2009 publications citing ADF

First author: Belanzoni, P., Silylene Defect at the Dihydrogen Terminated (100) Si Surface, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 14375, (2009)
Abstract: Density functional calculations for both periodic slabs and different size cluster models of the hydrogen-terminated (100) Surface of silicon are used to Study a new configuration, formed by a silylene center interacting with vicinal silicon dihydrides through nonconventional hydrogen bonds. A comparison between slab-model and cluster-model approaches to modeling Surface silylene defect formation processes is presented. The cluster models are used to analyze the structure and bonding of the silylene with a Lewis acid and base, showing the Zwitterionic nature of the defect. The silylene is also demonstrated to behave as a strong Bronsted acid. The stabilization of the silylene defect via interaction with species unavoidably present in the HF(aq)-etching solution is investigated. Finally, the negative chemical shift observed by X-ray photoelectron spectroscopy in the HF(aq)-etched (100) Si Surface is attributed to the occurrence of silylene defect.

First author: Di Santo, E., Activation of Ethane C-H and C-C Bonds by Gas Phase Th+ and U+: A Theoretical Study,JOURNAL OF PHYSICAL CHEMISTRY A, 113, 14699, (2009)
Abstract: Two different approaches of density functional theory were used to analyze the C-H and C-C bond activation mechanisms during the reaction of bare Th+ and U+ ions with ethane. We report a complete exploration of the potential energy Surfaces taking into consideration different spin states. According to B3LYP/SDD computations the double dehydrogenation of C2H6 is thermodynamically favorable only in the case of Th+. It is shown that the overall C-H and C-C bond activation processes are exothermic in the case of Th+ and endothermic for U+. In both cases, the C-C insertion transition state barrier exceeds the energy of the ground state reactants, preventing the observation of these species under thermal conditions.

First author: Seip, Torleif A. T., Surfaces and Clusters of Mg(NH2)(2) Studied by Density Functional Theory Calculations,JOURNAL OF PHYSICAL CHEMISTRY C, 113, 21648, (2009)
Abstract: Mg(NH2)(2) was studied by bulk, slab, and cluster calculations based on density functional theory within the generalized gradient approximation. Mg(NH2)(2) is confirmed to have a tetragonal unit cell belonging to the space group I4(1)/acd. Five different slabs and their corresponding cleavage energies have been calculated. The most stable Surface was the (112) surface, supported by low cleavage energy, special symmetry properties, and small structural changes found during ionic relaxation. Comparison of the density of states calculated front bulk, slab, and clusters indicated that occupied states in the band gap of clusters can be one reason why complex hydrides with nanoparticle structure have enhanced kinetics (in addition to the increased surface area). Calculations of the energy change during removal of NH3 and H-2 showed that it is energetically easier to remove NH3 than H-2 from Mg(NH2)(2), confirming a general trend for metal-N-H systems.

First author: Takahata, Yuji, Substituent effect in n-hexanes and n-hexatrienes based on core-electron binding energies calculated with density-functional theory, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 916, 119, (2009)
Abstract: It was shown that core-electron binding energy (CEBE) is a very convenient quantity to monitor substituent effect at each carbon atom in a substituted n-hexane (1-X-hexane), a chain sigma-system, and a substituted n-hexatriene (1-X-hexatriene), a chain pi-system. The core-electron binding energy was calculated using the density-functional theory with a scheme:Delta E(KS)(PW86-PW91)/TZP + C(ret)//HF/6-31G*The calculated CEBE(i) of ith orbital is equal to the sum of the ionization energy (-epsilon(i)) due to the Koopmans’ theorem and relaxation energy (R). The variation of the ionization energy (-epsilon(i)) parallels closely to that of CEBE(i). The relaxation energy curve does not follow the CEBE curve. The behavior of CEBE in a molecule M depends almost exclusively upon the electronic structure of its neutral parent molecule M, and not upon its core-ionized cation M(+). The substituent effect in the sigma-system is considered as inductive effect. The substituent effect in the pi-system consists of inductive and resonant/pi-electron effects. Assuming that the inductive effect of the pi-system, 1-X-hexatriene, can be approximated by that of the sigma-systems, 1-X-hexane, resonant effect of the pi-system was estimated.

First author: Daviso, Eugenio, The electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-CIDNP C-13 NMR, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106, 22281, (2009)
Abstract: Composed of the two bacteriochlorophyll cofactors, P-L and P-M, the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of Rhodobacter sphaeroides. Under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. The occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-CIDNP). This effect can be used to study the electronic structure of the special pair at atomic resolution by detection of the strongly enhanced nuclear polarization with laser-flash photo-CIDNP magic-angle spinning NMR on the carotenoid-less mutant R26. In the electronic ground state, P-L is strongly disturbed, carrying a slightly negative charge. In the radical cation state, the ratio of total electron spin densities between P-L and P-M is 2: 1, although it is 2.5:1 for the pyrrole carbons, 2.2:1 for all porphyrinic carbons, and 4: 1 for the pyrrole nitrogen. It is shown that the symmetry break between the electronic structures in the electronic ground state and in the radical cation state is an intrinsic property of the special pair supermolecule, which is particularly attributable to a modification of the structure of P-L. The significant difference in electron density distribution between the ground and radical cation states is explained by an electric polarization effect of the nearby histidine.

First author: Benito-Garagorri, David, Striking Differences between the Solution and Solid-State Reactivity of Iron PNP Pincer Complexes with Carbon Monoxide, ORGANOMETALLICS, 28, 6902, (2009)
Abstract: Several new iron(II) complexes of the types [Fe(PNP)X-2] (X = Cl, Br) containing tridentate PNP pincer-type ligands based oil 2,6-diaminopyridine and 2,6-diaminopyrimidine have been prepared. They all exhibit intermolecular Fe-X center dot center dot center dot H-N hydrogen bonds, forming supramolecular networks in the solid state. In the case of X = Cl these compounds react readily with gaseous CO both in the solid state and in solution to give selectively the octahedral complexes cis- and trans-[Fe(PNP)(CO)(Cl)(2)], respectively, whereas with X = Br mixtures of cis- and trans isomers are obtained. These transformations are accompanied by color and spin-state changes. CO binding is fully reversible in all cases, and heating solid samples of either cis- or trans-[Fe(PNP)(CO)(X)(2)] leads to complete regeneration of analytically pure [Fe(PNP)(X)(2)]. Mossbauer spectroscopy confirmed the high-spin nature of the parent five-coordinate Fe(II) complex (delta = 0.80(1) mm s(-1)) and the shift to two different low-spin octahedral species after reaction with CO in the solid (delta = 0.13(1) mm s(-1)) or in solution (delta = 0.15(1) mm s(-1)). Magnetization studies led to a magnetic moment close to 4.9 mu(B), reflecting the expected Four unpaired d-electrons in [Fe(PNP)Cl-2], which were confirmed by DFT calculations. The DFT study or the reaction pathway for CO capture led to low energy barriers (<= 3.4 kcal mol(-1)). The cis-trans isomerization reaction was found to take place with a low energy barrier (10.8 kcal mol(-1)), after initial loss of chloride, and involves also spin-state changes.

First author: Neugebauer, Johannes, Subsystem-Based Theoretical Spectroscopy of Biomolecules and Biomolecular Assemblies, CHEMPHYSCHEM, 10, 3148, (2009)
Abstract: The absorption properties of chromophores in biomolecular systems are subject to several fine-tuning mechanisms. Specific interactions with the surrounding protein environment often lead to significant changes in the excitation energies, but bulk dielectric effects can also play an important role. Moreover, strong excitonic interactions can Occur in systems with several chromophores at close distances. For interpretation purposes, it is often desirable to distinguish different types of environmental effects, such as geometrical, electrostatic, polarization, can be applied for theoretical analyses of such effects are reviewed herein, ranging from continuum and point-charge models to explicit quantum chemical subsystem methods for environmental effects. Connections to physical model theories are also outlined. Prototypical applications to optical spectra and excited states of fluorescent proteins, biomolecular photoreceptors, and photosynthetic protein complexes are discussed.

First author: Mal, Sib Sankar, Wheel-Shaped Cu-20-Tungstophosphate [Cu20X(OH)(24)(H2O)(12)(P8W48O184)](25-) Ion (X = Cl, Br, I) and the Role of the Halide Guest, INORGANIC CHEMISTRY, 48, 11636, (2009)
Abstract: We have synthesized the known [Cu20Cl(OH)(24)(H2O)(12)(P8W48O184)](25 center dot) (1) and report here its bromide and iodide analogues, [Cu20Br(OH)(24)(H2O)(12)(P8W46O184)](25-) (2) and [Cu20I(OH)(24)(H2O)(12)(P8W48O184)](25-) (3). These polyanions were characterized in the solid state by IR spectroscopy and 2 single-crystal X-ray diffraction Magnetic susceptibility and magnetization data over 18-300 K show that the Cu2+ ions in 1-2 are antiferromagnetically coupled, leading to a diamagnetic ground state. The effective exchange coupling constant J(eff) was estimated as similar to -3 K for both 1 and 2. Electron paramagnetic resonance measurements were made on 1 and 2 over 5-295 K at microwave frequencies of 9.5, 34, and 220 GHz. The observed (weak) signals were characteristic of randomly distributed Cu2+ ions only, with g values and hyperfine constants typical of the unpaired electron in a 3d(x2-y2) orbital of Cu2+. No signals attributable to the copper-hydroxo cluster were detected, supporting the conclusions from the magnetization measurements. DFT calculations were performed as well to obtain additional information on the anionic guest inside the cavity created by the copper-hydroxo cage related to electronic structure and energies of encapsulation. The polyanions 2 and 3 were also characterized by cyclic voltammetry (CV) in a pH 5 medium. Their CVs are composed by an initial two-step reduction of the Cu2+ centers to Cu-0 through Cu+, followed at more negative potential by the redox processes of the W centers. A comparison with the CV characteristics of the previously studied compound 1 indicates that the potential locations of the Cu or W waves of the three analogues do not depend significantly upon the identity of the central halide X. This observation is in accordance with conclusions of DFT calculations. The modified electrodes based on 2 and the room-temperature ionic liquid 1-butyl-3-methylimidazolium tetra fluoroborate triggers an efficient reduction of nitrate. To our knowledge, this is the first example of electrocatalytic nitrate reduction by a polyanion entrapped in room-temperature ionic liquid films

First author: Ramaswamy, Padmini, Synthesis, Structure, and Transformation Studies in a Family of Inorganic-Organic Hybrid Framework Structures Based on Indium, INORGANIC CHEMISTRY, 48, 11697, (2009)
Abstract: Eight new open-framework inorganic-organic hybrid compounds based on indium have been synthesized employing hydrothermal methods. All of the compounds have InO6, C2O4, and HPO3/HPO4/SO4 units connected to form structures of different dimensionality Thus, the compounds have zero- (I), two- (II, III, IV, V, VII, and VIII), and three-dimensionally (VI) extended networks. The formation of the first zero-dimensional hybrid compound is noteworthy In addition, concomitant polymorphic structures have been observed in the present study. The molecular compound, I, was found to be reactive, and the transformation studies in the presence of a base (pyridine) give rise to the polymorphic structures of II and III, while the addition of an acid (H3PO3) gives rise to a new indium phosphite with a pillared layer structure (T1). Preliminary density functional theory calculations suggest that the stabilities of the polymorphs are different, with one of the forms (II) being preferred over the other, which is consistent with the observed experimental behavior. The oxalate units perform more than one role in the present structures. Thus, the oxalate units connect two In centers to satisfy the coordination requirements as well as to achieve charge balance in compounds II, IV, and VI. The terminal oxalate units observed in compounds I, IV, and V suggest the possibility of intermediate structures. Both in-plane and out-of-plane connectivity of the oxalate units were observed in compound VI. The 31 compounds have been characterized by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and P-31 NMR studies.

First author: Conradie, Jeanet, A computational study and fragment analysis of the back-bonding in Titanocenyl Complexes containing a five-member L,L ‘-cyclic ligand, L,L ‘ = O,O ‘; S,S ‘ or Se,Se ‘, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 915, 51, (2009)
Abstract: A DFT computational study is performed on different Cp2TiIV(L,L’-BID) complexes with L,L’-BID = dioxolene, dithiolene or diselenolene. A fragment analysis of the titanocene-ligand bonding in the DFT optimized geometries showed that out of plane folding for maximum Ti <- L pi donation increases Cp2TiIV(O,O’-BID) (similar to 35 degrees) < Cp2TiIV(S,S’-BID) (43-49 degrees) < Cp2TiIV(Se,Se’-BID) (48-53 degrees).

First author: Zein, Samir, Density functional estimations of Heisenberg exchange constants in oligonuclear magnetic compounds: Assessment of density functional theory versus ab initio, JOURNAL OF CHEMICAL PHYSICS, 131, 51, (2009)
Abstract: Modern density functionals were assessed for the calculation of magnetic exchange constants of academic hydrogen oligomer systems. Full-configuration interaction magnetic exchange constants and wavefunctions are taken as references for several H-n model systems with different geometrical distributions from Ciofini [Chem. Phys. 309, 133 (2005)]. Regression analyses indicate that hybrid functionals (B3LYP, O3LYP, and PBE0) rank among the best ones with a slope of typically 0.5, i.e., 100% overestimation with a standard error of about 50 cm(-1). The efficiency of the highly ranked functionals for predicting the correct “exact states” (after diagonalization of the Heisenberg Hamiltonian) is validated, and a statistical standard error is assigned for each functional. The singular value decomposition approach is used for treating the overdetermination of the system of equations when the number of magnetic centers is greater than 3. Further discussions particularly about the fortuitous success of the Becke00-x-only functional for treating hydrogenic models are presented.

First author: Harb, Mohammad K., Preparation and Characterization of Homologous Diiron Dithiolato, Diselenato, and Ditellurato Complexes: [FeFe]-Hydrogenase Models, ORGANOMETALLICS, 28, 6666, (2009)
Abstract: In order to elucidate the influence of the bridging chalcogen atoms in hydrogenase model complexes, din-on dithiolato, diselenolato, and ditellurolato complexes have been prepared and characterized. Treatment of Fe-3(CO)(12) with 3,3-bis(thiocyanatomethyl)oxetane (1) or a mixture of 2-oxa-6,7-dithiaspiro[3.4]octane (2a)and 2-oxa-6,7,8-trithiaspiro[3.5]nonane (2b) in toluene at reflux afforded the model compound Fe-2(mu-S2C5H8O)(CO)(6) (3). The analogous diselenolato and ditellurolato complexes, Fe-2(mu-Se2C5H8O)(CO)(6) (4) and Fe-2(mu-Te2C5H8O)(CO)(6) (5), were obtained from the reaction of Fe-3(CO)(12) with 2-oxa-6,7-diselenaspiro[3.4]octane (6) and 2-oxa-6,7-ditelluraspiro-[3.4]octane (7), respectively. Compounds 3-5 were characterized by spectroscopic techniques (NMR, IR, photoelectron spectroscopy), mass spectrometry, single-crystal X-ray analysis, kind computational modeling. The electrochemical properties for the new compounds have been studied to assess their ability to catalyze electrochemical reduction of protons to give dihydrogen, and the catalytic rate is found to decrease on going from the sulfur to selenium to tellurium compounds. In the series 3-5 the reorganization energy on going to the corresponding cation decreased from 3 to 4 to 5. Spectroscopic and computational analysis suggests that the increasing size of the chalcogen atoms from S to Se to Te increases the Fe-Fe distance and decreases the ability of the complex to form the structure with a rotated Fe(CO)(3) group that has a bridging carbonyl ligand and a vacant coordination site for protonation. This effect is mirrored on reduction of 3-5 in that the rotated structure with a bridging carbonyl, which creates a vacant coordination site for protonation, is disfavored on going from the S to Se to Te complexes.

First author: van Rijt, Sabine H., Amide Linkage Isomerism As an Activity Switch for Organometallic Osmium and Ruthenium Anticancer Complexes, JOURNAL OF MEDICINAL CHEMISTRY, 52, 7753, (2009)
Abstract: We show that the binding mode adopted by picolinamide derivatives in organometallic Os(II) and Ru(II) half-sandwich complexes can lead to contrasting cancer cell cytotoxicity. N-Phenyl picolinamide derivatives (XY) in Os(II) (1, 3-5, 7, 9) and Ru(II) (2, 6, 8, 10) complexes [(eta(6)-arene)(Os/Ru)(XY)Cl](n+), where arene = p-cymene (1-8, 10) or biphenyl (9),can act as N,N- or N,O-donors. Electron-withdrawing substituents on the phenyl ring resulted in N,N-coordination and electron-donating substituents in N,O-coordination. Dynamic interconversion between N,O and N,N configurations can occur in solution and is time- and temperature- (irreversible) as well as pH-dependent (reversible), The neutral N,N-coordinated compounds (1-5 and 9) hydrolyzed rapidly (t(1/2) <= min), exhibited significant (32-70%) and rapid binding to guanine, but no binding to adenine. The N,N-coordinated compounds 1, 3, 4, and 9 exhibited significant activity against colon, ovarian,and cisplatin-resistant ovarian human cancer cell lines (3 >> 4 > 1 > 9). In contrast, N,O-coordinated complexes 7 and 8 hydrolyzed slowly, did not bind to guanine or adenine, and were nontoxic.

First author: Osuna, Silvia, Homolytic versus Heterolytic Dissociation of Alkalimetal Halides: The Effect of Microsolvation,CHEMPHYSCHEM, 10, 2955, (2009)
Abstract: Herein we report density functional calculations of homolytic and heterolytic dissociation energies of the diatomic alkalimetal halides MX (M = Li, Na, K, Rb, and Cs and X = F, Cl, Br, I, and At) and their corresponding microsolvated structures MX center dot(H2O)(n) (n = 1 to 4). Our results show that the homolytic dissociation energy of the MX center dot(H2O)(n) species increases with the number of water molecules involved in the microsolvated salts. On the other hand, the heterolytic dissociation energy follows exactly the opposite trend. As a result, while for the isolated diatomic alkalimetal halides, homolytic dissociation is always favored over heterolytic dissociation, the latter is preferred for CsF and CsCl already for n=2, and for n=4 it is the preferential mode of dissociation for more than half of the species studied.

First author: Gomes, Clara S. B., Synthesis, Structure, and Photophysical Characterization of Blue-Green Luminescent Zinc Complexes Containing 2-Iminophenanthropyrrolyl Ligands, INORGANIC CHEMISTRY, 48, 11176, (2009)
Abstract: New 2-iminophenanthro[9,10-c]pyrrole ligand precursors containing phenyl or 2,6-diisopropylphenyl groups at the imine nitrogen substituent, 2-arylformiminophenanthro[9,10-c]pyrroles (aryl=phenyl IIa, 2,6-diisopropylphenyl IIb) were synthesized and deprotonated in situ with NaH, originating solutions of the corresponding sodium salts (IVa, 10). The reaction of these salts with zinc chloride gave the homoleptic bis-ligand Zn(II) complexes [Zn((KN)-N-2,N’-2-ar formiminophenanthro[9,10-c]pyrrolyl)2] (aryl=phenyl 2a, 2,6-diisopropylphenyl 2b). The new ligand precursors and complexes were characterized by NMR, elemental analysis, UV/vis spectroscopy, and X-ray crystallography, when possible. The photophysical characterization was carried out using steady-state and picosecond time-resolved luminescence techniques in solution. The influence of the pi-extended conjugation of the condensed phenanthro group on the deprotonated iminopyrrolyl ligands coordinated to Zn2+ greatly enhances fluorescence quantum yields of the complexes (2a, 2b) in relation to those of their ligand precursors (IIa, IIb). Complex 2a shows emission in the green spectral region (lambda(max) = 494 nm), presenting the highest fluorescence quantum yield (phi(f) = 8.8%). In the case of the complex 2b (phi(f) = 3.9%), the bulkiness of the 2,6-diisopropyl substituents of the arylimino group highly restricts the aryl ring rotation toward coplanarity with the ligand framework, inducing a shift in the emission to the blue region (lambda(max) = 459 nm). The values of the radiative (k(f)) and radiationless rate constants (k(nr)) show that the fluorescence quantum yield enhancement in the complexes results from a 50-fold increase in kf values, indicating much more allowed pi-pi* transitions in complexes 2a and 2b than those occurring in the ligand precursors IIa and IIb, with an essentially n-pi* character. These assignments were confirmed by density-functional theory (DFT) and time-dependent DFT (TD-DFT) molecular orbital calculations, Simple 2-aryliminopyrrole ligand precursors (la, lb) and their Zn(II) complexes (1a, 1b) were also prepared to compare their photophysical properties with those of the corresponding 2-aryliminophenanthro[9,10-c]pyrrolyl compounds.

First author: Carofiglio, Tommaso, Melamine-Bridged Bis(porphyrin-Zn-II) Receptors: Molecular Recognition Properties,JOURNAL OF ORGANIC CHEMISTRY, 74, 9034, (2009)
Abstract: Dimeric metalloporphyrin hosts with tweezer-like structures have been synthesized by reacting the cyanuric chloride scaffold, CC, with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, P, and 5-(4-aminophenyl)-10,15,20-trimesitylporphyrin, M, to yield the homoconjugates free bases PP and MM and the heterodyad PM. Metalation with Zn(II), gives three structurally related ditopic receptors P(Zn)P(Zn), P(Zn)M(Zn), and M(Zn)M(Zn) with differential steric hindrance and conformational rigidity. The solution structure and supramolecular properties of these porphyrin dimers have been investigated as isolated molecules and in the presence of aliphatic alpha,omega-diamines of general formula H2N-(CH2)n-NH2 (n = 4-8) by spectroscopic and theoretical studies including multidimensional NMR, UV-vis, molecular modeling, and computational NMR methods. Binding constants in the range 4.2 x 10(6) to 3.4 x 10(7) M-1 are observed in dichloromethane at 298 K, with a 3 orders of magnitude increase as compared to monodentate nBuNH(2), thus indicating the occurrence of a host-guest ditopic interaction. Linear correlation graphs are obtained by plotting the Soret band shift (Delta v, cm(-1)) of the complex as a function of the diamine chain length. Combined NMR evidence and OPLS 2005 Force Field conformational analysis point to a mutual adaption of both the binding partners in the host-guest complex, whose geometry is mainly dictated by the steric impact of the bulky substituents at the porphyrin periphery.

First author: Stoyanov, Stanislav R., Transition metal and nitrogen doped carbon nanostructures, COORDINATION CHEMISTRY REVIEWS, 253, 2852, (2009)
Abstract: We review our theoretical first-principle studies of carbon nanostructures based on graphene sheets, carbon nanotubes, nanocones and fullerenes that are substitutionally doped with transition metal and nitrogen atoms. The results obtained show that metal doping leads to more stable systems in buckled rather than planar structures. The hybrid structures have low-lying excited states, allowing for catalytic activity, in analogy to metalloporphyrins and metallophthalocyanines, as confirmed in recent experiments with Fe-xN-doped carbon nanotubes. Metal-doped carbon nanocones and nanocapsules based on typical fullerenes manifest remarkable electronic and spin polarizations. Additional doping by boron atoms adjacent to the metals increases their HOMO-LUMO gap, stabilizes their electronic structures and causes that their ground states have higher spin multiplicity, where the spin density is spread over the systems. The metallic sites allow functionalization and potential activation of these nanosystems. The hybrid structures formed can have a broad range of applications in catalysis, molecular electronics, light-harvesting and nanomechanics.

First author: Vankova, Nina, NMR Chemical Shifts of Metal Centres in Polyoxometalates: Relativistic DFT Predictions,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 253, 5102, (2009)
Abstract: A DFT approach incorporating relativistic corrections and solvent effects was tested for NMR calculations on transition-metal centres in polyoxometalates. For a monoplatinum decavanadate derivative and a set of dilacunary polyoxotung-states V-51 and W-183 chemical shifts were calculated at several levels of theoretical treatment regarding solvent, counterion and exchange-correlation functional. Calculations were performed first in the gas phase to model isolated ions and next in a continuum model for water to evaluate the importance of solvation for the quality of the computed chemical shifts. We show that the use of the orbital-dependent Kohn-Sham exchange-correlation functional SAOP in ZORA spin-orbit calculations with solvent effects included via COSMO substantially improves the agreement between computed results and experimental benchmarks for V-51 chemical shifts (at least, in the case of [(H2PtV9O28)-V-IV](5-)). In the case of dilacunary polyoxotungstates our calculations confirm the necessity of modelling an ion pair in which a counterion is specifically included in the POM lacuna to attain accurate predictions of the corresponding W-183 NMR spectra. We show that if the counterion is relatively small (like Li+ and Na+), the explicit location of a water molecule in its vicinity (in addition to the overall COSMO treatment) improves further the accuracy of the correlation between computed and experimental shifts (to less than 5 ppm of the encompassed 6 range).

First author: Vila-Nadal, Laia, Theoretical Analysis of the Possible Intermediates in the Formation of [W6O19](2-),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 253, 5125, (2009)
Abstract: The structural features and the dynamic behaviour of different possible intermediates in the formation of the Lindqvist anion, [W6O19](2-), according to the stoichiometries observed in electrospray fragmentation experiments, were analyzed by DFT calculations. Two different and complementary techniques were used to take into account the effect of the solvent in the computations: (i) continuum solvation models and (ii) Car-Parrinello simulations with explicit solvent molecules. The interaction of the W-VI ions with the nucleophilic water molecules expands their coordination sphere, reaching in many cases octahedral coordination. Furthermore, a common structural motif (“building block”) is observed in the most stable structures of the intermediates with higher nuclearities.

First author: Carraro, Mauro, Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 253, 5164, (2009)
Abstract: Divacant Keggin-type polyoxotungstates [gamma-XW10O36](8-) with X = Si or Ge, were functionalized with chiral phosphoryl groups. The hybrid compounds [(R*PO)(2)(gamma-XW10O36)](4-) with R = N-protected aminoalkyl groups or O-protected amino acid derivatives, were isolated. The solution characterization of the products was performed by different techniques: (183)w, (31)p, C-13, and H-1 NMR spectroscopy, electrospray ionization mass spectrometry, UV/Vis spectroscopy, and circular dichroism (CD). The experimental data confirm the covalent grafting of the organic moieties onto the polyanionic surface. A chirality transfer, from the pendant organic arm to the inorganic framework is apparent from CD studies. Multiple Cotton effects were observed in the region of charge-transfer transitions pertaining to W-O bonds. Furthermore, the W-183 NMR spectra are consistent with the expected C-2 symmetry, resulting from introduction of two organic stereocenters. The title complexes were used in the presence of hydrogen peroxide to perform the oxidation of methyl p-tolyl sulfide. Implications for the design of enantioselective catalysts based on these derivatives are discussed.

First author: Janjua, Muhammad Ramzan Saeed Ashraf, A Quantum Mechanical Study of the Second-Order Nonlinear Optical Properties of Aryldiazenido-Substituted Hexamolybdates: A Surprising Charge Transfer, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 253, 5181, (2009)
Abstract: The second-order polarizabilities, transition moments, and density of states of aryldiazenido hexamolybdates derivatives were investigated by density functional theory (DFT). System 2 [Mo6O18(N2C6H5)](3-) has a considerably large second-order polarizability, 14.50 X 10(-30) esu, and it is larger than that of system 1 [Mo6O18(N2C6H4NO2)](3-) due to the absence of nitro group in the aryldiazenido ligand. The aryldiazenido ligand acts as an electron donor and the polyanion acts as an electron acceptor. The substitution of an amino (-NH2) group in the ortho/para positions on the aryldiazenido segment leads to a substantially higher nonlinear optical (NLO) response. The introduction of an electron donor (-NH2) in the ortho, meta, para, and ortho/para positions on the aryldiazenido ligand significantly enhances the second-order polarizabilities of aryldiazenido hexamolybdates in comparison to the electron acceptor (-NO2) as in system 1, because the electron-donating ability was reasonably enhanced when the electron donor is attached to the aryldiazenido ligand. Furthermore, orbital analysis shows that incorporation of another phenyl (aromatic) ring in the aryldiazenido ligand leads to a maximum NLO response by reverting the direction and degree of charge transfer (CT), which might result from the C=C pi-conjugated bridge. System 8 [Mo6O18 (N2C14H11)](3-) possesses a strikingly large and conspicuous static second-order polarizability (beta(vec)) computed to be 210.21 X 10(-30) esu. The NLO response can be tuned by subtle changes in the aryldiazenido segment; the present investigation provides important insight into the NLO properties of (aryldiazenido) hexamolybdate derivatives.

First author: Gotz, Andreas W., Performance of Kinetic Energy Functionals for Interaction Energies in a Subsystem Formulation of Density Functional Theory, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 5, 3161, (2009)
Abstract: We have tested the performance of a large set of kinetic energy density functionals of the local density approximation (LDA), the gradient expansion approximation (GEA), and the generalized gradient approximation (GGA) for the calculation of interaction energies within a subsystem approach to density functional theory. Our results have been obtained with a new implementation of interaction energies for frozen-density embedding into the Amsterdam Density Functional program. We present data for a representative sample of 39 intermolecular complexes and 15 transition metal coordination compounds with interaction energies spanning the range from -1 to -783 kcal/mol. This is the first time that kinetic energy functionals have been tested for such strong interaction energies as the ligand-metal bonds in the investigated coordination compounds. We confirm earlier work that GGA functionals offer an improvement over the LDA and are particularly well suited for weak interactions like hydrogen bonds. We do, however, not find a particular reason to prefer any of the GGA functionals over another. Functionals derived from the GEA in general perform worse for all of the weaker interactions and cannot be recommended. An unexpectedly good performance is found for the coordination compounds, in particular with the GEA-derived functionals. However, the presently available kinetic energy functionals cannot be applied in cases in which a density redistribution between the subsystems leads to strongly overlapping subsystem electron densities.

First author: Kolesnikov, V. I., Adsorption of heteropolyphosphates of alkaline metals on iron surface, JOURNAL OF FRICTION AND WEAR, 30, 404, (2009)
Abstract: The physical and chemical properties of heteropolyphosphates of alkaline metals are studied as promising antiwear and antiscoring additives to plastic lubricating materials. Quantum-chemical analysis of the interaction of the heteropolyphosphates with iron surfaces provides insight into the processes that evolve in these compounds during friction. The mechanism of opening of the heteropolyphosphatic cycles and their transition into linear structures is studied.

First author: Casida, Mark E., Time-dependent density-functional theory for molecules and molecular solids Preface,JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 914, 1, (2009)
Abstract: The physical and chemical properties of heteropolyphosphates of alkaline metals are studied as promising antiwear and antiscoring additives to plastic lubricating materials. Quantum-chemical analysis of the interaction of the heteropolyphosphates with iron surfaces provides insight into the processes that evolve in these compounds during friction. The mechanism of opening of the heteropolyphosphatic cycles and their transition into linear structures is studied.

First author: Casida, Mark E., Time-dependent density-functional theory for molecules and molecular solids, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 914, 3, (2009)
Abstract: Time-dependent density-functional theory (TDDFT) has become a well-established part of the modern theoretical chemist’s toolbox for treating electronic excited states. Yet, though applications of TDDFT abound in quantum chemistry, review articles specifically focusing on TDDFT for chemical applications are relatively rare. This article helps to fill the void by first giving a historical review of TDDFT, with emphasis on molecular excitations and aspects of TDDFT which are important for quantum chemical applications, followed by a discussion of some modern evolutions with emphasis on the articles in this volume, and ending with a few thoughts about the future of TDDFT.

First author: Ipatov, Andrei, Excited-state spin-contamination in time-dependent density-functional theory for molecules with open-shell ground states, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 914, 60, (2009)
Abstract: While most applications of the linear response formulation of time-dependent density-functional theory (TDDFT) have been to the calculation of the excited states of molecules with closed-shell ground states, Casida’s formulation of TDDFT opened the way to TDDFT calculations on molecules with open-shell ground states by allowing for different-orbitals-for-different-spin, Although a number of publications have now appeared applying TDDFT to molecules with open-shell ground states and give surprisingly good results for simple excitations, it is relatively easy to show that some excited states of open-shell molecules will have unphysically large amounts of spin contamination. There is thus a clear need for computational tools which can separate physical from unphysical excited spin states in TDDFT. We address this need by using analytic derivative techniques to develop formulae for the 1- and 2-electron reduced density difference matrices, in essential agreement with those obtained by Rowe in the equation-of-motion superoperator approach to Green’s functions in nuclear physics. The corresponding formula for excited-state spin contamination appears to be generally good enough for assigning excited-state spin symmetries, but does lead to a small overestimation of <(S) over cap (2)> in the cases considered here. This (apparently small) problem is eliminated when the Tamm-Dancoff approximation is used in TDDFT.

First author: De Angelis, Filippo, Spectroscopic properties of cyclometallated iridium complexes by TDDFT, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 914, 74, (2009)
Abstract: We provide a unified view of our recent work on TDDFT calculations on the class of Iridium(III) cyclometallated complexes, of relevance for their extensive use in OLED and LEEC devices. Our results, obtained for vastly different systems, allow us to trace some general conclusions concerning the modeling of these transition metal complexes. The effect of relativistic effects on both geometrical structures and emission properties is analyzed considering scalar relativistic corrections and quadratic response theory. Absorption spectra for these compounds can be satisfactorily reproduced by TDDFT calculations neglecting spin-orbit coupling, because of the strong intensity of singlet-singlet transitions which hinders the weaker singlet-triplet transitions. We also underline the importance of being able to simulate the emission spectra line-shapes, thus allowing for a direct comparison of calculated and experimental quantities and to estimate the emission color perceived by the human eye. Approximate treatments of spin-orbit coupling based on excited state analysis are in some case useful to rationalize experimental trends, but more rigorous and quantitative approaches are required for future applications. Finally, we stress the absolute relevance of solvation effects in the description of the excited states of this class of systems, with very large differences in the excited state properties calculated in vacuo and as a function of different solvents. These differences have profound consequences for the comprehension of the photophysical properties of this important class of systems and should always be considered in their effective modeling. On overall, our results indicate that electronic structure-driven tuning of the excited state properties of Iridium(Ill) cyclometallated complexes is possible, thus opening the way to a theoretical and computational strategy for the design of new phosphorescent compounds with specific target characteristics.

First author: He, Jiangang, Stabilities of 3d transition-metal doped Si-14 clusters, CHEMICAL PHYSICS LETTERS, 483, 30, (2009)
Abstract: The geometries, electronic structures, and stabilities of MSi14 clusters (M = Sc-Ni) have been studied by using density functional theory. The results demonstrate that the cage composed of fourteen Si atoms can completely encapsulate a 3d transition-metal atom. The binding forces of MSi14 clusters mainly origin from the electrostatic and orbital interactions. In binding (or embedding) energy calculation, the Wigner-Witmer spin conservation rule is needed in the cases of CrSi14 and MnSi14. Among MSi14 clusters, only CrSi14 shows the highest stability and chemical inertness simultaneously, indicating that only 20-electron rule can be applied to MSi14 species.

First author: de Oteyza, Dimas G., Customized Electronic Coupling in Self-Assembled Donor-Acceptor Nanostructures,ADVANCED FUNCTIONAL MATERIALS, 19, 3567, (2009)
Abstract: Charge transfer processes between donor-acceptor complexes and metallic electrodes are at the heart of novel organic optoelectronic devices such as solar cells. Here, a combined approach of surface-sensitive microscopy, synchrotron radiation spectroscopy, and state-of-the-art ab initio calculations is used to demonstrate, the delicate balance that exists between intermolecular and molecule-substrate interactions, hybridization, and charge transfer in model donor-acceptor assemblies at metal-organic interfaces. It is shown that charge transfer and chemical properties of interfaces based on single component layers : can hot be naively extrapolated to binary donor-acceptor assemblies. In particular, studying the self-assembly of supramolecular nanostrurtures on Cu(111), composed of fluorinated copper-phthalocyanines (F16CuPc) and diindenoperylene (DIP), it is found that, in reference to the associated single component layers, the donor (DIP) decouples electronically from the metal surface, while the acceptor (F16CuPc) suffiers strong hybridization with the substrate.

First author: Cerofolini, G. F., Counterintuitive assignment of the lines observed by x-ray photoelectron spectroscopy at the hydrogen-terminated (100) surface of silicon, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 42, 3567, (2009)
Abstract: Net-charge analysis, involving siladamantane moieties as local models of various surface silicon atoms, is used in combination with infrared spectroscopy to assign chemical species to the features observed in the x-ray photoelectron spectra from hydrogen-terminated (100) Si prepared by HFaq etching of the native oxide.

First author: Mitoraj, Mariusz P., On the Origin of the Trans-Influence in Square Planar d(8)-Complexes: A Theoretical Study, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 109, 3379, (2009)
Abstract: The trans influence of ligands T in trans-[Ni(Cl)(2)NH3T]” complexes with T-=B(Me)(2)(-), H-, CP-, CH2CH3-, CN-, HC C-, Cl-, F- for n = -1 and T=PF3, PH3, P(CH3)(3), CO for n = 0 has been analyzed with the help of the extended transition state (ETS) energy decomposition scheme as well as the natural orbitals for chemical valence (NOCV) method. The TCl2Ni-NH3 bond is made up of the bonding interaction between the empty sigma(Ni) acceptor orbital on the [TCl2Ni]” fragment and the sigma(NH3) donor orbital. The sigma(Ni) orbital is in turn an out-of-phase combination between d(z2) On the metal and an occupied sigma(T) orbital: sigma(Ni) = d(z2) – C-1 x sigma(T). It is shown that the trans influence is related to the contribution (C-1) to sigma(Ni) from sigma(T). Thus, the smaller the contribution C-1 to sigma(Ni) the larger the <sigma(ni)vertical bar=”” sigma(nh3)=””>overlap and the stronger the TCl2Ni-NH3 bond. The contribution C-1 is in turn related to the orbital energy epsilon(sigma(T)) of T. Thus the lower epsilon(sigma(T)) is, the smaller is C-1. There is thus an inverse relation between the trans influence of a ligand T and its electronegativity.

First author: Hedegard, Erik D., Partial charges as reactivity descriptors for nitrido complexes, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 913, 1, (2009)
Abstract: The experimental trend observed for the reactivity of cl-block nitrido complexes is one of increasing electrophilicity of the nitrogen ligand, upon going from early (group 4) to later (group 8) transition metals. Accordingly nitrido complexes of group 8 frequently react with electron donors despite the formal N(3-) formulation of the nitrido ligand would suggest nucleophilic behaviour. A number of typically applied population analyses from the literature have been used in a DFT framework to investigate their ability to reproduce this observed trend. It is found that population analyses in comparative studies are valuable tools and that the partial charges on the nitrogen atom vary in accordance with experimental reactivity for a set of model complexes with a fixed ligand sphere and oxidation state. Both negatively charged, [M(N)Cl(4)](2-), and neutral complexes, [M(N)salen], (in both cases M = V(V), Cr(V), Mn(V) and Fe(V)) follow this trend.

First author: Liu, Chun-Guang, Second-Order Nonlinear Optical Properties of Transition-Metal-Trisubstituted Polyoxometalate-Diphosphate Complexes: A Donor-Conjugated Bridge-Acceptor Paradigm for Totally Inorganic Nonlinear Optical Materials, JOURNAL OF PHYSICAL CHEMISTRY C, 113, 19672, (2009)
Abstract: To date, the most widely used second-order nonlinear optical (NLO) materials are the totally inorganic crystals. However, the small photoelectric coefficients of inorganic NLO materials are the bottleneck in practical applications. The donor-conjugated bridge-acceptor (D-A) model, which is successfully used in the development of organic second-order NLO materials. is still prohibitive in totally inorganic molecules. In the present paper, time-dependent density functional (TDDFT) has been employed to investigate the second-order NLO properties of a series of transition-metal-trisubstituted polyoxometalates (POMs)-diphosphate clusters. We find that these totally inorganic POM clusters possess D-A structure, and the large static first hyperpolarizability can be effectively designed based on this D-A model. The results show that the substituted transition metal centers can be viewed as electron acceptor, and the POM cluster serves as both electron donor and conjugated bridge. The three vanadium atoms derivative of 30-molybdobipyrophosphate POM cluster displays large static first hyperpolarizability by similar to 700 x 10(-30) esu, and it is similar to 70 times its large as that of typical organic NLO molecule p-nitroaniline (PNA) according to LB94/TZP calculations. Thus, this POM cluster seems to be promising totally inorganic materials for application in nonlinear optics.

First author: Cadenbach, Thomas, Molecular Alloys, Linking Organometallics with Intermetallic Hume-Rothery Phases: The Highly Coordinated Transition Metal Compounds [M(ZnR)(n)] (n >= 8) Containing Organo-Zinc Ligands, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131, 16063, (2009)
Abstract: This paper presents the preparation, characterization and bonding analyses of the closed shell 18 electron compounds [M(ZnR)(n)] (M = Mo, Ru, Rh, Ni, Pd, Pt, n = 8-12), which feature covalent bonds between n one-electron organo-zinc ligands ZnR (R = Me, Et, eta(5)-C-5(CH3)(5) = Cp*) and the central metal M. The compounds were obtained in high isolated yields (>80%) by treatment of appropriate GaCp* containing transition metal precursors 13-18, namely [Mo(GaCp*)(6)], [Ru-2(Ga)(GaCp*)(7)(H)(3)] or [Ru(GaCp*)(6)(Cl)(2)], [(Cp*Ga)(4)RhGa(eta(1)-Cp*)Me] and [M(GaCp*)(4)] (M = Ni, Pd, Pt) with ZnMe2 or ZnEt2 in toluene solution at elevated temperatures of 80-110 degrees C within a few hours of reaction time. Analytical characterization was done by elemental analyses (C, H, Zn, Ga), H-1 and C-13 NMR spectroscopy. The molecular structures were determined by single crystal X-ray diffraction. The coordination environment of the central metal M and the M-Zn and Zn-Zn distances mimic the situation in known solid state M/Zn Hume-Rothery phases. DFT calculations at the RI-BP86/def2-TZVPP and BP86/TZ2P+ levels of theory, AIM and EDA analyses were done with [M(ZnH)(n)] (M = Mo, Ru, Rh, Pd; n = 12,10, 9, 8) as models of the homologous series. The results reveal that the molecules can be compared to 18 electron gold clusters of the type M@Au-n, that is, W@Au-12, but are neither genuine coordination compounds nor interstitial cage clusters. The molecules are held together by strong radial M-Zn bonds. The tangential Zn-Zn interactions are generally very weak and the (ZnH)(n) cages are not stable without the central metal M.

First author: Spinney, Heather A., Triple-Bond Reactivity of an AsP Complex Intermediate: Synthesis Stemming from Molecular Arsenic, As-4, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131, 16233, (2009)
Abstract: While P-4 is the stable molecular form of phosphorus, a recent study illustrated the possibility of P-2 generation for reactions in organic media under mild conditions. The heavier group 15 element arsenic can exist as As-4 molecules, but As-4 cannot be stored as a pure substance because it is both light-sensitive and reverts thermally to its stable, metallic gray form. Herein we report As-4 activation giving rise to a mu-As-2 diniobium complex, serving in turn as precursor to a terminal arsenide anion complex of niobium. Functionalization of the latter provides the new AsPNMes(star) ligand, which when complexed with tungsten pentacarbonyl elicits extrusion of the (AsP)W(CO)(5) molecule as a reactive intermediate. Trapping reactions of the latter with organic dienes are found to furnish double Diels-Alder adducts in which the ASP unit is embedded in a polycyclic organic framework. Thermal generation of (AsP)W(CO)(5) in the presence of the neutral terminal phosphide complex P Mo(N[Pr-i]Ar)(3) leads to the cyclo-AsP2 complex (OC)(5)W(cyclo-AsP2)Mo(N[Pr-i]Ar)(3). The (AsP)W(CO)(5) trapping products were crystallized and characterized by X-ray diffraction methods, and computational methods were applied for analysis of the As-As and As-P bonds in the complexes.

First author: Sun, Mengtao, Near- and Deep-Ultraviolet Resonance Raman Spectroscopy of Pyrazine-Al-4 Complex and Al-3-Pyrazine-Al-3 Junction, JOURNAL OF PHYSICAL CHEMISTRY C, 113, 19328, (2009)
Abstract: Near- and deep-ultraviolet (UV) resonance Raman spectroscopy of pyrazine-Al-4 complex and Al-3-pyrazine-Al-3 junction was investigated theoretically with a quantum chemical method. Here, 325 and 244 nm were employed as near- and deep-UV sources in our theoretical study The intensities of static normal Raman spectra of pyrazine-Al-4 complex and Al-3-pyrazine-Al-3 junction were enhanced oil the orders of 10 and 10(3) by a static chemical mechanism, respectively The calculated absorption spectra reveal strong B-6(2) and B-13(2u) electronic transitions near 325 nm for pyrazine-Al-4 complex and 244 nm for Al-3-pyrazine-Al-3 junction, respectively. The analyses of orbital transitions in electronic transitions reveal they are the mixture of (metal to molecule) charge transfer excitation and intracluster excitation. The intensity of near-UV resonance Raman spectroscopy of pyrazine-Al-4 complex and the intensity of deep-UV resonance Raman spectroscopy of Al-3-pyrazine-Al-3 junction are strongly enhanced on the order of 10(5) and 10(4), respectively, compared to the Raman intensity of isolated pyrazine excited at 325 and 244 nm. The calculations of Mic theory and the three-dimensional finite-difference time domain method reveal strong surface plasmon resonance and strong electromagnetic enhancements at 325 and 244 nm for single and dimer nanoparticles at suitable sizes and gap distance, respectively. The strongest SERS enhancement in the system of junction is on the order of 10(8) at the incident lights of 325 and 244 nm. The total enhancements, including the chemical and electromagnetic enhancements, can reach Lip to 10(13). So, Al is a suitable material for near- and deep-UV surface-enhanced resonance Raman scattering

First author: Smith, Sarah J., Structural and Catalytic Characterization of a Heterovalent Mn(II)Mn(III) Complex That Mimics Purple Acid Phosphatases, INORGANIC CHEMISTRY, 48, 10036, (2009)
Abstract: The binuclear heterovalent manganese model complex [Mn(II)Mn(III)(L1)(OAc(2)] ClO(4)center dot H(2)O (H(2)L1 = 2-(((3-((bis(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl)( pyridin-2-ylmethyl)amino)-methyl)phenol) has been prepared and studied structurally, spectroscopically, and computationally. The magnetic and electronic properties of the complex have been related to its structure. The complex is weakly antiferromagnetically coupled (J similar to -5 cm 1, H = -2J S(1)center dot S(2)) and the electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectra identify the Jahn-Teller distortion of the Mn(III) center as predominantly a tetragonal compression, with a significant rhombic component. Electronic structure calculations using density functional theory have confirmed the conclusions derived from the experimental investigations. In contrast to isostructural M(II)Fe(III) complexes (M = Fe, Mn, Zn, Ni), the Mn(II)Mn(III) system is bifunctional possessing both catalase and hydrolase activities, and only one catalytically relevant pK(a) (= 8.2) is detected. Mechanistic implications are discussed.

First author: Blum, Volker, Ab initio molecular simulations with numeric atom-centered orbitals, COMPUTER PHYSICS COMMUNICATIONS, 180, 2175, (2009)
Abstract: We describe a complete set of algorithms for ab initio molecular simulations based on numerically tabulated atom-centered orbitals (NAOs) to capture a wide range of molecular and materials properties from quantum-mechanical first principles. The full algorithmic framework described here is embodied in the Fritz Haber Institute “ab initio molecular simulations” (FHI-aims) computer program package. Its comprehensive description should be relevant to any other first-principles implementation based on NAOs. The focus here is on density-functional theory (DFT) in the local and semilocal (generalized gradient) approximations, but an extension to hybrid functionals, Hartree-Fock theory, and MP2/GW electron self-energies for total energies and excited states is possible within the same underlying algorithms. An all-electron/full-potential treatment that is both computationally efficient and accurate is achieved for periodic and cluster geometries on equal footing, including relaxation and ab initio molecular dynamics. We demonstrate the construction of transferable, hierarchical basis sets allowing the, calculation to range from qualitative tight-binding like accuracy to meV-Ievel total energy convergence with the basis set. Since all basis functions are strictly localized, the otherwise computationally dominant grid-based operations scale as O(N) with system size N. Together with a scalar-relativistic treatment. the basis sets provide access to all elements from light to heavy. Both low-communication parallelization of all real-space grid based algorithms and a Scal-apack-based, customized handling of the linear algebra for all matrix operations are possible, guaranteeing efficient scaling (CPU time and memory) up to massively parallel computer systems with thousands of CPUs.

First author: Caramori, Giovanni F., The Effects of N-Heterocyclic Ligands on the Nature of the Ru-(NO) Bond in Ruthenium Tetraammine Nitrosyl Complexes, CROATICA CHEMICA ACTA, 82, 219, (2009)
Abstract: Quantum chemical calculations at the DFT level have been carried out to analyze quantitatively the Ru-II-(NO)(+), Ru-III-(NO)(0) and Ru-II-(NO)(0) bonds in trans-[Ru-II(NH3)(4)(L)(NO)](q) and trans[Ru-II(NH3)(4)(L)(NO)](q-1) complexes, where L = 4-picoline (4-pic), C-bound imidazole (imC), N-bound imidazole (imN), nicotinamide (me), pyridine (py), and pyrazine (pz). Equilibrium geometries and the vibrational frequencies are reported for the ground state GS and light-induced metastable states, MS1 and MS2, presenting good agreement with the experimental data. The nature of the Ru-II-(NO)(+) and Ru-II-(NO)(0) bonds was investigated by means of the energy decomposition analysis, EDA. The Ru-(NO) bonding situation has been analyzed in two different situations: prior and after one-electron reduction at the NO+ group. The EDA results for the complexes prior to the reduction of the NO+ indicate that the metal-ligand pi-orbital interactions between NO+ and the [Ru-II(NH3)(4)(L)](q-1) are the most important term and that the trans-ligands imN and nic contribute to an increase in the pi-donor strength of the metal centre towards NO+. For Ru-III-(NO)(0) bonds, the smallest values of Delta E-int, Delta E-Pauli, Delta E-elstat, and D-e are observed when L = imC or L = nic, independent of the state under consideration, GS or MS1, indicating that when L = imC or me the Ru-III-(NO)(0) bond in GS or in MS1 states is more labile. After the reduction of the NO+ group, the Ru-II-(NO)(0) becomes more labile when the traps-ligand is imC, which agrees with the experimental rate constants of NO0 dissociation.

First author: Kjelstrup-Hansen, Jakob, Charge transport in oligo phenylene and phenylene-thiophene nanofibers,ORGANIC ELECTRONICS, 10, 1228, (2009)
Abstract: Charge carrier mobilities have been measured in elongated crystalline aggregates with nanoscale cross-sectional dimensions. These molecular crystals are grown via dedicated epitaxial surface growth. They consist of well-ordered phenylene-thiophene (co-) oligomers that have been systematically tailored to study mobility of oligomers containing six rings and a variable number of thiophene rings. These organic nanoscale one-dimensional systems demonstrate charge mobilities as high as 1 cm(2) V(-1) s(-1). Density functional theory calculations have been performed in order to correlate the experimentally observed trends in mobility with molecular charge transport properties.

First author: Poltev, Valery I., DFT study of minimal fragments of nucleic acid single chain for explication of sequence dependence of DNA duplex conformation, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 912, 53, (2009)
Abstract: DFT studies of desoxydinucleoside monophosphate complexes with Na-ions (dDMPs), using DGAUSS and ADIF software reveal that the characteristic B-type conformation of DNA duplexes is initially predisposed in single strand in the form of a local minimum. Such predisposition may be important for biological functioning of DNA by facilitating an addition of new nucleotide in the processes of DNA duplication and restoration of double helix after unwinding. The computational results demonstrate the important contribution of intra-strand interactions to conformational stability and sequence-dependent variability of B-DNA duplexes. The main characteristics of the “canonical” BI conformations, such as the regions of torsion angles of sugar-phosphate backbone, C2′-endo or very close to C2′-endo sugar puckerings, and nearly parallel base-ring arrangements are already present in the single strand and are universal for all 16 dDMPs. The dihedral angle between the bases does not depend on the extent of their overlap, which suggests the major contribution of sugar-phosphate backbone to formation of these minima. The study reveals characteristic sequence dependence of the base arrangements. Namely, an extensive base-ring overlap takes place for all purine-purine and purine-pyrimidine sequences, and negligible ring overlap is observed in all pyrimidine-purine and pyrimidine-pyrimidine sequences. These arrangements closely resemble the geometrical characteristics of BI DNA in duplex crystals. Preliminary results of search for other energy minima related to helical DNA structures revealed the existence of BII-like minima for some dDMPs.

First author: Poleshchuk, O. Kh., Study of a surface of the potential energy for processes of alkanes free-radical iodination by B3LYP/DGDZVP method, JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 912, 67, (2009)
Abstract: We have analyzed by means of DFT calculations in conjunction with all-electron DGDZVP basis sets the thermodynamics of alkane free-radical iodination. The thermodynamic analysis of the radical iodination of some saturated hydrocarbons by t-butyl hypoiodite in the gas phase and solution with the use of the B3LYP/DGDZVP was carried out. The DFT calculations make predictions about the thermodynamic probability of the radical iodination of the saturated hydrocarbons when they interact with t-BuOl. The activation energy and the rate constants for reaction of hydrogen abstraction by the t-butoxyl radical prove a possibility of the iodination reaction by t-butyl hypoiodite. The probability of participation of polyvalent iodine in the process of iodination is discussed.

First author: Ducati, Lucas C., Molecules with All Triple Bonds: OCBBCO, N2BBN2, and [OBBBBO](2-), JOURNAL OF PHYSICAL CHEMISTRY A, 113, 11693, (2009)
Abstract: DFT calculations at the BP86/TZ2P level have been carried out for the compounds OCBBCO, N2BBN2, and [OBBBBO](2-). The calculations predict very short distances,and large bond dissociation energies for the central B-B bonds. The nature of the bonding situation was investigated with an energy decomposition analysis. It shows that the central boron-boron bonds’ are genuine triple bonds. The pi-bonding contributes between 38-40% to the total orbital interactions of the B B bonds. The compounds can be considered as donor-acceptor complexes L-BB-L between the central B-2 moiety in the third [(3)(1)Sigma(+)(g)] excited state and the ligands L = CO, N-2, BO-. The pi-backdonation L-BB-L for L = CO, N-2 is very strong, which suggests that the latter bonds should also be considered as triple bonds. The pi-bonding in [OB <- BB -> BO](2-) is weaker, which makes the latter bonds borderline cases for triple bonds. The triple-bond character explains the very large bond dissociation energies for the LB-BL and L-BB-L bonds.

First author: Cossairt, Brandi M., Properties and Reactivity Patterns of AsP3: An Experimental and Computational Study of Group 15 Elemental Molecules, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131, 15501, (2009)
Abstract: Facile synthetic access to the isolable, thermally robust AsP3 molecule has allowed for a thorough study of its physical properties and reaction chemistry with a variety of transition-metal and organic fragments. The electronic properties of AsP3 in comparison with P-4 are revealed by DFT and atoms in molecules (AIM) approaches and are discussed in relation to the observed electrochemical profiles and the phosphorus NMR properties of the two molecules. An investigation of the nucleus independent chemical shifts revealed that AsP3 retains spherical aromaticity. The thermodynamic properties of AsP3 and P-4 are described. The reaction types explored in this study include the thermal decomposition of the AsP3 tetrahedron to its elements, the synthesis and structural characterization of [(AsP3)FeCp*(dppe)][BPh4] (dppe = 1,2-bis(diphenylphosphino)ethane), 1, selective single As-P bond cleavage reactions, including the synthesis and structural characterization of AsP3(P(N(‘Pr)(2))N(SiMe3)(2))(2), 2, and activations of AsP3 by reactive early transition-metal fragments including Nb(H)(eta(2)-Bu-t(H)C=NAr)(N[(CH2Bu)-Bu-t]Ar)(2) and Mo(N[Bu-t]Ar)(3) (Ar = 3,5-Me2C6H3). In the presence of reducing equivalents, AsP3 was found to allow access to [Na][E3Nb(ODiPP)(3)] (Dipp = 2,6-diisopropylphenyl) complexes (E = As or P) which themselves allow access to mixtures of AsnP4-n(n = 1-4).

First author: Palusiak, Marcin, Unusual electron density topology and intramolecular steric pi-pi interaction in 1,3,5,7-cyclooctatetraene, CHEMICAL PHYSICS LETTERS, 481, 34, (2009)
Abstract: We explain the presence of the Cage Critical Point within the individual cyclooctatetraene ring as a result of the overlapping of p-type orbitals belonging to oppositely placed formally double CC bonds. This unusual ring topology is enabled by spatial arrangement of the double CC bonds in rigid skeleton of the COT ring in its natural tub-shaped conformation. Since the overlapping of the p-type orbitals may suggest some additional ‘through the space’ p-electron delocalization, this interaction is investigated in detail. Our results show that this interaction should be considered as a steric one and no extra stabilization from ‘through the space’ delocalization can be considered.

First author: Curley, John J., A Terminal Molybdenum Arsenide Complex Synthesized from Yellow Arsenic, INORGANIC CHEMISTRY, 48, 9599, (2009)
Abstract: A terminal molybdenum arsenide complex is synthesized in one step from the reactive As(4) molecule, The properties of this complex with its arsenic atom ligand are discussed in relation to the analogous nitride and phosphide complexes.

First author: Donzello, Maria Pia, Tetrakis(thiadiazole)porphyraziries. 6. Spectroelectrochemical and Density Functional Theory Studies of the Anions [TTDPzM](n-) (n=1-4; M = Zn-II, Mg-II(H2O), Cu-II, 2H(I)), INORGANIC CHEMISTRY, 48, 9890, (2009)
Abstract: Following previous cyclic voltammetric studies of tetrakis(thiadiazole)porphyrazines [TTDPzM] where M = Zn-II, Mg-II(H2O), Cu-II, or 2H(I) in nonaqueous media, a thin-layer spectroelectrochemical investigation was carried out in pyridine to characterize each stepwise one-electron reduction of the electrogenerated [TTDPzM](n-) complexes where n = 1-4. A similar UV-visible spectrum was observed for each form of the anion, independent of the central metal ion and detailed theoretical calculations by density functional theory (DFT) and time-dependent DFT (TDDFT) methods were applied to interpret the spectral features of [TTDPzZn](n-) (n = 1-4) which was selected as representative for describing the ground and excited-state electronic structures of the entire (TTDPzM](n-) series. The use of two exchange-correlation functionals, the pure, asymptotically correct statistical average of orbital potentials (SAOP) and the hybrid B3LYP functionals, proved to be essential for attaining a correct assignment of the key spectral features, The nature and intensity of the main spectral features are highlighted and interpreted on the basis of the ground-state electronic structure of the complexes.

First author: Irfan, Ahmad, Push-pull effect on the charge transfer, and tuning of emitting color for disubstituted derivatives of mer-Alq3, CHEMICAL PHYSICS, 364, 39, (2009)
Abstract: To design innovative and novel optical materials with high mobility, two kinds of disubstituted derivatives for meridianal isomer of tris(8-hydroxyquinolinato) aluminum (mer-Alq3) with push-pull (X-Y) substituents have been designed. The structures of tris(4-X-6-Y-8-hydroxyquinolinato)aluminum (type 1) and tris(4-Y-6-X-8-hydroxyquinolinato)aluminum (type 2) (where X = -CH3/-NH2 and Y = -CN/-Cl) in the ground (S-0) and first excited (S-1) states have been optimized at the B3LYP/6-31G* and CIS/6-31G* level of theory, respectively. All the designed derivatives of type 1 show blue shift while most of the type 2 derivatives show red shift as compared to the mer-Alq3. The emitting color could be tuned from blue to red. We have explained the distribution of HOMOs and LUMOs on different individual ligands. The reorganization energies of tris(4-methyl-6-chloro-8-hydroxyquinolinato)aluminum (1), tris(4-methyl-6-cyano-8-hydroxyquinolinato)aluminum (2), tris(4-chloro-6-methyl-8-hydroxyquinolinato)aluminum (5) and tris(4-cyano-6-methyl-8-hydroxyquinolinato)aluminum (6) are comparable with mer-Alq3. Thus these derivatives might be good candidates for emitting materials possessing comparable charge carrier mobility as mer-Alq3.

First author: Hattori, Tatsuya, The structure of monomeric and dimeric uranyl adsorption complexes on gibbsite: A combined DFT and EXAFS study, GEOCHIMICA ET COSMOCHIMICA ACTA, 73, 5975, (2009)
Abstract: We investigated the structure of uranyl sorption complexes on gibbsite (pH 5.6-9.7) by two independent methods, density functional theory (DFT) calculations and extended X-ray absorption. ne structure (EXAFS) spectroscopy at the U-L(III) edge. To model the gibbsite surface with DFT, we tested two Al(hydr)oxide clusters, a dimer and a hexamer. Based on polarization, structure, and relaxation energies during geometry optimization, the hexamer cluster was found to be the more appropriate model. An additional advantage of the hexamer model is that it represents both edges and basal faces of gibbsite. The DFT calculations of (monomeric) uranyl sorption complexes show an energetic preference for the corner-sharing versus the edge-sharing configuration on gibbsite edges. The energy difference is so small, however, that possibly both surface species may coexist. In contrast to the edge sites, sorption to basal sites was energetically not favorable. EXAFS spectroscopy revealed in all investigated samples the same interatomic distances of the uranyl coordination environment (R(U-Oax) approximate to 1.80 angstrom, R(U-Oeq) approximate to 2.40 angstrom), and towards the gibbsite surface (R(U-O) approximate to 2.87 angstrom, R(U-Al) approximate to 3.38 angstrom). In addition, two U-U distances were observed, 3.92 angstrom at pH 9.7 and 4.30 angstrom at pH 5.6, both with coordination numbers of similar to 1. The short U-U distance is close to that of the aqueous uranyl hydroxo dimer, UO(2)(OH)(2), reported as 3.875 angstrom in the literature, but significantly longer than that of aqueous trimers (3.81-3.82 angstrom), suggesting sorption of uranyl dimers at alkaline pH. The longer U-U distance (4.30 angstrom) at acidic pH, however, is not in line with known aqueous uranyl polymer complexes. Based on the EXAFS findings we further refined dimeric surface complexes with DFT. We propose two structural models: in the acidic region, the observed long U-U distance can be explained with a distortion of the uranyl dimer to form both a corner-sharing and an edge-sharing linkage to neighboring Al octahedra, leading to R(U-U) = 4.150 angstrom. In the alkaline region, a corner-sharing uranyl dimer complex is the most favorable. The U-O path at similar to 2.87 angstrom in the EXAFS spectra arises from the oxygen atom linking two Al cations in corner-sharing arrangement. The adsorption structures obtained by DFT calculations are in good agreement with the structural parameters from EXAFS analysis: U-Al (3.394 angstrom), U-U (3.949 angstrom), and U-O (2.823 angstrom) for the alkaline pH model, and U-Al (3.279 angstrom), U-U (4.150 angstrom), and U-O (2.743 angstrom) for the acidic pH model. This work shows that by combining EXAFS and DFT, consistent structural models for uranyl sorption complexes can be obtained, which are relevant to predict the migration behavior of uranium at nuclear facilities.

First author: Roos, Goedele, Enzymatic Catalysis: The Emerging Role of Conceptual Density Functional Theory,JOURNAL OF PHYSICAL CHEMISTRY B, 113, 13465, (2009)
Abstract: Experimentalists and quantum chemists are living in a different world. A wealth of theoretical enzymology-related publications is hardly known by experimentalists, and vice versa. Our aim is to bring both worlds together and to show the powerful possibilities of a multidisciplinary approach to study Subtle details of complicated enzymatic processes to a broad readership. MD simulations and QM/MM approaches often focus on the calculation of reaction paths based on activation energies, which is a time-consuming task. A valuable alternative is the reactivity descriptors founded in conceptual DFT like softness, electrophilicity, and the Fukui function, which describe the kinetic aspects of a reaction in terms of the response to perturbations in N and/or v(r), typical for a chemical reaction, of the reagents in the ground state. As such, the relative energies at the beginning of the reaction predict a sequence of activation energies only based on the properties of the reactants (Figure 5). In 2003, Geerlings et al. published a key review giving a detailed description of the principles and concepts of conceptual DFT and highlighting its success to study generalized acid/base reactions including addition, substitution, and elimination reactions. Since the time that this review appeared, conceptual DFT has proven its strength in literally hundreds of papers with application to organic and inorganic reactions. Its role in unravelling enzymatic reaction mechanisms, in handling experimentally difficult accessible biochemical problems, and in the interpretation of biochemical experimental observations is emerging and very promising.

First author: Aikens, Christine M., Effects of Core Distances, Solvent, Ligand, and Level of Theory on the TDDFT Optical Absorption Spectrum of the Thiolate-Protected Au-25 Nanoparticle, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 10811, (2009)
Abstract: Density functional theory calculations are employed to calculate geometries (R = H, CH3, CH2CH3, CH2CH2Ph) and excitation energies (R = H, CH3, CH2CH3) for the Au-25(SR)(18)(-) nanoparticle. The splitting between the first two peaks in the optical absorption spectrum is known to arise as a result of ligand-field splitting of superatom D orbitals, and the value of this splitting is found to be a very sensitive probe of gold-gold distances in the Au-25(SH)(18)(-) nanoparticle core. LDA functionals such as X alpha with a triple-zeta basis set are found to predict core geometries in good agreement with experiment, which suggests that this level of theory may be useful in future structural predictions. Asymptotically correct potentials SAOP and LB94 with triple-zeta basis sets yield excitation energies within 0.15-0.20 eV of experimental values; LB94 with a frozen-core basis set is found to be an inexpensive alternative to the preferred SAOP potential. The size of the ligand plays a minor role on the optical absorption spectrum and solvent effects on geometries and excitation energies are negligible, which demonstrates that the core geometric and electronic structure is primarily responsible for the discrete optical absorption exhibited by this nanoparticle.

First author: Zhang, Yi-Quan, Magnetic Anisotropy in a Family of Experimentally Synthesized and Theoretically Modeled M-6 ‘ M-8(CN24) Systems, CHEMPHYSCHEM, 10, 2496, (2009)
Abstract: A theoretical density functional study of the magnetic coupling interactions and magnetic anisotropy in a family of experimentally synthesized and theoretically modeled M-6’M-8(CN24) (M’ = Cu-II, Ni-II or Co-II; M = Fe-III or Cr-III) systems is presented. The calcu lations show that the interactions in the selected M-6’M-8(CN24) are all ferromagnetic and the near cubic symmetry of Cu6Fe8 is the origin of its negative magnetic anisotropy parameter D.

First author: Hopmann, Kathrin H., Density Functional Theory Calculations on Mossbauer Parameters of Nonheme Iron Nitrosyls, INORGANIC CHEMISTRY, 48, 9155, (2009)
Abstract: Density Functional Theory (DFT) calculations on transition metal nitrosyls often reveal unusual spin density profiles, involving substantial spatial separation of majority and minority spin densities. Against this context, there is a significant lack of studies where DFT calculations have been quantitatively calibrated against experimental spectroscopic properties. Reported herein are DFT calculations of Mossbauer isomer shifts and quadrupole splittings for 21 nonheme iron complexes (26 distinct iron sites) including 9 iron nitrosyls. Low- (S = 1/2) and high-spin (S = 3/2) {FeNO}(7) complexes, S = 1/2 {Fe(NO)(2)}(9) species, and polynuclear iron nitrosyls are all represented within the set of compounds examined. The general conclusion with respect to isomer shifts is that DFT (OLYP/STO-TZP) performs comparably well for iron nitrosyls and for iron complexes in general. However, quadrupole splittings are less accurately reproduced for nitrosyl complexes.

First author: Bart, Suzanne C., A New Tripodal Ligand System with Steric and Electronic Modularity for Uranium Coordination Chemistry, INORGANIC CHEMISTRY, 48, 9419, (2009)
Abstract: The synthesis of a potentially redox active tripodal ligand containing a tris(aryloxide) functionalized mesitylene anchor, (((ArOH)-Ar-tBu)(3)mes) (1), and its metalation with low-valent uranium to form [(((ArO)-Ar-tBu)(3)mes)U] (1-U) is reported. The results from characterization by X-ray crystallography, spectroscopic studies, and computational analysis, as well as initial reactivity studies, support a +3 uranium oxidation state. Comparison to the previously synthesized complex, [(((ArO)-Ar-tBu)(3)tacn)U] (2-U), featuring the redox-innocent triazacyclononane anchor reveals that changing the anchor from the flexible triazacyclononane to a rigid mesityl fragment increases the structural flexibility of the aryloxide substituents in complexes of 1. The synthesis and crystal structures of uranium(IV) amide complexes of 1-U and 2-U are discussed.

First author: Bugarcic, Tijana, Ruthenium(II) Arene Anticancer Complexes with Redox-Active Diamine Ligands,INORGANIC CHEMISTRY, 48, 9444, (2009)
Abstract: The synthesis and characterization of ruthenium(II) arene complexes of the general formula [(eta(6)-arene)Ru(XY)Z](+), where arene = p-cymene (p-cym), hexamethyl benzene (hmb), or biphenyl (bip), XY = o-phenylenediamine (o-pda), o-benzoquinonediimine (o-bqdi), or 4,5-dimethyl-o-phenylenediamine (dmpda), and Z = Cl, Br, or l, are reported (complexes 1-6). In addition, the X-ray crystal structures of [(eta(6)-p-cym)Ru(o-pda)Cl]PF(6) (1) and [(eta(6)-hmb)Ru-(o-bqdi)Cl]PF(6) (3PF(6)) are described. The Ru-N distances in 3PF(6) are significantly shorter [2.033(4) and 2.025(4) angstrom] compared to those in 1 [2.141(2) and 2.156(2) angstrom], All of the imine complexes (3-5) exhibit a characteristic broad (1)H NMR NH resonance at ca. delta 14-15. Complex 1 undergoes concomitant ligand-based oxidation and hydrolysis (38% after 24 h) in water. The oxidation also occurs in methanol. The iodido complex [(eta(6)-p-cym)Ru(o-bqdi)l]l (4) did not undergo hydrolysis, whereas the chlorido complex 3 showed relatively fast hydrolysis (t(1/2) = 7.5 min). Density functional theory calculations showed that the total bonding energy of 9-EtG in [(eta(6)-p-cym)Ru(o-pda)(9-EtG-N7)](2+) (1EtG) is 23.8 kJ/mol lower than that in [(eta(6)-p-cym)Ru(o-bqdi)(9-EtG-N7)](2+) (3EtG). The greater bonding energy is related to the contribution from strong hydrogen bonding between the NH proton of the chelating ligand and O6 of 9-EtG (1.69 angstrom). A loss of cytotoxic activity was observed upon oxidation of the amine ligand to an imine (e.g., IC(50) = 11 mu M for 1 and IC(50) > 100 mu M for 3, against A2780 ovarian cancer cells). The relationship between the cytotoxic activity and the solution and solid state structures of the imine and amine complexes is discussed.

First author: Miro, Pere, Towards a computational treatment of polyoxometalates in solution using QM methods and explicit solvent molecules, CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 87, 1296, (2009)
Abstract: This study is aimed at developing an explicit solvent model for highly charged species such as polyoxometalates. The model includes solvent molecules in the first solvation shell explicitly, and long-range bulk effects and counter-ions as a set of single point charges. The model strongly stabilizes the electronic structure of the Keggin anion. The energies of the Kohn-Sham orbitals obtained using our model lie very close to those computed using the COSMO continuum solvent model; moreover, the total solvation energy evaluated with our model compares well to the value calculated by COSMO.

First author: Amati, Mario, Bis(cyclopentadienyl)dihydrido Mo and W complexes as Lewis bases – A computational study about their adducts with BX3 (X = F, Cl) and Al(CH3)(3), CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 87, 1406, (2009)
Abstract: A computational investigation about the Lewis acid-base adducts between bases Cp2MH2 (M = Mo, W) and acids BX3 (X = F, Cl) and Al(CH3)(3) is presented. Density functional methods based on pure and hybrid correlation-exchange functionals and relativistic corrections based on the zero order relativistic approximation (ZORA) have been applied. A comparison with experimental data has been addressed to give insights about the nature of the acid-base interaction with the aim to evaluate the role of the transition metal in charge donation toward the acid centre. In this respect, the likelihood of proposed criteria for recognizing the presence of transition-metal direct charge donation has been discussed.

First author: Wren, John E. C., Neptunium(VII) in high-ionic-strength alkaline solutions – [NpO2(OH)(4)](1-) or [NpO4(OH)(2)](3-)?, CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 87, 1436, (2009)
Abstract: Relativistic density functional theory (ZORA-PBE, COSMO solvation) is used to address the title question, based on comparison with recent experimental data (1). Structural data (bond lengths), vibrational frequencies, and O-17 NMR chemical shifts are used to prove that [NpO4(OH)(2)](3-) is the predominant species in high-ionic-strength alkaline solutions of Np-VII. Neptunium(VII) complexes have stronger bonds than their formally isoelectronic uranium(VI) analogues. The experimentally observed 300 ppm shift in O-17 chemical shifts between the known [UO2(OH)(4)](2-) and Np-VII solution is shown to be partly a function of the central metal (Np-VII vs. U-VI) and not of the coordination environment (tetraoxo vs. dioxo). Comparing, for a given An (U-VI or Np-VII), actinyl complexes [AnO(2)X(4)](2-/1-), X = Cl, F, OH, a decreasing strength of the axial actinyl bond is observed that is traced to electronic factors (equatorial pi-competition).

First author: Goedecke, Catharina, The Dewar-Chatt-Duncanson model reversed – Bonding analysis of group-10 complexes [(PMe3)(2)M-EX3] (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl; X = H, F, Cl, Br, I), CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 87, 1470, (2009)
Abstract: Quantum chemical calculations using BP86 with TZ2P basis sets were carried out to elucidate the structures and the bond-bond dissociation energies of the donor-acceptor complexes [(PMe3)(2)M-EX3] with X = H, F, Cl, Br, I; E = B, Al, Ga, In, Tl; and M = Ni, Pd, Pt. The nature of the metal-ligand bond was investigated with an energy decomposition analysis. The geometry optimizations gave for most compounds T-shaped structures with nearly linear P-M-P angles where the EX3 ligand has either a staggered or eclipsed conformation with respect to the PMP plane. The energy differences between the conformations are very small which means that there is nearly free rotation about the M-EX3 axis. The equilibrium structures of eight nickel compounds have a distorted geometry where one E-X bond is engaged in attractive interactions with the metal atom which yields a distorted square-planar arrangement of the metal atom. The complex [(PMe3)(2)Ni-TlI3] exhibits two attractive interactions between Tl-I bonds and the metal which features a five-coordinated metal atom. The calculated bond dissociation energies show that the boron complexes exhibit a different trend for the D-e values than the heavier group-13 homologues. The results for the Pd and Pt complexes suggest that the [(PMe3)(2)M-BX3] bond strength increases with F < Cl < Br < I < H which means that the BH3 ligands are the most strongly bonded Lewis acids and BF3 is the most weakly bonded species . The trend for the heavier group-13 complexes [(PMe3)(2)M-EX3] where E = Al, Ga, In, Tl follows the opposite order F > Cl > Br > I > H. The energy decomposition analysis of the M-EX3 bonds indicates a substantial p contribution of between 12.7% and 30.3% to the total orbital interactions. There is no direct correlation between the strength of the orbital interactions or any of the other energy terms Delta E-elstat or Delta E-Pauli which correlates with the total interaction energy. The bond dissociation energy of the EX3 ligands after breaking the M-EX3 bonds is quite large. It is shown that the intrinsic strength of the M-EX3 bonds is much larger than the BDEs and that the trends of Delta E-int and D-e are not always the same. The EX3 ligands in [(PMe3)(2)M-BX3] always carry a large negative charge.

First author: Sutrisno, Andre, Experimental and theoretical investigations of selenium nuclear magnetic shielding tensors in Se-N heterocycles, CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 87, 1546, (2009)
Abstract: A preliminary study involving solid-state (77)Se NMR spectroscopy and first principles calculations of (77)Se NMR parameters in Se-N heterocycles is reported. (77)Se CP/MAS NMR spectra of the ring systems reveal expansive selenium chemical shift (CS) tensors, which are extremely sensitive to molecular geometry, symmetry, ligand substitution, and intermolecular contacts. For systems with known crystal structures, hybrid density functional theory (DFT) calculations of selenium nuclear magnetic shielding (NMS) tensors were carried out, and tensor orientations in the molecular frames examined. Additional DFT calculations of selenium NMS tensors are presented, along with a detailed analysis of pairs of occupied and virtual molecular orbitals that give rise to the Se NMS tensors. A new naturalized local molecular orbital (NLMO) analysis under the same DFT framework is also discussed. Collectively, the NMR data and first principles calculations provide understanding of the influences of electronic structure, bonding, and intermolecular interactions on the selenium NMS tensors, allowing for (i) prediction of unknown molecular structures and (ii) insight into the positions of the stereochemically active selenium lone pairs.

First author: Petz, Wolfgang, Carbodiphosphorane C(PPh3)(2) as a Single and Twofold Lewis Base with Boranes: Synthesis, Crystal Structures and Theoretical Studies on [H3B{C(PPh3)(2)}] and [{(mu-H)H4B2}{C(PPh3)(2)}](+),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 87, 4507, (2009)
Abstract: The donor-acceptor complex [(H3B){C(PPh3)(2)}] (2) has been synthesized by treating B2H6 with C(PPh3)(2) and its geometry determined by X-ray structure analysis Treatment of 2 with DIME yields the complex [{(mu-H)H4B2}{C(PPh3)}][B2H7] (4), which teas also been isolated and structurally characterized Compound 4 is the first complex of a carbodiphosphorane where the carbon donor atone binds with its two-electron lone pairs to two main-group Lewis acids larger than protons This reaction is likely to occur via initial formation of [(H3B)(2)-{C(PPh3)(2)}] (6), which subsequently reacts with B2H6 with loss of a hydride, to yield 4 Quantum chemical calculations of 2, 4(+) and 6 show that the carbon-boron bonds in these complexes are very strong, and analysis of the bonding situation using the EDA, NBO and AIM methods reveals typical bonding patterns between the divalent carbon(0) moieties and one or two Lewis acids. The carbon donor atolls of the carbodiphosphorane moiety remains strongly negatively charged even in the cation 4(+).

First author: Muniz, Jesus, Theoretical study on the series of [Au3Cl3M2] complexes, with M = Li, Na, K, Rb, Cs,JOURNAL OF MOLECULAR MODELING, 15, 1165, (2009)
Abstract: The prediction of the series of complexes [Au3Cl3M2] with M = Li, Na, K, Rb and Cs, has been achieved at the ab initio level of theory. All geometries were fully optimized at the MP2 level of theory; the central Au-3 cluster is capped by chlorine atoms and the alkaline metals lie above and below the plane of the central ring; aurophilic interactions were found on the metal cluster, and also a strong aromatic character coming from the delocalized d-electrons of the Au atoms according to nuclear independent chemical shift calculations. On the other hand, the chemical hardness parameter was used to test the stability of the series of complexes, and the Fukui indexes of electrophilic and nucleophilic attack were employed to explore possible sites where chemical reactivity may play a role.

First author: Courcot, Blandine, Structural and Vibrational Study of [Mo7O24](6-) and [W7O24](6-), JOURNAL OF PHYSICAL CHEMISTRY A, 113, 10540, (2009)
Abstract: Density functional methods have been used to investigate the structure and the vibrational modes Of [M7O24](6-) isopolyanions of rnolybdenum and tungsten. Relativistic effects have been considered through the zeroth-order regular approximation (ZORA) and interactions with an aqueous environment modeled by the COSMO approach. A structural study of the two compounds has been performed, and the geometrical parameters obtained are in good agreement with experimental data. However, when the solvent is introduced in the model, deviations are found, especially for some tungsten-oxygen bonds which involve pseudoterminal oxygens. Thus, different computational strategies have been tested to reject any reliance on the COSMO model and the optimization algorithms. The variations compared to solid-state bond lengths appear to be due to the solvent. Infrared and Raman spectra have been also calculated in the gas phase and in water leading, for the first time, to a detailed assignment of the vibrational frequencies. The vibrational contributions of the aminopyridinium counterion [C5H7N2](+) have been isolated, improving the assignment of experimental spectra. Inclusion of solvent causes a shift toward lower frequencies and an increase in the intensity of the peaks. Spectra obtained using pseudo-gas-phase calculations reproduce the experimental data most satisfactorily, especially when the experiments are performed oil the solid state.

First author: Gabuda, S. P., Supramolecular interactions and structural transformations in the metal-organic sorbent-acetone nanoreactor system, JOURNAL OF STRUCTURAL CHEMISTRY, 50, 887, (2009)
Abstract: By the H-1 NMR and Raman spectroscopy data it is shown that in the porous inclusion compound of Zn-2(C8H4O4)(2)[(N-2(CH2)(6)))]center dot n(CH3)(2)CO (n a parts per thousand 0-4.7) acetone molecules exist in two structural forms: ketonic (CH3)(2)CO, for which the H-1 NMR chemical shift value is delta(ket) = 0.8 ppm, and enolic CH3C(O)=CH2, for which delta(en)(OH) = 11 ppm, delta(en)(CH2) = 8.9 ppm, and delta(en)(CH3) = 1.6 ppm are found, the average value over three proton sites being <delta(en)>= 5.6 ppm. A sharp difference in chemical shift values for the keto and enol forms of acetone in the inclusion compounds can be assigned to the effect of structural chemical conditions in two types of adsorption centers.

First author: Shaw, Michael J., Consequences of the Protonation of the 19-Electron Anion [Co(eta(5)-C5H5)(1,5-C8H12)(-), ORGANOMETALLICS, 28, 5349, (2009)
Abstract: The electrochemical and chemical reduction of CoCp(1,5-COD) (1, Cp = eta(5)-C5H5-, COD = cyclooctadiene) has been reinvestigated in THF. Whereas the initially formed monoanion I- (E-1/2 = -3.01 V vs Fc, Fc = FeCp20/+) has been well-characterized electrochemically and by ESR spectroscopy, the long-term electrolysis product had been previously assigned as the isomerized anion [CoCp(1,3-COD)](-). New magnetic resonance data show that the ultimate product is the 17-electron cyclooctenyl complex CoCp(eta(3)-C8H13) (2, E-1/2 = -2.17 V), formed by the reaction of I- with adventitious proton donors. The eta(1):eta(3) -bonded isomer of 1, COCp(eta(1):eta(3) -C8H12) (3), reduces (E-1/2 = -2.97 V) to yield the same product 2 on the cyclic voltammetry (CV) time scale. Deliberate addition of the weak proton donor 2,4,6-trimethylphenol to solutions of 1 facilitates protonation and results in scan-rate- and concentration-dependent formation of 2 on the CV time scale as 1 is reduced in an ECE mechanism. Under these conditions, the reduced 2(-) anion undergoes further reaction with proton donors, which results in the formation of another electroactive product, 4, which is assigned the structure [CoCp(eta(3)-C8H13)H] oil the basis of NMR evidence and DFT calculations.

First author: Bordoni, Silvia, Ligand Control in Multihaptotropic O-Indenyl Rhenium Systems. Experimental and Theoretical Study, ORGANOMETALLICS, 28, 5382, (2009)
Abstract: The synthesis of a novel class of alcohol- and ether-functionalized indenyl ligands, focusing on the haptotropic rearrangements of the hybrid O-indenyl rhenium species, is herein described, eta(1)-Ind(x)(Ome)Re(CO)(5) (12(x)) and eta(3)-Ind(x)(OMe)Re(CO)(4) (13(x), x = a, d)[Ind(a)(OMe) = C(9)H(6)CH(2)CH(Me)OMe, 1(a); Ind(d)(OMe) = C(9)H(6)CH(CH(2))(3)CHOMe, 1d(a)] are examples of a and allylic intermediates in the Cp substitution. The tuning of stercoelcctronic effects of the functionalized alkyl chain or the coordinating solvent (MeCN, THF) allows the study of the relative stabilities of the intercepted solvento species eta(5)-Ind(h)(OMe) Re(CO)(2)(NCMe), 14(b), eta(5)-Ind(c)(OMe)Re(CO)(2)(THF), 15(c), or the chelate [eta(5):k(1)-O-Ind(b,c)(O)Re(CO)(2)], 16(b,c{)Ind(b)(OMe) = [C(9)H(6)CH(2)CH(Ph)OMe](-), 4(b); Ind(c)(OMe) = [C(9)H(6)CH(Ph)CH(2)OMe](-), 4(c)}. DFT calculations reported oil some of the Ind(o) systems have been compared with those of smaller (Cp(O)) 5(a) or larger (Flu(a)(O)) 10(a) congeners, confirming the experimental findings. As peculiar examples of the underrepresented low-valent rhenium alkoxy species, the isolation of k(1)-O-Hlnd(x)(O)Re(CO)(5) [X = a,b] is also reported.

First author: Sriskandakumar, Thamayanthy, Influence of Oxygenation on the Reactivity of Ruthenium-Thiolato Bonds in Arene Anticancer Complexes: Insights from XAS and DFT, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131, 13355, (2009)
Abstract: Thiolate ligand oxygenation is believed to activate cytotoxic half-sandwich [(eta(6)-arene)Ru(en)(SR)](+) complexes toward DNA binding. We have made detailed comparisons of the nature of the Ru-S bond in the parent thiolato complexes and mono- (sulfenato) and bis- (sulfinato) oxygenated species including the influence of substituents on the sulfur and arene. Sulfur K-edge XAS indicates that S(3p) donation into the Ru(4d) manifold depends strongly on the oxidation state of the sulfur atom, whereas Ru K-edge data suggest little change at the metal center. DFT results are in agreement with the experimental data and allow a more detailed analysis of the electronic contributions to the Ru-S bond. Overall, the total ligand charge donation to the metal center remains essentially unchanged upon ligand oxygenation, but the origin of the donation differs markedly. In sulfenato complexes, the terminal oxo group makes a large contribution to charge donation and Oven small electronic changes in the thiolato complexes are amplified upon ligand oxygenation, an observation which carries direct implications for the biological activity of this family of complexes. Details of Ru-S bonding in the mono-oxygenated complexes suggest that these should be most susceptible to ligand exchange, yet only if protonation of the terminal oxo group can occur. The potential consequences of these results for biological activation, are discussed.

First author: Richterova, V., New results in the ammonolysis of hexafluoro-cyclo-triphosphazene: Crystal structure of P3N3F5-NH-P3N3F4NH2, POLYHEDRON, 28, 3078, (2009)
Abstract: The reaction of hexafluoro-cyclo-triphosphazene P3N3F6 with ammonia in acetonitrile has been studied. New compounds, (2-imino-2,4,4,6,6-pentafluoro-2 lambda(5),4 lambda(5),6 lambda(5)-cyclo-triphosphaza-1,3,5-trienyl) -2-amino-4,4,6,6-tetrafluoro-2 lambda(5),4 lambda(5),6 lambda(5)-cyclo-triphosphaza-1,3,5-triene, P3N3F5-NH-P3N3F4NH2 (2) and cis and trans isomers of non-gem-2,4-diamino-2,4,6,6-tetrafluoro-2 lambda(5),4 lambda(5),6 lambda(5)-cyclo-triphosphaza-1,3,5-triene, P3N3F4(NH2)(2) (4, 5), were detected by GC/MS, and P-31 NMR spectroscopy in reaction mixtures. X-ray diffraction analysis of P3N3F5-NH-P3N3F4NH2 (2) revealed two conformational polymorphs, 2A and 2B, the latter being built up of two different conformers that were further denoted as 2B(a) (the same as the single conformer in 2A) and 2B(b). The compound 2 was characterized by spectroscopic methods and its 2D potential energy surface (PES) was described by density functional theory computations depending on two dihedral angles. The calculated PES spans over 30 kJ/mol in energy including 8 local minima and all first and second order saddle points. The occurrence of the two experimentally observed conformers 2B(a) and 2B(b) seems to be governed by crystal packing effects.

First author: Kim, Tae-Jin, Half-Metallocene Titanium(IV) Phenyl Phenoxide for High Temperature Olefin Polymerization: Ortho-Substituent Effect at Ancillary o-Phenoxy Ligand for Enhanced Catalytic Performance, MACROMOLECULES, 42, 6932, (2009)
Abstract: A series of mono- or dialkyl/lphenyl o-substituted phenoxy ligands in half-metallocene titanium(IV) complexes wits examined to determine the structure-catalytic activity relationship in high temperature olefin polymerization. Five different types of polymerization catalysts with different Cp/Cp* and mono- or disubstituted symmetric/asymmetric alkyl/phenyl phenoxide ancillary ligands were compared. This series wits examined for ethylene homopolymerization after activation with Ph(3)CB(C(6)F(5))(4) and mMAO-7 at high temperatures (140 degrees C). Type 4 complexes of compounds 15-18 [33.0-39.0 kg/(mmol of Ti.h)] showed much higher catalytic activity than those found in types 1-3 and 5 [3.6-27.6 kg/(mmol of Ti.h)], and among the type 4 complexes, the Cp*/2-phenylphenoxy combination of compound 18 [39 kg/(mmol of Ti.h)] Surpassed the Cp*/2-alkyl ligand systems of compounds 15-17 [33.0-36.0 kg/(mmol of Ti.h)]. The revolving nature of the phenoxy ligand around the Ti-O-C axis was identified by the NOSEY correlation peaks between the methyl protons of Cp* and protons of ancillary phenyl phenoxy ligand in compound 18. The conformational flexibility of the phenyl phenoxy ligand was further confirmed by a series of temperature-dependent ROSEY experiments based oil the optimization of two conformational structures related by this rotation. Rotational barriers of 4.3 and 6.6 kcal/mol were estimated from theoretical DFT studies. DFT calculations of the transition states for ethylene insertion and termination were carried out for representative examples of types 4 (15,16, 18), 3 (10,12), and 1 (3) catalysts as well as the constrained geometry catalyst (CGC) its a reference. The preference for back-side insertion was a unique feature of the monosubstituted type 4 catalysts. The type 4 catalysts showed significant activities for ethylene/1-octene copolymerization affording high molecular weight poly(ethylene-co-1-octene)s (M(w) = 107 000-164 000) with unimodal molecular weight distributions (M(w)/M(n) = 2.08-4.15). The activity increased in the order of type 3 [90-132 kg/(mmol of Ti.h), in toluene, ethylene 30 atm, 1-octene 8 mL, 140 degrees C, 10 min.] < CGC (222) < type 4 (228-354). Among the type 4 series, compound 18 showed the best performance, reaching an activity of 354 kg/(mmol of Ti.h). The polymer density of 0.9148 g/mL for compound 18 was lower than that found in CGC (0.9154 g/mL), indicating higher I-octene incorporation, which was further confirmed by an analysis of the (13)C NMR spectra of the polymers (18, 2.73 mol % and CGC, 2.55 mol %).

First author: Manzur, Jorge, Mononuclear and Polynuclear Copper(II) Complexes Derived from Pyridylalkylaminomethylphenol Polypodal Ligands, INORGANIC CHEMISTRY, 48, 8845, (2009)
Abstract: Four mononuclear complexes [Cu(HL1)CI]PF6 center dot CH3OH (1), [Cu(HSL1)CI]PF6 center dot 0.75H(2)O (2), [Cu(HL2)CI]PF6 center dot CH3OH (3), [Cu(HSL2)CI]PF6 center dot 1.5CH(3)OH (4), and two polynuclear complexes [Cu-2(SL2)(2)](PF6)(2)center dot 2CH(3)OH (5) and {Cu[Cu(SL2)(CI)](2)}(PF6)(2) (6) (HL1: 2-[(bis(2-pyridylmethyl)-amino)methyl]-4-methylphenol; HSL1: 2-[(bis(2-pyridylmethyl)amino) methyl]-4-methyl-6-(methyl-thio)phenol; HL2: 2-[(2-pyridylmethyl)(2′-pyridylethyl)-aminomethyl)]-4-methylphenol; HSL2: 2-[(2-pyridylmethyl)(2′-pyridylethyl)amino-methyl]-4-methyl-6-(methythio )phenol were obtained and characterized. The crystal structures of the mononuclear complexes 1-4 show the copper centers in a square-base pyramidal environment with the phenolic oxygen coordinated at the axial position. Dinuclear complex 5 has two copper centers with different geometry and bridged by phenoxo oxygens; one of the copper atoms is square pyrmidal while the other can be described with a highly distorted octahedral geometry with a long Cu-S distance (2.867 angstrom). Density functional theory calculations were used to obtain the reported structure of 6, since single crystals suitable for X-ray diffraction were not isolated. Magnetic studies done for 5 and 6 show an antiferromagnetic behavior for 5 (J = -134 cm(-1)) and a ferromagnetic behavior for 6 (J = +11.9 cm(-1)). Redox potentials for the mononuclear complexes were measured by cyclic voltammetry; the values show the effect of the chelating ring size (-213 mV and – 142 mV for Cu-HL1 and Cu-HL2, respectively) and the presence of the thiomethyl substituent (-213 mV and -184 mV for Cu-HL1 and Cu-HSL1, respectively).

First author: Vannucci, Aaron K., New Insights into Solvolysis and Reorganization Energy from Gas-Phase, Electrochemical, and Theoretical Studies of Oxo-Tp*Mo-V Molecules, INORGANIC CHEMISTRY, 48, 8856, (2009)
Abstract: Molecules of the general form Tp*MoO(OR)(2) [where Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate and (OR)(2) = (OMe)(2), (OEt)(2), and ((OPr)-Pr-n)(2) for alkoxide ligands and (OR)(2) = O(CH2)(3)O, O(CH2)(4)O, and O[CH(CH3)CH2CH(CH3)]O for diolato ligands] were studied using gas-phase photoelectron spectroscopy, cyclic voltammetry, and density functional theory (DFT) calculations to examine the effect of increasing ligand size and structure on the oxomolybdenum core, Oxidation potentials and first ionization energies are shown to be sensitive to the character of the diolato and alkoxide ligands. A linear correlation between the solution-phase oxidation potentials and the gas-phase ionization energies resulted in an unexpected slope of greater than unity. DFT calculations indicated that this unique example of a system in which oxidation potentials are more sensitive to substitution than vertical ionization energies is due to the large differences in the cation reorganization energies, which range from 0.2 eV or less for the molecules with diolato ligands to around 0.5 eV for the molecules with alkoxide ligands.

First author: Kepenekian, Mikael, What zeroth-order Hamiltonian for CASPT2 adiabatic energetics of Fe(II)N-6 architectures?, JOURNAL OF CHEMICAL PHYSICS, 131, 8856, (2009)
Abstract: Complete active space self-consistent field (CASSCF) calculations and subsequent second-order perturbative treatment (CASPT2) have been carried out on a series of metallic complexes based on a Fe(II)N-6 core. These compounds play a determinant role in the elaboration of potential bistable architectures such as spin-crossover materials. The adiabatic energies between the high-spin (HS) (S=2) and low-spin (LS) (S=0) states are evaluated with respect to the value of the shift ionization potential-electronic affinity (IPEA shift) recently introduced in the zeroth-order Hamiltonian [Ghigo et al., Chem. Phys. Lett. 396, 142 (2004)]. Based upon a series of experimental data, it is concluded that the commonly applied IPEA shift value (0.25 a.u.) is not satisfactory to properly discriminate the open-shell HS and closed-shell LS states. We suggest that a 0.50-0.70 a.u. value would be preferable for these specific adiabatic gap calculations.

First author: Constantinescu, Dana, Application of COSMO-RS Type Models to the Prediction of Excess Enthalpies,INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 48, 8710, (2009)
Abstract: This article presents a comparative study about the predictive capability of COSMO-SAC and COSMO-RS(Ol) models with respect to excess enthalpies of various binary systems. Results of the group contribution methods UNIFAC and modified UNIFAC (Do) are given for comparison. COSMO calculations were performed using sigma profiles based oil density functional theory (BP and B3LYP). These were generated by the quantum chemical programs Turbomole and Gaussian 03, with the basis sets used for the calculation being triple-xi valence polarization (TZVP) for Bill and 6-311G(d,p) in the case of B3LYP. All results are compared with experimental data stored in the Dortmund Data Bank for 10 85 1 binary data sets (5368 different binary mixtures) with over 165 000 experimental data points from nearly 2000 references and are analyzed according to the types of components in the mixture. As expected, the intensively trained mod. UNIFAC (Do) model performs best in predicting the excess enthalpy of binary systems in most cases, but also COSMO-RS type models often lead to astonishingly good results considering the very small number of parameters used. Overall, relative deviations for a common data set of 30.7% (mod. UNIFAC (Do)) and between 56.7% and 80.8% for the different COSMO-RS flavors were obtained. Whenever experimental data indicated a significant change of the excess enthalpy with temperature, the different COSMO-RS type models failed to reproduce this behavior.

First author: Smolentsev, Grigory, X-ray Emission Spectroscopy To Study Ligand Valence Orbitals in Mn Coordination Complexes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131, 13161, (2009)
Abstract: We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in X-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular X-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g., C, N, O center dot center dot center dot), to be distinguished. A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)(6)](2+), [Mn(H2O)(5)OH](+), and [Mn(H2O)(5)NH3](2+). An application of the method, with comparison between theory and experiment, is presented for the solvated Mn 2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N-3]BPh4, [LMn(B2O3Ph2)(ClO4)], and [LMn(acac)N]BPh4, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion, and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion.

First author: Rajapakshe, Asha, Insights into the nature of Mo(V) species in solution: Modeling catalytic cycles for molybdenum enzymes, INORGANICA CHIMICA ACTA, 362, 4603, (2009)
Abstract: The tris(pyrazolyl)borate and related tripodal N-donor ligands originally developed by Trofimenko stabilize mononuclear compounds containing (MoO2)-O-VI, (MoO)-O-VI, (MoO)-O-V, and (MoO)-O-IV units and effectively inhibit their polynucleation in organic solvents. Dioxo-Mo(VI) complexes of the type LMoO2(SPh), where L = hydrotris(3,5-dimethylpyrazol-1-yl) borate (Tp(*)), hydrotris(3-isopropylpyrazol-1-yl)borate (Tp(iPr)), and hydrotris(3,5-dimethyl-1,2,4-triazol-1-yl) borate (Tz) and related derivatives are the only model systems that mimic the complete reaction sequence of sulfite oxidase, in which oxygen from water is ultimately incorporated into product. The quasi-reversible, one-electron reduction of Tp(*)MoO(2)(SPh) in acetonitrile exhibits a positive potential shift upon addition of a hydroxylic proton donor, and the magnitude of the shift correlates with the acidity of the proton donor. These reductions produce two Mo(V) species, [Tp(*)Mo(V)O(2)(SPh)] and Tp(*)Mo(V)O(OH)(SPh), that are related by protonation. Measurement of the relative amounts of these two Mo(V) species by EPR spectroscopy enabled the pK(a) of the Mo-V(OH) unit in acetonitrile to be determined and showed it to be several pK(a) units smaller than that for water in acetonitrile. Similar electrochemical-EPR experiments for Tp(iPr)MoO(2)(SPh) indicated that the pK(a) for its Mo-V(OH) unit was similar to 1.7 units smaller than that for Tp(*)Mo(V)O(OH)(SPh). Density functional theory calculations also predict a smaller pK(a) for Tp(iPr)Mo(V)O(OH)(SPh) compared to Tp(*)Mo(V)O(OH)(SPh). Analysis of these results indicates that coupled electron-proton transfer (CEPT) is thermodynamically favored over the indirect process of metal reduction followed by protonation. The crystal structure of Tp(iPr)MoO(2)(SPh) is also presented.

First author: van Faassen, Meta, Atoms in boxes: From confined atoms to electron-atom scattering, JOURNAL OF CHEMICAL PHYSICS, 131, 4603, (2009)
Abstract: We show that both confined atoms and electron-atom scattering can be described by a unified basis set method. The central idea behind this method is to place the atom inside a hard potential sphere, enforced by a standard Slater type basis set multiplied by a cutoff factor. For confined atoms, where the wall is placed close to the atomic nucleus, we show how the energy of the highest occupied atomic orbital and the static polarizability of helium and neon atoms evolve with the confinement radius. To our knowledge, these are the first confined atom polarizability calculations that include correlation for many-electron atoms, through the use of time-dependent density-functional theory. By placing the atom in a large spherical box, with a wall outside the electron density, we obtain scattering phase shifts using a recently developed method [M. van Faassen, A. Wasserman, E. Engel, F. Zhang, and K. Burke, Phys. Rev. Lett. 99, 043005 (2007)]. We show that the basis set method gives identical results to previously obtained phase shifts for e-H and e-He(+) scattering.

First author: Wang, Nan, Drastically enhanced visible-light photocatalytic degradation of colorless aromatic pollutants over TiO2 via a charge-transfer-complex path: A correlation between chemical structure and degradation rate of the pollutants,JOURNAL OF CATALYSIS, 266, 199, (2009)
Abstract: Photocatalytic degradation of colorless aniline and phenolic pollutants was investigated over TiO2 under visible-light irradiation, which was confirmed to proceed via a charge-transfer-complex (CTC)-mediated pathway. The correlation between the chemical structure and the degradation rate of these pollutants was established experimentally and theoretically. It was found that an electron-donating substituent in benzene ring, which raises the highest occupied molecular orbital and lowers the ionization potential of the organic compound, is favorable to the CTC-mediated photodegradation of the pollutant, but an electron-withdrawing substituent has a reversed effect. The addition of sacrificial electron acceptors was adopted to enhance the degradation and mineralization of the aromatic pollutants. The increased degradation rate by 3 to 10 times suggests that the CTC-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants in the presence of sacrificial electron acceptors.

First author: Dutta, Sudipta, Understanding Peierls distortion in one-dimensional infinite V-chain and V-Bz multi-decker complex, CHEMICAL PHYSICS LETTERS, 479, 133, (2009)
Abstract: We perform first-principles calculations based on density-functional theory to study the stable structures of one-dimensional (1D) linear infinite vanadium (V) chain. The calculation shows that it prefers to dimerize according to the Peierls theorem. However, in 1D infinite neutral V-benzene (V-Bz) multi-decker complex, the dimerization almost disappears because of the screening effect of the intervening benzene rings. Additionally, we study the effect of electronic correlations on dimerization in 1D chains. Our numerical analysis reveals that, although the strong electron-electron interaction suppresses the dimerization, strong electron-phonon coupling overwhelms it to gain stability through dimerization in such systems.

First author: Liu, Chun-Guang, Second-Order Nonlinear Optical Properties of Trisubstituted Keggin and Wells-Dawson Polyoxometalates: Density Functional Theory Investigation of the Inorganic Donor-Conjugated Bridge-Acceptor Structure,INORGANIC CHEMISTRY, 48, 8115, (2009)
Abstract: The donor-conjugated bridge-acceptor (D-A) model, as a simple molecular scheme, has been successfully used in the development of second-order organic compound, organometallic compound, and metal complex nonlinear optical (NLO) materials. However, for the totally inorganic molecules, the use of this model is still prohibitive. In the present paper, time-dependent density functional theory (TDDFT) was used to investigate the second-order NLO properties of vanadium- and molybdenum-trisubstituted Keggin and Wells-Dawson polyoxometalates (POMs). The results show that these POM clusters possess D-A structures. The oxygen atoms in the cap region and metal (vanadium and molybdenum) atoms in another cap region in these POM clusters can be viewed as the electron donor and acceptor, respectively. The vanadium ion derivatives possess larger second-order NLO responses and dipole moment than molybdenum ions derivatives; thus, the three vanadium atoms in the cap region act as a strong acceptor related to the three molybdenum atoms in cap region in our D-A scheme. The vanadomolybdate with Wells-Dawson structure displays the good second-order NLO response because of the relevant long conjugated bridge and strong acceptor. This D-A model may be an effective approach for optimizing the first hyperpolarizabilities of inorganic POM clusters.

First author: Teets, Thomas S., Three-Coordinate, Phosphine-Ligated Azadipyrromethene Complexes of Univalent Group 11 Metals, INORGANIC CHEMISTRY, 48, 8134, (2009)
Abstract: Tetraarylazadipyrromethenes are Lewis basic, red-light absorbing dyes With optical properties conducive to sensing and therapeutic applications. Recently, transition metal complexes of these ligands have been described. Here, we report a series of three-coordinate Group 11 complexes of unsubstituted and methoxy-substituted tetraarylazadipyrromethenes. In each, two pyrrole nitrogens chelate a d(10) metal ion; triphenyl-or triethylphosphine occupies a third coordination site. New complexes are characterized by multinuclear NMR, X-ray crystallography, optical absorption and emission spectroscopy, and elemental analysis. Solid-state structures show trigonal planar geometries about the metal centers, and reveal pervasive intra- and intermolecular pi-stacking interactions. Visible light absorption intensifies with metal binding, in some cases shifting to longer wavelengths. The complexes weakly luminesce in the red region; emission wavelengths and quantum yields are similar to those of free azadipyrromethenes. Methoxy-substitution on the ligand red-shifts optical features, whereas substitution of triethylphosphine for triphenylphosphine in the third coordination site has minimal structural or spectral consequences.

First author: Hartl, Frantisek, Soluble Redox-Active Polymetallic Chains [{Ru-0(CO)(L)(bpy)}(m)](n) (bpy=2,2 ‘-bipyridine, L = PrCN, Cl-; m=0,-1): Electrosynthesis and Characterization, INORGANIC CHEMISTRY, 48, 8233, (2009)
Abstract: Electrochemical and spectroelectrochemical techniques were employed to study in detail the formation and so far unreported spectroscopic properties of soluble electroactive molecular chains with nonbridged metal-metal backbones, namely, [{Ru-0(CO)(PrCN)(bpy)}(m)](n) (m = 0, -1) and [{Ru-0(CO)(bpy)Cl}(m)](n) (m = -1, -2; bpy = 2,2′-bipyridine). The precursors cis-(Cl)-[Ru-II(CO)(MeCN)(bpy)Cl-2] (in PrCN) and mer-[Ru-II(CO)(bpy)Cl-3](-) (in tetrahydrofuran (THF) and PrCN) undergo one-electron reductions to reactive radicals [Ru-II(CO)(MeCN)(bpy(center dot-))Cl-2](-) and [Ru-II(CO)(bpy(center dot-))Cl-3](2-), respectively. Both [bpy(center dot-)]-containing species readily electropolymerize on concomitant dissociation of two chloride ligands and consumption of a second electron. Along this path, mer-to-fac isomerization of the bpy-reduced trichlorido complex (supported by density functional theory calculations) and a concentration-dependent oligomerization process contribute to the complex reactivity pattern. In situ spectroelectrochemistry (IR, UV/vis a has revealed that the charged polymer [{Ru-0(CO)(bpy)Cl}(-)](n) is stable in THF, but in PrCN it converts readily to [Ru-0(CO)(PrCN)(bpy)](n). An excess of chloride ions retards this substitution at low temperatures. Both polymetallic chains are completely soluble in the electrolyte solution and can be reduced reversibly to the corresponding [bpy(center dot-)]-containing species.

First author: Rayon, Victor M., Cyanide complexes of Ti(IV): A computational study, JOURNAL OF CHEMICAL PHYSICS,131, 8233, (2009)
Abstract: Density functional theory (B3LYP) and coupled-cluster techniques [CCSD(T)] including solvent effects have been used to study the homoleptic and mixed cyanide/isocyanide complexes of Ti(IV), [Ti(CN)(n)](4-n) (n=1-6). The most stable isomer is found to be the isocyanide form except for n=6 where the cyanide isomer is preferred. Calculations accounting for solvent effects show that, irrespective of the solvent employed, the hexacyanocomplex should be formed. We have additionally analyzed the bonding situation in these complexes in order to shed some light on the reasons for the predicted cyano-/isocyano preference. We have found that the more advantageous sigma-bonding capabilities of the cyanide form become increasingly important for larger n eventually favoring the cyanoisomer for n=6. We finally compare the bonding situation in hexacyanotitanate(IV) with that of hexacyanoferrate(II).

First author: Swart, Marcel, A new all-round density functional based on spin states and S(N)2 barriers, JOURNAL OF CHEMICAL PHYSICS, 131, 8233, (2009)
Abstract: We report here a new empirical density functional that is constructed based on the performance of OPBE and PBE for spin states and S(N)2 reaction barriers and how these are affected by different regions of the reduced gradient expansion. In a previous study [Swart, Solagrave, and Bickelhaupt, J. Comput. Methods Sci. Eng. 9, 69 (2009)] we already reported how, by switching between OPBE and PBE, one could obtain both the good performance of OPBE for spin states and reaction barriers and that of PBE for weak interactions within one and the same (SSB-sw) functional. Here we fine tuned this functional and include a portion of the KT functional and Grimme’s dispersion correction to account for pi-pi stacking. Our new SSB-D functional is found to be a clear improvement and functions very well for biological applications (hydrogen bonding, pi-pi stacking, spin-state splittings, accuracy of geometries, reaction barriers).

First author: Perez-Peralta, Nancy, Bonding of Xenon Hydrides, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 9700, (2009)
Abstract: We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability.

First author: Weng, Shou-Zheng, Diazapentacene Derivatives as Thin-Film Transistor Materials: Morphology Control in Realizing High-Field-Effect Mobility, ACS APPLIED MATERIALS & INTERFACES, 1, 2071, (2009)
Abstract: 5,7,12,14-Tetrachloro-6,13-diaza-6,13-dihydropentacene (TCDAHP) and 5,7,12, 14-tetrachloro-6,13-diazapentacene (TCDAP) were synthesized and assessed as the active channel materials for thin-film transistor applications. Analyses of the crystal structures of these molecules revealed that both exhibited slipped pi-pi stacking of the long and fused aromatic moiety. Although the packing Features of the two compounds are basically identical, their highest occupied molecular orbitals, which are relevant to hole transport, are very different. Better mobility was predicted for TCDAHP over TCDAP based on the dimeric structure in: the X-ray coordinates. The morphologies of thin films of TCDAHP and TCDAP prepared by thermal evaporation depend critically on the substrate on which the molecules were deposited: from the amorphous state on a SiO(2)/Si surface to the crystalline state on a pentacene buffer layer surface. The performance of chin-film transistors prepared on various Substrate surfaces was studied. While no field-effect mobility was observed for these films deposited on SiO(2)/Si, a high mobility of 1.4 cm(2)/(V s) For the TCDAHP film was achieved when deposited on a pentacene buffer layer prepared on a rubbed monolayer of n-nonyltrichlorosilane on a SiO(2)/Si surface, A similar device prepared from TCDAP gave a mobility of 0.13 cm(2)/(V s).

First author: Sulway, Scott A., Alkali Metal Complexes of Silyl-Substituted ansa-(Tris)allyl Ligands: Metal-, Co-Ligand- and Substituent-Dependent Stereochemistry, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 1, 4157, (2009)
Abstract: The structures of alkali metal complexes of silyl-substituted ansa-tris(allyl) ligands [RSi(C(3)H(3)SiMe(3))(3)](3-) (R = Me, L(1); or Ph, L(2)) are discussed. Triple deprotonation of L(1)H(3) by nBuNa/tmeda affords [L(1){Na(tmeda)}(3)] (4) in which the sodium cations are complexed by eta(n)-allyl ligands and the silyl substituents adopt [exo,exo][endo,exo](2) stereochemistries in one crystallographically disordered form and [endo,exo](3) in another. Triple deprotonation of L(2)H(3) with nBuLi/tmeda results in the formation of [L(2){Li(tmeda)}(3)] (5), the structure of which features silyl substituents with [exo,exo](2)[endo,exo] stereochemistries. The trisodium complex [L(2)Na(Na(tmeda)}(2)](2) (6) consists of a hexa(allylsodium) macrocycle that aggregates as a result of cation-pi interactions between the phenyl substituents and the sodium cations. An attempt to prepare the tripotassium complex of V resulted in the formation of the bimetallic potassium/lithium complex [L(2){K(OEt(2))(2)}(2)KLi(mu(4)-OtBu)](2) (7), in which the lithium tert-butoxide by-product is incorporated into a hexa(allylpotassium) macrocycle, Triple deprotonation of L(1)H(3) with nBuLi and the terdentate Lewis base pmdeta results in [L(1)L(i)-(pmdeta)}(3)] (8), in which the three allyl groups do not mu-bridge between lithium cations, resulting in an [exo,exo](3) stereochemistry of the silyl substituents. NMR spectroscopic studies reveal complicated solution-phase behaviour for 4, 6 and 7, whereas the solid-state structures of 5 and 8 are preserved in solution. Further insight into the structures and stereochemical preference of the ansa-tris(allyl) ligands in 4 and 5 is provided by detailed density functional theory calculations.

First author: Fu, Qiang, Exploring at nanoscale from first principles, FRONTIERS OF PHYSICS IN CHINA, 4, 256, (2009)
Abstract: Systems at the nanoscale can exhibit distinctive and unexpected properties in electrical, magnetic, mechanical, and chemical aspects. Understanding these properties not only is of importance from the fundamental scientific view but also offers great opportunities for future applications. Theoretical calculations can provide important information to interpret, modify, and predict the novel properties of objects at the nanoscale and therefore play a significant role in the process of exploring the nano world. In this review, six different areas are briefly presented, namely, prediction of new stable structures, modi. cation of properties (especially the electronic structures), design of novel devices for applications, the structures and catalytic effects of clusters, the mechanical and transport properties of gold nanowires, and improvement of materials for hydrogen storage. Based on these examples, we show what can be done and what can be found in the investigations of nanoscale systems with participation of theoretical calculations.

First author: Palusiak, Marcin, pi-Electronic Communication Through Mono and Multinuclear Gold(I) Complexes,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 109, 2507, (2009)
Abstract: We have theoretically studied gold(I) complexes of the type L-1-Au-1-L-2 and HCN-[Au-1-CN](n) (n = 1-8) using relativistic density functional theory at ZORA-BP86/TZ2P. Our purpose, besides determining structure and stability, is to analyze the bonding in our model systems in the conceptual framework of Kohn-Sham molecular orbital theory in combination with a quantitative bond energy decomposition scheme and analysis of the charge distribution. We focus on the pi-bonding interaction for a given ligand-gold coordination bond and how this is affected by the presence of the other ligand. We find pronounced pi-electronic communication through the gold(I) valence shell in complexes that involve a pi-donor as well as a pi-acceptor ligand.

First author: Pantazis, Dimitrios A., All-Electron Scalar Relativistic Basis Sets for the Lanthanides, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 5, 2229, (2009)
Abstract: Segmented all-electron relativistically contracted (SARC) basis sets are constructed for the elements (57)La-(71)Lu and optimized for density functional theory (DFT) applications. The basis sets are intended for use in combination with the DKH2 or ZORA scalar relativistic Hamiltonians for which individually optimized contractions are provided. Significant computational advantages can be realized owing to the loose contraction of the SARC basis sets compared to generally contracted basis sets, while their compact size allows them to replace effective core potentials for routine studies of lanthanide complexes. The new basis sets are evaluated in DFT calculations of the first four ionization energies of the lanthanides. They yield results that accurately reproduce the experimental trends, confirming a balanced treatment of different electronic configurations. The performance of the basis sets is further assessed in molecular systems with a comprehensive study of the lanthanide trihalides. Despite their compact size, the SARC basis sets demonstrate consistent, efficient, and reliable performance and will be especially useful in calculations of molecular properties that require explicit treatment of the core electrons.

First author: Sun, Zhong-Ming, Diversity of Functionalized Germanium Zintl Clusters: Syntheses and Theoretical Studies of [Ge9PdPPh3](3-) and [Ni@(Ge9PdPPh3)](2-), JOURNAL OF CLUSTER SCIENCE, 20, 601, (2009)
Abstract: A new Zintl cluster [Ge9PdPPh3](3-) has been isolated as (2,2,2-crypt)K+ salt through the reaction of K4Ge9 and Pd[PPh3](4) in ethylenediamine solutions and characterized via single-crystal X-ray crystallography. The as-prepared bimetallic [Ge9PdPPh3](3-) cluster could successfully trap a nickel atom to form a trimetallic cluster [Ni@(Ge9PdPPh3)](2-). The coordination of Ge-9(4-) by PdPPh3 induces a one-electron oxidation and encapsulation of the Ni atom into the Ge-9(3-) cage leads to a further one-electron oxidation and a geometry transformation from C-4v (nido) to C-3v (closo).

First author: Roy, Sudeshna, Platinum(II) compounds with chelating ligands based on pyridine and pyrimidine: Synthesis, characterizations, DFT calculations, cytotoxic assays and binding to a DNA model base, JOURNAL OF INORGANIC BIOCHEMISTRY, 103, 1278, (2009)
Abstract: Two chelating ligands based on secondary amines have been selected to prepare four new Pt(II) compounds. The ligands bis(pyridine-2-yl)amine, abbreviated dpa, and bis(pyrimidine-2-yl)amine, abbreviated dipm, are chosen to design a rigid chelating motif to allow the study of subtle differences in electronic properties and hydrogen bonding ability. Different carrier ligands (i.e. chloride and ammine) have also been introduced to allow a study of structure-activity relationships. Two of the four compounds are cisplatin analogues, whereas the other two are cationic and coordinatively saturated compounds. The four synthesized and characterized compounds are [Pt(dpa)Cl-2], [Pt(dpa)(NH3)(2)](NO3)(2), [Pt(dipm)Cl-2] and [Pt(dipm)(NH3)(2)](NO3)(2) With code numbers C1-C4. The spatial structures of all these compounds have also been optimized using DFT (density functional theory) calculations. The cytotoxicity of these compounds has been investigated in seven human tumor cell lines using the SRB (sulforhodamine B) assay. The most promising antitumor active compound appears to be C3, [Pt(dipm)Cl-2]. Two water-soluble compounds, C2 and C4 exhibit selective activity in EVSA-T cell line. In addition, the reaction of the cisplatin analogues with the model base 9-ethylguanine has been followed by proton and platinum NMR spectroscopy.

First author: Shaik, Sason, Charge-shift bonding and its manifestations in chemistry, NATURE CHEMISTRY, 1, 443, (2009)
Abstract: Electron-pair bonding is a central chemical paradigm. Here, we show that alongside the two classical covalent and ionic bond families, there exists a class of charge-shift (CS) bonds wherein the electron-pair fluctuation has the dominant role. Charge-shift bonding shows large covalent-ionic resonance interaction energy, and depleted charge densities, and features typical to repulsive interactions, albeit the bond itself may well be strong. This bonding type is rooted in a mechanism whereby the bond achieves equilibrium defined by the virial ratio. The CS bonding territory involves, for example, homopolar bonds of compact electronegative and/or lone-pair-rich elements, heteropolar bonds of these elements among themselves and with other atoms (for example, the metalloids, such as silicon and germanium), hypercoordinated molecules, and bonds whose covalent components are weakened by exchange-repulsion strain (as in [1.1.1]propellane). Here, we discuss experimental manifestations of CS bonding in chemistry, and outline new directions demonstrating the portability of the new concept.

First author: Li, An, Synthesis of cyanated tetracenes as the organic semiconductors, ORGANIC ELECTRONICS, 10, 1054, (2009)
Abstract: Two novel and air-stable cyanated tetracene derivatives, 5-cyanotetracene (1CT) and 5,11-dicyanotetracene (2CT), were synthesized as high-performance organic semiconductors. The stability of 2CT was evaluated by NMR and the electrochemical property was investigated by cyclic voltammetry (CV) and UV-vis spectrum. The reorganization energy of 2CT predicted by UB3LYP/6-311g(d,p) is 0.0881 eV, which is the lowest among existing compounds. The X-ray crystallographic analysis revealed that the 2CT single crystal has a promising face-to-face packing with a relative short intermolecular distance of 3.403 angstrom. Based on the theoretical model we previously developed, the calculated hole mobilities of these air-stable cyanated tetracene derivatives in a-b plane are 2.9 cm(2) V-1 s(-1) for 1CT and 2.2 cm(2) V-1 s(-1) for 2CT, respectively. These oxygen-resisted organics may offer potential to fabricate the flexible electronics under air conditions.

First author: Neugebauer, Johannes, On the calculation of general response properties in subsystem density functional theory, JOURNAL OF CHEMICAL PHYSICS, 131, 1054, (2009)
Abstract: A recently developed subsystem formalism within time-dependent density functional theory for excitation energies [J. Chem. Phys. 126, 134116 (2007)] is extended to the calculation of general response properties such as frequency-dependent polarizabilities or optical rotatory dispersion. Furthermore, explicit expressions for oscillator and rotatory strengths are presented. Polarizabilities and optical rotation tensors of the combined system are obtained as the sum of subsystem properties, so that a natural partitioning of the polarizability or the optical rotation is facilitated. This is of great advantage for the analysis of environmental effects on molecular response properties as it allows one to distinguish changes in the ground-state electronic structure of the subsystems from cooperative excited-state effects. A computational scheme that implements the formalism is presented together with applications highlighting the differences between embedding effects included in the subsystem potential and environmental response effects. The method avoids basis-set superposition errors in the calculation of response properties of large molecules, which occur in supermolecular calculations. Possible approximations to the full response algorithm are discussed.

First author: Witlicki, Edward H., Determination of Binding Strengths of a Host-Guest Complex Using Resonance Raman Scattering, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 9450, (2009)
Abstract: The detection of analyte-binding events by receptors is drawing together the fields of Raman spectroscopy and supramolecular chemistry. This study is intended to facilitate this cohering by examining a model system in the solution phase, The resonance Raman scattering (RRS) spectra of the complexation between tetrathiafulvalene (TTF) and cyclobis(paraquat-p-phenylene) (CBPQT(4+)) has been used as the model to characterize the binding event of a host-guest system. RRS spectra are generated by excitation (lambda(exc) = 785 nm) within the lowest-energy charge-transfer (CT) transition (lambda(max) = 865 nm) of the TTF subset of CBPQT(4+) complex. The paired binding curves from the RRS and UV-vis-NIR titration data agrees with prior work. and a Delta G of -5.7 +/- 0.6 kcal mol(-1) (MeCN, 298 K) was obtained for the complexation of TTF with CBPQT(4+). Computations on the complex and its components reproduce the energy shifts and resonance enhancements of the Raman band intensities, providing a basis to identify the structural and vibrational changes Occurring upon complexation. The changes in bond lengths coincide with partial depopulation of a TTF-based HOMO and population of a CBPQT(4+)-based LUMO through CT mixing in the ground state of 0.46e(-). The structural changes upon complexation generally lead to lower wavenumber vibrations and to changes in the normal mode descriptions.

First author: Scuppa, Stefano, Nonlinear Absorption Properties and Excited State Dynamics of Ferrocene, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 9286, (2009)
Abstract: We report on the first observation of reverse saturable absorption by ferrocene (Fc) in toluene using nanosecond pulses at 532 nm. Pump and probe experiments in the visible spectral region show the existence of an excited triplet state with an intersystem crossing quantum yield S-1 -> T-1 of 0.085 and a molar extinction coefficient epsilon(T)(Fc) of 5650 L mol(-1) cm(-1) at 700 nm. The full understanding of the nonlinear optical behavior of Fc cannot be obtained, however, with a model that includes only the one-photon absorption from T-1, but it is mandatory to consider also a simultaneous two-photon absorption from an excited singlet state of Fc (two-photon absorption cross section: 2.4 x 10(-41) cm(4) s ph(-1) mol(-1)). The optical spectrum of the ground and triplet state of Fc are calculated within a TD-DFT approach considering several functionals (PBE, BLYP, LDA, OPBE) for the optimization of molecular geometry.

First author: Alemayehu, Abraham B., Copper Corroles Are Inherently Saddled, INORGANIC CHEMISTRY, 48, 7794, (2009)
Abstract: X-ray crystallographic analyses of two sterically unhindered copper meso-triarylcorroles, Cu[5,15-P-2-10-(4-MeOP)C] and Cu[5,15-(4-CF3P)(2)-10-(4-MeOP)C] (P = phenyl and C = corrole), revealed substantially saddled corrole rings. These results are in marked contrast to those on highly sterically hindered cobalt(III) and iridium(III) corroles, which exhibit planar corrole macrocycles. The solution to this conundrum is that copper corroles are inherently saddled, as a result of a specific copper(d)-corrole(pi) orbital interaction. This orbital interaction results in a noninnocent corrole ligand, and the overall electronic structure may thus be described as Cu-II-corrole(center dot 2-). While many specific metal(d)-macrocycle(pi) orbital interactions are known for nonplanar metalloporphyrins, this work provides a rare example of such an orbital interaction providing the actual driving force for a significant nonplanar distortion. Our findings on copper corroles, along with those of others on cobalt and iridium corroles, thus constitute an intriguing and somewhat counterintuitive chapter in the structural chemistry of metallocorroles.

First author: Grobbelaar, Ebeth, Investigation of the electron density of iridium(I) Vaska-type complexes using DFT calculations and structural results: Structure of trans-carbonyl-chloro-bis(tricyclohexylphosphine)-iridium(I), INORGANICA CHIMICA ACTA, 362, 3949, (2009)
Abstract: [Ir(CO)Cl(PCy3)(2)] was obtained by the slow attack of 1,2-dichloromethane on (Bu4N)[Ir-2(mu-Dcbp)(CO)(2)(PCy3)(2)] (Dcbp = 3,5-dicarboxylatepyrazole). The Ir-CO, Ir-Cl and Ir-P bond distances are 1.778(10), 2.374(3)and 2.3486(8) angstrom, respectively. The Ir-P bond distances for a number of different Vaska complexes indicate the shortest bond distances for phoshines containing electron withdrawing groups. An excellent correlation between DFT (OLYP/ZORA/TZP)and experimental structures is obtained as reflected by the RMSD values (H excluded)of between 0.083 and 0.268 angstrom for the different complexes studied. The calculated Ir-P bond distances and nu(CO)stretching frequencies closely follow the trends obtained from the experimental results.

First author: Zhu, Yu-Lan, Theoretical investigation of electronic structures and excitation energies of hexaphyrin and its group 11 transition metal (III) complexes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 694, 3012, (2009)
Abstract: Density functional theory is carried out to study hexaphyrin and its bis-metal and mixed bis-metal (M = Cu3+, Ag3+, and Au3+) complexes. The electronic structures and bonding situations of them are studied by using natural bond orbital approach and the topological analysis of the electron localization function. Electronic spectra are investigated by using time-dependent density functional theory. The introduction of group 11 transition metals leads to red shifts in the spectra of these metal complexes with respect to that of hexaphyrin. Moreover, it is noteworthy that the spectra of copper contained complexes are mainly derived from combination of ligand-to-metal charge transfer and ligand-to-ligand charge transfer transitions. In addition, the relativistic time-dependent density functional theory with spin-orbit coupling calculations indicate that the effects of spin-orbit coupling on the excitation energies are so small that it is safe enough to neglect spin-orbit coupling for these systems.

First author: Kachmar, Ali, Conformational Changes in a Flexible, Encapsulated Dicarboxylate: Evidence from Density Functional Theory Simulations, JOURNAL OF PHYSICAL CHEMISTRY A, 113, 9075, (2009)
Abstract: The dynamical behavior of the [Mo12O12S12(OH)(12){O2C-(CH2)(N)-CO2}](2-) complexes is analyzed via first-principles molecular dynamics simulations. Experimental X-ray data play the role of initial configurations for our search in the configuration space. We show that different stable and metastable conformers are possible, and these are thermally accessible at relatively low temperatures. This is the main outcome of our first-principles molecular dynamics approach in which the temperature allowing for thermal activation has been set to T = 500 K, which is consistent with the variable temperature H-1 NMR spectra of these complexes in solution taken at comparable, although moderately lower, temperature. This implies that a relatively large manifold of folding configurations is available to the encapsulated guest species. Moreover, the high flexibility of both the host cage and the inserted guests allows for the accommodation of a rather wide variety of functional groups with potential applications in several fields.

First author: Hu, Shao-Wen, Theoretical Mechanism Study of UF6 Hydrolysis in the Gas Phase (II), JOURNAL OF PHYSICAL CHEMISTRY A, 113, 9243, (2009)
Abstract: In our previous work (J. Phys. Chem. A 2008, 112, 8877.), we found theoretical evidence indicating UF5OH is an intermediate produced in the first step of UF6 hydrolysis. In this work, we explored the probable reaction channels starting from UF5OH + UF6 and UF5OH + UF5OH systems using relativistic density functional theory calculations. Initially, the two uranium containing species associate to form complex UF6 center dot UF5OH or dimer (UF5OH)(2) through hydrogen bonding. The energy released is 12-16 kcal/mol, which may promote further reactions. After H2O or HF are eliminated from the complex or dimer, compounds containing U-C-U bond are produced. These compounds are potentially feasible to associate into larger clusters or solidify. Relative to the isolated initial species, the energies of the final products are -6 to -13 kcal/mol lower, indicating that the reactions may spontaneously proceed. The calculated IR spectra features can be used to indicate the formation and interaction type of the intermediates and products.

First author: Pilzak, Gregor S., Radical Cations of All-Trans Oligodiacetylenes: Optical Absorption and Reactivity toward Nucleophiles, JOURNAL OF PHYSICAL CHEMISTRY B, 113, 11095, (2009)
Abstract: High yields of the radical cations of oligodiacetylenes have been prepared by photoinduced electron transfer using a positively charged cosensitizer and by pulse radiolysis. The absorption maxima of the oligodiacetylene (ODA) radical cations show a bathochromic shift to the infrared region and a large increase of their lifetimes with chain elongation. Their reactivity toward nucleophiles decreases for longer ODAs, illustrating clearly the stabilizing effect of charge delocalization along the oligomeric chain. This also implies a very low reactivity of ODA radical cations toward trace amounts of water in optoelectronic devices.

First author: Krupicka, Martin, Hybrid Quantum Mechanical/Molecular Mechanical Investigation of the beta-1,4-Galactosyltransferase-I Mechanism, JOURNAL OF PHYSICAL CHEMISTRY