2012 publications citing ADF

First author: Jamshidi, Z, Binding of Noble Metal Clusters with Rare Gas Atoms: Theoretical Investigation, JOURNAL OF PHYSICAL CHEMISTRY A, 116, 12510, (2012)
Abstract: Binding of noble metal clusters (M-n, M = Cu, Ag and Au; n = 2-4) with rare gas atoms (Rg = Kr, Xe, and Rn) has been investigated at the density functional (CAM-B3LYP) and ab initio (MP2) levels of theory. The calculation shows significant affinity of neutral metal clusters for interaction with rare gas atoms. The binding energies indicate that gold clusters have the highest and silver clusters have the lowest affinity for interaction with rare gas atoms, and for the same metal clusters, there is a continuous increase in E-b from Kr to An. The M-Rg bonding mechanism have been interpreted by means of the quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and energy decomposition analysis (EDA). According to these theories, the M-Rg bonds are found to be partially electrostatic and partially covalent. EDA results identify that these bonds have less than 40% covalent character and more than 60% electrostatic, and also NBO calculations predict the amount of charge transfer from the lone pair of rare gas to sigma* and n*orbitals of metal clusters.

First author: Dau, PD, Photoelectron Spectroscopy of Palladium(I) Dimers with Bridging Allyl Ligands,ORGANOMETALLICS, 31, 8571, (2012)
Abstract: The dianionic Pd-I dimers [TBA](2)[(TPPMS)(2)Pd-2(mu-C3H5)(2)] (1) [TBA = tetrabutylammonium, TPPMS = PPh2(3-C6H4SO3)(-)] and [TBA](2)[(TPPMS)(2)Pd-2(mu-C3H5)(mu-Cl)] (2), containing two bridging allyl ligands and one bridging allyl ligand and one bridging chloride ligand, respectively, were synthesized. The electronic structures of these complexes were investigated by combining electrospray mass spectrometry with gas phase photodetachment photoelectron spectroscopy. The major difference between the photoelectron spectra of the anions of 1 and 2 is the presence of a low-energy detachment band with an adiabatic electron detachment energy of 2.44(6) eV in 1, which is not present in 2. The latter has a much higher adiabatic electron detachment energy of 3.24(6) eV. Density functional theory calculations suggest that this band is present in 1 due to electron detachment from the out-of-phase combination of the pi(2) orbitals, which are localized on the terminal carbon atoms of the bridging allyl ligands. In 2, the Pd centers stabilize the single pi(2) orbital of the bridging allyl ligand, and it is lowered in energy. The presence of the high-energy out-of-phase combination of the pi(2) allyl orbitals makes 1 a better nucleophile, which explains why species with two bridging allyl ligands react with CO2 in an analogous fashion to momoneric Pd eta(1)-allyls, whereas species with one bridging allyl and one bridging chloride ligand are unreactive.

First author: Harb, MK, Comparison of S and Se dichalcogenolato [FeFe]-hydrogenase models with central S and Se atoms in the bridgehead chain, TETRAHEDRON, 68, 10592, (2012)
Abstract: In order to study the influence of sulfur and selenium atoms incorporated into the structure of complexes that model the active site of [FeFe]-hydrogenases, a series of diiron dithiolato and diselenolato complexes of the form (mu-ECH2XCH2E-mu)Fe-2(CO)(6) have been prepared and characterized, where the diiron bridging atoms E are S or Se, and the linker bridgehead X is CH2, S. or Se. The electron energies have been compared by gas-phase photoelectron spectroscopy, and the oxidation, and reduction behaviors, as well as the ability to reduce protons from acetic acid to form H-2, have been compared by cyclic voltammetry. Density functional theory computations agree well with the structures and electron energies of these molecules, and shed additional light on the oxidation and reduction properties. The computations indicate that the HOMO of each molecule where the bridgehead X is S or Se contains substantial chalcogen ‘lone pair’ orbital character. The presence of the bridgehead chalcogen lone pairs favors the Fe(CO)(3) ‘rotated’ structures for both the cations and dianions of these complexes, but in different ways. In the cations one Fe(CO)(3) rotates to put one carbonyl ligand in a semibridging position, and the bridgehead chalcogen lone pair electrons donate to the vacant coordination site created on the iron to stabilize the positive charge. In the dianions one Fe(CO)(3) rotates to put one carbonyl ligand in a fully bridging position, and one bridging chalcogen atom breaks its bond with an iron atom, pulling the bridgehead chalcogen lone pair away from the iron to minimize the electron-electron repulsions.

First author: Taylor, AJ, Ultrafast Intramolecular Charge Separation in a Donor-Acceptor Assembly Comprising Bis(eta(5)-cyclopentadienyl)molybdenum Coordinated to an Ene-1,2-dithiolate-naphthalenetetracarboxylicdiimide Ligand,INORGANIC CHEMISTRY, 51, 13181, (2012)
Abstract: The first example of a Donor-spacer-Acceptor tryad, based upon a molybdenum-ene-1,2-dithiolate unit as the Donor and a naphthalene-diimide as the Acceptor, has been synthesized and its photophysical properties investigated. Synthesis required the preparation of a new pro-ligand containing a protected ene-1,2-dithiolate bound through a phenyl linkage to a naphthalenetetracarboxylicdiimide (NDI) group. Deprotection of this pro-ligand by base hydrolysis, followed by reaction with [Cp2MoCl2], produced the new dyad [Cp2Mo(SC(H)C(C6H4-NDI)S)] (2). Electrochemical studies showed that 2 can be reversibly oxidized to [2](+) and reduced to [2](-), [2](2-), and [2](3-). These studies, augmented by UV/vis, IR, and electron paramagnetic resonance (EPR) spectra of electrochemically generated [2](+) and [2](-), show that the highest occupied molecular orbital (HOMO) of 2 is ene-1,2-dithiolate-based and the lowest unoccupied molecular orbital (LUMO) is NDI-based; these conclusions are supported by density functional theory (DFT) calculations for the electronic ground state on a model of 2 which also showed that these two parts of the molecule are electronically distinct. The dynamics of the excited states of 2 in CH2Cl2 solution were investigated by picosecond time-resolved IR spectroscopy following irradiation by a 400 nm similar to 120 fs laser pulse. These investigations were complemented by an ultrafast transient absorption spectroscopic study from 420 to 760 nm of the nature of the excited states of 2 in CH2Cl2 solution following irradiation by a 383 nm similar to 120 fs laser pulse. These studies showed that irradiation of 2 at both 400 and 383 nm leads to the formation of the [(Cp)(2){Mo(dt)}(+)-Ph-{NDI}(-)] charge-separated state as a result of a cascade electron transfer initiated by the formation of an (NDI)-N-1* excited state. (NDI)-N-1* rapidly (ca. 0.2 ps) forms the local charge transfer state [Cp2Mo(dt)-{Ph}(+)-{NDI)(-)] which has a lifetime of about 1.7 ps and decays to produce the ground state and the charge-separated state [(Cp)(2){Mo(dt)}(+)-Ph-{NDI}(-)]; the latter has an appreciable lifetime, about 15 ns in CH2Cl2 at room temperature.

First author: Hansen, DF, Further studies into the reactivity and coordination chemistry of [Ge-9](4-) Zintl ions. The indium-containing anions [In(Ge-9)(2)](5-), [(Ge-9)(2)In(C6H5)](4-) and [Ge-9{In(C6H5)(3)}(2)](4-), JOURNAL OF ORGANOMETALLIC CHEMISTRY, 721, 53, (2012)
Abstract: Reactions between ethylenediamine solutions of K4Ge9 and triphenylindium yielded three novel Zintl ions, [In(Ge-9)(2)](5-) (1), [(Ge-9)(2)In(C6H5)](4-) (2), and [Ge-9{In(C6H5)(3)}(2)}](4-) (3). Species 1 exhibits an indium metal atom coordinated by two nine-atom germanium cages which bond to the central metal in an eta(3)-mode. The “staggered” arrangement of the two clusters confers the indium metal centre an octahedral coordination geometry. Species 2 displays trigonal planar coordination around the indium atom with an [In(C6H5)](2+) moiety acting as a bridge between the two halves of a [Ge-9-Ge-9](6-) dimer. Finally, species 3 is composed of a [Ge-9](4-) deltahedral Zintl ion acting as a Lewis base to two In(C6H5)(3) moieties. All three anions were characterized in the solid-state by single-crystal X-ray diffraction in [K(2,2,2-crypt)](5)[1]center dot 2en, [K(2,2,2-crypt)](4)[2]center dot 3tol and [K(2,2,2-crypt)](4)[3], respectively. The existence of the anions in solution was confirmed by electrospray mass-spectrometry. DFT level calculations were also conducted on all of the cluster anions.

First author: Li, JR, Photoinduced electron transfer processes in dye-semiconductor systems with different spacer groups,JOURNAL OF CHEMICAL PHYSICS, 137, 53, (2012)
Abstract: Photoinduced electron transfer processes in perylene-titanium dioxide dye-semiconductor systems are studied. In particular, the influence of saturated and unsaturated aliphatic spacer groups inserted between the chromophore and the semiconductor substrate is investigated. The study is based on a recently developed method that combines first-principles electronic structure calculations to characterize the dye-semiconductor systems and accurate multilayer multiconfiguration time-dependent Hartree simulations to reveal the underlying nonadiabatic dynamics. The results show that, in agreement with previous experimental studies, the spacer groups may affect the electron transfer dynamics significantly. Furthermore, the influence of electronic-vibrational coupling on the electron transfer dynamics and absorption spectra is discussed.

First author: Tian, Y, Speciation of nickel (II) chloride complexes in hydrothermal fluids: In situ XAS study, CHEMICAL GEOLOGY, 334, 345, (2012)
Abstract: In situ XAS data of Ni(II) chloride solutions with various salinities (0-7.68 m) were collected to investigate the stoichiometry and geometry of Ni(II) chloride complexes from room temperature up to 369 degrees C at 400 bar, and to 434 degrees C at 600 bar. Increasing temperature and/or salinity results in a change in the coordination of the Ni(II) chlorocomplexes from octahedral to (distorted) tetrahedral. Octahedral species predominate within the whole salinity range at room temperature and up to similar to 200 degrees C, and tetrahedral species become significant beyond this temperature. At 369 degrees C and 400 bar, octahedral species remain in equilibrium with tetrahedral species, and the number of chloride ligands in the first coordination shell depends on the Cl:Ni molar ratio. EXAFS refinements and ab initio XANES calculations show that the highest order chlorocomplex present over the investigated pressure, temperature and composition ranges is the distorted tetrahedral complex [NiCl3(H2O)](-), which predominates in the highest Cl concentration (7.68 m) solution at 434 degrees C and 600 bar. A quantitative thermodynamic analysis of the XANES and EXAFS data reveals that the XAS data are consistent with the speciation models derived from recent UV-Vis spectrophotometric measurements (25 degrees C-250 degrees C, 100 bar; Liu et al., 2012b) and the high temperature, high pressure solubility experiments of Lin and Popp (1984) and Fahlquist and Popp (1989), if the NiCl2(aq) species exists in both octahedral ([NiCl2(H2O)(4)]((aq))) and tetrahedral ([NiCl2(H2O)(2)]((aq))) forms, with the ratio of octahedral to tetrahedral decreasing at high temperature (>200 degrees C). The new XAS data show that the octahedral to tetrahedral transition in Ni(II) chloride complexes occurs at higher temperature and/or salinity than the corresponding Co(II) complexes (Liu et al., 2011).

First author: Pellarin, KR, Oxidative Addition of Phthaloyl Peroxide to Dimethylplatinum(II) Complexes,ORGANOMETALLICS, 31, 8291, (2012)
Abstract: Complexes [PtMe2(NN)], with NN = 2,2′-bipyridine (bipy), 4,4′-di-tert-butyl-2,2′-bipyridine (bu(2)bipy), di-2-pyridylamine (dpa), or di-2-pyridyl ketone (dpk), react easily with phthaloyl peroxide to give a mixture of the chelate complex [PtMe2{kappa(2)-O,O’-1,2-(O2C)(2)C6H4}(NN)], which was structurally characterized when NN = bu(2)bipy, and an oligomer or polymer [PtMe2{mu-kappa(2)-O,O’-1,2-(O2C)(2)C6H4}(NN)](n). In the case with NN = dpa, no phthalate chelate complex is formed. These complexes are easily hydrolyzed, and the complexes cis-[PtMe2(OH){kappa(1)-O-O2CC6H4-2-CO2H}(bipy)] and trans-[PtMe2{kappa(1)-O-O2CC6H4-2-CO2H}(dpkOH)] have been structurally characterized. It is argued that the oxidative addition of phthaloyl peroxide occurs by a polar mechanism and that the hydrolysis is easy because there is no special stability associated with the seven-membered platinum-phthalate chelate ring.

First author: Kocherzhenko, AA, Effects of the Environment on Charge Transport in Molecular Wires, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 25213, (2012)
Abstract: Supramolecular engineering offers opportunities for creating polymer-based materials with tailored conductive properties. However, this requires an understanding of intermolecular interaction effects on intramolecular charge transport. We present a study of hole transport along molecular wires consisting of fluorene-p-biphenyl or Zn-porphyrin monomer units, in dilute solutions. The intramolecular hole mobility was studied by pulse radiolysis time-resolved microwave conductivity. Experiments were supplemented by charge transport simulations employing a quantum-mechanical description of the hole and a classical description of the polymer and solvent dynamics. The model was parametrized using ab initio and molecular dynamics calculations. It was found that the solvent-induced energy disorder along a polymer chain in common solvents (benzene, cyclohexane, acetonitrile, water) is similar to 1 eV, significantly greater than the values of 0.05-0.2 eV commonly cited in the literature. Environment-induced disorder of this magnitude has profound consequences for intramolecular charge transport. The hole initial state upon injection onto a molecular wire also influences the mobility. Experiments and simulations demonstrate that supramolecular modification of polymers (coordination, rotaxination) can significantly enhance or suppress charge transport. Incorporating a molecular level description of the immediate supramolecular and solvent environment into charge transport models improves their predictive potential, providing a valuable tool for material design.

First author: Manna, D, Prediction of a New Series of Thermodynamically Stable Actinide Encapsulated Fullerene Systems Fulfilling the 32-Electron Principle, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 25630, (2012)
Abstract: Density functional theory (DFT) within the framework of zeroth order regular approximation has been used to predict a new class of stable clusters through encapsulation of an actinide or lanthanide atom/ion into the C-26 cage. The electronic structures, bonding, stability, aromaticity and spectroscopic properties of these endohedral metallofullerenes, M@C-26 (M = Pr-, Pa-, Nd, U, Pm+, Np+, Sm2+, Pu2+, Eu3+, Am3+, Gd4+, and Cm4+) have been investigated systematically using DFT and its time-dependent variant. On encapsulation of an f-block metal atom/ion with 6 valence electrons, the classical bare open shell C-26 cage with D-3h symmetry and ellipsoid shape is transformed to a more spherical closed shell D-3h structures with high HOMO-LUMO gap (in the range of 2.44-3.99 eV for M@C-26 clusters as compared to 1.62 eV for the bare C-26 cage). Calculated binding energy values imply that all of the M@C-26 clusters are stable with respect to dissociation into atomic fragments. Moreover, thermodynamic parameters indicate that the encapsulation process is highly favorable for all of the actinides and some of the lanthanides considered here. A higher stability and nearly spherical shape of M@C-26 system is rationalized through the fulfillment of 32-electron principle corresponding to the fully occupied spdf atomic shells for the encapsulated central atom, where considerable amount of overlap between the metal and cage orbitals has been found. Thus, the calculated structural and energetic parameters strongly suggest the possible formation of M@C-26 species under appropriate experimental conditions. Furthermore, the present work implies that the 32-electron principle might be important in designing of new materials involving lanthanides and actinides.

First author: Hatakeyama, T, Azaboradibenzo[6]helicene: Carrier Inversion Induced by Helical Homochirality, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 134, 19600, (2012)
Abstract: Azaboradibenzo[6]helicene, a new semiconductor material possessing helical chirality, has been synthesized via a tandem bora-Friedel Crafts-type reaction. Unprecedented carrier inversion between the racemate (displaying p-type semiconductivity) and the single enantiomer (displaying n-type semiconductivity) was observed and can be explained by changes in the molecular packing induced by helical homochirality.

First author: Asaduzzaman, AM, Relationship between dye-iodine binding and cell voltage in dye-sensitized solar cells: A quantum-mechanical look, JOURNAL OF COMPUTATIONAL CHEMISTRY, 33, 2492, (2012)
Abstract: It has been proposed that iodine binding to dyes may actually decrease the cell efficiency of a dye-sensitized solar cell. A previous experimental study showed that a two-atom change from oxygen to sulfur increased recombination of iodine with injected electrons by a factor of approximately 2. Here, it is shown that iodine binding is a plausible explanation for this effect. The steric and conjugation effects are quantified separately using a set of model compounds. Quantum-chemical calculations show that elongation of the hydrocarbon chain has only an insignificant effect on the iodine and bromine binding to the chalcogen atoms (O, S, Se). The conjugation, however, significantly disfavors the iodine and bromine interaction. Iodine and bromine binding to the dye and model compounds containing sulfur is significantly more favorable than to their oxygen containing counterparts. Bromine binding to dyes is shown to be stronger than that of iodine. Accordingly, bromine binding to dyes may contribute significantly to the observed lower efficiencies in cells using Br?3-/Br- as the redox couple.

First author: Ferraro, F, Bonding, energetic, electronic delocalization and optical properties of MCp3 complexes, where M = Sc, Y, La, Ac, Lu, Ce, Yb and Th, CHEMICAL PHYSICS LETTERS, 554, 219, (2012)
Abstract: In this work we evaluated the bonding nature and electronic properties of a series of metal-cyclopentadienyl MCp3 complexes. The Morokuma-Ziegler analysis show a covalent character increase of the metal-ligand bond in the following order: transition-metals > actinide > lanthanide containing molecules. NBO and frequency analysis shows a similar behavior. TD-DFT calculation shows a red shift for the a ” -> a’ transition, which is common to all the complexes. The NICSzz values and ELF analysis show a ring electron delocalization change due to a combined effect between the more external metal orbitals ‘nd’ and the interaction with the hydrogens of the neighboring ring.

First author: Giorgi, G, Neutron generation via the mechanism adsorption of pressurized deuterium on an electron deficient titanium matrix. An MD-DFT combined analysis on the mechanism of the Ti-D bond formation, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 37, 18959, (2012)
Abstract: In the present paper the mechanism behind the neutron generation experiment in titanium lattice alloyed with deuterium atoms is investigated via both a static Density Functional Theory and a Molecular Dynamics approach. In particular, the hypothesized formation of a three-centre-two-electrons (3c-2e) bond, which is typical of electron-deficient species alloyed with H and its heavy isotopes (D, T), is investigated. In the context of the static analysis, a two-fold approach is taken into account, i.e., a cluster one to describe the bonding environment and the nature of the orbitals involved in such a bond, and a periodic one through which the occurrence of this peculiar feature is investigated as a function of deuterium atom concentrations in the Ti lattice. The octahedral subcell is found to be the most suitable site for the formation of this bond. A saturation value of two deuterium atoms for the 3c-2e bond per octahedral/tetrahedral subcell is also reported. Molecular Dynamics analysis performed at ordinary T by means of a Nose thermostat reveals the possibility for two deuterium atoms to occupy at the same time the T-d and the O-h site of vicinal subcells.

First author: Schulten, C, Deoxygenation of carbon dioxide by electrophilic terminal phosphinidene complexes,CHEMICAL SCIENCE, 3, 3526, (2012)
Abstract: Deoxygenation of carbon dioxide was achieved using transient terminal phosphinidene chromium and tungsten complexes 2a,b. The overall reaction is exothermic according to DFT calculations on the model terminal P-methyl phosphinidene complex Me-2b; this was also supported by the calculated thermodynamic oxygen-transfer potential. The oxaphosphiran-3-one complex intermediates 3a,b possess an unprecedented bonding situation as some characteristics of a side-on bound carbon dioxide to the (formally) low-coordinated phosphorus centre come to the fore. This is expressed by equidistant P-C and P-O bonds and unusual bond strength relationship, i.e. P-C > P-O, as revealed by the relaxed force constants and other related parameters. The decomposition of 3a,b via CO extrusion yields terminal phosphinidene oxide complexes 4a,b which dimerise to the final products, the 1,3-dioxa-2,4-diphosphetane complexes 5a,b-8a,b. Additional experimental evidence for the transient formation of phosphinidene oxide complexes 4a,b was obtained by a cross dimerisation experiment using transient chromium and tungsten complexes 2a,b. First comparative investigations on the reaction of Li-Cl phosphinidenoid complex 10 and CO2 at low temperature revealed the formation of the carbamoyl-phosphane complex 11.

First author: Weymiens, W, Bis(azidophenyl)phosphole Building Block for Extended pi-Conjugated Systems, EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, 3, 6711, (2012)
Abstract: Novel bis(azidophenyl)phosphole sulfide building block 8 has been developed to give access to a plethora of phosphole-containing p-conjugated systems in a simple synthetic step. This was explored for the reaction of the two azido moieties with phenyl-, pyridyl- and thienylacetylenes, to give bis(aryltriazolyl)-extended p-systems, having either the phosphole sulfide (9) or the phosphole (10) group as central ring. These conjugated frameworks exhibit intriguing photophysical and electrochemical properties that vary with the nature of the aromatic end-group. The ?3-phospholes 10 display blue fluorescence (?em = 460469 nm) with high quantum yield (FF = 0.1340.309). The radical anion of pyridyl-substituted phosphole sulfide 9b was observed with UV/Vis spectroscopy. TDDFT calculations on the extended p-systems showed some variation in the shape of the HOMOs, which was found to have an effect on the extent of charge transfer, depending on the aromatic end-group. Some fine-tuning of the emission maxima was observed, albeit subtle, showing a decrease in conjugation in the order thienyl < phenyl < pyridyl. These results show that variations in the distal ends of such p-systems have a subtle but significant effect on photophysical properties.

First author: Ortega-Carrasco, E, Computational insights on the possibility of tri-coordinated cisplatinated adducts with protein models, JOURNAL OF INORGANIC BIOCHEMISTRY, 117, 230, (2012)
Abstract: In the organism, cisplatin binds to numerous proteins. These interactions can ultimately lead to the emergence of resistance and side effects. Little is known on these recognition processes with only few crystallographic structures of cisplatinated proteins released so far. Some of them, like the monoadduct of cisplatin with the hen egg white lysozyme, display unexpected structural features. Instead of the usual square planar configuration of the metal, an apparent T-shaped geometry is observed. This tri-coordinated structure could be a consequence of some crystallographic limitations. However, the increasing reports of tri-coordinated Pt(II) organometallic complexes questions whether it could also have some physiological relevance. Here, we present a computational study allying pure quantum mechanical and hybrid quantum mechanical/molecular mechanics methodologies to shed light on this particular question. Calculations on monoadducts of cis-diamminediaquo-platinum(II) with protein models show that square planar geometries are, as expected, the most stable ones. Dehydrations leading to trigonal geometries have Gibbs energies ranging from 8 to 31 kcal/mol and indicate that some of them may be possible in a proteic environment. Nonetheless. we also observed that such conditions are not afforded in the hen egg white lysozyme adduct.

First author: Chen, XK, Effect of dihydropyrazine on structures and charge transport properties of N-heteropentacenes matters: A theoretical investigation, ORGANIC ELECTRONICS, 13, 2832, (2012)
Abstract: A family of N-heteropentacenes acted as promising candidates for organic semiconductor materials is of immense interest. It should be attributed to the following reasons that (1) the positions, numbers and valence-states of N atom in N-heteropentacenes can effectively tune their electronic structure, stability, solubility, and molecular stacking; (2) diverse intermolecular interaction and pi-stacking motifs appear in their crystals. The effect of the position and number of the 6-pi-pyrazine on their structures and charge-transport properties has been systematically investigated in our previous work (J. Phys. Chem. C 115 (2011) 21416). Therefore, in this work, the study on the role of 8-pi-dihydropyrazine with another valence-state N atoms is our focus. Density functional theory, Marcus electron transfer theory and Brownian diffusion assumption coupled with kinetic Monte-Carlo simulation are applied into this investigation. Our theoretical results indicate that in contrast with pyrazine, dihydropyrazine introduced is more helpful for promoting p-type organic semiconductor materials. For molecule 4, hole mobility of its single crystal theoretically reach 0.71 cm(2) V-1 s(-1), and coupled with its fine hole-injection ability, it should be a promising candidate for p-type organic semiconductor materials. Although the lowest triplet-state energies of the molecules studied are very small, introduction of dihydropyrazine is very helpful for increasing the energies.

First author: Yan, B, Molecular structure and thermal behavior of N-Benzoyl-3,3-dinitroazetidine, RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A, 86, 1962, (2012)
Abstract: N-Benzoyl-3,3-dinitroazetidine (BDNAZ) has been synthesized and characterized by elemental analysis, FT-IR spectroscopy, H-1 NMR and X-ray single crystal diffraction technique. BDNAZ crystallizes in the monoclinic space group P2(1)/c. Its thermal behavior was studied under a non-isothermal condition by DSC and TG/DTG methods, the value of E (a) and A of the exothermic decomposition reaction of BDNAZ are 143.19 kJ mol(-1) and 10(14.34) s(-1), respectively. The specific heat capacity of BDNAZ was determined with a continuous C (p) mode of micro-calorimeter and theoretical calculation. The adiabatic time-to-explosion was evaluated as 109.9-124.4 s.

First author: Javan, MJ, Can anion interaction accelerate transformation of cytosine tautomers? Detailed view form QTAIM analysis, STRUCTURAL CHEMISTRY, 23, 1843, (2012)
Abstract: The relative stabilities and noncovalent interactions of the six low-lying energy tautomers of cytosine nucleobase with some biological anions (such as F-, Cl-, and CN-) have been investigated in gas phase by density functional theory (DFT) method in conjunction with 6-311++G (d,p) atomic basis set. Furthermore, to systematically investigate all possible tautomerisms from cytosine induced by proton transfer, we describe a study of structural tautomer interconversion in the gas phase and in a continuum solvent using DFT calculation. We carried out geometrical optimizations with the integral equation formalism of polarizable continuum (IEF-PCM) model to account for the solvent effect, and the results were compared with those in the gas phase. The result of calculation revealed that anions bind mostly in a bidentate manner via hydrogen bond, and stabilization energies of these complexes are larger than those in the case when anions bind in a monodentate manner. The quantum theory of atoms in molecules (QTAIM), natural bonding orbital (NBO) and energy decomposition analysis (EDA) have also been applied to understand the nature of hydrogen bond interactions in these complexes. NBO analysis reveals that the interaction patterns between the anions and the tautomers are sigma-type interaction between lone pairs and , and antibonding orbitals. Also, according to these theories, the interactions are found to be partially electrostatic and partially covalent. EDA results identify that these bonds have less than 35% covalent character and more than 65% electrostatic, and the covalent character increases in different anions in the order F- > CN- > Cl-. On the other hand, orbital interaction energies of complexes of F- anion are more than those of Cl- and CN- complexes. The lower orbital interaction energies in complexes of Cl- and CN(-)anions imply less charge transfer and stronger ionic bond character. Furthermore, relationship between the orbital interaction energy (E (2)) with hydrogen bonding energy (E (H center dot center dot center dot X)) and the electron density (rho(r)) with hydrogen bonding energy of F-, Cl- and CN- complexes have also been investigated.

First author: Pandey, KK, Structure and Bonding Analysis of the Cationic Electrophilic Phosphinidene Complexes of Iron, Ruthenium, and Osmium [(eta(5)-C5Me5)(CO)(2)M{(PNPr2)-Pr-i}](+), [(eta(5)-C5H5)(CO)(2)M{PNR2}](+) (R = Me, Pr-i), and [(eta(5)-C5H5)(PMe3)(2)M{PNMe2}](+) (M = Fe, Ru, Os), JOURNAL OF PHYSICAL CHEMISTRY A, 116, 11753, (2012)
Abstract: Quantum-chemical DFT calculations for the electronic, molecular structure and M-PNR2 bonding analyses of the experimentally known cationic electrophilic phosphinidene complexes [(eta(5)-C5Me5)(CO)(2)M{(PNPr2)-Pr-i}](+) and of the model complexes [(eta(5)-C5H5)(CO)(2)M{PNR2}](+) (R = Pr-i, Me) and [(eta(5)-C5H5)(PMe3)(2)M{PNMe2}](+) were carried out using BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters of the studied complexes are in good agreement with the reported experimental values. The short M-P bond distances and calculated Pauling bond orders (range of 1.23-1.68), suggest the presence of M-P multiple bond characters. The Hirshfeld charge analysis shows that the overall charge flows from phosphinidene ligand to metal fragment. The M-P sigma-bonding orbitals are well-occupied (>1.80e). The energy decomposition analysis revealed that the contribution of the electrostatic interaction Delta E-elstat is, in all studied complexes, significantly larger (55.2-62.6%) than the orbital interactions Delta E-orb. The orbital interactions between metal and PNR2 in [(eta(5)-C5H5)(L)(2)M{PNR2}](+) arise mainly from M <- PNR2 sigma-donation. The pi-bonding contribution (19-36%) is much smaller than the sigma-bonding. The interaction energies, as well as bond dissociation energies, depend on the auxiliary ligand framework around the metal and decrease in the order (eta(5)-C5H5) > (eta(5)-C5Me5) and CO > PMe3. Upon substitution of R = Pr-i with smaller group R = Me, the M-PNR2 bond strength slightly decreases.

First author: Bernadotte, S, Origin-independent calculation of quadrupole intensities in X-ray spectroscopy, JOURNAL OF CHEMICAL PHYSICS, 137, 11753, (2012)
Abstract: For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these so-called quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an origin-independent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole and electric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within time-dependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes.

First author: Hofener, S, Calculation of electronic excitations using wave-function in wave-function frozen-density embedding, JOURNAL OF CHEMICAL PHYSICS, 137, 11753, (2012)
Abstract: Recently, a general framework suitable for general frozen-density embedding (FDE) methods was published [S. Hofener, A. S. P. Gomes, and L. Visscher, J. Chem. Phys. 136, 044104 (2012)]. In the present article, we report the fragmentation of a supermolecule while treating all subsystems with coupled-cluster theory and the interaction of the subsystems with density-functional theory. This variant is denoted wave-function theory in wave-function theory FDE, or coupled-cluster theory in coupled-cluster theory FDE. Main target of this approach is not the embedding of a single molecule in large solvation shells, but rather the possibility to divide a complex system consisting of several molecules when all subsystems are to be treated with, e. g., coupled-cluster methods to provide a balanced and unbiased description. We present numerical results for hydrogen-bonded complexes which exhibit rather strong interactions. Cases with weakly interacting subsystems are expected to exhibit even higher accuracy. This facilitates the study of properties of larger complexes such as DNA base pairs with coupled-cluster methods.

First author: Heydova, R, Spin-Orbit Treatment of UV-vis Absorption Spectra and Photophysics of Rhenium(I) Carbonyl-Bipyridine Complexes: MS-CASPT2 and TD-DFT Analysis, JOURNAL OF PHYSICAL CHEMISTRY A, 116, 11319, (2012)
Abstract: The lowest-lying spectral transitions in [ReX(CO)(3)(bpy)] (X = Cl, Br, I; bpy = 2,2′-bipyridine) complexes were calculated by means of spin-orbit time-dependent density functional theory (SO-TD-DFT), and spin-orbit multistate complete active space second-order perturbation theory (SO-MS-CASPT2). Computational results are compared with absorption spectra measured in different solvents and used to qualitatively explain the temperature dependence of the phosphorescence decay parameters that were measured for the whole series of complexes. Spin-orbit excited-state calculations interpret g their electronic absorption spectra as arising from a bunch of spin mixed states with a singlet component of only 50-90% (depending on the halide),. and attribute the phosphorescence decay to thermal population of spin-mixed states with a Substantial singlet character.

First author: Verzijl, CJO, DFT-Based Molecular Transport Implementation in ADF/BAND, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 24393, (2012)
Abstract: We present a novel implementation of the first-principles approach to molecular charge transport using the nonequilibrium Green’s function, formalism in combination. with the ADF/BAND periodic band structure DFT code, together with results for several example systems. As a proof of concept, we first discuss transport calculations on 1D chains of Li and Al atoms. We then present a detailed study of BDT and archetypal molecular wires from the OPE-family, sandwiched between 3D Au contacts, comparing well with results from the literature. Our implementation further allows us to make a comparison of 3D contacts with and without periodic boundary conditions, the latter being particularly useful for modeling the needle shaped contacts used in break-junction experiments.

First author: Jose, D, Understanding of the Buckling Distortions in Silicene, JOURNAL OF PHYSICAL CHEMISTRY C,116, 24639, (2012)
Abstract: Silicene, the all Si analogue of graphene is structurally different due to the presence of buckling distortions in the individual six membered rings. The sufficiently strong coupling between the unoccupied molecular orbitals (UMOs) with occupied molecular orbitals (OMOs) leads to pseudo-Jahn-Teller distortion (PJT) and the characteristic buckling in silicenes. sigma-pi separation analyses reveal that the sigma-backbone gets stabilized, whereas the pi-backbone is destabilized due to buckling. However, the stabilization of puckering sigma-backbone overwhelms the pi-backbone destabilization. This is exactly opposite to that of graphene. The cations like Li+ can suppress the PJT distortions resulting in a planar structure. This leads to opening of band gap (similar to 1.62 eV). Si substituted benzenes binds more strongly with Li+ than benzene. The mutual competition/synergy between the orbital interactions of the ring with the cation and the pi-charge density across the surface of molecule governs the stability of these complexes.

First author: Ji, M, Luminescent Properties of Metal-Organic Framework MOF-5: Relativistic Time-Dependent Density Functional Theory Investigations, INORGANIC CHEMISTRY, 51, 12389, (2012)
Abstract: The electronically excited state and luminescence property of metal organic framework MOF-5 were investigated using relativistic density functional theory (DFT) and time-dependent DFT (TDDFT). The geometry, IR spectra, and UV-vis spectra of MOF-S in the ground state were calculated using relativistic DFT, leading to good agreement between the experimental and theoretical results. The frontier molecular orbitals and electronic configuration indicated that the luminescence mechanism in MOF-5 follows ligand-to-ligand charge transfer (LLCT), namely, pi* -> pi, rather than emission with the ZnO quantum dot (QD) proposed by Bordiga et al. The geometry and IR spectra of MOF-5 in the electronically excited state have been calculated using the relativistic TDDFT and compared with those for the ground state. The comparison reveals that the Zn4O13 QD is rigid, whereas the ligands BDC2- are nonrigid. In addition, the calculated emission band of MOF-5 is in good agreement with the experimental result and is similar to that of the ligand H2BDC. The combined results confirmed that the luminescence mechanism for MOF-5 should be LLCT with little mixing of the ligand-to-metal charge transfer. The reason for the MOF-5 luminescence is explained by the excellent coplanarity between the six-membered ring consisting of zinc, oxygen, carbon, and the benzene ring.

First author: Jones, TE, Role of Inter- and Intramolecular Bonding on Impact Sensitivity, JOURNAL OF PHYSICAL CHEMISTRY A, 116, 11008, (2012)
Abstract: A picture of impact sensitivity based on the bond bundles of the electron charge density is developed, allowing the role of both inter- and intramolecular bonding interactions to be investigated. Impact sensitive materials were found to have a convergent intramolecular bond bundle with a low electron count that serves as a trigger linkage, while insensitive materials do not The shape and electron count of the intramolecular bond bundles was found to change between the gas phase and solid state due to the formation of intermolecular bond bundles. In the case of polynitrobenzenes, this change was subtle and did not affect the trigger linkages. However, the intermolecular bond bundles in crystalline RDX (hexahydro-1,3,S-trinitro-1,3,5-triazine) change from C-N trigger linkages in the gas phase to N-N trigger linkages in the solid state. This observation offers a theoretical justification of the experimentally observed differences in the decomposition behavior of gas phase and crystalline RDX.

First author: Conradie, J, Reactivity of [Rh(beta-diketonato)(cod)] complexes: A DFT approach, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 719, 8, (2012)
Abstract: The density functional theory calculated energies of the highest molecular orbital of [Rh(R’COCH-COR)(cod)] relate to the electrochemical oxidation potential of rhodium(I) to rhodium(III) in [Rh(R’COCHCOR)(cod)I complexes. They also relate to the experimental second order substitution rate constant of the [Rh(R’COCHCOR)(cod)] + phen -> [Rh(phen)(cod)](+) + (R’COCHCOR)(-) reaction. The results are in close agreement with 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: Durand-Niconoff, JS, Relationship Between Local Reactivity Indices and the Hammett Constant for Isatoic Anhydride and Its Derivatives, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 112, 3570, (2012)
Abstract: Local reactivity is obtained for isatoic anhydride (ISA) (2H 3,1-benzoxazin-2,4(1H)-dione) and 20 of its derivatives, using reactivity indices such as: local softness, condensed Fukui function, relative electrophilicity index, and relative nucleophilicity index. The local reactivity results for ISA show the best sites for a nucleophilic attack and for an electrophilic attack. A linear model is proposed from statistical methods to describe the substituent effect for the relationship between gas phase reactivity indices with respect to the Hammett constant values.

First author: Ojea-Jimenez, I, Molecular Modeling of the Reduction Mechanism in the Citrate Mediated Synthesis of Gold Nanoparticles, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 23682, (2012)
Abstract: The synthesis of gold nanoparticles (Au NPs) via the reduction of tetrachloroauric acid by sodium citrate has become a standard procedure in nanotechnology. Simultaneously, gold-mediated reactions are gaining interest due to their catalytic properties, unseen in other metals. In this study, we have investigated the theoretical mechanism of this reaction under three different pH conditions (acid, mild acid, and neutral) and have corroborated our findings with experimental kinetic measurements by UV-vis absorption spectroscopy and transmission electron microscopy (TEM) analysis of the final particle morphology. We have demonstrated that, indeed, the pH of the medium ultimately determines the reaction rate of the reduction, which is the rate-limiting step in the Au NPs formation and involves decarboxylation of the citrate. The pH sets the dominant species of each of the reactants and, consequently, the reaction pathways slightly differ in each pH condition. The mechanism highlights the effect of the number of Cl- ligands in the metalocomplex, which ultimately originates the energetic differences in the reaction paths.

First author: Goedecke, C, Spacer Separated Donor-Acceptor Complexes [D -> C6F4 -> BF3] (D = Xe, CO, N-2) and the Dication [Xe -> C6F4 <- Xe](2+). A Theoretical Study, INORGANIC CHEMISTRY, 51, 11259, (2012)
Abstract: Quantum chemical calculations using density functional theory at the BP86/TZ2P+ level and ab initio calculations at MP2/def2-TZVPP have been carried out for the donor acceptor complexes [D -> C6F4 -> BF3] (D = Xe, CO, N-2,) and the dication [Xe -> C6F4 <- Xe](2+). The calculations predict rather short D -> C6F4(BF3) and (D)C6F4 -> BF3 bonds in the neutral systems which indicate rather strong binding interactions. The calculated partial charges which give large positive values for the donor moieties and negative values for the acceptor fragments and the large bond indices also suggest very strong donor acceptor interactions D -> C6F4 -> BF3 and Xe -> C6F42+<- Xe. An energy decomposition analysis suggests very strong intrinsic interactions for both systems. The donor acceptor bonds in [D -> C6F4 -> BF3] are much stronger than the direct donor acceptor interactions D -> BF3 which are only weakly bonded van der Waals complexes. The calculated donor acceptor interactions D -> C6F4(BF3) are 26.1 kcal/mol for D = Xe, 121.5 kcal/mol for D = CO, and 86.9 kcal/mol for D = N-2. The strength of the intrinsic (D)C6F4 -> BF3 interactions are calculated to be between 51.1-51.6 kcal/mol. The theoretical bond dissociation energies for the decomposition of [D -> C6F4 -> BF3] yielding D + C6F4 + BF3 suggests that the xenon compound [Xe -> C6F4 -> BF3] is metastable but may become stabilized in the condensed phase by intermolecular interactions. The complexes [OC -> C6F4 -> BF3] and [N-2 -> C6F4 -> BF3] are predicted to be thermodynamically stable. It is suggested that the above adducts are examples of spacer-separated donor acceptor complexes [D -> S -> A] which are a hitherto unrecognized class of molecules.

First author: Janjua, MRSA, Quantum Mechanical Design of Efficient Second-Order Nonlinear Optical Materials Based on Heteroaromatic Imido-Substituted Hexamolybdates: First Theoretical Framework of POM-Based Heterocyclic Aromatic Rings, INORGANIC CHEMISTRY, 51, 11306, (2012)
Abstract: This work was inspired by a previous report (Janjua et al. J. Phys. Chem. A 2009, 113, 3576-3587) in which the nonlinear-optical (NLO) response strikingly improved with an increase in the conjugation path of the ligand and the nature of hexamolybdates (polyoxometalates, POMs) was changed into a donor by altering the direction of charge transfer with a second aromatic ring. Herein, the first theoretical framework of POM-based heteroaromatic rings is found to be another class of excellent NLO materials having double heteroaromatic rings. First hyperpolarizabilities of a large number of push pull-substituted conjugated systems with heteroaromatic rings have been calculated. The beta components were computed at the density functional theory (D FT) level (BP86 geometry optimizations and LB94 time-dependent DFT). The largest beta values are obtained with a donor (hexamolybdates) on the benzene ring and an acceptor (-NO2) on pyrrole, thiophene, and furan rings. The pyrrole imido-substituted hexamolybdate (system 1c) has a considerably large first hyperpolarizability, 339.00 x 10(-30) esu, and it is larger than that of (arylimido)hexamolybdate, calculated as 0.302 x 10(-30) esu (reference system 1), because of the double aromatic rings in the heteroaromatic imido-substituted hexamolybdates. The heteroaromatic rings act as a conjugation bridge between the electron acceptor (-NO2) and donor (polyanion). The introduction of an electron donor into heteroaromatic rings significantly enhances the first hyperpolarizabilities because the electron-donating ability is substantially enhanced when the electron donor is attached to the heterocyclic aromatic rings. Interposing five-membered auxiliary fragments between strong donor (polyanion) or acceptor (-NO2) groups results in a large computed second-order NLO response. The present investigation provides important insight into the NLO properties of (heteroaromatic) imido-substituted hexamolybdate derivatives because these compounds exhibit enhanced hyperpolarizabilities compared to typical NLO arylimido hexamolybdates and heterocyclic aromatic rings reported in the literature.

First author: Takahata, Y, DFT calculation of core- and valence-shell electron excitation and ionization energies of 2,1,3-benzothiadiazole C6H4SN2, 1,3,2,4-benzodithiadiazine C6H4S2N2, and 1,3,5,2,4-benzotrithiadiazepine C6H4S3N2,JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 185, 475, (2012)
Abstract: The vertical core and valence shell electron excitation and ionization energies of the three title molecules, 1-3, were calculated by density functional theory (DFT) using adequate functional for each type of processes and atoms under study. The inner shells treated were C1s, N1s, S1s, S2s, S2p. Molecular geometry was optimized by DFT B3LYP/6-311 + (d,p). The basis set of triple zeta plus polarization (TZP) Slater-type orbitals was employed for DFT calculations. The Delta SCF method was used to calculate ionization energies. The average absolute deviation (AAD) from experiment of 26 valence-electron ionization energies calculated by DFT for the three molecules 1-3 was 0.14 eV; while that of 24 calculated core-electron binding energies (CEBEs) from experiment was 0.4 eV. Selected core excitation energies were calculated by the multiplet approximation for the three molecules. The AAD of twelve calculated core excitation energies by the multiplet approximation that exclude S2s cases was 0.56 eV. Time-dependent DFT (TDDFT) was employed to calculate the excitation energies and corresponding oscillator strengths of core- and valence-electrons of the molecules. Some selected occupied core orbitals were used to calculate the core-excitation energies with the TDDFT (Sterner-Frozoni-Simone scheme). The core excitation energies thus calculated were in an average error of ca. 28 eV compared to observed values. They were shifted to the value calculated by the multiplet approximation. Convoluted spectra based upon the shifted energies and accompanying oscillator strengths reproduce low-energy region of observed spectra reasonably well, whereas they deviate from experiment in high-energy region. Reasonable agreement between theory and experiment was obtained for the valence electron excitations of the molecules.

First author: Krishnamoorthy, BS, Molecular transition-metal boron compounds. Any interest?, SOLID STATE SCIENCES,14, 1617, (2012)
Abstract: Molecular metallaboranes, which feature complexes with M-B rather than M-C bonds, constitute a class of compounds which has revealed new possibilities for the way metal and borane fragments interact to generate novel structures, demonstrating an important role for the transition metal in the structural arrangement. Early transition-metal dimetallaboranes in particular adopt deltahedra with the same total connectivities as the borane anions or late transition-metal metallaboranes but with flattened geometries rather than spherical shapes. They are characterised by high metal coordination numbers, M-M cross-cluster distances within the single bond range, and formal (apparent) cluster electron counts three skeletal electron pairs short of that required for a canonical structure of the same nuclearity. A selection of these boron-rich dimetallaboranes is theoretically investigated and compared to illustrate the role of the transition metal in their cluster bonding.

First author: Cianchetta, I, Discoloration of the smalt pigment: experimental studies and ab initio calculations, JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, 27, 1941, (2012)
Abstract: Smalt is a blue pigment used by many European artists in mural and easel paintings, mainly in the period from the XV to XVIII century. It is a potassium glass where cobalt is added to the glassy matrix to get the blue hue. The pigment deteriorates with age, changing its colour from an intense blue to a grey-yellowish hue, causing severe problems in the conservation of the paintings. In this study a set of specimens of smalt dispersed in linseed oil was prepared and artificially aged to simulate the progressive deterioration of the pigment in a painting on canvas. The artificially aged smalt specimens were compared with some samples of naturally aged smalt taken from a banner painted at the end of XV century by Luca Signorelli, the “Baptism of Jesus”. A multi-technique approach, including SEM-EDX, spectro-colorimetry, X-ray absorption spectroscopy and ab initio calculations, was used to understand the progressive discoloration and to reveal its correlation with changes occurring in the pigment structure.

First author: Daku, LML, Accurate Spin-State Energetics of Transition Metal Complexes. 1. CCSD(T), CASPT2, and DFT Study of [M(NCH)(6)](2+) (M = Fe, Co), JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 8, 4216, (2012)
Abstract: Highly accurate estimates of the high-spin/low-spin energy, difference Delta E-HL(el) in the high-spin complexes [Fe(NCH)(6)](2+) and [Co(NCH)(6)](2+) have been obtained from the results of CCSD(T) calculations extrapolated to the complete basis set limit. These estimates are shown to be strongly influenced by scalar relativistic effects. They have been used to assess the performances of the CASPT2 method and 30 density functionals of the GGA, meta-GGA, global hybrid, RSH, and double-hybrid types. For the CASPT2 method, the results of the assessment support the proposal [Kepenekian, M.; Robert, V.; Le Guennic, B. J. Chem. Phys. 2009, 131, 114702] that the ionization potential-electron affinity (IPEA) shift defining the zeroth-order Hamiltonian be raised from its standard value of 0.25 au to 0.50-0.70 au for the determination of Delta E-HL(el) in Fe(II) complexes with a [FeN6] core. At the DFT level, some of the assessed functionals proved to perform within chemical accuracy (+/- 350 cm(-1)) for the spin-state energetics of [Fe(NCH)(6)](2+), others for that of [Co(NCH)(6)](2+), but none of them simultaneously for both complexes. As demonstrated through a reparametrization of the CAM-PBEO range-separated hybrid, which led to a functional that performs within chemical accuracy for the spin-state energetics of both complexes, performing density functionals of broad applicability may be devised by including in their training sets highly accurate data like those reported here for [Fe(NCH)(6)](2+) and [Co(NCH)(6)](2+).

First author: Krykunov, M, Accurate Theoretical Description of the L-1(a) and L-1(b) Excited States in Acenes Using the All Order Constricted Variational Density Functional Theory Method and the Local Density Approximation, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 8, 4434, (2012)
Abstract: We present the results of calculations on the vertical singlet L-1(a) and L-1(b) excitation energies in acenes within time dependent density functional theory (TDDFT), second order constricted variational DFT (CV(2)-DFT), and all order constricted variational DFT (CV(infinity)-DFT) using the local density approximation LDA(VWN). For the linear acenes it is shown that the application of the Tamm-Dancoff (TD) approximation to TDDFT (TDDFT-TD) substantially improves the agreement with experiment compared to pure TDDFT. This improvement leads to the correct ordering of the L-1(a) and L-1(b) excitation energies in naphthalene. As TDDFT-TD is equivalent to the second order CV(2)-TD method one might hope for further improvements by going to all orders in CV(infinity)-TD. Indeed, for linear acenes the application of the CV(infinity)-TD method brings the agreement with experiment to within 0.1 eV for both types of excitations using the simple LDA functional. The CV(infinity)-TD method based on LDA is also shown to be accurate for 15 nonlinear acenes with root-mean-square deviations of 0.24 eV for L-1(a) and 0.17 eV for L-1(b).

First author: Chen, X, DFT Study of Polyaniline and Metal Composites as Nonprecious Metal Catalysts for Oxygen Reduction in Fuel Cells, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 22737, (2012)
Abstract: A theoretical study on the oxygen reduction mechanism catalyzed by metal polyaniline is investigated in detail by means of density functional theory. In the oxygen reduction process, we find that -OH, not H2O2, is the reaction intermediate. The catalytic activities for the studied models decrease in the sequence CoFe-PANI > Fe-PANI (FeFe-PANI) > Co-PANI. This is due to a synergistic effect between heterogeneous metal atoms in CoFe-PANI, which facilitates additional electron donation from the active sites to the adsorbed oxygen reduction intermediates. The doping with cobalt may also decrease the HOMO-LUMO gap in CoFe-PANI, making it more active.

First author: Wang, X, Theoretical Investigations on Charge-Transfer Properties of Novel High Mobility n-Channel Organic Semiconductors – Diazapentacene Derivatives, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 22749, (2012)
Abstract: The charge-transfer properties of three diazapentacene derivatives, including 5,7,12,14-tetrachloro-6,13-diazapentacene (TCDAP), 5,7,12,14-tetrachloro-6,13-diaza-6,13-dihydropentacene (TCDAHP), and 5,7,12,14-tetrafluoro-6,13-diazapentacene (TFDAP), have been studied using density functional theory. The performance of five pure GGA and seven hybrid GGA functionals and G3MP2B3 method on the reorganization energy (lambda) and mobility (mu) predictions of TCDAP has been examined. Both the B3LYP functional and the G3MP2B3 method give reliable predictions for the lambda value. Using the reorganization energy at the G3MP2B3 level together with the transfer integral by BHandH, BHandHLYP, and M06-2X functionals yields electron mobilities of 3.44, 3.32, and 3.29 cm(2) V-1 S-1 for TCDAP, respectively, which come fortuitously close to the experimental value of 3.39 cm(2) V-1 S-1. Other density functionals also give mobility predictions in agreement with the experimental value to a factor of similar to 2. The TCDAHP, a -NH derivative of TCDAP, is predicted to have a large hole and electron mobility of 2.30 and 3.89 cm(2) V-1 S-1, respectively. Our results suggest that TCDAP is an n-channel material, while TCDAHP is an ambipolar organic semiconductor with simultaneous hole and electron transport properties. By the substitution of chlorine with fluorine in TCDAP, we find that TFDAP is very similar to TCDAP in terms of the molecular and crystal structure and HOMO/LUMO property. TFDAP is an n-type semiconductor but with a larger electron mobility of 3.51 cm(2) V-1 S-1. All theoretical predictions are based on the crystal structures obtained with PBC model and B97D functional. The transfer integral calculations along the four dominant hopping pathways reveal that the hole and electron transport processes occur via the parallel routes between two neighboring molecules with pi-stacking interactions. On the basis of the angular resolution anisotropic mobility analyses, TCDAP, TCDAHP, and TFDAP show remarkably different anisotropic behaviors in comparison with the 6,13-dihydro-6,13-diazapentacene (DHDAP).

First author: Lang, ZL, Building blocks and formation thermodynamics of alpha-Keggin-type [PW12O40](3-) anion,COMPUTATIONAL AND THEORETICAL CHEMISTRY, 999, 66, (2012)
Abstract: The formation mechanism is a fundamental scientific issue for polyoxometalate chemistry. The structural characterization and the thermodynamic behavior of various possible intermediates in the formation of alpha-Keggin-type [PW12O40](3-) anion in aqueous solution were analyzed by density functional method. Based on two proposed mechanisms (order of reaction with heteroatom), thermodynamic analysis indicates that [HPO4](2-), [WO3(OH)](-), [W2O7](2-), [W3O10](2-), [W4O13](2-), [W5O16](2-), and [PW2O9](-) will be mainly involved in the polymerization processes of [PW12O40](3-) anion. The starting reaction from isodimer has been determined through transition state search for the initial steps. Heteroatom has been introduced in the heterotrimer [PW2O9](-) at the second step which experiences almost the same barrier with isotrimer [W3O10](2-). From geometric topology and thermodynamics, the defect structures are more suitable for building blocks.

First author: Gryff-Keller, A, Shielding and Indirect Spin-Spin Coupling Tensors in the Presence of a Heavy Atom: An Experimental and Theoretical Study of Bis(phenylethynyl)mercury, JOURNAL OF PHYSICAL CHEMISTRY A, 116, 10615, (2012)
Abstract: Magnetic shielding and indirect spin-spin coupling phenomena are tensorial properties and both their isotropic and anisotropic parts do affect NMR spectra. The involved interaction tensors, (sigma) over cap and (J) over cap, can nowadays be theoretically calculated, although the reliability of such methods in the case of anisotropic parameters, Delta sigma and Delta J, in systems involving heavy nuclei, yet demands testing. In this communication the results of the experimental and theoretical investigations of bis(phenylethynyl)mercury (I) labeled with C-13 isotope at positions neighboring Hg are reported. The theoretical calculations of molecular geometry and values of NMR parameters for I have been performed by the ZORA/DFT method, including the relativistic scalar and spin-orbit coupling contributions, using the PBE0 functional and TZP (or jcpl) basis set. These values have been confronted with the experimentally measured ones. The isotropic parameters have been measured by the standard C-13 and Hg-199 NMR spectra. The shielding anisotropies for the atoms in the central part of molecule I have been determined in a liquid sample using magnetic relaxation measurements. The relaxation data have been interpreted within the rotational diffusion theory, assuming the symmetrical top reorientation model. The anisotropies of one-bond C-13-Hg-199 and two-bond C-13-Hg-C-13 spin-spin couplings have been determined exploiting the temperature-dependent C-13 NMR spectra of I in the ZLI1167 liquid-crystal phase. We have found that our theoretical calculations reproduce experimental values of both isotropic and anisotropic NMR parameters very well.

First author: Wick, CR, Structural Insight into the Prolyl Hydroxylase PHD2: A Molecular Dynamics and DFT Study,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 116, 4973, (2012)
Abstract: We describe computational studies of the mode of action of the prolyl hydroxylase domain containing protein (PHD2). Long-term molecular dynamics (MD) simulations were performed to investigate the rigidity of the crystallographically observed conformations of PHD2 in solution. We also describe the influence of the C-terminal oxygen-dependent degradation domain (CODD) of hypoxia inducible factor 1 alpha (HIF-1 alpha) on the overall behaviour of the protein, including the effect of the natural ligand 2-oxoglutarate (2OG) and an isoquinoline inhibitor. To study the geometry of the 2-His-1-carboxylate facial triad and its dependency on the protein environment, we performed DFT calculations on model systems and compared them with quantum mechanics/molecular mechanics (QM/MM) gas-phase energy minimisations, which allowed us to treat the whole protein. The combination of these methods provides insight into the behaviour of the 2-His-1-carboxylate facial triad with 2OG and an inhibitor of PHD2 on the atomistic scale.

First author: Flisak, Z, Counter anion binding in the phenoxyimine, salan and metallocene olefin polymerization catalysts activated with perfluorophenylborate, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 718, 124, (2012)
Abstract: Ion pair separation is a process that may influence the activity of homogeneous catalysts of olefin polymerization. We have studied the energy of separation for selected titanium and zirconium metallocene and post-metallocene catalytic ion pairs by means of DFT, dispersion-corrected DFT and Paired Interacting Orbitals method (PIO). Unusually weak cation-anion interactions in the bis(phenoxyimine) systems were attributed to strong electron-donating properties of the phenoxyimine ligands. Energy decomposition analysis (EDA) revealed that almost 70% of the counter ion binding energy results from electrostatic interactions. The PIO method made it possible to analyze the nature of the cation-anion binding and associate its strength with the total overlap population of PIOs.

First author: Azpiroz, JM, A first-principles study of II-VI (II = Zn; VI = O, S, Se, Te) semiconductor nanostructures,JOURNAL OF MATERIALS CHEMISTRY, 22, 21453, (2012)
Abstract: We present a systematic investigation of the structural, electronic and optical properties of wurtzite-like ZnX (X = O, S, Se, Te) nanostructures at the DFT/TDDFT level of theory. To provide a direct comparison with the experiment, realistic 1.0-1.5 nm quantum dots have been built up from the bulk. Low-lying computed excitation energies agree well with the available experimental data. The broad excitation profiles and narrow emission spectra typical of semiconductor quantum dots could be explained by the fact that the LUMO is the state accepting the electron of the low-lying TDDFT excitations calculated. Calculated binding energies for the Zn 3d shell have been found to be 0.5 eV lower than those of the corresponding bulk materials. Anion vacancies can explain the visible light emission of ZnX by introducing a trap state into the bandgap of the nanostructures, in agreement with previous theoretical and experimental works on ZnO. Calculations on rod- and sheet-like prototype clusters point to a significant quantum confinement effect on the optoelectronic properties of Zn-based nanomaterials.

First author: Wang, J, Isocyanide versus nitrile ligands and methyl versus trifluoromethyl substituents in metal carbonyl chemistry, POLYHEDRON, 47, 165, (2012)
Abstract: The relative energies of the nitrile and isocyanide metal carbonyl complexes LM(CO)(n) (L = RCN and RNC; R = CH3 and CF3; M = Cr, n = 5; M = Ni, n = 3; M = Fe, n = 4) have been compared using density functional theory. For the ligand pair CH3CN/CH3NC the acetonitrile metal carbonyl complexes lie at consistently lower energies than the isomeric methyl isocyanide complexes with energy differences of similar to 10 kcal/mol for the Cr and Ni complexes and similar to 5 kcal/mol for the Fe complexes. This relative energy order is reversed for the perfluorinated ligand pair CF3CN/CF3NC for which the trifluoromethyl isocyanide metal carbonyl complexes have lower energies than the isomeric trifluoroacetonitrile complexes. This can be related to the high pi-acceptor ability of CF3NC as indicated by the v(CO) and v(CN) frequencies as well as by Morokuma energy decomposition analysis. However, the energy differences for the fluorinated derivatives are rather small (1-3 kcal/mol) for the Cr and Ni complexes but somewhat larger (6-8 kcal/mol) for the Fe complexes. In the C, trigonal bipyramidal iron carbonyl structure eq-(CF3- NC)Fe(CO)4 the normally linear C-N-C(F-3) unit is bent to similar to 137 degrees thereby indicating unusually strong Fe -> CNCF3 pi back-bonding. For the uncomplexed nitrile/isocyanide pairs CX3CN/CX3NC (X = H, F) previous experimental and theoretical studies indicate the nitrile to lie similar to 23 kcal/mol in energy below the isomeric isocyanide. Thus the current research suggests that complexation with metal carbonyl fragments stabilizes isocyanides relative to the isomeric nitriles.

First author: de Silva, P, Revealing the Bonding Pattern from the Molecular Electron Density Using Single Exponential Decay Detector: An Orbital-Free Alternative to the Electron Localization Function, CHEMPHYSCHEM, 13, 3462, (2012)
Abstract: We introduce a new tool (single exponential decay detector: SEDD) to extract information about bonding and localization in atoms, molecules, or molecular assemblies. The practical evaluation of SEDD does not require any explicit information about the orbitals. The only quantity needed is the electron density (calculated or experimental) and its derivatives up to the second order.

First author: Majid, A, Optical, electronic and magnetic properties of Cr:GaN thin films, MATERIALS CHEMISTRY AND PHYSICS, 136, 809, (2012)
Abstract: Modifications in optical and electronic properties of wurtzite GaN induced by Cr doping were studied using various experimental techniques and Density Functional Theory (DFT) based calculations. Metal Oxide Chemical Vapor Deposited grown GaN/sapphire thin film samples were implanted by Cr ions at 300 keV to achieve three different doses of 5 x 10(14), 5 x 10(15) and 5 x 10(16) cm (2). X-ray diffraction, Atomic force microscopy, Spectroscopy ellipsometry, UV-vis spectrophotometery. Hall and Vibrating Sample Magnetometery measurements were carried out to study structural, optical, electrical and magnetic properties of as-grown, annealed as-grown and annealed implanted GaN samples. A dose dependent decrease in band gap of the material was observed in implanted samples. Complex refractive index, dielectric constants, energy band gap and carrier concentration based on these measurements are reported for the materials. Moreover, the results indicated substitution of Cr in host GaN lattice. Results of band structure (BS) based on DFT calculations using GGA for pure and Cr doped wurtzite GaN are also reported and discussed here. The results indicated that GaCrN is a potential material for optoelectronic and spintronics devices.

First author: Oziminski, WP, Aromaticity of heptafulvene charge transfer complexes with lithium and caesium atoms: A computational approach, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 998, 46, (2012)
Abstract: Geometry optimization of heptafulvene complexes with Li and Cs atoms at B3LYP/6-311++G(d,p) level of theory using Gaussian 03 software allowed us to estimate the magnitude of charge transfer from metal atoms to the heptafulvene moiety (charges equal to +0.938 and +0.994 for Li and Cs, respectively) and energies of dissociation of the complex (-36.65 and -20.4