+) (highly aromatic) species. The values of the nucleus-independent chemical shift parameters were also scanned along the intrinsic distortion path for the C-60 (-) and C-60 (+) species. In both cases, antiaromatic character decreases with increasing deviation from high-symmetry structures to low-symmetry global minimum points, resulting in the antiaromatic C-60 (-) and weakly aromatic C-60 (+).

First author: Hnyk, Drahomir, Expanding the structural chemistry of the weakly coordinating closo-carborane CB11H12 (-): its monoiodo derivatives with and without C (5v) symmetry, STRUCTURAL CHEMISTRY, 24, 927, (2013)
Abstract: Two iodo derivatives of closo-CB11H12 (-), i.e., 12-I-1-CB11H11 (-) (C (5v) symmetry) and 7-I-1-CB11H11 (-) (C (s) symmetry), were prepared (the latter for the first time) and the influence of differently positioned iodine substituents on the geometry of the CB11 icosahedral core was structurally examined both by X-ray diffraction and quantum-chemical computation at the MP2 level. Observed and computed molecular geometries are in overall agreement. Supramolecular architectures of these two anionic substituted monocarboranes are shown. According to DFT computations at the ZORA-SO/BP86 level, the B-11 chemical shifts of the boron atoms to which iodine substituents are bonded are dominated by spin-orbit coupling. Different positions of iodine atoms in these two isomers may result in different acidities of the (C)-H atoms in the icosahedral bodies, as suggested by visually analyzing the corresponding lowest unoccupied molecular orbitals.

First author: Schott, Eduardo, Molecular properties of two related families of substituted [Ru(2,2 ‘:6 ‘,2 ”-Terpyridine)(2)](2+) for application as sensitizers in dye-sensitized solar cells, DYES AND PIGMENTS, 97, 455, (2013)
Abstract: A theoretical study of two families of related compounds of 4′-R substituted 2,2′:6′,2 ”-terpyridines (TP) with Ruthenium as central metal is presented (one family is homoleptic and the other family is heteroleptic). The influence of the 4′-R substituent over the electronic structure, reactivity indexes and the electronic transitions in the UV-Vis spectra is studied. A proposal of a group of dyes not synthesized yet that could be efficient dyes to sensitize a semiconductor like TiO2 in an energy conversion device like a DSSC is made. Due to the presence of the carboxylic anchor group, the results of the direction of the calculated excitations and the charge transfer of the TP ligand, suggest that the most effective dyes are the heteroleptic TP with an electron-donor substituent over one terpyridine ligand and one carboxylic acid group in the 4′ position of the second TP ligand.

First author: Goldsmith, Bryan R., Isolated catalyst sites on amorphous supports: A systematic algorithm for understanding heterogeneities in structure and reactivity, JOURNAL OF CHEMICAL PHYSICS, 138, 455, (2013)
Abstract: Methods for modeling catalytic sites on amorphous supports lag far behind methods for modeling catalytic sites on metal surfaces, zeolites, and other crystalline materials. One typical strategy for amorphous supports uses cluster models with arbitrarily chosen constraints to model the rigid amorphous support, but these constraints arbitrarily influence catalyst site activity. An alternative strategy is to use no constraints, but this results in catalytic sites with unrealistic flexibility. We present a systematic ab initio method to model isolated active sites on insulating amorphous supports using small cluster models. A sequential quadratic programming framework helps us relate chemical properties, such as the activation energy, to active site structure. The algorithm is first illustrated on an empirical valence bond model energy landscape. We then use the algorithm to model an off-pathway kinetic trap in olefin metathesis by isolated Mo sites on amorphous SiO2. The cluster models were terminated with basis set deficient fluorine atoms to mimic the properties of an extended silica framework. We also discuss limitations of the current algorithm formulation and future directions for improvement.

First author: Ma, Zhibo, Photocatalytic Dissociation of Ethanol on TiO2(110) by Near-Band-Gap Excitation, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 10336, (2013)
Abstract: Ethanol on TiO2(110) has been studied using the temperature-programmed desorption (TPD), femtosecond two-photon photoemission spectroscopy (2PPE), and density functional theory (DFT) calculations. The first layer of ethanol (binds to Ti-5c) whose molecular state has been predicted to be more stable by DFT desorbs at 295 K. A photoinduced excited state that is associated with bridging hydroxyls has been detected at similar to 2.4 eV above the Fermi level on ethanol/TiO2(110) interface using 2PPE. Detailed TPD studies show that ethanol on Ti-5c can be photocatalytically converted to acetaldehyde by near-band-gap excitation with the hydrogen atoms transfer to bridging-bonded oxygen sites, which is consistent with the 2PPE results. TPD results also show a low-temperature water TPD peak that seems to bind to the Ti-5c sites in addition to the ethylene TPD product. These results suggest that the Ti-5c sites on TiO2(110) are the primary active sites for photocatalysis of ethanol on TiO2(110), while bridging-bonded oxygen sites also play an important role, as in the case of methanol. The kinetics of photocatalyzed ethanol dissociation on TiO2(110) has also been measured using the 2PPE technique, which is of heterogeneous nature.

First author: Raju, Muralikrishna, ReaxFF Reactive Force Field Study of the Dissociation of Water on Titania Surfaces,JOURNAL OF PHYSICAL CHEMISTRY C, 117, 10558, (2013)
Abstract: We studied the adsorption and dissociation of water at 300 K on the following TiO2 surfaces: anatase (101), (100), (112), (001), and rutile (110) at various water coverages, using a recently developed ReaxFF reactive force field. The molecular and dissociative adsorption configurations predicted by ReaxFF for various water coverages agree with previous theoretical studies and experiment. ReaxFF predicts a complex distribution of water on these surfaces depending on an intricate balance between the spacing of the adsorption sites (under-coordinated Ti and O surface atoms), water-surface interactions, and water-water interactions. Using molecular dynamics simulations to quantify water dissociation over the TiO2 surfaces at various water coverages, we find that the extent of water dissociation predicted by the ReaxFF reactive force field is in general agreement with previous density-functional theory studies and experiments. We demonstrate a correlation between the extent of water dissociation on different TiO2 surfaces and the strength of hydrogen bonding between adsorbed water molecules and water outside the adsorbed layer, as evidenced by the red shift of the O-H vibrational stretching mode of adsorbed water.

First author: Kandada, Ajay Ram Srimath, Role of Hot Singlet Excited States in Charge Generation at the Black Dye/TiO2 Interface, ACS APPLIED MATERIALS & INTERFACES, 5, 4334, (2013)
Abstract: Photoinduced electron transfer at low-band-gap ruthenium-based dye/TiO2 has been investigated by means of ultrafast transient absorption and DFT/TDDFT calculations. We demonstrate that although the charge generation mechanism is triplet mediated upon band gap excitation, as already proven in high band gap dyes such as the well-known N3 and N719, when excess energy is provided which allows to reach high energy singlet states still in the visible spectral range, ultrafast electron transfer takes place. No intersystem crossing process is observed and charge generation happens only from the singlet excited state.

First author: Matovic, Zoran D., Configurational, LFDFT and NBO analysis of chromium(III) complexes of edta-type ligands, POLYHEDRON, 55, 131, (2013)
Abstract: A new hexadentate chromium(III) complex, Na[Cr(1,3-pd3ap)]center dot 3H(2)O, containing an unsymmetrical edta-type ligand, the 1,3-propanediamine-N,N,N’-triacetate-N’-3-propionate ion (1,3-pd3ap), has been prepared, chromatographically separated and characterized. Only one [trans(O-5)] of the two possible geometrical isomers was isolated. In this isomer the two five-membered glycinate rings (R rings) occupy trans-axial sites, while the one glycinate ring and one beta-alaninate ring lie in the equatorial plane with the two diamine nitrogens (G rings). This result confirms the assignment made on the basis of Density Functional Theory (OFT), IR and UV-Vis spectral data analyses. The spectral data and electronic transition assignment, DFT-NBO, Ligand Field DFT and extensive strain analysis are discussed by a comparison with those of other [Cr(edta-type)](-) complexes of known configurations. The stoichiometry and stability of the complexes formed between the chromium(III) ion and 1,3-propanediamine-N,N,N’-triacetic-N’-propionic acid (H(4)1,3-pd3ap) were determined in aqueous solution by potentiometry at 25 degrees C and 0.1 M NaCl ionic strength. The existence of Cr(HnL), n = 0,1, 2 and 3 type complexes were verified. The formation of the Cr(OH)L complex was observed at higher pH values. The concentration distribution diagrams of the complexes were evaluated.

First author: Pandey, Krishna K., Nature of M-(eta(2)-H-SiR2) bonds in chromium, molybdenum and tungsten complexes [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiR2)] and [(eta(5)-C5H5)(CO)(2)M(eta(2)-H-SiMe2)]: A theoretical study,POLYHEDRON, 55, 241, (2013)
Abstract: Geometries, electronic structure, and bonding analysis of the coordinated hydrosilyl groups in chromium, molybdenum and tungsten complexes [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiMe2)] (1Cr, M = Cr; 1Mo, M = Mo; 1W, M = W), [(eta(5)-C5H5)(CO)(2)M(eta(2)-H-SiMe2)] (2Cr, M = Cr; 2Mo, M = Mo; 2W, M = W), [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiEt2)] (3Mo) [(eta(5)-C5H5)(dmpe)Mo(eta(2)-H-SiPh2)] (4Mo) and [(eta(5)-C5H5)(dmpe)M(eta(2)-H-Si(H)Ph)] (5Mo) (dmpe = Me2PCH2CH2PMe2) were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The optimized geometry of model complexes for [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiMe2)], [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiEt2)] and [(eta(5)-C5H5)(dmpe)M(eta(2)-H-Si(H)Ph)] are in excellent agreement with the experimental values. The M-H1 bond is directed toward the empty p orbital of the Si atom of the silylene ligands. A significant lengthening of the M-H1 and Si-H1 bonds and small Si-M-H1 bond angles (in the range 45.4 degrees-47.5 degrees) indicate the existence of three center two electron M-H-Si bonding. Upon substitution of the dmpe ligand by better pi-acceptor CO ligands, the calculated M-Si and M-H1 bond distances slightly increase, while Si-H1 bond distances decrease due to increase in M <- SiR2 sigma-bonding. The small values of Mayer bond orders of the M-H and H-Si bonds also indicate the hydride as bridging between the M and Si centers. The M-H-Si bonding orbital is polarized toward the H1 atom (the H1 atom contributes nearly 50% to the M-H-Si bonding orbital). Absolute values of various energy terms increase upon substitution of dmpe ligand by better pi-acidic CO ligands. The nature of substituent at Si atom in complexes 1Mo, 3Mo-5Mo has a small effect on the orbital interaction, Delta E-orb.

First author: Moustafa, Mohamed E., Photoswitchable Organoplatinum(IV) Complexes, ORGANOMETALLICS, 32, 2552, (2013)
Abstract: Organoplatinum(IV) complexes, [PtBrMe2(CH2-4-C6H4-N=N-NPh)(NN)], containing trans-azobenzene functional groups, have been prepared by trans oxidative addition of BrCH2-4-C6H4-N=N-Ph to the corresponding platinum(II) complexes [PtMe2(NN)], with NN = 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine, 1,4-di-2-pyridyl-5,6,7,8,9,10-hexahydrocycloocta[d]pyridazine. The complexes undergo efficient and almost quantitative trans-cis isomerization on irradiation of dilute solutions at 365 nm, as monitored by UV-visible spectroscopy, and somewhat less complete photolysis in concentrated solution, as monitored by H-1 NMR spectroscopy. The cis isomers undergo slow thermal isomerization back to the trans isomers, thus proving the photoswitching property of the complexes.

First author: Aseman, Marzieh Dadkhah, Secondary Kinetic Isotope Effects in Oxidative Addition of Benzyl Bromide to Dimethylplatinum(II) Complexes, ORGANOMETALLICS, 32, 2593, (2013)
Abstract: The secondary alpha-deuterium kinetic isotope effects (KIEs), (k(H)/k(D))(alpha), have been determined, at different temperatures and in solvents having different polarities, for reaction of PhCH2Br/PhCD2Br with the dimethylplatinum(II) complexes [PtMe2(NN)], in which the bidentate NN ligand is bpy (=2,2′-bipyridine) or bu(2)bpy (=4,4′-di-tert-butyl-2,2′-bipyridine). The values obtained for the secondary alpha-deuterium KIEs in acetone solution are close to 1 and may be normal or inverse, but much larger values are found for the reactions in benzene. An explanation is presented on the basis of solvent dependence of the degree of looseness of the transition state in the S(N)2 mechanism.

First author: Angel Espinosa-Jalapa, Noel, Coordination of 12-Electron Organometallic Fragments to the Arene Ring of Nonsymmetric Group 10 POCOP Pincer Complexes, ORGANOMETALLICS, 32, 2661, (2013)
Abstract: A series of heterobimetallic complexes have been prepared in good yields by,,6 coordination of [Cp*Ru](+), [CpRu](+), [CpFe](+), and [Cr(CO)(3)] fragments to the aromatic ring of nonsymmetric Ni(II), Pd(II), and Pt(II) naphthoresorcinate POCOP compounds, and the molecular structures of the new compounds have been unequivocally determined by single-crystal X-ray diffraction crystallography. The reaction is regiospecific, and only coordination at the noncyclometalated ring is observed. The coordination occurs in an orthogonal fashion, and as a consequence, the heterobimetallic species exhibit axial desymmetrization of the pincer fragment, generating molecules with planar chirality. In addition, the electronic properties of the metal center can be tuned by the effect of pi coordination of the second metal, as shown by electrochemical studies. The observed specificity of the reaction is discussed and supported with theoretical studies.

First author: Muratov, Dmitry V., Monocationic mu-Diborolyl Triple-Decker Complexes [CpCo(mu-1,3-C3B2Me5)M(ring)](+): Synthesis, Structures, and Electrochemistry, ORGANOMETALLICS, 32, 2713, (2013)
Abstract: Cationic triple-decker complexes with a bridging diborolyl ligand, [CpCo(mu-1,3-C3B2Me5)M(ring)](+) (M-(ring) = CoCp (2a), CoCp* (2b), RhCp (3a), RhCp* (3b), IrCp (4a), IrCp* (4b), Ru(C6H6) (5a), Ru(p-MeC6H4Pri) (5b), Ru(C6Me6) (5c), Ru(eta(6)-cycloheptatriene) (6)), were synthesized by reaction of CpCo(mu-1,3-C3B2Me5)Tl with [M(ring)Hal(2))(2). The structures of 2aBPh(4), 2bPF(6), 4aPF(6), 5aOTf, and 5cPF(6) were determined by X-ray diffraction. The electron-transfer ability of the complexes has been ascertained by electrochemical and spectroelectrochemical techniques. In general, they are able to shuttle reversibly in the sequence 2+/+/0/-, plausibly affording completely delocalized mixed-valence derivatives. DFT calculations revealed structural changes accompanying redox processes and satisfactorily predicted the potentials for the first reduction and first oxidation.

First author: Li, Peng, Ab Initio Molecular Dynamics Study of the Reaction of U+ and U2+ with H2O in the Gas Phase: Direct Classical Trajectory Calculations, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 3761, (2013)
Abstract: The gas phase reactions of U+ and U2+ with H2O were investigated using an ab initio molecular dynamics method. All of the information along the minimum energy path were calculated with density functional theory (DFT) and coupled cluster methods. For U+ with H2O, the molecular dynamics simulations yield a branching ratio of 86% for the H-2 elimination channel to 14% for the H atomic elimination channel in agreement with the quadruple ion trap mass spectrometry (QIT/MS) experimental ratio of 91% to 9%. In the case of U2+ + H2O, there is a crossing of the potential energy surfaces (PES) after the first transition state. Crossing seams between the PES and possible spin inversion processes were studied by means of the intrinsic reaction coordinate (IRC) approach. For U2+ with H2O, all trajectories are corresponds to H atom elimination channel, this is consistent with the Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) experimental results. The chemical bonding evolution along the reaction pathways was discussed by using topological methodologies of the electron localization function (ELF).

First author: Park, Kiyoung, Combined Spectroscopic and Computational Analysis of the Vibrational Properties of Vitamin B-12 in its Co3+, Co2+, and Co1+ Oxidation States, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 5397, (2013)
Abstract: While the geometric and electronic structures of vitamin B-12 (cyanocobalamin, CNCbl) and its reduced derivatives Co(2+)cobalamin (Co(2+)Cbl) and Co(1+)cobalamin (Co(1+)Cbl(-)) are now reasonably well established, their vibrational properties, in particular their resonance Raman (rR) spectra, have remained quite poorly understood. The goal of this study was to establish definitive assignments of the corrin-based vibrational modes that dominate the rR spectra of vitamin B-12 in its Co3+, Co2+, and Co1+ oxidation states. rR spectra were collected for all three species with laser excitation in resonance with the most intense corrin-based pi -> pi* transitions. These experimental data were used to validate the computed vibrational frequencies, eigenvector compositions, and relative rR intensities of the normal modes of interest as obtained by density functional theory (DFT) calculations. Importantly, the computational methodology employed in this study successfully reproduces the experimental observation that the frequencies and rR excitation profiles of the corrin-based vibrational modes vary significantly as a function of the cobalt oxidation state. Our DFT results suggest that this variation reflects large differences in the degree of mixing between the occupied Co 3d orbitals and empty corrin pi* orbitals in CNCbl, Co(2+)Cbl, and Co(1+)Cbl(-). As a result, vibrations mainly involving stretching of conjugated C-C and C-N bonds oriented along one axis of the corrin ring may, in fact, couple to a perpendicularly polarized electronic transition. This unusual coupling between electronic transitions and vibrational motions of corrinoids greatly complicates an assignment of the corrin-based normal modes of vibrations on the basis of their rR excitation profiles.

First author: Perras, Frederic A., Measuring dipolar and J coupling between quadrupolar nuclei using double-rotation NMR, JOURNAL OF CHEMICAL PHYSICS, 138, 5397, (2013)
Abstract: Among the interactions which govern NMR spectra, spin-spin coupling interactions provide the most direct form of structural information which is of interest to chemists. Dipolar coupling may be used to measure internuclear distances directly and J coupling may be used to identify bonding interactions and provide insights into the nature of the bonds. It is well known that the presence of a quadrupolar interaction reintroduces the dipolar interaction in spinning samples; however, similarly to the J coupling, this information is often lost if the observed nucleus is quadrupolar due to quadrupolar spectral broadening. Here we show for multiple spin pairs that double-rotation ( DOR) NMR fully removes the effects of the quadrupolar interaction on the NMR spectrum leaving only the effects of dipolar and J couplings. We also demonstrate that the J coupling multiplets do not disappear for quadrupolar A(2) spin pairs as they do for spin-1/2 nuclei. With DOR NMR, it is then straightforward to measure homonuclear J coupling constants between magnetically equivalent quadrupolar nuclei. A deeper understanding of the origins of the magnitudes and dominant mechanisms of J coupling for quadrupolar spin pairs in a series of related compounds is obtained by decomposing computed J coupling constants into their major molecular orbital contributions.

First author: Visser, Bradley R., Spectroscopic observation of gold-dicarbide: Photodetachment and velocity map imaging of the AuC2 anion, JOURNAL OF CHEMICAL PHYSICS, 138, 5397, (2013)
Abstract: Photoelectron spectra following photodetachment of the gold dicarbide anion, AuC2-, have been recorded using the velocity map imaging technique at several excitation wavelengths. The binding energy spectra show well-defined vibrational structure which, with the aid of computational calculations and Franck-Condon simulations, was assigned to a progression in the Au-C stretching mode, nu(3). The experimental data indicate that the features in the spectrum correspond to a (2)A’ <- (3)A’ transition, involving states which we calculate to have bond angles similar to 147 degrees but with a low barrier to linearity.

First author: Turbervill, Robert S. P., An Asymmetrically Derivatized 1,2,3-Triphospholide: Synthesis and Reactivity of the 4-(2 ‘-Pyridyl)-1,2,3-triphospholide Anion, INORGANIC CHEMISTRY, 52, 5527, (2013)
Abstract: Reactions between anionic heptaphosphide clusters ([P-7](3-)/[HP7](2-)) and 2-ethynylpyridine yielded the 4-(2′-pyridyl)-1,2,3-triphospholide anion ([P3C2H(2-C5H4N)](-); 1). This species was isolated as a compositionally pure [K(2,2,2-crypt)](+) salt in moderate yields. Preliminary coordination studies of 1 toward Mo(CO)(6) or Mo(Py)(3)(CO)(3) (py = pyridine) afforded the diamagnetic piano-stool complex [{eta(5)-P3C2H(2-C5H4N)}Mo(CO)(3)](-) (2). By contrast, reaction of 1 with Mo(COD)(CO)(4) (COD = 1,5-cyclooctadiene) yielded [{kappa P-2,N-P3C2H(2-C5H4N)}Mo(CO)(4)](-) (3) which readily loses a carbonyl on heating to give 2. Reaction of 2 with Mo(COD)(CO)(4) afforded the bimetallic system [{mu:eta(5),kappa P-2,N-P3C2H(2-C5H4N)}{Mo(CO)(3)}{Mo(CO)(4)}](-) (4).

First author: Taylor, Robert E., A Combined NMR and DFT Study of Narrow Gap Semiconductors: The Case of PbTe,JOURNAL OF PHYSICAL CHEMISTRY C, 117, 8959, (2013)
Abstract: In this study we present an alternative approach to separating.. contributions to the NMR shift originating from the Knight shift and chemical shielding by a combination of experimental solid-state NMR results and ab initio calculations. The chemical and Knight shifts are normally distinguished through detailed studies of the resonance frequency as a function of temperature and carrier concentration, followed by extrapolation of the shift to Zero carrier concentration. This approach is time-consuming and requires studies of multiple samples. Here, we analyzed Pb-207 and Te-125 NMR spin-lattice relaxation rates and NMR shifts for bulk and nanoscale PbTe. The shifts are compared with calculations of the Pb-207 and Te-128 chemical shift resonances to determine the chemical shift at zero charge carrier concentration. The results are in good agreement with literature values from carrier concentration dependent studies. The measurements are also compared to literature reports of the Pb-207 and Te-128 Knight shifts of n- and p-type PbTe semiconductors. The literature data have been converted to the currently accepted shift scale. We also provide possible evidence for the “self-cleaning effect” property of PbTe nanocrystals whereby defects are removed from the core of the particles while preserving the crystal structure.

First author: Zhang, Zhengyan, The Stabilization Effect of Dielectric Constant and Acidic Amino Acids on Arginine-Arginine (Arg-Arg) Pairings: Database Survey and Computational Studies, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 4827, (2013)
Abstract: Database survey in this study revealed that about one-third of the protein. structures deposited in the Protein Data Bank (PDB) Contain arginine arginine (Arg-Arg) pairing with a carbon center dot center dot center dot carbon (CZ center dot center dot center dot CZ). interaction distance less than 5 A. All the Arg-Arg pairings were found to bury in a polar environment: composed of acidic residues, water molecules, and strong polarizable or negatively charged moieties from binding site or bound ligand. Most of the Arg-Arg pairings are solvent exposed and 68.3% Arg-Arg pairings are Stabilized by acidic residues, forming Arg-Arg-Asp/Glu clusters. Density functional theory (DFT) was: then employed to study the effect of environment on the poring structures It Was revealed that Arg-Arg pairings become thermodynamically stable (about -1 kcal/mol) as the dielectric constant increases to 46.8 (DMSO), in good agreement with the results of the PDB survey. DFT calculations also demonstrated that perpendicular Arg-Arg pairing structures are favorable in low dielectric constant environment, while in high dielectric constant environment parallel Structures are favorable: Additionally, the acidic residues can stabilize the Arg-Arg pairing structures to a large degree:, Energy decomposition analysis of Arg-Arg pairings and Arg-Arg-Asp/Glu clusters showed that both solvation and electrostatic energies contribute significantly to their stability. The results, reported herein should be very helpful for understanding Arg-Arg pairing and its application in drug design.

First author: Cozzolino, Anthony F., The role of the Lewis acid-base properties in the supramolecular association of 1,2,5-chalcogenadiazoles, CANADIAN JOURNAL OF CHEMISTRY, 91, 338, (2013)
Abstract: The secondary bonding interactions that link the supramolecular structures assembled by 1,2,5-chalcogenadiazoles were analyzed through explicit orthogonalization of molecular orbitals (NBO), topological analysis of the electron density (AIM), and the electron localization function (ELF). The results of these analyses are consistent with a bonding description that attributes important covalent and electrostatic character to these interactions. Application of these analyses to the individual molecules highlighted the structural features from which each of those contributions originates, namely the polarity and modest strength of the E-N bond. Both of these effects increase along the series S, Se, Te. Perturbations to the heterocycle electronic structure that result in a weaker and more polar E-N bond cause an increase in the Lewis acidity at the chalcogen centre, which in turn leads to stronger secondary bonding interactions with Lewis bases. Additionally, the contribution of dispersion forces is not negligible and is most important in the case of sulfur.

First author: Pinter, Balazs, Revealing the Origins of Electrophilic Reactivity and Regioselectivity of Linear Acenes Using Interaction Energy Decomposition Potentials, EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, 91, 2994, (2013)
Abstract: The intrinsic electrophilic reactivity of linear acenes up to octacene was investigated by using interaction energy potentials and their components, namely Pauli repulsion, orbital interaction, and electrostatic interaction potentials using the Ziegler-Rauk decomposition scheme. We found that the shared regions above C1 and C2 of the outer ring are slightly more attractive towards an incoming electrophile than the inner ring secondary carbon atoms, mostly due to a more advantageous electrostatic interaction. This result agrees with the stability order of prereactive pi complexes formed between anthracene and the electrophilic HCl. Decomposition potentials determined in the bond formation regime indicate that longer acenes become more reactive because of the increasing orbital interaction. In addition, the orbital interaction potentials, which represent the overall effect of the high lying reactive orbital, exhibit straightforward patterns, predicting strongly preferred inner ring secondary carbon atoms over outer ring carbon atoms. Such an orbital-interaction controlled regioselectivity shows up in the total interaction energy potentials when the electrostatic interaction is scaled down, predicting the functionalization of acenes with electrophiles on the inner secondary carbon atoms, in agreement with the experimental regioselectivity. Upon analyzing the stability of transition states for the addition of HCl to anthracene, the Pauli repulsion shows up to be an important factor in controlling the stability of the transition states and favoring functionalization along the central C9 and C10 positions to outer ring carbon atoms. The resonance stabilization concept, which is generally accepted to account for the regioselectivity of higher acenes, could not be evidenced by our analysis.

First author: Seth, Michael, Modeling Transition Metal Reactions with Range-Separated Functionals, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 2286, (2013)
Abstract: The performance of range separated functionals for the calculation of reaction profiles of organometallic compounds is considered. Sets of high-level computational results are used as reference data for the most part The benchmark data include a number of reactions involving small molecules reacting with the Pd atom, PdCl-, PdCl2, and a Ni atom, the reaction of a model Grubbs catalyst, and the ligand binding in a real Grubbs catalyst. Range-separated functionals are found to improve upon most standard local functionals especially if an optimized range-separation parameter is used They do not represent an improvement upon the better-performed global hybrid functionals or a local functional that includes a larger number of adjustable parameters. Some unusual results for molecule-molecule interaction energies are observed and explained by a detailed analysis of the contributions to the bonding energies. The influence of range separation on the barriers and reaction energies is also investigated.

First author: Kiewisch, Karin, Quantum-Chemical Electron Densities of Proteins and of Selected Protein Sites from Subsystem Density Functional Theory, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 2425, (2013)
Abstract: The ability to calculate accurate electron densities of full proteins or of selected sites in proteins is a prerequisite for a fully quantum-mechanical calculation of proteinprotein and proteinligand interaction energies. Quantum-chemical subsystem methods capable of treating proteins and other biomolecular systems provide a route to calculate the electron densities of proteins efficiently and further make it possible to focus on specific parts. Here, we evaluate and extend the 3-partition frozen-density embedding (3-FDE) scheme [Jacob, C. R.; Visscher, L. J. Chem. Phys.2008, 128, 155102] for this purpose. In particular, we have extended this scheme to allow for the treatment of disulfide bridges and charged amino acid residues and have introduced the possibility to employ more general partitioning schemes. These extensions are tested both for the prediction of full protein electron densities and for focusing on the electron densities of a selected protein site. Our results demonstrate that 3-FDE is a promising tool for the fully quantum-chemical treatment of proteins.

First author: Cozzolino, Anthony F., ChalcogenNitrogen Secondary Bonding Interactions in the Gas Phase Spectrometric Detection of Ionized Benzo-2,1,3-telluradiazole Dimers, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 9, 2751, (2013)
Abstract: The mass spectra of benzo-2,1,3-chalcogenadiazoles, acquired from the equilibrium conditions of the UV-laser desorption/ionization plume, contain isotopic patterns that are characteristic of protonated and ionized dimers. Dispersion-corrected DFT modeling shows that the most stable structures of these dimers feature the supramolecular four-membered Te2N2 ring, which is pervasive in the crystal structures of these compounds. These observations provide the first evidence of the persistence of TeN supramolecular association in the gas phase.

First author: Zhao, Yin, Solubility Measurements and Prediction of Coenzyme Q10 Solubility in Different Solvent Systems,JOURNAL OF SOLUTION CHEMISTRY, 42, 764, (2013)
Abstract: The solubility of coenzyme Q10 in ethyl acetate, n-hexane, 1-butanol, 1-propanol, 2-propanol and ethanol in the temperature range 270.15-320.15 K, under atmospheric pressure, was measured by a gravimetric method and compared with the data predicted using the conductor like screening model for realistic solvation (COSMO-RS) method. The results show that the solubilities of coenzyme Q10 in the above solvents increase with temperature. The temperature dependences of predicted solubilities were consistent with the experimental data. The experimental data were correlated with the Apelblat equation. At the same temperature, the order of increasing solubility is ethyl acetate > n-hexane > 1-butanol > 1-propanol > 2-propanol > ethanol.

First author: Nebbache, Nadia, Theoretical analysis of the structure and bonding in electron-rich edge-bridged octahedral tungsten chloride clusters, SOLID STATE SCIENCES, 19, 150, (2013)
Abstract: The electronic structure of octahedral tungsten chlorides has been studied using density-functional theory calculations. All compounds contain isolated electron-rich W6Cl18 edge-bridged octahedral clusters. The electronic structure of these solid-state compounds is related to that of the isolated octahedral units. For all computed W6Cl18n- (n = 0, 1, 2) species, the different magnetic states are rather close in energy and the W-6 core significantly distorts from the octahedral symmetry. Theoretical results are compared with available structural and magnetic data.

First author: Holzmann, Nicole, Comparative Study of Phosphine and N-Heterocyclic Carbene Stabilized Group 13 Adducts [L(EH3)] and [L-2(E2Hn)], CHEMISTRY-A EUROPEAN JOURNAL, 19, 6467, (2013)
Abstract: Quantum chemical calculations using density functional theory at the BP86/TZ2P level have been carried out to determine the geometries and stabilities of Group13 adducts [(PMe3)(EH3)] and [(PMe3)2(E2Hn)] (E=BIn; n=4, 2, 0). The optimized geometries exhibit, in most cases, similar features to those of related adducts [(NHCMe)(EH3)] and [(NHCMe)2(E2Hn)] with a few exceptions that can be explained by the different donor strengths of the ligands. The calculations show that the carbene ligand L=NHCMe (:C(NMeCH)2) is a significantly stronger donor than L=PMe3. The equilibrium geometries of [L(EH3)] possess, in all cases, a pyramidal structure, whereas the complexes [L2(E2H4)] always have an antiperiplanar arrangement of the ligands L. The phosphine ligands in [(PMe3)2(B2H2)], which has Cs symmetry, are in the same plane as the B2H2 moiety, whereas the heavier homologues [(PMe3)2(E2H2)] (E=Al, Ga, In) have Ci symmetry in which the ligands bind side-on to the E2H2 acceptor. This is in contrast to the [(NHCMe)2(E2H2)] adducts for which the NHCMe donor always binds in the same plane as E2H2 except for the indium complex [(NHCMe)2(In2H2)], which exhibits side-on bonding. The boron complexes [L2(B2)] (L=PMe3 and NHCMe) possess a linear arrangement of the LBBL moiety, which has a BB triple bond. The heavier homologues [L2(E2)] have antiperiplanar arrangements of the LEEL moieties, except for [(PMe3)2(In2)], which has a twisted structure in which the PInInP torsion angle is 123.0 degrees. The structural features of the complexes [L(EH3)] and [L2(E2Hn)] can be explained in terms of donoracceptor interactions between the donors L and the acceptors EH3 and E2Hn, which have been analyzed quantitatively by using the energy decomposition analysis (EDA) method. The calculations predict that the hydrogenation reaction of the dimeric magnesium(I) compound LMgMgL with the complexes [L(EH3)] is energetically more favorable for L=PMe3 than for NHCMe.

First author: Belosevic, Svetlana, Preparation, configurational and DFT-NBO analysis of nickel(II) complexes with edta-type ligands containing six-membered backbone ring: crystal structure of [Ni(H2O)(6)][Ni(1,3-pdta)]center dot 2H(2)O,JOURNAL OF COORDINATION CHEMISTRY, 66, 1730, (2013)
Abstract: New hexadentate nickel(II) complex Mg[Ni(1,3-pd3ap)]center dot 10H(2)O containing unsymmetrical edta-type ligand, 1,3-propanediamine-N,N,N ‘-triacetate-N-3-propionate (1,3-pd3ap), has been prepared, chromatographically separated, and characterized. Only one [trans(O-5)] of the two possible geometrical isomers was isolated. In this isomer, the two five-membered glycinate rings (R rings) occupy trans-axial sites while the one glycinate ring and one beta-alaninate ring lie in the equatorial plane with the two diamine nitrogens (G rings). This result confirms the assignment made on the basis of the density functional theory (DFT), IR, and UVVis spectral data analysis. In order to see cation influence on the structural and electronic behavior, [Ni(H2O)(6)][Ni(1,3-pdta)]center dot 2H(2)O complex has also been prepared and its structure verified by an X-ray analysis. Spectral data and electronic transition assignment, DFTnatural bonding orbital, and an extensive strain analysis are discussed in comparison with those of other [Ni(edta-type)](2-) complexes of known configuration.

First author: Lukose, Binit, Stability and electronic properties of 3D covalent organic frameworks, JOURNAL OF MOLECULAR MODELING, 19, 2143, (2013)
Abstract: Covalent organic frameworks (COFs) are a class of covalently linked crystalline nanoporous materials, versatile for nanoelectronic and storage applications. 3D COFs, in particular, have very large pores and low mass densities. Extensive theoretical studies of their energetic and mechanical stability, as well as their electronic properties, have been carried out for all known 3D COFs. COFs are energetically stable and their bulk modulus ranges from 3 to 20 GPa. Electronically, all COFs are semiconductors with band gaps corresponding to the HOMO-LUMO gaps of the building units.

First author: Krishnamoorthy, Bellie Sundaram, Electronic, geometrical, and thermochemical studies on group-14 element-diruthenaborane cluster compounds: a theoretical investigation, THEORETICAL CHEMISTRY ACCOUNTS, 132, 2143, (2013)
Abstract: Density functional theory (DFT) calculations were used to probe the reaction of the diruthenaborane nido[1,2-(Cp*RuH)(2)B3H7] (Cp* = eta(5)-C5Me5), (1) with MeC CMe to form the major product nido-[1,2-(Cp*Ru)(2) (mu-H)(mu-BH2)-4,5-Me-2-4,5-C2B2H4] (2) along with minor product nido-(Cp*Ru)(2)-4,5-Me-2-4,5-C2B2H6 (3). The structural features of the other related diruthenacarboranes, nido-(Cp*Ru)(2)-4,5-Me-2-4,5-C2B2H6 (4) and closo-1,2-(Cp*RuH)(2)-4,5-Me-2-4,5-C2B3H3 (5), were also studied. Since metallaheteroboranes with p-block group-14 elements are rare, we extend our DFT studies to explore the reaction of 1 with heavier group-14 alkyne analogs, RE ER (E = Si, Ge, and Sn; R = alkyl or aryl groups). The geometrical and electronic structures of the products nido-[1,2-(Cp*Ru)(2)(mu-H) (mu-BH2)-4,5-Me-2-4,5-E2B2H4] (E = Si (6), Ge (7), Sn (8)) are described and compared with the ruthenacarborane analog, nido[ 1,2-(Cp*Ru)(2)(mu-H)(mu-BH2)-4,5-Me-2-4,5-C2B2H4] species, 2. The computed energetics and the geometries support the feasibility of the reaction and the stability of the products. NBO analysis was performed to delve further into the nature of the bonding in this kind of clusters.

First author: Graham, John P., Derivation of ligand sigma- and pi-bonding parameters from density functional theoretical calculations and Bursten ligand additivity relationships, JOURNAL OF COORDINATION CHEMISTRY, 66, 1477, (2013)
Abstract: New ligand additivity equations, based on the Bursten model, describing d orbital energies in square-planar and squarepyramidal complexes are proposed and tested for hypothetical binary Cr(0) and Mn(I) complexes of CO and CNMe. Density functional theory calculations are used to calculate the energies of d orbitals of binary octahedral, squareplanar, and squarepyramidal d(6) complexes of Mn(I) and Cr(0). Combination of the modified equations for unsaturated species with Bursten’s original equations for octahedral species allows for calculation of individual ligand bonding parameters and the separation of sigma- and -bonding effects. The calculated parameters provide interesting insight into the nature of metalligand bonding in the species studied. The method of separating sigma- and -bonding effects, applied here to CO and CNMe, is proposed as general method for solution of the Bursten equations for low-spin d(6) octahedral systems.

First author: Xi, Hong-Wei, Hydrogen bond and internal rotations barrier: DFT study on heavier group-14 analogues of formamide, JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, 26, 420, (2013)
Abstract: A theoretical study on heavier group-14 substituting effect on the essential property of formamide, strong hydrogen bond with water and internal rotational barrier was performed within the framework of natural bond orbital (NBO) analysis and based on the density functional theory calculation. For heavier group-14 analogues of formamide (YHONH2, Y=Si, Ge and Sn), the nNY=O conjugation strength does not always reduce as Y becomes heavier, for example, silaformamide and germaformamide have similar strength of delocalization. Heavier formamides prefer being H-bond donors to form FYOH2O complexes to being H-bond acceptors to form FYHH2O complexes. The NEDA analysis indicates that H-bond energies of FYOH2O complexes increase as moving down group 14 due to concurrently stronger charge transfer (CT) and electrostatic attraction and for the FYHH2O complexes H-bond strengths are similar. The model of CTs from FYO to H2O differs from that at FYHH2O complexes, which are contributed not only by aligning lone-pair orbital of O but also by another lone-pair orbital. At two lowest lying excited states (the triplet and S1 excited states), formamide and its heavier analogues form double H-bonds with H2O molecule at the same time. The barrier heights of internal rotation become gradually low from C to Sn, formamide (15.73 kcal/mol)>silaformamide (11.73 kcal/mol)>germaformamide (9.45 kcal/mol)>stannaformamide (7.50 kcal/mol) at the CCSD(T)/aug-cc-pVTZ//B3LYP/cc-pVTZ level. NBO analysis indicates that the barrier does not only come from the nN*YO conjugation, and for heavier analogues of formamide, the nN sigma*YO hyperconjugation effect and steric effect considerably contribute to the overall rotational barrier.

First author: Zhang, Bing, An efficient strategy for improving carrier transport performance – Introducing fluorine into aryl substituted tetracene, ORGANIC ELECTRONICS, 14, 1359, (2013)
Abstract: Why does the fluorination of just one phenyl in 5,11-diphenyltetracene (PPT) bring about so tremendous change of the charge carrier mobility? Herein, we carried out density functional theory (DFT) to provide insight into this remarkable difference by investigating their geometries, electronic structures, reorganization energies, transfer integrals, intermolecular interactions and band structures. The improved charge mobility from PPT to FPPT (5-(perfluorophenyl)-11-phenyltetracene) can be attributed to favorable molecular packing due to the increase of pi-pi interaction which is confirmed by Hirshfeld surfaces analysis. Furthermore, we calculated charge mobilities of novel compound 4,11-diphenyltetracene (PPT’) and its fluorinated derivative 4-(perfluorophenyl)-11-phenyltetracene (FPPT’), on the basis of the predicted packing motifs. The largest charge mobility of FPPT’ (2.49 cm(2)/V s) exhibits one-fold higher than PPT’ (1.07 cm(2)/V s) due to dense packing structures, which further confirms our finding that fluorination may be an effective means to improve the carrier mobility. This work paves the way towards the development of a computational protocol that could be implemented not only for rationalizing synthetic efforts but also for design of high-performance organic transport materials.

First author: Aramburu, J. A., Colour due to Cr3+ ions in oxides: a study of the model system MgO:Cr3+, JOURNAL OF PHYSICS-CONDENSED MATTER, 25, 1359, (2013)
Abstract: Seeking to understand why the cubic centre in MgO:Cr3+ has the same 10Dq value as emerald, ab initio cluster and periodic supercell calculations have been performed. It is found that the equilibrium Cr3+-O2- distance, R, in MgO:Cr3+ is equal to 2.03 angstrom and thus 0.06 angstrom higher than that measured for the emerald. Calculations carried out on the isolated CrO69- complex at R = 2.03 angstrom give 10Dq = 14 510 cm(-1), which is 10% smaller than the experimental figure for MgO:Cr3+. Nevertheless, when the internal electric field, E-R(r), due to the rest of the lattice ions is also taken into account, the calculated 10Dq = 16 210 cm(-1) coincides with the experimental value. Accordingly, the colour shift for different oxides doped with Cr3+ can be well understood on the basis of this extrinsic contribution to 10Dq usually ignored in a ligand field description. The calculated electrostatic potential, V-R(r), related to E-R(r), is found to be attractive when the electronic density is lying along < 110 > directions and vertical bar r vertical bar > 1 angstrom driven by the first shell of twelve Mg2+ ions. The action of V-R(r) upon the CrO69- complex slightly decreases the energy of t(2g)(xy, xz, yz) orbitals with respect to that for eg(3z(2) – r(2), x(2) – y(2)) orbitals, thus enhancing the 10Dq value by 0.2 eV. However, the addition of V-R(r) induces very small changes in the electronic density, a relevant fact that is related to the E-2(t(2g)(3)) -> (4)A(2)(t(2g)(3)) emission energy being nearly independent of the host lattice along the series of Cr3+-doped oxides.

First author: Olea Ulloa, Carolina, Theoretical study of the binding strength and magnetical response properties involved in the formation of the pi-donor/pi-acceptor [TTF-CBPQT](4+) host-guest system, POLYHEDRON, 54, 119, (2013)
Abstract: The forces involved into the formation of the pi-donor/pi-acceptor host-guest system [TTF-CBPQT](4+) has been evaluated theoretically by using dispersion corrected DFT (DFT-D) methodologies. Three models were taken into account as follows, solely the [TTF-CBPQT](4+) system (model 1), [TTF-CBPQT][(PF6)(4)] (2) and [TTF-CBPQT][(PF6)(4)] plus acetonitrile as solvent via the continuum approach for the solvation treatment (COSMO) (3), which denotes the variation of the interaction energy according to the employed model. For model 3, the total formation (binding strength) energy calculated amounts to -8.98 kcal/mol, which is in the range of the available experimental data. In addition the through-the-space magnetic response is described, in order to gain more insights into the pi-donor/pi-acceptor host-guest interaction.

First author: Vedha, Swaminathan Angeline, On the Nature of Hypercoordination in Dihalogenated Perhalocyclohexasilanes, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 3529, (2013)
Abstract: Hypercoordination in silicon has long been reviewed. Dihalogenated perhalocyclohexasilane inverse sandwich complexes (ISCs) are the only group of hypercoordinate Si complexes with anion donors that contact six neutral silicon atoms; opening prospective applications in Si self assembled nanostructures. Hypercoordinate bonds in 16 such ISCs were studied and their anion ring interactions have been understood with respect to halides. mu(6) mode of coordination was confirmed by the presence of 6 equivalent (3,-1) bond critical points through Bader’s QTAIM perspective. The presence of Lewis acid sites above and below the flat Si rings were examined through a reduced density gradient (RDG) analysis, and the ability of halide anions (X’ = F, Cl, Br, I) to hypercoordinate has been understood. Role of the ring halides (X) in tuning size and acidity of Lewis sites has been addressed. While the total interaction between the two anions and the ring is quantified through EDA, each SiX’ hypercoordinate bond was identified as either purely ionic or transient through QTAIM computations. CDA shows that these complexes are of donor-acceptor type with significant back donation The analysis shows that BrF’ and IF’ were found to reach maximum covalency within the group. Hence in future, tuning these ISCs for construction of nanocrystalline Si structures for optoelectronic properties can essentially utilize the collective, weak yet hypercoordinate Si in these complexes.

First author: Purcell, Walter, Characterization of acetylacetonato carbonyl dipheny1-2-pyridylphosphine rhodium(I): Comparison with other carbonyl complexes, JOURNAL OF MOLECULAR STRUCTURE, 1038, 220, (2013)
Abstract: Different rhodium(l)/(III) dipheny1-2-pyridylphosphine complexes were isolated and successfully characterized. The [Rh(acac)(CO)(DPP)] (DPP dipheny1-2-pyridylphosphine) complex crystallizes in the PT space group with four molecules per unit cell. The results clearly show that the differences between the two independent molecules are mainly centered around the orientation of the pyridyl ring within the two square planer molecules. The results also indicate that the phosphine ligands act as monodentate ligands in both molecules, with Rh-P and Rh-CO bond distances of 2.243(1); 2.235(1) and 1.791(4); 1.776(4) A respectively. A comparison of the v(CO) stretching frequencies of a relatively large number of rhodium complexes indicated little overlap between the v(CO) of different types of complexes (e.g. Rh(I) vs Rh(III)) and relatively small standard deviations within each type of complex. OFT calculations were used to determine the preferred pyridyl ring orientation. These calculations indicated that at least 12 areas of minimum energy, which exists as broad, low energy wells, are theoretically suitable for DPP group orientation within this kind of structure.

First author: Wiese, Stefan, beta-Diketiminato Nickel Imides in Catalytic Nitrene Transfer to Isocyanides,ORGANOMETALLICS, 32, 2300, (2013)
Abstract: The beta-diketiminato nickel(I) species [Me3NN]Ni(2-picoline) (1) serves as an efficient catalyst for carbodiimide (RN=C=NR’) formation in the reactions of a range of organoazides N3R with isocyanides R’NC. [Me3NN]-Ni(CNR)(2) (R = Bu-t, Ar (Ar = 2,6-Me2C6H3)) species provide carbodiimides RN=C=NAr’ upon reaction with Ar’N-3 (Ar’ = 3,5-Me2C6H3). Nitrene transfer takes place via the intermediacy of nickel imides. Reaction of [MexNN]Ni(2-picoline) (x = 2 or 3) with Ar’N-3 gives the new dinickel imides {[MexNN]Ni}(2)(mu-NAr’) (4 (x = 3) and 5 (x = 2)) as deep purple, diamagnetic substances The X-ray structure of {[Me2NN]Ni}(2)(mu-NAr’) (5) features short Ni-N-imide distances of 1.747(2) and 1.755(2) angstrom along with a short Ni-Ni distance of 2.7210(3) angstrom. These dinickel imides 4 and 5 react stoichiometrically with (BuNC)-Bu-t to provide the corresponding carbodiimides (BuN)-Bu-t=C=NAr’ in good yield. Azide transfer takes place upon reaction of 1 with TMS-N-3 to give the square planar nickel(II) azide [Me3NN]Ni(N-3)(2-picoline) (7). Stoichiometric reaction of dinickel dicarbonyl {[Me3NN]Ni)(2)(mu-CO)(2) with organoazides such as Ar’N-3 is sluggish, indicating that 1 is not an efficient catalyst for nitrene transfer from organoazides to CO to form isocyanates RN=C=O.

First author: Zarate, Ximena, A family of octahedral molybdenum cluster complexes [Mo6Cl8(H2O)(n)(OH)(6-n)](n-2) with n=0-6 as a pH-sensors: A theoretical study, CHEMICAL PHYSICS LETTERS, 567, 39, (2013)
Abstract: Theoretical computations of a series of clusters [Mo6Cl8(H2O)(n)(OH)(6-n)](n-2) are presented. UV-Vis absorption spectra, the ground states (S-0) and the lowest excited states (S-1 and T-1) were examined. Energy diagrams for luminescent decay were built in order to get insights about the emission processes of these systems. The fact that the systems show different emission energy profiles when the aqua and hydroxo coordinations are changed, indicates pH-dependence and supports the statement that these clusters are candidates to act as pH-sensors. Those properties are also shown by a reported family of luminescent [Re6S8(H2O)(n)(OH)(6-n)](n-4) clusters, with the same structure of the systems studied here.

First author: Woodward, W. Hunter, Carbonyl Bond Cleavage by Complementary Active Sites, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 7445, (2013)
Abstract: We have studied the size-selective reactivity of Al-n(-) clusters with formaldehyde to determine if carbonyl bonds may be broken by complementary active sites. Gas phase experiments reveal that Al-n(-), where n = 8-12, react with formaldehyde to form Aln-2CH2-, which demonstrates that the carbonyl bond is broken in the reaction with the cluster, while Al-13(-) is found to be resistant to reaction. The most likely leaving group is determined to be Al2O. We also found n = 15-19 to be reactive with the products being a mix of Aln-2CH2- and Al-n(OCH2)(m)(-). Theoretical investigations find that the adjacent Lewis acid and Lewis base sites stabilize the resonance structure in which the carbonyl is reduced to a single bond which encourages carbonyl cleavage. A transition state analysis of the cleavage of the carbonyl bond confirms the size selective cleavage of the carbonyl bond and supports the importance of complementary Lewis acid-Lewis base active sites in governing the reactivity.

First author: Adams, Richard D., Tetraruthenium carbonyl complexes containing germyl and stannyl ligands from the reactions of Ru-4(CO)(13)(mu-H)(2) with HGePh3 and HSnPh3, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 730, 20, (2013)
Abstract: The compounds Ru-4(CO)(12)(GePh3)(2)(mu-H)(4), 1 and Ru-4(CO)(12)(SnPh3)(2)(mu-H)(4), 2 were obtained from the reactions of Ru-4(CO)(13)(mu-H)(2) with HGePh3 and HSnPh3, respectively. Both compounds contain a nearly planar butterfly structure for the four metal atoms with two GePh3/SnPh3 ligands and four bridging hydride ligands around the periphery of the cluster. When heated, 1 and 2 were converted into the complexes Ru-4(CO)(12)(mu(4)-EPh)(2), 3, E = Ge, and 4, E = Sn, by cleavage of two phenyl groups from each of the GePh3 ligands. Compounds 3 and 4 contain square planar arrangements of the four ruthenium atoms with quadruply bridging germylyne and stannylyne ligands on opposite sides of the square plane. The bonding and electronic transitions of 3 were analyzed by DFT computational analyses.

First author: Mandal, Tarun K., An Interplay of Cooperativity between Cation center dot center dot center dot pi, Anion center dot center dot center dot pi and C-H center dot center dot center dot Anion Interactions, CHEMPHYSCHEM, 14, 1149, (2013)
Abstract: Mixed cation (Li+, Na+ and K+) and anion (F, Cl, Br) complexes of the aromatic -surfaces (top and bottom) are studied by using dispersion-corrected density functional theory. The selectivity of the aromatic surface to interact with a cation or an anion can be tuned and even reversed by the electron-donating/electron-accepting nature of the side groups. The presence of a methyl group in the OCH3, SCH3, OC2H5 in the side groups of the aromatic ring leads to further cooperative stabilization of the otherwise unstable/weakly stable anion complexes by bending of the side groups towards the anion to facilitate CHanion interactions. The cooperativity among the interactions is found to be as large as 100 kcalmol1 quantified by dissection of the three individual forces from the total interaction energy. The crystal structures of the fluoride binding tripodal and hexapodal ligands provide experimental evidence for such cooperative interactions.

First author: Jissy, A. K., Molecular Switching Behavior in Isosteric DNA Base Pairs, CHEMPHYSCHEM, 14, 1219, (2013)
Abstract: The structures and proton-coupled behavior of adeninethymine (A-T) and a modified base pair containing a thymine isostere, adeninedifluorotoluene (A-F), are studied in different solvents by dispersion-corrected density functional theory. The stability of the canonical WatsonCrick base pair and the mismatched pair in various solvents with low and high dielectric constants is analyzed. It is demonstrated that A-F base pairing is favored in solvents with low dielectric constant. The stabilization and conformational changes induced by protonation are also analyzed for the natural as well as the mismatched base pair. DNA sequences capable of changing their sequence conformation on protonation are used in the construction of pH-based molecular switches. An acidic medium has a profound influence in stabilizing the isostere base pair. Such a large gain in stability on protonation leads to an interesting pH-controlled molecular switch, which can be incorporated in a natural DNA tract.

First author: Davari, N., Excitation energies and ionization potentials at high electric fields for molecules relevant for electrically insulating liquids, JOURNAL OF APPLIED PHYSICS, 113, 1219, (2013)
Abstract: The electric-field dependence of the molecular ionization potential and excitation energies is investigated by density-functional theory calculations. It is demonstrated that the ionization potential has a strong field dependence and decreases with increasing field. The excitation energies depend weakly on the field and the number of available excited states decreases with increasing field since the ionization potential has a stronger field dependence. Above a specific field, different for each molecule, a two-state model is obtained consisting of the electronic ground state and the ionized state. Implications for streamer propagation and electrically insulating materials are discussed.

First author: van der Eide, Edwin F., Metal-Centered 17-Electron Radicals CpM(CO)(3)(center dot) (M = Cr, Mo, W): A Combined Negative Ion Photoelectron Spectroscopic and Theoretical Study, ORGANOMETALLICS, 32, 2084, (2013)
Abstract: Despite the importance of group 6 metal-centered 17-electron radicals CpM(CO)(3)(center dot) (M = Cr, Mo, W) in establishing many of the fundamental reactions now known for metal-centered radicals, spectroscopic characterization of their electronic properties and structures has been very challenging, due to their high reactivity. Here we report a gas-phase study of these species by photodetachment photoelectron spectroscopy (PES) of their corresponding 18-electron anions and by theoretical electronic structure calculations. Three well-separated spectral features are observed by PES for each anionic species. Electron affinities (EAs) of CpM(CO)(3)(center dot) were experimentally measured from the threshold of each spectrum and were found to be 2.38 +/- 0.02 (M = Cr), 2.63 +/- 0.02 (Mo), and 2.63 +/- 0.01 eV (W). These experimental values correlate well with the reported redox potentials measured in solution. Theoretical calculations for all anionic and neutral (radical) species gave calculated EAs and band gaps that are in good agreement with the experimental data. Molecular orbital (MO) analyses for each anion indicate that the top three occupied MOs are mainly metal-based and contribute to the first spectral feature, whereas the next two MOs are associated with Cp-M pi bonding and contribute to the second spectral feature. The calculations further exhibit appreciable anion-to-neutral structural changes for all three species, with the change for the W species being the smallest.

First author: Broeckaert, Lies, Combined NMR and DFT Study on the Complexation Behavior of Lappert’s Tin(II) Amide,ORGANOMETALLICS, 32, 2121, (2013)
Abstract: The complexation chemistry of the stannylene Sn{N[Si(CH3)(3)](2)}(2), first reported by Lappert in the 1970s, was investigated by Sn-119 NMR chemical shift measurements. To this end, experimental NMR data and theoretical density functional theory (DFT) calculations were combined to get an insight into the interaction between the stannylene and various solvent molecules with sigma- and/or pi-coordinating power. Small variations in the measured Sn-119 chemical shifts revealed a donor-acceptor interaction with the solvent molecules. In comparison to the noncoordinating solvent cyclohexane taken as a reference, a weak coordination was observed with aromatic solvent molecules (benzene and toluene) and a much stronger coordination with the sigma-donors THF and pyridine. Pyridine was confirmed to be the strongest donor, as evidenced by its large upfield chemical shift Delta delta(Sn-119) of 635 ppm. The experimental chemical shifts were reproduced by DFT (NMR) calculations, demonstrating similar trends in the interaction strength with the sigma- and pi-donors. The stannylene Sn{N[Si(CH3)(3)](2)}(2) showed the ability to react with Fe(CO)(5) and Fe-2(CO)(9) in the molar ratio 1/1 to provide L2SnFe(CO)(4) complexes. With a molar excess of Fe-2(CO)(9), L2Sn[Fe(CO)(4)](2) was generated irreversibly. Upon prolonged UV irradiation in the presence of W(CO)(6), in the molar ratio 1/1, a mixture of L2SnW(CO)(5) and two (L2Sn)(2)W(CO)(4) complexes was generated.

First author: Turbervill, Robert S. P., Synthesis and Characterization of Free and Coordinated 1,2,3-Tripnictolide Anions,ORGANOMETALLICS, 32, 2234, (2013)
Abstract: We have investigated the chemical reactivity of heptaatomic anionic clusters of the group IS elements ([E-7](3-)/[HE7](2-), E = P, As) toward the symmetric and asymmetrically substituted alkynes diphenylacetylene and phenylacetylene. The results reported herein, alongside a previous report on the reactivity of such clusters toward acetylene, describe a versatile route by which to access otherwise elusive 1,2,3-tripnictolide anions of the general formula [E3C2RR’](-) (R = R’ = H, E = P (1), As (2); R = R’ = C6H5, E = P (3) As (4); R = H, R’ = C6H5, E = P (5), As (6)). These species can be isolated as [K(18-crown-6)](+) or [K(2,2,2-crypt)](+) salts. All anions were characterized by multielement NMR spectroscopy and electrospray mass spectrometry. In addition, single-crystal X-ray diffraction structures of the novel species [K(18-crown-6)(THF)(2)][3], [K(2,2,2-crypt)][4]center dot xTHF (x = 0, 0.5), and [K(18-crown-6)THF][6] were also obtained. The chemical reactivity of these group 15 cyclopentadienyl analogues has been explored in a series of ligand displacement reactions with Mo(CO())3(L)(3) (L = CO, CH3CN) to yield the complex anions [(eta(5)-E3C2H2)Mo(CO)(3)](-) (E = P (7), As (8)), [{eta(5)-E3C2(C6H5)(2)}Mo(CO)(3)](-) (E = P (9), As (10)), and [{eta(5)-E3C2H(C6H5)}Mo(CO)(3)](-) (E = P (11), As (12)).

First author: Kazaryan, Andranik, Assessment of density functional methods for reaction energetics: Iridium-catalyzed water oxidation as case study, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 870, (2013)
Abstract: We investigate basis set convergence for a series of density functional theory (DFT) functionals (both hybrid and nonhybrid) and compare to coupled-cluster with single and double excitations and perturbative triples [CCSD(T)] benchmark calculations. The case studied is the energetics of the water oxidation reaction by an iridium-oxo complex. Complexation energies for the reactants and products complexes as well as the transition state (TS) energy are considered. Contrary to the expectation of relatively weak basis set dependence for DFT, the basis set effects are large, for example, more than 10 kcal mol1 difference from converged basis for the activation energy with small basis sets (DZ/6-31G** for Ir/other atoms, or SVP) and still more than 6 kcal mol1 for def2-TZVPP/6-31G**. Inclusion of the dispersion correction in DFT-D3 schemes affects the energies of reactant complex (RC), TS, and product complex (PC) by almost the same amount; it significantly improves the complexation energy (the formation of RC), but has little effect on the activation energy with respect to RC. With converged basis, some pure GGAs (PBE-D3, BP86-D3) as well as the hybrid functional B3LYP-D3 are very accurate compared to benchmark CCSD(T) calculations.

First author: Safi, Zaki S., Protonation of 5-methylhydantoin and its thio derivatives in the gas phase: A theoretical study,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 908, (2013)
Abstract: The gas phase proton affinities of 5-methylhydantoin and its thio derivatives were theoretically studied through the use of high-level density functional theory calculations. The structure of all possible tautomers and their conformers were optimized at the B3LYP/6-311+(d,p) level of theory. Final energies were obtained at the B3LYP/6-311+(2df,2p) level. The imidazolidone derivatives 5-methyl-2,4-dioxo imidazolidine, 5-methyl-2-oxo-4-thio imidazolidine, 5-methyl-2-thio-4-oxo imidazolidine, and 5-methyl-2,4-dithio imidazolidine possess moderately strong proton affinities. Protonation at sulfur would be larger than protonation at oxygen. The most stable protonated forms of 2O4O and 2S4O have the proton attached to the heteroatom in position 2, whereas protonation of 2O4S and 2S4S preferentially takes place at position 4. The barriers for proton migration between the different tautomers are rather large. The energy decomposition analysis analysis of the OH+ and SH+ interactions suggests that the bonding interactions come mainly from the covalent bond formation. The contribution of the Coulomb attraction is rather small.

First author: Benmachiche, Akila, Electronic structure and coordination chemistry of phenanthridine ligand in first-row transition metal complexes: A DFT study, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 985, (2013)
Abstract: The geometric parameters, electronic structures, and haptotropic migration of a series of hypothetical compounds of general formula CpM(C13H9N) and (CO)3M(C13H9N) (M = fist row transition metal, Cp = C5H5, and C13H9N = phenanthridine ligand) are investigated by means of the density functional theory. The phenanthridine ligand can bind to the metal through 1 to 6 coordination mode, in agreement with the electron count and the nature of the metal, showing its capability to adapt itself to the electronic demand of the metal as well as to the polycyclic aromatic hydrocarbons. In the investigated species, the most favored closed-shell count is 18-electron except for the Ti and V models which are deficient open-shell 16-electron configuration. This study has shown the difference in coordination ability of this heteropolycyclic ligand: the coordination of the central C5N ring is less favored than the terminal C6 rings, in agreement with the -electron density localization. Most of the investigated complexes are expected to exhibit a rich fluxional behavior. This flexibility favors the possibility for the existence of several isomers as well as their interconversion through haptotropic shifts.

First author: Koenig, Carolin, Exciton Coupling Mechanisms Analyzed with Subsystem TDDFT: Direct vs Pseudo Exchange Effects, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 3480, (2013)
Abstract: The dominant effect in exciton coupling is usually the so-called Coulomb coupling contribution, that is the Coulomb interaction between transition densities of localized excitations. At short distances, Dexter-type exchange effects are discussed to play a role, which are not well described by (semi)local functionals in time-dependent density functional theory (TDDFT) calculations. Overall, a large effect of the percentage of exact exchange on the resulting exciton splittings is known. Subsystem TDDFT allows one to analyze the exciton coupling mechanism by distinguishing direct from indirect effects, that is, changes in the actual coupling mechanism from modifications in the underlying local excitations. Our analysis shows that the strong influence of exact exchange is not due to a direct Dexter-type (exchange) coupling, but rather to an increased Coulomb (or pseudo-exchange) coupling triggered by a change in transition densities. This is demonstrated in calculations for 2-pyridone and chlorophyll dimers. We finally propose a route to efficient calculations of excited states of large pigment aggregates with hybrid functionals, which so far has been out of reach for quantum chemical methods.

First author: Renaud, Nicolas, Mapping the Relation between Stacking Geometries and Singlet Fission Yield in a Class of Organic Crystals, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 4, 1065, (2013)
Abstract: By generating two free charge carriers from a single high-energy photon, singlet fission (SF) promises to significantly improve the efficiency of a class of organic photovoltaics (OPVs). However, SF is generally a very inefficient process with only a small number of absorbed photons successfully converting into triplet states. In this Letter, we map the relation between stacking geometry and SF yield in crystals based on perylenediimide (PDI) derivatives. This structure-function analysis provides a potential explanation for the SF yield discrepancies observed among similar molecular crystals and may help to identify favorable geometries that lead to an optimal SF yield. Exploring the subtle relationship between stacking geometry and SF yield, this Letter suggests using crystal structure engineering to improve the design of SF-based OPVs.

First author: Al Ouahabi, Abdelaziz, Experimental and Theoretical Study of the n-Doped Successive Polyanions of Oligocruciform Molecular Wires: Up to Five Units of Charge, CHEMPHYSCHEM, 14, 958, (2013)
Abstract: The electronic structure of polyanions of sterically encumbered triisopropylsilyl-substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Visnear-infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even-order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis-NIR spectra indicates that the monoanions (T., P.) exhibit two transitions in the Vis-NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density.

First author: Reimann, Sebastian, 3-Pyrenylacrylates: Synthetic, Photophysical, Theoretical and Electrochemical Investigations, ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES, 68, 367, (2013)
Abstract: The Mizoroki-Heck coupling of 1-bromopyrene with acrylates provides a convenient access to a variety of 3-pyrenylacrylates in very good yields (up to 93%). Their photophysical properties combined with solvatochromic effects were studied. In addition, electrochemical oxidation potentials were determined by DPV (differential pulse voltammetry) measurements. The fine structure of the absorbance spectra obtained from photophysical measurements are compared with the results of theoretical calculations performed by time dependent TD-B3LYP methods using the 6-31G* basis set.

First author: Kaminski, Radoslaw, CLUSTERGEN: a program for molecular cluster generation from crystallographic data,JOURNAL OF APPLIED CRYSTALLOGRAPHY, 46, 540, (2013)
Abstract: A new program, CLUSTERGEN, for molecular cluster generation is introduced. CLUSTERGEN provides the quantum mechanics/molecular mechanics (QM/MM) input files for program packages such as ADF [Baerends et al. (2012). Vrije Universiteit, Amsterdam, The Netherlands] and GAUSSIAN [Frisch et al. (2009). Gaussian Inc., Pittsburgh, Pennsylvania, USA]. Additionally, it prints out a standard CRYSTAL [Dovesi et al. (2009). University of Turin, Italy] input and, in general, facilitates file-format manipulation. The CLUSTERGEN program is supported by an extensive manual and a user-friendly graphical interface. The code is freely available and carefully commented, which makes it easily modifiable. Exemplary applications of CLUSTERGEN concerning QM/MM calculations and derivation of nucleus-independent chemical shift indices are demonstrated.

First author: Gao, Wei, From clusters to liquid: what are the preferred ways for benzene and pyrrole to interact?,THEORETICAL CHEMISTRY ACCOUNTS, 132, 540, (2013)
Abstract: The various interactions occurring between pyrrole and benzene are a particularly appropriate model, as they are viewed as better X-H center dot center dot center dot pi examples. A combined and sequential use of Quantum Mechanical (QM) calculations and Molecular Dynamics (MD) simulations was applied to investigate the different intermolecular interactions for benzene and pyrrole as clusters and its liquid mixture. All the cluster structures were fully optimized by the B2PLYP-D methods (including dispersion correction) with jun-cc-pVTZ (a revised aug-cc-pVTZ basis set). MD simulation with OPLS-AA force field was used to study the liquid mixture of benzene/pyrrole at different temperatures. Two types of N-H center dot center dot center dot pi hydrogen bonds are preferred interactions compared with C-H center dot center dot center dot pi interactions, either as clusters or as its liquid mixture. Based on the QM results, we clarify the difference in red-shifts of N-H bond of N-H center dot center dot center dot pi hydrogen bonds observed by Jet FT-IR (Phys Chem Chem Phys 10: 2827, 2008). Meanwhile, the nature of various X-H center dot center dot center dot pi interactions is unveiled by atoms in molecules (AIM), natural bond orbital and energy decomposition analysis (EDA). Furthermore, in light of QM results, MD simulation results further characterize the behavior and structural properties of these interactions. Finally, we proposed an original idea to explain the strength variation of different N-H center dot center dot center dot pi hydrogen bond in liquid mixture based on AIM and EDA analysis.

First author: Justaud, Frederic, Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron-Alkynyl Electrophores: Five-Component Functional Molecules Obtained from C-H Bond Activation, CHEMISTRY-A EUROPEAN JOURNAL, 19, 5742, (2013)
Abstract: Treatment of [Cp*(dppe)FeCC-TTFMe3] (1) with Ag[PF6] (3equiv) in DMF provides the binuclear complex [Cp*(dppe)FeCCTTFMe2CHCHTTFMe2CC=Fe(dppe)Cp*][PF6]2 (2[PF6]2) isolated as a deep-blue powder in 69% yield. EPR monitoring of the reaction and comparison of the experimental and calculated EPR spectra allowed the identification of the radical salt [Cp*(dppe)FeCCTTFMe2CH][PF6]2 ([1-CH][PF6]) an intermediate of the reaction, which results from the activation of the methyl group attached in vicinal position with respect to the alkynyliron on the TTF ligand by the triple oxidation of 1 leading to its deprotonation by the solvent. The dimerization of [1-CH][PF6] through carboncarbon bond formation provides 2[PF6]2. The cyclic voltammetry (CV) experiments show that 2[PF6]2 is subject to two sequential well-reversible one-electron reductions yielding the complexes 2[PF6] and 2. The CV also shows that further oxidation of 2[PF6]2 generates 2[PF6]n (n=36) at the electrode. Treatment of 2[PF6]2 with KOtBu provides 2[PF6] and 2 as stable powders. The salts 2[PF6] and 2[PF6]2 were characterized by XRD. The electronic structures of 2n+ (n=02) were computed. The new complexes were also characterized by NMR, IR, Mossbauer, EPR, UV/Vis and NIR spectroscopies. The data show that the three complexes 2[PF6]n are iron(II) derivatives in the ground state. In the solid state, the dication 22+ is diamagnetic and has a bis(allenylidene-iron) structure with one positive charge on each iron building block. In solution, as a result of the thermal motion of the metalcarbon backbone, the triplet excited state becomes thermally accessible and equilibrium takes place between singlet and triplet states. In 2[PF6], the charge and the spin are both symmetrically distributed on the carbon bridge and only moderately on the iron and TTFMe2 electroactive centers.

First author: Zarzycki, Bartosz, P4 Activation at Ni0: Selective Formation of an NHC-Stabilized, Dinuclear Nickel Complex [Ni2(iPr2Im)4(,2:2-P2)], EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 19, 2051, (2013)
Abstract: The reaction of [Ni2(iPr2Im)4(cod)] (1) with white phosphorus led to dinuclear [{Ni(iPr2Im)2}2(,2:2-P2)] (2) in excellent yield. This reaction represents the first example of a conversion of white phosphorus into a complex of the type [{L2Ni}2(,2:2-P2)] and the first example of the formation of a complex of the type [{L2M}2(,2:2-P2)] for a group-10 metal stabilized by two simple, nonchelating, two-electron donor ligands by the reaction of a suitable precursor with P4. The X-ray structure of 2 revealed a bent Ni2P2 core with an NiPPNi dihedral angle in the solid state of 102.95 degrees. According to DFT calculations on the symmetrized model systems planar-D2h- and bent-C2v-[{Ni(iPr2Im)2}2(,2:2-P2)], this deviation of the Ni2P2 core from planarity is caused by a second-order JahnTeller distortion. Calculations on the related platinum compound [{Pt(iPr2Im)2}2(,2:2-P2)] confirmed this type of bent structure for the higher congener with an even higher barrier to planarization than that calculated for the nickel complex. Energy decomposition analysis and fragment molecular orbital analysis further illustrate the bonding mechanisms in these complexes.

First author: Liu, Yan-Chun, Structural and Bonding Analyses on a Homologous Metal-Metal Bond Guest-Host Series M2@C50X10 (M = Zn, Cd, Hg; X = CH, N, B), EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 19, 2220, (2013)
Abstract: A systematic density functional study was performed on the structures and bonding features in a homologous metal-metal (M-M) host-guest series M2@C50X10 (M = Zn, Cd, Hg; X = CH, N, B). Calculations indicated that D5d conformers are energy minima for Zn2@C50X10 (X = CH, N) and Cd2@C50X10 (X = CH, N, B), whereas Zn2@C50B10 has no imaginary frequency with the lowered C2h symmetry. Among these hybrid fullerene-metal complexes, those with dizinc and dicadmium guests adopt 5/5 coordination, except for an 2/2 case in C2h-Zn2@C50B10, to meet appropriate interactions between the metal atom and cage; and the 1/1 coordination mode can only be satisfied in just one (Hg2@C50N10) of the complexes with Hg-Hg guests, regardless of the enforced coordination surroundings. The nature of metalcage interactions between M22+ and C50X102 moieties and M-M bonds have been analyzed by means of the topological properties of electron densities and energy-partitioning methods, and results suggest that the two types of interactions are almost similar to those in their M2(C5H5)2 counterparts.

First author: Alegret, Nuria, Bingel-Hirsch Addition on Endohedral Metallofullerenes: Kinetic Versus Thermodynamic Control, CHEMISTRY-A EUROPEAN JOURNAL, 19, 5061, (2013)
Abstract: An extensive theoretical study of the BingelHirsch addition of bromomalonate on scandium nitride endohedral fullerenes has been carried out. The prototypical and highly symmetrical Sc3N@Ih-C80, with a structure that satisfies the isolated pentagon rule (IPR), and the non-IPR Sc3N@D3(6140)-C68 fullerene show analogous reaction paths despite the distinct topology of the carbon networks and different rotation freedom of the internal nitride cluster. For the two metallofullerenes, our results predict that the reaction takes place under kinetic control yielding open-cage fulleroids on [6,6] bonds, which is in good agreement with experimental data. The theoretical studies also show that predicting the reactivity of endohedral metallofullerenes is not straightforward and often an accurate analysis of the potential energy surface is required.

First author: Ndambuki, Sylvester, A Theoretical Analysis of Supported Quintuple and Quadruple Chromium-Chromium Bonds, INORGANIC CHEMISTRY, 52, 3860, (2013)
Abstract: The extended transition state (ETS) energy decomposition scheme has been combined with the natural orbitals for chemical valence (NOCV) density decomposition method (ETS-NOCV) in a study on the shortest, fully supported metal-metal bond (Cr-Cr = 1.73 angstrom) in Cr-2[Ar’NC(NMe2)NAr’](2) [Ar’ = C6H3-2,6(C6H3-2,6-Pr-2(i))(2)]. The scope of the ETS-NOCV method is further demonstrated by a metal-metal bond analysis of the paddlewheel M-2(O2CCH3)(4) (M = Cr, Mo, AAT) complexes. The influence of axial ligands as well as R’ goups on the bridging ligands is also analyzed. In addition to the quintuple bonding components (sigma(2), pi(4), delta(4)) for Cr-2[Ar’NC(NMe2)NAr’](2) and quadruple components (sigma(2), pi(4), delta(2)) for the paddlewheel complexes, we notice additional stability (17-27 kcal/mol) introduced to the metal-metal bond from participation of the lone pairs residing on the pi-systems of the bridging X-C-X (X = N, O) ligand. This is to our knowledge the first time that the strength of the metal-metal bonding components has been determined in a supported metal-metal bond by an energy decomposition scheme.

First author: Aparicio, Pablo A., Tungsten Redox Waves in [XMW11O40](n-) (X = P, Si, Al and M = W, Mo, V, Nb, Ti) Keggin Compounds – Effect of Localised/Delocalised Charges, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 52, 1910, (2013)
Abstract: In the 1960s, Pope and co-workers found a linear dependence between the redox potentials of a family of isostructural -[XW12O40]n Keggin anions and their molecular charge with a slope of 0.18 V per unit charge. That finding was restricted to variations in the internal atom or heteroatom of the molecule (X = PV, SiIV, AlIII, etc.). However, other ways to change the charge of Keggin anions are commonplace, such as previous reduction processes or chemical changes in the external positions of the W12O36 cage, and also lead to variations in their oxidising power. In the present theoretical work, we analyse the oxidising power, computed as reduction energies, for a family of differently charged -[XMW11O40]n Keggin derivatives (X = P, Si, Al and M = W, Mo, V, Nb, Ti). The nature of the unitary charge increment affects the reduction energy differently; the mildest change occurs upon variations in the internal position (heteroatom substitution), and the strongest change (by a factor of ca. 1.85 per additional charge unit compared to the previous one) occurs in the presence of a delocalised (or blue) electron. The replacement of a metal atom (M) from an external position by another one with different oxidation state has an intermediate effect.

First author: Garcia-Borras, Marc, DielsAlder and Retro-DielsAlder Cycloadditions of (1,2,3,4,5-Pentamethyl)cyclopentadiene to La@C-2v-C-82: Regioselectivity and Product Stability, CHEMISTRY-A EUROPEAN JOURNAL, 19, 4468, (2013)
Abstract: One of the most important reactions in fullerene chemistry is the DielsAlder (DA) reaction. In two previous experimental studies, the DA cycloaddition reactions of cyclopentadiene (Cp) and 1,2,3,4,5-pentamethylcyclopentadiene (Cp*) with La@C2v-C82 were investigated. The attack of Cp was proposed to occur on bond 19, whereas that of Cp* was confirmed by X-ray analysis to be over bond o. Moreover, the stabilities of the Cp and Cp* adducts were found to be significantly different, that is, the decomposition of La@C2v-C82Cp was one order of magnitude faster than that of La@C2v-C82Cp*. Herein, we computationally analyze these DA cycloadditions with two main goals: First, to compute the thermodynamics and kinetics of the cycloadditions of Cp and Cp* to different bonds of La@C2v-C82 to assess and compare the regioselectivity of these two reactions. Second, to understand the origin of the different thermal stabilities of the La@C82Cp and La@C82Cp* adducts. Our results show that the regioselectivity of the two DA cycloadditions is the same, with preferred attack on bond o. This result corrects the previous assumption of the regioselectivity of the Cp attack that was made based only on the shape of the La@C82 singly occupied molecular orbital. In addition, we show that the higher stability of the La@C82Cp* adduct is not due to the electronic effects of the methyl groups on the Cp ring, as previously suggested, but to higher long-range dispersion interactions in the Cp* case, which enhance the stabilization of the reactant complex, transition state, and products with respect to the separated reactants. This stabilization for the La@C82Cp* case decreases the Gibbs reaction energy, thus allowing competition between the direct and retro reactions and making dissociation more difficult.

First author: Tian, Dongxu, Dynamic motion of La atom inside the C-74 (D (3h)) cage: a relativistic DFT study, JOURNAL OF MOLECULAR MODELING, 19, 1591, (2013)
Abstract: The interaction between lanthanum atom (La) and C-74 (D (3h)) was investigated by all-electron relativistic density function theory (DFT). With the aid of the representative patch of C-74 (D (3h)), we studied the interaction between C-74 (D (3h)) and La and obtained the interaction potential. Optimized structures show that there are three equivalent stable isomers, with La located about 1.7 off center. There is one transition state between every two stable isomers. According to the minimum energy pathway, the possible movement trajectory of La atoms in the C-74 (D (3h)) cage was explored. The calculated energy barrier for La atoms moving from the stable isomer to the transition state is 18.4 kcal mol(-1). In addition, the dynamic NMR spectra of La@C-74 according to the trajectory was calculated.

First author: Zhang, Ji, Cyano or o-nitrophenyl? Which is the optimal electron-withdrawing group for the acrylic acid acceptor of D-pi-A sensitizers in DSSCs? A density functional evaluation, JOURNAL OF MOLECULAR MODELING, 19, 1597, (2013)
Abstract: We report a DFT, TDDFT and DFTB investigation of the performance of two donor-pi-acceptor (D-pi-A)-type organic dyes bearing different electron-withdrawing groups (EWG) for dye-sensitized solar cells (DSSCs) to evaluate which EWG is better for an acrylic acid acceptor, i.e., Cyano (-CN) or o-nitrophenyl (o-NO2-Ph). A series of theoretical criteria applied successfully in our previous work to explain the different performance of organic dyes related to open-circuit photovoltage (V (oc)) and short-circuit current density (J (sc)) were used to evaluate the performance of the dyes with just different EWG. Our calculated results reveal that dye 2 with o-NO2-Ph has a larger vertical dipole moment, more electrons transferred from the dye to the semiconductor and a lower degree of charge recombination, which could lead to larger V (oc); while the larger driving force and comparable light harvesting efficiency could lead to higher J (sc) , highlighting the potential of o-NO2-Ph as an EWG in an acrylic acid acceptor.

First author: Matovic, Zoran D., Antitumor effects of a tetradentate amido-carboxylate ligands and corresponding square-planar palladium(II) complexes toward some cancer cells. Crystal structure, DFT modeling and ligand to DNA probe Docking simulation, JOURNAL OF INORGANIC BIOCHEMISTRY, 121, 134, (2013)
Abstract: Novel square-planar palladium(II) complexes with O-N-N-O-type ligands H(4)mda (H(4)mda = malamido-N,N’-diacetic acid) and H(4)obp (H(4)obp = oxamido-N,N’-di-3-propionic acid) were prepared and characterized. The ligands coordinate to the palladium(II) ion via two pairs of deprotonated ligating atoms with square chelation. A four coordinate, square-planar geometry was verified crystallographicaly for the K-2 [Pd(mda)]center dot H2O complex. The binary and ternary systems of Pd(II) ion with H(4)mda or H(4)obp (L) as primary ligands and guanosine (A) as secondary ligand were studied in aqueous solutions in 0.1 M NaCl ionic medium at 25 degrees C by potentiometric titrations. In addition, calculations based on density functional methods (DFT) were carried out. A natural bonding orbital analysis indicated that the Pd-N bonds are three-centric in nature and mainly governed by charge transfer via a strong delocalization of the oxygen lone pair with “p” character into the bonding Pd-N orbital. Mononuclear palladium(II) complexes together with amido acid N,O-containing ligands were tested against several tumor cells and reveal significant antitumor activity and lower resistance of tumor cells in vitro than cisplatin. In this paper, interactions of palladium complexes with DNA are discussed in order to provide guidance and determine structure and antitumor activity relationships for continuing studies of these systems. Docking simulation on DNA dodecamer or 29-mer (Lippard solved crystal structures), suggests several favorable interactions with the hydrogen pocket/binding site for the incoming ligands. These results support amidoacids/Pd complexes as novel antitumor drugs and suggest that their potent cell life inhibition may contribute to its anti-cancer efficacy.

First author: Broniatowski, Marcin, Self-organization of non-amphiphilic molecules. Studies of thin films of long-chain homologous dialkylthioethers at the water/air interface, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 395, 176, (2013)
Abstract: In contrast to classical surfactants, the knowledge about the self-organization of alkanes and their hydrophobic derivatives is still limited. In this paper, we present the results of the studies of self-assembly of long-chain dialkylthioethers at the air/water interface. The substitution of one methylene group by the thioether divalent sulfur introduces significant dipole moment to the alkane chain without affecting the hydrophobicity, which profoundly influences the self-assembly of these molecules. Depending on the location of the thioether group in the hydrophobic chain, the investigated molecules can form Langmuir monolayers, which are stabilized by the thioether-water H-bonds formation, or random multilayers. The structures of the monolayers were investigated with the application of Grazing Incidence X-ray Diffraction. To elucidate important structural differences between thioether and alkane monolalyers of the same hydrocarbon chain length, we applied the methods of quantum chemistry (ETS-NOCV calculations). It turned out that the introduction of one sulfur atom affects the distribution of electron density not only in the proximity of this atom but generally along the chain. The combination of experimental and calculation methods provides to the better understanding of the fundamental question of the self-organization of long-chain alkanes and their non-amphiphilic derivatives at interfaces.

First author: Rodriguez, Juan I., An efficient method for computing the QTAIM topology of a scalar field: The electron density case, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 681, (2013)
Abstract: An efficient method for computing the quantum theory of atoms in molecules (QTAIM) topology of the electron density (or other scalar field) is presented. A modified NewtonRaphson algorithm was implemented for finding the critical points (CP) of the electron density. Bond paths were constructed with the second-order RungeKutta method. Vectorization of the present algorithm makes it to scale linearly with the system size. The parallel efficiency decreases with the number of processors (from 70% to 50%) with an average of 54%. The accuracy and performance of the method are demonstrated by computing the QTAIM topology of the electron density of a series of representative molecules. Our results show that our algorithm might allow to apply QTAIM analysis to large systems (carbon nanotubes, polymers, fullerenes) considered unreachable until now.

First author: Szatylowicz, Halina, Complexes of 4-substituted phenolates with HF and HCN: Energy decomposition and electronic structure analyses of hydrogen bonding, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 696, (2013)
Abstract: We have computationally studied para-X-substituted phenols and phenolates (X = NO, NO2, CHO, COMe, COOH, CONH2, Cl, F, H, Me, OMe, and OH) and their hydrogen-bonded complexes with B and HB (B = F and CN), respectively, at B3LYP/6-311++G** and BLYP-D/QZ4P levels of theory. Our purpose is to explore the structures and stabilities of these complexes. Moreover, to understand the emerging trends, we have analyzed the bonding mechanisms using the natural bond orbital scheme as well as KohnSham molecular orbital (MO) theory in combination with quantitative energy decomposition analyses [energy decomposition analysis (EDA), extended transition state-natural orbitals for chemical valence (ETS-NOCV)]. These quantitative analyses allow for the construction of a simple physical model that explains all computational observations.

First author: Gupta, Karthick Babu Sai Sankar, Bacteriopheophytin a in the Active Branch of the Reaction Center of Rhodobacter sphaeroides Is Not Disturbed by the Protein Matrix as Shown by C-13 Photo-CIDNP MAS NMR, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 3287, (2013)
Abstract: The electronic structure of bacteriopheophytin a (BPhe a), the primary electron acceptor (Phi(A)) in photosynthetic reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides, is investigated by photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) NMR spectroscopy at atomic resolution. By using various isotope labeling systems, introduced by adding different C-13 selectively labeled delta-aminolevulinic acid precursors in the growing medium of R. sphaeroides wild type (WT), we were able to extract light-induced C-13 NMR signals originating from the primary electron acceptor. The assignments are backed by theoretical calculations. By comparison of these chemical shifts to those obtained from monomeric BPhe a in solution, it is demonstrated that Phi(A) in the active branch appears to be electronically close to free bacteriopheophytin. Hence, there is little effect of the protein surrounding on the cofactor functionally which contributes with its standard redox potential to the electron transfer process that is asymmetric.

First author: Wang, Gang, Experimental and theoretical investigations on the tautomerism of 1-phenyl-2-thiobarbituric acid and its methylation reaction, JOURNAL OF MOLECULAR STRUCTURE, 1036, 372, (2013)
Abstract: In the present study, 1-phenyl-2-thiobarbituric acid (1) was synthesized and the tautomerism of this compound was investigated by FT-IR spectroscopy, X-ray analysis and H-1 NMR study as well as quantum chemical calculations. It is found that compound 1 exists in triketo form in the solid state and in CDCl3 solution while tautomerization was observed in DMSO-d(6), DMF-d(7) and CD3OD solution. The geometry optimization of eight possible tautomers of 1-phenyl-2-thiobarbituric acid was performed in gas phase and in different solvents using COSMO method. The calculated results are in good accordance with experimental data. Additionally, the methylation reaction of 1-phenyl-2-thiobarbituric acid was investigated for the first time by combination of experimental and theoretical methods. The methylation product might be varied with three possible isomers because of the structural features of 1-phenyl-2-thiobarbituric acid. We identified the obtained methylation product by X-ray diffraction and FT-IR spectroscopy, and transition state search and energy calculation were conducted to elucidate experimental data, the results revealed that the theoretical calculations are consistent with experimental data.

First author: Adams, Richard D., Dynamic Rotation of Bridging Aryl Ligands in Unsaturated Metal Carbonyl Cluster Complexes, ORGANOMETALLICS, 32, 1587, (2013)
Abstract: Variable-temperature NMR studies of the compound Os-3(CO)(10)(mu-eta(1)-C6H5)(mu-AuPPh3) (1) have revealed a dynamic process of hindered rotation of the bridging phenyl ligand about the metal metal bond. The activation parameters for the process, Delta H-double dagger = 73.33(42) kJ/mol and Delta S-double dagger = -2.66(1.25) J/(K mol), were determined by analysis of variable-temperature H-1 NMR spectra. A density functional theory analysis has provided a mechanism that involves a shift of the ligand out of the bridging position with the formation of an agostic interaction of one of the ortho-positioned CH bonds of the phenyl ring to the neighboring metal atom. The related compound Os-3(CO)(10)(mu-eta(1)-Py)(mu-AuPPh3) (2; Py = 2-C15H9) was synthesized and was found to exhibit a similar rotation of the bridging pyrenyl ligand about the metal-metal bond: Delta H-double dagger = 70.93(61) kJ/mol and Delta S-double dagger = -6.98(1.83) J/(K mol).

First author: Mousavi, Masoumeh, Bonding Analysis of the Trimethylenemethane (TMM) Complexes [(eta(6)-C6H6)M-TMM] (M = Fe, Ru, Os), [(eta(5)-C5H5)M-TMM] (M = Co, Rh, Ir), and [(eta(4)-C4H4)M-TMM] (M = Ni, Pd, Pt),ORGANOMETALLICS, 32, 1743, (2013)
Abstract: Quantum chemical calculations using gradient corrected density functional theory at the BP86/def2-TZVPP level have been carried out for the sandwichlike trimethylenemethane complexes of group 8 (eta(6)-C6H6)M-TMM (BzM-TMM), where M = Fe, Ru, Os, group 9 (eta(5)-C5H5)M-TMM (CpM-TMM), where M = Co, Rh, Ir, and group 10, (eta(4)-C4H4)M-TMM (CbM-TMM), where M = Ni, Pd, Pt. The nature of the metal-TMM bonding has been investigated with charge and energy decomposition analyses. The geometry optimization of the complexes gives sandwichlike structures where the terminal carbon atoms of the TMM ligands have significantly longer distances to the metal than to the central carbon. The calculated bond dissociations energies D-e of the TMM ligand are between 89.9 and 153.0 kcal/mol. The intrinsic interaction energies Delta E-int and the D-e values for the heavier group 8 and group 9 elements become larger for the heavier atoms in the order BzFe-TMM < BzRu-TMM < BzOs-TMM and CpCoTMM < CpRh-TMM < CpIr-TMM, respectively. The group 10 elements exhibit a V-shaped trend for Delta E-int and the De values with the sequence CbPd-TMM < CbNi-TMM < CbPt-TMM. The analysis of the bonding situation shows that the dominant orbital interactions come from the degenerate pi interactions between the singly occupied degenerate pi orbitals of the metal fragment and the TMM ligand. The degenerate pi orbital of TMM has coefficients only at the terminal atom. In agreement with the shape of the orbitals, the EDA-NOCV method suggests that the metal-TMM bonding takes place mainly between the terminal carbon atoms and the metal while the sigma bonding between the central carbon atom and the metal is rather weak. In contrast, the AIM analysis gives a bond path only between the metal atom and the closer central carbon atom but not to the more distant carbon atoms. This clearly shows that the AIM analysis does not faithfully represent the strongest pairwise interactions between the atoms in a molecule. The EDA-NOCV and the NBO methods agree that the TMM ligand in the complex carries only a small partial charge, which may be negative or positive.

First author: Danopoulos, Andreas A., Angular Distortions at Benzylic Carbons Due to Intramolecular Polarization-Induced Metal-Arene Interactions: A Case Study with Open-Shell Chromium(II) NHC Complexes, ORGANOMETALLICS, 32, 1842, (2013)
Abstract: The synthesis and full characterization of the unprecedented open-shell Cr(II) benzyl organometallic complexes [Cr(NHC)(2)(benzyl)(2)] (2) and [Cr(NHC*)(benzyl)(2)] (3) (NHC = N,N’-diisopropylimidazol-2-ylidene; NHC* = N,N’-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) from [Cr(benzyl)(3)(THF)(3)] and [CrCl2(THF)(2)]/[Mg(benzyl)(2)], respectively, uncovered unusually acute angles (93 degrees in 2 and 76 degrees in 3) at the sp(3) benzylic C of the coordinated benzyl ligands. Detailed theoretical analyses (DFT and CASPT2) of the four- and three-coordinate Cr(II) species were performed to elucidate the physical origin of the benzyl bending and led to the recognition of a noncovalent, intramolecular polarization-induced metal arene (PIMA) interaction as being responsible for it. The energetic contribution from a single PIMA interaction is estimated to be ca. 50 kJ/mol. A comparison with the origin of the angular distortions in the d(0) [Zr(benzyl)(4)] complex will also be presented. Sharing the common origin of an induced-dipole charge density scheme with intermolecular anion-pi interactions, the intramolecular PIMA interaction concept involving a transition metal unpaired d electron and arene-pi orbitals can be viewed as an extension of intermolecular anion-pi interactions and leads to remarkable quantitative prediction of the observed structural distortions. PIMA interactions may manifest themselves in diverse structural and dynamic phenomena and have broad implications in chemical sciences.

First author: Burgun, Alexandre, Oxidative Activation of Aryldiynyl-Iron Complexes: Regioselective Dimerization,ORGANOMETALLICS, 32, 1866, (2013)
Abstract: Chemical oxidations of the iron butadiynyl complexes Cp*(dppe)FeC CC CAr (Ar = Ph, 1a; Ar = C6H4-Me-4, 1b; Cp* = eta(5)-C5Me5, dppe = 1,2-bis-(diphenylphosphino)ethane) achieved with 1 equiv of ferrocenium hexafluorophosphate salt in THF at -78 degrees C provide the transient species 1a(PF6) and 1b(PF6), as demonstrated by ESR experiments. Above -35 degrees C, intramolecular C-C couplings take place regiospecifically, providing the binuclear complexes [{Cp*(dppe)Fe}(2)C8Ar2}(PF6)(2) (Ar = Ph, 2a; Ar = C6H4-Me-4, 2b), which were isolated after purification as thermally stable deep purple powders in 61 and 57% yields, respectively. The full characterization of the new products, including X-ray analysis of 2a(PF6)(2), electrochemical data, spectroscopic properties, and electronic structures investigated at the DFT level of theory are reported. NMR investigations have shown that the iron building blocks rotate slowly around the cyclobutene ring, allowing the observation of three rotamers in equilibrium. The cyclic voltammetry of the dimer 2b(PF6)(2) shows four redox events with the current peaks corresponding to two one-electron-oxidation and two one-electron-reduction processes. These compounds are diamagnetic in the solid state but ESR active in solution, indicating that the triplet excited state is readily accessible.

First author: Cimpoesu, Fanica, New insights in the bonding regime and ligand field in Wernerian complexes. A density functional study, POLYHEDRON, 52, 183, (2013)
Abstract: We advance challenging new observations about the bonding regime and ligand field (LF) effects in the Wernerian complexes, with the help of several computer experiments realized exploiting the specific leverages of the ADF (Amsterdam density functional) code. Assembling the molecular systems from preliminarily prepared metal ion and individual ligand fragments and analyzing the components of the total bonding energy (Pauli repulsion, electrostatic interactions and orbital part), we noticed interesting correlations between the orbital part and the simple formulas of the qualitatively defined ligand field stabilization energy (LFSE). The facts are beyond the obvious or predictable comprehension, since the orbital components incorporate the subtle balance of intra- and inter-fragment density rearrangements, charge transfer and orbital mixing. The energy decomposition analysis was performed considering metal ions and ligand sets in their nominal oxidation states, or with fractional charges, resulted after a preliminary step of electronegativity equalization driven charge transfer. We worked on series of prototypic simple octahedral units: [(MF6)-F-q](q-6), [M-q(CN)(6)](q-6) and [M-q(H2O)(6)](q) complexes with Mn-II and Mn-III ions selected from the M = Cr to Cu 3d series. Besides, as illustration of observed regularities in the case of more complex ligands and intermediate symmetries, we considered [M-q(bpca)(2)](q-2) complexes (Hbpca = bis(2-pyridilcarbonyl)amine) with D-2d symmetry. Using the ADF facilities of orbital population control and fractional occupation schemes, we devised two simple ways to estimate 10Dq parameters by numerical experiments that simulate the effects of Ligand Field stabilization and electron promotion. To the best of our knowledge, though simple, such considerations on bonding regime or methodological procedures designed to meet the phenomenological demands of LF models have not been discussed before. Interesting new aspects can yet be discovered exploring the subtle details of coordination bonding as intermediate between ionic and covalent bonding regime.

First author: Petersen, Montana V., Fluorinated phenolates in monomeric and dimeric Co(II) compounds, POLYHEDRON,52, 276, (2013)
Abstract: Five structures of two monometallic cobalt aryloxide compounds and two bimetallic cobalt-thallium compounds with bridging fluorinated aryloxide ligands (OC6F5 = OArF, OC6H3(CF3)(2) = OAr’) are presented with magnetic susceptibility and spectroscopic characterization data. The monometallic compounds, [Co(OArF)(2)(DME)](2), 1, and [Co(OAr’)(2)(DME)(2), 2, are prepared by metathesis reactions between two equivalents of TlOAr and one of CoI2. The heterobimetallic compounds [Tl2CO(OArF)(4)]center dot 2 toluene, 3a, and [TI2Co(OAr’)(4)](2)center dot 2 toluene, 4, were prepared with a 4:1 ratio of the thallium aryloxide to CoI2. An unsolvated form of [Tl2Co(OArF)(4)], 3b, was also structurally characterized. Magnetic susceptibility studies revealed that 3b is a simple, isolated high-spin Co-II with Curie-Weiss behavior. Dimeric compounds 1 and 2 are also high-spin Coll but exhibit antiferromagnetic coupling, via superexchange through two mu(2)-OArF ligands, as supported by DFT calculations. Compound 4 exhibits ferromagnetic behavior which is ascribed to the presence of mu(3)-OAr ligands, instead of mu(2)-OAr groups.

First author: Randles, Michael D., Mixed-metal cluster chemistry: 32. Synthesis, structure, and reactivity of a trimetallic molybdenum-iridium carbonyl cluster possessing a mu(3)-eta(2)-benzyne ligand, POLYHEDRON, 52, 957, (2013)
Abstract: The reaction of Mo2Ir2(mu-CO)(3)(CO)(7)(eta(5)-C5H5)(2) and Ir(C CCH2OH)(CO)(PPh3)(3) in refluxing toluene gives the molybdenum-iridium cluster MoIr2(mu(3)-eta(2)-C6H4)(mu-PPh2)(mu-CO)(2)(CO)(4)(eta(5)-C5H5) (1) in low yield. Mo2Ir2(mu-CO)(3)(CO)(6)(PPh3)(eta(5)-C5H5)(2) (2) is a possible intermediate en route to 1; reaction of Mo2Ir2(mu-CO)(3)(CO)(7)(eta(5)-C5H5)(2) and Ir(C CCH2OH)(CO)(PPh3)(3) in refluxing dichloromethane affords low yields of 2, and thermolysis of the latter in refluxing toluene gives modest yields of 1. A structural study reveals that 1 consists of a triangular MoIr2 core with a molybdenum-bound cyclopentadienyl group, two terminal carbonyls at each of the iridium atoms, one carbonyl bridging each of the Mo-Ir bonds, and a PPh2 moiety spanning the Ir-Ir linkage. The cluster coordination sphere is completed by a face-capping benzyne ligand that ligates eta(1)- to each iridium atom and eta(2)- to the group 6 metal. A structural study of 2 confirms the tetranuclear Mo2Ir2 core with molybdenum-bound cyclopentadienyl groups, six terminal and three-edge-bridging carbonyls, the latter deployed about an MoIr2 face, and a triphenylphosphine ligand ligated axially with respect to the carbonyl-bridged plane. Reaction of 1 with PPh3 in refluxing toluene gives MoIr2(mu(3)-eta(2)-C6H4)(mu-PPh2)(mu-CO)(2)(CO)(3)(PPh3)(eta(5)-C5H5) (3) in low yield. While X-ray structural authentication of 3 has thus far proven elusive, theoretical studies indicate that an equatorially substituted structure is favored energetically over the axially-substituted isomer by around 20 kJ mol(-1), but this energy difference is not sufficiently large so as to exclude formation of the axial isomer experimentally.

First author: Wang, Shi, Tetragonally compressed high-spin Mn(III) Schiff base complex: Synthesis, crystal structure, magnetic properties and theoretical calculations, POLYHEDRON, 52, 1199, (2013)
Abstract: The synthesis, X-ray crystal structures, magnetic properties and Density Functional Theory (DFT) calculations of a new six-coordinated high-spin (HS) Mn(III) Schiff base complex, [Mn-III(3-MeO-sal-N(1,5,9,13))]NO3 (1), are described. The crystal structure analysis show that the Mn site has a tetragonally compressed octahedral geometry. The magnetic susceptibilities measurements indicate the HS ground state in the temperature range 1.8-300 K, in contrast with a previously reported analogue, [Mn(5-Br-sal-N-1,5,8,12)]ClO4, which showed spin-crossover (SCO) behavior. The magnetic data are well fitted by Zero-Field-Splitting (ZFS) Hamiltonian, showing a D > 0 parameter, in line with the compressed octahedron pattern. Various DFT computations certified, in semi-quantitative respects, the fitted Spin Hamiltonian parameters. Computational experiments using fractional population schemes or Time-Dependent DFT approach yielded the specific ligand field parameters, contributing to the theoretical insight in the rare case of compressed Mn(III) complexes.

First author: Pandey, Krishna K., Bonding energy analysis in cationic borylene complexes of palladium and platinum: A theoretical study, POLYHEDRON, 52, 1431, (2013)
Abstract: Quantum chemical calculations at DFT/BP86/TZ2P have been carried out for cationic metal borylene complexes of palladium and platinum trans-[X(PMe3)(2)M(BR)](+) (X = Cl, Br, I; M = Pd, Pt; R = Mesityl, Xylyl, Ph, NMe2). The bonding analysis was carried out with charge decomposition and energy decomposition analysis. The calculated geometry of the platinum borylene complex trans-[Br(PMe3)(2)Pt(BMes)](+) is in excellent agreement with the experimental structural data for trans-[Br(PCy3)(2)Pt(BMes)](+). Pauling bond order of the optimized structures shows that the M-B bonds in these complexes have multiple M-B bond character, which is also supported by the performed energy decomposition analysis. The orbital interactions between the metal and boron arise mainly from M <- 4 BR sigma donation. In all complexes, the pi bonding contribution to the orbital interactions is relatively small. The bonding analysis clearly shows that the platinum borylene complexes [X(PMe3)(2)Pt(BR)](+) are more strongly stabilized by Pt-BR interactions than the platinum borylene complexes [X(PMe3)(2)Pd(BR)](+) which is probably the reason the complex platinum borylene complexes [X(PCy3)(2)Pt(BMes)](+) could become isolated. The contributions of the electrostatic interaction terms Delta E-elstat in the M=BR bonding are significantly larger in all borylene complexes than the covalent bonding Delta E-orb term. Thus, the M=BR bond in the studied cationic borylene complexes of palladium and platinum has a greater degree of ionic character. The larger gap between HOMOs of metal fragments [X(PMe3)(2)M)](+) and LUMO of BNMe2 allow relatively weak [X(PMe3)(2)M](+) -> BNMe2 pi-back bonding.

First author: Zhao, Lijuan, Structure and Bonding in MPb5- (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 2325, (2013)
Abstract: Bimetallic clusters of MPb5- (M = Cu, Ag, and Au) have been studied using density functional theory and photoelectron imaging spectroscopy. These anionic clusters and their neutrals were determined to be a Pb-5 trigonal bipyramid with the coinage metal atom on its triangular facet. This structure of each MPb5- or MPb5 was found to be more than 0.5 eV lower than other structural candidates and that of each MPb5- has a HOMO-LUMO gap of larger than 1.2 eV. The chemical bonding between M and Pb-5 in MPb5- was dominantly attributed to the interaction between the outer s orbital of M and the lowest unoccupied molecular orbital (LUMO) of Pb-5. The inner d orbitals of M and the occupied orbitals of Pb-5 unit only make a little contribution. The different bonding behaviors of Cu, Ag, and Au, which are noticeable in many other species, have little effect on the Pb-5 counterpart in MPb5-, indicating Pb-5 unit acts partially like a large artificial atom. Additionally, photoelectron spectra of MPb5- (M = Cu, Ag, and Au) provide good experimental data to evaluate different theoretical approaches dealing with relativistic effects in clusters containing heavy atoms.

First author: Jissy, A. K., What Stabilizes the LinPn Inorganic Double Helices?, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 4, 1018, (2013)
Abstract: Recently, inorganic double-helical structures based on simple lithium and phosphorus salts have been demonstrated. We have analyzed the nature of bonding in these double helices of LinPn (n = 7-9). Similar to DNA, noncovalent interactions and cooperativity play an important role in stabilizing the inorganic double helices. Cooperativity imparts an additional stabilization of 4.5 to 10.1 kcal/mol per Li-P pair. In addition, the ionicity of Li-P units further augments the stability of these inorganic double-helix structures in contrast with the canonical base pairs in DNA, where noncovalent interactions determine the duplex stability. Unwinding is shown to be unfavorable, and cleavage of a few edge Li-P bonds leads to spontaneous self-healing into the intact double-helix tract.

First author: Zijlstra, Hester, Stereodivergent S(N)2@P Reactions of Borane Oxazaphospholidines: Experimental and Theoretical Studies, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 4483, (2013)
Abstract: The stereo divergent ring-opening of 2-phenyl oxazaphospholidines with alkyl lithium reagents is reported. N-H oxazaphospholidines derived from both (+)-cis-1-amino-2-indanol and (-)-norephedrine provide inversion products in a highly stereoselective process. In contrast, N-Me oxazaphospholidines yield ring opening products with retention of configuration at the P center, as previously reported by Juge and co-workers. As a result, from a single amino alcohol auxiliary, both enantiomers of key P-stereogenic intermediates could be synthesized Theoretical studies of ring opening with model oxazaphospholidines at the DFT level have elucidated the streochemical course of this process. N-H substrates react in a single step via preferential backside S(N)2@P substitution with inversion at phosphorus. N-methylated substrates react preferentially via a two-step frontside S(N)2@P, yielding a ring-opened product in which the nucleophilic methyl binds to P with retention of configuration. DFT calculations have shown that the BH3 unit is a potent directing group to which the methyl lithium reagent coordinates via Li in all the reactions studied.

First author: Jackson, Timothy A., Geometric and Electronic Structures of Manganese-Substituted Iron Superoxide Dismutase, INORGANIC CHEMISTRY, 52, 3356, (2013)
Abstract: The active-site structures of the oxidized and reduced forms of manganese-substituted iron superoxide dismutase (Mn(Fe)SOD) are examined, for the first time, using a combination of spectroscopic and computational methods. On the basis of electronic absorption, circular dichroism (CD), magnetic CD (MCD), and variable-temperature variable-field MCD data obtained for oxidized Mn(Fe)SOD, we propose that the active site of this species is virtually identical to that of wild-type manganese SOD (MnSOD), with both containing a metal ion that resides in a trigonal bipyramidal ligand environment. This proposal is corroborated by quantum mechanical/molecular mechanical (QM/MM) computations performed on complete protein models of Mn(Fe)SOD in both its oxidized and reduced states and, for comparison, wild-type (WT) MnSOD. The major differences between the QM/MM optimized active sites of WT MnSOD and Mn(Fe)SOD are a smaller (His)N Mn N(His) equatorial angle and a longer (Gln146(69))NH center dot center dot center dot O(sol) H-bond distance in the metal-substituted protein. Importantly, these modest geometric differences are consistent with our spectroscopic data obtained for the oxidized proteins and high-field electron paramagnetic resonance spectra reported previously for reduced Mn(Fe)SOD and MnSOD. As Mn(Fe)SOD exhibits a reduction midpoint potential (4) almost 700 mV higher than that of MnSOD, which has been shown to be sufficient for explaining the lack of SOD activity displayed by the metal-subtituted species (Vance, C. K.; Miller, A. F. Biochemistry 2001, 40, 13079-13087), Em’s were computed for our experimentally validated QM/MM optimized models of Mn(Fe)SOD and MnSOD. These computations properly reproduce the experimental trend and reveal that the drastically elevated Em of the metal substituted protein stems from a larger separation between the second-sphere Gln residue and the coordinated solvent in Mn(Fe)SOD relative to MnSOD, which causes a weakening of the corresponding H-bond interaction in the oxidized state and alleviates steric crowding in the reduced state.

First author: Ndambuki, Sylvester, An analysis of unsupported triple and quadruple metal-metal bonds between two homonuclear group 6 transition elements based on the combined natural orbitals for chemical valence and extended transition state method, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 753, (2013)
Abstract: We have applied a newly developed energy and density decomposition scheme to the study of unsupported multiple metalmetal bonds between two Group 6D transition elements. The new scheme combines the extended transition state (ETS) energy decomposition method (Ziegler and Rauk, Theor. Chim. Acta 1977, 46, 1) with the natural orbitals for chemical valence (NOCV) density decomposition theory (Michalak et al., J. Phys. Chem. A 2008, 112, 1933) within a single framework. The ETSNOCV scheme is here applied to the quadruply metalmetal bonded complexes L2L2MML2L2 (1 sigma 242) and L3MML3 with a metal triple bond(1 sigma 24).

First author: Ramanantoanina, Harry, Density functional theory study of the multimode Jahn-Teller problem in the fullerene anion, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 802, (2013)
Abstract: The fullerene anion, C60, within the Ih point group, is a spherical molecule subject to the T circle times h JahnTeller (JT) distortion. The descent in symmetry goes to the three epikernel subgroups, namely D5d, D3d, and D2h. The last one completely removes the electronic degeneracy, whereas D5d and D3d structures are subject to further JT distortion, leading to C2h minimum energy structure. The multideterminantal density functional theory approach was applied to calculate the JT parameters for all seven different structures of lower symmetry. The multimode problem in this system was addressed using the intrinsic distortion path method, in which the JT distortion is expressed as a linear combination of all totally symmetric normal modes in the particular low symmetry minimum energy conformation. Results obtained by both methods are consistent and give direct insight into the coupling of electronic distribution and nuclear movements in C60.

First author: Andjelkovic, Ljubica, The choice of the exchange-correlation functional for the determination of the jahnteller parameters by the density functional theory, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 859, (2013)
Abstract: The JahnTeller (JT) parameters for small, aromatic, organic radicals, CnHn (n = 47), bis(cyclopentadienyl)cobalt(II) (cobaltocene), a sodium cluster (Na3), a silver cluster (Ag3), the hexaflurocuprate(II) ion ([CuF6]4), and tris(acetylacetonato)manganese(III) ([Mn(acac)3]) have been evaluated by the means of the multideterminantal density functional theory using the most common approximations, to clarify which type of exchange-correlation functional should be used in analysis of the JT effect. The results are compared with available experimental and theoretical data. The choice of the functional strongly depends on the chemical system at hand, but to obtain fast and qualitatively reliable results, the local density approximation may be taken as satisfactory, regardless of the diversity of the systems prone to a JT distortion.

First author: Aruda, Kenneth O., Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 110, 4212, (2013)
Abstract: This paper describes measurements of the dynamics of hot electron cooling in photoexcited gold nanoparticles (Au NPs) with diameters of similar to 3.5 nm, and passivated with either a hexadecylamine or hex-adecanethiolate adlayer, using ultrafast transient absorption spectroscopy. Fits of these dynamics with temperature-dependent Mie theory reveal that both the electronic heat capacity and the electron-phonon coupling constant are larger for the thiolated NPs than for the aminated NPs, by 40% and 30%, respectively. Density functional theory calculations on ligand-functionalized Au slabs show that the increase in these quantities is due to an increased electronic density of states near the Fermi level upon ligand exchange from amines to thiolates. The lifetime of hot electrons, which have thermalized from the initial plasmon excitation, increases with increasing electronic heat capacity, but decreases with increasing electron-phonon coupling, so the effects of changing surface chemistry on these two quantities partially cancel to yield a hot electron lifetime of thiolated NPs that is only 20% longer than that of aminated NPs. This analysis also reveals that incorporation of a temperature-dependent electron-phonon coupling constant is necessary to adequately fit the dynamics of electron cooling,

First author: Labouille, Stephanie, Theoretical Insights into the Nature of Divalent Lanthanide-Ligand Interactions,ORGANOMETALLICS, 32, 1265, (2013)
Abstract: The nature of the metal-ligand interaction in divalent samarium complexes is investigated by a variety of quantum chemical tools and compared to the analogous strontium-ligand interaction. The complexes under study are the decamethylsamarocene Sm(C5Me5)(2) the octamethyldiphosphasamarocene Sm(C4Me4P)(2), and the decamethylstrontocene Sr(C5Me5)(2). Molecular orbital descriptions, binding energy decompositions and topological analyses based on the electron density reveal the non-negligible role of covalency in the samarium-ligand interaction. The results are supported by an orbital energetic contribution in the metal-ligand interaction and a number of samarium-carbon bond critical points and electron localization function valence basins. The covalent contribution to the samarium-ligand bond contrasts with the highly ionic strontium-ligand interaction.

First author: Lin Yan, Density Functional Theory Studies on the Second-order Nonlinear Optical Properties of [V12O32](4-) and Its Alkali Metal Cation and Protonated Derivatives, CHEMICAL JOURNAL OF CHINESE UNIVERSITIES-CHINESE, 34, 615, (2013)
Abstract: The geometrical structures and second-order nonlinear optical (NLO) properties of [V12O32](4-) [ V12O32 M](3-) (M = Li+, Na+, K+) and the protonated derivatives were investigated via density functional theory (DFT) method. The results show that the alkali metal cation W. has little effect on the geometrical structure of the system and the first hyperpolarizability(beta(0)). However, the different positions and different orientations of the protons have different impact on beta(0) values. Compared with [V12O32](4-) the beta(0) values of the protonated systems, in which the middle bridging oxygen atoms are protonated, increase significantly. Besides, when the middle bridging oxygen atoms are protonated, meanwhile the protons point to inside of the bowl, this complex exhibits the largest beta(0) value.

First author: Beyhan, S. Maya, Bond energy decomposition analysis for subsystem density functional theory, JOURNAL OF CHEMICAL PHYSICS, 138, 615, (2013)
Abstract: We employed an explicit expression for the dispersion (D) energy in conjunction with Kohn-Sham (KS) density functional theory and frozen-density embedding (FDE) to calculate interaction energies between DNA base pairs and a selected set of amino acid pairs in the hydrophobic core of a small protein Rubredoxin. We use this data to assess the accuracy of an FDE-D approach for the calculation of intermolecular interactions. To better analyze the calculated interaction energies we furthermore propose a new energy decomposition scheme that is similar to the well-known KS bond formation analysis [F. M. Bickelhaupt and E. J. Baerends, Rev. Comput. Chem. 15, 1 (2000)], but differs in the electron densities used to define the bond energy. The individual subsystem electron densities of the FDE approach sum to the total electron density which makes it possible to define bond energies in terms of promotion energies and an explicit interaction energy. We show that for the systems considered only a few freeze-and-thaw cycles suffice to reach convergence in these individual bond energy components, illustrating the potential of FDE-D as an efficient method to calculate intermolecular interactions.

First author: Verzijl, C. J. O., Applicability of the wide-band limit in DFT-based molecular transport calculations, JOURNAL OF CHEMICAL PHYSICS, 138, 615, (2013)
Abstract: Transport properties of molecular junctions are notoriously expensive to calculate with ab initio methods, primarily due to the semi-infinite electrodes. This has led to the introduction of different approximation schemes for the electrodes. For the most popular metals used in experiments, such as gold, the wide-band limit (WBL) is a particularly efficient choice. In this paper, we investigate the performance of different WBL schemes relative to more sophisticated approaches including the fully self-consistent non-equilibrium Green’s function method. We find reasonably good agreement between all schemes for systems in which the molecule (and not the metal-molecule interface) dominates the transport properties. Moreover, our implementation of the WBL requires negligible computational effort compared to the ground-state density-functional theory calculation of a molecular junction. We also present a new approximate but efficient scheme for calculating transport with a finite bias. Provided the voltage drop occurs primarily inside the molecule, this method provides results in reasonable agreement with fully self-consistent calculations.

First author: Pickup, David F., Influence of Axial and Peripheral Ligands on the Electronic Structure of Titanium Phthalocyanines, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 4410, (2013)
Abstract: To discover how molecular changes affect the electronic structure of dye molecules for solar cells, we have investigated four titanium phthalocyanines customized by axial and peripheral ligands (monodentate oxo versus bidentate catechol and tert-butyl versus tert-butylphenoxy, respectively). X-ray absorption spectroscopy and photoelectron spectroscopy were combined with density functional theory (DFT) and crystal-field multiplet calculations to characterize the Ti 3d and N 2p valence electrons that form the frontier orbitals. When a monodentate oxo axial ligand was replaced by a bidentate catechol ligand, the multiplet structure of the Ti 2p-to-3d transitions was found to change systematically. The most noticeable change was an additional transition into the low-lying 3d(xy) level, which is attributed to a reduction in local symmetry from 4-fold to 2-fold at the Ti center. An increase of the Ti 2p core level binding energy was observed in the bidentate complex and compared to a calculated core level stabilization. DFT predicts a change of the LUMO from the inner phthalocyanine ring to the Ti d(xy) orbital and a reversal of the high-lying d(x)(-y)(2)(2) and d(z)(2) orbitals. The N Is edge was calculated using time-dependent density functional theory (TDDFT) and compared to experiment.

First author: Wang, Wenguang, Isolation of a Mixed Valence Diiron Hydride: Evidence for a Spectator Hydride in Hydrogen Evolution Catalysis, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 3633, (2013)
Abstract: The mixed-valence diiron hydrido complex (mu H)Fe-2(pdt)(CO)(2)(dppv)(2) ([H1](0), where pdt =1,3-propanedithiolate and dppv = cis-1,2-C2H2(PPh2)(2)), was generated by reduction of the differous hydride [H1](+) using decamethylcobaltocene. Crystallographic analysis shows that [H1](0) retains the stereochemistry of its precursor, where one dppv ligand spans two basal sites and the other spans apical and basal positions. The Fe-Fe bond elongates to 2.80 from 2.66 angstrom, but the Fe-P bonds only change subtly. Although the Fe-H distances are indistinguishable in the precursor, they differ by 0.2 angstrom in [H1](0). The X-band electron paramagnetic resonance (EPR) spectrum reveals the presence of two stereoisomers, the one characterized crystallographically and a contribution of about 10% from a second symmetrical (sym) isomer wherein both dppv ligands occupy apical-basal sites. The unsymmetrical (unsym) arrangement of the dppv ligands is reflected in the values of A(P-31), which range from 31 MHz for the basal phosphines to 284 MHz for the apical phosphine. Density functional theory calculations were employed to rationalize the electronic structure of [H1](0) and to facilitate spectral simulation and assignment of EPR parameters including H-1 and P-31 hyperfine couplings. The EPR spectra of [HI](0) and [D1](0) demonstrate that the singly occupied molecular orbital is primarily localized on the Fe center with the longer bond to H, that is, Fe-II-H center dot center dot center dot Fe-I. The coupling to the hydride is A(H-1) = 55 and 74 MHz for unsym- amd sym[H1](0), respectively. Treatment of [H1](0) with H+ gives 0.5 equiv of H-2 and [H1](+). Reduction of D+ affords D-2, leaving the hydride ligand intact. These experiments demonstrate that the bridging hydride ligand in this complex is a spectator in the hydrogen evolution reaction.

First author: Moonshiram, Dooshaye, Experimental demonstration of radicaloid character in a Ru-V=O intermediate in catalytic water oxidation, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 110, 3765, (2013)
Abstract: Water oxidation is the key half reaction in artificial photosynthesis. An absence of detailed mechanistic insight impedes design of new catalysts that are more reactive and more robust. A proposed paradigm leading to enhanced reactivity is the existence of oxyl radical intermediates capable of rapid water activation, but there is a dearth of experimental validation. Here, we show the radicaloid nature of an intermediate reactive toward formation of the O-O bond by assessing the spin density on the oxyl group by Electron Paramagnetic Resonance (EPR). In the study, an O-17-labeled form of a highly oxidized, short-lived intermediate in the catalytic cycle of the water oxidation catalyst cis,cis-[(2,2-bipyridine)(2)(H2O)Ru-III ORuIII(OH2)(bpy)2](4+) was investigated. It contains Ru centers in oxidation states [4,5], has at least one Ru-V = O unit, and shows vertical bar A(xx)vertical bar = 60G O-17 hyperfine splittings (hfs) consistent with the high spin density of a radicaloid. Destabilization of pi-bonding in the d(3) Ru-V = O fragment is responsible for the high spin density on the oxygen and its high reactivity.

First author: Zendaoui, Saber-Mustapha, Molecular properties and electronic structure of phenazine ligand in binuclear molybdenum and manganese metal complexes: A density functional theory study, POLYHEDRON, 51, 123, (2013)
Abstract: DFT calculations with full geometry optimization have been performed on the series of hypothetical and characterized binuclear compounds of general formula (L3M)(2)(C12N2H8) (M = Mo and Mn, L-3 = (CO)(3), (PH3)(3) and Cp- and C12N2H8 = phenazine ligand). The various structures with syn and anti configurations have been investigated. The phenazine ligand can bind to the metals involving its C-6 and C4N2 rings through eta(6)-eta(4) and eta(6)-eta(6) coordination modes giving rise to syn and anti structures, respectively, in agreement with the favored 34 electron count with closed-shell and open-shell configurations. This study has shown that the electronic communication between the metal centers depends on their oxidation state and the attached ligands. A more crowded attached ligand imposes an anti configuration despite its electron deficiency.

First author: Conradie, Jeanet, A DFT study of the reactivity of beta-diketonato-1,5-cyclo-octadieneiridium(I) complexes,POLYHEDRON, 51, 164, (2013)
Abstract: Good linear relationships exist between density functional theory (DFT) calculated orbital energies and charges of [Ir(beta-diketonato)(cod)] complexes and the experimental second order substitution rate constant of the [Ir(R’COCHCOR)(cod)] + phen [Ir(R’COCHCOR)(cod)(phen)] reaction. Both calculated and experimental values relate to the electron-donating and -withdrawing properties of the side groups R and R’ on the beta-diketonato ligand (RCOCHCOR’)- as described by the Gordy scale group electronegativities, Hammett meta substituent constants, Lever electronic parameters and the pK(a) of the free beta-diketone.

First author: El-Hamdi, Majid, X2Y2 Isomers: Tuning Structure and Relative Stability through Electronegativity Differences (X = H, Li, Na, F, Cl, Br, I; Y = O, S, Se, Te), INORGANIC CHEMISTRY, 52, 2458, (2013)
Abstract: We have studied the XYYX and X2YY isomers of the X2Y2 species (X = H, Li, Na, F, Cl, Br, I; Y = O, S, Se, Te) using density functional theory at the ZORA-BP86/QZ4P level. Our computations show that, over the entire range of our model systems, the XYYX isomers are more stable than the X2YY forms except for X = F and Y = S and Te, for which the F2SS and F2TeTe isomers are slightly more stable. Our results also point out that the Y-Y bond length can be tuned quite generally through the X-Y electronegativity difference. The mechanism behind this electronic tuning is the population or depopulation of the pi* in the YY fragment.

First author: Smieja, Jonathan M., Manganese as a Substitute for Rhenium in CO2 Reduction Catalysts: The Importance of Acids, INORGANIC CHEMISTRY, 52, 2484, (2013)
Abstract: Electrocatalytic properties, X-ray crystallographic studies, and infrared spectroelectrochemistry (IRSEC) of Mn(bpy-tBu)(CO)(3)Br and [Mn(bpy-tBu)(CO)(3)(MeCN)](OTf) are reported. Addition of Bronsted acids to CO2-saturated solutions of these Mn complexes and subsequent reduction of the complexes lead to the stable and efficient production of CO from CO2. Unlike the analogous Re catalysts, these Mn catalysts require the addition of Bronsted acids for catalytic turnover. Current densities up to 30 mA/cm(2) were observed during bulk electrolysis using 5 mM Mn(bpytBu)(CO)(3)Br, 1 M 2,2,2-trifluoroethanol, and a glassy carbon working electrode. During bulk electrolysis at -2.2 V vs SCE, a TOF of 340 s(-1) was calculated for Mn(bpy-tBu)(CO)(3)Br with 1.4 M trifluoroethanol, corresponding to a Faradaic efficiency of 100 +/- 15% for the formation of CO from CO2, with no observable production of H-2. When compared to the analogous Re catalysts, the Mn catalysts operate at a lower overpotential and exhibit similar catalytic activities. X-ray crystallography of the reduced species, [Mn(bpy-tBu)(CO)(3)], shows a five. coordinate Mn center, similar to its rhenium analogue. Three distinct species were observed in the IR-SEC of Mn(bpy-tBu)(CO)(3)Br. These were of the parent Mn(bpy-tBu)(CO)(3)Br complex, the dimer [Mn(bpy-tBu)(CO)(3)](2), and the [Mn(bpy-tBu)(CO)(3)](2), and the [Mn(bpytBu)(CO)(3)](-) anion.

First author: Chen, Xin, The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene,MOLECULES, 18, 3279, (2013)
Abstract: By means of density functional theory, the adsorption properties of O-2 molecule on both isolated and N-graphene supported gold clusters have been studied. The N-graphene is modeled by a C65NH22 cluster of finite size. The results indicate that the catalytic activity and the O-2 adsorption energies of odd-numbered Au clusters are larger than those of adjacent even-numbered ones. The O-2 molecule is in favor of bonding to the bridge sites of odd-numbered Au clusters, whereas for odd-numbered ones, the end-on adsorption mode is favored. The perpendicular adsorption orientation on N-graphene is preferred than the parallel one for Au-2, Au-3 and Au-4 clusters, while for Au-5, Au-6 and Au-7, the parallel ones are favored. When O-2 is adsorbed on N-graphene supported Au clusters, the adsorption energies are largely increased compared with those on gas-phase ones. The increased adsorption energies would significantly facilitate the electron transfer from Au d-orbital to pi* orbital of O-2, which would further weakening the O-O bond and therefore enhancing the catalytic activity. The carbon atoms on N-graphene could anchor the clusters, which could make them more difficult to structural distortion, therefore enhance their stability.

First author: Bordiga, Silvia, Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques, CHEMICAL REVIEWS, 113, 1736, (2013)
Abstract: By means of density functional theory, the adsorption properties of O-2 molecule on both isolated and N-graphene supported gold clusters have been studied. The N-graphene is modeled by a C65NH22 cluster of finite size. The results indicate that the catalytic activity and the O-2 adsorption energies of odd-numbered Au clusters are larger than those of adjacent even-numbered ones. The O-2 molecule is in favor of bonding to the bridge sites of odd-numbered Au clusters, whereas for odd-numbered ones, the end-on adsorption mode is favored. The perpendicular adsorption orientation on N-graphene is preferred than the parallel one for Au-2, Au-3 and Au-4 clusters, while for Au-5, Au-6 and Au-7, the parallel ones are favored. When O-2 is adsorbed on N-graphene supported Au clusters, the adsorption energies are largely increased compared with those on gas-phase ones. The increased adsorption energies would significantly facilitate the electron transfer from Au d-orbital to pi* orbital of O-2, which would further weakening the O-O bond and therefore enhancing the catalytic activity. The carbon atoms on N-graphene could anchor the clusters, which could make them more difficult to structural distortion, therefore enhance their stability.

First author: Mahadevi, A. Subha, Cation-pi Interaction: Its Role and Relevance in Chemistry, Biology, and Material Science, CHEMICAL REVIEWS, 113, 2100, (2013)
Abstract: By means of density functional theory, the adsorption properties of O-2 molecule on both isolated and N-graphene supported gold clusters have been studied. The N-graphene is modeled by a C65NH22 cluster of finite size. The results indicate that the catalytic activity and the O-2 adsorption energies of odd-numbered Au clusters are larger than those of adjacent even-numbered ones. The O-2 molecule is in favor of bonding to the bridge sites of odd-numbered Au clusters, whereas for odd-numbered ones, the end-on adsorption mode is favored. The perpendicular adsorption orientation on N-graphene is preferred than the parallel one for Au-2, Au-3 and Au-4 clusters, while for Au-5, Au-6 and Au-7, the parallel ones are favored. When O-2 is adsorbed on N-graphene supported Au clusters, the adsorption energies are largely increased compared with those on gas-phase ones. The increased adsorption energies would significantly facilitate the electron transfer from Au d-orbital to pi* orbital of O-2, which would further weakening the O-O bond and therefore enhancing the catalytic activity. The carbon atoms on N-graphene could anchor the clusters, which could make them more difficult to structural distortion, therefore enhance their stability.

First author: Shi, Jianwu, Intermolecular interactions in organic semiconductors based on annelated beta-oligothiophenes and their effect on the performance of organic field-effect transistors, ORGANIC ELECTRONICS, 14, 934, (2013)
Abstract: A series of derivatives based on annelated beta-oligothiophenes were synthesized and characterized as active layer in organic field-effect transistors (OFETs). Highest field-effect mobility of 0.52 V-1 s(-1) for 2,5-dibiphenyl-dithieno[2,3-b: 3′,2′-d] thiophene (DBP-DTT), 2.2 cm(2) V-1 s(-1) for 2,5-distyryl-dithieno[2,3-b: 3′,2′-d] thiophene (DEP-DTT), and 0.16 cm(2) V-1 s(-1) for 1,4-di[2-dithieno[2,3-b: 3′,2′-d] thiophen-2-yl-vinyl] benzene (DDTT-EP) were obtained, while 2,5-diphenyl-dithieno [2,3-b: 3′,2′-d] thiophene (DP-DTT) presents no field-effect behaviors. Their thermal, optical and electrochemical properties, topographical and X-ray diffraction patterns of films, and the single crystal structures were also investigated. With the end-capping groups changing in these materials, the intermolecular interactions could transform from S-S in DP-DTT to S-C in DBP-DTT, to S-pi in DEP-DTT, and to the coexisting of S-S and S-pi in DDTT-EP. According to the device performances and the results of transfer integral calculations, it was revealed that S-pi intermolecular interaction benefits not only improving the mobility but also reducing the threshold voltage (V-T), while S-S intermolecular interaction is not favorable for promoting the mobility.

First author: Risthaus, Tobias, Benchmarking of London Dispersion-Accounting Density Functional Theory Methods on Very Large Molecular Complexes, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 1580, (2013)
Abstract: A new test set (S12L) containing 12 supramolecular noncovalently bound complexes is presented and used to evaluate seven different methods to account for dispersion in DFT (DFT-D3, DFT-D2, DFT-NL, XDM, dDsC, TS-vdW, M06-L) at different basis set levels against experimental, back-corrected reference energies. This allows conclusions about the performance of each method in an explorative research setting on “real-life” problems. Most DFT methods show satisfactory performance but, due to the largeness of the complexes, almost always require an explicit correction for the nonadditive Axilrod-Teller-Muto three-body dispersion interaction to get accurate results. The necessity of using a method capable of accounting for dispersion is clearly demonstrated in that the two-body dispersion contributions are on the order of 20-150% of the total interaction energy. MP2 and some variants thereof are shown to be insufficient for this while a few tested D3-corrected semiempirical MO methods perform reasonably well. Overall, we suggest the use of this benchmark set as a “sanity check” against overfitting to too small molecular cases.

First author: Koenig, Carolin, Protein Effects on the Optical Spectrum of the Fenna-Matthews-Olson Complex from Fully Quantum Chemical Calculations, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 9, 1808, (2013)
Abstract: We present a fully quantum-chemical study on the optical spectra of the Fenna-Matthews-Olson (FMO) protein. We have investigated the structural and environmental effects on the site energies and excitonic couplings as well as on the UV/vis absorption spectra. Our largest model of the entire protein pigment network contains more than 7000 atoms. Structures of all bacteriochlorophyll pigments have been optimized in their binding pockets, comprising more than 1000 atoms in some cases. We find that the site energies are quite sensitive to structural and environmental changes in the model setup, while excitonic couplings are more robust. It is shown that nonoptimized pigment structures lead to site energies closer to the ones for pigments optimized in their binding pocket than to those for conformations fully optimized in vacuum. The determination of reliable site energies is one of the key factors for an understanding of the excited-state properties of the FMO protein.

First author: Gao, Wei, Natures of benzene-water and pyrrole-water interactions in the forms of sigma and pi types: theoretical studies from clusters to liquid mixture, JOURNAL OF MOLECULAR MODELING, 19, 1273, (2013)
Abstract: A combined and sequential use of quantum mechanical (QM) calculations and classical molecular dynamics (MD) simulations was made to investigate the sigma and pi types of hydrogen bond (HB) in benzene-water and pyrrole-water as clusters and as their liquid mixture, respectively. This paper aims at analyzing similarities and differences of these HBs resulted from QM and MD on an equal footing. Based on the optimized geometry at omega b97xD/aug-cc-pVTZ level of theory, the nature and property of sigma and pi types of HBs are unveiled by means of atoms in molecules (AIM), natural bond orbital (NBO) and energy decomposition analysis (EDA). In light of the above findings, MD simulation with OPLS-AA and SPC model was applied to study the liquid mixture at different temperatures. The MD results further characterize the behavior and structural properties of sigma and pi types HBs, which are somewhat different but reasonable for the clusters by QM. Finally, we provide a reasonable explanation for the different solubility between benzene/water and pyrrole/water.

First author: Trifonova, Eveniya A., Synthesis and structures of cationic bis(arene) rhenium complexes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 727, 60, (2013)
Abstract: Heating of KReO4 with benzene or its derivatives in the presence of AlCl3 and Zn gives cationic bis(arene) rhenium complexes [Re(n(6)-arene)(2)](+) (arene – benzene (1a), toluene (1b), o-xylene (1c), p-xylene (1d), mesitylene (1e)) in 30-40% yield. Similar reaction with naphthalene affords [Re(n(6)-naphthalene)(2)](vertical bar) (2) in 5% yield. The naphthalene complex 2 undergoes replacement of both ligands by (BuNC)-Bu-t at 80 degrees C giving the cation [Re(tBuNC) 6](+) while the benzene complex 1a does not react under these conditions. The energy decomposition analysis revealed that metal-arene bond in the cation 1a is stronger than in the neutral W(C6H6)(2) but weaker than in the dication [Os(C6H6) 2](2+). The structures of [1a] BF4 and [1e] BF4 were determined by X-ray diffraction.

First author: Lang, Xiu-Feng, Theoretical investigation on surface-enhanced Raman evidence for conformation transition of dimercaptoazobenzene adsorbed on gold nanoclusters, JOURNAL OF RAMAN SPECTROSCOPY, 44, 425, (2013)
Abstract: Probing and controlling the configurations and mechanical motions of the azobenzenes adsorbed on the metal substrates are preliminary for their applicability in various functional devices. In this work, we presented a detailed investigation of Raman properties of the dimercaptoazobenzene (DMAB) bound to gold nanoclusters using density functional calculations. It is demonstrated that the spectral features of the trans conformation of DMAB are quite different from the cis conformation, and the Raman intensities of the trans-DMAB are much larger. Magnitude of chemical enhancement for the adsorbed trans-DMAB is found to be close to or less than that for the adsorbed cis-DMAB for the molecule-cluster complexes. This change trend can be, to a large extent, governed by the energy difference between the highest occupied energy level of the molecule and the lowest unoccupied energy level of the gold. Moreover, it is further demonstrated that differences in Raman intensities of the two conformations can be amplified for the cluster-molecular-cluster junctions, and thus chemical enhancement is much larger for the trans conformation than the cis conformation, possibly facilitating the experimental identification of the trans/cis DMAB.

First author: Pastore, Mariachiara, Modeling Excited States and Alignment of Energy Levels in Dye-Sensitized Solar Cells: Successes, Failures, and Challenges, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 3685, (2013)
Abstract: Theoretical and computational modeling is a powerful tool to investigate and characterize the structural, electronic, and optical properties of the main components of dye-sensitized solar cells (DSCs). In this article we focus on the description of the ground and excited state properties of both standalone and TiO2-adsorbed metallorganic and fully organic dyes, relevant to modeling the dye -> semiconductor electron injection process, which is the primary charge generation step in DSCs. By reviewing previous data from our laboratory, integrated with new calculations, we wish to critically address the potential and limitations of current DFT and TDDFT computational methods to model DSCs. While ruthenium dyes are accurately described by standard DFT approaches, for highly conjugated organic dyes, characterized by strong charge transfer excited states, specifically tailored exchange-correlation functionals are needed. For ruthenium dye/semiconductor interfaces, a strategy is presented, which accurately describes the electronic and optical properties and the alignment of ground and excited state levels at the same time, allowing us to discuss the coupling and the energetics of the excited states underlying the ultrafast electron injection. For donor-acceptor organic dyes, a simple picture based on the dye lowest unoccupied molecular orbital (LUMO) broadening accounts for the different interfacial electronic coupling exhibited by dyes with different anchoring groups. The explored DFT/TDDFT methods, however, are not capable to deliver at the same time a balanced description of the dye@TiO2 excited states and of the alignment of the dye excited states with the semiconductor manifold of unoccupied states. This represents a challenge which should be addressed by next generation DFT or post-DFT methods.

First author: Trushin, Egor V., Anion-radical oxygen centers in small (AgO)(n) clusters: Density functional theory predictions, CHEMICAL PHYSICS LETTERS, 560, 37, (2013)
Abstract: Anion-radical form of the oxygen centers O is predicted at the DFT level for small silver oxide particles having the AgO stoichiometry. Model clusters (AgO)(n) appear to be ferromagnetic with appreciable spin density at the oxygen centers. In contrast to these clusters, the Ag2O model cluster have no unpaired electrons in the ground state. The increased O/Ag ratio in the oxide particles is proved to be responsible for the spin density at oxygen centers.

First author: Oehninger, Luciano, Novel titanocene derived from a partially alkylated s-indacene: Synthesis, characterization and comparative study with its zirconium analog, INORGANICA CHIMICA ACTA, 396, 35, (2013)
Abstract: The preparation of a novel titanium(IV) metallocene (2), including 2,6-diethyl-4,8-dimethyl-5-hydroindacenide (Ic’H) as ligand was successfully achieved and it was characterized by means of H-1, C-13 NMR and elemental analysis. Cyclic voltammetry studies were performed for complex 2 as well as for its zirconium analog 1. Both complexes were tested in the catalysis of ethylene polymerization, showing a considerable difference between their catalytic activities in a proportion of 625: 1 between complex 1 and 2. DFT calculations were performed in order to gain further knowledge about the geometry of the complexes and their electronic properties and therefore explain the difference between their reactivity.

First author: Lonie, David C., Metallization of magnesium polyhydrides under pressure, PHYSICAL REVIEW B, 87, 35, (2013)
Abstract: Evolutionary structure searches are used to predict stable phases with unique stoichiometries in the hydrogen-rich region of the magnesium/hydrogen phase diagram under pressure. MgH4, MgH12, and MgH16 are found to be thermodynamically stable with respect to decomposition into MgH2 and H-2 near 100 GPa, and all lie on the convex hull by 200 GPa. MgH4 contains two H- anions and one H-2 molecule per Mg2+ cation, whereas the hydrogenic sublattices of MgH12 and MgH16 are composed solely of Hd(2)(delta-) molecules. The high-hydrogen content stoichiometries have a large density of states at the Fermi level, and the T-c of MgH12 at 140 GPa is calculated to be nearly three times greater than that of the classic hydride, MgH2, at 180 GPa. DOI: 10.1103/PhysRevB.87.054107

First author: Mulet-Gas, Marc, Relevance of Thermal Effects in the Formation of Endohedral Metallofullerenes: The Case of Gd3N@C-s(39663)-C-82 and Other Related Systems, INORGANIC CHEMISTRY, 52, 1954, (2013)
Abstract: Thermal contributions to the free energy have to be taken into account to rationalize the formation of Gd3N@C-s(39663)-C-82, a nitride endohedral metallofullerene that shows a carbon cage with two fused pentagons which is not predicted to have the lowest electronic energy among the isomers of C-82. The lower symmetry and the larger number of pyracylene units of C-s(39663)-C-82 with respect to the cage in the lowest-energy metallofullerene, C-2v(39705)-C-82, favor its formation at high temperatures, as seen for other similar cage isomers that encapsulate metal clusters within the C-80 and C-82 families. These cages, which share common motifs with the prototypical I-h(7).C-80, are all related by C-2 insertions/extrusions and Stone-Wales transformations.

First author: Daumann, Lena J., Synthesis, Magnetic Properties, and Phosphoesterase Activity of Dinuclear Cobalt(II) Complexes, INORGANIC CHEMISTRY, 52, 2029, (2013)
Abstract: A series of dinuclear cobalt(II) complexes has been prepared and characterized to generate functional and spectroscopic models for cobalt(II) substituted phosphoesterase enzymes such as the potential bioremediator GpdQ Reaction of ligands based on 2,2′-(((2-hydroxy-5-methyl-1,3-phenylene)bis(methylene))bis((pyridin-2-y lmethyl)azanediyl)))diethanol (L1) and 2,6-bis(((2-methoxyethyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylpheno l (L2) with cobalt(II) salts afforded [Co-2(CO(2)EtH(2)L1)(CH3COO)(2)](PF6), [Co-2(CO(2)EtL2)(CH3COO)(2)](PF6), [Co-2(CH(3)L2)(CH3COO)(2)](PF6), [Co-2(BrL2)(CH3COO)(2)](PF6), and [Co-2(NO(2)L2)(CH3COO)(2)](PF6). Complexes of the L2 ligands contain a coordinated methyl-ether, whereas the L1 ligand contains a coordinated alcohol. The complexes were characterized using mass spectrometry, microanalysis, X-ray crystallography, UV-vis-NIR diffuse reflectance spectroscopy, IR absorption spectroscopy, solid state magnetic susceptibility measurements, and variable-temperature variable-field magnetic circular dichroism (VTVH MCD) spectroscopy. Susceptibility studies show that [Co-2(CO(2)EtH(2)L1)(CH3COO)(2)](PF6), [Co-2(CO(2)EtL2)(CH3COO)(2)](PF6), and [Co-2(CH(3)L2)(CH3COO)(2)](PF6) are weakly antiferromagnetically coupled, whereas [Co-2(BrL2)(CH3COO)(2)](PF6) and [Co-2(NO(2)L2)(CH3COO)(2)](PF6) are weakly ferromagnetically coupled. The susceptibility results are confirmed by the VTVH MCD studies. Density functional theory calculations revealed that magnetic exchange coupling occurs mainly through the phenolic oxygen bridge. Implications of geometry and ligand design on the magnetic exchange coupling will be discussed. Functional studies of the complexes with the substrate bis(2,4-dinitrophenyl) phosphate showed them to be active towards hydrolysis of phosphoester substrates.

First author: Manivannan, C., Studies on the inclusion behavior of 9-Aminoacridine into cyclodextrins: Spectroscopic and theoretical evidences, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 103, 18, (2013)
Abstract: 9-Aminoacridine (9-AA) is an important attractive pharmaceutical drug employed as chemotheraptic agent for wound dressings. However, 9-AA possesses limited solubility and rapid metabolic decomposition renders this potential drug to limit its applications. Here we propose Cyclodextrins (CDs) as a drug carrier to improve the bioavailability, solubility of 9-AA. The interaction between 9-AA and CDs (alpha-CD and beta-CD) has been studied using UV-Vis absorption, steady state time resolved fluorescence, H-1 NMR and FT-IR spectroscopy techniques. The spectroscopic measurements show that 9-AA does not form stable complex with alpha-CD and also confirmed by DFT calculations. On the other hand, 9-AA forms inclusion complex with beta-CD in a 1:1 stoichiometry ratio. Our DFT results suggest that 9-AA stabilizes inside the CD environment through hydrogen bonding that has unambiguously confirmed by AIM analysis. Thus our studies provide a useful insights in the development of Aminoacridine based drugs & its delivery through a suitable carrier like CDs.

First author: Mara, Michael W., Effects of Electronic and Nuclear Interactions on the Excited-State Properties and Structural Dynamics of Copper(I) Diimine Complexes, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 1921, (2013)
Abstract: The effects of structural constraints on the metal-to-ligand charge transfer (MLCT) excited state structural dynamics of cuprous bis-2,9-diphenyl-phenanthroline ([Cu(I)(dpp)(2)](+)) in both coordinating acetonitrile and noncoordinating toluene were studied using X-ray transient absorption (XTA) spectroscopy and density functional theory (DFT) calculations. The phenyl groups attached to the phenanthroline ligands not only effectively shield the Cu(I) center from solvent molecules, but also force a flattened tetrahedral coordination geometry of the Cu(I) center. Consequently, the MLCT state lifetime in [Cu(I)(dpp)(2)](+) is solvent-independent, unlike the previously studied 2,9-methyl substituted bis-phenanthroline Cu(I) complex. The MLCT state of [Cu(I)(dpp)(2)](+) still undergoes a “pseudo Jahn-Teller distortion,” with the angle between the two phenanthroline ligand planes decreased further by 7 degrees The XTA results indicate that, in the MLCT excited state of [Cu(I)(dpp)(2)](+), the phenyls at the 2, 9 positions of the phenanthroline rotate, breaking the pi-pi interaction with the phenanthroline ligands without ever rotating in-plane with the phenanthroline ligands. Hence, the transferred electron density from the Cu(I) center is localized on the phenanthroline moiety with no charge density present on the phenyl rings. The insight about the effect of the structural constraints on the MLCT state properties will guide the design of Cu(I) diimine complexes with suitable excited-state properties to function as earth-abundant dye sensitizers for solar electricity generation.

First author: Zarate, Ximena, Effects of the peripheral substituents (-NH2, -OH, -CH3, -H, -C6H5, -Cl, -CO2H and -NO2) on molecular properties of a Ni-Porphyrazine dimers family, POLYHEDRON, 50, 131, (2013)
Abstract: A theoretical study of the electronic structure, UV-Vis absorption spectra, reactivity and EPR parameters using density functional theory (DFT) and its extension time dependent-density functional theory (TD-DFT) was performed for a family of paramagnetic Ni(II)-Porphyrazines dimers connected by Ni(III)-dithiolene, with general formula [Ni(II)PzR(6)Ni(III)S(4)PzR(6)Ni(II)](1-) where the peripheral substituents R are -NH2 (1), -OH (2), -CH3 (3), -H (4), -C6H5 (5), -Cl (6), -CO2H (7) and -NO2 (8)). The simulated UV-Vis absorption spectra exhibit the usual B or Soret and Q bands. The energies of the electronic transitions, the g-tensors and the simulated EPR spectrum are in good agreement with previously reported experimental data. The results show that the odd electron in complexes with R being electron donor are delocalized over the bridge fragment and the systems with R being electron withdrawing are delocalized over the macrocycles Pz. Thus, along with the frontier MOs analysis and reactivity indexes, it was possible to conclude that the character of the peripheral substituents R affect the reactivity of this kind of systems where the most reactive are those with R being electron donor. In addition, the effect of the R groups on the frontier MOs energies is showed by the correlation of HOMO, LUMO and HOMO-LUMO gap energies with the Hammett constants. On the other hand, charge transfer from the ligands to the Ni atoms and back-donation from the Ni atoms to the ligands is observed in the charge transfer analysis.

First author: Starynowicz, Przemyslaw, Aqua(ethylenedisulfonato)europium(II) [Eu(O3SC2H4SO3)(H2O)] – Structure, spectroscopy and magnetic properties, POLYHEDRON, 50, 283, (2013)
Abstract: Aqua(ethylenedisulfonato)europium(II) was obtained by electrochemical reduction. The compound is polymeric and each metal cation is surrounded by six oxygen atoms from sulfonate groups and by two water molecules. The compound shows faint emission with maximum at 414.5 nm at room temperature and bright luminescence (lambda(max) = 408 nm) at 77 K. Magnetic susceptibility measurements show that interactions between Eu2+ cations are very weak; the shortest Eu-Eu distances are in the range 5.0-5.7 angstrom.

First author: Braunschweig, Holger, Ditopic Ambiphilicity of an Anionic Dimetalloborylene Complex, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 2313, (2013)
Abstract: In early reports, the boron atom of the anionic borido complexes [{(eta(5)-C5H4R)(OC)(2)Mn}(2)B](-) (R = H, Me) showed nucleophilic behavior in the presence of electrophiles such as methyl iodide and group 11 metal chlorides, akin to the ground-breaking boryl lithium of Yamashita and Nozaki. Later, a reaction with the well-known transition metal Lewis base [Pt(PCy3)(2)] suggested the possibility of boron-centered electrophilicity. In this paper we elucidate a third reactivity profile of the anion, nucleophilic substitution on heavier halides of group 14 metals by a manganese center. Meanwhile, other group 11 halides were found to interact with the boron center, but form structures different from those seen with gold. The basis of the discrimination of the anion between main group and transition metal halides is explored computationally, and the ditopic, ambiphilic reactivity of the anions is discussed.

First author: Pavanello, Michele, An accurate and linear-scaling method for calculating charge-transfer excitation energies and diabatic couplings, JOURNAL OF CHEMICAL PHYSICS, 138, 2313, (2013)
Abstract: Quantum-mechanical methods that are both computationally fast and accurate are not yet available for electronic excitations having charge transfer character. In this work, we present a significant step forward towards this goal for those charge transfer excitations that take place between non-covalently bound molecules. In particular, we present a method that scales linearly with the number of non-covalently bound molecules in the system and is based on a two-pronged approach: The molecular electronic structure of broken-symmetry charge-localized states is obtained with the frozen density embedding formulation of subsystem density-functional theory; subsequently, in a post-SCF calculation, the full-electron Hamiltonian and overlap matrix elements among the charge-localized states are evaluated with an algorithm which takes full advantage of the subsystem DFT density partitioning technique. The method is benchmarked against coupled-cluster calculations and achieves chemical accuracy for the systems considered for intermolecular separations ranging from hydrogen-bond distances to tens of Angstroms. Numerical examples are provided for molecular clusters comprised of up to 56 non-covalently bound molecules.

First author: Huss, Adam S., Relaxation and Dissociation Following Photoexcitation of the (mu-N-2)[Mo(N[t-Bu]Ar)(3)](2) Dinitrogen Cleavage Intermediate, JOURNAL OF PHYSICAL CHEMISTRY B, 117, 1429, (2013)
Abstract: Frequency resolved pump-probe spectroscopy was performed on isolated (mu-N-2)[Mo(N[t-Bu]Ar)(3)](2) (Ar = 3,5-C6H3Me2), an intermediate formed in the reaction of Mo(N[t-Bu]Ar)(3) to bind and cleave dinitrogen. Evidence is presented for 300 fs internal conversion followed by subpicosecond vibrational cooling on the ground electronic state in competition with bond dissociation. Fast cooling following photoexcitation leads to a relatively low overall dissociation yield of 5%, in quantitative agreement with previous work [Curley, J.J.; Cooke, T.R.; Reece, S.Y.; Mueller, P.; Cummins, C.C. J. Am. Chem. Soc. 2008, 130, 9394]. Coupling of vibrational modes to the excitation and internal conversion results in a nonthermal distribution of energy following conversion, and this provides sufficient bias to allow the nitrogen cleavage reaction to compete with breaking of the Mo-NN bond despite a higher energetic barrier on the ground state.

First author: Wang, Jing, A Rational Design for Dye Sensitizer: Density Functional Theory Study on the Electronic Absorption Spectra of Organoimido-Substituted Hexamolybdates, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 2245, (2013)
Abstract: The novel dyes of organoimido-substituted hexamolybdates for positive type dye-sensitized solar cells (p-type DSSCs) have been studied on the basis of time-dependent density functional theory (TDDFT) calculations. The electronic absorption spectra, light harvesting efficiency (LHE), charge separation efficiency (CSE), and holes injecting efficiency (HJE) of designed systems have been systematically investigated. The results reveal that the long pi-conjugated bridge and auxochrome play crucial roles in red-shifting the absorption bands and reinforcing the intensity of the bands. Based on [(n-C4H9)(4)N](2)[Mo6O18(N-1-C10H6-2-CH3)], the designed systems 6 and 4 are good candidates for p-type DSSC dyes due to the strong absorption in the visible region as well as high LHE, CSE, and HJE. The maximum absorption of the one-electron-reduced system obviously red-shifts to the visible region. Therefore, the highly efficient dyes of p-type DSSC can be prepared by reducing POM-based organic-inorganic hybrids which have both long pi-conjugated bridge and auxochrome.

First author: Piekos, Lukasz, Theoretical description of dihydrogen/hydride and trihydride molybdocene complexes: An insight from static and molecular dynamics simulations, JOURNAL OF COMPUTATIONAL CHEMISTRY, 34, 294, (2013)
Abstract: In this study ab initio CarParrinello molecular dynamics simulations, extended transition state (ETS)-natural orbitals for chemical valence (NOCV) and QTAIM bonding analyses, were performed to characterize the ansa-bridged molybdocene complexes [(C5H4)2XMe2MoH3]+ for X = C, Si, Ge, Sn, Pb, and nonbridged Cp2MoH?3+ system. The results have shown that the [(C5H4)2CMe2MoH(H2)]+ complex exhibits nonclassical dihydrogen/hydride (H2/H) conformation (97.6% of time of simulation), contrary to trihydride (H3) structure noted for nonbridged Cp2MoH?3+ (86.9%) and ansa-bridged [(C5H4)2SnMe2MoH3]+ (84.8%), [(C5H4)2PbMe2MoH3]+ (84.9%) systems. Further, [(C5H4)2SiMe2MoH3]+ and [(C5H4)2GeMe2MoH3]+ complexes, appeared to exist in both conformations (H2/H55.4%, H344.6% for Si-based system and H2/H36.2%, H363.8 % for germanium congener). It has been proven that the steric availability of the metal center, measured by the changes in the Cp-Mo-Cp angle (a), determines the existence of a given conformationnamely, the smaller value of the angle (molybdenum is sterically more accessible) the larger preference for the formation of dihydrogen/hydride structure. ETS-NOCV method allowed to conclude that increase in the Cp-Mo-Cp angle (from a ca. 120 degrees to a ca. 150 degrees) leads to the enhancement of donation from H2 and back-donation from Mo to the sigma*(H-H), what consequently leads to breaking of the H-H bond and formation of the trihydride structure. Systematical increase in the charge depletion from the sigma-bonding orbital of H2 can be related to the reduction of the energy gap between the major orbitals involved in this contribution, namely highest occupied molecular orbital (HOMO) of H2 with lowest unoccupied molecular orbital (LUMO) of [MoHL]+; Lambda E = 0.0868 a.u. [for L =(C5H4)2C], Lambda E = 0.0827 a.u. [for L = (C5H4)2Si] Lambda E = 0.0638 a.u. [for L = Cp2]. Further, the relatively low energetic barrier to hydrogen exchange (Lambda E+ = 3.3 kcal/mol) for carbon-bridged complex, [(C5H4)2CMe2MoHc(HaHb)]+ -> [(C5H4)2 CMe2MoHa(HbHc)]+, is related to strengthening of the MoH bonds when going from the substrate to the transition state (TS). Notably higher barrier to hydrogen rotation (Lambda E-# = 10.1 kcal/mol) in [(C5H4)2CMe2MoH(H2)]+ is due to lowering in the electrostatic stabilization as well as weakening of the donation (H2 ? Mo charge transfer) and practically lack-of back-donation (Mo – H2) in the rotated TS.

First author: Matovic, Zoran D., Synthetic, Crystallographic, and Computational Study of Copper(II) Complexes of Ethylenediaminetetracarboxylate Ligands, INORGANIC CHEMISTRY, 52, 1238, (2013)
Abstract: Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H(4)eda3p and Rieddadp (H(4)eda3p = ethylenediamine-N-acetic-N,N’,N’-tri-3-propionic acid; ateddadp = ethylenediamine-N,N’-diaceticN,N’-di-3-propionic acid) have been prepared. An octahedral trans(O-6) geometry (two propionate ligands coordinated in axial positions) has been established crystallographically for the Ba[Cu(eda3p)]center dot 8H(2)O compound, while Ba[Cu(eddadp)]center dot 8H(2)O is proposed to adopt a trans(O-5) geometry (two axial acetates) on the basis of density functional theory calculations and comparisons of IR and UV-vis spectral data. Experimental and computed structural data correlating similar copper(II) chelate complexes have been used to better understand the isomerism and departure from regular octahedral geometry within the series. The in-plane O-Cu-N chelate angles show the smallest deviation from the ideal octahedral value of 90 degrees, and hence the lowest strain, for the eddadp complex with two equatorial beta-propionate rings. A linear dependence between tetragonality and the number of five-membered rings has been established. A natural bonding orbital analysis of the series of complexes is also presented.

First author: Horga, F. I., Electronic and magnetic properties of Fe clusters inside finite zigzag single-wall carbon nanotubes, PHYSICAL REVIEW B, 87, 1238, (2013)
Abstract: Density functional calculations of the electronic structure of the Fe-12 cluster encapsulated inside finite single-wall zigzag carbon nanotubes of indices (11,0) and (10,0) have been performed. Several Fe-12 isomers have been considered, including elongated shape isomers aimed to fit well inside the nanotubes, and the icosahedral minimum energy structure. We analyze the structural and magnetic properties of the combined systems, and how those properties change compared to the isolated systems. A strong ferromagnetic coupling between the Fe atoms occurs both for the free and the encapsulated Fe-12 clusters, but there is a small reduction (3-7.4 mu(B)) of the spin magnetic moment of the encapsulated clusters with respect to that of the free ones (mu = 38 mu(B)). The reduction of the magnetic moment is mostly due to the internal redistribution of the spin charges in the iron cluster. In contrast, the spin magnetic moment of the carbon nanotubes, which is zero for the empty tubes, becomes nonzero (1-3 mu(B)) because of the interaction with the encapsulated cluster. We have also studied the encapsulation of atomic Fe and the growth of small Fe-n clusters (n = 2, 4, 8) encapsulated in a short (10,0) tube. The results suggest that the growth of nanowires formed by distorted tetrahedral Fe-4 units will be favorable in (10,0) nanotubes and nanotubes of similar diameter. DOI: 10.1103/PhysRevB.87.085402

Abstract: The molecule 5-methyltetrazole (5MTZ) can exist in two taumeric forms. The vertical ionization energies (VIEs) of both valence and core electrons of both the tautomers are calculated with our established DFT procedures and compared with available experimental data. For the 2H-tautomer, the average absolute deviations (AADs) for the outer-valence VIEs and core-electron binding energies (CEBEs) from experiment are below 0.1 eV, while the AAD for the inner-valence VIEs is much larger at 0.4 eV. For the 1H-tautomer, no observed valence VIEs have been reported and the AAD for the calculated CEBEs is 0.2 eV. The assignment of the experimental core-electron ionization spectrum is confirmed, but our results suggest a slight modification of the assignment of the UV photoelectron spectrum of the 2H-tautomer.

First author: Babashkina, Maria G., Crucial Influence of the Intramolecular Hydrogen Bond on the Coordination Mode of RC(S)NHP(S)(OiPr)(2) in Homoleptic Complexes with Ni-II, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 12, 545, (2013)
Abstract: Reaction of the deprotonated N-thiophosphorylated thioureas RC(S)NHP(S)(OiPr)(2) [R = EtNH (HLI), iPrNH (HLII), Et2N (HLIII), 2,5-Me2C6H3NH (HLIV), 4-Me2NC6H4NH(HLV)] with Ni-II leads to complexes of the formula [NiL2I-V]. The molecular structures of the complexes in the solid were elucidated by single-crystal X-ray diffraction analysis. In the complexes, the metal atom is found to be in a square-planar trans-N2S2 ([NiL2II,(IV)]) environment formed by the C=S sulfur atoms and the P-N nitrogen atoms, or in a square-planar trans-S2S2′ ([NiL2I,III]) environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands. Reaction of deprotonated N-thiophosphorylated thiourea HLV with NiCl2 leads to violet [Ni(L-1,3-N,S)(2)] or dark violet [Ni(L-1,5-S,S’)(2)] center dot (CH3)(2)C=O crystals that were isolated by recrystallization from a mixture of CH2Cl2 or acetone, respectively, and nhexane. DFT calculations confirmed that the [Ni(LI,II,IV,V-N,S)(2)] conformers are more stable (by 5-7 kcal/mol) than [Ni(L-I,L-II,L-IV,L-V-S,S’)(2)], whereas [Ni(L-III-N,S)(2)] is less stable (by 7-9 kcal/mol) than [Ni(L-III-S,S’)(2)]. The main reason for higher stability of the 1,3-N,S versus 1,5-S,S’ isomers is the formation of intramolecular N-H center dot center dot center dot S=P hydrogen bonds. The same hydrogen bonds are impossible in complex [NiL2III]. In solution, complex [NiL2III] has revealed an exclusively 1,5-S,S’-coordination, whereas compounds [NiL2I,II,IV,V] reveal at least two isomers in the H-1 and P-31{H-1} NMR spectra. The major species is assigned to the 1,3-N, S-coordinated isomer, and the minor signals are assigned to the 1,5-S,S’ isomer, which was confirmed by UV/Vis spectroscopic results. The electrochemical measurements reveal reversible one-electron reduction and irreversible oxidations both assigned to ligand-centred processes. Ligand-based oxidation processes agree well with TD-DFT results.

First author: Vlaisavljevich, Bess, Synthesis and Characterization of the First 2D Neptunyl Structure Stabilized by Side-on CationCation Interactions, CHEMISTRY-A EUROPEAN JOURNAL, 19, 2937, (2013)
Abstract: Reaction of the deprotonated N-thiophosphorylated thioureas RC(S)NHP(S)(OiPr)(2) [R = EtNH (HLI), iPrNH (HLII), Et2N (HLIII), 2,5-Me2C6H3NH (HLIV), 4-Me2NC6H4NH(HLV)] with Ni-II leads to complexes of the formula [NiL2I-V]. The molecular structures of the complexes in the solid were elucidated by single-crystal X-ray diffraction analysis. In the complexes, the metal atom is found to be in a square-planar trans-N2S2 ([NiL2II,(IV)]) environment formed by the C=S sulfur atoms and the P-N nitrogen atoms, or in a square-planar trans-S2S2′ ([NiL2I,III]) environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands. Reaction of deprotonated N-thiophosphorylated thiourea HLV with NiCl2 leads to violet [Ni(L-1,3-N,S)(2)] or dark violet [Ni(L-1,5-S,S’)(2)] center dot (CH3)(2)C=O crystals that were isolated by recrystallization from a mixture of CH2Cl2 or acetone, respectively, and nhexane. DFT calculations confirmed that the [Ni(LI,II,IV,V-N,S)(2)] conformers are more stable (by 5-7 kcal/mol) than [Ni(L-I,L-II,L-IV,L-V-S,S’)(2)], whereas [Ni(L-III-N,S)(2)] is less stable (by 7-9 kcal/mol) than [Ni(L-III-S,S’)(2)]. The main reason for higher stability of the 1,3-N,S versus 1,5-S,S’ isomers is the formation of intramolecular N-H center dot center dot center dot S=P hydrogen bonds. The same hydrogen bonds are impossible in complex [NiL2III]. In solution, complex [NiL2III] has revealed an exclusively 1,5-S,S’-coordination, whereas compounds [NiL2I,II,IV,V] reveal at least two isomers in the H-1 and P-31{H-1} NMR spectra. The major species is assigned to the 1,3-N, S-coordinated isomer, and the minor signals are assigned to the 1,5-S,S’ isomer, which was confirmed by UV/Vis spectroscopic results. The electrochemical measurements reveal reversible one-electron reduction and irreversible oxidations both assigned to ligand-centred processes. Ligand-based oxidation processes agree well with TD-DFT results.

First author: Chen, Fu, An Investigation of 1:1 Adducts of Gallium Trihalides with Triarylphosphines by Solid-State 69/71Ga and 31PNMR Spectroscopy, CHEMISTRY-A EUROPEAN JOURNAL, 19, 2826, (2013)
Abstract: Several 1:1 adducts of gallium trihalides with triarylphosphines, X3Ga(PR3) (X=Cl, Br, and I; PR3=triarylphosphine ligand), were investigated by using solid-state 69/71Ga and 31PNMR spectroscopy at different magnetic-field strengths. The 69/71Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the 71Ga quadrupolar coupling constants (CQ(71Ga)) range from approximately 0.9 to 11.0MHz. The spans of the gallium magnetic shielding tensors for these complexes, 1133, range from approximately 30 to 380ppm; those determined for phosphorus range from 10 to 40ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for InIIIphosphine complexes. This experimental trend, attributed to spin-orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of CQ(69/71Ga) for some of the adducts were determined from the analysis of the 31PNMR spectra acquired with magic angle spinning (MAS). The 1J(69/71Ga,31P) and J(69/71Ga, 31P) values, as well as their signs, were also determined; values of 1J(71Ga,31P) range from approximately 380 to 1590Hz. Values of 1J(69/71Ga,31P) and J(69/71Ga,31P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi-contact and spin-dipolar Fermi-contact mechanisms make important contributions to the 1J(69/71Ga,31P) tensors. The 31PNMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single-crystal X-ray diffraction data for Br3Ga[P(p-Anis)3] and I3Ga[P(p-Anis)3] were obtained.

First author: Zhang, Shou-Feng, Charge transport properties in a series of five-ring-fused thienoacenes: A quantum chemistry and molecular mechanic study, ORGANIC ELECTRONICS, 14, 607, (2013)
Abstract: The charge transport properties in a series of five-ring-fused thienoacenes are detailedly investigated here. With both high 3-D hole mobilities and good oxidative stability, the thiophene-benzene alternate structures in series B should be better than other two series as p-type organic semiconductors. In addition, a theoretical explanation for the difference between experimental hole mobilities in B-3 and B-3* is provided based on crystal structure prediction. The role of dynamic disorder in C-3 is also investigated here and the results indicate that dynamic disorder plays a crucial role both in the 1-D and 2-D carrier transporting process.

First author: Zabaradsti, Abedien, Theoretical study of molecular interactions of sulfur ylide with HF, HCN, and HN3,STRUCTURAL CHEMISTRY, 24, 271, (2013)
Abstract: The molecular interactions between sulfur ylide (SY) and HX molecules (X = F, CN, and N-3) were investigated using the MP2 method at 6-311++G(2d,2p) basis set. Three different patterns including non-classical hydrogen bond (HB) H center dot center dot center dot C and classical HB H center dot center dot center dot X were found for complex formation between SY and HX molecules. Stability of the H center dot center dot center dot C type complexes are greater than H center dot center dot center dot X complexes. Quantum theories of atoms in molecules, natural bond orbitals, and energy decomposition analysis methods have been applied to analyze the intermolecular interactions. Good correlations have been found between the interaction energies (SE), the second-order perturbation energy E ((2)) and the charge transfer qCT in the studied systems.

First author: Pandey, Lila B., Theoretical Investigation of Surface Reactions of Lactic Acid on MgO Clusters, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 765, (2013)
Abstract: Interaction of lactic acid with various sizes of magnesium oxide clusters (MgO)(x) (x = 2, 4, 6, 8, 9, 12, 15, 16, 18) is investigated. Density functional theory with the PBE functional and a polarized double-‘ basis set is employed to optimize the structures. For MgO dimer optimizations are also performed at the PBE/DZP, PBE/TZP, and MP2/TZV(d,p) levels of theory, and single-point CCSD(T)/TZV(d,p) calculations are computed at the PBE/TZP optimized geometries. CCSD(T)/TZV(d,p) calculations show that the PBE/DZP results are off by no more than 5 kcal/mol. Dissociative adsorption of a proton bound to oxygen is possible for the carboxylic acid group, the hydroxyl group, and for a simultaneous interaction of the carboxylic acid and hydroxyl groups. Associative adsorption of various functional groups is also possible, although these represent higher energy structures. All of the adsorptions are calculated to be exothermic. Dissociative adsorption of the carboxylic acid group of lactic acid at the lowest coordinated magnesium sites is determined to be the lowest energy structure. Adsorption energies are found to decrease in magnitude as the size of MgO increases. The geometry of the magnesium oxide cluster changes to a nanorod-like structure when lactic acid interacts with higher coordinated magnesium atoms in double layer systems, but remains simple cubic when a third layer is added. The coordination environment rather than the size of the MgO cluster appears to dominate the adsorption energy when the size becomes larger than (MgO)(12).

First author: Bernadotte, Stephan, Plasmons in Molecules, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 1863, (2013)
Abstract: The classification of electronic excitations in molecules and molecular nanostructures plays an important role when tailoring materials with desired properties. One example of such a class of excitations are plasmons. Plasmons appear in solid-state physics, where they are characterized as density oscillations in an electron gas that are driven by the restoring forces associated with the electromagnetic field induced by the density oscillations themselves. Here, we investigate how this concept can be transferred to molecular systems by performing a step-by-step analysis, starting from three-dimensional bulk systems and ending with molecules. On the basis of this analysis, we propose to scale the electron-electron interaction in quantum-chemical response calculations in order to identify plasmons in molecules. This approach is illustrated for molecular chains and clusters. Our results show that the concept of plasmons is still applicable for extended molecular systems and demonstrate that the proposed scaling approach provides an easy way of characterizing electronic excitations.

First author: Stuurman, Nomampondomise F., Conformational analysis of triphenylphosphine in square planar [Rh(beta-diketonato)(CO)(PPh3)] complexes. Crystal structure of [Rh(PhCOCHCO(CH2)(3)CH3)(CO)(PPh3)], INORGANICA CHIMICA ACTA, 395, 237, (2013)
Abstract: The crystal structure of [Rh(PhCOCHCO(CH2)(3)CH3)(CO)(PPh3)], 1, and the conformation analysis of PPh3 coordinated to 1 is presented. Two geometrical isomers are possible, which unexpectedly crystallized in the same space in the unit cell with an 89.7:10.3 ratio. Results from density functional theory calculations, in agreement with experimental structures, show that favored degenerate conformations of coordinated PPh3 in square planar [(PPh3)((MLLL3)-L-1-L-2)], [M(acac)(L’)(PPh3)] and [Rh(beta-diketonato)(CO)(PPh3)] complexes possess distinct features and can be obtained by applying the following principles (P helicity, view along P-M axis), (i) superimpose C-o of the vertical ring A onto the nadir plane perpendicular to the square plane and allow ring A to tilt towards the smallest ligand, (ii) allow ring B to tilt in the space below the smallest ligand in the quadrant between the nadir plane below the complex and a horizontal plane through the SQP of the complex, (iii) tilt ring C over the largest ligand and (iv) allow correlated tilting of rings A, B and C to minimize inter ring- ring and inter ring- ligand interactions. The steric influence of O beta-diketonato and CO is similar on the preferred orientation of the vertical phenyl ring A of PPh3 in [Rh(beta-diketonato)(CO)(PPh3)] complexes. The size of the side groups R and R’ on the beta-diketonato ligand (RCOCHCOR’) does not influence the preferred conformation of coordinated PPh3 in [Rh(beta-diketonato)(CO)(PPh3)].

First author: Boguslawski, Katharina, Optimized unrestricted Kohn-Sham potentials from ab initio spin densities,JOURNAL OF CHEMICAL PHYSICS, 138, 237, (2013)
Abstract: The reconstruction of the exchange-correlation potential from accurate ab initio electron densities can provide insights into the limitations of the currently available approximate functionals and provide guidance for devising improved approximations for density-functional theory (DFT). For open-shell systems, the spin density is introduced as an additional fundamental variable in spin-DFT. Here, we consider the reconstruction of the corresponding unrestricted Kohn-Sham (KS) potentials from accurate ab initio spin densities. In particular, we investigate whether it is possible to reconstruct the spin exchange-correlation potential, which determines the spin density in unrestricted KS-DFT, despite the numerical difficulties inherent to the optimization of potentials with finite orbital basis sets. We find that the recently developed scheme for unambiguously singling out an optimal optimized potential [Ch. R. Jacob, J. Chem. Phys. 135, 244102 (2011)] can provide such spin potentials accurately. This is demonstrated for two test cases, the lithium atom and the dioxygen molecule, and target (spin) densities from full configuration interaction and complete active space self-consistent field calculations, respectively.

First author: Johnson, Phillip S., Electronic structure of Fe- vs. Ru-based dye molecules, JOURNAL OF CHEMICAL PHYSICS, 138, 237, (2013)
Abstract: In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe-and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-pi* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-pi* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.

First author: Thomas, Martin, Resonance Raman spectra of ortho-nitrophenol calculated by real-time time-dependent density functional theory, JOURNAL OF CHEMICAL PHYSICS, 138, 237, (2013)
Abstract: A new approach for the calculation of resonance Raman spectra is presented. The new method is based on dynamic polarizabilities from real-time time-dependent density functional theory, and its estimations are compared to two established techniques for the prediction of resonance Raman spectra. These established methods either use dynamic polarizabilities from linear-response time-dependent density functional theory or employ excited-state gradients. The three different ways to calculate resonance Raman spectra are investigated using the example of ortho-nitrophenol. The three methods give very similar results, respectively, for the four different exchange-correlation functionals applied. Thus, the new approach is validated for the calculation of resonance Raman intensities and advantages as well as disadvantages are discussed. c 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4776218]

First author: Franks, Mark, Five Coordinate M(II)-Diphenolate [M = Zn(II), Ni(II), and Cu(II)] Schiff Base Complexes Exhibiting Metal- and Ligand-Based Redox Chemistry, INORGANIC CHEMISTRY, 52, 660, (2013)
Abstract: Five-coordinate Zn-II, Ni-II, and Cu-II complexes containing pentadentate N3O2 Schiff base ligands [1A](2-) and [1B](2-) have been synthesized and characterized. X-ray crystallographic studies reveal five coordinate structures in which each metal ion is bound by two imine N-donors, two phenolate O-donors, and a single amine N-donor. Electron paramagnetic resonance (EPR) spectroscopic studies suggest that the N3O2 coordination spheres of [Cu(1A)] and [Cu(1B)] are retained in CH2Cl2 solution and solid-state superconducting quantum interference device (SQUID) magnetometric studies confirm that [Ni(1A)] and [Ni(1B)] adopt high spin (S = 1) configurations. Each complex exhibits two reversible oxidation processes between +0.05 and +0.64 V vs [Fc](+)/[Fc]. The products of one- and two-electron oxidations have been studied by UV/vis spectroelectrochemistry and by EPR spectroscopy which confirm that each oxidation process for the Zn-II and Cu-II complexes is ligand-based with sequential formation of mono- and bis-phenoxyl radical species. In contrast, the one-electron oxidation of the Ni-II complexes generates Ni-III products. This assignment is supported by spectroelectrochemical and EPR spectroscopic studies, density functional theory (DFT) calculations, and the single crystal X-ray structure of [Ni(1A)][BF4] which contains Ni in a five-coordinate distorted trigonal bipyramidal geometry.

First author: Celik, Mehmet Ali, End-On and Side-On pi-Acid Ligand Adducts of Gold(I): Carbonyl, Cyanide, Isocyanide, and Cyclooctyne Gold(I) Complexes Supported by N-Heterocyclic Carbenes and Phosphines, INORGANIC CHEMISTRY,52, 729, (2013)
Abstract: N-Heterocyclic carbene ligand SIDipp (SIDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and trimesitylphosphine ligand have been used in the synthesis of gold(I) cyanide, t-butylisocyanide, and cyclooctyne complexes (SIDipp)Au(CN) (3), (Mes(3)P)Au(CN) (4), [(Mes(3)P)(2)Au][Au(CN)(2)] (5), [(SIDipp)Au((CNBu)-Bu-t)][SbF6] ([6][SbF6]), [(SIDipp)Au(cyclooctyne)][SbF6] ([8][sbF(6)]), and [(Mes(3)P)Au(cyclooctyne)][SbF6] ([9][SbF6]). A detailed computational study has been carried out on these and the related gold(I) carbonyl adducts [(SIDipp)Au(CO)][SbF6] ([1][SbF6]), [(Mes(3)P)Au(CO)][SbF6] ([2][SbF6]), and [(Mes(3)P)Au((CNBu)-Bu-t)(+) ([7](+). X-ray crystal structures of 3, 5, [6][SbF6], [8][SbF6], and [9][SbF6] revealed that they feature linear gold sites. Experimental and computational data show that the changes in pi-acid ligand on (SIDipp)Au+ from CO, CN-, (CNBu)-Bu-t, cyclooctyne as in [1](+), 3, [6](+), and [8](+) did not lead to large changes in the Au-C-carbene bond distances. A similar phenomenon was also observed in Au-P distance in complexes [2](+), 4, [7](+), and [9](+) bearing trimesitylphosphine. Computational data show that the Au-L bonds of “naked” [Au-L](+) or SIDipp and Mes(3)P supported [Au-L](+) (L = CO, CN-, (CINBu)-Bu-t to cyclooctyne) have higher electrostatic character than covalent character. The Au <- L sigma-donation and Au -> L pi-back-donation contribute to the orbital term with the former being the dominant component, but the latter is not negligible. In the Au-CO adducts [1](+) and [2](+), the cationic gold center causes the polarization of the C-O sigma and pi orbitals toward the carbon end making the coefficients at the two atoms more equal which is mainly responsible for the large blue shift in the CO stretching frequency. The SIDipp and Mes(3)P supported gold(I) complexes of cyanide and isocyanide also exhibit a significant blue shift in (v) over bar (CN) compared to that of the free ligands. Calculated results for Au(CO)Cl and Au(CF3)CO suggest that the experimentally observed blue shift in (v) over bar (CO) of these compounds may at least partly be caused by intermolecular forces.

First author: Koenig, Carolin, Direct determination of exciton couplings from subsystem time-dependent density-functional theory within the Tamm-Dancoff approximation, JOURNAL OF CHEMICAL PHYSICS, 138, 729, (2013)
Abstract: In subsystem time-dependent density functional theory (TDDFT) [J. Neugebauer, J. Chem. Phys. 126, 134116 (2007)] localized excitations are used to calculate delocalized excitations in large chromophore aggregates. We have extended this formalism to allow for the Tamm-Dancoff approximation (TDA). The resulting response equations have a form similar to a perturbative configuration interaction singles (CIS) approach. Thus, the inter-subsystem matrix elements in subsystem TDA can, in contrast to the full subsystem-TDDFT case, directly be interpreted as exciton coupling matrix elements. Here, we present the underlying theory of subsystem TDDFT within the TDA as well as first applications. Since for some classes of pigments, such as linear polyenes and carotenoids, TDA has been reported to perform better than full TDDFT, we also report applications of this formalism to exciton couplings in dimers of such pigments and in mixed bacteriochlorophyll-carotenoid systems. The improved description of the exciton couplings can be traced back to a more balanced description of the involved local excitations.

First author: Bag, Subhendu Sekhar, Triazolyl Donor/Acceptor Chromophore Decorated Unnatural Nucleosides and Oligonucleotides with Duplex Stability Comparable to That of a Natural Adenine/Thymine Pair, JOURNAL OF ORGANIC CHEMISTRY, 78, 278, (2013)
Abstract: We report the design and synthesis of triazolyl donor/acceptor unnatural nucleosides via click chemistry and studies on the duplex stabilization of DNA containing two such new nucleosides. The observed duplex stabilization among the self-pair/heteropair has been found to be comparable to that of a natural A/T pair. Our observations on the comparable duplex stabilization has been explained on the basis of possible pi-pi stacking and/or charge transfer interactions between the pairing partners. The evidence of ground-state charge transfer complexation came from the UV-vis spectra and the static quenching of fluorescence in a heteropair. We have also exploited one of our unnatural DNAs in stabilizing abasic DNA.

First author: Zarate, Ximena, Theoretical Study of Sensitizer Candidates for Dye-Sensitized Solar Cells: Peripheral Substituted Dizinc Pyrazinoporphyrazine-Phthalocyanine Complexes, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 430, (2013)
Abstract: We have carried out a theoretical study of the geometrical and electronic structures of a family of planar dimers constituted by zinc(II) pyrazinoporphyrazine and zinc(II) phthalocyanine with peripheral electron-donating and electron-withdrawing substituents R [where R = -OH (1), -C(CH3)(3) (2), -CH3 (3), -C6H5 (4), -H (5), – CO2H (7), -NO2 (7), and -PO3H2 (8)]. The complexes are connected by varying the bridge (B) ligand, where, in 1-9, B is -CH= and, in 10-12, B is -N=, -O-, and -S-, respectively. The -CO2H group was included in complexes identified as 9-12. This was done because of the known properties of this group in acting as an anchor to adsorb a dye onto a semiconductor oxide. The aim of this work was to provide a useful theoretical basis for the design and screening of new potential dye candidates to be used in these devices, based on the properties of the dyes suitable for their good performance in solar cells, such as frontier molecular orbital spatial distributions; charge-separated states in the electronic transitions in the visible region of the spectrum; and importantly, the energy diagram of the frontier MOs of these dyes and the conduction band (CB) of the semiconductor, where the LUMO energy levels that are above of the CB suggest which dyes are capable of electron injection into TiO2. In this sense, it is expected that complexes 1-5 and 9-12 should be very promising dyes to act as sensitizers. Finally, a linear correlation was found between the HOMO and LUMO energies of all of the systems and the Hammett constants, where these molecular orbitals become more stable when R is more electron-withdrawing.

First author: Nizovtsev, Anton S., Electronic Rearrangements during the Inversion of Lead Phthalocyanine, JOURNAL OF PHYSICAL CHEMISTRY A, 117, 481, (2013)
Abstract: The mechanism of inversion of lead phthalocyanine (PbPc), possessing a shuttlecock shape, was studied in detail within the bonding evolution theory framework. We have found that reaction pathway calculated using hybrid density functional theory (DFT) method, B3LYP, consists of five structural stability domains, which are connected by four bifurcation points. Reorganization of Pb’s basins with pronounced role of core ones is the basis of the catastrophes identified, whereas basins belonging to other atoms are almost not involved in the electronic structure changing. These results provide the new topological picture of processes underlying the conformational transitions of shuttlecock-shaped metal phthalocyanines adsorbed on surfaces.

First author: Rezabal, Elixabete, First Principle Approach to Solvation by Methylimidazolium-Based Ionic Liquids,JOURNAL OF PHYSICAL CHEMISTRY B, 117, 553, (2013)
Abstract: Understanding the nature of the inter- and intramolecular interactions of solutes and ionic liquid (IL) ion pairs from an electronic point of view is necessary for explaining the mechanisms behind the selectivity of ILs toward a certain solute. Due to the complexity of the underlying physicochemical interactions, and aiming at a reliable representation of the solute IL interactions, the model system chosen in this work is formed by one single ion pair and the solute of interest, in the gas phase. Ab initio molecular dynamics (MD) techniques are used for ensuring a complete scan of the potential energy surface. A representative number of structures extracted from this trajectory are optimized using more sophisticated DFT methods. Posterior bond analysis (with natural bonding orbitals (NBO), and Morokuma-like energy partition) provide a detailed picture of the solute IL bond nature for a set of various solutes, anions, and cations, to find a relationship between the gas phase electronic characteristics and the experimentally observed behavior. The approximation to the ILs solvation properties employing this very basic model shows that, on one side, the specific interaction of the solute with methylimiclazolium-based IL is a reliable indication of the overall affinity between the bulk IL and the solute, and can be considered a predictive tool for the bulk behavior. Furthermore, the systematic study carried out has permitted the rational comprehension of such properties and thus permits us to extend it to other systems.

First author: Sanyal, Somananda, Effect of Imide Functionalization on the Electronic, Optical, and Charge Transport Properties of Coronene: A Theoretical Study, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 825, (2013)
Abstract: We investigate the energetics, electronic structure, optical properties, and charge transfer characteristics of coronene and its imide-functionalized derivatives using quantum chemical calculations. We analyze the formation feasibility of pristine coronene and its different imide monomers, namely, coronene-5-diimide, coronene-6-diimide, and coronene-tetraimide, from a common parental compound, coronene octacarboxylic acid, and find that the most favorable derivative is the pure coronene. Our results also show that coronene-6-diimide is preferred over other possible imide compounds, which is well in accordance with the relative experimental abundance of coronene-6-diimide. The absorption characteristics obtained for both the monomer and dimer of coronene imides show bathochromic shifts for the low-energy peak positions in comparison to the pristine coronene because of the presence of the electron withdrawing imide groups, and the trend in transition energy follows the order of the electronic gap. Interestingly, we find a larger extent of red shift for the absorption maxima of the synthetically more feasible coronene-6-diimide among others. Moreover, our analysis also shows that the extent of red shift strongly depends on the position and orientations of the imide groups, and the low-energy peaks solely correspond to the pi-pi* electronic transitions. Furthermore, we also calculate the charge (electron and hole) transfer integrals for the plausible stable dimers, and find that effective hole transfer integrals are significantly larger than the electron transfer integral except for the coronene-tetraimide, for which the electron transfer integral is found to be greater than the hole transfer integral. The calculated carrier mobilities for the coronene crystal show that the hole mobility is significantly larger, almost 15 times, than the electron mobility. Our study provides a detailed understanding of the tunable optical and charge transfer properties for imide-functionalized coronene derivatives, and suggests their potential use in optoelectronic and field effect transistor devices.

First author: Lichtenberg, Crispin, Cationic, Neutral, and Anionic Allyl Magnesium Compounds: Unprecedented Ligand Conformations and Reactivity Toward Unsaturated Hydrocarbons, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,135, 811, (2013)
Abstract: Starting from bis(allyl)magnesium [Mg-(C3H5)(2)], a set of cationic, neutral, anionic, and dianionic allyl magnesium compounds has been isolated and characterized, including [Mg(C3H5)(THF)(5)][B(C6F5)(4)] (3), [Mg-(C3H5)(2)(1,4-dioxane)(THF)] (2), [KMg(C3H5)(3)(THF)] (6), and [MMg(C3H5)(4)] (8: M = K-2; 9: M = Ca). In solution, the allyl ligands of the compounds display fluxional behavior, even at low temperatures. Single crystal X-ray analysis reveals unusual mu(2)-eta(1):eta(3)- and unprecedented mu(3)-eta(1):eta(3):eta(3)-coordination modes in the heterobimetallic compounds 6 and [8.(THF)(2)]. Density functional theory calculations confirm that these metal-allyl conformations are energetically stable. The magnesium compounds have been investigated as initiators for butadiene polymerization and ethylene oligomerization. The heterobimetallic compounds display initiation properties, including higher reaction rates, that are distinctively different from those of the monometallic species. Reactivity trends depend on the formal charge of the magnesium compounds (dianionic, higher-order magnesiate > monoanionic, lower-order magnesiate) and on the nature of the counterion (K+ > Ca2+).

First author: von Eschwege, Karel G., Synthesis and kinetics of electronically altered photochromic dithizonatophenylmercury(II) complexes, JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY,252, 159, (2013)
Abstract: A series of phenyl-substituted dithizones were synthesized, and preparation of the corresponding series of photochromic phenylmercury(II) complexes is for the first time reported. Adaption of previous methods enhanced synthesis convenience and product yields. A single crystal X-ray data collection of the ortho-S-methyl nitroformazan reaction intermediate was done. ADF computed molecular orbitals of the title compound show the HOMO and LUMO orbitals stretching along the entire ligand. The spontaneous back reaction kinetics of dithizonatophenylmercury(II) was studied at varied concentrations, temperatures and in different solvents. An exponential correlation was found between the rate of reverse isomerization and temperature, while increased solvent polarity and decreased molar mass facilitate higher return rates. The kinetic study of the series of twelve electronically altered complexes yielded a lowest rate of 0.0002 s(-1) the ortho-methyl derivative, while the highest rate of 0.0106 s(-1) was measured for the meta-methoxy derivative.

First author: Safa, Muhieddine, Organoplatinum complexes with an ester substituted bipyridine ligand: Oxidative addition and supramolecular chemistry, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 724, 7, (2013)
Abstract: The synthesis and chemistry of the complex [PtMe2(bebipy)], 1, where bebipy 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine, are described. Complex 1 reacted with HCl to give [PtClMe(bebipy)] and [PtCl2(bebipy)], and all of these platinum(II) complexes gave pi-stacking in the solid state. Complex 1 reacted with X-2 by trans oxidative addition to give [PtX2Me2(bebipy)], X = Br, I, OH, and the complex with X = I is characterized by structure determination as [PtI2Me2(bebipy)]center dot 1.5I(2). Complex 1 usually reacted with RX by trans oxidative addition, to give [PtXRMe2(bebipy)], R = Me, X = I; R = CO2Et, X = Cl; R = CH2CO2H, X = Br; R = CH2-4-C6H4-CO2H, X = Br; R = CH2-4-C6H4-CH2CO2H, X = Br; R = CH2CONHC6H5, X = Br; R = CH2CONH-4-C6H4-t-Bu, X = Br; R = CH2-3-C6H4-CH2OH, X = Br. However, acetyl chloride reacted to give a mixture of compounds formed by cis and trans oxidative addition, and it is suggested that the reaction occurs by initial nucleophilic attack by platinum(II) at the carbonyl group with formation of a tetrahedral intermediate [Pt+Me2(CMeClO )(bebipy)]. The platinum(IV) complexes with hydrogen bonding groups formed supramolecular dimers or polymers in the crystalline state, but the ester groups of the bebipy ligands did not participate in the hydrogen bonding.

First author: Bagno, Alessandro, A DFT study of the vicinal (3)J(Sn-119,C-13) and (3)J(Sn-119,H-1) coupling constants in trimethyl- and chlorodimethylstannyl propanoates, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 724, 139, (2013)
Abstract: We have tested the performance of DFT protocols, both at the Scalar relativistic ZORA and non-relativistic level of theory, for the calculation of the (3)J(Sn-119,C-13) and (3)J(Sn-119,H-1) vicinal couplings for a series of flexible organotin(IV) derivatives with formula XMe2SnCHRCHR’COOMe (X = Me, Cl; R, R’ = Me, Ph). A satisfactory agreement between experimental and calculated vicinal couplings has been obtained by taking into account the conformational behaviour of the compounds investigated. The protocols used, mainly the relativistic one, were found to give a correct picture of the populations and a sufficiently high overall performance in calculating the vicinal couplings, thereby overcoming the use of empirical Karplus-type relationships to infer geometrical parameters from (3)J(Sn-119,C-13) and (3)J(Sn-119,H-1).

First author: Neogi, Debatra Narayan, Regiospecific C(naphthyl)-H bond activation by platinum(II): Isolation, characterization, reactivity and TD-DFT study of the platinum(II) and platinum(IV) organometallates having [C,N,S] donor set, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 724, 147, (2013)
Abstract: At room temperature, complex [Pt(eta(3)-C4H7)Cl](2) or [K2PtCl4] regiospecifically activates the C2(naphthyl)-H bond of 2′-alkylthiophenylazo-1-naphthalenes (1, HL) and affords green cycloplatinates [(PtLCl)-L-II] (2). The structure of platinum(II) cycloplatinate (2a) has been established by single-crystal X-ray crystallography. The platinum(II) centre is surrounded by a tridentate [C,N,S] ligand frame (L) and chloride ion in a distorted square planar fashion. The platinum(II) cycloplatinate (2a) contains a five-membered carboplatinacycle along with a five-membered (N, S) chelate ring. The cycloplatinates [(PtLCl)-L-II] readily react with halogens X-2 (X = Cl, Br, I) and afford blue violet platinum(IV) cycloplatinates [Pt-IV(C,N,S)X-3] (3-5). Methyl iodide (CH3I) reacts with [(PtLCl)-L-II] and produces [(PtLI)-L-II] (6a & 6b). The structures of platinum(IV) cyclometallates (3a & 4b) have been determined by single crystal X-ray crystallography. Time dependent density functional study (TD-DFT) of representative cycloplatinates has been undertaken. The simulated optical spectra of the cycloplatinates are in good agreement with the experimentally observed spectra of the corresponding cycloplatinates.

First author: Marashdeh, Ali, Effect of Transition Metal Dopants on Initial Mass Transport in the Dehydrogenation of NaAIH(4): Density Functional Theory Study, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 3, (2013)
Abstract: Sodium alanate (NaAlH4) is a prototype system for storage of hydrogen in chemical form. However, a key experimental finding, that early transition metals (TMs) like Ti, Zr, and Sc are good catalysts for hydrogen release (and reuptake) whereas traditional hydrogenation catalysts like Pd and Pt are poor catalysts for NaAlH4, has so far received little attention. We performed density functional theory (DFT) calculations at the PW91 generalized gradient approximation level on Ti, Zr, Sc, Pd, and Pt interacting with the (001) surface of nanocrystalline NaAlH4, employing a cluster model of the complex metal hydride to study the initial mass transport in the dehydrogenation process. A key difference between Ti, Zr, and Sc on one hand and Pd and Pt on the other is that exchange of the early TM atoms with a surface Na ion, whereby Na is pushed on to the surface, is energetically preferred over surface absorption in an interstitial site, as found for Pd and Pt. These theoretical findings are consistent with a crucial feature of the TM catalyst being that it can be transported with the reaction boundary as it moves into the bulk, enabling the starting material to react away while the catalyst eats its way into the bulk and affecting a phase separation between a Na-rich and an Al-rich phase. Additional periodic DFT/PW91 calculations in which NaAlH4 is modeled as a slab to model dehydrogenation of larger NaAlH4 particles and which only consider adsorption and absorption of Ti suggest that Ti prefers to absorb interstitially but with only a small energy preference over a geometry in which Ti has exchanged with Na. Additional nudged elastic band calculations based on periodic DFT show only a small barrier (0.02 eV) for exchange of Ti with a surface Na atom. The mechanism inferred from the cluster calculations is therefore consistent with the slab calculations and may well be important.

First author: Biltek, Scott R., Synthesis and Structural Characterization of an Atom-Precise Bimetallic Nanocluster, Ag4Ni2(DMSA)(4), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135, 26, (2013)
Abstract: A bimetallic ligand-protected cluster, Ag4Ni2(DMSA)(4) (DMSA = meso-2,3-climercaptosuccinic acid) was synthesized and characterized through electrospray ionization mass spectroscopy. Such bimetallic clusters involving a noble metal and a first-row transition metal have not been previously reported. Theoretical calculations revealed an octahedral structure with silver atoms occupying the corners of the square plane and the nickel atoms at the apexes. Close agreement between the predicted and observed spectroscopic features was found.

First author: Manet, Ilse, Pyrazinoporphyrazines with Externally Appended Pyridine Rings. 13. Structure, UV-Visible Spectral Features, and Noncovalent Interaction with DNA of a Positively Charged Binuclear (Zn-II/Pt-II) Macrocycle with Multimodal Anticancer Potentialities, INORGANIC CHEMISTRY, 52, 321, (2013)
Abstract: We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (Zn-II/Pt-II) porphyrazine hexacation, [(PtCl2)(CH3)(6)LZn](6+), and its octacationic analogue [(CH3)(8)LZn](8+), lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5′-d[GGG(TTAGGG)(3)]-3’/3′-d[CCC(AATCCC)(3)]-5′, as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the Zn-II/Pt-II hexacation [(PtCl2)(CH3)(6)LZn](6+) in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. TDDFT calculations of the lowest excited states of [(PtCl2)(CH3)(6)LZn](6+) in water provided an accurate description of the Qband spectral region. In particular, the calculated optical spectra were in agreement with the experimental ones, obtained in the presence of micelles favoring complete disruption of the aggregates. The model for dsDNA binding that emerges from the analysis of UV-vis absorption and time-resolved fluorescence data shows the presence of complexes of 1 dsDNA molecule with 1, 2, and 4 macrocycles. Comparing the results for the hexacation [(PtCl2)(CH3)(6)LZn](6+) with those for the [(CH3)(8)LZn](8+) foctacation, we observed a higher degree of monomerization for the [(PtCl2)(CH3)(6)LZn](6+) derivative.

First author: Akbari, Alireza, Synthesis, characterization, and DFT calculation of a Pd(II) Schiff base complex, TURKISH JOURNAL OF CHEMISTRY, 37, 867, (2013)
Abstract: The 4-((E)-(2-((E)-2, 4-dihydroxybenzylideneamino) ethylimino) methyl) benzene-1,3-diol tetradentate ligand, H2L, reacted with PdCl2 to produce the related complex. The complex was characterized by elemental analysis, infrared and electronic spectroscopy, thermogravimetric study, and molar conductance. Furthermore, the fully optimized geometries were calculated using the ADF 2009.01 package. Comparison between the calculated and experimental results covering molecular structures, assignment of fundamental vibrational modes, and thermodynamic properties were investigated. The optimized molecular geometries were compared with the experimental data obtained from X-ray data of a similar complex, which indicated that the theoretical results agree with the corresponding experimental values. The UV-Vis spectrum of the compound was also recorded and some properties, such as HOMO and LUMO energies and lambda(max), were determined using DFT (PW91) method. The absorption wavelengths were compared with the experimental data.

First author: Agrawal, Saurabh, Modeling the effect of ionic additives on the optical and electronic properties of a dye-sensitized TiO2 heterointerface: absorption, charge injection and aggregation, JOURNAL OF MATERIALS CHEMISTRY A, 1, 14675, (2013)
Abstract: We present a joint experimental and theoretical study with the aim of investigating the individual effects of Li-TFSI and EMIM-TFSI additives on the optical and charge transfer properties of D102 dye in solution as well as at the dye-sensitized TiO2 interface. Experimental results show that while the spectral shifts are negligible for the dye in solution, when moving to the TiO2 film in air the addition of both lithium and EMIM salts clearly gives rise to a slight red-shift with the appearance of a lower-energy shoulder in the absorption spectrum. Computational modelling confirms the weak tendency to have stable dye/additive complexes in solution and predicts appreciable spectral red-shifts as a consequence of the interaction of the dye with Li+ and EMIM+ cations. We also predict a strong effect of the additives on the electronic coupling between the dye’s LUMO and the TiO2 conduction band states, reflecting on the calculated injection rates. Further, by modeling the formation and the optical response of selected dye/additive aggregate models, we find a general broadening of the absorption band, accounting for the experimentally observed lower-energy shoulder in the D102 absorption spectrum recorded on TiO2 films where Li and EMIM salts are added.

First author: Molina, Bertha, Structures and chiroptical properties of the BINAS-monosubstituted Au-38(SCH3)(24) cluster,NANOSCALE, 5, 10956, (2013)
Abstract: The structure and optical properties of a set of R-1,1′-binaphthyl-2,2′-dithiol (R-BINAS) monosubstituted A-Au-38(SCH3)(24) clusters are studied by means of time dependent density functional theory (TD-DFT). While it was proposed earlier that BINAS selectively binds to monomer motifs (SR-Au-SR) covering the Au-23 core, our calculations suggest a binding mode that bridges two dimer (SR-Au-SR-Au-RS) motifs. The more stable isomers show a negligible distortion induced by BINAS adsorption on the Au-38(SCH3)(24) cluster which is reflected by similar optical and Circular Dichroism (CD) spectra to those found for the parent cluster. The results furthermore show that BINAS adsorption does not enhance the CD signals of the Au-38(SCH3)(24) cluster.

First author: Chen, Xin, Mechanism of oxygen reduction reaction catalyzed by Fe(Co)-N-x/C, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 19330, (2013)
Abstract: Fe(Co)-N-x/C is an important candidate catalyst for the next generation proton exchange membrane fuel cells (PEMFC), but the relationship between the structure and the oxygen reduction activity is still unclear. In this work, the different active site structures of Fe(Co)-N-x/C are explored and the oxygen reduction catalytic mechanisms are studied by means of density functional theory (DFT). Different kinds of Me-N-x/C motifs, including the edge site around the graphene sheet and the internal site in the graphene sheet (as well as in the graphyne sheet), are constructed and investigated. The calculated results suggest that for the edge active sites, high O-2 adsorption strength may result in direct oxidation of metal ions thus losing their catalytic activity. The internal active sites are stable in acidic solution and display catalytic ability of oxygen reduction. The catalytic activity of the internal site is affected by three factors: the kind of internal metal ion, the bonded nitrogen or carbon atoms with metal ions and the size of the graphene sheet.

First author: Chistyakov, V. A., Possible Mechanisms of Fullerene C-60 Antioxidant Action, BIOMED RESEARCH INTERNATIONAL, 15, 19330, (2013)
Abstract: Novel mechanism of antioxidant activity of buckminsterfullerene C-60 based on protons absorbing and mild uncoupling of mitochondrial respiration and phosphorylation was postulated. In the present study we confirm this hypothesis using computer modeling based on Density Functional Theory. Fullerene’s geroprotective activity is sufficiently higher than those of the most powerful reactive oxygen species scavengers. We propose here that C-60 has an ability to acquire positive charge by absorbing inside several protons and this complex could penetrate into mitochondria. Such a process allows for mild uncoupling of respiration and phosphorylation. This, in turn, leads to the decrease in ROS production.

First author: Saeki, Akinori, Direct Evaluation of Organic Photovoltaic Performance by Xe-flash Time-Resolved Microwave Conductivity, KOBUNSHI RONBUNSHU, 70, 370, (2013)
Abstract: Organic photovoltaic (OPV) devices have emerged as viable candidates for sunlight energy harvesting. However, a reliable technique for the rapid screening of materials and processes is a prerequisite towards faster development in this area. Here we review such a versatile evaluation technique for bulk heterojunction OPVs by the combination of time-resolved microwave conductivity (TRMC) and 10 mu s white-light pulses from a Xe flash-lamp. This technique allows direct and efficient examination of p in blend ratio, solvent choice, and annealing effects without requiring fabrication of the actual device. Based on the established correlation between the device performances and TRMC transients in the typical BHJ of P3HT and phenyl-C-61-butyric acid methyl ester (PCBM), we extended the research to low bandgap polymers and demonstrated the feasibility of this evaluation. The TRMC technique can be used not only for the speedy process optimization of novel conjugated polymers, but also for rational engineering of novel molecular design.

First author: Pinter, Balazs, trans effect and trans influence: importance of metal mediated ligand-ligand repulsion,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 17354, (2013)
Abstract: The trans effect and trans influence were investigated and rationalized in the aminolysis, a typical nucleophilic substitution reaction, of trans-TPtCl2NH3 complexes (T = NH3, PH3, CO and C2H4) using energy decomposition analysis, both along the reaction paths and on the stationary points, and Natural Orbital for Chemical Valence analysis. In order to scrutinize the underlying principles and the origin of the kinetic trans effect, plausible structural constraints were introduced in the decomposition analysis, which allowed eliminating the distance dependence of the interaction energy components. It was established that the trans effect can be rationalized with the interaction of the TPtCl2 and NH3 fragments in the reactant state and TPtCl2 and (NH3)(2) fragments in the transition state. It was evinced quantitatively that the sigma-donor ability of T indeed controls the stability of the reactant, whereas in the case of p-acids, backdonation stabilizes the transition state, for which conceptually two mechanisms are available: intrinsic and induced pi-backdonation. In the destabilization of the reactant and also in the labilization of the leaving group (trans influence) repulsion plays a more important role than orbital sharing effects, which are the cornerstones of the widely accepted interpretations of the trans influence, such as competition for donation or limitation of the donation of the leaving group by the trans ligand T. This repulsive interaction was rationalized both in terms of donated electron density and also in the molecular orbital framework. NOCV orbitals indeed clearly show that the sigma-trans effect can be envisioned as a donation from the trans ligand not only to the metal but also to the sigma* orbital of the metal-leaving group bond, which manifests as a repulsion between the metal and the leaving group.

First author: Navamani, K., Effect of structural fluctuations on charge carrier mobility in thiophene, thiazole and thiazolothiazole based oligomers, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 17947, (2013)
Abstract: Charge transport properties of thiophene, thiazole and thiazolothiazole based oligomers have been studied using electronic structure calculations. The charge transport parameters such as charge transfer integral and site energy are calculated through matrix elements of Kohn-Sham Hamiltonian. The reorganization energy for the presence of excess positive and negative charges and rate of charge transfer calculated from Marcus theory are used to find the mobility of charge carriers. The effect of structural fluctuations on charge transport was studied through the polaron hopping model. Theoretical results show that for the studied oligomers, the charge transfer kinetics follows the static non-Condon effect and the charge transfer decay at particular site is exponential, non-dispersive and the rate coefficient is time independent. It has been observed that the thiazole derivatives have good hole and electron mobility.

First author: Casella, Girolamo, Spectroscopic signatures of the carbon buckyonions C-60@C-180 and C-60@C-240: a dispersion-corrected DFT study, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 18030, (2013)
Abstract: We have investigated, using dispersion corrected DFT methods, the structure and the spectroscopic properties of carbon buckyonions C-60@C-180 and C-60@C-240. C-60, C-180 and C-240 showed a noticeable variation of their geometries in C-60@C-180 and C-60@C-240, upon encapsulation. Inclusion of the dispersion correction term in the calculations has a significant effect on the geometry. C-60@C-180 has a large positive interaction energy, while for C-60@C-240 a negative value is found indicating that only C-240 can easily accommodate C-60. In both cases dispersion interactions strongly contribute to the stabilization of the complexes. Vibrational frequencies, electronic transitions and NMR properties have been computed. The results show that encapsulation leads to appreciable variation in the characteristic resonances thus offering a useful tool for a spectroscopic identification of these species.

First author: Turbervill, Robert S. P., ‘Classical’ and ‘Abnormal’ Bonding in Tin (II) N-Heterocyclic Carbene Complexes,AUSTRALIAN JOURNAL OF CHEMISTRY, 66, 1131, (2013)
Abstract: Reaction of Sn(OTf)(2) (OTf = OSO2CF3-) with one and two equivalents of the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) yielded the complexes [Sn(IPr)(OTf)(2)] (1) and [Sn(IPr)(aIPr)(OTf)][OTf] (2), respectively. Both species were characterised by single crystal X-ray diffraction, multi-element NMR spectroscopy, and elemental analysis. Both compounds display an NHC ligand bonded to the tin(II) metal centre via the C2 carbon in a ‘classical’ mode, while 2 also contains an ‘abnormal’ C4/C5-bonded carbene (aIPr). These observations highlight the subtle steric and electronic effects affecting the coordination modes of these ligands. Solution phase NMR experiments on 1 and 2 reveal complex behaviour resulting in the protonation of the IPr ligands to yield the 1,3-bis(2,6-diisopropylphenyl)imidazolium cation via an unidentified reaction mechanism.

First author: Addy, David A., Synthesis and Reactivity of Half-Sandwich Ruthenium kappa(2)-Aminoborane Complexes,AUSTRALIAN JOURNAL OF CHEMISTRY, 66, 1211, (2013)
Abstract: Cationic half-sandwich ruthenium complexes featuring kappa(2)-bound aminoborane ligands can readily be accessed from 16-electron precursors via chloride abstraction in the presence of H2BNR2 (R = Pr-i, Cy). Complexes [Cp*Ru(L) (kappa(2)-H2BNR2)][BAr4f] (2a: R = Pr-i, L = PCy3; 2b: R = Pr-i, L = PPh3; 2c: R = Pr-i, L = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene; 3a: R = Cy, L = PCy3; Ar-f = C6H3(CF3)(2)-3,5) were isolated in yields of similar to 60%, and characterised in the solid state by X-ray crystallography (for 2a, 2c, and 3a). Low-field B-11 NMR shifts for the coordinated aminoborane fragment, together with short Ru center dot center dot center dot B contacts (of the order of 1.97 angstrom) imply a relatively tightly bound borane ligand, a finding which is given further credence by the results of density functional theory studies (e.g. bond dissociation energies in the range 24 kcal mol(-1); 1 kcal mol(-1) = 4.186 kJ mol(-1)). In terms of reactivity, kappa(2) systems of this type, while potentially offering a versatile route to asymmetric kappa(1) systems, in fact undergo borane extrusion even in the presence of a single equivalent of added ligand.

First author: Davis, Benjamin L., Lewis base assisted B-H bond redistribution in borazine and polyborazylene, CHEMICAL COMMUNICATIONS, 49, 9095, (2013)
Abstract: Lewis bases react with borazine and polyborazylene, yielding borane adducts. In the case of NH3 (I), ammonia-borane (AB) is formed and quantified using NMR spectroscopy against an internal standard. Calculations indicate that the formation of B(NH2)(3) may provide the driving force of this redistribution. Given the complexity and expense of currently known spent AB regeneration pathways, it is suggested that this redistribution chemistry be used to recover AB and improve regeneration methods.

First author: Safin, Damir A., Experimental and theoretical investigations of the Ni-II complex with N-phosphorylated thiourea iPrNHC(S)NHP(O)(OPh)(2), CRYSTENGCOMM, 15, 7845, (2013)
Abstract: The N-phosphorylated thiourea iPrNHC(S)NHP(O)(OPh)(2) (HL) has been synthesized by the reaction of iPrNH(2) and (PhO)(2)P(O)NCS. Recrystallization of HL from aqueous acetone leads to [iPrNH(3)](+)[P(O)(2)(OPh)(2)](-) in a quantitative yield. Reaction of the deprotonated HL with NiCl2 leads to violet [NiL2] crystals with a 1,3-N,S-coordination mode of the ligands. Static DFT and ab initio molecular dynamics studies indicated that [NiL2] is stabilized predominantly by intramolecular N-H center dot center dot center dot O=P hydrogen bonding and dynamically by secondary C-Ph-H center dot center dot center dot S interactions. All compounds have been characterized by IR, diffuse reflectance, UV-vis and NMR spectroscopy, single crystal X-ray diffraction analysis and elemental analysis. Thermal properties investigated in an air atmosphere by means of TGA revealed a residue corresponding to NiPS3.

First author: Sandroni, Martina, Heteroleptic diimine copper(I) complexes with large extinction coefficients: synthesis, quantum chemistry calculations and physico-chemical properties, DALTON TRANSACTIONS, 42, 14628, (2013)
Abstract: Using the HETPHEN approach, five new heteroleptic copper(I) complexes composed of a push-pull 4,4′-styryl-6,6′-dimethyl-2,2′-bipyridine ligand and a bulky bis[(2-diphenylphosphino)phenyl]-ether (DPEphos) or a bis2,9-mesityl phenanthroline (Mes(2)Phen) were prepared and characterized by electronic absorption spectroscopy, electrochemistry, and TD-DFT calculations. These complexes exhibit very intense absorption bands in the visible region with extinction coefficient in the range of 5-7 x 10(4) M-1 cm(-1). The analysis of the position, intensity and band shape indicates a strong contribution from an intra-ligand charge-transfer transition centered on the styrylbipyridine ligand along with MLCT transitions. These new complexes experimentally demonstrate that good light harvesting properties with bis-diimine copper(I) complexes are a reality if one chooses suitable ligands in the coordination sphere. This constitutes a milestone towards using bis-diimine copper(I) complexes for solar energy conversion (artificial photosynthesis and solar cells).

First author: Lomachenko, Kirill A., High energy resolution core-level X-ray spectroscopy for electronic and structural characterization of osmium compounds, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 16152, (2013)
Abstract: A comprehensive study of the bulk solid OsCl3 and the molecular ion [Os(bpy)(2)(CO)Cl](+) is presented illustrating the application of RIXS and HERFD XANES spectroscopies to the investigation of both bulk materials and molecular complexes. In order to analyze the experimental results, DFT simulations were performed taking into account spin-orbit interaction. Calculations for both compounds resulted in good agreement with the experimental RIXS and HERFD XANES data, shedding light on the details of their local atomic and electronic structure. In particular, the spatial distribution of molecular orbitals was obtained, which allowed the determination of the origin of the absorption peaks. It was shown that for materials containing heavy atoms, only the application of advanced RIXS and HERFD XANES spectroscopies makes it possible to extract the information on local atomic and electronic structure details from XANES data.

First author: Li, Fang-Fang, Ti2S@D-3h(24109)-C-78: a sulfide cluster metallofullerene containing only transition metals inside the cage, CHEMICAL SCIENCE, 4, 3404, (2013)
Abstract: A new titanium-based sulfide clusterfullerene, Ti2S@D-3h(24109)-C-78, has been successfully synthesized by arc-discharging graphite rods packed with pure TiO2 and graphite powder under an atmosphere of SO2 and helium. Multistage HPLC methods were utilized to isolate and purify the Ti2S@C-78, and mass spectrometric characterization confirmed the composition of a Ti2S cluster within a C-78 cage. UV-Vis-NIR absorption spectroscopy, electrochemical characterization and extensive DFT calculations led to the assignment of the cage symmetry to D-3h(24109)-C-78 and suggested an almost linear arrangement of the internal Ti2S cluster, with a formal transfer of six electrons from the cluster to the C-78 cage.

First author: Qi Zheng-Xing, A First Principle Theoretical Study on the Dehydration Process of MgCl2 center dot 6(H2O) to MgCl2 center dot 4(H2O), CHINESE JOURNAL OF STRUCTURAL CHEMISTRY, 32, 1257, (2013)
Abstract: A simplified supramolecule MgCl2 center dot 6(H2O) is used to investigate the dehydration process of bischofite crystal. The molecular structure is constructed from the crystal data, and retains its original structure after optimization by the first principle calculation. The transition states of dehydration process from MgCl2 center dot 6(H2O) to MgCl2 center dot 4(H2O) and reformation to MgCl2 center dot 4(H2O) were also calculated. The results show that MgCl2 center dot 6(H2O) releases its two water molecules successively. We also disclose the recrystallization process of MgCl2 center dot 4(H2O), which explains its disordered structure. This work will help to understand the dehydration process of bischofite.

First author: Esterhuysen, Catharine, Complexation behavior of two-coordinated carbon compounds containing fluorenyl ligands, DALTON TRANSACTIONS, 42, 13349, (2013)
Abstract: DFT calculations using BP86 in conjunction with the SVP and TZVPP basis sets as well as ab initio calculations at SCS-MP2 have been carried out for six dicoordinated carbon molecules CLL’ where L is a fluorenyl carbene while L’ is a phosphine PH3 (1) or PPh3 (2) or a carbene, i.e. NHCMe (3), benzannulated NHCMe (4), cycloheptatrienylidene (5) and benzannulated cycloheptatrienylidene (6). The complexes of these compounds with one and two AuCl moieties were also calculated. The monoaurated adducts of 1-4 have the AuCl fragment eta(1) coordinated to the central carbon atom. The complexes 5(AuCl) and 6(AuCl) have AuCl eta(2) bonded across a C=C double bond. Three different bonding modes are found as energy minima for the diaurated species LL’C-(AuCl)(2). The AuCl fragments are found to be either both coordinated eta(1), both coordinated eta(2) across double bonds, or a combination of the two. According to the electronic structure analysis of the free compounds, 1 and 2 might best be classified as carbenes, 3 and 4 as bent allenes while 5 and 6 are typical allenes. The complexation with AuCl reveals that 1-4 may exhibit chemical behaviour which is typical for carbones and thus, they may be termed “hidden carbones”. The AuCl complexes show that compounds 5 and 6 are classical allenes.

First author: Kraemer, Tobias, Structural trends in ten-vertex endohedral clusters, M@E-10 and the synthesis of a new member of the family, [Fe@Sn-10](3-), DALTON TRANSACTIONS, 42, 12120, (2013)
Abstract: The synthesis of a new endohedral ten-vertex Zintl ion cluster, [Fe@Sn-10](3-), isoelectronic with [Fe@Ge-10](3-), is reported. In an attempt to place this new cluster within the context of the known structural chemistry of the M@E-10 family (M = transition metal, E = main group element), we have carried out a detailed electronic structure analysis of the different structural types: viz bicapped square antiprismatic ([Ni@Pb-10](2-), [Zn@In-10](8-)), tetra-capped trigonal prismatic ([Ni@In-10](10-)) and the remarkable pentagonal prismatic [Fe@Ge-10](3-) and [Co@Ge-10](3-). We establish that the structural trends can be interpreted in terms of a continuum of effective electron counts at the E-10 cage, ranging from electron deficient (<4n + 2) in [Ni@In-10](10-) to highly electron rich (>4n + 2) in [Fe@Ge-10](3-). The effective electron count differs from the total valence electron count in that it factors in the increasingly active role of the metal d electrons towards the left of the transition series. The preference for a pentagonal prismatic geometry in [Fe@Ge-10](3-) emerges as a natural consequence of backbonding to the cage from four orthogonal 3d orbitals of the low-valent metal ion. Our calculations suggest that the new [Fe@Sn-10](3-) cluster should also exhibit structural consequences of backbonding from the metal to the cage, albeit to a less extreme degree than in its Ge analogue. The global minimum lies on a very flat surface connecting D-4d, C-2v and C-3v-symmetric minima, suggesting a very plastic structure that may be easily deformed by the surrounding crystal environment. If so, then this provides a new and quite distinct structural type for the M@E-10 family.

First author: Nouri, Hela, A modified cyclen azaxanthone ligand as a new fluorescent probe for Zn2+, DALTON TRANSACTIONS, 42, 12157, (2013)
Abstract: A new cyclen derivative L, bearing a methyl-chromeno-pyridinylidene hydrazone moiety, was synthesized and studied in MeOH, as potential fluorescent “OFF-on-ON” sensors for Zn(II). Photophysical properties of this ligand being PET regulated, L was only weakly emissive in the absence of metal ions (OFF). L fluorescence was increased modestly upon addition of one equivalent of Zn(II), and further increased upon addition of a second equivalent. Therefore, Zn : L behaved as a highly sensitive ON sensor for zinc. This efficiency was correlated to Zn(II) coordination via the hydrazone moiety of the fluorophore, producing an efficient CHelation-Enhanced Fluorescence (CHEF) effect. A complementary theoretical study carried out with DFT calculations further elucidated the optical properties.

First author: Ramanantoanina, Harry, Ligand field density functional theory calculation of the 4f(2) -> 4f(1)5d(1) transitions in the quantum cutter Cs2KYF6:Pr3+, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 13902, (2013)
Abstract: Herein we present a Ligand Field Density Functional Theory (LFDFT) based methodology for the analysis of the 4f(n) -> 4f(n-1)5d(1) transitions in rare earth compounds and apply it for the characterization of the 4f(2) -> 4f(1)5d(1) transitions in the quantum cutter Cs2KYF6:Pr3+ with the elpasolite structure type. The methodological advances are relevant for the analysis and prospection of materials acting as phosphors in light-emitting diodes. The positions of the zero-phonon energy corresponding to the states of the electron configurations 4f(2) and 4f(1)5d(1) are calculated, where the praseodymium ion may occupy either the Cs+-, K+- or the Y3+-site, and are compared with available experimental data. The theoretical results show that the occupation of the three undistorted sites allows a quantum-cutting process. However size effects due to the difference between the ionic radii of Pr3+ and K+ as well as Cs+ lead to the distortion of the K+- and the Cs+-site, which finally exclude these sites for quantum-cutting. A detailed discussion about the origin of this distortion is also described.

First author: Orian, Laura, Large excited state two photon absorptions in the near infrared region of surprisingly stable radical cations of (ferrocenyl)indenes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 12971, (2013)
Abstract: Multiphoton absorptions are important non-linear optical processes which allow us to explore excited states with low energy photons giving rise to new possibilities for photoinduced processes. Among these processes, multiphoton absorptions from excited states are particularly interesting because of the large susceptibilities characteristic of excited states. Here we explore the nonlinear transmission measurements recorded with 9 ns laser pulses at 1064 nm of the radical cations of (2-ferrocenyl) indene and of (2-ferrocenyl)-hexamethylindene, two interesting very stable molecules. The non-linear transmission data can be interpreted with a multiphoton sequence of three photon absorptions, the first being a one photon absorption related to the intramolecular charge transfer and the second a two photon absorption from the excited state created with the first process. The two photon absorption cross section is found to be several orders of magnitude larger than those usually found for two photon absorbing systems excited from the ground state.

First author: Fukazawa, Aiko, S-Pechmann dye: a thiolactone-containing organic dye with a pronounced electron-accepting character and its solid-state photophysical properties, CHEMICAL COMMUNICATIONS, 49, 7117, (2013)
Abstract: A sulfur analogue of a Pechmann dye has been synthesized. In addition to long-wavelength absorption and fluorescence, it showed multiple redox processes with low reduction potentials in cyclic voltammetry. The size effect of sulfur is responsible for its enhanced electron-accepting character.

First author: Chekkal, Faiza, Structural and spin diversity of M(indenyl)(2) transition-metal complexes: a DFT investigation,NEW JOURNAL OF CHEMISTRY, 37, 2293, (2013)
Abstract: Full geometry optimization has been carried out for all the low-energy isomers of M(indenyl)(2) (M = Sc-Ni, Y-Mo, Re, Ru-Pd). Depending on the electron-richness of the molecule, indenyl adopts various hapticities, some of them involving full or partial coordination of the C-6 ring. Our results suggest that a judicious choice of substituents on the ligands should lead to the stabilization of eta(6)-coordinated indenyl ligands. Indenyl is also shown to be quite flexible with respect to the spin ground state. Substituted iron and nickel bis-indenyl species should be characterizable in their triplet state. Thus, both from the point of view of coordination and the metal spin ground state, indenyl and cyclopentadienyl appear to behave quite differently.

First author: Guha, Subarna, A coumarin-based “turn-on” fluorescent sensor for the determination of Al3+: single crystal X-ray structure and cell staining properties, DALTON TRANSACTIONS, 42, 10198, (2013)
Abstract: An efficient Al3+ receptor, 6-(2-hydroxybenzylideneamino)-2H-chromen-2-one (HBC), has been synthesized by condensing salicylaldehyde with 6- aminocoumarin. The molecular structure of HBC has been determined by a single crystal X-ray analysis. It was established that in the presence of Al3+, HBC shows 25 fold enhancement of fluorescence intensity which might be attributed to the chelationenhanced fluorescence (CHEF) process. HBC binds Al(NO3) 3 in a 1 : 1 stoichiometry with a binding constant (K) of 7.9 x 104 M-1. Fe3+ and Mn2+ quench the emission intensity of the [HBC + Al3+] system to an insignificant extent at a concentration 10 times higher compared to that of Al3+. HBC is highly efficient in the detection of intracellular Al3+ under a fluorescence microscope.

First author: Pellarin, Kyle R., Oxidation of dimethylplatinum(II) complexes with a peroxyacid, DALTON TRANSACTIONS,42, 10444, (2013)
Abstract: The complexes [PtMe2(NN)], NN = 2,2′-bipyridine = bipy, 1a; NN = di-2-pyridylamine = dpa, 1b; NN = di-2-pyridyl ketone = dpk, 1c, NN = 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine, bebipy, react with m-chloroperoxybenzoic acid to give the platinum(IV) complexes [Pt(OH)(O2C-3-C6H4Cl)Me-2(NN)], NN = bipy, 2, or [Pt(OH)-(OH2 center dot center dot center dot O2C-3-C6H4Cl)Me-2(NN)], NN = bipy, 3a; dpa, 3b; bebipy, 3d, or [Pt(OH)(2)Me-2(dpkOH)](3)[Pt(OH)-(OH2)Me-2(dpkOH)][H(O2C-3-C6H4Cl)(2)]ce nter dot 2MeOH, 4(3)center dot 5 center dot 2MeOH. The reactions are proposed to occur by a polar oxidative addition mechanism, followed in most cases by the coordination of water. Complex 3a crystallises as a supramolecular polymer, the compound 4(3)center dot 5 center dot 2MeOH crystallises as a supramolecular sheet structure, and 3d easily forms a gel, all through strong intermolecular hydrogen bonding.

First author: Chen, Dianyu, Synthesis and properties of a novel quarternerized imidazolium [alpha-PW12O40](3-) salt as a recoverable photo-polymerization catalyst, DALTON TRANSACTIONS, 42, 10587, (2013)
Abstract: A recoverable photo-polymerization catalyst based on an imidazolium and a polyoxometalate, viz., (BMIm)(2)(DMIm)PW12O40 (where, BMIm = 1-butyl-3-methylimidazolium, DMIm = 3,3′-dimethyl-1,1′-diimidazolium) is reported. It catalyzes photo-polymerization of several industrially important monomers like styrene, methyl methacrylate, butyl methacrylate and vinyl acetate. The catalyst is recoverable and hence can be reused. The molecular weight and polydispersity index can be controlled reasonably and a reaction pathway is proposed. The synthesis of this novel catalyst is reported and the catalyst has been characterized using standard techniques such as single crystal X-ray diffraction studies, cyclic voltammetry and various spectroscopic methods such as Fourier transform infrared spectroscopy, H-1 NMR spectroscopy, EPR spectroscopy and UV-Vis spectroscopy. DFT calculations have been used to explain the catalyst’s photo-chemical activity.

First author: Reddya, K. Hari Krishna, Stabilization of diborane(4) by transition metal fragments and a novel metal to pi Dewar-Chatt-Duncanson model of back donation, DALTON TRANSACTIONS, 42, 10633, (2013)
Abstract: The feasibility of using transition metal fragments to stabilize B2H4 in planar configuration by donating 2 electrons to the boron moiety is investigated. Building upon the existing theoretical and experimental data and aided by the isolobal analogy, the model transition metal complexes Cr(CO)(4)B2H4 (6), Mn(CO)-CpB2H4 (7), Fe(CO)(3)B2H4 (8) and CoCpB2H4 (9) are chosen to illustrate this unique bonding feature bond strengthening with pi-back donation. Other possible types of complexes with B2H4 and the metal fragment are also explored and the energies are compared. One of the low energy isomers wherein the planar B2H4 interacts with the metal fragment in an in-plane fashion represents a unique case study for the Dewar-Chatt-Duncanson model. In this complex the back-donation from the metal fills the p bonding orbital between the two boron atoms thus forming a B=B double bond.

First author: Ba, Fatou, Diferrocenylpyrylium salts and electron rich bispyran from oxidative coupling of ferrocenylpyran. Example of redox systems switched by proton transfer, NEW JOURNAL OF CHEMISTRY, 37, 2066, (2013)
Abstract: Electro or chemical oxidation of ferrocenylmethylenepyran gave an ethanediferrocenylbispyrylium salt through the dimerization of a ferrocenylpyran radical-cation (C-C bond making). Electro or chemical reduction gave back the ferrocenylmethylenepyran (C-C bond breaking). This electrochemical reverse system constitutes an example of C-C bond making-breaking process in a metallocenyl series with rather high stability. DFT calculations and electrochemical studies were carried out in order to determine the electronic structure of the radical cation intermediate, the role of the ferrocenyl groups and the mechanism of the C-C bond making and C-C bond breaking processes. Reversible deprotonation of the ethanediferrocenylbispyrylium salt afforded an extended diferrocenylbismethylenepyran, which was subsequently reversibly oxidized to an ethenediferrocenylbispyrylium salt. X-Ray crystallographic data of diferrocenylbismethylenepyran and ethenediferrocenylbispyrylium salt allowed to determine the molecular movements, which come with the electron transfer (ET). A comparison with the behavior of the corresponding isoelectronic bisdithiafulvenes (extended TTF) and bisdithiolium salts was made.

First author: Rossini, Aaron J., Structural variation in ethylenediamine and -diphosphine adducts of (2,6-Me2C6H3S)(2)Pb: a single crystal X-ray diffraction and Pb-207 solid-state NMR spectroscopy study, DALTON TRANSACTIONS, 42, 9533, (2013)
Abstract: Coordination complexes of (2,6-Me2C6H3S)(2)Pb (1) with flexible bidentate ligands have been prepared to explore new bonding environments for Pb(II) thiolates. The reaction of 1 with a series of ethylenediamine and ethylenediphosphine ligands resulted in isolation of the adducts [(2,6-Me2C6H3S)(2)Pb](2)(tmeda) (9), [(2,6-Me2C6H3S)(2)Pb](3)(dmpe) (10) and [(2,6-Me2C6H3S)(2)Pb] 2(dppe) (11) [tmeda = N, N, N’, N’-tetramethylethylenediamine; dmpe = bis(dimethylphosphino) ethane; dppe = bis(diphenylphosphino) ethane]. The X-ray crystal structure of 9 shows a dinuclear species in which tmeda is chelating a psi-trigonal bipyramidal S2N2 Pb centre via axial and equatorial sites. The structure of 10 displays a trinuclear structural unit in which dmpe is chelating a psi-trigonal bipyramidal S2P2 Pb centre via equatorial sites. Compounds 9 and 10 also contain a second unique metal centre with psi-tetrahedral S3Pb bonding motifs. The structure of 11 shows the dppe ligand bridging two psi-tetrahedral S2P metal bonding environments. Static Pb-207 solid-state NMR (SSNMR) spectra of 9-11 and [Ph4As][(PhS)(3)Pb] (12) were acquired with cross polarization (CP)-CPMG and frequency swept pulse (WURST)-CPMG pulse sequences, and the efficiencies of these pulse sequences are compared. The 207Pb SSNMR spectra reveal that the lead chemical shift anisotropies (CSA) vary greatly between the different Pb sites, and are generally large in magnitude. DFT calculations are utilized to relate the orientations of the Pb-207 nuclear magnetic shielding tensors to the molecular structures, and to aid in spectral assignment where multiple Pb centres are present. The combination of X-ray diffraction, Pb-207 SSNMR and DFT is shown to be invaluable for the structural characterization of these important structural motifs, and should find wide-ranging application to numerous lead coordination compounds.

First author: Johansson, Mikael P., Intramolecular halogen-halogen bonds?, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 11543, (2013)
Abstract: By analysing the properties of the electron density in the structurally simple perhalogenated ethanes, X3C-CY3 (X, Y = F, Cl), a previously overlooked non-covalent attraction between halogens attached to opposite carbon atoms is found. Quantum chemical calculations extrapolated towards the full solution of the Schrodinger equation reveal the complex nature of the interaction. When at least one of the halogens is a chlorine, the strength of the interaction is comparable to that of hydrogen bonds. Further analysis shows that the bond character is quite different from standard non-covalent halogen bonds and hydrogen bonds; no bond critical points are found between the halogens, and the sigma-holes of the halogens are not utilised for bonding. Thus, the nature of the intramolecular halogen…halogen bonding studied here appears to be of an unusually strong van der Waals type.

First author: Oniwa, Kazuaki, Single crystal biphenyl end-capped furan-incorporated oligomers: influence of unusual packing structure on carrier mobility and luminescence, JOURNAL OF MATERIALS CHEMISTRY C, 1, 4163, (2013)
Abstract: We report the synthesis and characterization of two new furan-based biphenyl end-capped oligomers, 2-([1,1′-biphenyl]-4-yl)-5-(5-([1,1′-biphenyl]-4-yl) thiophen-2-yl) furan (BPFT) and 5,5′-di([1,1′-biphenyl]-4-yl)-2,2′-bifuran (BP2F) as candidate semiconductors for organic light-emitting field effect transistors (OLETs). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed the high thermostability of these furan-based semiconductors. X-Ray crystallography of single crystals grown by physical vapor transfer (PVT) method revealed a complicated herringbone packing of BPFT stacking with unusual flat and bent structures, which is different from that of BP2F and the bithiophene-based analogue 5,5′-di([1,1′-biphenyl]-4-yl)-2,2′-bithiophene (BP2T). BPFT single crystal showed a higher absolute quantum yield (51%) compared to that of BP2F and BP2T. Density Functional Theory (DFT) calculations showed that the different excitation energies between flat and bent structures led to the asymmetric transition dipoles in dark state of BPFT H-aggregates, which explains the highest PLQY of BPFT single crystal. Single crystal FET based on BPFT showed an ambipolar characteristic with high hole and electron mobilities, while single crystal FET based on BP2F exhibited p-type characteristic with a high hole mobility. Light emission was observed from the single-crystal FET based on BPFT.

First author: Azpiroz, Jon M., A DFT/TDDFT study on the optoelectronic properties of the amine-capped magic (CdSe)(13) nanocluster, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10996, (2013)
Abstract: Motivated by the recent experiments by Wang et al. (Angew. Chem., Int. Ed. 2012, 51, 6154-6157), in which the alkylamine-capped magic-size (CdSe)(13) has been isolated for the first time, we report on the computational modeling of the putative low-lying isomers of (CdSe)(13), both bare and ligand-protected. According to Density Functional Theory (DFT) calculations, the core@cage configuration Se@Cd13Se12, consisting of a Se atom incarcerated in the center of a puckered Cd13Se12 cage, lies lower in energy than fullerene-and wurtzite-like structures. Methylamine-capped nanoclusters present average bond energies per ligand of about 20 kcal mol(-1), while bond energy decomposition schemes show this interaction to be mostly electrostatically-driven. The computed Time-Dependent-DFT (TDDFT) spectrum of the lowest-lying methylamine-protected (CdSe)(13) isomer essentially coincides with the experiment, with a notable blueshift of the absorption features induced by the ligands. The LUMO has been found to be the acceptor orbital for all the lowest-lying electronic excitations, in both the bare and methylamine-capped clusters, which could explain the narrow emission profiles inherent in semiconductor nanostructures. In addition, the attachment of pyridine and aniline molecules has been evaluated. Interestingly, the molecular orbitals of these aromatic amines located on the edges of the valence and conduction bands may act as trap states, in agreement with experimental evidences. In the particular case of pyridine molecules, unoccupied orbitals intrude into the HOMO-LUMO gap of the cluster.

First author: Scherer, Wolfgang, A Unifying Bonding Concept for Metal Hydrosilane Complexes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 6092, (2013)
Abstract: Motivated by the recent experiments by Wang et al. (Angew. Chem., Int. Ed. 2012, 51, 6154-6157), in which the alkylamine-capped magic-size (CdSe)(13) has been isolated for the first time, we report on the computational modeling of the putative low-lying isomers of (CdSe)(13), both bare and ligand-protected. According to Density Functional Theory (DFT) calculations, the core@cage configuration Se@Cd13Se12, consisting of a Se atom incarcerated in the center of a puckered Cd13Se12 cage, lies lower in energy than fullerene-and wurtzite-like structures. Methylamine-capped nanoclusters present average bond energies per ligand of about 20 kcal mol(-1), while bond energy decomposition schemes show this interaction to be mostly electrostatically-driven. The computed Time-Dependent-DFT (TDDFT) spectrum of the lowest-lying methylamine-protected (CdSe)(13) isomer essentially coincides with the experiment, with a notable blueshift of the absorption features induced by the ligands. The LUMO has been found to be the acceptor orbital for all the lowest-lying electronic excitations, in both the bare and methylamine-capped clusters, which could explain the narrow emission profiles inherent in semiconductor nanostructures. In addition, the attachment of pyridine and aniline molecules has been evaluated. Interestingly, the molecular orbitals of these aromatic amines located on the edges of the valence and conduction bands may act as trap states, in agreement with experimental evidences. In the particular case of pyridine molecules, unoccupied orbitals intrude into the HOMO-LUMO gap of the cluster.

First author: Huber, Stefan M., On the directionality of halogen bonding, PHYSICAL CHEMISTRY CHEMICAL PHYSICS,15, 10350, (2013)
Abstract: The origin of the high directionality of halogen bonding was investigated quantum chemically by a detailed comparison of typical adducts in two different orientations: linear (most stable) and perpendicular. Energy decomposition analyses revealed that the synergy between charge-transfer interactions and Pauli repulsion are the driving forces for the directionality, while electrostatic contributions are more favourable in the less-stable, perpendicular orientation.

First author: Zeonjuk, Lei Liu, On the gas-phase dimerization of negatively charged closo-dodecaborates: a theoretical study, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10358, (2013)
Abstract: We have studied the intriguing gas-phase dimerization of the B12In- (n = 9, 8) anions to B24I2n2- dianions by means of density functional theory calculations. The dimerization of B12I9 to B24I182 has been detected experimentally in a previous study (Phys. Chem. Chem. Phys., 2011, 13, 5712) utilizing electrospray ionization ion trap mass spectrometry (ESI-IT-MS), whereas the formation of B24I162- from B12I8- is modeled here prior to experiment. Calculations are carried out to determine the molecular and electronic structures, the bonding situation and the stability of the dimers relative to the respective monomers. The dimerization process is found to be thermodynamically favorable, and the stability of the lowest-energy structures is substantiated by molecular dynamics simulations. The calculations imply that the experimentally observed B24I182- and the hypothetical B24I162- species are formed through dimerization of the respective B12In- (n = 9, 8) monomers, rather than through loss of two I radicals from B24I2n+22- dimers. Electronic properties such as natural charges, vertical detachment energies (VDEs), frontier molecular orbitals (FMOs), and HOMO-LUMO gaps are computed and analyzed in detail for all monomers and dimers. The analysis shows that the most stable B24I2n2- dimers are formed through two 2c-2e B-B and two 3c-2e B-I-B bridges between the parent B12In (n = 9, 8) monomers. These new bridging bonds engage the deiodinated (bare) faces of the two B-12 icosahedra, as well as one (per monomer) of the nearest boron neighbors and its iodine substituent.

First author: Grice, Kyle A., Carbon monoxide release catalysed by electron transfer: electrochemical and spectroscopic investigations of [Re(bpy-R)(CO)(4)](OTf) complexes relevant to CO2 reduction, DALTON TRANSACTIONS, 42, 8498, (2013)
Abstract: [Re(bpy-tBu)(CO)(4)](OTf) (bpy-tBu = 4,4′-di-tert-butyl-2,2′-bipyridine, OTf = trifluoromethanesulfonate) (1) and [Re(bpy)(CO)(4)](OTf) (bpy = 2,2′-bipyridine) (2) were synthesized and studied as proposed intermediates in the electrocatalytic reduction of carbon dioxide (CO2) by Re(bpy-R)(CO)(3)X. Both compounds demonstrated increased current responses in cyclic voltammograms under CO2. Complex 1 was also characterized by X-ray crystallography. Infrared-spectroelectrochemistry (IR-SEC) of 1 and 2 indicated that upon exposure of the cationic tetracarbonyl compounds to a reducing potential, a CO ligand is labilised and [Re(bpy-R)(CO)(3)(CH3CN)](+) species are formed. This is proposed to occur via an electron-transfer-catalysed process wherein a catalytic amount of reduced species propagates a ligand exchange reaction. Addition of a catalytic amount of potassium intercalated graphite (KC8), a chemical reductant, to a solution of 1 or 2 also yielded quantitative formation of [Re(bpy-R)(CO)(3)(CH3CN)](+), which indicates that the CO loss is catalysed by electron transfer, and not the electrode itself.

First author: Erasmus, Johannes J. C., Chemical and electrochemical oxidation of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)]: an experimental and DFT study, DALTON TRANSACTIONS, 42, 8655, (2013)
Abstract: An experimental and computational chemistry study of the reactivity of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the beta-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k(1), and a higher electrochemical oxidation potential, E-pa(Rh), linearly related by ln k(1) = -11(1) E-pa(Rh) – 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E-HOMO = -0.34(8)E-pa(Rh) – 5.04(4) = 0.032(5) ln k(1) – 4.96(4). k(1) of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes is slower than that of related [Rh(beta-diketonato)(CO)(PPh3)] and [Rh(beta-diketonato)(P(OPh)(3))(2)] complexes due to the better pi-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium.

First author: Freitag, Sarah, Phosphastannirane: A Phosphorus/Tin(II) Lewis Pair that Undergoes Alkyne and Alkene Addition, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 5640, (2013)
Abstract: An experimental and computational chemistry study of the reactivity of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the beta-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k(1), and a higher electrochemical oxidation potential, E-pa(Rh), linearly related by ln k(1) = -11(1) E-pa(Rh) – 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E-HOMO = -0.34(8)E-pa(Rh) – 5.04(4) = 0.032(5) ln k(1) – 4.96(4). k(1) of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes is slower than that of related [Rh(beta-diketonato)(CO)(PPh3)] and [Rh(beta-diketonato)(P(OPh)(3))(2)] complexes due to the better pi-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium.

First author: Khan, Shabana, Stabilization of a Two-Coordinate [GeCl](+) Cation by Simultaneous sigma and pi Donation from a Monodentate Carbodiphosphorane, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 5644, (2013)
Abstract: An experimental and computational chemistry study of the reactivity of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the beta-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k(1), and a higher electrochemical oxidation potential, E-pa(Rh), linearly related by ln k(1) = -11(1) E-pa(Rh) – 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E-HOMO = -0.34(8)E-pa(Rh) – 5.04(4) = 0.032(5) ln k(1) – 4.96(4). k(1) of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes is slower than that of related [Rh(beta-diketonato)(CO)(PPh3)] and [Rh(beta-diketonato)(P(OPh)(3))(2)] complexes due to the better pi-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium.

First author: Wurzenberger, Xaver, Enticing Cobalt into Planarity: Can a Pair of Diolato Ligands Make It Happen?,ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 5159, (2013)
Abstract: An experimental and computational chemistry study of the reactivity of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the beta-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k(1), and a higher electrochemical oxidation potential, E-pa(Rh), linearly related by ln k(1) = -11(1) E-pa(Rh) – 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E-HOMO = -0.34(8)E-pa(Rh) – 5.04(4) = 0.032(5) ln k(1) – 4.96(4). k(1) of [Rh(beta-diketonato)(CO)(P(OCH2)(3)CCH3)] complexes is slower than that of related [Rh(beta-diketonato)(CO)(PPh3)] and [Rh(beta-diketonato)(P(OPh)(3))(2)] complexes due to the better pi-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium.

First author: Conradie, Jeanet, Carbonyl Substitution in beta-Diketonatodicarbonyl-rhodium(I) by Cyclo-octadiene: Relationships with Experimental, Electronic and Calculated Parameters, SOUTH AFRICAN JOURNAL OF CHEMISTRY-SUID-AFRIKAANSE TYDSKRIF VIR CHEMIE, 66, 54, (2013)
Abstract: The substitution rate constant of the reaction between [Rh(beta-diketonato)(CO)(2)] and cyclo-octadiene is related to various empirical parameters and density functional theory calculated energies and charges, beta-diketonato = R’COCHCOR. Results indicate that especially the Hammett meta substituent constants (sigma), the Lever electronic parameters (E-L) and the density functional theory calculated energies and charges predict the substitution rate constant to a high degree of accuracy, for example: ln k(2) = 8.48 (sigma(R) + sigma(R’)) -2.24 (R-2 = 0.99) = 31.8 Sigma E-L -63.0 (R-2 = 0.99) = -9.16 E-HOMO -52.1 (R-2 = 0.97) = 101 Sigma Q(Mulliken)(Rh(CO)(2)) -49.9 (R-2 = 0.99).

First author: Atkins, Andrew J., The chemical sensitivity of X-ray spectroscopy: high energy resolution XANES versus X-ray emission spectroscopy of substituted ferrocenes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 8095, (2013)
Abstract: X-ray spectroscopy at the metal K-edge is an important tool for understanding catalytic processes and provides insight into the geometric and electronic structures of transition metal complexes. In particular, X-ray emission-based methods such as high-energy resolution fluorescence detection (HERFD), X-ray absorption near-edge spectroscopy (XANES) and valence-to-core X-ray emission spectroscopy (V2C-XES) hold the promise of providing increased chemical sensitivity compared to conventional X-ray absorption spectroscopy. Here, we explore the ability of HERFD-XANES and V2C-XES spectroscopy to distinguish substitutions beyond the directly coordinated atoms for the example of ferrocene and selected ferrocene derivatives. The experimental spectra are assigned and interpreted through the use of density functional theory (DFT) calculations. We find that while the pre-edge peaks in the HERFD-XANES spectra are affected by substituents at the cyclopentadienyl ring containing pi-bonds [A. J. Atkins, Ch. R. Jacob and M. Bauer, Chem.-Eur. J., 2012, 18, 7021], the V2C-XES spectra are virtually unchanged. The pre-edge in HERFD-XANES probes the weak transition to unoccupied metal d-orbitals, while the V2C-XES spectra are determined by dipole-allowed transitions from occupied ligand orbitals to the 1s core hole. The latter turn out to be less sensitive to changes beyond the first coordination shell.

First author: Falivene, Laura, Electronic bond tuning with heterocyclic carbenes, DALTON TRANSACTIONS, 42, 7281, (2013)
Abstract: We discuss the impact of the nature of the heterocyclic carbene ring, when used as a complex forming ligand, on the relative stability of key intermediates in three typical Ru, Pd and Au promoted reactions. Results show that P-heterocyclic carbenes have a propensity to increase the bonding of the labile ligand and of the substrate in Ru-promoted olefin metathesis, whereas negligible impact is expected on the stability of the ruthenacycle intermediate. In the case of Pd cross-coupling reactions, dissociation of a P-heterocyclic carbene is easier than dissociation of the N-heterocyclic analogue. In the case of the Au-OH synthon, the Au-OH bond is weakened with the P-heterocyclic carbene ligands. A detailed energy decomposition analysis is performed to rationalize these results.

First author: Zarzycki, Bartosz, Symmetrical P-4 cleavage at cobalt half sandwich complexes [(eta(5)-C5H5)Co(L)] (L = CO, NHC) – a computational case study on the mechanism of symmetrical P-4 degradation to P-2 ligands, DALTON TRANSACTIONS, 42, 7468, (2013)
Abstract: A full theoretical mechanistic investigation on the symmetrical cleavage of P-4 at the active complex fragments [(eta(5)-C5H5)Co(L)] (L = CO, (i)Pr(2)Im; (i)Pr(2)Im = 1,3-di-iso-propylimidazolin-2-ylidene), which results in the formation of the complex [{(eta(5)-C5H5)Co}(2)(mu,eta(2:2)-P-2)(2)] 9, is presented. The overall reaction mechanism is a complex, multistep process. Rate-determining steps of the reaction sequence are two consecutive dissociations of the co-ligands L, which induce the decisive structural rearrangements of the P-4 unit. The choice of the co-ligand L (= CO, (i)Pr(2)Im) influences the kinetic barrier as well as the energy balance of the overall reaction path significantly. The calculations further reveal a strong influence of the entropic effect on the overall reaction. As a consequence, the energy balance of the overall formation of 9 starting from [(eta(5)-C5H5)Co(CO)] precursors is almost thermoneutral and has to overcome high kinetic barriers, whereas the reaction starting from [(eta(5)-C5H5)Co((i)Pr(2)Im)] precursors is exothermic, featuring lower transition barriers with stabilized intermediates. From the direct comparison of both reaction coordinates it seems that the entropic effect of the co-ligands is even stronger than their electronic influence, as for both investigated systems the reactions’ energy profiles are almost identical up to intermediate [{(eta(5)-C5H5)Co(L)}(2)(mu,eta(2:2)-P-4)] 5 (L = CO, (i)Pr(2)Im). After the formation of 5, the first CO dissociation step renders the reaction endothermic for L = CO, whereas in the case of (i)Pr(2)Im dissociation the reaction progresses exothermically. Energy decomposition analysis and fragment analysis provide a picture of the bonding mechanisms between the metal complex fragments and P-4 in the case of the most significant intermediates and the final product.

First author: Xu, Wei, On structure and bonding of lanthanoid trifluorides LnF(3) (Ln = La to Lu), PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 7839, (2013)
Abstract: The trends in the series of lanthanoid (lanthanide) trifluoride molecules LnF(3) (Ln = La to Lu) are governed by the valence-active Ln(4f, 5d, 5p, 6s) shells. The series is investigated by quasi-relativistic density functional theory at both the scalar and spin-orbit-coupled levels. Integrating many of the previous experimental and theoretical deductions, we obtain the following comprehensive picture: (1) The comparatively small Ln-F bond length contraction of 14 pm from La to Lu is rather smooth but weakly modulated by spin-orbit coupling. (2) From La to Lu the floppy structure becomes more quasiplanar. (3) The heterolytic LnF bond energies (1/3LnF(3) -> 1/3Ln(3+) + F-) at the spin-orbit averaged level increase smoothly from 15.3 to 16.3 eV for La to Lu, only the ‘divalent’ lanthanoids Eu and Yb are outliers with 0.2 eV higher bond energies. (4) The homolytic LnF bond energies (1/3LnF(3) -> 1/3Ln + F) however show an overall W-shaped double-periodicity with maxima for LaF3, GdF3 and LuF3, decreasing from La to Eu and from Gd to Yb, the large individual variations being caused by different spin-orbit coupling and Coulomb interaction effects in Ln(0) and LnF(3). (5) The Ln-F interaction is basically ionic (increasing with decreasing ionic radii) with some dative Ln(3+) <- F- bonding. (6) The latter is of the Ln(5d)-> F(2p) type with a rather constant bond order from La to Lu, with small Ln(5p) and very small Ln(4f) semi-core contributions decreasing from La to Lu. All these trends are rationalized.

First author: Zlatar, Matija, Computational study of the spin-state energies and UV-Vis spectra of bis(1,4,7-triazacyclononane) complexes of some first-row transition metal cations, PHYSICAL CHEMISTRY CHEMICAL PHYSICS,15, 6631, (2013)
Abstract: We report here computed spin-state energies and UV-Vis spectra for several transition metal complexes with a triazacyclononane ligand. Our results show that the spin ground-state is correctly obtained with either OPBE or SSB-D, except for the high-spin ground-state of the Co(II) complex that was properly described only by SSB-D. The UV-Vis spectra from TD-DFT reproduce in general rather well the experimental spectra, but in cases of the Cr(III) and Co(II) complexes it clearly failed. Better results for the UV-Vis spectra have been obtained by using Ligand Field DFT.

First author: Safin, Damir A., Complexation properties of N-thiophosphorylated thiourea 2-PyNHC(S)NHP(S)(OiPr)(2) towards Ni-II, DALTON TRANSACTIONS, 42, 5252, (2013)
Abstract: Reaction of the deprotonated N-thiophosphorylated thiourea 2-PyNHC(S) NHP(S)(OiPr)(2) (HL) with NiCl2 leads to the complex [Ni{2-PyNHC(S) NP(S)(OiPr)(2)}(2)] ([NiL2]) with unprecedented 1,5,7-N, N’, S-coordination of the ligand. Recrystallization of [NiL2] from a mixture of CH2Cl2-n-hexane or acetone-n-hexane leads to [Ni-(L-1,5,7-N, N’, S)(2)]center dot CH2Cl2 and [Ni(L-1,5,7-N, N’, S)(2)], respectively. The latter complex, in turn, shows a temperature-induced polymorphism. [NiL2] in solution shows a paramagnetic distorted octahedral structure where the metal center is coordinated through the nitrogen atoms of the phosphorylamide and pyridyl group functions, and oxygen atoms of the phosphorylamide unit. Furthermore, in the solid state at low temperature, [Ni(L-1,5,7-N, N’, S)(2)] is shown from high-frequency EPR measurements to possess an S = 1 ground state with large anisotropy.

First author: Jacobsen, Heiko, Topology maps of bond descriptors based on the kinetic energy density and the essence of chemical bonding, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 5057, (2013)
Abstract: Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are intuitively linked to familiar concepts of chemical bonding. The function nu(r), termed localized-orbital locator and based on the positive-definite kinetic energy density tau(+), is employed to characterize classes of covalent bonds in terms of its full topology of all critical points of rank three. Not only does nu(r) reveal patterns in chemical bonding, it also discloses features and the influence of extended electronic cores. Gradient paths define the extension of the valence space around an atomic centre; they separate various core level regions from bonding domains, and partition molecules in sensible bonded subunits. Location and nu(r)-values of critical points add a quantitative aspect to the bond characterization; profiles of unconventional chemical linkages such as charge-shift bonds emerge in a natural way.

First author: Ciancaleoni, Gianluca, A combined NMR/DFT study on the ion pair structure of [((PR2R2)-R-1)Au(eta(2)-3-hexyne)]BF4 complexes, DALTON TRANSACTIONS, 42, 4122, (2013)
Abstract: The interionic structure of four gold(I) pi-alkyne ion pairs, with general formula [((PR2R2)-R-1)Au(eta(2)-3-hexyne)]BF4 (R-1 = R-2 = Bu-t, 1a; R-1 = Bu-t, R-2 = o-diphenyl, 2a; R-1 = R-2 = 2,4,6-trimethoxyphenyl, 3a; R-1 = R-2 = 2,4-di-tert-butylphenoxy, 4a), was studied by F-19, H-1-HOESY NMR spectroscopy. In all the cases the anion locates mainly close to the alkyne, but the degree of specificity of location strongly depends on the P-ligand and it is high for ion pairs bearing poorly electron donating (PR2R2)-R-1 ligands (particularly, 4a) and low for ion pairs with strongly electron donating (PR2R2)-R-1 ones (such as 3a). This result is rationalized through relativistic DFT calculations, showing that the electronic properties of the P-ligand finely tune the charge accumulation on the alkyne and, consequently, its ability of attracting the anion.

First author: Carrion, Samanta M., Density functional study of geometrical, electronic and magnetic properties of W-n clusters (n=2-16, 19, 23), EUROPEAN PHYSICAL JOURNAL D, 67, 4122, (2013)
Abstract: Geometrical, electronic and magnetic properties of W-n atomic clusters, with n = 1-16, 19, 23, are explored using different generalized gradient approximations to the density functional theory and basis sets of double-zeta quality augmented with polarization functions. From a geometrical point of view, tungsten aggregates with n = 15 and above exhibit a clear tendency to adopt structures derived from the body-centered cubic system. Total energy second-differences indicate that tungsten octamer becomes a specially stable isomer. For larger sizes, the different generalized gradient approximations do not predict the same stability pattern. Vertical ionization energies show a smooth, but slow trend to the experimental work function of polycrystalline tungsten. Vertical electron affinities agree very well with experimental measures of detachment electron energies. Calculated magnetic moments indicate that mainly singlet, triplet and quintet electronic states characterize small tungsten aggregates. A W-15 isomer with a geometry derived from the body-centered cubic system, however, is characterized by an electronic state with 14 unpaired electrons.

First author: Strassberger, Zea, Catalytic cleavage of lignin beta-O-4 link mimics using copper on alumina and magnesia-alumina, GREEN CHEMISTRY, 15, 768, (2013)
Abstract: Copper on gamma-alumina and on mixed magnesia-alumina, Cu/MgO-Al2O3, catalyse the hydrodeoxygenation (HDO) of beta-O-4 lignin-type dimers, giving valuable aromatics. The typical selectivity to phenol is as high as 20%. By changing the support’s acidity we can modify the dispersion of copper. Interestingly, more HDO occurs with larger copper agglomerates than with finely dispersed particles. The presence of copper also increases the selectivity of the HDO cleavage. Three different pathways are hypothesized for the reaction on the catalyst surface. Thus, copper activates ketones more and especially more selective towards cleavage than their corresponding alcohols. DFT calculations of bond dissociation energies correlate well with this experimental observation. Excitingly, ethylbenzene is formed in proportional amounts to phenol, showing that these catalysts can reduce the oxygen content of lignin-type product streams. Considering its low price and ready availability, we conclude that copper on alumina is a promising alternative catalyst for lignin depolymerization.

First author: Vargas, Alfredo, Towards accurate estimates of the spin-state energetics of spin-crossover complexes within density functional theory: a comparative case study of cobalt(II) complexes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 3752, (2013)
Abstract: We report a detailed DFT study of the energetic and structural properties of the spin-crossover Co(II) complex [Co(tpy)(2)](2+) (tpy = 2,2′:6′,2 ”-terpyridine) in the low-spin (LS) and the high-spin (HS) states, using several generalized gradient approximation and hybrid functionals. In either spin-state, the results obtained with the functionals are consistent with one another and in good agreement with available experimental data. Although the different functionals correctly predict the LS state as the electronic ground state of [Co(tpy)(2)](2+), they give estimates of the HS-LS zero-point energy difference Delta E degrees(HL)(tpy) which strongly depend on the functional used. This dependency on the functional was also reported for the DFT estimates of the zero-point energy difference Delta E degrees(HL)(bpy) in the HS complex [Co(bpy)(3)](2+) (bpy = 2,2′-bipyridine) [A. Vargas, A. Hauser and L. M. Lawson Daku, J. Chem. Theory Comput., 2009, 5, 97]. The comparison of the Delta E degrees(HL)(tpy) and Delta E degrees(HL)(bpy) estimates showed that all functionals correctly predict an increase of the zero-point energy difference upon the bpy -> tpy ligand substitution, which furthermore weakly depends on the functionals, amounting to Delta(Delta E degrees(HL))(bpy -> tpy) approximate to +2760 cm(-1). From these results and basic thermodynamic considerations, we establish that, despite their limitations, current DFT methods can be applied to the accurate determination of the spin-state energetics of complexes of a transition metal ion, or of these complexes in different environments, provided that the spin-state energetics is accurately known in one case. Thus, making use of the availability of a highly accurate ab initio estimate of the HS-LS energy difference in the complex [Co(NCH)(6)](2+) [L. M. Lawson Daku, F. Aquilante, T. W. Robinson and A. Hauser, J. Chem. Theory Comput., 2012, 8, 4216], we obtain for [Co(tpy)(2)](2+) and [Co(bpy)(3)](2+) best estimates of Delta E degrees(HL)(bpy) approximate to -2800 cm(-1) and Delta E degrees(HL)(tpy) approximate to 0 cm(-1), in good agreement with the known magnetic behaviour of the two complexes.

First author: Arroniz, Carlos, First diastereoselective [3+2] cycloaddition reaction of diethyl isocyanomethylphosphonate and maleimides, ORGANIC & BIOMOLECULAR CHEMISTRY, 11, 1640, (2013)
Abstract: Bicyclic alpha-iminophosphonates were prepared via the first diastereoselective silver catalyzed [3 + 2] cycloaddition reaction of diethyl isocyanomethylphosphonate and diversely N-substituted maleimides. The reduction of the resulting imine by catalytic hydrogenation led to cyclic alpha-aminophosphonates, which are a-aminoester surrogates. The relative stereochemistry of the adducts was confirmed by X-ray crystallographic analysis of 4. The diastereoselectivity of the cycloaddition reaction was rationalised by theoretical studies.

First author: Liu, Chun-Guang, Quantum chemical studies on a series of transition metal carbon dioxide complexes: Metal-carbon bonding and electronic structures, MOLECULAR PHYSICS, 111, 257, (2013)
Abstract: The bonding features and electronic structures of a series of transition metal carbon dioxide complexes have been studied by density functional theory (DFT) calculations combined with natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). NBO analysis shows that the interaction between the metal center and the carbon atom of the carbon dioxide ligand (MC) is stronger than the other interaction between the metal center and the carbon dioxide ligand. Natural hybrid orbital (NHO) analysis gives the detailed bonding features of the MC bond for each complex. The NBO charge distribution on the carbon dioxide unit in all studied complexes is negative, which indicates charge transfer from the metal center to the carbon dioxide ligand for all studied complexes. The hyperconjugation effect of the metal center and the two CO bonds of the carbon dioxide ligand has been estimated using the NBO second-order perturbation stabilization energy. It was found that the NBO second-order stabilization energy of CO???nM* is sensitive to the coordinated sphere and the metal center. Frontier molecular orbital (FMO) analysis shows that complexes 1 and 4 may be good nucleophilic reagents for activation of the carbon dioxide molecule. However, the EDAs show that the MCO2 bond interaction energy of complex 4 is about two times as large as that of complex 1. The high MCO2 bond interaction energy of complex 4 may limit its practical application.

First author: Piemontesi, Cyril, Synthesis of 3,3-disubstituted oxindoles by one-pot integrated Bronsted base-catalyzed trichloroacetimidation of 3-hydroxyoxindoles and Bronsted acid-catalyzed nucleophilic substitution reaction, ORGANIC & BIOMOLECULAR CHEMISTRY, 11, 1533, (2013)
Abstract: Treatment of 3-hydroxyoxindoles with trichloroacetonitrile (1.3 equiv.) and a catalytic amount of DBU (0.1 equiv.) followed by addition of nucleophiles (1.5 equiv.) and diphenylphosphoric acid (0.2 equiv.) afforded the 3,3-disubstituted oxindoles in good to excellent yields. DFT computations supported the notion that the reaction went through the 1-alkyl-2-oxo-2H-indol-1-ium intermediate.

First author: Garcia-Simon, Cristina, Self-Assembled Tetragonal Prismatic Molecular Cage Highly Selective for Anionic p Guests, CHEMISTRY-A EUROPEAN JOURNAL, 19, 1445, (2013)
Abstract: The metal-directed supramolecular synthetic approach has paved the way for the development of functional nanosized molecules. In this work, we report the preparation of the new nanocapsule 3.(CF3SO3)8 with a A4B2 tetragonal prismatic geometry, where A corresponds to the dipalladium hexaazamacrocyclic complex Pd-1, and B corresponds to the tetraanionic form of palladium 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (2). The large void space of the inner cavity and the supramolecular affinity for guest molecules towards porphyrin-based hosts converts this nanoscale molecular 3D structure into a good candidate for hostguest chemistry. The interaction between this nanocage and different guest molecules has been studied by means of NMR, UV/Vis, ESI-MS, and DOSY experiments, from which highly selective molecular recognition has been found for anionic, planar-shaped p guests with association constants (Ka) higher than 109?M-1, in front of non-interacting aromatic neutral or cationic substrates. DFT theoretical calculations provided insights to further understand this strong interaction. Nanocage 3.(CF3SO3)8 can not only strongly host one single molecule of M(dithiolene)2 complexes (M=Au, Pt, Pd, and Ni), but also can finely tune their optical and redox properties. The very simple synthesis of both the supramolecular cage and the building blocks represents a step forward for the development of polyfunctional supramolecular nanovessels, which offer multiple applications as sensors or nanoreactors.

First author: Ravelli, Davide, Electronic and EPR spectra of the species involved in [W10O32](4-) photocatalysis. A relativistic DFT investigation, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 2890, (2013)
Abstract: The decatungstate anion [W10O32](4)-is widely used as a photocatalyst in different transformations, during which it undergoes one-electron reduction to [W10O32](5-), possibly protonated; the bi-reduced species [W10O32](6-) is obtained by ensuing disproportionation. Relativistic DFT calculations were used to predict the UV-VIS spectra and EPR parameters of all such species.

First author: Kovalenko, Andriy, Multiscale modeling of solvation in chemical and biological nanosystems and in nanoporous materials, PURE AND APPLIED CHEMISTRY, 85, 159, (2013)
Abstract: Statistical-mechanical, 3D-RISM-KH molecular theory of solvation (3D reference interaction site model with the Kovalenko-Hirata closure) is promising as an essential part of multiscale methodology for chemical and biomolecular nanosystems in solution. 3D-RISM-KH explains the molecular mechanisms of self-assembly and conformational stability of synthetic organic rosette nanotubes (RNTs), aggregation of prion proteins and beta-sheet amyloid oligomers, protein-ligand binding, and function-related solvation properties of complexes as large as the Gloeobacter violaceus pentameric ligand-gated ion channel (GLIC) and GroEL/ES chaperone. Molecular mechanics/Poisson-Boltzmann (generalized Born) surface area [MM/PB(GB)SA] post-processing of molecular dynamics (MD) trajectories involving SA empirical nonpolar terms is replaced with MM/3D-RISM-KH statistical-mechanical evaluation of the solvation thermodynamics. 3D-RISM-KH has been coupled with multiple time-step (MTS) MD of the solute biomolecule driven by effective solvation forces, which are obtained analytically by converging the 3D-RISM-KH integral equations at outer time-steps and are calculated in between by using solvation force coordinate extrapolation (SFCE) in the subspace of previous solutions to 3D-RISM-KH. The procedure is stabilized by the optimized isokinetic Nose-Hoover (OIN) chain thermostatting, which enables gigantic outer time-steps up to picoseconds to accurately calculate equilibrium properties. The multiscale OIN/SFCE/3D-RISM-KH algorithm is implemented in the Amber package and illustrated on a fully flexible model of alanine dipeptide in aqueous solution, exhibiting the computational rate of solvent sampling 20 times faster than standard MD with explicit solvent. Further substantial acceleration can be achieved with 3D-RISM-KH efficiently sampling essential events with rare statistics such as exchange and localization of solvent, ions, and ligands at binding sites and pockets of the biomolecule. 3D-RISM-KH was coupled with ab initio complete active space self-consistent field (CASSCF) and orbital-free embedding (OFE) Kohn-Sham (KS) density functional theory (DFT) quantum chemistry methods in an SCF description of electronic structure, optimized geometry, and chemical reactions in solution. The (OFE)KS-DFT/3D-RISM-KH multi scale method is implemented in the Amsterdam Density Functional (ADF) package and extensively validated against experiment for solvation thermochemistry, photochemistry, conformational equilibria, and activation barriers of various nanosystems in solvents and ionic liquids (ILs). Finally, the replica RISM-KH-VM molecular theory for the solvation structure, thermodynamics, and electrochemistry of electrolyte solutions sorbed in nanoporous materials reveals the molecular mechanisms of sorption and supercapacitance in nanoporous carbon electrodes, which is drastically different from a planar electrical double layer.

First author: Zanuy, David, Examining the formation of specific interactions between poly(3,4-ethylenedioxythiophene) and nucleotide bases, RSC ADVANCES, 3, 2639, (2013)
Abstract: The formation of specific interaction between poly(3,4-ethylenedioxythiophene) (PEDOT) and adenine (A), cytosine (C) and thymine (T) single stranded homonucleotides has been investigated, complementing our previous investigation on complexes formed by PEDOT and guanine (G) homonucleotide (B. Teixeira-Dias et al, Soft Matter, 2011, 7, 9922-9932). Results derived from UV-vis and FTIR spectroscopy suggest that A and, especially, C homonucleotides form adducts dominated by non-specific electrostatic interactions, while complexes with T homonucleotides show a behavior that differ from those found for A-, C- and G-containing systems. Results provided by molecular dynamics simulations were consistent with these experimental observations. Thus, specific interactions are much less abundant in A-and C-containing complexes than in those involving G. Moreover, simulations allowed us to detect a structural reorganization in the T-containing complexes, which occurs after their initial formation. This has been attributed to the optimization of electrostatic interactions rather than to the formation of new specific interactions, as was previously found in complexes with G. From the analysis of the interaction of the different nucleotides with an EDOT molecule it is concluded that the most stabilizing specific interaction corresponds to the formation of N-H center dot center dot center dot O-EDOT hydrogen bonds. Stabilization comes from electrostatic interactions, although the covalent contribution is non negligible.

First author: Sassmannshausen, Joerg, Taming the shrew: [TMEDALi-Zn(C2H4)(2)L] as a model compound for anionic ethene polymerisation, NEW JOURNAL OF CHEMISTRY, 37, 494, (2013)
Abstract: We describe the synthesis of the compound [(TMEDA)Li(mu-TMP)(mu-CH=CH2)Zn(C2H3)] (1) (TMEDA = N,N,N’,N’-tetramethylethylenediamine, TMP = 2,2,6,6-tetramethylpiperidide), which serves as a potential model compound for anionic ethene polymerisation, and its decomposition into the metallated compound [Li(mu-Me2NCH2CH2N(Me)CH2)(mu-TMP)Zn(C2H3)] (4). The previously reported compound [(PMDETA)K(mu-TMP)(mu-CHQCH(2))-Zn(CH2SiMe3)] (2) (PMDETA = N,N,N’,N ”,N ”-pentamethyldiethylene-triamine) and 1 are used as potential model compounds for anionic ethene polymerisation. Detailed Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level of theory on both 1 and 2 in conjunction with Bader AIM and NBO analyses revealed a substantial interaction between the Zn-CH atom and the Li (in 1, d(Li-CH) = 2.43 angstrom) or K (in 2, d(K-CH) = 3.01 angstrom). In fact, in the case of 1, this interaction is even stronger (estimated to be 20-30 kJ mol(-1)) than those reported in the previously reported DFT studies of the reaction with butyl lithium and ethene in the presence of diamino ligands. Our theoretical results are in good agreement with experimentally observed parameters.

First author: Soleimani, Esmaiel, Synthesis, spectral and thermal behavior of two novel complexes of Cr(III) with dibromobenziloxime, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 111, 129, (2013)
Abstract: The reaction of 4,4′-dibromobenzilmonoxime (BBOH) with CrCl3 center dot 6H(2)O in DMF gives the mono nuclear Cr(III) complex, [Cr(BBO)(3)] (1). Reaction of complex (1) with a methanolic solution of KOH at room temperature leads to a dinuclear Cr(III)-Cr(III) complex, [Cr(BBO)(2)(OH)](2) (2). Both complexes were characterized on the basis of their elemental analysis, molar conductivity, Mass, IR, electronic spectra, and thermal analysis methods in addition to magnetic susceptibility technique. These studies suggest that oxime ligand is bonded to Cr(III) ions through the oxygen atom of the carbonyl, and the nitrogen atom of the oxime groups. In addition, the presence of a hydroxo bridge in the dimeric complex (2) is inferred from the IR spectral studies. The electronic spectral data of both complexes are in good agreement with the octahedral coordination of Cr(III) ion. The electronic spectra of the complexes revealed two bands due to d-d transitions, and one band assignable to an oxygen (p (pi)) -> Cr(e (g) *) LMCT transition observed in both Cr(III) complexes. An additional charge transfer transition, assignable to mu-OH(p (pi)) -> Cr(e (g) *), was only observed for the dimeric Cr(III) complex (2). The ligand field parameters for these complexes, i.e., splitting energy and Racah parameter were calculated to be 18,382 and 557 cm(-1) for [Cr(BBO)(3)] (1), 18,248 and 553 cm(-1) for [Cr(BBO)(2)(OH)](2) (2) respectively.The reaction of 4,4′-dibromobenzilmonoxime (BBOH) and CrCl3 center dot 6H(2)O in DMF has yielded the monomeric complex [Cr(BBO)(3)]. Addition of KOH to this monomeric complex afforded the dimeric complex [Cr(BBO)(2)(OH)](2).

First author: Pan, Qing-Jiang, Bisactinyl halogenated complexes: relativistic density functional theory calculation and experimental synthesis, RSC ADVANCES, 3, 1572, (2013)
Abstract: Relativistic density functional theory was used to explore a series of bisactinyl complexes, [(phen)(An(VI)O(2))(mu(2)-F)(F)](2) (An = U (1), Np (2) and Pu (3); phen = phenanthroline; mu(2) = doubly bridged), [(phen)((UO2)-O-V)(mu(2)-F)(F)](2)(2-) (4), [(phen)((UO2)-O-VI)(mu(2)-X)(X)](2) (X = Cl (5), Br (6) and I (7)), [(L)((UO2)-O-VI)(mu(2)-F)(F)](2) (L = bpy (8), 2NH(3) (9) and 2F (10); bpy = 2,2′-bipyridine) and [NH4](4)[(F)(2)((UO2)-O-VI)(mu(2)-F)(F)](2) (11). The effects of varying actinyl ions (UO22+, NpO22+ and PuO22+), oxidation states of uranium (VI and V) and equatorial ligands (phen -> bpy -> 2NH(3) -> 2F and F -> Cl -> Br -> I) on the structures and electronic properties of complexes were examined. The calculated distances and bond orders of An=O indicate the partial triple bonding character, and agree with the trends in the An=O stretching vibrational frequencies. The free energies of formation reactions of 1-11 calculated in the aqueous solution demonstrate that 1, 8 and 11 are thermodynamically stable. In this work, we have successfully synthesized 1 and [Me2NH2](4)[(F)(2)((UO2)-O-VI)(mu(2)-F)(F)](2) (12), which is represented by theoretical model complex 11. Their characterizations of the single crystal X-ray diffraction and infrared are consistent with the calculated results; the measured fine-structured fluorescent emissions were assigned as transitions from the U=O bonding to the U (f) orbital by analyzing the electronic structure and absorption spectra.

First author: Liao, Meng-Sheng, Factors that distort the heme structure in Heme-Nitric Oxide/OXygen-Binding (H-NOX) protein domains. A theoretical study, JOURNAL OF INORGANIC BIOCHEMISTRY, 118, 28, (2013)
Abstract: DFT and dispersion-corrected DFT calculations were carried out to probe the factors that distort the heme structure in Heme-Nitric oxide/OXygen-binding (H-NOX) protein domains. Various model systems that include heme, heme + surrounding residues, and heme + surrounding residues + additional protein environment were examined: the latter system was calculated with a quantum mechanics/molecular mechanics (QM/MM) method. The computations were extended to a myoglobin (Mb) protein, in which the heme structure is quite planar, in contrast to that in H-NOX. The natural tendency of the heme is to be planar. The strong structural distortion in H-NOX is mainly brought about by the intermolecular interactions between the whole heme molecule (heme ring plus its peripheral substituents) and the surrounding residues, among which the polar residues (Tyr140, Pro115, Mse98) play major roles in distorting the heme structure. The two peripheral propionate substituents that are oriented on the same side of the heme plane can also make the molecule distort, but the distortion caused by this factor is not significant. In Mb, the surrounding residues considered are all nonpolar and do not cause a structural distortion. The different structural features of the heme macrocycle in the different proteins (H-NOX and Mb) are reproduced by the calculations. The dispersion correction is necessary, since it improves the calculated structures. The effects of the distortion on the binding affinity of the axial ligand to the heme were also examined.

First author: Riddlestone, Ian M., Salt metathesis for the synthesis of M-Al and M-H-Al bonds, DALTON TRANSACTIONS,42, 249, (2013)
Abstract: Salt metathesis has been exploited in the synthesis of M-Al bonds, stabilized by a variety of chelating N-donor substituents at aluminium and including the first examples of such systems featuring ancillary guanidinato frameworks. Importantly, this synthetic approach can be extended to the synthesis of sigma-alane complexes through the use of hydride-containing transition metal nucleophiles. Cp’Mn(CO)(2)-[H(Cl)Al-{((NPr)-Pr-i)(2)CPh}] synthesized via this route features an alane ligand bound in a more ‘side-on’ fashion than other alane complexes, although DFT calculations imply that the potential energy surface associated with variation in the Mn-H-Al angle is a very soft one.

First author: Ramanantoanina, Harry, General treatment of the multimode Jahn-Teller effect: study of fullerene cations,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 1252, (2013)
Abstract: A general model for the analysis of the Adiabatic Potential Energy Surfaces (APES) of the molecules that are subject to the multimode Jahn-Teller effect is presented. The method utilizes the information obtained by DFT calculations on a distorted stationary point on the APES. The essence of the model is to express the distortion along a model minimal energy path called Intrinsic Distortion Path (IDP), projecting the geometry of the system on the normal modes of the either high-symmetry (HS) or low symmetry (LS) nuclear configuration. This allows us to determine the significance of all of the involved normal modes along a relevant particular path of distortion, and the direct calculation of the vibronic coupling constants. The IDP analysis is illustrated by the discussion of the multimode H circle times (g + 2h) JT effect in fullerene cations (C-60(+)) giving a deep insight into the origin and the mechanism of vibronic coupling in fullerene based molecules.

First author: Pubill-Ulldemolins, Cristina, Rhodium-NHC complexes mediate diboration versus dehydrogenative borylation of cyclic olefins: a theoretical explanation, DALTON TRANSACTIONS, 42, 746, (2013)
Abstract: In rhodium catalysed borylation of cyclic olefins, the synergy between bidentate NHC ligands, that modify cationic Rh(I) species, and the use of non-polar solvents, such as cyclohexane, is the key factor to favour a less energetically demanding route towards the formation of diborated products versus allyl boronate esters.

First author: Ronca, Enrico, Influence of the dye molecular structure on the TiO2 conduction band in dye-sensitized solar cells: disentangling charge transfer and electrostatic effects, ENERGY & ENVIRONMENTAL SCIENCE, 6, 183, (2013)
Abstract: We report a thorough theoretical and computational investigation of the effect of dye adsorption on the TiO2 conduction band energy in dye-sensitized solar cells that is aimed at assessing the origin of the shifts induced by surface adsorbed species in the position of the TiO2 conduction band. We thus investigate a series of working dye sensitizers and prototypical surface adsorbers and apply an innovative approach to disentangle electrostatic and charge-transfer effects occurring at the crucial dye-TiO2 interface. We clearly demonstrate that an extensive charge rearrangement accompanies the dye-TiO2 interaction, which amounts to transfer of up to 0.3-0.4 electrons from the dyes bound in a dissociative mode to the semiconductor. Molecular monodentate adsorption leads to a much smaller CT. We also find that the amount of CT is modulated by the dye donor groups, with the coumarin dyes showing a stronger CT. A subtle modulation of the semiconductor conduction band edge energy is found by varying the nature of the dye, in line with the experimental data from the literature obtained by capacitance and open circuit voltage measurements. We then decompose the total conduction band shift into contributions directly related to the sensitizer properties, considering the effect of the electric field generated by the dye on the semiconductor conduction band. This effect, which amounts to ca. 40% of the total shift, shows a linear correlation with the TiO2 conduction band shifts. A direct correlation between the dye dipole and the observed conduction band shift is retrieved only for dyes of similar structure and dimensions. We finally found a near-exact proportionality between the amount of charge transfer and the residual contribution to the conduction band shift, which may be as large as 60% of the total shift. The present findings constitute the basis for obtaining a deeper understanding of the crucial interactions taking place at the dye-semiconductor interface, and establish new design rules for dyes with improved DSC functionality.

First author: Boettcher, Tobias, (NHCMe)SiCl4: a versatile carbene transfer reagent synthesis from silicochloroform,CHEMICAL SCIENCE, 4, 77, (2013)
Abstract: A new synthetic pathway for the N-heterocyclic carbene adduct (NHCMe)SiCl4 (2) (NHCMe = 1,3-dimethylimidazolidin-2-ylidene) using silicochloroform is presented. Supported by DFT calculations, the energy for dissociation of 2 into the carbene and the SiCl4 fragment was found to be comparable to carbene transfer reagents based on silver(I) chloride. Compound 2 was used to transfer the NHC ligand to three different phosphorus(III) chloro compounds, resulting in the neutral complexes (NHCMe)PCl3 (3a), (NHCMe)PCl2Ph (3b) and (NHCMe)PCl2Me (3c). The sterically non-demanding NHC ligand allowed the phosphorus(III) in complex 3a to be oxidized to phosphorus(V) without loss of the NHC ligand, and afford (NHCMe)PF4H (4). Furthermore, bis-carbene complexes of Ni(II) (5) and Pd(II) (6) were obtained by reacting 2 with the respective metal chlorides.

First author: Chen, Ning, Sc2S@C-2(7892)-C-70: a metallic sulfide cluster inside a non-IPR C-70 cage, CHEMICAL SCIENCE, 4, 180, (2013)
Abstract: A new cage isomer of C-70, Sc2S@C-2(7892)-C-70, has been isolated and characterized by mass spectrometry, UV-Vis-NIR absorption spectroscopy, cyclic voltammetry and DFT calculations. The combined experimental and computational studies lead to the unambiguous assignment of the cage symmetry to C-2(7892)-C-70. The comparison between Sc2S@C-2(7892)-C-70 and related endohedral structures has been discussed. A close structural resemblance between Sc2S@C-2(7892)-C-70 and Sc2S@C-s(10 528)-C-72 suggests that the conversion of these two molecules may be the result of a simple insertion of C-2 and the structural difference between Sc2S@C-2(7892)-C-70 and Sc3N@C-2v(7854)-C-70 shows that the nature and geometry of the encaged cluster plays an important role on the selection of the non-IPR cage.

First author: Acharya, Suvra, Synthesis, characterization, X-ray structure and spectroscopic study of platinum(II) complexes with tridentate diazene ligands having O,N,S donor set, INORGANICA CHIMICA ACTA, 394, 757, (2013)
Abstract: At room temperature, 2-hydroxy-1-(2′-alkylthiophenylazo)naphthalenes and 1-hydroxy-2-(2′-alkylthiophenylazo)napthalenes (HL) slowly react with di-mu-chloro-bis(eta(3)-2-methylallyl)platinum(II) in chloroform and afford complexes of the type [Pt-II(L) Cl]. Potassium tetrachloroplatinate also reacts with the HL group of ligands in acetonitrile medium under reflux condition and produces complexes of the type [Pt-II (L)Cl]. All the platinum complexes [Pt-II(L)Cl] have been successfully isolated in pure form and characterized by spectroscopic techniques. The solid state structures of [Pt-II(L-3)Cl] (3) and [Pt-II(L-9)Cl] (9) have been determined by single crystal X-ray diffraction. The crystal structures have revealed that diazene ligands bind to the metal ion as monoanionic terdentate O,N,S donors and the fourth coordination position is occupied by a halide ion. All the platinum(II) complexes absorb strongly in the ultraviolet and visible region. The TD-DFT (time-dependent density functional theory) calculation has been carried out for better understanding of the electronic structure of platinum(II) complexes and the nature of spectral transitions. The low energy absorptions are attributed to intraligand charge transfer transitions having admixtures of metal-to-ligand charge-transfer transitions whereas the high energy absorptions are due to ILCT and LLCT transitions. The reactivity of [Pt-II(L) Cl] with iodine and methyl iodide has been studied.