2014 publications citing ADF

First author: Falls, Zackary, The Dynamic Equilibrium Between (AlOMe)(n) Cages and (AlOMe)(n)center dot(AlMe3)(m) Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation, MACROMOLECULES, 47, 8556, (2014)
Abstract: Species likely to be present in methylaluminoxane (MAO) are studied via dispersion-corrected DFT, which we show is able to accurately predict thermochemical parameters for the dimerization of trimethylaluminum (TMA). Both cage-like, (AlOMe)(n),(c), and TMA-bound nanotubes, (AlOMe)(n,t) (AlMe3)(m), are found to be important components of MAO. The most stable structures have aluminum/oxygen atoms in environments whose average hybridization approaches sp(3)/sp(2). The (AlOMe)(n),(t) (AlMe3)m isomers with the lowest free energies possess Al-mu-MeAl bonds. At 298 K a novel T-d-(AlOMe)(16),c oligomer is one of the most stable structures among the six stoichiometries with the lowest free energies: (AlOMe)(20,c) (AlMe3)(2), T-d-(AlOMe)(16,c), (AlOMe)(18,c), (AlOMe)(20,c) (AlMe3), (AlOMe)(10,t) (AlMe3)(4), and (AlOMe)(20,c). As the temperature rises, the abundance of (AlOMe)(n,t) (AlMe3)(m) decreases, and that of (AlOMe)(n,c) increases. Because the former are expected to be precursors for the active species in polymerization, this may in part be the reason why the cocatalytic activity of MAO decreases at higher temperatures.

First author: Jerabek, Paul, Coinage Metals Binding as Main Group Elements: Structure and Bonding of the Carbene Complexes [TM(cAAC)(2)) and [TM(cAAC)(2)](+) (TM = Cu, Ag, Au), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 17123, (2014)
Abstract: Quantum chemical calculations using density functional theory have been carried out for the cyclic (alkyl)(amino)carbene (cAAC) complexes of the group 11 atoms [TM(cAAC)(2)] (TM = Cu, Ag, Au) and their cations [TM(cAAC)(2)](+). The nature of the metal-ligand bonding was investigated with the charge and energy decomposition analysis EDA-NOCV. The calculations show that the TM-C bonds in the charged adducts [TM(cAAC)(2)](+) are significantly longer than in the neutral complexes [TM(cAAC)(2)], but the cations have much higher bond dissociation energies than the neutral molecules. The intrinsic interaction energies ?Eint in [TM(cAAC)(2)](+) take place between TM+ in the S-1 electronic ground state and (cAAC)(2). In contrast, the metal-ligand interactions in [TM(cAAC)(2)] involve the TM atoms in the excited P-1 state yielding strong TM p(pi) -> (cAAC)(2) p backdonation, which is absent in the cations. The calculations suggest that the cAAC ligands in [TM(cAAC)(2)] are stronger p acceptors than s donors. The trends of the intrinsic interaction energies and the bond dissociation energies of the metal-ligand bonds in [TM(cAAC)(2)] and [TM(cAAC)(2)](+) give the order Au > Cu > Ag. Calculations at the nonrelativistic level give weaker TM-C bonds, particularly for the gold complexes. The trend for the bond strength in the neutral and charged adducts without relativistic effects becomes Cu > Ag > Au. The EDA-NOCV calculations suggest that the weaker bonds at the nonrelativistic level are mainly due to stronger Pauli repulsion and weaker orbital interactions. The NBO picture of the C-TM-C bonding situation does not correctly represent the nature of the metal-ligand interactions in [TM(cAAC)(2)].

First author: Wolf, Larry M., Origin of Inversion versus Retention in the Oxidative Addition of 3-Chloro-cyclopentene to Pd(0)L-n, JOURNAL OF ORGANIC CHEMISTRY, 79, 12136, (2014)
Abstract: The preference for syn versus anti oxidative addition of 3-chloro-cyclopentene to Pd(0)L-n was investigated using density functional theory (L = PH3, PMe3, PF3, ethylene, maleic anhydride, pyridine, imidazol-2-ylidene). Both mono- and bis-ligation modes were studied (n = 1 and 2). The pathways were analyzed at the B2PLYP-D3/def2-TZVPP//TPSS-D3/def2-TZVP level, and an interaction/distortion analysis was performed at the ZORA-TPSS-D3/TZ2P level for elucidating the origin of the selectivity preferences. Mechanistically, the anti addition follows an S(N)2 type mechanism, whereas the syn addition has partial S(N)1 and S(N)2′ character. Contrary to the traditional rationale that orbital interactions are dominant in the anti pathway, analysis of the variation of the interaction components along the intrinsic reaction coordinate shows that the syn pathway exhibits stronger overall orbital interactions. This orbital preference for the syn pathway diminishes with increasing donor capacity of the ligand. It is caused by the donation of the isolated p orbitals on the migrating chlorine atom to the PdLn fragment, which is lacking in the anti pathway, whereas the HOMOLUMO overlap between the fragments is greater for the anti pathway. Electrostatically, the syn pathway is preferred for weakly donating and withdrawing ligands, whereas the anti pathway is favored with strongly donating ligands.

First author: Yang, Yang, Multireference Ab lnitio Study of Ligand Field d-d Transitions in Octahedral Transition-Metal Oxide Clusters, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 29196, (2014)
Abstract: We have used multiconfigurational (MC) and multireference (MR) methods (CASSCF, CASPT2, and MRCI) to study dd transitions and other optical excitations for octahedral [M(H2O)(6)](n+) clusters (M = Ti, V, Mn, Cr, Fe, Co, Ni, Cu) as models of hematite and other transition-metal oxides of interest in solar fuels. For [Fe(H2O)(6)](3+), all calculations substantially overestimate the dd transition energies (similar to 3.0 versus similar to 1.5 eV) compared to what has been experimentally assigned. This problem occurs even though theory accurately describes (1) the lowest dd transition energy in the atomic ion Fe3+ (similar to 4.4 eV), (2) the t(2g)eg splitting (similar to 1.4 eV) in [Fe(H2O)(6)](3+), and (3) the ligand-to-metal charge transfer (LMCT) energy in [Fe(H2O)(6)](3+). Indeed, the results for Fe3+ and the t(2g-eg) splitting suggest that the lowest dd excitation energy in the hexa-aqua complex should be similar to 3 eV (or slightly below because of JahnTeller stabilization), as we find. Possible origins for the dd discrepancy are examined, including Fe2+ and low-spin Fe3+ impurities. For the [M(H2O)(6)](n)+ clusters not involving Fe(III), our MR calculations show reasonable correlation (mostly within 0.5 eV) with experiments for the dd transitions, including consistent trends for the intensities of spin-allowed and spin-forbidden transitions. Our calculations also greatly complement experimental data because (1) experimental results for some species are insufficient or even scarce, (2) some of the experimental peaks were not observed directly but were inferred, and (3) the nature or existence of some shoulder peaks and weak peaks is uncertain. Our MR calculations have also been used to study convergence of the results with choice of active space, including the importance of the double shell effect in which there are 10 active d orbitals per transition-metal atom rather than 5. The results show that the larger active space does not significantly change the excitation energy, although it lowers the absolute energies for complexes with high 3d occupations. This indicates that reasonable accuracy can be achieved using MR methods in studies of transition-metal oxide clusters using minimal active spaces. This study establishes fundamental principles for the further modeling of larger cluster models of pure and doped hematite and other metal oxides.

First author: Johansson, Mikael P., At What Size Do Neutral Gold Clusters Turn Three-Dimensional?, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 29370, (2014)
Abstract: Recent experiments and calculations have established the transition from two-dimensional (2D) to three-dimensional (3D) structures at a cluster size of 8 and 12 atoms for gold cluster cations and anions. For neutral gold clusters, however, experimental data are scarce, and existing theoretical studies disagree on the 2D3D crossover point. We present the results of global structure optimizations of neutral gold clusters Au-n for n = 913 using a genetic algorithm and meta-generalized density functional theory. The relative energies of the lowest-lying isomers are computed using the revTPSS functional and the random phase approximation (RPA). Thermal, scalar relativistic, and spinorbit effects are included, and basis set extrapolations are performed for the RPA calculations. For the 2D3D transition of gold cluster cations and anions, this methodology yields near-quantitative agreement with cross section and electron diffraction measurements. For neutral gold clusters, the 2D and 3D structures are predicted to be almost isoenergetic at n = 11 gold atoms, while clusters with n > 11 are manifestly 3D. Thus, neutral gold clusters turn 3D at an unusually large size of 11 gold atoms.

First author: Odoh, Samuel O., UO22+ Uptake by Proteins: Understanding the Binding Features of the Super Uranyl Binding Protein and Design of a Protein with Higher Affinity, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 17484, (2014)
Abstract: The capture of uranyl, UO22+, by a recently engineered protein (Zhou et al. Nat. Chem. 2014, 6, 236) with high selectivity and femtomolar sensitivity has been examined by a combination of density functional theory, molecular dynamics, and free-energy simulations. It was found that UO22+ is coordinated to five carboxylate oxygen atoms from four amino acid residues of the super uranyl binding protein (SUP). A network of hydrogen bonds between the amino acid residues coordinated to UO22+ and residues in its second coordination sphere also affects the proteins uranyl binding affinity. Free-energy simulations show how UO22+ capture is governed by the nature of the amino acid residues in the binding site, the integrity and strength of the second-sphere hydrogen bond network, and the number of water molecules in the first coordination sphere. Alteration of any of these three factors through mutations generally results in a reduction of the binding free energy of UO22+ to the aqueous protein as well as of the difference between the binding free energies of UO22+ and other ions (Ca2+, Cu2+, Mg2+, and Zn2+), a proxy for the proteins selectivity over these ions. The results of our free-energy simulations confirmed the previously reported experimental results and allowed us to discover a mutant of SUP, specifically the GLU64ASP mutant, that not only binds UO22+ more strongly than SUP but that is also more selective for UO22+ over other ions. The predictions from the computations were confirmed experimentally.

First author: Adams, Matt R., Organotin bond dissociation energies: An interesting challenge for contemporary computational methods, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1050, 7, (2014)
Abstract: Organotin compounds are very important in material design as well as in biomedical and biochemical applications. However, little is known about their BDEs experimentally or computationally. Thus, a variety of common quantum chemical methods in combination with several approaches to treating relativistic effects of the tin core electrons were used to calculate the BDEs of organotin compounds. Our results show that the BDEs are very sensitive to the choice of the computational method and to the treatment of relativistic effects.

First author: Majid, Abdul, A computational study of anion photoelectron spectroscopy of zinc oxide nanoclusters,COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1050, 23, (2014)
Abstract: The density functional theory (DFT) based calculations were carried out to study anion photoelectron spectroscopy of ZnO clusters. Detailed calculations were performed to study the molecular orbital configurations, molecular charge distributions, Mullikan’s atomic charge distributions, isosurface plots, thermodynamic properties, vibrational spectra and Franck Condon spectra of geometrically optimized ground states of neutral and anion structures of ZnO and (ZnO)(2) clusters. The results indicated that the symmetric structure of ZnO cluster shows only one IR active mode whereas non-polar structure of (ZnO)(2) shows six modes of vibration including three IR active modes. The Franck-Condon spectrum of these structures revealed that an increase in number of atoms in cluster causes an increase in number of Franck-Condon factors with a smaller overlap integral and an increase in depth of the potential well. Zero to zero ground state vibronic transition was observed to be most probable among all vibronic transitions with a Franck-Condon factor of 0.987 for ZnO and 0.982 for (ZnO)(2) clusters.

First author: Gendron, Frederic, Magnetic Properties and Electronic Structures of Ar3UIV-L Complexes with Ar = C-5(CH3)(4)H- or C5H5- and L = CH3, NO, and Cl, INORGANIC CHEMISTRY, 53, 13174, (2014)
Abstract: Electronic structures and magnetic properties of the U4+ complexes (C5Me4H)(3)UNO, (C5Me4H)(3)UCl, (C5H5)(3)UCH3, and (C5H5)(3)UCl are investigated by quantum chemical calculations. On the basis of wave function calculations including spinorbit (SO) interactions, all complexes have nondegenerate nonmagnetic ground states. However, for L = CH3 and Cl magnetic doublet excited states are very low in energy, rendering the magnetic susceptibility strongly temperature dependent above ca. 50-100 K. In contrast, (C5Me4H)(3)UNO exhibits temperature-independent paramagnetism even at room temperature. The calculated susceptibilities agree well with available experimental data. An analysis of the ground states and the magnetic behavior is performed using crystal-field (CF) models with parameters extracted from the ab initio calculations, and with the help of natural orbitals contributing to the electron density, generated from scalar relativistic and SO wave functions for the ground states and selected excited states. Electronic g-factors calculated from the CF models agree well with ab initio data. The UNO bond order in (C5Me4H)(3)UNO decreases somewhat due to SO coupling, because U-NO bonding p orbitals with strong U 5f(pi) character mix with nonbonding pi orbitals under the SO interaction. This complex also exhibits pronounced multireference character. All complexes afford U-ligand 5f covalent character.

First author: Cowie, Bradley E., Platinum Complexes of a Borane-Appended Analogue of 1,1 ‘-Bis(diphenylphosphino)ferrocene: Flexible Borane Coordination Modes and in situ Vinylborane Formation, CHEMISTRY-A EUROPEAN JOURNAL, 20, 16899, (2014)
Abstract: A bis(phosphine) borane ambiphilic ligand, [Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4PtBu{C6H4(BPh2)-ortho})] (FcPPB), in which the borane occupies a terminal position, was prepared. Reaction of FcPPB with tris(norbornene) platinum(0) provided [Pt(FcPPB)] (1) in which the arylborane is eta(BCC)-B-3-coordinated. Subsequent reaction with CO and CNXyl (Xyl= 2,6-dimethylphenyl) afforded [PtL(FcPPB)] {L= CO (2) and CNXyl (3)} featuring h 2BC-and eta B-1-arylborane coordination modes, respectively. Reaction of 1 or 2 with H2 yielded [PtH(m-H)(FcPPB)] in which the borane is bound to a hydride ligand on platinum. Addition of PhC2H to [Pt(FcPPB)] afforded [Pt(C2Ph)(m-H)(FcPPB)] (5), which rapidly converted to [Pt(FcPPB’)] (6; FcPPB’=[Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4PtBu{C6H4(BPh2)-ortho}]) in which the newly formed vinylborane is eta(BCC)-B-3-coordinated. Unlike arylborane complex 1, vinylborane complex 6 does not react with CO, CNXyl, H-2 or HC2Ph at room temperature.

First author: Ording-Wenker, Erica C. M., Protonation of a Biologically Relevant Cu-II mu-Thiolate Complex: Ligand Dissociation or Formation of a Protonated Cu-I Disulfide Species?, CHEMISTRY-A EUROPEAN JOURNAL, 20, 16913, (2014)
Abstract: The proton-induced electron-transfer reaction of a Cu-II mu-thiolate complex to a Cu-I-containing species has been investigated, both experimentally and computationally. The Cu-II mu-thiolate complex [Cu-II 2(LMeS) 2] 2+ is isolated with the new pyridyl-containing ligand LMeSSLMe, which can form both Cu-II thiolate and Cu-I disulfide complexes, depending on the solvent. Both the Cu-II and the Cu-I complexes show reactivity upon addition of protons. The multivalent tetranuclear complex [Cu-I 2Cu(II) 2(LS) 2(CH3CN)(6)](4+) crystallizes after addition of two equivalents of strong acid to a solution containing the mu-thiolate complex [Cu-II (2)((LS)-S-Me)(2)](2+) and is further analyzed in solution. This study shows that, upon addition of protons to the Cu-II thiolate compound, the ligand dissociates from the copper centers, in contrast to an earlier report describing redox isomerization to a Cu-I disulfide species that is protonated at the pyridyl moieties. Computational studies of the protonated Cu-II mu-thiolate and Cu-I disulfide species with LSSL show that already upon addition of two equivalents of protons, ligand dissociation forming [Cu-I(CH3CN)(4)](+) and protonated ligand is energetically favored over conversion to a protonated Cu-I disulfide complex.

First author: Nimmala, Praneeth Reddy, Au-36(SPh)(24) Nanomolecules: X-ray Crystal Structure, Optical Spectroscopy, Electrochemistry, and Theoretical Analysis, JOURNAL OF PHYSICAL CHEMISTRY B, 118, 14157, (2014)
Abstract: The physicochemical properties of gold:thiolate nanomolecules depend on their crystal structure and the capping ligands. The effects of protecting ligands on the crystal structure of the nanomolecules are of high interest in this area of research. Here we report the crystal structure of an all aromatic thiophenolate-capped Au-36(SPh)(24) nanomolecule, which has a face-centered cubic (fcc) core similar to other nanomolecules such as Au-36(SPh-tBu)(24) and Au-36(SC5H9)(24) with the same number of gold atoms and ligands. The results support the idea that a stable core remains intact even when the capping ligand is varied. We also correct our earlier assignment of Au-36(SPh)(23) which was determined based on MALDI mass spectrometry which is more prone to fragmentation than ESI mass spectrometry. We show that ESI mass spectrometry gives the correct assignment of Au-36(SPh)(24), supporting the X-ray crystal structure. The electronic structure of the title compound was computed at different levels of theory (PBE, LDA, and LB94) using the coordinates extracted from the single crystal X-ray diffraction data. The optical and electrochemical properties were determined from experimental data using UVvis spectroscopy, cyclic voltammetry, and differential pulse voltammetry. Au-36(SPh)(24) shows a broad electrochemical gap near 2 V, a desirable optical gap of similar to 1.75 eV for dye-sensitized solar cell applications, as well as appropriately positioned electrochemical potentials for many electrocatalytic reactions.

First author: Pandey, Krishna Kumar, Effects of density functionals and dispersion interactions on geometries, bond energies and harmonic frequencies of E equivalent to UX3 (E = N, P, CH; X = H, F, Cl), SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 133, 846, (2014)
Abstract: Quantum-chemical calculations have been performed to evaluate the geometries, bonding nature and harmonic frequencies of the compounds [E equivalent to UX3] at DFT, DFT-D3, DFT-D3(BJ) and DFT-dDSc levels using different density functionals BP86, BLYP, PBE, revPBE, PW91, TPSS and M06-L. The stretching frequency of U equivalent to N bond in [N equivalent to UF3] calculated with DFT/BLYP closely resembles with the experimental value. The performance of different density functionals for accurate U equivalent to N vibrational frequencies follows the order BLYP > revPBE > BP86 > PW91 > TPSS > PBE > M06-L. The BLYP functional gives accurate value of the U equivalent to E bond distances. The uranium atom in the studied compounds [E equivalent to UX3] is positively charged. Upon going from [E equivalent to UF3] to [E equivalent to UCl3], the partial Hirshfeld charge on uranium atom decreases because of the lower electronegativity of chlorine compared to flourine. The Gopinathan-Jug bond order for U equivalent to E bonds ranges from 2.90 to 3.29. The U equivalent to E bond dissociation energies vary with different density functionals as M06-L < TPSS < BLYP < revPBE < BP86 < PBE approximate to PW91. The orbital interactions Delta E-orb, in all studied compounds [E equivalent to UX3] are larger than the electrostatic interaction Delta E-elstat, which means the U equivalent to N bonds in these compound have greater degree of covalent character (in the range 63.8-77.2%). The U-E sigma-bonding interaction is the dominant bonding interaction in the nitride and methylidyne complexes while it is weaker in [P equivalent to UX3]. The dispersion energy contributions to the total bond dissociation energies are rather small. Compared to the Grimme’s D3(BJ) corrections, the Corminboeuf’s dispersion corrections are larger with metaGGA functionals (TPSS, M06-L) while smaller with GGA functionals.

First author: Yoder, Tara S., Iron Pyrite Nanocrystal Inks: Solvothermal Synthesis, Digestive Ripening, and Reaction Mechanism, CHEMISTRY OF MATERIALS, 26, 6743, (2014)
Abstract: Colloidal iron pyrite nanocrystals (or FeS2 NC inks) are desirable as active materials in lithium ion batteries and photovoltaics and are particularly suitable for large-scale, roll-to-roll deposition or inkjet printing. However, to date, FeS2 NC inks have only been synthesized using the hot-injection technique, which requires air-free conditions and may not be desirable at an industrial scale. Here, we report the synthesis of monodisperse, colloidal, spherical, and phase-pure FeS2 NCs of 5.5 +/- 0.3 nm in diameter via a scalable solvothermal method using iron diethyldithiocarbamate as the precursor, combined with a postdigestive ripening process. The phase purity and crystallinity are determined using X-ray diffraction, transmission electron microscopy, far-infrared spectroscopy, and Raman spectroscopy techniques. Through this study, a hypothesis has been verified that solvothermal syntheses can also produce FeS2 NC inks by incorporating three experimental conditions: high solubility of the precursor, efficient mass transport, and sufficient stabilizing ligands. The addition of ligands and stirring decrease the NC size and led to a narrow size distribution. Moreover, using density functional theory calculations, we have identified an acid-mediated decomposition of the precursor as the initial and critical step in the synthesis of FeS2 from iron diethyldithiocarbamate.

First author: Junold, Konstantin, Reactions of the Donor-Stabilized Silylene Bis[N,N ‘-diisopropyl-benzamidinato(-)]silicon(II) with Bronsted Acids, CHEMISTRY-A EUROPEAN JOURNAL, 20, 16462, (2014)
Abstract: Reaction of the donor-stabilized silylene 1 (which is three-coordinate in the solid state and four-coordinate in solution) with [HMCp(CO)(3)] (M = Mo, W; Cp = cyclopentadienyl) leads to the cationic five-coordinate silicon( IV) complexes 2 and 3, respectively, and reaction of 1 with CH3COOH yields the neutral six-coordinate silicon( IV) complex 4. Compounds 2-4 were structurally characterized by crystal structure analyses and multinuclear NMR spectroscopic studies in the solid state and in solution. The formation of 2-4 can be formally described in terms of a Bronsted acid/base reaction, coupled with a redox process (Si-II -> Si-IV, H+ -> H-).

First author: Baranac-Stojanovic, Marija, Aromaticity and Stability of Azaborines, CHEMISTRY-A EUROPEAN JOURNAL,20, 16558, (2014)
Abstract: The influence of the relative boron and nitrogen positions on aromaticity of the three isomeric 1,2-, 1,3-, and 1,4-azaborines has been investigated by computing the extra cyclic resonance energy, NICS(0)(pi zz) index and by visualizing the pi-electron (de) shielding pattern as a response of the pi system to a perpendicular magnetic field. The origin of the known stability trend, in which the 1,2-/1,3-isomer is the most/least stable, was examined by using an isomerization energy decomposition analysis. The 1,3-arrangement of B and N atoms creates a charge separation in the pi-electron system, which was found to be responsible for the lowest stability of 1,3-azaborine. This charge separation can, in turn, be considered as a driving force for the strongest cyclic pi-electron delocalization, making this same isomer the most aromatic. Despite the well-known fact that the B-N bond attenuates electron delocalization due to large electronegativity difference between the atoms, the 1,4-B, N relationship reduces aromaticity to a greater extent by making the pi-electron delocalization more one-directional (from N to B) than cyclic. Thus, 1,4-azaborine was found to be the least aromatic. Its lower stability with respect to the 1,2-isomer was explained by the larger exchange repulsion.

First author: Grainger, Rachel, The ortho-Substituent Effect on the Ag-Catalysed Decarboxylation of Benzoic Acids,CHEMISTRY-A EUROPEAN JOURNAL, 20, 16680, (2014)
Abstract: A combined experimental and computational investigation on the Ag-catalysed decarboxylation of benzoic acids is reported herein. The present study demonstrates that a substituent at the ortho position exerts dual effects in the decarboxylation event. On one hand, ortho-substituted benzoic acids are inherently destabilised starting materials compared to their meta-and para-substituted counterparts. On the other hand, the presence of an ortho-electron-with-drawing group results in an additional stabilisation of the transition state. The combination of both effects results in an overall reduction of the activation energy barrier associated with the decarboxylation event. Furthermore, the Fujita-Nishioka linear free energy relationship model indicates that steric bulk of the substituent can also exert a negative effect by destabilising the transition state of decarboxylation.

First author: Phillips, Nicholas, Expanded-Ring N-Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations, CHEMISTRY-A EUROPEAN JOURNAL, 20, 16721, (2014)
Abstract: Strategies for the synthesis of highly electrophilic Au-I complexes from either hydride-or chloride-containing precursors have been investigated by employing sterically encumbered Dipp-substituted expanded-ring NHCs (Dipp = 2,6-iPr(2)C(6)H(3)). Thus, complexes of the type (NHC) AuH have been synthesised (for NHC = 6-Dipp or 7-Dipp) and shown to feature significantly more electron-rich hydrides than those based on ancillary imidazolylidene donors. This finding is consistent with the stronger s-donor character of these NHCs, and allows for protonation of the hydride ligand. Such chemistry leads to the loss of dihydrogen and to the trapping of the [(NHC)Au](+) fragment within a dinuclear gold cation containing a bridging hydride. Activation of the hydride ligand in (NHC) AuH by B(C6F5)(3), by contrast, generates a species (at low temperatures) featuring a [HB(C6F5)(3)](-) fragment with spectroscopic signatures similar to the “free” borate anion. Subsequent rearrangement involves B-C bond cleavage and aryl transfer to the carbophilic metal centre. Under halide abstraction conditions utilizing Na[BArf(4)] (Arf = C6H3(CF3)2-3,5), systems of the type [(NHC) AuCl] (NHC = 6-Dipp or 7-Dipp) generate dinuclear complexes [{(NHC) Au}(2)-(mu-Cl)](+) that are still electrophilic enough at gold to induce aryl abstraction from the [BAr4f](-) counterion.

First author: Navamani, K., Effect of Structural Fluctuations on Charge Carrier Dynamics in Triazene Based Octupolar Molecules, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 27754, (2014)
Abstract: The charge transport in 2,4,6-tris(thiophene-2-yl)-1,3,5-triazene based octupolar molecules is studied. The effect of structural fluctuation on charge transfer integral and site energy is included while studying the charge transfer kinetics through kinetic Monte Carlo simulation. The charge transfer kinetic parameters such as rate coefficient, dispersive parameter, disorder drift time, mobility, and hopping conductivity are studied for both steady state (Delta epsilon not equal 0) and non-steady state (Delta epsilon = 0). It has been found that the hopping conductivity depends on the charge transfer rate and electric permittivity of the medium. The disorder drift time (S-t) is acting as the crossover point between adiabatic band and nonadiabatic hopping charge transfer mechanism. The calculated hole and electron mobilities in 2,4,6-tris[5-(3,4,6-trioctyloxyphenyl)thiophene-2-yl]-1,3,5-triazene (1b) and 2,4,6-tris[5′-(3,4,6-tridodecyloxyphenyl)-2,2′-bithiophene-5-yl]-1,3,5-t riazene (2) are in good agreement with experimental results. The theoretical results show that the methoxy-substituted octupolar molecule 1c is having good hole and electron transporting ability with mobility values of 0.15 and 1.6 cm(2)/(V s).

First author: Saielli, Giacomo, Understanding Cage Effects in Imidazolium Ionic Liquids by Xe-129 NMR: MD Simulations and Relativistic DFT Calculations, JOURNAL OF PHYSICAL CHEMISTRY B, 118, 13963, (2014)
Abstract: (129)Xe NMR has been recently employed to probe the local structure of ionic liquids (ILs). However, no theoretical investigation has been yet reported addressing the problem of the dependence of the chemical shift of xenon on the cage structure of the IL. Therefore, we present here a study of the chemical shift of Xe-129 in two ionic liquids, [bmim][Cl] and [bmim][PF6], by a combination of classical MD simulations and relativistic DFT calculations of the xenon shielding constant. The bulk structure of the two ILs is investigated by means of the radial distribution functions, paying special attention to the local structure, volume, and charge distribution of the cage surrounding the xenon atom. Relativistic DFT calculations, based on the ZORA formalism, on clusters extracted from the trajectory files of the two systems, yield an average relative chemical shift in good agreement with the experimental data. Our results demonstrate the importance of the cage volume and the average charge surrounding the xenon nucleus in the IL cage as the factors determining the effective shielding.

First author: Hatzell, Marta C., Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion, ENVIRONMENTAL SCIENCE & TECHNOLOGY, 48, 14041, (2014)
Abstract: The amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10(-5)) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g(-1)) had a positive rise potential of 59 +/- 4 mV in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g(-1)) had a negative rise potential (-31 +/- 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 +/- 2 mV (unaltered) to -6 +/- 0.5 mV (oxidized), producing a whole cell potential (53 +/- 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 +/- 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. These results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.

First author: Belanzoni, P., DFT investigation on hydrogen bonding in cyclohexane-1,2,3,4,5-pentol crystal structure,JOURNAL OF STRUCTURAL CHEMISTRY, 55, 1596, (2014)
Abstract: The cyclohexane-1,2,3,4,5-pentol,C6H12O5 is a natural product extracted from Adiscanthus fusciflorus (Rutaceae). It crystallizes in the non-centrosymmetric space group P2(1) with one molecule in the asymmetric unit and it has been postulated to have at least ten strong O-HaEuro broken vertical bar O intermolecular interactions, two per each OH group of one molecule, producing a three-dimensional network. The crystal packing is defined by O-HaEuro broken vertical bar O hydrogen bonds. Due to the crucial role of the hydrogen bonds in defining the crystal structure, theoretical investigations in the gas phase have been carried out in order to explore the hydrogenbonding mechanism through a quantitative Kohn-Sham molecular orbital and corresponding energy decomposition analyses. The existence of a covalent component in hydrogen bonds has been proved which originates from donor-acceptor orbital interactions in the sigma-electron system. Our analyses show that the stability of the crystal structure is enhanced by the formation of two hydrogen bonds with two vicinal molecules for each OH group in C6H12O5 molecule with respect to the formation of one or two hydrogen bonds with only one vicinal molecule, thus confirming the proposed existence of ten strong O-HaEuro broken vertical bar O intermolecular interactions for each molecule in the asymmetric unit. The presence of a cooperativity effect is observed which originates from a charge separation induced by the two vicinal molecules hydrogenbonded to an OH group in C6H12O5 molecule.

First author: Hatakeyama, Takuji, Synthesis of Heteroatom-fused Polycyclic Aromatic Compounds via Tandem Hetero-Friedel-Crafts Reactions and Their Applications, JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN, 72, 1391, (2014)
Abstract: Polycyclic aromatic compounds possessing heteroatoms are one of the most important materials for organic electronics. Because of the lack of a suitable synthetic methodology, only a few polycyclic aromatic compounds with ring junction heteroatoms, heteroatom-doped nanographenes, have been synthesized to date, even though theoretical investigations have suggested that those molecules are attractive not only as the electronic materials but also as substructures of heteroatom-doped nanocarbons. Herein, we describe development of novel tandem hetero-Friedel-Crafts reactions and their application for the synthesis of heteroatom-fused polycyclic aromatic compounds. These compounds showed strong luminescence or carrier transport ability, thus can be a promissing class of organic materials for optelectronic devices. We have demonstrated their potential utility by fablicating phosphorescent organic light-emitting diodes with a sufficiently high efficiency and a long device lifetime.

First author: Holzmann, Nicole, Analysis of the E-E Bond in Group-13 Complexes [(PMe3)(2)(E2Mn)] (E = B- In, n=4, 2, 0), CROATICA CHEMICA ACTA, 87, 413, (2014)
Abstract: Quantum chemical calculations at the BP86/def2-TZVPP level have been carried out for the donor-acceptor complexes RPMe3)2(E21-I)] for n = 4, 2, 0. The focus of this works lies on the E E bonding situation. The electronic structure of the molecules was analyzed with the EDA-NOCV method and with NBO calculations. The EDA-NOCV analysis of the E E interactions in [(PMe3)2(E2H4] (n = 4, 2, 0) provide deep insights into the nature and the strength of the bonds. The calculated intrinsic interactions AL’in, suggest that the trend for the bond strength of the E E single bond [(PMe3)(H)2E E(H)2(PMe3)1 has the order B > Ga > AI > In. The orbital interactions AEorb which exhibit the same trend as have one dominant contribution which comes from the coupling of the singly occupied orbitals in the (PMe3)(H)2E fragments. A slightly different trend B > Ga In > Al is found for the interaction energy AEin, of the E E bonds in [(PMe3XH)E E(H)(PMe3)]. The orbital term Eorb which has the order B> Ga > In > Al has one major and one minor component which in case of the boron compound may be identified with a a and air bond. The heavier homologues RPMe3)(H)E E(H)(PMe3)] (E = Al In) have pyramidally coordinated atoms E. The dominant orbital interactions in the latter species come from the formation of a “slipped” it bond while the minor component comes from the formation of the a bond. This can be explained with the change in the hybridization of the orbitals at atom E along the formation of the E E bond. The compounds [(PMe3)E E(PMe3)] exhibit three different types of bonding situations depending on atoms E. The boron system [(PMe3)BEB(PMe3)] has a classical triple bond which consist of a a bond that provides 56 % to the orbital interactions and two degenerate it bonds which contribute 40 % to the covalent bonding. The aluminium and gallium complexes RPMe3)E E(PMe3)] (E = Al, Ga) are also triply bonded species where the covalent bonding has one strong and two weaker components. The strong component comes from the “slipped” it bond while the minor components come from the formation of the a and it bonds. The indium complex [(PMe3)1n In(PMe3)] has only an In In single bond and two electron lone pairs at the indium atoms. The charge donation Me3P E2(H,,) 4– PMe3 has for all atoms E the trend for n 4 > 2 > O.

First author: Chambrey, Stephane, Can Green Dimethyl Carbonate Synthesis be More Effective? A Catalyst Recycling Study Benefiting from Experimental Kinetics and DFT Modeling, JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY,25, 2350, (2014)
Abstract: Dibutyldimethoxystannanes are known to catalyze the reaction between carbon dioxide and methanol leading to dimethyl carbonate. Despite similarities between din-butyl-and ditert-butyldimethoxystannane, the recycled complexes have different structural features. In the din-butyl series, a decatin(IV) complex has been characterized and is less active than the stannane precursor. Kinetic experiments likely indicate that all the tin centers are not active, which is confirmed in comparing with the related dinuclear 1,3-dimethoxytetran-butyldistannoxane complex. In the ditert-butyl series, the tritin(IV) complex isolated upon recycling features the steric effect of bulky tBu ancillary ligands. Interestingly enough, the SnOH…O(H)CH3 hydrogen bonding found in the structure prefigures Sn-OH/Sn-OCH3 interchange, a crucial step for closing the catalytic cycle. Density functional calculations highlight that the Sn-OH/Sn-OCH3 exchange is endothermic. Taken together, the results cast a clear light on the significant role of complexes of low nuclearity for dimethyl carbonate synthesis.

First author: Dunk, Paul W., Bottom-up formation of endohedral mono-metallofullerenes is directed by charge transfer,NATURE COMMUNICATIONS, 5, 2350, (2014)
Abstract: An understanding of chemical formation mechanisms is essential to achieve effective yields and targeted products. One of the most challenging endeavors is synthesis of molecular nanocarbon. Endohedral metallofullerenes are of particular interest because of their unique properties that offer promise in a variety of applications. Nevertheless, the mechanism of formation from metal-doped graphite has largely eluded experimental study, because harsh synthetic methods are required to obtain them. Here we report bottom-up formation of mono-metallofullerenes under core synthesis conditions. Charge transfer is a principal factor that guides formation, discovered by study of metallofullerene formation with virtually all available elements of the periodic table. These results could enable production strategies that overcome long-standing problems that hinder current and future applications of metallofullerenes.

First author: Yurenko, Yevgen P., Nucleic Acid Quadruplexes Based on 8-Halo-9-deazaxanthines: Energetics and Noncovalent Interactions in Quadruplex Stems, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 5353, (2014)
Abstract: Structural and energetic features of artificial DNA quadruplexes consisting of base tetrads and their stacks with Na+/K+ ion(s) inside the central pore and incorporating halogenated derivatives of xanthine, 8-fluoro-9-deazaxanthine (FdaX), 8-chloro-9-deazaxanthine (CldaX), 8-bromo-9-deazaxanthine (BrdaX), or 8-iodo-9-deazaxanthine (IdaX), have been investigated by modern state-of-the-art computational tools. The DNA (or RNA) quadruplex models based on 8-halo-9-deazaxanthines are predicted to be more stable relative to those with unmodified xanthine due to the increased stabilizing contributions coming from all three main types of weak interactions (H-bonding, stacking, and ion coordination). Methods for analyzing the electron density are used to understand the nature of forces determining the stability of the system and to gain a predictive potential. Quadruplex systems incorporating polarizable halogen atoms (chlorine, bromine, or iodine) benefit significantly from the stabilizing stacking between the individual tetrads due to an increased dispersion contribution as compared to xanthine and guanine, natural references used. Ion coordination induces a significant rearrangement of electron density in the quadruplex stem as visualized by electron deformation density (EDD) and analyzed by ETS-NOCV and Voronoi charges. Na+ induces larger electron polarization from the quadruplex toward the ion, whereas K+ has a higher propensity to electron sharing (identified by QTAIM delocalization index). We expect that our results will contribute to the development of novel strategies to further modify and analyze the natural G-quadruplex core.

First author: Kanters, Rene P. F., CLUSTER: Searching for Unique Low Energy Minima of Structures Using a Novel Implementation of a Genetic Algorithm, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 5729, (2014)
Abstract: A new flexible implementation of a genetic algorithm for locating unique low energy minima of isomers of clusters is described and tested. The strategy employed can be applied to molecular or atomic clusters and has a flexible input structure so that a system with several different elements can be built up from a set of individual atoms or from fragments made up of groups of atoms. This cluster program is tested on several systems, and the results are compared to computational and experimental data from previous studies. The quality of the algorithm for locating reliably the most competitive low energy structures of an assembly of atoms is examined for strongly bound Si-Li clusters, and ZnF2 clusters, and the more weakly interacting water trimers. The use of the nuclear repulsion energy as a duplication criterion, an increasing population size, and avoiding mutation steps without loss of efficacy are distinguishing features of the program. For the Si-Li clusters, a few new low energy minima are identified in the testing of the algorithm, and our results for the metal fluorides and water show very good agreement with the literature.

First author: Song, Yuzhi, The NLO properties of hybrid materials based on molybdate/ hexamolybdate derivatives: A theoretical perspective for electro-optic modulation, SYNTHETIC METALS, 198, 277, (2014)
Abstract: The role of hexamolybdate (Lindqvist)/molybdate on the nonlinear optical response (NLO) has been systematically examined by means of density functional theory (DFT) method. It shows that the unaccompanied Lindqvist anion has zero value of nonlinear optical response because of the centrosymmetric nature. According to the guidelines of nonlinear optics, centrosymmetric compounds do not exhibit nonlinear optical response. The hexamolybdate/molybdate accompanied with phenyl rings exhibits prominent NLO response which is much higher than those of phenyl rings without Lindqvist anion/molybdate. The system 3 ([Mo6O18C14H10N2O2](2-)) possesses a large NLO response computed to be 460.68 x 10(-30) esu. Here, the robust synergistic effect of Lindqvist anion linked to organic rings qualifies it a good candidate for NLO applications. The introduction of two phenyl rings in Lindqvist anion significantly increases the first hyperpolarizability as compared to the Lindqvist anion (system 1) or two phenyl rings (system 2) independently. The present study offers an important understanding into the NLO properties of hexamolybdate/molybdate derivatives.

First author: Mognon, Lorenzo, Ru-Zn Heteropolynuclear Complexes Containing a Dinucleating Bridging Ligand: Synthesis, Structure, and Isomerism, INORGANIC CHEMISTRY, 53, 12407, (2014)
Abstract: Mononuclear complexes in- and out-[Ru(Cl)(trpy)(Hbpp)](+) (in-0, out-0; Hbpp is 2,2′-(1H-pyrazole-3,5-diyl)dipyridine and trpy is 2,2′:6′,2?-terpyridine) are used as starting materials for preparation of Ru-Zn heterodinuclear out-{[Ru(Cl)(trpy)][ZnCl2](mu-bpp)} (out-2) and heterotrinuclear in,in- and out,out-{[Ru(Cl)(trpy)](2)(mu-[Zn(bpp)(2)])}(2+) (in-3, out-3) constitutional isomers. Further substitution of the Cl ligand from the former complexes leads to Ru-aqua out,out-{[Ru(trpy)(H2O)](2)(mu-[Zn(bpp)(2)])}(4+) (out-4) and the oxo-bridged Ru-O-Ru complex in,in-{[Ru-III(trpy)](2)(mu-[Zn(bpp)(2)(H2O)]mu-(O)}(4+) (in-5). All complexes are thoroughly characterized by the usual analytical techniques as well as by spectroscopy by means of UV-vis, MS, and when diamagnetic NMR. CV and DPV are used to extract electrochemical information and monocrystal X-ray diffraction to characterize complexes out-2, in-3, out-3, and in-5 in the solid state. Complex out-3 photochemically isomerizes toward in-3, as can be observed by NMR spectroscopy and rationalized by density functional theory based calculations.

First author: Samper, Katia G., Understanding the interaction of an antitumoral platinum(II) 7-azaindolate complex with proteins and DNA, BIOMETALS, 27, 1159, (2014)
Abstract: The reactivity of the [Pt(dmba)(aza-N1)(dmso)] complex 1, (a potential antitumoral drug with lower IC50 than cisplatin in several tumoral cell lines) with different proteins and oligonucleotides is investigated by means of mass spectrometry (ESI-TOF MS). The results obtained show a particular binding behaviour of this platinum(II) complex. The interaction of 1 with the assayed proteins apparently takes place by Pt-binding to the most accessible coordinating amino acids, presumably at the surface of the protein -this avoiding protein denaturation or degradation- with the subsequent release of one or two ligands of 1. The specific reactivity of 1 with distinct proteins allows to conclude that the substituted initial ligand (dmso or azaindolate) is indicative of the nature of the protein donor atom finally bound to the platinum(II) centre, i.e. N- or S-donor amino acid. Molecular modeling calculations suggest that the release of the azaindolate ligand is promoted by a proton transfer to the non-coordinating N present in the azaindolate ring, while the release of the dmso ligand is mainly favoured by the binding of a deprotonated Cys. The interaction of complex 1 with DNA takes always place through the release of the azaindolate ligand. Interestingly, the interaction of 1 with DNA only proceeds when the oligonucleotides are annealed forming a double strand. Complex 1 is also capable to displace ethidium bromide from DNA and it also weakly binds to DNA at the minor groove, as shown by Hoechst 33258 displacement experiments. Furthermore, complex 1 is also a good inhibitor of cathepsin B (an enzyme implicated in a number of cancer related events). Therefore, although compound 1 is definitely able to bind proteins that can hamper its arrival to the nuclear target, it should be taken into consideration as a putative anticancer drug due to its strong interaction with oligonucleotides and its effective inhibition of cat B.Reactivity of a Pt complex: The interaction of a potential antitumoral drug, [Pt(dmba)(aza-N1)(dmso)], with distinct proteins and oligonucleotides has been studied by means of ESI-TOF MS. The particular reactivity of this complex in front of the assayed biomolecules required the use of spectroscopic techniques and theoretical calculations to elucidate its mechanism. This information will contribute to its consideration as a putative anticancer drug.

First author: Haghdani, Shokouh, Complex Frequency-Dependent Polarizability through the p -> pi* Excitation Energy of Azobenzene Molecules by a Combined Charge-Transfer and Point-Dipole Interaction Model, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 11282, (2014)
Abstract: The complex frequency-dependent polarizability and pi ? pi* excitation energy of azobenzene compounds are investigated by a combined charge-transfer and point-dipole interaction (CT/PDI) model. To parametrize the model, we adopted time-dependent density functional theory (TDDFT) calculations of the frequency-dependent polarizability extended with excited-state lifetimes to include also its imaginary part. The results of the CT/PDI model are compared with the TDDFT calculations and experimental data demonstrating that the CT/PDI model is fully capable to reproduce the static polarizability as well as the pi ? pi* excitation energy for these compounds. In particular, azobenzene molecules with different functional groups in the para-position have been included serving as a severe test of the model. The pi ? pi* excitation is to a large extent localized to the azo bond, and substituting with electron-donating or electron-attracting groups on the phenyl rings results in charge-transfer effects and a shift in the excitation energy giving rise to azobenzene compounds with a range of different colors. In the CT/PDI model, the pi ? pi* excitation in azobenzenes is manifested as drastically increasing atomic induced dipole moments in the azo group as well as in the adjacent carbon atoms, whereas the shifts in the excitation energies are due to charge-transfer effects.

First author: Frei, Reto, Fast and Highly Chemoselective Alkynylation of Thiols with Hypervalent Iodine Reagents Enabled through a Low Energy Barrier Concerted Mechanism, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 16563, (2014)
Abstract: Among all functional groups, alkynes occupy a privileged position in synthetic and medicinal chemistry, chemical biology, and materials science. Thioalkynes, in particular, are highly useful, as they combine the enhanced reactivity of the triple bond with a sulfur atom frequently encountered in bioactive compounds and materials. Nevertheless, general methods to access these compounds are lacking. In this article, we describe the mechanism and full scope of the alkynylation of thiols using ethynyl benziodoxolone (EBX) hypervalent iodine reagents. Computations led to the discovery of a new, three-atom concerted transition state with a very low energy barrier, which rationalizes the high reaction rate. On the basis of this result, the scope of the reaction was extended to the synthesis of aryl- and alkyl-substituted alkynes containing a broad range of functional groups. New sulfur nucleophiles such as thioglycosides, thioacids, and sodium hydrogen sulfide were also alkynylated successfully to lead to the most general and practical method yet reported for the synthesis of thioalkynes.

First author: Khatua, Munmun, Confinement of (HF)2 in C-n (n=60, 70, 80,90) cages, CHEMICAL PHYSICS LETTERS,616, 49, (2014)
Abstract: Density functional theory calculations are performed to assess the influence of confinement on the strength of H F hydrogen bond in (HF)(2)@C-n (n= 60, 70, 80, 90). The (HF)(2) entrapping process into C-60 cage is thermodynamically unfavorable whereas it is favorable in other cages. The hydrogen bond is shorter in confined cages than that in free dimer. The interaction energy between two HF units is maximum in Cgo whereas the bond is the shortest in C-70. It appears that in confined situation a shorter bond does not necessarily mean a stronger bond. Energy decomposition analysis and electron density analysis are performed to explain the results.

First author: Fransted, Kelly A., Ultrafast Structural Dynamics of Cu(I)-Bicinchoninic Acid and Their Implications for Solar Energy Applications, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 10497, (2014)
Abstract: In this study, ultrafast optical transient absorption and X-ray transient absorption (XTA) spectroscopy are used to probe the excited-state dynamics and structural evolution of copper(I) bicinchoninic acid ([Cu(I)(BCA)(2)](+)), which has similar but less frequently studied biquinoline-based ligands compared to phenanthroline-based complexes. The optical transient absorption measurements performed on the complex in a series of polar protic solvents demonstrate a strong solvent dependency for the excited lifetime, which ranges from approximately 40 ps in water to over 300 ps in 2-methoxyethanol. The XTA experiments showed a reduction of the prominent 1s -> 4pz edge peak in the excited-state X-ray absorption near-edge structure (XANES) spectrum, which is indicative of an interaction with a fifth ligand, most likely the solvent. Analysis of the extended X-ray absorption fine structure (EXAFS) spectrum shows a shortening of the metal-ligand bond in the excited state and an increase in the coordination number for the Cu(II) metal center. A flattened structure is supported by DFT calculations that show that the system relaxes into a flattened geometry with a lowest-energy triplet state that has a dipole-forbidden transition to the ground state. While the short excited-state lifetime relative to previously studied Cu(I) diimine complexes could be attributed to this dark triplet state, the strong solvent dependency and the reduction of the 1s -> 4pz peak in the XTA data suggest that solvent interaction could also play a role. This detailed study of the dynamics in different solvents provides guidance for modulating excited-state pathways and lifetimes through structural factors such as solvent accessibility to fulfill the excited-state property requirements for efficient light harvesting and electron injection.

First author: Shakourian-Fard, Mehdi, Trends in Physisorption of Ionic Liquids on Boron-Nitride Sheets, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 26003, (2014)
Abstract: The adsorption of ionic liquids (ILs) on the hexagonal boron-nitride (h-BN) surface was studied at the M06-2X/cc-pVDZ level of theory. Three types of ionic liquids based on 1-butyl-3-methylimidazolium [Bmim](+), 1-butylpyridinium [Bpy](+), and butyltrimethylammonium [Btma](+) cations, paired with tetrafluoroborate [BF4](-), hexafluorophosphate [PF6](-), and bis(trifluoromethylsilfonyl)imide [Tf2N](-) anions were chosen as the adsorbates to better understand the trends in adsorption behavior of ILs on the h-BN surface. We have identified the various stable configurations of the h-BN-ionic liquid (h-BN center dot center dot center dot IL) complexes based on their binding energies and investigated the effect of charge transfer behavior and noncovalent interactions on the adsorption of ILs. ChelpG analysis indicated that, upon adsorption of ionic liquids on the h-BN surface, the overall charge on the cation, anion, and h-BN surface changes and the transfer (CT) between ILs and h-BN surface occurs. The order for the magnitude of charge transfer between different ILs and the h-BN surface is as follows: [Bmim][Tf2N] (-0.059e) > [Btma][PF6] (0.036e) > [Bpy][Tf2N] (0.028e) > [Btma][Tf2N] (0.021e) > [Bmim][PF6] (0.009e) > [Bpy][BF4] (0.007e) > [Bpy][PF6] (-0.006e) > [Btma][BF4] (-0.003e) > [Bmim][BF4] (-0.001e), respectively. Orbital energy and density of states (DOSs) calculations also show that the HOMOLUMO energy gap of ILs decreases upon adsorption on the h-BN surface. The order of the HOMOLUMO gap energy changes of ILs upon adsorption on the h-BN surface is as follows: [Btma][PF6] (3.25 eV) > [Btma][BF4] (2.84 eV) > [Bpy][PF6] (2.41 eV) > [Bpy][BF4] (2.29 eV) > [Bmim][BF4] (1.76 eV) > [Bmim][PF6] (1.54 eV) > [Btma][Tf2N] (1.26 eV) > [Bmim][Tf2N] (1.19 eV) > [Bpy][Tf2N] (0.86 eV), respectively. The binding energies based on QTAIM analysis indicate that the [BF4](-), [PF6](-), and [Tf2N](-) anions in the ILs have a stronger interaction with the h-BN surface than [Bmim](+), [Bpy](+), and [Btma](+) cations. The role of cooperative pi center dot center dot center dot pi, CH center dot center dot center dot pi, and X center dot center dot center dot pi (X = N, O, F atoms from anions) interactions on the adsorption of ILs on the h-BN surface was elucidated by analyzing the noncovalent interactions between ILs and the h-BN surface. Energy decomposition analysis (EDA) carried out for the h-BN center dot center dot center dot IL complexes indicates that the contribution of the Delta E-disp component in each complex is also more than electrostatic (Delta E-elect) and orbital (Delta E-orb) components (Delta E-disp > Delta(Eelect) > Delta E-orb), with the exception of the h-BN[Btma][BF4] complex whose Delta E-disp and Delta E-elect components are almost equal. For the complexes with the same cations, dispersion interaction increases by increasing size of anion from [BF4](-) to [PF6](-) and [Tf2N](-). This is confirmed by more favorable enthalpy of adsorption for ILs on the h-BN surface.The thermochemical analysis also indicates that the free energy of adsorption (Delta G(ads)) of ILs on the h-BN surface is negative, and thus, the adsorption occurs spontaneously. Our first-principles study offers fundamental insights into the nature of the physisorption and solvation behavior of ionic liquids on h-BN.

First author: Fernandez, Israel, Controlling the Oxidative Addition of Aryl Halides to Au(I), JOURNAL OF COMPUTATIONAL CHEMISTRY, 35, 2140, (2014)
Abstract: By means of density functional theory calculations, we computationally analyze the physical factors governing the oxidative addition of aryl halides to gold(I) complexes. Using the activation strain model of chemical reactivity, it is found that the strain energy associated with the bending of the gold(I) complex plays a key role in controlling the activation barrier of the process. A systematic study on how the reaction barrier depends on the nature of the aryl halide, ligand, and counteranion allows us to identify the best combination of gold(I) complex and aryl halide to achieve a feasible (i.e., low barrier) oxidative addition to gold(I), a process considered as kinetically sluggish so far.

First author: Lobello, Maria Grazia, A computational approach to the electronic, optical and acid-base properties of Ru(II) dyes for photoelectrochemical solar cells applications, POLYHEDRON, 82, 88, (2014)
Abstract: We provide a unified review of recent work carried out on computational investigations of a large series of Ru(II)-polypyridyl complexes effectively employed as solar cells sensitizers in dye-sensitized solar cells (DSCs). The use of methods rooted into Density Functional Theory (DFT) and its Time-Dependent extension (TDDFF) are demonstrated to be powerful tools to describe the electronic and optical properties of metallorganic ruthenium solar cells sensitizers, allowing us to unravel the interplay between their UV-Vis spectral changes and the complexes acid-base properties. This theoretical approach can be used to reproduce and understand the experimental data and also to design and predict the electronic and optical properties of new ruthenium-based sensitizer dyes.

First author: Al-Fahemi, Jabir H., QSPR study on nematic transition temperatures of thermotropic liquid crystals based on DFT-calculated descriptors, LIQUID CRYSTALS, 41, 1575, (2014)
Abstract: The individual correlations between nematic transition temperatures and the molecular descriptors derived from density functional theory (DFT) method are investigated. Significant quantitative structure-property relationships (QSPRs) for T-N of a set of 42 theromtropic liquid crystal were established through principle component analysis (PCA) and multiple linear regression (MLR). A promising six-descriptor linear model with good statistical fitting and predicting capability were developed with the help of DFT. The model is based on E-HOMO, E-LUMO, mu, S, W and X. The reliability of this model is clear from its correlation coefficient (R-2=0.95) and cross-validation coefficient (R-CV(2)=0.93).

First author: Zhang, Shou-Feng, Understanding the effects of the number of pyrazines and their positions on charge-transport properties in silylethynylated N-heteropentacenes, JOURNAL OF MOLECULAR MODELING, 20, 1575, (2014)
Abstract: The charge-transport properties of a series of silylethynylated N-heteropentacenes (TIPS-PEN-xN; x = 2, 4) were systematically investigated using Marcus electron-transfer theory coupled with kinetic Monte Carlo simulations. Electronic structure calculations showed that introducing more pyrazine rings decreases the energy levels of the lowest unoccupied molecular orbitals (LUMOs) and should aid electron transfer. The number and the positions of the pyrazine rings greatly influence the molecular packing in crystals and hence the intermolecular electronic coupling. Furthermore, the introduction of internal (rather than external) pyrazine rings leads to a better charge-transport network. Transport parameters evaluated from the hopping and band-like models both demonstrate that, among the TIPS-PEN-xN molecules, B-TIPS-PEN-4N-which has two internal pyrazine rings-is the most promising n-type material.

First author: Azizi, Elmira, Interactions of small gold clusters, Au-n (n=1-3), with graphyne: Theoretical investigation,JOURNAL OF MOLECULAR GRAPHICS & MODELLING, 54, 80, (2014)
Abstract: The interactions of gold atom and clusters (Au-2 and Au-3) with the active sites of graphyne (GY) have been investigated using density functional theory (PBE, PBE-D3, and B3LYP-D3). In order to compare performance of OFT functional (BP86, PBE, TPSSh, B3LYP, PBE-D3, TPSSh-D3, and B3LYP-D3), the interactions of Au-2 with various functional groups such as -sp, -sp(2) and aromatic sp(2) carbon atoms, -sp, -sp(2) and aromatic sp(2)-bonds have been investigated and also compared with the ab initio MP2 results. Additionally, the nature of interactions for graphyne-Au-2 complexes are interpreted by means of the natural-bond orbital (NBO), the quantum theory of atoms in molecules (QTAIM) and energy decomposition analysis (EDA) and compared with those of related graphene-Au-2. This study suggests that graphyne shows complex behavior in comparison to those of graphene and could also be useful in modeling of the next generation electronic devices.

First author: Dommerholt, Jan, Highly accelerated inverse electron-demand cycloaddition of electron-deficient azides with aliphatic cyclooctynes, NATURE COMMUNICATIONS, 5, 80, (2014)
Abstract: Strain-promoted azide-alkyne cycloaddition (SPAAC) as a conjugation tool has found broad application in material sciences, chemical biology and even in vivo use. However, despite tremendous effort, SPAAC remains fairly slow (0.2-0.5 M-1 s(-1)) and efforts to increase reaction rates by tailoring of cyclooctyne structure have suffered from a poor trade-off between cyclooctyne reactivity and stability. We here wish to report tremendous acceleration of strain-promoted cycloaddition of an aliphatic cyclooctyne (bicyclo[6.1.0]non-4-yne, BCN) with electron-deficient aryl azides, with reaction rate constants reaching 2.0-2.9 M-1 s(-1). A remarkable difference in rate constants of aliphatic cyclooctynes versus benzoannulated cyclooctynes is noted, enabling a next level of orthogonality by a judicious choice of azidecyclooctyne combinations, which is inter alia applied in one-pot three-component protein labelling. The pivotal role of azide electronegativity is explained by density-functional theory calculations and electronic-structure analyses, which indicates an inverse electron-demand mechanism is operative with an aliphatic cyclooctyne.

First author: Safin, Damir A., Supramolecular Coordination Complexes of the N-Thiophosphorylated 2,5-Dithiobiurea [NHC(S)NHP(S)(OiPr)(2)](2) with Zn-II and Cd-II Ions – Cation-Induced Dinuclear Mesocate Structure versus Tetranuclear Nanoscaled Aggregate, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 5, 5522, (2014)
Abstract: The reaction of the deprotonated N-thiophosphorylated bis-thiourea N,N’-bis(diisopropoxythiophosphorylamidothiocarbonyl) hydrazine {[NHC(S)NHP(S)(OiPr)(2)](2), H2L} with ZnCl2 leads to the complex [Zn-2{[NHC(S)NP(S)(OiPr)(2)](2)}(2)] ([Zn2L2]), in which two metal cations are each 1,5-S,S’-coordinated through the sulfur atoms of the thiocarbonyl and thiophosphoryl groups of the pendant deprotonated thioacyl-amidothiophosphate functions. The same reaction with CdCl2 leads to the tetranuclear nanoscaled aggregate [(Cd-2{[NC(S)NHP(S)(OiPr)(2)](2)}(2))(2)] ([(Cd2L2)(2)]). This complex contains ligands that are doubly deprotonated through their hydrazine NH groups and exhibit unprecedented mu(4) and mu(5) coordination modes. DFT calculations have shown that both complexes are stabilized not only by typical coordination bonds (Zn-S, Cd-S) but also by numerous intramolecular “noncovalent” interactions: polar C-H center dot center dot center dot S and N-H center dot center dot center dot S, nonpolar C-H center dot center dot center dot H-C, and sigma-hole bonding (S center dot center dot center dot S).

First author: Elder, Philip J. W., Structural Changes Upon Oxidation of ((PBu2)-Bu-t)(2) and 1,4-(CH2)(2)((PBu)-Bu-t)(4): Transannular P-P Interactions in Cations of the 1,4-C2P4 Ring, HETEROATOM CHEMISTRY, 25, 501, (2014)
Abstract: Density functional theory (DFT) calculations for the six-membered ring 1,4-(CH2)(2)((PBu)-Bu-t)(4) (1), the dimer ((PBu2)-Bu-t)(2) (2) and the 2,5-chalcogenated derivatives of 1, 3a (E = S) and 3b (E = Se), and the corresponding cation radicals and dications predict significant structural changes upon oxidation. The formation of a transannular P-P single bond (ca. 2.25 angstrom) in the three cyclic dications 1(2+), 3a(2+), and 3b(2+) is indicated by geometry and consideration of the frontier orbitals. The calculations also indicate a weak transannular interaction in the cyclic cation radicals. The nature of these transannular P-P bonding interactions is analyzed through a consideration of the molecular orbitals involved. Cyclic Voltammetry studies of 1 and 2 reveal two well-separated oxidation processes. Both processes are irreversible for 1 at normal scan rates, whereas for 2 the first process is quasi-reversible. The cation radical 1(+center dot) could not be detected by in situ electron paramagnetic resonance studies of the first electrochemical oxidation, but a spectrum for the radical cation 2(+center dot) could be observed. The difference in the redox behavior of 1 and 2 is considered with respect to the structural parameters and DFT calculations. Chemical oxidation of 1 with NO+[Al(ORF)(4)]-(R-F = C(CF3)(3)) in CH2Cl2 led to a complex mixture; the protonated cation H1(+) (1,4-(CH2)(2)((PBu)-Bu-t)(3)((HPBu)-Bu-t)(+)) was identified as one of the major products on the basis of multinuclear

First author: Harb, Mohammad K., Effects of Alkane Linker Length and Chalcogen Character in [FeFe]-Hydrogenase Inspired Compounds, HETEROATOM CHEMISTRY, 25, 592, (2014)
Abstract: Models of [FeFe]-hydrogenases containing diselenolato ligands with different bridge linker length have been prepared: Fe-2(mu-Se(CH2)(4)Se-mu)(CO)(6) (4DS), and Fe-2(mu-Se(CH2)(5)Se-mu)(CO)(6) (5DS) as well as dithiolato Fe-2(mu-S(CH2)(4)S-mu)(CO)(6) (4DT) and compared with Fe-2(mu-S(CH2)(3)S-mu)(CO)(6) (PDT) and Fe-2(mu-Se(CH2)(3)Se-mu)(CO)(6) (PDS). Compounds 4DT, PDS, 4DS, and 5DS were characterized by spectroscopic techniques including NMR, IR, mass spectrometry, ultraviolet photoelectron spectroscopy (UPS), elemental analysis, and X-ray crystal structure analysis. Combinations of electrochemical measurements, UPS, and density functional theory calculations indicate that oxidations of these five compounds are not significantly affected by chalcogen character but instead are governed by linker length. Cations for all compounds are calculated to adopt a bridged CO “rotated” structure with a vacant site on one of the Fe centers. In 4DT, 4DS, and 5DS, the alkane linker forms an agostic interaction with the vacant site on the rotated Fe. The reduction potentials for these compounds shift positively on average 0.16 V for each carbon added to the alkane linker with shifts being as large as 0.23 V between PDT and 4DT, and as small as 0.09 V between 4DS and 5DS. Catalytic reduction of protons from acetic acid in CH2Cl2 occurs at -1.79 and -1.86 V for PDT and 4DT and -2.02, -2.09, and -2.04 V for PDS, 4DS, and 5DS, indicating that chalcogen character is the primary factor that affects catalytic potential. On average the S-containing compounds catalyze proton reduction at potentials, which are 0.23 V less negative than the Se-containing compounds in this study.

First author: Ehret, Fabian, Non-innocent Redox Behavior of Amidinato Ligands: Spectroscopic Evidence for Amidinyl Complexes, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 640, 2781, (2014)
Abstract: The compounds [Ru-II(bmaa(-))(bpy)(2)](PF6) [1(PF6)], [Ru-II(bmaa(-))(Cym)Cl] (2), and [Ru-II(bmaa(-))(Cym)(py)](PF6) [3(PF6)] [bmaa(-) = N,N-bis(4-methoxyphenyl)acetamidinato, bpy = 2,2′-bipyridine, Cym = p-cymene, py = pyridine] were studied spectroelectrochemically (EPR, UV/Vis) to reveal metal-centered oxidation for 1(+) but bmaa(-)-based oxidation to yield amidinyl ligands in 2(+) and 3(2+).

First author: Zhang, Xiao-Yu, Effects of carbon chain on hole-transport properties in naphtho[2,1-b:6,5-b ‘]difuran derivatives: Remarkable anisotropic mobilities, ORGANIC ELECTRONICS, 15, 3341, (2014)
Abstract: Theoretical investigations of hole-transport properties in two naphtho[2,1-b:6,5-b’]difuran derivatives as novel p-type organic semiconductor based on the Marcus-Hush theory combining quantum mechanics are carried out. This work focuses on the effects of carbon chain on molecular orbitals, partial charge difference, ionization potential, internal energy relaxation, and hole-transport behaviors. Through computational modeling, we are shedding light on the favorable function of C8-DPNDF single crystal as p-type organic material. With the introduction of octyl group, C8-DPNDF single crystal possesses high hole-transfer mobilites (1.589 cm(2) V-1 s(-1)) and remarkable anisotropic behavior. The simulated anisotropic mobility curve of C8-DPNDF demonstrates the maximum value of the mobility appears when the measuring conducting channel is along the b-axis of the single crystal. The adiabatic ionization potential (AIP) and vertical ionization potential (VIP) of C8-DPNDF are about 6.312 and 6.399 eV, that is, slightly smaller than those of DPNDF. The relatively small IP values can ensure effective hole injection from the source electrode. The data obtained from the present work can be used to prove that C8-DPNDF molecule has the potential to develop into high-efficient p-type organic semiconductor materials, whose hole-transport mobility can be further improved when the measuring transistor channel is controlled carefully.

First author: Zheng, Yi, Interaction between phosphomolybdic anion and imidazolium cation in polyoxometalates-based ionic liquids: a quantum mechanics study, JOURNAL OF MOLECULAR MODELING, 20, 3341, (2014)
Abstract: In this study, interaction between the phosphomolybdic anions ([PMoO](3-)) and 1-butyl-3-methyl imidazolium cations ([Bmim](+)) has been systematically studied by the density functional theory at the PBE-D3/TZP level. The stable geometries of the ion pairs with no imaginary frequencies were obtained and characterized. Multiple H-bonds formed between the cation and anion were revealed with the type of C-H center dot center dot center dot O. The interaction energy between the constituent [PMoO](3-) anion and [Bmim](+) cation is obviously larger than those in common ionic liquid. This is the possible reason for the relatively higher melting point of polyoxometalates (POMs)-based ionic liquids. It was observed that the interaction between the ion pairs was mainly contributed from the electrostatic interaction between [PMoO](3-) and [Bmim](+). The nature of the H-bonds was analyzed by the atoms in molecules (AIM) theory, harmonic vibrational frequency, the natural bond orbital (NBO), and the non-covalent interaction (NCI) approaches. The charge transfer and the orbital interaction between the ion pairs have also been identified, which may have an important influence on the electronic property of the ion pairs.

First author: Hooper, J., Chiral surface networks of 3-HPLN – A molecular analog of rounded triangle assembly, SURFACE SCIENCE, 629, 65, (2014)
Abstract: The self-assembly of 3-hydroxyphenalenone (3-HPLN) on the Ag(111) surface has been studied with scanning tunneling microscopy and first-principles computations. The prochiral 3-HPLN molecule forms zipper-like chains when deposited on the Ag(111) surface, representing a 2D analog of their arrangement in bulk crystals. Upon annealing, local chiral trimer motifs form and serve as building blocks in extended 2D supramolecular networks not observed in 3D crystals. The extended network is porous and is held together via weak van der Waals interactions. The dispersion forces between trimers suggest that their handedness is overall racemic, but the asymmetric packing of 3-HPLN trimers around the pores leads to a chiral network. The offset alignment of neighboring 3-HPLN molecules in the unit cell resembles the offset between neighboring particles that are seen in the most efficient packings of rounded triangles. Computations illustrate that charge is transferred from the Ag(111) surface to the lowest unoccupied orbital of 3-HPLN, and a number of networks (including a honeycomb, as well as an alternative close-packed arrangement) are investigated.

First author: Merzoug, Meriem, Coordination diversity of the phenazine ligand in binuclear transition metal sandwich complexes: Theoretical investigation, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 770, 69, (2014)
Abstract: DFT calculations with full geometry optimization have been carried out for all the low-energy isomers of [M(C12N2H8)](2) (M = Sc-Ni and C12N2H8 = phenazine ligand = Phz). Depending on the metal atoms, phenazine adopts various hapticities that involve full or partial coordination of the C-6 and C4N2 rings. Phenazine is also shown to be quite flexible with respect to the spin ground state. The phenazine ligand can be bound to the metals involving its C-6 and C4N2 rings or its outer C-6 ones through various coordination modes such as eta(4)-eta(4), eta(6)-eta(4) and eta(6)-eta(6), giving rise to the conformations of types (a) and (b). This study has shown that the electronic communication between the metal centers depends on their oxidation state in harmony with the neutral, monoanionic and dianionic phenazine forms. The major structures showed the preference of the coordination in separate way of the metal centers apart from the Ti, V and Co ones. The MO plots, WBIs (Weber bond indices) obtained from the Weinhold nature bond order analysis and the metal-metal bond lengths gave a deeper insight on the metal-metal bonding. Energy decomposition analysis showed that the interactions in the studied compounds are governed by half covalent and half electrostatic character.

First author: Majid, Abdul, A density functional theory study of 3d-4f exchange interactions in Cr-Nd codoped GaN,JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 368, 384, (2014)
Abstract: The density functional theory based calculations of Cr, Nd and Cr/Nd co-doped wurtzite GaN generated using GGA and TB-mBJ exchange correlation functionals are being reported. All the structures were geometrically optimized and fully relaxed. The dopants introduced new energy levels in the forbidden energy gap, whose hybridization and interaction are discussed in detail to explain electronic and ferromagnetic properties of the materials. The 3d-3d interaction seems to be responsible for double exchange interaction in Cr:GaN whereas spin polarization caused by 4f-5d-CB interaction causes ferromagnetism in Nd:GaN. A model is proposed to explain the ferromagnetic ordering and 3d-4f exchange interactions in new codoped system Cr/Nd:GaN according to which 4f-5d-CB-3d interaction via 4f-5d, 4f-2p and 2p-3d coupling plays role.

First author: Sulka, Martin, Theoretical Study of Plutonium(IV) Complexes Formed within the PUREX Process: A Proposal of a Plutonium Surrogate in Fire Conditions, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 10073, (2014)
Abstract: We present a relativistic quantum chemical study to determine the best surrogate for plutonium(IV) to be used in experimental investigations of the behavior of plutonium-nitrate-TBP in fire conditions that might occur in the nuclear fuel refining process known as PUREX. In this study geometries and stabilities of Pu(NO3)(6)(2-) and Pu(NO3)(4)(TBP)(2) complexes were compared to that of equivalent complexes of selected elements from the lanthanide and actinide series (Ce, Th, U) chosen on the basis of similar ionic radii and stability as tetravalent species. PBE and PBE0 DFT functionals have proven to be sufficient and affordable for qualitative studies, performing as good as the wave function based correlated method MP2. On the basis of our results, cerium(IV) appears to be a good surrogate for plutonium(IV).

First author: Mrkalic, Emina M., Synthesis of novel palladium(II) complexes with oxalic acid diamide derivatives and their interaction with nucleosides and proteins. Structural, solution, and computational study, DALTON TRANSACTIONS, 43, 15126, (2014)
Abstract: Novel palladium complexes, KH[Pd(obap)](2).3H(2)O (3) with oxamido-N-aminopropyl-N’-benzoic acid and [Pd(apox)] (4) with N,N’-bis(3-aminopropyl)ethanediamide, were synthesized. Exhaustive synthetic, solution and structural studies of the two Pd(II) complexes are reported. The binary and ternary systems of the Pd(II) ion with H(2)apox or H(3)obap as primary ligands and nucleosides (Ado or Cyt) as secondary ligands, are investigated in order to better understand their equilibrium chemistry. The relative stabilities of the ternary complexes are determined and compared with those of the corresponding binary complexes in terms of their Delta log K values. The species distribution of all complexes in solution is evaluated. Fluorescence spectroscopy data shows that the fluorescence quenching of HSA is a result of the formation of the [PdL]-HSA complex. The structure of complex 3 is confirmed using X-ray crystallography. The results are compared to those obtained for palladium complexes of similar structures. Density functional theory (DFT) has been applied for modelling and energetic analysis purposes. The nature of the Pd-N(0) bond interaction is analyzed using NBO. We report here docking simulation experiments in order to predict the most probable mechanism of pro-drug-action. The next free binding energy order of the best scores from the [PdL]-DNA docking simulations, cis-[Pt(NH3)(2)(H2O)(2)](2+) > [Pd(obap)] > [Pd(mda)], has been observed in the case of DNA alteration. For the ER and cytosolic stress mechanisms the results of the docking simulations to the chaperons Grp78 and Hsc70 are promising for possible applications as potent protein inhibitors (K-1 of [Pd(mda)]/GRP78 being similar to 66 mu M and K-1 for [Pd(obap)]/HSC70 being 14.39 mu M).

First author: Buechert, Marina, 2,2 ‘-Bipyridine-Based Dendritic Structured Compounds for Second Harmonic Generation,CHEMISTRY-A EUROPEAN JOURNAL, 20, 14351, (2014)
Abstract: Parallel alignment of dipolar electron-donor–bridge-electron-acceptor entities can strongly enhance their nonlinear optical properties. This favorable arrangement can be in principle achieved by linking these units covalently or through metal coordination. Four dipolar single-strand chromophores decorated with a 5-electron-donor-5-electron-acceptor-modified 2,2-bipyridine functionality were synthesized. For two of these chromophores triple-stranded dendritic structures were successfully formed. All of the compounds were characterized with respect to their linear and nonlinear optical properties. For the aldehyde derivatives an enhancement of the first hyperpolarizability of 4.5 rather than 3 was obtained when going from single to triple strands. Theoretical calculations with density functional theory suggest that interstrand transitions contribute to the optical properties of the dendritic structures.

First author: Breitenfeld, Jan, Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl-Aryl Kumada Coupling Reactions,ORGANOMETALLICS, 33, 5708, (2014)
Abstract: The mechanism of alkylaryl Kumada coupling catalyzed by the nickel pincer complex Nickamine was studied. Experiments using radical-probe substrates and DFT calculations established a bimetallic oxidative addition mechanism. Kinetic measurements showed that transmetalation rather than oxidative addition was the turnover-determining step. The transmetalation involved a bimetallic pathway.

First author: Zhang, Zhiyong, Spin-orbit DFT with analytic gradients and applications to heavy element compounds,THEORETICAL CHEMISTRY ACCOUNTS, 133, 5708, (2014)
Abstract: We have implemented the unrestricted DFT approach with one-electron spin-orbit operators in the massively parallel NWChem program. Also implemented is the analytic gradient in the DFT approach with spin-orbit interactions. The current capabilities include single-point calculations and geometry optimization. Vibrational frequencies can be calculated numerically from the analytically calculated gradients. The implementation is based on the spin-orbit interaction operator derived from the effective core potential approach. The exchange functionals used in the implementation are functionals derived for non-spin-orbit calculations, including GGA as well as hybrid functionals. Spin-orbit Hartree-Fock calculations can also be carried out. We have applied the spin-orbit DFT methods to the Uranyl aqua complexes. We have optimized the structures and calculated the vibrational frequencies of both (UO22+)(aq) and (UO2+)(aq) with and without spin-orbit effects. The effects of the spin-orbit interaction on the structures and frequencies of these two complexes are discussed. We also carried out calculations for Th-2, and several low-lying electronic states are calculated. Our results indicate that, for open-shell systems, there are significant effects due to the spin-orbit effects and the electronic configurations with and without spin-orbit interactions could change due to the occupation of orbitals of larger spin-orbit interactions.

First author: Miro, Pere, Uranyl-Peroxide Nanocapsules in Aqueous Solution: Force Field Development and First Applications, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 24730, (2014)
Abstract: The self-assembly of uranyl-peroxide nanocapsules in aqueous solution is unique in uranium chemistry and has potential applications in the fabrication and reprocessing of actinide-based materials. We present the first study of these species in aqueous solution by means of classical molecular dynamics simulations. To this end, we parametrized a uranyl-peroxide force field from interaction energies computed with second order MollerPlesset perturbation theory and fit to a BornHugginsMayer potential. Bonded parameters were fit from density functional theory calculations. The solvent and counterion structures surrounding four different systems ([((UO2)-O-VI)](2+), [((UO2)-O-VI)(2)(mu(2)-O-2)](2+), [((UO2)-O-VI)(5)(mu(2)-O-2)(5)], and [((UO2)-O-VI)(20)(mu 2-O-2)(30)](20-)) were studied in aqueous solution. The largest studied system is predicted to encapsulate an ice-like water cluster.

First author: Wang, Guanjun, Identification of an iridium-containing compound with a formal oxidation state of IX,NATURE, 514, 475, (2014)
Abstract: One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states(1-4). The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists(5). The highest experimentally known formal oxidation state of any chemical element is at present VIII2-4, although higher oxidation states have been postulated(6,7). Compounds with oxidation state VIII include several xenon compounds(8) (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2-4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state(1). In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices(9). The valence electron configuration of iridium in IrO4 is 5d(1), with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4](+)), which was recently predicted to be stable(10) and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4](+) species(11,12), but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4](+) and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a T-d-symmetrical structure and a d(0) electron configuration, is the most stable of all possible [IrO4](+) isomers.

First author: Raggi, G., Relativistic DFT calculations of magnetic moments of pristine and thiolated Mn@Au-x (x=6, 12),PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 21506, (2014)
Abstract: In this work we present the results of relativistic DFT calculations of magnetic moments for manganese inserted into a gold ring (Mn@Au-6) or a cage-like structure (Mn@Au-12) both pristine and n-thiolated. Optimization has been carried out to obtain different isomers always favouring the endohedral gold clusters with Mn inside. For the total magnetic moment (from electronic population analysis) verification of the jellium model has been performed in each case. It is concluded that the magnetic moments arise largely from the doped manganese atom and that thiolation can modulate its value, which is not present in the pure form. In the Mn@Au-12 clusters we observed the formation of a hole in their structure; this could be a characteristic of insertion of a highly ferromagnetic dopant in some metal clusters, such as gold, and this could act as a precursor of the formation of gold magnetic nanotubes.

First author: Caramori, Giovanni F., Ruthenium(II) complexes of N-heterocyclic carbenes derived from imidazolium-linked cyclophanes, DALTON TRANSACTIONS, 43, 14710, (2014)
Abstract: The present work seeks to characterize, in the light of electronic structure calculations, an unusual metal-[(eta(1)-NHC)(2):(eta(6)-arene)] bonding situation in a set of ruthenium(II) complexes containing the ortho-xylytene-linked-bis(NHC)cyclophane ligand (NHC-cyclophane) (1), which binds to the ruthenium center through two carbene carbons and one of the arene rings. The nature of ruthenium(II)-[(eta(1)-NHC)(2):(eta(6)-arene)] bonding was investigated in the tight of EDA-NOCV, NBO and QTAIM analyses by adopting 1 as a model compound. The interplay between the ortho-cyclophane scaffold with different families of five-membered carbenes, such as imidazole, 1, triazole-based NHCs (Enders’ carbenes), 2, and P-heterocyclic carbenes (PHCs), 3, was investigated. The metal [(eta(1)-NHC)(2):(eta(6)-arene)] bonding situation was also extended to heavier analogues, such as N=heterocyclic silylenes (NHSi) and N-heterocyclic germylenes (NHGe), in order to address how the basicity of NHC, NHSi and NHGe is affected by the cyclophane framework. The results reveal that ruthenium(II)-[(eta(1)-NHC)(2):(eta(6)-arene)] is more covalently than electrostatically bonded and that the degree of covalence is larger in PHCs than in NHCs or Enders’ carbenes. It is also revealed that the covalent character in the ruthenium(II)-[(eta(1)-NHGe)(2):(eta(6)-arene)] and ruthenium(II)-[(eta(1)-NHSi)(2):(eta(6)-arene)] bonds is larger than in ruthenium(II)-[(eta(1)-NHC)(2):(eta(6)-arene)].

First author: Linares-Flores, C., Reactivity trends of Fe phthalocyanines confined on graphite electrodes in terms of donor-acceptor intermolecular hardness: Linear versus volcano correlations, CHEMICAL PHYSICS LETTERS, 614, 176, (2014)
Abstract: In this work, we have studied the interaction between the hydrazine N2H4 molecule with several FeN4 macrocyclic complexes (FePc’s). In order to modulate the electron density located on the metal center using iron-phthalocyanine (FePc) as the reference, we used substituted iron-phthalocyanines with different types of substituents electron-donating groups such as iron-tetraamino-phthalocyanine (4 beta(NH2)FePc) and iron-octamethoxyphthalocyanine (8 beta(OCH3)FePc), and with electron-withdrawing groups such as iron-tetranitrophthalocyanine(4 beta(NO2)FePc) and iron-hexadecachlorophthalocyanine (16(Cl)FePc), respectively.We have found that the energy of interaction between hydrazine and the Fe center in the macrocycle increases as the electron-withdrawing power of the substituents increases. When rate constants instead of currents are compared in a semilog plot versus Delta epsilon(D-A), a linear correlation is found where log k increases as the intermolecular hardness of the systems decreases.

First author: Vonci, Michele, Modular Molecules: Site-Selective Metal Substitution, Photoreduction, and Chirality in Polyoxometalate Hybrids, CHEMISTRY-A EUROPEAN JOURNAL, 20, 14102, (2014)
Abstract: The first members of a promising new family of hybrid amino acid-polyoxometalates have emerged from a search for modular functional molecules. Incorporation of glycine (Gly) or norleucine (Nle) ligands into an yttrium-tungstoarsenate structural backbone, followed by crystallization with p-methylbenzylammonium (p-MeBzNH(3)(+)) cations, affords (p-MeBzNH(3))(6)K-2(GlyH)[As-4(II)((YW3VI)-W-III)(W44Y4O159)-Y-VI-O-III( Gly)(8)-(H2O)(14)]center dot 47H(2)O (1) and enantiomorphs (p-MeBzNH(3))(15)(NleH)(3) [As-4(III)((Mo2Mo2VI)-Mo-V)(W44Y4O160)-Y-VI-O-III(Nle)(9)(H2O)(11)][As-4 (III)((Mo2W2VI)-W-VI)-(W44Y4O160)-Y-VI-O-III(Nle)(9)(H2O)(11)] (generically designated 2: l-Nle, 2a; d-Nle, 2b). An intensive structural, spectroscopic, electrochemical, magnetochemical and theoretical investigation has allowed the elucidation of site-selective metal substitution and photoreduction of the tetranuclear core of the hybrid polyanions. In the solid state, markedly different crystal packing is evident for the compounds, which indicates the role of noncovalent interactions involving the amino acid ligands. In solution, mass spectrometric and small-angle X-ray scattering studies confirm maintenance of the structure of the polyanions of 2, while circular dichroism demonstrates that the chirality is also maintained. The combination of all of these features in a single modular family emphasizes the potential of such hybrid polyoxometalates to provide nanoscale molecular materials with tunable properties.

First author: Daday, Csaba, Wavefunction in Density Functional Theory Embedding for Excited States: Which Wavefunctions, which Densities?, CHEMPHYSCHEM, 15, 3205, (2014)
Abstract: We present a detailed analysis of our recently proposed wavefunction in density functional theory method to include differential polarization effects through state-specific embedding potentials. We study methylenecyclopropene and acrolein in water by using several wavefunction approaches to validate the supermolecular reference and to assess their response to embedding. We find that quantum Monte Carlo, complete-active space second-order perturbation theory, and coupled cluster methods give very consistent solvatochromic shifts and a similar response to embedding. Our scheme corrects the excitation energies produced with a frozen environment, but the values are often overshot. To ameliorate the problem, one needs to use wavefunction densities to polarize the environment. The choice of the exchange-correlation functional in the construction of the potential has little effect on the excitation, whereas the approximate kinetic-energy functional appears to be the largest source of error.

First author: Abreu, Marissa Baddick, Does the 18-Electron Rule Apply to CrSi12?, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 3492, (2014)
Abstract: Understanding the bonding between silicon and transition metals is valuable for devising strategies for incorporating magnetic species into silicon. CrSi12 is the standard example of a cluster whose apparent high stability has been explained by the 18-electron rule. We critically examine the bonding and nature of stability of CrSi12 and show that its electronic structure does not conform to the 18-electron rule. Through theoretical studies, we find that CrSi12, has 16 effective valence electrons assigned to the Cr atom and an unoccupied 3d(z)(2) orbital. We demonstrate that the cluster’s apparent stability is rooted in a crystal field-like splitting of the 3d orbitals analogous to that of square planar complexes. CrSi14 is shown to follow the 18-electron rule and exhibits all conventional markers characteristic of a magic cluster.

First author: Petrov, Pavel A., Synthesis, molecular and electronic structures of a paramagnetic trimetallic cluster containing an unusual Mo-3(mu(3)-Se)(2)(mu-Se)(3) core, POLYHEDRON, 81, 6, (2014)
Abstract: The electron precise [Mo-3(mu(3)-Se)(mu-Se)(3)(dppe)(3)Br-3](+) incomplete cuboidal complex, with six cluster skeletal electrons (CSE), was converted into the paramagnetic bicapped [Mo-3(mu(3)-Se)2(mu-Se)(3)(dppe)(3)](+) cluster (1(+)), with an unusual seven metal electron population, by treatment with elemental Ga. The cluster core consists of an almost equilateral Mo3 triangle (Mo-Mo distances are in the range 2.7583(7)-2.7748(7) A with an average value of 2.77(3) A), capped by two selenide ligands. The remaining selenium atoms bridge adjacent metal atoms, defining a virtually planar Mo-3(mu-Se)(3) unit, with the capping Se atoms positioned above and below this plane. The new complex possesses a doublet ground state with the unpaired electron density delocalized over the three metal atoms. DFT calculations show that the HOMO has “a(1)” symmetry, precluding any Jahn-Teller distortion on the cluster core and giving support to EPR and structural observations.

First author: Wu, Ren-Ming, Theoretical investigations on electronic and charge transport properties of novel organic semiconductors – Triisopropylsilylethynyl(TIPS)-functionalized anthradifuran and anthradithiophene derivatives,COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1046, 107, (2014)
Abstract: Triisopropylsilylethynyl(TIPS)-functionalized polyacenes, a new family of novel organic semiconductors, have attracted extensive interests due to their high solubility, good air stability, and high performance in organic field effect transistors (OFETs). In present study, the electronic and charge transport properties of a series of chalcogen-doped TIPS-pentacene (PENT) derivatives have been studied by density functional theory (DFT). Their electronic structures, ionization energies, electron affinities, reorganization energies, transfer integrals of possible hopping pathways, hole and electron mobilities, and anisotropic mobilities have be calculated to discuss the role of various factors affecting the charge transport properties of these novel organic semiconductors. Fluorination and chlorination effects on the electronic properties and reorganization energies of the studied molecules have also been studied. The calculated results show that the fluorination and chlorination are efficient strategies for tuning the molecular orbital level to decrease the charge injection barrier from metal electrode and improve their oxidative stabilities. Though the fluorination indeed lowers the lowest unoccupied molecular orbital (LUMO) levels of TIPS-PENT derivatives, it also leads to much larger reorganization energies and smaller electron transfer integrals. Thus, it may be not an effective way for TIPS-PENT derivatives to convert a p-type semiconductor to an n-type one. Our calculated hole mobilities for available experiment crystal structures are in good agreement with the experimental observation. The computed hole mobilities for TIPS-anthradithiophene (ADT) and TIPS-teracenothiophene (TT) are 0.622 and 1.186 cm(2)V(-1) s(-1), respectively, which are in good agreement with the corresponding experimental values of 0.6 and 1.25 cm(2) V-1 s(-1), respectively. Their relative calculated electron mobilities are 0.607 and 0.637 cm(2) V-1 s(-1), respectively. The results show that they have high balanced hole and electron mobilities and may be promising candidates for ambipolar organic semiconductors. The studies on anisotropic mobilities of the selected derivatives show that they exhibit remarkable anisotropic behaviors and the hole and electron transfers along the parallel hopping pathway make the dominant contribution on their charge carrier mobilities.

First author: Rabilloud, Franck, Description of plasmon-like band in silver clusters: The importance of the long-range Hartree-Fock exchange in time-dependent density-functional theory simulations, JOURNAL OF CHEMICAL PHYSICS,141, 107, (2014)
Abstract: Absorption spectra of Ag-20 and Ag-55(q) (q = +1, -3) nanoclusters are investigated in the framework of the time-dependent density functional theory in order to analyse the role of the d electrons in plasmon-like band of silver clusters. The description of the plasmon-like band from calculations using density functionals containing an amount of Hartree-Fock exchange at long range, namely, hybrid and range-separated hybrid (RSH) density functionals, is in good agreement with the classical interpretation of the plasmon-like structure as a collective excitation of valence s-electrons. In contrast, using local or semi-local exchange functionals (generalized gradient approximations (GGAs) or meta-GGAs) leads to a strong overestimation of the role of d electrons in the plasmon-like band. The semi-local asymptotically corrected model potentials also describe the plasmon as mainly associated to d electrons, though calculated spectra are in fairly good agreement with those calculated using the RSH scheme. Our analysis shows that a portion of non-local exchange modifies the description of the plasmon-like band.

First author: Brandenburg, Jan Gerit, Crystal Packing Induced-Carbon-Carbon Double-Triple Bond Isomerization in a Zirconocene Complex, ORGANOMETALLICS, 33, 5358, (2014)
Abstract: We present a combined theoretical and experimental analysis of the carboncarbon bond character in two prototypical zirconocene complexes. The two cyclic seven-membered ring zirconium compounds 2a and 2b differ by the substitution of a tert-butyl by a trimethylsilyl group. Due to the coordination of the ?-system to the metal atom, a formally forbidden (eta(2)-allenyl)/enamido-Zr to (eta(2)-alkyne)/?N-imine-Zr complex isomerization is feasible. State-of-the-art dispersion-corrected density functional theory (DFT-D3) is used in both the solid and condensed phase to examine and quantify the experimental structures (X-ray diffraction) and C-13 NMR magnetic shielding. The complementary investigations demonstrate the importance of nonlocal London dispersion interactions. Both X-ray structures agree excellently with the results of the solid-state DFT-D3 calculations. Interestingly, 2b exhibits a mixed allenealkyne form in the solid state, while its gas phase structure has a strong allene character. The substitution leading to 2a prevents this isomerization in the solid state by the intramolecular stabilization of the allene structure. NMR solid and liquid phase measurements confirm the theoretically proposed transition. By combining the experimental and theoretical information, the rather unusual triple/single to double/double-bond transition is attributed to an intermolecular London dispersion induced crystal packing effect.

First author: Moustafa, Mohamed E., Carbon Hydrogen versus Nitrogen Oxygen Bond Activation in Reactions of N-Oxide Derivatives of 2,2 ‘-Bipyridine and 1,10-Phenanthroline with a Dimethylplatinum(II) Complex, ORGANOMETALLICS, 33, 5402, (2014)
Abstract: The reactions of the potential oxygen atom donor ligands 1,10-phenanthroline N-oxide (phenO) and 2,2-bipyridine N-oxide (bipyO) with the dimethylplatinum(II) complex [Pt2Me4(mu-SMe2)(2)] are reported. The reaction with the more rigid ligand phenO gave [PtMe2(2N,O-phenO)], which underwent oxidative addition with 4-t-Bu-C6H4CH2Br to give the platinum(IV) complex [PtBrMe2(CH2C6H4-4-t-Bu)(phenO)]. The complex [PtMe2(phenO)] reacted with methanol in air to give [Pt(OH)(OMe)Me-2(phenO)], but under an inert atmosphere it gave [Pt(OH)(OMe)Me-2(phen)], in a reaction involving NO bond activation. In contrast, the reaction of [Pt(2)Me4(mu-SMe2)(2)] with bipyO occurred by CH bond activation to give methane and [PtMe(kappa N-2,C-C5H4N-C5H3NO)(SMe2)], which underwent ligand substitution with pyridine, triphenylphosphine, or bis(diphenylphosphino)methane (dppm) to give [PtMe(kappa N-2,C-C5H4N-C5H3NO)(NC5H5)], [PtMe(kappa N-2,C-C5H4N-C5H3NO)(PPh3)], or the binuclear [{PtMe(kappa N-2,C-C5H4N-C5H3NO)}2(?-dppm)], respectively. With bis(diphenylphosphino)ethane (dppe), ligand substitution gave [PtMe(kappa C-1-C5H4N-C5H3NO)(dppe)], which contains a monodentate metalated bipyO ligand. The mechanisms of the key reactions are discussed.

First author: Adams, Richard D., Facile C-H Bond Formation by Reductive Elimination at a Dinuclear Metal Site,ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53, 11006, (2014)
Abstract: The electronically unsaturated dirhenium complex [Re-2(CO)(8)(mu-AuPPh3)(mu-Ph)] (1) was obtained from the reaction of [Re-2(CO)(8){mu-eta(2)-C(H)=C(H)nBu}(mu-H)] with [Au-(PPh3)Ph]. The bridging {AuPPh3} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re-2(CO)(8)(mu-H)(mu-Ph)] (2) by reaction of 1 with HSnPh3. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 degrees C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses.

First author: Goure, Eric, Cis/Trans Isomerizations in Diiron Complexes Involving Aniline or Anilide Ligands, INORGANIC CHEMISTRY, 53, 10060, (2014)
Abstract: We have recently reported a deprotonation-induced valence inversion within a phenoxido-bridged mixed-valent diiron(II,III) complex. The initial aniline coordinated to the Fe-II site reacts with triethylamine, and the resulting complex contains an anilide ligand coordinated to the Fe-III ion. The behavior of these complexes in acetonitrile is indeed more intricate. Owing to the very distinctive spectroscopic signatures of the complexes, the conjunction of NMR, Mossbauer, and UV-visible absorption spectroscopies allows one to evidence two isomerization reactions, one involving the aniline linked to Fe-II and the other the anilide on Fe-III. Theoretical calculations sustain this conclusion. Aniline in the cis position versus the bridging phenoxide is shown to be the most stable isomer while the anilide trans to the phenoxido bridge is favored. The trans isomer of the aniline complex is more acidic than the cis one by 1 pk(a) unit. Isomerization of the anilide complex is 10 times faster than the analogous isomerization of the aniline complex. Both reactions are proposed to proceed through a unique mechanism. This is the first time that such isomerization reactions are evidenced in dinuclear complexes.

First author: Jarzembska, Katarzyna N., Shedding Light on the Photochemistry of Coinage-Metal Phosphorescent Materials: A Time-Resolved Laue Diffraction Study of an Ag-I-Cu-I Tetranuclear Complex, INORGANIC CHEMISTRY, 53, 10594, (2014)
Abstract: The triplet excited state of a new crystalline form of a tetranudear coordination d(10)-d(10)-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing Ag-I and Cu-I metal centers has been explored using the Laue pump probe technique with approximate to 80 ps time resolution. The relatively short lifetime of 1 mu s is accompanied by significant photoinduced structural changes, as large as the Ag1 center dot center dot center dot Cu2 distance shortening by 0.59(3) angstrom. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag center dot center dot center dot Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag center dot center dot center dot Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronudear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies.

First author: Le Gac, Stephane, A Pentanuclear Lead(II) Complex Based on a Strapped Porphyrin with Three Different Coordination Modes, INORGANIC CHEMISTRY, 53, 10660, (2014)
Abstract: We have previously described Pb(II) and BOB) bimetallic complexes with overhanging carboxylic acid strapped porphyrins in which one metal ion is bound to the N-core (“out-of-plane”, OOP), whereas the second one is bound to the strap (“hanging-atop”, HAT). In such complexes, the hemidirected coordination sphere of a HAT Pb(II) cation provides sufficient space for an additional binding of a neutral ligand (e.g., DMSO). Interestingly, investigations of the HAT metal coordination mode in a single strap porphyrin show that a HAT Pb(H) can also interact via intermolecular coordination bonds, allowing the self-assembly of two bimetallic complexes. In the pentanuclear Pb(H) complex we are describing in this Article, three different coordination modes were found. The OOP Pb(H) remains inert toward the supramolecular assembling process, whereas the HAT Pb(II) cation, in addition to its intramolecular carboxylate and regular exogenous acetate groups, coordinates an additional exogenous acetate. These two acetates are shared with a third lead(H) cation featuring a holo-directed coordination sphere, from which a centro-symmetric complex is assembled. Density functional theory calculations show some electron-density pockets in the vicinity of the hemidirected HAT Pb(II) atoms, which are associated with the presence of a stereochemically active lone pair of electrons. On the basis of the comparison with other HAT Pb(II) and Bi(III) systems, the “volume” of this lone pair correlates well with the bond distance distributions and the number of the proximal oxygen atoms tethered to the post-transition metal cation. It thus follows the order 6-coordinate Bi(M) > 6-coordinate Pb(II) > 5-coordinate Pb(II).

First author: Li, Peng, Water O-H Bond Activation by Gas-Phase Plutonium Atoms: Reaction Mechanisms and Ab Initio Molecular Dynamics Study, CHEMPHYSCHEM, 15, 3078, (2014)
Abstract: A thorough description of the reaction mechanisms, taking into account different possible spin states, offers insights into the gas-phase reaction of plutonium atoms with water. Two possible reactions (isomerization and dehydrogenation) are presented. These reactions are found to be exothermic, with the best thermochemical conditions observed for the dehydrogenation reaction at around 23.5 kcal.mol(-1). The nature of the chemical-bonding evolution along the reaction pathways are investigated by employing various methods including electron localization function, atoms in molecules, and Mayer bond order. Total, partial, and overlap population density of state diagrams and analyses are also presented. Reaction rates at elevated temperatures (T=2982-000 K) are calculated by using variational transition-state theory with one-dimensional tunneling effects. In dynamics simulations, only the dehydrogenation reaction is observed, and found to be in good agreement with experimental values.

First author: Chulhai, Dhabih V., Simulating Surface-Enhanced Raman Optical Activity Using Atomistic Electrodynamics-Quantum Mechanical Models, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 9069, (2014)
Abstract: Raman optical activity has proven to be a powerful tool for probing the geometry of small organic and biomolecules. It has therefore been expected that the same mechanisms responsible for surface-enhanced Raman scattering may allow for similar enhancements in surface-enhanced Raman optical activity (SEROA). However, SEROA has proved to be an experimental challenge and mirror-image SEROA spectra of enantiomers have so far not been measured. There exists a handful of theories to simulate SEROA, all of which treat the perturbed molecule as a point-dipole object. To go beyond these approximations, we present two new methods to simulate SEROA: the first is a dressed-tensors model that treats the molecule as a point-dipole and point-quadrupole object; the second method is the discrete interaction model/quantum mechanical (DIM/QM) model, which considers the entire charge density of the molecule. We show that although the first method is acceptable for small molecules, it fails for a medium-sized one such as 2-bromohexahelicene. We also show that the SEROA mode intensities and signs are highly sensitive to the nature of the local electric field and gradient, the orientation of the molecule, and the surface plasmon frequency width. Our findings give some insight into why experimental SEROA, and in particular observing mirror-image SEROA for enantiomers, has been difficult.

First author: Brzhezinskaya, Maria, Electronic structure of hydrogenated carbon nanotubes studied by core level spectroscopy, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 196, 99, (2014)
Abstract: The high-resolution near edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy were used to elucidate the nature of chemical bonding between carbon and hydrogen atoms on the surface and inside hydrogenated single-walled carbon nanotubes (H-SWNTs). The measured spectra showed formation of chemical bonding between the hydrogen and carbon atoms in H-SWNTs. In order to obtain a detailed understanding origin of the chemical bond between C and H atoms, density functional calculations and theoretical analysis of experimental NEXAFS spectra were carried out.

First author: Wang, En-liang, Electron Momentum Spectroscopy of Valence Orbitals of n-Propyl Iodide: Spin-Orbit Coupling Effect and Intramolecular Orbital Interaction, CHINESE JOURNAL OF CHEMICAL PHYSICS, 27, 503, (2014)
Abstract: The binding energy spectrum and electron momentum distributions for the outer valence orbitals of n-propyl iodide molecule have been measured using the electron momentum spectrometer employing non-coplanar asymmetric geometry at impact energy of 2.5 keV plus binding energy. The ionization bands have been assigned in detail via the high accuracy SACCI general-R method calculation and the experimental momentum profiles are compared with the theoretical ones calculated by Hartree-Fock and B3LYP/aug-cc-pVTZ(C,H)6-311G**(I). The spin-orbit coupling effect and intramolecular orbital interaction have been analyzed for the outermost two bands, which are assigned to the iodine 5p lone pairs, using NBO method and non-relativistic as well as relativistic calculations. It is found that both of the interactions will lead to the observed differences in electron momentum distributions. The experimental results agree with the relativistic theoretical momentum profiles, indicating that the spin-orbit coupling effect dominates in n-propyl iodide molecule.

First author: Garino, Claudio, Determination of the electronic and structural configuration of coordination compounds by synchrotron-radiation techniques, COORDINATION CHEMISTRY REVIEWS, 277, 130, (2014)
Abstract: In this review we provide an overview of the potential of synchrotron radiation techniques to understand the structural and electronic properties of coordination compounds. Besides the largely employed multi-wavelength anomalous dispersion (MAD) and X-ray absorption spectroscopy (XAS), in both near (XANES) and post (EXAFS) edge regions, we also discuss the contribution arising from more specialized techniques that have become more widely used in the last years, such as the total scattering approach in the XRPD data analysis and X-ray emission spectroscopy (XES). Comparison with the commonly used laboratory techniques (XRD, UV-vis, luminescence, NMR, EPR) is used to underline the added value of synchrotron radiation techniques when applied to already well characterized samples. The fundamental role of DFT calculations in interpreting both diffraction and spectroscopic data to understand structural and electronic properties of coordination complexes is highlighted. A perspective summary is reported at the end of the manuscript.

First author: Cong, Xing-Shun, Isolation and Identification of 3-Ethyl-8-methyl-2,3-dihydro-1H-cyclopenta[a]chrysene from Shengli Lignite, ENERGY & FUELS, 28, 6694, (2014)
Abstract: In this review we provide an overview of the potential of synchrotron radiation techniques to understand the structural and electronic properties of coordination compounds. Besides the largely employed multi-wavelength anomalous dispersion (MAD) and X-ray absorption spectroscopy (XAS), in both near (XANES) and post (EXAFS) edge regions, we also discuss the contribution arising from more specialized techniques that have become more widely used in the last years, such as the total scattering approach in the XRPD data analysis and X-ray emission spectroscopy (XES). Comparison with the commonly used laboratory techniques (XRD, UV-vis, luminescence, NMR, EPR) is used to underline the added value of synchrotron radiation techniques when applied to already well characterized samples. The fundamental role of DFT calculations in interpreting both diffraction and spectroscopic data to understand structural and electronic properties of coordination complexes is highlighted. A perspective summary is reported at the end of the manuscript.

First author: Xu, Zhenggang, Computational study of the cycloaddition reactivity of the osmium silylyne, INORGANICA CHIMICA ACTA, 422, 40, (2014)
Abstract: The [2+2] cycloaddition reactivity of an osmium silylyne compound 2, [Cp*((Pr3P)-Pr-i)(H)Os=Si(Trip)][HB(C6F5)(3)], with PhC CPh or P (CBu)-Bu-t was studied by density functional theory (DFT) computations. Results indicate that these two reactions are under kinetic control in room temperature and the kinetic products were detected by NMR in experiments. Further tests revealed that the interplay between steric effects and the bonding interactions between two reacting fragments is majorly responsible for the energy differences in different isomers.

First author: Li, Peng, Reaction of Np atom with H2O in the gas phase: reaction mechanisms and ab initio molecular dynamics study, JOURNAL OF MOLECULAR MODELING, 20, 40, (2014)
Abstract: The gas-phase reaction of an Np atom with H2O was investigated using density functional theory and ab initio molecular dynamics. The reaction mechanisms and the corresponding potential energy profiles for different possible spin states were analyzed. Three reaction channels were found in the mechanism study: the isomerization channel, the H-2 elimination channel, and the H atom elimination channel. The latter two were observed in the dynamics simulation. It was found that the branching ratio of the title reaction depends on the initial kinetic energy along the transition vector. Product energy distributions for the reaction were evaluated by performing direct classical trajectory calculations on the lowest sextet potential energy surface. The results indicate that most of the available energy appears as the translational energy of the products. The overall results indicate that the H-2 elimination channel with low kinetic energy is thermodynamically favored but competes with the H atom elimination channel with higher kinetic energy.

First author: Perrin, Mickael L., Large negative differential conductance in single-molecule break junctions, NATURE NANOTECHNOLOGY, 9, 830, (2014)
Abstract: Molecular electronics aims at exploiting the internal structure and electronic orbitals of molecules to construct functional building blocks(1). To date, however, the overwhelming majority of experimentally realized single-molecule junctions can be described as single quantum dots, where transport is mainly determined by the alignment of the molecular orbital levels with respect to the Fermi energies of the electrodes(2) and the electronic coupling with those electrodes(3,4). Particularly appealing exceptions include molecules in which two moieties are twisted with respect to each others(5,6) and molecules in which quantum interference effects are possible(7,8). Here, we report the experimental observation of pronounced negative differential conductance in the current-voltage characteristics of a single molecule in break junctions. The molecule of interest consists of two conjugated arms, connected by a non-conjugated segment, resulting in two coupled sites. A voltage applied across the molecule pulls the energy of the sites apart, suppressing resonant transport through the molecule and causing the current to decrease. A generic theoretical model based on a two-site molecular orbital structure captures the experimental findings well, as confirmed by density functional theory with non-equilibrium Green’s functions calculations that include the effect of the bias. Our results point towards a conductance mechanism mediated by the intrinsic molecular orbitals alignment of the molecule.

First author: Chen, Wei-Chao, Assembly of Keggin-/Dawson-type Polyoxotungstate Clusters with Different Metal Units and SeO32- Heteroanion Templates, CRYSTAL GROWTH & DESIGN, 14, 5099, (2014)
Abstract: Using a pH-dependent synthetic approach, the combination of different simple metal salts or metal coordination complexes with SeO32- heteroanion templates was employed to synthesize five distinct assemblies of Keggin-/Dawson-type tungstoselenites: (C2H8N)(10)KNa[(alpha-SeW9O34){Zr(H2O)}{WO(H2O)}(WO2)(SeO3){alpha-SeW8O3 1Zr(H2O)}]2 center dot 14H(2)O (1) at pH = 1.3; (C2H8N)(10)KNa5[(Se2W18O60)(2)(mu(2)-O)(4)]center dot 12H(2)O (2) at pH = 2.5; (C2H8N)(4)Na-4[Se2W18O62(H2O)(2)]center dot 13H(2)O (3) at pH = 3.6; (C2H8N)(4)K3Na10[(alpha-SeW9O33)(2){Ce-2(CH3COO)(H2O)(3)W3O6}(alpha-Se2W 14O52)]center dot 26H(2)O (4) at pH = 4.5; K10Na5[alpha-SeW9O33)(2){Ce-2(H2O)(4)W3O6}{alpha-Se2W14O51(OH)}]center dot 24H(2)O (5) at pH = 4.5. All five compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric, UV/vis spectroscopy, and ESI-MS. Moreover, their electrochemical properties were investigated. Keggin-type polyoxoanion of 1 remains the first reported Zr-containing tungstoselenites based on {alpha-SeW9} building blocks. X-ray analysis revealed that the 4d metal Zr centers have seven- and eight-coordinated modes, and SeO3 acts as the templates as well as the linkers. With the increasing of the pH, Dawson-type polyoxoanions of 2 and 3 based on the first reported basic lacunary {alpha-Se2W14} building blocks are obtained by using 3d-4f metal coordination complexes. Polyoxoanions of 4 and 5 remain similar structures stabilized by the 4f metal Ce centers at pH = 4.5 and that contain the basic Keggin-type {alpha-SeW9} and Dawson-type {alpha-Se2W14} building blocks in 13 at the same time, presenting the mixed multiple lacunary building blocks being combined into the single polyoxoanion architecture. Furthermore, the density functional theory calculations have been performed on polyoxoanions of 1 and 5 as the representatives to investigate their electronic properties.

First author: da Silva, G. B., Triply differential (e, 2e) studies of phenol, JOURNAL OF CHEMICAL PHYSICS, 141, 5099, (2014)
Abstract: We have measured (e, 2e) triple differential cross sections (TDCS) for the electron-impact ionisation of phenol with coplanar asymmetrical kinematics for an incident electron energy of 250 eV. Experimental measurements of the angular distribution of the slow outgoing electrons at 20 eV are obtained when the incident electron scatters through angles of -5 degrees, -10 degrees, and -15 degrees, respectively. The TDCS data are compared with calculations performed within the molecular 3-body distorted wave model. In this case, a mixed level of agreement, that was dependent on the kinematical condition being probed, was observed between the theoretical and experimental results in the binary peak region. The experimental intensity of the recoil features under all kinematical conditions was relatively small, but was still largely underestimated by the theoretical calculations.

First author: Hu, Zhongwei, Simulation of resonance hyper-Rayleigh scattering of molecules and metal clusters using a time-dependent density functional theory approach, JOURNAL OF CHEMICAL PHYSICS, 141, 5099, (2014)
Abstract: Resonance hyper-Rayleigh scattering (HRS) of molecules and metal clusters have been simulated based on a time-dependent density functional theory approach. The resonance first-order hyperpolarizability (beta) is obtained by implementing damped quadratic response theory using the (2n + 1) rule. To test this implementation, the prototypical dipolar molecule para-nitroaniline (p-NA) and the octupolar molecule crystal violet are used as benchmark systems. Moreover, small silver clusters Ag-8 and Ag-20 are tested with a focus on determining the two-photon resonant enhancement arising from the strong metal transition. Our results show that, on a per atom basis, the small silver clusters possess two-photon enhanced HRS comparable to that of larger nanoparticles. This finding indicates the potential interest of using small metal clusters for designing new nonlinear optical materials.

First author: Liao, Meng-Sheng, Theoretical Comparative Study of Oxygen Adsorption on Neutral and Anionic Ag-n and Au-n Clusters (n=2-25), JOURNAL OF PHYSICAL CHEMISTRY C, 118, 21911, (2014)
Abstract: Using density functional theory, we performed a theoretical comparative study of oxygen adsorption on neutral and anionic Ag-n and Au-n clusters in a large size range of n = 2-25. Ionization potentials (IPs) and electron affinities (EAs) of the pure clusters and the M-n(q)-O-2 binding energies E-bind(M-n(q)-O-2) in the (MnO2)(q) complexes (M = Ag, Au; q = 0, -1) were determined. Three density fiinctionals, namely, BP86, revPBE, and B3LYP, were used in the calculations, among which the BP86 functional gave the best results for IPs and EAs, while B3LYP gave the best results for Ebind(M-n(q)-O-2)” A number of differences between the silver and gold dusters and their reactivities toward O-2 adsorption are accounted for by the calculations. One interesting result is that the calculated Au-n(-)-O-2 binding energies are in good, quantitative agreement with the measured relative reactivities of the Au-n(-) cluster anions toward O-2 adsorption.

First author: Horbatenko, Yevhen, Reaction Mechanisms for the Formation of Mono- And Dipropylene Glycol from the Propylene Oxide Hydrolysis over ZSM-5 Zeolite, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 21952, (2014)
Abstract: Stepwise and concerted mechanisms for the formation of mono- and dipropylene glycol over ZSM-5 zeolite were investigated. For the calculations, a T128 cluster model of zeolite was used with a QM/QM scheme to investigate the reaction mechanism. The active inner part of zeolite was represented by a T8 model and was treated at the DFT (BP86) level, including D3 Grimme dispersion, and the outer part of the zeolite was treated at the DFTB level. The solvent effects were taken into account by including explicitly water molecules in the cavity of the zeolite. The Gibbs energies were calculated for both mechanisms at 70 degrees C. In the case of the stepwise mechanism for the monopropylene glycol formation, the rate-limiting step is the opening of the epoxide ring. The activation energy for this process is 35.5 kcal mol(-1), while in the case of the concerted mechanism the rate-limiting step is the simultaneous ring opening of the epoxide and the attack by a water molecule. This process has an activation energy of 27.4 kcal mol(-1). In the case of the stepwise mechanism of the dipropylene glycol formation, the activation energy for the rate-limiting step is the same as for the monopropylene glycol formation, and in the case of the concerted mechanism, the activation energy for the rate-limiting step is 30.8 kcal mol(-1). In both cases (mono- and dipropylene glycol formation), the concerted mechanism should be dominant over the stepwise one. The barrier for monopropylene glycol formation is lower than that for dipropylene glycol formation. Consequently, our results show that the formation of the monopropylene glycol is faster, although the formation of dipropylene glycol as a byproduct cannot be avoided using this zeolite.

First author: Peric, Marko, DFT investigation of the influence of Jahn-Teller distortion on the aromaticity in square-planar arsenic and antimony clusters, POLYHEDRON, 80, 69, (2014)
Abstract: Density functional theory (DFT) calculations were performed to investigate aromaticity of tetra atomic metalloid clusters, As-4(2-) and Sb-4(2-). The careful analysis of nuclear independent chemical shifts (NICS) revealed strong sigma antiaromatic and week pi aromatic character of investigated species. This unexpected behavior is explained through the analysis of antagonistic paratropic and diatropic contributions, and with detailed adaptive natural density partitioning (AdNDP) analysis. Furthermore, we investigated aromatic/antiaromatic behavior of Jahn-Teller (JT) active species As-4(-) and Sb-4(-). NICS parameters have been scanned along the Intrinsic Distortion Path (IDP) showing strong antiaromaticity which decreases with increasing deviation from D-4h to D-2h symmetry.

First author: Chong, Daesung, One-Electron Oxidation of ReCp(CO)(2)L (L = PPh3, eta(2)-2-Butene, eta-Diphenylacetylene): Electrochemical, Spectroscopic, and Computational Studies of the Electronic Properties and Dimerization Tendencies of 17-Electron Rhenium Complexes, ORGANOMETALLICS, 33, 4706, (2014)
Abstract: Electrochemical oxidation of ReCp(CO)(2)L (Cp = eta(5)-C5H5; L = PPh3 (2), eta(2)-2-C2Me2H2 (3), eta-C2Ph2 (4)) has been studied in CH2Cl2/[NBu4][B(C6F5)(4)]. All three complexes undergo quasi-Nernstian one-electron oxidations with E-1/2 values (vs ferrocene) of 0.49 V (2/2(+)), 0.45 V (3/3(+)), and 0.15 V (4/4(+)). A second reversible one-electron oxidation is observed for 4 at 0.97 V. The radical cation 2(+) efficiently forms the Re Re-bonded dimer dication 2(2)(2+), which was isolated after chemical oxidation of 2 by [thianthrene][B(C6F5)(4)]. The 17-electron complex 3(+) shows no tendency to dimerize. On the basis of the E-1/2 value of 3 and expected potential shifts when replacing a methyl group by a hydrogen, a ligand electronic parameter, E-L, of 0.38 was calculated for pi-bonded ethylene, which is much lower than the existing literature value of 0.76. IR, ESR, and UV-vis spectra were recorded for 4(+). DFT calculations were performed on the neutral complexes, the monocations 2, 3(+), and 4(+), and the dimer dication 2(2)(2+). The SOMO of 2(+) is similar to that of the parent piano-stool complex [ReCp(CO)(3)](+) (1(+)) in being metal-based (55%) and directionally disposed to formation of a metal metal bond with another radical cation. A Re Re bond distance of 3.315 angstrom was calculated for the resulting dimer 2(2)(2+). Although the SOMO of 3(+) is also predominantly (60%) metal-based, the orbital lacks the geometry necessary to form a metal metal-bonded dimer. The HOMO of 4 is highly delocalized, having only about one-third metal character and two-thirds coming from the Cp and diphenylactylene ligands. One-electron oxidation of 4 brings about a significant change in electronic structure, with the SOMO of 4(+) seeing increased contributions from diphenylacetylene and the two carbonyls (14%), along with a decreased metal contribution (27%). The diphenylacetylene contributions are large enough to justify pi-C2Ph2 being designated as a “non-innocent” ligand in this system.

First author: Bubrin, Martina, Structure and Spectroelectrochennical Response of Arene-Ruthenium and Arene-Osmium Complexes with Potentially Hemilabile Noninnocent Ligands, ORGANOMETALLICS, 33, 4973, (2014)
Abstract: Nine of the compounds [M(L2-)(p-cymene)] (M = Ru, Os, L2- = 4,6-di-tert-butyl-N-aryl-o-amidophenolate) were prepared and structurally characterized (Ru complexes) as coordinatively unsaturated, formally 16 valence electron species. On L2–ligand based oxidation to EPR-active itninosemiquinone radical complexes, the compounds seek to bind a donor atom (if available) from the N-aryl substituent, as structurally certified for thioether and selenoether functions, or from the donor solvent. Simulated cyclic voltammograms and spectroelectrochemistry at ambient and low temperatures in combination with DFT results confirm a square scheme behavior (ECEC mechanism) involving the L-n ligand ligand. as the main electron transfer site and the metal with fractional (delta) oxidation as the center for redox-activated coordination. Attempts to crystallize [Ru(Cym)(Q(SMe))](PF6) produced single crystals of [Ru-III(Q(SMe)(center dot-))(2)](PF6) after apparent dissociation of the arene ligand.

First author: In-noi, Orrasa, Electrochemical, Spectroscopic, and Computational Study of Bis(mu-methylthiolato)diironhexacarbonyl: Homoassociative Stabilization of the Dianion and a Chemically Reversible Reduction/Reoxidation Cycle, ORGANOMETALLICS, 33, 5009, (2014)
Abstract: The redox characteristics of (mu-SMe)(2)Fe-2(CO)(6) from the 1+ to 2- charge states are reported. This [2Fe-2S] compound is related to the active sites of [FeFe]-hydrogenases but notably without a linker between the sulfur atoms. The 1+ charge state was studied both by ionization in the gas phase by photoelectron spectroscopy and by oxidation in the solution phase by cyclic voltammetry. The adiabatic ionization is to a cation whose structure features a semibridging carbonyl, similar to the structure of the active site of [FeFe]-hydrogenases in the same oxidation state. The reduction of the compound by cyclic voltammetry gives an electrochemically irreversible cathodic peak, which often suggests disproportionation or other irreversible chemical processes in this class of molecules. However, the return scan through electrochemically irreversible oxidation peaks that occur at potentials around 1 V more positive than the reduction led to the recovery of the initial neutral compound. The dependence of the CVs on scan rate, IR spectroelectrochemistry of reduction and oxidation cycles, chronocoulometry, and DFT computations indicate a mechanism in which stabilization of the dianion plays a key role. Initial one-electron reduction of the compound is accompanied in the same cathodic peak with a second slower electron reduction to the dianion. Geometric reorganization and solvation stabilize the [2Fe-2S](2-) dianion such that the potential for addition of the second electron is slightly less negative than that of the first (potential inversion). The return oxidation peaks at more positive potentials follow from rapid pairing of the dianion with another neutral molecule in solution (termed homoassociation) to form a stabilized [4Fe-4S](2-) dianion. Two one-electron oxidations of this [4Fe-4S](2-) dianion result in regeneration of the initial neutral compound. The implications of this homoassociation for the [FeFe]-hydrogenase enzyme, in which the H-cluster active site features a [2Fe-2S] site associated with a [4Fe-4S] cubane cluster via a thiolate bridge, are discussed.

First author: Bruna, Sonia, New insights into the chemistry of di- and trimetallic iron dithiolene derivatives. Structural, Mossbauer, magnetic, electrochemical and theoretical studies, DALTON TRANSACTIONS, 43, 13187, (2014)
Abstract: Reaction of Fe-3(CO)(12) with 1,2-dithiolene HSC6H2Cl2SH affords a mixture of complexes [Fe-2(CO)(6)(mu-SC6H2Cl2S)] 1, [Fe-2(SC6H2Cl2S)(4)] 2 and [Fe-3(CO)(7)(mu(3)-SC6H2Cl2S)(2)] 3. In the course of the reaction the trimetallic cluster 3 is first formed and then converted into the known dinuclear compound 1 to afford finally the neutral diiron tetrakis(dithiolato) derivative 2. Compounds 2 and 3 have been studied by Mossbauer spectroscopy, X-ray crystallography and theoretical calculations. In compound 2 the metal atoms are in an intermediate-spin Fe-III state (S-Fe = 3/2) and each metal is bonded to a bridging dithiolene ligand and a non-bridging thienyl radical (S = 1/2). Magnetic measurements show a strong antiferro-magnetic coupling in complex 2. Cyclic voltammetry experiments show that the mixed valence trinuclear cluster 3 undergoes a fully reversible one electron reduction. Additionally, compound 3 behaves as an electrocatalyst in the reduction process of protons to hydrogen.

First author: Painter, Phillip P., Facilitating the Cope Rearrangement by Partial Protonation: Implications for Synthesis and Biosynthesis, ORGANIC LETTERS, 16, 4818, (2014)
Abstract: The theoretical investigation of concerted and stepwise Cope rearrangements of natural products led to the prediction that some concerted Cope rearrangements can be promoted by noncovalent association of their transition state structures with ammonium cations.

First author: Gutierrez-Gonzalez, Israel, Structural and electronic properties of the P3HT-PCBM dimer: A theoretical Study, CHEMICAL PHYSICS LETTERS, 612, 234, (2014)
Abstract: A density functional theory (DFT) study of the supramolecular dimer formed by a 8-unit oligomer of the poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) is presented. A dispersion-corrected exchange-correlation potential was used to afford for the long-range van der Waals interactions. Our calculations predict two stable isomers in which the P3HT 8-mer forms a U-shaped structure surrounding the PCBM. From time-dependent DFT calculations it was determined that the maximum absorption intensity of the P3HT-PCBM dimer undergoes a blue-shift of about 80nm with respect to the isolated P3HT oligomer in qualitative agreement with the experimental facts.

First author: Popov, Ivan A., Complexes between Planar Boron Clusters and Transition Metals: A Photoelectron Spectroscopy and Ab Initio Study of CoB12- and RhB12-, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 8098, (2014)
Abstract: Small boron clusters are known to be planar, and may be used as ligands to form novel coordination complexes with transition metals. Here we report a combined photoelectron spectroscopy and ab initio study of CoB12- and RhB12-. Photoelectron spectra of the two doped-B-12 dusters show similar spectral patterns, suggesting they have similar structures. Global minimum searches reveal that both CoB12- and RhB12- possess half-sandwich-type structures with the quasi-planar B-12 moiety coordinating to the metal atom. The B-12 ligand is found to have similar structure as the bare B-12 cluster with C-3v symmetry. Structures with Co or Rh inserted into the quasi-planar boron framework are found to be much higher in energy. Chemical bonding analyses of the two B-12 half sandwiches reveal two sets of sigma bonds on the boron unit: nine classical two-center two-electron (2c-2e) sigma bonds on the periphery of the B-12 unit and four 3c-2e sigma bonds within the boron unit. Both sigma and pi bonds are found between the metal and the B-12 ligand: three M-B single sigma bonds and one delocalized 4c-2e pi bond. The exposed metal sites in these complexes can be further coordinated by other ligands or become reaction centers as model catalysts.

First author: Lee, Choongkeun, Theoretical Investigation of Water Oxidation Processes on Small MnxTi2-xO4 (x=0-2) Complexes, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 8204, (2014)
Abstract: Understanding the water oxidation process on small metal oxide complexes is fundamental for developing photocatalysts for solar fuel production. Titanium oxide and manganese oxide complexes have high potential as components of a cheap, nontoxic, and stable photocatalyst. In this theoretical work, the water oxidation process on MnxTi2-xO4 (x = 0-2) dusters is investigated at the BP86 level of theory using two water molecules and fully saturated systems. In the oxidation cycle using two water molecules, Mn reduces the reaction energy; however, Mn does not reduce the reaction energy on the fully saturated system. When two water molecules are used, the highest reaction energy in the water oxidation cycle is lower than 3 eV, but the highest reaction energy is higher than 3 eV on fully saturated systems except for the pure titanium oxide complex which has a highest reaction energy of 2.56 eV. Dehydrogenation processes in the water oxidation cycle require higher energy than the O-O formation or water adsorption processes. The overall dehydrogenation energy is usually smaller on complexes including at least one Mn atom and it is smallest on the Mn2O4 complex that has two water molecules. Considering the highest reaction energy in the overall water oxidation cycle, water oxidation at the manganese atom of MnTiO4 hydrated with two water molecules is the most favorable in energy.

First author: Biltek, Scott R., Isolation and Structural Characterization of a Silver-Platinum Nanocluster, Ag4Pt2(DMSA)(4),JOURNAL OF PHYSICAL CHEMISTRY A, 118, 8314, (2014)
Abstract: We report the synthesis, isolation, and characterization of the ligand-protected bimetallic cluster, Ag4Pt2(DMSA)(4) (DMSA = meso-2,3,-dimercaptosuccinic acid). The procedure is similar to the one employed for the synthesis of Ag4Ni2(DMSA)(4). Theoretical studies suggest that the Pt and Ni atoms have square planar configurations. Because the crystal field splitting of 5d orbitals is typically larger than that for 3d orbitals, the Pt-based cluster has an optical spectrum that is significantly blue-shifted as compared to the Ni-based cluster.

First author: Smith, Jordan C., Boron Substitution in Aluminum Cluster Anions: Magic Clusters and Reactivity with Oxygen, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 8485, (2014)
Abstract: We have studied the size-selective reactivity of AlnBm- clusters in = 1,2 with O-2 to investigate the effect of congener substitution in energetic aluminum clusters. Mixed-metal clusters offer an additional strategy for tuning the electronic and geometric structure of clusters and by substituting an atom with a congener; we may investigate the effect of structural changes in clusters with similar electronic structures. Using a fast-flow tube mass spectrometer, we formed aluminum boride cluster anions and exposed them to molecular oxygen. We found multiple stable species with Al12B- and Al11B2- being highly resistant to reactivity with oxygen. These clusters behave in a similar manner as Al-13(-), which has previously been found to be stable in oxygen because of its icosahedral geometry and its filled electronic shell. Al-13(-) and Al12B- have icosahedral structures, while Al11B2- forms a 1 distorted icosahedron. All three of these clusters have filled electronic shells, and Al12B- has a larger HOMO-LUMO gap due to its compact geometry. Other cluster sizes are investigated, and the structures of the AlnB- series are found to have endohedrally doped B atoms, as do many of the AlnB2- clusters. The primary etching products are found to be a loss of two Al2O molecules, with boron likely to remain in the cluster.

First author: Boubnov, Alexey, Selective Catalytic Reduction of NO Over Fe-ZSM-5: Mechanistic Insights by Operando HERFD-XANES and Valence-to-Core X-ray Emission Spectroscopy, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 13006, (2014)
Abstract: An in-depth understanding of the active site requires advanced operand techniques and the preparation of defined catalysts. We elucidate here the mechanism of the selective catalytic reduction of NO by NH3 (NH3-SCR) over a Fe-ZSM-5 zeolite catalyst. 1.3 wt % Fe-ZSM-5 with low nuclearity Fe sites was synthesized, tested in the SCR reaction and characterized by UV-vis, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy. Next, this defined Fe-zeolite catalyst was studied by complementary high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and valence-to-core X-ray emission spectroscopy (V2C XES) under different model in situ and realistic working (operando) conditions identical to the catalyst test bench including the presence of water vapor. HERFD-XANES uncovered that the coordination (between 4 and 5), geometry (tetrahedral, partly 5-fold), and oxidation state of the Fe centers (reduced in NH3, partly in SCR mixture, slight reduction in NO) strongly changed. V2C XES supported by DFT calculations provided important insight into the chemical nature of the species adsorbed on Fe sites. The unique combination of techniques applied under realistic reaction conditions and the corresponding catalytic data unraveled the adsorption of ammonia via oxygen on the iron site. The derived reaction model supports a mechanism where adsorbed NO reacts with ammonia coordinated to the Fe3+ site yielding Fe2+ whose reoxidation is slow.

First author: Wu, Qun-Yan, Theoretical Investigation on Multiple Bonds in Terminal Actinide Nitride Complexes,INORGANIC CHEMISTRY, 53, 9607, (2014)
Abstract: A series of actinide (An) species of L-An-N compounds [An = Pa-Pu, L = [N(CH2CH2NSiPr3i)(3)](3-), Pr-i = CH(CH3)(2)] have been investigated using scalar relativistic density functional theory (DFT) without considering spin-orbit coupling effects. The ground state geometric and electronic structures and natural bond orbital (NBO) analysis of actinide compounds were studied systematically in neutral and anionic forms. It was found that with increasing actinide atomic number, the bond length of terminal multiple An-N1 bond decreases, in accordance with the actinide contraction. The Mayer bond order of An-N1 decreases gradually from An = Pa to Pu, which indicates a decrease in bond strength. The terminal multiple bond for L-An-N compounds contains one sigma and two pi molecular orbitals, and the contributions of the 6d orbital to covalency are larger in magnitude than the 5f orbital based on NBO analysis and topological analysis of electron density. This work may help in understanding of the bonding nature of An-N multiple bonds and elucidating the trends and electronic structure changes across the actinide series. It can also shed light on the construction of novel An-N multiple bonds.

First author: Ciancaleoni, Gianluca, When the Tolman Electronic Parameter Fails: A Comparative DFT and Charge Displacement Study of [(L)Ni(CO)(3)](0/-) and [(L)Au(CO)(0/+), INORGANIC CHEMISTRY, 53, 9907, (2014)
Abstract: In this study we have examined 42 [(L)M(CO)(n)](+/-/0) complexes (M = Ni and Au), including neutral ligands, such as phosphines and carbenes, and anionic ones. For each complex, the carbonyl stretching frequency (nu(CO)) and the amount of charge donated from the ligand to the metal (CT) have been computed on the basis of DFT calculations. For nickel complexes, the two observables nicely correlate with each other, as expected from the theory underlying the Tolman electronic parameter. On the contrary, for gold complexes a more complex pattern can be observed, with an apparent differentiation between phosphine ligands and carbon-based ones. Such differences have been explained analyzing the AuL bond in terms of Dewar-Chatt-Duncanson bonding constituents (sigma donation and pi back-donation). Our analysis demonstrates that in linear gold(I) complexes, nu(CO) depends only on the metal-to-ligand pi back-donation.

First author: Jahangir, Sajid, Absolute configuration of 1,5-diazepin-2-ones: A critical test case for density functional theory, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1044, 15, (2014)
Abstract: The absolute configuration of a series of 4(R)-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-ones is assigned by comparison of experimental and calculated CD spectra using time-dependent density functional theory (TDDFT) in combination with four different functionals (B3PW91, CAM-B3LYP, M06-2X, BMK). Closest agreement with experiment is obtained with B3PW91. All compounds except those bearing an acyl group at N5 exist in two nearly isoenergetic conformations of the seven-membered ring (G <= 0.5 kcal mol(-1) with the local pair natural orbital coupled-electron pair approximation LPNO-CEPA/1/def2-TZVPP//B3LYP/6-311G(d,p)). Agreement between simulated and experimental CD spectra was found to critically depend on a proper description of conformer population as well as the position of the calculated longest-wavelength transitions of the individual conformers.

First author: Tefera, Anteneh G., Optimal packing size of non-ligated CdSe nanoclusters for microstructure synthesis,JOURNAL OF APPLIED PHYSICS, 116, 15, (2014)
Abstract: Structural and electrostatic properties of nanoclusters of CdSe of diameter 1-2 nm are studied with first principle calculations to determine the optimal size for synthesizing microstructures. Based on robustness of the core structure, i.e., the retention of tetrahedral geometry, hexagonal ring structure, and overall wurtzite structure to surface relaxations, we conclude that nanoclusters of similar to 2 nm diameter are the best candidates to form a dense microstructure with minimal interstitial space. Se-terminated surfaces retain a zigzag structure as Se atoms are pulled out and Cd atoms are pulled in due to relaxation, therefore, are best suited for inter-nanocluster formations.

First author: Mahmoodinia, Mehdi, Structural and electronic properties of the Pt-n-PAH complex (n=1, 2) from density functional calculations, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 18586, (2014)
Abstract: A detailed density functional study of the Pt atom and the Pt dimer adsorption on a polyaromatic hydrocarbon (PAH) is presented. The preferred adsorption site for a Pt atom is confirmed to be the bridge site. Upon adsorption of a single Pt atom, however, it is found here that the electronic ground state changes from the triplet state (5d(9)6s(1) configuration) to the closed-shell singlet state (5d(10)6s(0) configuration), which consequently will affect the catalytic activity of Pt when single Pt atoms bind to a carbon surface. The preferred adsorption site for the Pt dimer in the upright configuration is the hollow site. In contrast to the adsorption of a single Pt atom, the formation of a Pt-C bond in the adsorption of a Pt dimer is not accompanied by a change in the spin state, so the most stable electronic state is still the triplet state. While the atomic charge on the Pt atoms and dimers (in parallel configuration) in the Pt-n-PAH complex is positive, a negative charge is found on the upper Pt atom for the upright configuration, indicating that single layers of Pt atoms will have a different catalytic activity as compared to Pt clusters on a carbon surface. Comparing the Pt C bond length and the charge transfer on different sites, the magnitude of the charge transfer decreases with bond elongation, indicating that the catalytic activity of the Pt atom and dimer can be changed by modifying its chemical surroundings. The adsorption energy for the Pt dimer on a PAH surface is larger than that for two individual Pt atoms on the surface indicating that aggregation of Pt atoms on the PAH surface is favorable.

First author: Catalano, Jaclyn, Pb-207 and Sn-119 Solid-State NMR and Relativistic Density Functional Theory Studies of the Historic Pigment Lead-Tin Yellow Type I and Its Reactivity in Oil Paintings, JOURNAL OF PHYSICAL CHEMISTRY A,118, 7952, (2014)
Abstract: Lead soaps (lead carboxylates) have been detected in traditional oil paintings in layers containing the pigment leadtin yellow type I (LTY-I). LTY-I has been used by artists from at least the second quarter of the 15th century until the first half of the 18th century. Soap formation can lead to protrusions in paint layers and increased transparency, causing the paint support to become visible. We have characterized LTY-I by Sn-119 and Pb-207 solid-state NMR (ssNMR) spectroscopy. Using a combination of NMR techniques and DFT molecular cluster calculations, we identify the individual species in LTY-I and determine their Sn-119 and Pb-207 chemical-shift tensors. The presence of starting materials from the synthesis, minium, and tin(IV) oxide was also verified. Knowledge of the chemical-shift tensor components and the impurities in LTY-I is important for examining the chemistry of degradation processes and soap formation. We demonstrate that ssNMR can be used to detect reaction between Pb2SnO4 and added palmitic acid in a model paint sample containing LTY-I.

First author: Le, Hung M., Nanostructures of C-60-Metal-Graphene (Metal = Ti, Cr, Mn, Fe, or Ni): A Spin-Polarized Density Functional Theory Study, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 21057, (2014)
Abstract: We used plane-wave density functional theory (DFT) to investigate the properties of C-60-Mgraphene (C-60-MG) nanostructures (M = Ti, Cr, Mn, Fe, or Ni). The calculated binding energies suggested that C-60 could be mounted on a metalgraphene surface with good bonding stability. The high-spin C-60-Cr-G nanostructure was found to be more stable than the previously reported low-spin configuration. Also, C-60-Ti was found to stand symmetrically upright on the graphene surface, while in the remaining four cases, the orientation of C-60-M in the C-60-M-G nanostructures were bent, and the geometry of each structure is somewhat different, depending on the identity of the bridging metal atom. The large geometric distortion of C-60-M in the tilted C-60-M-G nanostructures (with Cr, Fe, Mn, and Ni) is attributed to the spin polarization in the 3d orbitals and dispersion interactions between graphene and C-(60). Additional DFT calculations on smaller C-M-60-benzene complexes with atomic-orbital (AO) basis sets provided consistent results on structural geometry and numbers of unpaired electrons. The DFT calculations using AO basis sets suggested that the C-60-M unit was flexible with respect to the bending motion. The knowledge of metal-dependent geometric differences derived in this study may be useful in designing nanostructures for spintronic and electronic applications.

First author: Calandrini, Vania, Structural Biology of Cisplatin Complexes with Cellular Targets: The Adduct with Human Copper Chaperone Atox1 in Aqueous Solution, CHEMISTRY-A EUROPEAN JOURNAL, 20, 11719, (2014)
Abstract: Cisplatin is one of the most used anticancer drugs. Its cellular influx and delivery to target DNA may involve the copper chaperone Atox1 protein. Although the mode of binding is established by NMR spectroscopy measurements in solution-the Pt atom binds to Cys12 and Cys15 while retaining the two ammine groups-the structural determinants of the adduct are not known. Here a structural model by hybrid Car-Parrinello density functional theory-based QM/MM simulations is provided. The platinated site minimally modifies the fold of the protein. The calculated NMR and CD spectral properties are fully consistent with the experimental data. Our in silico/in vitro approach provides, together with previous studies, an unprecedented view into the structural biology of cisplatin-protein adducts.

First author: Dolega, Anna, Synthesis and characterization of mononuclear Zn(II), Co(II) and Ni(II) complexes containing a sterically demanding silanethiolate ligand derived from tris(2,6-diisopropylphenoxy)silanethiol, DALTON TRANSACTIONS,43, 12766, (2014)
Abstract: Four heteroleptic complexes of nickel(II), cobalt(II) and zinc(II), containing a monodentate silanethiolate ligand derived from tris(2,6-diisopropylphenoxy)silanethiol (TDST), were prepared and characterized. Nickel(II) and cobalt(II) complexes of the formula M(NH3)(2)(TDST)(2) (M = Ni(II) complex 1, M = Co(II) complex 2) were obtained from the respective chlorides. Zinc complexes of the general formula Zn(acac)(TDST)(L), where L = EtOH (complex 3) or H2O (complex 4), were obtained from zinc acetylacetonate. A single-crystal X-ray structural analysis revealed that all crystalline products are solvent adducts. The geometries of ligands in the complexes are typical: distorted tetrahedral in zinc and cobalt(II) complexes and square planar in nickel(II) compounds. Magnetic studies performed for Ni(II) and Co(II) compounds confirmed the diamagnetic character of the first complex and high-spin paramagnetic configuration of the latter. Nickel(II) and cobalt(II) complexes were additionally characterized by UV-Vis and IR spectroscopy. IR bands for ligands in the complexes were assigned with the help of the DFT vibrational frequency calculations.

First author: Fernandez Villanueva, Estefania, On the existence and characteristics of pi-beryllium bonds, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 17531, (2014)
Abstract: The existence of pi-beryllium bonds explains the stability of the complexes between ethylene and acetylene and BeX2 (X = H, F, and Cl) derivatives. These linkers involve a significant charge transfer from the pi(CC) bonding orbitals into the empty p orbitals of Be and to a much smaller degree into the sigma(star)(BeH) antibonding orbitals. The significant deformation of the BeX2 moiety and the slight deformation of the unsaturated hydrocarbon result in distortion energies as high as the dissociation energy of the complex. The pi-beryllium bonds are about four times stronger than conventional pi-hydrogen bonds and even stronger than the strongest pi-hydrogen bond reported to date in the literature. The topology of their electron density is characterized as being very flat in the bonding region between the pi-system and Be, which leads to topologically unstable structures close to catastrophe points. Among the functionals considered in our study M06 is the one that leads to values in better agreement with CCSDM/aug-cc-pVTZ calculations used as a reference. B3LYP underestimates some interactions, whereas M06-2X overestimates all of them. MP2 also yields good agreement with the CCSD(T) method.

First author: Vosmeer, C. Ruben, A comparison between QM/MM and QM/QM based fitting of condensed-phase atomic polarizabilities, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 17857, (2014)
Abstract: Recently we reported a combined QM/MM approach to estimate condensed-phase values of atomic potarizabilities for use in (bio)motecular simulation. The setup relies on a MM treatment of the solvent when determining atomic polarizabilities to describe the response of a QM described solute to its external electric field. In this work, we study the effect of using alternative descriptions of the solvent molecules when evaluating atomic polarizabilities of a methanol solute. In a first step, we show that solute polarizabilities are not significantly affected upon substantially increasing the MM dipole moments towards values that are typically reported in literature for water solvent molecules. Subsequently, solute polarization is evaluated in the presence of a QM described solvent (using the frozen-density embedding method). In the latter case, lower oxygen polarizabilities were obtained than when using MM point charges to describe the solvent, due to introduction of Pauli-repulsion effects.

First author: Zhu, Bo, Bonding interactions between sulfur dioxide (SO2) and mono-ruthenium(ii)-substituted Keggin-type polyoxometalates: electronic structures of ruthenium-SO2 adducts, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 18017, (2014)
Abstract: Density functional theory (DFT) calculations and natural bond orbital (NBO) analysis were carried out to investigate the electronic structures and bonding features between the ruthenium(ii) atom and the SO2 molecule in two ruthenium-sulfur dioxide (SO2) adducts, trans-Ru(NH3)(4)(SO2)Cl+ and l{SiW11O39}Ru-II(SO2)(6-). In addition, the bonding interactions between SO2 and the metal-ruthenium fragment were determined by binding energy (Delta E-abs) calculation and electronic structures. The results indicate that the eta(1)-S-planar model in both trans-Ru(NH3)(4)(SO2)Cl+ and E{SiW11O39}Ru-II(SO2)(6-) are more favorable. NBO analysis of the bonding interaction between ruthenium and sulfur centers in the [{SiW11O39}Ru-II(SO2)](6-) complex shows that it possesses a sigma and a pi bond. It predicts that the polyoxometalate [SiW11O39Ru](6-) can serve as a potential adsorbent for the SO2 molecule because of the strong Ru-S bond relative to Ru(NH3)(4)Cl+.

First author: Cheng, Lan, Analytic Energy Derivatives in Relativistic Quantum Chemistry, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 114, 1108, (2014)
Abstract: In this review, we discuss the current status of analytic derivative theory in relativistic quantum chemistry. A brief overview of the basic theory for the available relativistic quantum chemical methods as well as the state-of-the-art development of their analytic energy derivatives is given. Among the various relativistic quantum chemical methods, cost-effective approaches based on spin separation and/or on the matrix representation of two-component theory have been proven particularly promising for the accurate and efficient treatment of relativistic effects in electron correlation calculations. We highlight analytic derivative techniques for these cost-effective relativistic quantum chemical approaches including direct perturbation theory, the spin-free Dirac-Coulomb approach, and the exact two-component theory in its one-electron variant. An outlook is given on future developments of analytic energy derivative techniques for relativistic quantum chemical methods, again with an emphasis on cost-effective schemes.

First author: Cordova-Mateo, Esther, Electroactive polymers for the detection of morphine, JOURNAL OF POLYMER RESEARCH, 21, 1108, (2014)
Abstract: The interaction between morphine (MO), a very potent analgesic psychoactive drug, and five electroactive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-methylthiophene) (P3MT), polypyrrole (PPy), poly(N-methylpyrrole (PNMPy) and poly[N-(2-cyanoethyl)pyrrole] (PNCPy), has been examined using theoretical calculations on model complexes and voltammetric measures considering different pHs and incubation times. Quantum mechanical calculations in model polymers predict that the strength of the binding between the different polymers and morphine increases as follows: PEDOT < PNMPy < Py < < P3MT a parts per thousand PNCPy. The most relevant characteristic of P3MT is its ability to interact with morphine exclusively through non-directional interactions. On the other hand, the variations of the electroactivity and the anodic current at the reversal potential evidence that the voltammetric response towards the presence of MO is considerably higher for P3MT and PNCPy than that for the other polymers at both acid (P3MT > PNMPy) and neutral (P3MT a parts per thousand PNCPy) pHs. Energy decomposition analyses of the interaction of MO with different model polymers indicate that the stronger affinity of MO for P3MT and PNCPy as compared to PEDOT, PNMPy, and PPy is due to more favorable orbital interactions. These more stabilizing orbital interactions are the result of the larger charge transfer from MO to P3MT and PNCPy model polymers that takes place because of the higher stability of the single occupied molecular orbital (SOMO) of these model polymers. Therefore, to design polymers with a large capacity to detect MO we suggest looking at polymers with high electron affinity.

First author: Dannenhoffer, Adam, Dimerization of cobalt-substituted Keggin phosphotungstate, [PW11O39Co(X)](5-), in nonpolar solvents, JOURNAL OF COORDINATION CHEMISTRY, 67, 2830, (2014)
Abstract: The tetraheptylammonium (THA) salt of cobalt-substituted polyoxotungstate with Keggin-like structure, (THA)(5)[PW11O39CoII(X)], was investigated by P-31 NMR and UV/VIS spectroscopies in toluene. A solution obtained after transferring PW11Co from aqueous solution into toluene, using THABr as a transfer agent, and rigorous drying, gives multiple peaks in the P-31 NMR spectrum. The spectrum in dry toluene significantly simplifies, after extracting a hexane solution several times with water, which removes simple inorganic ions. However, even the dry toluene solution after purification has P-31 NMR and UV/VIS spectra which cannot be explained using the known equilibrium between (THA)(5)[PW11O39Co(H2O)] and (THA)(5)[PW11O39Co(__)]. Both (PNMR)-P-31 and UV/VIS spectroscopies indicate the existence of dimers in dry toluene solutions, (THA)(10)[(PW11O39Co)(2)]. Pure (THA)(5)[PW11O39Co(_)] with five-coordinate cobalt can, however, be obtained in dry toluene in the presence of excess inert salt (high ionic strength conditions). Quantum mechanical/molecular mechanical calculations also support dimer formation in toluene.

First author: Migal, Yu. F., Interaction of silicate additives and iron surface, JOURNAL OF FRICTION AND WEAR, 35, 414, (2014)
Abstract: A quantum-chemical analysis of the interaction of the basic structural element of silicates (silicate group SiO4) and iron surface has been carried out. The cluster model and slab model were used. The adhesion energy and influence of the silicate group on the local atomic structure of a surface was estimated. It has been shown that a strong covalent bond is formed between this group and the surface, which occurs upon the adsorption of the group. Intensive force action causes the destruction of an adsorptive complex accompanied by tearing out the Fe atoms.

First author: Nicu, Valentin Paul, On the Complementarity of ECD and VCD Techniques, CHIRALITY, 26, 525, (2014)
Abstract: An unprecedented complementarity of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectroscopic techniques is demonstrated by showing that each technique reveals the structure of a different molecular segment. Using a flexible molecule of biological significance we show that the synergetic use of ECD and VCD yields more complete structural characterization as it provides improved and more reliable conformer resolution.

First author: Wolters, Lando P., New Concepts for Designing d(10)-M(L)(n) Catalysts: d Regime, s Regime and Intrinsic Bite-Angle Flexibility, CHEMISTRY-A EUROPEAN JOURNAL, 20, 11370, (2014)
Abstract: Our aim is to understand the electronic and steric factors that determine the activity and selectivity of transition-metal catalysts for cross-coupling reactions. To this end, we have used the activation strain model to quantum-chemically analyze the activity of catalyst complexes d(10)-M(L)(n) toward methane C-H oxidative addition. We studied the effect of varying the metal center M along the nine d(10) metal centers of Groups 9, 10, and 11 (M=Co-, Rh-, Ir-, Ni, Pd, Pt, Cu+, Ag+, Au+), and, for completeness, included variation from uncoordinated to mono-to bisligated systems (n=0, 1, 2), for the ligands L=NH3, PH3, and CO. Three concepts emerge from our activation strain analyses: 1) bite-angle flexibility, 2) d-regime catalysts, and 3) s-regime catalysts. These concepts reveal new ways of tuning a catalyst’s activity. Interestingly, the flexibility of a catalyst complex, that is, its ability to adopt a bent L-M-L geometry, is shown to be decisive for its activity, not the bite angle as such. Furthermore, the effect of ligands on the catalyst’s activity is totally different, sometimes even opposite, depending on the electronic regime (d or s) of the d(10)-M(L)(n) complex. Our findings therefore constitute new tools for a more rational design of catalysts.

First author: de Silva, Piotr, Simultaneous Visualization of Covalent and Noncovalent Interactions Using Regions of Density Overlap, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 3745, (2014)
Abstract: We introduce a density-dependent bonding descriptor that enables simultaneous visualization of both covalent and noncovalent interactions. The proposed quantity is tailored to reveal the regions of space, where the total electron density results from a strong overlap of shell, atomic, or molecular densities. We show that this approach is successful in describing a variety of bonding patterns as well as nonbonding contacts. The Density Overlap Regions Indicator (DORI) analysis is also exploited to visualize and quantify the concept of electronic compactness in supramolecular chemistry. In particular, the scalar field is used to compare the compactness in molecular crystals, with a special emphasis on quaterthiophene derivatives with enhanced charge mobilities.

First author: Rampino, Sergio, Full Parallel Implementation of an All-Electron Four-Component Dirac Kohn Sham Program, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 3766, (2014)
Abstract: A full distributed-memory implementation of the DiracKohnSham (DKS) module of the program BERTHA (Belpassi et al., Phys. Chem. Chem. Phys. 2011, 13, 12368-12394) is presented, where the self-consistent field (SCF) procedure is replicated on all the parallel processes, each process working on subsets of the global matrices. The key feature of the implementation is an efficient procedure for switching between two matrix distribution schemes, one (integral-driven) optimal for the parallel computation of the matrix elements and another (block-cyclic) optimal for the parallel linear algebra operations. This approach, making both CPU-time and memory scalable with the number of processors used, virtually overcomes at once both time and memory barriers associated with DKS calculations. Performance, portability, and numerical stability of the code are illustrated on the basis of test calculations on three gold clusters of increasing size, an organometallic compound, and a perovskite model. The calculations are performed on a Beowulf and a BlueGene/Q system.

First author: Blachly, Patrick G., Use of Broken-Symmetry Density Functional Theory To Characterize the IspH Oxidized State: Implications for IspH Mechanism and Inhibition, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 3871, (2014)
Abstract: With current therapies becoming less efficacious due to increased drug resistance, new inhibitors of both bacterial and malarial targets are desperately needed. The recently discovered methylerythritol phosphate (MEP) pathway for isoprenoid synthesis provides novel targets for the development of such drugs. Particular attention has focused on the IspH protein, the final enzyme in the MEP pathway, which uses its [4Fe-4S] cluster to catalyze the formation of the isoprenoid precursors IPP and DMAPP from HMBPP. IspH catalysis is achieved via a 2e (-)/2H(+) reductive dehydroxylation of HMBPP; the mechanism by which catalysis is achieved, however, is highly controversial. The work presented herein provides the first step in assessing different routes to catalysis by using computational methods. By performing broken-symmetry density functional theory (BS-DFT) calculations that employ both the conductor-like screening solvation model (DFT/COSMO) and a finite-difference Poisson-Boltzmann self-consistent reaction field methodology (DFT/SCRF), we evaluate geometries, energies, and Mossbauer signatures of the different protonation states that may exist in the oxidized state of the IspH catalytic cycle. From DFT/SCRF computations performed on the oxidized state, we find a state where the substrate, HMBPP, coordinates the apical iron in the [4Fe-4S] cluster as an alcohol group (ROH) to be one of two, isoenergetic, lowest-energy states. In this state, the HMBPP pyrophosphate moiety and an adjacent glutamate residue (E126) are both fully deprotonated, making the active site highly anionic. Our findings that this low-energy state also matches the experimental geometry of the active site and that its computed isomer shifts agree with experiment validate the use of the DFT/SCRF method to assess relative energies along the IspH reaction pathway. Additional studies of IspH catalytic intermediates are currently being pursued.

First author: Liu, Ling, The relationship between intermolecular interactions and charge transport properties of trifluoromethylated polycyclic aromatic hydrocarbons, ORGANIC ELECTRONICS, 15, 1896, (2014)
Abstract: Polycyclic aromatic hydrocarbons (PAHs) with the electron-withdrawing groups such as halogen atom, cyanide, perfluoroalkyl (PFA), or perfluoroary, etc. exhibit good air stability and better solid-state charge carrier mobility. To obtain a better understanding of structure property relationships of this kind of compounds, a series PAH(CF3)(n) derivatives a1, a2, b1, b2, c1, and c2, which contain different numbers of trifluoromethyls and benzene rings, were chosen and studied by both band-like model and hopping model. Their crystals contain different intermolecular interactions. It turns out that intermolecular hydrogen bonding interactions are mainly responsible for electron transport, while pi-stacking interactions dominate hole transport. When the pi-stacking and intermolecular hydrogen bonding interactions coexist in the same direction, a competitive relationship occurs between hole and electron transport, which tend to cause enhancement of electron transport, and restrain hole transport.

First author: Martin, David P., Exploring the Influence of the Protein Environment on Metal-Binding Pharmacophores,JOURNAL OF MEDICINAL CHEMISTRY, 57, 7126, (2014)
Abstract: The binding of a series of metal-binding pharmacophores (MBPs) related to the ligand 1-hydroxypyridine-2-(1H)-thione (1,2-HOPTO) in the active site of human carbonic anhydrase II (hCAII) has been investigated. The presence and/or position of a single methyl substituent drastically alters inhibitor potency and can result in coordination modes not observed in small-molecule model complexes. It is shown that this unexpected binding mode is the result of a steric clash between the methyl group and a highly ordered water network in the active site that is further stabilized by the formation of a hydrogen bond and favorable hydrophobic contacts. The affinity of MBPs is dependent on a large number of factors including donor atom identity, orientation, electrostatics, and van der Waals interactions. These results suggest that metal coordination by metalloenzyme inhibitors is a malleable interaction and that it is thus more appropriate to consider the metal-binding motif of these inhibitors as a pharmacophore rather than a “chelator”. The rational design of inhibitors targeting metalloenzymes will benefit greatly from a deeper understanding of the interplay between the variety of forces governing the binding of MBPs to active site metal ions.

First author: Climent, Claudia, Optical Properties of 4-Bromobenzaldehyde Derivatives in Chloroform Solution, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 6914, (2014)
Abstract: In this work we give a deeper insight into the electronic structure of a series of purely organic molecules that were recently employed as building blocks in crystals with very efficient phosphorescent emission. With this purpose, the low-lying excited states of a series of 4-bromobenzaldehyde derivatives in chloroform solution are explored by means of time-dependent density functional theory (TDDFT) calculations, together with the absorption, fluorescence, and phosphorescence experimental spectra. The optical properties of the studied molecular models are extensively discussed, in terms of the frontier molecular orbitals involved in the relevant electronic transitions, the recorded and simulated absorption profiles, and the molecular geometries and transition energies of the emitting states. The calculations eventually help in the assignment of the character of the lowest lying singlet and triplet emitting states for these compounds.

First author: Pushkar, Yulia, Spectroscopic Analysis of Catalytic Water Oxidation by [Ru-II(bpy)(tpy)H2O)(2+) Suggests That Ru-V=O Is Not a Rate-Limiting Intermediate, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 11938, (2014)
Abstract: Modern chemistry’s grand challenge is to significantly improve catalysts for water splitting. Further progress requires detailed spectroscopic and computational characterization of catalytic mechanisms. We analyzed one of the most studied homogeneous single-site Ru catalysts, [Ru-II(bpy)(tpy)H2O](2+) (where bpy = 2,2′-bipyridine, tpy = 2,2′;6′,2 ”-terpyridine). Our results reveal that the [Ru-V(bpy)(tpy)=O](3+) intermediate, reportedly detected in catalytic mixtures as a rate-limiting intermediate in water activation, is not present as such. Using a combination of electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy, we demonstrate that 95% of the Ru complex in the catalytic steady state is of the form [Ru-IV(bpy)(tpy)=O](2+). [Ru-V(bpy)(tpy)=O](3+) was not observed, and according to density functional theory (DFT) analysis, it might be thermodynamically inaccessible at our experimental conditions. A reaction product with unique EPR spectrum was detected in reaction mixtures at about 5% and assigned to Ru-III-peroxo species with (-OOH or -OO- ligands). We also analyzed the [Ru-II(bpy)(tpy)Cl](+) catalyst precursor and confirmed that this molecule is not a catalyst and its oxidation past Ru-III state is impeded by a lack of proton-coupled electron transfer. Ru-Cl exchange with water is required to form active catalysts with the Ru-H2O fragment. [Ru-II(bpy)(tpy)H2O](2+) is the simplest representative of a larger class of water oxidation catalysts with neutral, nitrogen containing heterocycles. We expect this class of catalysts to work mechanistically in a similar fashion via [Ru-IV(bpy)(tpy)=O](2+) intermediate unless more electronegative (oxygen containing) ligands are introduced in the Ru coordination sphere, allowing the formation of more oxidized Ru-V intermediate.

First author: Sartorel, Andrea, Oxygenation by Ruthenium Monosubstituted Polyoxotungstates in Aqueous Solution: Experimental and Computational Dissection of a Ru(III)-Ru(V) Catalytic Cycle, CHEMISTRY-A EUROPEAN JOURNAL,20, 10932, (2014)
Abstract: Molecular polyoxometalates with one embedded ruthenium center, with general formula [RuII/III-( DMSO)XW11O39](n-) (X = P, Si; n = 4-6), are readily synthesized in gram scale under microwave irradiation by a flash hydrothermal protocol. These nanodimensional and polyanionic complexes enable aerobic oxygenation in water. Catalytic oxygen transfer to dimethylsulfoxide (DMSO) yielding the corresponding sulfone (DMSO2) has been investigated with a combined kinetic, spectroscopic and computational approach addressing: (i) the Ru-III catalyst resting state; (ii) the bimolecular event dictating its transformation in the rate-determining step; (iii) its aerobic evolution to a high-valent ruthenium oxene species; (iv) the terminal fate to diamagnetic dimers. This pathway is reminiscent of natural heme systems and of bioinspired artificial porphyrins. The in silico characterization of a key bis-Ru(IV)-mu-peroxo-POM dimeric intermediate has been accessed by density functional theory. This observation indicates a new landmark for tracing POMbased manifolds for multiredox oxygen reduction/activation, where metal-centered oxygenated species play a pivotal role.

First author: Marchione, Demian, The Chemical Bond in Gold(I) Complexes with N-Heterocyclic Carbenes,ORGANOMETALLICS, 33, 4200, (2014)
Abstract: In this contribution we report a comparative analysis of the chemical bond between an N-heterocyclic carbene and different Au(I) metal fragments of general formula [(NHC)AuL](+) or [(NHC)AuL], where NHC is imidazol-2-ylidene and L is chosen from some ligands frequently used both in coordination and in organometallic chemistry. The focus is on the nature of the Au(I) C (of NHC) bond in terms of Dewar-Chatt-Duncanson components and its modulation by the ancillary ligand L. In the case of L = Cl (metal fragment AuCl), we present a comparative analysis of the binding mode with 1,3-dimethylimidazol-2-ylidene and 13-diphenylimidazol-2-ylidene, where the hydrogens bonded at the nitrogens of NHC have been substituted with methyl and phenyl groups. We applied a model-free definition and a theoretical analysis of the electron-charge displacements making up the donation and back-donation components of the Dewar-Chatt-Duncanson model. We thus show that the nature of the NHC gold bond is strongly dependent on the electronic structure of the ancillary ligand L. The results clearly confirm that the NHC is not a purely sigma-donor for our systems, but has a pi-back-donation component that amounts to up to half of the sigma-donation (as found in NHC AuCl) or is entirely negligible (as found in [NHC AuCO])(+).

First author: Jacobsen, Heiko, The Local Kinetic Energy Profile of an Inverted Carbon-Carbon Bond Reveals and Refines its Charge-Shift Character, CHEMPHYSCHEM, 15, 2522, (2014)
Abstract: Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are linked to the concept of charge-shift bonding. This is illustrated in a detailed study of twelve molecules, possessing carbon-carbon covalent as well as carbon-carbon charge-shift bonds in various degrees of orders, including propellanes and heteropropellanes. Regions of slow electrons are fundamental for such a correlation, and a RoSE (region of slow electrons) indicator v(+/-), based on the positive definite kinetic energy density tau, is employed to characterize classes of charge-shift bonds in terms of its full topology of all critical points of rank three.

First author: Shi, Guosheng, Orbital Effect-Induced Anomalous Anion-p Interactions between Electron-Rich Aromatic Hydrocarbons and Fluoride, CHEMPHYSCHEM, 15, 2588, (2014)
Abstract: Anion-p interactions generally exist between an anion and an electron-deficient p-ring because of the electron-accepting character of the ring. In this paper, we report orbital effect-induced anomalous binding between electron-rich pi systems and F- through anion-p interactions calculated at the MP2/631+G(d,p) and omega B97X-D/6-31+G(d,p) levels of theory. We find that anion-p interactions between F- and electron-rich p rings increase markedly with increasing number of p electrons and size of the p rings. This is contrary to intuition because anion-p interactions would be expected to gradually decrease because of gradually increasing Coulombic repulsion between the negative charge of the anions and gradually increasing number of p electrons of the aromatic surfaces. Energy decomposition analysis showed that the key to this anomalous effect is the more effective delocalization of negative charge to the unoccupied pi* orbitals of larger p rings, which is termed an “orbital effect”.

First author: Calandrini, Vania, Platination of the copper transporter ATP7A involved in anticancer drug resistance,DALTON TRANSACTIONS, 43, 12085, (2014)
Abstract: The clinical efficacy of the widely used anticancer drug cisplatin is severely limited by the emergence of resistance. This is related to the drug binding to proteins such as the copper influx transporter Ctr1, the copper chaperone Atox1, and the copper pumps ATP7A and ATP7B. While the binding modes of cisplatin to the first two proteins are known, the structural determinants of platinated ATP7A/ATP7B are lacking. Here we investigate the interaction of cisplatin with the first soluble domain of ATP7A. First, we establish by ESI-MS and H-1, C-13, and N-15 NMR that, in solution, the adduct is a monomer in which the sulfur atoms of residues Cys19 and Cys22 are cis-coordinated to the [Pt(NH3)(2)](2+) moiety. Then, we carry out hybrid Car-Parrinello QM/MM simulations and computational spectroscopy calculations on a model adduct based on the NMR structure of the apo protein and featuring the experimentally determined binding mode of the metal ion. These calculations show quantitative agreement with CD spectra and H-1, C-13, and N-15 NMR chemical shifts, thus providing a quantitative molecular view of the 3D binding mode of cisplatin to ATP7A. Importantly, the same comparison rules out a variety of alternative models with different coordination modes, that we explored to test the robustness of the computational approach. Using this combined in silico-in vitro approach we provide here for the first time a quantitative 3D atomic view of the platinum binding to the first soluble domain of ATP7A.

First author: Ording-Wenker, Erica C. M., Thermodynamics of the Cu-II mu-Thiolate and Cu-I Disulfide Equilibrium: A Combined Experimental and Theoretical Study, INORGANIC CHEMISTRY, 53, 8494, (2014)
Abstract: The redox equilibrium between dinuclear Cu-II mu-thiolate and Cu-I disulfide structures has been analyzed experimentally and via DFT calculations. Two new ligands, (LSSL2)-S-2 and (LSSL4)-S-4, and their Cu-II mu-thiolate and Cu-I disulfide complexes were synthesized. For (LSSL2)-S-2, these two redoxisomeric copper species are shown to be in equilibrium, which depends on both temperature and solvent. For (LSSL4)-S-4 the mu-thiolate species forms as the kinetic product and further evolves into the disulfide complex under thermodynamic control, which creates the unprecedented possibility to both species under the same reaction conditions. The energies of the mu-thiolate and disulfide complexes for two series of related ligands have been calculated with DFT; the results rationalize the experimentally observed structures, and emphasize the important role that steric requirements play in the formation of the Cull thiolate structure.

First author: Gendron, Frederic, Magnetic Resonance Properties of Actinyl Carbonate Complexes and Plutonyl(VI)-tris-nitrate, INORGANIC CHEMISTRY, 53, 8577, (2014)
Abstract: Electronic structures and magnetic properties of actinyl ions AnO(2)(n+) (An = U, Np, and Pu) and the equatorially coordinated carbonate complexes [UO2(CO3)(3)](5-), [NpO2(CO3)(3)](4-), and [PuO2(CO3)(3)](4-) are investigated by ab initio quantum chemical calculations. The complex [PuO2(NO3)(3)](-) is also included because of experimentally available g-factors and for comparison with a previous study of [NpO2(NO3)(3)](-) (Chem.-Eur. J. 2014, 20, 7994-8011). The results are rationalized with the help of crystal-field (CF)-type models with parameters extracted from the ab initio calculations, and with the help of natural orbitals and natural spin orbitals contributing to the magnetic properties and the unpaired spin distribution, generated from the spin-orbit wave functions. These orbitals resemble textbooklike representations of the actinide 5f orbitals. Calculated paramagnetic susceptibilities are used to estimate dipolar C-13 chemical shifts for the carbonate ligands. Their signs and order of magnitude are compared to paramagnetic effects observed experimentally in NMR spectra. The results indicate that the experimental spectra are also influenced by contact shifts.

First author: Fernandez, Israel, Ene-ene-yne Reactions: Activation Strain Analysis and the Role of Aromaticity,CHEMISTRY-A EUROPEAN JOURNAL, 20, 10791, (2014)
Abstract: The trend in reactivity of the thermal cycloisomerization reactions of 1,3-hexadien-5-ynes, A=B-C=D-E F, were explored and analyzed by using density functional theory at the M06-2X/def2-TZVPP level. These reactions proceed through formally aromatic transition states to form a bent-allene intermediate with relatively high activation barriers. Activation-strain analyses show that the major factor controlling this Hopf cyclization is the geometrical strain energy associated with the rotation of the terminal [A] group. This rotation is necessary for achieving a favorable HOMO-LUMO overlap with the yne-moiety [F] associated with the formation of the new A-F single bond. In addition, the relationship between the aromaticity of the corresponding cyclic transition states (all six-membered rings) and the computed activation barriers were analyzed. The calculations also indicate that the aromatization of the bent-allene structures takes place through two consecutive 1,2-hydrogen shifts, the second one exhibiting negligible energy barriers.

First author: Siodla, Tomasz, Toward a Physical Interpretation of Substituent Effects: The Case of Fluorine and Trifluoromethyl Groups, JOURNAL OF ORGANIC CHEMISTRY, 79, 7321, (2014)
Abstract: The application of ab initio and DFT computational methods at six different levels of theory (MP2/cc-pVDZ, MP2/aug-cc-pVTZ, B3LYP/cc-pVDZ, B3LYP/aug-cc-pVTZ, M06/cc-pVDZ, and M06/aug-cc-pVTZ) to meta- and para-substituted fluoro- and trifluoromethylbenzene derivatives and to 1-fluoro- and 1-trifluoromethyl-2-substituted trans-ethenes allowed the study of changes in the electronic and geometric properties of F- and CF3-substituted systems under the impact of other substituents (BeH, BF2, BH2, Br, CFO, CHO, Cl, CN, F, Li, NH2, NMe2, NO, NO2, OH, H, CF2, and CH3). Various parameters of these systems have been investigated, including homodesmotic reactions in terms of the substituent effect stabilization energy (SESE), the pi and sigma electron donor-acceptor indexes (pEDA and sEDA, respectively), the charge on the substituent active region (cSAR, known earlier as qSAR), and bond lengths, which have been regressed against Hammett constants, resulting mostly in an accurate correspondence except in the case of p-fluorobenzene derivatives. Moreover, changes in the characteristics of the ability of the substituent to attract or donate electrons under the impact of the kind of moiety to which the substituent is attached have been considered as the indirect substituent effect and investigated by means of the cSAR model. Regressions of cSAR(X) versus cSAR(Y) for any systems X and Y allow final results to be obtained on the same scale of magnitude.

First author: Jacquot, Lea, Multiple One-Electron Transfers in Bipyridine Complexes of Bis(phospholyl) Thulium,ORGANOMETALLICS, 33, 4100, (2014)
Abstract: The synthesis of original neutral bis(phospholyl) thulium complexes, Dtp(2)Tm(L), where L is tetramethylbiphosphinine (tmbp) and bipyridine (bipy), is reported. The electronic structures of these complexes have been investigated and it appears that, in both cases, an electron transfer occurs from the divalent metal to the ligand, a consequence of the strong reduction potential of the bis(phospholyl) thulium fragment, Dtp(2)Tm. When 1 equiv of bipyridine is added to the Dtp(2)Tm(tmbp) complex, another electron transfer occurs to form the Dtp(2)Tm(bipy) complex along with free tmbp ligand. Astonishingly, despite the apparent trivalent nature of the thulium center, the Dtp(2)Tm(bipy) complex is still reactive toward neutral bipyridine to form a new complex in which one phospholyl ligand is replaced by a bipyridine radical anion. An experimental kinetic analysis is reported to rationalize this unprecedented redox reaction with thulium and reveals an associative type of mechanism.

First author: Azpiroz, Jon M., DFT/TDDFT Study of the Adsorption of N3 and N719 Dyes on ZnO(10(1)over-bar0) Surfaces, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 5885, (2014)
Abstract: ZnO has attracted a great deal of research as a potential replacement of TiO2 for dye-sensitized solar cells (DSSCs), owing to the unique combination of interesting electronic properties (i.e., high electron mobility) and structural richness. Here, we present a DFT/TDDFT study about the interaction of the prototypical N3 and N719 Ru(II) sensitizers on ZnO models to understand some of the atomistic details that are crucial to the dye/semiconductor interaction. We pay particular attention to the adsorption mode of the sensitizer and to the effect of the complexation on the electronic structure of the dye. The sensitizers are predicted to strongly interact with the ZnO surface. In particular, the interaction is strengthened when three dye carboxylic groups are involved in the adsorption. Moreover, if the anchoring group bears a proton, the adsorption is predicted to be dissociative. The charge density donation from the dye to the semiconductor raises the valence and conduction band edges of the latter, in such a way that the optical gap of ZnO widens. Proton transfer from the dye to the semiconductor balances the charge donation effect and restores the electronic levels of the noninteracting fragments. The impact of dye/semiconductor interaction on the adsorbed dye optical properties is then discussed.

First author: Jang, Eun Sil, Copper(II) Anilides in sp(3) C-H Amination, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 10930, (2014)
Abstract: We report a series of novel beta-diketiminato copper(II) anilides [Cl2NN]Cu-NHAr that participate in C-H amination. Reaction of H2NAr (Ar = 2,4,6-Cl3C6H2 (Ar-Cl3), 3,5-(CF3)(2)C6H3 (Ar-F6), or 2-py) with the copper(II) t-butoxide complex [Cl2NN]-Cu-(OBu)-O-t yields the corresponding copper(II) anilides [Cl2NN]-Cu-NHAr. X-ray diffraction of these species reveal three different bonding modes for the anilido moiety: kappa(1)-N in the trigonal [Cl2NN]Cu-NHArCl3 to dinuclear bridging in {[Cl2NN]Cu}(2)(mu-NHArF6)(2) and kappa(2)-N,N in the square planar [Cl2NN]Cu(kappa(2)-NH-2-py). Magnetic data reveal a weak antiferromagnetic interaction through a pi-stacking arrangement of [Cl2NN]Cu-NHArCl3; solution EPR data are consistent with monomeric species. Reaction of [Cl2NN]Cu-NHAr with hydrocarbons R-H (R-H = ethylbenzene and cyclohexane) reveals inefficient stoichiometric C-H amination with these copper(II) anilides. More rapid C-H amination takes place, however, when (BuOOBu)-Bu-t-Bu-t is used, which allows for HAA of R-H to occur from the (BuO center dot)-Bu-t radical generated by reaction of [Cl2NN]Cu and (BuOOBu)-Bu-t-Bu-t. The principal role of these copper(II) anilides [Cl2NN]Cu-NHAr is to capture the radical R-center dot generated from HAA by (BuO center dot)-Bu-t to give functionalized aniline R-NHAr, resulting in a novel amino variant of the Kharasch-Sosnovsky reaction.

First author: Zhekova, Hristina R., A Perspective on the Relative Merits of Time-Dependent and Time-Independent Density Functional Theory in Studies of the Electron Spectra Due to Transition Metal Complexes. An Illustration Through Applications to Copper Tetrachloride and Plastocyanin, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 114, 1019, (2014)
Abstract: Evaluation of the excitation energies in CuCl42- and plastocyanin was carried out with three different density functional theory (DFT) methods: time-dependent DFT (TDDFT), Delta DFT, and Delta self consistent field (SCF)-DFT. Use was made of two local (local density approximation and BP86), two hybrid (B3LYP and PBE0), and one long-range corrected (LC-BP86) functionals to probe the effect of the exact exchange on the excitation energies. Some well-known deficiencies observed in TDDFT were explained on the basis of lacking orbital relaxation and two-electron terms not considered in adiabatic TDDFT. Delta self consistent field (SCF)-DFT reproduces well the position of the charge-transfer excitations and yields results in best agreement with experiment regardless of the system or functional used. We conclude that the orbital relaxation and proper account of higher-order terms neglected in adiabatic TDDFT are of great importance for the simulation of excitation spectra.

First author: Donzello, Maria Pia, Tetra-2,3-pyrazinoporphyrazines with Externally Appended Pyridine Rings. 15. Effects of the Pyridyl Substituents and Fused Exocyclic Rings on the UV-Visible Spectroscopic Properties of Mg(II)-Porphyrazines: A Combined Experimental and DFT/TDDFT Study, INORGANIC CHEMISTRY, 53, 8009, (2014)
Abstract: Two new Mg-II porphyrazine macrocycles, the octakis(2-pyridyl)porphyrazinato-magnesium(II), [Py(8)PzMg-(H2O)], and the tetrakis-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato-magnesium(II), [Py(8)QxPzMg(H2O)], were prepared by Mg-template macrocyclization processes, and their general physicochemical properties were examined. The previously reported porphyrazine analog, the tetrakis-2,3-[5,6-di(2-pyridyl)-pyrazino]porphyrazinato-magnesium(II), [Py(8)PyzPzMg(H2O)], has been also considered in the present work. The UV visible solution spectra in nonaqueous solvents of this triad of externally octapyridinated Mg-II complexes exhibit the usual profile observed for phthalocyanine and porphyrazine macrocycles, with intense absorptions in the Soret (300-450 nm) and Q band (600-800 nm) regions. It is observed that the Q band maximum sensibly shifts toward the red with peak values at 635 -> 658 -> 759 nm along the series [Py(8)PzMg(H2O)], [Py8PyzPzMg(H2O)], and [Py(8)QxPzMg(H2O)], as the extension of the macrocycle pi-system increases. TDDFT calculations of the electronic absorption spectra were performed for the related water-free model compounds [Py(8)PzMg], [Py(8)PyzPzMg], and [Py(8)QxPzMg] to provide an interpretation of the UV visible spectral changes occurring upon introduction of the pyrazine and quinoxaline rings at the periphery of the Pz macrocycle. To discriminate the electronic effects of the fused exocylic rings from those of the appended 2-pyridyl rings, the UV-visible spectra of [PzMg] and [PyzPzMg] were also theoretically investigated. The theoretical results prove to agree very well with the experimental data, providing an accurate description of the UV-visible spectra. The observed spectral changes are interpreted on the basis of the electronic structure changes occurring along the series.

First author: Liu, Yifei, Diarylethene-Containing Carbon-Rich Ruthenium Organometallics: Tuning of Electrochromism,INORGANIC CHEMISTRY, 53, 8172, (2014)
Abstract: The association of a dithienylethene (DTE) system with ruthenium carbon-rich systems allows reaching sophisticated and efficient light- and electro-triggered multifunctional switches R-[Ru]-C equivalent to C-DTE-C equivalent to C-[Ru] -R, featuring multicolor electrochromism and electrochemical cydization at remarkably low voltage. The spin density on the DTE ligand and the energetic stabilization of the system upon oxidation could be manipulated to influence the closing event, owing to the noninnocent behavior of carbon-rich ligands in the redox processes. A combination of spectroscopic (UV-vis-NIR-IR and EPR) and electrochemical studies, with the help of quantum chemical calculations, demonstrates that one can control and get a deeper understanding of the electrochemical ring closure with a slight modification of ligands remote from the DTE unit. This electrochemical cyclization was established to occur in the second oxidized state (EEC mechanism), and the kinetic rate constant in solution was measured. Importantly, these complexes provide an unprecedented experimental means to directly probe the remarkable efficiency of electronic (spin) delocalization between two trans carbon-rich ligands through a metal atom, in full agreement with the theoretical predictions. In addition, when no cyclization occurs upon oxidation, we could achieve a redox-triggered magnetic switch.

First author: Poor Kalhor, Mahboubeh, Reactivity of silica supported zirconium hydride towards N2O and CO2 probe molecules: a computational point of view, NEW JOURNAL OF CHEMISTRY, 38, 3717, (2014)
Abstract: The reactivity of supported zirconium hydrides toward probe molecules like N2O and CO2 has shown that both hydrides are converted to the corresponding hydroxide and formate species, which were characterized by IR and NMR spectroscopies. Their reactivity towards these probe molecules is analyzed through DFT (density functional theory) calculations. The computed spectroscopic IR and NMR signatures are fully consistent with experimental observations.

First author: Moustafa, Mohamed E., Photoswitchable organoplatinum complexes containing an azobenzene derivative of 3,6-di(2-pyridyl)pyridazine, CANADIAN JOURNAL OF CHEMISTRY, 92, 706, (2014)
Abstract: The new, unsymmetrical azobenzene-tagged ligand 4-(4-azobenzene)-3,6-di(2-pyridyl) pyridazine, adpp, forms complexes with platinum(II) and platinum(IV), which exist as a mixture of geometrical isomers. The complexes are characterized primarily by their NMR spectra, while the structures of the ligand and its complexes [PtMe2(adpp)], [PtBrMe2(CH2C6H4-4-t-Bu)(adpp)], and [PtBrMe2(CH(2)C(6)H3-(3),5-t-Bu-2)(adpp)] have been structurally characterized. In solution, the compounds undergo easy photochemical trans-cis switching of the azobenzene group, with subsequent slow thermal isomerization back to the more stable trans-azobenzene isomer.

First author: Kravtsova, Antonina N., Atomic and electronic structure of free niobium nanoclusters: Simulation of the M-4,M-5-XANES spectrum of Nb-13(+), JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 195, 189, (2014)
Abstract: The atomic and electronic structure of free niobium nanoclusters has been studied on the basis of X-ray absorption near-edge structure (XANES) spectroscopy and density functional theory. M-4,M-5-XANES spectra have been calculated for several structural models of the 13-atomic niobium cluster. The calculations have been done on the basis of both full multiple scattering theory within the muffin-tin approximation for a potential and full-potential finite difference method. The comparison of the experimental M-4,M-5-edge XANES spectrum (Peredkov et al., J. Electron Spectros. Relat. Phenomena 184 (2011) 113-118) with the simulated X-ray absorption spectra of Nb-13(+) hints to a highly-symmetric icosahedral structure of the cluster. An internuclear distance of 2.2 +/- 0.1 angstrom between neighboring “surface” atoms of the icosahedron and 2.09 angstrom between the central “bulk” atom and “surface” atoms, respectively, has been found upon comparison of the experimental and theoretical XANES spectra.

First author: Kondinski, Aleksandar, How Counterions Affect the Solution Structure of Polyoxoaurates: Insights from UV/Vis Spectral Simulations and Electrospray Mass Spectrometry, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 195, 3771, (2014)
Abstract: The solution structure of the two presently known polyoxoaurates, [Au4As4O20](8-) (Au4As4) and [Au4Se4O16](4-) (Au4Se4), was elucidated by a combination of time-dependent density-functional-theory (TD-DFT) calculations, experimental UV/Vis spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The TD-DFT-predicted electronic spectra for molecular models including different numbers of counterions, along with the main Au4As4 and Au4Se4 structural motifs, were analyzed and compared with the experimental UV/Vis spectra of the two polyanions. The performed analysis revealed important structural differences between the arsenate and the selenite derivatives in aqueous solution. For the selenite oxoaurate, the bare Au4Se4 polyanion itself shows very good agreement between predicted and experimental excitation energies. In contrast, the solution state of the arsenate oxoaurate appears to be best described by a dimeric assembly of the type [Na5Au8As8O40](11-) (Na5Au8As8) with a stoichiometry and structure very similar to those reported for the solid state. Indirect experimental evidence that Na5Au8As8 is the dominant species in aqueous solution is provided by ESI-MS measurements. Our work demonstrates that the combination of experimental UV/Vis spectroscopy and TD-DFT calculations complemented with electrospray mass spectrometry may serve as an alternative strategy for rationalizing the solution chemistry of polyoxometalates, which cannot be studied by conventionally used spectroscopic techniques, such as NMR or EPR spectroscopy.

First author: Makhoul, Rim, Synthesis and Properties of a Mixed-Valence Compound with Single-Step Tunneling and Multiple-Step Hopping Behavior, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 195, 3899, (2014)
Abstract: The organic precursor bis(trimethylsilylethynyl)TTFMe2 (3, TTF = tetrathiafulvalene) was prepared as a 1:1 mixture of the cis and trans isomers. Pure samples of 3-cis and 3-trans were obtained by crystallization and identified by XRD analysis. The treatment of pure 3-trans and a 1:1 mixture of 3-cis/trans with (i) potassium carbonate, (ii) the iron complex Cp*(dppe)FeCl [5, Cp* = eta(5)-C5Me5, dppe = 1,2-bis(diphenylphosphanyl)ethane] in the presence of KPF6, and (iii) tBuOK provided Cp*(dppe)Fe-C C-TTFMe2-C C-Fe(dppe) Cp* as the pure geometric isomer 6-trans (85%) and as the 60:40 mixture 6-cis/ trans (63%), respectively. The oxidation of 6-trans with [(C5H5)(2)Fe]PF6 gave [6-trans][PF6](n) (n = 1-3). Visible, IR, near-IR (NIR), and electron paramagnetic resonance (EPR) spectroscopy together with DFT data show that [6-trans][PF6] is a class II mixed-valence complex (H-ab = 85 cm(-1)) in which the spin distribution depends on the conformation of the molecule. Intramolecular electron transfer occurs through single-step tunneling and a multistep hoping mechanism. The triplet state is thermally accessible for [6-trans][PF6](2).

First author: Mousavi, Masoumeh, Deformation density and energy decomposition to describe interactions between (eta(5)-C5H5)M and highly reactive molecules C4H4 and (C3H3)(-), JOURNAL OF MOLECULAR MODELING, 20, 3899, (2014)
Abstract: Using DFT calculations, an energy decomposition analysis (EDA) combined with natural orbitals for chemical valence (NOCV), EDA-NOCV approach was used to describe the nature of the interaction between eta(5)-cyclopentadienyl metal complexes (eta(5)-C5H5) M, with M=Co, Rh, and cyclobutadiene (Cb) and cyclopropenyl anion (C3H3)(-) molecules, which are highly reactive molecules in their free state. EDA-NOCV draws a covalent picture for these interactions. With this interpretation of interactions, the character of aromaticity could be the result of the delocalization of six electrons in p orbitals of the (eta(5)-C5H5) M fragment and Cb/C3H3-1 ligand. This description of the bonding interaction might also justify the experimental observation that, in complexes of CpM-Cb (M=Co, Rh), the viability of the Friedel-Crafts acylation and other electrophilic substitutions on the four-membered ring is greater than that of the five-membered ring.

First author: Poater, Jordi, Aromaticity and Magnetic Properties of 1-and 2-Indenones and Their Aza Derivatives,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, 20, 5370, (2014)
Abstract: The almost unknown series of 1- and 2-indenones and their aza-derivatives have been analyzed with the aim of understanding the higher stability and aromaticity of the 1-one compared to the 2-one series. The effect of tetrafluorination of the six-membered ring on their relative stability and aromaticity and the corresponding 19F-19F spin-spin coupling constants (SSCC) have been analyzed for the compounds of these two series. Magnetic NICS and electronic PDI, FLU, and MCI aromaticity criteria, complemented by an energy decomposition analysis, allow the higher stability and aromaticity of 1-indenones compared with 2-indenones to be attributed to the p-component of the orbital interaction term. The reduced aromatic character of the 2-one series also provides an explanation for the F-19-F-19 SSCC observed in the tetrafluorinated 2-one compounds, which differ significantly from those of 1,2,3,4-tetrafluorobenzene.

First author: Deb, A. K. Singha, Nano Cavity Induced Isotope Separation of Zinc: Density Functional Theoretical Modeling,JOURNAL OF CHEMICAL AND ENGINEERING DATA, 59, 2472, (2014)
Abstract: Density functional theoretical calculation was performed to understand the isotopic fraction of zinc in the nano cavity of different crown ethers and crown ethers anchored on solid resin matrix. The structure, energetic, thermodynamics, and vibration IR spectra were also evaluated. The gas phase binding energy of Zn2+ with crown ether of varied cavity can be correlated with NPA charge transfer but no such correlation is obtained with the fraction of electron transfer, Delta N. The reduced partition function ratio (RPFR) of complexes of Zn2+ ion with different solvents, crown ethers, and grafted crown ethers was also computed to predict the isotope separation factor of the Zn2+ ion. The present study reveals that with increasing cavity size of the crown ether the RPFR was found to be decreased leading to a high value of isotope separation factor as observed in the experiments. An attempt was made to correlate the calculated RPFR and separation factor with binding energy of different zinc-crown ether systems. Further, it is shown that the smaller the solvation energy of the metal ion the higher will be distribution constant of Zn2+ ion as confirmed by experiments indicating solvents with low dielectric constant should be used for chromatographic separation process. The present study should be useful in screening the nano cavity based grafted resin and for future development of new grafted materials for Zn and other isotope separation.

First author: Zhekova, Hristina, Applications of Time Dependent and Time Independent Density Functional Theory to the First pi to pi* Transition in Cyanine Dyes, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 3299, (2014)
Abstract: The first pi -> pi* transition in a number of cyanine dyes was studied using both time dependent and time independent density functional methods using a coupled cluster (CC2) method as the benchmark scheme. On the basis of 10 different functionals, it was concluded that adiabatic time dependent density functional theory (ATDDFT) almost independently of the functional gives rise to a singlet triplet separation that is too large by up to 1 eV, leading to too high singlet energies and too low triplet energies. This trend is even clearer when the Tamm-Dancoff (TD) approximation is introduced and can in ATDDFT/TD be traced back to the representation of the singlet triplet separation by a HF-type exchange integral between pi and pi*. The time independent DFT methods (Delta SCF and RSCF-CV-DFT) afford triplet energies that are functional independent and close to those obtained by ATDDFT. However, both the singlet energies and the singlet triplet separations increases with the fraction a of HF exchange. This trend can readily be explained in terms of the modest magnitude of a KS-exchange integral between pi and pi* in comparison to the much larger HF-exchange integral. It was shown that a fraction alpha of 0.5 affords good estimates of both the singlet energies and the singlet-triplet separations in comparison to several ab initio benchmarks.

First author: Chakraborty, Prateeti, Combined Experimental and Theoretical Investigation of Ligand and Anion Controlled Complex Formation with Unprecedented Structural Features and Photoluminescence Properties of Zinc(II) Complexes,CRYSTAL GROWTH & DESIGN, 14, 4111, (2014)
Abstract: By using two potential tridentate ligands, HL1 [4-chloro-2-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol] and 4-chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol], which differ by one methylene group in the alkyl chain, four new Zn-II complexes, namely, [Zn((LH)-H-2)(2)](ClO4)(2) (1), [Zn(L-1))(H2O)(2)][Zn(L-1)(SCN)(2)] (2), [Zn(L-1))(dca)](n) (3), and [Zn-2(L-1)(2)(N-3)(2)(H2O)(2)] (4) [where dca = dicyanamide anion] were synthesized and structurally characterized. The results indicate that the slight structural difference between the ligands, HL1 and HL2, because of the one methylene group connecting the nitrogen atoms provokes a chemical behavior completely different from what was expected. Any attempt to isolate the Zn(L-2) complexes with thiocyanato, dicyanamido, and azide was unsuccessful, and perchlorate complex 1 was always obtained. In contrast, with HL1) we obtained structural diversity on varying the anions, but we failed to isolate the analogous perchlorate complex of HI). Single-crystal X-ray analyses revealed that the morpholine nitrogen of ligand L2 is protonated and thus does not take part in coordination with Zn-II in complex 1. On the other hand, the morpholine nitrogen of L-1 is coordinated to Zn-II in 2-4. Of these, 2 and 4 are rare examples of a cocrystallized cationic/anionic complex and of a dinuclear complex bridged by a single azide, respectively. Some of these unexpected findings and some interesting noncovalent interactions leading to the formation of dimeric entities in solid-state compound 4 were rationalized by a DFT approach. Photoluminescence properties of the complexes as well as the ligands were investigated in solution at ambient temperature and at 77 K. The very fast photoinduced electron transfer (PET) from the nitrogen lone pair to the conjugated phenolic moiety is responsible for very low quantum yield (Phi) exhibited by the ligands, whereas complexation prevents PET, thus enhancing the Phi in the complexes. The origin of the electronic and photoluminescence properties of the ligands and complexes was assessed in light of theoretical calculations.

First author: Tehrani, Zahra Aliakbar, Watson-Crick versus imidazopyridopyrimidine base pairs: theoretical study on differences in stability and hydrogen bonding strength, STRUCTURAL CHEMISTRY, 25, 1271, (2014)
Abstract: Matsuda and coworkers demonstrated that imidazopyridopyrimidine nucelobases (N (N) , O (O) , N (O) , tO (O) , and O (N) ) can mimic Watson-Crick nucleobase in forming H-bonds in DNA double helix. In the present study, we address the question about the strengths of the H-bonds in imidazopyridopyrimidine base pairs compared to those in Watson-Crick ones by focusing particularly on the nature of these interactions. Optimized structures of imidazopyridopyrimidine, imidazopyridopyrimidine-Watson-Crick, and Watson-Crick base pairs are obtained at the DFTB3LYP/6-311++G (d,p). The nature and strength of the intramolecular H-bonds in these base pairs have been investigated based on natural bond orbital (NBO method) to consider the effect of charge transfer, “atoms-in-molecules” (AIM) topological parameters, and decomposition of the interaction energies using the energy decomposition analysis (EDA). These investigations imply that N (N) -O (O) and N (O) -O (N) can form base pairs with four H-bonds (most stable than those of Watson-Crick base pairs) when they incorporated into DNA double helix. Furthermore, it can be deduced that O (N) and N (N) nucleobases form energetically more favorable pairs with adenine and guanine than the normal Watson-Crick counter parts. These results can be helpful for the stabilization and regulation of a variety of new base-pairing motif of DNA structures.

First author: Ronca, Enrico, Effect of Sensitizer Structure and TiO2 Protonation on Charge Generation in Dye-Sensitized Solar Cells, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 16927, (2014)
Abstract: We report a joint theoretical and experimental investigation on the effect of TiO2 protonation on the interfacial electronic coupling and injection rates in organic dyesensitized solar cells (DSCs). We model the electronic structure of different organic dyesensitized TiO2 cluster models at different degrees of surface protonation and experimentally show the enhancement in the photocurrent generation upon the acidic treatment of the substrate. By merging theory and experiments, we elucidate the role of TiO2 protonation on the relative alignment and electronic coupling (injection rates) between the dye’s lowest unoccupied molecular orbital and the semiconductor conduction band states, also in relation to the different electronic structure of the anchored dye (length of conjugation, conjugated vs not conjugated anchoring group). The photocurrent enhancement observed with TiO2 protonation is attributed to a combined effect of both red-shifted absorption of the protonated TiO2 films and to an overall improvement in the interfacial charge generation

First author: Ronca, Enrico, Time-Dependent Density Functional Theory Modeling of Spin-Orbit Coupling in Ruthenium and Osmium Solar Cell Sensitizers, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 17067, (2014)
Abstract: We report on the relevance of spin-orbit coupling on the optical properties of Ru(II)- and Os(II)-polypyridyl dyes effectively employed in dye-sensitized solar cells (DSCs). We include relativistic effects on time-dependent density functional theory calculations of selected complexes by using different levels of calculations, i.e., the scalar zero-order regular approximation (ZORA) and the fully relativistic ZORA including spin-orbit coupling, in such a way so as to disentangle and evaluate the spin- orbit effect. The widely investigated [M(bpy)(3)](2+) (M = Ru(II) and Os(II)) have been selected as benchmark complexes in our calculations; this is followed by investigation of “realistic” dyes used in DSCs, such as the prototypical N3 dye, its Os-based analogue, and a panchromatic Os(II) dye. We find that in Ru(II) complexes, spin- orbit coupling leads to a slight correction of the spectral shape, whereas only when we include the spin-orbit coupling we are able to reproduce the low-energy absorption bands characteristic of the Os(II) complexes. This study allows us to find a quantitative correlation between the strength of spin-orbit coupling and the metal center, highlighting the secondary effect of the different ligands experienced by the metal center.

First author: Bloch, Eric D., Reversible CO Binding Enables Tunable CO/H-2 and CO/N-2 Separations in Metal-Organic Frameworks with Exposed Divalent Metal Cations, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 10752, (2014)
Abstract: Six metal organic frameworks of the M-2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobdc(4-) = 2,5-dioxido-1,4-benzenedicarbox-ylate) structure type are demonstrated to bind carbon monoxide reversibly and at high capacity. Infrared spectra indicate that, upon coordination of CO to the divalent metal cations lining the pores within these frameworks, the C-O stretching frequency is blue-shifted, consistent with nonclassical metal-CO interactions. Structure determinations reveal M-CO distances ranging from 2.09(2) angstrom for M = Ni to 2.49(1) angstrom for M = Zn and M-C-O angles ranging from 161.2(7)degrees for M = Mg to 176.9(6) for M = Fe. Electronic structure calculations employing density functional theory (DFT) resulted in good agreement with the trends apparent in the infrared spectra and crystal structures. These results represent the first crystallographically characterized magnesium and zinc carbonyl compounds and the first high-spin manganese(II), iron(II), cobalt(II), and nickel(II) carbonyl species. Adsorption isotherms indicate reversible adsorption, with capacities for the Fe, Co, and Ni frameworks approaching one CO per metal cation site at 1 bar, corresponding to loadings as high as 6.0 mmol/g and 157 cm(3)/cm(3). The six frameworks display (negative) isosteric heats of CO adsorption ranging from 52.7 to 27.2 kJ/mol along the series Ni > Co > Fe > Mg > Mn > Zn, following the Irving Williams stability order. The reversible CO binding suggests that these frameworks may be of utility for the separation of CO from various industrial gas mixtures, including CO/H-2 and CO/N-2. Selectivities determined from gas adsorption isotherm data using ideal adsorbed solution theory (IAST) over a range of gas compositions at 1 bar and 298 K indicate that all six M-2(dobdc) frameworks could potentially be used as solid adsorbents to replace current cryogenic distillation technologies, with the choice of M dictating adsorbent regeneration energy and the level of purity of the resulting gases.

First author: Gao, Yang, Structural and electronic properties of uranium-encapsulated Au-14 cage, SCIENTIFIC REPORTS, 4, 10752, (2014)
Abstract: The structural properties of the uranium-encapsulated nano-cage U@Au-14 are predicted using density functional theory. The presence of the uranium atom makes the Au-14 structure more stable than the empty Au-14-cage, with a triplet ground electronic state for U@Au-14. Analysis of the electronic structure shows that the two frontier single-occupied molecular orbital electrons of U@Au-14 mainly originate from the 5f shell of the U atom after charge transfer. Meanwhile, the bonding orbitals and charge population indicate that the designed U@Au-14 nano-cage structure is stabilized by ionocovalent interactions. The current findings provide theoretical basis for future syntheses and further study of actinide doped gold nanoclusters, which might subsequently facilitate applications of such structure in radio-labeling, nanodrug carrier and other biomedical applications.

First author: Fronzoni, Giovanna, Vibrationally resolved high-resolution NEXAFS and XPS spectra of phenanthrene and coronene, JOURNAL OF CHEMICAL PHYSICS, 141, 10752, (2014)
Abstract: We performed a combined experimental and theoretical study of the C1s Near-Edge X-ray Absorption Fine-Structure (NEXAFS) spectroscopy and X-ray Photoelectron Spectroscopy in the gas phase of two polycyclic aromatic hydrocarbons (phenanthrene and coronene), typically formed in combustion reactions. In the NEXAFS of both molecules, a double-peak structure appears in the C1s -> LUMO region, which differ by less than 1 eV in transition energies. The vibronic coupling is found to play an important role in such systems. It leads to weakening of the lower-energy peak and strengthening of the higher-energy one because the 0 – n (n > 0) vibrational progressions of the lower-energy peak appear in nearly the same region of the higher-energy peak. Vibrationally resolved theoretical spectra computed within the Frank-Condon (FC) approximation and linear coupling model agree well with the high-resolution experimental results. We find that FC-active normal modes all correspond to in-plane vibrations.

First author: Kevorkyants, Ruslan, FDE-vdW: A van der Waals inclusive subsystem density-functional theory, JOURNAL OF CHEMICAL PHYSICS, 141, 10752, (2014)
Abstract: We present a formally exact van der Waals inclusive electronic structure theory, called FDE-vdW, based on the Frozen Density Embedding formulation of subsystem Density-Functional Theory. In subsystem DFT, the energy functional is composed of subsystem additive and non-additive terms. We show that an appropriate definition of the long-range correlation energy is given by the value of the non-additive correlation functional. This functional is evaluated using the fluctuation-dissipation theorem aided by a formally exact decomposition of the response functions into subsystem contributions. FDE-vdW is derived in detail and several approximate schemes are proposed, which lead to practical implementations of the method. We show that FDE-vdW is Casimir-Polder consistent, i.e., it reduces to the generalized Casimir-Polder formula for asymptotic inter-subsystems separations. Pilot calculations of binding energies of 13 weakly bound complexes singled out from the S22 set show a dramatic improvement upon semilocal subsystem DFT, provided that an appropriate exchange functional is employed. The convergence of FDE-vdW with basis set size is discussed, as well as its dependence on the choice of associated density functional approximant.

First author: Guerra, Celia Fonseca, Rationalizing the Structural Variability of the Exocyclic Amino Groups in Nucleobases and Their Metal Complexes: Cytosine and Adenine, CHEMISTRY-A EUROPEAN JOURNAL, 20, 9494, (2014)
Abstract: The exocyclic amino groups of cytosine and adenine nucleobases are normally almost flat, with the N atoms essentially sp(2) hybridized and the lone pair largely delocalized into the heterocyclic rings. However, a change to marked pyramidality of the amino group (N then sp(3) hybridized, lone pair essentially localized at N) occurs during i) involvement of an amino proton in strong hydrogen bonding donor conditions or ii) with monofunctional metal coordination following removal of one of the two protons.

First author: Monti, Adriano, In-Silico Design of a Donor-Antenna-Acceptor Supramolecular Complex for Photoinduced Charge Separation, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 15600, (2014)
Abstract: We investigate via density functional theory a series of donor-antenna-acceptor molecular rectifiers designed as modules for artificial photosynthesis devices. We consider triad modules containing phenothiazine (PTZ) as the electron donor and different derivatives of naphthalene diimide (NDI) as the antenna and secondary electron acceptor. The choice of the molecular components in the triad is guided by the redox and optical properties of each subunit. Using time-dependent DFT in combination with the long-range corrected xc-functional CAM-B3LYP we investigate how photoinduced charge transfer states are affected by systematic modifications of the triad molecular structure. In particular, we show how by controlling the length of the molecular bridges connecting the different charge separator subunits it is possible to control the driving force for the relaxation of the excitonic state into the full charge-separated state. On the basis of these findings we propose a supramolecular triad consisting of inexpensive and readily available molecular components that can find its implementation in artificial devices for solar energy transduction.

First author: Mudedla, S. K., Computational Study on the Interaction of Modified Nucleobases with Graphene and Doped Graphenes, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 16165, (2014)
Abstract: The interaction between graphene-based nanomaterials and modified nucleobases (MBs) is important in the development and design of new biosensors. The adsorption of MBs on the surface of graphene (G), boron-doped graphene (BG), nitrogen-doped graphene (NG), and silicon-doped graphene (SiG) has been investigated using electronic structure calculations and associated analysis methods. It is found from the calculations that the MBs stack with the surface of G, BG, NG, and SiG models and that the pi-pi stacking interaction plays a dominant role in the stabilization of the intermolecular complexes. The stability of MBs on the surface of SiG is the highest when compared to that of G, BG, and NG models. The highest interaction energies of MBs with SiG is due to the presence of Si center dot center dot center dot O(N) and pi-pi stacking interactions. The theory of atoms in molecules (AIM) analysis indicates that Si center dot center dot center dot O(N) interaction has both electrostatic and covalent characters. The calculation of charge transfer by employing the natural bond orbital method showed the donor nature of MBs. It is also found that the variations in the density of states and highest occupied molecular orbital-lowest unoccupied molecular orbital gap of SiG occur upon adsorption of MBs. These results illustrate that SiG can act as a sensor for the detection of MBs.

First author: Savic, Aleksandar, Synthesis, characterization and cytotoxic activity of novel platinum(II) iodido complexes,EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY, 82, 372, (2014)
Abstract: Novel Pt(II) complexes of general formula [PtI2(L1-3)], (C1-C3): where L1-3 are isobutyl, n-pentyl and isopentyl esters of (S,S)-1,3-propanediamine-N,N’-di-2-(3-cyclohexyl)propanoic acid has been synthesized and characterized by elemental analysis, UV/Vis, IR, (H-1, C-13 and HSQC, Pt) NMR spectroscopy and ESI mass spectrometry. Spectroscopic data and computational studies have shown the usual square planar coordination geometry of synthesized complexes, with coordination of ligands via nitrogen donor atoms. The cytotoxic activity of novel ligands and corresponding complexes were investigated on a palette of different cells line. Complexes C1-C3 exhibited activity comparable to cisplatin, with IC50 values (04) ranging from 4.6 +/- 0.6 to 17.2 +/- 2, and showed the highest potential in HeLa, LS-174 and EA.hy.926 cells. Ligands L1-L3 exhibited two- to four-times less activity than corresponding complexes. Analysis of the mode of action in HeLa cells, by ICP-MS study, showed markedly higher intracellular accumulation and DNA binding affinity of C1-C3 versus cisplatin, after 4 h and 20 h post-treatment. Annexin-V-FITC assay, flow cytometry and fluorescence microscopy study demonstrated occurrence of cell death through both apoptotic and necrotic changes. Tested complexes, at corresponding IC50 concentrations, caused considerable “sub-G1” peak, without other substantial alterations of cell cycle, while only Cl induced higher level of phosphatidylserine externalization (11.7%), comparing to ligand L1 (4.9%) and cisplatin (8.4%). Structure-activity comparison indicated variations of C1-C3 cytotoxicity, related to the drug/ligand lipophilicity (C log P value), while intracellular platinum content and DNA platination increased on increase of length and branching of ester chain, in sequence: Cl (isobutyl) < C2 (n-pentyl) < C3 (isopentyl).

First author: Junold, Konstantin, The Donor-Stabilized Silylene Bis[N,N ‘-diisopropylbenzamidinato(-)] silicon(II): Synthesis, Electronic Structure, and Reactivity, CHEMISTRY-A EUROPEAN JOURNAL, 20, 9319, (2014)
Abstract: A convenient and robust synthesis of bis[N, N’-di-isopropylbenzamidinato(-)] silicon(II) (1), a donor-stabilized silylene, has been developed (35 g scale). To get further information about the reactivity profile of 1, a series of oxidative addition reactions were studied. Treatment of 1 with PhSe-SePh (Se-Se bond activation), C6F6 (C-F activation), and CO2 (C=O activation/cycloaddition) yielded the neutral six-coordinate silicon(IV) complexes 10, 11, and 13, respectively. Treatment of 1 with N2O resulted in the formation of the dinuclear five-coordinate silicon(IV) complex 12 (oxidative addition/dimerization), which contains a four-membered Si2O2 ring. Compounds 10-13 were characterized by NMR spectroscopic studies in the solid state and in solution and by crystal structure analyses. Silylene 1 is three-coordinate in the solid state (from crystal structure analysis) and exists as the four-coordinate isomer 1′ in benzene solution (from computational studies). Based on state-of-the-art relativistic DFT analyses, the four-coordinate species 1′ was demonstrated to be the thermodynamically favored isomer in benzene solution (favored by Delta G=6.6 kcal mol(-1) over the three-coordinate species 1). The reason for this was studied by bonding analyses of 1 and 1′. Furthermore, the 29Si NMR chemical shifts of 1 and 1′ were computed, and in the case of 1′ it was analyzed how this NMR spectroscopic parameter is affected by solvation. These studies further supported the assumption that the silylene is four-coordinate in solution.

First author: Earl, Lyndsey D., Tuning the Extended Structure and Electronic Properties of Gold(I) Thienyl Pyrazolates,INORGANIC CHEMISTRY, 53, 7106, (2014)
Abstract: A series of thienyl pyrazole proligands and gold(l) thienyl pyrazolate cyclic trinuclear complexes (CTCs) have been synthesized. The relationship between the structure and emission properties of bridging thienyl pyrazolates within gold(I) cyclic trinuclear complexes suggests that the nature of dual emission is sensitive to ligand conjugation length. Density functional theory has been used to support the assignment of metal-sensitized, ligand-localized phosphorescence from monothienyl complexes, while low-lying, ligand-localized LUMOs present in bithienyl systems prohibit metal-sensitized phosphorescence. Soluble n-hexyl derivatives have been synthesized to explore the electrochemical properties of gold(I) thienyl pyrazolates CTCs, and conductive electropolymerized thin films were realized.

First author: Pallares, Ivan G., Spectral and Electronic Properties of Nitrosylcobalamin, INORGANIC CHEMISTRY, 53, 7676, (2014)
Abstract: Nitrosylcobalamin (NOCbl) is readily formed when Co(II)-balamin reacts with nitric oxide (NO) gas. NOCbl has been implicated in the inhibition of various B-12-dependent enzymes, as well as in the modulation of blood pressure and of the immunological response. Previous studies revealed that among the known biologically relevant cobalamin species, NOCbl possesses the longest bond between the Co ion and the axially bound 5,6-dimethylbenzimidazole base, which was postulated to result from a strong trans influence exerted by the NO ligand. In this study, various spectroscopic (electronic absorption, circular dichroism, magnetic circular dichroism, and resonance Raman) and computational (density functional theory (DFT) and time-dependent DFT) techniques were used to generate experimentally validated electronic structure descriptions for the “base-on” and “base-off” forms of NOCbl. Further insights into the principal Co ligand bonding interactions were obtained by carrying out natural bond orbital analyses. Collectively, our results indicate that the formally unoccupied Co 3d(z)(2) orbital engages in a highly covalent bonding interaction with the filled NO pi* orbital and that the Co-NO bond is strengthened further by sizable pi-backbonding interactions that are not present in any other Co(Ill)Cbl characterized to date. Because of the substantial NO- to Co(III) charge donation, NOCbl is best described as a hybrid of Co(III)-NO- and Co(II)-NO center dot resonance structures. In contrast, our analogous computational characterization of a related species, superoxocobalamin, reveals that in this case a Co(III)-O-2(-) description is adequate due to the larger oxidizing power of O-2 versus NO. The implications of our results with respect to the unusual structural features and thermochromism of NOCbl and the proposed inhibition mechanisms of B-12-dependent enzymes by NOCbl are discussed.

First author: Chang, Yu-Chang, Alkyl(quinolin-8-yl)phosphine Oxides as Hemilabile Preligands for Palladium-Catalyzed Reactions, ORGANOMETALLICS, 33, 3523, (2014)
Abstract: Preligands of quinolyl-substituted secondary phosphine oxides (SPOs, 2a-d) were prepared and characterized. The unique palladium complex 3, having a distorted-square-pyramidal structure, was obtained from the reaction of 2 equiv of 2c with Pd(COD)Cl-2 or [Pd(mu(2)-Cl)(eta(3)-allyl)](2). In the crystal structure of 3, an apical chloride ligand and a supramolecular tetradentate ligand composed of a deprotonated 2c’ and a neutral 2c’ were resolved (2c’: PA form of 2c). Intriguingly, the gas-phase optimized geometry of 3 converged to a distorted-square-planar structure, which was predicted by density functional calculations. The solid-state distorted-square-pyramidal structure of 3 can only be explained with the consideration of environmental effects (i.e., the electrostatic interactions between the surrounding molecules). As also evidenced by P-31 NMR experiments performed in different deuterated solvents, the crystal structure of 3 is retained in solution. In the crystal structure of 3, a long Pd-Cl bond was analyzed by energy decomposition analysis, showing that the bond is dominated by electrostatic character. Furthermore, application of these SPOs using the Heck reaction shows good reactivity toward common aryl bromides. The hemilabile preligand 2c also tautomerizes to the competent ligand 2c’ for palladium-catalyzed three-component reactions.

First author: Li Qian, Theoretical Studies on the Carrier Transport Properties of Halogen, Cyan Group and N-atom Modified Tetrathiafulvalene Derivatives, CHEMICAL JOURNAL OF CHINESE UNIVERSITIES-CHINESE, 35, 1471, (2014)
Abstract: The density functional theory and hopping model with band theory were employed to calculate the charge carrier transport properties of six planar polycyclic aromatic hydrocarbon fused tetrathiafulvalene (TTF) derivatives. The effects of halogen, cyan substitutions and nitrogen were investigated in details. It was confirmed that the introduction of N-atoms reduced the molecular reorganization energy especially when the N-atoms were modified next to the TTF core. Comparing to the halogen the cyan group modified molecules behave lower reorganization energy and lower frontier energy level. The calculated electron drift mobility of molecule 6 is 1. 15 cm(2) . V-1 . s(-1). More over the molecule maintains the lowest LUMO energy level, implying that the molecule may exhibit good electron transport property. The calculated electron dirft mobility (0. 37 cm(2) . v(-1) . s(-1)) of molecule 2 is very close to hole dirft mobility(0. 34 cm(2) . V-1 . s(-1)), indicating molecule 2 is suitable for bipolar devices. Moreover, the weak interactions of S center dot center dot center dot S, S center dot center dot center dot N and N center dot center dot center dot N between molecules in crystal were inspected. The results show that the introduction of S or N atom contributes to HOMO( or LUMO), leading to an increase of hole(or electron) transport property.

First author: Izarova, Natalya V., The Mixed Gold-Palladium Polyoxo-Noble-Metalate [(NaAu4Pd8O8)-Pd-III-O-II(AsO4)(8)](11-), CHEMISTRY-A EUROPEAN JOURNAL, 20, 8556, (2014)
Abstract: The first fully inorganic, discrete gold-palladium-oxo complex [(NaAu4Pd8O8)-Pd-III-O-II(AsO4)(8)](11-) has been synthesized in aqueous medium. The combination of single-crystal XRD, elemental analysis, mass spectrometry, and DFT calculations allowed establishing the structure and composition of the novel polyanion, and UV/Vis studies suggest that it is stable in neutral aqueous media.

First author: Noodleman, Louis, Linking Chemical Electron Proton Transfer to Proton Pumping in Cytochrome c Oxidase: Broken-Symmetry DFT Exploration of Intermediates along the Catalytic Reaction Pathway of the Iron-Copper Dinuclear Complex, INORGANIC CHEMISTRY, 53, 6458, (2014)
Abstract: After a summary of the problem of coupling electron and proton transfer to proton pumping in cytochrome c oxidase, we present the results of our earlier and recent density functional theory calculations for the dinuclear Fe-a(3)-Cu-B reaction center in this enzyme. A specific catalytic reaction wheel diagram is constructed from the calculations, based on the structures and relative energies of the intermediate states of the reaction cycle. A larger family of tautomers/protonation states is generated compared to our earlier work, and a new lowest-energy pathway is proposed. The entire reaction cycle is calculated for the new smaller model (about 185-190 atoms), and two selected arcs of the wheel are chosen for calculations using a larger model (about 205 atoms). We compare the structural and redox energetics and protonation calculations with available experimental data. The reaction cycle map that we have built is positioned for further improvement and testing against experiment.

First author: Hermann, Markus, Reaction Mechanisms of Small-Molecule Activation by Amidoditetrylynes R2N-EE-NR2 (E = Si, Ge, Sn), INORGANIC CHEMISTRY, 53, 6482, (2014)
Abstract: The calculated reaction profiles using density functional theory at the BP86/TZVPP level for the reaction of small molecules with amidoditetrylynes R2N-EE-NR2 (E = Si, Ge, Sn) are discussed. Four projects are presented that feature the virtue of cooperation between theory and experiment. First, the calculated reaction paths for hydrogenation of the model systems (Me2N)EEL(NMe2) (E = Si, Ge, Sn), which possess E-E single bonds, are examined. The results for the germanium model systems are compared with hydrogenation of the real system (LGeGeL dagger)-Ge-dagger where L-dagger = NAr*(SiMe3) (Ar* = C6H2{C(H)Ph-2}(2)Me-2,6,4). The second project introduced the multiply bonded amidodigermyne (LGeGeL dagger dagger)-Ge-dagger dagger, which carries the extremely bulky substituents L-dagger dagger = N(Ar-dagger dagger)(SiPr3i), where Ar-dagger dagger = C6H2{C(H)Ph-2}(2)Pr-i-2,6,4. The theoretical reaction profile for dihydrogen addition to (LGeGeL dagger dagger)-Ge-dagger dagger is discussed. Hydrogenation gives L-dagger dagger(H)GeGe(H)L-dagger dagger as the product, which is in equilibrium with the hydrido species Ge(H)L-dagger dagger. The latter germanium hydride and tin homologue Sn(H)L-dagger dagger were found to be effective catalysts for hydroboration reactions, which is the topic of the third project. Finally, the calculated reaction course for the reduction of CO2 to CO with the arnidodigermyne LtGeGeLt is discussed.

First author: Herve, Alexandre, U-CN versus Ce-NC Coordination in Trivalent Complexes Derived from M[N(SiMe3)(2)](3) (M = Ce, U), INORGANIC CHEMISTRY, 53, 6995, (2014)
Abstract: Reactions of [MN3*] (M = Ce, U; N* = N(SiMe3)(2)) and NR4CN (R = Me, Et, or Bu-n) or KCN in the presence of 18-crown-6 afforded the series of cyanido-bridged dinuclear compounds [NEt4][(MN3*)(2)(mu-CN)] (M = Ce, 2a, and U, 2b), [K(18-crown-6)(THF)(2)][(CeN3*)(2)(mu-CN)] (2’a), and [K(18-crown-6)][(UN3*)(2)(mu-CN)] (2’b), and the mononuclear mono-, bis-, and tris(cyanide) complexes [NEt4][MN3*(CN)] (M = Ce, 1a(Et), and U, 1b(Et)), [NMe4]-[MN3*(CN)] (M = Ce, 1a(Et), and U, 1b(Et)), [K(18-crown-6)][MN3*(CN)] (M = Ce, 1’a, and U, 1’b), [(NBu4)-Bu-n](2)[MN3*(CN)(2)] (M = Ce, 3a, and U, 3b), [K(18-crown-6)](2)[MN3*(CN)(2)] (M = Ce, 3’a, and U, 3’b), and [(NBu4)-Bu-n](2)[MN2*(CN)(3)] (M = Ce, 4a, and U, 4b). The mono- and bis(cyanide) complexes were found to be in equilibrium. The formation constant of 3’b (K-3,K-b) from l’b at 10 degrees C in THF is equal to 5(1) X 10(-3), and -Delta H-3’b, = 104(2) kJ mol(-1) and -Delta S-3’b, = 330(5) J mol(-1) K-1. The bis(cyanide) compound 3a or 3h was slowly transformed in solution into an equimolar mixture of the mono- and tris(cyanide) derivatives with elimination of (NBu4N)-Bu-n*. The crystal structures of 1a(Me), 1b(Me), 1’a center dot toluene, 1’b center dot toluene, 2’a, 2’b, 3a, 3’a, 3’b, 3’a center dot 2benzene, 3’b center dot 2benzene, 4a center dot 0.5THF, and 4b center dot Et2O were determined. Crystals of the bis(cyanide) uranium complexes 3’b and 3’b center dot 2benzene are isomorphous with those of the cerium counterparts 3’a and 3’a center dot 2benzene, but they are not isostructural since the data revealed distinct coordination modes of the CN group, through the C or N atom to the U or Ce metal center, respectively. This differentiation has been analyzed using density functional theory calculations. The observed preferential coordination of the cyanide and isocyanide ions toward uranium or cerium in the bis(cyanide) complexes is corroborated by the consideration of the binding energies of these groups to the metals and by the comparison of DFT optimized geometries with the crystal structures. The better affinity of the cyanide ligand toward U-III over Ce-III metal center is related to the better energy matching between the 6d/5f uranium orbitals and the cyanide ligand ones, leading to a non-negligible covalent character of the bonding.

First author: Yun, Lin, Synthesis and Reactivity Studies of a Tin(II) Corrole Complex, INORGANIC CHEMISTRY, 53, 7047, (2014)
Abstract: A series of tris(pentafluorophenyl)corrole (TPFC) tin(IV) and tin(II) complexes were prepared and studied by various characterization techniques including H-1, F-19, and Sn-119 NMR and UV-vis spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. The unusual 4-coordinate, monomeric, divalent tin(II) complex [(TPFC)-Sn-II](-) (2a) showed highly efficient reactivity toward alkenes and alkyl halides via a nudeophilic addition pathway leading to the quantitative formation of alkyl stannyl corrole compounds. DFT calculations confirmed the divalent nature of the tin center in 2a, and an NBO analysis showed about 99.99% Sn lone pair character, of which 83.6% was Sn 5s and 16.35% was Sn 5p character.

First author: Steffen, Andreas, Fluorescence in Rhoda- and Iridacyclopentadienes Neglecting the Spin-Orbit Coupling of the Heavy Atom: The Ligand Dominates, INORGANIC CHEMISTRY, 53, 7055, (2014)
Abstract: We present a detailed photophysical study and theoretical analysis of 2,5-bis(arylethynyl)rhodacyclopenta-2,4-dienes (1a-c and 2a-c) and a 2,5-bis(arylethynyl)-iridacyclopenta-2,4-diene (3). Despite the presence of heavy atoms, these systems display unusually intense fluorescence from the Si excited state and no phosphorescence from T-1. The S-1 -> T-1 intersystem crossing (ISC) is remarkably slow with a rate constant of 10(8) s(-1) (i.e., on the nanosecond time scale). Traditionally, for organometallic systems bearing 4d or 5d metals, ISC is 2-3 orders of magnitude faster. Emission lifetime measurements suggest that the title compounds undergo S-1 -> T-1 interconversion mainly via a thermally activated ISC channel above 233 K. The associated experimental activation energy is found to be Delta H-ISC(double dagger) = 28 kJ mol(-1) (2340 cm(-1)) for 1a, which is supported by density functional theory (DFT) and time-dependent DFT calculations [Delta H-ISC(double dagger)(calc.) = 11 kJ mol(-1) (920 cm(-1)) for 1a-H]. However, below 233 K a second, temperature-independent ISC process via spin-orbit coupling occurs. The calculated lifetime for this S-1 -> T-1 ISC process is 1.1 s, indicating that although this is the main path for triplet state formation upon photoexcitation in common organometallic luminophores, it plays a minor role in our Rh compounds. Thus, the organic pi-chromophore ligand seems to neglect the presence of the heavy rhodium or iridium atom, winning control over the excited-state photophysical behavior. This is attributed to a large energy separation of the ligand-centered highest occupied molecular orbital (HOMO) and lowest unoccupied MO (LUMO) from the metal-centered orbitals. The lowest excited states S-1 and T-1 arise exclusively from a HOMO-to-LUMO transition. The weak metal participation and the cumulenic distortion of the T-1 state associated with a large S-1-T-1 energy separation favor an “organic-like” photophysical behavior.

First author: Weymuth, Thomas, Inverse Quantum Chemistry: Concepts and Strategies for Rational Compound Design,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 114, 823, (2014)
Abstract: The rational design of molecules and materials is becoming more and more important. With the advent of powerful computer systems and sophisticated algorithms, quantum chemistry plays a decisive role in the design process. While traditional quantum chemical approaches predict the properties of a predefined molecular structure, the goal of inverse quantum chemistry is to find a structure featuring one or more desired properties. Herein, we review inverse quantum chemical approaches proposed so far and discuss their advantages as well as their weaknesses.

First author: Weymuth, Thomas, Gradient-Driven Molecule Construction: An Inverse Approach Applied to the Design of Small- Molecule Fixating Catalysts, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 114, 838, (2014)
Abstract: Rational design of molecules and materials usually requires extensive screening of molecular structures for the desired property. The inverse approach to deduce a structure for a predefined property would be highly desirable, but is, unfortunately, not well defined. However, feasible strategies for such an inverse design process may be successfully developed for specific purposes. We discuss options for calculating jacket potentials that fulfill a predefined target requirementa concept that we recently introduced (Weymuth and Reiher, MRS Proceedings 2013, 1524, DOI:10.1557/opl.2012.1764). We consider the case of small-molecule activating transition metal catalysts. As a target requirement we choose the vanishing geometry gradients on all atoms of a subsystem consisting of a metal center binding the small molecule to be activated. The jacket potential can be represented within a full quantum model or by a sequence of approximations of which a field of electrostatic point charges is the simplest. In a second step, the jacket potential needs to be replaced by a chemically viable chelate-ligand structure for which the geometry gradients on all of its atoms are also required to vanish. To analyze the feasibility of this approach, we dissect a known dinitrogen-fixating catalyst to study possible design strategies that must eventually produce the known catalyst.

First author: Liu, Hongguang, Adjusting the Local Arrangement of pi-Stacked Oligothiophenes through Hydrogen Bonds: A Viable Route to Promote Charge Transfer, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 2320, (2014)
Abstract: We show that substituting quaterthiophene cores with strong H-bond aggregators, such as urea groups, provides an efficient way to adjust the mutual in-plane displacements of the semiconducting units and promote charge transfer. Our 2-D structure-property mapping reveals that the insertion of substituents induces up to 2.0 angstrom longitudinal and transversal displacements between the pi-conjugated moieties. Some of these relative displacements lead to improved cofacial orbital overlaps that are otherwise inaccessible due to Pauli repulsion. Our results also emphasize that the fine-tuning of in-plane displacements is more effective than achieving “tighter” packing to promote charge-transfer properties.

First author: Fihey, Arnaud, Density Functional Theory Study of the Conformation and Optical Properties of Hybrid Au-n-Dithienylethene Systems (n=3, 19, 25), JOURNAL OF PHYSICAL CHEMISTRY A, 118, 4695, (2014)
Abstract: We present a theoretical study of Au-n-dithienylethene hybrid systems (n = 3, 19, 25), where the organic molecule is covalently linked to a nanometer-scaled gold nanoparticle (NP). We aim at gaining insights on the optical properties of such photochromic devices and proposing a size-limited gold aggregate model able to recover the optical properties of the experimental system. We thus present a DFT-based calculation scheme to model the ground-state (conformation, energetic parameters) and excited-state properties (UV-visible absorption spectra) of this type of hybrid systems. Within this framework, the structural parameters (adsorption site, orientation, and internal structure of the photochrome) are found to be slightly dependent on the size/shape of the gold aggregate. The influence of the gold fragment on the optical properties of the resulting hybrid system is then discussed with the help of TD-DFT combined with an analysis of the virtual orbitals involved in the photochromic transitions. We show that, for the open hybrid isomer, the number of gold atoms is the key parameter to recover the photoactive properties that are experimentally observed. On the contrary, for hybrid closed systems, the three-dimensional structure of the metallic aggregate is of high impact. We thus conclude that Au-25 corresponds to the most appropriate fragment to model nanometer-sized NP-DTE hybrid device.

First author: Heshmat, Mojgan, The Importance of Large-Amplitude Motions for the Interpretation of Mid-Infrared Vibrational Absorption and Circular Dichroism Spectra: 6,6 ‘-Dibromo-[1,1 ‘-binaphthalene]-2,2 ‘-diol in Dimethyl Sulfoxide,JOURNAL OF PHYSICAL CHEMISTRY A, 118, 4766, (2014)
Abstract: Using the 6,6′-dibromo-[1,1′-binaphthalene]-2,2′-diol molecule and its vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra measured in deuterated dimethyl sulfoxide as example, we present a first detailed study of the effects induced in VCD spectra by the large-amplitude motions of solvent molecules loosely bound to a solute molecule. We show that this type of perturbation can induce significant effects in the VA and VCD spectra. We also outline a computational procedure that can effectively model the effects induced in the spectra and at the same time provide detailed structural information regarding the relative orientations of moieties involved in a solute solvent molecular complex.

First author: Batiste, Laurent, Coinage-Metal Mediated Ring Opening of cis-1,2-Dimethoxycyclopropane: Trends from the Gold, Copper, and Silver Fischer Carbene Bond Strength, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 9296, (2014)
Abstract: N-heterocyclic carbene (NHC) supported coinage metal cations proved to react in the gas phase with the electron-rich cis-1,2-dimethoxycyclopropane. Upon Collision Induced Dissociation (CID), several spectrometric fragment-ion signals were observed, one corresponding to the recovery of the bare cation IMes-M+ (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and the second to the methoxymethylidene metal complex IMes-M-[HCOCH3](+). The gold and copper complexes appear to stabilize the carbene sufficiently enough to promote the latter channel. On the contrary, the silver complex binds weakly to the methoxymethylidene moiety as observed by the predominance of the bare cation IMes-M+ channel. Density Functional Theory (DFT) investigations of the Potential Energy Surface and Bond Energy Decomposition Analyses provided results that correlate well with the experimental data. In the case of the bare cation channel, two distinct reaction pathways were found: a straightforward decoordination of the cydopropane and a cationic rearrangement of the three-membered ring into a dimethoxypropylene isomer before dissociation. However, for the abstraction of the methoxymethylidene moiety by the metal cation, only one pathway was found. In analogy to earlier studies by other groups, we found the trend Au > Cu > Ag for the metal carbene bond strength.

First author: Morales-Verdejo, Cesar, Novel mono- and heterobimetallic chromium-nickel s-indacene complexes: synthesis, characterization, and DFT studies, CANADIAN JOURNAL OF CHEMISTRY, 92, 677, (2014)
Abstract: The preparation of a novel heterobimetallic chromium-nickel compound (3), including 2,6-diethyl-4,8-dimethyl-5-hydroindacenide (IcH’) as bridging ligand was successfully achieved and it was characterized by means of H-1 NMR, C-13 NMR, and FT-IR spectroscopies and elemental analysis. Cyclic voltammetry studies were performed for complex 3 as well as for its respective mononuclear species. Theoretical calculations of this compound were carried out to gain further understanding of this novel molecular system.

First author: Holzmann, Nicole, Bonding Situation in Dimeric Group 15 Complexes [(NHC)(2)(E-2)] (E = N-Bi),ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES, 69, 385, (2014)
Abstract: Quantum chemical calculations using density functional theory at the BP86 level in conjunction with triple-zeta polarized basis sets have been carried out for the title compounds. The nature of the bonding between the diatomic fragment and the NHC ligands is investigated with an energy decomposition analysis. The chemical bonds in the [(NHCMe)(2)(E-2)] complexes can be discussed in terms of donor acceptor interactions which consist of two NHCMe -> E-2 <- NHCMe donor components and two weaker components of the NHCMe <- E-2 -> NHCMe pi backdonation. The out-of-phase (+)/(-) contribution of the a donation is always stronger than the in-phase (+)/(+) contribution. The electronic reference state of N-2 in the dinitrogen complex [(NHCMe)(2)(N-2)] is the highly excited 1(1)Gamma(g) state which explains the anti-periplanar arrangement of the ligands. The gauche arrangement of the ligands in the heavier homologues [(NHCMe)(2)(E-2)] (E = P-Bi) may be discussed using either the excited 1(1)Gamma(g) state or the X-1 Sigma(+)(g): ground state of E-2 as reference states for the donor acceptor bonds. The EDA-NOCV calculations suggest that the latter bonding model is better suited for the complexes where E = As-Bi while the phosphorus complex is a borderline case.

First author: Galembeck, Sergio E., Effects of the protonation state in the interaction of an HIV-1 reverse transcriptase (RT) amino acid, Lys101, and a non nucleoside RT inhibitor, GW420867X, JOURNAL OF MOLECULAR MODELING, 20, 385, (2014)
Abstract: Interactions between an inhibitor and amino acids from a binding pocket could help not only to understand the nature of these interactions, but also to support the design of new inhibitors. In this paper, we explore the key interaction between a second generation non-nucleoside reverse transcriptase inhibitor (NNRTI), GW420867X, and HIV-1 RT amino acid Lys101 (K101), by quantum mechanical methods. The neutral, protonated, and zwitterionic complexes of GW420867X-K101 were studied. The interaction energies were determined by SCS-MP2/def2-cc-pVQZ, and the electron density was analyzed by natural bond orbital (NBO), atoms in molecules (AIM) and reduced gradient analysis. A large increase in the interaction was observed with the tautomerization of neutral or neutral protonated species. The monomers interact by two medium-strength hydrogen bonds, one partially covalent and another noncovalent. There are some van der Waals intramolecular interactions that are topologically unstable. The nature of the intermolecular interactions was also analyzed using quantitative molecular orbital (MO) theory in combination with an energy decomposition analysis (EDA) based on dispersion-corrected density functional theory (DFT) at BLYP-D/TZ2P.

First author: Swasey, Steven M., Chiral Electronic Transitions in Fluorescent Silver Clusters Stabilized by DNA, ACS NANO, 8, 6883, (2014)
Abstract: Fluorescent, DNA-stabilized silver clusters are receiving much attention for sequence-selected colors and high quantum yields. However, limited knowledge of duster structure is constraining further development of these “Ag-N-DNA’ nanomaterials. We report the structurally sensitive, chiroptical activity of four pure Ag-N-DNA with wide ranging colors. Ubiquitous features in circular dichroism (CD) spectra include a positive dichroic peak overlying the lowest energy absorbance peak and highly anisotropic, negative dichroic peaks at energies well below DNA transitions. Quantum chemical calculations for bare chains of silver atoms with nonplanar curvature also exhibit these striking features, Indicating electron flow along a chiral, filamentary metallic path as the origin for low-energy AgN-DNA transitions. Relative to the bare DNA, marked UV changes in CD spectra of AgN-DNA and silver cation DNA solutions indicate that ionic silver content constrains nucleobase conformation. Changes in solvent composition alone can reorganize cluster structure, reconfiguring chiroptical properties and fluorescence.

First author: La Pierre, Henry S., Synthesis and Characterization of a Uranium(II) Monoarene Complex Supported by delta Backbonding, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53, 7158, (2014)
Abstract: The low-temperature (< -35 degrees C) reduction of the trivalent uranium monoarene complex [{((ArO)-Ar-Ad,Me)(3)mes} U] (1), with potassium spheres in the presence of a slight excess of 2.2.2-cryptand, affords the quantitative conversion of 1 into the uranium(II) monoarene complex [K(2.2.2-crypt)]-[(((ArO)-Ar-Ad,Me)(3)mes) U] (1-K). The molecular and electronic structure of 1-K was established experimentally by single-crystal X-ray diffraction, variable-temperature H-1 NMR and X-band EPR spectroscopy, solution-state and solid-state magnetism studies, and optical absorption spectroscopy. The electronic structure of the complex was further investigated by DFT calculations. The complete body of evidence confirms that 1-K is a uranium(II) monoarene complex with a 5f (4) electronic configuration supported by delta backbonding and that the nearly reversible, room-temperature reduction observed for 1 at -2.495 V vs. Fc/Fc(+) is principally metal-centered.

First author: Faucher, Alexandra, Feasibility of arsenic and antimony NMR spectroscopy in solids: An investigation of some group 15 compounds, SOLID STATE NUCLEAR MAGNETIC RESONANCE, 61-62, 54, (2014)
Abstract: The feasibility of obtaining As-75 and Sb-121/123 NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been / measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, Sb-121/123 NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured As-75 and Sb-121 nuclear quadrupole coupling constants, CQ(As-75)=7.8 MHz and Cd 121 Sb)= 159 MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of As-75 and Sb-121 NMR spectra (at 154 and 215 MHz, respectively, i.e., at Bo= 21.14 T) with linewidths in excess of 1 MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).

First author: Freitag, Roxanne, X-Ray Diffraction and DFT Calculation Elucidation of the Jahn-Teller Effect Observed in Mn(dibenzoylmethanato)(3), JOURNAL OF CHEMICAL CRYSTALLOGRAPHY, 44, 352, (2014)
Abstract: The crystal structure of Mn(dibenzoylmethanato)(3), solved by X-ray diffraction at 100 K, showed elongation Jahn-Teller distortion, i.e. elongation of the two Mn-O bonds along the z-axis. DFT calculations were used to understand and visualize the elongation and compression Jahn-Teller distortion of Mn(dibenzoylmethanato)(3.)TOC entry: Structure, computational chemistry and Jahn-Teller distortion of Mn(PhCOCHCOPh)(3).

First author: Jacob, Christoph R., Subsystem density-functional theory, WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE, 4, 325, (2014)
Abstract: Subsystem density-functional theory (subsystem DFT) has developed into a powerful alternative to Kohn-Sham DFT for quantum chemical calculations of complex systems. It exploits the idea of representing the total electron density as a sum of subsystem densities. The optimum total density is found by minimizing the total energy with respect to each of the subsystem densities, which breaks down the electronic-structure problem into effective subsystem problems. This enables calculations on large molecular aggregates and even (bio-) polymers without system-specific parameterizations. We provide a concise review of the underlying theory, typical approximations, and embedding approaches related to subsystem DFT such as frozen-density embedding (FDE). Moreover, we discuss extensions and applications of subsystem DFT and FDE to molecular property calculations, excited states, and wave function in DFT embedding methods. Furthermore, we outline recent developments for reconstruction techniques of embedding potentials arising in subsystem DFT, and for using subsystem DFT to incorporate constraints into DFT calculations.

First author: Pantazis, Dimitrios A., All-electron basis sets for heavy elements, WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE, 4, 363, (2014)
Abstract: All-electron (AE) calculations for chemical systems containing atoms of elements beyond krypton are becoming increasingly accessible and common in many fields of computational molecular science. The type, the size, and the internal construction of AE basis sets for heavy elements depend critically on the level of quantum chemical theory and, most importantly, on the way relativistic effects are treated. For this reason, general-purpose basis sets for heavy elements are rare; instead, different AE basis sets have been developed that are adapted to the requirements and peculiarities of each (approximate) relativistic treatment. Ranging from fully relativistic four-component approaches to more popular scalar relativistic approximations, today there exist complete families of AE basis sets that can cover most research needs and can be employed in diverse applications for the proper description of various molecular and atomic properties including electronic structure, chemical reactivity, and a wide range of spectroscopic parameters.

First author: Nithya, R., Charge transport and optical properties of cross-conjugated organic molecules: A theoretical study, ORGANIC ELECTRONICS, 15, 1607, (2014)
Abstract: The structure, charge transport and optical properties of two-dimensional cruciform molecules 1,4-distyryl-2,5-bis(arylethynyl)benzenes, 1,4-distyryl-2,5-bis(arylethynyl)pyridines and 1,4-bis(ethylenediyl)dipyridine-2,5-bis(benzene) have been studied using density functional theory methods. The effective charge transfer integral and site energy corresponding to hole and electron transports in the above molecules were calculated directly from the matrix elements of Kohn-Sham Hamiltonian. The charge carrier mobility on the cruciform molecules was calculated using Monte Carlo simulation based on the Marcus rate theory and the results show that these cruciform molecules are the p-type organic semiconductors. The excited state calculations were performed using the time-dependent density functional theory method in gas phase, hexane and dichloromethane mediums. The trifluoromethyl substituted 1,4-distyryl-2,5-bis(arylethynyl)benzenes molecule possesses the maximum absorption and emission wavelength of 443 and 504 nm, respectively in dichloromethane medium.

First author: Safa, Muhieddine, Chelating imidazole ligands promote oxidative addition in dimethylplatinum(II) complexes,JOURNAL OF ORGANOMETALLIC CHEMISTRY, 761, 42, (2014)
Abstract: The oxidative addition chemistry of the complexes [PtMe2{(mim)(2)C=CH2}], 1, and [PtMe2{(-mim)(2)CHMe}], 2, where mim = N-methylimidazol-2-yl, is described. Complex 1 undergoes oxidative addition with alkyl halides RX to give [PtXRMe2{(mim)(2)C = CH2}], X = I, R = Me; X = Br, R = CH2Ph, CH2C6H4-4-CF3, CH2C6H4-2-CF3, CH2C6H3-3,5-t-Bu-2; X = Cl, R = CH2Cl, and with hydrogen peroxide to give [Pt(OH)(2)Me-2{(mim)(2)C=CH2}]. Complex 2 undergoes oxidative addition with alkyl halides RX to give [PtXRMe2{(mim)(2)CHMe}], X = I, R = Me; X = Br, R = CH2C6H4-4-CF3, CH2C6H4-2-CF3, and with iodine and hydrogen peroxide to give [PtX2Me2{(mim)(2)CHMe}], X=I or OH. The stereochemistry of the reaction has been determined in each case, and several complexes have been structurally characterized. The high reactivity of complexes 1 and 2 towards oxidative addition is rationalized in terms of the strong donating property of the imidazolyl ligands, as supported by theoretical (DFT) studies.

First author: Thirumoorthi, Ramalingam, Experimental and computational investigations of arsenic(III) and phosphorus(III) complexes of bis(diphenylthiophosphinoyl) methanediide, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 761, 93, (2014)
Abstract: The reactions of Li-2[C(PPh2S)(2)] with EI3 (E = As, P) have been investigated in order to determine the nature of the coordination mode between the methanediide ligand and lighter pnictogens. Treatment of this reagent in toluene with AsI3 in a 1: 1 M ratio produces the heteroleptic complex AsI[C(PPh2S)(2)] (2a), which was characterized by multinuclear NMR spectra and by a crystal structure determination. Attempts to isolate the phosphorus analogue PI[C(PPh2S)(2)] (2b) were unsuccessful. The dianionic methanediide ligand [C(PPh2S)(2)](2-) in 2a is S,C,S-coordinated to the As-III centre. The lengths of the weak As-S bonds differ markedly (2.852(2) and 2.443(2) angstrom) and the As-C bond distance 1.864(6) angstrom falls midway between single and double bond values. DFT calculations for AsI[C(PPh2S)(2)] reveal that the structure with a symmetrically coordinated ligand is lower in energy than the experimental structure by only 8.3 kJ mol(-1) suggesting that the stabilization of the latter in the solid state is due to packing effects. The calculated bond orders for the M-C bond in MI[C(PPh2S)(2)] are 1.23 (M = As) and 1.31 (M = P). The pi M-C interaction is predicted to be significantly stronger in the corresponding cations [M{C(PPh2S)(2)}](+) with bond orders of 1.68 (M = As) and 1.75 (M = P).

First author: Kauch, Malgorzata, What Factors Influence the Metal-Proton Spin-Spin Coupling Constants in Mercury- and Cadmium-Substutited Rubredoxin?, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 4471, (2014)
Abstract: The indirect metal proton spin spin coupling constants between protons in cysteine groups and the mercury or cadmium nucleus have been calculated for a small model of Me rubredoxin complex (Me = Cd, Hg) by means of density functional theory with zeroth-order regular approximation Hamiltonian (DFT-ZORA). The calculated spin spin coupling constants, in spite of the moderate size of the model system, are in good agreement with the values measured in NMR experiment, which are in the 0.29-0.56 Hz range for the Cd complex and in the 0.57-2.20 Hz range for the Hg complex. The robustness of the chosen method has been verified by calculations with a number of different exchange-correlation functionals and basis sets. Additionally, it has been shown that the short- and long-distance metal proton coupling constants are affected mainly by the values of the metal-proton distance and the H-N-C-C dihedral angle.

First author: Kanoun, Mohammed Benali, Quantifying the Impact of Relativity and of Dispersion Interactions on the Activation of Molecular Oxygen Promoted by Noble Metal Nanoparticles, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 13707, (2014)
Abstract: We compared the mechanism of O-2 dissociation catalyzed by Cu-38, Ag-38, and Au-38 nanoparticles. Overall, our results indicate that O-2 dissociation is extremely easy on Cu-38, with an almost negligible barrier for the O-O breaking step. It presents an energy barrier close to 20 kcal/mol on Ag-38, which decreases to slightly more than 10 kcal/mol on Au-38. This behavior is analyzed to quantify the impact of relativity and of dispersion interactions through a comparison of nonrelativistic, scalar-relativistic, and dispersion-corrected DFT methods. Nonrelativistic calculations show a clear trend down the triad, with larger in size nanoparticle (NP), weaker O-2 adsorption energy, and higher O-2 dissociation barrier, which is so high for Au-38 to be in sharp contrast with the mild conditions used experimentally. Inclusion of relativity has no impact on the O-2 adsorption energy, but it reduces the energy barrier for O-2 dissociation on Au-38 from 30.1 to 11.4 kcal/mol, making it even lower than that on Ag-38 and consistent with the mild conditions used experimentally. Dispersion interactions have a remarkable role in improving the adsorption ability of O-2 on the heavier Ag-38 and especially Au-38 NPs, contributing roughly 50% of the total adsorption energy, while they have much less impact on O-2 adsorption on Cu-38.

First author: Turek, Jan, Palladium(II) Complexes of 1,2,4-Triazole-Based N-Heterocyclic Carbenes: Synthesis, Structure, and Catalytic Activity, ORGANOMETALLICS, 33, 3108, (2014)
Abstract: Six palladium(II) complexes bearing three different triazole-based N-heterocyclic carbene (NHC) ligands, [1-tert-butyl-4-{2-[(N,N-dimethylamino)methyl]phenyl}-3-phenyl-1H-1,2,4- triazol-4-ium-5-ide, 1-tert-butyl-4-(2-methoxyphenyl)-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide, and 1-tert-butyl-4-(4-methylphenyl)-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide], were synthesized and fully characterized. NMR spectroscopy and X-ray diffraction analysis revealed that the amino-group-substituted NHC ligand is coordinated in bidentate fashion, forming a monocarbene chelate complex with an additional intramolecular Pd <- N bond with the nitrogen donor atom. The 4-methylphenyl- and 2-methoxyphenyl-substituted NHC ligands coordinate as C-monodentate donors, forming simple biscarbene Pd(II) complexes. The evaluation of the catalytic performance in the Suzuki-Miyaura cross-coupling reaction revealed very promising performance of the intramolecularly coordinated monocarbene complexes under relatively mild conditions even in direct comparison with the commercially available PEPPSI catalyst. In contrast, the biscarbene complexes proved inactive in this catalytic process. According to theoretical calculations (EDA and NOCV analysis), functionalization of the 1,2,4-triazole-based NHC with the 2-[(N,N-dimethylamino)methyl]phenyl group has a significant effect on the stability of the NHC metal bond.

First author: Jimenez-Izal, Elisa, Doped Aluminum Cluster Anions: Size Matters, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 4309, (2014)
Abstract: The global minima of the cluster anions with the generic chemical formula (XAl12)(2-), where X = Be, Mg, Ca, Sr, Ba, and Zn, are determined by an extensive search of their potential energy surfaces using the Gradient Embedded Genetic Algorithm (GEGA). All the characterized global minima have an icosahedral-like structure, resembling that of the Al-13(-) cluster. These cages comprise closed-shell electronic configurations with 40 electrons, therefore, in accordance to the jellium model, they are predicted to be highly stable and amenable to experimental detection. The two preferred sites for the dopant species, at the center and at surface of the icosahedral cage, are stabilized depending on the atomic radius of X Thus, while the small dopants (X = Be, Zn) sit preferably at the center of the cage, the preferred site for X = Mg, Ca, Sr, and Ba is at the surface. Since these dianions are not stable towards electron detachment, one Li cation is added in order to yield stable systems. Our computations show that in the global minimum form of Li(XAl12), the lithium cation, ionically bonded to the Al atoms, does not change the structure of the (XAl12)2 core.

First author: Passarello, Marco, Importance of C*-H Based Modes and Large Amplitude Motion Effects in Vibrational Circular Dichroism Spectra: The Case of the Chiral Adduct of Dimethyl Fumarate and Anthracene, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 4339, (2014)
Abstract: The role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbox ylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths.

First author: Li, Peng, Gas- Phase Water Activation by Th Atom: Reaction Mechanisms and Topological Analysis,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 114, 760, (2014)
Abstract: Density functional theory calculations were performed to investigate the gas-phase reaction of Th atom with water. Three reaction pathways were identified, which leads to the formation of ThOH + H, ThO + H-2, and H2ThO. The latter two are generated via the intermediate HThOH, and the H2ThO specie is generated from the isomerization of the HThOH intermediate. A thorough description of the reaction mechanism taking into account different possible spin states together with analysis of the electronic factors offer insights into the reactivity of the actinides atom. The obtained results are compared with the available experimental data. The three reaction pathways were found to be exothermic, in which the isomerization channel was observed with best thermochemical conditions around 123.9 kcal/mol. The nature of the chemical bonding evolution along the reaction pathways was studied using topological analysis including electron localization function, atoms-in-molecules, and natural bond orbital.

First author: Tanaka, Mie, Electronic Structures of Platinum(II) Complexes with 2-Arylpyridine and 1,3-Diketonate Ligands: A Relativistic Density Functional Study on Photoexcitation and Phosphorescent Properties, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 12443, (2014)
Abstract: The electronic structures of heteroleptic cyclometalated platinum(II) complexes a-f with 2-arylpyridine derivatives and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione which are candidate materials for phosphorescent organic electroluminescent diodes (OLEDs) were theoretically investigated using relativistic density functional theory (DFT) calculations including spin-orbit effects. The electronic excitation bands and phosphorescent emission wavelengths of the complexes were theoretically calculated and compared with the corresponding experimental results. It was theoretically confirmed that the color of the phosphorescent emission is controlled by the pi-pi* electronic excited state localized on each 2-arylpyridine derivative ligand. Our calculations also gave good predictions for spectral red shifts originating from excimer formations for a-f.

First author: Berkefeld, Andre, Silicon alpha-Effect: A Systematic Experimental and Computational Study of the Hydrolysis of C-alpha- and C-gamma-Functionalized Alkoxytriorganylsilanes of the Formula Type ROSiMe2(CH2)(n)X (R = Me, Et; n=1, 3; X = Functional Group), ORGANOMETALLICS, 33, 2721, (2014)
Abstract: To understand the silicon alpha-effect in terms of an enhanced reactivity of the Si-OC bond of alpha-silanes of the formula type ROSiMe2CH2X compared to analogous gamma-silanes ROSiMe2(CH2)(3)X (R = Me, Et; X = functional group), a systematic experimental and computational study of the kinetics and mechanisms of hydrolysis of such compounds was performed. For this purpose, a series of suitable model compounds was synthesized and studied for their hydrolysis kinetics in CD3CN/D2O under basic and acidic conditions, using H-1 NMR spectroscopy as the analytical tool. To get more information about the reaction mechanisms, the experimental investigations were complemented by computational studies. These investigations demonstrated that the silicon alpha-effect cannot be rationalized in terms of a special single effect. The reactivities observed rather result from a summation of different components, such as electronic and steric effects, pD dependence, and hydrogen bonds between the functional group (or even protonated functional group) and the alkoxy leaving group. Therefore, the term “silicon alpha-effect” should not be used furthermore to explain the hydrolysis reactivity at the silicon atom of alkoxyorganylsilanes with functional groups in alpha- or gamma-position of the organyl groups (so-called alpha- or gamma-silanes).

First author: Marcos, Enrique, Effect of the Meso-Substituent in the Huckel-to-Mobius Topological Switches, JOURNAL OF ORGANIC CHEMISTRY, 79, 5036, (2014)
Abstract: Expanded porphyrins have emerged as a new promising class of molecules for the creation of new Huckel-to-Mobius topological switches with distinct aromaticities and magnetic and electric properties. In this work, we report a theoretical investigation of the conformational switch between the Huckel planar and the singly twisted Mobius structure for eight different meso-substituted [28]-hexaphyrins (with different steric effects and electron-withdrawing and -releasing character). Our results show how a change in the nature of the meso-substituent is able to turn an endothermic interconversion process with a high energy barrier into an exothermic and almost barrierless Huckel-Mobius transition. We also provide a thorough analysis of the main factors (aromaticity, intramolecular hydrogen bonds, ring strain, and steric effects) that play a role in this interconversion process. Overall, these results are very relevant to find new ways to control the thermochemistry and kinetics of these topological switches and even “freeze” the switch in the desired Mobius or Huckel conformation.

First author: Janssen, Guido V., Diastereoselective One-Pot Synthesis of Tetrafunctionalized 2-Imidazolines, JOURNAL OF ORGANIC CHEMISTRY, 79, 5219, (2014)
Abstract: A convenient trans-selective one-pot synthesis of tetrafunctionalized 2-imidazolines is described. Our approach to these valuable heterocyclic scaffolds involves a formal 1,3-dipolar cycloaddition between nitrile ylides or nitrilium triflates and imines. A detailed experimental study in combination with a high-level computational exploration of reaction routes reveals a plausible reaction pathway that accounts for the observed diastereoselectivity.

First author: Hayashi, Sachio, Theoretical Investigation on the Optical Properties of Diphosphine-protected Au-8 Cluster Complexes, CHEMISTRY LETTERS, 43, 880, (2014)
Abstract: Herein, we have theoretically investigated the optical properties of the two Au-8 complexes with different shapes of the Au-8 cluster core. From the results of TD-DFT and DFT calculations, it was found that the shape of the Au-8 clusters in the two Au-8 complexes greatly influenced their optical properties, such as absorption and photoluminescence spectra. In particular, the intensities of their photoluminescence spectra are greatly decreased with an increase of the Au-Au bond length variation of the Au core cluster in the S-1 states of the Au-8 complexes.

First author: Gorczak, Natalie, Different Mechanisms for Hole and Electron Transfer along Identical Molecular Bridges: The Importance of the Initial State Delocalization, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 3891, (2014)
Abstract: We report measurements of hole and electron transfer along identical oligo-p-phenylene molecular bridges of increasing length. Although the injection barriers for hole and electron transfer are similar, we observed striking differences in the distance dependence and absolute magnitude of the rates of these two processes. Electron transfer is characterized by an almost distance-independent, fast charge-transfer rate. Hole transfer presents a much slower rate that decreases significantly with the length of the bridge. Time-dependent density functional calculations show that the observed differences can be explained by the delocalization of the respective initial excitation. The evaluation of the initial state is therefore essential when comparing charge-transfer rates between different donor-bridge-acceptor systems.

First author: Lobello, Maria Grazia, Design of Ru(II) sensitizers endowed by three anchoring units for adsorption mode and light harvesting optimization, THIN SOLID FILMS, 560, 86, (2014)
Abstract: We report the design, synthesis and computational investigation of a class of Ru(II)-dyes based on mixed bipyridine ligands for use in dye-sensitized solar cells. These dyes are designed to preserve the optimal anchoring mode of the prototypical N719 sensitizer by three carboxylic groups, yet allowing for tunable optimization of their electronic and optical properties by selective substitution at one of the 4-4′ positions of a single bipyridine ligand with pi-excessive heteroaromatic groups. We used Density Functional Theory/Time Dependent Density Functional Theory calculations to analyze the electronic structure and optical properties of the dye and to investigate the dye adsorption mode on a TiO2 nanoparticle model. Our results show that we are effectively able to introduce three carboxylic anchoring units into the dye and achieve at the same time an enhanced dye light harvesting, demonstrating the design concept. As a drawback of this type of dyes, the synthesis leads to a mixture of dye isomers, which are rather tedious to separate.

First author: Hernandez, Dayan Paez, Magnetic properties of a fourfold degenerate state: Np4+ ion diluted in Cs2ZrCl6 crystal, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 194, 74, (2014)
Abstract: The magnetic properties of the octahedral cluster NpCl62- diluted in Cs2ZrCl6 crystal have been calculated using a first principle method, SO-CASPT2. The spin Hamiltonian parameters modeling the fourfold degenerate ground state are extracted from calculations according to a first principle procedure. The agreement with the model parameters issued from experimental EPR data is good. The spin and orbital contributions to the model parameters are evaluated. Calculations are compared to crystal field theory at the different steps of calculations: while this theory is a very good framework to explain the main magnetic behavior, it is shown that it is not able to render precisely all the small effects.

First author: Elkechai, Aziz, Redox properties of biscyclopentadienyl uranium(V) imido-halide complexes: a relativistic DFT study, JOURNAL OF MOLECULAR MODELING, 20, 74, (2014)
Abstract: Calculations of ionization energies (IE) and electron affinities (EA) of a series of biscyclopentadienyl imidohalide uranium(V) complexes Cp* U-2(=N-2,6-Pr-i(2)-C6H3)(X) with X=F, Cl, Br, and I, related to the U-IV/U-V and U-V/U-VI redox systems, were carried out, for the first time, using density functional theory (DFT) in the framework of the relativistic zeroth order regular approximation (ZORA) coupled with the conductor-like screening model (COSMO) solvation approach. A very good linear correlation (R-2=0.993) was obtained, between calculated ionization energies at the ZORA/BP86/TZP level, and the experimental half-wave oxidation potentials E-1/2. A similar linear correlation between the computed electron affinities and the electrochemical reduction U-IV/U-III potentials (R-2=0.996) is obtained. The importance of solvent effects and of spin-orbit coupling is definitively confirmed. The molecular orbital analysis underlines the crucial role played by the 5f orbitals of the central metal whereas the Nalewajski-Mrozek (N-M) bond indices explain well the bond distances variations following the redox processes. The IE variation of the complexes, i.e., IE(F)<ie(cl)<ie(br)<ie(i) is=”” also=”” well=”” rationalized=”” considering=”” the=”” frontier=”” mo=”” diagrams=”” of=”” these=”” species.=”” finally,=”” this=”” work=”” confirms=”” relevance=”” hirshfeld=”” charges=”” analysis=”” which=”” bring=”” to=”” light=”” an=”” excellent=”” linear=”” correlation=”” (r-2=”0.999)” between=”” variations=”” uranium=”” and=”” e-1=”” 2=”” in=”” reduction=”” process=”” u-v=”” species.<=”” p=””>

First author: Jimenez-Izal, Elisa, CdS nanoclusters doped with divalent atoms, JOURNAL OF MOLECULAR MODELING,20, 74, (2014)
Abstract: ZnS and CdS small nanoclusters have been predicted to trap alkali metals and halogen atoms. However would this kind of nanocompounds be able to encapsulate dianions and dications? This would be very interesting from an experimental point of view, since it would allow the isolation of such divalent ions. Moreover, the resulting endohedral complexes would serve as building blocks for new cluster-assembled materials, with enhanced stability arising from the electrostatic interaction between the incarcerated ions. In this work we have studied the structure and stability of (X@(CdS)(i))(+/- 2) with X = Be, Mg, Ca, O, S, Se and i = 9, 12, 15, 16 on the basis of Density Functional Theory and Quantum Molecular Dynamics simulations. Most of the nanoclusters are found to trap both chalcogen and alkaline earth atoms. Furthermore, the chalcogen doped clusters are calculated to be both thermodynamically and thermally stable. However, only a few of alkaline earth metal doped structures are predicted to be thermally stable. Therefore, the charge of the dopant atom appears to be crucial in the endohedral doping. Additionally, the absorption spectra of the title compounds have been simulated by means of Time Dependent Density Functional Theory (TDDFT) calculations. The calculated optical features show a blueshift with respect to the bulk CdS wurtzite. Furthermore, doping modifies notably the optical spectra of nanoclusters, as the absorption spectra shift to lower energies upon encapsulation.

First author: Yao, Jun, Structural/electronic properties and reaction energies of a series of mono- and bis-uranyl dihalides equatorially coordinated by N/O ligands, JOURNAL OF MOLECULAR MODELING, 20, 74, (2014)
Abstract: Monometallic (UO2)(X)(2)(L)(3) (L=pyridine (py), X=F (1), Cl (2), Br (3) and I (4); L=tetrahydrofuran (thf), X=Cl (5); L=pyrrole (pl), X=Cl (6)) as well as bimetallic [(UO2)(mu(2)-X)(X)(L)(2)](2) (L=py, X=F (7), Cl (8), Br (9) and I (10); L=thf, X=Cl (11); L=pl, X=Cl (12); mu(2)=doubly bridged) were examined using relativistic density functional theory. With changing from F, Cl, Br to I irregardless of in mono-or bis-uranyl complexes, bond lengths of U=O were calculated to be decreasing, resulting from strengthening of axial U=O bonds while weakening equatorial X -> U coordination. This is further evidenced by calculated bond orders of U=O and stretching vibrational frequencies. A similar situation was is found in 2, 5 and 6 as well as in 8, 11 and 12, where N/O ligands are varied but the chlorine atoms are retained. The present study reveals that all these complexes have U(f)-character low-lying unoccupied orbitals, and their pi*(U=O) antibonds are located on higher-energy orbitals. Complex 1 was calculated to show sigma(U=O) bonding character for HOMO, and pyridine-character for other occupied orbitals; the fluorine ligand occurs in a relatively low-energy region. In contrast, the pi(p) characters of heavier halogen atoms significantly contribute to most frontier molecular orbitals of 2, 3 and 4. Unlike this electronic feature of 2, complexes 5 and 6 exhibit mainly thf and pyrrole characters, respectively, for their high-lying occupied orbitals. Electronic structures of bisuranyl complexes 7-12, albeit a little more complicated, are revealed to be similar to those of the corresponding monouranyl complexes. Finally, energies of formation reactions of the above complexes were calculated and compared with available experimental results.

First author: Parafiniuk, Monika, On the origin of internal rotation in ammonia borane, JOURNAL OF MOLECULAR MODELING, 20, 74, (2014)
Abstract: The internal rotation in ammonia borane (AB) was studied on the basis of natural orbitals for chemical valence (NOCV) and eigenvectors for Pauli repulsion (NOPR). We found that the total hyperconjugation stabilization (ca. 5 kcal mol(-1)), based on the charge transfer from the occupied sigma (B-H) orbitals into the empty sigma*(N-H), slightly favors the staggered conformation over the eclipsed one; however, the barrier to internal rotation in ammonia borane can be understood predominantly in a ‘classical’ way, as originating from the steric (Pauli) repulsion contributions (of the kinetic origin) that act solely between N-H and B-H bonds. Repulsion between the lone pair of ammonia and the adjacent B-H bonds was found to be dominant in absolute terms; however, it does not determine the rotational barrier. Similar conclusions on the role of CH <-> HC repulsion appeared to be valid for isoelectronic ethane.

First author: Pandey, Krishna K., Relevance of Dispersion Interactions in the Germylidyne and Stannylidyne Complexes of Manganese: Structure and Bonding-Energy Analysis, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 20, 2916, (2014)
Abstract: Density functional theory (DFT) and dispersion-corrected DFT calculations were used to study the nature of Mn E bonds in the cationic manganese-ylidyne complexes trans[H(dmpe)(2)Mn E(Mes)](+) (E = Ge, Sn) and [H(dmpe)(2)Mn Sn(C6H3-2,6-Mes(2))](+) by using BP86, PBE, and PW91 functionals. The calculated geometrical parameters of the stannylidyne complexes are in good agreement with the available experimental values. Significant non-covalent interactions appear between the metal fragment and the ligands in the studied complexes, which were determined by the QTAIM-defined topological analysis. The electronic structure of the Mn E bonds was examined by Voronoi deformation density (VDD) charges and Nalewazskii-Mrozek bond orders. The overall electronic charge transfers from [E(Mes)] or [E(C6H3-2,6-Mes(2))] to [H(dmpe)(2)Mn] fragment. The energy decomposition analysis shows that the Mn Ge bond has more covalent character than ionic, and the percentage of ionic character increases from Ge to Sn. The bond dissociation energy at the DFT/BP86 level for the Mn Ge bond (67.6 kcal/mol) is larger than that of the Mn Sn bond (55.8 kcal/mol). The D3(BJ) dispersion interactions between metal fragment and EMes ligands add nearly 17.0 kcal/mol to the Mn E bond dissociation energies. The dispersion energy contribution increases with the bulkiness of the ligand substituent. The distortion of the Mn-E-C bond angle has been discussed in terms of a Jahn-Teller distortion.

First author: Soman, Rahul, Intermolecular Interactions in Fluorinated Tetraarylporphyrins: An Experimental and Theoretical Study, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 20, 2653, (2014)
Abstract: Crystallographic studies of the fluorinated tetraarylporphyrin 5,10,15,20-tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyri n and its metal complexes [MTF4DMAP; M = 2H center dot 2H2O, 1; NiII center dot THF, 2; CuII center dot 5H2O, 3; and ZnII center dot(THF)2, 4; THF = tetrahydrofuran] are reported. To analyse the weak intermolecular interactions, we have used a combination of energy decomposition analysis and Hirshfeld surface analysis, which allowed us to elucidate the nature of various close contacts. The energy decomposition analysis shows that dispersive interactions involving fluorine atoms significantly contribute to the stabilizing intermolecular interactions. Cooperative weak interactions such as C-F center dot center dot center dot H/C/F, C-H center dot center dot center dot and H center dot center dot center dot H are responsible for the formation and stabilization of the supramolecular self assemblies.

First author: Ramos, Pablo, Quantifying Environmental Effects on the Decay of Hole Transfer Couplings in Biosystems,JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 2546, (2014)
Abstract: In the past two decades, many research groups worldwide have tried to understand and categorize simple regimes in the charge transfer of such biological systems as DNA. Theoretically speaking, the lack of exact theories for electron-nuclear dynamics on one side and poor quality of the parameters needed by model Hamiltonians and nonadiabatic dynamics alike (such as couplings and site energies) on the other are the two main difficulties for an appropriate description of the charge transfer phenomena. In this work, we present an application of a previously benchmarked and linear-scaling subsystem density functional theory (DFT) method for the calculation of couplings, site energies, and superexchange decay factors (beta) of several biological donor-acceptor dyads, as well as double stranded DNA oligomers composed of up to five base pairs. The calculations are all-electron and provide a clear view of the role of the environment on superexchange couplings in DNA-they follow experimental trends and confirm previous semiempirical calculations. The subsystem DFT method is proven to be an excellent tool for long-range, bridge-mediated coupling and site energy calculations of embedded molecular systems.

First author: Allan, David R., High-pressure studies of palladium and platinum thioether macrocyclic dihalide complexes,ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS, 70, 469, (2014)
Abstract: The mononuclear macrocyclic Pd-II complex cis[PdCl2([9]aneS(3))]([9]aneS(3) = 1,4,7-trithiacyclo-nonane) converts at 44 kbar into an intensely coloured chain polymer exhibiting distorted octahedral coordination at the metal centre and an unprecedented [1233] conformation for the thioether ligand. The evolution of an intramolecular axial sulfur-metal interaction and an intermolecular equatorial sulfur-metal interaction is central to these changes. High-pressure crystallographic experiments have also been undertaken on the related complexes [PtCl2([9]aneS(3))], [PdBr2([9]aneS(3))], [PtBr2([9]aneS(3))], [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] in order to establish the effects of changing the halide ligands and the metal centre on the behaviour of these complexes under pressure. While all complexes undergo contraction of the various interaction distances with increasing pressure, only [PdCl2([9]aneS(3))] undergoes a phase change. Pressure-induced I center dot center dot center dot I interactions were observed for [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] at 19 kbar, but the corresponding Br center dot center dot center dot Br interactions in [PdBr2([9]aneS(3))] and [PtBr2([9]aneS(3))] only become significant at much higher pressure (58 kbar). Accompanying density functional theory (DFT) calculations have yielded interaction energies and bond orders for the sulfur-metal interactions.

First author: Frenking, Gernot, Dative Bonds in Main-Group Compounds: A Case for More Arrows!, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53, 6040, (2014)
Abstract: The mononuclear macrocyclic Pd-II complex cis[PdCl2([9]aneS(3))]([9]aneS(3) = 1,4,7-trithiacyclo-nonane) converts at 44 kbar into an intensely coloured chain polymer exhibiting distorted octahedral coordination at the metal centre and an unprecedented [1233] conformation for the thioether ligand. The evolution of an intramolecular axial sulfur-metal interaction and an intermolecular equatorial sulfur-metal interaction is central to these changes. High-pressure crystallographic experiments have also been undertaken on the related complexes [PtCl2([9]aneS(3))], [PdBr2([9]aneS(3))], [PtBr2([9]aneS(3))], [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] in order to establish the effects of changing the halide ligands and the metal centre on the behaviour of these complexes under pressure. While all complexes undergo contraction of the various interaction distances with increasing pressure, only [PdCl2([9]aneS(3))] undergoes a phase change. Pressure-induced I center dot center dot center dot I interactions were observed for [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] at 19 kbar, but the corresponding Br center dot center dot center dot Br interactions in [PdBr2([9]aneS(3))] and [PtBr2([9]aneS(3))] only become significant at much higher pressure (58 kbar). Accompanying density functional theory (DFT) calculations have yielded interaction energies and bond orders for the sulfur-metal interactions.

First author: Georgieva, I., Lanthanide and transition metal complexes of bioactive coumarins: Molecular modeling and spectroscopic studies, JOURNAL OF INORGANIC BIOCHEMISTRY, 135, 100, (2014)
Abstract: The present paper summarizes theoretical and spectroscopic investigations on a series of active coumarins and their lanthanide and transition metal complexes with application in medicine and pharmacy. Molecular modeling as well as IR, Raman, NMR and electronic spectral simulations at different levels of theory were performed to obtain important molecular descriptors: total energy, formation energy, binding energy, stability, conformations, structural parameters, electron density distribution, molecular electrostatic potential, Fukui functions, atomic charges, and reactive indexes. The computations are performed both in gas phase and in solution with consideration of the solvent effect on the molecular structural and energetic parameters. The investigations have shown that the advanced computational methods are reliable for prediction of the metal-coumarin binding mode, electron density distribution, thermodynamic properties as well as the strength and nature of the metal-coumarin interaction (not experimentally accessible) and correctly interpret the experimental spectroscopic data. Known results from biological tests for cytotoxic, antimicrobial, anti-fungal, spasmolytic and anti-HIV activities on the studied metal complexes are reported and discussed.

First author: Nithya, R., Structural, optical, and charge transport properties of cyclopentadithiophene derivatives: a theoretical study, STRUCTURAL CHEMISTRY, 25, 715, (2014)
Abstract: Density functional theory calculations were carried out to investigate the structural and opto-electronic properties of cyclopenta[2,1-b:3,4-b’]dithiophene (CPDT) derivatives. The ground state, cationic and anionic geometries of cyclopentadithiophene derivatives were optimized at B3LYP/6-311G(d,p) level of theory. Based on these geometries, ionic state properties such as ionization potentials, electron affinities, hole extraction potential, and electron extraction potential of cyclopentadithiophene derivatives have been calculated. The charge transfer integral, spatial overlap integral, and site energy were calculated from the matrix elements of Kohn-Sham Hamiltonian. Computed results show that the mobility of charge carriers in CPDT derivatives is strongly affected by the substitution of electron withdrawing group at bridge-head and alpha-positions. The excited state geometry of CPDT derivatives were optimized using configuration interaction singles method. On the basis of ground and excited states geometry, absorption and emission spectra of cyclopentadithiophene derivatives were calculated using the time-dependent density functional theory method. It has been observed that the substitution of EWG in cyclopentadithiophene core alters the absorption and emission spectra. The nonlinear optical property of CPDT derivatives have been studied through computed static polarizability and first hyperpolarizability.

First author: Liu, Z., The nature of the P-P bond in carbene-stabilized diphosphorus complex, STRUCTURAL CHEMISTRY, 25, 793, (2014)
Abstract: The nature of the P-P bond in the recently synthesized N-heterocyclic carbene-stabilized diphosphorus complex has been investigated by the built-in fragment-oriented approach using DFT calculations. The result leads us to investigate the stabilization of diphosphorus. It is concluded that a weakening factor, which can be engendered through such methods as orbital mixing, antibonding interaction, or ligand-receptor interactions, is the key to stabilize the highly reactive diphosphorus molecule.

First author: Poltev, Valeri, The Role of Molecular Structure of Sugar-Phosphate Backbone and Nucleic Acid Bases in the Formation of Single-Stranded and Double-Stranded DNA Structures, BIOPOLYMERS, 101, 640, (2014)
Abstract: Our previous DFT computations of deoxydinucleoside monophosphate complexes with Na+-ions (dDMPs) have demonstrated that the main characteristics of Watson-Crick (WC) right-handed duplex families are predefined in the local energy minima of dDMPs. In this work, we study the mechanisms of contribution of chemically monotonous sugar-phosphate backbone and the bases into the double helix irregularity. Geometry optimization of sugar-phosphate backbone produces energy minima matching the WC DNA conformations. Studying the conformational variability of dDMPs in response to sequence permutation, we found that simple replacement of bases in the previously fully optimized dDMPs, e.g. by constructing Pyr-Pur from Pur-Pyr, and Pur-Pyr from Pyr-Pur sequences, while retaining the backbone geometry, automatically produces the mutual base position characteristic of the target sequence. Based on that, we infer that the directionality and the preferable regions of the sugar-phosphate torsions, combined with the difference of purines from pyrimidines in ring shape, determines the sequence dependence of the structure of WC DNA. No such sequence dependence exists in dDMPs corresponding to other DNA conformations (e.g., Z-family and Hoogsteen duplexes). Unlike other duplexes, WC helix is unique by its ability to match the local energy minima of the free single strand to the preferable conformations of the duplex.

First author: Ram, Jokhan, Equilibrium theory of molecular fluids: Structure and freezing transitions, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 538, 121, (2014)
Abstract: In this article we review equilibrium theory of molecular fluids which includes structure and freezing transitions. The application of the theory to evaluate the pair correlation functions using Integral Equation methods and Computer Simulations have been discussed. Freezing of classical complex fluids based on the density functional approach is also discussed and compare a variety of its versions. Transitions discussed are sensitive to the value of direct correlation functions of the effective liquid which is required as an input information in the theory. Accurate evaluation of pair correlation functions is emphasized. Calculation of these correlation functions which pose problems in the case of ordered phases is discussed. The pair correlation functions of the ordered phase, which are supposed to be made up of two contributions, one that preserves the symmetry of the isotropic phase and a second that breaks it, are discussed. A new free-energy functional developed for an inhomogeneous system that contains both symmetry conserved and symmetry broken parts of the direct pair correlation function is discussed. The most useful three dimensional reference interaction site model (3D-RISM) and its extension done recently by many workers is discussed. Application of this theory to a large variety of complex systems in combination with the density functional theory method implemented in the Amsterdam density functional software package is discussed. Coupling of the 3D-RISM salvation theory with molecular dynamics in the Amber molecular dynamics package is also given. The importance of the density functional theory for the study of the structure and phase behaviour of hard polyhedral is also discussed. The dynamical density functional and its generalized form applied for many important class of problems such as binary mixture, anisotropic particles dynamics of freezing and wetting, colloidal samples, particle self diffusion in complex environment, colloidal sedimentation and active self-propelled particles is discussed.

First author: Raupach, Marc, Quantitative Investigation of Bonding Characteristics in Ternary Zintl Anions: Charge and Energy Analysis of [Sn2E215(ZnPh)](-) (E-15 = Sb, Bi) and [Sn2Sb5(ZnPh)(2)](3-), JOURNAL OF COMPUTATIONAL CHEMISTRY, 35, 1045, (2014)
Abstract: The analysis of chemical bonding in Zintl anions and complexes thereof is mostly based on frontier molecular orbital (FMO) analysis. While this approach delivers remarkable insights, it falls short of providing quantitative measures for chemical bonding in these compounds. Here, we investigate the organozinc-ligated Zintl anions [Sn2E215(ZnPh)](-) (E-15=Sb, Bi) and [Sn2Sb5(ZnPh)(2)](3-) with charge and energy analysis methods. Partial charge analysis confirms that natural population analysis is more reliable than the Hirshfeld method for the diffuse charge density of the Zintl anions. In a subsequent step, the combined method energy decomposition analysis with natural orbitals for chemical valence is used to deliver quantitative results for the chemical bond between the organozinc fragment and the Zintl anionic cage. From this analysis, we conclude that the shared-electron description represents the chemical bonding in these compounds more appropriate. The bonding is characterized by a sigma-type bond polarized toward the ZnPh fragment and a strong -donation (15-20% of orbital interaction) into the p-orbitals at zinc. Electrostatic contributions, which are not considered in FMO analyses, make up around two-thirds of the attractive metal-ligand interaction and should not be neglected in the discussion of chemical bonding in these compounds. Usage of ligands with better sigma- or -accepting ability might thus serve to further stabilize the interesting class of compounds with multinary Zintl anions in the future.

First author: Kulasekera, Erandi, DFT Calculation of Static First Hyperpolarizabilities and Linear Optical Properties of Metal Alkynyl Complexes, ORGANOMETALLICS, 33, 2434, (2014)
Abstract: Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are reported for a set of organometallic compounds for which the first hyperpolarizability values, beta, have previously been determined in the laboratory. These calculations, which utilized a variety of density functionals and basis sets, address such aspects as the implications of molecular conformation and the extent of bond delocalization on the calculated beta values. We also explore here the simplification of ligands for computational expedience and the influence of incorporation or exclusion of solvent corrections on beta. The results of our study are likely to be of value in guiding subsequent efforts toward the reliable predictive calculation of the first hyperpolarizabilities and linear optical properties for organometallic compounds of interest to experimentalists.

First author: Wahlicht, Sven, 7-Azaindol-1-yl(organo)silanes and Their PdCl2 Complexes: Pd-Capped Tetrahedral Silicon Coordination Spheres and Paddlewheels with a Pd-Si Axis, ORGANOMETALLICS, 33, 2479, (2014)
Abstract: Supported by excess triethylamine, 7-azaindole (HL) and dichlorodimethylsilane (Me2SiCl2), methyltrichlorosilane (MeSiCl3), and tetrachlorosilane (SiCl4) react, respectively, with formation of the 7-azaindol-1-yl-substituted silanes Me2SiL2, MeSiL3, and SiL4. In these compounds the silicon atom adopts [4+2], [4+3], and [4+4] coordination, respectively, with the pyridine N atoms of the 7-azaindol-1-yl groups capping the tetrahedral Si coordination sphere from distances of >3 angstrom. Two pyridine nitrogen atoms of these silanes replace the acetonitrile ligands of [PdCl2(NCMe)(2)], thus forming the complexes Me2Si(mu-L)2PdCl(2), MeSiL(mu-L)(2)PdCl2, and SiL2(mu-L)(2)PdCl2. In addition to capping of the silicon coordination sphere by the pyridine N atoms of the dangling 7-azaindol-1-yl groups (in MeSiL(mu-L)(2)Pda(2) and SiL2(mu-L)(2)PdCl2), these three palladium complexes exhibit capping of one tetrahedral face of the Si coordination sphere by the palladium atom (with Si center dot center dot center dot Pd separations of 3.34, 3.43, and 3.31 angstrom, respectively). According to computational analyses, the paddlewheel complex ClSi(mu-L)(4)PdCl should be energetically favored over its isomer SiL2(mu-L)(2)PdCl2; however, isomerization into this paddlewheel compound requires higher temperatures (150 degrees C) or the addition of a Lewis acid (such as GaCl3).

First author: Burgun, Alexandre, Hexatriynediyl Chain Spanning Two Cp*(dppe)M Termini (M = Fe, Ru): Evidence for the Dependence of Electronic and Magnetic Couplings on the Relative Orientation of the Termini, ORGANOMETALLICS, 33, 2613, (2014)
Abstract: The binuclear complexes Cp*(dppe)FeC CC CC CM(dppe)Cp* (6, M = Fe; 8, M = Ru) were obtained in good yield by treatment of the iron chloro complex Cp*(dppe)Fe-Cl (5) in the presence of KF with the bis(silylated) hexatriyne Me3SiC CC CC CSiMe3 and the ruthenium complex Cp*(dppe)RuC CC CC CSiMe3 (7), respectively. The oxidized species 6(PF6)(n) (n = 1, 2) and 8(PF6) were obtained in ca. 80% yield by treatment of the parent neutral compounds with 1 or 2 equiv of [Cp2Fe](PF6) in THF or dichloromethane at -78 degrees C. The CV of these compounds show three reversible waves with a separation larger than 0.5 V. The salts 6(PF6)(n) (n = 1, 2), and 8(PF6) were characterized by XRD. Quantum chemistry calculations performed at the DFT level on the oxidized species show a strong contribution of the -C-6- spacer to the delocalization of the spin density. IR spectra analyzed with the support of TD-DFT calculations are consistent with the delocalization of the odd electron on the fast IR time scale for the two mixed-valence complexes 6(PF6) and 8(PF6). Combined ESR measurements on rigid glass and on single crystal samples clearly establish that the electronic properties of MV species and particularly their magnetic anisotropies depend on the conformation of the molecules. In the case of the doubly oxidized species 6(PF6)(2), which carries two unpaired electrons, it is shown that the singlet vs triplet ground states can be inverted by the rotation of one metal end with respect to the other around the all-carbon chain axis. Very strong NIR bands are found for the symmetric 6(PF6) and nonsymmetric 8(PF6) MV (mixed-valence) derivatives allowing the determination of very large electronic couplings (H-ab = 3070 and 4025 cm(-1), respectively).

First author: Gourlaouen, Christophe, NIR Dual Luminescence from an Extended Porphyrin. Spectroscopy, Photophysics and Theory, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 3616, (2014)
Abstract: Spectroscopic and photophysical properties of an extended Zn porphyrin with fused bis(tetraazaanthracene) arms including a 2,9-diphenyl-1,10-phenanthroline incorporated in a polyether macrocycle are investigated in solvents of different polarity pointing to the presence of two emitting singlet excited states. The absorption and emission features are identified and ascribed, on the basis of solvent polarity dependence, to a pi-pi* and to a charge transfer (CT) state, respectively. Whereas the intraligand pi-pi* transition is assigned to the intense absorption observed at 442-455 nm, the CT states contribute to the bands at 521-525 nm and 472-481 nm. The theoretical analysis of the absorption spectrum confirms the presence of two strong bands centered at 536 and 437 nm corresponding to CT and pi-pi* states, respectively. Weak CT transitions are calculated at 657 and 486 nm. Two emission maxima are observed in toluene at 724 nm from a (1)pi-pi* state and at 800 nm from a (CT)-C-1 state, respectively. (CT)-C-1 bands shift bathochromically by increasing the solvent polarity whereas the energy of the (1)pi-pi band is less affected. Likewise, the emission yield and lifetime energy (CT)-C-1 band are strongly affected by solvent polarity. This is rationalized by a (1)pi-pi* -> (CT)-C-1 internal conversion driven by solvent polarity, this process being competitive with the (1)pi-pi* to ground state deactivation channel. Time resolved absorption spectra indicate the presence of two triplet states, a short-lived one (nanoseconds range) and a longer lived one (hundreds of microsecond range) ascribed to a (3)pi-pi* and a (CT)-C-3, respectively. For them, a conversion mechanism similar to that of the singlet excited states is suggested.

First author: Ahmed, Marawan, Structures of Cycloserine and 2-Oxazolidinone Probed by X-ray Photoelectron Spectroscopy: Theory and Experiment, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 3645, (2014)
Abstract: The electronic structures and properties of 2-oxazolidinone and the related compound cycloserine (CS) have been investigated using theoretical calculations and core and valence photoelectron spectroscopy. Isomerization of the central oxazolidine heterocycle and the addition of an amino group yield cycloserine. Theory correctly predicts the C, N, and O Is core spectra, and additionally, we report theoretical natural bond orbital (NBO) charges. The valence ionization energies are also in agreement with theory and previous measurements. Although the lowest binding energy part of the spectra of the two compounds shows superficial similarities, further analysis of the charge densities of the frontier orbitals indicates substantial reorganization of the wave functions as a result of isomerization. The highest occupied molecular orbital (HOMO) of CS shows leading carbonyl pi character with contributions from other heavy (non-H) atoms in the molecule, while the HOMO of 2-oxazolidinone (OX2) has leading nitrogen, carbon, and oxygen p pi characters. The present study further theoretically predicts bond resonance effects of the compounds, evidence for which is provided by our experimental measurements and published crystallographic data.

First author: Kratochvilova, Irena, Theoretical and Experimental Study of Charge Transfer through DNA: Impact of Mercury Mediated T-Hg-T Base Pair, JOURNAL OF PHYSICAL CHEMISTRY B, 118, 5374, (2014)
Abstract: DNA-Hg complexes may play an important role in sensing DNA defects or in detecting the presence of Hg in the environment. A fundamental way of characterizing DNA-Hg complexes is to study the way the electric charge is transferred through the molecular chain. The main goal of this contribution was to investigate the impact of a mercury metal cation that links two thymine bases in a DNA T-T mismatched base pair (T-Hg-T) on charge transfer through the DNA molecule. We compared the charge transfer efficiencies in standard DNA, DNA with mismatched T-T base pairs, and DNA with a T-Hg(II)-T base pair. For this purpose, we measured the temperature dependence of steady-state fluorescence and UV-vis of the DNA molecules. The experimental results were confronted with the results obtained employing theoretical DFT methods. Generally, the efficiency of charge transfer was driven by mercury changing the spatial overlap of bases.

First author: Landman, Marile, Conformation analysis of triphenylphosphine in trans and cis triphenylphosphine-substituted Fischer carbene complexes, JOURNAL OF MOLECULAR STRUCTURE, 1065, 29, (2014)
Abstract: The synthesis and selected crystal structures of novel (M = Cr or Mo) and known (M = W) [(CO)(4)(PPh3) M = C(OEt)R] complexes, M = Cr, R = 2-thienyl (1), 2-furyl (2); M = Mo, R = 2-thienyl (3), 2-furyl (4); M = W, R = 2-thienyl (5), 2-furyl (6), are presented. Experimental crystal structures and DFT calculations of selected trans- and cis-triphenylphosphine-substituted Fischer carbene complexes, illustrate that the minimum energy conformation of triphenylphosphine (PPh3) in octahedral [(CO)(4)(PPh3)ML]-complexes generally have distinct features that can be described in terms of the “plane of nadir energy”, a plane linking all points of minimum steric compression between the ligands. The generally observed orientation of PPh3 involves a correlated feathering of the phenyl groups with the P-C-ipso bond of one phenyl group orientated near parallel to the nadir plane, and a meta carbon (C-m) of the other two phenyl groups orientated as near as possible to the nadir plane, orthogonal to the first. Although the orientation of PPh3 in 6-trans, [(CO)(4)(PPh3)W = C(OEt)2-furyl], deviates from this, DFT correctly calculated the unexpected and not generally observed PPh3 orientation.

First author: Padial, Joan Simo, Stabilisation of 2,6-Diarylpyridinium Cation by Through- Space Polar- p Interactions,CHEMISTRY-A EUROPEAN JOURNAL, 20, 6268, (2014)
Abstract: The through-space polar- interactions between pyridinium ion and the adjacent aromatic rings in 2,6-diarylpyridines affect the pK(a)values. Hammett analysis illustrates that the basicity of pyridines correlates well with the sigma values of the substituents at the paraposition of the flanking aryl rings.

First author: Yamashita, Masataka, Synthesis and Solid-State Structures of a TetrathiafulvaleneConjugated Bistetracene,CHEMISTRY-A EUROPEAN JOURNAL, 20, 6309, (2014)
Abstract: A tetrathiafulvalene (TTF)-conjugated bistetracene was synthesized and characterized in the molecular electronic structures based on the spectroscopic measurements and the single-crystal X-ray diffraction analysis. UV/Vis absorption and electrochemical measurements of 5 revealed the considerable electronic communication between two tetracenedithiole units by through-bond and/or through-space interactions. The difference in the crystal-packing structures of 5, showing polymorphism, results in a variety of intermolecular electronic-coupling pattern. Of these, the -stacking structure of 5A gave a large transfer integral of HOMOs (97meV), which value is beyond hexacene and rubrene, thus, quite beneficial to achieve the high hole mobility.

First author: Krykunov, Mykhaylo, Introducing constricted variational density functional theory in its relaxed self-consistent formulation (RSCF-CV-DFT) as an alternative to adiabatic time dependent density functional theory for studies of charge transfer transitions, JOURNAL OF CHEMICAL PHYSICS, 140, 6309, (2014)
Abstract: We have applied the relaxed and self-consistent extension of constricted variational density functional theory (RSCF-CV-DFT) for the calculation of the lowest charge transfer transitions in the molecular complex X-TCNE between X = benzene and TCNE = tetracyanoethylene. Use was made of functionals with a fixed fraction (alpha) of Hartree-Fock exchange ranging from alpha = 0 to alpha = 0.5 as well as functionals with a long range correction (LC) that introduces Hartree-Fock exchange for longer inter-electronic distances. A detailed comparison and analysis is given for each functional between the performance of RSCF-CV-DFT and adiabatic time-dependent density functional theory (TDDFT) within the Tamm-Dancoff approximation. It is shown that in this particular case, all functionals afford the same reasonable agreement with experiment for RSCF-CV-DFT whereas only the LC-functionals afford a fair agreement with experiment using TDDFT. We have in addition calculated the CT transition energy for X-TCNE with X = toluene, o-xylene, and naphthalene employing the same functionals as for X = benzene. It is shown that the calculated charge transfer excitation energies are in as good agreement with experiment as those obtained from highly optimized LC-functionals using adiabatic TDDFT. We finally discuss the relation between the optimization of length separation parameters and orbital relaxation in the RSCF-CV-DFT scheme.

First author: Mirtschink, Andre, Energy density functionals from the strong-coupling limit applied to the anions of the He isoelectronic series, JOURNAL OF CHEMICAL PHYSICS, 140, 6309, (2014)
Abstract: Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge Z < 2, which includes weakly bound negative ions and a quantum phase transition at a critical value of Z, representing a big challenge for density functional theory. We use accurate wavefunction calculations to validate our results, comparing energies and Kohn-Sham potentials, thus also providing useful reference data close to and at the quantum phase transition. We show that our functional is able to bind H- and to capture in general the physics of loosely bound anions, with a tendency to strongly overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which improve the results.

First author: Xiong, Ruichang, An Improvement to COSMO-SAC for Predicting Thermodynamic Properties, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 53, 8265, (2014)
Abstract: A modified COSMO-SAC model is presented to calculate thermodynamic properties of pure fluids and mixtures using statistical thermodynamics and the surface charge density of each compound obtained from a quantum mechanics (QM) calculation. The main differences from the previous models are that the new model includes a dispersion contribution in the mixture interaction, and is reparametrized using measured pure and mixture thermodynamic data simultaneously. With a single set of universal parameters, the new model provides higher accuracy than our previous models for predicting mixture thermodynamic properties while maintaining the same accuracy for pure compound thermodynamic properties. The overall root-mean-square deviation (RMSD) in the logarithms of partition coefficients for 992 octanol water partitioning systems and 829 other solvent water partitioning systems with this new model is reduced by about 10% compared to the results from previous models. Also, the agreement between the predicted and measured partition coefficients over a wide range of values is improved as a result of better activity coefficient predictions at high dilution by inclusion of the dispersive mixture interaction in the model. The accuracy in the vapor liquid equilibrium (VLE) predictions is comparable to, or better than, the previous model that was developed for phase equilibria calculations only. The new model also provides parameters for use with the Amsterdam Density Functional (ADF) in addition to DMol(3).

First author: Caramori, Giovanni F., Ruthenophanes: Evaluating Cation-pi Interactions in [Ru(eta(6)-C16H12R4)(NH3)(3)](2+/3+) Complexes. A Computational Insight, ORGANOMETALLICS, 33, 2301, (2014)
Abstract: The nature of cation-pi interactions in a set of [Ru(eta(6)-C16H12R4)(NH3)(3)](2+3+) (R = F, CN, CH3, and others), complexes was investigated with Su-Li energy decomposition analysis and the natural orbitals for chemical valence and the extended transition state method EDA-NOCV. The long-distance effects of electron-donating and electron-withdrawing substituents as well as protonation of the ipso carbon on the nature of cation-pi interactions were investigated. Both energy decomposition analyses, Su-Li EDA and EDA-NOCV, are in total agreement, showing that the presence of electron-donating substituents such as CH3, NH2, and H3CO tends to stabilize the ruthenium-arene interaction while electron-withdrawing substituents such as F, CN, and NO2 tend to weaken such interactions. The electrostatic component of the ruthenium arene interaction is the most affected by the substitution, despite the fact that the covalent character is much more significant than the electrostatic character. EDA-NOCV reveals that the most important orbital stabilization comes from donation and back-donation between the interacting fragments, while the sigma density deformations present a moderate contribution to total orbital stabilization energy in ruthenium-arene interactions of complexes 1-8.

First author: Zaiter, Abdellah, Selectivity of Azine Ligands Toward Lanthanide(III)/Actinide(III) Differentiation: A Relativistic DFT Based Rationalization, INORGANIC CHEMISTRY, 53, 4687, (2014)
Abstract: Polyazines emerge as highly selective ligands toward actinide versus lanthanide separation. Electronic structures of several mono- and polyazine f-complexes of general formula MX3L (M+3 = Ce, Nd, Eu, U, Am, and Cm; X = RCp- or NO3-; L = N-donor ligand) related to Ln(III)/An(III) differentiation have been investigated using scalar relativistic ZORA/DFT calculations. In all cases, DFT calculations predict shorter An-N bonds than Ln-N ones whatever the azine used, in good agreement with available experimental data. The An-N bonds are also characterized by higher stretching frequencies than Ln-N bonds. The electronic structures of all species have been studied using different population analyses, among them natural population (NPA) and the quantum theory of atoms in molecule approach (QTAIM), as well as using different bond indices. The ability for Ln(III)/An(III) differentiation of the terdentate bipyrazolate BPPR ligand in the M(BPPR)(NO3)(3) complexes (M3+ = Ce, Eu, U and Am; R = H, 2,2-dimethylpropyl) where BPP = 2,6-bis(dialkyl-1H-pyrazol-3-yl)pyridine has been studied, with a special emphasis on the total metal-ligand bonding energy (TBE). The ZORA/DFT approach was found to properly reproduce the higher selectivity of the polyazine BPP ligand compared to monoazines, especially for the Eu-III/Am-III pair operating in spent nuclear fuel, using computed TBEs as criterion. Moreover, the orbital part of the total bonding energy appears also to rationalize well the observed selectivity.

First author: Yuen, Wai Kong, Ground-state electronic properties of LiH calculated from the “Bounce” version of quantum Monte Carlo, JOURNAL OF COMPUTATIONAL SCIENCE, 5, 542, (2014)
Abstract: We calculate several ground-state electronic properties of LiH at its equilibrium geometry using the so-called “Bounce” version of quantum Monte Carlo. The importance sampling is performed with a single-determinant large (QZ4P) STO basis set. The computer codes were written to exploit the efficiencies engineered into modern, high-performance computing software.Our objective is to test the accuracy of the Bounce algorithm when applied to calculate electronic properties represented by operators that do not commute with the Hamiltonian. Our approach is to implement the algorithm for short, medium and long length reptiles. The highest quality Bounce-calculated energy and electric properties are found by using longest length reptiles. Nevertheless, these results are not competitive with those calculated using reptation quantum Monte Carlo for the same long-length reptiles.

First author: Lazzarini, Irene C., Magnetic Study of a Pentanuclear {(Co2Co3II)-Co-III} Cluster with a Bent {Co-3(II)} Motif,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 5, 2561, (2014)
Abstract: We have synthesised and structurally characterised a new pentanuclear mixed-valent cobalt cluster of formula [(Co3Co2III)-Co-II(OH)(2)(piv)(6)(L)(2)(H2O)(4)] (piv = trimethylacetate, H2L = salicylideneanthranillic acid) from reaction of a dinuclear cobalt pivalate precursor with a Schiff base type ligand under mild reaction conditions. The core structure can be conveniently described as two fused Co-3-(3)-OH triangles with a strict unique sharing vertex point. A complete picture of the magnetic behaviour of this compound is presented. Through combined use of susceptibility, magnetisation, and EPR data as well as broken-symmetry DFT calculations, we have supported the magnetic data that show weak and anisotropic exchange interaction between Co-II ions affording an S-eff = 1/2 ground state that is not completely isolated from the low-lying excited doublets at low temperature. Under the optimum applied field of 2 kOe, a frequency-dependent out-of-phase susceptibility signal can be observed below 4 K. However, no reliable relaxation rates could be extracted due to the narrow temperature range in which this behaviour was observed.

First author: Xu, Huan, Molecular Packing-Induced Transition between Ambipolar and Unipolar Behavior in Dithiophene-4,9-dione-Containing Organic Semiconductors, ADVANCED FUNCTIONAL MATERIALS, 24, 2907, (2014)
Abstract: By changing the packing motif of the conjugated cores and the thin-film microstructures, unipolar organic semiconductors may be converted into ambipolar materials. A combined experimental and theoretical investigation is conducted on the thin-film organic field-effect transistors (OFETs) of three organic semiconductors that have the same conjugated core structure of s-indaceno[1,2-b: 5,6-b’] dithiophene-4,9-dione but with different n-alkyl groups. The optical and electrochemical measurements suggest that the three organic semiconductors have very similar energy levels; however, their OFETs exhibit dramatically different transport characteristics. Transistors based on compound 1a or 1c show ambipolar transport properties, while those based on compound 1b show p-type unipolar behavior. Specifically, compound 1c is characterized as a good ambipolar semiconductor with the highest electron mobility of 0.22 cm 2 V-1 s(-1) and the highest hole mobility of 0.03 cm 2 V-1 s(-1). Complementary metal oxide semiconductor (CMOS) inverters incorporated with compound 1c show sharp inversions with high gains above 50. Theoretical investigations reveal that the drastic difference in the transport properties of the three materials is due to the difference in their molecular packing and film microstructures.

First author: Franchini, Mirko, Accurate Coulomb Potentials for Periodic and Molecular Systems through Density Fitting,JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 1994, (2014)
Abstract: We present a systematically improvable density fitting scheme designed for accurate Coulomb potential evaluation of periodic and molecular systems. The method does not depend on the way the density is calculated, allowing for a basis set expansion as well as a numerical representations of the orbitals. The scheme is characterized by a partitioning of the density into local contributions that are expanded by means of cubic splines. For three-dimensional periodic systems, the long-range contribution to the Coulomb potential is treated with the usual reciprocal space representation of the multipole moments, while in one- and two-dimensional systems, it is calculated via a new algorithm based on topological extrapolation. The efficiency and numerical robustness of the scheme is assessed for a number of periodic and nonperiodic systems within the framework of density-functional theory.

First author: Romanov, Alexander S., Triple-decker complex CpCo(mu-C3B2Me5) Rh(C2H4)(2): Synthesis, structure and bonding, INORGANICA CHIMICA ACTA, 415, 120, (2014)
Abstract: The reaction of the thallium derivative [CpCo(mu-C3B2Me5)]Tl with [Rh(C2H4)(2)Cl](2) affords the mu-diborolyl bis(ethylene) triple-decker complex CpCo(mu-C3B2Me5) Rh(C2H4)(2) (4). Structure of 4 was determined by X-ray diffraction. According to DFT calculations, the ethylene dissociation energies for the triple-decker complexes CpCo(mu-C3B2R5) Rh(C2H4)(2) (R = H, Me) are ca. 6 kcal mol(-1) lower than for cyclopentadienyl analogs (C5R5) Rh(C2H4)(2). Energy decomposition analysis revealed that the bonding of anions [CpCo (C3B2R5)] – with [Rh(C2H4)(2)](+) is also weaker than that of [C5R5] -; the attractive interactions in both cases are 60-63% electrostatic and 37-40% covalent. The electrostatic potentials at the Rh nuclei suggest that the donor ability of the anions increases in the following order: Cp < [CpCo(C3B2H5)] <= [CpCo(C3B2Me5)] < Cp*.

First author: Giordanino, Filippo, Interaction of NH3 with Cu-SSZ-13 Catalyst: A Complementary FTIR, XANES, and XES Study, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 1552, (2014)
Abstract: In the typical NH3-SCR temperature range (100-500 degrees C), ammonia is one of the main adsorbed species on acidic sites of Cu-SSZ-13 catalyst. Therefore, the study of adsorbed ammonia at high temperature is a key step for the understanding of its role in the NH3-SCR catalytic cycle. We employed different spectroscopic techniques to investigate the nature of the different complexes occurring upon NH3 interaction. In particular, FTIR spectroscopy revealed the formation of different NH3 species, that is, (i) NH3 bonded to copper centers, (ii) NH3 bonded to Bronsted sites, and (iii) NH4+center dot nNH(3) associations. XANES and XES spectroscopy allowed us to get an insight into the geometry and electronic structure of Cu centers upon NH3 adsorption, revealing for the first time in Cu-SSZ-13 the presence of linear Cu+ species in O-fw-Cu-NH3 or H3N-Cu-NH3 configuration.

First author: Dognon, Jean-Pierre, Theoretical insights into the chemical bonding in actinide complexes, COORDINATION CHEMISTRY REVIEWS, 266, 110, (2014)
Abstract: The chemical bonding in actinide compounds is usually analyzed by inspecting the shape and the occupation of the orbitals or by calculating bond orders which are based on orbital overlap and occupation numbers. However, this may not give a definite answer because the choice of the partitioning method may strongly influence the result leading sometimes to qualitatively different answers. This review highlights that the joint and complementary tools such as charge, orbital, quantum chemical topology and energy decomposition analyses are very powerful to understand chemical bonding in the field of actinide chemistry. However, understanding the actinide-ligand bond is not straightforward and requires caution in the use of these methods. This review is illustrated through applications to newly discovered bent actinocene compounds and actinide endohedral clusters fulfilling a 32-electron rule.

First author: de Silva, Piotr, Atomic shell structure from the Single-Exponential Decay Detector, JOURNAL OF CHEMICAL PHYSICS, 140, 110, (2014)
Abstract: The density of atomic systems is analysed via the Single-Exponential Decay Detector (SEDD). SEDD is a scalar field designed to explore mathematical, rather than physical, properties of electron density. Nevertheless, it has been shown that SEDD can serve as a descriptor of bonding patterns in molecules as well as an indicator of atomic shells [P. de Silva, J. Korchowiec, and T. A. Wesolowski, ChemPhysChem 13, 3462 (2012)]. In this work, a more detailed analysis of atomic shells is done for atoms in the Li-Xe series. Shell populations based on SEDD agree with the Aufbau principle even better than those obtained from the Electron Localization Function, which is a popular indicator of electron localization. A link between SEDD and the local wave vector is given, which provides a physical interpretation of SEDD.

First author: Khatua, Munmun, Confinement induced binding of noble gas atoms, JOURNAL OF CHEMICAL PHYSICS,140, 110, (2014)
Abstract: The stability of Ng(n)@B12N12 and Ng(n)@B16N16 systems is assessed through a density functional study and ab initio simulation. Although they are found to be thermodynamically unstable with respect to the dissociation of individual Ng atoms and parent cages, ab initio simulation reveals that except Ne-2@B12N12 they are kinetically stable to retain their structures intact throughout the simulation time (500 fs) at 298 K. The Ne-2@B12N12 cage dissociates and the Ne atoms get separated as the simulation proceeds at this temperature but at a lower temperature (77 K) it is also found to be kinetically stable. He-He unit undergoes translation, rotation and vibration inside the cavity of B12N12 and B16N16 cages. Electron density analysis shows that the He-He interaction in He-2@B16N16 is of closed-shell type whereas for the same in He-2@B12N12 there may have some degree of covalent character. In few cases, especially for the heavier Ng atoms, the Ng-N/B bonds are also found to have some degree of covalent character. But the Wiberg bond indices show zero bond order in He-He bond and very low bond order in cases of Ng-N/B bonds. The energy decomposition analysis further shows that the Delta E-orb term contributes 40.9% and 37.3% towards the total attraction in the He-2 dimers having the same distances as in He-2@B12N12 and He-2@B16N16, respectively. Therefore, confinement causes some type of orbital interaction between two He atoms, which akins to some degree of covalent character.

First author: Paretzki, Alexa, Correlated Coordination and Redox Activity of a Hemilabile Noninnocent Ligand in Nickel Complexes, CHEMISTRY-A EUROPEAN JOURNAL, 20, 5414, (2014)
Abstract: The compound [Ni(Q(M))(2)], Q(M)=4,6-di-tert-butyl-N-(2-methylthiomethylphenyl)-o-iminobenzoquinone, is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom and without any NiS bonding interaction. One-electron oxidation results in additional twofold NiS coordination (d(NiS)approximate to 2.38 angstrom) to produce a complex cation of [Ni(Q(M))(2)](PF6) with hexacoordinate Ni-II and two distinctly different mer-configurated tridentate ligands. The O,O-trans arrangement in the neutral precursor is changed to an O,O-cis configuration in the cation. The EPR signal of [Ni(Q(M))(2)](PF6) has a very large g anisotropy and the magnetic measurements indicate an S=3/2 state. The dication was structurally characterized as [Ni(Q(M))(2)](ClO4)(2) to exhibit a similar NiN2O2S2 framework as the monocation. However, the two tridentate (O,N,S) ligands are now equivalent according to the formulation [Ni-II(Q(M)(0))(2)](2+). Cyclic voltammetry reflects the qualitative structure change on the first, but not on the second oxidation of [Ni(Q(M))(2)], and spectroelectrochemistry reveals a pronounced dependence of the 800-900nm absorption on the solvent and counterion. Reduction of the neutral form occurs in an electrochemically reversible step to yield an anion with an intense near-infrared absorption at 1345nm (epsilon=10400M(-1)cm(-1)) and a conventional g factor splitting for a largely metal-based spin (S=1/2), suggesting a [(Q(M)(.-))Ni-II(Q(M)(2-))](-) configuration with a tetracoordinate metal atom with antiferromagnetic Ni-II-(Q(M)(.-)) interactions and symmetry-allowed ligand-to-ligand intervalence charge transfer (LLIVCT). Calculations are used to understand the NiS binding activity as induced by remote electron transfer at the iminobenzoquinone redox system.

First author: Warren, Mark R., Solid- State Interconversions: Unique 100% Reversible Transformations between the Ground and Metastable States in Single- Crystals of a Series of Nickel( II) Nitro Complexes, CHEMISTRY-A EUROPEAN JOURNAL, 20, 5468, (2014)
Abstract: The solid-state, low-temperature linkage isomerism in a series of five square planar group10 phosphino nitro complexes have been investigated by a combination of photocrystallographic experiments, Raman spectroscopy and computer modelling. The factors influencing the reversible solid-state interconversion between the nitro and nitrito structural isomers have also been investigated, providing insight into the dynamics of this process. The cis-[Ni(dcpe)(NO2)(2)] (1) and cis-[Ni(dppe)(NO2)(2)] (2) complexes show reversible 100% interconversion between the (1)-NO2 nitro isomer and the (1)-ONO nitrito form when single-crystals are irradiated with 400nm light at 100K. Variable temperature photocrystallographic studies for these complexes established that the metastable nitrito isomer reverted to the ground-state nitro isomer at temperatures above 180K. By comparison, the related trans complex [Ni(PCy3)(2)(NO2)(2)] (3) showed 82% conversion under the same experimental conditions at 100K. The level of conversion to the metastable nitrito isomers is further reduced when the nickel centre is replaced by palladium or platinum. Prolonged irradiation of the trans-[Pd(PCy3)(2)(NO2)(2)] (4) and trans-[Pt(PCy3)(2)(NO2)(2)] (5) with 400nm light gives reversible conversions of 44 and 27%, respectively, consistent with the slower kinetics associated with the heavier members of group10. The mechanism of the interconversion has been investigated by theoretical calculations based on the model complex [Ni(dmpe)Cl(NO2)].

First author: Sheikhshoaie, Iran, Combined experimental and theoretical studies on the X-ray crystal structure, Fr-IR, H-1 NMR, C-13 NMR, UV-Vis spectra, NLO behavior and antimicrobial activity of 2-hydroxyacetophenone benzoylhydrazone,SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 124, 548, (2014)
Abstract: A Schiff base ligand, 2-hydroxyacetophenone benzoylhydrazone (HL) was synthesized and fully characterized with FT-IR, elemental analyses, UV-Vis, H-1 NMR and C-13 NMR spectra. DFT calculations using B3LYP/6-31+G(d,p) and PW91/DZP are performed to optimize the molecular geometry. Optimized structures are used to calculate FT-IR, UV-Vis, H-1 NMR and C-13 NMR spectra of the compound. Also the energies of the frontier molecular orbitals (FMOs) have been determined. The results obtained from the optimization and spectral analyses are in good agreement with the experimental data. To investigate non-linear optical properties, the electric dipole moment (mu), polarizability (alpha) and molecular first hyperpolarizability (beta) were computed. The linear polarizabilities and first hyperpolarizabilities of the studied molecule indicate that the compound can be a good candidate of nonlinear optical materials. In addition, the minimal inhibitory concentration (MIC) of this compound against Staphylococcus aureus, and Candida albicans was determined.

First author: Blanco-Rodriguez, Ana Maria, Photophysics of Singlet and Triplet Intraligand Excited States in [ReCl(CO)(3)(1-(2-pyridyl)-imidazo[1,5-alpha]pyridine)] Complexes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 5963, (2014)
Abstract: Excited-state characters and dynamics of [ReCl(CO)(3)(3-R-1-(2-pyridyl)-imidazo[1,5-alpha]pyridine)] complexes (abbreviated ReGV-R, R = CH3, Ph, PhBut, PhCF3, PhNO2, PhNMe2) were investigated by pico- and nanosecond time-resolved infrared spectroscopy (TRIR) and excited-state DFT and TD-DFT calculations. Near UV excitation populates the lowest singlet state 5, that undergoes picosecond intersystem crossing (ISC) to the lowest triplet T-1. Both states are initially formed hot and relax with similar to 20 ps lifetime. TRIR together with quantum chemical calculations reveal that S-1 is predominantly a pi pi* state localized at the 1-(2-pyridyl)-imidazo[1,5-alpha]pyridine (= impy) ligand core, with impy -> PhNO2 and PhNMe2 -> impy intraligand charge-transfer contributions in the case of ReGV-PhNO2 and ReGV-PhNMe2, respectively. T-1 is predominantly ire(impy) in all cases. It follows that excited singlet and corresponding triplet states have to some extent different characters and structures even if originating nominally from the same preponderant one-electron excitations. ISC occurs with a solvent-independent (CH2Cl2, MeCN) 20-30 ps lifetime, except for ReGV-PhNMe2 (10 ps in CH2Cl2, 100 Ps in MeCN). ISC is 200-300 times slower than in analogous complexes with low-lying MLCT states. This difference is interpreted in terms of spin orbit interaction and characters of orbitals involved in one-electron excitations that give rise to S-1 and T-1 states. ReGV-R present a unique case of octahedral heavy-metal complexes where the S-1 lifetime is long enough to allow for separate spectroscopic characterization of singlet and triplet excited states. This study provides an insight into dynamics and intersystem crossing pathways of low-lying singlet and triplet excited states localized at bidentate ligands bound directly to a heavy metal atom. Rather long (IL)-I-1 lifetimes indicate the possibility of photonic applications of singlet excited states.

First author: Nardis, Sara, Phenyl Derivative of Iron 5,10,15-Tritolylcorrole, INORGANIC CHEMISTRY, 53, 4215, (2014)
Abstract: The phenyl iron complex of 5,10,15-tritolylcorrole was prepared by reaction of the starting chloro iron complex with phenylmagnesium bromide in dichloromethane. The organometallic complex was fully characterized by a combination of spectroscopic methods, X-ray crystallography, and density functional theory (DFT) calculations. All of these techniques support the description of the electronic structure of this phenyl iron derivative as a low-spin iron(IV) coordinated to a closed-shell corrolate trianion and to a phenyl monoanion. Complete assignments of the H-1 and C-13 NMR spectra of the phenyl iron derivative and the starting chloro iron complex were performed on the basis of the NMR spectra of the regioselectively beta-substituted bromo derivatives and the DFT calculations.

First author: Chambers, Geoffrey M., Ni-I/Ru-II Model for the Ni-L State of the [NiFe]Hydrogenases: Synthesis, Spectroscopy, and Reactivity, INORGANIC CHEMISTRY, 53, 4243, (2014)
Abstract: This study describes the characterization of a mixed-valence Ru-II/Ni-I complex, a structural model for the Ni-L state of the [NiFe]hydrogenases. One-electron oxidation of (cymene)Ru(mu-pdt)Ni(diphos) ([1], diphos = dppe, C2H4(PPh2)(2); [2](0), diphos = dcpe, C2H4(P(C6H11)(2))(2)] affords the mixed-valence cations [(cymene)Ru(pdt)Ni(diphos)](+) ([1](+) and [2](+)). Crystallographic and spectroscopic measurements indicate that these cations are described as Ru-II/Ni-I. Although [110 and [1]+ are very similar structurally, the following changes are notable: the Ni P distances elongate upon oxidation, and the Ru Ni distance changes insignificantly. The molecular and electronic structures of the Ni center in [1]* approaches that observed in the [NiFe]hydrogenases. Density functional theory calculations indicate that [11 is best described as Ru-II/Ni-I, consistent with its oxidation to Ru-II/Ni-I in [1](+). The fast electron self-exchange rate of 10(7) M-1 s(-1) between [110 and [1]+ suggests minor reorganization, more consistent with a Ni-0/Ni-I oxidation state change than a Ni-I/Ni-II couple. In solution, [1]* slowly converts to [H1]. and [1-H]’, with the latter being a complex of the thioaldehyde SCHCH2CH2S arising from C-H activation of the pdt backbone. Treatment of [1](+) with the H-atom abstracting reagent 2,2,6,6-tetramethylpiperidine-1-oxy also gives [1-H](+).

First author: Braunschweig, Holger, Strained ansa Half-Sandwich Complexes of Ruthenium and Osmium and a Non-Iron Metallopolymer by Ring-Opening Polymerization, ORGANOMETALLICS, 33, 1536, (2014)
Abstract: Herein we report the first non-iron polymer obtained from an ansa half-sandwich complex. This polymeric organometallic material was obtained from a new disilanediyl-bridged ruthenium complex upon thermally induced ring-opening polymerization (ROP). Additionally, a corresponding distannanediyl-bridged osmium species is reported, the first example of an ansa half-sandwich complex of this element.

First author: Marotta, Gabriele, An Integrated Experimental and Theoretical Approach to the Spectroscopy of Organic-Dye-Sensitized TiO2 Heterointerfaces: Disentangling the Effects of Aggregation, Solvation, and Surface Protonation,CHEMPHYSCHEM, 15, 1116, (2014)
Abstract: We report a joint experimental and computational study into the spectroscopic properties of a prototypical D5 organic dye, both in solution and adsorbed on a TiO2 surface, with the aim of modeling and quantifying the UV/Vis spectral shifts that occur in the different explored environments. Going from the dye in solution to dye-sensitized TiO2, various factors may shift the position of the UV/Vis absorption maximum, both towards longer and shorter wavelengths. Here we have focused on the effect of dye aggregation on TiO2, surface protonation, and solvent effects. The D5 dye forms stable aggregates on the TiO2 surface that cause spectral blueshifts. We used different sensitization conditions to vary the dye loading and thus the extent of dye aggregation. For each sensitization condition, we explored protonated and native TiO2 films. Computational modeling of different dimeric aggregates with increasing intermolecular interactions and simulation of the associated optical responses also confirm the observed spectral blueshifts. Our results show that both the presence of surface protons and solvent stabilize the excited state of the adsorbed dye molecules, which causes a marked redshift in the absorption maximum and thus moves in the opposite direction to the shift due to the increase in the surface coverage.

First author: Castro, Abril C., Exploring the Potential Energy Surface of E2P4 Clusters (E=Group 13 Element): The Quest for Inverse Carbon-Free Sandwiches, CHEMISTRY-A EUROPEAN JOURNAL, 20, 4583, (2014)
Abstract: Inverse carbon-free sandwich structures with formula E2P4 (E=Al, Ga, In, Tl) have been proposed as a promising new target in main-group chemistry. Our computational exploration of their corresponding potential-energy surfaces at the S12h/TZ2P level shows that indeed stable carbon-free inverse-sandwiches can be obtained if one chooses an appropriate Group13 element for E. The boron analogue B2P4 does not form the D-4h-symmetric inverse-sandwich structure, but instead prefers a D-2d structure of two perpendicular BP2 units with the formation of a double BB bond. For the other elements of Group13, Al-Tl, the most favorable isomer is the D-4h inverse-sandwich structure. The preference for the D-2d isomer for B2P4 and D-4h for their heavier analogues has been rationalized in terms of an isomerization-energy decomposition analysis, and further corroborated by determination of aromaticity of these species.

First author: Li, Yan, Are Triphenylamine-Functionalized or Carbazole-Functionalized Iridium Complexes the More Effective Phosphorescent Materials? A Theoretical Perspective, CHEMISTRY-A EUROPEAN JOURNAL, 20, 4671, (2014)
Abstract: The ground and excited states, charge injection/transport, and phosphorescence properties of eleven carbazole- and triphenylamine-functionalized Ir-III complexes were investigated by using the DFT method. By analyzing the spin-orbit coupling (SOC) matrix elements, radiative decay rate constants k(r), and the electronic structures and energies at the S-0(opt) and T-1(opt) states, it was possible to rationalize the order of the experimental phosphorescence quantum yields of a series of Ir-III complexes and to predict that [Ir(Nph-2-Cz-tz)(3)] has a higher phosphorescence quantum yield than [Ir(TPA-tz)(3)] (TPA=triphenylamine, tz=thiazolyl, Cz=carbazole, Nph=N-phenyl). Carbazole-functionalized Ir-III complexes were shown to be efficient phosphorescent materials that have not only fast but also balanced electron/hole-transport performance as well as high phosphorescence quantum yields. The phosphorescence emission spectra can be modulated by modifying or replacing a pyridyl substituent.

First author: Abdullaev, F. Kh, Bright solitons in Bose-Einstein condensates with field-induced dipole moments, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 47, 4671, (2014)
Abstract: We introduce an effectively one-dimensional model of a bosonic gas of particles carrying collinear dipole moments which are induced by an external polarizing field with the strength periodically modulated along the coordinate, which gives rise to an effective nonlocal nonlinear lattice in the condensate. The existence, shape and stability of bright solitons, appearing in this model, are investigated by means of the variational approximation and numerical methods. The mobility of solitons and interactions between them are studied too.

First author: Sampson, Matthew D., Manganese Catalysts with Bulky Bipyridine Ligands for the Electrocatalytic Reduction of Carbon Dioxide: Eliminating Dimerization and Altering Catalysis, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 5460, (2014)
Abstract: With the goal of improving previously reported Mn bipyridine electrocatalysts in terms of increased activity and reduced overpotential, a bulky bipyridine ligand, 6,6′-dimesityl-2,2′-bipyridine (mesbpy), was utilized to eliminate dimerization in the catalytic cycle. Synthesis, electrocatalytic properties, X-ray diffraction (XRD) studies, and infrared spectroelectrochemistry (IR-SEC) of Mn(mesbpy)(CO)(3)Br and [Mn(mesbpy)(CO)(3)(MeCN)(OTf) are reported. Unlike previously reported Mn bipyridine catalysts, these Mn complexes exhibit a single, two-electron reduction wave under nitrogen, with no evidence of dimerization. The anionic complex, [Mn(mesbpy)(CO)(3)](-), is formed at 300 mV more positive potential than the corresponding state is formed in typical Mn bipyridine catalysts. IR-SEC experiments and chemical reductions with KC8 provide insights into the species leading up to the anionic state, specifically that both the singly reduced and doubly reduced Mn complexes form at the same potential. When formed, the anionic complex binds CO2 with H+, but catalytic activity does not occur until a similar to 400 mV more negative potential is present. The Mn complexes show high activity and Faradaic efficiency for CO2 reduction to CO with the addition of weak Bronsted acids. IR-SEC experiments under CO2/H+ indicate that reduction of a Mn(I)-CO2H catalytic intermediate may be the cause of this unusual “over-reduction” required to initiate catalysis.

First author: Nagata, Koichi, Syntheses and Structures of Terminal Arylalumylene Complexes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53, 3881, (2014)
Abstract: Terminal arylalumylene complexes of platinum [Ar-Al-Pt(PCy3)(2)] (Ar=2,6-[CH(SiMe3)(2)](2)C6H3 (Bbp) or 2,6-[CH(SiMe3)(2)](2)-4-(tBu)C6H2 (Tbb)) have been synthesized either by the reaction of a dialumene-benzene adduct with [Pt(PCy3)(2)], or by the reduction of 1,2-dibromodialumanes Ar(Br)Al-Al(Br)Ar in the presence of [Pt(PCy3)(2)]. X-Ray crystallographic analysis reveals that the AlPt bond lengths of these arylalumylene complexes are shorter than the previously reported shortest AlPt distance. DFT calculations suggest that the AlPt bonds in the arylalumylene complexes have a significantly high electrostatic character.

First author: Lo, Warrick K. C., Five-Coordinate [Pt-II(bipyridine)(2)(phosphine)](n+) Complexes: Long-Lived Intermediates in Ligand Substitution Reactions of [Pt(bipyridine)(2)](2+) with Phosphine Ligands, INORGANIC CHEMISTRY, 53, 3595, (2014)
Abstract: The reaction of [Pt(N-N)(2)](2+) [N-N = 2,2′-bipyridine (bpy) or 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me(2)bpy)] with phosphine ligands [PPh3 or PPh(PhSO3)(2)(2-)] in aqueous or methanolic solutions was studied by multinuclear (H-1, C-13, P-31, and Pt-195) NMR spectroscopy, X-ray crystallography, UV-visible spectroscopy, and high-resolution mass spectrometry. NMR spectra of solutions containing equimolar amounts of [Pt(N-N)(2)](2+) and phosphine ligand give N: evidence for rapid formation of long-lived, 5-coordinate [Pt-II(N-N)(2)(phosphine)](n+) complexes. In the presence of excess phosphine ligand, these intermediates undergo much slower entry of a second phosphine ligand and loss of a bpy ligand to give [Pt-II(N-N)(phosphine)(2)](n+) as the final product. The coordination of a phosphine ligand to the Pt(II) ion in the intermediate [Pt(N-N)(2)(phosphine)](n+) complexes is supported by the observation of P-31-Pt-195 coupling in the P-31 NMR spectra. The 5-coordinate nature of [Pt(bpy)(2){PPh(PhSO3)(2)}] is confirmed by X-ray crystallography. X-ray crystal structural analysis shows that the Pt(II) ion in [Pt(bpy)(2){PPh(PhSO3)(2)}]center dot 5.5H(2)O displays a distorted square pyramidal geometry, with one bpy ligand bound asymmetrically. These results provide strong support for the widely accepted associative ligand substitution mechanism for square planar Pt(II) complexes. X-ray structural characterization of the distorted square planar complex [Pt(bpy)(PPh3)(2)](ClO4)(2) confirms this as the final product of the reaction of [Pt(bpy)(2)](2+) with PPh3 in CD3OD. The results of density functional calculations on [Pt(bpy)(2)](2+), [Pt(bpy)(2)(phosphine)](n+), and [Pt(bpy)(phosphine)2](n+) indicate that the bonding energy follows the trend of [Pt(bpy)(phosphine)(2)](n+) > [Pt(bpy)(2)(phosphine)](n+) > [Pt(bpy)(2)](2+) for stability and that the formation reactions of [Pt(bpy)(2)(phosphine)](n+) from [Pt(bpy)(2)](2+) and [Pt(bpy)(phosphine)(2)](n+) from [Pt(bpy)(2)(phosphine)](n+) are energetically favorable. These calculations suggest that the driving force for the formation of [Pt(bpy)(phosphine)(2)](n+) from [Pt(bpy)(2)](2+) is the formation of a more energetically favorable product.

First author: Cummins, Christopher C., The Stannylphosphide Anion Reagent Sodium Bis(triphenylstannyl) Phosphide: Synthesis, Structural Characterization, and Reactions with Indium, Tin, and Gold Electrophiles, INORGANIC CHEMISTRY,53, 3678, (2014)
Abstract: Treatment of P-4 with in situ generated [Na][SnPh3] leads to the formation of the sodium monophosphide [Na][P(SnPh3)(2)] and the Zintl salt [Na](3)[P-7]. The former was isolated in 46% yield as the crystalline salt [Na(benzo-15-crown-5)][P(SnPh3)(2)] and used to prepare the homoleptic phosphine P(SnPh3)(3), isolated in 67% yield, as well as the indium derivative (XL)(2)InP(SnPh3)(2) (XL = S(CH2)(2)NMe2), isolated in 84% yield, and the gold complex (Ph3P)AuP(SnPh3)(2). The compounds [Na(benzo-15-crown-5)][P(SnPh3)(2)], P(SnPh3)(3), (XL)(2)InP(SnPh3)(2), and (Ph3P)AuP(SnPh3)(2) were characterized using multinuclear NMR spectroscopy and X-ray crystallography. The bonding in (Ph3P)AuP(SnPh3)(2) was dissected using natural bond orbital (NBO) methods, in response to the observation from the X-ray crystal structure that the dative P -> Au bond is slightly shorter than the shared electron-pair P-Au bond. The bonding in (XL)(2)InP(SnPh3)(2) was also interrogated using P-31 and C-13 solid-state NMR and computational methods. Co-product [Na](3)[P-7] was isolated in 57% yield as the stannyl heptaphosphide P-7(SnPh3)(3), following salt metathesis with ClSnPh3. Additionally, we report that treatment of P-4 with sodium naphthalenide in dimethoxyethane at 22 degrees C is a convenient and selective method for the independent synthesis of Zintl ion [Na](3)[P-7]. The latter was isolated as the silylated heptaphosphide P-7(SiMe3)(3), in 67% yield, or as the stannyl heptaphosphide P-7(SnPh3)(3) in 65% yield by salt metathesis with ClSiMe3 or ClSnPh3, respectively.

First author: Sanyal, Somananda, Functional Corannulene: Diverse Structures, Enhanced Charge Transport, and Tunable Optoelectronic Properties, CHEMPHYSCHEM, 15, 885, (2014)
Abstract: Chemical functionalization of various hydrocarbons, such as coronene, corannulene, and so forth, shows good promise in electronics applications because of their tunable optoelectronic properties. By using quantum chemical calculations, we have investigated the changes in the corannulene buckybowl structure, which greatly affect its electronic and optical properties when functionalized with different electron-withdrawing imide groups. We find that the chemical nature and position of functional groups strongly regulate the stacking geometry, -stacking interactions, and electronic structure. Herein, a range of optoelectronic properties and structure-property relationships of various imide-functionalized corannulenes are explored and rationalized in detail. In terms of carrier mobility, we find that the functionalization strongly affects the reorganization energy of corannulene, while the enhanced stacking improves hopping integrals, favoring the carrier mobility of crystals of pentafluorophenylcorannulene-5-monoimide. The study shows a host of emerging optoelectronic properties and enhancements in the charge-transport characteristics of functionalized corannulene, which may find possible semiconductor and electronics applications.

First author: Manna, Debashree, Pu@C-24: A New Example Satisfying the 32-Electron Principle, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 7211, (2014)
Abstract: A transition in point group symmetry from C-2 to D-6d in the classical cage isomer of C-24 cluster is observed after encapsulation of a plutonium atom within it. This encapsulation leads to highly stable Pu@C-24 cluster, which is well supported by the structural, energetic, and thermodynamic aspects. This study has been carried out with first five low-lying isomers of C24 fullerene, among which one is classical fullerene consisting of only five- and six-membered rings (MR) and remaining four isomers are nonclassical fifflerene consisting of five and six MR along with varying number of four MR. The structural and stability aspects are investigated extensively for the Pu@C24 cluster. For the purpose of comparison we have also considered some other lanthanides/actinides with 8 valence electrons (Cm2+, Sm, and Gd2+) and investigated the encapsulation process into different C24 isomers. It has been found that the Pu@C24 cluster is the most stable one among all the metallofullerenes considered here. For Pu@C24, it has been observed that HOMO-LUMO gap is changed from 1.83 to 3.26 eV after encapsulation of a Pu atom into the bare classical C24 cage. It is interesting to note that the bare C24 nonclassical (C2 symmetry) cluster is the most stable one; however, after encapsulation, the classical isomer becomes the most stable with significant energy differences. The detail vibrational and electronic spectral studies have also been carried out for the classical Pu@C24 metallofullerene. High HOMO-LUMO gaps and positive binding energy values for the Pu@C24 clusters and negatives values of reaction enthalpy and free energy corresponding to the encapsulation process indicate toward possible formation of Pu@C24 and subsequent experimental detection. High stability of the Pu@C24 cluster can be rationalized through the fulfilment of 32 valence electron count corresponding to the fully occupied spdf shells for the central metal atom.

First author: Su, Peifeng, Energy Decomposition Scheme Based on the Generalized Kohn-Sham Scheme, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 2531, (2014)
Abstract: In this paper, a new energy decomposition analysis scheme based on the generalized Kohn-Sham (GKS) and the localized molecular orbital energy decomposition analysis (LMO-EDA) scheme, named GKS-EDA, is proposed. The GKS-EDA scheme has a wide range of DFT functional adaptability compared to LMO-EDA. In the GKS-EDA scheme, the exchange, repulsion, and polarization terms are determined by DFT orbitals; the correlation term is defined as the difference of the GKS correlation energy from monomers to supermolecule. Using the new definition, the GKS-EDA scheme avoids the error of LMO-EDA which comes from the separated treatment of E-X and E-C functionals. The scheme can perform analysis both in the gas and in the condensed phases with most of the popular DFT functionals, including LDA, GGA, meta-GGA, hybrid GGA/meta-GGA, double hybrid, range-separated (long-range correction), and dispersion correction. By the GKS-EDA scheme, the DFT functionals assessment for hydrogen bonding, vdW interaction, symmetric radical cation, charge-transfer, and metal-ligand interaction is performed.

First author: Neff, Julia L., Epitaxial Growth of Pentacene on Alkali Halide Surfaces Studied by Kelvin Probe Force Microscopy, ACS NANO, 8, 3294, (2014)
Abstract: In the field of molecular electronics, thin films of molecules adsorbed on insulating surfaces are used as the functional building blocks of electronic devices. Control of the structural and electronic properties of the thin films is required for reliably operating devices. Here, noncontact atomic force and Kelvin probe force microscopies have been used to investigate the growth and electrostatic landscape of pentacene on KBr(001) and KCl(001) surfaces. We have found that, together with molecular islands of upright standing pentacene, a new phase of tilted molecules appears near step edges on KBr. Local contact potential differences (LCPD) have been studied with both Kelvin experiments and density functional theory calculations. Our images reveal that differently oriented molecules display different LCPD and that their value is independent of the number of molecular layers. These results point to the formation of an interface dipole, which may be explained by a partial charge transfer from the pentacene to the surface. Moreover, the monitoring of the evolution of the pentacene islands shows that they are strongly affected by dewetting: Multi layers build up at the expense of monolayers, and in the Kelvin images, previously unknown line defects appear, which reveal the epitaxial growth of pentacene crystals.

First author: Verma, Anuj A., NO oxidation: A probe reaction on Cu-SSZ-13, JOURNAL OF CATALYSIS, 312, 179, (2014)
Abstract: The site requirements and mechanism of dry NO oxidation were examined on a series of Cu-SSZ-13 catalysts (silicon/aluminum atomic ratio = 4.5) with Cu:total-aluminum (Cu/AI(tot)) atomic ratios ranging from 0.02 to 1.6. Catalysts with Cu/Al-tot atomic ratio <0.2 exhibit immeasurable NO oxidation rates (per mole Cu), while NO oxidation rates increase monotonically with Cu/Al-tot atomic ratio from 0.2 up to 0.5. Hydrated Cu-SSZ-13 catalysts with Cu/Al-tot atomic ratio < 0.2 exhibit a near infrared feature at 12,500 cm(-1) under ambient conditions that we assign to a d-d transition of an isolated, hydrated Cu2+ ion. X-ray absorption near edge structure (XANES) measurements on the same catalysts under ambient conditions quantitatively match a [Cu(H2O)(6)](2+) reference. The 12,500 cm(-1) feature intensity is constant above Cu/Al-tot atomic ratio = 0.2, implying that the additional Cu ions adopt other configurations. Catalysts with Cu/Al-tot atomic ratio > 0.2 also showed an increasing percentage of CuxOy species (clustered Cu2+ ions x >= 2, y >= 1) as quantified by XANES under ambient conditions. Saturation of these isolated Cu2+ sites at Cu/Al-tot atomic ratio = 0.2 is consistent with the expected number of 6-membered ring Al-tot pair sites available to accommodate them. The hydrated isolated Cu2+ ions in catalysts with Cu/Al-tot atomic ratio < 0.2 are quantitatively converted to dehydrated isolated Cu2+ ions under NO oxidation conditions and do not contribute measurably to the rate of NO oxidation. In contrast, in situ XANES experiments show that the CuxOy species remain present under NO oxidation conditions (300 ppm NO, 150 ppm NO2, and 10% O-2, at 300 degrees C) and contribute linearly to the rate of NO oxidation per mole Cu (at 300 degrees C). We used density functional theory (OFT) calculations to compare the ability of isolated Cu ions and Cu dimers (Cu2Oy) species to support NO oxidation. Only the Cu dimers can accommodate adsorption and dissociation of O-2 necessary to catalyze NO oxidation. We hypothesize that activated oxygen enables NO to form NO2 in a kinetically-relevant step. These findings reveal that dry NO oxidation (300 ppm NO, 150 ppm NO2, and 10% O-2) can be used as a probe reaction to identify clustering of Cu ions on Cu-SSZ-13.

First author: Raju, Muralikrishna, Mechanisms of Oriented Attachment of TiO2 Nanocrystals in Vacuum and Humid Environments: Reactive Molecular Dynamics, NANO LETTERS, 14, 1836, (2014)
Abstract: Oriented attachment (OA) of nanocrystals is now widely recognized as a key process in the solution-phase growth of hierarchical nanostructures. However, the microscopic origins of OA remain unclear. We perform molecular dynamics simulations using a recently developed ReaxFF reactive force field to study the aggregation of various titanium dioxide (anatase) nanocrystals in vacuum and humid environments. In vacuum, the nanocrystals merge along their direction of approach, resulting in a polycrystalline material. By contrast, in the presence of water vapor the nanocrystals reorient themselves and aggregate via the OA mechanism to form a single or twinned crystal. They accomplish this by creating a dynamic network of hydrogen bonds between surface hydroxyls and surface oxygens of aggregating nanocrystals. We determine that OA is dominant on surfaces that have the greatest propensity to dissociate water. Our results are consistent with experiment, are likely to be general for aqueous oxide systems, and demonstrate the critical role of solvent in nanocrystal aggregation. This work opens up new possibilities for directing nanocrystal growth to fabricate nanomaterials with desired shapes and sizes.

First author: Suresh, D., Tunable Fluorophores Based on 2-(N-Arylimino)pyrrolyl Chelates of Diphenylboron: Synthesis, Structure, Photophysical Characterization, and Application in OLEDs, CHEMISTRY-A EUROPEAN JOURNAL, 20, 4126, (2014)
Abstract: Reactions of 2-(N-arylimino)pyrroles (HNC4H3C(H)N-Ar) with triphenylboron (BPh3) in boiling toluene afford the respective highly emissive N,N-boron chelate complexes, [BPh2{N-2,N-NC4H3C(H)N-Ar}] (Ar=C6H5 (12), 2,6-Me-2-C6H3 (13), 2,6-iPr(2)-C6H3 (14), 4-OMe-C6H4 (15), 3,4-Me-2-C6H3 (16), 4-F-C6H4 (17), 4-NO2-C6H4 (18), 4-CN-C6H4 (19), 3,4,5-F-3-C6H2 (20), and C6F5 (21)) in moderate to high yields. The photophysical properties of these new boron complexes largely depend on the substituents present on the aryl rings of their N-arylimino moieties. The complexes bearing electron-withdrawing aniline substituents 17-20 show more intense (e.g., phi(f)=0.71 for Ar=4-CN-C6H4 (19) in THF), higher-energy (blue) fluorescent emission compared to those bearing electron-donating substituents, for which the emission is redshifted at the expense of lower quantum yields (phi(f)=0.13 and 0.14 for Ar=4-OMe-C6H4 (15) and 3,4-Me-2-C6H3 (16), respectively, in THF). The presence of substituents bulkier than a hydrogen atom at the 2,6-positions of the aryl groups strongly restricts rotation of this moiety towards coplanarity with the iminopyrrolyl ligand framework, inducing a shift in the emission to the violet region ((max)=410-465nm) and a significant decrease in quantum yield (phi(f)=0.005, 0.023, and 0.20 for Ar=2,6-Me-2-C6H3 (13), 2,6-iPr(2)-C6H3 (14), and C6F5 (21), respectively, in THF), even when electron-withdrawing groups are also present. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have indicated that the excited singlet state has a planar aryliminopyrrolyl ligand, except when prevented by steric hindrance (ortho substituents). Calculated absorption maxima reproduce the experimental values, but the error is higher for the emission wavelengths. Organic light-emitting diodes (OLEDs) have been fabricated with the new boron complexes, with luminances of the order of 3000cdm(-2) being achieved for a green-emitting device.

First author: Turbervill, Robert S. P., Hydropnictination Reactions of Carbodiimides and Isocyanates with Protonated Heptaphosphide and Heptaarsenide Zintl Ions, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2014, 1660, (2014)
Abstract: By following a similar procedure to that employed for the synthesis of [HP7](2-) (1), the synthesis and characterization of the hydrogenheptaarsenide dianion [HAs7](2-) (2) was achieved. Building on previous research that has shown that [HP7](2-) can react with carbodiimides to yield amidine-functionalized cluster anions [P7C(NHR)(NR)](2-), we have found that the analogous hydroarsination reactions are also possible by reaction of 2 with RC=N=CR to yield [As7C(NHR)(NR)](2-) [R = Dipp (3), iPr (4) and Cy (5); Dipp = 2,6-diisopropylphenyl]. Furthermore, we also demonstrate that such hydropnictination reactions can be extended to other heteroallenes such as isocyanates (O=C=NAd; Ad = adamantyl) to afford the amide-derivatized cluster anions [E7C(CO)(NHAd)](2-) [E = P (6) and As (7)]. All new compounds were characterized by multinuclear NMR spectroscopy, elemental analyses and electrospray mass spectrometry. Clusters 2, 4, 6 and 7 were also characterized by single-crystal X-ray diffraction of [K(18-crown-6)](2)[2], [K(18-crown-6)](2)[4], [K(18-crown-6)](2)[6]py (py = pyridine) and [K(18-crown-6)](2)[7]py. Crystal structures confirming composition and connectivity were also obtained for anions 3 and 5.

First author: Mancini, Daiana T., Tc-99 NMR as a promising technique for structural investigation of biomolecules: theoretical studies on the solvent and thermal effects of phenylbenzothiazole complex, MAGNETIC RESONANCE IN CHEMISTRY, 52, 129, (2014)
Abstract: The phenylbenzothiazole compounds show antitumor properties and are highly selective. In this paper, the Tc-99 chemical shifts based on the (Tc-99m)(CO)(3)(NNO) complex conjugated to the antitumor agent 2-(4 ‘-aminophenyl)benzothiazole are reported. Thermal and solvent effects were studied computationally by quantum-chemical methods, using the density functional theory (DFT) (DFT level BPW91/aug-cc-pVTZ for the Tc and BPW91/IGLO-II for the other atoms) to compute the NMR parameters for the complex. We have calculated the Tc-99 NMR chemical shifts of the complex in gas phase and solution using different solvation models (polarizable continuum model and explicit solvation). To evaluate the thermal effect, molecular dynamics simulations were carried, using the atom-centered density matrix propagation method at the DFT level (BP86/LanL2dz). The results highlight that the Tc-99 NMR spectroscopy can be a promising technique for structural investigation of biomolecules, at the molecular level, in different environments.

First author: Wang, Haopeng, The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters,JOURNAL OF CHEMICAL PHYSICS, 140, 129, (2014)
Abstract: Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of MgmAln-(m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e. g., in Mg3Al11 and Mg2Al12-, did the aluminum moieties exhibit Zintl anion-like characteristics.

First author: Wiegand, Thomas, Indirect “No-Bond” (PP)-P-31-P-…31 Spin-Spin Couplings in P,P-[3]Ferrocenophanes: Insights from Solid-State NMR Spectroscopy and DFT Calculations, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 2316, (2014)
Abstract: No-bond P-31-P-31 indirect dipolar couplings, which arise from the transmission of nuclear spin polarization through interaction of proximal nonbonded electron pairs have been investigated in the solid state for a series of closely related substituted P,P-[3]ferrocenophanes and model systems. Through variation and combination of ligands (phenyl, cyclohexyl, isopropyl) at the two phosphorus sites, the (PP)-P-… distances in these compounds can be varied from 3.49 to 4.06 angstrom. Thus, the distance dependence of the indirect no-bond coupling constant J(nb), can be studied in a series of closely related compounds. One- and two-dimensional solid-state NMR experiments serve to establish the character of these couplings and to measure the isotropic coupling constants L., which were found to range between 12 and 250 Hz. To develop an understanding of the magnitude of J(nb), in terms of molecular structure, their dependences on intramolecular internuclear distances and relative orbital orientations is discussed by DFT-calculations on suitable models. In agreement with the literature the dependence of j(nb) on the P.-P distance is found to be exponential; however, the steepness of this curve is highly dependent on the internuclear equilibrium distance. For a quantitative description, the off-diagonal elements of the expectation value of the Kohn-Sham-Fock operator in the LMO basis for the LMOs of the two phosphorus lone-pairs is proposed. This parameter correlates linearly with the calculated jnb values and possesses the same distance-dependence. In addition, the simulations indicate a distinct dependence of jnb on the dihedral angle defined by the two C P bonds providing ligation to the molecular backbone. For disordered materials or those featuring multiple sites, conformers, and/or polymorphism, a new double-quantum NMR method termed DQDRENAR can be used to conveniently measure internuclear P-31-P-31 distances. If conducted on compounds with known P P distances, such measurements can also serve to estimate the magnitude of the anisotropy Delta J of these no-bond indirect spin spin couplings. The DFT results suggest that in the present series of compounds the magnitude of Delta J is strongly correlated with that of the isotropic component, as both parameters have analogous distance dependences. While our studies indicate a sizable J-anisotropy for the model compound 1,8-bis(diphenylphosphino)napthalene (Delta J similar to -70 Hz), the corresponding values for the P,P43]ferrocenophanes are significantly smaller, affecting their DQ:DRENAR curves only in a minor way. Based on the above insights, the structural aspects of conformational disorder and polymorphism observed in some of the P,P-[3]ferrocenophanes are discussed.

First author: Garcia-Lastra, J. M., Sharp Lines Due to Cr3+ and Mn2+ Impurities in Insulators: Going Beyond the Usual Tanabe-Sugano Approach, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 2377, (2014)
Abstract: This work is aimed at understanding the different behavior of optical sharp lines (corresponding to 10Dq-independent transitions) of Mn2+ and Cr3+ If in normal and inverted perovskites that cannot be explained within the usual Tanabe-Sugano approach. In particular, we want to clarify why on passing from KMgF3:M to LiBaF3:M (M = Mn2+, Cr3+) the energy, E((6)A(1) -> (4)A(1)), for Mn2+ decreases by A = 1100 cm(-1), while A < 100 cm(-1) for the energy E((6)A(1) -> (4)A(2)) corresponding to Cr3+. The origin of this surprising difference in these model systems is clarified by writing the transition energies of MF6 complexes through the ten Coulomb and exchange integrals consistent with the cubic symmetry and not considered in the usual Tanabe-Sugano approach. It is shown that E((6)A -> (4)A1) depends on exchange integrals K(3z(2) – r(2), xy) and K(x(2) – y(2), xy), while E(E-2 -> (4)A2) depends on K(xz, yz) where the two involved electrons display a g character. These exchange integrals have been calculated just considering a MF6 unit subject to the internal electric field due to the rest of the lattice ions. In addition to a reasonably reproduction of the main trends observed experimentally for the model systems, the present calculations prove that the exchange integrals are not related in a simple way to the covalency of involved orbitals. Particular attention is also paid to explain why the transitions, which are 10Dq-independent are less sensitive to the host lattice change than those which do depend on 10Dq. The present work shows that K(xz, yz)for Cr3+ is particularly insensitive to the host lattice change and thus sheds light on the origin of the near independence of E(E-2 -> (4)A(2)) along the series of oxides doped with such an impurity.

First author: Hooper, James, Composition and Constitution of Compressed Strontium Polyhydrides, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 6433, (2014)
Abstract: The structures of the strontium polyhydrides, SrHn with n > 2, under pressure are studied using evolutionary algorithms coupled with density functional theory calculations. A number of phases with even n are found to be thermodynamically stable below 150 GPa. Particularly interesting is the SrH4 stoichiometry, which comprises the convex hull at 50, 100, and 150 GPa. Its hydrogenic sublattice contains H-2 and H- units, and throughout the pressure range considered, it adopts one of two configurations which were previously predicted for CaH4 under pressure. At 150 GPa, the SrH6 stoichiometry has the lowest enthalpy of formation. The most stable configuration assumes P (3) over bar symmetry, and its lattice consists of one-dimensional H-2 center dot center dot center dot H- hydrogenic chains. Symmetrization of these chains results in the formation of (1)(infinity)[H-delta(-)] helices, which are reminiscent of the trigonal phase of sulfur. The R (3) over barm-SrH6 phase, which is comprised of these helices, becomes dynamically stable by 250 GPa and has a high density of states at the Fermi level. We explore the geometric relationships between R (3) over barm-SrH6 and the Im (3) over barm-CaH6 and Imm2-BaH6 structures found in prior investigations.

First author: Tiferet, Eitan, The Energy Landscape of Uranyl- Peroxide Species, CHEMISTRY-A EUROPEAN JOURNAL,20, 3646, (2014)
Abstract: Nanoscale uranyl peroxide clusters containing UO22+ groups bonded through peroxide bridges to form polynuclear molecular species (polyoxometalates) exist both in solution and in the solid state. There is an extensive family of clusters containing 28uranium atoms (U-28 clusters), with an encapsulated anion in the center, for example, [UO2(O-2)(3-x)(OH)(x)(4-)], [Nb(O-2)(4)(3-)], or [Ta(O-2)(4)(3-)]. The negative charge of these clusters is balanced by alkali ions, both encapsulated, and located exterior to the cluster. The present study reports measurement of enthalpy of formation for two such U-28 compounds, one of which is uranyl centered and the other is peroxotantalate centered. The [(Ta(O-2)(4)]-centered U-28 capsule is energetically more stable than the [(UO2)(O-2)(3)]-centered capsule. These data, along with our prior studies on other uranyl-peroxide solids, are used to explore the energy landscape and define thermochemical trends in alkali-uranyl-peroxide systems. It was suggested that the energetic role of charge-balancing alkali ions and their electrostatic interactions with the negatively charged uranyl-peroxide species is the dominant factor in defining energetic stability. These experimental data were supported by DFT calculations, which agree that the [(Ta(O-2)(4)]-centered U-28 capsule is more stable than the uranyl-centered capsule. Moreover, the relative stability is controlled by the interactions of the encapsulated alkalis with the encapsulated anion. Thus, the role of alkali-anion interactions was shown to be important at all length scales of uranyl-peroxide species: in both comparing clusters to clusters; and clusters to monomers or extended solids.

First author: Monakhov, Kirill Yu., Magnetochemical Complexity of Hexa- and Heptanuclear Wheel Complexes of Late-3d Ions Supported by N, O- Donor PyridylMethanolate Ligands, CHEMISTRY-A EUROPEAN JOURNAL, 20, 3769, (2014)
Abstract: The scaffold geometries, stability and magnetic features of the (pyridine-2-yl)methanolate (L) supported wheel-shaped transition-metal complexes with compositions [M6L12] (1), [Na< subset of>(ML2)(6)](+) (2), and [M< subset of>(ML2)(6)](2+) (3), in which M=Co-II, Ni-II, Cu-II, and Zn-II were investigated with density functional theory (DFT). The goals of this study are manifold: 1)To advance understanding of the magnetism in the synthesized compounds [Na< subset of>(ML2)(6)](+) and [M< subset of>(ML2)(6)](2+) that were described in Angew. Chem. Int. Ed. 2010, 49, 4443 (I-{Na< subset of>Ni-6}, I-{Ni< subset of>Ni-6}) and Dalton Trans. 2011, 40, 10526 (II-{Na< subset of>Co-6}, II-{Co< subset of>Co-6}); 2)To disclose how the structural, electronic, and magnetic characteristics of 1, 2, and 3 change upon varying M-II from d(7) (Co2+) to d(10) (Zn2+); 3)To estimate the influence of the Na+ and M2+ ions (XQ+) occupying the central voids of 2 and 3 on the external and internal magnetic coupling interactions in these spin structures; 4)To assess the relative structural and electrochemical stabilities of 1, 2, and 3. In particular, we focus here on the net spin polarization, the determination of the strength and the sign of the exchange coupling energies, the rationalization of the nature of the magnetic coupling, and the ground-state structures of 1, 2, and 3. Our study combines the broken symmetry DFT approach and the model Hamiltonian methodology implemented in the computational framework CONDON 2.0 for the modeling of molecular spin structures, to interpret magnetic susceptibility measurements of I-{Na< subset of>Ni-6} and I-{Ni< subset of>Ni-6}. We illustrate that whereas the structures, stability and magnetism of 1, 2, and 3 are indeed influenced by the nature of 3d transition-metals in the {M-6} rims, the XQ+ ions in the inner cavities of 2 and 3 impact these properties to an even larger degree. As exemplified by I-{Ni< subset of>Ni-6}, such heptanuclear complexes exhibit ground-state multiplets that cannot be described by simplistic model of spin-up and spin-down metal centers. Furthermore, we assess how future low-temperature susceptibility measurements at high magnetic fields can augment the investigation of compound3 with M=Co, Ni.

First author: Hu, Shao-Wen, Effect of H2O on the hydrolysis of UF6 in the gas phase, JOURNAL OF MOLECULAR STRUCTURE, 1062, 29, (2014)
Abstract: In our previous works (Hu et al., 2008, 2009), we found the theoretical evidence that indicates UF5OH is an intermediate produced in the first step of UF6 hydrolysis, UF6 + H2O. When UF6/H2O ratio is high, UF5OH may react with UF6 or another UF5OH, forming species containing U-O-U bond. In this work, we considered another situation – the hydrolysis of UF6 in excess of H2O, and explored the probable initial reactions of UF6 + 2H(2)O and UF6 + 3H(2)O systems using the same relativistic density functional theory calculations. Water molecules may form dimer or trimer and then coordinate with UF6, forming complexes UF6 center dot 2H(2)O or UF6 center dot 3H(2)O, which are more stable than UF6 center dot H2O. Compared to the conversion UF6 center dot H2O -> UF5 OH center dot HF, the energy barriers of reactions UF6 center dot 2H(2)O -> UF5OH center dot H2O center dot HF and UF6 center dot 3H(2)O -> UF5OH center dot 2H(2)O center dot HF are 4 and 6 kcal/mol lower respectively. The additional H2O molecules catalyze the reactions by bridging the hydrogen which transfers from ligand H2O to F and stabilizes the transition states. In addition, as water content increases, the reaction step UF6 + 3H(2)O becomes exothermic and the products-HF, UF5 OH and two H2O molecules-tend to bond tightly into a stable complex.

First author: Chadha, Preeti, Manganese(II) Alkyl/pi-Allyl Complexes Resistant to Ligand Redistribution,ORGANOMETALLICS, 33, 1467, (2014)
Abstract: The reaction of [Li(THF)(4)][(Mn{C-(SiMe3)(3)})(3)(mu-Cl)(4)(THF)] (1) with K(allyl(TMS2)) (allyl(TMS2) = 1,3-C3H3(SiMe3)(2)) afforded [(eta(3)-allyl(TIMS2))Mn{C(SiMe3)(3)}-{ClLi(THF)(3)}] (2). Attempted sublimation of 2 yielded [(eta(3)-allyl(TMS2))Mn{C(SiMe3)(3)}(THF)] (3), indicating that 2 extrudes LiCl at elevated temperatures. Additionally, LiCl in 2 was displaced by reaction with PMe3, quinuclidine, and dmap (dmap = 4-(dimethylamino)pyridine), providing [(eta(3)-allyl(TMS2))Mn{C(SiMe3)(3)}(L)] (L = PMe3 (4), quinuclidine (5), dmap (6)). Treatment of PMe3 complex 4 with BPh3 yielded bright red [(allyl(TMS2))Mn{C(SiMe3)(3)}] (7) accompanied by a precipitate of Ph3B(PMe3). Mixed alkyl/pi-ally manganese(II) complexes 2-7 are pyrophoric red solids with a high-spin d(5) configuration, and all were crystallographically characterized. In the solid-state structures, the allyl ligands in 2-6 adopt a syn,syn configuration, whereas in base-free 7, the allyl ligand has a syn,anti configuration. Complexes 4, 5, and 7 sublimed cleanly (5 mTorr) at 70, 90, and 50 degrees C, respectively. Complex 4 exhibited a particularly favorable combination of volatility and thermal stability, given that its appearance and powder X-ray diffraction pattern were unchanged after 24 h in a sealed flask at 100 degrees C. Compounds 2-7 are the first high-spin d(5) mixed alkyl/allyl complexes, and 7 is the first room-temperature-stable example of a mononuclear transition-metal complex bearing only alkyl and allyl ligands.

First author: Johnson, Phillip S., Crystal fields of porphyrins and phthalocyanines from polarization-dependent 2p-to-3d multiplets, JOURNAL OF CHEMICAL PHYSICS, 140, 1467, (2014)
Abstract: Polarization-dependent X-ray absorption spectroscopy is combined with density functional calculations and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal phthalocyanines and octaethylporphyrins (Mn, Fe, Co, Ni). The polarization dependence facilitates the assignment of the multiplets in terms of in-plane and out-of-plane orbitals and avoids ambiguities. Crystal field values from density functional calculations provide starting values close to the optimum fit of the data. The resulting systematics of the crystal field can be used for optimizing electron-hole separation in dye-sensitized solar cells.

First author: Tian, Yuan, Speciation and thermodynamic properties of manganese(II) chloride complexes in hydrothermal fluids: In situ XAS study, GEOCHIMICA ET COSMOCHIMICA ACTA, 129, 77, (2014)
Abstract: The speciation of Mn(II) in acidic brines under a wide range of conditions (30-550 degrees C, 600 bar, 0.100-10.344 m chloride and 0.110-2.125 m bromide) was investigated using in situ X-ray Absorption Spectroscopy (XAS). Increasing temperature and/or salinity results in a structural change of the Mn(II) complexes from octahedral to (distorted) tetrahedral. Octahedral species predominate at room temperature within the whole salinity range and persist up to similar to 400 degrees C in low salinity solutions (m(Cl) < 1 m), and tetrahedral species become significant above 300 degrees C. A combination of EXAFS refinements, Density Functional Theory calculations and ab initio XANES simulations shows that at temperatures >= 400 degrees C, the highest order chlorocomplex predominating in high salinity solutions (m(Cl) > 3 m, Cl:Mn ratio > 53) is MnCl3(H2O)(-), and that a lower order chlorocomplex, MnCl2(H2O)(2(aq)), is the predominant species in low salinity solutions (m(Cl) < 0.5 m, Cl:Mn ratio < 10). A similar result was also found in Mn bromide solutions: MnBr3(H2O)(-) and MnBr2(H2O)(2(aq)) are the dominant species at 500 degrees C in high salinity solutions (e.g., 2.125 m, Br:Mn ratio = 33.73) and in low salinity solutions (e.g., 0.110 m, Br:Mn ratio = 2.04), respectively. XANES spectra of Mn(II) chloride solutions were used to retrieve formation constants of MnCl2(H2O)(2(aq)) and MnCl3(H2O)(-) at 600 bar. The speciation and thermodynamic model of this study are consistent with previous solubility and UV-Vis spectroscopic studies.

First author: Perekalin, Dmitry S., Synthesis of cyclohexadienyl ruthenium arene complexes by replacement of acetonitrile ligands in [(eta(5)-C6H7)Ru(MeCN)(3)](+), JOURNAL OF ORGANOMETALLIC CHEMISTRY, 754, 1, (2014)
Abstract: Heating of the cyclohexadienyl ruthenium complex [(eta(5)-C6H7)Ru(MeCN)3](+) (1) with arenes results in replacement of acetonitrile ligands giving complexes [(eta(5)-C6H7)Ru(arene)](+) (arene toluene, o-xylene, hexamethylbenzene, p-toluidine, benzo-15-crown-5, ethyl ester of N-acetylphenylalanine) in 53-93% yields. Similar reaction of 1 with naphthalene produces labile complex [(eta(5)-(CH7)-H-6)Ru(naphthalene)](+) which readily undergoes solvolysis in acetone. The reaction of 1 with 1,5-cyclooctadiene unexpectedly gives the benzene complex [(eta(3), eta(2)-C8H11)Ru(C6H6)](+) in 44% yield, as a result of formal abstraction of two hydrogen atoms. Energy decomposition analysis revealed that the cyclohexadienyl ruthenium cation [(eta(5)-C6H7)Ru](+) is less arenophilic then [CpRu](+) due to weaker orbital interaction with arenes. The structure of [(eta(5)-C6H7)Ru(benzo-15-crown-5)]PF6 was established by X-ray diffraction.

First author: Goetz, Andreas W., Calculation of nuclear spin-spin coupling constants using frozen density embedding,JOURNAL OF CHEMICAL PHYSICS, 140, 1, (2014)
Abstract: We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between Hg-199 and C-13 upon coordination of dimethylsulfoxide solvent molecules.

First author: Kubas, Adam, Electronic couplings for molecular charge transfer: Benchmarking CDFT, FODFT, and FODFTB against high-level ab initio calculations, JOURNAL OF CHEMICAL PHYSICS, 140, 1, (2014)
Abstract: We introduce a database (HAB11) of electronic coupling matrix elements (H-ab) for electron transfer in 11 pi-conjugated organic homo-dimer cations. High-level ab inito calculations at the multireference configuration interaction MRCI+Q level of theory, n-electron valence state perturbation theory NEVPT2, and (spin-component scaled) approximate coupled cluster model (SCS)-CC2 are reported for this database to assess the performance of three DFT methods of decreasing computational cost, including constrained density functional theory (CDFT), fragment-orbital DFT (FODFT), and self-consistent charge density functional tight-binding (FODFTB). We find that the CDFT approach in combination with a modified PBE functional containing 50% Hartree-Fock exchange gives best results for absolute H-ab values (mean relative unsigned error = 5.3%) and exponential distance decay constants beta (4.3%). CDFT in combination with pure PBE overestimates couplings by 38.7% due to a too diffuse excess charge distribution, whereas the economic FODFT and highly cost-effective FODFTB methods underestimate couplings by 37.6% and 42.4%, respectively, due to neglect of interaction between donor and acceptor. The errors are systematic, however, and can be significantly reduced by applying a uniform scaling factor for each method. Applications to dimers outside the database, specifically rotated thiophene dimers and larger acenes up to pentacene, suggests that the same scaling procedure significantly improves the FODFT and FODFTB results for larger pi-conjugated systems relevant to organic semiconductors and DNA.

First author: Meng, Wenjing, Empirical and Theoretical Insights into the Structural Features and Host-Guest Chemistry of M8L4 Tube Architectures, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 3972, (2014)
Abstract: We demonstrate a general method for the construction of M8L4 tubular complexes via subcomponent self-assembly, starting from Cu-I or Ag-I precursors together with suitable elongated tetraamine and 2-formylpyridine subcomponents. The tubular architectures were often observed as equilibrium mixtures of diastereomers having two different point symmetries (D-2d or D2 reversible arrow D-4) in solution. The equilibria between diastereomers were influenced through variation in ligand length, substituents, metal ion identity, counteranion, and temperature. In the presence of dicyanoaurate(I) and Au-I, the D-4-syrnmetric hosts were able to bind linear Au(Au(CN)(2))(2)(-) (with two different configurations) as the best-fitting guest. Substitution of dicyanoargentate(I) for dicyanoaurate(I) resulted in the formation of Ag(Au(CN)(2))(2)(-) as the optimal guest through transmetalation. Density fiinctional theory was employed to elucidate the host-guest chemistries of the tubes.

First author: Hall, Gabriel B., Intramolecular Electron Transfer in Bipyridinium Disulfides, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 4012, (2014)
Abstract: Reductive cleavage of disulfide bonds is an important step in many biological and chemical processes. Whether cleavage occurs stepwise or concertedly with electron transfer is of interest. Also of interest is whether the disulfide bond is reduced directly by intermolecular electron transfer from an external reducing agent or mediated intramolecularly by internal electron transfer from another redox-active moiety elsewhere within the molecule. The electrochemical reductions of 4,4′-bipyridyl-3,3′-disulfide (1) and the di-N-methylated derivative (2(2+)) have been studied in acetonitrile. Simulations of the cyclic voltammograms in combination with DFT (density functional theory) computations provide a consistent model of the reductive processes. Compound 1 undergoes reduction directly at the disulfide moiety with a substantially more negative potential for the first electron than for the second electron, resulting in an overall two-electron reduction and rapid cleavage of the S S bond to form the dithiolate. In contrast, compound 2(2+) is reduced at less negative potential than 1 and at the dimethyl bipyridinium moiety rather than at the disulfide moiety. Most interesting, the second reduction of the bipyridinium moiety results in a fast and reversible intramolecular two-electron transfer to reduce the disulfide moiety and form the dithiolate. Thus, the redox-active bipyridinium moiety provides a low energy pathway for reductive cleavage of the S S bond that avoids the highly negative potential for the first direct electron reduction. Following the intramolecular two-electron transfer and cleavage of the S S bond the bipyridinium undergoes two additional reversible reductions at more negative potentials.

First author: Li, Wei-Li, Strong electron correlation in UO2-: A photoelectron spectroscopy and relativistic quantum chemistry study, JOURNAL OF CHEMICAL PHYSICS, 140, 4012, (2014)
Abstract: The electronic structures of actinide systems are extremely complicated and pose considerable challenges both experimentally and theoretically because of significant electron correlation and relativistic effects. Here we report an investigation of the electronic structure and chemical bonding of uranium dioxides, UO2- and UO2, using photoelectron spectroscopy and relativistic quantum chemistry. The electron affinity of UO2 is measured to be 1.159(20) eV. Intense detachment bands are observed from the UO2- low-lying (7s sigma(g))(2)(5f phi(u))(1) orbitals and the more deeply bound O2p-based molecular orbitals which are separated by a large energy gap from the U-based orbitals. Surprisingly, numerous weak photodetachment transitions are observed in the gap region due to extensive two-electron transitions, suggesting strong electron correlations among the (7s sigma(g))(2)(5f phi(u))(1) electrons in UO2- and the (7s sigma(g))(1)(5f phi(u))(1) electrons in UO2. These observations are interpreted using multi-reference ab initio calculations with inclusion of spin-orbit coupling. The strong electron correlations and spin-orbit couplings generate orders-of-magnitude more detachment transitions from UO2- than expected on the basis of the Koopmans’ theorem. The current experimental data on UO2- provide a long-sought opportunity to arbitrating various relativistic quantum chemistry methods aimed at handling systems with strong electron correlations.

First author: Sarkar, Uttam K., Plasmon induced and pH controlled semiconductive conformation of 1H-2(phenylazo) imidazole on silver nanoparticles, JOURNAL OF MOLECULAR STRUCTURE, 1061, 104, (2014)
Abstract: A pH controlled SERS study of 1H-2(phenylazo) imidazole (PaiH) is reported. A combination of different conformations is evident; majority preferring a particular conformation at a given pH. PaiH is in cis-form at concentrations 10(-6)-10(-5) M at pH = 7 which undergoes azo to hydrozone conformation in alkaline pH whereas the azo-Ns participate in the electronic interaction at acidic pH. Significant reduction of HOMO-LUMO gap indicates the possibility of PaiH of being an organic semiconductor.

First author: Saranya, G., A theoretical study on optical and charge transport properties of anthra-[1,2-b:4,3-b ‘:5,6-b ”:8,7-b !”]tetrathiophene molecules, CHEMICAL PHYSICS, 433, 48, (2014)
Abstract: The optical and charge transport properties of 1,2,4,5-tetrakis(5-methylthiophen-2yl) benzene (TMTB), electron donating and withdrawing groups substituted anthra-[1,2-b:4,3-b’:5,6-b ”:8,7-b”‘]tetrathiophene (ATT) molecules have been studied. The ground and excited states geometry was optimized using the density functional theory (DFT) and time-dependent DFT methods. The absorption and emission spectra were calculated at TD-B3LYP/6-311G(d,p) level of theory. It has been observed that the effect of solvent and the substitution of functional groups on the calculated absorption and emission spectra of ATT molecules is negligible. The charge transfer integral, site energy and reorganization energy for hole and electron transport in ATT molecules have been calculated. Molecular dynamics simulations were performed to find the most favorable conformation. The calculated charge transport properties show that the rate of charge transfer strongly depends on pi-stacking angle and the studied molecules can be used as an organic semiconductor.

First author: Alvarado-Soto, L., Electronic structure and molecular properties of [Re6-x Os (x) Se8Cl6]((4-x)-) (x=0-3) clusters: A study based on time-dependent density functional theory including spin-orbit and solvent effects, JOURNAL OF STRUCTURAL CHEMISTRY, 55, 363, (2014)
Abstract: Relativistic time-dependent density functional (TDDFT) calculations including spin-orbit interactions via the zero order regular approximation (ZORA) and solvent effects are carried out on the [Re6-x Os (x) Se8Cl6]((4-x)-) (x = 0-3) cluster. These calculations indicate that the lowest energy electronic transitions of the MMCT and LMCT type are similar to those observed in strongly luminescent 24-electron hexanuclear rhenium chalcogenide clusters [Re6Se8Cl6](4-). Thus our calculations predict that [Re6-x Os (x) Se8Cl6]((4-x)-) (x = 0-3) clusters could be luminescent.

First author: Brindell, Malgorzata, Base-Catalyzed Hydrolysis of a RuII-Chloro-dmso Complex and Its Reactivity towards L-Methionine, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2014, 1333, (2014)
Abstract: The ruthenium(II) complex cis-[RuCl2(dmso)(4)] is known for its antiproliferative properties. This has stimulated the discovery of a wide group of new ruthenium complexes considered as potential anticancer drugs. The stability of these ruthenium complexes under physiological conditions and their interaction with protein amino acid residues are particularly important because of their intravenous administration. The studies presented here are devoted to the stability of cis-[RuCl2(dmso)(4)] under physiological pH conditions and its reactivity towards L-methionine. Immediate dissociation of one dmso ligand from the parent complex after dilution in water leads to the formation of fac-[RuCl2(H2O)(dmso)(3)], which under basic conditions undergoes stepwise dissociation of chloride ions without further dmso release. The hydrolysis of fac-[RuCl2(H2O)(dmso)(3)] at pH 7.4 and also base-catalyzed hydrolysis were investigated in detail by application of kinetic and spectroscopic (UV/Vis, NMR) measurements. The combined experimental and theoretical study revealed that L-methionine coordinates to fac-[RuCl(OH)(H2O)(dmso)(3)] by substituting a water ligand with simultaneous dmso release. Detailed NMR characterization of the product indicated that methionine coordinates through the NH2 group rather than the thioether moiety. This conclusion was further supported by theoretical calculations with the application of ETS-NOCV analysis.

First author: Ali, Sk. Musharaf, Thermodynamical Criteria of the Higher Selectivity of Zirconium Oxycations over Hafnium Oxycations towards Organophosphorus Ligands: Density Functional Theoretical Investigation, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2014, 1533, (2014)
Abstract: Density Functional theory (DFT) has been used to optimize the structures of Cyanex925 [bis(2,4,4-trimethylpentyl)octylphosphine oxide], tributyl phosphate (TBP), and their complexes with Hf and Zr oxycations by employing the triple-zeta valence plus polarization (TZVP) basis set. The effect of noncovalent interactions was examined by using the TPSSH and M06-2X density functionals. The free energy of extraction G(ext) from the aqueous to organic phase was calculated by using the standard thermodynamic procedure in conjunction with the conductor-like screening model (COSMO). The calculated G(ext), either with an implicit or explicit solvation model, fails to capture the experimentally reported preferential selectivity of ZrO2+ ions over HfO2+ ions in the absence of nitrate anions towards Cyanex925 over TBP. The presence of nitrate anions along with the second solvation shell (n = 6 + 1 water molecules) around the oxycation shows consistent results with the calculated G(ext) for the selectivity as reported in solvent extraction experiments [the calculated G(ext) value (-4.72 kcal/mol) is in qualitative agreement with the experimental G(ext) (-0.82 kcal/mol) results; separation factor (SF) approximate to exp(-G(ex)/RT)]. Different bonding analyses indicate the electrostatic nature of the interactions between the metal oxycations and the organophosphorus ligands. The present study will further assist in the design of new ligand/solvent systems for the preferential extraction of ZrO2+ ions over HfO2+ ions in solvent extraction experiments.

First author: Ciancaleoni, Gianluca, An ab Initio Benchmark and DFT Validation Study on Gold(I)-Catalyzed Hydroamination of Alkynes, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 1021, (2014)
Abstract: High level ab initio calculations have been carried out on an archetypal gold(I)-catalyzed reaction: hydroamination of ethyne. We studied up to 12 structures of possible gold(I)-coordinated species modeling different intermediates potentially present in a catalytic cycle for the addition of a protic nucleophile to an alkyne. The benchmark is used to evaluate the performances of some popular density functionals for describing geometries and relative energies of stationary points along the reaction profile. Most functionals (including hybrid or meta-hybrid) give accurate structures but large nonsystematic errors (4-12 kcal/mol) along the reaction energy profile. The double hybrid functional B2PLYP outperforms all considered functionals and compares very nicely with our reference ab initio benchmark energies. Moreover, we present an assessment of the accuracy of commonly used approaches to include relativistic effects, such as relativistic effective potentials and a scalar ZORA Hamiltonian, by a comparison with the results obtained using a relativistic all-electron four-component Dirac-Kohn-Sham method. The contribution of nonscalar relativistic effects in gold(I)-catalyzed reactions, as we investigated here, is expected to be on the order of 1 kcal/mol.

First author: Yu, You, Planar substrate-binding site dictates the specificity of ECF-type nickel/cobalt transporters, CELL RESEARCH, 24, 267, (2014)
Abstract: The energy-coupling factor (ECF) transporters are multi-subunit protein complexes that mediate uptake of transition-metal ions and vitamins in about 50% of the prokaryotes, including bacteria and archaea. Biological and structural studies have been focused on ECF transporters for vitamins, but the molecular mechanism by which ECF systems transport metal ions from the environment remains unknown. Here we report the first crystal structure of a NikM, TtNikM2, the substrate-binding component (S component) of an ECF-type nickel transporter from Thermoanaerobacter tengcongensis. In contrast to the structures of the vitamin-specific S proteins with six transmembrane segments (TSs), TtNikM2 possesses an additional TS at its N-terminal region, resulting in an extracellular N-terminus. The highly conserved N-terminal loop inserts into the center of TtNikM2 and occludes a region corresponding to the substrate-binding sites of the vitamin-specific S components. Nickel binds to NikM via its coordination to four nitrogen atoms, which are derived from Met1, His2 and His67 residues. These nitrogen atoms form an approximately square-planar geometry, similar to that of the metal ion-binding sites in the amino-terminal Cu2+-and Ni2+-binding (ATCUN) motif. Replacements of residues in NikM contributing to nickel coordination compromised the Ni-transport activity. Furthermore, systematic quantum chemical investigation indicated that this geometry enables NikM to also selectively recognize Co2+. Indeed, the structure of TtNikM2 containing a bound Co2+ ion has almost no conformational change compared to the structure that contains a nickel ion. Together, our data reveal an evolutionarily conserved mechanism underlying the metal selectivity of EcfS proteins, and provide insights into the ion-translocation process mediated by ECF transporters.

First author: Agnihotri, Neha, Computational studies of charge transfer in organic solar photovoltaic cells: A review,JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS, 18, 18, (2014)
Abstract: Photoinduced charge transfer (CT) is a fundamental process that determines the overall energy conversion efficiency of organic solar photovoltaic cells (OPVs). This review focuses on the advantages and pitfalls of theoretical/computational methods available to describe CT excitations in donor-acceptor (D-A) complexes. Studies of porphyrin-fullerene constructs as model D-A systems will be used to illustrate progress in this area.

First author: Wei, Yonghuai, Theoretical design of organoimido-substituted hexamolybdates with different electron donors for dye-sensitized solar cells, DYES AND PIGMENTS, 102, 6, (2014)
Abstract: Novel organoimido-substituted hexamolybdates dyes were designed by introducing 3,4-ethyl-enedioxythiophene (EDOT) or thienothiophene (IT) unit as electron donor based on [Mo6O18(MBTH)](2-). The electronic structures, absorption spectra and transition natures of designed systems have been theoretically investigated according to density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. Compared with dye 1, the absorption spectra of these designed organoimido-substituted hexamolybdates dyes exhibit both strong and broad absorptions from 400 to 800 nm, as well as remarkably red shift owing to the long pi-conjugated bridge and high delocalization. Especially for dye 6, which contains a biTT unit, it has the largest maximum absorption wavelength (lambda(max)) at 733 nm and may show a higher short-circuit current density (J(sc)) as it possesses higher light harvesting efficiency (LHE) and reasonable driving force (Delta E-RP). Our work reveals that the designed molecule 6 is promising candidate for high performance solar cell materials.

First author: Canton, Sophie E., Probing the Anisotropic Distortion of Photoexcited Spin Crossover Complexes with Picosecond X-ray Absorption Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 4536, (2014)
Abstract: For numerous spin crossover complexes, the anisotropic distortion of the first coordination shell around the transition metal center governs the dynamics of the high-spin/low-spin interconversion. However, this structural parameter remains elusive for samples that cannot be investigated with crystallography. The present work demonstrates how picosecond X-ray absorption spectroscopy is able to capture this specific deformation in the photoinduced high-spin state of solvated [Fe(terpy)(2)](2+), a complex which belongs to the prominent family of spin crossover building blocks with nonequivalent metal-ligand bonds. The correlated changes in Fe-N-Axial, Fe-N-Distal, and bite angle N-Distal-Fe-N-Axial extracted from the measurements are in very good agreement with those predicted by DFT calculations in D-2d symmetry. The outlined methodology is generally applicable to the characterization of ultrafast nuclear rearrangements around metal centers in photoactive molecular complexes and nanomaterials, including those that do not display long-range order.

First author: Nunzi, Francesca, Shape and Morphology Effects on the Electronic Structure of TiO2 Nanostructures: From Nanocrystals to Nanorods, ACS APPLIED MATERIALS & INTERFACES, 6, 2471, (2014)
Abstract: We carry out an accurate computational analysis on the nature and distribution of electronic trap states in shape-tailored anatase TiO2 structures, investigating the effect of the morphology on the electronic structure. Linear nanocrystal models up to 6.nm in length with various morphologies, reproducing both flattened and elongated rod-shaped TiO2 nanocrystals, have been investigated by DFT calculations, to clarify the effect of the crystal facet percentage on the nanocrystal electronic structure, with particular reference to the energetics and distribution of trap states. The calculated densities of states below the conduction band edge have been very well fitted assuming an exponential distribution of energies and have been correlated with experimental capacitance data. In good agreement with the experimental phenomenology our calculations show that elongated rod-shaped nanocrystals with higher values of the ratio between (100) and (101) facets exhibit a relatively deeper distribution of trap states. Our results point at the crucial role of the nanocrystal morphology on the trap state density, highlighting the importance of a balance between the low-energy (101) and high-energy (100)/(001) surface facets in individual TiO2 nanocrystals.

First author: Groom, Laura R., Reactions of a Cyclopentadienyl-Amidinate Titanium Benzimidamido Complex,ORGANOMETALLICS, 33, 1002, (2014)
Abstract: We report the first reactivity study of a transition-metal benzimidamido complex, namely Cp*Ti{PhC((NPr)-Pr-i)(2)}{NC(Ar-F5)(NOBu)-Bu-t} (5, Ar-F5 = C6F5). Reaction with CO2 and (BuNCO)-Bu-t gave the cycloaddition products Cp*Ti[PhC((NPr)-Pr-i)(2)}{OC(O)N(C{(ArNOBu)-N-F5-Bu-t)} and Cp*Ti[PhC((NPr)-Pr-i)(2)}{OC((NBu)-Bu-t)N(C{Ar-F5}(NOBu)-Bu-t)} (10), respectively, whereas with CS2 slow extrusion of ArFcCN from 5 occurred to ultimately form Cp*Ti{PhC((NPr)-Pr-i)(2)}{SC(S)N((OBu)-Bu-t)}. Reaction of 5 with ArC(O)H (Ar = Ph, 4-C6H4Me, 4-(C6H4Bu)-Bu-t, 4-C6H4OMe, 4-C6H4NMe2, 4-C6H4CF3) also gave the isolable metallacyclic complexes Cp*Ti{PhC(NiPr)(2)}[N(C{Ar-F5}(NOBu)-Bu-t)C(Ar)(H)O} (13) via reversible [2 + 2] cycloaddition reactions. In contrast, reaction with HC(O)NMe2 formed Me2N{NC(Ar-F5)(NOBu)-Bu-t}H (16) within 1 h at room temperature. Upon heating, 10 and 13 also underwent retrocyclization, forming the organic products (BuNCNC)-Bu-t(Ar-F5)(NOBu)-Bu-t and ArC{NC(Ar-F5)(NOBu)-Bu-t}H (14), respectively. Selected examples of 14 and 16 were studied by DFT and UV visible spectroscopy. Addition of isonitriles (BuNC)-Bu-t and XyINC (Xyl = 2,6-C6H3Me2) to Cp*Ti{PhC(NiPr)(2)}{NC(Ar)(NOBu)-Bu-t} (Ar = Ar-F5 (5), 2,6-C6H3F2 (Ar-F2)) afforded the sigma adducts Cp*Ti{PhC((NPO2)-P-i}{NC(Ar)(NOBu)-Bu-t}(CNR) (Ar = ArF5, R = Bu-t, Xyl (19); Ar = Ar-F2, R = Xyl). Subsequently, 19 formed Cp*Ti{PhC((NPr)-Pr-i)(2)}{NC((NOBu)-Bu-t)C6F4N(Xyl)C}(F) (20) via C-F bond activation. Reaction of 5 with 2 equiv of B(Ar-F5)3 gave Cp*Ti{PhC((NPr)-Pr-i)(2)}{ON(B{Ar-F5}(3))C(Ar-F5)N(H)(B{Ar-F5}}(3))} with elimination of 2-methylpropene.

First author: Garbacz, Piotr, Experimental Characterization of the Hydride H-1 Shielding Tensors for HIrX2(PR3)(2) and HRhCl2(PR3)(2): Extremely Shielded Hydride Protons with Unusually Large Magnetic Shielding Anisotropies, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 1203, (2014)
Abstract: The hydride proton magnetic shielding tensors for a series of iridium(III) and rhodium(III) complexes are determined. Although it has long been known that hydridic protons for transition-metal hydrides are often extremely shielded, this is the first experimental determination of the shielding tensors for such complexes. Isolating the H-1 NMR signal for a hydride proton requires careful experimental strategies because the spectra are generally dominated by ligand H-1 signals. We show that this can be accomplished for complexes containing as many as 66 ligand protons by substituting the latter with deuterium and by using hyperbolic secant pulses to selectively irradiate the hydride proton signal. We also demonstrate that the quality of the results is improved by performing experiments at the highest practical magnetic field (21.14 T for the work presented here). The hydride protons for iridium hydride complexes HIrX2(PR3)(2) (X = Cl, Br, or I; R = isopropyl, cyclohexyl) are highly shielded with isotropic chemical shifts of approximately -50 ppm and are also highly anisotropic, with spans (=delta(11)-delta(33)) ranging from 85.1 to 110.7 ppm. The hydridic protons for related rhodium complexes HRhCl2(PR3)(2) also have unusual magnetic shielding properties with chemical shifts and spans of approximately -32 and 85 ppm, respectively. Relativistic density functional theory computations were performed to determine the orientation of the principal components of the hydride proton shielding tensors and to provide insights into the origin of these highly anisotropic shielding tensors. The results of our computations agree well with experiment, and our conclusions concerning the importance of relativistic effects support those recently reported by Kaupp and co-workers.

First author: Savoie, Brett M., Unequal Partnership: Asymmetric Roles of Polymeric Donor and Fullerene Acceptor in Generating Free Charge, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 2876, (2014)
Abstract: Natural photosynthetic complexes accomplish the rapid conversion of photoexcitations into spatially separated electrons and holes through precise hierarchical ordering of chromophores and redox centers. In contrast, organic photovoltaic (OPV) cells are poorly ordered, utilize only two different chemical potentials, and the same materials that absorb light must also transport charge; yet, some OPV blends achieve near-perfect quantum efficiency. Here we perform electronic structure calculations on large clusters of functionalized fullerenes of different size and ordering, predicting several features of the charge generation process, outside the framework of conventional theories but clearly observed in ultrafast electro-optical experiments described herein. We show that it is the resonant coupling of photogenerated singlet excitons to a high-energy manifold of fullerene electronic states that enables efficient charge generation, bypassing localized charge-transfer states. In contrast to conventional views, our findings suggest that fullerene cluster size, concentration, and dimensionality control charge generation efficiency, independent of exciton delocalization.

First author: Lucena, Ana F., Oxo-Exchange of Gas-Phase Uranyl, Neptunyl, and Plutonyl with Water and Methanol,INORGANIC CHEMISTRY, 53, 2163, (2014)
Abstract: A challenge in actinide chemistry is activation of the strong bonds in the actinyl ions, AnO(2)(+) and AnO(2)(2+), where An = U, Np, or Pu. Actinyl activation in oxo-exchange with water in solution is well established, but the exchange mechanisms are unknown. Gas-phase actinyl oxo-exchange is a means to probe these processes in detail for simple systems, which are amenable to computational modeling. Gas-phase exchange reactions of UO2+, NpO2+, PuO2+, and UO22+ with water and methanol were studied by experiment and density functional theory (DFT); reported for the first time are experimental results for UO22+ and for methanol exchange, as well as exchange rate constants. Key findings are faster exchange of UO22+ versus UO2+ and faster exchange with methanol versus water; faster exchange of UO2+ versus PuO2+ was quantified. Computed potential energy profiles (PEPs) are in accord with the observed kinetics, validating the utility of DFT to model these exchange processes. The seemingly enigmatic result of faster exchange for uranyl, which has the strongest oxo-bonds, may reflect reduced covalency in uranyl as compared with plutonyl.

First author: Brela, Mateusz, Analysis of the Bonding between Two M(mu-NAr not equal) Monomers in the Dimeric Metal(II) Imido Complexes {M(mu-NAr not equal)}(2) [M = Si, Ge, Sn, Pb; Ar-# = C6H3-2,6-(C6H3-2,4,6-R-3)(2)]. The Stabilizing Role Played by R = Me and iPr, INORGANIC CHEMISTRY, 53, 2325, (2014)
Abstract: The nature of the bonding between the two M(mu-NA(not equal)) imido monomers [M = Si, Ge, Sn, Pb; Ar-# = C6H3-2,6-(C6H2-2,4,6-R-3)(2); R = Me, iPr] in the {M(mu-NAr not equal)}(2) dimer is investigated with the help of a newly developed energy and density decomposition scheme as well as molecular dynamics. The approach combines the extended transition state energy decomposition method with the natural orbitals for chemical valence density decomposition scheme within the same theoretical framework. The dimers are kept together by two a bonds and two g bonds. The a bonding has two major contributions. The first is a dative transfer of charge from nitrogen to M. It amounts to 188 kcal/mol for {Si(mu-NAr not equal)}(2), -152 kcal/mol for {Ge(p-NA not equal)}(2) with 105 kcal/mol for {Sn(p-NA?)}2, and 79 kcal/mol for {Pb(mu-NA,)}2. The second is a charge buildup within the ring made up of the two dimers. It amounts to 82 kcal/mol for M = Si with 61 kcal/mol for M = Ge and similar to-50 kcal/mol for M = Sn and Pb. We finally have pi bonding with a donation of charge from M to nitrogen. It has a modest contribution of,similar to-30 kcal/mol. The presence of isopropyl (iPr) groups is further shown to stabilize{M(mu-NA not equal)}(2) [M = Si, Ge, Sn, Pb; Ar not equal = C6H3-2,6-(C6H2-2,4,6-iPr(3))(2)] compared to the methylated derivatives (R = Me) through attractive van der Waals dispersion interactions.

First author: Nasser, Nasser, Chemistry of gold(III) with pyridine-carboxamide ligands, POLYHEDRON, 69, 61, (2014)
Abstract: The pyridine-carboxamide ligand PhNHC(=O)-2-C5H4N reacts with Na+[AuCl4](-) either by cation exchange, to give [PhNHC(=O)-2-C5H4NH][AuCl4], or by ligand substitution to give [AuCl2(kappa(2)-N,N’-PhNC(=O)-2-C5H4N)]. Similar reactions with bis(pyridine-carboxamide) ligands gave complexes [AuCl2(kappa(2)-N,N’-RNC(=O)-2-C5H4N)], with R = (CH2)(3)NHC(=O)-2-C5H4N or 2-C6H4NHC (=O)-2-C5H4N, in which the ligands are bidentate, but no complexes with tetradentate ligands could be isolated. The complex [AuCl2(kappa(2)-N,N’-PhNC(=O)-2-C5H4N)] in methanol solution is an efficient catalyst for oxidative cyanation of PhNMe2 to give PhMeNCH2CN, and it is proposed that the catalysis involves gold(I), gold(II) and gold(III) intermediates.

First author: Fernandez, Israel, Origin of the “Endo Rule” in Diels-Alder Reactions, JOURNAL OF COMPUTATIONAL CHEMISTRY, 35, 371, (2014)
Abstract: Detailed density functional theory calculations definitively rationalize the preference for the endo cycloadduct (also known as endo rule) in text-book thermal Diels-Alder reactions involving maleic anhydride and cyclopentadiene or butadiene. This selectivity is mainly caused by an unfavorable steric arrangement in the transition-state region of the exo pathway which translates into a more destabilizing activation strain. In contrast with the widely accepted, orbital-interaction-based explanation for the endo rule, it is found that neither the orbital interactions nor the total interaction between the deformed reactants contributes to the endo selectivity.

First author: Henkensmeier, Dirk, Anion conducting polymers based on ether linked polybenzimidazole (PBI-OO),INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 39, 2842, (2014)
Abstract: Anion conducting polymers are potentially interesting for fuel cells, electrochemical pumps, and dye sensitized solar cells. Ether-containing polybenzimidazoles (PBI-OO and PBI-OPO) were synthesized and turned into anion conducting polymers by methylation. The thermal stability was shown to depend on the polymer structure and degree of methylation (dom). Tensile strength and modulus decrease between 50% and 75% dom, but stay constant or slightly increase over 75% dom again. At 65 degrees C, hydroxide, iodide, chloride, carbonate and bicarbonate conductivities of 0.1, 0.6, 19, 20, 31 mS/cm were obtained, respectively. The low hydroxide conductivity is due to the formation of a C-O bond in position 2 of the imidazolium, which reduces the number of free ions and is known to lead to imidazolium ring opening and further degradation steps. The effect of introduction of phenoxy groups into the main chain on the charge distribution, especially on position 2 and the methyl groups (positive charge on the methyl groups decreases the thermal stability), as well as on the ion bonding was thoroughly investigated by DFT calculations and correlated with experimental data.

First author: Azpiroz, Jon M., Effect of Structural Dynamics on the Opto-Electronic Properties of Bare and Hydrated ZnS QDs, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 3274, (2014)
Abstract: Quantum mechanical calculations on the structural and optoelectronic features of two realistic wurtzite-like ZnS quantum dot (QD) models, namely, (ZnS)(33) and (ZnS)(116), are presented both in vacuo and in an explicit water solution environment. Car-Parrinello molecular dynamics (CPMD) simulation and excited-state, Time-Dependent Density Functional Theory (DFT/TDDFT) calculations on extended models are combined to unravel hitherto inaccessible atomistic features of the investigated systems. Ultrasmall QDs are predicted to exhibit strong dynamical fluctuations. Accordingly, the bare (ZnS)(33) model undergoes a drastic structural rearrangement and evolves from the starting bulk-like structure to an amorphous phase. The geometrical changes occurring over the time are reflected on the opto-electronic properties. The band-edge states and the optical absorption onset both sizably vary along the CPMD trajectory. Eventually, the optical gap decreases due to the emergence of high-lying occupied orbitals. These midgap states are mainly localized in undercoordinated S sites and could act as trap states for the photogenerated holes. Water molecules are predicted to form strong Zn-OH2 bonds with the surface Zn atoms. Hydration seems to lower the surface energy, stabilize the wurtzite polymorph, hinder the Zn-S bond breaking, and largely prevent the appearance of trap states. Besides, adsorbed water molecules produce a notable blue-shift of the optical gap. The electrostatic field induced by the solvent shell and the electron-donor properties of the water molecules are supposed to be responsible for the opening of the gap. Moreover, capping the QDs with water molecules increases the intensity of the lowest-lying electronic excitations. This study sheds light on the important optoelectronic modifications occurring for realistic QD in water solution and offers at the same time the methodological framework to investigate photocatalytic reactions mediated by ZnS.

First author: Wang, Haopeng, Aluminum Zintl anion moieties within sodium aluminum clusters, JOURNAL OF CHEMICAL PHYSICS, 140, 3274, (2014)
Abstract: Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, NamAln-,were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

First author: Joly, Damien, A Robust Organic Dye for Dye Sensitized Solar Cells Based on Iodine/Iodide Electrolytes Combining High Efficiency and Outstanding Stability, SCIENTIFIC REPORTS, 4, 3274, (2014)
Abstract: Among the new photovoltaic technologies, the Dye-Sensitized Solar Cell (DSC) is becoming a realistic approach towards energy markets such as BIPV (Building Integrated PhotoVoltaics). In order to improve the performances of DSCs and to increase their commercial attractiveness, cheap, colourful, stable and highly efficient ruthenium-free dyes must be developed. Here we report the synthesis and complete characterization of a new purely organic sensitizer (RK1) that can be prepared and synthetically upscaled rapidly. Solar cells containing this orange dye show a power conversion efficiency of 10.2% under standard conditions (AM 1.5G, 1000 Wm(-2)) using iodine/iodide as the electrolyte redox shuttle in the electrolyte, which is among the few examples of DSC using an organic dyes and iodine/iodide red/ox pair to overcome the 10% efficiency barrier. We demonstrate that the combination of this dye with an ionic liquid electrolyte allows the fabrication of solar cells that show power conversion efficiencies of up to 7.36% that are highly stable with no measurable degradation of initial performances after 2200 h of light soaking at 65 degrees C under standard irradiation conditions. RK1 achieves one of the best output power conversion efficiencies for a solar cell based on the iodine/iodide electrolyte, combining high efficiency and outstanding stability.

First author: Kumara, Chanaka, X-ray Crystal Structure and Theoretical Analysis of Au25-xAgx(SCH2CH2Ph)(18)(-) Alloy,JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 461, (2014)
Abstract: The atomic arrangement of Au and Ag atoms in Au25-xAgx(SR)(18) was determined by X-ray crystallography. Ag atoms were selectively incorporated in the 12 vertices of the icosahedral core. The central atom and the metal atoms in the six [-SR-Au-SR-Au-SR-] units were exclusively gold, with 100% Au occupancy. The composition of the crystals determined by X-ray crystallography was Au18.3Ag6.7(SCH2CH2Ph)(18). This composition is in reasonable agreement with the composition Au18.8Ag6.2(SCH2CH2Ph)(18) measured by electrospray mass spectrometry. The structure can be described in terms of shells as Au-1@Au5.3Ag6.7@6X[-SR-Au-SR-Au-SR-]. Density functional theory calculations show that the electronic structure and optical absorption spectra are sensitive to the silver atom arrangement within the nanocluster.

First author: Tory, Joanne, Solvent-Dependent Formation of Os(0) Complexes by Electrochemical Reduction of [Os(CO)(2,2 ‘-bipyridine)(L)Cl-2]; L = Cl-, PrCN, INORGANIC CHEMISTRY, 53, 1382, (2014)
Abstract: Cyclic voltammetry and ultraviolet-visible/infrared (UV-vis/IR) spectroelectrochemistry were used to study the cathodic electrochemical behavior of the osmium complexes mer[Os-III(CO) (bpy)Cl-3] (bpy = 2,2′-bipyridine) and trans(Cl)- [Os-II(CO) (PrCN)(bpy)Cl-2] at variable temperature in different solvents (tetrahydrofuran (THF), butyronitrile (PrCN), acetonitrile (MeCN)) and electrolytes (Bu4NPF6, Bu4NCl). The precursors can be reduced to mer-[Os-II(CO) (bpy(center dot-))Cl-3](2-) and trans(Cl)-[Os-II(CO)(PrCN) (bpy(center dot-))Cl-2](-), respectively, which react rapidly at room temperature, losing the chloride ligands and forming Os(0) species. mer-[Os-III(CO) (bpy)Cl-3] is reduced in THF to give ultimately an Os-Os-bonded polymer, probably [Os-0(CO) (THF)(bpy)], whereas in PrCN the well-soluble, probably mononuclear [Os (CO) (PrCN)(bpy)], species is formed. The same products were observed for the 2 electron reduction of trans(Cl)-[Os-II(CO)(PrCN) (bpy)Cl-2] in both solvents. In MeCN, similar to THF, the [Os-0(CO) (MeCN)(bpy)],, polymer is produced. It is noteworthy that the bpy ligand in mononuclear [Os-0(CO) (PrCN)(bpy)] is reduced to the corresponding radical anion at a significantly less negative potential than it is in polymeric [Os-0(CO) (THF)(bpy)](n) : Delta E-1/2 = 0.67 V. Major differences also exist in the IR spectra of the Os(0) species: the polymer shows a broad v(CO) band at much smaller wavenumbers compared to the soluble Os(0) monomer that exhibits a characteristic v(Pr-CN) band below 2200 cm(-1) in addition to the intense and narrow v(CO) absorption band. For the first time, in this work the M-0-bpy (M = Ru, Os) mono- and dicarbonyl species soluble in PrCN have been formulated as a mononuclear complex. Density functional theory (DFT) and time-dependent-DFT calculations confirm the Os(0) oxidation state and suggest that [Os-0(CO) (PrCN)(bpy)] is a square planar moiety. The reversible bpy-based reduction of [Os-0(CO) (PrCN)(bpy)] triggers catalytic reduction of CO2 to CO and HCOO-.

First author: Wolters, Lando P., Understanding E2 versus S(N)2 Competition under Acidic and Basic Conditions,CHEMISTRYOPEN, 3, 29, (2014)
Abstract: Our purpose is to understand the mechanism through which pH affects the competition between base-induced elimination and substitution. To this end, we have quantum chemically investigated the competition between elimination and substitution pathways in H2O+C2H5OH2+ and OH-+C2H5OH, that is, two related model systems that represent, in a generic manner, the same reaction under acidic and basic conditions, respectively. We find that substitution is favored in the acidic case while elimination prevails under basic conditions. Activation-strain analyses of the reaction profiles reveal that the switch in preferred reactivity from substitution to elimination, if one goes from acidic to basic catalysis, is related to (1)the higher basicity of the deprotonated base, and (2)the change in character of the substrates LUMO from C-H bonding in C2H5OH2+ to C-H antibonding in C2H5OH.

First author: Carvalho, Alexandra T. P., Electronic Structure Investigation and Parametrization of Biologically Relevant Iron-Sulfur Clusters, JOURNAL OF CHEMICAL INFORMATION AND MODELING, 54, 613, (2014)
Abstract: The application of classical molecular dynamics simulations to the study of metalloenzymes has been hampered by the lack of suitable molecular mechanics force field parameters to treat the metal centers within standard biomolecular simulation packages. These parameters cannot be generalized, nor be easily automated, and hence should be obtained for each system separately. Here we present density functional theory calculations on [Fe2S2(SCH3)(4)](2+/+), [Fe3S4(SCH3)(3)](+/0) and [Fe4S4(SCH3)(4)](2+/+) and the derivation of parameters that are compatible with the AMBER force field. Molecular dynamics simulations performed using these parameters on respiratory Complex II of the electron transport chain showed that the reduced clusters are more stabilized by the protein environment, which leads to smaller changes in bond lengths and angles upon reduction. This effect is larger in the smaller iron sulfur cluster, [Fe2S2(SCH3)(4)](2+/+).

First author: Pandey, Krishna K., Accurate Structure and Bonding Description of the Transition MetalDisulfur Monoxide Complexes [( PMe3) 2M( S2O)] ( M = Ni, Pd, Pt): Grimme Dispersion Corrected DFT Study, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 640, 370, (2014)
Abstract: The application of classical molecular dynamics simulations to the study of metalloenzymes has been hampered by the lack of suitable molecular mechanics force field parameters to treat the metal centers within standard biomolecular simulation packages. These parameters cannot be generalized, nor be easily automated, and hence should be obtained for each system separately. Here we present density functional theory calculations on [Fe2S2(SCH3)(4)](2+/+), [Fe3S4(SCH3)(3)](+/0) and [Fe4S4(SCH3)(4)](2+/+) and the derivation of parameters that are compatible with the AMBER force field. Molecular dynamics simulations performed using these parameters on respiratory Complex II of the electron transport chain showed that the reduced clusters are more stabilized by the protein environment, which leads to smaller changes in bond lengths and angles upon reduction. This effect is larger in the smaller iron sulfur cluster, [Fe2S2(SCH3)(4)](2+/+).

First author: Antipas, G. S. E., On the elusive anti-bayerite structure, SOLID STATE IONICS, 255, 65, (2014)
Abstract: Sequential deprotonation of the Cr3+ hexahydrate in an alkaline environment up to the stage of a charge-neutral active hydroxide was studied via density functional theory. The deprotonation could be characterized as autocatalytic since upon completion of every H-abstraction stage, Cr was found to mediate O-H dissociation in the next stage by pre-conditioning the ligand O atom that contributes the highest 2s density into Cr-4s based molecular orbitals; the latter amounts to a greater Cr-O distance due to increased charge density along the Cr-O axis. A direct effect of such Cr-4s/O-2s mixing is the reduction of electronegativity of the ligand-O atom and a corresponding high Voronoi deformation density (VDD) of the attached ligand-H atoms. Based on bonding energy decomposition, a facial to meridional isomer ratio of between 2:1 and 3:1 was derived as the most probable stereochemical mix of the active hydroxide; the latter forms, by mutual donation and acceptance, six hydrogen bonds with second hydration shell molecules.

First author: Addicoat, Matthew A., Extension of the Universal Force Field to Metal-Organic Frameworks, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 880, (2014)
Abstract: The Universal Force Field (UFF) (Rappe et al., J. Am. Chem. Soc. 1992) provides a general approach to molecular mechanics for molecules and materials composed of elements throughout the periodic table. Though the method is tunable by the specification of bond orders and the introduction of effective charges, the presently available list of atom types is insufficient to treat various systems containing transition metals, including metal organic frameworks (MOFs). As MOFs are composite materials built of a combination of individually stable building blocks, a plethora of MOF structures are possible, and the prediction of their structure with a low-cost method is important. We have extended the UFF parameter set to include transition metal elements Zn, Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, and Al, as they occur in MOFs, and have proposed additional O parameters that provide reliable structures of the metal oxide clusters of the connectors. We have benchmarked the performance of the MOF extension to UFF (UFF4MOF) with respect to experimentally available data and to DFT calculations. The parameters are available in various well-spread programs, including GULP, deMonNano, and ADF, and all information is provided to include them in other molecular mechanics codes.

First author: Wang, Zhuxiang, A density functional theory study of the competitive complexation of pyridine against H2O and Cl- to Cm3+ and Ce4+, RADIOCHIMICA ACTA, 102, 101, (2014)
Abstract: Density functional theory was used to study the coordination of Cm3+ and Ce4+ with pridine (Py), water (H2O) and chloride anion (Cl-). The competitive coordination of Cl- and Py was investigated to simulate the ligand exchange between Cl(-)and Py at high concentration of hydrochloric acid (HCl), where Cm3+ and Ce4+ may exist in the form of [CmCl6](3-) and [CeCl6](2-), while that of water and Py to simulate the process at low concentration or without the presence of Cl-.The calculations show that Ce4+ has higher affinity to Py than Cm3+ in the absence of Cl-, while it binds much more weakly at high concentration of HCl. This is consistent with experimental data that at high concentration of HCl, Ce4+ has much shorter retention time than Cm3+ using tertiary pyridine resin (TPR). In view of the strengthening of M-Cl and the weakening of M-OW at bonds upon the coordination of Py, we conclude that the distinct coordination abilities of the three ligands to Ce4+ and Cm3+ are due to different strengths of the inner-shell electrostatic interaction between the ligands and the central metal ions.

First author: Werle, Christophe, Unusual outcome of the thermolytic condensation of diazoarylmethanes with a [tricarbonyl(eta(6)-2-p-tolyl)chromium] 2-oxazolyl chelate of tetracarbonylrhenium, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 751, 754, (2014)
Abstract: A new Cr(CO)(3)-bound cyclorhenated 2-phenyl, 2-oxazoline derivative was synthesized and treated with two different phenyldiazomethanes, namely Ph2CN2 and (t-Bu)(Ph)N-2 under thermolytic conditions in apolar solvents. With the former diazomethane the reaction affords mainly a new bimetallic electron-saturated species resulting from the insertion of the Ph2C moiety into the C-Ar-Re bond of the rhenacyclic substrate. With the latter diazomethane substituted with one t-butyl group, the reaction quite unexpectedly leads to a new Re(CO)(4) metallacycle in which an ortho position is occupied by a (Ph)(t-Bu)(H)C-group, as a possible consequence of an unprecedented insertion-transposition of the Recentred moiety by C-H bond activation. The results are supported by 6 X-ray structures and analytical informations.

First author: Pandey, Krishna K., Accurate theoretical description of the M-PNR2 bonds in phosphinidene complexes of manganese and rhenium [(CO)(5)M-PNR2](+) (R = Me, Pr-i, Bu-t) and [(PMe3)(CO)(4)M-(PNPr2)-Pr-i](+): A DFT-D3 study, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 751, 781, (2014)
Abstract: Geometry and bond energy analysis of M-P bonds in the terminal phosphinidene complexes of manganese and rhenium [(CO)(5)MePNR2](+) (R = Me, Pr-i, Bu-t) and [(PMe3)(CO)(4)(MePNPr2)-Pr-i](+) were investigated at the DFT, DFT-D3 and DFT-D3(BJ) methods using functionals (BP86, revPBE, PW91 and TPSS). In all studied complexes, the pi-bonding contributions to the total M-P bonds are significantly smaller (12.4-16.0%) than the sigma-bonding components. The phosphinidene (PNR2) ligands are predominantly sigma-donors. The electrostatic interaction Delta E-elstat, in all complexes I-VIII, are larger than the orbital energies Delta E-orb, which means, the M-PNR2 bonds in these complexes have greater degree of ionic characters (more than 50%). The DFT-D3 method provide quite accurate estimate of the dispersion energy for the studied complexes. The contribution of dispersion interactions is large in computing accurate bond dissociation energies between the interacting fragments. The BDEs are largest for the functional PW91 and smallest for the functional revPBE. The dispersion corrections are in the range 6.4-11.1 kcal/mol (BP86), 7.2-8.6 kcal/mol (revPBE) and 5.7-8.6 kcal/mol (TPSS), which are smaller than the corresponding DFT-D3(BJ) dispersion corrections 7.6-11.8 kcal/mol (BP86), 8.7-12.8 kcal/mol (revPBE) and 5.8-9.0 kcal/mol (TPSS). The dispersion corrections calculated by DFT-D3 scheme increase on going from M = Mn to M Re and smallest for the complexes [(PMe3)(CO)(4)M((PNPr2)-Pr-i)](+).

First author: Duan, Yu-Ai, Theoretical studies on the hole transport property of tetrathienoarene derivatives: The influence of the position of sulfur atom, substituent and pi-conjugated core, ORGANIC ELECTRONICS, 15, 602, (2014)
Abstract: Chemical modifications such as changing the position of heteroatom, introducing different substituents and p-conjugated cores are powerful molecular design tools to modulate their optical and electrochemical performance. In this context, in-depth density functional theory investigations on the geometries, frontier molecular orbitals, reorganization energies, transfer integrals, anisotropic mobilities and band structures of tetrathienoarene derivatives were carried out to provide insights into the effects of these chemical modifications on their hole transport properties. The electrostatic potential, Hirshfeld surface analysis, energy decomposition analysis (EDA) and anisotropic mobility were also employed to shed light on the intricate interplays among molecular packings, intermolecular interactions and transport properties. It is found that compared with 2, 1a with sulfur atom inside has lower frontier orbital energy level, smaller reorganization energy and larger transfer integral and hole mobility. However, more S . . . S interactions in 2 could provide more effective transport channels for charge carrier transport. The introduction of hexylthienyl groups (1c) results in an enhancement of pi-pi interaction and leads to an increase in the highest occupied molecular orbital (HOMO) and transfer integrals. Meanwhile, the strongest intermolecular interaction energy of pathway A in 1c renders its transport behavior with typical one-dimensional (1D) transport. Moreover, anthracene as the pi-conjugated core seemed to possess better transport properties in comparison with dibenzothiophene or chrysene acting as core. In addition, the dispersion energy of all investigated compounds plays a leading role in determining the energetically accessible stacking motifs. We hope that our speculation would facilitate the future design and preparation of high-performance charge-transport materials.

First author: Yan, Biao, Thermodynamic properties, detonation characterization and free radical of N-2 ‘,4 ‘-dinitrophenyl-3,3-dinitroazetidine, JOURNAL OF CHEMICAL THERMODYNAMICS, 69, 152, (2014)
Abstract: The thermal behavior of N-2′,4′-dinitrophenyl-3,3-dinitroazetidine (DNPDNAZ) was studied under a non-isothermal conditions by DSC and TG/ DTG methods. The apparent activation energy (E-a) and pre-exponential factor (A) of the intense exothermic decomposition reaction of DNPDNAZ were 172.26 kJ.mol(-1) and 10(13.15) s(-1), respectively. The specific molar heat capacity (C-p,C- m) of DNPDNAZ was determined by a continuous Cp mode of microcalorimetry and theoretical calculation. The detonation velocity (D) and pressure (P) of DNPDNAZ were estimated using the nitrogen equivalent equation according to the experimental density. The free radical signals of DNPDNAZ and 1,3,3-trinitroazetidine (TNAZ) were detected by electron spin resonance (ESR) technique, which is used to estimate their sensitivity.

First author: Wang, GuangYu, Theoretical study on the transport properties of oligothiophene-diketopyrrolopyrrole derivatives: quinoidal versus aromatic, THEORETICAL CHEMISTRY ACCOUNTS, 133, 152, (2014)
Abstract: Density functional theory calculations were carried out to investigate the transport mechanism of three oligothiophene-diketopyrrolopyrrole (T-DPP) derivatives. The results show that quinoidal molecule 1 that has dicyanovinyl has lower the lowest unoccupied molecular orbital (LUMO) energy level and larger adiabatic electron affinity (EA(a)) comparing with quinoidal 2 that has monocyanovinyl as terminal groups, signifying that to increase the extent of quinoid could improve the stability of the molecules in the air. Moreover, quinoidal molecules 1 and 2 have lower LUMO energy level, larger EA(a), and electron-transfer integral (V (e)) comparing than aromatic molecule 3, which indicates that quinoidal T-DPP derivatives are more in favor of electron than hole transport compared with their aromatic ones. Thus, constructing quinoidal architecture was also an effective way to design n-type transport materials besides the conventional idea that introducing electron-withdrawing groups.

First author: Lucier, Bryan E. G., Unravelling the Structure of Magnus’ Pink Salt, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 1333, (2014)
Abstract: A combination of multinuclear ultra-wideline solid-state NMR, powder X-ray diffraction (pXRD), X-ray absorption fine structure experiments, and first principles calculations of platinum magnetic shielding tensors has been employed to reveal the previously unknown crystal structure of Magnus’ pink salt (MPS), [Pt(NH3)(4)][PtCl4], study the isomeric Magnus’ green salt (MGS), [Pt(NH3)(4)][PtCl4], and examine their synthetic precursors K2PtCl4 and Pt(NH3)(4)Cl-2 center dot H2O. A simple synthesis of MPS is detailed which produces relatively pure product in good yield. Broad Pt-195, N-14, and Cl-35 SSNMR powder patterns have been acquired using the WURST-CPMG and BRAIN-CP/WURST-CPMG pulse sequences. Experimentally measured and theoretically calculated platinum magnetic shielding tensors are shown to be very sensitive to the types and arrangements of coordinating ligands as well as intermolecular Pt-Pt metallophilic interactions. High-resolution Pt-195 NMR spectra of select regions of the broad Pt-195 powder patterns, in conjunction with an array of N-14 and Cl-35 spectra, reveal clear structural differences between all compounds. Rietveld refinements of synchrotron pXRD patterns, guided by first principles geometry optimization calculations, yield the space group, unit cell parameters, and atomic positions of MPS. The crystal structure has P-1 symmetry and resides in a pseudotetragonal unit cell with a distance of >5.5 angstrom between Pt sites in the square-planar Pt units. The long Pt-Pt distances and nonparallel orientation of Pt square planes prohibit metallophilic interactions within MPS. The combination of ultra-wideline NMR, pXRD, and computational Methods offers much promise for future investigation and characterization of Pt-containing systems.

First author: Hu, Han-Shi, Actinide-Silicon Multiradical Bonding: Infrared Spectra and Electronic Structures of the Si(mu-X)AnF(3) (An = Th, U; X = H, F) Molecules, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 1427, (2014)
Abstract: We report a series of Si(mu-X)AnF(3) (An = Th, U; X = H, F) complexes with silicon-actinide(IV) single bonds and unexpected multiradical features that form rare triplet silylenes. These bridged molecules have been prepared in microscopic scale through reactions of laser-ablated uranium and thorium atoms with silicon fluorides and identified from infrared spectra in argon and neon matrixes and relativistic quantum chemical calculations. Similar neon matrix experiments for the reactions of uranium with CF4 and CHF3 were carried out for comparison. Our density functional theory calculations show that the Si-U single-bonded species Si(mu-X)UF3 (X = H, F) with U(IV) oxidation state and the quasi-agostic bridge ligand of H or F are most stable among all the isomers, whereas the naively anticipated triple-bonded species XSi=UF3 with U(VI) oxidation state and the double-bonded species XSi center dot=(UF3)-U-center dot with U(V) oxidation state lie markedly higher in energy. Similar thorium products from reactions with XSiF3 are also found to prefer the Si(mu-X)ThF3 structures with Si-Th single bonds and bridged H or F ligands. High level ab initio wave function theory calculations with the CCSD(T) and CASPT2 methods confirm that the ground states are quintet for Si(mu-X)UF3 and triplet for Si(mu-X)ThF3 with two unpaired electrons on the silylene group. These silicon-bearing molecules as the lowest-energy isomer of XSiAnF(3) represent the first silicon-actinide systems with unusual “triplet” silylenes and Si-An single bonds with multiradical character. They are in dramatic contrast to the uranium-carbon analogs, XC UF3, which form triple-bonded singlet ground states with C-3v symmetry. The calculated vibrational frequencies of the Si(mu-X)AnF(3) complexes agree well with experimental observations. These results accentuate the critical difference of chemical bonding of 3p- and 2p-row main-group elements with actinides. The. Lewis electron-pair model and the octet rule break down for these silicon compounds.

First author: Pandey, Krishna K., Structure and bonding energy calculations of nitrosyl, thionitrosyl and selenonitrosyl complexes [(PNP)Ir(NX)(+) (X=0, S, Se): A DFT study, POLYHEDRON, 68, 87, (2014)
Abstract: Structure and bonding analyses of the complexes [(PNP)Ir(NX)](+) (X = O, S, Se; PNP = N(CHCHPMe2)(2)) were investigated at the DFT, DFT-D3 and DFT-D3(BJ) levels using BP86, BLYP, PBE, revPBE and TPSS functionals. The Ir-NX bond in the thionitrosyl complex is longer than that in the nitrosyl and selenonitrosyl complexes, which is consistent with the observed trend for their experimental values. The Ir-NX bond has essentially Ir=NX double bond character, which supports the sigma-donor and pi-acceptor abilities of the [NX](+) ligands. The non-covalent P-NX distances decrease in the order DFT > DFT-D3 > DFT-D3(BJ). The Ir-NX bond has a larger covalent character (85.7, 75.9 and 74.6%). Dispersion interactions between the metal and [NX](+) fragments are in the range 3.2-5.5 kcal/mol (BP86), 3.2-5.4 kcal/mol (BLYP), 1.9-3.1 kcal/mol (PBE), 3.5-5.5 kcal/mol (revPBE) and 2.6-3.8 kcal/mol (TPSS), which are smaller than the corresponding DFT-D3(BJ) dispersion corrections 4.9-8.6 kcal/mol (BP86), 5.2-7.9 kcal/mol (BLYP), 2.7-4.0 kcal/mol (PBE), 5.3-7.6 kcal/mol (revPBE) and 2.7-5.2 kcal/mol (TPSS). The dispersion corrected DFT (DFT-D3 and DFT-D3(BJ)) methods provide quite an accurate estimate of the dispersion energy, which can be judged by the observation that the experimental and optimized Ir-NX bond distances are consistent with the most accurate dispersion corrected DFT-D3(BJ) bond dissociation energy of Ir-NX bonds.

First author: Gayfulin, Yakov M., Synthesis, structure and DFT calculations of the first bioctahedral chalcohalide rhenium cluster complex (Et4N)(4)(Me2NH2)(2) [Re12CS17Br6], POLYHEDRON, 68, 334, (2014)
Abstract: The first example of dodecanuclear chalcohalide rhenium cluster complex, (Et4N)(4)(Me2NH2)(2)[Re12CS17Br6] (1), has been synthesized by reaction of polymeric cluster solid Re12CS17 with excess of Et4NBr in boiling DMF. The compound was characterized by a set of methods, including IR and UV-Vis spectroscopy, elemental analysis, EDS, mass-spectrometry, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. The crystal structure presents an interesting case of 1D supramolecular architecture based on notably short Br center dot center dot center dot Br interactions of 3.432 angstrom between the terminal bromide trans-ligands of adjacent [Re12CS17Br6](6-) cluster anions. The DFT calculations performed for the [Re12CS17Br6](6-) anion showed good agreement between calculated and experimental data.

First author: Jerabek, P., Comparative bonding analysis of N-2 and P-2 versus tetrahedral N-4 and P-4, THEORETICAL CHEMISTRY ACCOUNTS, 133, 334, (2014)
Abstract: The nature of the chemical bonds in E-2 and tetrahedral E-4 (E = N, P) has been analysed with the help of an energy decomposition method. The pi bonds in P-2 are not particularly weak. On the contrary, the contribution of P-P pi bonding to the chemical bond in P-2 is even higher than the contribution of N-N pi bonding to the chemical bond in N-2. The higher stability of P-4 (T-d) and the much lower stability of N-4 (T-d) with regard to the diatomic species come from the substantially larger weakening of the N-N sigma-bonds compared with the P-P sigma-bonds in the tetrahedral species. The sum of the six P-P sigma-bond energies in P-4 is higher than the sum of two sigma- and four pi-bonds in two P-2, but the six N-N sigma-bonds in N-4 are weaker than two sigma- and four pi-bonds in two N-2. The crucial factor that leads to the weak N-N bonds in N-4, is the rather long N-N bonds which are 32.8 % longer than in N-2. In contrast, the P-P bonds in P-4 are only 16.2 % longer than in P-2. Since the equilibrium distances in E-2 and E-4 are determined by Pauli repulsion, it can be concluded that the origin for the different stabilities of N-4 and P-4 relative to the diatomic molecules is the exchange repulsion. The nitrogen atoms encounter stronger Pauli repulsion, because the 2s and 2p valence orbitals have a similar radius while the 3s and 3p radii are more different.

First author: Lee, Choongkeun, Water Adsorption and Dissociation Processes on Small Mn-Doped TiO2 Complexes,JOURNAL OF PHYSICAL CHEMISTRY A, 118, 598, (2014)
Abstract: Metal oxide complexes have high catalytic potential in many fields, such as oxidation, dehydrogenation, dehydration, reductive coupling, etc. The adsorption of molecules is a fundamental process in catalytic reactions on the metal oxide complex. In this study, water adsorption and dissociation processes on small Mn-doped TiO2 complexes are investigated at the density functional theory (DFT) level of theory. Water adsorption at terminal Mn atoms is typically found to have an energy around -0.7 eV, which is smaller than the -1.2 eV observed at terminal Ti atoms. Dissociation energies at Mn atoms are determined to be about -0.6 eV, which are also smaller than the approximately -1.2 eV dissociation energies at Ti atoms. Molecular adsorption without dissociation is favorable in energy after water adsorbs at each metal atom. Mn doping reduces the reaction energy; the reaction energy of the doped system is not similar to that of the pure manganese oxide complex.

First author: Cukrowski, Ignacy, Physical Nature of Interactions in Zn-II Complexes with 2,2 ‘-Bipyridyl: Quantum Theory of Atoms in Molecules (QTAIM), Interacting Quantum Atoms (IQA), Noncovalent Interactions (NCI), and Extended Transition State Coupled with Natural Orbitals for Chemical Valence (ETS-NOCV) Comparative Studies, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 623, (2014)
Abstract: In the present account factors determining the stability of ZnL, ZnL2, and ZnL3 complexes (L = bpy, 2,2′-bipyridyl) were characterized on the basis of various techniques: the quantum theory of atoms in molecules (QTAIM), energy decomposition schemes based on interacting quantum atoms (IQA), and extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV). Finally, the noncovalent interactions (NCI) index was also applied. All methods consistently indicated that the strength of the coordination bonds, Zn-O and Zn-N, decreases from ZnL to ZnL3. Importantly, it has been identified that the strength of secondary intramolecular heteropolar hydrogen bonding interactions, CH center dot center dot center dot O and CH center dot center dot center dot N, increases when going from ZnL to ZnL3. A similar trend appeared to be valid for the pi-bonding as well as electrostatic stabilization. In addition to the above leading bonding contributions, all techniques suggested the existence of very subtle, but non-negligible additional stabilization from the CH center dot center dot center dot HC electronic exchange channel; these interactions are the weakest among all considered here. From IQA it was found that the local diatomic interaction energy, E-int(H,H), amounts at HF to -2.5, -2.7, and -2.9 kcal mol(-1) for ZnL, ZnL2, and ZnL3, respectively (-2.1 kcal mol(-1) for ZnL at MP2). NOCV-based deformation density channels showed that formation of CH–HC contacts in Zn complexes causes significant polarization of sigma(C-H) bonds, which accordingly leads to charge accumulation in the CH center dot center dot center dot HC bay region. Charge depletion from sigma(C-H) bonds was also reflected in the calculated spin-spin (1)J(C-H) coupling constants, which decrease from 177.06 Hz (ZnL) to 173.87 Hz (ZnL3). This last result supports our findings of an increase in the local electronic CH center dot center dot center dot HC stabilization from ZnL to ZnL3 found from QTAIM, IQA, and ETS-NOCV. Finally, this work unites for the first time the results from four methods that are widely used for description of chemical bonding.

First author: Hu, Ke, Intramolecular and Lateral Intermolecular Hole Transfer at the Sensitized TiO2 Interface, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 1034, (2014)
Abstract: Characterization of the redox properties of TiO2 interfaces sensitized to visible light by a series of cyclometalated ruthenium polypyridyl compounds containing both a terpyridyl ligand with three carboxylic acid/carboxylate or methyl ester groups for surface binding and a tridentate cyclometalated ligand with a conjugated triarylamine (NAr3) donor group is described. Spectroelectrochemical studies revealed non-Nernstian behavior with nonideality factors of 1.37 +/- 0.08 for the Ru-III/II couple and 1.15 +/- 0.09 for the NAr3 center dot+/0 couple. Pulsed light excitation of the sensitized thin films resulted in rapid excited-state injection (k(inj) > 10(8) s(-1)) and in some cases hole transfer to NAr3 [TiO2(e(-))/Ru-III-NAr3 -> TiO2(e(-))/Ru-II-NAr3 center dot+]. The rate constants for charge recombination [TiO2(e(-))/Ru-III-NAr3 -> TiO2/Ru-II-NAr3 or TiO2(e(-))/Ru-II-NAr3 center dot+ -> TiO2/Ru-II-NAr3] were insensitive to the identity of the cyclometalated compound, while the open-circuit photovoltage was significantly larger for the compound with the highest quantum yield for hole transfer, behavior attributed to a larger dipole moment change (Delta mu = 7.7 D). Visible-light excitation under conditions where the Ru-III centers were oxidized resulted in injection into TiO2 [TiO2/Ru-III-NAr3 + h nu -> TiO2(e(-))/Ru-III-NAr3 center dot+] followed by rapid back interfacial electron transfer to another oxidized compound that had not undergone excited-state injection [TiO2(e(-))/Ru-III-NAr3 -> TiO2/Ru-II-NAr3]. The net effect was the photogeneration of equal numbers of fully reduced and fully oxidized compounds. Lateral intermolecular hole hopping (TiO2/Ru-II-NAr3 + TiO2/Ru-III-NAr3 center dot+ -> 2TiO(2)/Ru-III-NAr3) was observed spectroscopically and was modeled by Monte Carlo simulations that revealed an effective hole hopping rate of (130 ns)(-1).

First author: Samantaray, Manoja K., WMe6 Tamed by Silica: Si-O-WMe5 as an Efficient, Well-Defined Species for Alkane Metathesis, Leading to the Observation of a Supported W-Methyl/Methylidyne Species, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 1054, (2014)
Abstract: The synthesis and full characterization of a well-defined silica-supported :Si-O-W(Me)(5) species is reported. Under an inert atmosphere, it is a stable material at moderate temperature, whereas the homoleptic parent complex decomposes above -20 degrees C, demonstrating the stabilizing effect of immobilization of the molecular complex. Above 70 degrees C the grafted complex converts into the two methylidyne surface complexes [( SiO-)W( CH)Me-2] and [( SiO-)(2)W( CH)Me]. All of these silica-supported complexes are active precursors for propane metathesis reactions.

First author: Fantacci, Simona, Impact of Spin-Orbit Coupling on Photocurrent Generation in Ruthenium Dye-Sensitized Solar Cells, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 375, (2014)
Abstract: Relativistic TDDFT calculations have been performed employing a novel computational approach to evaluate the impact of spin orbit coupling (SOC) in the optical and photovoltaic properties of panchromatic Ru-II dyes for dye-sensitized solar cells (DSCs). The employed computational setup accurately reproduces the optical properties of the investigated dyes, allowing an assessment of the factors responsible for the varying SOC with the dye metal ligand environment. While for the prototypical panchromatic black dye sensitizer a negligible SOC effect is found, the SOC-induced spectral broadening calculated for the recently reported DX1 dye partly enhances the light-harvesting efficiency and consequently the photocurrent generation in DSCs based on this dye.

First author: Jissy, A. K., Design and Applications of Noncanonical DNA Base Pairs, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5, 154, (2014)
Abstract: While the Watson-Crick base pairs are known to stabilize the DNA double helix and play a vital role in storage/replication of genetic information, their replacement with non-Watson-Crick base pairs has recently been shown to have interesting practical applications. Nowadays, theoretical calculations are routinely performed on very complex systems to gain a better understanding of how molecules interact with each other. We not only bring together some of the basic concepts of how mispaired or unnatural nucleobases interact with each other but also look at how such an understanding influences the prediction of novel properties and development of new materials. We highlight the recent developments in this field of research. In this Perspective, we discuss the success of DFT methods, particularly, dispersion-corrected DFT, for applications such as pH-controlled molecular switching, electric-field-induced stacking of disk-like molecules with guanine quartets, and optical birefringence of alkali-metal-coordinated guanine quartets. The synergy between theoretical models and real applications is highlighted.

First author: Pandey, Krishna K., Dispersion interactions with density functional theory: Bonding description of V-NS bond in vanadium-thionitrosyl complex [(nacnac)(OAr)V(NS)], COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1028, 1, (2014)
Abstract: Dispersion corrected quantum chemical calculations of the complex [(nacnac)(OAr)V(NS)] were investigated at DFT, DFT-D3 and DFT-D3(BJ) level using BP86, PBE, revPBE, PW91 and TPSS functionals. The V-NS bond has essentially multiple bond character. The V-NS bond is relatively stronger than the calculated V-NO bond in the complex [(nacnac)(OAr)V(NO)]. The thionitrosyl ligand is stable in doublet state while [V(nacnac)(OAr)] fragment is stable in quartet state. The V-NS bond dissociation energies considering either doublet or quartet states of the interacting fragments vary in the order 77.2 (revPBE) < 82.1 (BP86) < 87.1 (PW91). The dispersion interaction energy has significant contribution to the V-NS bond dissociation energy. The dispersion corrections with DFT-D3 methods are smaller than the corresponding DFT-D3(BJ). The V-NS bond has a larger covalent character than the ionic character.

First author: Nizovtsev, Anton S., On the Pd-C bonding in RPdX and RPdL2X (R = CH3, C6H5; L = PH3; X = H, F, Cl, Br, I) compounds, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1028, 92, (2014)
Abstract: In this contribution we study chemical bonding between (i) Pd and C(sp(3)) and (ii) Pd and C(sp(2)) atoms in different substrates by means of electron localization function and energy decomposition analyses. All Pd-C bonds were found to possess both covalent and electrostatic character with a slightly larger contribution of the latter. Some of the other electronic structure features of compounds under investigation are discussed.

First author: Lee, Kyuho, Design of a Metal-Organic Framework with Enhanced Back Bonding for Separation of N-2 and CH4, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 698, (2014)
Abstract: Gas separations with porous materials are economically important and provide a unique challenge to fundamental materials design, as adsorbent properties can be altered to achieve selective gas adsorption. Metal organic. frameworks represent a rapidly expanding new class of porous adsorbents with a large range of possibilities for designing materials with desired functionalities. Given the large number of possible, framework structures, quantum mechanical computations can provide useful guidance in prioritizing the synthesis of the most useful materials for a given, application. Here, we show that such calculations can predict a new metal-organic framework of potential utility for separation of dinitrogen from methane, a particularly challenging separation of critical value for utilizing natural gas. An open V(II) site incorporated into a metal-organic framework can provide a material with a considerably higher methane, based on strong selective back bonding with the former but not the enthalpy of adsorption for dinitrogen latter.

First author: Goetz, Andreas W., An Extensible Interface for QM/MM Molecular Dynamics Simulations with AMBER,JOURNAL OF COMPUTATIONAL CHEMISTRY, 35, 95, (2014)
Abstract: We present an extensible interface between the AMBER molecular dynamics (MD) software package and electronic structure software packages for quantum mechanical (QM) and mixed QM and classical molecular mechanical (MM) MD simulations within both mechanical and electronic embedding schemes. With this interface, ab initio wave function theory and density functional theory methods, as available in the supported electronic structure software packages, become available for QM/MM MD simulations with AMBER. The interface has been written in a modular fashion that allows straight forward extensions to support additional QM software packages and can easily be ported to other MD software. Data exchange between the MD and QM software is implemented by means of files and system calls or the message passing interface standard. Based on extensive tests, default settings for the supported QM packages are provided such that energy is conserved for typical QM/MM MD simulations in the microcanonical ensemble. Results for the free energy of binding of calcium ions to aspartate in aqueous solution comparing semiempirical and density functional Hamiltonians are shown to demonstrate features of this interface.

First author: Wang, Xiaofeng, Preparation and catalytic activity of PVP-protected Au/Ni bimetallic nanoparticles for hydrogen generation from hydrolysis of basic NaBH4 solution, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY,39, 905, (2014)
Abstract: Poly(N-vinyl-2-pyrrolidone)(PVP)-protected Au/Ni bimetallic nanoparticles (BNPs) were prepared in one-vessel via chemical reduction of the corresponding ions with dropwise addition of NaBH4, and their catalytic activity in the hydrogen generation from hydrolysis of a basic NaBH4 solution was examined. The structure, particle size, and chemical composition of the resultant BNPs were characterized by Ultraviolet visible spectrophotometry (UV-Vis), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HR-TEM). The effects of processing parameters such as metal composition, metal ion concentration, and mole ratio of PVP to metal ion on the hydrolysis of a basic NaBH4 solution were studied in detail. The results indicated that as-prepared Au/Ni BNPs showed a higher catalytic activity than corresponding monometallic NPs (MNPs) in the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution. Among all the MNPs and BNPs, Au/Ni BNPs with the atomic ratio of 50/50 exhibited the highest catalytic activity, showing a hydrogen generation rate as high as 2597 mL-H-2 min(-1) g-catalyst(-1) at 30 degrees C, which can be ascribed to the presence of negatively charged Au atoms and positively charged Ni atoms. Based on the kinetic study of the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution over the PVP-protected Au/Ni BNPs, the corresponding apparent activation energy was determined as 30.3 kJ/mol for the BNPs with the atomic ratio of 50/50.

First author: de la Cruz Cruz, Jose Ignacio, Phosphine-Substituted (eta(5)-Pentadienyl) Manganese Carbonyl Complexes: Geometric Structures, Electronic Structures, and Energetic Properties of the Associative Substitution Mechanism, Including Isolation of the Slipped eta(3)-Pentadienyl Associative Intermediate, ORGANOMETALLICS, 33, 278, (2014)
Abstract: The molecule (eta(5)-Me(2)Pdl)Mn(CO)(3) (eta(5)-Me(2)Pdl = 2,4-dimethyl-eta(5)-pentadienyl) has been prepared by a new method and used as a starting material to prepare the molecules (eta(5)-Me(2)Pdl)Mn(CO)(n)(PMe3)(3-n) (n = 2, 1) by phosphine substitution for carbonyls. The first carbonyl substitution is achieved thermally in refluxing cyclohexane, and the second carbonyl substitution requires photolysis. At room temperature in benzene the associative intermediate (eta(3)-Me(2)Pdl)Mn(CO)(3)(PMe3) that precedes the initial loss of carbonyl is observed. Single-crystal structures are reported for all complexes, including the associative intermediate of the first substitution in which the pentadienyl ligand has slipped to the eta(3) bonding mode. These molecules offer an opportunity to examine fundamental principles of the interactions between metals and pentadienyl ligands in comparison to the well-developed chemistry of metal cyclopentadienyl (Cp) complexes as a function of electron richness at the metal center. Photoelectron spectra of these molecules show that the Me(2)Pdl ligand has pi ionizations at energy lower than that for the analogous Cp ligand and donates more strongly to the metal than the Cp ligand, making the metal more electron rich. Phosphine substitutions for carbonyls further increase the electron richness at the metal center. Density functional calculations provide further insight into the electronic structures and bonding of the molecules, revealing the energetics and role of the pentadienyl slip from eta(5) to eta(3) bonding in the early stages of the associative substitution mechanism. Computational comparison with dissociative ligand substitution mechanisms reveals the roles of dispersion interaction energies and the entropic free energies in the ligand substitution reactions. An alternative scheme for evaluating the computational translational and rotational entropy of a dissociative mechanism in solution is offered.

First author: Pinter, Balazs, Dimers of N-Heterocyclic Carbene Copper, Silver, and Gold Halides: Probing Metallophilic Interactions through Electron Density Based Concepts, CHEMISTRY-A EUROPEAN JOURNAL, 20, 734, (2014)
Abstract: Homobimetallic metallophilic interactions between copper, silver, and gold-based [(NHC)MX]-type complexes (NHC=N-heterocyclic carbene, i.e, 1,3,4-trimethyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene; X=F, Cl, Br, I) were investigated by means of ab initio interaction energies, Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework, and the noncovalent interaction (NCI) index. It was found that the dimers of these complexes predominantly adopt a head-to-tail arrangement with typical MM distance of 3.04-3.64 angstrom, in good agreement with the experimental X-ray structure determined for [{(NHC)AuCl}(2)], which has an AuAu distance of 3.33 angstrom. The interaction energies between silver- and gold-based monomers are calculated to be about -25kcalmol(-1), whereas that for the Cu congener is significantly lower (-19.7kcalmol(-1)). With the inclusion of thermal and solvent contributions, both of which are destabilizing, by about 15 and 8kcalmol(-1), respectively, an equilibrium process is predicted for the formation of dimer complexes. Energy-decomposition analysis revealed a dominant electrostatic contribution to the interaction energy, besides significantly stabilizing dispersion and orbital interactions. This electrostatic contribution is rationalized by NHC((+))halogen((-)) interactions between monomers, as demonstrated by electrostatic potentials and derived charges. The dominant NOCV orbital indicates weakening of the backdonation in the monomers on dimer formation, whereas the second most dominant NOCV represents an electron-density deformation according to the formation of a very weak MM bond. One of the characteristic signals found in the reduced density gradient versus electron density diagram corresponds to the noncovalent interactions between the metal centers of the monomers in the NCI plots, which is the manifestation of metallophilic interaction.

First author: Orian, Laura, Indenyl Effect Due to Metal Slippage? Computational Exploration of Rhodium-Catalyzed Acetylene [2+2+2] Cyclotrimerization, CHEMPHYSCHEM, 15, 219, (2014)
Abstract: The mechanism of CpRh (Cp=cyclopentadienyl) and IndRh (Ind=indenyl)-catalyzed acetylene [2+2+2] cyclotrimerization has been revisited aiming at finding an explanation for the better performance of the latter catalyst found experimentally. The hypothesis that an ancillary ligand of the precatalyst remains bonded to the metal center throughout the whole catalytic cycle, based on the experimental evidence that the nature of this ligand can exert some control in cocyclotrimerization of different alkynes, is considered. Strong hapticity variations occur in both the CpRh- and IndRh-catalyzed processes. As the Ind ligand undergoes a more facile slippage than Cp, the energy profile is far smoother in the IndRh-catalyzed cyclotrimerization. This difference in the energetics of the process translates into an enhanced activity of the IndRh catalyst, in nice agreement with experiment.

First author: Liang, Yanhong, Chain or Ring: Which One Is Favorable in Nitrogen-Rich Molecules N6XHm, N8XHm, and N10XHm (X = B, Al, Ga, m = 1 and X = C, Si, Ge, m = 2)?, JOURNAL OF PHYSICAL CHEMISTRY A, 118, 248, (2014)
Abstract: A series of nitrogen-rich molecules N6XHm, N8XHm, and N10XHm (X = B, Al, Ga, m = 1 and X = C, Si, Ge, m = 2) consisting of N-3 and N-5 radicals, are systematically investigated by using B3LYP and B3PW91 DFT methods. It is found that for the nitrogen-rich molecules, the structures with N-3-chains (N-5-ring) are more stable than those containing a N-3-ring (N-5-chain). This result could be well-explained by the intrinsic stability of the N-3 and N-5 radicals and their charge distribution in nitrogen-rich molecules. The dissociation energies further indicate that the B-doped and C-doped structures are the most stable among the molecules with three elements of group 13 and 14, respectively. Energy decomposition analysis shows the bond of boron-nitrogen is stronger than that of carbon-nitrogen. Detailed bonding analysis demonstrates that the B-N bond is determined by sigma and pi interactions between the B and N atoms, whereas C-N bonds by only sigma interactions. These results imply that the boron atom is more suitable than the carbon atom for building the nitrogen-rich molecules studied in this article.

First author: Jalilov, Almaz S., Structure and Electronic Spectra of Purine-Methyl Viologen Charge Transfer Complexes,JOURNAL OF PHYSICAL CHEMISTRY B, 118, 125, (2014)
Abstract: The structure and properties of the electron donor acceptor complexes formed between methyl viologen and purine nucleosides and nucleotides in water and the solid state have been investigated using a combination of experimental and theoretical methods. Solution studies were performed using UV-vis and H-1 NMR spectroscopy. Theoretical calculations were performed within the framework of density functional theory (DFT). Energy decomposition analysis indicates that dispersion and induction (charge-transfer) interactions dominate the total binding energy, whereas electrostatic interactions are largely repulsive. The appearance of charge transfer bands in the absorption spectra of the complexes are well-described by time-dependent DFT and are further explained in terms of the redox properties of purine monomers and solvation effects. Crystal structures are reported for complexes of methyl viologen with the purines 2′-deoxyguanosine 3′-monophosphate (DAD’DAD’ type) and 7-deazaguanosine (DAD’ADAD’ type). Comparison of the structures determined in the solid state and by theoretical methods in solution provides valuable insights into the nature of charge-transfer interactions involving purine bases as electron donors.

First author: Thorp-Greenwood, Flora L., Experimental and theoretical characterisation of phosphorescence from rhenium polypyridyl tricarbonyl complexes, POLYHEDRON, 67, 505, (2014)
Abstract: Synthetic, spectroscopic and theoretical methods are used to probe the photophysics of five rhenium polypyridyl tricarbonyl complexes, which exhibit strong phosphorescence behaviour. Particular focus is placed on the effect of polypyridyl ligand structure on absorption and emission properties, for instance by extending conjugation or by addition of electron donating groups. Experimental methods are performed in a consistent and controlled manner, thereby giving data that is ideally suited for comparison with theory. Modifications in ligand structure give rise to large changes in absorption energies, but rather smaller differences in emission. Density functional theory (DFT) and its time-dependent formulation (TD-DFT) perform rather better in predicting emission than absorption. The effect of environment on photo-physical properties was probed theoretically by protonating nitrogen(s) of dipyrido[3,2-a:2′,3′-c]phenazine (dppz). This has a large effect on calculated spectra and leads to more complex patterns of absorption and emission that require spin-orbit coupling to be included in DEL calculations for full explanation.

First author: Rodriguez-Fortea, Antonio, Maximum aromaticity or maximum pentagon separation; which is the origin behind the stability of endohedral metallofullerenes?, FARADAY DISCUSSIONS, 173, 201, (2014)
Abstract: Two different interpretations have been recently proposed to rationalize the stabilization of some hosting cages in endohedral metallofullerenes as a consequence of the larger localization of the negative charge on pentagonal rather than on hexagonal faces. We try to figure out the physical origin that mainly governs the stability of charged fullerenes; is it aromaticity or electrostatics?

First author: Purushothaman, Indu, CO2 adducts of Lewis acid-base pairs (LBCO(2)LA; LB = PMe3, NHC and LA = AlH3, AlCl3, BH3) – analogous to carboxylic acids and their derivatives, RSC ADVANCES, 4, 60421, (2014)
Abstract: The relationship between the structure and bonding of two different classes of molecules helps to understand and correlate their physiochemical activity. Here, we report the structure-bonding analogy between CO2 adducts of a Lewis acid (LA)-Lewis base (LB) pairs, LBCO(2)LA (LB = PMe3 and NHC; LA = AlH3, AlCl3 and BH3) and carboxylic acids and their derivatives, RCO2R’ (R, R’ = alkyl, H) by quantum mechanical calculations. The direction of charge flow in LBCO(2)LA is from LB to LA, whereas the reverse direction of charge flow (R’ to R) is observed for RCO2R’ leading to a formally negatively charged CO2 group ((2)A(1)) in both systems. This negatively charged bent CO2 group plays a deterministic role towards its bonding interaction with other fragments. The bonding analysis by the EDA-NOCV method indicates that both the LB and R groups form an electron sharing bond with the carbon atom of the bent CO2 fragment, whereas both LA and R’ form a donor-acceptor interaction with the oxygen atom. Our analysis suggests that the CO2 adducts of the Lewis acid (LA)-Lewis base (LB) pairs, LBCO(2)LA, can be considered as inorganic analogues of carboxylic acids and their derivatives, RCO2R’.

First author: Ren, Xin-Yao, Unveiling photophysical properties of cyclometalated iridium(III) complexes with azadipyrromethene and dipyrromethene ancillary: a theoretical perspective, RSC ADVANCES, 4, 62197, (2014)
Abstract: A density functional theory/time-depended density functional theory was used to investigate a series of heteroleptic Ir(III) complexes (1-4) employing azadipyrromethene and closely related dipyrromethene derivatives as (NN)-N-Lambda ancillary ligands, in an effort to explore the underlying reasons of non-radiative behaviour of 1 and further adjust the photophysical properties by the modification of (NN)-N-Lambda ancillary ligands. The results reveal that the non-emissive phenomenon of 1 can be attributed to the weak (ILCT)-I-3 character of the emissive excited state and large structure distortion, as well as the small T-1(opt)-S-0(opt) energy gap. Upon tailoring the (NN)-N-Lambda ancillary ligands, the geometry distortion of 2-4 becomes obviously smaller in comparison with 1, accordingly, the spectrum properties are also markedly affected. For instance, the enlargement of frontier molecular orbital energy gaps from 1 to 4 results in the blue-shift of their absorption and emission spectra, which is considered to be dominated by the ancillary ligand, while there is a little contribution from the Ir(III) center. Importantly, further analysis on the quantum yield (Phi(PL)) of these complexes also indicates a vital role of (NN)-N-Lambda ancillary ligands. It is intriguing to note that the designed complex 4 without pendant phenyl rings substituent in the ancillary ligand, possesses an efficient indirect spin-orbital coupling route, larger transition electric dipole moment (mu(S3)), higher T-1(opt)-S-0(opt) energy gap and smaller S-3-T-1 splitting energy (Delta E(S3-T1)), which ensure its higher Phi(PL) compared to other complexes.

First author: Wang, Feng, Fragment based electronic structural analysis of L-phenylalanine using calculated ionization spectroscopy and dual space analysis, RSC ADVANCES, 4, 60597, (2014)
Abstract: Two sets of amino acid-containing fragment schemes, the alanine/benzene scheme and the glycine/toluene scheme, are employed to study the electronic structure of an aromatic amino acid, L-phenylalanine (Phe). The calculated ionization energies (IEs) and the theoretical momentum distributions (TMDs) of the valence orbitals for the related molecules are analyzed to reveal the intra-molecular interactions through the fragments-in-molecules scheme. Density functional theory (DFT) based and Green function based quantum mechanical calculations as well as available experimental measurements are used in this study. It is found that the strong chemical bonding character of Phe seems to appear in the middle valence region of 11-20 eV, which largely shows the dependency of the fragment schemes. The valence energy region of 14 < IE < 20 eV in Phe is dominated by the glycine/toluene scheme, whereas the valence space of 11 < IE < 14 eV is dominated by the alanine/benzene scheme. The innermost valence space (i.e. IE > 20 eV) and the outermost valence space (i.e. the frontier orbitals) are less affected by the fragment schemes. These observations are confirmed using combined information on the position and momentum spaces in dual space analysis (DSA).

First author: Li, Elise Yu-Tzu, Semi-quantitative assessment of the intersystem crossing rate: an extension of the El-Sayed rule to the emissive transition metal complexes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 26184, (2014)
Abstract: The main goal of this study is to provide systematic elucidation of the parameters that influence S -> T intersystem crossing (ISC). Particular attention is paid to: (i) the computation of S-n -> T-m spin-orbit coupling strength based on a non-adiabatic approach, (ii) crucial factors that facilitate ISC, such as the atomic number, ligand structure, and particularly the types of electronic transition, (iii) formulating a discussion on the standpoints of the fundamental photophysical theory. Combining the theoretical and empirical approaches, we then make semi-quantitative assessment of the ISC rate for certain representative transition metal (TM) complexes, the results of which allow us to develop a set of empirical rules that harness ISC for organometallics analogous to El-Sayed’s rule for the classic organic compounds. We therefore present a critical and timely theoretical approach with the results matching quantitatively the experimental data, which serves as a prototype to access the photophysics of TM complexes in a facile and precise manner beneficial to researchers in the field of optoelectronics.

First author: Fihey, Arnaud, A DFT study of a new class of gold nanocluster-photochrome multi-functional switches,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 26240, (2014)
Abstract: With the help of a computational scheme combining molecular dynamics, DFT and TD-DFT methods, the conformational, electronic and optical properties of a new class of hybrid compounds where a photochromic molecule belonging to the dithienylethene family (DTE) is covalently linked to a Au-25 nanocluster (gold nanocluster or GNC) are investigated. We compare two types of hybrid GNC-DTE systems where the aromatic linker between the metallic and the DTE moieties is either a phenyl or a thiophene ring. By examining the perturbation of the DTE electronic structure after grafting upon the GNC, we show that the hybrid system with a phenyl linker should preserve its photochromic activity. For the latter system, we have then studied the possible energy and electron transfer between the GNC and the DTE units. The energy transfer between the two moieties can be a priori discarded while a uni-directional electron transfer should take place from the GNC to the excited DTE. We show that this transfer can be controlled by switching the state of the molecule.

First author: Deb, Tapash, Steric and electronic effects on arylthiolate coordination in the pseudotetrahedral complexes [(Tp(Ph,Me))Ni-SAr] (Tp(Ph,Me) = hydrotris{3-phenyl-5-methyl-1-pyrazolyl}borate), DALTON TRANSACTIONS, 43, 17489, (2014)
Abstract: Synthesis and characterization of several new pseudotetrahedral arylthiolate complexes [(Tp(Ph,Me)) Ni-SAr] (Tp(Ph,Me) = hydrotris{3-phenyl-5-methyl-1-pyrazolyl}borate; Ar = Ph, 2,4,6-(Pr3C6H2)-Pr-i, C6H4-4-Cl, C6H4-4-Me, C6H4-4-OMe) are reported, including X-ray crystal structures of the first two complexes. With prior results, two series of complexes are spanned, [(Tp(Ph,Me)) Ni-S-2,4,6-R ” 3C6H2] (R ” = H, Me, Pr-i) plus the xylyl analogue [(Tp(Ph,Me))Ni-S-2,6-Me2C6H3], as well as [(Tp(Ph,Me))Ni-S-C6H4-4-Y] (Y = Cl, H, Me, OMe), intended to elucidate steric and/or electronic effects on arylthiolate coordination. In contrast to [(Tp(Me,Me))Ni-SAr] analogues that adopt a sawhorse conformation, the ortho-disubstituted complexes show enhanced trigonal and Ni-S-Ar bending, reflecting the size of the 3-pyrazole substituents. Moreover, weakened scorpionate ligation is implied by spectroscopic data. Little spectroscopic effect is observed in the series of para-substituted complexes, suggesting the observed effects are primarily steric in origin. The relatively electron-rich and encumbered complex [(TpPh, Me) Ni-S-2,4,6-iPr3C6H2] behaves uniquely when dissolved in CH3CN, forming a square planar solvent adduct with a bidentate scorpionate ligand, [(kappa(2)-Tp(Ph,Me))Ni(NCMe)(S-2,4,6-(Pr3C6H2)-Pr-i)]. This adduct was isolated and characterized by X-ray crystallography. Single-point DFT and TD-DFT calculations on a simplified [(kappa(2)-Tp)Ni(NCMe)(SPh)] model were used to clarify the electronic spectrum of the adduct, and to elucidate differences between Ni-SAr bonding and spectroscopy between pseudotetrahedral and square planar geometries.

First author: Adaila, Kawther, Synthesis, characterization, DFT calculations, and antimicrobial activity of Pd(II) and Co(III) complexes with the condensation derivative of 2-(diphenylphosphino) benzaldehyde and Girard’s T reagent, JOURNAL OF COORDINATION CHEMISTRY, 67, 3633, (2014)
Abstract: Complexes of Pd(II) and Co(III) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard T reagent were synthesized, characterized, and their antimicrobial activities were evaluated. The ligand and the complexes were characterized by elemental analysis, IR and NMR spectroscopies, and X-ray crystallography. In both complexes, the deprotonated ligand was coordinated to the metal through the phosphorus, the imine nitrogen, and the carbonyl oxygen atoms. In the octahedral Co(III) complex, two molecules of ligands were coordinated to metal ion, while square-planar environment of Pd(II) complex was constituted of one tridentate ligand and chloride in the fourth coordination place. The ligand and complexes showed moderate antibacterial activity. The molecular structures of the obtained metal complexes and the relative stabilities of two stereoisomers of the ligand were calculated using density functional theory at the S12g/TZ2P level.

First author: Baranac-Stojanovic, Marija, Gauche preference in 1,2-difluoroethane originates from both orbital and electrostatic stabilization interactions, RSC ADVANCES, 4, 43834, (2014)
Abstract: The origin of the gauche preference in 1,2-difluoroethane has been investigated by using an energy decomposition analysis (EDA). The EDA results show that favourable orbital interactions are not the sole source of stabilization in this conformer. Electrostatic interactions, too, are more attractive in the gauche than in the anti form. This finding opposes our traditional view of electrostatic interactions and their influence on conformational equilibria, but points out that they should be considered as an all-charge phenomenon, rather than partial interaction between pairs of bonds.

First author: Huang, Fang, 2-(1-Aryliminoethyl)-9-arylimino-5,6,7,8-tetrahydrocycloheptapyridyl iron(II) dichloride: synthesis, characterization, and the highly active and tunable active species in ethylene polymerization, DALTON TRANSACTIONS, 43, 16818, (2014)
Abstract: A series of 2-(1-arylimino) ethyl-9-arylimino-5,6,7,8-tetrahydrocycloheptapyridine derivatives was synthesized and fully characterized, and thereafter reacted with iron dichloride to form their corresponding iron(II) complexes. The single crystals of representative organic and iron complex compounds were obtained and analyzed by the X-ray diffraction analysis, indicating the distorted bipyramidal geometry around the iron core. Moreover, DFT calculations were performed on selected species to determine their structural features. On treatment with either MAO or MMAO, all iron complex pre-catalysts showed high activities (up to 1.56 x 10(7) gPE mol(-1)(Fe) h(-1)) toward ethylene polymerization. Regarding the nature of the ligands and reaction parameters, their catalytic activities and the characters of the obtained polyethylenes have been carefully investigated. The ring strain of the fused-cycloheptane of the ligands within iron complexes was considered to affect their catalytic performance in ethylene polymerization. The active species were activated and controlled by using a co-catalyst of MMAO preferred over MAO, and the obtained polyethylenes with MMAO showed narrower molecular polydispersity than the corresponding polyethylenes with MAO.

First author: Haag, Moritz P., Studying chemical reactivity in a virtual environment, FARADAY DISCUSSIONS, 169, 89, (2014)
Abstract: Chemical reactivity of a set of reactants is determined by its potential (electronic) energy (hyper)surface. The high dimensionality of this surface renders it difficult to efficiently explore reactivity in a large reactive system. Exhaustive sampling techniques and search algorithms are not straightforward to employ as it is not clear which explored path will eventually produce the minimum energy path of a reaction passing through a transition structure. Here, the chemist’s intuition would be of invaluable help, but it cannot be easily exploited because (1) no intuitive and direct tool for the scientist to manipulate molecular structures is currently available and because (2) quantum chemical calculations are inherently expensive in terms of computational effort. In this work, we elaborate on how the chemist can be reintroduced into the exploratory process within a virtual environment that provides immediate feedback and intuitive tools to manipulate a reactive system. We work out in detail how this immersion should take place. We provide an analysis of modern semi-empirical methods which already today are candidates for the interactive study of chemical reactivity. Implications of manual structure manipulations for their physical meaning and chemical relevance are carefully analysed in order to provide sound theoretical foundations for the interpretation of the interactive reactivity exploration.

First author: Tonner, Ralf, The dimeric nature of bonding in gallium: from small clusters to the alpha-gallium phase,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 24244, (2014)
Abstract: We consider the structural similarity of small gallium clusters to the bulk structure of alpha-gallium, which has been previously described as a molecular metal, via density functional theory-based computations. Previous calculations have shown that the tetramer, the hexamer, and the octamer of gallium are all structurally similar to the alpha-phase. We perform an analysis of the bonding in these clusters in terms of the molecular orbitals and atoms in molecules description in order to assess whether we can see similarities at these sizes to the bonding pattern, which is ascribed to the co-existence of covalent and metallic bonding in the bulk. The singlet Ga-4 and Ga-8 clusters can be constructed in a singlet ground state from the Ga-dimers in the first excited triplet state of the Ga-2-molecule, the (3)Sigma(-)(g) state. Molecular orbital (MO) analysis confirms that the dimer is an essential building block of these small clusters. Comparison of the AIM characteristics of the bonds within the clusters to the bonds in the bulk a-phase supports the identification of the covalent bond in the bulk as related to the (3)Sigma(-)(g) state of the dimer.

First author: Liang, Ai-Hua, Theoretical Studies on Phosphorescent Materials: The Conjugation-Extended Pt-II Complexes, AUSTRALIAN JOURNAL OF CHEMISTRY, 67, 1522, (2014)
Abstract: A theoretical study on the Pt-II complex A based on a dimesitylboron (BMes(2))-functionalized [Pt(C<^>N)(acac)] (C<^>N=2-phenyl-pyridyl, acac=acetylaceton) complex, as well as three conjugation-extended analogues of the methylimidazole (C*) ligand BMes(2)-[Pt(C<^>C*)(acac)] complexes B-D is performed. Their theoretical geometries, electronic structures, emission properties, and the radiative decay rate constants (k(r)) were also investigated. The energy differences between the two highest occupied orbitals with dominant Pt d-orbital components (dd(occ)) of D both at the ground and excited states are the smallest of all. Compared with B, the charge transfer in D possesses a marked trend towards the extended conjugated group, while C changed inconspicuously. The lowest-lying absorptions and the phosphorescence of them can be described as a mixed metal-to-ligand charge transfer (MLCT)/intra-ligand * charge transfer (ILCT) and (MLCT)-M-3/(ILCT)-I-3, respectively. The variation of charge transfer properties induced by extended conjugation and the radiative decay rate constants (k(r)) calculated revealed that D is a more efficient blue phosphorescence material with a 497nm emission transition.

First author: Liu, Ling, Electron transport via phenyl-perfluorophenyl interaction in crystals of fluorine-substituted dibenzalacetones, RSC ADVANCES, 4, 50188, (2014)
Abstract: Although substitution with fluorine creates stability in organic electronic materials by altering the molecular crystal packing, the charge transport properties of the materials are significantly affected. Phenyl-perfluorophenyl (pi-pi(F)) interaction is a unique intermolecular interaction formed between electropositive perfluorophenyl and electronegative non-fluorinated phenyl, and may have a different charge transport as compared to the pi-pi interaction formed between ordinary phenyl rings. Three crystals with both pi-pi(F) interaction and intermolecular hydrogen bonding interaction were chosen to study the relationship between intermolecular interactions and their charge transport properties in both the band-like model and the hopping model. In contrast to ordinary pi-pi interaction, which has been reported to be mainly responsible for hole transport, the pi-pi(F) interaction is mainly responsible for electron transport. Thus, intermolecular pi-pi(F) interaction is an effective packing style to realize the n-type charge carrier. In summary, C-H/center dot center dot center dot F interactions are mainly responsible for electron transport while the C-H/center dot center dot center dot O interaction is responsible for hole transport.

First author: Hayashi, Satoko, Relativistic effects on the Te-125 and S-33 NMR chemical shifts of various tellurium and sulfur species, together with Se-77 of selenium congeners, in the framework of a zeroth-order regular approximation: applicability to tellurium compounds, RSC ADVANCES, 4, 44795, (2014)
Abstract: The relativistic effects on absolute magnetic shielding tensors [sigma(Z: Z = Te, Se and S)] are explicitly evaluated for various tellurium, selenium and sulfur species using the DFT(BLYP)-GIAO method. Calculations of sigma(Te), sigma(Se) and sigma(S) are performed under the spin-orbit ZORA relativistic (Rlt-so) and nonrelativistic (Non) conditions with the Slater-type basis sets of the quadruple zeta all electron with four polarization functions (QZ4Pae). Structures optimized at the MP2 level under nonrelativistic conditions are employed for the evaluations. While the range of the relativistic effects on the total shielding tensors for Te (Delta sigma(t)(Te)(Rlt-so) = sigma(t)(Te)(Rlt-so) – sigma(d+p)(Te)(Non)) is predicted to be -55 to 658 ppm, that for Delta sigma(t)(S) is predicted to be 5 to 32 ppm, except for Me2SBr2 (TBP), where Delta sigma(t)(S)(Rlt-so) = -29 ppm. The range for Delta sigma(t)(Se) is 2 to 153 ppm. The magnitudes of the relativistic effects on sigma(t)(Te), sigma(t)(Se) and sigma(t)(S) are about 25 : 5 : 1. The applicability of sigma(t)(Te)(Rlt-so) to analyze delta(Te)(obsd) is also examined, mainly with the OPBE//OPBE method under the spin-orbit ZORA relativistic conditions with QZ4Pae, in addition to the above method.

First author: Huang, Yining, Recent Advances in Solid-State Zn-67 NMR Studies: From Nanoparticles to Biological Systems, ANNUAL REPORTS ON NMR SPECTROSCOPY, VOL 81, 81, 1, (2014)
Abstract: In this chapter, we summarize the tremendous advances in Zn-67 solid-state NMR (SSNMR) spectroscopy and its applications over the last two decades. Zn-67 is the only NMR-active isotope of zinc with NMR unfavourable nuclear properties such as a small gyromagnetic ratio, a low natural abundance and a relatively large quadrupole moment. As a result, Zn-67 SSNMR spectroscopy had historically been very challenging. However, in recent years, Zn-67 SSNMR spectroscopy has increasingly played an important role in characterizing zinc-containing solids. The increased feasibility of Zn-67 SSNMR spectroscopy can be credited, in large part, to several factors such as the increased accessibility of ultrahigh-magnetic-field NMR instruments, the development of sensitivity-enhancement techniques for quadrupolar nuclei and the availability of first-principle calculations of NMR parameters of solids. The examples provided in this chapter illustrate that Zn-67 SSNMR spectroscopy is indeed a powerful tool for characterizing a wide range of zinc-containing materials from semiconducting nanoparticles to biological systems.

First author: Chen, Lei, The mechanism of N-Ag bonding determined tunability of surface-enhanced Raman scattering of pyridine on MAg (M = Cu, Ag, Au) diatomic clusters, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 20665, (2014)
Abstract: Binary coinage metal clusters can show a significantly different enhancement in surface-enhanced Raman scattering (SERS) from that of pure element clusters, owing to their tunable surface plasmon resonance energies affected by the composition and atomic ordering. Yet, the tunability by composition requires a deep understanding in order to further optimize the SERS-based detection technique. Here, to fill this deficiency, we conducted detailed analyses of the SERS of pyridine adsorbed through N-Ag bonding on the homonuclear diatomic metal cluster Ag-2 and heteronuclear diatomic metal clusters of AuAg and CuAg, as well as the involved charge transfer under an intracluster excitation, based on calculations using time-dependent density functional theory with a short-time approximation for the Raman cross-section. We find that although the SERS enhancements for all complexes can reach the order of 10(3)-10(4), the corresponding wavelengths used for SERS excitation are significantly different. Our molecular orbital analysis reveals that the complexes based on heteronuclear metal clusters can produce varied electronic transitions owing to the polarization between different metal atoms, which tune the SERS enhancements with altered optical properties. Our analyses are expected to provide a theoretical basis for exploring the multi-composition SERS substrates applicable for single molecular detection, nanostructure characterization, and biological molecular identification.

First author: Saielli, Giacomo, Computational F-19 NMR. 2. Organic compounds, RSC ADVANCES, 4, 41605, (2014)
Abstract: Fluorine-19 NMR chemical shifts have been calculated for a wide variety of fluorinated organic molecules by relativistic density functional methods. The study includes, along with common fluorine-containing functional groups, several fluorinated biologically active molecules or models thereof. These calculations further showcase the predictive power of DFT-NMR, and illustrate how they can be used to assign F-19 spectra for the structure determination of organofluorine compounds.

First author: Emel’yanova, N. S., Quantum chemical approaches to the explanation of differences in NO-donor activity of iron-sulfur nitrosyl complexes, RUSSIAN CHEMICAL BULLETIN, 63, 37, (2014)
Abstract: The geometries and electronic structures of iron-sulfur nitrosyl complexes with azaheterocyclic thiols with mu-SCN bridging ligands, [Fe-2(SCN4Ph)(2)(NO)(4)] (1) and [Fe-2(SCN4Me)(2)(NO)(4)] (2), were calculated within the framework of the density functional theory (DFT) with the BP86, TPSS, B3LYP, and OPBE functionals in order to explain differences in their NO-donor activities. Chemical bonding in the complexes was analyzed using the NBO approach, according to Mulliken, and using the Voronoi scheme. NBO analysis of complex 1 revealed a strong interaction between orbitals of the lone electron pairs of the Fe atom and the antibonding orbitals of the Fe-N bond which leads to strengthening of the Fe-NO bond. In complex 2, the Fe-NO bond is more polar than in complex 1.

First author: Viger-Gravel, Jasmine, Probing halogen bonds with solid-state NMR spectroscopy: observation and interpretation of J(Se-77,P-31) coupling in halogen-bonded P=Se center dot center dot center dot I motifs,CRYSTENGCOMM, 16, 7285, (2014)
Abstract: Halogen bonds constitute an important and topical class of non-covalent interaction. We report a combined X-ray diffraction, multinuclear (Se-77, P-31, C-13) solid-state magnetic resonance, and computational study of a series of crystalline triphenylphosphine selenide-iodoperfluorobenzene complexes which feature P=Se center dot center dot center dot I-C halogen bonds. Selenium-77 chemical shifts increase due to halogen bonding with iodine and correlate with the P=Se distance, which in turn correlates with the strength of the halogen bond. J(Se-77, P-31) coupling constants increase in magnitude as the halogen bond weakens. This observation is understood via a natural localized molecular orbital (NLMO) DFT approach which shows that contributions from the selenium lone pair orbital tend to dominate both the magnitude and trends in J(Se-77, P-31), with the selenium-phosphorus bonding orbital being the second largest contributor. This work suggests that J couplings measured via NMR spectroscopy may play an important role in the characterization of halogen bonds, in clear analogy with their role in the characterization of hydrogen bonds.

First author: Owczarek, Magdalena, Weak hydrogen and dihydrogen bonds instead of strong N-H center dot center dot center dot O bonds of a tricyclic [1,2,4,5]-tetrazine derivative. Single-crystal X-ray diffraction, theoretical calculations and Hirshfeld surface analysis, CRYSTENGCOMM, 16, 7638, (2014)
Abstract: Octahydro-1H,6H-bis[1,4]oxazino[4,3-b:4′,3′-e][1,2,4,5]tetrazine, 1, and its monohydrated analog, 2, were obtained by an oxidation process of N-aminomorpholine with iodine. Both compounds crystallize in monoclinic space groups P2(1)/c and C2/c for 1 and 2, respectively. Despite the presence of a strong hydrogen bond donor – the NH group – the crystal packing of 1 is determined by weak C-H center dot center dot center dot O and C-H center dot center dot center dot N hydrogen bonds. In order to explore more precisely this intriguing fact, the theory of Atoms In Molecules (AIM) was used to examine intermolecular interactions in a crystal. An analysis of the topological properties of electron density with the determination of bond critical point revealed a set of contacts which were carefully scrutinized to determine whether they fulfill the criteria of hydrogen and dihydrogen bond existence in the AIM method. Their stability was checked by DFT calculations. In the case of 2, the crystal packing is realized by strong O1w-H1w center dot center dot center dot N and N-H center dot center dot center dot O1w hydrogen bonds with water. The possibility of accepting more than one hydrogen atom by each lone electron pair of water is discussed based on the AIM method and Natural Bond Orbital (NBO) analysis. Hirshfeld surfaces were employed to confirm the existence of intermolecular interactions in 1 and 2.

First author: Charnock, G. T. P., A partial differential equation for pseudocontact shift, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 20184, (2014)
Abstract: It is demonstrated that pseudocontact shift (PCS), viewed as a scalar or a tensor field in three dimensions, obeys an elliptic partial differential equation with a source term that depends on the Hessian of the unpaired electron probability density. The equation enables straightforward PCS prediction and analysis in systems with delocalized unpaired electrons, particularly for the nuclei located in their immediate vicinity. It is also shown that the probability density of the unpaired electron may be extracted, using a regularization procedure, from PCS data.

First author: Ribierre, J. C., Influence of the grain orientation on the charge transport properties of organic field-effect transistors, RSC ADVANCES, 4, 36729, (2014)
Abstract: We report the effects of crystalline grain orientation on the charge transport properties of a J-aggregate bisazomethine dye (DE2) in thin films. Highly oriented DE2 organic field-effect transistors are fabricated using an insulating alignment layer of poly(tetrafluoroethylene) in the gate dielectric. An enhancement of about one and two orders of magnitude in hole mobility is achieved when the molecules and the crystalline grains are aligned perpendicular and parallel to the transistor channel, respectively. Ambipolar transport is observed only for the parallel alignment. To gain additional insights into the role of molecular packing on the charge transport properties of DE2, quantum chemical calculations are carried out to determine and compare the energetic splittings of the highest occupied molecular orbitals (HOMO) and of the lowest unoccupied molecular orbitals (LUMO) in the film. The results provide evidence that DE2 is intrinsically an ambipolar organic semiconductor and demonstrates the important role played by grain boundary orientation on charge trapping processes. Overall, the demonstration of field-effect mobilities as high as 0.01 cm(2) V (- 1) s(-1) and the observation of ambipolar transport in our devices represent an obvious milestone for the possible use of J-aggregate thin films in organic electronic devices. In addition, this work provides significant insights into the interplay between crystalline grain orientation and ambipolar charge transport properties in organic thin films.

First author: den Hartog, Tim, A lithiomethyl trimethylammonium reagent as a methylene donor, CHEMICAL COMMUNICATIONS, 50, 10604, (2014)
Abstract: Straightforward deprotonation of soluble tetramethylammonium salts with alkyllithium reagents gives lithiomethyl trimethylammonium reagents. Coordination of the Li cation is crucial to the stability of these ‘N-C ylides’. These reagents were used to prepare epoxides, aziridines and allylic alcohols.

First author: Seel, A. G., Low energy structural dynamics and constrained libration of Li(NH3)(4), the lowest melting point metal, CHEMICAL COMMUNICATIONS, 50, 10778, (2014)
Abstract: The lattice and molecular dynamics for the solid phases of the lowest melting-point metal, Li(NH3)(4), are determined by incoherent inelastic neutron scattering. Measurements of internal molecular displacements and distortions of the Li(NH3)(4) units have been modelled and assigned using density functional theory calculations for the solid and molecular system. Inelastic neutron scattering measurement allow for the first determination of NH3 librational transitions.

First author: Zhong, Xin, Pressure stabilization of long-missing bare C-6 hexagonal rings in binary sesquicarbides,CHEMICAL SCIENCE, 5, 3936, (2014)
Abstract: Carbon (C) is able to form various bonding patterns, including graphene sheets, chains and dimers, but stable bare six-membered C-6 hexagonal rings, which are the fundamental structural motifs of graphite and graphene have long been missing. Here we report the stabilization of such bare C-6 rings under high pressures in the charge-transfer systems of binary sesquicarbides Y2C3 and La2C3 as predicted by first-principles swarm structure searching simulations. We found that the external pressure can be used to efficiently tune structural transitions in the sesquicarbides from the ambient-pressure cubic phases into high-pressure orthorhombic phases, accompanied by significant C-C bonding modification from C-C dimers to bare C-6 rings and polymerized graphene-like double C-6 sheets. The bare C-6 rings are stabilized in Y2C3 and La2C3 at pressures above 32 and 13 GPa, respectively, which are readily accessible to experiments. Chemical bonding analysis reveals that the bare C-6 rings feature a benzene-like sp(2) C-C bonding pattern with a delocalized p system. Y or La -> C charge transfer and the need for denser structure packing are found to be part of the underlying mechanisms behind the stabilization of the bare C-6 rings.

First author: Braunschweig, Holger, Gauging metal Lewis basicity of zerovalent iron complexes via metal-only Lewis pairs,CHEMICAL SCIENCE, 5, 4099, (2014)
Abstract: A range of pentacoordinate iron complexes of the form [Fe(CO)(5-n)L-n] (L = neutral donor, n = 0-2) were treated with gallium chloride or bromide, leading to hexacoordinate metal-only Lewis pairs (MOLPs) of the form [L-n(OC)(5-n)Fe -> GaX3] (X = Cl, Br). These complexes were used to gauge the Lewis basicity of the pentacoordinate iron precursors through comparison of their experimentally-and computationally-derived Fe-Ga distances and the degree of pyramidalization at the Ga center. The data indicate that consecutive replacement of CO groups with donor ligands increases the Lewis basicity of [Fe(CO)(5-n)L-n] complexes, with the largest effect seen upon going from n = 0 to n = 1. While the Lewis basicity differences are clear between tri-, tetra-and pentacarbonyl complexes, the difference between the ligands within each group is less clear. A series of transfer experiments were also performed, in which the GaCl3 was transferred consecutively to Fe complexes with increasing numbers of donor ligands.

First author: Marenich, Aleksandr V., Computational electrochemistry: prediction of liquid-phase reduction potentials,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 15068, (2014)
Abstract: This article reviews recent developments and applications in the area of computational electrochemistry. Our focus is on predicting the reduction potentials of electron transfer and other electrochemical reactions and half-reactions in both aqueous and nonaqueous solutions. Topics covered include various computational protocols that combine quantum mechanical electronic structure methods (such as density functional theory) with implicit-solvent models, explicit-solvent protocols that employ Monte Carlo or molecular dynamics simulations (for example, Car-Parrinello molecular dynamics using the grand canonical ensemble formalism), and the Marcus theory of electronic charge transfer. We also review computational approaches based on empirical relationships between molecular and electronic structure and electron transfer reactivity. The scope of the implicit-solvent protocols is emphasized, and the present status of the theory and future directions are outlined.

First author: Nithya, R., Theoretical studies on charge transport and optical properties of tris(N-saclicylideneanilines), RSC ADVANCES, 4, 25969, (2014)
Abstract: The structural, charge transport and optical properties of the discotic liquid crystalline molecule tris(N-saclicylideneanilines) (TSANs) have been studied using quantum chemical methods. The TSANs have enol-imine and keto-enamine tautomeric forms, and the relative energy calculations show that the keto form is more stable than the enol form. The effective charge transfer integral and site energy corresponding to the hole and electron transport in TSAN molecules were calculated directly from the matrix elements of Kohn-Sham Hamiltonian. The calculated charge carrier mobility using the Monte Carlo simulation of the polaron hopping transport method shows that the TSAN molecules are n-type organic semiconductors and the charge transport strongly depends on the substituted functional groups and the orientation of the pi-stacked molecules. The absorption and emission spectra of TSANs have been analyzed using a time-dependent density functional theory (TDDFT) method. The results obtained from this study will reveal the relationships between the molecular structure and charge transport as well as the optical properties of the TSAN molecules.

First author: Gruden-Pavlovic, M., A density functional study of the spin state energetics of polypyrazolylborato complexes of first-row transition metals, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 14514, (2014)
Abstract: Density Functional Theory (DFT) was used to analyse and explain spin state energetics of first-row transition metals (Mn-II, Fe-II, Co-II; Cr-III, Mn-III, Fe-III, Co-III; Mn-IV) in polypyrazolylborato complexes. We explored the effects of substitutions at the 3 and 5 positions of the pyrazolyl rings, as well as the influence of Jahn-Teller (JT) distortions on spin-state switching. Although the stabilizations due to JT distortion are sometimes substantial, this does not lead to switching of the spin ground-state. On the other hand, electron withdrawing or donating substituents do lead to significant changes in the spin-crossover (SCO) properties of the investigated complexes.

First author: Mori, K., Predicting phosphorescent lifetimes and zero-field splitting of organometallic complexes with time-dependent density functional theory including spin-orbit coupling, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 14523, (2014)
Abstract: The (photo)physical properties of organometallic complexes are crucially affected by relativistic effects. In a non- or scalar-relativistic picture, triplet states are threefold degenerate. Spin-orbit coupling lifts this degeneracy (zero-field splitting, ZFS) and enables phosphorescence from the three triplet-like states to the ground state. The fine structure and radiative lifetimes of phosphorescent organometallic complexes are important properties for designing efficient organic light-emitting diodes (OLEDs). Here we show that experimental ZFSs and phosphorescent lifetimes for a large variety of organometallic complexes are well reproduced by self-consistent spin-orbit coupling TDDFT (SOC-TDDFT) calculations with a continuum solvation model. By comparing with perturbative SOC-TDDFT and gas phase calculations, we find that both full spin-orbit and solvation effects are important for the predicted properties. SOC-TDDFT is thus shown to be a useful predictive tool for the rational design of phosphors in OLEDs and other optoelectronic devices.

First author: Ramanantoanina, Harry, Ligand field density functional theory for the prediction of future domestic lighting,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 14625, (2014)
Abstract: We deal with the computational determination of the electronic structure and properties of lanthanide ions in complexes and extended structures having open-shell f and d configurations. Particularly, we present conceptual and methodological issues based on Density Functional Theory (DFT) enabling the reliable calculation and description of the f -> d transitions in lanthanide doped phosphors. We consider here the optical properties of the Pr3+ ion embedded into various solid state fluoride host lattices, for the prospection and understanding of the so-called quantum cutting process, being important in the further quest of warm-white light source in light emitting diodes (LED). We use the conceptual formulation of the revisited ligand field (LF) theory, fully compatibilized with the quantum chemistry tools: LFDFT. We present methodological advances for the calculations of the Slater-Condon parameters, the ligand field interaction and the spin-orbit coupling constants, important in the non-empirical parameterization of the effective Hamiltonian adjusted from the ligand field theory. The model shows simple procedure using less sophisticated computational tools, which is intended to contribute to the design of modern phosphors and to help to complement the understanding of the 4f(n) -> 4f(n-1)5d(1) transitions in any lanthanide system.

First author: Fernandez, Israel, The activation strain model and molecular orbital theory: understanding and designing chemical reactions, CHEMICAL SOCIETY REVIEWS, 43, 4953, (2014)
Abstract: In this Tutorial Review, we make the point that a true understanding of trends in reactivity (as opposed to measuring or simply computing them) requires a causal reactivity model. To this end, we present and discuss the Activation Strain Model (ASM). The ASM establishes the desired causal relationship between reaction barriers, on one hand, and the properties of reactants and characteristics of reaction mechanisms, on the other hand. In the ASM, the potential energy surface Delta E(zeta) along the reaction coordinate zeta is decomposed into the strain Delta E-strain(zeta) of the reactants that become increasingly deformed as the reaction proceeds, plus the interaction Delta E-int(zeta) between these deformed reactants, i.e., Delta E(zeta) = Delta E-strain(zeta) + Delta E-int(zeta). The ASM can be used in conjunction with any quantum chemical program. An analysis of the method and its application to problems in organic and organometallic chemistry illustrate the power of the ASM as a unifying concept and a tool for rational design of reactants and catalysts.

First author: Alkan, Fahri, Calculation of chemical-shift tensors of heavy nuclei: a DFT/ZORA investigation of Hg-199 chemical-shift tensors in solids, and the effects of cluster size and electronic-state approximations, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 14298, (2014)
Abstract: Calculations of the nuclear magnetic resonance chemical-shielding tensors of a suite of mercury-containing materials using various cluster models for the structures provide a stringent test of the procedures for forming models and for calculation with various methods. The inclusion of higher co-ordination shells in the molecular clusters permits quantum chemical calculations of Hg-199 chemical-shielding tensor elements within 3% of the experimental values. We show that it is possible to reduce the size of computationally expensive molecular-cluster calculations with limited effect on calculated NMR parameters by carefully introducing the frozen core approximation. The importance of the relativistic Hamiltonian for accurate predictions of chemical-shielding values is demonstrated within the molecular cluster approach. The results demonstrate that careful design of a cluster to represent the solid-state structure, inclusion of relativistic components in the Hamiltonian at least at the spin-orbit level, and judicious use of approximations are essential to obtain good agreement with experimental results.

First author: Poater, Jordi, B-DNA structure and stability: the role of hydrogen bonding, pi-pi stacking interactions, twist-angle, and solvation, ORGANIC & BIOMOLECULAR CHEMISTRY, 12, 4691, (2014)
Abstract: We have computationally investigated the structure and stability of B-DNA. To this end, we have analyzed the bonding in a series of 47 stacks consisting of two base pairs, in which the base pairs cover the full range of natural Watson-Crick pairs, mismatched pairs, and artificial DNA base pairs. Our analyses provide detailed insight into the role and relative importance of the various types of interactions, such as, hydrogen bonding, pi-pi stacking interactions, and solvation/desolvation. Furthermore, we have analyzed the functionality of the twist-angle on the stability of the structure. Interestingly, we can show that all stacked base pairs benefit from a stabilization by 6 to 12 kcal mol(-1) if stacked base pairs are twisted from 0 degrees to 36 degrees, that is, if they are mutually rotated from a congruent superposition to the mutually twisted stacking configuration that occurs in B-DNA. This holds especially for stacked AT pairs but also for other stacked base pairs, including GC. The electronic mechanism behind this preference for a twisted arrangement depends on the base pairs involved. We also show that so-called “diagonal interactions” (or cross terms) in the stacked base pairs are crucial for understanding the stability of B-DNA, in particular, in GC-rich sequences.

First author: Borgogno, Andrea, Predicting the spin state of paramagnetic iron complexes by DFT calculation of proton NMR spectra, DALTON TRANSACTIONS, 43, 9486, (2014)
Abstract: Many transition-metal complexes easily change their spin state S in response to external perturbations (spin crossover). Determining such states and their dynamics can play a central role in the understanding of useful properties such as molecular magnetism or catalytic behavior, but is often far from straightforward. In this work we demonstrate that, at a moderate computational cost, density functional calculations can predict the correct ground spin state of Fe(II) and Fe(III) complexes and can then be used to determine the H-1 NMR spectra of all spin states. Since the spectral features are remarkably different according to the spin state, calculated H-1 NMR resonances can be used to infer the correct spin state, along with supporting the structure elucidation of numerous paramagnetic complexes.

First author: Okuda, Yasuhiro, The origin of exo-selectivity in methyl cyanoformate addition onto the C=C bond of norbornene in Pd-catalyzed cyanoesterification, DALTON TRANSACTIONS, 43, 9537, (2014)
Abstract: A computational investigation has been carried out to elucidate the origin of the exclusive exo-selectivity in the Pd-catalyzed cyanoesterification of strained cyclic olefins, norbornene and norbornadiene. A hybrid density functional was selected for the level of theory with a triple-zeta quality basis set, which was proposed in an earlier study to provide an experimentally sound ground state electronic structure description for palladium(II) and palladium(IV) complexes from multi-edge X-ray absorption spectroscopic measurements. Given that the product of oxidative addition can be isolated, we focused on the olefin coordination as the earliest possible origin of exo-selectivity. The calculated geometric structure for the trans-Pd(CN)(COOR)(PPh3)(2) complex at the BHandHLYP/ def2TZVP/ PCM(toluene) level is in an excellent agreement with its experimental structure from crystallographic measurements. Upon dissociation of one of its phosphane ligands, the coordinatively unsaturated trans-isomer is only 17 kJ mol(-1) away from the isomerization transition state, leading to the 14-electron cis-isomers that are 17 to 37 kJ mol(-1) lower in energy than the trans-isomers. Regardless of the initial complex for olefin coordination, the exo-isomer for the norbornene complex is at least 8 kJ mol(-1) lower than the corresponding endo-isomer. The origin of this considerable difference in Gibbs free energy can be attributed to the remarkably different steric and agostic hydrogen interactions between the methylene and the ethylene bridges of the norbornene and the adjacent cis-ligands at the Pd-II center.

First author: Pandey, Krishna K., Assessment of density functionals and paucity of non-covalent interactions in aminoylyne complexes of molybdenum and tungsten [(eta(5)-C5H5)(CO)(2)M equivalent to EN(SiMe3)(R)] (E = Si, Ge, Sn, Pb): a dispersion-corrected DFT study, DALTON TRANSACTIONS, 43, 9955, (2014)
Abstract: Electronic, molecular structure and bonding energy analyses of the metal-aminosilylyne, -aminogermylyne, -aminostannylyne and -aminoplumbylyne complexes [(eta(5)-C5H5)(CO)(2)M equivalent to EN(SiMe3)(Ph)] (M = Mo, W) and [(eta(5)-C5H5)(CO)(2)Mo equivalent to GeN(SiMe3)(Mes)] have been investigated at DFT, DFT-D3 and DFT-D3(BJ) levels using BP86, PBE, PW91, RPBE, TPSS and M06-L functionals. The performance of metaGGA functionals for the geometries of aminoylyne complexes is better than GGA functionals. Significant dispersion interactions between O center dot center dot center dot H, E center dot center dot center dot C(O) and E center dot center dot center dot H pairs appeared in the dispersion-corrected geometries. The non-covalent distances of these interactions follow the order DFT > DFT-D3(BJ) > DFT-D3. The values of Nalewajski-Mrozek bond order (1.22-1.52) and Pauling bond order (2.23-2.59) of the optimized structures at BP86/TZ2P indicate the presence of multiple bonds between metal and E atoms. The overall electronic charges transfer from transition-metal fragments to ligands. The topological analysis based on QTAIM has been performed to determine the analogy of non-covalent interactions. The strength of M equivalent to EN(SiMe3)(R) bonds has been evaluated by energy decomposition analysis. The electrostatic interactions are almost equal to orbital interactions. The M <- E sigma-donation is smaller than the M -> E pi-back donation. Upon going from E = Si to E = Pb, the M-E bond orders decrease as Si > Ge > Sn > Pb, consistent with the observed geometry trends. The M-E uncorrected bond dissociation energies vary with the density functionals as RPBE < BP86 < PBE < TPSS < PW91. The largest DFT-D3 dispersion corrections to the BDEs correspond to the BP86 functional, ranging between 5.6-8.1 kcal mol(-1), which are smaller than the DFT-D3(BJ) dispersion corrections (10.1-12.0 kcal mol(-1)). The aryl substituents on nitrogen have an insignificant effect on M-E-N bending. The bending of the M-E-N bond angle has been discussed in terms of Jahn-Teller distortion. The larger noncovalent interaction and smaller absolute values of.E (HOMO-LUMO) with the M06-L functional are responsible for lowering the M-E-N bond angle.

First author: Cimpoesu, Fanica, The theoretical account of the ligand field bonding regime and magnetic anisotropy in the DySc2N@C-80 single ion magnet endohedral fullerene, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 11337, (2014)
Abstract: Considering the DySc2N@C-80 system as a prototype for Single Ion Magnets (SIMs) based on endohedral fullerenes, we present methodological advances and state-of-the art computations analysing the electronic structure and its relationship with the magnetic properties due to the Dy(III) ion. The results of the quantum chemical calculations are quantitatively decrypted in the framework of ligand field (LF) theory, extracting the full parametric sets and interpreting in heuristic key the outcome. An important result is the characterization of the magnetic anisotropy in the ground and excited states, drawing the polar maps of the state-specific magnetization functions that offer a clear visual image of the easy axes and account for the pattern of response to perturbations by the magnetic field applied from different space directions. The state-specific magnetization functions are derivatives with respect to the magnetic field, taken for a given eigenvalue of the computed spectrum. The methodology is based on the exploitation of the data from the black box of the ab initio spin-orbit (SO) calculations. The ground state is characterized by the Jz = +/- 15/2 quantum numbers with easy axis along the Dy-N bond. The implemented dependence on the magnetic field allowed the first-principles simulation of the magnetic properties. The computational approach to the properties of endohedral fullerenes is an important goal, helping to complement the scarcity of the experimental data on such systems, determined by the limited amount of samples.

First author: Ramanantoanina, Harry, The angular overlap model extended for two-open-shell f and d electrons,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 12282, (2014)
Abstract: We discuss the applicability of the Angular Overlap Model (AOM) to evaluate the electronic structure of lanthanide compounds, which are currently the subject of incredible interest in the field of luminescent materials. The functioning of phosphors is well established by the f-dtransitions, which requires the investigation of both the ground 4fn and excited 4f(n-1)5d(1) electron configurations of the lanthanides. The computational approach to the problem is based on the effective Hamiltonian adjusted from ligand field theory, but not restricted to it. The AOM parameterization implies the chemical bonding concept. Focusing our interest on this interaction, we take the advantages offered by modern computational tools to extract AOM parameters, which ensure the transparency of the theoretical determination and convey chemical intuitiveness of the non-empirical results. The given model contributes to the understanding of lanthanides in modern phosphors with high or low site symmetry and presents a non-empirical approach using a less sophisticated computational procedure for the rather complex problem of the ligand field of both 4f and 5d open shells.

First author: de Gier, Hilde D., Non-innocent side-chains with dipole moments in organic solar cells improve charge separation, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 12454, (2014)
Abstract: Providing sustainable energy is one of the biggest challenges nowadays. An attractive answer is the use of organic solar cells to capture solar energy. Recently a promising route to increase their efficiency has been suggested: developing new organic materials with a high dielectric constant. This solution focuses on lowering the coulomb attraction between electrons and holes, thereby increasing the yield of free charges. In here, we demonstrate from a theoretical point of view that incorporation of dipole moments in organic materials indeed lowers the coulomb attraction. A combination of molecular dynamics simulations for modelling the blend and ab initio quantum chemical calculations to study specific regions was performed. This approach gives predictive insight in the suitability of new materials for application in organic solar cells. In addition to all requirements that make conjugated polymers suitable for application in organic solar cells, this study demonstrates the importance of large dipole moments in polymer side-chains.

First author: Vijayakumar, M., Molecular structure and stability of dissolved lithium polysulfide species, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 10923, (2014)
Abstract: The ability to predict the solubility and stability of lithium polysulfide is vital in realizing longer lasting lithium-sulfur batteries. Herein we report combined experimental and computational analyses to understand the dissolution mechanism of lithium polysulfide species in an aprotic solvent medium. Multi-uclear NMR, variable temperature ESR and sulfur K-edge XAS analyses reveal that the lithium exchange between polysulfide species and solvent molecules constitutes the first step in the dissolution process. Lithium exchange leads to de-lithiated polysulfide ions (S-n(2-)) which subsequently form highly reactive free radicals through dissociation reaction (S-n(2-) -> 2S(n/2)(center dot-)). The energy required for the dissociation and possible dimer formation reactions of the polysulfide species is analyzed using density functional theory (DFT) based calculations. Based on these findings, we discuss approaches to optimize the electrolyte in order to control the polysulfide solubility.

First author: Perras, Frederic A., Boron-boron J coupling constants are unique probes of electronic structure: a solid-state NMR and molecular orbital study, CHEMICAL SCIENCE, 5, 2428, (2014)
Abstract: Diboron compounds are a part of a relatively unexplored, yet immensely useful, class of compounds. Their main use is for beta-boration reactions where a boron center is rendered nucleophilic with the use of a metal catalyst or a Lewis base (alkoxide, amine, or NHC) to form a sp(2)-sp(3) diboron compound. The reactivity of these reagents is largely dictated by the nature of the B-B bond (strength and polarity); however, no experimental methods have been used to directly probe both of these quantities. We demonstrate that unprecedented experimental information regarding the B-B bond may be obtained using B-11 solid-state NMR spectroscopy. For example, the B-11 quadrupolar coupling constants can be understood on the basis of the polarization of the B-B bond. B-11 double-quantum-filtered (DQF) J-resolved NMR spectroscopy was applied to easily and accurately measure J(B-11, B-11) coupling constants with high precision. These are shown to be well correlated with the orbital energy of the B-B s-bonding natural bond orbital as well as the hybridisation states of the boron atoms in the bond. An increase in the p character of the bond by electron-donating ligands or via the formation of a sp(2)-sp(3) diboron compound weakens the bond, increases the bond length, and decreases the J(B-11,B-11) coupling constants. These experiments provide a detailed experimental characterization of the B-B bond and may be useful in understanding the reactivity of diboron compounds and in designing new systems. The potential applicability of B-11 DQF Jresolved NMR spectroscopy towards analyzing complex mixtures of diboron compounds and towards measuring B-11 J coupling across multiple intervening bonds is also investigated and shows much promise.

First author: Gendron, David, Synthesis and properties of pyrrolo[3,2-b]pyrrole-1,4-diones (isoDPP) derivatives,JOURNAL OF MATERIALS CHEMISTRY C, 2, 4276, (2014)
Abstract: The synthesis of three pyrrolo[3,2-b] pyrrole-1,4-dione (isoDPP) derivatives is described, namely 1,3,4,6-tetraphenylpyrrolo[3,2-b] pyrrole-2,5(1H, 4H)-dione 2, 1,4-diphenyl-3,6-di(thiophen-2-yl) pyrrolo[3,2-b]-pyrrole-2,5(1H, 4H)-dione 3, and 1,4-bis(4-(hexyloxy) phenyl)-3,6-di(thiophen-2-yl) pyrrolo[3,2-b] pyrrole-2,5(1H, 4H)-dione 7 in which the molecular structures differ in the aromatic ring (phenyl or thiophene) attached to the nitrogen atom. Thin films of 2, 3, and 7 could be formed by evaporation under vacuum. In the case of 2 and 3 GIWAXS measurements showed that the film structural ordering was similar to that measured in single crystals. In contrast GIWAXS showed that 7 had features associated with liquid crystalline materials. Time dependent density functional theory (TDDFT) calculations predicted that the transition between the lowest energy singlet excitation (S-1) and the ground state (S-0) would be optically forbidden due to the centrosymmetric geometries of compounds. Photophysical measurements showed that the compounds were weakly luminescent, with low radiative rates in solution of order 10(6) s(-1), which are consistent with the TDDFT predictions. Furthermore, photoinduced absorption (PIA) spectroscopy showed that there is a long-lived low energy state, which has been assigned as a triplet and provides a further non-radiative decay pathway for the excited state.

First author: Ghisolfi, Alessio, A comparative synthetic, magnetic and theoretical study of functional M4Cl4 cubane-type Co(II) and Ni(II) complexes, DALTON TRANSACTIONS, 43, 7847, (2014)
Abstract: We describe the synthesis, structures, and magnetochemistry of new M4Cl4 cubane-type cobalt( II) and nickel(II) complexes with the formula [M(mu(3)-Cl)Cl(HL center dot S)](4) (1: M = Co; 2: M = Ni), where HL center dot S represents a pyridyl-alcohol-type ligand with a thioether functional group, introduced to allow subsequent binding to Au surfaces. Dc and ac magnetic susceptibility data of 1 and 2 were modeled with a full spin Hamiltonian implemented in the computational framework CONDON 2.0. Although both coordination clusters 1 and 2 are isostructural, with each of their transition metal ions in a pseudo-octahedral coordination environment of four Cl atoms and N,O-donor atoms of one chelating HL center dot S ligand, the substantially different ligand field effects of Co(II) and Ni(II) results in stark differences in their magnetism. In contrast to compound 1 which exhibits a dominant antiferromagnetic intramolecular coupling (J = -0.14 cm(-1)), 2 is characterised by a ferromagnetic coupling (J = +10.6 cm(-1)) and is considered to be a single-molecule magnet (SMM), a feature of special interest for future surface deposition studies. An analysis based on density functional theory (DFT) was performed to explore possible magnetostructural correlations in these compounds. Using a two-J model Hamiltonian, it revealed that compound 1 has four positive and two (small) negative J(Co)…(Co) isotropic interactions leading to a SHS = 6 ground state. Taking into account the magnetic anisotropy, one would recover a MS = 0 ground state since D > 0 from computations. In 2, all the J constants are positive and, in this framework, the zero-field splitting energy characterising the axial anisotropy was estimated to be negative (D = -0.44 cm(-1)). The computational results are consistent with compound 2 being an SMM.

First author: Pereira Gomes, Andre Severo, Electronic structure investigation of the evanescent AtO+ ion, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 9238, (2014)
Abstract: The electronic structure of the XO and XO+ (X = I, At) species, as well that of a AtO+- H2O complex have been investigated using relativistic wave-function theory and density functional theory (DFT)-based approximations (DFAs). The n-electron valence state perturbation method with the perturbative inclusion of spin-orbit coupling including spin-orbit polarization effects (SO-NEVPT2) was shown to yield transition energies within 0.1 eV of the reference four-component intermediate Fock-space coupled cluster (DC-IHFSCCSD) method at a significantly lower computational cost and can therefore be used as a benchmark to more approximate approaches in the case of larger molecular systems. These wavefunction calculations indicate that the ground state for the AtO+ and AtO+- H2O systems is the Omega = 0(+) component of the (3)Sigma(-) LS state, which is quite well separated (by similar or equal to 0.5 eV) from the Omega = 1 components of the same state and from the Omega = 2 state related to the (1)Delta LS state (by similar or equal to 1 eV). Time-dependent DFT calculations, on the other hand, place the Omega = 1 below the Omega = 0(+) component with the spurious stabilization of the former increasing as one increases the amount of Hartree-Fock exchange in the DFAs, while those employing the Tamm-Dancoff approximation and DFAs not including Hartree-Fock exchange yield transition energies in good agreement with SO-NEVPT2 or DC-IHFSCCSD for the lower-lying states. These results indicate the ingredients necessary for devising a DFA-based computational protocol applicable to the study of the properties of large AtO+ clusters so that it may (at least) qualitatively reproduce reliable reference (SO-NEVPT2) calculations.

First author: Majid, Abdul, DFT study of electronic and structural properties of Sm:GaN, COMPUTATIONAL MATERIALS SCIENCE, 88, 71, (2014)
Abstract: First principle calculations of Sm:GaN carried out using GGA-PBE, mBJ and GGA + U are presented to demonstrate the structural, electronic and magnetic properties of the system. The effects of Hubbard correction (i.e. U) on band structure and location of Sm 4f levels are discussed in detail. The application of U indicated a considerable splitting of occupied and unoccupied 4f band unlike that of GGA and mBJ. The introduction of Sm related gap states caused narrowing of band gap which is expected to facilitate the tuning of optical transitions. The results also indicated the production of intermediate bands in the band gap of host material which points to possible use of this material in photovoltaic cell generation. The observed spin polarization of 4f and 5d and 6s states of Sm shows possibility of ferromagnetic exchange interactions in the material for spintronic devices.

First author: Kuo, Chi-Hsien, Substituent effect on the crystal packing and electronic coupling of tetrabenzocoronenes: a structure-property correlation, JOURNAL OF MATERIALS CHEMISTRY C, 2, 3928, (2014)
Abstract: Tetrabenzo[a,d,j,m] coronene (TBC) is a contorted polyaromatic molecule which shows near co-facial pi-pi stacking in the crystalline state and the high electronic coupling resulting from the packing renders it a potential candidate as a transistor material. Substitution at the periphery perturbs the packing due to steric as well as dipolar interactions and thus changes the electronic coupling between neighbouring molecules. In the light of the high sensitivity of charge mobility toward electronic coupling, a new series of TBC derivatives with substituents at 1-, 2-, 3-, 6-, 7-, 8- positions were designed, synthesized, and characterized. Needle-like single crystals were prepared using the physical vapor transport (PVT) method for these unsymmetrically substituted derivatives and were used for crystal structure analyses as well as the single crystal field-effect transistor (SCFET) device fabrication. The derivatives with fluoro-containing substituents exhibit anti-parallel cofacial or slightly shifted pi-pi stacking, whereas those with bulky alkyl substituents show skewed and more significantly shifted pi-pi stacking. A systematic comparison of the crystal packings and the calculated electronic couplings/charge mobilities with the measured SCFET mobilities shows a rough correlation and sheds light on the origin of the large hole-mobility of the SCFET with hexa-fluorinated TBC as the channel material.

First author: Pascual-Borras, Magda, O-17 NMR chemical shifts in oxometalates: from the simplest monometallic species to mixed-metal polyoxometalates, CHEMICAL SCIENCE, 5, 2031, (2014)
Abstract: We report a theoretical analysis on O-17 NMR chemical shifts for a family of prototypical polyoxometalate anions. The huge diversity of structures and compositions in this family of oxometalates provides a unique resource for evaluating the influence of the metal type and connectivity over the resonance of O-17 nuclei. For a set of 75 signals, we show that DFT calculations performed with the GGA-type OPBE functional, including spin-orbit and scaling corrections, provide a mean absolute error < 30 ppm, a small value considering that the range of delta(O-17) values in these systems is similar to 1200 ppm. For terminal M=O oxygens, the chemical shifts primarily depend on the energy gap between pi(*)(M-O) and sigma(M-O) orbitals. When M is in its highest oxidation state, the energy of pi(*)(M-O) increases as we replace M going to the left and down in the periodic table. Consequently, we must expect large energy gaps and upfield shifts for O atoms linked to more electropositive ions. Although there is not a direct relationship between delta(O-17) and the negative charge of the oxygen, it is not entirely wrong to correlate atomic charge and chemical shift because the ionicity of the M-O bond, the orbital energy gap and the charge density of oxygen are related. The O-17 NMR chemical shifts move upfield with an increasing number of bound metal ions because of the larger energy gap in the involved orbitals. Finally, we explored the effect of protonation on delta(O-17) in oxometalates and demonstrated that O-17 NMR can be a powerful tool to identify the site(s) of protonation at low pH.

First author: Mottet, Matthieu, Quantum entanglement in carbon-carbon, carbon-phosphorus and silicon-silicon bonds,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 8872, (2014)
Abstract: The chemical bond is an important local concept to understand chemical compounds and processes. Unfortunately, like most local concepts, the chemical bond and the bond order do not correspond to any physical observable and thus cannot be determined as an expectation value of a quantum chemical operator. We recently demonstrated [Boguslawski et al., J. Chem. Theory Comput., 2013, 9, 2959-2973] that one- and two-orbital-based entanglement measures can be applied to interpret electronic wave functions in terms of orbital correlation. Orbital entanglement emerged as a powerful tool to provide a qualitative understanding of bond-forming and bond-breaking processes, and allowed for an estimation of bond orders of simple diatomic molecules beyond the classical bonding models. In this article we demonstrate that the orbital entanglement analysis can be extended to polyatomic molecules to understand chemical bonding.

First author: Sanyal, Somananda, BN-decorated graphene nanoflakes with tunable opto-electronic and charge transport properties, JOURNAL OF MATERIALS CHEMISTRY C, 2, 2918, (2014)
Abstract: The electronic structures, optical and charge transport properties of various boron-nitrogen (BN) substituted hexagonal graphene nanoflakes (h-GNFs) are investigated with the aim of tailoring the intrinsic properties of pristine h-GNFs, using first-principles density functional theory. We consider coronene as the smallest h-GNF and compare the structure-property responses with its iso-electronic BN analogues. Three BN analogues of pristine coronene, namely mid-BN-coronene (middle hexagonal ring CC bonds are substituted by BN), peri-BN-coronene (all peripheral CC bonds are substituted by BN) and full-BN-coronene (all CC bonds are replaced by BN) are considered. The results show tunable optoelectronic properties depending on the BN concentrations and its position. The study also considers examining the effects of the BN concentration on the opto-electronic properties of larger sized h-GNFs. In addition, we find that the bulk electronic and charge transport (carriers mobilities) properties of different BN analogues of coronene strongly depend on the nature of BN substitution, with increasing electron mobility found with an increase in BN concentration. We provide microscopic understanding for the tunable properties by analyzing certain intrinsic quantities, such as the extent of orbital delocalization, electronic gap, electrostatic potential, reorganization energy, charge transfer integrals, density of states, etc. The study suggests that optoelectronic and charge transport properties can be tailored through appropriate tuning of the BN contents in h-GNFs, thereby paving the way for designing advanced optoelectronic devices.

First author: Heshmat, Mojgan, Solvent induced enhancement of enantiomeric excess: a case study of the Henry reaction with cinchona thiourea as the catalyst, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 7315, (2014)
Abstract: Enantiomeric excess (ee) in asymmetric catalysis may be strongly dependent on the solvent. The reaction product may range from an almost racemic mixture to an ee of over 90% for different solvents. We study this phenomenon for the C-C coupling reaction between nitromethane and benzaldehyde (the Henry reaction) with cinchona thiourea as the catalyst, where solvents that are strong Lewis bases induce a high ee. We show that the effect of the solvent does not consist of a change in the reaction mechanism. Instead, the solvation “prepares” the molecule, which is very flexible, in a specific conformation. The reaction barriers in this conformer are not lower than for other conformers, but are sufficiently differentiated between the enantiomers to give rise to a large ee. It is the strong Lewis basicity of the solvent that leads to the clear preference in solution for the “asymmetric” conformer. Although general rules or predictions for how solvent effects could be harnessed to produce a desired ee in general would be hard to formulate, this study does show that it is in this case (and presumably in many other cases as well) specific solute-solvent interactions rather than effects of the dielectric continuum of the solvent that are the root cause of the solvent effect. This is in agreement with experiment for the Henry reaction.

First author: Aguado-Ullate, Sonia, A theoretical study of the activity in Rh-catalysed hydroformylation: the origin of the enhanced activity of the pi-acceptor phosphinine ligand, CATALYSIS SCIENCE & TECHNOLOGY, 4, 979, (2014)
Abstract: The factors governing the activity in Rh-catalyzed hydroformylation were investigated using a set of computational tools. We performed DFT calculations on the phosphinine-modified Rh catalyst [HRh(CO)(3)(PC5H2R3)] and compared it to the phosphane-modified HRh(CO)(3)(PR3) and HRh(CO)(2)(PR3)(2) complexes. The pi-acceptor phosphinine ligand coordinates preferentially at the equatorial site of the pentacoordinated Rh complex with the heterocycle perpendicular to the equatorial plane, although the ligand freely rotates around the Rh-P bond. The overall energy barrier can be divided into the following contributions: alkene complex formation, alkene rotation and alkene insertion. In the absence of steric effects (model systems), the overall barrier correlates with the computed barrier for alkene rotation. This proves that pi-acceptor ligands reduce back-donation to the alkene, leading to a lower rotational barrier and, consequently, to a higher activity. The Rh-P donor-acceptor interactions were quantified using a modified version of energy decomposition analysis (EDA). In Rh-phosphinine systems, the efficient directionality of the pi-back-donation, rather than the overall acceptor ability, is responsible for the high catalytic activity. Introducing steric effects increases the energy required to coordinate the alkene, increasing the overall barrier. The factors governing the activity in Rh-monophosphane catalysts seem to be related to those derived for Rh-diphosphane during the development of a QSAR model (Catal. Sci. Technol. 2012, 2, 1694). To investigate whether the findings for mono- can be extrapolated to diphosphane ligands, we re-examined our previous QSAR model using the Topological Maximum Cross Correlation (TMACC) method based on easy-to-interpret 2D-descriptors. The TMACC descriptors highlight heteroatoms close to phosphorus as activity-increasing atoms, whereas highly substituted carbon atom groups are highlighted as activity-decreasing groups.

First author: Gruden-Pavlovic, Maja, Theoretical study of the magnetic anisotropy and magnetic tunnelling in mononuclear Ni(II) complexes with potential molecular magnet behavior, CHEMICAL SCIENCE, 5, 1453, (2014)
Abstract: Magnetic molecules that present a slow decay of their magnetization (molecular magnets) are very interesting both from a fundamental and applied points of view. While many approaches focus strongly on finding systems with strong magnetic anisotropy giving rise to large spin-reversal barriers, less is known on the behavior of magnetic tunnelling, which is also a fundamental component of molecular magnet behavior. In this work, we propose a model to describe both the spin-reversal barrier and magnetic tunnelling in Ni(II) trigonal bipyramidal complexes, which could be easily extended to other transitionmetal systems. Based on this model, we show the criteria that lead to the optimal complexes to find molecular magnet behavior. We test our proposal with multi-reference configuration-interaction (MRCI) and ligand-field-density-functional-theory (LF-DFT) first-principles calculations applied over several families of mononuclear Ni(II) complexes. As a salient result, we find that the complex [NiCl3(Hdabco)(2)](+) (dabco is 1,4-diazabicyclo[2.2.2]-octane) displays both a very large magnetic anisotropy energy, 524 cm(-1), and a small tunnelling splitting, 0.2 cm(-1), when compared to other systems containing the same metal. We expect molecular magnet behaviour to be observed when small magnetic fields are employed to disrupt tunnelling. These values are reached due to the choice of ligands that favor a complete destruction of the Jahn-Teller distortions through spin-orbit coupling and an unquenched orbital momentum.

First author: Cavigliasso, G., On the selective cleavage of nitrous oxide by metal-amide complexes, DALTON TRANSACTIONS, 43, 4631, (2014)
Abstract: Computational investigation of nitrous oxide cleavage by metal-amide systems has shown that a bimetallic mechanism is compatible with the remarkable experimental observation of selective N-N bond scission by a di-molybdenum system, and that the interplay between the bonding energetics of reactants and products can both provide an explanation for the observed cleavage selectivity and be utilized to modify and design chemical behaviour.

First author: Anak, Berkahem, Time-dependent density functional study of UV-visible absorption spectra of small noble metal clusters (Cu-n, Ag-n, Au-n, n=2-9, 20), RSC ADVANCES, 4, 13001, (2014)
Abstract: The absorption UV-visible spectra of noble metal clusters Cu-n, Ag-n, Au-n, n = 2-9 and 20 are investigated in the framework of the time-dependent density functional theory using the long-range corrected density functionals LC-M06L and CAM-B3LYP and high-quality Gaussian basis sets. Some calculations including the spin-orbit coupling are also presented. The contribution of the d electrons to the optical response was found to be lower than it was when a purely local exchange functional was used. Calculated spectra are compared with experimental ones for clusters embedded in a rare-gas matrix.

First author: Pandey, Krishna K., Insights into the nature of M E bonds in [(PMe3)(4)M E(Mes)](+) (M = Mo, W) and [(PMe3)(5)W E(Mes)](+): a dispersion-corrected DFT study, RSC ADVANCES, 4, 13034, (2014)
Abstract: Structures and bonding energy analysis of terminal cationic metal-ylidyne complexes [(PMe3)(4)M E(Mes)](+) (M = Mo, W) and [(PMe3)(5)W E(Mes)](+) (E = Si, Ge, Sn, Pb) were investigated by DFT, DFT-D3 and DFT-D3(BJ) methods using BP86, PBE and PW91 functionals. The Nalewajski-Mrozek (N-M) bond orders and Pauling bond orders show that the M-E bonds in the studied cationic complexes are essentially M E triple bonds. Atomic orbital populations reveal that the out-of-plane pi-bonding in all complexes is stronger than the in-plane pi-bonding. The bonding of the M-E sigma-bond is quite strong, as is the total M-E pi-bond strength, and increases upon going from molybdenum to tungsten. The contribution of the orbital interactions Delta E-orb is significantly larger (58-63%) than the electrostatic contributions Delta E-elstat in all the complexes studied. The absolute values of the bond dissociation energies decrease in the order Si > Ge > Sn > Pb. The D3-dispersion energies with zero-damping are in the range 13.0-17.9 kcal mol(-1) (BP86), 7.1-10.6 kcal mol(-1) (PBE) and 7.7-10.6 kcal mol(-1) (PW91), which are smaller than the corresponding DFT-D3(BJ) energies of 21.0-24.6 kcal mol(-1) (BP86), 9.9-13.6 kcal mol(-1) (PBE) and 10.6-13.6 kcal mol(-1) (PW91). The percentage dispersion-corrections to the bond dissociation energies increase as E becomes heavier. The effects of relativistic core contractions in heavier nuclei, i.e. tungsten and lead, are also evaluated.

First author: Musgrave, Rebecca A., Iron(II) complexes of ditopic carbanionic carbenes, DALTON TRANSACTIONS, 43, 4335, (2014)
Abstract: Reaction of dimesityliron(II) (Fe-2(mes)(4)) with the N-heterocyclic carbenes 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) and 1,3-bis(2,6-dimethylphenyl)hexahydropyrimidin-2-ylidene (6-Xyl) afforded the novel trigonal planar complexes [Fe(IPr)(mes)(2)] (1) and [Fe(6-Xyl)(mes)(2)] (2), respectively. Both species were structurally characterized by single crystal X-ray diffraction and display structures and magnetic responses consistent with a quintet ground state (S = 2). Reaction of 1 with KC8 in THF afforded K+ salts of the anionic complex [{:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}(2)Fe(mes)](-) (3) and the homoleptic organometallic anion [Fe(mes)(3)](-) (4). By contrast, reduction of 2 resulted in extensive decomposition and intractable product mixtures. Complex 3 is coordinated by two ditopic carbanionic carbenes via the C4/C5 position while the C2 position retains unquenched carbenic character and remains vacant for further coordination. This was corroborated by reacting solutions of 3 with one and two equivalents of triethylaluminium (AlEt3) which resulted in the formation of [{Et3Al:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}{:C[N(2,6-(Pr2C6H3)-Pr-i)](2)-( CH)C}Fe(mes)](-) (5) and [{Et3Al:C[N(2,6-(Pr2C6H3)-Pr-i)](2)(CH)C}(2)Fe(mes)](-) (6), respectively. Both of these species were structurally characterized as [K(2,2,2-crypt)](+) salts.

First author: Robinson, Sarah, Alkali metal derivatives of an ortho-phenylene diamine, DALTON TRANSACTIONS, 43, 4351, (2014)
Abstract: Treatment of the ortho-phenylene diamine C6H4-1,2-{N(H)Tripp}(2) (1, PDAH(2), Tripp = 2,4,6-triisopropylphenyl) with two equivalents of MR (M = Li, R = Bu-n; M = Na or K, R = CH2C6H5) afforded the dimetallated alkali metal ortho-phenylene diamide dianion complexes [(PDALi(2))(THF)(3)] (2), [{(PDANa(2))(THF)(2)}(2)] (3), and [{(PDAK(2))(THF)(3)}(2)] (4). In contrast, treatment of 2 with two equivalents of rubidium or cesium 2-ethylhexoxide, or treatment of 1 with two equivalents of MR (M = Rb or Cs, R = CH2C6H5) did not afford the anticipated dialkali metal ortho-phenylene diamide dianion derivatives and instead formally afforded the monometallic ortho-diiminosemiquinonate radical anion species [PDAM] (M = Rb, 5; M = Cs, 6). The structure of 2 is monomeric with one lithium coordinated to the two nitrogen centres and the other lithium eta(4)-coordinated to the diazabutadiene portion of the PDA scaffold. Similar structural cores are observed for 3 and 4, except that the larger sodium and potassium ions give dimeric structures linked by multi-hapto interactions from the PDA backbone phenyl ring to an alkali metal centre. Complex 5 was not characterised in the solid state, but the structure of 6 reveals coordination of cesium ions to both PDA amide centres and multi-hapto interactions to a PDA backbone phenyl ring in the next unit to generate a one-dimensional polymer. Complexes 2-6 have been variously characterised by X-ray crystallography, multi-nuclear NMR, FTIR, and EPR spectroscopies, and CHN microanalyses.

First author: Liu, Yan-Chun, Can a linear metal-metal bonded array of tetravanadium be stabilized between two dicyclopenta[a,e]pentalene ligands? A theoretical investigation, NEW JOURNAL OF CHEMISTRY, 38, 1092, (2014)
Abstract: The 14-pi cross-linked annulene dicyclopenta[a,e] pentalene (dcpp) is suggested for the first time to function as a sandwich ligand. According to density functional theory (DFT) calculations, upon being sandwiched between two dcpp ligands, the tetravanadium chain, without the support of auxiliary ligands, has two unpaired electrons and has a tendency for deformation to gain extra stability through multicenter bondings in the ground state. The one-electron ligand chlorine can lead to two types of structures, one with two chlorine atoms connecting to the two central vanadium atoms and the other one with two chlorine atoms connecting to the two terminal vanadium atoms, both of which are energetically more favorable in the triplet state. In the carbonyl end-capping complex, the tetravanadium is stable as a linear metal-metal bonded array with alternating single and double bonds and all electrons paired for bonding, although a triplet state conformer exists with two extra carbonyl ligands bound to the two central vanadium atoms which is more energy favorable by 15.1 kcal mol(-1). Bonding features within the tetravanadium moiety were obtained based on electron density analyses. We hope these discussions are helpful for the design of new extended metal atom chain (EMAC) systems and for the pursuit of effective catalysts based on the dcpp sandwich complexes.

First author: Ganesan, Aravindhan, From building blocks of proteins to drugs: a quantum chemical study on structure-property relationships of phenylalanine, tyrosine and dopa, RSC ADVANCES, 4, 8617, (2014)
Abstract: Density functional theory and ab initio methods have been employed to address the impacts of hydroxyl (OH) group substitutions on the physico-chemical properties of levodopa (or (L)-dopa) against the natural amino acids, phenylalanine and tyrosine. (L)-dopa, which is an important therapeutic drug for Parkinson’s disease, shares structural homology with the amino acids, whose structures differ only by OH substitutions in their phenyl side chains. It is revealed that the backbone geometries of the aromatic molecules do not show apparent OH-dependent differences; however, their other molecular-level properties, such as molecular dipole moment, electronic properties and aromaticity, change significantly. The core binding energy spectra indicate that the atom sites that undergo modifications exhibit large energy shifts, so as to accommodate the changes in the intra-molecular chemical environment of the molecules. The binding energies of the modified C 1s sites in the molecules shift as much as 1.8 eV, whereas the electronic changes in their O 1s spectra happen in the higher energy region (ca. 536 eV). The valence spectra provide enhanced insights into the reactivity and chemical properties of the aromatic molecules. The impacts of OH moieties on the valence spectra are predominantly focussed in the energy band <16 eV, where the frontier molecular orbitals display much reorganization and energy shifts from the amino acids to (L)-dopa. Of the three molecules, (L)-dopa also has the least HOMO-LUMO energy gap, which can readily explain its proactivity as a drug compound. Furthermore, the nuclear independent chemical shift calculations suggest that (L)-dopa also has more aromaticity features than those of the amino acids. The OH groups, therefore, play a more prominent role in shaping the physicochemical properties of (L)-dopa, which significantly improve its drug potency.

First author: Senthilnathan, Dhurairajan, The metal delivery mechanism of transferrin and the role of bent metallocene metals towards anticancer activity – a theoretical exploration, RSC ADVANCES, 4, 9556, (2014)
Abstract: The metal delivery mechanism of the metalloenzyme transferrin and the antitumor active interaction of the metal ions, generated by the rapid hydrolysis of bent metallocene metals (Cp2MCl2; M = Ti, V, Nb, Mo), with the transferrin enzyme have been investigated. The initial and rate determining steps of the metal delivery mechanism have been identified. Comparisons are drawn between the antitumor action of various external metal ions and the role of the weak interactions that decide the site-specific decarboxylation reaction of transferrin have been investigated. Computational results reveal that the metal delivery mechanism starts by the site-specific concerted decarboxylation of transferrin leading to the thermodynamically unstable metal-oxo product and this unstable metal-oxo product delivers the metal ion to the nucleic acid via ATP. The computed reaction barriers for the decarboxylation step nicely correlate with the antitumor activity of the bent metallocenes.

First author: Duan, Haohong, Ultrathin rhodium nanosheets, NATURE COMMUNICATIONS, 5, 9556, (2014)
Abstract: Despite significant advances in the fabrication and applications of graphene-like materials, it remains a challenge to prepare single-layered metallic materials, which have great potential applications in physics, chemistry and material science. Here we report the fabrication of poly(vinylpyrrolidone)-supported single-layered rhodium nanosheets using a facile solvothermal method. Atomic force microscope shows that the thickness of a rhodium nanosheet is <4 angstrom. Electron diffraction and X-ray absorption spectroscopy measurements suggest that the rhodium nanosheets are composed of planar single-atom-layered sheets of rhodium. Density functional theory studies reveal that the single-layered Rh nanosheet involves a delta-bonding framework, which stabilizes the single-layered structure together with the poly(vinylpyrrolidone) ligands. The poly(vinylpyrrolidone)-supported single-layered rhodium nanosheet represents a class of metallic two-dimensional structures that might inspire further fundamental advances in physics, chemistry and material science.

First author: Martelli, Fausto, Hydration properties of lanthanoid(III) carbonate complexes in liquid water determined by polarizable molecular dynamics simulations, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 3693, (2014)
Abstract: In this work we have studied the structure and dynamics of complexes formed by three and four carbonates and a central lanthanoid(III) ion in liquid water by means of polarizable molecular dynamics simulations. With this aim we have developed a force field employing an extrapolation procedure that was previously developed for lanthanoid(III) aqua ions and then we have validated it against DFT-based data. In this way we were able to shed light on properties of the whole series, finding some similarities and differences across the series, and to help in interpreting experiments on those systems. We found that the bi-dentate tri-carbonate complexes are the most stable for all the atoms, but a variation of the number of water molecules in the first ion shell, and the associated exchange dynamics, is observed from lighter to heavier elements. On the other hand, for four-carbonate systems only one water molecule is observed in the first shell, with 10-20% probability, for La(III) and Ce(III), while for the rest of the series it seems impossible for a water molecule to enter the first ion shell in the presence of such an excess of carbonate ligands. Finally, the good performance of our extrapolation procedure, based on ionic radii, makes us confident in extending such approaches to study the structure and dynamics of other systems in solution containing Ln(III) and An( III) ions. This parametrization method results particularly useful since it does not need expensive quantum chemistry calculations for all the atoms in the series.

First author: Vijayakumar, M., Elucidating graphene-ionic liquid interfacial region: A combined experimental and computational study, NANO ENERGY, 3, 152, (2014)
Abstract: Graphene and ionic liquids are promising candidates for electrode materials and electrolytes, respectively, for modern energy storage devices such as supercapacitors. Understanding the interactions at the interfacial region between these materials is crucial for optimizing the overall performance and efficiency of supercapacitors. The interfacial region between graphene and an imidazolium-based ionic liquid is analyzed in a combined experimental and computational study. This dual approach reveals that the imidazolium-based cations mostly orient themselves parallel to the graphene surface due to pi-pi stacking interaction and form a primary interfacial layer, which is subsequently capped by a layer of anions from the ionic liquid. However, it also becomes apparent that the molecular interplay at the interfacial region is highly influenced by functional group defects on the graphene surface, in particular by hydroxyl groups.

First author: Qiao, Yan, Theoretical investigations toward the tandem reactions of N-aziridinyl imine compounds forming triquinanes via trimethylenemethane diyls: mechanisms and stereoselectivity, ORGANIC & BIOMOLECULAR CHEMISTRY, 12, 1220, (2014)
Abstract: In this paper, we have investigated the tandem reaction mechanism for the N-aziridinyl imine compounds forming triquinanes via trimethylenemethane (TMM) diyls in detail. Based on the calculated results, the reaction is initiated by the cleavage of the N-aziridinyl in the substrate, followed by an intramolecular 1,3-dipolar (3 + 2) cycloaddition preferentially leading to a linearly-fused tetrahydrocyclopentapyrazole intermediate. Next, the intermediate loses N-2 to form the singlet TMM diyl M3S, which can then undergo another concerted (3 + 2) cycloaddition to generate the linearly-fused cis-trans or cis-syn triquinane products. In addition, M3S can also undergo intersystem crossing to the triplet TMM diyl M3T, and the six possible reaction pathways associated with M3T have also been identified. The calculated results reveal that the cis-trans fused pathway associated with M3S is energetically preferred with the highest free energy barrier of 25.0 kcal mol(-1). In comparison, the cyclization of M3T requires much higher activation free energies (Delta G(not equal) = 34.4-57.8 kcal mol(-1)). At the experimental temperature 110 degrees C, only the linearly-fused cis-trans and cis-syn pathways associated with M3T (Delta G(not equal) = 34.4 and 35.5 kcal mol(-1) respectively) are possible. The calculated results also indicate that for both M3S and M3T, the linearly-fused cis-trans triquinane should be the main product, which is consistent with the experimental observation. At last, conformational and NBO analyses on key transition states identified the cis-trans stereocontrol factors. Further calculations indicate that the methyl substituent on the allene group of the reactant substrate improves the stereoselectivity of the reaction but does not affect the rate-determining step.

First author: Lobello, Maria Grazia, Engineering of Ru(II) dyes for interfacial and light-harvesting optimization, DALTON TRANSACTIONS, 43, 2726, (2014)
Abstract: A new Ru(II) dye, Ru(L1)(L2) (NCS)(2), L1 = (4-(5-hexylthiophen-2-yl)-4′(4-carboxyl-phenyl 2,2′-bipyridine) and L2 = (4-4′-dicarboxy-2,2′- bipyridine), labelled MC112, based on a dissymmetric bipyridine ligand for improved interfacial and optical properties, was synthesized and used in DSCs, yielding photovoltaic efficiencies of 7.6% under standard AM 1.5 sunlight and an excellent device stability. Increased light harvesting and IPCE maximum were observed with MC112 compared to the prototypical homoleptic N719 dye, due to the functionalized bipyridyne ligand acting as an antenna. In addition, the mixed bipyridyne ligand allowed MC112 binding to TiO2 to occur via three anchoring carboxylic groups, thus exhibiting similar interfacial properties to those of the N719 dye. DFT/TDDFT calculations were performed on the new dye, both in solution and adsorbed on a TiO2 surface model, revealing that the peculiar photovoltaic properties of the MC112 dye are related to its anchoring mode. The new design rule thus allows us to engineer both light-harvesting and interfacial properties in the same dye.

First author: Friedman, Ran, Structural and computational insights into the versatility of cadmium binding to proteins,DALTON TRANSACTIONS, 43, 2878, (2014)
Abstract: Cadmium is a highly toxic group XII metal, similar to zinc and mercury. Unlike zinc, which is one of the most common metal cofactors in biology, cadmium is highly toxic. Many Zn2+-binding proteins can bind Cd2+-ions without significantly affecting their structures. Here, the protein data bank is analysed with regard to protein-cadmium interactions, which shows that cadmium can bind to a variety of ion binding sites in proteins. Statistical analysis of Cd2+-side chain interactions is compared with a similar analysis of other ions. This analysis reveals that with regard to amino acid side-chain preference, Cd2+ is more similar to Mn2+ than to Zn2+ or Hg2+. Finally, the interaction energies of three native metal binding proteins are calculated where Cd2+ binds instead of Zn2+, Ca2+ or Cu2+. The interaction energies are decomposed into individual components whose contributions are discussed.

First author: Azpiroz, Jon M., Benchmark Assessment of Density Functional Methods on Group II-VI MX (M = Zn, Cd; X = S, Se, Te) Quantum Dots, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 10, 76, (2014)
Abstract: In this work, we build a benchmark data set of geometrical parameters, vibrational normal modes, and low-lying excitation energies for MX quantum dots, with M = Cd, Zn, and X = S, Se, Te. The reference database has been constructed by ab initio resolution-of-identity second-order approximate coupled cluster RI-CC2/def2-TZVPP calculations on (MX)(6) model molecules in the wurtzite structure. We have tested 26 exchange-correlation density functionals, ranging from local generalized gradient approximation (GGA) and hybrid GGA to meta-GGA, meta-hybrid, and long-range corrected. The best overall functional is the hybrid PBE0 that outperforms all other functionals, especially for excited state energies, which are of particular relevance for the systems studied here. Among the DFT methodologies with no Hartree-Fock exchange, the M06-L is the best one. Local GGA functionals usually provide satisfactory results for geometrical structures and vibrational frequencies but perform rather poorly for excitation energies. Regarding the CdSe cluster, we also present a test of several basis sets that include relativistic effects via effective core potentials (ECPs) or via the ZORA approximation. The best basis sets in terms of computational efficiency and accuracy are the SBKJC and def2-SV(P). The LANL2DZ basis set, commonly employed nowadays on these types of nanoclusters, performs very disappointingly. Finally, we also provide some suggestions on how to perform calculations on larger systems keeping a balance between computational load and accuracy.

First author: Stenlid, Joakim Halldin, Searching for the thermodynamic limit – a DFT study of the step-wise water oxidation of the bipyramidal Cu-7 cluster, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 2452, (2014)
Abstract: Oxidative degradation of copper in aqueous environments is a major concern in areas such as catalysis, electronics and construction engineering. A particular challenge is to systematically investigate the details of this process for non-ideal copper surfaces and particles under the conditions found in most real applications. To this end, we have used hybrid density functional theory to study the oxidation of a Cu-7 cluster in water solution. Especially, the role of a large water coverage is explored. This has resulted in the conclusion that, under atmospheric H-2 pressures, the thermodynamically most favored state of degradation is achieved upon the generation of four H-2 molecules (i.e. Cu-7 + 8H(2)O -> Cu-7(OH)(8) + 4H(2)) in both condensed and gas phases. This state corresponds to an average oxidation state below Cu(I). The calculations suggest that the oxidation reaction is slow at ambient temperatures with the water dissociation as the rate-limiting step. Our findings are expected to have implication for, among other areas, the copper catalyzed water-gas shift reaction, and for the general understanding of copper corrosion in aqueous environments.

First author: Cao, Guo-Jin, Theoretical and experimental studies of the interactions between Au-2(-) and nucleobases,PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 2928, (2014)
Abstract: Combined anion photoelectron spectroscopy and relativistic quantum chemical studies are conducted on nucleobase-Au-2(-) cluster anions. The vertical detachment energies of uracil-Au-2(-) (UAu2-), thymineAu(2)(-) (TAu2-), cytosine-Au-2(-) (CAu2-), adenine-u(2)(-) (Au-2(-)), guanine-Au-2(-) (GAu(2)(-)) are determined to be 2.71 +/- 0.08 eV, 2.74 +/- 0.08 eV, 2.67 +/- 0.08 eV, 2.65 +/- 0.08 eV and 2.73 +/- 0.08 eV, respectively, based on the measured photoelectron spectra. Through computational geometry optimizations we have identified the lowest-energy structures of these nucleobase-Au(2)(-)cluster anions. The structures are further confirmed by comparison of theoretically calculated vertical and adiabatic electron detachment energies with experimental measurements. The results reveal that the Au-2(-) anion remains as an intact unit and interacts with the nucleobases through N-H center dot center dot center dot Au or C-H center dot center dot center dot Au nonconventional hydrogen bonds. The nucleobase-Au-2(-) cluster anions have relatively weak N-H center dot center dot center dot Au hydrogen bonds and strong C-H center dot center dot center dot Au hydrogen bonds compared to those of nucleobase-Au- anions.

First author: Chen, Xin, Electrocatalytic Dechlorination of Atrazine Using Binuclear Iron Phthalocyanine as Electrocatalysts, ELECTROCATALYSIS, 5, 68, (2014)
Abstract: The electrochemical reduction approach has been suggested as a promising method for detoxification of chlorine-containing aromatic hydrocarbons. In this study, the electrocatalytic dechlorination of atrazine was studied by using a non-noble catalyst, binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT). Both experimental and theoretical results indicate that dechlorination of atrazine occurs rapidly on bi-FePc/MWNT electrode. The reaction depends on the adsorption of the chlorinated organic compound on the electrode surface and the reaction rate with hydroxy. By liquid chromatography-tandem mass spectrometer technique, the dechlorination product of atrazine can be assigned to 2-hydroxy-4-ethylamino-6-isopropylamino-1,3,5-triazine, which could be disposed by more convenient and economic biodegradation method.

First author: Yurenko, Yevgen P., Exploring non-covalent interactions in guanine- and xanthine-based model DNA quadruplex structures: a comprehensive quantum chemical approach, PHYSICAL CHEMISTRY CHEMICAL PHYSICS,16, 2072, (2014)
Abstract: The study aimed to cast light on the structure and internal energetics of guanine-and xanthine-based model DNA quadruplexes and the physico-chemical nature of the non-covalent interactions involved. Several independent approaches were used for this purpose: DFT-D3 calculations, Quantum Theory of Atoms in Molecules, Natural Bond Orbital Analysis, Energy Decomposition Analysis, Compliance Constant Theory, and Non-Covalent Interaction Analysis. The results point to an excellent degree of structural and energetic compatibility between the two types of model quadruplexes. This fact stems from both the structural features (close values of van der Waals volumes, pore radii, geometrical parameters of the H-bonds) and the energetic characteristics (comparable values of the energies of formation). It was established that hydrogen bonding makes the greatest (similar to 50%) contribution to the internal stability of the DNA quadruplexes, whereas the aromatic base stacking and ion coordination terms are commensurable and account for the rest. Energy decomposition analysis performed for guanine (Gua) and xanthine (Xan) quartets B4 and higher-order structures consisting of two or three stacked quartets indicates that whereas Gua structures benefit from a high degree of H-bond cooperativity, Xan models are characterized by a more favorable and cooperative pi-pi stacking. The results of electron density topological analysis show that Na+/K+ ion coordination deeply affects the network of non-covalent interactions in Gua models due to the change in the twist angle between the stacked tetrads. For Xan models, ion coordination makes tetrads in stacks more planar without changing the twist angle. Therefore, the presence of the ion seems to be essential for the formation of planar stacks in Xan-based DNA quadruplexes. Detailed study of the nature of ion-base coordination suggests that this interaction has a partially covalent character and cannot be considered as purely electrostatic. Investigation of the H-bond and ion-base coordination strengths by various independent approaches agrees well with the results of QTAIM analysis.

First author: Loison, Claire, Multi-scale modeling of mycosubtilin lipopeptides at the air/water interface: structure and optical second harmonic generation, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 2136, (2014)
Abstract: Monolayers of the lipopeptide mycosubtilin are studied at the air/water interface. Their structure is investigated using molecular dynamics simulations. All-atom models suggest that the lipopeptide is flexible and aggregates at the interface. To achieve simulation times of several microseconds, a coarse-grained (CG) model based on the MARTINI force field was also used. These CG simulations describe the formation of half-micelles at the interface for surface densities up to 1 lipopeptide per nm(2). In these aggregates, the tyrosine side chain orientation is found to be constrained: on average, its main axis, as defined along the C-OH bond, aligns along the interface normal and points towards the air side. The origin of the optical second harmonic generation (SHG) from mycosubtilin monolayers at the air/water interface is also investigated. The molecular hyperpolarizability of the lipopeptide is obtained from quantum chemistry calculations. The tyrosine side chain contribution to the hyperpolarizability is found to be dominant. The orientation distribution of tyrosine, associated with a dominant hyperpolarizability component along the C-OH bond of the tyrosine, yields a ratio of the susceptibility elements X-ZZZ((2))/X-ZXX((2)) consistent with the experimental measurements recently reported by M. N. Nasir et al.

First author: Garner, Edward B., III, Electronic structure predictions of the properties of non-innocent P-ligands in group 6B transition metal complexes, DALTON TRANSACTIONS, 43, 2069, (2014)
Abstract: Neutral group 6B (Cr, Mo, W) pentacarbonyl complexes M(CO)(5)-L possessing various P-ligands such as phosphines, phosphaalkenes, and phospha-quinomethanes can form radical cations and anions under redox conditions. There is significant interest in whether the radical site is localized on the metal or on a “non-innocent” ligand. Density functional theory was used to predict whether the radicals of the complexes behave as metal or ligand-centered radicals and whether these compounds could form in solution or as an ion pair with various oxidizing and reducing agents. The quinone-like ligands are predicted to be ligand centered radicals when they are anions and metal centered radicals when they are cations. The predicted reaction energies for single electron transfer (SET) reactions involving the quinone like ligands are negative or near thermoneutral for both radicals in polar solutions and as solid state ion pairs. The energetics of the SET reactions can be controlled by the nature of L, the nature of the oxidizing/reducing agent, and the solvent polarity. Such complexes could be used as flexible catalysts for single electron transfer reactions.

First author: de Visser, Sam P., Computational modelling of oxygenation processes in enzymes and biomimetic model complexes, CHEMICAL COMMUNICATIONS, 50, 262, (2014)
Abstract: With computational resources becoming more efficient and more powerful and at the same time cheaper, computational methods have become more and more popular for studies on biochemical and biomimetic systems. Although large efforts from the scientific community have gone into exploring the possibilities of computational methods for studies on large biochemical systems, such studies are not without pitfalls and often cannot be routinely done but require expert execution. In this review we summarize and highlight advances in computational methodology and its application to enzymatic and biomimetic model complexes. In particular, we emphasize on topical and state-of-the-art methodologies that are able to either reproduce experimental findings, e.g., spectroscopic parameters and rate constants, accurately or make predictions of short-lived intermediates and fast reaction processes in nature. Moreover, we give examples of processes where certain computational methods dramatically fail.

First author: Luber, Sandra, EXAFS simulation refinement based on broken-symmetry DFT geometries for the Mn(IV)-Fe(III) center of class I RNR from Chlamydia trachomatis, DALTON TRANSACTIONS, 43, 576, (2014)
Abstract: Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides into deoxyribonucleotides necessary for DNA biosynthesis. Unlike the conventional class Ia RNRs which use a diiron cofactor in their subunit R2, the active site of the RNR-R2 from Chlamydia trachomatis (Ct) contains a Mn/Fe cofactor. The detailed structure of the Mn/Fe core has yet to be established. In this paper we evaluate six different structural models of the Ct RNR active site in the Mn(IV)/Fe(III) state by using Mossbauer parameter calculations and simulations of Mn/Fe extended X-ray absorption fine structure (EXAFS) spectroscopy, and we identify a structure similar to a previously proposed DFT-optimized model that shows quantitative agreement with both EXAFS and Mossbauer spectroscopic data.