2016 publications citing ADF

First author: Miller, DP, Electronic Structure of Iron Porphyrin Adsorbed to the Pt(111) Surface, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 29173, (2016)
Abstract: Systematic density functional theory calculations that treat the strong on-site 3d electron electron interactions on iron via a Hubbard U-eff = 3.0 eV and the van der Waals (vdW) interactions between the substrate and adsorbate within the vdW-DF framework are employed to study the adsorption of the iron porphyrin (FeP) molecule to the Pt(111) surface. The more accurate vdW-DF-optPBE and vdW-DF-optB88 functionals found the same binding site to be the most stable and yielded binding energies that were within similar to 20% of each other, whereas the binding energies computed with the vdW-DF-revPBE functional were substantially weaker. This work highlights the importance of vdW interactions for organometallic molecules chemisorbed to transition metal surfaces. The stability of the binding sites was found to depend upon the number of Fe-Pt and C-Pt bonds that were formed. Whereas in the gas phase the most stable spin state of FeP is the intermediate spin S = 1 state, the high spin S = 2 state is preferred for the FeP Pt(111) system on the binding sites considered herein. The spin switch results from the elongation of the Fe-N bonds that occur upon adsorption.

First author: Martins, LSC, All-electron Gaussian basis sets of double zeta quality for the actinides, JOURNAL OF CHEMICAL PHYSICS, 145, 29173, (2016)
Abstract: For the actinides, two segmented all-electron basis sets of valence double zeta quality plus polarization functions (DZP) are developed. One of them must be used along with the non-relativistic Hamiltonian, whereas the other with the Douglas-Kroll-Hess (DKH) one. Adding diffuse functions of s, p, d, f, and g symmetries to the non-relativistic and relativistic sets, augmented basis sets are developed. These functions are essential to describe correctly electrons far away from the nuclei. For some compounds, geometric parameters, atomic charges and valence orbital populations of the actinides, and bond dissociation energies are calculated using the Becke 3-parameter (exchange) and the Lee, Yang, and Parr (correlation) functional in conjunction with the DZP-DKH basis set. For Am and No, the static electric mean dipole polarizabilities are also reported. Comparison with benchmark theoretical and experimental values found in the literature is carried out. It is verified that the performances of the relativistic compact size basis sets generated in this work are regular, efficient, and reliable. They will be extremely helpful in molecular property calculations that need explicitly to consider the core electrons.

First author: Senn, F, Constricted variational density functional theory for spatially clearly separated charge-transfer excitations, JOURNAL OF CHEMICAL PHYSICS, 145, 29173, (2016)
Abstract: Constricted Variational Density Functional Theory (CV-DFT) is known to be one of the successful methods in predicting charge-transfer excitation energies. In this paper, we apply the CV-DFT method to the well-known model systems ethylene-tetrafluoroethylene (C2H4 x C2F4) and the zincbacteriochlorin-bacteriochlorin complex (ZnBC-BC). The analysis of the CV-DFT energies enables us to understand the – 1/R charge-transfer behaviour in CV-DFT for large separation distances R. With this we discuss the importance of orbital relaxations using the relaxed version of CV(infinity)-DFT, the R-CV(infinity)-DFT method. Possible effects of the optimization of the transition matrix for the relaxed self-consistent field version of CV(infinity)-DFT, RSCF-CV(infinity)-DFT in the case of large fragment separations are shown and we introduce two possible gradient restrictions to avoid the unwanted admixing of other transitions.

First author: Levandowski, BJ, Hyperconjugative, Secondary Orbital, Electrostatic, and Steric Effects on the Reactivities and Endo and Exo Stereoselectivities of Cyclopropene Diels-Alder Reactions, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 16731, (2016)
Abstract: The factors controlling the reactivities and stereoselectivities in the Diels-Alder reactions of substituted cyclopropenes with butadiene were explored with M06-2X density functional theory. Differences in reactivities result from differences in the hyperconjugative aromaticities and anti-aromaticities of the cyclopropenes. When the 3-substituent is a sigma-donor, the ground state is destabilized, and the reactivity is enhanced. Acceptors have the opposite effect. Electrostatic, secondary orbital, and steric effects are all found to influence stereoselectivities.

First author: Einrem, RF, Synthesis and Molecular Structure of Tc-99 Corroles, CHEMISTRY-A EUROPEAN JOURNAL, 22, 18747, (2016)
Abstract: The first Tc-99 corroles have been synthesized and fully characterized. A single-crystal X-ray structure of a (TcO)-Tc-99 triarylcorrole revealed nearly identical geometry parameters as the corresponding ReO structure. A significant spectral shift between the Soret maxima of TcO (410-413 nm) and ReO (438-441 nm) corroles was observed and, based on two-component spin-orbit ZORA TDDFT calculations, ascribed to relativistic effects in the Re case. The syntheses reported herein potentially pave the way toward Tc-99m-porphyrinoid-based radiopharmaceuticals.

First author: Yepes, D, Deeper Insight into the Factors Controlling H-2 Activation by Geminal Aminoborane-Based Frustrated Lewis Pairs, CHEMISTRY-A EUROPEAN JOURNAL, 22, 18801, (2016)
Abstract: H-2 activation mediated by geminal aminoboranebased frustrated Lewis pairs (FLPs; R2N-CH2-BR'(2)) has been computationally explored within the density functional theory framework. It is found that the activation barrier of this process as well as the geometry of the corresponding transition states strongly depend on the nature of the substituents directly attached either to the acidic or the basic centers of the FLPs. The physical factors controlling the whole activation path are quantitatively described in detail by means of the activation strain model of reactivity combined with the energy decomposition analysis method. This methodology suggests a highly orbital-controlled mechanism where the degree of charge transfer cooperativity between the most important donor-acceptor orbital interactions, namely LP(N)->sigma*(H-2) and sigma(H-2)-> p(pi)(B), along the reaction coordinate constitutes a suitable indicator of the reaction barrier.

First author: Letterman, RG, Calibrating Reaction Enthalpies: Use of Density Functional Theory and the Correlation Consistent Composite Approach in the Design of Photochromic Materials, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 9982, (2016)
Abstract: Acquisition of highly accurate energetic data for chromium-containing molecules and various chromium carbonyl complexes is a major step toward calibrating bond energies and thermal isomerization energies from mechanisms for Cr-centered photochromic materials being developed in our laboratories. The performance of six density functionals in conjunction with seven basis sets, utilizing Gaussian-type orbitals, has been evaluated for the calculation of gas-phase enthalpies of formation and enthalpies of reaction at 298.15 K on various chromium-containing systems. Nineteen molecules were examined: Cr(CO)(6), Cr(CO)(5), Cr(CO)(5)(C2H4), Cr(CO)(5)(C2C1H3), Cr(CO)(5)(cis-(C2Cl2H2)), Cr(CO)5(gem-(C2Cl2H2)), Cr(CO)(5)(trans-(C2Cl2H2)), Cr(CO)(5)(C2Cl3H), Cr(CO)(5)(C2Cl4), CrO2, CrF2, CrCl2, CrCl4, CrBr2, CrBr4, CrOCl2, CrO2Cl2, CrOF2, and CrO2F2. The performance of 69 density functionals in conjunction with a single basis set utilizing Slater-type orbitals (STO) and a zeroth-order relativistic approximation was also evaluated for the same test set. Values derived from density functional theory were compared to experimental values where available, or values derived from the correlation consistent composite approach (ccCA). When all reactions were considered, the functionals that exhibited the smallest mean absolute deviations (MADs, in kcal mol(-1)) from ccCA-derived values were B97-1 (6.9), VS98 (9.0), and KCIS (9.4) in conjunction with quadruple-C STO basis sets and B97-1 (9.3) in conjunction with cc-pVTZ basis sets. When considering only the set of gas-phase reaction enthalpies (Delta H-r degrees(gas),), the functional that exhibited the smallest MADs from ccCA-derived values were B97-1 in conjunction with cc-pVTZ basis sets (9.1) and PBEPBE in conjunction with polarized valence triple-zeta basis set/effective core potential combination for Cr and augmented and multiple polarized triple-C Pople style basis sets (9.5). Also of interest, certainly because of known cancellation of errors, PBEPBE with the least-computationally expensive basis set combination considered in the present study (valence double-zeta basis set/effective core potential combination for Cr and singly-polarized double-C Pople style basis sets) also provided reasonable accuracy (11.1). An increase in basis set size was found to have an improvement in accuracy for the best performing functional (B97-1).

First author: Ghosh, A, Unprecedented Enhancement of Noble Gas-Noble Metal Bonding in NgAu(3)(+) (Ng = Ar, Kr, and Xe) Ion through Hydrogen Doping, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 9998, (2016)
Abstract: Behavior of gold as hydrogen in certain gold compounds and a very recent experimental report on the noble gas noble metal interaction in Ar complexes of mixed Au-Ag trimers have motivated us to investigate the effect of hydrogen doping on the Ng-Au (Ng = Ar, Kr, and Xe) bonding through various ab initio based techniques. The calculated results show considerable strengthening of the Ng-Au bond in terms of bond length, bond energy, stretching vibrational frequency, and force constant. Particularly, an exceptional enhancement of Ar-Au bonding strength has been observed in ArAuH2+ species as compared to that in ArAu3+, system, as revealed from the CCSD(T) calculated Ar-Au bond energy value of 32 and 72 kJ mol(-1) for ArAu3+ and ArAuH2+, respectively. In the calculated IR spectra, the Ar Au stretching frequency is blue-shifted by 65% in going from ArAu3+ to ArAuH2+ species. Similar trends have been obtained in the case of all Ar, Kr, and Xe complexes with Ag and Cu trimers. Among all the NgM(3-k)H(k)(+) complexes (where k = 0-2), the strongest binding in NgMH(2)(+) complex is attributed to significant enhancement in the covalent characteristics of the Ng-M bond and considerable increase in charge-induced dipole interaction, as shown from the topological analysis.

First author: Kusler, K, What Is the Preferred Conformation of Phosphatidylserine-Copper(II) Complexes? A Combined Theoretical and Experimental Investigation, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 12883, (2016)
Abstract: Phosphatidylserine (PS) has previously been found to bind Cu2+ in a ratio of 1 Cu2+ ion per 2 PS lipids to form a complex with an apparent dissociation constant that can be as low as picomolar. While the affinity of Cu2+ for lipid membranes containing PS lipids has been well characterized, the structural details of the Cu-PS2 complex have not yet been reported. Coordinating to one amine and one carboxylate moiety on two separate PS lipids, the Cu-PS2 complex is unique among ion lipid complexes in its ability to adopt both cis and trans conformations. Herein, we determine which stereoisomer of the Cu-PS2 complex is favored in lipid bilayers using density functional theory calculations and electron paramagnetic resonance experiments. It was determined that a conformation in which the nitrogen centers are cis to each other is the preferred binding geometry. This is in contrast to the complex formed when two glycine molecules bind to Cu2+ in bulk solution, where the cis and trans isomers exist, in equilibrium, indicating that the lipid environment has a significant steric effect on the Cu2+ binding conformation. These findings are relevant for understanding lipid oxidation caused by Cu2+ binding to lipid membrane surfaces and will help us understand how ion binding to lipid membranes can affect their physical properties.

First author: Boguslawski, K, Targeting excited states in all-trans polyenes with electron-pair states, JOURNAL OF CHEMICAL PHYSICS, 145, 12883, (2016)
Abstract: Wavefunctions restricted to electron pair states are promising models for strongly correlated systems. Specifically, the pair Coupled Cluster Doubles (pCCD) ansatz allows us to accurately describe bond dissociation processes and heavy-element containing compounds with multiple quasi-degenerate single-particle states. Here, we extend the pCCD method to model excited states using the equation of motion (EOM) formalism. As the cluster operator of pCCD is restricted to electron-pair excitations, EOM-pCCD allows us to target excited electron-pair states only. To model singly excited states within EOM-pCCD, we modify the configuration interaction ansatz of EOM-pCCD to contain also single excitations. Our proposed model represents a simple and cost-effective alternative to conventional EOM-CC methods to study singly excited electronic states. The performance of the excited state models is assessed against the lowest-lying excited states of the uranyl cation and the two lowestlying excited states of all-trans polyenes. Our numerical results suggest that EOM-pCCD including single excitations is a good starting point to target singly excited states.

First author: Wu, T, Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory, JOURNAL OF CHEMICAL PHYSICS, 145, 12883, (2016)
Abstract: Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 x 10(-1) cm(2) V-1 s(-1) which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA-and RNA-based molecular electronic devices.

First author: Vannay, L, Visualizing and Quantifying Interactions in the Excited State, CHEMISTRY-A EUROPEAN JOURNAL, 22, 18442, (2016)
Abstract: Determining the location and nature of the electron pairs within a molecule provides an intuitive representation of electronic structures. Yet, most of the available theoretical representations are not suitable for describing excited state phenomena. The density overlap region indicator (DORI) scalar field, which depends only on the density and its derivatives, overcomes previous limitations, while keeping the intuitiveness of popular scalar fields. Here, its usefulness is demonstrated by pinpointing visual and numerical DORI signatures for both intra- and intermolecular excited state situations.

First author: Zhang, WT, Theoretical Investigation and Design of Highly Efficient Blue Phosphorescent Iridium(III) Complexes Bearing Fluorinated Aromatic Sulfonyl Groups, CHEMPHYSCHEM, 17, 4149, (2016)
Abstract: Aromatic sulfonyl groups have attracted increasing interest due to their unique electronic features. In this article, a series of Ir-III complexes bearing fluorinated phenylsulfonyl groups were evaluated by density functional theory and time-dependent density functional theory methods. To explore their phosphorescence efficiencies, factors that determine the radiative decay rate constant, k(r), and the nonradiative decay rate constant, k(nr), were computed. As demonstrated by the results, complex 4, which has fluorinated phenylsulfonyl groups at the 5-positions of the phenyl rings for all three C<^>N ligands, was found to have the highest phosphorescence efficiencies with the largest kr and smallest knr values among these complexes. Moreover, it was found to exhibit significantly blueshifted behavior relative to complex 1 and emits in the blue region, and thus, it can serve as a highly efficient blue emitter for application in organic light-emitting diodes. These findings successfully illustrated the structure-properties relationship and provided valuable information for the development of future highly efficient blue-emitting phosphors.

First author: Chakraborty, D, Sequestration and Activation of Small Gas Molecules on BN-Flakes and the Effect of Various Metal Oxide Molecules therein, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 27782, (2016)
Abstract: The possibility of sequestrating gas molecules (H-2, CO, NO, O-3, H2O, and O-2) through pristine as well as metal oxide molecule (MO, M = Cu, Ag, Au) supported boron nitride flakes (BNF) has been investigated through density functional theory (DFT) based computations. Thermodynamic (at 298 K) as well as energetic criteria reveal reasonable stability of the MO@BNF moieties. Orbital and electrostatic interactions play crucial roles in stabilizing these systems. MO@BNF moieties, in general, can sequestrate some representative gas molecules, viz., H-2, CO, NO, O-3, H2O, and O-2 in a thermodynamically as well as energetically more facile way as compared to that on pristine BNF. In particular, reversible H-2 storage might be feasible at ambient temperature and pressure through MO@BNF. NBO as well as AIM results indicate that the chosen gas molecules, in general, attain an “active” state upon getting adsorbed on MO@BNF moieties as compared to their respective free counterparts.

First author: Anggara, T, Periodic DFT Characterization of NOx Adsorption in Cu-Exchanged SSZ-13 Zeolite Catalysts, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 27934, (2016)
Abstract: We report a density functional theory (generalized gradient approximation (GGA)) and hybrid-exchange (HSE06 and B3LYP) characterization of NOx adsorption on Cu-exchanged SSZ-13, in particular to compare predictions of computational models, to understand the relative stability of adsorbates under reaction conditions, and to aid in the interpretation of experiments. We consider Cu exchanged near a single Al tetrahedral site without and with a proximal Bronsted acid. Computed structures, vibrational spectra, and oxidation states are consistent with prior observations. The GGA generally overpredicts adsorbate binding energies to extents that are species specific. The tendency for a Cu site to coadsorb two species is in particular exaggerated within the GGA. Proximal acid sites generally have a small effect on adsorbate binding. Computed vibrational spectra support the assignment of various experimentally observed features, including the assignment of an experimentally observed feature near 2100 cm(-1) to an Al site charge-compensated by NO. First-principles thermodynamic analysis shows that Cu-bound nitrite and nitrate are thermodynamically preferred under oxidizing conditions in the presence of NO or NO2.

First author: Cukrowski, I, On the Stability of Cis- and Trans-2-Butene Isomers. An Insight Based on the FAMSEC, IQA, and ETS-NOCV Schemes, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 2783, (2016)
Abstract: In the present account, the real space fragment attributed molecular system energy change (FAMSEC) approach, interacting quantum atoms energy decomposition scheme as well as molecular orbitals based the extended transition state scheme coupled with natural orbitals for chemical valence (ETS-NOCV) have been, for the first time, successfully used to delineate factors of importance for stability of the 2-butene conformers (cis-eq, cis-TS, trans-eq, trans-TS). Our results demonstrate that atoms of the controversial H-H contact in cis-eq (i) are involved in attractive interaction dominated by the exchange-correlation term, (ii) are weekly stabilized, (iii) show trends in several descriptors found in other typical H-bonds, and (iv) are part of most stabilized CH-HC fragment (loc-FAMSEC = -3.6 kcal/mol) with most favourably changed intrafragment interactions on trans-eq! cis-eq. Moreover, lower stability of cis-eq vs. trans-eq is linked with the entire HC=CH (ethylenic) fragment which destabilized cis-eq (mol-FAMSEC, +13.9 kcal/mol) the most. Although the H-H contact can be linked with smaller, relative to trans-, rotational energy barrier in cis-2-butene, we have proven that to rationalize this phenomenon one must account for changes in interactions between various fragments that constitute the entire molecule. Importantly, we discovered a number of comparable trends in fundamental properties of equivalent molecular fragments on a methyl group rotation; for example, interaction between BP-free H-atoms in trans-eq (involving CAH bonds of the methyl and ethylenic units) and BP-linked H-atoms in cis-eq. Clearly, rotational energy barrier cannot be entirely (i) rationalized by the properties of or (ii) attributed to the H-H contact in cis-eq.

First author: Wheaton, CA, Complexes of gold(I) with a chiral diphosphine and bis(pyridine) ligands: Isomeric macrocycles and a polymer, POLYHEDRON, 120, 88, (2016)
Abstract: The self-assembly of [Au-2(mu-(+/-)binap)X-2], which have weakly coordinated anions X- = trifluoroacetate, triflate or nitrate, with bis(amidopyridyl) ligands (NN) has given three different macrocyclic complexes of general formula [Au-4(mu-(+/-)binap)(2)(mu-NN)(2)]X-4, an open complex [Au-2(mu-(+/-)binap)(kappa(1)-NN)(2)]X-2, and a polymer [{Au-2(mu-(+/-)binap)(mu-NN)}(n)]X-2n, Macrocycles with both homochiral (RR/SS) and heterochiral (RS/SR) combinations of the two binap ligands in the cations [Au-4(mu-binap)(2)(mu-NN)(2)](4+) have been structurally characterized. The polymeric complex has the syndiotactic (heterochiral) architecture. The donor ability of the anion X- is shown to affect both the degree of self-assembly in solution, through competition with the bis(amidopyridyl) ligand for coordination to gold(I), and the conformation of the bis(amidopyridyl) ligand in the products, through hydrogen bonding effects. In solution, there is a rapid equilibrium between cyclic and open chain oligomers, as determined by ESI-MS and NMR studies.

First author: Heinen, J, Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory, CHEMISTRY-A EUROPEAN JOURNAL, 22, 18045, (2016)
Abstract: For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions.

First author: Miorelli, J, Nearsightedness of Oxygen-Containing Functional Groups, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 9579, (2016)
Abstract: Matter is nearsighted, that is, for a fixed chemical potential, the charge density is only sensitive to perturbations within a radius R. While it is known that the resultant change in the density at point r(0) from some perturbation at some other point R (Delta n(r(0),R)) is a monotonically decreasing function, a plausible range of a chemically significant Delta n(r(0),R) and the value of R needed to cause these perturbations has not been well studied. Using the functional group, which upon satisfying the necessary atoms/bonds specific to that functional group retains a characteristic chemistry, this paper provides an initial study into the magnitude of both An and R, the radius beyond which to affect a given property. Values for Delta n are shown to be robust across a variety of DFT functionals and provide a framework for the transfer of the functional group concept to other disciplines, such as metallurgy.

First author: Karimova, NV, Time Dependent Density Functional Theory Study of Magnetic Circular Dichroism Spectra of Gold Clusters Au-9(PH3)(8)(3+) and Au-9(PPh3)(8)(3+), JOURNAL OF PHYSICAL CHEMISTRY A, 120, 9625, (2016)
Abstract: Magnetic circular dichroism (MCD) spectroscopy is a source of important data about the electronic structure and optical properties of different chemical systems. Theoretical simulation of the MCD spectra can be used to assist in the understanding of empirically measured MCD spectra. In the present paper, a theoretical investigation of electronic and optical properties of phosphine-protected gold clusters with a Au-9(3+) core with D-2h symmetry was performed with time-dependent density functional theory. The influence of ligands on the optical properties of the gold core was investigated. Simulations of the optical absorption and MCD spectra were performed for the bare gold Au-9(3+) cluster as well as for ligand-protected Au-9(PH3)(8)(3+) and Au-9(PPh3)(8)(3+) species. MCD spectra were calculated at a temperature of 298 K and a magnetic field of 7 T. A comparative analysis of theoretical and experimental data was also performed. The obtained results show that the theoretically simulated MCD spectrum for the Au-9(PPh3)(8)(3+) ion in gas phase exhibits a reasonable agreement with experimental results for the [Au-9(PPh3)(8)](NO3)(3) system, although with a red shift of up to 0.5 mu m(-1). Overall, MCD provides significant additional details about the electronic structure of the considered systems compared to the absorption spectra.

First author: Haindl, S, The intersection of allenylidenes and mesomeric betaines. 1-Methylpyridinium-2-acetylide and its palladium complexes, TETRAHEDRON, 72, 7906, (2016)
Abstract: The anion of 2-ethynyl-1-methylpyridinium salts, which polymerized rapidly, can be represented as the mesomeric betaine 1-methylpyridinium-2-acetylide or as the cumulene-type structure 1-methylpyridin2-allenylidene. Palladium complexes have been prepared starting from 2-ethynylpyridine and Pd(PPh3)4 or PdCl2(PPh3)2 followed by methylation of the resulting complexes to the title compounds. Results of calculations and spectroscopic measurements are discussed with respect to the zwitterionic or allenylidene resonance forms.

First author: Kuribara, K, Solvation structure and thermodynamics for Pr(III), Nd(III) and Dy(III) complexes in ionic liquids evaluated by Raman spectroscopy and DFT calculation, JOURNAL OF MOLECULAR STRUCTURE, 1125, 186, (2016)
Abstract: The coordination states of trivalent praseodymium, neodymium, and dysprosium complexes in the ionic liquid, triethyl-n-pentylphosphonium bis(trifluoromethyl-sulfonyl) amide ([P-2225][TFSA]) were investigated by Raman spectroscopy. The effect of the concentration of rare earth ions on the Raman spectra was investigated, ranging from 0.23 to 0.45 mol kg(-1) of Pr(III), Nd(III), and Dy(III) in [P-2225][TFSA]. Based on a conventional analysis, the solvation numbers, n, of Pr(III), Nd(III), and Dy(III) in [P-2225][TFSA] were determined to be 4.99, 5.01, and 5.00 at 298 K and 5.04, 5.06, and 5.07 at 373 K, respectively.

First author: Kremennaya, MA, THEORETICAL AND EXPERIMENTAL STUDY OF MONONUCLEAR Cu(II) ACETATE-BIPYRIDINE COMPLEX, JOURNAL OF STRUCTURAL CHEMISTRY, 57, 1348, (2016)
Abstract: Cu(II) acetate-bipyridine complex has been synthesized. A series of experimental and theoretical spectroscopic studies was carried out for the freshly prepared sample. The local atomic and electronic structure was theoretically analyzed based on functional density theory and the structural models of the complex was obtained for various solvents. IR and XANES spectra were experimentally measured and modelled in the framework of functional density theory in a generalized gradient approximation to provide information on the chemical bond and local surroundings of copper. The powder X-ray pattern of the Cu(II) complex was obtained. The measured ESR spectra of the acetate-bipyridine complex at room temperature for the solid sample and solution in DMF confirms the formation of the mononuclear square planar complex.

First author: Polozhentsev, OE, MOLECULAR AND ELECTRONIC STRUCTURE OF HYDROLIZED PLATINUM ANTICANCER DRUGS AS REVEALED BY X-RAY ABSORPTION, IR, UV-VIS SPECTROSCOPIES AND DFT CALCULATIONS,JOURNAL OF STRUCTURAL CHEMISTRY, 57, 1477, (2016)
Abstract: The present study deals with the electronic structure of the bioactive anticancer drugs based on platinum(II) complexes: cisplatin PtCl2(NH3)(2), carboplatin PtC6H12N2O4 and oxaliplatin PtC8H14N2O4, which are being used in cancer treatment. The purpose of the work was to examine the molecular and electronic structure of platinum(II) coordination complexes when they undergo hydrolysis, which is crucial in order to better understand their antitumor properties. The density functional theory (DFT) was used to investigate the electronic structure of the platinum(II) complexes under study. The process of hydrolysis was simulated, and the structure and geometry of hydrolyzed platinum complexes were determined. The electronic structure, energy levels of occupied and unoccupied MOs and the distribution of the total and partial electron density of states (DOS) were shown and the UV-Vis and oscillation spectra of the hydrolyzed platinum(II) complexes were calculated. The theoretical calculations were verified by the experimentally obtained data by applying the method of X-ray absorption at PtL3 edge as well as UV-Vis and IR spectroscopic techniques.

First author: Swart, M, Spinning around in Transition-Metal Chemistry, ACCOUNTS OF CHEMICAL RESEARCH, 49, 2690, (2016)
Abstract: CONSPECTUS: The great diversity and richness of transition metal chemistry, such as the features of an open d-shell, opened a way to numerous areas of scientific research and technological applications. Depending on the nature of the metal and its environment, there are often several energetically accessible spin states, and the progress in accurate theoretical treatment of this complicated phenomenon is presented in this Account.

First author: Tisato, F, Insights into the cytotoxic activity of the phosphane copper(I) complex [Cu(thp)(4)][PF6], JOURNAL OF INORGANIC BIOCHEMISTRY, 165, 80, (2016)
Abstract: The phosphane Cu(I) complex [Cu(thp)(4)][PF6], I (thp = tris(hydroxymethyl)phosphane) shows notable in vitro antitumour activity against a wide range of solid tumours. Uptake experiments performed in 1-treated colon cancer cells by atomic absorption spectrometry, reveal that the antiproliferative activity is consistent with the intracellular copper content. The solution chemistry of this agent, investigated by means of X-ray Absorption Spectroscopy and spectrophotometric titrations in aqueous media, indicates that 1 is labile giving coordinative unsaturated [Cu(thp)(n)](+) species (n = 3 and 2) at micromolar concentrations. [Cu(thp)(n)](+) are reactive species that yield the mixed-ligand complex [Cu(thp)(2)(BCS)](-) (BCS: bathocuproinedisulphonate((2-))) upon interaction with N,N-diimine. Analogously, [Cu(thp)(n)](+) interact with the methionine-rich peptide sequence (Ac-MMMMPMTFK-NH2; Pepl), relevant in the recruiting of physiological copper, giving [Cu(thp)(Pepl)](+) and [Cu(Pepl)](+) species. The formation of these adducts was assessed by electrospray mass spectrometry in the positive ion mode and validated by density functional theory investigations. The possibility to trans-chelate Cu(I) from pure inorganic [Cu(thp)(n)](+) assemblies into more physiological adducts represents a pathway that complex 1 might follow during the internalization process into cancer cells.

First author: Lutz, JJ, Deviations from Born-Oppenheimer mass scaling in spectroscopy and ultracold molecular physics, JOURNAL OF MOLECULAR SPECTROSCOPY, 330, 43, (2016)
Abstract: We investigate Born-Oppenheimer breakdown (BOB) effects (beyond the usual mass scaling) for the electronic ground states of a series of homonuclear and heteronuclear alkali-metal diatoms, together with the Sr-2 and Yb-2 diatomics. Several widely available electronic structure software packages are used to calculate the leading contributions to the total isotope shift for commonly occurring isotopologs of each species. Computed quantities include diagonal Born-Oppenheimer corrections (mass shifts) and isotopic field shifts. Mass shifts dominate for light nuclei up to and including K, but field shifts contribute significantly for Rb and Sr and are dominant for Yb. We compare the ab initio mass-shift functions for Li-2, LiK and LiRb with spectroscopically derived ground-state BOB functions from the literature. We find good agreement in the values of the functions for LiK and LiRb at their equilibrium geometries, but significant disagreement with the shapes of the functions for all 3 systems. The differences may be due to contributions of nonadiabatic terms to the empirical BOB functions. We present a semiclassical model for the effect of BOB corrections on the binding energies of near-threshold states and the positions of zero-energy Feshbach resonances.

First author: Wilson, RE, Structural and Electronic Properties of Fluoride Complexes of Nb-V, Ta-V, and Pa-V: The Influence of Relativistic Effects on Group V Elements, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 330, 5467, (2016)
Abstract: Aqueous fluorido complexes of niobium and tantalum were studied by using synchrotron-based extended X-ray absorption spectroscopy (EXAFS) as model systems for comparison of the structural and coordination chemistry of the group V metals Nb, Ta, and their pseudo-homologue Pa-V. The EXAFS measurements indicate differences in the coordination chemistry of Nb and Ta in these systems that were not intuitively based on their similar charge and ionic radii. The Ta speciation is dominated by six- and seven-coordinate fluorido complexes, while the chemical speciation of Nb under the same conditions is dominated by its hydrolyzed oxyfluoride complexes. Quantum chemical computations were performed to more fully describe these observations, and these results are compared to our earlier study on the fluorido complexes of protactinium. Computations performed with and without the inclusion of scalar relativistic effects reveal that the differences in chemistry among the group V elements and their pseudo-homologue protactinium are due to the increasing influence of relativistic effects as Z increases from niobium to protactinium.

First author: Majid, A, Controlling the electronic properties of Gd: MoS2 monolayer with perpendicular electric field, JOURNAL OF ELECTROCERAMICS, 37, 29, (2016)
Abstract: A systematic computational study to demonstrate electric field dependence of electronic properties of Gd doped MoS(2)monolayer is being reported. Density functional theory (DFT) based calculated were performed using ADF-BAND package to investigate the effects of applied electric field on pure and Gd doped monolayer of MoS(2)using supercell approach. A detailed analysis of electric field dependence of host and dopant related states in the monolayers was carried out and discussed to explore the possible implications in devices. The findings on the basis of calculated results indicate that band gap of the monolayer decrease with increase in value of applied electric field. A model indicating this behaviour is also reported. It was further revealed that the formation energy of the monolayers exhibits a consistent decrease with increase in electric field.

First author: Chiang, NH, Conformational Contrast of Surface-Mediated Molecular Switches Yields Angstrom-Scale Spatial Resolution in Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy, NANO LETTERS, 16, 7774, (2016)
Abstract: Tip-enhanced Raman spectroscopy (TERS) combines the ability of scanning probe microscopy (SPM) to resolve atomic-scale surface features with the single-molecule chemical sensitivity of surface-enhanced Raman spectroscopy (SERS). Here, we report additional insights into the nature of the conformational dynamics of a free-base porphyrin at room temperature adsorbed on a metal surface. We have interrogated the conformational switch between two metastable surface-mediated isomers of meso-tetrakis(3,5-ditertiarybutylphenyl)-porphyrin (H2TBPP) on a Cu(111) surface. At room temperature, the barrier between the porphyrin ring buckled up/down conformations of the H2TBPP-Cu(111) system is easily overcome, and a 2.6 angstrom lateral resolution by simultaneous TERS and STM analysis is achieved under ultrahigh vacuum (UHV) conditions. This work demonstrates the first UHV-TERS on Cu(111) and shows TERS can unambiguously distinguish the conformational differences between neighboring molecules with Angstrom-scale spatial resolution, thereby establishing it as a leading method for the study of metal-adsorbate interactions.

First author: de Cozar, A, New Insights into the Reactivity of Cisplatin with Free and Restrained Nucleophiles: Microsolvation Effects and Base Selectivity in Cisplatin-DNA Interactions, CHEMPHYSCHEM, 17, 3932, (2016)
Abstract: The reactivity of cisplatin towards different nucleophiles has been studied by using density functional theory (DFT). Water was considered first to analyze the factors that govern the transformation of cisplatin into more electrophilic aquated species by using an activation-strain model. It was found that the selectivity and reactivity of cisplatin is a delicate trade-off between strain and interaction energies and that the second chloride is a worse leaving group than the first. When similar studies were carried out with imidazole, guanine (G), and adenine (A), it was found that in general the second nucleophilic substitution reactions have lower activation barriers than the first ones. Finally, simulations of the structural restrictions imposed by the DNA scaffold in intra-and interstrand processes showed that the geometries of the reaction products are nonoptimal with respect to the unrestrained A and G nucleophiles, although the energetic cost is not considerable under physiological conditions, which thus permits nucleophilic substitution reactions that lead to highly distorted DNA.

First author: Ajdacic, V, Decarbonylative Dibromination of 5-Phenylthiophene-2-carbaldehyde with Bromine, SYNTHESIS-STUTTGART, 48, 4423, (2016)
Abstract: The decarbonylative dibromination of 2-thiophenecarboxaldehyde derivatives with bromine under mild conditions is developed. The mechanism for the decarbonylation is investigated by experimental and instrumental techniques and is extended by a computational study. Alongside removal of the formyl group, this method enables functionalization of the starting compounds in a single reaction step, which can be further exploited for the synthesis of 2,5-diaryl-3-bromothiophenes and 2,3,5-triarylthiophenes.

First author: Chen, X, A comparative DFT study of oxygen reduction reaction on mononuclear and binuclear cobalt and iron phthalocyanines, RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A, 90, 2413, (2016)
Abstract: The oxygen reduction reaction (ORR) catalyzed by mononuclear and planar binuclear cobalt (CoPc) and iron phthalocyanine (FePc) catalysts is investigated in detail by density functional theory (DFT) methods. The calculation results indicate that the ORR activity of Fe-based Pcs is much higher than that of Co-based Pcs, which is due to the fact that the former could catalyze 4e(-) ORRs, while the latter could catalyze only 2e(-) ORRs from O-2 to H2O2. The original high activities of Fe-based Pcs could be attributed to their high energy level of the highest occupied molecular orbital (HOMO), which could lead to the stronger adsorption energy between catalysts and ORR species. Nevertheless, the HOMO of Co-based Pcs is the ring orbital, not the 3d Co orbital, thereby inhibiting the electron transfer from metal to adsorbates. Furthermore, compared with mononuclear FePc, the planar binuclear FePc has more stable structure in acidic medium and more suitable adsorption energy of ORR species, making it a promising non-precious electrocatalyst for ORR.

First author: Huang, TT, Enhanced spin-orbit coupling driven by state mixing in organic molecules for OLED applications, ORGANIC ELECTRONICS, 39, 311, (2016)
Abstract: We investigate the energy gap variation as well as spin-orbit coupling (SOC) integrals between various low-lying singlet and triplet excited states for a series of fluorescein derivatives. We find that when the electron-donating property of the substituent group on the benzene moiety of fluorescein is gradually increased, the charge transfer states are lowered in energy and a mixing with nearby pi pi* or n pi* states occurs, which causes a twisting in the p orbital on the carbonyl group and a non-zero SOC integral between the originally non-coupled (1)pi pi* and (3)pi pi* states. We also find an enhancement of about 3-4 times in the SOC integrals upon sulfur substitution for the oxygen in the carbonyl groups, and that with substantial energy lowering in pi pi* and especially in pi pi* states, the SOC between the S-1 state with energetically close triplet states is also increased significantly, signifying the possibility of enhanced phosphorescence or thermally-delayed fluorescence emission.

First author: Chatterjee, S, How different is pyrimidine as a core component of DNA base from its diazine isomers: A DFT study?, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 1836, (2016)
Abstract: Recent photoemission spectroscopic (X-ray photoemission spectra) study revealed less dramatic chemical changes for pyrimidine (PyM, 1, 3-diazine) with in its ionization potential. Present systematic study using density functional theory calculations shows that PyM is indeed quite different from its diazine isomers (PyD, 1, 2-diazine and PyA, 1, 4-diazine). It is discovered that the most stable isomer PyM is relaxed from C-2V to C-1 point symmetry with a total electronic energy deduction of -15.86 kcal.mol(-1). Although not substantial, PyM has the smallest molecule shape (electronic spatial extent) and the largest HOMO-LUMO energy gap of 5.65 eV; only one absorption band in the region of 200-300 nm of the UV-Vis spectrum but three clusters of chemical shift in the carbon and hydrogen NMR spectra. The energy decomposition analyses revealed that the interaction energy (E-Int) of PyM is preferred over PyA by 4.08 kcal.mol(-1) and over PyD by 22.32 kcal.mol(-1), with the preferred NCN bond revealed by graph theory.

First author: Zhao, CX, Cation-anion radical interactions between halopyridinium cations and metal dithiolene complexes [M(C2S2)(2)CN](-center dot): A theoretical study of halogen bonds in conducting or magnetic molecular materials,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 1872, (2016)
Abstract: Metal dithiolene complexes have been extensively used for the elaboration of conducting or magnetic materials, whose molecular arrangements can be sensitively influenced by strong and directional noncovalent interactions. In this work, halogen bonds between N-methyl-3-halopyridinium cations and cyano-substituted anion radicals, [M(C2S2)(2)CN](-center dot) (M=Ni, Pd, and Pt), were systematically investigated at the M06 level of theory. The CN…X interactions in these systems are predicted to be considerably strong and play a vital role in the controlling of the crystal structures of molecular conductors and magnets. The electrostatics contributes mainly to the attraction of these halogen bonds, while the orbital interaction is also important. Particularly, the formation of these interactions has little effect on the distribution of SOMOs, which is strongly delocalized on the two dithiolene moieties. These results will assist in the design of functional materials that exhibit exotic conducting or magnetic properties.

First author: Bensalem, N, Coordination capabilities of anthracene ligand in binuclear sandwich complexes: DFT investigation, STRUCTURAL CHEMISTRY, 27, 1781, (2016)
Abstract: DFT calculations with full geometry optimization using BP86 and mPW1PW91 functionals have been carried out on binuclear hypothetical compounds of the type M-2(Ant)(2) (Ant = anthracene). This work investigates the possibility for such compounds to exist for the M = Ti-Ni series. The analysis of their electronic and molecular structures in relation to their electron counts allows a comprehensive rationalization of the bonding of these compounds. A very rich coordination chemistry of anthracene has been highlighted. This richness comes from the very large electronic and structural flexibility of anthracene, which is able to adapt itself to the electronic demand of metals. Each of the C-6 rings of anthracenes can be coordinated in various hapticities and symmetries depending on the nature of the metal and the structure’ spin state. This flexibility favors the possibility of existence of several isomers closeness in energy. The asymmetry between the two anthracenes causes binuclear complexes to exhibit very different coordination with different oxidation states. In some cases, the M-M bonding is not privileged despite the metals’ electronic deficiency.

First author: Conradie, J, XPS Fe 2p peaks from iron tris(beta-diketonates): Electronic effect of the beta-diketonato ligand, POLYHEDRON, 119, 142, (2016)
Abstract: The Fe 2p photoelectron lines, as measured by X-ray photoelectron spectra (XPS), of a series of tris(beta-diketonato)iron(III) complexes, are sensitive to the electron donating and withdrawing properties of the ligand attached to the iron atom. The maximum binding energy of the Fe 2p(3/2) envelope revealed a linear relationship with the combined Gordy scale group electronegativity of the R-groups substituted on the respective beta-diketonato ligand (RCOCHCOR’)(-). A linear relationship between the binding energies and other electronic parameters was also obtained. Within these relationships, there are specific clusters of complexes defined by the amount of CF3 groups substituted per beta-diketonato ligand. These specific clusters of complexes show an opposite trend inversely proportional to the general trend. It was also shown that the Fe 2p photoelectron peaks can be fitted with calculated multiplet splitting peaks, according to the synthetically generated multiplet splitting test spectra, as calculated by Gupta and Sen for a free Fe(III) ion. The tris(beta-diketonato)iron(III) complexes containing unsymmetrically substituted beta-diketonato ligands (RCOCHCOR’))(-), were fitted with two different sets of multiplet splitting peaks, which are assigned to the fac and mer isomers of these complexes.

First author: Bouchouit, M, Synthesis, X-ray structure, theoretical investigation, corrosion inhibition and antimicrobial activity of benzimidazole thioether and theirs metal complexes, POLYHEDRON, 119, 248, (2016)
Abstract: Synthesis, characterization, corrosion inhibition as well as antimicrobial activity of the coordination compounds {Co(bbms)Cl-2}, {Zn(bbms)Cl-2}, {Co(btmb)Cl-2) and {Zn(btmb)Cl-2} containing benzimidazole thioether have been described. Co(bbms) and Zn(bbms) as well as Co(btmb) and Zn(btmb) are isostructural with space group Pbca and P21 respectively.

First author: Gieseking, RL, Quantum Mechanical Identification of Quadrupolar Plasmonic Excited States in Silver Nanorods, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 9324, (2016)
Abstract: Quadrupolar plasmonic modes in noble metal nanoparticles have gained interest in recent years for various sensing applications. Although quantum mechanical studies have shown that dipolar plasmons can be modeled in terms of excited states where several to many excitations contribute coherently to the transition dipole moment, new approaches are needed to identify the quadrupolar plasmonic states. We show that quadrupolar states in Ag nanorods can be identified using the semiempirical INDO/SCI approach by examining the quadrupole moment of the transition density. The main longitudinal quadrupolar states occur at higher energies than the longitudinal dipolar states, in agreement with previous classical electrodynamics results, and have collective plasmonic character when the nanorods are sufficiently long. The ability to identify these states will make it possible to evaluate the differences between dipolar and quadrupolar plasmons that are relevant for sensing applications.

First author: Pramudya, Y, Design Principles for High H-2 Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298 K, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 15204, (2016)
Abstract: Physisorption is an effective route to meet hydrogen gas (H-2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H-2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H-2 binding enthalpy of 5 linkers which were chelated with 11 different transition metals (Tm), including abundant first-row Tm (Sc through Cu), totaling 60 molecular compounds with more than 4 configurations related to the different number of H-2 that interact with the molecular compound. It was found that first-row Tm gave similar and sometimes superior van der Waals interactions with H-2 than precious Tm. Based on these linkers, 30 new covalent organic frameworks (COFs) were constructed. The H-2 uptakes of these new COFs were determined using quantum mechanics (QM)-based force fields and grand canonical Monte Carlo (GCMC) simulations. For the first time, the range for the adsorption pressure was explored for 0-700 bar and 298 K. It was determined that Co-, Ni-, and Fe-based COFs can give high H-2 uptake and delivery when compared to bulk H-2 on this unexplored range of pressure.

First author: Kahlfuss, C, Electron-Triggered Metamorphism in Porphyrin-Based Self-Assembled Coordination Polymers, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 15234, (2016)
Abstract: Viologen-centered electron transfer is used to trigger a complete dissociation of a porphyrin-based supramolecular architecture. In the oxidized state, self-assembly is induced by iterative association of individual porphyrin-based tectons. Dissociation of the self-assembled species is actuated upon changing the redox state of the bipyridium units involved in the tectons from their dicationic state to their radical cation state, the driving force of the disassembling process being the formation of an intramolecularly locked conformation partly stabilized by g-dimerization of both viologen cation radicals.

First author: van Rensburg, AJ, Electrochemical and X-ray photoelectron spectroscopic insights into Molybdenum(0) Fischer ethoxycarbene complexes, ELECTROCHIMICA ACTA, 219, 204, (2016)
Abstract: The electrochemical analysis, theoretical examination, as well as the first X-ray photoelectron spectroscopic (XPS) study on molybdenum(0) Fischer carbene complexes are presented. The intramolecular communication between the carbene ligand, molybdenum metal centre, and the ancillary ligands is illustrated by linear relationships and trends obtained between experimentally measured redox and XPS binding energy values and theoretically calculated energies and charges. The ease of oxidation of the three series of Mo(0) Fischer carbene complexes presented, namely four pentacarbonyl Mo(0) Fischer carbene complexes of general formula [(CO)(5)MoC(OEt)(Ar)], with Ar = 2-thienyl (1), 2-furyl (2), 2-(N-methyl)pyrrolyl (3), 2,2′-bithienyl (4), four triphenylphosphine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO)(4)(PPh3) MoC(OEt) (Ar)], with Ar = 2-thienyl (5), 2-furyl (6), 2-(N-methyl) pyrrolyl (7), 2,2′-bithienyl (8), and four triphenylarsine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO)(4)(AsPh3) MoC(OEt)(Ar)], with Ar = 2-thienyl (9), 2-furyl (10), 2-(N-methyl) pyrrolyl (11), 2,2′-bithienyl (12), all showed the same trend, namely (most difficult to oxidize at a higher potential): 2-thienyl approximate to 2,2′-bithienyl > 2-furyl > 2-(N-methyl) pyrrolyl. The pentacarbonyl complexes [(CO)(5)MoC (OEt)(Ar)] have the highest oxidation potentials, followed by the oxidation potential of [(CO)(4)(PPh3) MoC (OEt)(Ar)], while [(CO)(4)(AsPh3) MoC(OEt)(Ar)] oxidized at a potential 0.12 – 0.15 V lower than the PPh3 substituted complexes [(CO)(4)(PPh3) MoC(OEt)(Ar)]. Substitution of carbonyl ligand(s) in the pentacarbonyl complexes 1-4, by one (complexes 5-12) or two ([(dppe)(CO)(3)MoC(OEt)(2-furyl)] complex (13), dppe = 1,2-bis(diphenylphosphino) ethane) weaker pi-acceptor ligands (phosphines/ arsines) in Fischer carbene complexes leads to a decrease in the binding energy of the Mo 3d(5/2) photoelectron lines of the X-ray photoelectron spectra of the Fischer carbene complexes and an increase in the binding energy of the carbene carbon C 1 s photoelectron lines.

First author: Witte, K, Magnesium K-Edge NEXAFS Spectroscopy of Chlorophyll alpha in Solution, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 11619, (2016)
Abstract: The interaction of the central magnesium atom of chlorophyll a (Chl alpha) with the carbon and nitrogen backbone was investigated by magnesium K near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in fluorescence detection mode. A crude extract of Chl alpha was measured as a 1 X 10(-2) mol/L ethanol solution (which represents an upper limit of concentration without aggregation) and as dried droplets. For the first time, the investigation of Mg bound to Chl alpha in a liquid environment by means of X-ray absorption spectroscopy is demonstrated. A pre-edge feature in the dissolved as well as in dried Chl alpha NEXFAS spectra has been identified as a characteristic transition originating from Mg in the Chl alpha molecule. This result is confirmed by theoretical DFT calculations leading to molecular orbitals (MO) which are mainly situated on the magnesium atom and nitrogen and carbon atoms from the pyrrole rings. The description is the first referring to the MO distribution with respect to the central Mg ion of Chl alpha and the surrounding atoms. On this basis, new approaches for the investigations of dynamic processes of molecules in solution and structure function relationships of photosynthetic pigments and pigment protein complexes in their native environment can be developed.

First author: Abella, L, Sc3O@I-h(7)-C-80: A Trimetallic Oxide Clusterfullerene Abundant in the Raw Soot, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 26159, (2016)
Abstract: The trimetallic oxide clusterfullerene (OCF) Sc3O@C-80 has been obtained with rather high abundance in the raw soot. Most of the formed product, however, remained nonextracted in the soot so that only a small amount of it was isolated and purified. The tiny quantity of pure product acquired made only possible characterization by UV-vis-NIR spectroscopy. DFT computations predict Sc3O@I-h(7)-C-80 to be the isolated isomer and provide further information about the electronic structure and other (magnetic and electrochemical) properties of this singular OCF. Significant spin density on the endohedral Sc ions and in cavea redox processes are two main features of Sc3O@I-h(7)-C-80, which is isoelectronic to the anion of the prototypical nitride Sc3N@I-h(7)-C-80. Polymerization is predicted to be a favored process that could explain the very low yields obtained once the product is purified.

First author: Hu, MY, In Situ Natural Abundance O-17 and Mg-25 NMR Investigation of Aqueous Mg(OH)(2) Dissolution in the Presence of Supercritical CO2, ENVIRONMENTAL SCIENCE & TECHNOLOGY, 50, 12373, (2016)
Abstract: We report an in situ high-pressure NMR capability that permits natural abundance O-17 and Mg-25 NMR characterization of dissolved species in aqueous solution and in the presence of supercritical CO2 fluid (scCO(2)). The dissolution of Mg(OH)(2) (brucite) in a multiphase water/scCO(2) fluid at 90 atm pressure and 50 degrees C was studied in situ, with relevance to geological carbon sequestration. O-17 NMR spectra allowed identification and distinction of various fluid species including dissolved CO2 in the H2O-rich phase, scCO(2), aqueous H2O, and HCO3. The widely separated spectral peaks for various species can all be observed both dynamically and quantitatively at concentrations as low as 20 mM. Measurement of the concentrations of these individual species also allows an in situ estimate of the hydrogen ion concentration, or pCH values, of the reacting solutions. The concentration of Mg2+ can be observed by natural abundance Mg-25 NMR at a concentration as low as 10 mM. Quantum chemistry calculations of the NMR chemical shifts on cluster models aided in the interpretation of the experimental results. Evidence for the formation of polymeric Mg2+ clusters at high concentrations in the H2O-rich phase, a possible critical step needed for magnesium carbonate formation, was found.

First author: Chaquin, P, Deformation forces in promolecules revisited: Binding of homonuclear diatomic molecules and calculation of stretching vibrational frequencies in diatomic and larger systems, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1096, 33, (2016)
Abstract: Internuclear forces in a molecule, as an integral over a geometrical factor and the electron density, can be decomposed into a part having as origin promolecular densities of the participating atoms, and a contribution from the deformation density. At the hand of homo-nuclear diatomic molecules we show that the binding energy is linked to the deformation force except for transition metal dimers. However, vibrational frequencies involving pure bond-length variations are rather well reproduced, even for heteroatomic diatomics. For larger assemblies, frequencies for bending modes are underestimated, but the model may serve for a rough analysis of a vibrational spectrum.

First author: Stankovic, B, Theoretical study of nitrodibenzofurans: A possible relationship between molecular properties and mutagenic activity, JOURNAL OF HAZARDOUS MATERIALS, 318, 623, (2016)
Abstract: In this study we present a theoretical investigation of the molecular properties of nitrodibenzofurans (NDFs) and dinitrodibenzofurans (DNDFs) and their relation to mutagenic activity. Equilibrium geometries, relative energies, vertical ionization potentials (IP), vertical electron activities (EA), electronic dipole polarizabilities, and dipole moments of all NDFs and three DNDFs calculated by Density Functional Theory (DFT) methods are reported. The Ziegler/Rauk Energy Decomposition Analysis (EDA) is employed for a direct estimate of the variations of the orbital interaction and steric repulsion terms corresponding to the nitro group and the oxygen of the central ring of NDFs. The results indicate differences among NDF isomers for the cleavage of the related bonds and steric effects in the active site. The results show a good linear relationship between polarizability (), anisotropy of polarizability (Delta alpha), the summation of IR intensities (Sigma I-IR) and the summation of Raman activities (Sigma A(Raman)) over all 3N-6 vibrational modes and experimental mutagenic activities of NDF isomers in Salmonella typhimurium TA98 strain. The polarizability changes with respect to the nu(sNO+CN) vibrational mode are in correlation with the mutagenic activities of NDFs and suggest that intermolecular interactions are favoured along this coordinate.

First author: Andjelkovic, L, Resolving the origin of the multimode Jahn-Teller effect in metallophthalocyanines, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 29122, (2016)
Abstract: A detailed Density Functional Theory (DFT) analysis was performed in order to study the multimode Jahn-Teller (JT) problem in the electronic ground state of manganese phthalocyanine (MnPc). A comparison with the magnesium phthalocyanine ion (MgPc-) and the phthalocyanine trianion (Pc3-), also prone to the JT effect, is presented. Our results clarify the origin and provide the microscopic insight into the symmetry breaking process. The JT distortion is highly influenced by the coordination of phthalocyanine to the Mn-II ion, and occurs over the whole system, while the MgPc- complex ion possesses mainly ligand-based instability.

First author: Khemiri, N, Theoretical investigation on two different mechanisms of fulleropyrrolidine formation, THEORETICAL CHEMISTRY ACCOUNTS, 135, 29122, (2016)
Abstract: Fulleropyrrolidine synthesis by photo-addition of glycine methyl ester (GME) to [60] fullerene has been recently realized and experimentally studied. Two possible hypotheses were suggested for its formation pathway, but there was no consensus about the most favorable one. Thus, in order to find the most probable mechanism, we performed a detailed theoretical investigation of the reaction between GME and [60] fullerene studying both mechanisms suggested experimentally. The first hypothesis involves two additions of two GME radicals in two steps to C-60 followed by a NH3 departure, whereas the second one involves azomethine ylide formation in a first step and followed by a cycloaddition to [60] fullerene. All the transition states and the intermediates in the reaction steps for both mechanisms were determined. The energetic profiles of both mechanisms were drawn and compared. Several levels of theory were used for the purpose, with the aim to investigate which low-cost level is sufficient to settle and which mechanism is probably involved. For the purpose, semiempirical (AM1), DFT on geometries optimized at AM1 level, and finally DFT on geometries optimized at DFT level were considered. At DFT level, GGA (PBE), hybrid (PBE0) and meta-GGA (M06-2X) were used, with a 6-31+ G(d) basis set. We proved that the release of NH3 and the ring formation step in the first mechanism require a higher energy barrier compared to the second mechanism reaction steps like tautomerization and H2O departure. Thus, we can conclude that the second mechanism involving in a first step the azomethine ylide formation is more favorable than the first mechanism. The interest in using in a first step a semiempirical determination of reaction paths is highlighted, and the choice of the exchange-correlation functional is discussed.

First author: Kaloni, TP, Band gap modulation in polythiophene and polypyrrole-based systems, SCIENTIFIC REPORTS, 6, 29122, (2016)
Abstract: In this paper, the structural and electronic properties of polythiophene and polyprrrole-based systems have been investigated using first-principles calculations both in periodic and oligomer forms. Of particular interest is the band gap modulation through substitutions and bilayer formation. Specifically, S has been substituted by Se and Te in polythiophene, leading to polyseleophene and polytellurophene, respectively, and N has been substituted by P and As in polypyrrole. The values obtained of the binding energy suggest that all the systems studied can be realized experimentally. Stacking (bilayer formation) of pure polythiophene, polypyrrole and their derivatives leads to linear suppression of the band gap or HOMO-LUMO gap as a function of the stacking. Mixed bilayers, including one formed from polythiophene on top of polypyrrole, have also been considered. Overall, a wide range of band gaps can be achieved through substitutions and stacking. Hybrid (B3LYP) calculations also suggest the same trend in the band gap as PBE calculations. Trends in the binding energy are similar for both periodic and molecular calculations. In addition, G-point phonon calculations were performed in order to check the stability of selected systems.

First author: Hayashi, A, Encapsulation of Two Potassium Cations in Preyssler-Type Phosphotungstates: Preparation, Structural Characterization, Thermal Stability, Activity as an Acid Catalyst, and HAADF-STEM Images, INORGANIC CHEMISTRY, 55, 11583, (2016)
Abstract: Dipotassium cation (K+)-encapsulated Preyssler-type phosphotungstate, [P5W30O110K2](13-), was prepared by heating monobismuth (Bi3+)-encapsulated Preyssler-type phosphotungstate, [P5W30O110Bi-(H2O)](12-), in acetate buffer in the presence of an excess amount of potassium cations. Characterization of the isolated potassium salt, K-13[P5W30O110K2] (1a), and its acid form, H-13[P5W30O110K2] (1b), by single crystal X-ray structure analysis, P-31 and W-183 nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), high-resolution electrospray ionization mass spectroscopy (HR-ESI-MS), and elemental analysis revealed that two potassium cations are encapsulated in the Preyssler-type phosphotungstate molecule with formal D-5h symmetry, which is the first example of a Preyssler-type compound with two encapsulated cations. Incorporation of two potassium cations enhances the thermal stability of the potassium salt, and the acid form shows catalytic activity for hydration of ethyl acetate. Packing of the Preyssler-type molecules was observed by high resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

First author: Decleva, P, Attosecond electronic and nuclear quantum photodynamics of ozone monitored with time and angle resolved photoelectron spectra, SCIENTIFIC REPORTS, 6, 11583, (2016)
Abstract: Recently we reported a series of numerical simulations proving that it is possible in principle to create an electronic wave packet and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. We considered the ozone molecule: for this system the electronic wave packet leads to a dissociation process. In the present work, we investigate more specifically the time-resolved photoelectron angular distribution of the ozone molecule that provides a much more detailed description of the evolution of the electronic wave packet. We thus show that this experimental technique should be able to give access to observing in real time the creation of an electronic wave packet in a neutral molecule and its impact on a chemical process.

First author: Conradie, MM, X-ray and electronic structure of tris(benzoylacetonato-kappa O-2,O ‘)iron(III), JOURNAL OF MOLECULAR STRUCTURE, 1123, 199, (2016)
Abstract: Solid state crystal data of d(5) tris(benzoylacetonato-kappa O-2,O’)iron(III), [Fe(ba)(3)], are presented. The mer isomer crystallized in the solid state. Density functional theory calculations show that both fac and mer isomers of [Fe(ba)(3)] can exist. Both fac and mer [Fe(ba)3] are high spin d5 complexes with the same ordering of the d-based molecular orbitals in order of increasing orbital energy, namely d(xy) < d(yz) approximate to d(xz) < d(z2) approximate to d(x2-y2).

First author: Dadsetani, M, Theoretical study of optical activity of 1:1 hydrogen bond complexes of water with S-warfarin, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 168, 180, (2016)
Abstract: The molecular interaction between S-warfarin (SW) and a single water molecule was investigated using the B3LYP method at 6-311 ++G(d,p) basis set. The vibrational spectra of the optimized complexes have been investigated for stabilization checking. Quantum theories of atoms in molecules, natural bond orbitals, molecular electrostatic potentials and energy decomposition analysis methods have been applied to analyze the intermolecular interactions. The intermolecular charge transfer in the most stable complex is in the opposite direction from those in the other complexes. The optical spectra and the hyperpolarizabilities of SW-water hydrogen bond complexes have been computed.

First author: Iturbe, C, Design and synthesis of non-symmetric phenylpyridine type ligands. Experimental and theoretical studies of their corresponding iridium complexes, POLYHEDRON, 118, 159, (2016)
Abstract: In this work three non-symmetric phenylpyridine type ligands, L1, L2 and 13, were designed, and their corresponding Iridium complexes, C1, C2 and C3, synthetized, in order to understand the effect of ligand asymmetry on the properties of the complexes, and to explore their potentiality in devices. The complexes were structurally characterized by NMR experiments and by X-ray Diffraction, and physicochemically by technics as UV/Vis and cyclic voltammetry. Theoretical DFT calculations of the energy and electronic density of the frontier orbitals of the complexes under study were also performed. The energy of the HOMO and LUMO correlated well with the experimental electrochemical data, and supported the understanding of the processes observed.

First author: Patra, R, DFT analysis of the electronic structure of Fe(IV) species active in nitrene transfer catalysis: influence of the coordination sphere, JOURNAL OF MOLECULAR MODELING, 22, 159, (2016)
Abstract: Nitrene transfer reactions to various hydrocarbon molecules can be efficiently catalyzed by Fe complexes through a mechanism reminiscent of the oxygen transfer function of oxygenase enzymes. Such enzymes exhibit a high-valent iron oxo Fe(IV) = O as the active species, and it has also been proposed that an analogous species, i.e., Fe(IV) = NR (NR being the nitrene group) is responsible for the nitrene transfer activity. We describe here the influence of the Fe(IV) coordination sphere on some key parameters for nitrene transfer efficacy, such as the spin state of the Fe(IV) cation, the electronic affinity, and the bond dissociation energy of the NHR moiety. We explore here the electronic properties of Fe(IV) = NTs (NTs = tolylsulfonylimido group) mononuclear complexes with ligands involving phenolate and nitrogen donor groups, as catalytic properties with such ligands have been found to be quite promising. Six tetradentate ligands were studied, which derive from three different scaffolds: 2-methylenepyridine-N, N-bis(2-methylene-4,6-dichlorophenol) and 2-methylenepyridine-N, Nbis( 2-methylene-4,6-dimethylphenol), N, N-dimethyl-N’, N’bis(2-methylene-4,6-dichlorophenol) ethylenediamine, and N, N-dimethyl-N’, N’-bis(2-methylene-4,6-dimethylphenol) ethylenediamine, N, N’-bis(2-methylene-4,6-dichlorophenol)N, N’-dimethyl-1,2-diaminoethane and N, N’-bis(2-methylene4,6-dimethylphenol)-N, N’-dimethyl-1,2-diaminoethane. Thanks to thorough DFT computations, we present some rationalization of the electronic properties of the resulting Fe(IV) = NTs complexes in relation to their coordination sphere and compare them to other Fe(IV) nitrene active species. We show in particular the important role of the anionic character and strong p-donation of the phenolate groups.

First author: Sibbald, PA, A theoretical analysis of substituent electronic effects on phosphine-borane bonds, JOURNAL OF MOLECULAR MODELING, 22, 159, (2016)
Abstract: Phosphine-borane adducts are a well-known moiety in synthetic and coordination chemistry. These complexes form a dative bond in which the Lewis basic phosphorus atom donates electron density into an empty p-orbital of the Lewis acidic boron atom. However, donation of the phosphorus lone pair is not the only stabilizing interaction, as hyperconjugation and electrostatic interaction also play important roles in bonding. This paper describes a detailed density functional theory level (B3LYP) study completed to determine the impact electron-donating and withdrawing substituents have on phosphine-borane bonds through the investigation of a series of para-substituted PAr3-BH3 and PH3-BAr3 phosphineborane adducts. Natural bond orbital (NBO) partitioning was used to calculate the distribution of electron density between the phosphine and borane fragments. Extended transition state and natural orbitals for chemical valence (ETS-NOCV) analysis was used to isolate contributions to the overall electronic interaction of the phosphine-borane adducts. Molecular orbital composition and charge donation was calculated using AOMix. The resulting data was correlated with Hammett sigma constants.

First author: Pande, S, Structural Evolution of Core-Shell Gold Nanoclusters: Au-n(-) (n=42-50), ACS NANO, 10, 10013, (2016)
Abstract: Gold nanoclusters have attracted great attention in the past decade due to their remarkable size dependent electronic, optical, and catalytic properties. However, the structures of large gold clusters are still not well-known because of the challenges in global structural searches. Here we report a joint photoelectron spectroscopy (PES) and theoretical study of the structural evolution of negatively charged core-shell gold nanoclusters (Au-n(-)) for n = 42-50. Photoelectron spectra of size-selected Au-n(-) clusters are well resolved with distinct spectral features, suggesting a dominating structural type. The combined PES data and density functional calculations allow us to systematically identify the global minimum or candidates of the global minima of these relatively large gold nanoclusters, which are found to possess low-symmetry structures with gradually increasing core sizes. Remarkably, the four-atom tetrahedral core, observed first in Au-33(-), continues to be highly robust and is even present in clusters as large as Au-42(-). Starting from Au-43(-), a five-atom trigonal bipyramidal core appears and persists until Au-47(-). Au-48(-) possesses a six-atom core, while Au-49(-) and Au-50(-) feature seven- and eight-atom cores, respectively. Notably, both Au-46(-) and Au-47(-) contain a pyramidal Au-20 motif, which is stacked with another truncated pyramid by sharing a common 10-atom triangular face. The present study sheds light on our understanding of the structural evolution of the medium-sized gold nanoclusters, the shells and core as well as how the core-shell structures may start to embrace the golden pyramid (bulk-like) fragment.

First author: de Ruiter, JM, Electrochemical and Spectroscopic Study of Mononuclear Ruthenium Water Oxidation Catalysts: A Combined Experimental and Theoretical Investigation, ACS CATALYSIS, 6, 7340, (2016)
Abstract: One of the key challenges in designing light-driven artificial photosynthesis devices is the optimization of the catalytic water oxidation process. For this optimization it is crucial to establish the catalytic mechanism and the intermediates of the catalytic cycle, yet a full description is often difficult to obtain using only experimental data. Here we consider a series of mononuclear ruthenium water oxidation catalysts of the form [Ru(cy)(L)(H2O)](2+) (cy = p-cymene, L = 2,2′-bipyridine and its derivatives). The proposed catalytic cycle and intermediates are examined using density functional theory (DFT), radiation chemistry, spectroscopic techniques, and electrochemistry to establish the water oxidation mechanism. The stability of the catalyst is investigated using online electrochemical mass spectrometry (OLEMS). The comparison between the calculated absorption spectra of the proposed intermediates with experimental spectra, as well as free energy calculations with electrochemical data, provides strong evidence for the proposed pathway: a water oxidation catalytic cycle involving four proton-coupled electron transfer (PCET) steps. The thermodynamic bottleneck is identified as the third PCET step, which involves O-O bond formation. The good agreement between the optical and thermodynamic data and DFT predictions further confirms the general applicability of this methodology as a powerful tool in the characterization of water oxidation catalysts and for the interpretation of experimental observables.

First author: Kuhn, A, Synthesis, electrochemical and DFT study of octahedral bis(beta-diketonato)-titanium(IV) complexes, INORGANICA CHIMICA ACTA, 453, 247, (2016)
Abstract: The synthesis and electrochemistry of seven new and four known bis(beta-diketonato)-titanium(IV) complexes are reported. Integrated electrochemical and quantum chemistry techniques have been used to show that the reduction potential of this series of eleven bis(beta-diketonato)-titanium(IV) complexes, [Ti((RCOCHCOR2)-C-1)(2)biphen], are significantly influence by the electronic properties of the 1,3-beta-diketonato-substituents (R-1, R-2), due to the efficient beta-diketonato-metal pi-conjugated character of the lowest unoccupied molecular orbital (LUMO) of the complexes. Electron density in the redox center is controlled by both inductive and resonance effects as seen by the spin density plots. Electron withdrawing substituents make the reduction potentials more positive by stabilizing the reduced species. Both metal and ligand based redox processes are observed; the reversible metal Ti-IV/Ti-III reduction is followed by a considerably more negative, irreversible ligand reduction. The density functional theory calculated electronic structure of the first reduction is a Ti-III species while the second reduced species, is Ti-III coupled to a beta-diketonato radical. A number of important relationships between the electronic properties of the substituents and the redox behaviour have been developed. The experimentally measured reduction potentials, E-pc, gave excellent correlation in the linear relationship between experimental E-pc vs. calculated LUMO energies, E-LUMO (R-2 = 0.98).

First author: Bruce, MI, Syntheses and structures of some complexes containing M-3(mu-dppm)(3) moieties (M = Cu, Ag) linking C-4{M ‘ L-x} groups [M ‘ L-x = Re(CO)(3)(Bu-2(t)-bpy), Ru(dppe)Cp*], INORGANICA CHIMICA ACTA, 453, 654, (2016)
Abstract: Reactions between [Ru(C equivalent to CC equivalent to CH)(dppe)Cp*] and [M-2(NCMe)(x)(dppm)(2)](2+) (M = Cu, x = 4; Ag, x = 2) have given complexes containing M-3(mu-dppm)(3) clusters attached to one or two -C equivalent to CC equivalent to C[Ru(dppe)Cp*] groups. Single crystal X-ray studies are recorded for [{M-3(mu-dppm)(3)}{mu 3-C equivalent to CC equivalent to C[Ru(dppe)Cp*]}] (BF4)(2).nS (M = Cu, Ag) [isomorphous (orthorhombic) for S = (ill-defined) acetone]. A different (triclinic) polymorph has also been defined for M = Ag, nS = 5THF. Together with [{Cu-3(mu-dppm)(3)}{mu 3-C equivalent to CC equivalent to C [Ru(dppe)CP*]}(2)]PF6.4Me(2)CO, the structures definitively confirm the complexes as clear examples of mono- or bis-diyndiyl-M3 systems, devoid of close approaches to the vacant M-3 faces of the former by counterions in the case of their acetone solvates, except in the case of the BF4 counterion in the AgBF4/thf solvate. Cyclic voltammetric studies suggest that there are only weak electronic interactions between the ruthenium centres in the bis(diynyl) complexes, consequent upon weak overlaps between the carbon chain and the M-3(mu-dppm)(3) clusters, as confirmed by DFT calculations on model complexes [(M3(p.dHpm)3){ C equivalent to CC equivalent to C[Ru(dHpe)CP]}(n)](3-n)[n = 1, 2; dHpm = CH2(PH2)(2), dHpe = H2P(CH2)(2)PH2]. The complexes [Ag3Cl2(dppm)(3)]PF6, [M-3(mu-dppm)(3)(X){mu(3)-C equivalent to CC equivalent to C[Re(CO)(3)(Bu-2(t)-bPY)]}]PF6 (M = Cu, X = C equivalent to CC equivalent to C[Re(CO)(3)(Bu-2(t)-bpy)]; M = Ag; X = CO, [Ag6(mu-dppm)(4)[C equivalent to CC equivalent to C[Re(CO)(3)(Bu-2(t)-bPY)]}(4)](PF6)(2) have also been prepared and structurally characterised. In the M-3 clusters, some asymmetry in the attachment of at least one of the mu(3) ligands is apparent, which results from interactions with solvate molecules.

First author: Gendron, F, Ligand NMR Chemical Shift Calculations for Paramagnetic Metal Complexes: 5f(1) vs 5f(2) Actinides, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 5309, (2016)
Abstract: Ligand paramagnetic NMR (pNMR) chemical shifts of the 5f(1) complexes UO2(CO3)(3)(5-) and NpO2(CO3)(3)(4-), and of the 5f(2) complexes PuO2(CO3)(3)(4-) and (C5H5)(3)UCH3 are investigated by wave function theory calculations, using a recently developed sum-over-states approach within complete active space and restricted active space paradigm including spin-orbit (SO) coupling [J. Phys. Chem. Lett. 2015, 20, 2183-2188]. The experimental C-13 pNMR shifts of the actinyl triscarbonate complexes are well reproduced by the calculations. The results are rationalized by visualizing natural spin orbitals (NSOs) and spin-magnetizations generated from the SO wave functions, in comparison with scalar relativistic spin densities. The analysis reveals a complex balance between spin-polarization, spin and orbital magnetization delocalization, and spin-compensation effects due to SO coupling. This balance creates the magnetization due to the electron paramagnetism around the nucleus of interest, and therefore the pNMR effects. The calculated proton pNMR shifts of the (C5H5)(3)UCH3 complex are also in good agreement with experimental data. Because of the nonmagnetic ground state of (C5H5)(3)UCH3, the H-1 pNMR shifts arise mainly from the magnetic coupling contributions between the ground state and low-energy excited states belonging to the Sf manifold, along with the thermal population of degenerate excited states at ambient temperatures.

First author: Park, YC, Self-Consistent Constricted Variational Theory RSCF-CV(infinity)-DFT and Its Restrictions To Obtain a Numerically Stable Delta SCF-DFT-like Method: Theory and Calculations for Triplet States, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 5438, (2016)
Abstract: In this paper, the relaxed self-consistent field infinite order constricted variational density functional theory (RSCF-CV(infinity)-DFT) for triplet calculations is presented. Here, we focus on two main features of our implementation. First, as an extension of our previous work by Krykunov and Ziegler (J. Chem. Theory Comput. 2013, 9, 2761), the optimization of the transition matrix representing the orbital transition is implemented and applied for vertical triplet excitations. Second, restricting the transition matrix, we introduce RSCF-CV(infinity)-DFT-based numerically stable Delta SCF-DFT-like methods, the most general of them being SVD-RSCF-CV(infinity)-DFT. The reliability of the different methods, RSCF-CV(infinity)-DFT and its restricted versions, is examined using the benchmark test set of Silva Junior et al. (J. Chem. Phys. 2008, 129, 104103). The obtained excitation energies validate our approach and implementation for RSCF-CV(infinity)-DFT and also show that SVD-RSCF-CV(infinity)-DFT mimics very well Delta SCF-DFT, as the root-mean-square deviations between these methods are less than 0.1 eV for all functionals examined.

First author: Mrukiewicz, M, Strong modulation of electric permittivity at an isotropic-nematic phase transition in a liquid crystal mixture for optical devices based on the Kerr effect, JOURNAL OF MOLECULAR LIQUIDS, 223, 873, (2016)
Abstract: We report dielectric and electro-optical characteristics of a new bicomponent mixture, which at room temperature exhibits an isotropic phase. The mixture is based on the commonly known 4-Cyano-4′-pentylbiphenyl (5CB) compound and its structural homologue with a fluorine atom substituted laterally at a rigid molecular core. Due to a potential application of the studied mixture for optical devices based bathe Kerr effect, the extensive study of the dielectric and optical properties of investigated mixture was done in a vicinity of an isotropic to a nematic phase transition. The investigated mixture is characterized by a large dielectric pretransitional effect. Under an electric field in the isotropic phase, a paranematic phase with a strong DC-modulation of electric permittivity was observed. Moreover, an unexpected increase of electric permittivity was observed exactly at clearing temperature. This behaviour was confirmed by an electro-optical observation. Relaxation processes at the phase transition are discussed and their parameters for pure compounds and the bicomponent mixture were calculated and analyzed. All experimental results are compared with observations obtained for the pure 5CB compound as a reference.

First author: Burnin, A, Direct growth by arc discharge and computational study of zinc sulfide nanotubes, JOURNAL OF MATERIALS SCIENCE, 51, 9716, (2016)
Abstract: In this work, we report the first evidence of the direct growth of zinc sulfide nanotubes in an electric arc discharge. The synthesized material was characterized using transmission electron microscopy and energy dispersive X-ray spectroscopy. In addition to the experimental effort, the morphology of the capped nanotube was studied computationally at the PW91/DZ level of theory and compared to that of the material obtained experimentally.

First author: Ganji, MD, A comparative study of structural and electronic properties of formaldehyde molecule on monolayer honeycomb structures based on vdW-DF prospective, APPLIED SURFACE SCIENCE, 384, 175, (2016)
Abstract: In order to develop the potential applications of monolayer sheets as gas sensors, the adsorption of formaldehyde (H2CO) molecule on graphene, hexagonal silicon carbide (h-SiC) as well as hexagonal aluminum nitride (h-AlN) monolayer sheets have been investigated. In this work we have used the so-called van der Waals density functional (vdW-DF) method. It was found that H2CO molecule adsorption on h-AlN nanosheet had relatively higher adsorption energy and shorter binding distance and finally much more reactive in the adsorption of H2CO compared with the h-SiC and graphene sheets. The density of states (DOS) was calculated and the results show that the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap of h-AlN and h-SiC sheets is significantly reduced upon the H2CO adsorption compared to the graphene which leads to an enhancement in the electrical conductivity of respective systems. We have evaluated these findings by well-known Mulliken as well as Hirshfeld and Voronoi charges analyses for aforementioned systems. The purpose of this work is to achieve deep insights into the influence of H2CO molecule on the electronic properties of h-AlN and h-SiC monolayer sheets, and how these effects could be used to design more sensitive gas sensing devices. Based on the DFT calculation results, the h-AlN and also h-h-SiC sheets are anticipated to be potential novel sensor for detecting the presence of H2CO toxic gas.

First author: Pastore, M, Interfacial charge separation and photovoltaic efficiency in Fe(II)-carbene sensitized solar cells, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 28069, (2016)
Abstract: The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(II)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(II)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(II)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

First author: Sharma, B, Bisboronic Acids for Selective, Physiologically Relevant Direct Glucose Sensing with Surface-Enhanced Raman Spectroscopy, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 13952, (2016)
Abstract: This paper demonstrates the direct sensing of glucose at physiologically relevant concentrations with surface-enhanced Raman spectroscopy (SERS) on gold film-over-nanosphere (AuFON) substrates functionalized with bisboronic acid receptors. The combination of selectivity in the bisboronic acid receptor and spectral resolution in the SERS data allow the sensors to resolve glucose in high backgrounds of fructose and, in combination with multivariate statistical analysis, detect glucose accurately in the 1-10 mM range. Computational modeling supports assignments of the normal modes and vibrational frequencies for the monoboronic acid base of our bisboronic acids, glucose and fructose. These results are promising for the use of bisboronic acids as receptors in SERS-based in vivo glucose monitoring sensors.

First author: Robinson, TP, On the Ambiphilic Reactivity of Geometrically Constrained Phosphorus(III) and Arsenic(III) Compounds: Insights into Their Interaction with Ionic Substrates, CHEMISTRY-A EUROPEAN JOURNAL, 22, 15712, (2016)
Abstract: The ambiphilic nature of geometrically constrained Group15 complexes bearing the N,N-bis(3,5-di-tert-butyl-2-phenolate)amide pincer ligand (ONO3-) is explored. Despite their differing reactivity towards nucleophilic substrates with polarised element-hydrogen bonds (e.g., NH3), both the phosphorus(III), P(ONO) (1a), and arsenic(III), As(ONO) (1b), compounds exhibit similar reactivity towards charged nucleophiles and electrophiles. Reactions of 1a and 1b with KOtBu or KNPh2 afford anionic complexes in which the nucleophilic anion associates with the pnictogen centre ([(tBuO)Pn(ONO)](-) (Pn=P (2a), As (2b)) and [(Ph2N)Pn(ONO)](-) (Pn=P (3a), As (3b)). Compound 2a can subsequently be reacted with a proton source or benzylbromide to afford the phosphorus(V) compounds (tBuO)HP(ONO) (4a) and (tBuO)BzP(ONO) (5a), respectively, whereas analogous arsenic(V) compounds are inaccessible. Electrophilic substrates, such as HOTf and MeOTf, preferentially associate with the nitrogen atom of the ligand backbone of both 1a and 1b, giving rise to cationic species that can be rationalised as either ammonium salts or as amine-stabilised phosphenium or arsenium complexes ([Pn{ON(H)O}](+) (Pn=P (6a), As (6b)) and [Pn{ON(Me)O}](+) (Pn=P (7a), As (7b)). Reaction of 1a with an acid bearing a nucleophilic counteranion (such as HCl) gives rise to a phosphorus(V) compound HPCl(ONO) (8a), whereas the analogous reaction with 1b results in the addition of HCl across one of the As-O bonds to afford ClAs{(H)ONO} (8b). Functionalisation at both the pnictogen centre and the ligand backbone is also possible by reaction of 7a/7b with KOtBu, which affords the neutral species (tBuO)Pn{ON(Me)O} (Pn=P (9a), As (9b)). The ambiphilic reactivity of these geometrically constrained complexes allows some insight into the mechanism of reactivity of 1a towards small molecules, such as ammonia and water.

First author: Mondal, T, Exploring the Oxidative-Addition Pathways of Phenyl Chloride in the Presence of Pd-II Abnormal N-Heterocyclic Carbene Complexes: A DFT Study, CHEMISTRY-A EUROPEAN JOURNAL, 22, 15778, (2016)
Abstract: DFT calculations were performed to elucidate the oxidative addition mechanism of the dimeric palladium(II) abnormal N-heterocyclic carbene complex 2 in the presence of phenyl chloride and NaOMe base under the framework of a Suzuki-Miyaura cross-coupling reaction. Pre-catalyst 2 undergoes facile, NaOMe-assisted dissociation, which led to monomeric palladium(II) species 5, 6, and 7, each of them independently capable of initiating oxidative addition reactions with PhCl. Thereafter, three different mechanistic routes, path a, path b, and path c, which originate from the catalytic species 5, 7, and 6, were calculated at M06-L-D3(SMD)/LANL2TZ(f)(Pd)/6-311++G**//M06-L/LANL2DZ(Pd)/6-31+G* level of theory. All studied routes suggested the rather uncommon Pd-II/Pd-IV oxidative addition mechanism to be favourable under the ambient reaction conditions. Although the Pd-0/Pd-II routes are generally facile, the final reductive elimination step from the catalytic complexes were energetically formidable. The Pd-II/Pd-IV activation barriers were calculated to be 11.3, 9.0, 26.7kcalmol(-1) (G(L)(S-D3)) more favourable than the Pd-II/Pd-0 reductive elimination routes for path a, path b, and path c, respectively. Out of all the studied pathways, path a was the most feasible as it comprised of a Pd-II/Pd-IV activation barrier of 24.5kcalmol(-1) (G(L)(S-D3)). To further elucidate the origin of transition-state barriers, EDA calculations were performed for some key saddle points populating the energy profiles.

First author: Francisco, H, Charge and Geometrical Effects on the Catalytic N2O Reduction by Rh-6(-) and Rh-6(+) Clusters, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 23648, (2016)
Abstract: The catalytic conversion of nitrous oxide (N2O) is of crucial environmental relevance because this chemical compound is a greenhouse gas with an important contribution to climate change, even larger than CO2 depleting the ozone layer. Recently, reduction of N2O catalyzed by rhodium subnanoclusters has been the subject of intensive research, both experimental and theoretical, finding dependencies of reaction rate on the size and geometry and electronic structure of the cluster. In this work, the catalytic reduction mechanism of N2O by Rh-6(-) and Rh-6(+) ionic clusters has been studied by means of density functional theory calculations within the zero order-regular approximation (ZORA), which explicitly includes relativistic effects. The N2O + Rh-6(-) and N2O + Rh-6(+) reaction pathways were approached starting from a comprehensive search of different stable adsorption modes; transition states were determined as well. We have obtained that the Rh-6(-) anions present the lowest activation barriers without spin selectivity. The N2O reduction pathway on the Rh-6(-) anion was more favorable that the simple desorption channel, whereas on Rh-6(+) both channels are in competition, as was experimentally observed. The N2O reduction on Rh-6(-) and Rh-6(+) is sensitive to the charge; it seems to be independent of geometry.

First author: Ferreira, H, Electronic properties of Fe charge transfer complexes – A combined experimental and theoretical approach, ELECTROCHIMICA ACTA, 216, 339, (2016)
Abstract: Dye-sensitized solar cell technology holds huge potential in renewable electricity generation of the future. Due to demand urgency, ways need to be explored to reduce research time and cost. Against this background, quantum computational chemistry is illustrated to be a reliable tool at the onset of studies in this field, simulating charge transfer, spectral (solar energy absorbed) and electrochemical (ease by which electrons may be liberated) tuning of related photo-responsive dyes. Comparative experimental and theoretical DFT studies were done under similar conditions, involving an extended series of electrochemically altered phenanthrolines, bipyridyl and terpyridyl complexes of FeII. Fe-II/III oxidation waves vary from 0.363 V for tris(3,6-dimethoxybipyridyl)Fe-II to 0.894 V (versus Fc/Fc(+)) for the 5-nitrophenanthroline complex. Theoretical DFT computed ionization potentials in the bipyridyl sub-series achieved an almost 100% linear correlation with experimental electrochemical oxidation potentials, while the phenanthroline sub-series gave R-2 = 0.95. Apart from the terpyridyl complex which accorded an almost perfect match, in general, TDDFT oscillators were computed at slightly lower energies than what was observed experimentally, while molecular HOMO and LUMO renderings reveal desired complexes with directional charge transfer propensities.

First author: Munoz-Castro, A, D-6h-Au-42 Isomer: A Golden Aromatic Toroid Involving Superatomic -Orbitals that Follow the Huckel (4n+2) rule, CHEMPHYSCHEM, 17, 3204, (2016)
Abstract: Recently, it has been shown that the superatom concept is intimately connected to relevant tools of great chemical significance, such as the Lewis structure model and the VSEPR theory, which has been employed to understand hybridized and dimeric-like molecules. This suggests a potential rational construction of superatomic clusters mimicking more complex structures. Here, we extend another well-employed concept to the superatomic clusters, to construct a novel Au-42 isomer with resemblance to cyclic aromatic molecules. It is shown that the Huckel (4n+2) rule is ready to be applied, predicting aromatic behavior latterly supported by the favorable evaluation of the induced shielding cone formation. The D(6)h isomer of Au-42 described here exhibits inherent characteristics mimicking aromatic hydrocarbon rings, displaying -superatomic orbitals and related properties. This new cluster is the first member of the superatomic clusters family to exhibit an aromatic -electron system.

First author: Adams, RD, Synthesis and Reactivity of Electronically Unsaturated Dirhenium Carbonyl Compounds Containing Bridging Gold-Carbene Groups, INORGANIC CHEMISTRY, 55, 10475, (2016)
Abstract: The electronically unsaturated compounds Re-2(CO)(8)[mu-Au(NHC)](mu-Ph), 1, and Re-2(CO)(8)[mu-Au-(NHC)](2), 2, were obtained from the reaction of Re-2(CO)(8)[mu-eta(2)-C(H)-C(H)Bu-n](mu-H) with MeAu(NHC), NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. Compound 1 was converted to the new compound Re-2(CO)(8)[mu-Au(NHC)](mu-H), 3, by reaction with H2. Addition of CO to 3 yielded the new compound Re-2(CO)(9)[Au(NHC)](mu-H), 4, which contains a terminally coordinated Au(NHC) group on one of the rhenium atoms, and the hydrido ligand was shifted to bridge the Re-Au bond. The mechanism of the formation of 4 was established by DFT computational analyses. Compound 3 also reacted with C2H2 by an addition with insertion into the Re-H bonds to yield the compound Re-2(CO)(8)[mu-Au(NHC)](mu-C2H3), 5, which contains a sigma-pi coordinated, bridging C2H3 ligand. The stereochemistry of the insertion was found to proceed preferentially with a cis- (syn-) stereochemistry. Compound 1 reacted with HCl to yield Re-2(CO)(8)[mu-Ph](mu-H), 6, and ClAu(NHC) by selective removal of the bridging Au(NHC) group. All new compounds were characterized by single-crystal X-ray diffraction analyses.

First author: Casella, G, DFT calculation of NMR delta(Cd-113) in cadmium complexes, POLYHEDRON, 117, 48, (2016)
Abstract: We have tested several DFT protocols, at the non-relativistic and relativistic ZORA (scalar and spin-orbit) levels, for the calculation of the Cd-113 chemical shifts, delta(Cd-113), for a number of cadmium complexes accounting for both different local coordination environments on the metal center, involving N, 0 and S ligands, and different geometrical arrangements. Moreover, suitable models as reference compounds for delta(Cd-113) evaluation have been set up in order to propose a complete computational approach to calculate delta(Cd-113) for cadmium complexes. Inclusion of relativistic corrections did not lead to any sensible improvement in the quality of results and, in this context, non-relativistic method, namely: B3LYP/Sadlej (Cd); 6-31g(d,p) (light atoms), showed to be the best approach to calculate delta(Cd-113) for the classes of compounds investigated.

First author: Pimachev, A, Large enhancement in photocurrent by Mn doping in CdSe/ZTO quantum dot sensitized solar cells, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 26771, (2016)
Abstract: We find a large enhancement in the efficiency of CdSe quantum dot sensitized solar cells by doping with manganese. In the presence of Mn impurities in relatively small concentrations (2.3%) the photoelectric current increases by up to 190%. The average photocurrent enhancement is about 160%. This effect cannot be explained by a light absorption mechanism because the experimental and theoretical absorption spectra demonstrate that there is no change in the absorption coefficient in the presence of the Mn impurities. To explain such a large increase in the injection current we propose a tunneling mechanism of electron injection from the quantum dot LUMO state to the Zn2SnO4 (ZTO) semiconductor photoanode. The calculated enhancement is approximately equal to 150% which is very close to the experimental average value of 160%. The relative discrepancy between the calculated and experimentally measured ratios of the IPCE currents is only 6.25%. For other mechanisms (such as electron trapping, etc.) the remaining 6.25% cannot explain the large change in the experimental IPCE. Thus we have indirectly proved that electron tunneling is the major mechanism of photocurrent enhancement. This work proposes a new approach for a significant improvement in the efficiency of quantum dot sensitized solar cells.

First author: Monti, A, A Dynamic View of Proton-Coupled Electron Transfer in Photocatalytic Water Splitting, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 23074, (2016)
Abstract: Solar-driven water splitting is a key reaction step in a photoelectrochemical cell for solar fuel production. We propose a photoanode in which a TiO2 substrate is functionalized with a supramolecular complex consisting of a fully organic naphthalene-diimide (NDI) dye covalently bound to a mononuclear Ru-based water oxidation catalyst. By performing ab initio Molecular Dynamics simulations, we elucidate microscopic details of water oxidation at the photoanode induced by visible light absorption. The fast photoinduced electron injection from the NDI into the semiconductor provides the driving force for the activation of the Ru catalyst. The proton coupled electron transfer nature of this catalytic reaction path is unveiled through the explicit description of the water environment, which is essential to determine the proton diffusion channel and the free energy change along the reaction. The mechanistic insight into the photocatalytic processes obtained with our computational strategy can facilitate the design of new and efficient photoelectrochemical devices.

First author: Segala, M, Evaluation of Electron Donation as a Mechanism for the Stabilisation of Chalcogenate-Protected Gold Nanoclusters, CHEMPHYSCHEM, 17, 3102, (2016)
Abstract: Models based on Au(111) face have been extensively used to describe self-assembled monolayers, as well nanoparticles and nanoclusters. However, for very small clusters (< 2 nm), the chemisorption of ligands leads to surface reconstruction, making necessary the use of a more reliable model that is able to simulate the main electronic and geometrical features of these small systems. In this work, a simple model to describe the geometries and the metal-ligand bonding in chalcogenate- protected gold nanoclusters is proposed. Three different models with Au-n(+) and [XCH3](-) (n=10, 15, 19, 22 and X=S, Se, Te) are used in this work. The obtained structures are in close agreement not only with the available crystallographic data, but also with much more expensive computational procedures, confirming that the proposed models are robust enough to describe the metal-ligand bonding. The results reveal that the Au-X distances are dependent on both the nature of the chalcogen and the coordination mode. The shortest Au-X distances are observed in the face-centred cubic mode, indicating that the central gold atom seems to play a role in determining the adsorption strength. The proposed models show unambiguously chalcogen -> cluster sigma-donation, as supported by energy decomposition analysis coupled with the natural orbitals for chemical valence and natural bond orbital analyses. In all cases, the metal-ligand interactions are characterised as being more covalent than electrostatic.

First author: Knoppe, S, Second-Order Nonlinear Optical Scattering Properties of Phosphine-Protected Au-20 Clusters, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 55, 10500, (2016)
Abstract: We report the first hyperpolarizability of the [Au-20(PP3)(4)]Cl-4 cluster (PP3: tris(2-(diphenylphosphino)ethyl)phosphine) using the Hyper-Rayleigh Scattering technique. This is the first determination of nonlinear optical properties of a phosphine-protected “superatomic” gold cluster. Weak contributions of multiphotonexcited fluorescence were observed in the spectral dispersion of the generated light upon excitation at 1300 and 1064 nm. The first hyperpolarizability of the intrinsically chiral cluster is weaker than that of thiolate-protected gold clusters of similar size and inherent chirality.

First author: Chen, CH, Zigzag Sc2C2 Carbide Cluster inside a [88]Fullerene Cage with One Heptagon, Sc2C2@C-s(hept)-C-88: A Kinetically Trapped Fullerene Formed by C-2 Insertion?, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 13030, (2016)
Abstract: A non-isolated pentagon rule metallic carbide clusterfullerene containing a heptagonal ring, Sc2C2@C-s(hept)-C-88, was isolated from the raw soot obtained by electric arc vaporization of graphite rods packed with Sc2O3 and graphite powder under a helium atmosphere. The Sc2C2@C-s(hept)-C-88 was purified by multistage high-performance liquid chromatography (HPLC), cocrystallized with Ni(octaethylporphyrin), and characterized by single-crystal X-ray diffraction. The diffraction data revealed a zigzag Sc2C2 unit inside an unprecedented C-s(hept)-C-88 carbon cage containing 13 pentagons, 32 hexagons, and 1 heptagon. Calculations suggest that the observed nonclassical fullerene could be a kinetically trapped species derived from the recently reported Sc2C2@C-2v(9)-C-86 via a direct C-2 insertion.

First author: Paschoal, D, Predicting Pt-195 NMR Chemical Shift Using New Relativistic All-Electron Basis Set, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 2360, (2016)
Abstract: Predicting NMR properties is a valuable tool to assist the experimentalists in the characterization of molecular structure. For heavy metals, such as Pt-195, only a few computational protocols are available. In the present contribution, all-electron Gaussian basis sets, suitable to calculate the Pt-195 NMR chemical shift, are presented for Pt and all elements commonly found as Pt-ligands. The new basis sets identified as NMR-DKH were partially contracted as a triple-zeta doubly polarized scheme with all coefficients obtained from a Douglas-Kroll-Hess (DKH) second-order scalar relativistic calculation. The Pt-195 chemical shift was predicted through empirical models fitted to reproduce experimental data for a set of 183 Pt(II) complexes which NMR sign ranges from -1000 to -6000 ppm. Furthermore, the models were validated using a new set of 75 Pt(II) complexes, not included in the descriptive set. The models were constructed using non-relativistic Hamiltonian at density functional theory (DFT-PBEPBE) level with NMR-DKH basis set for all atoms. For the best model, the mean absolute deviation (MAD) and the mean relative deviation (MRD) were 150 ppm and 6%, respectively, for the validation set (75 Pt-complexes) and 168 ppm (MAD) and 5% (MRD) for all 258 Pt(II) complexes. These results were comparable with relativistic DFT calculation, 200 ppm (MAD) and 6% (MRD).

First author: Borges, CHG, Copaifera duckei Oleoresin and Its Main Nonvolatile Terpenes: In Vitro Schistosomicidal Properties, CHEMISTRY & BIODIVERSITY, 13, 1348, (2016)
Abstract: In this article, the in vitro schistosomicidal effects of three Brazilian Copaifera oleoresins (C. duckei, C. langsdorffii, and C. reticulata) are reported. From these botanical sources, the oleoresin of C. duckei (OCd) demonstrated to be the most promising, displaying LC50 values of 75.8, 50.6, and 47.2 g/ml at 24, 48, and 72 h of incubation, respectively, against adult worms of Schistosoma mansoni, with a selectivity index of 10.26. Therefore, the major compounds from OCd were isolated, and the diterpene, (-)-polyalthic acid (PA), showed to be active (LC50 values of 41.7, 36.2, and 33.4 g/ml, respectively, at 24, 48, and 72 h of incubation). Moreover, OCd and PA affected the production and development of eggs, and OCd modified the functionality of the tegument of S. mansoni. Possible synergistic and/or additive effects of this balsam were also verified when a mixture of the two of its main compounds (PA and ent-labd-8(17)-en-15,18-dioic acid) in the specific proportion of 3:1 (w/w) was tested. The obtained results indicate that PA should be considered for further investigations against S. mansoni, such as, synergistic (combination with praziquantel (PZQ)) and in vivo studies. It also shows that diterpenes are an important class of natural compounds for the investigation of agents capable of fighting the parasite responsible for human schistosomiasis.

First author: Jash, B, Enantiospecific formation of a metal-mediated base pair inside a DNA duplex, INORGANICA CHIMICA ACTA, 452, 181, (2016)
Abstract: The metal-mediated base pair P-Ag(I)-P involving the bidentate ligand 1H-imidazo[4,5-f][1,10]phenanthroline (P) was investigated within a B-DNA duplex. The underlying tetrahedral complex exists as a pair of enantiomers. Interestingly, one of the isomers forms preferentially within the B-DNA context, as was shown in a combined computational and experimental approach by means of circular dichroism spectroscopy. Towards this end, the homoleptic Ag(I) complexes of 1-methyl-1H-imidazo[4,5-f][1,10]phenanthroline and both enantiomers of 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-1-yl)propane-1,2-diol were investigated outside the DNA context as well as the P-Ag(I)-P base pair within the DNA context. In this paper, we also propose a simplified nomenclature for the enantiomers of undistorted tetrahedral complexes bearing asymmetric bidentate ligands.

First author: Sebera, J, The effect of chemical modification of DNA base on binding of Hg-II and Ag-I in metal-mediated base pairs, INORGANICA CHIMICA ACTA, 452, 199, (2016)
Abstract: The Gibbs free energy of formation of metallo-base pair was calculated for the base pairs composed of T, U, F, CN, C and I nucleosides and Hg-II and Ag-I metals. The effect of particular metal and the effect of pH on relative stabilization of metallo-base pairs were studied with calculated Gibbs free energies. The stability of Hg-mediated base pairs gradually decreased owing to the F and CN chemical modification of thymine at carbon C5 and owing to the imino to imidazole change of N3 nitrogen atom linked with Hg-II. The prevalence of Ag-I-stabilization versus Hg-II-stabilization was calculated for the metallo-base pairs composed of T, U, F, CN, C and I nucleosides where nucleophilicity of N3 nitrogen atom gradually decreased. The calculated relative stabilizations of metallo-base pairs agreed qualitatively with the increase in melting temperatures measured previously for respective duplexes upon adding Hg-II and Ag-I metals (Okamoto et al., 2009). The absolute magnitude of (1)J(Hg,N) and (2)J(N,N) coupling constants across metal-mediated linkage increased owing to F and CN modification of T and further increase of magnitudes off-couplings was calculated for imino to imidazole change of metal-bound nitrogen.

First author: Goez, A, Benchmarking Electron Densities and Electrostatic Potentials of Proteins from the Three-Partition Frozen Density Embedding Method, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 4843, (2016)
Abstract: The fragment-based Three-Partition Frozen Density Embedding (3-FDE) approach [Jacob, C. R; Visscher, L. J. Chem. Phys. 2008, 128, 155102] is used to generate protein densities and electrostatic potentials, which are critically assessed in comparison to supermolecular Kohn Sham Density Functional Theory (DFT) results obtained with sophisticated exchange correlation functionals. The influence of several parameters and user choices is explored with respect to accuracy and reliability. In addition, a recently implemented combination of the 3-FDE scheme with hybrid functionals is applied in production calculations for the first time. We demonstrate that the 3-FDE method not only closely reproduces results from corresponding supermolecular calculations for routine situations (peptides/proteins in solution) but can even surpass conventional Kohn Sham DFT in accuracy for difficult cases, such as zwitterionic structures in vacuo. This is due to the fact that the fragmentation inherently limits the overdelocalitation caused by the self-interaction emir in common DFT apprwtimations. The method is thus not only able to reduce the computational effort for the description of large biological entities but also can strongly reduce the artifacts brought about by the SIE.

First author: Yousef, TA, Semiempirical studies, spectral analysis, in vitro antibacterial and DNA degradation studies of heterocyclic thiosemicarbazone ligand and its metal complexes, JOURNAL OF MOLECULAR LIQUIDS, 222, 762, (2016)
Abstract: We have synthesized (Z)-1-(3,3-dimethy1-5-oxocyclohexylidene)-3-(pyridin-2-yl)thiourea (H2DEPT) and their Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), Hg(II), Zn(II) and U(VI)O-2 complexes. They were characterized using FT-IR, UV-vis H-1 NMR, and C-13 NMR, magnetic and thermal technique. To interpret the experimental data, theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, MM, Zindo/1, MM+ and PM3, methods. The combined use of experiments and computations allowed a firm assignment of the majority of observed bands for the compound. The calculated stretching frequencies have been found to be in good agreement with the experimental frequencies. The electronic and charge transfer properties have been explained on the basis of highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs) and density of states (DOS). The theoretical results showed good agreement with the experimental values. Furthermore, the kinetic and thermodynamic parameters for the different decomposition steps were calculated using the Coats-Redfern and Horowitz-Metzger methods. Finally, the antibacterial results suggest that Cr(III), Mn(II), Cd(II), Fe(III), Ni(II), Zn(II) metal complexes showed potential antibacterial activity. The biochemical studies showed that, all complexes have powerful and complete degradation effect on DNA except H2DEPT and its Zn(II) complex. For the foremost majority of cases the activity of the ligand is greatly enhanced by the presence of a metal ion. Thus presented results may be useful in design new more active or specific structures.

First author: De Waele, V, Unraveling the Key Features of the Reactive State of Decatungstate Anion in Hydrogen Atom Transfer (HAT) Photocatalysis, ACS CATALYSIS, 6, 7174, (2016)
Abstract: The decatungstate anion [W10O32](4-) is a widely used photocatalyst for promoting hydrogen atom transfer (HAT) reactions. The mechanism implicated in the activation of organic substrates, however, still needs to be clarified and has been claimed to involve an unknown relaxed excited state of triplet multiplicity, tagged wO. A subpicosecond investigation allowed us to follow early events leading to the chemically reactive species. A hot singlet excited state (S-1(HOT)) has been individuated through pump probe experiments, yielding SI by ultrafast decay (<1 ps). The reactive species wO arises from S, in competition with decay to S0 (efficiency ca. 0.5) and has been detected spectroscopically by flash photolysis experiments, with peculiar absorption bands in the near-UV (370 nm) and visible (600-800 nm) regions. TDDFT calculations demonstrated that excitation to S-1 occurs through a ligand to metal charge transfer (LMCT) transition, involving a displacement of electron density from dicoordinated (bridging) oxygen to tungsten atoms. Population of wO ensues and involves a reorganization of the singly occupied orbital centered on oxygen (not tungsten) atoms. As a result, monocoordinated 0 centers acquire a partial radical character that well explains the known chemistry, essentially hydrogen atom transfer (HAT), and highlights the similarity with n pi* carbonyl triplets. This rationalization may help in devising other photocatalysts able to promote HAT processes from unactivated precursors.

First author: Luo, YH, Assembly of a high stable POM-based Cu(I) coordination polymer with visible-light-driven photocatalytic properties, INORGANIC CHEMISTRY COMMUNICATIONS, 72, 13, (2016)
Abstract: A new coordination polymer (CP), [(PW12O40)(2)Cu-6(I)(trz)6]center dot H2O (1), has been prepared by hydrothermal method. Six Cu(I) ions are bridged by six trz molecules and six surface oxygen atoms of PW12 to generate a wheel-type Cu-6(I) cluster, and each Cu-6(I) cluster was capped with two PW12 anions to form a dumbbell-like second building block (SBB). 1 can remain intact in solution with pH range from 1 to 10, boiling water and boiling organic solvents, which shows the high heat stability, acid and alkali resistance. It also shows efficient visible-light-driven photocatalytic activities in the degradation of organic dyes.

First author: Liu, XR, Theoretical Investigation of Donor-Acceptor Copolymers Based on C-, Si-, and Ge-Bridged Thieno[3,2-b]dithiophene for Organic Solar Cell Applications, JOURNAL OF ELECTRONIC MATERIALS, 45, 5427, (2016)
Abstract: The aim of this work is to modify the electron-donating block in donor-acceptor (D-A) copolymers to improve their electronic and photophysical properties for organic solar cell(OSC) applications. Based on the reported polymer PCPDTTTTz (Pa1), which includes electron-rich cyclopenta[2,1-b:3,4-b’]dithiophene (CPDT), electron-withdrawing tetrazine, and bridge thiophene, we substituted CPDT with electron-rich dithienocyclopentadithiophene, dithienosiloledithiophene, and dithienogermolodithiophene to design three D-A copolymers (Pa2 to Pa4). The calculation results indicate that Pa3 and Pa4 show lower highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels and larger open-circuit voltage (V-oc) than Pa1. Polymers Pa2 to Pa4 exhibit better performance with stronger and wider optical absorption and good hole transport properties in comparison with Pa1. The predicted power conversion efficiencies for the designed polymers Pa2 to Pa4 in OSC applications are similar to 5.7%, similar to 5.9%, and 6.0%, respectively. These results clearly indicate that modifying the electron-donating block in D-A copolymers can effectively improve their electronic and photophysical properties and OSC performance. The designed polymers Pa2 to Pa4 may be promising donor candidates for OSC applications.

First author: Li, JB, Stability of functionalized corannulene cations [R-C20H10](+): An influence of the nature of R-Group, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 2266, (2016)
Abstract: The first comprehensive theoretical study of stability of hub-functionalized corannulene cations [R-C20H10](+) as the function of the nature of R-group was accomplished. The initial set of linear alkyl R-group of different length (R=(CH2)(n)CH3, n=0-9) was augmented by groups which form stable organic cations, such as tert-butyl, isopropyl, allyl, and phenyl. Investigation of relative stability (with bonding energy as the measure) was accompanied by detailed study of changes in aromaticity using a large set of descriptors, as well as by the evaluation of energetics of possible migration of R-group from the hub-site to the spoke-position. Decrease in stability of functionalized corannulene cations with lengthening of R-group and/or replacing it with branched alkyl group was found to be the general trend. At the same time, -conjugated groups such as allyl or phenyl ones, stabilize the system. All methods/approaches applied unambiguously indicated that the actual stability of the hub-functionalized corannulene cations is indeed a multi faceted phenomenon. Important contributions come from different interplay between attractive (E(orb)vs. E-elstat) and repulsive (E-Pauli) components of the bonding, from changes in aromatic behavior of rings in polyaromatic fragment, and from activation barrier for the process of migration of R-group.

First author: Gro, L, GenLocDip: A Generalized Program to Calculate and Visualize Local Electric Dipole Moments, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 2324, (2016)
Abstract: Local dipole moments (i.e., dipole moments of atomic or molecular subsystems) are essential for understanding various phenomena in nanoscience, such as solvent effects on the conductance of single molecules in break junctions or the interaction between the tip and the adsorbate in atomic force microscopy. We introduce GenLocDip, a program for calculating and visualizing local dipole moments of molecular subsystems. GenLocDip currently uses the Atoms-In-Molecules (AIM) partitioning scheme and is interfaced to various AIM programs. This enables postprocessing of a variety of electronic structure output formats including cube and wavefunction files, and, in general, output from any other code capable of writing the electron density on a three-dimensional grid. It uses a modified version of Bader’s and Laidig’s approach for achieving origin-independence of local dipoles by referring to internal reference points which can (but do not need to be) bond critical points (BCPs). Furthermore, the code allows the export of critical points and local dipole moments into a POVray readable input format. It is particularly designed for fragments of large systems, for which no BCPs have been calculated for computational efficiency reasons, because large interfragment distances prevent their identification, or because a local partitioning scheme different from AIM was used. The program requires only minimal user input and is written in the Fortran90 programming language. To demonstrate the capabilities of the program, examples are given for covalently and non-covalently bound systems, in particular molecular adsorbates.

First author: Fernando, A, Theoretical Investigation of Water Oxidation Catalysis by a Model Manganese Cubane Complex, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 21148, (2016)
Abstract: Manganese is selected by nature for the water oxidation process. In this study, we use an in silico approach to study a manganese cubane complex Mn4O4(H2O)(x)(OH)(y) x = 4-8, y = 8-4 with water-derived ligands. We investigate oxidation state configurations ranging from all Mn(IV) to all Mn(III) states. Understanding these simplest architectures for water splitting is essential for the bottom up design of commercially viable electrocatalysts. Both mu(3)-oxo and mu(3)-hydroxo versions of the catalysts were examined; mu(3)-hydroxo versions are generally higher in energy in all the oxidation state configurations except for the Mn-4(III III III III) state (this rearranges to a Mn-4(II III III IV) state) and the Mn-4(III III III IV) state (this rearranges to a Mn-4(II III IV IV) state). Out of all the oxidation state configurations we studied, we observed that Mn-4(IV IV IV IV), Mn-4(III IV IV IV), and Mn-4(III III IV V) configurations are thermodynamically viable for water oxidation. All three reaction pathways proceed via nucleophilic attack from a solvent water molecule to the manganese oxo species. The highest thermodynamic energy step corresponds to the formation of the manganese oxo species, which is a significant microscopic property that reoccurred in all these reaction pathways. This can be an important descriptor for selecting efficient water splitting catalysts.

First author: Walter, MR, Synthesis of Co-II-NO- Complexes and Their Reactivity as a Source of Nitroxyl, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 12459, (2016)
Abstract: Metal-nitroxyl (M-HNO/M-NO-) coordination units are found in denitrification enzymes of the global nitrogen cycle, and free HNO exhibits pharmacological properties related to cardiovascular physiology that are distinct from nitric oxide (NO). To elucidate the properties that control the binding and release of coordinated nitroxyl or its anion at these biological metal sites, we synthesized {CoNO}(8) (1, 2) and {CoNO}(9) (3, 4) complexes that contain diimine-dipyrrolide supporting ligands. Experimental (NMR, IR, MS, EPR, XAS, XRD) and computational data (DFT) support an oxidation state assignment for 3 and 4 of high spin Co-II (S-Co = 3/2) coordinated to (NO-)-N-3 (S-NO = 1) for S-tot = 1/2. As suggested by DFT, upon protonation, a spin transition occurs to generate a putative low spin Co-II-(HNO)-H-1 (S-Co = S-tot = 1/2); the Co-NO bond is similar to 0.2 angstrom longer, more labile, and facilitates the release of HNO. This property was confirmed experimentally through the detection and quantification of N2O (similar to 70% yield), a byproduct of the established HNO self-reaction (2HNO -> N2O + H2O). Additionally, 3 and 4 function as HNO donors in aqueous media at pH 7.4 and react with known HNO targets, such as a water-soluble Mn-III-porphyrin ([Mn-III(TPPS)](3-); TPPS = meso-tetrakis(4-sulfonatophenyl)porphyrinate) and ferric myoglobin (metMb) to quantitatively yield [Mn(TPPS)(NO)](4-) and MbNO, respectively.

First author: Mangione, G, Electronic structure of CuTPP and CuTPP(F) complexes: a combined experimental and theoretical study II, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 24890, (2016)
Abstract: The unoccupied electronic structure of thick films of tetraphenylporphyrin and tetrakis(pentafluorophenyl)porphyrin Cu(II) complexes (hereafter, CuTPP and CuTPP(F)) deposited on Au(111) has been studied by combining the outcomes of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with those of spin-unrestricted time-dependent density functional (TD-DFT) calculations carried out either within the scalar relativistic zeroth order regular approximation (ZORA) framework (C, N and F K-edges) or by using the Tamm-Dancoff approximation coupled to ZORA and including spin-orbit effects (Cu L-2,L-3-edges). Similarly to the modelling of NEXAFS outcomes pertaining to other Cu(II) complexes, the agreement between theory and experiment is more than satisfactory, thus confirming the open-shell TD-DFT to be a useful tool to look into NEXAFS results pertinent to Cu(II) compounds. The combined effect of metalation and phenyl (Ph) fluorine decoration is found to favour an extensive mixing between (Ph)sigma* and pristine porphyrin macrocyle (pmc) (pmc)pi* virtual levels. The lowest lying excitation in the C and N K-edge spectra of both CuTPP and CuTPP(F) is associated with a ligand-to-metal-charge-transfer transition, unambiguously revealed in the N-CuTPP K-edge spectral pattern. Moreover, the comparison with literature data pertaining to the modelling of the L-Cu(II)(2,3) features in the phthalocyanine-Cu(II) (CuPc) complex provided further insights into how metal-to-ligand-charge-transfer transitions associated with excitations from 2p(Cu(II)) AOs to low-lying, ligand-based pi* MOs may contribute to the Cu(II) L-2,L-3-edge intensity and thus weaken its believed relationship with the Cu(II)-ligand symmetry-restricted covalency. Despite the coordinative pocket of CuTPP/CuTPP(F) mirroring CuPc, the ligand-field strength exerted by the phthalocyanine ligand on the Cu(II) centre is experimentally found and theoretically confirmed to be slightly stronger than that experienced by Cu in CuTPP and CuTPP(F). On the whole, the obtained results complement those published in the near past by the same group on the occupied and empty states of the H2TPP and H2TPP(F) free ligands as well as on the occupied states of both CuTPP and CuTPP(F), thus providing the final piece to get a thorough description of electronic perturbations associated with the metalation and the Ph halogen decoration of H2TPP.

First author: Zhao, RD, A new insight into pi-pi stacking involving remarkable orbital interactions, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 25452, (2016)
Abstract: For more than half a century, the phenomenon of pi-pi stacking has attracted much attention in several research fronts including materials science, chemical synthesis, and even drug design. Despite intense theoretical and experimental exploration, no unified description of the factors contributing to p-p stacking interactions and their weak bonding process has been proposed. In this work, based on calculations of the simplest prototype of pi-pi stacking, namely the benzene sandwich dimer (together with benzene-phenol, toluene and benzonitrile) using the density functional theory with dispersion correction, previously rarely studied intermolecular orbital interaction is discussed in detail and shown to involve considerable hybridizations of some of the orbitals which make a large contribution to the total interaction energy. We now propose a unified model for the often nebulous pi-pi stacking process and its analogs: firstly when the two monomers are too far apart, the dispersion effect will play a dominant role in bringing them together, but when they are too close, Pauli repulsion will force them apart. Secondly, at the equilibrium distance, electrostatic interaction, Pauli repulsion, dispersion and intermolecular orbital interaction are all pronounced, with part of the molecular orbitals of the two monomers interacting with each other to form a weak intermolecular bond.

First author: Zhou, J, Computational understanding and experimental characterization of twice-as-smart quadruplex ligands as chemical sensors of bacterial nucleotide second messengers, SCIENTIFIC REPORTS, 6, 25452, (2016)
Abstract: A twice-as-smart ligand is a small molecule that experiences a structural switch upon interaction with its target (i.e., smart ligand) that concomitantly triggers its fluorescence (i.e., smart probe). Prototypes of twice-as-smart ligands were recently developed to track and label G-quadruplexes: these higher-order nucleic acid structures originate in the assembly of four guanine(G)-rich DNA or RNA strands, whose stability is imparted by the formation and the self-assembly of G-quartets. The first prototypes of twice-as-smart quadruplex ligands were designed to exploit the self-association of quartets, being themselves synthetic G-quartets. While their quadruplex recognition capability has been thoroughly documented, some doubts remain about the precise photophysical mechanism that underlies their peculiar spectroscopic properties. Here, we uncovered this mechanism via complete theoretical calculations. Collected information was then used to develop a novel application of twice-as-smart ligands, as efficient chemical sensors of bacterial signaling pathways via the fluorescent detection of naturally occurring extracellular quadruplexes formed by cyclic dimeric guanosine monophosphate (c-di-GMP).

First author: Lethiec, CM, Dependence of Plasmon Energies on the Acoustic Normal Modes of Ag-n (n=20, 84, and 120) Clusters, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 20572, (2016)
Abstract: The vibrational and optical properties of Ag-20, Ag-84, and Ag-120 closed-shell clusters are investigated through a combination of continuum mechanics and density functional theory approaches. The acoustic vibrational frequencies associated with these tetrahedral silver clusters are found to be in close correspondence for the two theories, demonstrating the ability of finite element calculations to reproduce first-principles computational results, even down to few-atom structures. TDDFT calculations of the absorption spectra of these clusters indicate a strong plasmon-like mode both for equilibrium structures of the clusters and for structures where the acoustic breathing mode is excited by amounts that are accessible to ultrafast experiments. The plasmon-like mode energy is found to vary linearly with the acoustic mode displacement (for small displacements), with a slope that increases with increasing cluster size. For larger clusters, the TDDFT slope is larger than the FDTD, slope, which indicates that there are systematic errors in the continuum theory result for small particles. We also examine the ground and plasmon excited potential energy curves and show that the displacement in equilibrium geometry between these curves is too small to give breathing mode excitation that is consistent with observations based on vertical excitation alone. This suggests that breathing mode excitation arises during internal conversion after the initial photoexcitation.

First author: Chulhai, DV, Simulating Ensemble-Averaged Surface-Enhanced Raman Scattering, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 20833, (2016)
Abstract: The ability to simulate surface-enhanced Raman scattering (SERS) is a vital tool in elucidating the chemistry of molecules near the vicinity of plasmonic metal nanoparticles. However, typical methods do not include the dynamics of the molecule(s) of interest and are often limited to a single or few molecules. In this work, we combine molecular dynamics simulations with the dressed-tensor formalism to simulate the SERS spectra-of Ag nanoparticles coated with a full monolayer of pyridine molecules. This method allows: us to simulate the ensemble-averaged SERS spectra of more realistic large scale systems, while accounting for the organization of molecules in the hotspots. Through these simulations, we find that the preferential, binding location and orientation of the molecules,: the choice of electrodynamics Method, and the inclusion of field gradient effects influence both the enhancement distribution and the spectral signatures. We also show that both the translational and rotational motions of a pyridine molecule near a nanoparticle junction may be effectively tracked through its SERS spectrum.

First author: Turley, HK, Probing Two-Photon Molecular Properties with Surface-Enhanced Hyper-Raman Scattering: A Combined Experimental and Theoretical Study of Crystal Violet, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 20936, (2016)
Abstract: The surface-enhanced hyper-Raman scattering spectra of crystal violet are experimentally measured and theoretically calculated for excitation energies spanning the two lowest-lying electronic states (12,700-27,400 cm(-1)). The theory and experiment are in qualitative agreement over the measured energy range, indicating that first-principles calculations capture many of the complex resonance contributions in this prototypical octupolar system. The discrepancies between theory and experiment are investigated by comparing spectra obtained in different local environments as well as from higher-order surface-enhanced spectroscopies. A comparison between relative surface-enhanced hyper-Raman scattering band ratios plotted as a function of excitation wavelength and crystal violet’s absorption spectra elucidates correlations between groups of vibrations and the excited electronic states. Our results suggest that the spectral features across the range of resonance excitation energies (similar to 15,500-27,400 cm(-1)) are dominated by strong A-term scattering.

First author: Mondal, S, Why CpAl-Cr(CO)(5) is linear while CpIn-Cr(CO)(5) is not? Understanding the structure and bonding of the CpE-Cr(CO)(5) (E = Group 13 element) complexes, THEORETICAL CHEMISTRY ACCOUNTS, 135, 20936, (2016)
Abstract: Density functional theory computations at the BP86-D3/def2-TZVP level are reported for the CpE-Cr(CO)(5) complexes (E = Group 13 element). In principle, we have answered two important facts: first the nature and trend of the E-Cr bonding along B to Tl complexes; second, the deviation of Cp (centroid)-E-Cr angle in In and Tl from linearity. The bonding situation in the complexes is examined via the natural bond orbital, adaptive natural density partitioning, and energy decomposition analysis schemes. Our results reveal that the E-Cr bonding in the lighter compounds is mainly ionic, while this bonding in the In and Tl complexes is dominated by an orbitalic contribution. We also clarify the origin of deviation of Cp (centroid)-E-Cr angle for the In and Tl complexes using simple molecular orbital arguments and find that the repulsive intermolecular contacts in the crystals are not the real source of this deviation as was claimed.

First author: Hjertenaes, E, Potential Energy Surfaces and Charge Transfer of PAH-Sodium-PAH Complexes, CHEMPHYSCHEM, 17, 2908, (2016)
Abstract: To further understanding of the role of sodium in carbon cathode degradation in Hall-Heroult cells, potential-energy surfaces and charge-transfer curves are presented for finite-size complexes of sodium intercalated between various polycyclic aromatic hydrocarbons. Calculations for lithium and potassium are included to highlight the disparate intercalation behaviour of the alkali metals in graphite intercalation compounds. Static energy barriers from DFT are used to compute macroscopic diffusion coefficients according to transition-state theory. Comparing the calculated diffusion coefficient to experimental values from the literature sheds light on the role of lattice diffusion of sodium-graphite intercalation compounds in sodium intrusion in graphitic carbon cathodes.

First author: Stankovic, B, Substituted naphthalenes: Stability, conformational flexibility and description of bonding based on ETS-NOCV method, CHEMICAL PHYSICS LETTERS, 661, 136, (2016)
Abstract: For all dimethylnaphthalenes (DMNs) the transition from a planar ring conformation to a nonplanar one results in energy increase in the range 1.7-2.4 kcal/mol. There is a linear relationship between averaged rigidity constant and relative energy of DMNs. The relative stability of DMNs does not follow the aromatic stabilization based on NICS values. The ETS-NOCV analysis shows that more efficient bonding in the pi-electron system is the origin of enhanced stability in laterally substituted (CH3, Cl and NO2) naphthalenes. The results for C-aryl-CH3 system indicate more steric repulsion in going from 2,7-DMN to 1,8-DMN following the increase of relative energies.

First author: Wang, PP, Role of the electronic excited-state hydrogen bonding in the nitro explosives detection by [Zn-2(oba)(2)(bpy)], CHEMICAL PHYSICS LETTERS, 661, 257, (2016)
Abstract: This paper investigates the luminescent properties of luminescent metal-organic framework (LMOF) [Zn-2(oba)(2)(bpy)], and its selectivity for the detection of nitro-explosives via fluorescence quenching, using the density functional and time-dependent density functional theories. The luminescent mechanism of the LMOF follows the electron transfer from ligand to ZnO quantum dot. The hydrogen bondings formed between LMOF and electron-withdrawing nitro-explosives as well as electron-donating aromatic compounds have different influences on the luminescent mechanism of the LMOF. The hydrogen bonding in the excited state was investigated to display the relationship between hydrogen bonding and fluorescence.

First author: Jiang, B, The Anion Effect on Li+ Ion Coordination Structure in Ethylene Carbonate Solutions, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 3554, (2016)
Abstract: Rechargeable lithium ion batteries are an attractive alternative power source for a wide variety of applications. To optimize their performances, a complete description of the solvation properties of the ion in the electrolyte is crucial. A comprehensive understanding at the nanoscale of the solvation structure of lithium ions in nonaqueous carbonate electrolytes is, however, still unclear. We have measured by femtosecond vibrational spectroscopy the orientational correlation time of the CO stretching mode of Li+-bound and Li+ unbound ethylene carbonate molecules, in LiBF4, LiPF6, and LiClO4 ethylene carbonate solutions with different concentrations. Surprisingly, we have found that the coordination number of ethylene carbonate in the first solvation shell of Li+ is only two, in all solutions with concentrations higher than 0.5 M. Density functional theory calculations indicate that the presence of anions in the first coordination shell modifies the generally accepted tetrahedral structure of the complex, allowing only two EC molecules to coordinate to Li+ directly. Our results demonstrate for the first time, to the best of our knowledge, the anion influence on the overall structure of the first solvation shell of the Li+ ion. The formation of such a cation/solvent/anion complex provides a rational explanation for the ionic conductivity drop of lithium/carbonate electrolyte solutions at high concentrations.

First author: Lv, JY, Thiocyanate-Free Ruthenium(II) Tetrabenzoporphyrin Sensitizers for Photoelectrochemical Cell: A DFT/TD-DFT Probe for Stability of Axial Donor Ligands, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 1342, (2016)
Abstract: Although previously studied [(HOOC)(4)(TBPor) Ru(NCS)(2)](2-) (A; TBPor=tetrabenzoporphrin) avoided the intrinsic p-stacking aggregation of planar metallophorphryins via incorporating two axial ligands, these isothiocyanato groups are believed to be the weakest part of the sensitizer while operating in dye-sensitized solar cells (DSSCs). In this work, a series of thiocyanate-free ruthenium porphyrin complexes featuring with phenyl/substituted-phenyl axial groups, [(HOOC)(4)(TBPor) Ru(L’) (2)](2-) (L’ – Ph (1), PhF2 (2), PhCl2 (3), PhBr2 (4), and PhI2 (5)), have been examined using density functional theory (DFT) and time-dependent DFT (TD-DFT). Both analyses of electronic structures and calculations of interaction energies demonstrate that the Ru-L’ interaction in 1-5 is significantly enhanced relative to the Ru-NCS in A, which will raise chemical stability of the former in DSSCs. Single-electron oxidation mechanism has been proposed. Oxidation potentials (E’) are increased by 0.2-0.6 V when changing axial groups from NCS to Ph/PhX2. The spin-orbit coupling (SOC) relativistic effects can be negligible in computing E-0 values. TD-DFT calculations show that 1-5 have more intense Q band in the visible region than A does. Taken together, high chemical stability, suitable oxidation potential and expanding absorption spectra would allow for potential applications of the thiocyanate-free sensitizers in DSSCs.

First author: Zhou, YC, Phonon-electron coupling and tunneling effect on charge transport in organic semi-conductor crystals of C-n-BTBT, JOURNAL OF CHEMICAL PHYSICS, 145, 1342, (2016)
Abstract: C-n-[1] benzothieno[3,2-b][1]-benzothiophene (BTBT) crystals show very high hole mobilities in experiments. These high mobilities are beyond existing theory prediction. Here, we employed different quantum chemistry methods to investigate charge transfer in C-n-BTBT crystals and tried to find out the reasons for the underestimation in the theory. It was found that the hopping rate estimated by the Fermi Golden Rule is higher than that of the Marcus theory due to the high temperature approximation and failure at the classic limit. More importantly, molecular dynamics simulations revealed that the phonon induced fluctuation of electronic transfer integral is much larger than the average of the electronic transfer integral itself. Mobilities become higher if simulations implement the phonon-electron coupling. This conclusion indicates that the phonon-electron coupling promotes charge transfer in organic semi-conductors at room temperature.

First author: Mauck, CM, Singlet Fission via an Excimer-Like Intermediate in 3,6-Bis(thiophen-2-yl)diketopyrrolopyrrole Derivatives, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 11749, (2016)
Abstract: Singlet fission (SF) in polycrystalline thin films of four 3,6-bis(thiophen-2-yl) diketopyrrolopyrrole (TDPP) chromophores with methyl (Me), n-hexyl (C6), triethylene glycol (TEG), and 2-ethylhexyl (EH) substituents at the 2,5-positions is found to involve an intermediate excimer-like state. The four different substituents yield four distinct intermolecular packing geometries, resulting in variable intermolecular charge transfer (CT) interactions in the solid. SF from the excimer state of Me, C6, TEG, and EH takes place in tau(SF) = 22, 336, 195, and 1200 ps, respectively, to give triplet yields of 200%, 110%, 110%, and 70%, respectively. The transient spectra of the excimer-like state and its energetic proximity to the lowest excited singlet state in these derivatives suggests that this state may be the multiexciton (1)(T1T1) state that precedes formation of the uncorrelated triplet excitons. The excimer decay rates correlate well with the SF efficiencies and the degree of intermolecular donor-acceptor interactions resulting from pi-stacking of the thiophene donor of one molecule with the DPP core acceptor in another molecule as observed in the crystal structures. Such interactions are found to also increase with the SF coupling energies, as calculated for each derivative. These structural and spectroscopic studies afford a better understanding of the electronic interactions that enhance SF in chromophores having strong intra- and intermolecular CT character.

First author: Arcisauskaite, V, Biradical character in the ground state of [Mn@Si-12](+): a DFT and CASPT2 study, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 24006, (2016)
Abstract: Both density functional theory and multi-configurational ab initio (CASPT2) calculations are used to explore the potential energy surface of the hexagonal prismatic cluster [Mn@Si-12](+). Unlike isoelectronic Cr@Si-12, the ground state is a biradical, with triplet and open-shell singlet states lying very close in energy. The results are discussed in the context of recent experimental studies using infra-red multiple photon dissociation spectroscopy and X-ray MCD spectroscopy.

First author: Huerta, E, Molecular Basis for the Recognition of Higher Fullerenes into Ureidopyrimidinone-Cyclotriveratrylene Self-Assembled Capsules, CHEMISTRY-A EUROPEAN JOURNAL, 22, 13496, (2016)
Abstract: Fullerenes C-60, C-70, and C-84 may be readily encaged within a hydrogen-bonded dimeric capsule, based on two concave cyclotriveratrylene (CTV) scaffolds, each containing three self-complementary 2-ureido-4-[1H]-pyrimidinone (UPy) subunits. NMR spectroscopy and circular dichroism studies, complemented by dispersion-corrected DFT calculations, are reported with the aim of characterizing such capsule-fullerene complexes both structurally and energetically. Six fullerenes are considered: in agreement with experiments, calculations find that encapsulation is most favorable for C-84 (on a par with C-90), and follows the trend C-60<c-70<c-76<c-78</c-70<c-76<c-78

First author: Dimuthu, KL, Theoretical Insights into the Origin of Photoluminescence of Au-25(SR)(18)(-) Nanoparticles, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 11202, (2016)
Abstract: Understanding fundamental behavior of luminescent nanomaterials upon photoexcitation is necessary to expand photocatalytic and biological imaging applications. Despite the significant amount of experimental work into the luminescence of Au-25(SR)(18)(-) clusters, the origin of photoluminescence in these clusters still remains unclear. In this study, the geometric and electronic structural changes of the Au-25(SR)(18)(-) (R = H, CH3, CH2CH3, CH2CH2CH3) nanoclusters upon photo excitation are discussed using time-dependent density functional theory (TD-DFT) methods. Geometric relaxations in the optimized excited states of up to 0.33 angstrom impart remarkable effects on the energy levels of the frontier orbitals of Au-25(SR)(18)(-) nanoclusters. This gives rise to a Stokes shift of 0.49 eV for Au-25(SH)(18)(-) in agreement with experiments. Even larger Stokes shifts are predicted for longer ligands. Vibrational frequencies in the 75-80 cm(-1) range are calculated for the nuclear motion involved in the excited-state nuclear relaxation; this value is in excellent agreement with vibrational beating observed in time-resolved spectroscopy experiments. Several excited states around 0.8, 1.15, and 1.25 eV are calculated for the Au-25(SH)(18)(-) nanocluster. Considering the typical underestimation of DFT excitation energies, these states are likely responsible for the emission observed experimentally in the 1.15-1.55 eV range. All excited states arise from core-based orbitals; charge-transfer states or other “semi-ring” or ligand-based states are not implicated.

First author: Azam, M, Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units, SCIENTIFIC REPORTS, 6, 11202, (2016)
Abstract: Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2′-(1E, 1’E)-(2,2- dimethylpropane-1,3-dyl) bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes.

First author: Rimal, G, Giant photocurrent enhancement by transition metal doping in quantum dot sensitized solar cells, APPLIED PHYSICS LETTERS, 109, 242, (2016)
Abstract: A huge enhancement in the incident photon-to-current efficiency of PbS quantum dot (QD) sensitized solar cells by manganese doping is observed. In the presence of Mn dopants with relatively small concentration (4 at. %), the photoelectric current increases by an average of 300% (up to 700%). This effect cannot be explained by the light absorption mechanism because both the experimental and theoretical absorption spectra demonstrate several times decreases in the absorption coefficient. To explain such dramatic increase in the photocurrent we propose the electron tunneling mechanism from the LUMO of the QD excited state to the Zn2SnO4 (ZTO) semiconductor photoanode. This change is due to the presence of the Mn instead of Pb atom at the QD/ZTO interface. The ab initio calculations confirm this mechanism. This work proposes an alternative route for a significant improvement of the efficiency for quantum dot sensitized solar cells.

First author: Nodling, AR, Lewis Acids as Activators in CBS-Catalysed Diels-Alder Reactions: Distortion Induced Lewis Acidity Enhancement of SnCl4, CHEMISTRY-A EUROPEAN JOURNAL, 22, 13171, (2016)
Abstract: The effect of several Lewis acids on the CBS catalyst (named after Corey, Bakshi and Shibata) was investigated in this study. While H-2 NMR spectroscopic measurements served as gauge for the activation capability of the Lewis acids, in situ FT-IR spectroscopy was employed to assess the catalytic activity of the Lewis acid oxazaborolidine complexes. A correlation was found between the Delta delta(H-2) values and rate constants k(DA), which indicates a direct translation of Lewis acidity into reactivity of the Lewis acid-CBS complexes. Unexpectedly, a significant deviation was found for SnCl4 as Lewis acid. The SnCl4-CBS adduct was much more reactive than the Delta delta(H-2) values predicted and gave similar reaction rates to those observed for the prominent AlBr3-CBS adduct. To rationalize these results, quantum mechanical calculations were performed. The frontier molecular orbital approach was applied and a good correlation between the LUMO energies of the Lewis acid-CBS-naphthoquinone adducts and k(DA) could be found. For the SnCl4-CBS-naphthoquinone adduct an unusual distortion was observed leading to an enhanced Lewis acidity. Energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV) calculations revealed the relevant interactions and activation mode of SnCl4 as Lewis acid in Diels-Alder reactions.

First author: Wong, VHL, Synthesis, Structure and Catalytic Activity of NHC-Ag-I Carboxylate Complexes, CHEMISTRY-A EUROPEAN JOURNAL, 22, 13320, (2016)
Abstract: A general synthetic route was used to prepare 15 new N-heterocyclic carbene (NHC)-Ag-I complexes bearing anionic carboxylate ligands [Ag(NHC)(O2CR)], including a homologous series of complexes of sterically flexible ITent ligands, which permit a systematic spectroscopic and theoretical study of the structural and electronic features of these compounds. The complexes displayed a significant ligand-accelerated effect in the intramolecular cyclisation of propargylic amides to oxazolidines. The substrate scope is highly complementary to that previously achieved by NHC-Au and pyridyl-Ag-I complexes.

First author: Jablonska, A, Comparison of the coordination geometries of Zn(II) and Cd(II) ions in complexes with water, methanol and bulky aryloxysilanethiolate ligands, POLYHEDRON, 115, 219, (2016)
Abstract: Zinc and cadmium complexes containing silanethiolate anions and methanol or water were synthesized and characterized by X-ray diffraction, FT-IR and NMR spectroscopy, and DFT calculations. The Zn/Cd complexes 1 and 2 exhibit the same composition but different coordination spheres of the metal ions, [Cd{SSi(OAr)(3)}(2)(CH3OH)]center dot CH3OH (1) versus [Zn{SSi(OAr)(3))(2)(CH3OH)(2)] (2) where Ar = 2,6-diisopropylphenyl. Contrary to zinc, the cadmium ion utilizes very weak donors to complete its coordination sphere; it forms contacts to phenyl rings of the silanethiolate ligand. Two zinc analogs of the general formula [Zn {SSi(OAr)(3))(2)(L)(2)] where L = CH3OH (2) or H2O (3) are compared. In 3, methanol is replaced by water even at low concentration of water in the reaction mixture. The exchange is accompanied by the reorganization of the hydrophobic environment of the water/methanol ligand in the complex. A tetranuclear zinc complex [Zn-4(CH3OH)(4)(SSi(OAr)(3))(4)(CH3COO)(4)](4) featuring an unusual unsupported [Zn-4(CH3COO)(4)](4+) core was also obtained and characterized.

First author: Luo, L, Mechanistic insights into regioselective polymerization of 1,3-Dienes catalyzed by a bipyridine-ligated iron complex: A DFT study, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 1274, (2016)
Abstract: The regioselective polymerizations of isoprene and 3-methyl-pentadiene catalyzed by a cationic iron (II) complex bearing bipyridine ligand have been computationally studied. Having achieved an agreement between calculation and experiment, it is found that the open-shell unpaired 3d-electrons localize on Fe center rather than partially distribute on the redox-active bipyridine ligand. The steric effect plays a more important role in controlling the regioselectivity in comparison with electronic factors. The deformation energy is mainly contributed by monomer and Fe-alkyl moieties rather than the bipyridine ligands themselves, although noncyclopentadienyl ancillary ligands are often deformed in most insertion transition states for selective polymerization of olefin.

First author: Gostynski, R, Jahn-Teller distortion in tris[4,4,4-trifluoro-1-(2-thieny1)-1,3-butanedionato]manganese(III) isomers: An X-ray and computational study, JOURNAL OF MOLECULAR STRUCTURE, 1119, 48, (2016)
Abstract: The solid state crystal data of a mer isomer of the [Mn(CF3COCHCOC4H3S)(3)] complex, [Mn(tfth)(3)], exhibits elongation Jahn-Teller distortion (elongation of the metal-ligand bonds along the z-axis and shortening of the metal-ligand bonds along both the x and y-axes). Density functional theory calculations (DFT) show that one fac and three mer isomers of [Mn(tfth)3] can exist. The difference between the three mer isomers of [Mn(tfth)3] is that the Jahn-Teller elongation of the two trans axial Mn-O bonds along the z-axis occur along three different O-tfth-M-n-O-tfth bonds. DFT calculations further show that the ground state geometry of all the [Mn(tfth)3] isomers exhibits elongation Jahn-Teller distortion.

First author: Akbari, A, Theoretical study of ht-[(ph)Pt(mu-PN)(mu-NP)PtMe2]-(CF3CO2) structure as a heavy dimer complex and comparison of results with experimental X-ray data, ARABIAN JOURNAL OF CHEMISTRY, 9, S259, (2016)
Abstract: DFT calculations performed using Amsterdam Density Functional (ADF 2009.01b) program to estimate best geometry of an unsymmetrical cationic organo-diplatinum complex containing two bridging 2-diphenylphosphinopyridine,(PN), ligands and a platinum-platinum donoracceptor bond, ht-[(ph) Pt(mu-PN)(mu-NP) PtMe2](CF3CO2), as a moderately heavy dimer complex of platinum(II). The obtained geometry is in excellent agreement with the crystallographic data.

First author: Ruzankin, SP, Analysis of spin-polarized solutions in the basis set of paired orbitals, JOURNAL OF STRUCTURAL CHEMISTRY, 57, 997, (2016)
Abstract: This work is a brief review of the authors’ applications of Lowdin-Amos-Hall paired orbitals for the analysis of spin-polarized DFT solutions. The possibilities of this approach are demonstrated on the example (1) of models of Fe(III) hydroxocomplexes with two forms of the terminal oxo center, which are involved in the detachment of methane hydrogen, and (2) models of vanadium oxide experiencing the dissociation of the vanadyl group.

First author: Gayfulin, YM, Reversible Redox Transformations of Bridging Sulfide Ligands within Bioctahedral Rhenium Cluster Anions, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 57, 4066, (2016)
Abstract: The present study provides new experimental data on the reactivity of sulfur-based ligands connected to Re atoms. It was recently discovered that oxidation of mu-S ligands within the bioctahedral [Re12CS14(mu-S)(3)(CN)(6)](6-) cluster anion using H2O2 led to the formation of mu-SO2 and mu-SO3 products. This work is focused on the investigation of the opposite process reduction of the [Re12CS14(mu-SO2)(3)(CN)(6)](6-) anion to [Re12CS14(mu-S)(3)(CN)(6)](6-) by sulfide ions in an aqueous medium under mild conditions. The reduction results in a slow change of the solution colour, making it possible to investigate in detail the intermediate products. Analysis of the reaction mixture by ESI mass spectrometry revealed that a series of cluster anions [Re12CS17On(CN)(6)](6-) (n = 0-5) was generated during the process. This indicates stepwise chemical reduction of bridging SO2 ligands proceeding through the formation of mu-SO ligands. In this way, twelve-nuclear rhenium clusters demonstrate a unique, fully reversible redox cycle of their mu-bridging ligands, keeping the cluster core unchanged. Two mixed-ligand cluster anions, [Re12CS14(mu-SO2)(2)(mu-S)(CN)(6)](6-) and [Re12CS14(mu-SO2)(mu-S)(2)(CN)(6)](6-), were found to be the major reaction intermediates. The former was crystallised with [Cu(NH3)(5)](2+) and [Cd(NH3)(n)](2+) ammine cations and investigated by single-crystal X-ray diffraction. To understand the electronic structure and charge distribution in [Re12CS17On(CN)(6)](6-) cluster anions, DFT calculations were also carried out.

First author: Huidobro-Meezs, IL, The Role of Bulkiness in Haptotropic Shifts of Metal-Cumulene Complexes, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 57, 4226, (2016)
Abstract: In metal-cumulene complexes, the metal easily slides through the double bonds of the chain. A series of late-transition-metal-[5] cumulene complexes has been studied by theoretical and experimental methods in order to understand the factors that control such haptotropic shifts. The bulkiness of the cumulene terminal groups plays a central role in the tautomeric preferences. The quantum theory of atoms in molecules and the electron localizability indicator show that the M-C bond closer to the terminal groups is significantly weakened by steric interactions between these groups and the rest of ligands around the metal center. The results emphasize that special attention should be paid to the orientation of both the bulky substituents at the cumulene and other voluminous ligands around the metal, because the orientation of such moieties is important in predicting the direction of the haptotropic equilibrium correctly.

First author: Ponikiewski, L, Reactions of the Lithiated Diphosphine tBu(2)P-P(SiMe3)Li with [(eta(6)-C6H6)RuCl2](2) in the Presence of Tertiary Phosphines, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 57, 4241, (2016)
Abstract: tBu(2)P-P(SiMe3)Li reacted with [(eta(6)-C6H6)RuCl2](2) at -40 degrees C in the presence of PR3 (PR3 = PEt3, PEt2Ph, PEtPh2) by the nucleophilic addition of the tBu(2)P-P(SiMe3) moiety to the benzene ring to yield solely the complexes [(R3P)(2)Ru(Cl){eta(5)-C6H6(Me3SiP-PtBu2)}] (1). These products decomposed slowly at ambient temperature to yield benzene, Ru clusters, and small amounts of the dinuclear ruthenium complexes [{(R3P)(2)Ru}(2)(mu,eta(2:2)-P-2)(2)Ru(PR3)(2)] (Ru-Ru) (6). Single-crystal X-ray diffraction studies of [(PhEt2P)(2)Ru(Cl){eta(5)-C6H6(Me3SiP-PtBu2)}] (1b) and [(Ph2EtP)(2)Ru(Cl){eta(5)-C6H6(Me3SiP-PtBu2)}] (1c) revealed that the addition of the tBu(2)P-P(SiMe3) group occurred through an exo pathway. Complex 6a (R = Et) displays a planar rectangular P-4 system consisting of two P-2 units and a Ru-Ru distance that lies in the range of a single bond.

First author: Terrett, R, What computational chemistry and magnetic resonance reveal concerning the oxygen evolving centre in Photosystem II, JOURNAL OF INORGANIC BIOCHEMISTRY, 162, 178, (2016)
Abstract: Density Functional Theory (DFT) computational studies of the Mn-4/Ca Oxygen Evolving Complex (OEC) region of Photosystem II in the paramagnetic S-2 and S-3 states of the water oxdizing catalytic cycle are described. These build upon recent advances in computationally understanding the detailed S-1 state OEC geometries, revealed by the recent high resolution Photosystem II crystal structures of Shen et al., at 1.90 angstrom and 1.95 angstrom (Petrie et al, 2015, Angew. Chem. Int. Ed., 54, 7120). The models feature a ‘Low Oxidation Paradigm’ assumption for the mean Mn oxidation states in the functional enzyme, with the mean oxidation levels being 3.0, 3.25 and 3.5 in S-1, S-2 and S-3, respectively. These calculations are used to infer magnetic exchange interactions within the coupled OEC cluster, particularly in the Electron Paramagnetic Resonance (EPR)-visible S-2 and S-3 states. Detailed computational estimates of the intrinsic magnitudes and molecular orientations of the Mn-55 hyperfine tensors in the S-2 state are presented. These parameters, together with the resultant spin projected hyperfine values are compared with recent appropriate experimental EPR data (Continuous Wave (CW), Electron-Nuclear Double Resonance (ENDOR) and ELDOR (Electron-Electron Double Resonance)-Detected Nuclear Magnetic Resonance (EDNMR)) from the OEC. It is found that an effective Coupled Dimer magnetic organization of the four Mn in the OEC cluster in the S-2 and S-3 states is able to quantitatively rationalize the observed Mn-55 hyperfine data. This is consistent with structures we propose to represent the likely state of the OEC in the catalytically active form of the enzyme.

First author: Kolesnikov, IV, Metal-polymer tribosystems: Basic recommendations for creating composites, JOURNAL OF FRICTION AND WEAR, 37, 507, (2016)
Abstract: The interconnection of triboelectric, segregation-diffusion and tribochemical processes at metal-polymer contact area have been revealed. A system approach allows the methods for control of friction properties of metal-polymer friction assemblies to be developed. These methods are based on data that describe the effect of the triboelectric field on diffusion processes in metal-polymer tribosystems and the formation of friction transfer film. The formation of the transfer film has been studied by IR-spectroscopy, and element content on the grain boundaries-by Auger-spectroscopy.

First author: Makowski, M, Assessing Accuracy of Exchange-Correlation Functionals for the Description of Atomic Excited States, ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH, 230, 1425, (2016)
Abstract: The performance of exchange-correlation functionals for the description of atomic excitations is investigated. A benchmark set of excited states is constructed and experimental data is compared to Time-Dependent Density Functional Theory (TDDFT) calculations. The benchmark results show that for the selected group of functionals good accuracy may be achieved and the quality of predictions provided is competitive to computationally more demanding coupled-cluster approaches. Apart from testing the standard TDDFT approaches, also the role of self-interaction error plaguing DFT calculations and the adiabatic approximation to the exchange-correlation kernels is given some insight.

First author: Sahoo, S, Effect of location and filling of d-states on methane activation in single site Fe-based catalysts, CHEMICAL PHYSICS LETTERS, 660, 48, (2016)
Abstract: Theoretical studies on the activation of the C-H bond in methane by an Iron atom bound to four different sites on a silica model support indicate that the lowest activation barrier is found for the case when the Fe is bound to three exposed silicon sites. A molecular orbital analysis reveals that the transition state is stabilized by two filled 3d orbitals that mix with the HOMO and LUMO of methane respectively, indicating how the energy and occupation of the 3d orbitals determine the reaction barrier. The studies offer a strategy for identifying candidates with optimal electronic structure for maximizing C-H bond activation using non-precious metals.

First author: Chen, ZQ, How Do Distance and Solvent Affect Halogen Bonding Involving Negatively Charged Donors?, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 8784, (2016)
Abstract: It was reported that negatively charged donors can form halogen bonding, which is stable, especially, in a polar environment. On the basis of a survey of the Protein Data Bank, we noticed that the distance between the negative charge center and the halogen atom of an organohalogen may vary greatly. Therefore, a series of model systems, composed of 4-halophenyl-conjugated polyene acids and ammonia, were designed to explore the potential effect of distance on halogen bonding in different solvents. Quantum mechanics (QM) calculations demonstrated that the longer the distance, the stronger the bonding. The energy decomposition analysis on all of the model systems demonstrated that electrostatic interaction contributes the most (44-56%) to the overall binding, followed by orbital interaction (42-36%). Natural bond orbital calculations showed that electron transfer takes place from the acceptor to the donor, whereas the halogen atom becomes more positive during the bonding, which is in agreement with the result of neutral halogen bonding. QM/molecular mechanics calculations demonstrated that the polarity of binding pockets makes all of the interactions attractive in a protein system. Hence, the strength of halogen bonding involving negatively charged donors could be adjusted by changing the distance between the negative charge center and halogen atom and the environment in which the bonding exists, which may be applied in material and drug design for tuning their function and activity.

First author: Yang, LH, Water exit pathways and proton pumping mechanism in B-type cytochrome c oxidase from molecular dynamics simulations, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1857, 1594, (2016)
Abstract: Cytochrome c oxidase (CcO) is a vital enzyme that catalyzes the reduction of molecular oxygen to water and pumps protons across mitochondria( and bacterial membranes. While proton uptake channels as well as water exit channels have been identified for A-type CcOs, the means by which water and protons exit B-type CcOs remain unclear. In this work, we investigate potential mechanisms for proton transport above the dinuclear center (DNC) in ba(3)-type CcO of Thermus thermophilus. Using long-time scale, all-atom molecular dynamics (MD) simulations for several relevant protonation states, we identify a potential mechanism for proton transport that involves propionate A of the active site heme a(3) and residues Asp372, His376 and Glul 26(II), with residue His376 acting as the proton-loading site. The proposed proton transport process involves a rotation of residue His376 and is in line with experimental findings. We also demonstrate how the strength of the salt bridge between residues Arg225 and Asp287 depends on the protonation state and that this salt bridge is unlikely to act as a simple electrostatic gate that prevents proton backfiow. We identify two water exit pathways that connect the water pool above the DNC to the outer P-side of the membrane, which can potentially also act as proton exit transport pathways. Importantly, these water exit pathways can be blocked by narrowing the entrance channel between residues Gln151(II) and Arg449/Arg450 or by obstructing the entrance through a conformational change of residue Tyr136, respectively, both of which seem to be affected by protonation of residue His376.

First author: Park, K, Resonance Raman spectroscopic study of the interaction between Co(II)rrinoids and the ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, 21, 669, (2016)
Abstract: The human-type ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri (LrPduO) catalyzes the adenosylation of Co(II)rrinoids to generate adenosylcobalamin (AdoCbl) or adenosylcobinamide (AdoCbi(+)). This process requires the formation of “supernucleophilic” Co(I)rrinoid intermediates in the enzyme active site which are properly positioned to abstract the adeonsyl moiety from co-substrate ATP. Previous magnetic circular dichroism (MCD) spectroscopic and X-ray crystallographic analyses revealed that LrPduO achieves the thermodynamically challenging reduction of Co(II)rrinoids by displacing the axial ligand with a non-coordinating phenylalanine residue to produce a four-coordinate species. However, relatively little is currently known about the interaction between the tetradentate equatorial ligand of Co(II)rrinoids (the corrin ring) and the enzyme active site. To address this issue, we have collected resonance Raman (rR) data of Co(II)rrinoids free in solution and bound to the LrPduO active site. The relevant resonance-enhanced vibrational features of the free Co(II)rrinoids are assigned on the basis of rR intensity calculations using density functional theory to establish a suitable framework for interpreting rR spectral changes that occur upon Co(II)rrinoid binding to the LrPduO/ATP complex in terms of structural perturbations of the corrin ring. To complement our rR data, we have also obtained MCD spectra of Co(II)rrinoids bound to LrPduO complexed with the ATP analogue UTP. Collectively, our results provide compelling evidence that in the LrPduO active site, the corrin ring of Co(II)rrinoids is firmly locked in place by several amino acid side chains so as to facilitate the dissociation of the axial ligand.

First author: Soma, S, Distorted tetrahedral nickel-nitrosyl complexes: spectroscopic characterization and electronic structure, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, 21, 757, (2016)
Abstract: The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitrogen-based ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), was prepared by the reaction of the potassium salt of the ligand with the nickel-nitrosyl precursor [Ni(NO)(Br)(PPh (3) ) (2) ]. The obtained nitrosyl complexes as well as the corresponding chlorido complexes [Ni(NO)(Cl)(PPh (3) ) (2) ] and [Ni(Cl)(L3)] were characterized by X-ray crystallography and different spectroscopic methods including IR/far-IR, UV-Vis, NMR, and multi-edge X-ray absorption spectroscopy at the Ni K-, Ni L-, Cl K-, and P K-edges. For comparative electronic structure analysis we also performed DFT calculations to further elucidate the electronic structure of [Ni(NO)(L3)]. These results provide the nickel oxidation state and the character of the Ni-NO bond. The complex [Ni(NO)(L3)] is best described as [Ni (II) (NO (-) )(L3)], and the spectroscopic results indicate that the phosphane complexes have a similar [Ni (II) (NO (-) )(X)(PPh (3) ) (2) ] ground state.

First author: van Leeuwen, R, Editorial for PCCP themed issue “Developments in Density Functional Theory”, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 20864, (2016)
Abstract: The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitrogen-based ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), was prepared by the reaction of the potassium salt of the ligand with the nickel-nitrosyl precursor [Ni(NO)(Br)(PPh (3) ) (2) ]. The obtained nitrosyl complexes as well as the corresponding chlorido complexes [Ni(NO)(Cl)(PPh (3) ) (2) ] and [Ni(Cl)(L3)] were characterized by X-ray crystallography and different spectroscopic methods including IR/far-IR, UV-Vis, NMR, and multi-edge X-ray absorption spectroscopy at the Ni K-, Ni L-, Cl K-, and P K-edges. For comparative electronic structure analysis we also performed DFT calculations to further elucidate the electronic structure of [Ni(NO)(L3)]. These results provide the nickel oxidation state and the character of the Ni-NO bond. The complex [Ni(NO)(L3)] is best described as [Ni (II) (NO (-) )(L3)], and the spectroscopic results indicate that the phosphane complexes have a similar [Ni (II) (NO (-) )(X)(PPh (3) ) (2) ] ground state.

First author: Zaccaria, F, The role of alkali metal cations in the stabilization of guanine quadruplexes: why K+ is the best, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 20895, (2016)
Abstract: The alkali metal ion affinity of guanine quadruplexes has been studied using dispersion-corrected density functional theory (DFT-D). We have done computational investigations in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. In both cases, an alkali metal cation is needed to assist self-assembly. Our quantum chemical computations on these supramolecular systems are able to reproduce the experimental order of affinity of the guanine quadruplexes for the cations Li+, Na+, K+, Rb+, and Cs+. The strongest binding is computed between the potassium cation and the quadruplex as it occurs in nature. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Until now, the relative importance of these two factors has remained unclear and debated. By assessing the quantum chemical ‘size’ of the cation, determining the amount of deformation of the quadruplex needed to accommodate the cation and through the energy decomposition analysis (EDA) of the interaction energy between the cation and the guanines, we reveal that the desolvation and size of the alkali metal cation are both almost equally responsible for the order of affinity.

First author: Kovyrshin, A, Analytical gradients for excitation energies from frozen-density embedding, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 20955, (2016)
Abstract: The formulation of analytical excitation-energy gradients from time-dependent density functional theory within the frozen-density embedding framework is presented. In addition to a comprehensive mathematical derivation, we discuss details of the numerical implementation in the Slater-function based Amsterdam Density Functional (ADF) program. Particular emphasis is put on the consistency in the use of approximations for the evaluation of second-and third-order non-additive kinetic-energy and exchange-correlation functional derivatives appearing in the final expression for the excitation-energy gradient. We test the implementation for different chemical systems in which molecular excited-state potential-energy curves are affected by another subsystem. It is demonstrated that the analytical implementation for the evaluation of excitation-energy gradients yields results in close agreement with data from numerical differentiation. In addition, we show that our analytical results are numerically more stable and thus preferable over the numerical ones.

First author: Unsleber, JP, No need for external orthogonality in subsystem density-functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21001, (2016)
Abstract: Recent reports on the necessity of using externally orthogonal orbitals in subsystem density-functional theory (SDFT) [Annu. Rep. Comput. Chem., 8, 2012, 53; J. Phys. Chem. A, 118, 2014, 9182] are re-investigated. We show that in the basis-set limit, supermolecular Kohn-Sham-DFT (KS-DFT) densities can exactly be represented as a sum of subsystem densities, even if the subsystem orbitals are not externally orthogonal. This is illustrated using both an analytical example and in basis-set free numerical calculations for an atomic test case. We further show that even with finite basis sets, SDFT calculations using accurate reconstructed potentials can closely approach the supermolecular KS-DFT density, and that the deviations between SDFT and KS-DFT decrease as the basis-set limit is approached. Our results demonstrate that formally, there is no need to enforce external orthogonality in SDFT, even though this might be a useful strategy when developing projection-based DFT embedding schemes.

First author: Chulhai, DV, External orthogonality in subsystem time-dependent density functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21032, (2016)
Abstract: Subsystem density functional theory (subsystem DFT) is a DFT partitioning method that is exact in principle, but depends on approximations to the kinetic energy density functional (KEDF). One may avoid the use of approximate KEDFs by ensuring that the inter-subsystem molecular orbitals are orthogonal, termed external orthogonality (EO). We present a method that extends a subsystem DFT method, that includes EO, into the time-dependent DFT (TDDFT) regime. This method therefore removes the need for approximations to the kinetic energy potential and kernel, and we show that it can accurately reproduce the supermolecular TDDFT results for weakly and strongly coupled subsystems, and for systems with strongly overlapping densities (where KEDF approximations traditionally fail).

First author: El Bakouri, O, Planar vs. three-dimensional X-6(2-), X2Y42-, and X3Y32- (X, Y = B, Al, Ga) metal clusters: an analysis of their relative energies through the turn-upside-down approach, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21102, (2016)
Abstract: Despite the fact that B and Al belong to the same group 13 elements, the B-6(2-) cluster prefers the planar D-2h geometry, whereas Al-6(2-) favours the Oh structure. In this work, we analyse the origin of the relative stability of D2h and Oh forms in these clusters by means of energy decomposition analysis based on the turn-upside-down approach. Our results show that what causes the different trends observed is the orbital interaction term, which combined with the electrostatic component do (Al-6(2-) and Ga-6(2-)) or do not (B-6(2-)) compensate the higher Pauli repulsion of the Oh form. Analysing the orbital interaction term in more detail, we find that the preference of B-6(2-) for the planar D-2h form has to be attributed to two particular molecular orbital interactions. Our results are in line with a dominant delocalisation force in Al clusters and the preference for more localised bonding in B metal clusters. For mixed clusters, we have found that those with more than two B atoms prefer the planar structure for the same reasons as for B-6(2-).

First author: Hernandez-Fernandez, F, Effect of metallation, substituents and inter/intra-molecular polarization on electronic couplings for hole transport in stacked porphyrin dyads, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21122, (2016)
Abstract: We carried out a systematic study of the hole transport properties for a series of symmetrically stacked porphyrin dimers. In the first part of this study, we evaluated the sensitivity of electronic couplings to orbital relaxation due to molecular ionization and intermolecular interactions for a series of halogenated porphyrins. The effect of polarization was estimated by comparing electronic couplings from fragment orbital density functional theory (FODFT) and frozen density embedding electron transfer (FDE-CT). For the dimers considered, the effect of polarization was estimated to be less than 20%, in line with previous studies on different molecular dimers. Thus, we decided to employ a computationally cheaper FODFT method to continue our study of the effect of metals and substituents on the electronic couplings for hole transfer. We find that, compared to the non-metallated porphyrins, Ni, Fe and Pt significantly reduce the coupling, while Zn, Ti, Cd and Pd increase it. The effect of substituents was studied on a series of meso-substituted porphyrins (meso-tetrapyridineporphyrin, meso-tetraphenylporphyrin and derivatives) for which we could relate a reduction of the coupling to steric effects that reduce the overlap between the frontier orbitals of the monomers.

First author: Du, WGH, A broken-symmetry density functional study of structures, energies, and protonation states along the catalytic O-O bond cleavage pathway in ba(3) cytochrome c oxidase from Thermus thermophilus, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21162, (2016)
Abstract: Broken-symmetry density functional calculations have been performed on the [Fe-a3, Cu-B] dinuclear center (DNC) of ba(3) cytochrome c oxidase from Thermus thermophilus in the states of [Fea(3)(3+)-(HO2) – Cu-B(2+), Tyr237(-)] and [Fe-a3(4+) = O2-, OH–Cu-B(2+), Tyr237(center dot)], using both PW91-D3 and OLYP-D3 functionals. Tyr237 is a special tyrosine cross-linked to His233, a ligand of Cu-B. The calculations have shown that the DNC in these states strongly favors the protonation of His376, which is above propionate-A, but not of the carboxylate group of propionate-A. The energies of the structures obtained by constrained geometry optimizations along the O-O bond cleavage pathway between [Fe-a3(3+)-(O-OH)(-)-Cu-B(2+), Tyr237(-)] and [Fe-a3(4+)=O2-center dot center dot center dot HO–Cu-B(2+), Tyr237(center dot)] have also been calculated. The transition of [Fe-a3(3+)=(O-OH)(-)-Cu-B(2+), Tyr237(center dot)] -> [Fe-a3(4+)=O2-center dot center dot center dot HO–Cu-B(2+), Tyr237(center dot)] shows a very small barrier, which is less than 3.0/2.0 kcal mol(-1) in PW91-D3/OLYP-D3 calculations. The protonation state of His376 does not affect this O-O cleavage barrier. The rate limiting step of the transition from state A (in which O-2 binds to Fe-a3(2+)) to state P-M ([Fe-a3(4+)=O2-, OH–Cu-B(2+), Tyr237(center dot)], where the O-O bond is cleaved) in the catalytic cycle is, therefore, the proton transfer originating from Tyr237 to O-O to form the hydroperoxo [Fe-a3(3+)-(O-OH)(-)-Cu-B(2+), Tyr237(-)] state. The importance of His376 in proton uptake and the function of propionate-A/neutralAsp372 as a gate to prevent the proton from back-flowing to the DNC are also shown.

First author: Ramos, P, Constrained subsystem density functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21172, (2016)
Abstract: Constrained Subsystem Density Functional Theory (CSDFT) allows to compute diabatic states for charge transfer reactions using the machinery of the constrained DFT method, and at the same time is able to embed such diabatic states in a molecular environment via a subsystem DFT scheme. The CSDFT acronym is chosen to reflect the fact that on top of the subsystem DFT approach, a constraining potential is applied to each subsystem. We show that CSDFT can successfully tackle systems as complex as single stranded DNA complete of its backbone, and generate diabatic states as exotic as a hole localized on a phosphate group as well as on the nucleobases. CSDFT will be useful to investigators needing to evaluate the environmental effect on charge transfer couplings for systems in condensed phase environments.

First author: Nicu, VP, Revisiting an old concept: the coupled oscillator model for VCD. Part 1: the generalised coupled oscillator mechanism and its intrinsic connection to the strength of VCD signals, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21202, (2016)
Abstract: Motivated by the renewed interest in the coupled oscillator (CO) model for VCD, in this work a generalised coupled oscillator (GCO) expression is derived by introducing the concept of a coupled oscillator origin. Unlike the standard CO expression, the GCO expression is exact within the harmonic approximation. Using two illustrative example molecules, the theoretical concepts introduced here are demonstrated by performing a GCO decomposition of the rotational strengths computed using DFT. This analysis shows that: (1) the contributions to the rotational strengths that are normally neglected in the standard CO model can be comparable to or larger than the CO contribution, and (2) the GCO mechanism introduced here can affect the VCD intensities of all types of modes in symmetric and asymmetric molecules.

First author: Nicu, VP, Revisiting an old concept: the coupled oscillator model for VCD. Part 2: implications of the generalised coupled oscillator mechanism for the VCD robustness concept, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 21213, (2016)
Abstract: Using two illustrative examples it is shown that the generalised coupled oscillator (GCO) mechanism implies that the stability of the VCD sign computed for a given normal mode is not reflected by the magnitude of the ratio zeta between the rotational strength and dipole strength of the respective mode, i.e., the VCD robustness criterium proposed by Gobi and Magyarfalvi. The performed VCD GCO analysis brings further insight into the GCO mechanism and also into the VCD robustness concept. First, it shows that the GCO mechanism can be interpreted as a VCD resonance enhancement mechanism, i.e. very large VCD signals can be observed when the interacting molecular fragments are in favourable orientation. Second, it shows that the uncertainties observed in the computed VCD signs are associated to uncertainties in the relative orientation of the coupled oscillator fragments and/or to uncertainties in the predicted nuclear displacement vectors, i.e. not uncertainties in the computed magnetic dipole transition moments as was originally assumed. Since it is able to identify such situations easily, the VCD GCO analysis can be used as a VCD robustness analysis.

First author: Romanczyk, PP, Dissociative electron transfer in polychlorinated aromatics. Reduction potentials from convolution analysis and quantum chemical calculations, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 22573, (2016)
Abstract: Formal potentials of the first reduction leading to dechlorination in dimethylformamide were obtained from convolution analysis of voltammetric data and confirmed by quantum chemical calculations for a series of polychlorinated benzenes: hexachlorobenzene (-2.02 V vs. Fc(+)/Fc), pentachloroanisole (-2.14 V), and 2,4-dichlorophenoxy- and 2,4,5-trichlorophenoxyacetic acids (-2.35 V and -2.34 V, respectively). The key parameters required to calculate the reduction potential, electron affinity and/or C-Cl bond dissociation energy, were computed at both DFT-D and CCSD(T)-F12 levels. Comparison of the obtained gas-phase energies and redox potentials with experiment enabled us to verify the relative energetics and the performance of various implicit solvent models. Good agreement with the experiment was achieved for redox potentials computed at the DFT-D level, but only for the stepwise mechanism owing to the error compensation. For the concerted electron transfer/C-Cl bond cleavage process, the application of a high level coupled cluster method is required. Quantum chemical calculations have also demonstrated the significant role of the pi(star)(ring) and sigma(star)(C-Cl) orbital mixing. It brings about the stabilisation of the non-planar, C-2v-symmetric C6Cl6 center dot- radical anion, explains the experimentally observed low energy barrier and the transfer coefficient close to 0.5 for C6Cl5OCH3 in an electron transfer process followed by immediate C-Cl bond cleavage in solution, and an increase in the probability of dechlorination of di- and trichlorophenoxyacetic acids due to substantial population of the vibrational excited states corresponding to the out-of-plane C-Cl bending at ambient temperatures.

First author: Etcheverry-Berrios, A, Multiscale Approach to the Study of the Electronic Properties of Two Thiophene Curcuminoid Molecules, CHEMISTRY-A EUROPEAN JOURNAL, 22, 12808, (2016)
Abstract: We studied the electronic and conductance properties of two thiophene-curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), in which the only structural difference is the position of the sulfur atoms in the thiophene terminal groups. We used electrochemical techniques as well as UV/Vis absorption studies to obtain the values of the HOMO-LUMO band gap energies, showing that molecule 1 has lower values than 2. Theoretical calculations show the same trend. Self-assembled monolayers (SAMs) of these molecules were studied by using electrochemistry, showing that the interaction with gold reduces drastically the HOMO-LUMO gap in both molecules to almost the same value. Single-molecule conductance measurements show that molecule 2 has two different conductance values, whereas molecule 1 exhibits only one. Based on theoretical calculations, we conclude that the lowest conductance value, similar in both molecules, corresponds to a van der Waals interaction between the thiophene ring and the electrodes. The one order of magnitude higher conductance value for molecule 2 corresponds to a coordinate (dative covalent) interaction between the sulfur atoms and the gold electrodes.

First author: Mohapatra, C, The Structure of the Carbene Stabilized Si2H2 May Be Equally Well Described with Coordinate Bonds as with Classical Double Bonds, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 10429, (2016)
Abstract: The cyclic alkyl(amino) carbene stabilized Si2H2 has been isolated in the molecular form of composition (Me-cAAC:)(2)Si2H2 (1) and (CycAAC:)(2)Si2H2 (2) at room temperature. Compounds 1 and 2 were synthesized from the reduction of HSiCl3 using 3 equiv of KC8 in the presence of 1 equiv of Me-cAAC: and Cy-cAAC:, respectively. These are the first molecular examples of Si2H2 characterized by single crystal X-ray structural analysis. Moreover, electrospray ionization mass spectrometry and H-1 as well as Si-29 NMR data are reported. Furthermore, the structure of compound 1 has been investigated by theoretical methods. The theoretical analysis of 1 explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene.

First author: Behnia, A, Selective Oxygen Atom Insertion into an Aryl-Palladium Bond, ORGANOMETALLICS, 35, 2645, (2016)
Abstract: The chemistry of a palladium(II) complex containing both an alkyl- and an aryl-palladium bond is reported. The reaction of [Pd(CH2CMe2C6H4)(MesN=CHCH=NMes)] with bromine or iodine leads to reductive elimination of 1,1-dimethylcyclobutabenzene with formation of [PdX2(MesN=CHCH=NMes)] (X = Br, I). However, the reaction with hydrogen peroxide gives [Pd-(CH2CMe2C6H4O)(MesN=CHCH=NMes)] by overall oxygen atom insertion into the aryl-palladium rather than the alkyl-palladium bond. This complex [Pd(CH2CMe2C6H4O)(MesN=CHCH=NMes)] reacts with bromine, iodine, or hydrogen peroxide to give 3,3-dimethyl-2,3-dihydrobenzofuran and the corresponding complex [PdX2(MesN=CHCH=NMes)]. The mechanisms of reaction and basis for selectivity are discussed. The results support the view that oxygen atom insertion is a mechanistically viable pathway for selective catalytic oxidation of hydrocarbons by the green oxidant hydrogen peroxide.

First author: Adhikary, J, Unique mononuclear Mn-II complexes of an end-off compartmental Schiff base ligand: experimental and theoretical studies on their bio-relevant catalytic promiscuity, DALTON TRANSACTIONS, 45, 12409, (2016)
Abstract: Three new mononuclear manganese(II) complexes, namely [Mn(HL)(2)]center dot 2ClO(4) (1), [Mn(HL)(N(CN)(2)) (H2O)(2)]center dot ClO4 (2) and [Mn(HL)(SCN)(2)] (3) [LH = 4-tert-butyl-2,6-bis-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol], have been synthesized and structurally characterized. An “end-off” compartmental ligand (LH) possesses two symmetrical compartments with N2O binding sites but accommodates only one manganese atom instead of two due to the protonation of the imine nitrogen of one compartment. Although all three complexes are mononuclear, complex 1 is unique as it has a 1 : 2 metal to ligand stoichiometry. The catalytic promiscuity of complexes 1-3 in terms of two different bio-relevant catalytic activities namely catecholase and phenoxazinone synthase has been thoroughly investigated. EPR and cyclic voltametric studies reveal that radical formation rather than metal centered redox participation is responsible for their catecholase-like and phenoxazinone synthase-like catalytic activity. A computational approach suggests that imine bond bound radical generation rather than phenoxo radical formation is most likely responsible for the oxidizing properties of the complexes.

First author: Peng, BQ, Adsorption of Antibiotics on Graphene and Biochar in Aqueous Solutions Induced by pi-pi Interactions, SCIENTIFIC REPORTS, 6, 12409, (2016)
Abstract: The use of carbon based materials on the removal of antibiotics with high concentrations has been well studied, however the effect of this removal method is not clear on the actual concentration of environments, such as the hospital wastewater, sewage treatment plants and aquaculture wastewater. In this study, experimental studies on the adsorption of 7 antibiotics in environmental concentration of aqueous solutions by carbon based materials have been observed. Three kinds of carbon materials have shown very fast adsorption to antibiotics by liquid chromatography-tandem mass spectrometry (LC-MS-MS) detection, and the highest removal efficiency of antibiotics could reach to 100% within the range of detection limit. Surprisedly, the adsorption rate of graphene with small specific surface area was stronger than other two biochar, and adsorption rate of the two biochar which have approximate specific surface and different carbonization degree, was significantly different. The key point to the present observation were the pi-pi interactions between aromatic rings on adsorbed substance and carbon based materials by confocal laser scanning microscope observation. Moreover, adsorption energy markedly increased with increasing number of the pi rings by using the density functional theory (DFT), showing the particular importance of pi-pi interactions in the adsorption process.

First author: Morseth, ZA, Role of Macromolecular Structure in the Ultrafast Energy and Electron Transfer Dynamics of a Light-Harvesting Polymer, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 7937, (2016)
Abstract: Ultrafast energy and electron transfer (EnT and ET, respectively) are characterized in a light-harvesting assembly based on a pi-conjugated polymer (poly(fluorene)) functionalized with broadly absorbing pendant organic isoindigo (iI) chromophores using a combination of femtosecond transient absorption spectroscopy and large-scale computer simulation. Photoexcitation of the pi-conjugated polymer leads to near-unity The of the excitation through a combination of EnT and ET to the iI pendants. The excited pendants formed by EnT rapidly relax within 30 ps, whereas recombination of the charge-separated state formed following ET occurs within 1200 ps. A computer model of the excited-state, processes is developed by combining all-atom Molecular dynamics simulations, which provides a molecular-level view of the assembly structure, with a kinetic model that accounts for the multiple excited-state quenching pathways. Direct comparison of the simulations with experimental data reveals that the underlying structure has a dramatic effect on the partitioning between EnT and ET in the polymer assembly, where the distance and orientation of the pendants in relation to the backbone serve to direct the dominant quenching pathway.

First author: Belferdi, F, Regioselective demethylation of quinoline derivatives. A DFT rationalization, JOURNAL OF MOLECULAR STRUCTURE, 1118, 10, (2016)
Abstract: Demethylation of compound 2,7-dimethoxyquinoline-3-carbaldehyde (1) under bar, is carried out using BBr3. However, all attempts led, either to the starting material or to the regioselective demethylation at position 2 affording the product (4a) under bar. The nature (donor or acceptor) and the position of the R (CHO or CN) group is likely to play a role in the preventing the demethylation at position 7. To address this phenomena, the demethylation of 2-chloro-7-methoxyquinoline-3-carbaldehyde (2) under bar and 2,7-dimethoxyquinoline-3-carbaldehyde 3 has been carried out. To support the results obtained, theoretical computations at DFT level (vide infra) have been carried out upon compound (1) under bar. The exploration of how the gas-phase demethylation process on Quinoline can be affected at a position 7 center by stepwise substation effects using different electro-donor and attractor groups, show that demethylation process seems to be more favorable when substituent is an electro-donor. This is sustained by bond energy and thermodynamic analyses (vide infra).

First author: Shi, YA, Synthesis, crystal structure, electrochemistry and third-order nonlinear optical properties of two novel ferrocene derivatives, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 817, 36, (2016)
Abstract: Two novel ferrocene derivatives, N, N-diphenyl-4-E-((1-ferrocenyl) ethenyl) aniline (1), N, N-(4,4-diethoxyphenyl)- 4-E-((1-ferrocenyl) ethenyl) aniline (2), were designed, synthesized and fully characterized by H-1 NMR, C-13 NMR, FT-IR and MALDI-TOF-MS spectra. Structure of (1) was confirmed by X-ray diffraction analysis. The UVevisible absorption spectra of the two compounds were investigated and verified by density functional theory (DFT) calculations. Electrochemical and third-order nonlinear optical (NLO) properties have been shown by cyclic voltammetric experiments and open/closed aperture Z-scan measurements. The results show that the two compounds both are highly pi-electron delocalization system, indicating potential applications as NLO materials. It is noteworthy that (1) possesses larger twophoton absorption (2 PA) coefficient beta, 2 PA cross section sigma and the third-order nonlinear susceptibility (chi((3))) than (2).

First author: Garbacz, P, Nuclear relaxation in an electric field enables the determination of isotropic magnetic shielding, JOURNAL OF CHEMICAL PHYSICS, 145, 36, (2016)
Abstract: It is shown that in contrast to the case of nuclear relaxation in a magnetic field B, simultaneous application of the magnetic field B and an additional electric field E causes transverse relaxation of a spin-1/2 nucleus with the rate proportional to the square of the isotropic part of the magnetic shielding tensor. This effect can contribute noticeably to the transverse relaxation rate of heavy nuclei in molecules that possess permanent electric dipole moments. Relativistic quantum mechanical computations indicate that for Tl-205 nucleus in a Pt-Tl bonded complex, Pt(CN)(5)Tl, the transverse relaxation rate induced by the electric field is of the order of 1 s(-1) at E = 5 kV/mm and B = 10 T.

First author: Singh, SK, An ab Initio Study of the Effect of Substituents on the n -> pi* Interactions between 7-Azaindole and 2,6-Difluorosubstituted Pyridines, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 6258, (2016)
Abstract: The n -> pi* interaction is a weak but important noncovalent interaction present in biomolecules and other compounds. Complexes between 7-azaindole and 2,6-difluorinated pyridines were demonstrated earlier to interact not only via an expected strong hydrogen bond but also by a weaker and unexpected n -> pi* interaction between the nucleophilic nitrogen atom of the 7-azaindole and the electrophilic pi-system of the pyridine ring. This system provides a unique and convenient framework upon which to investigate the effect that distal substitution on the 7-azaindole ring has on the strength of the n -> pi* interaction. Herein we describe our thorough analysis of these effects by applying a variety of diverse methods including NBO, ETS-NOCV, and AIM. Very good agreement in trends was observed among all these diverse methods of analysis. Substitution at the position para to the nucleophilic nitrogen atom of the 7-azaindole ring with electron-donating groups weakened the hydrogen bond interaction with the 2,6-difluoropyridine but enhanced the n -> pi* interaction. Substitution with electron-withdrawing groups had the opposite effect. In addition, good correlation of the results of the calculations with the substituents’ Hammett sigma(p) values was observed. Energy decomposition analysis (EDA) corroborated the conclusions derived by the other methods of analysis.

First author: Papai, M, Effect of tert-Butyl Functionalization on the Photoexcited Decay of a Fe(II)-N-Heterocyclic Carbene Complex, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 17234, (2016)
Abstract: Understanding and subsequently being able to manipulate the excited-state decay pathways of functional transition-metal complexes is of utmost importance in order to solve grand challenges in solar energy conversion and data storage. Herein, we perform quantum chemical calculations and spin-vibronic quantum dynamics simulations on the Fe-N-heterocyclic carbene complex, [Fe(btbip)(2)](2+) (btbip = 2,6-bis(3-tert-butyl-imidazole-1-ylidene)pyridine). The results demonstrate that a relatively minor structural change compared to its parent complex, [Fe(bmip)(2)](2+) (bmip = 2,6-bis(3-methyl-imidazole-1-ylidene)pyridine), completely alters the excited-state relaxation. Ultrafast deactivation of the initially excited metal-to-ligand charge transfer ((MLCT)-M-1,3) states occurs within 350 fs. In contrast to the widely adopted mechanism of Fe(II) photophysics, these states decay into close-lying singlet metal-centered ((MC)-M-1) states. This occurs because the tert-butyl functionalization stabilizes the (MC)-M-1 states, enabling the (MLCT)-M-1,3 -> (MC)-M-1 population transfer to occur close to the Franck-Condon geometry, making the conversion very efficient. Subsequently, a spin cascade occurs within the MC manifold, leading to the population of triplet and quintet MC states. These results will inspire highly involved ultrafast experiments performed at X-ray free electron lasers and shall pave the way for the design of novel high-efficiency transition-metal-based functional molecules.

First author: Tang, Y, On the Nature of Support Effects of Metal Dioxides MO2 (M = Ti, Zr, Hf, Ce, Th) in Single-Atom Gold Catalysts: Importance of Quantum Primogenic Effect, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 17514, (2016)
Abstract: Fundamental understanding of support effects and metal-support interaction is critical in heterogeneous catalysis. In this work, theoretical investigations are carried out to study the nature of support effects of different tetravalent-metal dioxides of MO2 (M = Ti, Zr, Ce, Hf, Th) in single-atom gold catalysts using density functional theory with on-site Coulomb interactions (DFT+U). The properties of gold adatom on the stoichiometric (MO2) and reduced (MO2-x) surfaces as well as CO adsorption on Au-1/MO2 and Au-1/MO2-x have been investigated systematically. Our calculations indicate that the fundamental quantum primogenic effect that causes the radial contraction and low orbital energies of 3d and 4f orbitals in these MO2 oxides plays a vital role in determining the valence states and charge distribution of single-atom gold as well as the adsorption modes of CO on various MO2 supports. We find that gold atoms supported on different surfaces exhibit oxidation states from Au(-I) to Au(0) to Au(I), depending on the nature of the metal oxide supports. The support-dependent oxidation states and charge distribution of Au can further influence the adsorption mode of CO. While CO adsorbs strongly on Au(I) in Au-1/MO2 (M = Ti, Ce) via Au-C sigma-bonding, weaker adsorption occurs on Au(0) in Au-1/MO2 (M = Zr, Hf, Th) with charge back-donation to CO 2 pi* antibonding orbitals. In contrast, at Au-1/MO2-x of reduced support, CO adsorption is stronger for M = Zr, Hf, and Th than for M = Ce. These results provide essential understanding on the nature of support effects of metal oxides in heterogeneous catalysis.

First author: Seegerer, A, Remote-Stereocontrol in Dienamine Catalysis: Z-Dienamine Preferences and Electrophile-Catalyst Interaction Revealed by NMR and Computational Studies, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 9864, (2016)
Abstract: Catalysis with remote-stereocontrol provides special challenges in design and comprehension. One famous example is the dienamine catalysis, for which high ee values are reported despite insufficient shielding of the second double bond. Especially for dienamines with variable Z/E-ratios of the second double bond, no correlations to the ee values are found. Therefore, the structures, thermodynamics, and kinetics of dienamine intermediates in S-N-type reactions are investigated. The NMR studies show that the preferred dienamine conformation provides an effective shielding if large electrophiles are used. Calculations at SCS-MP2/CBS-level of theory and experimental data of the dienamine formation show kinetic preference for the Z-isomer of the second double bond and a slow isomerization toward the thermodynamically preferred E-isomer. Modulations of the rate-determining step, by variation of the concentration of the electrophile, allow the conversion of dienamines to be observed. With electrophiles, a faster reaction of Z- than of E-isomers is observed experimentally. Calculations corroborate these results by correlating ee values of three catalysts with the kinetics of the electrophilic attack and reveal the significance of CH-pi and stacking interactions in the transition states. Thus,, for the first time a comprehensive understanding of the remote stereocontrol in gamma-functionalization reactions of dienamines and an explanation to the “Z/E-dilemma” are presented. The combination of bulky catalyst subsystems and large electrophiles provides a shielding of one face and causes different reactivities of E/Z-dienamines in nucleophilic attacks from the other face. Kinetic preferences for the formation of Z-dienamines and their unfavorable thermodynamics support high ee values.

First author: Zhao, LL, Reaction Mechanism of the Hydrogermylation/Hydrostannylation of Unactivated Alkenes with Two-Coordinate E-II Hydrides (E=Ge, Sn): A Theoretical Study, CHEMISTRY-A EUROPEAN JOURNAL, 22, 11728, (2016)
Abstract: Quantum chemical calculations using density functional theory with the TPSS+ D3(BJ) and M06-2X+D3(ABC) functionals have been carried out to understand the mechanisms of catalyst-free hydrogermylation/hydrostannylation reactions between the two-coordinate hydrido-tetrylenes E(H)(L+) (E=Ge or Sn, L+ = N(Ar+)(SiiPr(3)); Ar+ = C6H2{C(H)Ph-2}(2)iPr-2,6,4) and a range of unactivated terminal (C2H3R, R=H, Ph, or tBu) and cyclic [(CH)(2)(CH2)(2)(CH2)(n), n=1, 2, or 4] alkenes. The calculations suggest that the addition reactions of the germylenes and stannylenes to the cyclic and acyclic alkenes occur as one-step processes through formal [2+2] addition of the E-H fragment across the C-C pi bond. The reactions have moderate barriers and are weakly exergonic. The steric bulk of the tetrylene amido groups has little influence on the activation barriers and on the reaction energies of the anti-Markovnikov pathway, but the Markovnikov addition is clearly disfavored by the size of the substituents. The addition of the tetrylenes to the cyclic alkenes is less exergonic than the addition to the terminal alkenes, which agrees with the experimentally observed reversibility of the former reactions. The hydrogermylation reactions have lower activation energies and are more exergonic than the stannylene addition. An energy decomposition analysis of the transition state for the hydrogermylation of cyclohexene shows that the reaction takes place with simultaneous formation of the Ge-C and (Ge) H-C’ bonds. The dominant orbitals of the germylene are the sigma-type lone pair MO of Ge, which serves as a donor orbital, and the vacant p(pi) MO of Ge, which acts as acceptor orbital for the pi* and pi MOs of the olefin. Inspection of the transition states of some selected reactions suggests that the differences between the activation energies come from a delicate balance between the deformation energies of the interacting species and their interaction energies.

First author: Braunschweig, H, Interactions of Isonitriles with Metal-Boron Bonds: Insertions, Coupling, Ring Formation, and Liberation of Monovalent Boron, CHEMISTRY-A EUROPEAN JOURNAL, 22, 11736, (2016)
Abstract: borylene, and base-stabilized borylene complexes of manganese and iron undergo a range of different reactions when treated with isonitriles including single, double, and partial isonitrile insertions into metal-boron bonds, ring formation, isonitrile coupling, and the liberation of new monovalent boron species. Two of the resulting cyclic species have also been found to react selectively with anhydrous HCl to form ring-opened products. The diverse isonitrile-promoted reactivity of transition-metal-boron compounds has been explored computationally.

First author: Hamieh, A, Investigation of Surface Alkylation Strategy in SOMC: In Situ Generation of a Silica-Supported Tungsten Methyl Catalyst for Cyclooctane Metathesis, ORGANOMETALLICS, 35, 2524, (2016)
Abstract: An efficient and potentially scalable method is described for the synthesis of the silica-supported complexes [(equivalent to Si-O)WMe5] and [(equivalent to:Si-O)WMe2(equivalent to CH)] obtained by in situ alkylation of the surface-grafted tungsten chloride [(equivalent to Si-O)WCl5] (1). [(equivalent to Si-O)WCl5] can be readily prepared by the reaction of commercially available and stable tungsten hexachloride WCI6 with partially dehydroxylated silica at 700 degrees C (SiO2-700). Further reaction with ZnMe2 at room temperature rapidly forms a mixture of surfacealkylated tungsten complexes. They were fully characterized by microanalysis, FTIR, mass balance, and solid-state NMR (H-1, C-13, H-1-C-13 HETCOR, H-1-H-1 double quantum and triple quantum) and identified as [(equivalent to Si-O)WMes] and another product, [(equivalent to Si-O)WMe2(equivalent to CH)]. The latter might have been generated by partial decomposition of the tungsten methyl chloride compound, which is formed during the stepwise alkylation of [(equivalent to Si-O)WCl3]. DFT calculations were carried out to check the relative stability of the tungsten methyl chloride intermediates and the feasibility of the reaction and corroborate the experimental results. This tungsten complex and its derivative were found to be active catalysts for the metathesis of cydooctane.

First author: Grimme, S, Ultra-fast computation of electronic spectra for large systems by tight-binding based simplified Tamm-Dancoff approximation (sTDA-xTB), JOURNAL OF CHEMICAL PHYSICS, 145, 2524, (2016)
Abstract: The computational bottleneck of the extremely fast simplified Tamm-Dancoff approximated ( sTDA) time-dependent density functional theory procedure [ S. Grimme, J. Chem. Phys. 138, 244104 ( 2013)] for the computation of electronic spectra for large systems is the determination of the ground state Kohn-Sham orbitals and eigenvalues. This limits such treatments to single structures with a few hundred atoms and hence, e. g., sampling along molecular dynamics trajectories for flexible systems or the calculation of chromophore aggregates is often not possible. The aim of this work is to solve this problem by a specifically designed semi-empirical tight binding ( TB) procedure similar to the well established self-consistent-charge density functional TB scheme. The new special purpose method provides orbitals and orbital energies of hybrid density functional character for a subsequent and basically unmodified sTDA procedure. Compared to many previous semi-empirical excited state methods, an advantage of the ansatz is that a general eigenvalue problem in a non-orthogonal, extended atomic orbital basis is solved and therefore correct occupied/virtual orbital energy splittings as well as Rydberg levels are obtained. A key idea for the success of the new model is that the determination of atomic charges ( describing an effective electron-electron interaction) and the one-particle spectrum is decoupled and treated by two differently parametrized Hamiltonians/basis sets. The three-diagonalization-step composite procedure can routinely compute broad range electronic spectra ( 0-8 eV) within minutes of computation time for systems composed of 500-1000 atoms with an accuracy typical of standard time-dependent density functional theory ( 0.3-0.5 eV average error). An easily extendable parametrization based on coupled-cluster and density functional computed reference data for the elements H-Zn including transition metals is described. The accuracy of the method termed sTDA-xTB is first benchmarked for vertical excitation energies of open-and closed-shell systems in comparison to other semi-empirical methods and applied to exemplary problems in electronic spectroscopy. As side products of the development, a robust and efficient valence electron TB method for the accurate determination of atomic charges as well as a more accurate calculation scheme of dipole rotatory strengths within the Tamm-Dancoff approximation is proposed.

First author: Buter, J, Stereoselective Synthesis of 1-Tuberculosinyl Adenosine; a Virulence Factor of Mycobacterium tuberculosis, JOURNAL OF ORGANIC CHEMISTRY, 81, 6686, (2016)
Abstract: Despite its status as one of the world’s most prevalent and deadly bacterial pathogens, Mycobacterium tuberculosis (Mtb) infection is not routinely diagnosed by rapid and highly reliable tests. A program to discover Mtb-specific biomarkers recently identified two natural compounds, 1-tuberculosinyl adenosine (1-TbAd) and N-6-tuberculosinyl adenosine (N-6-TbAd). Based on their association with virulence, the lack of similar compounds in nature, the presence of multiple stereocenters, and the need for abundant products to develop diagnostic tests, synthesis of these compounds was considered to be of high value but challenging. Here, a multigram-scale stereoselective synthesis of 1-TbAd and N-6-TbAd is described. As a key-step, a chiral auxiliary-mediated Diels-Alder cycloaddition was developed, introducing the three stereocenters with a high exo endo ratio (10:1) and excellent enantioselectivity (>98% ee). This constitutes the first entry into the stereoselective synthesis of diterpenes with the halimane skeleton. Computational studies explain the observed stereochemical outcome.

First author: Pratik, SM, Janus all-cis-1,2,3,4,5,6-Hexafluorocyclohexane: A Molecular Motif for Aggregation-Induced Enhanced Polarization, CHEMPHYSCHEM, 17, 2373, (2016)
Abstract: Recently synthesized all-cis-1,2,3,4,5,6-hexafluorocyclohexane is the least stable among all possible configurational isomers of 1,2,3,4,5,6-hexafluorocyclohexane. This molecule has a remarkably large dipole moment (6.2D) as well as high facial polarization. Solid-state, dispersion-corrected DFT (DFT-D3) calculations are performed on the crystalline phase of all-cis-1,2,3,4,5,6- hexafluorocyclohexane, which reveal that dispersion interactions play a crucial role in its stabilization. A number of thermodynamically favorable orientations of dimers, trimers and tetramers are demonstrated for this molecule. Parallel-stacked aggregates, from dimers to higher-order aggregates, which are absent in the crystal, are found to be thermodynamically most favorable due to the presence of strong short-range C-HF-C intermolecular hydrogen-bonding networks. Because of their cooperative nature, binding energies, dipole moments, and polarizations per molecule increase from monomer to tetramer, whereas the HOMO-LUMO gaps follow the opposite trend. Based on the DFT-D3 calculations, it is proposed that this parallel-stacked arrangement can be further extended to prepare stable a 1D crystal such that a large dipole moment and macroscopic polarizations can arise, which might be useful in designing electronic and nonlinear optical devices. Because the molecule has conformational flexibility, the potential energy surface is investigated for ring flipping and the effects of fluorine substitution are studied by comparing the barrier with respect to cyclohexane and all-cis-1,2,3-trifluorocyclohexane.

First author: York, JT, Determining the Impact of Ligand and Alkene Substituents on Bonding in Gold(I)-Alkene Complexes Supported by N-Heterocyclic Carbenes: A Computational Study, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 6064, (2016)
Abstract: The nature of the gold(I)-alkene bond in [(NHC)Au(alkene)](+) complexes (where NHC is the N-heterocycliccarbene 1,3-bis(2,6-dimethylphenyl)imidazole-2-ylidine and its derivatives) has been studied using density functional theory. By utilization of a series of electron withdrawing and electron-donating substituents ranging from -NO2 to -NH2, an examination of substituent effects has been undertaken with 4-substituted NHC ligands, monosubstituted ethylene derivatives, and 4-substituted styrene derivatives. Natural population, natural bond orbital (NBO), molecular orbital, and bond energy decomposition analysis (EDA) methods have been used to quantify a number of important parameters, including the charge of the coordinated alkenes and the magnitude of alkene ->[(NHC)Au](+) and [(NHC)Au](+)-> alkene electron donation. EDA methods have also been used to quantify the strength of the [(NHC)Au](+)-(alkene) bond and the impact of both ligand and alkene substitution on different components of the interaction, including polarization, orbital, electrostatic, and Pauli repulsive contributions. Finally, molecular orbital analysis has been used to understand the activation of the alkenes in terms of orbital composition and stabilization within the [(NHC)Au(alkene)(+) complexes relative to the free alkenes. These results provide important insight into the fundamental nature of gold(I)-alkene bonding and the impact of both ligand and alkene substitution on the electronic structure of these complexes.

First author: Zhang, SZ, The Interactions between Imidazolium-Based Ionic Liquids and Stable Nitroxide Radical Species: A Theoretical Study, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 6089, (2016)
Abstract: In this work, the interactions between imidazolium-based ionic liquids and some stable radicals based on 2,2,6,6-tetramethylpiperidine-1-yloxyl (TEMPO) have been systematically investigated using density functional theory calculations at the level of M06-2x. Several different substitutions, such as hydrogen. bonding forrnation substituent (OH) and ionic substituents (N(CH3)(3)(+) and OSO3-), are presented at the 4-position of the spin probe, which leads to additional hydrogen bonds or ionic interactions between these substitutions and ionic liquids. The interactions in the systems of the radicals containing ionic substitutions with ionic liquids are predicted much stronger than those in the systems of neutral radicals, resulting in a significant reduction of the mobility of ionic radicals in ionic liquids. To further understand the nature of these interactions, the natural bond order, atoms in molecules, noncovalent interaction index, electron density difference, energy decomposition analysis, and charge decomposition analysis schemes were employed. The additional ionic interactions between ionic radicals and counterions in ionic liquids are dominantly contributed from the electrostatic term, while the orbital interaction plays a major role in other interactions. The results reported herein are important to understand radical processes ionic liquids and will be very useful in the design of task-specific ionic liquids to make the processes more efficient.

First author: Melendez, FJ, Analysis of the topology of the electron density and the reactivity descriptors of biomolecules with insecticide activity, THEORETICAL CHEMISTRY ACCOUNTS, 135, 6089, (2016)
Abstract: Modifications of the phytosanitary control in fruit in the pre- and post-harvest processes by exogenous application of biomolecules with insecticide activity have motivated the theoretical-experimental investigation of biomolecular systems. Essential oils such as limonene, monoterpenes like 3-carene, and halogenated monoterpenes like mertensene have shown interesting insecticide activity. In this work, a complete characterization of the topology descriptors of the electron density of these 3 compounds has been carried out in the gas phase using the Quantum Theory of Atoms in Molecules formulation. In addition, the global and local descriptors of the reactivity have been quantified by means of Density functional theory, using the hybrid functional of correlation and exchange B3LYP. To determine the reactivity descriptors in terms of the ionization potential (I) and electron affinity (A), two methods were used: (1) the Koopmans’ theorem with the DZ basis set and (2) the vertical difference of the total electronic energy method with a TZ basis set. In this last approach, an electron is aggregated with or removed from the neutral molecule. Both methods showed the same trends in the properties calculated by topology of electron density as well as those obtained by global and local reactivity.

First author: Ito, S, Exploration of 1-Arylmethyl-1,3-diphosphacyclobutane-2,4-diyls as Hole Transfer Materials, CHEMISTRYSELECT, 1, 3310, (2016)
Abstract: This paper describes the p type semiconductor characteristics of 1-arylmethyl-substituted air-tolerant 1,3-diphosphacyclobutane-2,4-diyls, focusing preliminarily on their hole transfer parameters deduced from their crystal and density functional theory (DFT) structures. 1-(2-Anthrylmethy)-3-t-butyl-2,4-bis (2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl functions as a p-type field-effect transistor (FET) with semiconductor parameters comparable to its benzyl-substituted derivative. Thienylmethyl groups induced the FET response, and thus we investigated the utility of the 2-thieno[3,2-b] thio-phenemethyl group. Critical parameters, including reorganization energies (lambda), hole couplings (V), and hole hopping rates (W) were estimated based on experimental and DFT data. The benzyl and 2-anthrylmethy groups constructed hole transfer pathways comparable to that of acenes, whereas the 2-thieno [3,2-b] thiophenemethyl substituent resulted in the assembly of a unique three-dimensional network. The findings described in this study may lead to the fabrication of superior FET devices based on the chemistry of 1,3-diphosphacyclobutane-2,4-diyl.

First author: Ciancaleoni, G, Bonding Analysis in Homo- and Hetero-Trihalide Species: A Charge Displacement Study, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 1, 3804, (2016)
Abstract: The bonding in homo-(X-3(-)) and hetero-trihalides (XYX-), with X = F, Cl, Br, and I; Y = I, has been analyzed through the charge displacement (CD) method, coupled with energy decomposition analysis (EDA). We focus our attention on how the different bond components vary with the distance between the terminal and the central halogen atoms. The results clearly show that all the homo-halide systems X-3(-) feature the same trend of the charge transfer (CT) versus the asymmetry of the three-body system, defined as the ratio between the two bond lengths d(X1-X2) and d(X2-X3), whereas in the case of the hetero-trihalides BrIBr- and ClICl-, the CT values are similar, but systematically lower with respect to the homo-trihalide case. Comparison with solid-state geometries also allows us to estimate the influence of the crystal lattice (the packing and the interactions with the surrounding fragments) on the geometry. Following the results reported here, the CD method is confirmed to be a useful alternative computational tool to analyze the nature and the origin of weak intermolecular interactions such as halogen and hydrogen bonding.

First author: Ardizzoia, GA, A Quantitative Description of the sigma-Donor and pi-Acceptor Properties of Substituted Phenanthrolines, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 1, 3829, (2016)
Abstract: The bond between molybdenum and substituted 1,10-phenanthroline ligands in a series of [Mo(CO)(4)(phen*)] complexes has been studied by combining experimental data (nu(CO)) with DFT calculations. First, natural orbitals for chemical valence (NOCV) were calculated: The resulting charge-transfer magnitudes (Delta q(i)) associated with the deformation density channels (Delta rho(i)) were related to sigma-donation and pi-back-donation. Then, energy decomposition analysis was performed by applying the extended transition state (ETS) scheme. The outcomes of the ETS-NOCV approach has allowed us to quantify the energetic contribution of both ligand-to-metal (E-sigma) and metal-to-ligand (E-pi) interactions. A new parameter (T-phen) has been introduced comprising both E-sigma and E-pi and thus providing a descriptor for the overall electronic contribution given by phenanthrolines to the metal-ligand bond. This was corroborated by the linear correlation found between T-phen and the nu(CO) vibration modes of [Mo(CO)(4)(phen*)] complexes, at least for those containing a 2,9-unsubstituted phenanthroline. The case of [Mo(CO)(4)(phen*)] derivatives with a 2,9-substituted phen* is also discussed.

First author: Munzer, JE, Difluoroborenium Cation Stabilized by Hexaphenyl-Carbodiphosphorane: A Concise Study on the Molecular and Electronic Structure of [(Ph3P)(2)C(sic)BF2][BF4], EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 1, 3852, (2016)
Abstract: The reaction of hexaphenyl-carbodiphosphorane C(PPh3)(2) (CDP, 1) with BF3OEt2 provides the corresponding difluoroborenium cation [CDP-BF2](+) (2(+)) through fluoride abstraction. Advanced NMR spectroscopy methods, including F-19,P-31 HMQC; P-31,C-13 HMQC; F-19,H-1 HOESY; F-19 NOESY; P-31,C-13 INEPT; and H-1, P-31, F-19, and B-11 diffusion NMR measurements, were performed, and they revealed strong ion pairing of 2(+) with the [BF4](-) counterion in chloroform solution. Structural and computational studies showed strong donor-acceptor interactions, in which the sigma and lone pairs of electrons of C(PPh3)(2) donate into the vacant orbitals of the [BF2](+) fragment. The C-B bond shows the highest interaction energy of 242.9 kcalmol(-1) found for the corresponding carbodiphosphorane adducts.

First author: Prokes, L, Laser Ablation Synthesis of Gold Selenides by using a Mass Spectrometer as a Synthesizer: Laser Desorption Ionization Timeof- Flight Mass Spectrometry, CHEMISTRY-A EUROPEAN JOURNAL, 22, 11261, (2016)
Abstract: Methods for the rapid construction of new chemical motifs have the potential to accelerate the development of nanoscience. The synthesis of new chemical entities by laser ablation has been systematically demonstrated by using mixtures of gold and selenium. The compounds generated are detected by time- of- flight mass spectrometry and, for selected compounds, the structure is investigated by using density functional theory optimization. In total, 67 new gold selenide clusters have been synthesized, demonstrating an unsuspected richness in gold chemistry. Chemical species generated in the gas phase might inspire new routes for the synthesis of novel compounds in the solid state.

First author: Grabowski, SJ, Comparison of Hydrogen and Gold Bonding in [XHX](-), [XAuX](-), and Isoelectronic [NgHNg](+), [NgAuNg](+) (X=Halogen, Ng=Noble Gas), CHEMISTRY-A EUROPEAN JOURNAL, 22, 11317, (2016)
Abstract: Quantum chemical calculations at the MP2/aug-cc- pVTZ and CCSD(T)/aug-cc-pVTZ levels have been carried out for the title compounds. The electronic structures were analyzed with a variety of charge and energy partitioning methods. All molecules possess linear equilibrium structures with D-infinity h symmetry. The total bond dissociation energies (BDEs) of the strongly bonded halogen anions [XHX](-) and [XAuX](-) decrease from [FHF](-) to [IHI](-) and from [FAuF](-) to [IAuI](-). The BDEs of the noble gas compounds [NgHNg](+) and [NgAuNg](+) become larger for the heavier atoms. The central hydrogen and gold atoms carry partial positive charges in the cations and even in the anions, except for [IAuI](-), in which case the gold atom has a small negative charge of -0.03 e. The molecular electrostatic potentials reveal that the regions of the most positive or negative charges may not agree with the partial charges of the atoms, because the spatial distribution of the electronic charge needs to be considered. The bonding analysis with the QTAIM method suggests a significant covalent character for the hydrogen bonds to the noble gas atoms in [NgHNg](+) and to the halogen atoms in [XHX](-). The covalent character of the bonding in the gold systems [NgAuNg](+) and [XAuX](-) is smaller than in the hydrogen compound. The energy decomposition analysis suggests that the lighter hydrogen systems possess dative bonds X–> H+<- X- or Ng -> H+<- Ng while the heavier homologues exhibit electron sharing through two-electron, three-center bonds. Dative bonds X–> Au+<- X- and Ng -> Au+<- Ng are also diagnosed for the lighter gold systems, but the heavier compounds possess electron-shared bonds.

First author: Mei, L, An Unprecedented Two-Fold Nested Super-Polyrotaxane: SulfateDirected Hierarchical Polythreading Assembly of Uranyl Polyrotaxane Moieties, CHEMISTRY-A EUROPEAN JOURNAL, 22, 11329, (2016)
Abstract: The hierarchical assembly of well-organized submoieties could lead to more complicated superstructures with intriguing properties. We describe herein an unprecedented polyrotaxane polythreading framework containing a two-fold nested super-polyrotaxane substructure, which was synthesized through a uranyl-directed hierarchical polythreading assembly of one-dimensional polyrotaxane chains and two-dimensional polyrotaxane networks. This special assembly mode actually affords a new way of supramolecular chemistry instead of covalently linked bulky stoppers to construct stable interlocked rotaxane moieties. An investigation of the synthesis condition shows that sulfate can assume a vital role in mediating the formation of different uranyl species, especially the unique trinuclear uranyl moiety [(UO2)(3)O(OH)(2)](2+), involving a notable bent [O=U=O] bond with a bond angle of 172.0(9)degrees. Detailed analysis of the coordination features, the thermal stability as well as a fluorescence, and electrochemical characterization demonstrate that the uniqueness of this super-polyrotaxane structure is mainly closely related to the trinuclear uranyl moiety, which is confirmed by quantum chemical calculations.

First author: Cortese, AJ, Oxygen Anion Solubility as a Factor in Molten Flux Crystal Growth, Synthesis, and Characterization of Four New Reduced Lanthanide Molybdenum Oxides: Ce4.918(3)Mo3O16, Pr4.880(3)Mo3O16, Nd4.910(3)Mo3O16, and Sm4.952(3)Mo3O16, CRYSTAL GROWTH & DESIGN, 16, 4225, (2016)
Abstract: Four new reduced lanthanide molybdenum oxides containing mixed valent Mo(V/VI)O-4 tetrahedra were prepared in single crystal form by utilizing a high temperature molten salt flux synthesis involving an in situ reduction step. Calculations support the experimentally observed result that large alkali metal cations such as cesium are superior compared to the smaller alkali metal cations such as sodium in solvating O2- to facilitate oxide crystal growth in halide melts. All four compounds were structurally characterized by single crystal and powder X-ray diffraction methods and were found to crystallize in the cubic space group Pn (3) over barn. The temperature dependence of the magnetic susceptibility of these compounds was measured, and all were found to exhibit simple paramagnetism.

First author: Boereboom, JM, Toward Hamiltonian Adaptive QM/MM: Accurate Solvent Structures Using Many-Body Potentials, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 3441, (2016)
Abstract: Adaptive quantum mechanical (QM)/molecular mechanical (MM) methods enable efficient molecular simulations of chemistry in solution. Reactive subregions are modeled with an accurate QM potential energy expression while the rest of the system is described in a more approximate manner (MM). As solvent molecules diffuse in and out of the reactive region, they are gradually included into (and excluded from) the QM expression. It would be desirable to model such a system with a single adaptive Hamiltonian, but thus far this has resulted in distorted structures at the boundary between the two regions. Solving this long outstanding problem will allow microcanonical adaptive QM/MM simulations that can be used to obtain vibrational spectra and dynamical properties. The difficulty lies in the complex QM potential energy expression, with a many-body expansion that contains higher order terms. Here, we outline a Hamiltonian adaptive multiscale scheme within the framework of many-body potentials. The adaptive expressions are entirely general, and complementary to all standard (nonadaptive) QM/MM embedding schemes available. We demonstrate the merit of our approach on a molecular system defined by two different MM potentials (MM/MM’). For the long-range interactions a numerical scheme is used (particle mesh Ewald), which yields energy expressions that are many-body in nature. Our Hamiltonian approach is the first to provide both energy conservation and the correct solvent structure everywhere in this system.

First author: Novak, M, Modulating Electron Sharing in Ion-pi-Receptors via Substitution and External Electric Field: A Route toward Bond Strengthening, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 3788, (2016)
Abstract: Substituted coronenes, a family of ion-pi receptors whose ion-affinities can be explained exclusively neither via ion-quadrupole nor induction/polarization mechanisms, are studied. The best descriptors of ion-affinity among these species are those characterizing charge-transfer between ions and the pi-systems, e.g. vertical ionization potential, electron affinity, and the relative energies of charge-transfer excited-states (CTESs). The variation of the electric multipole moments, polarizability, binding energy, and relative energy of CTESs in the presence of an external electric field (EEF) is evaluated. The results indicate that the EEF has a negligible effect on the polarizability and quadrupole moment of the systems. However, it significantly affects the binding energies, CTES energies, and the dipole moments of the receptors. Contrary to the changes in the dipole moment, the variation pattern of the binding energy is more consistent with the pattern observed for the CTES energy changes. Finally, by analyzing the exchange correlation component of the binding energy we demonstrate that the increased binding energy, i.e. bond strengthening, originates from enhanced electron sharing and multicenter covalency between the ions and the pi-systems as a result of the state-mixing between the ground-state and the CTESs. According to our findings, we hypothesize that the electron sharing and in extreme cases the multicenter covalency are the main driving forces for complexation of ions with extended pi-receptors such as carbon nanostructures.

First author: Peeples, CA, Implementation of the SM12 Solvation Model into ADF and Comparison with COSMO, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 4033, (2016)
Abstract: In this article, an implementation of the newest iteration of the Minnesota solvation model, SM12, into the Amsterdam density functional (ADF) computational package is presented. ADF makes exclusive use of Slater-type orbitals (STO), which correctly represent the true atomic orbitals for atoms, whereas SM12 and the underlying charge model 5 (CM5) have previously only been tested on Gaussian-type orbitals (GTO). This new implementation is used to prove the basis set independence of both CM5 and SM12. A detailed comparison of the SM12 and COSMO solvation models, as implemented in ADF, is also presented. We show that this new implementation of SM12 has a mean unsigned error (MUE) of 0.68 kcal/mol for 272 molecules in water solvent, 4.10 kcal/mol MUE for 112 charged ions in water, and 0.92 kcal/mol MUE for 197 solvent calculations of various molecules. SM12 outperforms COSMO for all neutral molecules and performs as well as COSMO for cationic molecules, only falling short when anionic molecules are taken into consideration, likely due to CM5’s use of Hirshfeld charges and their poor description of anionic molecules, though CM5 seems to improve upon this discrepancy.

First author: Su, DM, A relativistic DFT probe of polypyrrolic macrocyclic diuranium(III) complexes with terminal solvents and iodines, JOURNAL OF MOLECULAR MODELING, 22, 4033, (2016)
Abstract: Relativistic density functional theory finds that two isomers of a diuranium(III) complex of a polypyrrolic macrocycle (H4L) feature active sites on uranium moieties, allowing for their potential application in activating industrially and economically important small molecules. To address this, a series of adducts [(X)(n)U-2(L)]((2-m)+) (X = THF, I- and HI; n = 1 and 2; m=0, 1 and 2) have been examined. The coordination from X to the exposed uranium(s) changes the general geometry and electronic structure slightly. Thermodynamic calculations reveal that iodine termination is energetically favored over THF/HI coordination.

First author: Manzetti, S, The accurate wavefunction of the active space of the rhenium dimer resolved using the ab initio Brueckner coupled-cluster method, STRUCTURAL CHEMISTRY, 27, 1071, (2016)
Abstract: Rhenium is a unique metal in the 5d-series of transition metals having the highest boiling point in the periodic table. It is also known to exist in poly-coordinated states with other rhenium atoms. Based on the existence of strikingly unusual states of elements in astrophysical bodies of nebulae, interstellar debris, exoplanets and other part of the universe, a set of ab initio calculations of the rhenium dimer has been conducted to provide detailed description of its molecular properties that are applicable to the astrochemical research. Ab initio calculations and NBO analysis revealed that rhenium forms quintuple bond in its diatomic state and that it displays preferred state of triplet configuration with high-lying electrons. Calculations also revealed that the two states of rhenium dimer vary in their bonding nature. The singlet spin space is composed of five single bonds, while the triplet state comprises four bonds and two additional lone pairs. Interestingly, while these two states vary in subdivision of electrons at the highest d-level, they share the same frequencies while having different zero-point energies. The calculations reveal intrinsic synergy between the atoms composed of natural bond orbitals, the bonding pattern and the thermochemical properties of Re-2, all features being of significant importance to physical and chemical sciences.

First author: Pandey, KK, Relativistic DFT calculations of structure and Sn-119 NMR chemical shifts for bent M-Sn-C bonding in Power’s metallostannylenes of chromium, molybdenum, tungsten and iron and diaryl stannylenes, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 815-816, 23, (2016)
Abstract: Dispersion corrected density functional theory calculations of the metallostannylene complexes [(eta(5)-C5H5)(CO)(3)M(SnC6H3-2,6-Ar-2)] (1-6; M = Cr, Mo, W; Ar = Mes, Trip), [(eta(5)-C5H5)(CO)(2)Fe(SnC6H3-2,6-Dip(2))] (7) and [(eta(5)-C5H5)(CO)(2)Fe(SnC6H3-2,6-Trip(2))] (8) and monomeric diaryl stannylenes [Sn(C6H2-2,6-Mes(2)-4-Cl)(2)] (9), [Sn(C6H2-2,6-Mes(2)-4-SiMe3)(2)] (10), [Sn(C6H-2,6-Mes(2)-3,5-iPr(2))(2)] (11), [Sn(C6H3-2,6-Mes(2))(2)] (12) and [Sn(C6H3-2,6-Dip(2))(2)] (13) (Mes = C6H2-2,4,6-Me-3; Trip = C6H2-2,4,6-iPr(3); Dip = C6H2-2,6-iPr(2)) have been carried out at the BP86-D3(BJ)/TZ2P/ZORA level of theory. The calculated geometrical parameters of the studied metallostannyles (Power et al., Organometallics 21 (2002) 5622; 30 (2011) 6316) and diaryl stannylenes (Power et al., Organometallics 34 (2015) 2222) are in good agreement with the available experimental values. The bent geometries at tin are consistent with the presence of a divalent Sn(II) center. The M-Sn-C bond angles in metallostannylenes are smaller than C-Sn-C bond angles in diaryl stannylenes. The lengthening of M – Sn bonds and decrease in M-Sn-C bond angles are found in the solvent (benzene) phase geometries optimized. The Sn-119 NMR chemical shifts (ppm) have been calculated with the direct implementation of the gauge including atomic orbitals (GIAO) method. The calculated Sn-119 chemical shifts with ZORA spin orbit level in gas phase yield reliable results. While switching from ZORA spin orbit level to ZORA scalar level results Sn-119 upfield shift of ca. 300e400 ppm. Due to greater percentage s character of Sn lone pair in the chromium complexes [(eta(5)-C5H5)(CO)(3)M(SnC6H3-2,6-Mes(2))] (1) and [(eta(5)-C5H5)(CO)(3)M(SnC6H3-2,6-Trip(2))] (4), the upfield Sn-119 NMR chemical shifts are observed. The relationship between computed (dcalcd) Sn-119 NMR chemical shifts and 1/Delta E(LUMO-HOMO)) clearly exhibit a linear trend. The difference between Sn-119 NMR chemical shifts of metallostannylenes (1-8) and diaryl stannylenes (9-13) has been analyzed. The Sn-C bonds in diaryl stannylenes are weaker than the Sn-C bonds in metallostannylenes. The Sn nuclei are more shielded in diaryl stannylenes than in metallostannylenes. As a consequence, the upfield values of Sn-119 NMR chemical shifts are observed for diaryl stannylenes both experimentally and theoretically. Upfield Sn-119 chemical shifts, which deviate much from the experimental values, are observed for optimized geometries of metallostannylenes in solvent (benzene) phase. The decrease in asymmetric parameter (h) causes a downfield Sn-119 NMR chemical shift accompanied by an increase in Sn-119 chemical shift anisotropy.

First author: Makarewicz, E, On the nature of interactions in the (F2OXeNCCH3)-N-… complex: Is there the Xe(IV)N bond?, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 1876, (2016)
Abstract: Nature of the bonding in isolated XeOF2 molecule and (F2OXeNCCH3)-N-… complexes have been studied in the gas phase (0 K) using Quantum Chemical Topology methods. The wave functions have been approximated at the MP2 and DFT levels of calculations, using the APFD, B3LYP, M062X, and B2PLYP functionals with the GD3 dispersion correction. The nature of the formal XeO bond in the XeOF2 monomer depends on the basis set used (all-electron vs. the ecp-28 approximation for Xe). Within the all-electron basis set approach the bond is represented by two bonding attractors, V-i (= 1,2)(Xe,O), with total population of about 1.06e and highly delocalized electron density in both bonding basins. No bonding basins are observed using the ecp-28 approximation. These results shows that the nature of xenon-oxygen is complicated and may be described with mesomeric equilibrium of the Lewis representations: Xe(+)O(-) and Xe(-)O(+). For both the xenon-oxygen and xenon-fluorine interactions the charge-shift model can be applied. The (F2OXeNCCH3)-N-… complex exists in two structures: parallel, stabilized by non-covalent (CO)-O-… and (XeN)-N-… interactions and linear stabilized by the (XeN)-N-… interaction. Topological analysis of ELF shows that the (F2OXeNCCH3)-N-… molecule appears as a weakly bound intermolecular complex. Intermolecular interaction energy components have also been studied using Symmetry Adapted Perturbation Theory.

First author: Shen, J, DFT Study on the Mechanism of the Electrochemical Reduction of CO2 Catalyzed by Cobalt Porphyrins, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 15714, (2016)
Abstract: The electrochemical reduction of CO2 is a promising way to store renewable energy in fuels or other chemicals. However, the high overpotential and low efficiency of the reaction hinder the development of the area. More work is needed on the investigation of the mechanism in order to obtain new insights into developing efficient catalysts. We report here a density functional theory (DFT) study of the electrochemical reduction of CO2 on cobalt porphyrin. The CO2- anion adduct is demonstrated to be the key intermediate formed only when the cobalt center of the complex is in the Co-I oxidation state. We find that formic acid can be produced as minor product through a [Co(P)-(OCHO)] intermediate, while CO is the main product through a decoupled proton electron transfer. CH4 is produced as minor product from subsequent CO reduction by concerted proton-coupled electron transfers assumed for each electrochemical step. Our theoretical interpretations are consistent with the experimental results presented in our recent experiments and give deeper insights into the mechanism of the CO2 electrochemical reduction on cobalt porphyrin complexes.

First author: Visser, BR, First spectroscopic observation of gold(I) butadiynylide: Photodetachment velocity map imaging of the AuC4H anion, JOURNAL OF CHEMICAL PHYSICS, 145, 15714, (2016)
Abstract: The velocity map imaging technique was used in the investigation of gold(I) butadiynylide, AuC4H-, with images recorded at two excitation wavelengths. The resultant photodetachment spectra show a well defined vibrational progression in the neutral with an energy spacing of 343 ± 3 cm(-1). The adiabatic electron affinity was determined to be 1.775 ± 0.005 eV and assigned to the X-1 Sigma(+) <- X-2 Sigma(+) transition between the anionic and neutral ground states. Franck-Condon simulations performed on density functional theory optimized geometries assisted the assignment of linear geometries to the neutral and anion and the observed vibrational progression to that of the Au-(CH)-H-4 stretch.

First author: Chakraborty, D, Optical response and gas sequestration properties of metal cluster supported graphene nanoflakes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 18811, (2016)
Abstract: The possibility of obtaining metal cluster (M3O+, M = Li, Na, K) supported pristine, B-doped and BN-doped graphene nanoflakes (GR, BGR and BNGR, respectively) has been investigated by carrying out density functional theory (DFT) based calculations. Thermochemical analysis reveals the good stability of M3O+@GR/BGR/BNGR moieties. The dynamic stability of M3O+@GR/BGR/BNGR moieties is confirmed through an atom-centered density matrix propagation simulation at 298 K up to 500 fs. Orbital and electrostatic interactions play pivotal roles in stabilizing the metal-cluster supported graphene nanoflakes. The metal clusters lower the Fermi levels of the host nanoflakes and enable them to exhibit reasonably good optical response properties such as polarizability and static first hyperpolarizability. In particular, Na3O+/(KO+)-O-3@BGR complexes exhibit very large first hyperpolarizability values at the static field limit. All the M3O+@BGR/BNGR moieties demonstrate broadband optical absorption encompassing the ultraviolet, visible as well as infrared domains. The metal-cluster supported graphene nanoflakes, in general, can sequestrate polar molecules, viz. CO, NO and CH3OH, in a thermodynamically more favorable way than GR, BGR and BNGR. In the adsorbed state, the CO, NO and CH3OH molecules, in general, attain an ‘active’ state as compared to their free counterparts.

First author: Rauhalahti, M, Magnetic response properties of gaudiene – a cavernous and aromatic carbocage, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 18880, (2016)
Abstract: spherical and cavernous carbocage molecule exhibiting faces with larger ring sizes than regular fullerenes is a suitable species for investigating how molecular magnetic properties depend on the structure of the molecular framework. The studied all-carbon gaudiene (C-72) is a highly symmetrical molecule with three-and four-fold faces formed by twelve membered rings. Here, we attempt to unravel the magnetic response properties of C-72 by performing magnetic shielding and current density calculations with the external magnetic field applied in different directions. The obtained results indicate that the induced current density flows mainly along the chemical bonds that are largely perpendicular to the magnetic field direction. However, the overall current strength for different directions of the magnetic field is nearly isotropic differing by only 10% indicating that C-72 can to some extent be considered to be a spherical aromatic molecule, whose current density and magnetic shielding are ideally completely isotropic. The induced magnetic field is found to exhibit long-range shielding cones in the field direction with a small deshielding region located perpendicularly to the field outside the molecule. The magnetic shielding is isotropic inside the molecular framework of C-72, whereas an orientation-dependent magnetic response appears mainly at the exterior of the molecular cage.

First author: Alkan, F, Spin-orbit effects on the Sn-119 magnetic-shielding tensor in solids: a ZORA/DFT investigation, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 18914, (2016)
Abstract: Periodic-boundary and cluster calculations of the magnetic-shielding tensors of Sn-119 sites in various co-ordination and stereochemical environments are reported. The results indicate a significant difference between the predicted NMR chemical shifts for tin(II) sites that exhibit stereochemically-active lone pairs and tin(IV) sites that do not have stereochemically-active lone pairs. The predicted magnetic shieldings determined either with the cluster model treated with the ZORA/Scalar Hamiltonian or with the GIPAW formalism are dependent on the oxidation state and the co-ordination geometry of the tin atom. The inclusion of relativistic effects at the spin-orbit level removes systematic differences in computed magnetic-shielding parameters between tin sites of differing stereochemistries, and brings computed NMR shielding parameters into significant agreement with experimentally-determined chemical-shift principal values. Slight improvement in agreement with experiment is noted in calculations using hybrid exchangecorrelation functionals.

First author: Ramanantoanina, H, Core electron excitations in U4+: modelling of the nd(10)5f(2) -> nd(9)5f(3) transitions with n=3, 4 and 5 by ligand field tools and density functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 19020, (2016)
Abstract: Ligand field density functional theory (LFDFT) calculations have been used to model the uranium M-4,M-5, N-4,N-5 and O-4,O-5-edge X-ray absorption near edge structure (XANES) in UO2, characterized by the promotion of one electron from the core and the semi-core 3d, 4d and 5d orbitals of U4+ to the valence 5f. The model describes the procedure to resolve non-empirically the multiplet energy levels originating from the two-open-shell system with d and f electrons and to calculate the oscillator strengths corresponding to the dipole allowed d(10)f(2) -> d(9)f(3) transitions appropriate to represent the d electron excitation process. In the first step, the energy and UO2 unit-cell volume corresponding to the minimum structures are determined using the Hubbard model (DFT+U) approach. The model of the optical properties due to the uranium nd(10)5f(2) -> nd(9)5f(3) transitions, with n = 3, 4 and 5, has been tackled by means of electronic structure calculations based on the ligand field concept emulating the Slater-Condon integrals, the spin-orbit coupling constants and the parameters of the ligand field potential needed by the ligand field Hamiltonian from Density Functional Theory. A deep-rooted theoretical procedure using the LFDFT approach has been established for actinide-bearing systems that can be valuable to compute targeted results, such as spectroscopic details at the electronic scale. As a case study, uranium dioxide has been considered because it is a nuclear fuel material, and both atomic and electronic structure calculations are indispensable for a deeper understanding of irradiation driven microstructural changes occurring in this material.

First author: Ramanathan, N, PCl3-C6H6 heterodimers: evidence for P center dot center dot center dot pi phosphorus bonding at low temperatures, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 19350, (2016)
Abstract: A phosphorous trichloride (PCl3)-benzene (C6H6) heterodimer was generated in a low temperature N-2 matrix and was characterized using infrared spectroscopy. The structure of the heterodimer produced in the matrix isolation experiment was discerned through ab initio computations. Computations disclosed that the experimentally detected dimer is stabilized through strong non-covalent phosphorus bonded P center dot center dot center dot pi interaction, considered as a class of pnicogen bonding. This experimentally unmapped P center dot center dot center dot pi interaction so far has been reconnoitered using atoms in molecules and natural bond orbital and energy decomposition analyses. The influence of substitutions on both the PCl3 and C6H6 monomeric units of the heterodimer was subsequently examined to understand the strength of P center dot center dot center dot pi interaction as a result of these substitutions.

First author: Novotny, J, Lone-pair-pi interactions: analysis of the physical origin and biological implications, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 19472, (2016)
Abstract: Lone-pair-pi (lp-pi) interactions have been suggested to stabilize DNA and protein structures, and to participate in the formation of DNA-protein complexes. To elucidate their physical origin, we have carried out a theoretical multi-approach analysis of two biologically relevant model systems, water-indole and water-uracil complexes, which we compared with the structurally similar chloride-tetracyanobenzene (TCB) complex previously shown to contain a strong charge-transfer (CT) binding component. We demonstrate that the CT component in lp-pi interactions between water and indole/uracil is significantly smaller than that stabilizing the Cl–TCB reference system. The strong lp(Cl-)-pi(TCB) orbital interaction is characterized by a small energy gap and an efficient lp-pi(star) overlap. In contrast, in lp-pi interactions between water and indole or uracil, the corresponding energy gap is larger and the overlap less efficient. As a result, water-uracil and water-indole interactions are weak forces composed by smaller contributions from all energy components: electrostatics, polarization, dispersion, and charge transfer. In addition, indole exhibits a negative electrostatic potential at its pi-face, making lp-pi interactions less favorable than O-H center dot center dot center dot pi hydrogen bonding. Consequently, some of the water-tryptophan contacts observed in X-ray structures of proteins and previously interpreted as lp-pi interactions [Luisi, et al., Proteins, 2004, 57, 1-8], might in fact arise from O-H center dot center dot center dot pi hydrogen bonding.

First author: Calegari, F, Charge migration induced by attosecond pulses in bio-relevant molecules, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 49, 19472, (2016)
Abstract: After sudden ionization of a large molecule, the positive charge can migrate throughout the system on a sub-femtosecond time scale, purely guided by electronic coherences. The possibility to actively explore the role of the electron dynamics in the photo-chemistry of bio-relevant molecules is of fundamental interest for understanding, and perhaps ultimately controlling, the processes leading to damage, mutation and, more generally, to the alteration of the biological functions of the macromolecule. Attosecond laser sources can provide the extreme time resolution required to follow this ultrafast charge flow. In this review we will present recent advances in attosecond molecular science: after a brief description of the results obtained for small molecules, recent experimental and theoretical findings on charge migration in bio-relevant molecules will be discussed.

First author: Qu, N, A computational investigation of polypyrrolic macrocyclic actinyl complexes: effects of explicit solvent coordination on structure, vibrational spectra and redox property, THEORETICAL CHEMISTRY ACCOUNTS, 135, 19472, (2016)
Abstract: Eighteen actinyl complexes of a Schiff-base polypyrrolic macrocycle (H4L), [(Sol)(An(m)O(2))(H2L)]n(-)(Sol = Vacant, pyridine (py) and tetrahydrofuran (THF); An=U, Np and Pu; m = VI and n = 0, m = V and n = 1) were investigated using relativistic density functional theory. Comparison of complexes with and without the explicit solvent coordination to the metal center, and changes in actinide element and metal oxidation state provide insight into their effects on structural and energetic properties of the complexes. Compared with those of the solvent-free complexes, the An=O bond lengths of the solvated complexes differ within 0.01 angstrom, and the deviation of the O=An=O angles is less than 1 degrees. The H center dot center dot center dot O-endo bonds are relatively sensitive to the explicit solvent coordination, showing the largest discrepancy of 0.05 angstrom. Charges and electron-spin densities of actinides are only slightly affected by the inclusion of the explicit solvent. Reduction potentials of actinyl complexes have been addressed, and their dependence on the bulk solvent polarity is being discussed, using a simple model based on the Born equation.

First author: Durec, M, Modified Guanines as Constituents of Smart Ligands for Nucleic Acid Quadruplexes, CHEMISTRY-A EUROPEAN JOURNAL, 22, 10912, (2016)
Abstract: Repetitive guanine-rich nucleic acid sequences play a crucial role in maintaining genome stability and the cell life cycle and represent potential targets for regulatory drugs. Recently, it has been demonstrated that guanine-based ligands with a porphyrin core can be used as markers of G-quadruplex assemblies in cell tissues. Herein, model systems of guanine-based ligands are explored by DFT methods. The energies of formation of modified guanine tetrads and those of modified tetrads stacked on the top of natural guanine tetrads have been calculated. The interaction energy has been decomposed into contributions from hydrogen bonding, stacking, and ion coordination and a twist-rise potential energy scan has been performed to find the individual local minima. Energy decomposition analysis reveals the impact of various substituents (F, Cl, Br, I, Me, NMe2) on individual energy terms. In addition, cooperative reinforcement in forming the modified and stacked tetrads, as well as the frontier orbitals participating in the hydrogenbonding framework involving the HOMO-LUMO gap between the occupied sigma(HOMO) on the proton-accepting C=O and =N- groups and unoccupied sigma(LUMO) on the N-H groups, has been studied. The investigated systems are demonstrated to have a potential in ligand development, mainly due to stacking enhancement compared with natural guanine, which is used as a reference.

First author: Nagurniak, GR, Shedding Light on the Nature of Host-Guest Interactions in PAHs-ExBox(4+) Complexes, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 15480, (2016)
Abstract: Host-guest (HG) systems formed by polycyclic aromatic hydrocarbons and ExBox(4+) are suitable models to gain a deeper understanding of pi-pi interactions, which are fundamental in supramolecular chemistry. The physical nature of HG interactions between ExBox(4+) (1) and polycyclic aromatic hydrocarbons (PAHs) (2-12) is investigated at the light of the energy decomposition (EDA-NOCV), noncovalent interactions (NCI), and magnetic response analyses. The EDA-NOCV results show that the dispersion forces play a crucial role in the HG interactions in PAHs subset of wExBox(4+) complexes. The HG interaction energies are dependent on both the size of the PAH employed and the number of pi-electrons in the guest molecules. The parallel face-to-face arrangement between HG aromatic moieties is also fundamental to maximize the dispersion interaction and consequently for the attractive energy which leads to the inclusion complex formation.

First author: Liu, L, The importance of dynamics studies on the design of sandwich structures: a CrB24 case, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 18336, (2016)
Abstract: Computational prediction and design of sandwich structures have drawn a lot of attention because of their interesting bond characteristics and broad applications. Most studies focus on the thermodynamic stability. In this study, we performed a series of Born-Oppenheimer molecular dynamics (BO-MD) simulations to investigate the dynamic stability of the well-known sandwich structure CrB24. The aim was to find at which temperature the sandwich structure is stable. The MD results showed that the sandwich structure has an extremely poor dynamic stability. Additionally, one highly symmetric endohedral structure with a chromium atom at the center of a B-24 cage was found. As a demonstration, we attempted to point out the importance of dynamics studies on the future design of sandwich structures.

First author: Zanetti-Polzi, L, Extending the essential dynamics analysis to investigate molecular properties: application to the redox potential of proteins, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 18450, (2016)
Abstract: Here, a methodology is proposed to investigate the collective fluctuation modes of an arbitrary set of observables, maximally contributing to the fluctuation of another functionally relevant observable. The methodology, based on the analysis of fully classical molecular dynamics (MD) simulations, exploits the essential dynamics (ED) method, originally developed to analyse the collective motions in proteins. We apply this methodology to identify the residues that are more relevant for determining the reduction potential (E-0) of a redox-active protein. To this aim, the fluctuation modes of the single-residue electrostatic potentials mostly contributing to the fluctuations of the total electrostatic potential (the main determinant of E-0) are investigated for wild-type azurin and two of its mutants with a higher E-0. By comparing the results here obtained with a previous study on the same systems [Zanetti-Polzi et al., Org. Biomol. Chem., 2015, 13, 11003] we show that the proposed methodology is able to identify the key sites that determine E-0. This information can be used for a general deeper understanding of the molecular mechanisms on the basis of the redox properties of the proteins under investigation, as well as for the rational design of mutants with a higher or lower E-0. From the results of the present analysis we propose a new azurin mutant that, according to our calculations, shows a further increase of E-0 .

First author: Zhang, DW, Effects of p-(Trifluoromethoxy)benzyl and p-(Trifluoromethoxy)phenyl Molecular Architecture on the Performance of Naphthalene Tetracarboxylic Diimide-Based Air Stable n-Type Semiconductors, ACS APPLIED MATERIALS & INTERFACES, 8, 18277, (2016)
Abstract: N,N’-Bis(4-trifluoromethoxyphenyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-POCF3) and N,N’-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) have similar optical and electrochemical properties with a deep LUMO level of approximately 4.2 eV, but exhibit significant differences in electron mobility and molecular packing. NDI-POCF3 exhibits nondetectable charge mobility. Interestingly, NDI-BOCF3 shows air-stable electron transfer performance with enhanced mobility by increasing the deposition temperature onto the octadecyltrichlorosilane (OTS)-modified SiO2/Si substrates and achieves electron mobility as high as 0.7 cm(2) V-1 s(-1) in air. The different mobilities of those two materials can be explained by several factors including thin-film morphology and crystallinity. In contrast to the poor thin-film morphology and crystallinity of NDI-POCF3, NDI-BOCF3 exhibits larger grain sizes and improved crystallinities due to the higher deposition temperature. In addition, the theoretical calculated transfer integrals of the intermolecular lowest unoccupied molecular orbital (LUMO) of the two materials further show that a large intermolecular orbital overlap of NDI- BOCF3 can transfer electron more efficiently than NDI-POCF3 in thin-film transistors. On the basis of fact that the theoretical calculations are consistent with the experimental results, it can be concluded that the p-(trifluoromethoxy) benzyl (BOCF3) molecular architecture on the former position of the naphthalene tetracarboxylic diimides (NDI) core provides a more effective way to enhance the intermolecular electron transfer property than the p-(trifluoromethoxy) phenyl (POCF3) group for the future design of NDI-related air-stable n-channel semiconductor.

First author: Shelby, ML, Ultrafast Excited State Relaxation of a Metalloporphyrin Revealed by Femtosecond X-ray Absorption Spectroscopy, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 8752, (2016)
Abstract: Photoexcited Nickel(II) tetramesitylporphyrin (NiTMP), like many open-shell metalloporphyrins, relaxes rapidly through multiple electronic states following an initial porphyrin-based excitation, some involving metal centered electronic configuration changes that could be harnessed catalytically before excited state relaxation. While a NiTMP excited state present at 100 ps was previously identified by X-ray transient absorption (XTA) spectroscopy at a synchrotron source as a relaxed (d,d) state, the lowest energy excited state (J. Am. Chem. Soc., 2007, 129, 9616 and Chem. Sci., 2010, 1, 642), structural dynamics before thermalization were not resolved due to the similar to 100 ps duration of the available X-ray probe pulse. Using the femtosecond (fs) X-ray pulses of the Linac Coherent Light Source (LCLS), the Ni center electronic configuration from the initial excited state to the relaxed (d,d) state has been obtained via ultrafast Ni K-edge XANES (X-ray absorption near edge structure) on a time scale from hundreds of femtoseconds to 100 ps. This enabled the identification of a short-lived Ni(I) species aided by time-dependent density functional theory (TDDFT) methods. Computed electronic and nuclear structure for critical excited electronic states in the relaxation pathway characterize the dependence of the complex’s geometry on the electron occupation of the 3d orbitals. Calculated XANES transitions for these excited states assign a short-lived transient signal to the spectroscopic signature of the Ni(I) species, resulting from intramolecular charge transfer on a time scale that has eluded previous synchrotron studies. These combined results enable us to examine the excited state structural dynamics of NiTMP prior to thermal relaxation and to capture intermediates of potential photocatalytic significance.

First author: Cameron, JM, Investigating the Transformations of Polyoxoanions Using Mass Spectrometry and Molecular Dynamics, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 8765, (2016)
Abstract: The reactions of [gamma-SiW10O36](8-) represent one of the most important synthetic gateways into a vast array of polyoxotungstate chemistry. Herein, we set about exploring the transformation of the lacunary polyoxoanion [beta(2)-SiW11O39](8-) into [gamma-SiW10O36](8-) using high-resolution electrospray mass spectrometry, density functional theory, and molecular dynamics. We show that the reaction proceeds through an unexpected {SiW9} precursor capable of undertaking a direct beta -> gamma isomerization via a rotational transformation. The remarkably low-energy transition state of this transformation could be identified through theoretical calculations. Moreover, we explore the significant role of the countercations for the first time in such studies. This combination of experimental and the theoretical studies can now be used to understand the complex chemical transformations of oxoanions, leading to the design of reactivity by structural control.

First author: Vengut-Climent, E, Glucose-Nucleobase Pseudo Base Pairs: Biomolecular Interactions within DNA, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 55, 8643, (2016)
Abstract: Noncovalent forces rule the interactions between biomolecules. Inspired by a biomolecular interaction found in aminoglycoside-RNA recognition, glucose-nucleobase pairs have been examined. Deoxyoligonucleotides with a 6-deoxyglucose insertion are able to hybridize with their complementary strand, thus exhibiting a preference for purine nucleobases. Although the resulting double helices are less stable than natural ones, they present only minor local distortions. 6-Deoxyglucose stays fully integrated in the double helix and its OH groups form two hydrogen bonds with the opposing guanine. This 6-deoxyglucose-guanine pair closely resembles a purine-pyrimidine geometry. Quantum chemical calculations indicate that glucose-purine pairs are as stable as a natural T-A pair.

First author: Martin-Rodriguez, A, DFT approaches to transport calculations in magnetic single-molecule devices, THEORETICAL CHEMISTRY ACCOUNTS, 135, 8643, (2016)
Abstract: Electron transport properties of single-molecule devices based on the [Fe(tzpy)(2)(NCS)(2)] complex placed between two gold electrodes have been explored using three different atomistic DFT methods. This kind of single-molecule devices is quite appealing because they can present magnetoresistance effects at room temperature. The three employed computational approaches are: (i) self-consistent non-equilibrium Green functions (NEGF) with periodic models that can be described as the most accurate between the state-of-art methods, and two non-self-consistent NEGF approaches using either periodic or non-periodic description of the electrodes (ii and iii). The analysis of the transmission spectra obtained with the three methods indicates that they provide similar qualitative results. To obtain a reasonable agreement with the experimental data, it is mandatory to employ density functionals beyond the commonly employed GGA (i.e., hybrid functionals) or to include on-site corrections for the Coulomb repulsion (GGA+U method).

First author: Plasser, F, Communication: Unambiguous comparison of many-electron wavefunctions through their overlaps, JOURNAL OF CHEMICAL PHYSICS, 145, 8643, (2016)
Abstract: A simple and powerful method for comparing many-electron wavefunctions constructed at different levels of theory is presented. By using wavefunction overlaps, it is possible to analyze the effects of varying wavefunction models, molecular orbitals, and one-electron basis sets. The computation of wavefunction overlaps eliminates the inherent ambiguity connected to more rudimentary wavefunction analysis protocols, such as visualization of orbitals or comparing selected physical observables. Instead, wavefunction overlaps allow processing the many-electron wavefunctions in their full inherent complexity. The presented method is particularly effective for excited state calculations as it allows for automatic monitoring of changes in the ordering of the excited states. A numerical demonstration based on multireference computations of two test systems, the selenoacrolein molecule and an iridium complex, is presented.

First author: de Gier, HD, Promising Strategy To Improve Charge Separation in Organic Photovoltaics: Installing Permanent Dipoles in PCBM Analogues, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 4664, (2016)
Abstract: A multidisciplinary approach involving organic synthesis and theoretical chemistry was applied to investigate a promising strategy to improve charge separation in organic photovoltaics: installing permanent dipoles in fullerene derivatives. First, a PCBM analogue with a permanent dipole in the side chain (PCBDN) and its reference analogue without a permanent dipole (PCBBz) were successfully synthesized and characterized. Second, a multiscale modeling approach was applied to investigate if a PCBDN environment around a central donor-acceptor complex indeed facilitates charge separation. Alignment of the embedding dipoles in response to charges present on the central donor-acceptor complex enhances charge separation. The good correspondence between experimentally and theoretically determined electronic and optical properties of PCBDN, PCBBz, and PCBM indicates that the theoretical analysis of the embedding effects of these molecules gives a reliable expectation for their influence on the charge separation process at a microscopic scale in a real device. This work suggests the following strategies to improve charge separation in organic photovoltaics: installing permanent dipoles in PCBM analogues and tuning the concentration of these molecules in an organic donor/acceptor blend.

First author: Bistoni, G, pi Activation of Alkynes in Homogeneous and Heterogeneous Gold Catalysis, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 5239, (2016)
Abstract: The activation of alkynes toward nucleophilic attack upon coordination to gold-based catalysts (neutral and positively charged gold clusters and gold complexes commonly used in homogeneous catalysis) is investigated to elucidate the role of the sigma donation and pi back-donation components of the Au-C bond (where we consider ethyne as prototype substrate). Charge displacement (CD) analysis is used to obtain a well-defined measure of sigma donation and pi back-donation and to find out how the corresponding charge flows affect the electron density at the electrophilic carbon undergoing the nucleophilic attack. This information is used to rationalize the activity of a series of catalysts in the nucleophilic attack step of a model hydroamination reaction. For the first time, the components of the Dewar-Chatt-Duncanson model, donation and back-donation, are put in quantitative correlation with the kinetic parameters of a chemical reaction.

First author: Fernando, A, Deciphering the Ligand Exchange Process on Thiolate Monolayer Protected Au-38(SR)(24) Nanoclusters, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 14948, (2016)
Abstract: Ligand exchange reactions are used widely to modify and tune the properties of thiolate monolayer protected nanoclusters. We employed density functional theory calculations to investigate the ligand exchange process on the Au-38(SH)(24) nanocluster. The Au-38 duster consists of eight possible unique sites for ligand exchange, including six sites from the dimeric staple motifs and two sites from monomeric units. The most favorable site for ligand exchange is found to be between a core gold atom and the -SH moiety on the monomeric unit. Ligand substitution between a core gold atom and a terminal -SH group or between a terminal -SH group and a staple gold atom at both sides of the dimer units is a more favorable site for the ligand exchange process than substitution of the central -SH moiety. However, substitution of the central -SH moiety on Au38 is more favorable than for the corresponding position on Au-25.

First author: Xu, WH, Is the chemistry of lawrencium peculiar?, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 17351, (2016)
Abstract: It is explicitly verified that the atomic 7p(1) ground-state configuration of Lr originates from relativistic effects. Without relativity one has 6d(1). All three ionization potentials IP1-3 of Lr resemble those of Lu. Simple model studies on mono-and trihydrides, monocarbonyls or trichlorides suggest no major chemical differences between Lr and the lanthanides.

First author: Novotny, J, Interpreting the Paramagnetic NMR Spectra of Potential Ru(III) Metallodrugs: Synergy between Experiment and Relativistic DFT Calculations, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 8432, (2016)
Abstract: Ruthenium-based compounds are potential candidates for use as anticancer metallodrugs. The central ruthenium atom can be in the oxidation state +2 (e.g., RAPTA, RAED) or +3 (e.g., NAMI, 10). In this study we focus on paramagnetic NAMI analogs of a general structure [4-R-pyH](+)trans-[(RuCl4)-Cl-III(DMSO)(4-R-py)](-), where 4-R-py stands for a 4-substituted pyridine. As paramagnetic systems are generally considered difficult to characterize in detail by NMR spectroscopy, we performed a systematic structural and methodological NMR study of complexes containing variously substituted pyridines. The effect of the paramagnetic nature of these complexes on the H-1 and C-13 NMR chemical shifts was systematically investigated by temperature-dependent NMR experiments and density-functional theory (DFT) calculations. To understand the electronic factors influencing the orbital (delta(orb), temperature independent) and paramagnetic (delta(para), temperature-dependent) contributions to the total NMR chemical shifts, a relativistic two component DFT approach was used. The paramagnetic contributions to the C-13 NMR chemical shifts are correlated with the distribution of spin density in the ligand moiety and the C-13 isotropic hyperfine coupling constants, A(iso)(C-13), for the individual carbon atoms. To analyze the mechanism of spin distribution in the ligand, the contributions of molecular spin orbitals (MSOs) to the hyperfine coupling constants and the spatial distribution of the z-component of the spin density in the MSOs calculated at the relativistic four-component DFT level are discussed and rationalized. The significant effects of the substituent and the solvent on delta(para), particularly the contact contribution, are demonstrated. This work should contribute to further understanding of the link between the electronic structure and the NMR chemical shifts in open-shell systems, including the ruthenium-based metallodrugs investigated in this account.

First author: Olavarria-Contreras, IJ, C-Au Covalently Bonded Molecular Junctions Using Nonprotected Alkynyl Anchoring Groups, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 8465, (2016)
Abstract: We report on an approach to realize carbon-gold (C-Au) bonded molecular junctions without the need for an additive to deprotect the alkynyl carbon as endstanding anchor group. Using the mechanically controlled break junction (MCBJ) technique, we determine the most probable conductance value of a family of alkynyl terminated oligophenylenes (OPA(n)) connected to gold electrodes through such an akynyl moiety in ambient conditions. The molecules bind to the gold leads through an sp-hybridized carbon atom at each side. Comparing our results with other families of molecules that present organometallic C-Au bonds, we conclude that the conductance of molecules contacted via an sp-hybridized carbon atom is lower than the ones using spa hybridization due to strong differences in the coupling of the conducting orbitals with the gold leads.

First author: Hamdaoui, M, Evidence of a Donor-Acceptor (Ir-H)-> SiR3 Interaction in a Trapped Ir(III) Silane Catalytic Intermediate, ORGANOMETALLICS, 35, 2207, (2016)
Abstract: The ionic iridacycle [(2-phenylenepyridine-kappa N,kappa C)-IrCp*(NCMe)][BArF24] ([2][BArF24]) displays a remarkable capability to catalyze the O-dehydrosilylation of alcohols at room temperature (0.4 x 10(3) < TON < 10(3), 8 x 10(3) < TOFi < 1.9 x 10(5) h(-1) for primary alcohols) that is explained by its exothermic reaction with Et3SiH, which affords the new cationic hydrido-Ir(III)-silylium species [3][BArF24]. Isothermal calorimetric titration (ITC) indicates that the reaction of [2][BArF24] with Et3SiH requires 3 equiv of the latter and releases an enthalpy of -46 kcal/mol in chlorobenzene. Density functional theory (DFT) calculations indicate that the therrnochemistry of this reaction is largely dominated by the concomitant bis-hydrosilylation of the released MeCN ligand. Attempts to produce [3][BF4] and [3][OTf] salts resulted in the formation of a known neutral hydrido-iridium(III) complex, i.e. 4, and the release of Et3SiF and Et3SiOTf, respectively. In both cases formation of the cationic p-hydrido-bridged bis-iridacyclic complexes [5][BF4] and [5][OTf], respectively, was observed. The structure of [5][OTf] was established by X-ray diffraction analysis. Conversion of [3] [BArF24] into 4 upon reaction with either 4-N,N-dimethylaminopyridine or [nBu(4)][OTf] indicates that the Ir center holds a +III formal oxidation state and that the Et3Si+ moiety behaves as a Z-type ligand according to Green’s formalism. [3][BArF24], which was trapped and structurally characterized and its electronic structure investigated by state-of-the-art DFT methods (DFT-D, EDA, ETS-NOCV, QTAIM, ELF, NCI plots and NBO), displays the features of a cohesive hydridoiridium(III)-> silylium donor-acceptor complex. This study suggests that the fate of [3](+) in the O-dehydrosilylation of alcohols is conditioned by the nature of the associated counteranion and by the absence of Lewis base in the medium capable of irreversibly capturing the silylium species.

First author: Gaggioli, CA, Strong Electron-Donating Ligands Accelerate the Protodeauration Step in Gold(I)-Catalyzed Reactions: A Quantitative Understanding of the Ligand Effect, ORGANOMETALLICS, 35, 2275, (2016)
Abstract: We have conducted a theoretical exploration of the ligand electronic effect in the protodeauration step of a model gold(I) cyclization reaction, for which experimental data are available. The mechanism of the protodeauration is investigated through a density functional theory (DFT) approach, and the electron-donating power of the ligand is quantified through the charge displacement function (CDF). We find that the frequently encountered assumption in the literature that “strong electron donating ligands accelerate the protodeauration” can be set into a quantitative framework by our combined DFT/CDF theoretical approach, which allows us also to rationalize the highest catalytic efficiency of Buchwald phosphine type ligands in this process. We analyze the ligand effect on the gold complex substrate (LAu-S) bond strength, namely the bond to be broken during the protodeauration, and we find that the LAu-S interaction energies linearly correlate with the activation barriers. Finally, energy decomposition analysis (EDA) is used to investigate the LAu-S bond, and we show that changes in the interaction energies are mainly due to changes in the electrostatic component, whose value is in turn modulated by the ligand electron-donating power.

First author: Gieseldng, RL, Semiempirical Modeling of Ag Nanoclusters: New Parameters for Optical Property Studies Enable Determination of Double Excitation Contributions to Plasmonic Excitation, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 4542, (2016)
Abstract: Quantum mechanical studies of Ag nanoclusters have shown that plasmonic behavior can be modeled in terms of excited states where collectivity among single excitations leads to strong absorption. However, new computational approaches are needed to provide understanding of plasmonic excitations beyond the single excitation level. We show that semiempirical INDO/CI approaches with appropriately selected parameters reproduce the TD-DFT optical spectra of various closed-shell Ag clusters. The plasmon-like states with strong optical absorption comprise linear combinations of many singly excited configurations that contribute additively to the transition dipole moment, whereas all other excited states show significant cancellation among the contributions to the transition dipole moment. The computational efficiency of this approach allows us to investigate the role of double excitations at the INDO/SDCI level. The Ag cluster ground states are stabilized by slight mixing with doubly excited configurations, but the plasmonic states generally retain largely singly excited character. The consideration of double excitations in all cases improves the agreement of the INDO/CI absorption spectra with TD-DFT, suggesting that the SDCI calculation effectively captures some of the ground-state correlation implicit in DFT. These results provide the first evidence to support the commonly used assumption that single excitations are in many cases sufficient to describe the optical spectra of plasmonic excitations quantum mechanically.

First author: Nechay, MR, Histone Deacetylase 8: Characterization of Physiological Divalent Metal Catalysis, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 5884, (2016)
Abstract: Histone deacetylases (HDACs) are responsible for the removal of acetyl groups from histones, resulting in gene silencing. Overexpression of HDACs is associated with cancer, and their inhibitors are of particular interest as chemotherapeutics. However, HDACs remain a target of mechanistic debate. HDAC class 8 is the most studied HDAC, and of particular importance due to its human oncological relevance. HDAC8 has traditionally been considered to be a Zn-dependent enzyme. However, recent experimental assays have challenged this assumption and shown that HDAC8 is catalytically active with a variety of different metals, and that it may be a Fe-dependent enzyme in vivo. We studied two opposing mechanisms utilizing a series of divalent metal ions in physiological abundance (Zn2+, Fe2+, Co2+, Mn2+, Ni2+, and Mg2+). Extensive sampling of the entire protein with different bound metals was done with the mixed quantum-classical QM/DMD method. Density functional theory (DFT) on an unusually large cluster model was used to describe the active site and reaction mechanism. We have found that the reaction profile of HDAC8 is similar among all metals tested, and follows one of the previously published mechanisms, but the rate-determining step is different from the one previously claimed. We further provide a scheme for estimating the metal binding affinities to the protein. We use the quantum theory of atoms in molecules (QTAIM) to understand the different binding affinities for each metal in HDAC8 as well as the ability of each metal to bind and properly orient the substrate for deacetylation. The combination of this data with the catalytic rate constants is required to reproduce the experimentally observed trend in metal-depending performance. We predict Co2+ and Zn2+ to be the most active metals in HDAC8, followed by Fe2+, and Mn2+ and Mg2+ to be the least active.

First author: Kiawi, DM, Water Dissociation upon Adsorption onto Free Iron Clusters Is Size Dependent, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 2381, (2016)
Abstract: Cationic iron clusters, produced through laser ablation and subsequently complexed with a water molecule Fe-n(+)-H2O (n = 6-15) are mass-selectively investigated via infrared multiple photon dissociation (IR-MPD) spectroscopy in the 300-1700 cm(-1) spectral range. The experimental data are complemented by density functional theory calculations at the OPBE/TZP level for the Fe-13(+)-H2O system. The observed spectra can be explained by a mixture of clusters where for a majority water is adsorbed molecularly but for a small but significant fraction also dissociation of water molecules occurs. The bands observed at frequencies 300-700 cm(-1) exhibit regular, size-dependent frequency shifts, showing that (a) dissociation takes places on all cluster sizes and (b) the interaction of water with the cluster surface is not influenced much by the particular cluster structure. The intensity evolution of the absorption bands suggests that dissociation is increasingly probable for larger cluster sizes.

First author: Lu, SI, Application of discrete solvent reaction field to second-order susceptibility of organic molecular crystal, THEORETICAL CHEMISTRY ACCOUNTS, 135, 2381, (2016)
Abstract: This article presents an assessment of methods to study the second harmonic generation (SHG) response of organic molecular crystal. We incorporated the discrete solvent reaction field model, density functional theory, and the local field approximation (designated as the LF-DRF/DFT) to investigate the SHG susceptibilities of the chromophore of 2-carboxylic acid-4-nitropyridine-1-oxide (POA). In experiment, the POA appears in two different polymorphic crystal structures easily identified by noticeable differences in the melting points and SHG susceptibilities. In this work, we tried to utilize the LF-DRF/DFT in a supermolecular framework to differentiate the two crystals. While focusing on the ratio of the calculated SHG susceptibilities for the two crystals, at optical wavelength of 1064 nm, the S12 g and SSB-D exchange-correlation functionals within a 5 x 5 x 5 extended architecture produced 2.16 and 2.08, differing from the experimental estimate of 2.16 by 0 and 3.7 %, respectively.

First author: Zaccaria, F, Insights on Selenium and Tellurium Diaryldichalcogenides: A Benchmark DFT Study, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 1672, (2016)
Abstract: Selenium based diaryl dichalcogenides are compounds that are receiving attention in organic synthesis as eco-friendly oxidation agents as well as in pharmaceutical chemistry, where, together with tellurium-based derivatives, are appealing drugs mainly for their antioxidant properties. A benchmark study to establish optimal density functional theory (DFT) methods for the description of their molecular and electronic structure as well as for their energetics is presented here. Structural features, such as the orientation of the phenyl rings, as well as energetic aspects, i.e., the chalcogen-chalcogen bond strength, are discussed, with the aim of applying the novel insights to quantum mechanics-based investigations of their reactivity and to facilitate drug design.

First author: Boes, JR, Neural Network and ReaxFF Comparison for Au Properties, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 979, (2016)
Abstract: We have studied how ReaxFF and Behler-Parrinello neural network (BPNN) atomistic potentials should be trained to be accurate and tractable across multiple structural regimes of Au as a representative example of a single-component material. We trained these potentials using subsets of 9,972 Kohn-Sham density functional theory calculations and then validated their predictions against the untrained data. Our best ReaxFF potential was trained from 848 data points and could reliably predict surface and bulk data; however, it was substantially less accurate for molecular clusters of 126 atoms or fewer. Training the ReaxFF potential to more data also resulted in overfitting and lower accuracy. In contrast, BPNN could be fit to 9,734 calculations, and this potential performed comparably or better than ReaxFF across all regimes. However, the BPNN potential in this implementation brings significantly higher computational cost.

First author: Pan, S, A Noble Interaction: An Assessment of Noble Gas Binding Ability of Metal Oxides (Metal=Cu, Ag, Au), INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 1016, (2016)
Abstract: An in silico study is performed on the structure and the stability of noble gas (Ng) bound MO complexes (M-Cu, Ag, Au). To understand the stability of these Ng bound complexes, dissociation energies, dissociation enthalpy, and dissociation free energy change are computed. The stability of NgMO is also compared with that of the experimentally detected NgMX (X = F, Cl, Br). It is found that MO has lower Ng binding ability than that of MX. All the dissociation processes producing Ng and MO are endothermic in nature and for the Kr-Rn bound MO (M=Cu, Au), and Xe and Rn bound AgO cases, the corresponding dissociation processes are turned out to be endergonic in nature at standard state. The Wiberg bond indices of Ng-M bonds and Ng -> M electron transfer gradually increase from Ar to Rn and for the same Ng they follow the order of NgAuO>NgCuO>NgAgO. Energy decomposition analysis shows that the Ng-M bonds in NgMO are partly covalent and partly electrostatic in nature. Electron density analysis further highlights the partial covalent character in Ng-M bonds.

First author: Gowda, V, Structure Elucidation of an Yttrium Diethyldithiocarbamato-Phenanthroline Complex by X-ray Crystallography, Solid-State NMR, and ab-initio Quantum Chemical Calculations, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 116, 3278, (2016)
Abstract: We present a structural analysis method for molecular and electronic structure of yttrium diethyldithiocarbamato-phenanthroline complex {[Y(S2CNR2)(3)PHEN] with R = C2H5 and PHEN = 1,10-phenanthroline} combining solid-state NMR spectroscopy, XRD, and first principles DFT calculations. Replacing the Nd3+ ion with Y3+ in the reported crystal structure of [Nd(S2CNR2)(3)PHEN] complex generated an approximate 3D structure of the title complex. The structure was then subjected to first principles quantum chemical geometry optimisation using periodic DFT method. The quality of the method is discussed by comparing predicted and experimental powder XRD patterns. Full assignment of C-13 and N-15 solid-state CP-MAS NMR spectra as well as analyses of the principal values of the chemical shift tensors were carried out using periodic scalar relativistic DFT modelling. Spin-orbit relativistic effects, estimated by SO-ZORA formalism for one molecular unit, were evaluated. Finally, the X-ray structure of the title complex was determined, which proved that the former procedure is appropriate. The most important orbital interactions were investigated by Natural Bond Orbital analysis. The isotropic shielding values for S2CN-carbons were analysed by Natural Localised Molecular Orbital analysis. The present approach can be further extended to study other rare earth metal complexes, particularly those having similar but not yet solved crystal structures.

First author: Wolf, P, Correlating Synthetic Methods, Morphology, Atomic-Level Structure, and Catalytic Activity of Sn-beta Catalysts, ACS CATALYSIS, 6, 4047, (2016)
Abstract: Sn-beta zeolites prepared using different recipes feature very different catalytic activities for aqueous phase glucose isomerization, suggesting the presence of different active sites. A systematic study of the morphology and atomic-level structure of the materials using DNP NMR spectroscopy in combination with first-principles calculations allows for the discrimination between potential sites and leads to a proposal of specific structural features that are important for high activity. The results indicate that the materials showing the highest activity possess a highly hydrophobic, defect-free zeolite framework. Those materials show so-called closed and associated partially hydrolyzed Sn(IV) sites in the T6 and T5/T7 lattice positions. On the other hand, postsynthetically synthesized Sn-beta samples prepared in two steps via dealumination and subsequent solid-state ion exchange from Al-beta show significantly lower activity, which is associated with a hydrophilic framework and/or a lower accessibility and different lattice position of the Sn sites in the zeolite crystal. Further, we provide a method to distinguish between different Sn sites on the basis of NMR cartography using chemical shift and chemical shift anisotropy as readily measurable parameters. This cartography allows identifying not only the nature of the active sites (closed, defect-open, and hydrolyzed-open) but also their position within the BEA framework.

First author: Raimbault, N, Gauge-Invariant Formulation of Circular Dichroism, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 3278, (2016)
Abstract: Standard formulations of magnetic response properties, such as circular dichroism spectra, are plagued by gauge dependencies, which can lead to unphysical results. In this work, we present a general gauge-invariant and numerically efficient approach for the calculation of circular dichroism spectra from the current density. First we show that in this formulation the optical rotation tensor, the response function from which circular dichroism spectra can be obtained, is independent of the origin of the coordinate system. We then demonstrate that its trace is independent of the gauge origin of the vector potential. We also show how gauge invariance can be retained in practical calculations with finite basis sets. As an example, we explain how our method can be applied to time-dependent current-density-functional theory. Finally, we report gauge-invariant circular dichroism spectra obtained using the adiabatic local-density approximation. The circular dichroism spectra we thus obtain are in good agreement with experiment.

First author: Conradie, J, Bond stretch isomers of d(4) tris(benzoylacetonato-kappa O-2,O ‘)Mn(III), COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1087, 1, (2016)
Abstract: Density functional theory calculations show that one fac and three mer geometries of complex [Mn(ba)(3)] are possible. It is shown that elongation Jahn Teller distortion can occur along different bonds in the same mer [Mn(ba)(3)] complex. A sample of [Mn(ba)(3)] is thus expected to contain a mixture of different electronic states and bond stretch isomers in dynamic equilibrium with one other.

First author: Pandey, KK, The nature of M-PNR2 bonds in the electrophilic phosphinidene complexes [(L)(CO)(3)M{PNR2}](+) (L = PMe3, PPh3; M = Co, Rh, Ir; R = Me, Pr-i): Structure, bonding and P-31 NMR study, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 813, 84, (2016)
Abstract: Theoretical insights into the structure and the nature of M-PNR2 bonding in the cationic electrophilic phosphinidene complexes [(L)(CO)(3)M{PNR2}](+) (M = Co, Rh, Ir; R = Pr-i, Me; L = PMe3, PPh3) have been investigated at DFT level with emphasis on the density functional BP86, PBE, PW91 and TPSS and dispersion interactions, DFT-D3(BJ). Dispersion corrected functional yields accurate geometries. The geometry optimized with PBE-D3(BJ) functional is in excellent agreement with the experimental geometry of structurally characterized cobalt phosphinidene complex [(PPh3)(CO)(3)Co{PNiPr2}](+) (IV). The effects of metal atom, trans-influence of phosphine ligands (PMe3, PPh3) and substituent at nitrogen atom of PNR2 ligand on the M-PNR2 bond distances and M-P-N bond angles have been studied. The lengthening of M-PNR2 bonds trans to PMe3 ligand than those trans to PPh3 are due greater transinfluence of the PMe3 ligand. The P-31 NMR chemical shifts of phosphinidene and phosphine ligands phosphorus in the complexes I-XII have been calculated out at PBE-D-3(BJ)/TZ(2)P/ZORA with scalar (SC) and spin orbit (SO) relativistic level of theory in solvent chloroform. The computed values of P-31 NMR chemical shifts are within the range of experimental values. The Mulliken charge analysis shows that the overall charge flows from phosphinidene ligand to metal fragment. The energy decomposition analysis divulged that the contribution of the electrostatic interaction Delta E-elstat in all studied complexes is larger (54.5%-61.3%) than the orbital interactions Delta(Eorb). The pi-bonding contribution is much smaller than the sigma-bonding (85.4%-87.0%).

First author: Couce-Rios, A, The Origin of Anti-Markovnikov Regioselectivity in Alkene Hydroamination Reactions Catalyzed by [Rh(DPEphos)](+), CHEMISTRY-A EUROPEAN JOURNAL, 22, 9311, (2016)
Abstract: The development of regioselective anti-Markovnikov alkene’s hydroamination is a long-standing goal in catalysis. The [Rh(COD)(DPEphos)](+) complex is the most general and regioselective group 9 catalyst for such a process. The reaction mechanism for intermolecular hydroamination of alkenes catalyzed by [Rh(DPEphos)](+) complex is analyzed by means of DFT calculations. Hydroamination (alkene vs. amine activation routes) as well as oxidative amination pathways are analyzed. According to the computational results the operating mechanism can be generally described by alkene co-ordination, amine nucleophilic addition, proton transfer through the metal center and reductive elimination steps. The mechanism for the formation of the oxidative amination side product goes via a beta-elimination after the nucleophilic addition and metal center protonation steps. The origin of the regioselectivity for the addition process (Markovnikov vs. anti-Markovnikov additions) is shown to be not charge but orbitally driven. Remarkably, eta(2) to eta(1) slippage degree on the alkene coordination mode is directly related to the regioselective outcome.

First author: Roue, S, Double Insertion of Thiophene Rings in Polyynediyl Chains to Stabilize Nanoscaled Molecular Wires with [Cp*(dppe)Fe] Termini, ORGANOMETALLICS, 35, 2057, (2016)
Abstract: The dinuclear iron complexes [Cp*(dppe)Fe-C C C4H2S-(C C)(x)-C4H2S-C C-Fe(dppe)Cp*] (2, x = 1; 3 x = 2) and [Cp*(dppe)Fe-C C-C4H2S-C C-C C-Fe(dppe) Cp*] (4) were prepared in one -pot procedures from known organometallic precursors. Compound 2 was obtained from Cp,*(dppe)Fe-C C-C4H2S-C C-C4H2S-C CH (6) and Cp*(dppe)FeCl (5) in 74% yield. Its relative 3, isolated in 84%, resulted from the oxidative coupling of Cp*(dppe)Fe-C C-C4H2S-C CH (7) in the presence of Cu(OAc)(2) and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU). Complex 4 was obtained from the bridging ligand 2,5-bis(trimethylsilylbutadiynyl)thiophene (8) and two equiv of 5. The new complexes were characterized by ESI-mass spectrometry, IR, multi-nuclear NMR, cyclic voltammetry, and Mossbauer spectroscopy. Complex 3 was also analyzed by X-ray diffraction on a single crystal. The data are consistent with a sizable metal metal interaction across the 14- and 16 -carbon atoms of the bridges. The singly and doubly oxidized forms 2(PF6)(n) and 3(PF6)(n) (n = 1, 2) were obtained by oxidation of the corresponding 18 -electron iron(II) precursors with 1 and 2 equivs of ferrocenium salt, while 4 decomposed very quickly upon oxidation. The thermally stable salts 2(PF6)(n) and 3(PF6)(n) (n = 1, 2) were subjected to analyses by ESI-mass spectrometry, IR, Mossbauer, ESR, UV-vis, and NIR spectroscopies. The radical cations 2(PF6) and 3(PF6) belong to Class II of the mixed-valence Robin and Day classification with quite sizable electronic coupling parameters for large metal-metal separation (2(PF6), H-ab = 262 cm(-1), d(FeFe) = 17.7 angstrom; 3(PF6), H-ab = 203 cm(-1), d(FeFe) = 19.7 angstrom). Paramagnetic H-1 NMR spectroscopy was also performed on the dicationic salts to measure the magnetic exchange between the distant spin carriers (2(PF6)(2), Delta G(ST) = -120 cm(-1)). The data were analyzed with the support of quantum chemistry calculations at the DFT level of theory.

First author: Pathak, AD, Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 15838, (2016)
Abstract: MgCl2 hydrates are considered as high-potential candidates for seasonal heat storage materials. These materials have high storage capacity and fast dehydration kinetics. However, as a side reaction to dehydration, hydrolysis may occur. Hydrolysis is an irreversible reaction, which produces HCl gas thus affecting the durability of heat storage systems. In this study, we present the parameterization of a reactive force field (ReaxFF) for MgCl2 hydrates to study the dehydration and hydrolysis kinetics of MgCl2 center dot H2O and MgCl2 center dot 2H(2)O. The ReaxFF parameters have been derived by training against quantum mechanics data obtained from Density Functional Theory (DFT) calculations consisting of bond dissociation curves, angle bending curves, reaction enthalpies, and equation of state. A single-parameter search algorithm in combination with a Metropolis Monte Carlo algorithm is successfully used for this ReaxFF parameterization. The newly developed force field is validated by examining the elastic properties of MgCl2 hydrates and the proton transfer reaction barrier, which is important for the hydrolysis reaction. The bulk moduli of MgCl2 center dot H2O and MgCl2 center dot 2H(2)O obtained from ReaxFF are in close agreement with the bulk moduli obtained from DFT. A barrier of 20.24 kcal mol(-1) for the proton transfer in MgCl2 center dot 2H(2)O is obtained, which is in good agreement with the barrier (19.55 kcal mol(-1)) obtained from DFT. Molecular dynamics simulations using the newly developed ReaxFF on 2D-periodic slabs of MgCl2 center dot H2O and MgCl2 center dot 2H(2)O show that the dehydration rate increases more rapidly with temperature in MgCl2 center dot H2O than in MgCl2 center dot 2H(2)O, in the temperature range 300-500 K. The onset temperature of HCl formation, a crucial design parameter in seasonal heat storage systems, is observed at 340 K for MgCl2 center dot H2O, which is in agreement with experiments. The HCl formation is not observed for MgCl2 center dot 2H(2)O. The diffusion coefficient of H2O through MgCl2 center dot H2O is lower than through MgCl2 center dot 2H(2)O, and can become a rate-limiting step. The diffusion coefficient increases with temperature and follows the Arrhenius law both for MgCl2 center dot H2O and MgCl2 center dot 2H(2)O. These results indicate the validity of the ReaxFF approach for studying MgCl2 hydrates and provide important atomistic-scale insight of reaction kinetics and H2O transport in these materials.

First author: van Rooyen, PH, Orientation of trimethylolethane cyclic phosphite in rhodium complexes: Structure of [Rh(CH3COCHCOCH3)(CO)(P(OCH2)(3)CCH3)], POLYHEDRON, 111, 161, (2016)
Abstract: Density functional theory calculations showed that rotation of the (P(OCH2)(3)CCH3) group in the rhodium-acetylacetonato complex [Rh(acac)(CO)(P(OCH2)(3)CCI-H-3)] has a negligible influence on the energy of the complex. Density functional theory calculations further showed that the minimum energy orientation of the cyclic (P(OCH2)(3)CCH3) group in square planar rhodium-(P(OCH2)(3)CCH3)-(CO) complexes containing a bidentate ligand that is larger than the acetylacetonato ligand, is with one of the P O bonds near parallel (within 10) to the plane defined by the four atoms coordinated to Rh. The three P O bonds of the rigid (P(OCH2)(3)CCH3) group adopt a C-3-symmetrical conformation around the Rh P axis. The lowest energy geometry of [Rh(BID)(O-3)(p(OCH2)(3)CCH3)1 (BID = bidentate ligand with two O donor atoms and charge-1) complexes is where one P O bond is aligned near parallel to the Rh OBID trans to CO bond, while the geometry with a P-O bond orientated near parallel to the Rh Cco bond, is slightly higher in energy, but still possible experimentally. The highest energy orientation of the (P(OCH2)(3)CCH3) group in square planar 1Rh(BID)(CO)(P(OCH2)(3)CCH3)] complexes, is with one of the P-O bonds near perpendicular to the plane described by the four atoms coordinated to Rh. The orientation of the cyclic (P(OCH2)(3)CCH3) group in available experimental structures of square planar [Rh(BID)(CO) (P(OCH2)(3)CCH3)] complexes, confirms this finding.

First author: Garcia-Lastra, JM, Electronic Structure of Low-Dimensional Carbon pi-Systems, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 12362, (2016)
Abstract: X-ray absorption spectroscopy (XAS) is combined with density functional theory (DFT) to determine the orbitals of one- and two-dimensional carbon pi-systems (lycopene, beta-carotene, retinal, retinol, retinoic acid, coronene, triphenylene). Considerable fine structure is observed for the transition from the C is level to the lowest unoccupied molecular orbital (LUMO) and explained by DFT. The wave functions of the one-dimensional chain molecules display the node structure of a vibrating string. The XAS transition energy is decomposed into contributions from the C is core level, the pi* final state, and the electron hole interaction. For the latter, we develop a simple model that accurately represents a full Delta-self-consistent field (Delta SCF) calculation. The distortion of the LUMO because of its interaction with the C is hole is investigated. These results illustrate the electronic states of prototypical pi-bonded carbon structures with low-dimensional character, such as those used in molecular complexes for solar cells, confined graphene structures, and molecular wires.

First author: Mahmoodinia, M, Influence of Carbon Support on Electronic Structure and Catalytic Activity of Pt Catalysts: Binding to the CO Molecule, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 12452, (2016)
Abstract: Single-atom catalysts, especially with single Pt atoms, exhibit potentially improved catalytic activity as compared to metal clusters and metal surfaces. Here, the atop and bridged bondings of the CO molecule on the Pt/C system are studied. Vibrational frequencies, Mulliken populations, charge transfer, charge density differences, and density of states are examined to determine the influence of the carbon support on electronic properties and catalytic activity of the Pt adatom and dimer. Comparing orbital populations and the amount of electron transfer to/from the CO molecule shows that the net amount of electron transfer to the antibonding 2 pi* orbitals of the CO molecule is higher for the supported Pt dimer than for the substrate-free Pt dieter, which leads to a lower vibrational frequency and a larger C-O bond distance. The hybridization between the pi orbitals of the polycyclic aromatic hydrocarbons surface and the d orbitals of the Pt adatoms is responsible for enhancing the back-donation of electrons to the 2 pi* orbitals of the CO molecule, which results in a larger peak below the Fermi level for the 2 pi* states of the CO molecule in the corresponding density of state analysis. Therefore, it can be concluded that the carbon support significantly enhances the catalytic activity of the Pt atoms in contact with the surface for activating the CO molecule. The calculated C-O vibrational stretching frequencies provide valuable guidance for experiments considering the use of atom-type catalyst as building blocks for designing new catalysts.

First author: Kuncheria, J, Oxidation of a binuclear ruthenium carbonyl complex, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 812, 183, (2016)
Abstract: The aerobic oxidation of the binuclear ruthenium(0) carbonyl complexes [Ru-2(CO)(5)(mu-dppm)2], dppm = P(h)2PCH(2)PPh(2), 1, and [Ru-2(mu-H)(CO)(5)(mu-dppm)(2)]X-+(-), 2, has been studied. In acidic solution a 4-electron oxidation of 2 occurs to give [Ru-2(mu-OH)(2)CO)(4)(mu-dppm)2]X2, X = ReO4 or BF4. However, in neutral solution aerobic oxidation occurs in 2-electron steps, with parallel 2-electron oxidation of a carbonyl ligand. The reaction of complex 1 in acetone solution gave a diruthenium(I) formate derivative [Ru2(mu-OH)(O2CH)(CO)(3)(mu-dppm)2], while reaction in dichloromethane solution gave a diruthenium(II) carbonate derivative [Ru-2(CO3)(CO)(Cl)(mu-OH)(mu-CO)(mu-dppm)(2)]. The aerobic oxidation of 1 in the presence of methyl isocyanide and NH4[PF6] gave [Ru-2(CO)(2)(CNMe)(4)(mu-dppm)(2)][PF6](2). The structural characterization of the products is described, and likely mechanisms of reaction are discussed.

First author: Petz, W, Proton Affinities of Cationic Carbone Adducts [AC(PPh3)(2)](+) (A = Halogen, Hydrogen, Methyl) and Unusual Electronic Structures of the Cations and Dications [AC(H)(PPh3)(2)](2+), CHEMISTRY-A EUROPEAN JOURNAL, 22, 8536, (2016)
Abstract: This work reports the syntheses and the first crystal structures of the cationic carbone adducts [FC(PPh3)(2)](+) and [BrC(PPh3)(2)](+) and the protonated dication [FC(H)(PPh3)(2)](2+), which are derived from the carbone C(PPh3)(2). Quantum chemical calculations and bonding analyses were carried out for the series of cations [AC(PPh3)(2)](+) and dications [AC(H)(PPh3)(2)](2+), where A = H, Me, F, Cl, Br, I. The bonding analysis suggests that the cations are best described as phosphane complexes L -> (CA)(+) -> L (L= PPh3), which are related to the neutral borylene adducts L -> (BA) <- L (L= cyclic carbene; A = H, aryl) that were recently isolated. The carbone adducts [AC(PPh3)(2)](+) possess a pi electron lone pair at carbon and they can easily be protonated to the dications [AC(H)(PPh3)(2)](2+). The calculations of the di-cations indicate that the molecules are best represented as complexes L -> (CHA)(2+) <- L (L= PPh3) where a carbene dication is stabilized by the ligands. The central carbon atom in the cations and even in the dications carries a negative partial charge, which is larger than the negative charge at fluorine. There is also the peculiar situation in which the carbon-fluorine bonds in [FC(PPh3)(2)](+) and [FC(H)(PPh3)(2)](2+) exhibit the expected polarity with the negative end at fluorine, but the carbon atom has a larger negative charge than fluorine. Given the similarity of carbodiphosphorane C(PPh3)(2) and carbodicarbene C(NHC)(2), we expect that analogous compounds [AC(NHC)(2)](+) and [AC(H)(NHC)(2)](2+) with similar features as [AC(PPh3)(2)](+) and [AC(H)(PPh3)(2)](2+) can be isolated.

First author: Miro, P, Self-Assembly of Uranyl-Peroxide Nanocapsules in Basic Peroxidic Environments, CHEMISTRY-A EUROPEAN JOURNAL, 22, 8571, (2016)
Abstract: A wide range of uranyl-peroxide nanocapsules have been synthesized using very simple reactants in basic media; however, little is known about the process to form these species. We have performed a density functional theory study of the speciation of the uranyl ions under different experimental conditions and explored the formation of dimeric species via a ligand exchange mechanism. We shed some light onto the importance of the excess of peroxide and alkali counterions as a thermodynamic driving force towards the formation of larger uranyl-peroxide species.

First author: Schnee, G, Deprotonation of Al2Me6 by Sterically Bulky NHCs: Scope, Rationale through DFT Studies, and Application in the Methylenation of Carbonyl Substrates, ORGANOMETALLICS, 35, 1726, (2016)
Abstract: The sterically bulky NHCs 1,3-di-tert-butylimidazol-2-ylidene ((IBu)-Bu-t), 1,3-di-tent-butylimidazolin-2-ylidene ((SBu)-Bu-t), and 1,3-di-tert-butyl-3,4,5,6-tetrahydripyrimidin-2-ylidene (C6(t)Bu) were found to readily react with excess Al2Me6 at room temperature to form salts 2, 3, and 4, respectively, consisting of the polynuclear Me3Al(mu(3)-CH2)(AlMe2)(2)(mu(2)-CH3)(-) anion associated with either the cation (IBu)-Bu-t-H+, (SBu)-Bu-t-H+, or C6-Bu-t-H+. Such a reaction involving the deprotonation of an Al2Me6 moiety by a NHC does not proceed with less sterically hindered NHCs such as 1,3-bis(2,6-dii opropylphenyOimidazol-2-ylidene (IDipp) and 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), for which only the classical Lewis pair adducts (NHC)AlMe3 were isolated. In line with experimental and density functional theory (DFT) calculations data, such reactivity thus appears to be driven by steric frustration, resulting in the destabilization of the corresponding (NHC)AlMe3 adducts, then more prone to dissociate and hence allowing Al2Me6 activation/deprotonation. The DFT-estimated profile of the reaction of model adduct ((IBu)-Bu-t)AlMe3 (I) with Al2Me6 agrees with a ready adduct dissociation at low energy cost, with a subsequent deprotonation of Al2Me6 by the NHC fragment to afford model salt II (isostructural to salt 2). Anion Me3Al(mu(3)-CH2)(AlMe2)(2)(mu(2)-CH3)(-) behaves as an efficient CH22- group transfer agent with the methylenation of aldehydes and ketones to afford the corresponding methylene organics in good conversions. Bonding analysis of the latter anion agrees with an enhanced nucleophilicity of the Al-CH2 moiety (compared to the Al-Me groups), in line with the observed reactivity. DFT calculations also allowed a detailed bonding description of the pentacoordinate methylene carbon in the anion Me3Al(mu(3)-CH2)(AlMe2)(2)(mu(2)-CH3)(-).

First author: Conradie, J, Metalloporphyrin-Nitroxyl Interactions: The Low-Energy States of Reduced Manganese, Iron, and Cobalt Porphyrin Nitrosyls, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 4972, (2016)
Abstract: DFT calculations employing the OLYP and B3LYP functionals have been used to map out the low energy states of the metalloporphyrin-nitroxyl adducts “M(Por) + NO-” and “M(Por) + HNO”, where M = Fe, Co, and Mn and Pore-is the dianion of unsubstituted porphyrin. For [Fe(Por)(NO)](-), the calculations yield two low-energy solutions, with M-s = 0 and 1. The Ms = 0 solution is thought to represent the experimentally observed diamagnetic ground states of {FeNO}(8) porphyrins, and both functionals yield FeNO geometrical parameters in excellent agreement with a recent crystal structure. For [Co(Por)(NO)](-), the lowest-energy solution for both OLYP and B3LYP is a true {CoNO}(9) state that appears to be best described as a high-spin Co(II) center with a d(xy)(2)d(xz)(2)d(yz)(1)d(z2)(2)d(x2-y2)(1) configuration antiferromagnetically coupled to a NO- diradical. Such an electronic configuration is expected to lead to diagnostic structural features, including long equatorial Co-N distances (similar to 2.1 angstrom), a strong displacement (similar to 0.4 angstrom) of the metal from the mean plane of the equatorial nitrogens, and a relatively short Co-N(O) distance (1.8 angstrom), which should all be experimentally observable. The d(x2-y2)(1) electronic configuration should also lead to characteristic EPR hyperfine parameters. The calculations also indicate a number of other low-energy states for [Co (Por)(NO)](-), including multiple {CoNO}(8) porphyrin anion radical states. For [Mn(Por)(NO)](-), both functionals indicate a rather complex electronic state landscape, including multiple {MnNO}6 porphyrin anion radical states as well as a high-spin S = 3/2 {MnNO}(7) state. Both functionals clearly indicate a low-spin Pe(Il) state for [Fe(Por)(HNO)]. On the other hand, two comparably low-energy states are predicted for both [Co(Por)(HNO)] and [Mn(Por)(HNO)]. For [Co(Por)(HNO)], the two states are a low-spin Co(II) state with a d(xy)(2)d(xz)(2)d(y)(2)d(z2)(1) configuration and a low-spin Co(III)(HNO)(center dot-) state. For [Mn(Por)(HNO)], the two states may be described as low-(S = 1/2) and intermediate spin (S = 3/2) Mn(II). The latter state has a relatively long Mn-N(O) distance of about 2.07 angstrom, which may be indicative of facile HNO dissociation.

First author: Kanno, S, Design of spin-forbidden transitions for polypyridyl metal complexes by time-dependent density functional theory including spin-orbit interaction, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 14466, (2016)
Abstract: We explore spin-forbidden transitions for a Ru dye with an N3 skeleton and an Fe dye with a DX1 skeleton by time-dependent density functional theory with spin orbit interaction. The modified N3-based Ru dye with iodine anions has an absorption edge in the long wavelength region which is not observed in the original N3 dye. The long wavelength absorption edge originates from the spin-orbit interaction with iodine. Although the Fe dye has a small spin-orbit interaction, because of less spin-orbit interaction from the light metal, spin-forbidden transitions also occur for DX1-based Fe dye systems with iodine anions. This result indicates that the introduction of iodine can strengthen the spin orbit interaction for a dye sensitizer and offers a new approach for designing spin-forbidden transitions.

First author: Liu, C, Entangled Uranyl Organic Frameworks with (10,3)-b Topology and Polythreading Network: Structure, Luminescence, and Computational Investigation, INORGANIC CHEMISTRY, 55, 5540, (2016)
Abstract: Two 3D uranyl organic frameworks (UOFs) with entangled structures, (HPhen)(2)[(UO2)(2)L-2]center dot 4.5H(2)O (1) and [(UO2)(3) (H2O)(4)L-2]center dot 6H(2)O (2), were synthesized using a rigid tripodal linker (4,4′,4 ”-(phenylsilanetriyl)tribenzoic acid, H3L). Compound 1 represents a 2-fold interpenetrating UOF with the unique (10,3)-b topology. Compound 2 is composed of three interlocked sets of identical singlet networks and thus exhibits a rare 3D polythreading network with (3,4)-connected topology. These two compounds have been characterized by IR, UV-vis, and photoluminescent spectroscopy. A density functional theory (DFT) study on the model compounds of 1 and 2 shows good agreement of structural parameters and U=O stretching vibrational frequencies with experimental data. The experimentally measured absorption bands were well reproduced by the time-dependent DFT calculations.

First author: El-Hamdi, M, Complexes of Adamantane-Based Group 13 Lewis Acids and Superacids: Bonding Analysis and Thermodynamics of Hydrogen Splitting, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 1355, (2016)
Abstract: The electronic structure and chemical bonding in donor-acceptor complexes formed by group 13 element adamantane and perfluorinated adamantane derivatives EC9R15 (E=B, Al; R=H, F) with Lewis bases XR3 and XC9H15 (X=N, P; R= H, CH3) have been studied using energy decomposition analysis at the BP86/TZ2P level of theory. Larger stability of complexes with perfluorinated adamantane derivatives is mainly due to better electrostatic and orbital interactions. Deformation energies of the fragments and Pauli repulsion are of less importance, with exception for the boron-phosphorus complexes. The MO analysis reveals that LUMO energies of EC9R15 significantly decrease upon fluorination (by 4.7 and 3.6 eV for E=B and Al, respectively) which results in an increase of orbital interaction energies by 27-38 (B) and 15-26 (Al) kcal mol(-1). HOMO energies of XR3 increase in order PH3<nh3<pme3<pc9h15<nme3</nh3<pme3<pc9h15<nme3

First author: Koval, P, Optical response of silver clusters and their hollow shells from linear-response TDDFT, JOURNAL OF PHYSICS-CONDENSED MATTER, 28, 1355, (2016)
Abstract: We present a study of the optical response of compact and hollow icosahedral clusters containing up to 868 silver atoms by means of time-dependent density functional theory. We have studied the dependence on size and morphology of both the sharp plasmonic resonance at 3-4 eV (originated mainly from sp-electrons), and the less studied broader feature appearing in the 6-7 eV range (interband transitions). An analysis of the effect of structural relaxations, as well as the choice of exchange correlation functional (local density versus generalised gradient approximations) both in the ground state and optical response calculations is also presented. We have further analysed the role of the different atom layers (surface versus inner layers) and the different orbital symmetries on the absorption cross-section for energies up to 8 eV. We have also studied the dependence on the number of atom layers in hollow structures. Shells formed by a single layer of atoms show a pronounced red shift of the main plasmon resonances that, however, rapidly converge to those of the compact structures as the number of layers is increased. The methods used to obtain these results are also carefully discussed. Our methodology is based on the use of localised basis (atomic orbitals, and atom-centered and dominant-product functions), which bring several computational advantages related to their relatively small size and the sparsity of the resulting matrices. Furthermore, the use of basis sets of atomic orbitals also allows the possibility of extending some of the standard population analysis tools (e.g. Mulliken population analysis) to the realm of optical excitations. Some examples of these analyses are described in the present work.

First author: Mastrorilli, P, Uncovering Intramolecular pi-Type Hydrogen Bonds in Solution by NMR Spectroscopy and DFT Calculations, CHEMISTRY-A EUROPEAN JOURNAL, 22, 7964, (2016)
Abstract: Reaction between the phosphinito bridged diplatinum species [(PHCy2)Pt(mu-PCy2){kappa P-2,O-mu-P(O)Cy-2}Pt(PHCy2)](Pt-Pt) (1), and (trimethylsilyl) acetylene at 273K affords the sigma-acetylide complex [(PHCy2)(eta(1)-Me3SiC C)Pt(mu-PCy2)Pt(PHCy2){kappa P-P(OH)Cy-2}](Pt-Pt) (2) featuring an intramolecular pi-type hydrogen bond. Scalar and dipolar couplings in- volving the POH proton were detected by 2D NMR experiments. Relativistic DFT calculations of the geometry, relative energy, and NMR properties of model systems of 2 confirmed the structural assignment and allowed the energy of the pi-type hydrogen bond to be estimated (ca. 22 kJ mol(-1)).

First author: Boughlala, Z, Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism, CHEMISTRYOPEN, 5, 247, (2016)
Abstract: We have analyzed the structure and bonding of gas-phase Cl X and [HCl X](+) complexes for X+ = H+, CH3+, Li+, and Na+, using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl- and HCl for the various cations. The Cl-X bond becomes longer and weaker along X+ = H+, CH3+, Li+, and Na+. Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn-Sham molecular orbital (KS-MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities.

First author: Ghosh, A, The Valence States of Copernicium and Flerovium, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 5, 2989, (2016)
Abstract: Compared with its lighter congener HgF4, copernicium tetrafluoride, CnF(4), is predicted to be significantly more stable with respect to decomposition to the elements. Tetravalent flerovium on the other hand is unlikely to be experimentally accessible, except possibly as FlF(4). Because of the large 7p(1/2-3/2) energy splitting, many divalent flerovium compounds are also expected to be thermodynamically unstable. The two dihalides FlF(2) and FlCl(2), however, are predicted to be thermodynamically stable; flerovium thus is not quite as noble as xenon, which is not known to form a chloride.

First author: Celedon, S, Side-Chain Metallopolymers Containing Second-Order NLO-Active Bimetallic Ni-II and Pd-II Schiff-Base Complexes: Syntheses, Structures, Electrochemical and Computational Studies, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 5, 3012, (2016)
Abstract: Unsymmetric Schiff-base metalloligand precursor 2 is synthesized by condensation of phenol-functionalized ferrocenylenaminone 1 with 2-hydroxy-5-nitrobenzaldehyde. Heterobimetallic complexes 3 and 4 result from the N2O2-tetradentate coordination of Ni-II and Pd-II metal ions with the doubly deprotonated form of 2, respectively. Linking 3 and 4 to polyacrylic acid through an esterification reaction leads to the formation of the corresponding side-chain metallopolymers 5 and 6. The new compounds were fully characterized (IR, UV/Vis, NMR, MS, CV, SEC) and structures of 2-4 unequivocally determined by single-crystal X-ray diffraction techniques. Decomposition temperatures higher than 250 degrees C were found by DSC and TGA techniques for 3-6. Harmonic light scattering measurements showed that compounds 2-5 exhibit rather high second-order nonlinear responses, between 200×10(-30) and 970×10(-30) esu, with the hyperpolarizability (1.91) value increasing significantly on passing from Ni-II complex 3 to its respective metallopolymer 5. The structural and electronic properties of 2-4 are analyzed by DFT and TD-DFT calculations.

First author: Chen, X, The role of chelating ligands and central metals in the oxygen reduction reaction activity: a DFT study, RUSSIAN JOURNAL OF ELECTROCHEMISTRY, 52, 555, (2016)
Abstract: A detailed investigation of oxygen reduction reaction (ORR) catalyzed by various metal chelates has been performed by DFT study. The results indicate that the ORR activity is determined by both of the central metal ions and chelating ligands, among which the former play a key role. For the same ligand, the central metal ions Fe, Co, or Mn give higher ORR activity, while the others almost have no catalytic activity, which is due to the fact that the O-2 and oxygen containing species are either excessively adsorbed (on central Cr) or difficult to be adsorbed on the active sites (for central Zn, Cu, or Ni). Furthermore, the ORR activity for Fe chelates is slightly increased with the increase of ligand field strength, while for other metal chelates there seems to be no clear trends between ligand field strength and ORR activity. The origin of the ORR activity for the studied metal chelates is mainly attributed to the appropriate energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

First author: Kruse, CP, Variable Borohydride Hapticity in Nickel(II) Scorpionate Complexes [(TpR,Me)Ni(n-BH4)]: TpR,Me = hydrotris{3-R-5-methyl-1-pyrazolyl}borate; R = Ph, n=3 vs. R = Me, n=4, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 52, 2474, (2016)
Abstract: A second-generation scorpionate ligand was utilized to prepare the nickel(II) borohydride complex [(Tp(Ph,Me))Ni((3)-BH4)], wherein the borohydride was coordinated through two bridging B-H bonds, leaving two terminal B-H bonds uncoordinated as determined by X-ray crystallography. The distorted square-pyramidal complex is paramagnetic (S = 1), with 18 valence electrons, and contrasts with a previously reported 20-electron pseudo-octahedral first-generation analogue, [(Tp(Me,Me))Ni((4)-BH4)] (P. J. Desrochers, et al. Inorg. Chem. 2003, 42, 7945-7950). These distinct borohydride coordination modes were distinguished by FTIR spectroscopy, and rationalized by DFT calculations on simplified models, [(Tp)Ni((n)-BH4)] (n = 3, 4). The difference in borohydride hapticities is attributed to the steric effect of the scorpionate 3-pyrazole phenyl substituents disposed proximally to the metal, thus demonstrating the subtle versatility of Trofimenko’s scorpionate ligands in controlling ligand field geometries. The precursor complex [(Tp(Ph,Me))Ni((2)-NO3)] was also prepared and characterized.

First author: Bortoli, M, Addition-Elimination or Nucleophilic Substitution? Understanding the Energy Profiles for the Reaction of Chalcogenolates with Dichalcogenides, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 2752, (2016)
Abstract: We have quantum chemically explored the mechanism of the substitution reaction between CH3X- and the homo- and heterodichalcogenides CH3X’X ” CH3 (X, X’, X ” = S, Se, Te) using relativistic density functional theory at ZORA-OLYP/TZ2P and COSMO for simulating the effect of aqueous solvation. In the gas phase, all substitution reactions proceed via a triple-well additionelimination mechanism that involves a stable three-center intermediate. Aqueous solvation, in some cases, switches the character of the mechanism to double-well S(N)2 in which the stable three-center intermediate has become a labile transition state. We rationalize reactivity trends and some puzzling aspects of these elementary reactions, in particular, vanishing activation energies and ghost three-center intermediates, using the activation strain model (ASM).

First author: Goesten, MG, Evidence for a chemical clock in oscillatory formation of UiO-66, NATURE COMMUNICATIONS, 7, 2752, (2016)
Abstract: Chemical clocks are often used as exciting classroom experiments, where an induction time is followed by rapidly changing colours that expose oscillating concentration patterns. This type of reaction belongs to a class of nonlinear chemical kinetics also linked to chaos, wave propagation and Turing patterns. Despite its vastness in occurrence and applicability, the clock reaction is only well understood for liquid-state processes. Here we report a chemical clock reaction, in which a solidifying entity, metal-organic framework UiO-66, displays oscillations in crystal dimension and number, as shown by X-ray scattering. In rationalizing this result, we introduce a computational approach, the metal-organic molecular orbital methodology, to pinpoint interaction between the tectonic building blocks that construct the metal-organic framework material. In this way, we show that hydrochloric acid plays the role of autocatalyst, bridging separate processes of condensation and crystallization.

First author: Wei, HL, A theoretical study of charge-transport parameters for a hydrogen-bonded organic semiconductor: the indigo and s-indaceno [1,2-b:5,6-b ‘] dithiophene-4,9-dione derivatives, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 31, 2752, (2016)
Abstract: The properties of synthesized ambipolar organic semiconductor (OSC) materials, containing hydrogen bonding, i.e. the 6,6′-dibromoindigo and the three s-indaceno [1, 2-b:5, 6-b’] dithiophene-4,9-dione derivatives, have been systematically studied using a density functional theory. The hydrogen bonding formed between the interlayer molecules, though it does not affect the charge mobility in the same layer, influences the interorbital overlapping of HOMO and LUMO states between the layers, and influences the charge mobility directly. In addition, the hydrogen bonding between the layers may reinforce the pi-pi stacking and make the center-to-center distance closer, which indirectly enhances charge mobility, and can turn a monopole OSC into an ambipolar one.

First author: Matthiesen, JE, Electrochemical Conversion of Muconic Acid to Biobased Diacid Monomers, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 4, 3575, (2016)
Abstract: Electrocatalysis is evolving as a competitive alternative to conventional heterogeneous catalysis for the conversion of platform chemicals from biomass. Here, we demonstrate the electrocatalytic conversion of cis,cis-muconic acid, a fermentation product, to trans,trans-muconic acid, trans-3-hexenedioic acid, and adipic acid used for the production of biobased polyamides and polyesters such as nylon, nylon derivatives, and polyethylene terephthalate (PET). The electrocatalytic hydrogenation in this work considers a wide range of early, late, and post -transition metals (Cu, Fe, Ni, Mo, Pb, Pd, Sn, and Zn) with low and high hydrogen overpotentials, and varying degrees of metal hydrogen binding strengths. The binding strength was determined to be an important factor for the conversion rate, faradaic efficiency, and product distribution. Selectivities are also discussed in relation to thermodynamic data, which suggests the possibility to tune the kinetics of reaction to allow for the variable production of the multiple biobased monomers.

First author: Tidey, JP, High-pressure studies of three polymorphs of a palladium(II) oxathioether macrocyclic complex, ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING, 72, 357, (2016)
Abstract: The three reported phases of the mononuclear macrocyclic Pd-II complex [PdCl2([9]aneS(2)O)] [(1); [9]aneS(2)O = 1-oxa-4,7-dithiacyclononane] were each studied up to pressures exceeding 9 GPa using high-pressure single-crystal Xray diffraction. The alpha- and gamma-phases both exhibit smooth compression of the unit-cell parameters with third-order Birch-Murnaghan bulk moduli of 14.4 (8) and 7.6 (6) GPa, respectively. Between 6.81 and 6.87 GPa beta-[PdCl2([9]aneS(2)O)] was found to undergo a reversible transition to a phase denoted as beta’ and characterized by a tripling of the unit-cell volume. Across the phase transition, rearrangement of the conformation of the bound macrocycle at two of the resulting three unique sites gives rise to an extensively disordered structure.

First author: Babashkina, MG, CdS Nanoparticles Fabricated from the Single-Source Precursor [Cd{Et2NC(S)NP(S)(OiPr)(2)}(2)]: In Depth Experimental and Theoretical Studies, CRYSTAL GROWTH & DESIGN, 16, 3287, (2016)
Abstract: Reaction of the diethylammonium salt of N-thiophosphorylated thioureate [Et2NC(S)NP(S)(OiPr)(2)]- (L-) with CdCl2 in aqueous ethanol leads to the complex [CdL2]. The compound crystallizes in the triclinic space group P $(1) over bar $ with Z = 2 and the metal cation is found in a tetrahedral S2S'(2) coordination environment formed by the C-S and P-S sulfur atoms. The Hirshfeld surface analysis showed that the structure of [CdL2] is dominated by H center dot center dot center dot H, S center dot center dot center dot H, and O center dot center dot center dot H contacts. According to charge and energy decomposition scheme ETS-NOCV, topological noncovalent index (NCI) and quantum theory of atoms in molecules (QTAIM) calculations, both inter-and intramolecular noncovalent CH center dot center dot center dot S and C-H center dot center dot center dot H-C interactions are the main factors that stabilize [CdL2]. Calculated. NMR data, based on the GIAO approach, are in very, good agreement with experimental data. The complex [CdL2] is an efficient single-source precursor for the formation.of TOPO-capped CdS nanoparticles of about 5 nm diameter with wurtzite structure (TOPO = tri-n-octylphosphine oxide). Their growth was monitored over a period of time by means of UV-vis spectroscopy. From ETS-NOCV modeling, the TOPO molecules were found to strongly adhere to the CdS nanoparticles through dative-covalent Cd-O bonds as well as through secondary noncovalent C-H center dot center dot center dot Cd and C-H center dot center dot center dot S interactions. The characteristic band edge luminescence was observed in the emission spectra of all samples. The TEM microscopy showed well-dispersed spherical CdS nanoparticles; the composition was supported by EDX.

First author: Jiang, N, Nanoscale Chemical Imaging of a Dynamic Molecular Phase Boundary with Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy, NANO LETTERS, 16, 3898, (2016)
Abstract: Nanoscale chemical imaging of a dynamic molecular phase boundary has broad implications for a range of problems in catalysis, surface science, and molecular electronics. While scanning probe microscopy (SPM) is commonly used to study molecular phase boundaries, its information content can be severely compromised by surface diffusion, irregular packing, or three-dimensional adsorbate geometry. Here, we demonstrate the simultaneous chemical and structural analysis of N-N’-bis(2,6-diisopropylphenyl)-1,7-(4′-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) molecules by UHV tip-enhanced Raman spectroscopy. Both condensed and diffusing domains of PPDI coexist on Ag(100) at room temperature. Through comparison with time-dependent density functional theory simulations, we unravel the orientation of PPDI molecules at the dynamic molecular domain boundary with unprecedented similar to 4 nm spatial resolution.

First author: Vorobyev, V, Synthesis and crystal structure of mer-nitroaquatriamminenitrosylruthenium(II) nitrate [RuNO(NH3)(3)(NO2)(H2O)](NO3)(2), INORGANIC CHEMISTRY COMMUNICATIONS, 68, 1, (2016)
Abstract: The reaction between mer-[RuNO(NH3)(3)(NO2)(OH)]Cl center dot 0.5H(2)O and an excess of 16 M HNO3 leads to the protonation of the starting complex and crystallization of the complex with a coordinated water molecule and nitrite anion. The crystal structure of the product has been. determined. The coordinated water molecule tends to be a weak acid with a measured pK(a) of 2.4.

First author: Liu, RY, Geometrical isomers of tris(beta-diketonato)metal(III) complexes for M = Cr or Co: Synthesis, X-ray structures and DFT study, INORGANICA CHIMICA ACTA, 447, 59, (2016)
Abstract: Solid state crystal data of three tris(beta-diketonato)metal(III) complexes (M = Cr or Co), representative of the three different molecular symmetries that these complexes can obtain, namely D-3, C-3 or C-1 symmetry, are presented and compared with related experimental structures. Density functional theory calculations show that both fac and mer isomers of tris(beta-diketonato) metal(III) complexes containing unsymmetrical beta-diketonato ligands can exist, in agreement with experimental NMR data. The orbital ordering for both the S = 3/2 [Cr(acac)(3)] and S = 0 [Co(acac)(3)] (Hacac = acetylacetone) complexes in order of increasing orbital energy is: d(xy) < d(xz); d(yz) < d(z2); d(x2-y2).

First author: Smith, ARG, Exact exchange and the density functional theory of metal-to-ligand charge-transfer in fac-Ir(ppy)(3), ORGANIC ELECTRONICS, 33, 110, (2016)
Abstract: The low-energy excitations of iridium(III) complexes, such as fac-Ir(ppy)(3), are known to have significant metal-to-ligand charge-transfer character. Hence the degree of exact exchange included in the density functional description of the complex is expected to be important. To investigate this we report both ground state and time-dependent density functional calculations with a range of functionals (with different degrees of exact exchange) and examine the changes in the predictions as we vary the degree of exact exchange within a single functional (while holding the rest of the parameterisation fixed). We find that although the optimal degree of exact exchange (similar to 20%) gives results in good agreement with experiment for fac-Ir(ppy)(3) and the blue emissive fac-Ir(ptz)(3), other parameterisations lead to predictions that are both qualitatively and quantitatively inconsistent with experiment. Other differences in the functionals lead to much smaller differences in the predicted properties of the complex. Thus the B3LYP and X3LYP functionals provide the best description of experimental data.

First author: Zhang, LY, Density functional study on the effect of aromatic rings flanked by bithiophene of novel electron donors in small-molecule organic solar cells, MATERIALS CHEMISTRY AND PHYSICS, 175, 13, (2016)
Abstract: In order to further improve the short-circuit current (J(SC)) and the overall performance of the already synthesized donor molecule (1s) used in organic heterojunction solar cells, six new A-A-D-A-A type small molecules composed of different donor (D, electron rich) and same acceptor (A, electron poor) moieties were designed and characterized by using density functional theory (DFT), time-dependent density functional theory (TD-DFT) and Marcus theory. Through calculating frontier molecular orbital energy levels and spectra properties, we found that HOMO level goes up while E-g goes down along with the cycle extension of the center part flanked by bithiophene. Next, character of excited state, ionization potentials (IPs) and charge transport properties were also investigated to provide an in-depth insight into the charge transfer/transport characteristics and the J(SC) of organic solar cells. The results reveal that compounds 3c, 3n and 3 degrees exhibit favorable J(SC) and comparable performance to original molecule (1s) and show promising potential in organic solar cells.

First author: Fihey, A, How Metals Can Help Multiphotochromism: An Ab Initio Study, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 11140, (2016)
Abstract: Dimers of dithienylethenes containing a metallic center in their bridging unit often exhibit a full and stepwise photochromism, and their photoactivity typically surpasses the majority of their metal-free counterparts that are often plagued by the impossibility to switch all units. In this work, we investigate five different photochromic dimers with a relativistic spin orbit time dependent density functional theory (SO-TD-DFT) approach and explore the possible sources of this enhanced photoactivity. In particular the potential intersystem crossing (ISC) from an intense singlet state in the UV region to a triplet state presenting the necessary topology to trigger the ring closing of the switch is unravelled in several cases. The efficiency of this crossing is found to be dependent on both the nature of the metallic center and the structure of the dithienylethene ligand but, in general, improves the probability for the second ring closing starting from the partially switched dimer. This work provides the first theoretical evidence of the presence of strong relativistic effects yielding ISC to a “photochromic” triplet state in these complex systems. This allows for the rationalization of several experimental outcomes.

First author: Szell, PMJ, Cl-35 Solid-State NMR and Computational Study of Chlorine Halogen Bond Donors in Single-Component Crystalline Chloronitriles, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 11121, (2016)
Abstract: Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (sigma-hole) and an electron donor, which has gained popularity in the field of crystal engineering due to its strength and linearity. Here, we present a Cl-35 solid-state NMR study of chlorine atoms as halogen bond donors, with interpretation aided by crystallographic symmetry and computational chemistry. In a series of chlorinated benzonitrile compounds, the magnitude of the Cl-35 quadrupolar coupling constant (C-Q) was found to increase, and the quadrupolar asymmetry parameter (eta) was found to decrease upon halogen bonding. A natural localized molecular orbital (NLMO) analysis attributes these changes to an increase in the contribution from the lone pair NLMOs to vertical bar C-Q vertical bar. This is distinguished from a short proton-chlorine contact, which causes an increase in the magnitude of the alpha-bond contribution and a decrease in the lone pair contribution, resulting in an overall decrease in vertical bar C-Q vertical bar. This first direct Cl-35 solid-state NMR study of chlorine as a halogen bond donor provides new physical insight into the relationship between NMR observables and the halogen bond.

First author: Zlatar, M, Excited States of Pt(PF3)(4) and Their Role in Focused Electron Beam Nanofabrication, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 10667, (2016)
Abstract: Electron induced chemistry of metal-containing precursor molecules is central in focused electron beam induced deposition (FEBID). While some elementary processes leading to precursor decomposition were quantitatively characterized, data for neutral dissociation is missing. We provide this data for the model precursor Pt(PF3)(4) by using the available cross sections for electronic excitation and characterizing fragmentation of the excited states theoretically by TDDFT. The potential energy curves for a number of states visible in the experimental electron energy loss spectra are dissociative, either directly or via conical intersections, indicating that the quantum yield for dissociation is close to 100%. Taking into account typical electron energy distribution at the FEBID spot reveals that the importance of neutral dissociation exceeds that of dissociative electron attachment, which has been so far considered to be the dominant decomposition process. We thus established neutral dissociation as an important, albeit often neglected, channel for FEBID using Pt(PF3)(4). The calculations revealed a number of other phenomena that can play a role in electron induced chemistry of this compound, e.g., a considerable increase of bond dissociation energy with sequential removal of multiple ligands.

First author: Majid, A, A density functional theory study of electronic properties of substitutional alloying of monolayer MoS2 and CeS2 surface models, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1084, 98, (2016)
Abstract: The electronic properties of Mo1-xCexS2 alloy surfaces, calculated using density functional theory, for full compositional range are being reported. The calculation, carried out within generalized gradient approximation, revealed that substitutional incorporation of Ce on cationic sublattice of MoS2 caused an increase in population of states near Fermi level in the band structure. A consistent decrease in Fermi energy was observed whereas semiconductor to metal transition taken place at 16.67% concentration of Ce into MoS2. The structural modifications and formation of alloys from an energetic point of view is discussed in detail.

First author: Adonin, SA, Binuclear bromide complex of Bi(III): Thermally induced changes in optical properties, JOURNAL OF MOLECULAR STRUCTURE, 1112, 21, (2016)
Abstract: Binuclear bromobismuthate complex (H(2)bipy)(2)[Bi2Br10] (1) displays the optical properties: 1) thermochromism, 2) disappearance/appearance of luminescence at 298/77 K. To investigate this feature, a combination of X-ray diffractometry, differential scanning calorimetry (DSC) and quantum chemical calculations has been used.

First author: Ruger, R, Tight-binding approximations to time-dependent density functional theory – A fast approach for the calculation of electronically excited states, JOURNAL OF CHEMICAL PHYSICS, 144, 21, (2016)
Abstract: We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

First author: Alemayehu, AB, Tungsten Biscorroles: New Chiral Sandwich Compounds, CHEMISTRY-A EUROPEAN JOURNAL, 22, 6914, (2016)
Abstract: The oxidative metalation method, involving the interaction of free-base meso-triarylcorroles and W(CO)(6) in refluxing decalin, led to a set of three tungsten(VI) biscorroles, the first homoleptic sandwich compounds involving corroles. Single-crystal X-ray structures of two of the complexes revealed square-antiprismatic coordination and strongly domed corroles with long W-N distances of 2.15-2.22 angstrom and a substantial displacement of approximate to 1.17 angstrom of the metal relative to the mean N-4 planes of the ligands. The structures correspond to approximate C-2 symmetry and are thus chiral. DFT calculations strongly indicate that the enantiomers are configurationally stable and hence amenable to chiral resolution. Their other notable properties include a strongly blueshifted Soret band at (357 ± 2)nm, a relatively intense W(dz2 ) near-IR feature at (781 ± 3)nm, and a low electrochemical HOMO-LUMO gap of approximately 1.3V. The results obtained herein suggest that metallobiscorroles may emerge as a new class of inherently chiral chromophores with novel optical and electrochemical properties.

First author: Hong, S, Atomistic-Scale Analysis of Carbon Coating and Its Effect on the Oxidation of Aluminum Nanoparticles by ReaxFF-Molecular Dynamics Simulations, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 9464, (2016)
Abstract: We developed a ReaxFF reactive force field for Al/C interactions to investigate carbon coating and its effect on the oxidation of aluminum nanoparticles (ANPs). The ReaxFF parameters were optimized against quantum mechanics-based (QM-based) training sets and validated with additional QM data and data from experimental literature. ReaxFF-molecular dynamics (MD) simulations were performed to determine whether this force field description was suitable to model the surface deposition and oxidation on complex materials (i.e., carbon-coated ANPs). Our results show that the ReaxFF description correctly reproduced the Al/C interaction energies obtained from the QM calculations and qualitatively captured the processes of the hydrocarbons’ binding and their subsequent reactions on the bare ANPs. The results of the MD simulations indicate that a carbon coating layer was formed on the surface of the bare ANPs, while H atoms were transferred from the hydrocarbons to the available Al binding sites typically without breaking C C bonds. The growth of the carbon layer depended strongly on the hydrocarbon precursors that were used. Moreover, the MD simulations of the oxidation of the carbon-coated ANPs indicate that the carbon-coated ANPs were less reactive at low temperatures, but they became very susceptible to oxidation when the coating layer was removed at elevated at elevated temperatures. These results are consistent with the experimental literature, and thus, the ReaxFF description that was developed in this study enables us to gain atomistic-scale insights into the role of the carbon coating in the oxidation of ANPs.

First author: Melendez, FJ, Theoretical study of global and local reactivities of coumarin and its hydroxylated derivatives, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 663, (2016)
Abstract: Coumarins are bioactive substances of the benzo–pyrone family, which have shown antioxidant, antiviral, anti-inflammatory and antitumor activities, among others. 7-Hydroxycoumarin and 6,7-dihydroxycoumarin (esculetin) are two coumarin derivatives that have been reported to exhibit antitumor activity, but the action mechanism underlying this activity remains unknown. In this work, to elucidate this mechanism, a theoretical study of the local and global electronic reactivity properties of a series of hydroxylated and dihydroxylated coumarin derivatives with possible antitumor action is performed using Density Functional Theory in aqueous solution. The substitution by one or two hydroxyl groups in the benzene ring of coumarin produces better charge-donor than charge-acceptor compounds. All the studied compounds are generally stable in water and exhibit permanent polarization in the solvent. With one hydroxyl substitution, 7-hydroxycoumarin is the most polar and polarizable derivative, whereas 5,7-dihydroxycoumarin is the most polar and polarizable compound with two hydroxyl substitutions. 5,7-Dihydroxycoumarin is suggested to possess antitumor activity.

First author: Arras, J, Intermolecular Sn-119,P-31 Through-Space Spin-Spin Coupling in a Solid Bivalent Tin Phosphido Complex, INORGANIC CHEMISTRY, 55, 4669, (2016)
Abstract: A bivalent tin complex [Sn(NP)(2)] (NP = [(2-Me2NC6H4)P(C6H5)](-)) was prepared and characterized by X-ray diffraction and solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. In agreement with the X-ray structures of two polymorphs of the molecule, P-31 and Sn-119 CP/MAS NMR spectra revealed one crystallographic phosphorus and tin site with through-bond (1)J(Sn-117/119,P-31) and through-space (TS)J(Sn-117/119,P-31) spin-spin couplings. Density functional theory (DFT) calculations of the NMR parameters confirm the experimental data. The observation of through-space (TS)J(Sn-117/119,P-31) couplings was unexpected, as the distances of the phosphorus atoms of one molecule and the tin atom of the neighboring molecule (>4.6 angstrom) are outside the sum of the van der Waals radii of the atoms P and Sn (4.32 angstrom). The intermolecular Sn…P separations are clearly too large for bonding interactions, as supported by a natural bond orbital (NBO) analysis.

First author: Stasyuk, OA, How amino and nitro substituents direct electrophilic aromatic substitution in benzene: an explanation with Kohn-Sham molecular orbital theory and Voronoi deformation density analysis, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 11624, (2016)
Abstract: The substituent effect of the amino and nitro groups on the electronic system of benzene has been investigated quantum chemically using quantitative Kohn-Sham molecular orbital theory and a corresponding energy decomposition analysis (EDA). The directionality of electrophilic substitution in aniline can accurately be explained with the amount of contribution of the 2p(z) orbitals on the unsubstituted carbon atoms to the highest occupied pi orbital. For nitrobenzene, the molecular pi orbitals cannot explain the regioselectivity of electrophilic substitution as there are two almost degenerate pi orbitals with nearly the same 2p(z) contributions on the unsubstituted carbon atoms. The Voronoi deformation density analysis has been applied to aniline and nitrobenzene to obtain an insight into the charge rearrangements due to the substituent. This analysis method identified the orbitals involved in the C-N bond formation of the pi system as the cause for the pi charge accumulation at the ortho and para positions in the case of the NH2 group and the largest charge depletion at these same positions for the NO2 substituent. Furthermore, we showed that it is the repulsive interaction between the pi(HOMO) of the phenyl radical and the pi(HOMO) of the NH2 radical that is responsible for pushing up the pi(HOMO) of aniline and therefore activating this pi orbital of the phenyl ring towards electrophilic substitution.

First author: Pan, S, sigma-Aromatic cyclic M-3(+) (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 11661, (2016)
Abstract: The sigma-aromaticity of M-3(+) (M = Cu, Ag, Au) is analyzed and compared with that of Li-3(+) and a prototype sigma-aromatic system, H-3(+). Ligands (L) like dimethyl imidazol-2-ylidene, pyridine, isoxazole and furan are employed to stabilize these monocationic M-3(+) clusters. They all bind M-3(+) with favorable interaction energy. Dimethyl imidazol-2-ylidene forms the strongest bond with M-3(+) followed by pyridine, isoxazole and furan. Electrostatic contribution is considerably more than that of orbital contribution in these M-L bonds. The orbital interaction arises from both L -> M sigma donation and L <- M back donation. M-3(+) clusters also bind noble gas atoms and carbon monoxide effectively. In general, among the studied systems Au-3(+) binds a given L most strongly followed by Cu-3(+) and Ag-3(+). Computation of the nucleus-independent chemical shift (NICS) and its different extensions like the NICS-rate and NICS in-plane component vs. NICS out-of-plane component shows that the s-aromaticity in L bound M-3(+) increases compared to that of bare clusters. The aromaticity in pyridine, isoxazole and furan bound Au-3(+) complexes is quite comparable with that in the recently synthesized Zn-3(C-5(CH3)(5))(3)(+). The energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital also increases upon binding with L. The blue-shift and red-shift in the C-O stretching frequency of M-3(CO)(3)(+) and M-3(OC)(3)(+), respectively, are analyzed through reverse polarization of the sigma- and pi-orbitals of CO as well as the relative amount of OC -> M s donation and M -> CO pi back donation. The electron density analysis is also performed to gain further insight into the nature of interaction.

First author: Szatylowicz, H, Towards physical interpretation of substituent effects: the case of meta- and para-substituted anilines, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 11711, (2016)
Abstract: Quantum chemical modeling was used to investigate the electron-donating properties of the amino group in a series of meta-and para-X-substituted anilines (X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, and NO). Different methods (HF, B3LYP, and M06-2X) and basis sets (6-31+G(d,p), 6-311++G(d,p), and aug-cc-pVDZ) were applied and compared with the MP2 approach. The B3LYP/6-311++G(d,p) method was chosen as the most appropriate one. The substituent properties were described by sigma, cSAR(X) and SESE descriptors; the amino group was characterized by structural (d(CN), d(NH) and Sigma(NH2)) and electronic [delta(N) and cSAR(NH2)] parameters; whereas the transmitting moiety was characterized by aromaticity indices HOMA and NICS, as well as by QTAIM characteristics at the ring critical point. All the used parameters were found to be mutually interrelated with much better correlations for the para-derivatives than the meta-derivatives. It was numerically confirmed that sensitivity of the amino group to the substituent effect was greater by over three times when the substituent was located in the para-position. In the case of the meta-derivatives, variability of characteristics for both the reaction center and the substituent was small. The reverse substituent effect was clearly shown by comparison of the cSAR(X) characteristics for monosubstituted benzenes, and meta- and para-substituted anilines.

First author: Mandal, S, Viability of aromatic all-pnictogen anions, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 11738, (2016)
Abstract: Aromaticity in novel cyclic all-pnictogen heterocyclic anions, P2N3- and P3N2-, and in their heavier analogues is studied using quantum mechanical computations. All geometrical parameters from optimized geometry, bonding, electron density analysis from quantum theory of atoms in molecules, nucleus-independent chemical shift, and ring current density plots support their aromaticity. The aromatic nature of these molecules closely resembles that of the prototypical aromatic anion, C5H5-. These singlet C-2v symmetric molecules are comprised of five distinct canonical structures and are stable up to at least 1000 fs without any significant distortion. Mechanistic study revealed a plausible synthetic pathway for P3N2- – a click reaction between N-2 and P-3(-), through a C-2v symmetric transition state. Besides this, the possibility of P3N2- as a eta(5)-ligand in metallocenes is studied and the nature of bonding in metallocenes is discussed through the energy decomposition analysis.

First author: Mondal, S, 10-pi-Electron arenes a la carte: structure and bonding of the [E-(CnHn)-E](n-6) (E = Ca, Sr, Ba; n=6-8) complexes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 11909, (2016)
Abstract: In this paper, we provide solid evidence to show that among an overwhelming structural diversity, alkaline earth metals (Ca, Sr, Ba) have the ability to form inverted sandwich compounds with C6H6, C7H7+, and C8H82+ of D-nh symmetry and general formula [E-(CnHn)-E](n-6) (n = 6-8) with planar 10-pi-electron aromatic cores by virtue of transferring two electrons per metal atom to the ring. However, the origin of the orbital interaction between the metals and the carbon ring is quite different; while [E-(C6H6)-E] complexes are dominated by delta-interactions, both pi- and delta-interactions are important in [E-(C7H7)-E](+) and [E-(C8H8)-E](2+) complexes.

First author: Kravtsova, AN, In silico study of the atomic and electronic structure of quantum dots of the CdTe family doped with atoms of rare earth elements, JOURNAL OF STRUCTURAL CHEMISTRY, 57, 491, (2016)
Abstract: An in silico study of semiconductor quantum dots of the CdTe family doped with atoms of rare earth elements is performed based of density functional theory. An ab initio computer design of quantum dots based on CdTe nanoparticles doped with Eu D Gd atoms is carried out. Partial densities of states of CdTe:Eu and CdTe:Gd quantum dots are calculated and analyzed. X-ray absorption near edge (XANES) spectra near the Eu K-, L (1)-, and L (3)- and Gd K-, L (1)-, and L (3)-edges of CdTe:Eu and CdTe:Gd quantum dots are calculated. The sensitivity of XANES spectroscopy for the verification of parameters of a nanosized atomic structure of quantum dots based on CdTe particles doped with atoms of rare earth elements and the determination of the local atomic structure around the atoms of rare earth elements in quantum dots is demonstrated.

First author: Lacerda, LCT, Oxidative dehydration reaction of glycerol into acrylic acid: A first-principles prediction of structural and thermodynamic parameters of a bifunctional catalyst, CHEMICAL PHYSICS LETTERS, 651, 161, (2016)
Abstract: The production of biodiesel generates crude glycerol as a byproduct. The search for glycerol conversion routes has attracted the attention of researchers and thus, this work evaluated the properties of the catalysts T-Nb2O5 and T-Nb2O5/V treated with H2O2 applied to the reaction of oxidative dehydration of glycerol. The peroxo groups from the treatment with H2O2 had a greater oxidation capacity in relation to those in the pure catalyst. Furthermore, the catalyst doped with vanadium presented lower energy costs during the process. Those results might be helpful for designing new catalysts for the production of strategic chemical products from glycerol.

First author: Xie, J, Size and Promoter Effects in Supported Iron Fischer-Tropsch Catalysts: Insights from Experiment and Theory, ACS CATALYSIS, 6, 3147, (2016)
Abstract: The fundamentals of structure sensitivity and promoter effects in the Fischer-Tropsch synthesis of lower olefins have been studied. Steady state isotopic transient kinetic analysis, switching (CO)-C-12 to (CO)-C-13 and H-2 to D-2, was used to provide coverages and residence times for reactive species on supported iron carbide particles of 2-7 nm with and without promoters (Na + S). CO coverages appeared to be too low to be measured, suggesting dissociative adsorption of CO. Fitting of CH4 response curves revealed the presence of parallel side-pools of reacting carbon. CHx coverages decreased with increasing particle size, and this is rationalized by smaller particles having a higher number of highly active low coordination sites. It was also established that the turnover frequency CHx coverage. To calculate H coverages, new equations were derived to fit HD response curves, again leading to a parallel side-pool model. The H coverages appeared to be lower for bigger particles. The H coverage was suppressed upon addition of promoters in line with lower methane selectivity and higher lower olefin selectivity. Density functional theory (DFT) was applied on H adsorption for a fundamental understanding of this promoter effect on the selectivities, with a special focus on counterion effects. Na2S is a better promoter than Na2O due to both a larger negative charge donation and a more effective binding configuration. On the unpromoted Fe5C2 (111) surface, H atoms bind preferably on C after dissociation on Fe. On Na2S-promoted Fe5C2 surfaces, adsorption on carbon sites weakens, and adsorption on iron sites strengthens, which fits with lower H coverage, less CH4 formation, and more olefin formation.

First author: Nguyen, TAN, Structures and Bonding Situation of Iron Complexes of Group-13 Half-Sandwich ECp* (E = B to TI) Based on DFT Calculations, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 642, 609, (2016)
Abstract: Quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, and TZ2P+) were carried out for the Fe(CO)(4) of group-13 half-sandwich ECp* [Fe(CO)(4)-ECp*] (Fe4-E) (E = B to Tl). The chemical bonding of the Fe(CO)(4)-ECp* bond was analyzed with charge- and energy decomposition methods. The calculated equilibrium structures of complexes Fe4-E show that the ligands ECp* are bonded in an end-on way to the fragment Fe(CO)(4) in Fe4-E with E = B to Ga. The compound Fe4-In has a distorted end-on ligand InCp*. In contrast, Fe4-Tl has a side-on bonded ligand TlCp*. The calculated bond dissociation energies (BDEs) suggest that the bond in the iron group-13 half-sandwich complexes Fe4-E decreases from Fe4-B to Fe4-Tl. Natural bond orbital (NBO) analysis of the bonding situation reveals that the Fe(CO)<- 4ECp* donation in Fe4-E comes from the sigma lone-pair orbital of ECp*. Bonding analysis indicates that the ligand ECp* in complexes are strong sigma donors and the NOCV pairs of the bonding show small pi-back donation from the Fe(CO)(4) to the ECp* ligands.

First author: Barrera, M, On the performance of ruthenium dyes in dye sensitized solar cells: a free cluster approach based on theoretical indexes, JOURNAL OF MOLECULAR MODELING, 22, 609, (2016)
Abstract: The performance of ruthenium dye sensitized solar cells (DSSC) with different types of ligand was studied by means of a theoretical model where the ruthenium complex is bound to two [Ti(OH)(3)](+) units, instead of the more usual cluster TiO2 model. Electron injection is proposed to proceed from a thermalized (MLCT)-M-3 state rather than from higher vibrational excited states. The efficiency of the dye linked to the two [Ti(OH)(3)](+) units was determined in terms of a global index (xi), calculated as the product of three theoretical indexes (F-I) built from the results of time-dependent density functional theory (TDDFT) calculations. The index considers the harvested and delivered energy (F-1), the charge transferred to the semiconductor (F-2), and dye regeneration (F-3). The results show that this set of parameters is unique for each dye, and allows the comparative evaluation of the performance of a series of dyes, with a different ancillary ligand at each stage of the cell operation. The method provides insights that can help explain the improved performance of N3 and black dyes compared to other dyes.

First author: Shah, SAA, Synthesis, modeling and photovoltaic properties of a benzothiadiazole based molecule for dye-sensitized solar cells, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 27, 4501, (2016)
Abstract: A benzothiadiazole based solution-processable organic dye D1 (N (4)-Phenyl-N (4),N (7),N (7)-tri{4-[(2-ethoxycarbonyl)-2-cyanovinyl]phenyl}benzo[c][1,2,5]thiadiazole-4,7-diamine) was synthesized. Dye-sensitized solar cells (DSSCs) were fabricated based on D1 and a commercially available benzothiadiazole based RK1 dye. The photovoltaic parameters of these cells were studied under simulated AM 1.5 illumination (100 mW cm(-2)). The DSSC sensitized by RK1 dye provided a power conversion efficiency of 5.7 % with high values of short-circuit photocurrent density, open-circuit photovoltage, and fill factor. Under the same conditions, the cell sensitized with D1 dye showed a very poor performance due to the lower values of short-circuit photocurrent density and open-circuit photovoltage. In order to provide insight into poor performance of the DSSC sensitized by D1, molecular structure of D1 was analyzed by density functional theory. Its frontier orbitals were calculated to investigate effectiveness of charge transport and reasons of the poor performance. This computational study revealed that the photovoltaic performance of the benzothiadiazole based DSSCs can be enhanced significantly by inserting a phenyl ring between the benzothiadiazole unit and the anchoring group.

First author: Xu, HT, Selectively catalytic activity of metal-organic frameworks depending on the N-position within the pyridine ring of their building blocks, JOURNAL OF SOLID STATE CHEMISTRY, 237, 323, (2016)
Abstract: Iron metal-organic frameworks (MOFs) [Fe(L)(2)(SCN)(2)](proportional to) (L1: 4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene for 1Fe; and L2: 3-bpdh=2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene for 2Fe) were assembled in a MeOH-H2O solvent system. 1Fe exhibits a two-dimensional extended-grid network, whereas 2Fe exhibits a stair-like double-chain; the N-position within the pyridine ring of the complexes was observed to regulate the MOF structure as layers or chains. Furthermore, selectively catalytic activity was observed for the layered MOF but not the chain-structured MOF; micro/nanoparticles of the layered MOF were therefore investigated for new potential applications of micro/nano MOFs.

First author: Viveka, S, Structural, spectral, and theoretical investigations of 5-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid, RESEARCH ON CHEMICAL INTERMEDIATES, 42, 4497, (2016)
Abstract: The present research work has focused on combined experimental and theoretical studies of one of the biologically important pyrazole-4-carboxylic acid derivatives, viz. 5-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid (C11H10N2O2). The starting material 5-methyl-1-phenyl-1H-4-pyrazolecarboxylate (1) was obtained by the cyclocondensation of ethyl acetoacetate, N,N-dimethylformamide dimethyl acetal (DMF-DMA), and phenylhydrazine, which upon basic hydrolysis yielded the corresponding acid (2). The target compound (2) was characterized by H-1 and C-13 NMR (solution in DMSO), Fourier transform infrared (FT-IR) spectroscopy, thermo gravimetric analysis, and by single-crystal X-ray diffraction technique. The single crystals of compound (2) were obtained at room temperature by slow evaporation of ethanol as solvent and crystallized in the space group P2 (1)/n of monoclinic system. The experimental FT-IR and H-1 and C-13 NMR chemical shifts have been compared to those calculated by means of density functional theory (DFT) at the B3LYP/TZ2P level of theory. The continuum-like screening model was used for geometry optimization of a single molecule and for subsequent calculations of NMR shielding constants in solution (DMSO). Finally, the HOMO-LUMO energy levels were also constructed to study the electronic transition within the molecule by time-dependent TD-DFT method.

First author: Farberovich, OV, Ultrafast quantum spin-state switching in the Co-octaethylporphyrin molecular magnet with a terahertz pulsed magnetic field, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 405, 169, (2016)
Abstract: Molecular spin crossover switches are the objects of intense theoretical and experimental studies in recent years. This interest is due to the fact that these systems allow one to control their spin state by applying an external photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research is currently devoted to the study of the effect of the photoexcitation on the bi-stable states of spin crossover single molecular magnets (SMMs). The main limitation of photo-induced bi-stable states is their short lifetime. In this paper we present the results of a study of the spin dynamics of the Co-octaethylporphyrin (CoOEP) molecule in the Low Spin (LS) state and the High Spin (HS) state induced by applying the magnetic pulse of 36.8 T. We show that the spin switching in case of the HS state of the CoOEP molecule is characterized by a long lifetime and is dependent on the magnitude and duration of the applied field. Thus, after applying an external stimuli the system in the LS state after the spin switching reverts to its ground state, whereas the system in the HS state remains in the excited state for a long time. We found that the temperature dependency of magnetic susceptibility shows an abrupt thermal spin transition between two spin states at 40 K. Here the proposed theoretical approach opens the way to create modern devices for spintronics with the controllable spin switching process.

First author: Yue, NLS, Chemistry of palladium(II) with bis(3-amidopyridine) ligands, INORGANICA CHIMICA ACTA, 445, 37, (2016)
Abstract: The coordination chemistry of palladium(II) with bis(3-amidopyridine) ligands [LL = 2,6-C5H3N(CONH-3-C5H4N)(2), 1; 1,3-C6H4(CONH-3-C5H4N)(2), 2; 1,3-C6H4(CONMe-3-C5H4N)(2), 3; 2,5-C4H2S(CONMe-3-C5H4N)(2), 4] has been investigated. Neutral binuclear macrocyclic complexes trans,trans-[Pd2X4(mu-LL)(2)] have been characterized with X = Cl or Br and LL = 1. Cationic complexes have been characterized as mononuclear bis(chelate) derivatives [Pd(LL)(2)](2+), when LL = 3 or 4, but a lantern complex [Pd-2(mu-LL)(4)](4+), when LL = 2. The tendency for chelation versus bridging coordination of the flexible ligands 1-4 is analyzed in terms of substituent effects on the preferred ligand conformations. In the dipalladium complexes, the macrocycle or lantern structure can accommodate guest molecules.

First author: Jian, T, Manganese-centered tubular boron cluster-MnB16-: A new class of transition-metal molecules, JOURNAL OF CHEMICAL PHYSICS, 144, 37, (2016)
Abstract: We report the observation of a manganese-centered tubular boron cluster (MnB16-), which is characterized by photoelectron spectroscopy and ab initio calculations. The relatively simple pattern of the photoelectron spectrum indicates the cluster to be highly symmetric. Ab initio calculations show that MnB16- has a Mn-centered tubular structure with C-4v symmetry due to first-order Jahn-Teller effect, while neutral MnB16 reduces to C-2v symmetry due to second-order Jahn-Teller effect. In MnB16-, two unpaired electrons are observed, one on the Mn 3d(z2) orbital and another on the B-16 tube, making it an unusual biradical. Strong covalent bonding is found between the Mn 3d orbitals and the B-16 tube, which helps to stabilize the tubular structure. The current result suggests that there may exist a whole class of metal-stabilized tubular boron clusters. These metal-doped boron clusters provide a new bonding modality for transition metals, as well as a new avenue to design boron-based nanomaterials.

First author: Fan, JX, Theoretical Study on Charge Transport Properties of Intra- and Extra-Ring Substituted Pentacene Derivatives, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 2390, (2016)
Abstract: A series of pentacene derivatives, halogen-substituted and thiophene- and pyridine-substituted, have been studied with a focus on the electronic properties and charge transport properties using density functional theory and classical Marcus charge-transfer theory. The transport properties of holes and electrons have been studied to get insight into the effect of halogenation and heteroatom substitution on transport and injection of charge carriers. The calculation results revealed that fluorination and chlorination can effectively lower the lowest unoccupied molecular orbital (LUMO) level, modulate the hole and electron reorganization energy, improve the stacking mode of the crystal structure, and enhance the ambipolar characteristic. Chlorination gives a better ambipolar characteristic. On the basis of halogen substitution, the substitution of terminal benzene ring of triisopropyl-silylethynyl-pentacene (TIPS-PEN) by a thiophene or pyridine will greatly lower the LUMO level and improve the stacking mode, leading to more suitable ambipolar materials. Hence, both intra- and extra-ring substitution are favorable to enhance the ambipolar transport property of TIPS-PEN.

First author: Fernando, A, Theoretical Investigation of Water Oxidation on Fully Saturated Mn2O3 and Mn2O4 Complexes, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 2480, (2016)
Abstract: Understanding the factors that affect efficiency of manganese oxides as water oxidation catalysts is an essential step toward developing commercially viable electrocatalysts. It is important to understand the performance of the smallest versions of these catalysts, which will in return be advantageous with bottom up catalytic design. Density functional theory calculations have been employed to investigate water oxidation processes on Mn-2(mu-OH)(mu-O)(H2O)(3)(OH)(5) (Mn2O4 center dot 6H(2)O), Mn-2(mu-OH)(2)(H2O)(3)(OH)(4) (Mn2O3 center dot 6H(2)O), and Mn-2(mu-OH)(2)(H2O)(4)(OH)(4) (Mn2O3 center dot 7H(2)O) complexes. The effect of different oxidation states of manganese is considered in this study. Thermodynamically, the lowest energy pathway for the fully saturated Mn2O4 center dot 6H(2)O complex occurs through a nucleophilic attack of a solvent water molecule to a Mn(IV1/2)O oxo moiety. The lowest energy pathway on the on the Mn2O3 center dot 6H(2)O complex proceeds with an attack of Mn(VI)O group to the surface hydroxo group on the same manganese atom; this pathway is related to the third lowest energy pathway on the Mn2O4 center dot 6H(2)O complex. The water oxidation process on the fully saturated Mn2O3 center dot 7H(2)O complex also involves a nucleophilic attack from a solvent water molecule to a Mn(V)O moiety. The formation of these manganese oxo groups can be used as a descriptor for selecting a manganese-based water splitting catalyst due to the high electrochemical potentials required for the generation of these groups.

First author: Dimuthu, KL, Effect of Aliphatic versus Aromatic Ligands on the Structure and Optical Absorption of Au-20(SR)(16), JOURNAL OF PHYSICAL CHEMISTRY C, 120, 8354, (2016)
Abstract: Despite the recent determination of the crystal structure of the Au-20(TBBT)(16) (TBBT = SPh-t-Bu) nanocluster, it is not certain if Au-20(SR)(16) adopts the same structure when R is an aliphatic ligand. To this end, we perform a theoretical investigation using density functional theory (DFT) and time-dependent DFT (TDDFT). We optimize a methylthiolate version of the new crystal structure geometry of Au-20(TBBT)(16) and compare the stability and optical properties with the three lowest energy isomers of Au-20(SCH3)(16) predicted previously. Furthermore, TDDFT calculations are performed for the Au-20(TBBT)(16) structure determined via X-ray crystallography and the related Au-20(SPh)(16) nanocluster. All the calculated optical absorption spectra are compared against the available experimental spectrum of Au-20(PET)(16) (PET = SCH2CH2Ph) and Au-20(TBBT)(16). We observe that the new geometry of the Au-20(SCH3)(16) nanocluster with an Au-7 core is more stable than the previous isomers.

First author: Pathak, AD, A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl2 hydrates and MgCl2 hydrates for seasonal heat storage, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 10059, (2016)
Abstract: Salt hydrates store solar energy in chemical form via a reversible dehydration-hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The mixture of CaCl2 and MgCl2 hydrates has been shown experimentally to have exceptional cycle stability and improved kinetics. However, the optimal operating conditions for the mixture are unknown. To understand the appropriate balance between dehydration and hydrolysis kinetics in the mixtures, it is essential to gain in-depth insight into the mixture components. We present a GGA-DFT level study to investigate the various gaseous structures of CaCl2 hydrates and to understand the relative stability of their conformers. The hydration strength and relative stability of conformers are dominated by electrostatic interactions. A wide network of intramolecular homonuclear and heteronuclear hydrogen bonds is observed in CaCl2 hydrates. Equilibrium product concentrations are obtained during dehydration and hydrolysis reactions under various temperature and pressure conditions. The trend of the dehydration curve with temperature in CaCl2 hydrates is similar to the experiments. Comparing these results to those of MgCl2 hydrates, we find that CaCl2 hydrates are more resistant towards hydrolysis in the temperature range of 273-800 K. Specifically, the present study reveals that the onset temperatures of HCl formation, a crucial design parameter for MgCl2 hydrates, are lower than for CaCl2 hydrates except for the mono-hydrate.

First author: Izzet, G, Hierarchical Self-Assembly of Polyoxometalate-Based Hybrids Driven by Metal Coordination and Electrostatic Interactions: From Discrete Supramolecular Species to Dense Monodisperse Nanoparticles, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 5093, (2016)
Abstract: The metal-driven self-assembly processes of a covalent polyoxometalate (POM)-based hybrid bearing remote terpyridine binding sites have been investigated. In a strongly dissociating solvent, a discrete metallomacrocycle, described as a molecular triangle, is formed and characterized by 2D diffusion NMR spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and molecular modeling. In a less dissociating solvent, the primary supramolecular structure, combining negatively charged POMs and cationic metal linkers, further self-assemble through intermolecular electrostatic interactions in a reversible process. The resulting hierarchical assemblies are dense monodisperse nanoparticles composed of ca. 50 POMs that were characterized by SAXS and transmission electron microscopy (TEM). This multiscale organized system directed by metal coordination and electrostatic interactions constitutes a promising step for the future design of POM self-assemblies with controllable structure-directing factors.

First author: Kondinski, A, Rotational Isomerism, Electronic Structures, and Basicity Properties of “Fully-Reduced” V-14-type Heteropolyoxovanadates, INORGANIC CHEMISTRY, 55, 3777, (2016)
Abstract: We investigated computationally the alpha-, gamma-, and beta-isomeric structures, relative stabilities, and the electronic and basicity properties of magnetic [(V14E8O50)-E-IV](12-) (hereafter referred to as {V14E8}) heteropolyoxovanadates (heteroPOVs) and their heavier chalcogenide-substituted [(V4EE8O42X8)-E-IV](12)- ({V14E8X8}) derivatives for E =Si-IV, Ge-IV, and Sn-IV and X = S, Se, and Te, We used density functional theory (DFT) with scalar relativistic corrections in combination with the conductor-like screening model of solvation. The main purpose of this investigation is to introduce the structure-property relations in heteroPOVs as well as to assist the synthesis and molecular deposition of these molecular vanadium-oxide spin clusters on surfaces. “Fully-reduced” polyoxoanions {V14E8} and {V14E8X8} are virtually comprised of [(V14O38)-O-IV](20-) {V-14} skeletons of different symmetries, that is, D-2d for alpha-, D-2 for gamma-, and D-4h for beta-isomers, which are stabilized by the four {E2O3}(2+) and four {F20X2}2 moieties, respectively. Our DFT calculations reveal stability trends alpha > gamma > beta for polyoxoanions {V14E8} and {V14E8X8}, based on relative energies and HOMO-LUMO energy gaps. The a-isomeric polyoxoanions {V14E8} and {V14E8X8} with the high negative net charges may easily pick up protons at the terminal E-O-t and E-X-t sites, respectively, which is evidenced by strongly negative enthalpies of monoprotonation. Energetically favorable sites on polyoxoanions alpha-{V14E8} and alpha-{VAX(8)} for electrostatic pairing with countercations were also determined. Among beta and gamma isomers, the hitherto unknown gamma[V14Sn8O50](12-) and gamma-[V14Sn8O42S8](12-) seem to be the most viable targets for isolation. Furthermore, these Sn-substituted polyoxoanions are of high interest for electrochemical studies because of their capability to act as two-electron redox catalysts.

First author: Martinez, JP, Reaction Mechanism and Regioselectivity of the Bingel-Hirsch Addition of Dimethyl Bromomalonate to La@C-2v-C-82, CHEMISTRY-A EUROPEAN JOURNAL, 22, 5953, (2016)
Abstract: We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel-Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C-2v-C-82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C-2v-C-82 by using dispersion-corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C-2v-C-82 is not particularly regioselective under Bingel-Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely.

First author: Lamine, W, Ill-advised self-interaction contribution in modelling anionic attack along a reaction path, MOLECULAR PHYSICS, 114, 1066, (2016)
Abstract: It is shown that modelling a catalytic reaction involving an atomic anion, such as iodide, may lead to unrealistic reaction paths because of the underestimation of the anion energy. The self-interaction error, at the origin of this feature is enhanced by the fact that electronic delocalisation, usually overestimated in DFT calculations, cannot occur in a single atom. The quantification of this error is approached by a linear transit calculation, from a transition state towards separate fragments. This is an efficient way to correct this error for GGA functionals. Interestingly the self-interaction error is shown to be less dependent of the Hartree-Fock exchange amount in hybrid functionals than expected. Unexpectedly, no significant improvement with long-range corrected functionals is obtained.

First author: Kohout, M, Atomic shell structure determined by the curvature of the electron position uncertainty, MOLECULAR PHYSICS, 114, 1297, (2016)
Abstract: The electron density logarithm is closely connected to the Shannon information entropy characterising the spread of the electron density. It can be seen as the uncertainty to predict the position of an electron. The position uncertainty curvature, defined as the negative of the Laplacian of the electron density logarithm, describes regions of space where the uncertainty of the electron position is higher, respectively lower, than the average in the surrounding. The atomic shells can be located in regions of high-position uncertainty curvature, thus resolving the atomic shell structure of the atoms Li to Xe. The shell boundaries are given as minima of the uncertainty curvature. This indicator, based alone on the electron density, is suitable to describe the bonding situation in molecules and solids.

First author: Zendaoui, SM, Ten-Electron Donor Indenyl Anion in Binuclear Transition-Metal Sandwich Complexes: Electronic Structure and Bonding Analysis, CHEMISTRYSELECT, 1, 940, (2016)
Abstract: Whereas dinuclear sandwich complexes of pentalene, azulene and naphthalene are not uncommon, their bis-indenyl counterparts are scarce, with only two M-2(indenyl) 2 examples known so far. This paper investigates by the means of DFT calculations the possibility for such compounds to exist for the M= Sc-Ni and Y-(Re)-Pd series. Stable diamagnetic species are predicted for total valence electron counts (TNE) of 34 and 40. The most favored situation corresponds to TNE = 34. For this electron count, which exhibits full ligand hapticity, no formal metal-metal bond exists, but only weak non-bonding attraction. Adding supplementary electrons (TNE > 34) results in partial ligand decoordination. When TNE < 34, metal-metal bonding is predicted to compensate electron deficiency, with the largest formal bond order for TNE = 26. However, in the case of the series of the first-row metals, the metal-metal interaction is rather weak, thus favoring the existence of low-lying high-spin states. On the other hand, all the second-row (and Re) complexes are computed to be diamagnetic. It is concluded that there is no specific reason for M-2(indenyl) 2 complexes not being isolable.

First author: Guo, YR, A theoretical probe for pentavalent bis-imido uranium complexes containing diverse axial substituents and equatorial donors: U-N multiple bond and structural/electronic properties, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1082, 21, (2016)
Abstract: Pentavalent trans-bis(imido) uranium complexes, [U-V(NR)(2)(THF)(2)(cis-I-2)](-) (2R), [U-V(NR)(2)(THF)(3)(trans-I-2)](-) (3R) and [U-V((NBu)-Bu-t)(2)(THF)(3)(cis-I-2)](-) (3(t)Bu’), have been examined using relativistic density functional theory, where the R substituent is changed from CF3, Ph, H, Me, Bu-t to Cy. The calculated electron -spin density indicates the 5f(1) configuration on the uranium center, which is mainly reflected by the HOMO with over 96% metal character. The U-V-N triple bond in these complexes is evidenced by computed bond length, bond order and electronic structure, although being weaker than U-VI-N in their hexavalent analogues and U-V-O in uranyl analogues. The U-NH stretching vibrational frequencies of 2H and 3H are calculated between 698 and 745 cm(-1), while the U-N-C ones of other complexes are found in the range from 1043 to 1285 cm(-1). This shift is caused by the strong coupled interaction between sizable substituent and U-N bond. The present study unravels that the changes of the R substituents as well as the number and the position of equatorial donors are capable of tuning structural and electronic properties of bis-imido complexes.

First author: Kang, S, Update to ACE-molecule: Projector augmented wave method on lagrange-sinc basis set, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 644, (2016)
Abstract: The projector augmented wave (PAW) method was implemented in a quantum chemistry package that uses Lagrange-sinc basis set, namely ACE-Molecule. Its numerical accuracy has been assessed for the AE6 test set and compared with that of Hartwigsen-Goedecker-Hutter type pseudopotentials with nonlinear core correction. The PAW method shows a rapid convergence toward complete basis set limits of all electron calculations, whereas the pseudopotential method has a significant deviation even at small grid spacing. To alleviate spurious egg-box effects, the so-called supersampling method is adopted to the operation of projector functions. It improved accuracy of total energy calculations at substantially large grid spacing but did not show significant difference in atomization energies from the results without supersampling, which is due to error cancellation.

First author: Ali, SM, Complexation thermodynamics of diglycolamide with f-elements: solvent extraction and density functional theory analysis, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 9816, (2016)
Abstract: Comparative extraction of trivalent lanthanide and actinide ions (La3+, Eu3+, Lu3+, Am3+ and Cm3+) with tetra-n-octyl diglycolamide (TODGA) was studied and showed the trend: Lu3+ > Eu3+ > Cm3+ > Am3+ > La3+. The structure, bonding, energetic and thermodynamic parameters of the trivalent lanthanide and actinide ions (La3+, Eu3+, Lu3+, Am3+ and Cm3+) with a tridentate ligand, tetra-methyl diglycolamide (TMDGA), are reported in the gas and solvent phases in order to understand their complexation and extraction behaviour. The calculations were performed using the generalized gradient approximated BP86 density functional and the hybrid B3LYP functional using SVP and TZVPP basis sets. The calculated structure obtained at the BP86/SVP level of optimization was found to be in close agreement with the X-ray data and also with the structure obtained at the B3LYP/TZVP level of theory. The free energy of extraction was found to be exergonic for the explicit monomer water model. From the solvent extraction experiment the order of extraction was observed as Lu3+ > Eu3+ > Cm3+ > Am3+ > La3+, which was in line with the trends predicted based on the free energy changes in the gas phase calculations (DGgp). The Born-Haber thermodynamic cycle and the COSMO (conductor like screening model) solvation model were applied to calculate the free energy of extraction, DGext, of lanthanide and actinide ions in the aqueous-dodecane biphasic system and DGext, however, predicted different extraction trends. After dispersion correction (B3LYP-D3), the free energy of extraction for the metal ions was found to follow the order: Lu3+ > Eu3+ > La3+, which was also observed in the solvent extraction experiments. Both COSMO and DCOSMO-RS models predict the same metal ion selectivity trend. Different bonding analyses indicate the electrostatic and less covalent nature of interactions between the ligands and the metal ions.

First author: Lin, ZG, Platinum-Containing Polyoxometalates: syn- and anti-[Pt-2(II)(-PW11O39)(2)](10-) and Formation of the Metal-Metal-Bonded di-Pt-III Derivatives, CHEMISTRY-A EUROPEAN JOURNAL, 22, 5514, (2016)
Abstract: The first examples of dimeric, di-Pt-II-containing heteropolytungstates are reported. The two isomeric di-platinum(II)-containing 22-tungsto-2-phosphates [anti-Pt-2(II)(-PW11O39)(2)](10-) (1a) and [syn-Pt-2(II)(-PW11O39)(2)](10-) (2a) were synthesized in aqueous pH3.5 medium using one-pot procedures. Polyanions 1a and 2a contain a core comprising two face-on PtO4 units, with a PtPt distance of 2.9-3 angstrom. Both polyanions were investigated by single-crystal XRD, IR, TGA, UV/Vis, (PNMR)-P-31, ESI-MS, CID-MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt-2(II)} moiety in 1a and 2a can undergo fully reversible two-electron oxidation to {Pt-2(III)}, accompanied by formation of a single Pt-Pt bond. Hence we have discovered the novel subclass of Pt-III-containing heteropolytungstates.

First author: Munoz-Castro, A, Surface on Surface. Survey of the Monolayer Gold-Graphene Interaction from Au-12 and PAH via Relativistic DFT Calculations, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 7358, (2016)
Abstract: Gold-graphene interaction at the interface is evaluated through different polyaromatic hydrocarbons (PAH), accounted by C6H6, C24H12, C54H16, and C96H18, focusing into different energetic terms related to the overall interaction. Our results characterize the neutral gold-PAH interaction nature with 45% of dispersion character, 35% of electrostatic, and 20% of covalent character, suggesting that moderate van der Waals character is mostly involved in the interaction, which increases according to the size of the respective PAH. The resulting surface charge distribution in the graphene model is a relevant parameter to take into account, since the ability of the surface charge to be reorganized over the polycyclic structure in both contact and surrounding regions is important in order to evaluate interactions and different interacting conformations. Our results suggest that for a Au-12 contact surface of radius 4.13 angstrom, the covalent, electrostatic and dispersion character of the interaction are effectively accounted in a graphene surface of about 6.18 angstrom, as given by circumcoronene, depicting a critical size where the overall interaction character can be accounted.

First author: Protchenko, AV, Enabling and Probing Oxidative Addition and Reductive Elimination at a Group 14 Metal Center: Cleavage and Functionalization of E-H Bonds by a Bis(boryl)stannylene, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 4555, (2016)
Abstract: By employing strongly sigma-donating boryl ancillary ligands, the oxidative addition of H-2 to a single site Sn-II system has been achieved for the first time, generating (boryl)(2)SnH2. Similar chemistry can also be achieved for protic and hydridic E-H bonds (N-H/O-H, Si-H/B-H, respectively). In the case of ammonia (and water, albeit more slowly), E-H oxidative addition can be shown to be followed by reductive elimination to give an N- (or O-)borylated product. Thus, in stoichiometric fashion, redox-based bond cleavage/formation is demonstrated for a single main group metal center at room temperature. From a mechanistic viewpoint, a two-step coordination/proton transfer process for N-H activation is shown to be viable through the isolation of species of the types Sn(boryl)(2)center dot NH3 and [Sn(boryl)(2)(NH2)](-) and their onward conversion to the formal oxidative addition product Sn(boryl)(2)(H)(NH2).

First author: Gorgannezhad, L, Complex of manganese (II) with curcumin: Spectroscopic characterization, DFT study, model-based analysis and antiradical activity, JOURNAL OF MOLECULAR STRUCTURE, 1109, 139, (2016)
Abstract: The complex formation between curcumin (Cur) and Manganese (II) chloride tetrahydrate (MnCl2 center dot 4H(2)O) was studied by UV-Vis and IR spectroscopy. Spectroscopic data suggest that Cur can chelate Manganese cations. A simple multi-wavelength model-based method was used to define stability constant for complexation reaction regardless of the spectra overlapping of components. Also, pure spectra and concentration profiles of all components were extracted using this method. Density functional theory (DFT) was also used to view insight into complexation mechanism. Antioxidant activity of Cur and Cur-Mn(II) complex was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging method. Bond dissociation energy (BDE), the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and Molecular electrostatic potential (MEP) of Cur and the complex also were calculated at PW91/TZ2P level of theory using ADF 2009.01 package. The experimental results show that Cur has a higher DPPH radical scavenging activity than Cur-Mn(II). This observation is theoretically justified by means of lower BDE and higher HOMO and LUMO energy values of Cur ligand as compared with those of Cur-Mn(II) complex.

First author: Chen, X, How the Substituents in Corannulene and Sumanene Derivatives Alter Their Molecular Assemblings and Charge Transport Properties?-A Theoretical Study with a Dimer Model, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 813, (2016)
Abstract: The substituent effects on the structures, intermolecular interactions and charge transport properties of a series of corannulene and sumanene derivatives were investigated by DFT method. The intermolecular interaction energy and the potential energy surface of the dimers were also calculated and analyzed in detail, which showed several local energy minima and demonstrated the possible dimer structures in experiment. In addition, the reorganization energy, transfer integral, and carrier mobility were explored to measure the charge transport properties of these substituted corannulenes and sumanenes at different configurations for investigating the substituent effects. Our study is closely related to the experiment and previous theoretical investigation and provides a better understanding of the structure-property relationships for these substituted corannulenes and sumanenes.

First author: Pandey, KK, Theoretical insights into the relative bonding of normal and abnormal N-heterocyclic carbenes in [PdCl2(NHCR)(2)] and [PdCl2(NHCR)(aNHC(R))] (R=H, Ph, Mes), INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 537, (2016)
Abstract: Quantum chemical insights into normal Pd-C2(NHCR) and abnormal Pd-C5(aNHC(R)) bonding, dominated by dispersion interactions in N-hetereocyclic carbene complexes [PdCl2(NHCR)(2)] (I, R=H; II, R=Ph; III, R=Mes (2,4,6-trimethyl)phenyl)) and [PdCl2(NHCR)(aNHC(R)] (IV, R=H; V, R=Ph; VI, R=Mes) have been investigated at DFT and DFT-D3(BJ) level of theory with particular emphasis on the effects of the noncovalent interactions on the structures and the nature of Pd-C2(NHCR) and Pd-C5(aNHC(R)) bonds. The optimized geometries are good agreement with the experimental values. The Pd-C bonds are essentially single bond. Hirshfeld charge distributions indicate that the abnormal aNHC(R) carbene ligand is relatively better electron donor than the normal NHCR carbene ligand. The C2 atom has larger %s contribution along Pd-C2 bond than the C5 atom along Pd-C5 bond. As a consequence the Pd-C2(NHCR) bonds are relative stronger than the Pd-C5(aNHC(R)) bonds. Thus, the results of natural hybrid orbital analysis support the key point of the present study. Calculations predict that for bulky substituent (R=Ph, Mes) at carbene, the Pd-C2(NHCR) bond is stronger than Pd-C5(aNHC(R)) bond due to large dispersion energy in [PdCl2(NHCR)(2)] than in [PdCl2(NHCR)(aNHC(R))]. However, in case of non-bulky substituent with small and almost equal contribution of dispersion energy, the Pd-C2(NHCR) bond is relative weaker than Pd-C5(aNHC(R)) bond. The bond dissociation energies are dependent on the R substituent, the DFT functional and the inclusion of dispersion interactions. Major point of this study is that the abnormal aNHCs are not always strongly bonded with metal center than the normal NHCs. Effects of dispersion interaction of substituent at nitrogen atoms of carbene ligand are found to play a crucial role on estimation of relative bonding strengths of the normal and abnormal aNHCs with metal center.

First author: Kroutil, O, Pt center dot center dot center dot H Nonclassical Interaction in Water-Dissolved Pt(II) Complexes: Coaction of Electronic Effects with Solvent-Assisted Stabilization, INORGANIC CHEMISTRY, 55, 3252, (2016)
Abstract: The structure of the hydration shell of cisplatin, cis[Pt(NH3)(2)Cl-2], and its aquated derivatives cis-[Pt(NH3)(2)Cl(H2O)](+), cis-[Pt(NH3)(2)OH(H2O)](+), and cis-[Pt(NH3)(2)(H2O)(2)](2+) were studied by a number of density functional molecular dynamics (DFT-MD) simulations (from 30 to 250 ps) in which Pt(II) complexes were immersed in a periodic box with 72 explicit water molecules. Furthermore, Pt(II) complex-water binding energy curves and full DFT optimizations of dusters derived from the lowest potential energy DFT-MD frames offered a deeper insight into the structure of the first hydration shell and electronic changes connected with the formation of a nonclassical Pt center dot center dot center dot H-O-H (Pt center dot center dot center dot Hw) hydrogen bond (inverse hydration). The probability of a Pt center dot center dot center dot Hw interaction decreases with increasing charge of the platinum complex due to disadvantageous electrostatics. The main stabilization comes from the charge transfer being followed by polarization and dispersion. Ligands form a framework for the network of H-bond interactions between the solvent molecules, which play an important role in the promotion/suppression of the formation of the Pt center dot center dot center dot Hw interactions. In the +2 charged diaqua complex the Pt center dot center dot center dot Hw interaction is still attractive but cannot compete with classical H bonds between solvent molecules. Thus, the formation of a Pt center dot center dot center dot Hw interaction is the result of a suitable solvent H-bonding network and the probability of its incidence decreases with increasing flexibility of the solvent.

First author: Abella, L, La3N@C-92: An Endohedral Metallofullerene Governed by Kinetic Factors?, INORGANIC CHEMISTRY, 55, 3302, (2016)
Abstract: Different structures have been proposed so far for the C-92 isomer that encapsulates M3N (M = La, Ce, Pr). We show here that the electrochemical properties of the predicted most abundant (thermodynamic) isomer for La3N@C-92 does not agree with experiment. After a systematic search within the huge number of possible C-92 isomers, we propose other candidates with larger electrochemical gaps for La3N@C-92 before its structure could be finally determined by X-ray crystallography. We do not discard that the thermodynamic isomer could be detected in future experiments though.

First author: Era, M, PbBr-Based Layered Perovskite Organic-Inorganic Superlattice Having Carbazole Chromophore; Hole-Mobility and Quantum Mechanical Calculation, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 16, 3159, (2016)
Abstract: We have successfully evaluated hole mobility in a spin-coated film of a lead-bromide based layered perovskite having carbazole chromophore-linked ammonium molecules as organic layer by using FET measurement. The values of hole mobility, threshold voltage and on/off ratio at room temperature were evaluated to be 1.7 x 10(-6) cm(2) V-1 s(-1), 27 V and 28 V, respectively. However, the spin-coated films on Si substrates were not so uniform compared with those on fused quartz substrates. To improve the film uniformity, we examined the relationship between substrate temperature during spin-coating and film morphology in the layered perovskite spin-coated films. The mean roughness of the spin-coated films on Si substrates was dependent on the substrate temperature. At 353 K, the mean roughness was minimized and the carrier mobility was enhanced by one order of magnitude; the values of hole mobility and threshold voltage were estimated to be 3.4 x 10(-5) cm(2) V-1 s(-1), and 22 V at room temperature in a preliminary FET evaluation, respectively. In addition, we determined a crystal structure of the layered perovskite by X-ray diffraction analysis. To gain a better understanding of the observed hole transports, we conducted quantum mechanical calculations using the obtained crystal structure information. The calculated band structure of the layered organic perovskite showed that the valence band is composed of the organic carbazole layer, which confirms that the measured hole mobility is mainly derived from the organic part of the layered perovskite. Band and hopping transport mechanisms were discussed by calculating the effective masses and transfer integrals for the 2D periodic system of the organic layer in isolation.

First author: Pietra, F, Tuning the Lattice Parameter of InxZnyP for Highly Luminescent Lattice-Matched Core/Shell Quantum Dots, ACS NANO, 10, 4754, (2016)
Abstract: Colloidal quantum dots (QDs) show great promise as LED phosphors due to their tunable narrow-band emission and ability to produce high-quality white light. Currently, the most suitable QDs for lighting applications are based on cadmium, which presents a toxicity problem for consumer applications. The most promising cadmium-free candidate QDs are based on InP, but their quality lags much behind that of cadmium based QDs. This is not only because the synthesis of InP QDs is more challenging than that of Cd-based QDs, but also because the large lattice parameter of InP makes it difficult to grow an epitaxial, defect-free shell on top of such material. Here, we propose a viable approach to overcome this problem by alloying InP nanocrystals with Zn2+ ions, which enables the synthesis of InxZnyP alloy QDs having lattice constant that can be tuned from 5.93 angstrom (pure InP QDs) down to 5.39 angstrom by simply varying the concentration of the Zn precursor. This lattice engineering allows for subsequent strain-free, epitaxial growth of a ZnSezS1-z shell with lattice parameters matching that of the core. We demonstrate, for a wide range of core and shell compositions (i.e., varying x, y, and z), that the photoluminescence quantum yield is maximal (up to 60%) when lattice mismatch is minimal.

First author: Zhang, J, Force Field Benchmark of Organic Liquids. 2. Gibbs Energy of Solvation (vol 55, pg 1192, 2015), JOURNAL OF CHEMICAL INFORMATION AND MODELING, 56, 819, (2016)
Abstract: Colloidal quantum dots (QDs) show great promise as LED phosphors due to their tunable narrow-band emission and ability to produce high-quality white light. Currently, the most suitable QDs for lighting applications are based on cadmium, which presents a toxicity problem for consumer applications. The most promising cadmium-free candidate QDs are based on InP, but their quality lags much behind that of cadmium based QDs. This is not only because the synthesis of InP QDs is more challenging than that of Cd-based QDs, but also because the large lattice parameter of InP makes it difficult to grow an epitaxial, defect-free shell on top of such material. Here, we propose a viable approach to overcome this problem by alloying InP nanocrystals with Zn2+ ions, which enables the synthesis of InxZnyP alloy QDs having lattice constant that can be tuned from 5.93 angstrom (pure InP QDs) down to 5.39 angstrom by simply varying the concentration of the Zn precursor. This lattice engineering allows for subsequent strain-free, epitaxial growth of a ZnSezS1-z shell with lattice parameters matching that of the core. We demonstrate, for a wide range of core and shell compositions (i.e., varying x, y, and z), that the photoluminescence quantum yield is maximal (up to 60%) when lattice mismatch is minimal.

First author: Ehbets, J, Synthesis and Hydrolysis of Alkoxy(aminoalkyl)diorganylsilanes of the Formula Type R-2(RO)Si(CH2)(n)NH2 (R = Alkyl, n=1-3): A Systematic Experimental and Computational Study, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 56, 1641, (2016)
Abstract: Alkoxy(aminoalkyl)silanes are important precursors for the formation of amino-functionalized polysiloxanes, which are used in many technical applications. To better understand the mechanism of the hydrolytic cleavage of the Si-alkoxy moiety of alkoxy(aminoalkyl)silanes (an important key step in the formation of amino-functionalized polysiloxanes), a systematic experimental and computational study on the hydrolysis of alkoxy(aminoalkyl)diorganylsilanes of the formula type R-2(RO)Si(CH2)(n)NH2 (R = alkyl, n = 1-3) was conducted. For reasons of comparison, silanes of the formula types R-2(RO)SiC(H) MeCH2NH2 and R-2(RO)Si(CH2)(n)X [R = alkyl; n = 1-3; X = N(H)Me, NMe2, piperidino, NMe3+I-, N(H)COOMe, N(Me)COOMe] and compounds Me-2(MeO)Si(CH2)(6)Me and Me-2(MeO)Si(CH2)(6)NH2 were included in this study. For this purpose, the various silanes were synthesized and studied for their hydrolysis kinetics in CD3CN/D2O under acidic and basic conditions by using H-1 NMR spectroscopy as the analytic tool. These experimental investigations were complemented by computational studies (calculation of proton affinities, reaction barriers, and energies relative to reactants of intermediate transition complexes). The different hydrolysis reactivities observed are the result of a number of parameters, such as electronic and steric effects, the strong impact of the pD value, and intra-molecular N-H center dot center dot center dot O hydrogen bonds between the protonated amino group and the alkoxy leaving group. This comprehensive study provided deep insight into the mechanism of hydrolysis of analogous alpha-, beta-, and gamma-amino-functionalized alkoxy(aminoalkyl)diorganylsilanes of the formula type R-2(RO)Si(CH2)(n)NH2 (R = organyl, n = 1-3) and a series of related alpha/beta/gamma analogues with other nitrogen-based functional groups.

First author: Majerz, I, Proton Transfer Influence on Geometry and Electron Density in Benzoic Acid-Pyridine Complexes, HELVETICA CHIMICA ACTA, 99, 286, (2016)
Abstract: The influence of the proton transfer on the geometry of donor and acceptor molecule in benzoic acid-pyridine complexes is investigated by theoretical calculations at the B3LYP/6-311++ G** level of theory. Systematic shifts of the H-atom in the H-bond are reflected in the geometry of the COOH group and the lengths of aromatic ring bond lengths of the proton acceptor. Changes in electron densities have been studied by atoms in molecules analysis. A systematic natural bond orbital analysis has been performed to study the proton transfer mechanism. Two donor orbitals are engaged in the proton transfer process which is accompanied by a change in orbital delocalization of H-atom that can switch between two donor orbitals so the path of proton transfer in intermolecular H-bond is not determined by the orbital shape. Theoretical results have been confirmed by experimental results published previously.

First author: Sedlak, R, New Insight into the Nature of Bonding in the Dimers of Lappert’s Stannylene and Its Ge Analogs: A Quantum Mechanical Study, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 1696, (2016)
Abstract: The strength and nature of the connection in Lappert’s stannylene dimer ({Sn[CH(SiMe3)(2)](2)}(2)) and its smaller analogs, simplified stannylenes, as well as similar Ge complexes were studied by means of DFT-D3 calculations, energy decomposition analysis (EDA), electrostatic potential (ESP), and natural population analysis. The trans-bent structure of the investigated molecules was rationalized by means of EDA, ESP, and molecular orbital (MO) analyses. The different ESPs for the monomers studied are a result of different hybridization of the Sn (Ge) atoms. The comparably strong stabilization in the largest and the smallest systems with a dramatically different substituent size is explained by the different nature of the binding between monomers. For all complexes, it has been found that the total attractive interaction is mostly provided by the electrostatic component (>50%), followed by orbital interaction and dispersion. In the largest molecule (Lappert’s stannylene), the dispersion interaction plays a more significant role in stabilization and its magnitude is comparable to that of orbital interaction; on the other hand in the smallest molecule (SnH2), where bulky substituents are replaced by H only, the dispersion energy is less important and the E-E bond is more of a charge transfer character, caused by donor-acceptor orbital interactions. The charge transfer in Ge dimers is greater than in the Sn ones due to shorter distances between monomers, which cause better (HOMO/LUMO) overlaps. The easier dimerization of Lappert’s stannylene as compared to Kira’s ({Sn[(Me3Si)(2)CHCH2CH2CH(SiMe3)(2)-x(2)C,C’]}) stannylene is explained by the different orientation of their substituents-asymmetry promotes dimerization.

First author: Su, J, On the oxidation states of metal elements in MO3 (-) (M=V, Nb, Ta, Db, Pr, Gd, Pa) anions, SCIENCE CHINA-CHEMISTRY, 59, 442, (2016)
Abstract: Relativistic quantum chemistry investigations are carried out to tackle the puzzling oxidation state problem in a series of MO (3) (-) trioxide anions of all d- and f-block elements with five valence electrons. We have shown here that while the oxidation states of V, Nb, Ta, Db, Pa are, as usual, all +V with divalent oxygen O(-II) in MO (3) (-) anions, the lanthanide elements Pr and Gd cannot adopt such high +V oxidation state in similar trioxide anions. Instead, lanthanide element Gd retains its usual +III oxidation state, while Pr retains a +IV oxidation state, thus forcing oxygen into a non-innocent ligand with an uncommon monovalent radical (O-aEuro cent) of oxidation state -I. A unique Pr-aEuro cent – (aEuro cent)(O)(3) biradical with highly delocalized unpairing electron density on Pr(IV) and three O atoms is found to be responsible for stabilizing the monovalent-oxygen species in PrO (3) (-) ion, while GdO (3) (-) ion is in fact an OGd+(O (2) (2-) ) complex with Gd(III). These results show that a na < ve assignment of oxidation state of a chemical element without electronic structure analysis can lead to erroneous conclusions.

First author: Cao, HY, Electronic structures and solvent effects of unsymmetrical neo-confused porphyrin: DFT and TDDFT-IEFPCM investigations, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1081, 18, (2016)
Abstract: Unsymmetrical porphyrin derivatives and metal-coordinated porphyrin have received great attention in potential application for their intriguing photo-physical and photo-chemical properties. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were applied to simulate the molecular and electronic structures with the electronic absorption spectra of the unsymmetrical neo-confused porphyrin (NeoCP) derivatives. Molecular structure and fragment charge distribution results revealed that the carbon-nitrogen-swap structure lead to the redistribution of charges and the differentiation of inner hydrogen in the Neo-confused Porphyrin ring. Introducing the unsymmetrical strategy onto the porphyrin skeleton effectively varied the energy levels of molecular orbitals, resulting in significant multi-band photon absorption and Soret band splitting for the porphyrin derivatives. Ni coordinated NeoCP (NiNeoCP) showed broader visible light absorption capacity and better light absorption performance due to the contribution of Ni atom. The blue-shifted Q bands illuminate that the light absorption performance of NeoCP and NiNeoCP varies in different polarity solvents based on the integral equation formalism polarizable continuum model (IEF-PCM) results. These theoretical researches would be conducive to the molecular design of novel multi-band photon absorption porphyrin derivatives.

First author: Ding, XL, Theoretical study on the neutral and ionic Cu(I) phosphorescent complexes with 2-(2 ‘-quinolyl)benzimidazole and phosphine mixed, ORGANIC ELECTRONICS, 31, 111, (2016)
Abstract: The electronic structures and photophysical properties of a series of the neutral and ionic Cu(I) complexes with 2-(2′-quinolyl) benzimidazole and phosphine mixed ligand were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. To investigate the differences between the neutral and ionic complexes, the highest occupied molecular orbital (HOMO) energy, the lowest virtual molecular orbital (LUMO) energy, Delta EH-L (the energy gap between HOMO and LUMO), the ionization potentials (IPs), electron affinities (EAs) and reorganization energies (lambda) were computed. To explain the reason of the metal-to-ligand charge transfer (MLCT) hardly detection in the neutral complexes, the absorption and emission spectra were studied in detail. To evaluate the photoluminescence quantum yield (PLQY), the non-radiative and radiative decay rate constants (k(nr) and k(r)) were also presented. As a result, these calculations reveal that the structural distortion between the ground and excited states plays an important role in governing the PLQY. The charge transfer and the transport equilibrium property were markedly improved due to the lack of mobile counterions in the neutral form. Introducing the ether linkage together with the enhanced N boolean AND N pi-conjugation in 2b had obviously faster k(r) but slower k(nr), which led to its higher PLQY relative to the introducing the ether linkage only or lacking of a proton and the counterions in complexes.

First author: Qu, H, Infrared Photodissociation Spectroscopy and Density Functional Theory Study of Carbon Suboxide Complexes [M(CO)(4)(C3O2)](+) (M = Fe, Co, Ni), JOURNAL OF PHYSICAL CHEMISTRY A, 120, 1978, (2016)
Abstract: Infrared photodissociation spectra are measured for mass selected cation complexes with a chemical formula [MC7O6](+) (M = Fe, Co, Ni) formed via pulsed laser evaporation of metal target in expansions of helium gas seeded by CO. The geometries of the complexes are determined by comparison of the experimental spectra with the simulated spectra from density functional calculations. All of these complexes are identified to have [M(CO)(4)(C3O2)](+) structures involving a carbon suboxide ligand, which binds the metal center in an eta(1) fashion. The antisymmetric CO stretching vibration of C3O2 is slightly red-shifted upon coordination. The donor-acceptor bonding interactions between C3O2 and the metal centers are analyzed using the EDA-NOCV method. The results show that M <- C3O2 sigma donation is stronger than the M -> C3O2 pi back-donation in these cation complexes.

First author: Simpson, S, Modulating Bond Lengths via Backdonation: A First-Principles Investigation of a Quinonoid Zwitterion Adsorbed to Coinage Metal Surfaces, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 6633, (2016)
Abstract: First-principles calculations reveal that upon adsorption to the Cu(111) surface, the C-C single bonds within the p-benzoquinonemonoimine zwitterion (ZI) contract by about 6%. A detailed analysis reveals that the bond shortening is primarily a result of backdonation from Cu orbitals of s and d symmetry to the lowest unoccupied orbital (LUMO) of the ZI. This LUMO is pi*-antibonding across the molecule and pi-bonding across the C-C bond that shortens. We illustrate that the level alignment between the Fermi level of the surface and the frontier molecular orbitals of the ZI, the topology of the LUMO, and the distance between the substrate and the adsorbate are important factors enabling bond strengthening via backdonation. An extended transition state-natural orbitals for chemical valence (ETS-NOCV) analysis is applied to molecular models for this system, and it confirms that the surface -> LUMO backdonation on Cu(111) is larger than on Ag(111) and Au(111).

First author: Yue, NLS, Palladium(II) macrocycles and lanterns, POLYHEDRON, 108, 67, (2016)
Abstract: The coordination chemistry of palladium(II) with the bis(amidopyridine) ligands [LL = Ar(CONMe-4-C5H4N)(2), with Ar = 1,3-C6H4 (1), 5-t-Bu-1,3-C6H3 (2) and 2,5-C4H2S (3) has been investigated. The reaction of [PdCl2(NCPh)(2)] with the ligands in a 1:1 ratio gave the corresponding neutral binuclear macrocyclic complexes trans,trans-[Pd2Cl4(mu-LL)(2)] in all cases. The cavity size and shape in these complexes is highly dependent on the ligand conformation and can change to accommodate guest molecules. The reaction of [PdCl2(NCPh)(2)] with the ligands in a 1:2 ratio gave the mononuclear bis(chelate) derivative [Pd(LL)(2)](2+), with LL = 3, but the binuclear “lantern” or “paddlewheel” complexes [Pd-2(mu-LL)(4)(mu-Cl)](3+), with LL=1 or 2. The selective encapsulation of a chloride ion in these complexes is favored by multiple secondary bonding interactions of the types Cl center dot center dot center dot Pd and Cl center dot center dot center dot HC.

First author: Lichtenberg, C, Aminotroponiminates: Alkali Metal Compounds Reveal Unprecedented Coordination Modes, ORGANOMETALLICS, 35, 894, (2016)
Abstract: The coordination chemistry of alkalimetal aminotroponiminates (ATIs) was investigated based on (i) a lithium ATI, (ii) the first example of a sodium ATI, and (iii) the first example of a structurally characterized potassium ATI. In the lithium derivative of this series, the ATI ligand adopts a well-known kappa N-2 binding mode. In contrast, the sodium and potassium ATIs show two different types of unprecedented polymeric structures in the solid state, unraveling a surprisingly rich coordination chemistry for the ATI ligand family. In the solid-state structure of the potassium compound, ATI ligands bridge the metal atoms in a mu(2)-kappa N-2 binding mode. The sodium compound reveals a mu(2)-kappa N-2 kappa C-5 coordination mode with an unusual interaction of a metal center with a C-7 ATI ligand backbone. NMR studies suggest that this type of interaction might also be accessible in solution. It was further studied by DFT calculations. The tendency of monoanionic ATI ligands to interact with transition-metal centers via their C-7 ligand backbone was investigated experimentally and theoretically using Rh+ and W-0 as examples for potentially arenophilic metals.

First author: Murphy, CJ, Charge-Transfer-Induced Magic Cluster Formation of Azaborine Heterocycles on Noble Metal Surfaces, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 6020, (2016)
Abstract: We report a combined experimental and theoretical study of the adsorption and assembly of a nitrogen-boron-containing heterocycle, 1,2-dihydro-1,2-azaborine, on Au(111) and Cu(111). Despite the inherent molecular dipole moment, the self-assembly behavior is found to be highly surface dependent, with isolated molecules prevalent on Cu(111) and discrete (“magic”) clusters on Au(111). The ability to form clusters of a particular size can be understood in terms of a balance between attractive intermolecular interactions, including directional B-H center dot center dot center dot H-N dihydrogen bonding, and repulsive forces from Coulombic interactions between the charged molecules dictated by differences in the charge transfer and Pauli repulsion between the adsorbate and the surface. This work highlights the importance of metal-molecule charge transfer in the adsorption and assembly of dipolar molecules on surfaces and demonstrates that their surface-bound properties cannot be predicted a priori from gas-phase dipole moments alone.

First author: Kozlova, SG, Lability of lone electron pairs at Bi(III) and polymorphism of TBA(4)[Mo8O26(BiI3)(2)]: Theoretical study, INORGANICA CHIMICA ACTA, 443, 1, (2016)
Abstract: Interaction between the [Mo8O26](4) polyoxoanion and BiX3 in the [Mo8O26(BiX3)(2)](4) (X = Cl, Br, I) was studied by Density Functional Theory (DFT) methods. The calculations show that the stereochemically active lone pair of Bi(III) is labile, which can be the reason of polymorphism that occurs in (Bu4N)(4)[Mo8O26(BiI3)(2)].

First author: Teyar, B, Electronic Structure and Magnetic Properties of Dioxo-Bridged Diuranium Complexes with Diamond-Core Structural Motifs: A Relativistic DFT Study, INORGANIC CHEMISTRY, 55, 2870, (2016)
Abstract: Electronic structures and magnetic properties of the binuclear bis(mu-oxo) U-IV/U-IV K-2[{(((ArO)-Ar-nP,Me)(3)tacn)-U-IV}(2)(mu-O)(2)] and U-V/U-V [{(((ArO)-Ar-nP,Me)(3)tacn)U-V}(2)(mu-O)(2)] (tacn = triazacyclononane, nP = neopentyl) complexes, exhibiting [U(mu-O)(2)U] diamond-core structural motifs, have been investigated computationally using scalar relativistic Density Functional Theory (DFT) combined with the Broken Symmetry (BS) approach for their magnetic properties. Using the B3LYP hybrid functional, the BS ground state of the pentavalent [U-V(mu-O)(2)U-V] 5f(1)-5f(1) complex has been found of lower energy than the high spin (HS) triplet state, thus confirming the antiferromagnetic character in agreement with experimental magnetic susceptibility measurements. The nonmagnetic character observed for the tetravalent K-2[U-IV(mu-O)(2)U-IV] 5f(2)-5f(2) species is also predicted by our DFT calculations, which led practically to the same energy for the HS and BS states. As reported for related dioxo diuranium(V) systems, superexchange is likely to be responsible for the antiferromagnetic coupling through the pi-network orbital pathway within the (mu-O)(2) bridge, the dissymmetrical structure of the U2O2 core playing a determining role. In the case of the U-IV species, our computations indicate that the K+ counterions are likely to play a role for the observed magnetic property. Finally, the MO analysis, in conjunction with NPA and QTAIM analyses, clarify the electronic structures of the studied complexes. In particular, the fact that the experimentally attempted chemical oxidation of the U-V species does not lead straightforwardly to binuclear complexes U-VI is clarified by the MO analysis.

First author: Azarias, C, Modeling the photosensitizing properties of thiolate-protected gold nanoclusters, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 7737, (2016)
Abstract: An accurate computational strategy for studying the structural, redox and optical properties of thiolated gold nanoclusters (GNCs) using (Time-Dependent) Density Functional Theory is proposed. The influence of the pseudopotential/basis set, solvent description and the choice of the functional has been investigated to model the structural and electronic properties of the Au-25(SR)(18)(-) system, with R being an organic ligand. This study aims to describe with a comparable precision both the GNC and the organic ligands and rationalize the effect of coating on different GNC properties. Two differently coated GNCs have been considered: the system with R = CH2CH2Ph and the GNC coated with 17 alkyl chains (C6H13) and functionalized by one fluorophore pyrene derivative (CH2CH2(NH)(CO) Py). The computational protocol we propose should then be used to design more efficient metal cluster-sensitized solar cells.

First author: Muniz, J, Bond formation, electronic structure, and energy storage properties on polyoxometalate-carbon nanocomposites, THEORETICAL CHEMISTRY ACCOUNTS, 135, 7737, (2016)
Abstract: Keggin polyoxometalate structures are molecular clusters that, anchored to carbon matrices, have been used to form electrodes for energy storage devices, such as lithium batteries and supercapacitors. [PMo12O40](3-) polyanions (PMo12) are examples of this kind of nanostructures that, grafted on amorphous carbon, have the capability to enhance the capacitive properties of these electrochemical ensembles. However, there is yet a poor understanding of the fundamental mechanisms for bond formation between them and carbon structures. It has been found experimentally that the presence of functional groups such as phi-NH2 and phi-OH assists on the chemical absorption of PMo12, but there is not enough information on the actual mechanism of the process. In order to gather further knowledge on these issues, we have performed quantum mechanical calculations, based on the density functional theory of atomic arrangements using graphene as carbon structure model, different functional groups, and PMo12. Our aim was to look for the nature of bonding among them, and to dig into the charge properties to relate them with the experimental observation. From the computations performed with PMo12 polyanion near to a graphene sheet, with and without the presence of functional groups, we conclude that there is a non-covalent/electrostatic bonding, made of weak pi-pi stacking interactions between PMo12 and graphene. Calculations show that phi-NH2 and phi-OH functional groups are able to form covalent bonds with PMo12 in top and side fashion arrangements, being the latter the most stable. This is a powerful argument to explain the empirical observation on these groups, enhancing the PMo12 adsorption over carbon structures. We also found that the presence of the functional groups together with PMo12 creates electronic states that may act as alternative pathways that ions can track within electrochemical cells. Our results offer first-principle information relevant to the understanding of these composite materials, and the methodology could be directly applied to other Keggin structures or different functional groups, attached to graphene, to find potential advantages for energy storage devices.

First author: Servis, MJ, A Molecular Dynamics Study of Tributyl Phosphate and Diamyl Amyl Phosphonate Self-Aggregation in Dodecane and Octane, JOURNAL OF PHYSICAL CHEMISTRY B, 120, 2796, (2016)
Abstract: A molecular dynamics model for tributyl phosphate (TBP) and diamyl amyl phosphonate (DAAP) is presented using the Generalized AMBER Force Field (GAFF) and the AM1-BCC method for calculated atomic charges with a modification to the phosphorus-containing dihedral parameters. The density and average molecular dipole in a neat liquid simulation, and dimerization in dodecane and octane diluents, compare favorably to experimental values. At low extractant concentration, investigation of the dimer structure reveals the offset “head-to-head” orientation as the predominant structure over a range of TBP and DAAP concentrations with a phosphoryl oxygen separation distance between dimerized extractants of 3-5.5 angstrom. At high extractant concentrations, a graph analysis of extractant aggregates was used to determine concentrations of each aggregate size and the average coordination number, which gives a measure of the linearity of the aggregates. For aggregates up to 7 extractant molecules, the mean free energy of association per molecule was found to be 0.55-0.59 and 0.72 kcal/mol for TBP and DAAP, respectively. In both diluents, TBP formed large aggregates more frequently than DAAP, and those aggregates were more nonlinear than their DAAP equivalents. This finding anticipates differences in aggregation chemistry between TBP and DAAP in PUREX extraction systems.

First author: Hlina, JA, Metal-Metal Bonding in Uranium-Group 10 Complexes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 3333, (2016)
Abstract: Heterobimetallic complexes containing short uranium-group 10 metal bonds have been prepared from monometallic IUIV(OArP-kappa O-2,P)(3) (2) {[(ArO)-O-P](-) = 2-tert-butyl-4-methyl-6-(diphenylphosphino)phenolate}. The U-M bond in IUIV(mu-OArP-1 kappa O-1,2 kappa P-1)(3)M-0, M = Ni (3-Ni), Pd (3-Pd), and Pt (3-Pt), has been investigated by experimental and DFT computational methods. Comparisons of 3-Ni with two further U-Ni complexes XUIV(mu-OArP-1 kappa O-1,2 kappa P-1)(3)Ni-0, X = Me3SiO (4) and F (5), was also possible via iodide substitution. All complexes were characterized by variable-temperature NMR spectroscopy, electrochemistry, and single crystal X-ray diffraction. The U-M bonds are significantly shorter than any other crystallographically characterized d-f-block bimetallic, even though the ligand flexes to allow a variable U-M separation. Excellent agreement is found between the experimental and computed structures for 3-Ni and 3-Pd. Natural population analysis and natural localized molecular orbital (NLMO) compositions indicate that U employs both 5f and 6d orbitals in covalent bonding to a significant extent. Quantum theory of atoms-in-molecules analysis reveals U-M bond critical point properties typical of metallic bonding and a larger delocalization index (bond order) for the less polar U-Ni bond than U-Pd. Electrochemical studies agree with the computational analyses and the X-ray structural data for the U-X adducts 3-Ni, 4, and 5. The data show a trend in uranium-metal bond strength that decreases from 3-Ni down to 3-Pt and suggest that exchanging the iodide for a fluoride strengthens the metal-metal bond. Despite short U-TM (transition metal) distances, four other computational approaches also suggest low U-TM bond orders, reflecting highly transition metal localized valence NLMOs. These are more so for 3-Pd than 3-Ni, consistent with slightly larger U-TM bond orders in the latter. Computational studies of the model systems (PH3)(3)MU(OH)(3)I (M = Ni, Pd) reveal longer and weaker unsupported U-TM bonds vs 3.

First author: Karakas, A, Computational studies on linear, second and third-order nonlinear optical properties of novel styrylquinolinium dyes, CHEMICAL PHYSICS LETTERS, 648, 3333, (2016)
Abstract: The electric dipole moments (mu), static dipole polarizabilities (alpha) and first hyperpolarizabilities (beta) of styrylquinolinium dyes, D8 and D21, have been computed by density functional theory (DFT). The one photon absorption (OPA) characterizations have been investigated using UV-vis spectroscopy and further interpreted using computational chemistry. The time-dependent Hartree-Fock (TDHF) method has been used to describe the dynamic dipole polarizabilities, dynamic second-order and also static and dynamic third-order nonlinear optical (NLO) properties. D8-D21 have rather high beta and second hyperpolarizabilities (gamma). The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO-LUMO band gaps for D8-D21 have been evaluated by DFT.

First author: Artemova, S, Automatic Molecular Structure Perception for the Universal Force Field, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 1191, (2016)
Abstract: The Universal Force Field (UFF) is a classical force field applicable to almost all atom types of the periodic table. Such a flexibility makes this force field a potential good candidate for simulations involving a large spectrum of systems and, indeed, UFF has been applied to various families of molecules. Unfortunately, initializing UFF, that is, performing molecular structure perception to determine which parameters should be used to compute the UFF energy and forces, appears to be a difficult problem. Although many perception methods exist, they mostly focus on organic molecules, and are thus not well-adapted to the diversity of systems potentially considered with UFF. In this article, we propose an automatic perception method for initializing UFF that includes the identification of the system’s connectivity, the assignment of bond orders as well as UFF atom types. This perception scheme is proposed as a self-contained UFF implementation integrated in a new module for the SAMSON software platform for computational nanoscience (http://www.samson-connect.net). We validate both the automatic perception method and the UFF implementation on a series of benchmarks.

First author: Tykarska, M, The inversion phenomenon of the helical twist sense in antiferroelectric liquid crystal phase from electronic and vibrational circular dichroism, LIQUID CRYSTALS, 43, 462, (2016)
Abstract: The investigation of the helical pitch and the helical twist sense for several liquid crystal compounds in antiferroelectric phase have been performed. Electronic circular dichroic (ECD) and vibrational circular dichroic (VCD) spectroscopies have proved the existence of unwound helical structure in antiferroelctric phase. Obtained results may confirm the assumption connected via the inversion phenomena in liquid crystalline chiral phase with the change of the concentration of different conformers promoting opposite handedness. Two examples of such conformers, obtained by conformational analysis, have been proposed.

First author: Ramanathan, N, Non-covalent C-Cl center dot center dot center dot pi interaction in acetylene-carbon tetrachloride adducts: Matrix isolation infrared and ab initio computational studies, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 157, 69, (2016)
Abstract: Non-covalent halogen-bonding interactions between n cloud of acetylene (C2H2) and chlorine atom of carbon tetrachloride (CCl4) have been investigated using matrix isolation infrared spectroscopy and quantum chemical computations. The structure and the energies of the 1:1 C2H2-CCl4 adducts were computed at the B3LYP, MP2 and M05-2X levels of theory using 6-311++G(d,p) basis set. The computations indicated two minima for the 1:1 C2H2-CCl4 adducts; with the C-Cl center dot center dot center dot pi adduct being the global minimum, where pi cloud of C2H2 is the electron donor. The second minimum corresponded to a C-H…Cl adduct, in which C2H2 is the proton donor. The interaction energies for the adducts A and B were found to be nearly identical. Experimentally, both C-Cl center dot center dot center dot pi and C-H center dot center dot center dot Cl adducts were generated in Ar and N2 matrixes and characterized using infrared spectroscopy. This is the first report on halogen bonded adduct, stabilized through C-Cl center dot center dot center dot pi interaction being identified at low temperatures using matrix isolation infrared spectroscopy. Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses were performed to support the experimental results. The structures of 2:1 ((C2H2)(2)-CCl4) and 1:2 (C2H2-(CCl4)(2)) multimers and their identification in the low temperature matrixes were also discussed.

First author: Gorczak, N, Computational design of donor-bridge-acceptor systems exhibiting pronounced quantum interference effects, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 6773, (2016)
Abstract: Quantum interference is a well-known phenomenon that dictates charge transport properties of single molecule junctions. However, reports on quantum interference in donor-bridge-acceptor molecules are scarce. This might be due to the difficulties in meeting the conditions for the presence of quantum interference in a donor-bridge-acceptor system. The electronic coupling between the donor, bridge, and acceptor moieties must be weak in order to ensure localised initial and final states for charge transfer. Yet, it must be strong enough to allow all bridge orbitals to mediate charge transfer. We present the computational route to the design of a donor-bridge-acceptor molecule that features the right balance between these contradicting requirements and exhibits pronounced interference effects.

First author: Zhang, J, Efficient Simulation of Large Materials Clusters Using the Jaguar Quantum Chemistry Program: Parallelization and Wavefunction Initialization, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 357, (2016)
Abstract: An outline of the improvements to the pseudospectral electronic structure program Jaguar is presented, showing efficient and robust performance of hybrid-DFT calculations for large systems with thousands of basis functions, focusing on materials applications. The improvements include re-engineered parallelization, the design of a fragment-based initial guess generation method, and the validation of small eigenvalue cutoff values. An OpenMP/MPI hybrid parallelization has been implemented for the pseudospectral algorithm, which extends Jaguar’s scalability to up to 256 cores in tests of TiO2 clusters with 1295-4961 basis functions. In the largest test case, the code delivers 84.4x speedup for 128 cores in total calculation time. In addition, a fragment-based initial guess method has been constructed for large systems containing many transition metals, where the conventional (atomic) approach often fails. Overall, Jaguar is now capable of efficiently and robustly performing hybrid-DFT geometrical optimizations for large systems with more than 600 atoms in reasonable runtimes.

First author: Bushnell, EAC, Identifying Similarities and Differences Between Analogous Bisdithiolene and Bisdiselenolene Complexes: A Computational Study, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 116, 369, (2016)
Abstract: Due to ligand non-innocence and reversible one-electron-transfer processes dithiolene complexes have been intensively studied both experimentally and computationally. While the substitution of the ligating sulfur atoms by selenium provides a means to delicately tune the behavior of dithiolene compounds, diselenolene complexes have not been as thoroughly examined. Yet, the search for such ligands has been ongoing since the 1970s. Thus, we have looked at several metal-bisdiselenolene complexes and have compared key properties of these complexes with their bisdithiolene analogues to determine the effect of substituting the chalcogen atom. The results herein show that substitution of the sulfur atoms by selenium within these complexes only subtly changes the thermodynamics and kinetic reactivity of bisdithiolene complexes while not significantly affecting the geometries of the complexes. The significance being that the relatively minor structural changes that occur upon redox is a key feature of dithiolene complexes. Due to ligand non-innocence and reversible one-electron-transfer processes dithiolene complexes have been intensively studied, however, diselenolene complexes have not. First-principles calculations show that substitution of the sulfur atoms by selenium within the investigated complexes does offer the ability to subtly tune the thermodynamics and kinetic reactivity of bisdithiolene complexes, while not significantly affecting the geometries of the complexes.

First author: Milewska, K, Highly tilted liquid crystalline materials possessing a direct phase transition from antiferroelectric to isotropic phase, MATERIALS CHEMISTRY AND PHYSICS, 171, 33, (2016)
Abstract: Pure compounds and multicomponent mixtures with a broad temperature range of high tilted liquid crystalline antiferroelectric phase and a direct phase transition from antiferroelectric to isotropic phase, were obtained. X-ray diffraction analysis confirms these kinds of materials form a high tilted anticlinic phase, with a fixed layer spacing and very weak dependency upon temperature, after the transition from the isotropic phase. Due to this, not only pure orthoconic antiferroelectric liquid crystals but also those with a moderate tilt should generate a good dark state. Furthermore, due to the increased potential for forming anticlinic forces, such materials could minimize a commonly observed asymmetry of a rise and fall switching times at a surface stabilized geometry.

First author: Lashgari, A, NEW PHOSPHORUS COMPOUNDS K[PCL3(X)] (X= SCN, CN): PREPARATION AND DFT AND SPECTROSCOPIC STUDIES, JOURNAL OF THE CHILEAN CHEMICAL SOCIETY, 61, 2821, (2016)
Abstract: Two new phosphorus complexes, potassium trichlorothiocyanophosphate (III) (PTCTCP; K[PCl3(SCN)]) and potassium trichlorocyanophosphate (III) (PTCCP; K[PCl3(CN)]) were synthesized from the reaction of KSCN and KCN, respectively, with PCl3. The chemical formulas and compositions of these compounds were determined by elemental analysis and spectroscopic methods, such as phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy ((P-NMR)-P-31), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and mass spectrophotometry. All of the theoretical calculations and determinations of the properties of these compounds were performed as part of the Amsterdam Density Functional (ADF) program. Excitation energies were assessed using time-dependent perturbation density functional theory (TD-DFT). In addition, the molecular geometry was optimized and the frequencies and excitation energies were calculated using standard Slater-type orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all of the atoms. The assignment of the principal transitions and total densities of state (TDOS) for orbital analysis were performed using the GaussSum 2.2 program.

First author: Khlebopros, RG, On the possibility of phase transitions with the formation of SiO2 peroxide forms in the earth mantle and their effect on mantle convection, JOURNAL OF STRUCTURAL CHEMISTRY, 57, 417, (2016)
Abstract: Based on the hypothesis advanced by S. P. Gabuda that the SiO2 molecule could undergo a transition from the linear form to the isomeric form with a ring-shaped (bent) structure, an idea is proposed that when the mantle substance melts, a phase transition of the bent SiO2 form into the linear SiO2 form can occur in the lower mantle. This phase transition might be of great importance for the lower-mantle convection processes and also for the rise of mantle plumes carrying both heat energy, and broad range of platinum group and rare elements to the Earth surface.

First author: Sagan, F, Non-Covalent Interactions in Hydrogen Storage Materials LiN(CH3)(2)BH3 and KN(CH3)(2)BH3, CRYSTALS, 6, 417, (2016)
Abstract: In the present work, an in-depth, qualitative and quantitative description of non-covalent interactions in the hydrogen storage materials LiN(CH3)(2)BH3 and KN(CH3)(2)BH3 was performed by means of the charge and energy decomposition method (ETS-NOCV) as well as the Interacting Quantum Atoms (IQA) approach. It was determined that both crystals are stabilized by electrostatically dominated intra- and intermolecular M…H-B interactions (M = Li, K). For LiN(CH3)(2)BH3 the intramolecular charge transfer appeared (B-HLi) to be more pronounced compared with the corresponding intermolecular contribution. We clarified for the first time, based on the ETS-NOCV and IQA methods, that homopolar BH…HB interactions in LiN(CH3)(2)BH3 can be considered as destabilizing (due to the dominance of repulsion caused by negatively charged borane units), despite the fact that some charge delocalization within BH…HB contacts is enforced (which explains H…H bond critical points found from the QTAIM method). Interestingly, quite similar (to BH…HB) intermolecular homopolar dihydrogen bonds CH…HC appared to significantly stabilize both crystalsthe ETS-NOCV scheme allowed us to conclude that CH…HC interactions are dispersion dominated, however, the electrostatic and sigma/sigma*(C-H) charge transfer contributions are also important. These interactions appeared to be more pronounced in KN(CH3)(2)BH3 compared with LiN(CH3)(2)BH3.

First author: Szatylowicz, H, Effect of Intra- and Intermolecular Interactions on the Properties of para-Substituted Nitrobenzene Derivatives, CRYSTALS, 6, 417, (2016)
Abstract: To study the influence of intra- and intermolecular interactions on properties of the nitro group in para-substituted nitrobenzene derivatives, two sources of data were used: (i) Cambridge Structural Database and (ii) quantum chemistry modeling. In the latter case, pure intramolecular interactions were simulated by gradual rotation of the nitro group in para-nitroaniline, whereas H-bond formation at the amino group allowed the intermolecular interactions to be accounted for. BLYP functional with dispersion correction and TZ2P basis set (ADF program) were used to perform all calculations. It was found that properties of the nitro group dramatically depend on both its orientation with respect to the benzene ring as well as on the substituent in the para-position. The nitro group lies in the plane of the benzene ring for only a small number of molecules, whereas the mean value of the twist angle is 7.3 deg, mostly due to intermolecular interactions in the crystals. This distortion from planarity and the nature of para-substituent influence the aromaticity of the ring (described by HOMA index) and properties of the nitro group due to electronic effects. The results obtained by QM calculations fully coincide with observations found for the data set of crystal structures.

First author: Xu, CQ, Periodicity and Covalency of [MX2](-) (M = Cu, Ag, Au, Rg; X = H, Cl, CN) Complexes, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 6, 1395, (2016)
Abstract: Covalency and ionicity are key concepts in chemical science. Here we report a systematic investigation of the electronic structures and chemical bonding of [MX2](-) (M = Cu, Ag, Au, Rg; X = H, Cl, CN) to illustrate the periodicity and covalency of the group 11 binary compounds. Various modern chemical bonding theories have been utilized to analyze the interactions between the metal ions and ligands. The energy decomposition approach (EDA) results suggest that the strength of the metal-ligand bonding in [MX2](-) increases from Cu to Rg. Both relativistic effects and electron correlation play vital roles in the periodicity and enhancement of covalency in the heavier binary complexes. A gradual transition from Cu-X bonding with apparent ionic character to Rg-X bonding with relatively strong covalent character has been revealed from the chemical bonding analyses. The covalency of the M-X bond is enhanced by the strong relativistic effects of the metal and the decreased electronegativity of the ligands. In all the complexes studied, the monovalent metal(I) atoms interact with the neighboring atoms through significant s-d hybridizations. Spin-orbit coupling is found to be significant in [RgX(2)](-), and the splitting energy of the spinors is as large as 2.5 eV.

First author: Nhung, NTA, Structural variations and chemical bonding in platinum complexes of Group 14 heavier tetrylene homologues (germylene to plumbylene), INDIAN JOURNAL OF CHEMISTRY SECTION A-INORGANIC BIO-INORGANIC PHYSICAL, 55, 269, (2016)
Abstract: The structures of Pt(II) complexes containing the heavier homologues of germylene, stannylene, and plumbylene [PtCl2-{NHEMe}] (Pt-NHE) with E = Ge to Pb, in which the ligand {NHEMe} retains one lone pair at the E central atom, have been computed using density functional theory calculations at the BP86 level with def2-SVP, def2-TZVPP, and TZ2P+ basis sets. The bonding of the complexes has been analyzed by charge and energy decomposition analysis methods. The results of bonding analysis show that NHEMe ligands exhibit donor-acceptor bonds with the sigma lone pair electrons of heavier NHEMe donated into the vacant orbital of the metal fragment, and the Pt-E bonds having PtCl2 <- NHEMe strong sigma-donation. The divalent heavier tetrylenes(II) have the same role as the divalent heavier tetrylones(0) character since the ligand can retain the two lone pairs at E atom. Currently experimental efforts are directed towards the synthesis of tetrylenes Pt(II) complexes from natural products. Hence, the results in this study will provide an insight into the properties and chemical bonding of complexes being synthesised.

First author: Petrov, PA, Cluster [Re3S5(Dppe)(3)](+) and its oxidation to [Re3S4(SO2)(Dppe)(3)](+), RUSSIAN JOURNAL OF COORDINATION CHEMISTRY, 42, 196, (2016)
Abstract: The reaction of cluster [Re3S4(Dppe)(3)Br-3]Br with sodium tert-butyl thiolate affords trinuclear cationic cluster [Re3S5(Dppe)(3)]Br (I). The oxidation of cluster I with air gives [Re3S4(SO2)(Dppe)(3)]Cl (II), which is characterized by X-ray diffraction analysis in the form of solvate II center dot 3.5CH(2)Cl(2) (CIF file CCDC 1401732). The DFT calculations indicate the triplet ground state of the [Re3S5(Dppe)(3)](+) cation and a significant spin density on the equatorial sulfide ligands, favoring the oxidation of the cluster.

First author: Plasser, F, Efficient and Flexible Computation of Many-Electron Wave Function Overlaps, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 1207, (2016)
Abstract: A new algorithm for the computation of the overlap between many-electron wave functions is described. This algorithm allows for the extensive use of recurring intermediates and thus provides high computational efficiency. Because of the general formalism employed, overlaps can be computed for varying wave function types, molecular orbitals, basis sets, and molecular geometries. This paves the way for efficiently computing nonadiabatic interaction terms for dynamics simulations. In addition, other application areas can be envisaged, such as the comparison of wave functions constructed at different levels of theory. Aside from explaining the algorithm and evaluating the performance, a detailed analysis of the numerical stability of wave function overlaps is carried out, and strategies for overcoming potential severe pitfalls due to displaced atoms and truncated wave functions are presented.

First author: Bistoni, G, Advances in Charge Displacement Analysis, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 1236, (2016)
Abstract: We define new general density-based descriptors for the quantification of charge transfer and polarization effects associated with the interaction between two fragments and the formation of a chemical bond. Our aim is to provide a simple yet accurate picture of a chemical interaction by condensing the information on the charge rearrangement accompanying it into a few chemically meaningful parameters. These charge displacement (CD) parameters quantify the total charge displaced upon bond formation and decompose it into a charge transfer component between the fragments and charge rearrangements taking place within the fragments. We then show how the new parameters can be easily calculated using the well-known CD function, which describes the charge flow along a chosen axis accompanying the formation of a bond. The approach presented here can be useful in a wide variety of contexts, ranging from weak interactions to electronic excitations to coordination chemistry. In particular, we discuss here how the scheme can be used for the characterization of the donation and back-donation components of metal ligand bonds, in combination with the natural orbitals for chemical valence (NOCV) theory. In doing so, we discuss the interesting relationship between the proposed parameters and the corresponding NOCV eigenvalues, commonly used as a measure of the electron charge displacement associated with a given bonding contribution. As a prototype case study, we investigate the bond between a N-heterocyclic carbene and different metallic fragments. Finally, we show that our approach can be used in combination with the energy decomposition of the extended transition state method, providing an estimate of both charge transfer and polarization contributions to the interaction energy.

First author: Hu, ZW, Simulating Third-Order Nonlinear Optical Properties Using Damped Cubic Response Theory within Time-Dependent Density Functional Theory, JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 12, 1294, (2016)
Abstract: A general implementation for damped cubic response properties is presented using time-dependent density functional theory (TDDFT) and Slater-type orbital basis sets. To directly calculate two-photon absorption (TPA) cross sections, we also present an implementation of a reduced damped cubic response approach. Validation of the implementations includes a detailed comparison between response theory and the sum-over-states approach for calculating the nonlinear optical properties of LiH, as well as a comparison between the simulated and experimental TPA and third-harmonic generation (THG) spectra for the dimethylamino-nitrostilbene (DANS) molecule. The study of LiH demonstrates the incorrect pole structure obtained in response theory due to the adiabatic approximation typically employed for the exchange-correlation kernel. For DANS, we find reasonable agreement between simulated and experimental TPA and THG spectra. Overall, this work shows that care must be taken when calculating higher-order response functions in the vicinity of one photon poles due to the approximate kernels typically used in the simulations.

First author: Matsumiya, M, Analysis of coordination states for Dy(II) and Dy(III) complexes in ionic liquids by Raman spectroscopy and DFT calculation, JOURNAL OF MOLECULAR LIQUIDS, 215, 308, (2016)
Abstract: The coordination states of the divalent and trivalent dysprosium complexes in ionic liquid, triethyl-pentyl-phosphonium bis(trifluoromethylsulfonyl) amide [P-2225][TFSA] were investigated by Raman spectroscopy and DFT calculations. The concentration dependences of the deconvoluted Raman spectra were investigated for 0.23-0.45 mol kg(-1) of pure Dy(III) and the mixed sample of Dy(II)/Dy(III) = 1/3 at the molar ratio in [P-2225][TFSA]. According to the conventional analysis, the solvation number; n of Dy(II) and Dy(III) in [P-2225][TFSA] were determined to ben = 4.12 and 5.00, respectively.

First author: Gao, Y, Actinide-embedded gold superatom models: Electronic structure, spectroscopic properties, and applications in surface-enhanced Raman scattering, NANO RESEARCH, 9, 622, (2016)
Abstract: Actinide elements encaged in a superatomic cluster can exhibit unique properties due to their hyperactive valence electrons. Herein, the electronic and spectroscopic properties of Th@Au-14 are predicted and compared with that of the isoelectronic entities [Ac@Au-14](-) and [Pa@Au-14](+) using density functional theory. The calculation results indicate that these clusters all adopt a closedshell superatomic 18-electron configuration of the 1S(2)1P(6)1D(10) Jellium state. The absorption spectrum of Th@Au-14 can be interpreted by the Jelliumatic orbital model. In addition, calculated spectra of pyridine-Th@Au-14 complexes in the blue laser band exhibit strong peaks attributable to charge transfer (CT) from the metal to the pyridine molecule. These charge-transfer bands lead to a resonant surface-enhanced Raman scattering (SERS) enhancement of similar to 10(4). This work suggests a basis for designing and synthesizing SERS substrate materials based on actinide-embedded gold superatom models.

First author: Cheng, J, Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application, JOURNAL OF MEMBRANE SCIENCE, 501, 100, (2016)
Abstract: A modified imidazole, namely guanidimidazole (Gim) was designed and synthesized as a novel quaternizing- and cross-linking agent for alkaline polymer electrolyte membrane fabrication. The resulting membrane was more alkali tolerant and swelling resistant than that quaternized purely by 1-methylimidazole owing to the enhanced resonance and cross-linking ability of Gim, the former confirmed by a LUMO (lowest unoccupied molecular orbital) energy calculation. The membrane also showed good ionic conductivity, mechanical strength and thermal stability. A H-2/O-2 fuel cell using the synthesized membrane showed a peak power density of 39 mW cm(-2) at 50 degrees C. This work preliminarily demonstrates the beneficial effect of imidazole modification by both experimental and computational investigation; it provides a new cation design strategy that may potentially achieve simultaneous improvement of alkali stability and swelling resistance of alkaline electrolyte membranes.

First author: Bowen, AM, Exploiting orientation-selective DEER: determining molecular structure in systems containing Cu(II) centres, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 5981, (2016)
Abstract: Orientation-selective DEER (Double Electron-Electron Resonance) measurements were conducted on a series of rigid and flexible molecules containing Cu(II) ions. A system with two rigidly held Cu(II) ions was afforded by the protein homo-dimer of copper amine oxidase from Arthrobacter globiformis. This system provided experimental DEER data between two Cu(II) ions with a well-defined distance and relative orientation to assess the accuracy of the methodology. Evaluation of orientation-selective DEER (os DEER) on systems with limited flexibility was probed using a series of porphyrin-based Cu(II) nitroxide and Cu(II) Cu(II) model systems of well-defined lengths synthesized for this project. Density functional theory was employed to generate molecular models of the conformers for each porphyrin-based Cu(II) dimer studied. Excellent agreement was found between DEER traces simulated using these computed conformers and the experimental data. The performance of different parameterised structural models in simulating the experimental DEER data was also investigated. The results of this analysis demonstrate the degree to which the DEER data define the relative orientation of the two Cu(II) ions and highlight the need to choose a parameterised model that captures the essential features of the flexibility (rotational freedom) of the system being studied.

First author: Ponzi, A, Photoionization of furan from the ground and excited electronic states, JOURNAL OF CHEMICAL PHYSICS, 144, 5981, (2016)
Abstract: Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

First author: Roy, SK, A combined photoelectron spectroscopy and relativistic ab initio studies of the electronic structures of UFO and UFO-, JOURNAL OF CHEMICAL PHYSICS, 144, 5981, (2016)
Abstract: The observation of the gaseous UFO- anion is reported, which is investigated using photoelectron spectroscopy and relativisitic ab initio calculations. Two strong photoelectron bands are observed at low binding energies due to electron detachment from the U-7 sigma orbital. Numerous weak detachment bands are also observed due to the strongly correlated U-5f electrons. The electron affinity of UFO is measured to be 1.27(3) eV. High-level relativistic quantum chemical calculations have been carried out on the ground state and many low-lying excited states of UFO to help interpret the photoelectron spectra and understand the electronic structure of UFO. The ground state of UFO- is linear with an O-U-F structure and a H-3(4) spectral term derived from a U 7s sigma(2)5f phi(1)5f delta(1) electron configuration, whereas the ground state of neutral UFO has a H-4(7/2) spectral term with a U 7s sigma(2)5f phi(1)5f delta(1) electron configuration. Strong electron correlation effects are found in both the anionic and neutral electronic configurations. In the UFO neutral, a high density of electronic states with strong configuration mixing is observed in most of the scalar relativistic and spin-orbit coupled states. The strong electron correlation, state mixing, and spin-orbit coupling of the electronic states make the excited states of UFO very challenging for accurate quantum chemical calculations.

First author: Ogawa, J, Structural Effects of the Donor Moiety on Reduction Kinetics of Oxidized Dye in Dye-Sensitized Solar Cells, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 3612, (2016)
Abstract: One of the major factors influencing the regeneration rate of the oxidized dye in dye-sensitized solar cells (DSSCs) is the energy difference (Delta G) between the levels of the dye’s HOMO and redox couple in the electrolyte. To investigate other factors that influence this process, we examined the effect of structural differences of donor moieties on the reduction rate of the oxidized dye of organic dyes that is composed of an acceptor unit, a pi-conjugated linker unit, and a donor unit, including carbazole dye (MK-1), triphenylamine dye (MK-88), and coumarin dye (MK-31). The DSSCs using MK-88 showed the fastest regeneration rate even though the Delta G was not the largest among the dye structures evaluated. The regeneration rates of all of the dyes were enhanced by reducing the number of adsorbed dyes. On the basis of the results, we attribute the fast regeneration of MK-88 to the large collision cross section of the oxidized dye, that is, the increased reduction rate to the larger exposure of the HOMO of the dyes to the redox species. The effect of the exposed surface area on the reduction rate was as large as the free-energy difference, suggesting a new design strategy for efficient sensitizers.

First author: Halbert, S, Elucidating the Link between NMR Chemical Shifts and Electronic Structure in d(0) Olefin Metathesis Catalysts, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 2261, (2016)
Abstract: The nucleophilic carbon of d(0) Schrock alkylidene metathesis catalysts, [M] = CHR, display surprisingly low downfield chemical shift (delta(iso)) and large chemical shift anisotropy. State-of-the-art four component relativistic calculations of the chemical shift tensors combined with a two-component analysis in terms of localized orbitals allow a molecular-level understanding of their orientations, the magnitude of their principal components (delta(11) > delta(22) > delta(33)) and associated delta(iso). This analysis reveals the dominating influence of the paramagnetic contribution yielding a highly deshielded alkylidene carbon. The largest paramagnetic contribution, which originates from the coupling of alkylidene sigma(MC) and pi(MC)* orbitals under the action of the magnetic field, is analogous to that resulting from coupling sigma(cc) and pi(CC)* in ethylene; thus, delta(11) is in the MCH plane and is perpendicular to the MC internuclear direction. The higher value of carbon-13 delta(iso) in alkylidene complexes relative to ethylene is thus due to the smaller energy gap between sigma(MC) and pi(MC)* vs this between sigma(CC) and pi(CC)* in ethylene. This effect also explains why the highest value of delta(iso) is observed for Mo and the lowest for Ta, the values for W and Re being in between. In the presence of agostic interaction, the chemical shift tensor principal components orientation (delta(22) or delta(33) parallel or perpendicular to pi(MX)) is influenced by the MCH angle because it determines the orientation of the alkylidene CHR fragment relative to the MC internuclear axis. The orbital analysis shows how the paramagnetic terms, understood with a localized bond model, determine the chemical shift tensor and thereby delta(iso).

First author: Hamzaoui, B, Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application, CHEMISTRY-A EUROPEAN JOURNAL, 22, 3000, (2016)
Abstract: Single-site, well-defined, silica-supported tantallaaziridine intermediates [Si-O-Ta((2)-NRCH2)(NMe2)(2)] [R=Me (2), Ph (3)] were prepared from silica-supported tetrakis(dimethylamido)tantalum [Si-O-Ta(NMe2)(4)] (1) and fully characterized by FTIR spectroscopy, elemental analysis, and H-1,C-13 HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by -H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N-alkyl aryl amine substrates being more efficient than N-dialkyl amines.

First author: Blass, BL, Structural, Computational, and Spectroscopic Investigation of [Pd(kappa(3)-1,1 ‘-bis(di-tert-butylphosphino)ferrocenediyl)X](+) (X = Cl, Br, I) Compounds, ORGANOMETALLICS, 35, 462, (2016)
Abstract: The reaction of [Pd(dtbpf)Cl-2] (dtbpf = 1,1′-bis(di-tert-butylphosphino)ferrocene) with sodium bromide yields [Pd(dtbpf)Br] [Br], which displays an interaction between the iron and palladium atoms. The structure of this compound has been obtained and is compared to those of the previously reported [Pd(dtbpf)X](+) (X = Cl, I) analogues. Similar to [Pd(dtbpf)Cl](+), [Pd(dtbpf)Br](+) appears to undergo a solid-state isomerization at low temperature to a species in which the Fe Pd interaction is disrupted. In addition to H-1 and P-31{H-1} NMR and visible spectroscopy, the [Pd(dtbpf)X](+) (X = Cl, Br) compounds were also characterized by zero-field Fe-57 Mossbauer spectroscopy. DFT calculations on [Pd(dtbpf)X](+) (X = Cl, Br, I) show that the Fe-Pd interaction is weak and noncovalent and that the strength of the interaction decreases as the halide becomes larger. A related trend is noted in the potential at which oxidation of the iron center occurs; the larger the halide, the less positive the potential at which oxidation occurs. Finally, the catalytic activity of [Pd(dtbpf)X](+) (X = Cl, Br, I) in the arylation of an aromatic ketone was examined and compared to the activity of [Pd(dtbpf)Cl-2].

First author: Biasiolo, L, Cyclization of 2-Alkynyldimethylaniline on Gold(I) Cationic and Neutral Complexes, ORGANOMETALLICS, 35, 595, (2016)
Abstract: The cyclization reaction of 2-(1-hexynyl)dimethylaniline (S) on gold(I) has been studied by NMR spectroscopy, in order to characterize the ion pair structure of the product, [LAuSc]BF4. The latter is a good model for the catalytic intermediate between the nucleophilic attack and the protodeauration step of a typical gold catalytic cycle. F-19, H-1 HOESY NMR results demonstrate that in [LAuSc]BF4, with L being three different ligands, the anion mainly interacts with the ammonium moiety of the substrate, thanks to its formal positive charge, even if the ligand can tune the exact position of the anion. Furthermore, also gold chloride is able to promote the cyclization of S, forming [ClAuSc], which is the first example of a new class of precatalysts with potentially interesting catalytic properties. Preliminary data on its catalytic performances and a detailed DFT characterization of its electronic properties are presented, both of which indicate that S-c behaves as a carbene.

First author: Morgenstern, A, The influence of zero-flux surface motion on chemical reactivity, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 5638, (2016)
Abstract: Visualizing and predicting the response of the electron density, rho(r), to an external perturbation provides a portion of the insight necessary to understand chemical reactivity. One strategy used to portray electron response is the electron pushing formalism commonly utilized in organic chemistry, where electrons are pictured as flowing between atoms and bonds. Electron pushing is a powerful tool, but does not give a complete picture of electron response. We propose using the motion of zero-flux surfaces (ZFSs) in the gradient of the charge density, (del) over bar rho(r), as an adjunct to electron pushing. Here we derive an equation rooted in conceptual density functional theory showing that the movement of ZFSs contributes to energetic changes in a molecule undergoing a chemical reaction. Using a substituted acetylene, 1-iodo-2-fluoroethyne, as an example, we show the importance of both the boundary motion and the change in electron counts within the atomic basins of the quantum theory of atoms in molecules for chemical reactivity. This method can be extended to study the ZFS motion between smaller gradient bundles in rho(r) in addition to larger atomic basins. Finally, we show that the behavior of del rho(r) within atomic basins contains information about electron response and can be used to predict chemical reactivity.

First author: Monasterio, Z, Cationic 1,2,3-Triazolium Alkynes: Components To Enhance 1,4-Regioselective Azide-Alkyne Cycloaddition Reactions, ORGANIC LETTERS, 18, 788, (2016)
Abstract: 4-Alkynyl-1,2,3-triazolium cations undergo thermal [3 + 2] cycloaddition reactions with azides roughly 50- to 100-fold faster than comparable noncharged alkynes. Further, the reaction is highly 1,4-regioselective (dr up to 99:1) owing to the selective stabilization of 1,4-TS transition states via conjugative pi-acceptor :assistance of the alkyne triazolium ring. The novel cationic triazolium alkynes also accelerate the CuAAC reaction to provide bis(1,2,3-triazoles) in an “ultrafast” way (<5 min).

First author: Luo, YF, Theoretical Insights into the Phosphorescence Quantum Yields of Cyclometalated (C boolean AND C*) Platinum(II) NHC Complexes: pi-Conjugation Controls the Radiative and Nonradiative Decay Processes, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 3462, (2016)
Abstract: In this article, the radiative and nonradiative decay processes of four cyclometalated (C<^>C*) platinum(II) N-heterocyclic carbene (NHC) complexes were unveiled via density functional theory and time-dependent density functional theory. In order to explore the influence of pi-conjugation on quantum yields of (NHC)Pt(acac) (NHC=N-heterocyclic carbene, acac = acetylacetonate) complexes, the factors that determine the radiative process, including singlet triplet splitting energies, transition dipole moments, and spin orbit coupling (SOC) matrix elements between the lowest triplet states and singlet excited states were calculated. In addition, the SOC matrix elements between the lowest triplet state and the ground state as well as Huang-Rhys factors were also computed to describe the temperature independent nonradiative decay processes. Also, the triplet potential energy surfaces were investigated to elucidate the temperature-dependent nonradiative decay processes. The results indicate that complex Pt-1 has higher radiative decay rate than complexes Pt-2-4 due to the larger SOC matrix elements between the lowest triplet states and singlet excited states. However, complexes Pt-2-4 have smaller Huang-Rhys factors, smaller SOC matrix elements between the lowest triplet and the ground states, and higher active energy barriers than complex Pt-1, indicating that complexes Pt-2-4 have smaller nonradiative decay rate constants. According to these results, one may discern why complex Pt-2 has higher phosphorescence quantum efficiency than complex Pt-1; meanwhile, it can be inferred that the nonradiative decay process plays an important role in the whole photodeactivation process. In addition, on the basis of complex Pt-2, Pt-5 was designed to investigate the influence of substitution group on the photodeactivation process of rigid (NHC)Pt(acac) complex.

First author: Chauhan, V, Ni9Te6(PEt3)(8)C-60 Is a Superatomic Superalkali Superparamagnetic Cluster Assembled Material (S-3-CAM), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 1916, (2016)
Abstract: First-principles theoretical studies enable an electronic and magnetic characterization of the recently synthesized Ni9Te6(PEt3)(8)C-60 ionic material consisting of Ni9Te6(PEt3)(8) superatoms and C-60. The PEt3 ligands are shown to create an internal coulomb well that lifts the quantum states of the Ni9Te6 cluster, lowering its ionization potential to 3.39 eV thus creating a superalkali motif. The metallic core has a spin magnetic moment of 5.3 mu(B) in agreement with experiment. The clusters are marked by low magnetic anisotropy energy (MAE) of 2.72 meV and a larger intra-exchange coupling exceeding 0.2 eV, indicating that the observed paramagnetic behavior around 10K is due to super-paramagnetic relaxations. The magnetic motifs separated by C-60 experience a weak superexchange that stabilizes a ferromagnetic ground state as observed around 2 K. The calculated MAE is sensitive to the charged state that could account for the observed change in magnetic transition temperature with size of the ligands or anion.

First author: Dominikowska, J, Source of Cooperativity in Halogen-Bonded Haloamine Tetramers, CHEMPHYSCHEM, 17, 474, (2016)
Abstract: Inspired by the isostructural motif in -bromoacetophenone oxime crystals, we investigated halogen-halogen bonding in haloamine quartets. Our Kohn-Sham molecular orbital and energy decomposition analysis reveal a synergy that can be traced to a charge-transfer interaction in the halogen-bonded tetramers. The halogen lone-pair orbital on one monomer donates electrons into the unoccupied sigma*(N-X) orbital on the perpendicular N-X bond of the neighboring monomer. This interaction has local sigma symmetry. Interestingly, we discovered a second, somewhat weaker donor-acceptor interaction of local symmetry, which partially counteracts the aforementioned regular sigma-symmetric halogen-bonding orbital interaction. The halogen-halogen interaction in haloamines is the first known example of a halogen bond in which back donation takes place. We also find that this cooperativity in halogen bonds results from the reduction of the donor-acceptor orbital-energy gap that occurs every time a monomer is added to the aggregate.

First author: Zhong, YX, A theoretical probe of high-valence uranium and transuranium silylamides: Structural and redox properties, CHEMICAL PHYSICS LETTERS, 646, 75, (2016)
Abstract: Relativistic density functional theory was used to explore the structural and redox properties of 18 prototypical actinyl silylamides including a variation of metals (U, Np and Pu), metal oxidation states (VI and V) and equatorial ligands. A theoretical approach associated with implicit solvation and spin-orbit/multiplet corrections was proved to be reliable. A marked shift of reduction potentials of actinyl silylamides caused by changes of equatorial coordination ligands and implicit solvation was elucidated by analyses of electronic structures and single-electron reduction mechanism.

First author: Alfurayj, IA, Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)(4)Cl-2 (detu = N,N ‘-Diethylthiourea), INORGANIC CHEMISTRY, 55, 1469, (2016)
Abstract: Consecutive thermochromic lattice distortional and spin crossover equilibria in solid-state Ni(detu)(4)Cl-2 (detu = N,N’-diethylthiourea) are investigated by variable-temperature X-ray crystallography (173-333 K), DFT calculations, and differential scanning calorimetry. Thermochromism and anomalous magnetism were reported previously (S. L. Holt, Jr., et al. J. Am. Chem. Soc. 1964, 86, 519-520); the latter was attributed to equilibration of a singlet ground state and a thermally accessible triplet state, but structural data were not obtained. A crystal structure at 173(2) K revealed [Ni(detu)(4)](2+) centers with distorted planar ligation of nickel(II) to the four sulfur atoms, with an average Ni S bond length of 2.226(3) angstrom. The nickel ion was displaced out-of-plane by 0.334 angstrom toward a proximal apical chloride at a nonbonding distance of 3.134(1) angstrom. Asymmetry in the trans S-Ni-S angles was coupled to a monoclinic <-> tetragonal lattice distortion (T-1/2 = 254 ± 11 K), resulting in thermochromism. Spin crossover occurs by tetragonal modulation of nickel(II) with approach of the proximal chloride at higher temperatures (T-1/2 = 383 ± 18 R), which is consistent with a contraction of -0.096(4) angstrom in the Ni center dot center dot center dot Cl separation observed at 293 K. A high-spin (S = 1) square-pyramidal [Ni(dmtu)(4)Cl](+) model (dmtu = N,N’-dimethylthiourea) was optimized by DFT calculations, which estimated limiting equatorial Ni-S bond lengths of 2.45 angstrom and an apical Ni-Cl bond of 2.43 angstrom. Electronic spectra of the spin isomers were calculated by TD-DFT methods. Assignment of the FTIR spectrum was assisted by frequency calculations and isotope substitution.

First author: Tang, QQ, Sc2O@C-3v(8)-C-82: A Missing Isomer of Sc2O@C-82, INORGANIC CHEMISTRY, 55, 1926, (2016)
Abstract: By introducing CO2 as the oxygen source during the arcing process, a new isomer of Sc2O@C-82, Sc2O@C-3v(8)-C-82, previously investigated only by computational studies, was discovered and characterized by mass spectrometry, UV-vis-NIR absorption spectroscopy, cyclic voltammetry, Sc-45 NMR, density functional theory (DFT) calculations, and single-crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C-3v (8) and suggests that Sc2O cluster is disordered inside the cage. The comparative studies of crystallographic data further reveal that the Scl-O-Sc-2 angle is in the range of 131.0-148.9 degrees, much larger than that of the Sc2S@C3 (8)-C-82, demonstrating a significant flexibility of dimetallic clusters inside the cages. The electrochemical studies show that the electrochemical gap of Sc2O@C-3v(8)-C-82 is 1.71 eV, the largest among those of the oxide cluster fullerenes (OCFs) reported so far, well correlated with its rich abundance in the reaction mixture of OCF synthesis. Moreover, the comparative electrochemical studies suggest that both the dimetallic clusters and the cage structures have major influences on the electronic structures of the cluster fullerenes. Computational studies show that the cluster can rotate and change the Sc-O-Sc angle easily at rather low temperature.

First author: Jian, JW, Observation of Main-Group Tricarbonyls [B(CO)(3)] and [C(CO)(3)](+) Featuring a Tilted One-Electron Donor Carbonyl Ligand, CHEMISTRY-A EUROPEAN JOURNAL, 22, 2376, (2016)
Abstract: A combined experimental and theoretical study on the main-group tricarbonyls [B(CO)(3)] in solid noble-gas matrices and [C(CO)(3)](+) in the gas phase is presented. The molecules are identified by comparing the experimental and theoretical IR spectra and the vibrational shifts of nuclear isotopes. Quantum chemical ab initio studies suggest that the two isoelectronic species possess a tilted (1)((1)-CO)-bonded carbonyl ligand, which serves as an unprecedented one-electron donor ligand. Thus, the central atoms in both complexes still retain an 8-electron configuration. A thorough analysis of the bonding situation gives quantitative information about the donor and acceptor properties of the different carbonyl ligands. The linearly bonded CO ligands are classical two-electron donors that display classical sigma-donation and -back-donation following the Dewar-Chatt-Duncanson model. The tilted CO ligand is a formal one-electron donor that is bonded by sigma-donation and -back-donation that involves the singly occupied orbital of the radical fragments [B(CO)(2)] and [C(CO)(2)](+).

First author: Tainter, CJ, Reactive Force Field Modeling of Zinc Oxide Nanoparticle Formation, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 2950, (2016)
Abstract: A ReaxFF reactive force field is developed and used for molecular dynamics studies of reactions that occur when diethyl zinc is exposed to a graphene surface that has been functionalized with epoxide groups. From past experiments, it is known that these conditions lead to zinc oxide nanoparticle formation. Molecular dynamics simulations are used to provide atom-level detail into the nanoparticle formation process, including the mechanisms whereby oxygen is abstracted from the graphene surface, thus enabling condensation reactions in which multiple zinc-containing species form zinc oxide fragments and ultimately nanoparticles. Structural properties of the nanoparticles show nonstoichiometric zinc oxide structures with average coordination numbers of 3.6 around each zinc. Time-dependent density functional theory calculations show that the absorption spectra of these clusters are red-shifted by a few tenths of an electronvolt compared to that of a wurtzite crystal structure, representing transitions from oxygen 2p’s near the cluster surface to zinc 4s’s in the interior.

First author: Dong, HF, Fluorescent MoS2 Quantum Dots: Ultrasonic Preparation, Up-Conversion and Down-Conversion Bioimaging, and Photodynamic Therapy, ACS APPLIED MATERIALS & INTERFACES, 8, 3107, (2016)
Abstract: Small size molybdenum disulfide (MoS2) quantum dots (QDs) with desired optical properties were controllably synthesized by using tetrabutylammonium-assisted ultrasonication of multilayered MoS2 powder via OH mediated chain-like Mo-S bond cleavage mode. The tunable up-bottom approach of precise fabrication of MoS2 QDs finally enables detailed experimental investigations, of their optical properties. The synthesized MoS2 QDs present good down conversion photoluminescence behaviors and exhibit remarkable up-conversion photoluminescence for bioimaging. The mechanism of the emerging photoluminescence was investigated. Furthermore, superior O-1(2) production ability of MoS2 QDs to commercial photosensitizer PpIX was demonstrated, which has great potential application for photodynamic therapy. These early affording results of tunable synthesis of MoS2 QDs with desired photo properties can lead to application in fields of biomedical and optoelectronics.

First author: Yang, YF, Diels-Alder Reactivities of Benzene, Pyridine, and Di-, Tri-, and Tetrazines: The Roles of Geometrical Distortions and Orbital Interactions, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 1660, (2016)
Abstract: The cycloadditions of benzene and ten different azabenzenes (pyridine, three diazines, three triazines, and three tetrazines) with the ethylene dienophile have been explored with density functional theory (M06-2X) and analyzed with the distortion/interaction model. Activation barriers correlate closely with both distortion energies and interaction energies over an activation energy range of 45 kcal/mol. The replacement of CH with N increases Diels-Alder reactivity due not only to the more favorable orbital interaction, but also to a decrease in distortion energy. The rates of reactions are greatly influenced by the nature of the bonds being formed: two C-C bonds > one C-C bond, and one C-N bond > two C-N bonds. The activation energy of Diels-Alder reactions correlates very well with reaction energies and with the NICS(0) values of the aromatic dienes. The distortion energy of the Diels-Alder reaction transition states mostly arises from the diene out-of-plane distortion energy.

First author: Schober, C, Critical analysis of fragment-orbital DFT schemes for the calculation of electronic coupling values, JOURNAL OF CHEMICAL PHYSICS, 144, 1660, (2016)
Abstract: We present a critical analysis of the popular fragment-orbital density-functional theory (FO-DFT) scheme for the calculation of electronic coupling values. We discuss the characteristics of different possible formulations or “flavors” of the scheme which differ by the number of electrons in the calculation of the fragments and the construction of the Hamiltonian. In addition to two previously described variants based on neutral fragments, we present a third version taking a different route to the approximate diabatic state by explicitly considering charged fragments. In applying these FO-DFT flavors to the two molecular test sets HAB7 (electron transfer) and HAB11 (hole transfer), we find that our new scheme gives improved electronic couplings for HAB7 (-6.2% decrease in mean relative signed error) and greatly improved electronic couplings for HAB11 (-15.3% decrease in mean relative signed error). A systematic investigation of the influence of exact exchange on the electronic coupling values shows that the use of hybrid functionals in FO-DFT calculations improves the electronic couplings, giving values close to or even better than more sophisticated constrained DFT calculations. Comparing the accuracy and computational cost of each variant, we devise simple rules to choose the best possible flavor depending on the task. For accuracy, our new scheme with charged-fragment calculations performs best, while numerically more efficient at reasonable accuracy is the variant with neutral fragments.

First author: Jin, JY, The [B-3(NN)(3)](+) and [B-3(CO)(3)](+) Complexes Featuring the Smallest -Aromatic Species B-3(+), ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 55, 2078, (2016)
Abstract: We report the spectroscopic identification of the [B-3(NN)(3)](+) and [B-3(CO)(3)](+) complexes, which feature the smallest -aromatic system B-3(+). A quantum chemical bonding analysis shows that the adducts are mainly stabilized by L[B3L2](+) sigma-donation.

First author: Jankowska, M, Spin-Orbit ZORA and Four-Component Dirac-Coulomb Estimation of Relativistic Corrections to Isotropic Nuclear Shieldings and Chemical Shifts of Noble Gas Dimers, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 395, (2016)
Abstract: Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for nonrelativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton, and xenon dimers and free atoms. Relativistic corrections were calculated with the scalar and spin-orbit zeroth-order regular approximation Hamiltonian in combination with the large Slater-type basis set QZ4P as well as with the four-component Dirac-Coulomb Hamiltonian using Dyall’s acv4z basis sets. The relativistic corrections to the nuclear magnetic shieldings and chemical shifts are combined with nonrelativistic coupled cluster singles and doubles with noniterative triple excitations [CCSD(T)] calculations using the very large polarization-consistent basis sets aug-pcSseg-4 for He, Ne and Ar, aug-pcSseg-3 for Kr, and the AQZP basis set for Xe. For the dimers also, zero-point vibrational (ZPV) corrections are obtained at the CCSD(T) level with the same basis sets were added. Best estimates of the dimer chemical shifts are generated from these nuclear magnetic shieldings and the relative importance of electron correlation, ZPV, and relativistic corrections for the shieldings and chemical shifts is analyzed.

First author: Day, PN, Linear and Nonlinear Optical Response in Silver Nanoclusters: Insight from a Computational Investigation, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 507, (2016)
Abstract: We report a detisity functional theory (DFT) and time-dependent DFT (TDDFT) investigation of the thiolated silver nanoclusters [Ag-44(SR)(30)](4-), Ag-14(SR)(12)(PR'(3))(8), Ag-31(SG)(19), Ag-32-(SG)(19), and Ag-15(SG)(11), which were synthesized’ and for which one-photon absorption (OPA) characterization is available. Our computational investigation based on careful examination of the exchange-correlation functional used in DFT geometry optimization and for the linear optical properties predictions by TDDFT, demonstrated good agreement with the measured linear absorption spectra, however dependent on the applied functional. Following the benchrnarking, we evaluated the two-photon absorption (TPA) response Using TDDFT, noting that accurate prediction of OPA is important for suppositions on the spectral range for TPA enhancement because of the sensitivity to the excitation energies. Although the TPA cross-section results are complicated by resonance effects and quantifying TPA cross sections for these systems is difficult, our results indicate that the nanoclusters Ag-15 and Ag-31/32 are likely to have large TPA cross sections. The spherical symmetry of the Ag-44 and Ag-14 nanoclusters leads to applicability of superatom theory, while it is not as useful for the more oblate geometries of the Ag-15 and Ag-31/32 systems.

First author: Niu, XH, Anomalous Size Dependence of Optical Properties in Black Phosphorus Quantum Dots, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 370, (2016)
Abstract: Understanding electron transitions in black phosphorus nanostructures plays a crucial role in applications in electronics and optoelectronics. In this work, by employing time-dependent density functional theory calculations, we systematically study the size-dependent electronic, optical absorption, and emission properties of black phosphorus quantum dots (BPQDs). Both the electronic gap and the absorption gap follow an inversely proportional law to the diameter of BPQDs in conformity to the quantum confinement effect. In contrast, the emission gap exhibits anomalous size dependence in the range of 0.8-1.8 nm, which is blue-shifted with the increase of size. The anomaly in fact arises from the structure distortion induced by the excited-state relaxation, and it leads to a huge Stokes shift in small BPQDs.

First author: Kunkel, DA, 2D Cocrystallization from H-Bonded Organic Ferroelectrics, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 435, (2016)
Abstract: The synthesis of 2D H-bonded cocrystals from the room-temperature ferroelectric organics croconic acid (CA) and 3-hydroxyphenalenone (3-HPLN) is demonstrated through self-assembly on a substrate under ultrahigh vacuum. 2D cocrystal polymorphs of varied stoichiometry were identified with scanning tunneling microscopy, and one of the observed structural building blocks consists of two CA and two 3-HPLN molecules. Computational analysis with density functional theory confirmed that the experimental (CA)(2)(3-HPLN)(2) tetramers are lower in energy than single-component structures due to the ability of the tetramers to pack efficiently in two dimensions, the promotion of favorable electrostatic interactions between tetramers, and the optimal number of intermolecular hydrogen bonds. The structures investigated, especially the experimentally found tetrameric building blocks, are not polar. However, it is demonstrated computationally that cocrystallization can, in principle, result in heterogeneous structures with dipole moments that exceed those of homogeneous structures and that 2D structures with select stoichiometries could favor metastable polar structures.

First author: Wang, YL, Relativistic Effects Break Periodicity in Group 6 Diatomic Molecules, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 1126, (2016)
Abstract: The finding of the periodic law is a milestone in chemical science. The periodicity of light elements in the Periodic Table is fully accounted for by quantum mechanics. Here we report that relativistic effects change the bond multiplicity of the group 6 diatomic molecules M-2 (M = Cr, Mo, W, Sg) from hextuple bonds for Cr-2, Mo-2, W-2 to quadruple bonds for Sg(2), thus breaking the periodicity in the nonrelativistic domain. The same trend is also found for other superheavy-element diatomics Rf(2), Db(2), Bh(2), and Hs(2).

First author: Su, J, Probing the Electronic Structure and Chemical Bonding of Mono-Uranium Oxides with Different Oxidation States: UOx- and UOx (x=3-5), JOURNAL OF PHYSICAL CHEMISTRY A, 120, 1084, (2016)
Abstract: Uranium oxide clusters UOx- (x = 3-5) were produced by laser vaporization and characterized by photoelectron spectroscopy and quantum theory. Photoelectron spectra were obtained for UOx- at various photon energies with well-resolved detachment transitions and vibrational resolution for x = 3 and 4. The electron affinities of UOx were measured as 1.12, 3.60, and 4.02 eV for x = 3, 4, and 5, respectively. The geometric and electronic structures of both the anions and the corresponding neutrals were investigated by quasi-relativistic electron-correlation quantum theory to interpret the photoelectron spectra and to provide insight into their chemical bonding. For UOx clusters with x <= 3, the O atoms appear as divalent closed-shell anions around the U atom, which is in various oxidation states from U-II(fds)(4) in UO to U-VI(fds)(0) in UO3. For x > 3, there are no longer sufficient valence electrons from the U atom to fill the O(2p) shell, resulting in fractionally charged and multicenter delocalized valence states for the O ligands as well as eta(1)- or eta(2)-bonded O-2 units, with unusual spin couplings and complicated electron correlations in the unfilled poly oxo shell. The present work expands our understanding of both the bonding capacities of actinide elements with extended spdf valence shells as well as the multitude of oxygen’s charge and bonding states.

First author: Jacobsen, H, Coordination chemistry of oxygen difluoride – an ETS-NOCV analysis, CANADIAN JOURNAL OF CHEMISTRY, 94, 149, (2016)
Abstract: Oxygen difluoride most likely does not form stable complexes with transition metal fragments but initiates formation of halides, oxides, and oxyhalides. This conclusion is drawn as the result of density functional calculations (BP86/TZVP). The interaction between OF2 as potential ligand and the transition metal fragment Cr(CO)(5) provides the model scenario. A combined charge and energy decomposition scheme (ETS-NOCV) for bond analysis illustrates the difference in bond behavior between typical donor ligands and oxygen difluoride.

First author: Jin, JY, Infrared Photodisssociation Spectroscopy of Boron Carbonyl Cation Cornplexes, CHINESE JOURNAL OF CHEMICAL PHYSICS, 29, 47, (2016)
Abstract: The boron carbonyl cation complexes B(CO)(3)(+), B(CO)(4)(+) and B-2(CO)(4)(+) are studied by infrared photodissociation spectroscopy and theoretical calculations. The B(CO)(4)(+) ions are characterized to be very weakly bound complexes involving a B(CO)(3)(+) core ion, which is predicted to have a planar D-3h structure with the central boron retaining the most favorable 8-electron configuration. The B-2(CO)(4+) cation is determined to have a planar D-2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDANOCV method indicates that the OC -> B sigma donation is stronger than the B -> CO pi back donation in both ions.

First author: Groh, MF, Controlled Synthesis of Pnicogen-Chalcogen Polycations in Ionic Liquids, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 29, 880, (2016)
Abstract: Three new pnicogen-chalcogen polycations were synthesized under specific conditions in the Lewis-acidic ionic liquids (ILs) [EMIm]XnAlX(3) and [BMIm]XnAlX(3) (X = Cl, Br; [EMIm]: 1-ethyl-3-methylimidazolium, [BMIm]: 1-butyl-3-methylimidazolium) and crystallized as their tetrahalogenidoaluminate salts. Single-crystal X-ray diffraction revealed the new polycation [Bi6Te4Br2](4+) in triclinic [Bi6Te4Br2](AlBr4)(4) as the reaction product of bismuth, tellurium, and bismuth tribromide. Substitution of the elements with Bi2Te3 yielded the heterocubane [Bi4Te4](4+) in tetragonal [Bi4Te4](AlBr4)(4), which crystallizes isotypically to its known chlorine counterpart. The latter is also accessible from ILs. The interactions between cations and anions were evaluated by quantum-chemical calculations. Bi2S3, which is insoluble in most media, readily dissolves in the employed IL and forms the new augmented heterocubane [Bi3S4AlCl](3+), which crystallizes with the complex anion [S(AlCl3)(3)](2-) as triclinic [Bi3S4AlCl][S(AlCl3)(3)]AlCl4. Quantum-chemical calculations support the assignment of elements in this compound. The monoclinic crystal structure of [Sb13Se16](AlCl4)(6)(Al2Cl7) contains a new member of the small family of pnicogen-chalcogen spiro-heterocubanes.

First author: Thornley, WA, Photolysis of Isoelectronic Ruthenium Nitrosyl and Diazonium Complexes in Frozen PVC Matrices: Retention of Dinitrogen on Ruthenium Following Photochemical Phenyl Radical Loss, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 29, 464, (2016)
Abstract: Photolysis of RuCl3(eta(1)-NO)(PPh3)(2) in poly (vinyl chloride) (PVC) matrices at 85 K results in reversible linkage isomerism of the nitrosyl ligand to form the isonitrosyl complex RuCl3(eta(1)-ON)(PPh3)(2). Metal-to-ligand charge-transfer (MLCT) excitation of the isoelectronic phenylazo complex, RuCl3(eta 1-N2Ph) (PPh3)(2), has previously been shown to result in generation of the phenyl radical, presumably through decomposition a photogenerated diazenyl radical. Examination of this photolysis in a PVC matrix at cryogenic temperatures has permitted direct observation of an isotopically sensitive product band that may be assigned to a 17-electron ruthenium dinitrogen species, suggesting that this photochemical decomposition does not proceed through formation of a diazenyl intermediate but through homolytic cleavage of the parent diazonium complex to give the phenyl radical and the 17-electron RuCl3(eta(1)-N-2) (PPh3)(2).

First author: Wilson, AV, A Matrix Isolation and Computational Study of Molecular Palladium Fluorides: Does PdF6 Exist?, INORGANIC CHEMISTRY, 55, 1108, (2016)
Abstract: Palladium atoms generated by thermal evaporation and laser ablation were reacted with and trapped in F-2/Ar, F-2/Ne, and neat F-2 matrices. The products were characterized by electronic absorption and infrared spectroscopy, together with relativistic density functional theory calculations as well as coupled cluster calculations. Vibrational modes at 540 and 617 cm(-1) in argon matrices were assigned to molecular PdF and PdF2, and a band at 692 cm(-1) was assigned to molecular PdF4. A band at 624 cm(-1) can be assigned to either PdF3 or PdF6, with the former preferred from experimental considerations. Although calculations might support the latter assignment, our conclusion is that in these detailed experiments there is no convincing evidence for PdF6.

First author: Zlatar, M, Origin of the Zero-Field Splitting in Mononuclear Octahedral Mn-IV Complexes: A Combined Experimental and Theoretical Investigation, INORGANIC CHEMISTRY, 55, 1192, (2016)
Abstract: The aim of this work was to determine and understand the origin of the electronic properties of Mn-IV complexes, especially the zero-field splitting (ZFS), through a combined experimental and theoretical investigation on five well-characterized mononuclear octahedral Mn-IV compounds, with various coordination spheres (N-6, N3O3, N2O4 in both trans (trans-N2O4) and cis configurations (cis-N2O4) and O4S2). High-frequency and -field EPR (HFEPR) spectroscopy has been applied to determine the ZFS parameters of two of MnLtrans-N2O4 and Mn(LO4S)2 these compounds,. While at X-band EPR, the axial-component of the ZFS tensor, D, was estimated to be +0.47 cm(-1) for MnLO4S2, and a D-value of +2.289(5) cm(-1) was determined by HFEPR, which is the largest D-magnitude ever measured for a Mn-IV complex. A moderate D value of -0.997(6) cm(-1) has been found for MnLtrans-N2O4. Quantum chemical calculations based on two theoretical frameworks (the Density Functional Theory based on a coupled perturbed approach (CP-DFT) and the hybrid Ligand-Field DFT (LF-DFT)) have been performed to define appropriate methodologies to calculate the ZFS tensor for Mn-IV centers, to predict the orientation of the magnetic axes with respect to the molecular ones, and to define and quantify the physical origin of the different contributions to the ZFS. Except in the case of MnLtrans-N2O4, the experimental and calculated D values are in good agreement, and the sign of D is well predicted, LF-DFT being more satisfactory than CP-DFT. The calculations performed on MnLcis-N2O4 are consistent with the orientation of the principal anisotropic axis determined by single-crystal EPR, validating the calculated ZFS tensor orientation. The different contributions to D were analyzed demonstrating that the d-d transitions mainly govern D in Mn-IV ion. However, a deep analysis evidences that many factors enter into the game, explaining why no obvious magnetostructural correlations can be drawn in this series of Mn-IV complexes.

First author: Makarewicz, E, How many electrons form chemical bonds in the NgBeS (Ng = Ar, Kr, Xe) molecules? Topological study using the electron localisation function (ELF) and electron localisability indicator (ELI-D), STRUCTURAL CHEMISTRY, 27, 57, (2016)
Abstract: Nature of bonding in the NgBeS (Ng = Ar, Kr, Xe) molecules has been studied using topological analysis of ELF, ELI-D functions with the wave function approximated at the DFT (M062X, B3LYP + ZORA), MP2, CCSD and CASSCF level of calculations. Both Xe-Be and Be=S bonds display topological features typical for the covalent-dative bonding. The V-2(Xe) attractor characterising electron density, involved in interaction with the beryllium atom, is closer to the C(Be) core than to C(Xe). The population of the respective basin ranges between 1.59e (B3LYP + ZORA) and 1.83e (CCSD). The beryllium-sulphur bond is described by the bonding disynaptic basin V(Be,S) with the population between 3.22e (CASSCF) and 3.48e (M062X). The approximate weights for the Be-S and Be=S resonance forms are 0.3 and 0.7, respectively, in all molecules. Both the NgBe and BeS bonds are highly polarised with the values of the p (SBe) and p (NgBe) polarity indices (CCSD) of 0.8 and 0.9-1.0 for all studied molecules.

First author: Terrett, R, Effect of concomitant oxidation and deprotonation of hydrated Mn centres in rationalising the FTIR difference silence of D1-Asp170 in Photosystem II, JOURNAL OF INORGANIC BIOCHEMISTRY, 155, 101, (2016)
Abstract: The observation of negligible FTIR differences in carboxylate vibrational modes for the D1-Asp170 residue of Photosystem II (PSII) on successive one-electron oxidations of the Mn4CaO5 oxygen-evolving complex (OEC) is counterintuitive in light of the apparent ligation of D1-Asp170 to an oxidisable Mn ion in the X-ray crystallographic structures of PSII. Here, we show computational support for the hypothesis that suppression of the FTIR difference spectrum in the 1100 cm(-1) to 1700 cm(-1) region of D1-Asp170 occurs by concomitant Mn oxidation and deprotonation of water ligands bound to the ligated metal centre. Density functional theory calculations on the model species [(MnCa)-Ca-II(COOH)(OH)(2)(H2O)(2)](+) over two successive oxidations of the Mn ion are performed, where those oxidations are accompanied by deprotonation of water and mu-hydroxo ligands coordinated to the Mn ion. In contrast, dramatically increased FTIR difference activity is observed where these oxidations are unaccompanied by proton loss.

First author: Coppens, P, Can we deconvolute electron density changes from the dominant influence of the atomic rearrangement on molecular excitation in time-resolved diffraction studies?, PHYSICA SCRIPTA, 91, 101, (2016)
Abstract: Recent studies have produced experimental triplet excited state structures with lifetimes of nanoseconds to microseconds. Photodifference maps, showing the total change on excitation, in principle include both the effect of the atomic shifts on excitation and that of the orbital transitions. The latter can be calculated theoretically thus achieving a formal deconvolution of the atomic and electronic shifts. In the three examples presented electronic shifts on excitation are orders of magnitude smaller than the effect of the atomic shifts and their electron shells and therefore not experimentally accessible at this time.

First author: Morgenstern, A, Bond dissociation energies from the topology of the charge density using gradient bundle analysis, PHYSICA SCRIPTA, 91, 101, (2016)
Abstract: New and more robust models of chemical bonding are necessary to further our understanding of chemical phenomena. Among these are bond bundle and gradient bundle methods, which analyze bonding interactions in terms of property distributions over geometrically defined volumes. These methods have been shown to provide a systematic framework from which to search for structure-property relationships. In addition to providing a brief review of some of the relationships found using this framework, we present new findings that relate the lowering of kinetic energy in bonding regions to bond dissociation energy.

First author: Pandey, KK, The nature of M-B and B-N bonding in iminoboryl complexes of rhodium and iridium cis,mer-[(L)(3)(Br)(2)M(B NSiMe3)] (L = PMe3, CO): Dispersion corrected DFT study, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 803, 21, (2016)
Abstract: Dispersion corrected quantum-chemical calculations of iminoboryl complexes cis,mer-[(L)(3)(Br)(2)M(B NSiMe3)] (M = Rh, Ir; L = PMe3, CO) were studied with and without dispersion interactions using density functionals BP86, BLYP, PBE, PW91 and TPSS. The calculations of the B-11 NMR chemical shifts were carried out at DFT-D3(BJ)/BP86/TZ2P/ZORA with scalar and spin orbit relativistic level of theory in solvent C6D6. The calculated geometrical parameters of the rhodium iminoboryl complex cis, mer-[(Me3P)(3)(Br)(2)Rh(B NSiMe3)] (Braunschweig et al., J. Am. Chem. Soc. 130 (2008) 7974-7983) are in good agreement with the available experimental values. The calculated M-B and B-N bond distances, Mayer bond orders and Pauling bond orders suggest that the M-B bond has more than single bond character and B-N bond has less than triple bond character. The calculated bond dissociation energies (BDEs) of the M-B bonds follow the order BLYP < BP86 < TPSS < PBE < PW91. The absolute value of orbital interactions is significantly larger than the electrostatic interactions. The B-11 NMR shielding is larger for carbonyl complexes cis,mer-[(CO)(3)Br2M(B NSiMe3)] than the phosphine complexes cis,mer-[(PMe3)(3)Br2M(B NSiMe3)]. On going from rhodium to iridium in the complexes cis,mer-[(L)(3)(Br)(2)M(B NSiMe3)] (L = PMe3, CO), the B-11 NMR chemical shift decreases. The calculation of B-11 chemical shifts by means of the ZORA relativistic scalar yields reliable results.

First author: Yue, NLS, Dimerization of an organoplatinum complex triggered by oxidative addition: A model for dynamic ring-opening polymerization, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 803, 45, (2016)
Abstract: The bis(pyridine) ligand thiophene-2,5-dicarboxylic acid bis(N-methyl-N-4-pyridyl-amide), 1, reacts with [Pt2Me4(mu-SMe2)(2)], with displacement of Me2S, to give the chelate complex [PtMe2(1)], 2, which then reacts with methyl iodide to give [PtIMe3(1)], 3. Complex 3 spontaneously dimerizes to give a macrocyclic complex [{PtIMe3(mu-1)}(2)], 4, which exists as a mixture of anti and syn isomers 4a and 4b, as characterized by both NMR spectroscopy and X-ray structure determination. In the complex 4*, formed by oxidative addition of CD3I, the CH3 and CD3 ligands are scrambled between the axial and equatorial coordination sites at platinum(IV). The dimerization can be considered as a model for the first step in a dynamic ring-opening polymerization and occurs to give a new conformation of the flexible ligand.

First author: Moura, RT, On the calculation and interpretation of covalency in the intensity parameters of 4f-4f transitions in Eu3+ complexes based on the chemical bond overlap polarizability, JOURNAL OF LUMINESCENCE, 170, 420, (2016)
Abstract: The concepts of chemical bond overlap polarizability (alpha(OP)) and of specific ionic valence (v) were used to characterize the Eu3+ -ligating atom bonds in complexes. The underlying chemical bond properties, namely, bond distance, overlap integral, force constant, and the energy excitation, were successfully calculated for the Eu3+ -ligating atom diatomic-like species under the influence of the molecular environment. The quantities alpha(OP) and v were used to reshape and reinterpret the expressions of the forced electric dipole (FED) and the dynamic coupling (DC) mechanisms responsible for the intensity parameters of 4f-4f transitions. These parameters were calculated with this new approach for a series of Eu3+ complexes: [EuL3L’] with L=AIND, BIND, TTA, BTFA, FOD, ABSe, ABSeCl, DPM and L’=(H2O)(2), NO3, DPbpy, DBSO, TPPO, Phen, for which the experimental intensity parameters and some E-00 (=D-5(0)-> F-7(0)) energies are available. Comparisons between the theoretical and experimental results suggest that this new methodology is reliable and an important step toward an approach to calculate the 4f-4f intensities free of adjustable parameters, which has been accomplished for complexes without aquo ligand.

First author: Shyichuk, A, Energy transfer upconversion dynamics in YVO4:Yb3+,Er3+, JOURNAL OF LUMINESCENCE, 170, 560, (2016)
Abstract: A new approach to calculate the effective Ln-Ln energy transfer rates in a doped crystal matrices was proposed and successfully applied to the YVO4:Yb3+,Er3+- upconversion system. This approach is based on the known set of Ln-Ln distances obtained from the crystal structure of the matrix and the probabilities of their occurrence. The non-radiative energy transfer rates were calculated in the intermediate coupling scheme taking into account the shielding of the 4f electrons. The required partial (that is, forced electric dipole-only, lacking the dynamic coupling contribution) Judd-Ofelt Omega(lambda) parameters were calculated using the Simple Overlap Model (SOM). The spectral overlap factor F was estimated from optical absorption measurements. A simplified one level-one manifold” energy level scheme was applied. The F-4(7/2), H-2(11/2) and S-4(3/2) states of Er3+ were treated as an effective level. The set of rate equations containing radiative, non-radiative and energy transfer processes was solved numerically using fourth-order Runge-Kutta method. Both continuous and pulsed excitation modes were simulated. The dependence of the upconversion intensity upon the pump power was found. The simulations resulted in good agreement with the experimental results and provided new insights into the dynamics of the upconversion process and a connection between the macroscopic properties and the microscopic description.

First author: Ferreira, LO, Degradation of organic compounds in a fenton system based on chitosan/Fe-0/Fe2O3 composites: a theoretical and experimental study, JOURNAL OF THE IRANIAN CHEMICAL SOCIETY, 13, 377, (2016)
Abstract: Chitosan is a polymer with interesting characteristics for use in catalysis, such as biocompatibility, high chemical reactivity and stability under various conditions. Seeking new applications, a new hybrid material was synthesized for use in the degradation of organic compound. A synthesis route proposed led to the formation of a material in the form of film. The characterization data indicated the presence of hematite, as well as metallic iron. In addition, a theoretical model for interaction of iron with chitosan was proposed. Molecular dynamics simulations indicate that non-Coulomb interactions modulate the adsorption process between reactive red dye and chitosan. The catalytic behavior of these hybrid materials was investigated for the H2O2 decomposition to O-2 and the degradation of reactive red dye. The hybrid material showed high degradation capacity, confirming this material as an efficient heterogeneous Fenton catalysts.

First author: Chatterjee, S, How similar is the electronic structures of beta-lactam and alanine?, RADIATION PHYSICS AND CHEMISTRY, 119, 1, (2016)
Abstract: The C1s spectra of beta-lactam i.e. 2-azetidinone (C3H5NO), a drug and L-alanine (C3H7NO2), an amino acid, exhibit striking similarities, which may be responsible for the competition between 2-azetidinone and the alanyl-alanine moiety in biochemistry. The present study is to reveal the degree of similarities and differences between their electronic structures of the two model molecular pairs. It is found that the similarities in C1s and inner valence binding energy spectra are due to their bonding connections but other properties such as ring structure (in 2-azetidinone) and chiral carbon (alanine) can be very different. Further, the inner valence region of ionization potential greater than 18 eV for 2-azetidinone and alanine is also significantly similar. Finally the strained lactam ring exhibits more chemical reactivity measured at all non-hydrogen atoms by Fukui functions with respect to alanine.

First author: Ray, A, A Comparison of Four Different Conformations Adopted by Human Telomeric G-Quadruplex Using Computer Simulations, BIOPOLYMERS, 105, 83, (2016)
Abstract: The telomeric G-quadruplexes for their unique structural features are considered as potential anticancer drug targets. These, however, exhibit structural polymorphism as different topology types for the intra-molecular G-quadruplexes from human telomeric G-rich sequences have been reported based on NMR spectroscopy and X-ray crystallography. These techniques provide detailed atomic-level information about the molecule but relative conformational stability of the different topologies remains unsolved. Therefore, to understand the conformational preference, we have carried out quantum chemical calculations on G-quartets; used all-atom molecular dynamics (MD) simulations and steered molecular dynamics (SMD) simulations to characterize the four human telomeric G-quadruplex topologies based on its G-tetrad core-types, viz., parallel, anti-parallel, mixed(3+1)-form1 and mixed-(3+1)-form2. We have also studied a non-telomeric sequence along with these telomeric forms giving a comparison between the two G-rich forms. The structural properties such as base pairing, stacking geometry and backbone conformations have been analyzed. The quantum calculations indicate that presence of a sodium ion inside the G-tetrad plane or two potassium ions on both sides of the plane give it an overall planarity which is much needed for good stacking to form a helix. MD simulations indicate that capping of the G-tetrad core by the TTA loops keep the terminal guanine bases away from water. The SMD simulations along with equilibrium MD studies indicate that the parallel and non-telomeric forms are comparatively less stable. We could come to the conclusion that the anti-parallel form and also the mixed-(3+1)-form1 topology are most likely to represent the major conformation.

First author: Keypour, H, Synthesis and characterization of new Mn(II) and Cd(II) Schiff base complexes containing homopiperazine moiety: Spectral, X-ray crystal structural and theoretical studies, INORGANICA CHIMICA ACTA, 440, 139, (2016)
Abstract: Two new symmetrical Mn(II) and Cd(II) pentaaza macrocyclic Schiff base complexes were prepared via templated [1 + 1] cyclocondensation of 2,6 diacetylpyridine and an amine containing homopiperazine moiety in the presence of related metal ions. These complexes have been characterized by elemental analysis, IR spectra, EI-MS, conductivity measurements and in the case of Cd(II) complex by H-1 and C-13 NMR spectroscopy. In addition, Crystal structures of complexes have been determined by X-ray crystallographic technique. This reveals that in the solid state both complexes adopt a distorted pentagonal pyramidal geometry, with the pentaaza macrocycle positioned in the equatorial plane and the chloride ion in the axial site. Also, the bonding situation between the [MCl](+) (M = Mn2+, Cd2+) fragment and Ligand (L) in [MLCl](+) (M = Mn, Cd) complexes, were carried out by NBO and energy-decomposition analysis (EDA), as well as its natural orbitals for chemical valence variation (EDA-NOCV). The results confirmed that the contribution of the electrostatic interactions in the M <- L bonds of the complexes is predominantly more than 50%.

First author: Cazaux, S, The sequence to hydrogenate coronene cations: A journey guided by magic numbers, SCIENTIFIC REPORTS, 6, 139, (2016)
Abstract: The understanding of hydrogen attachment to carbonaceous surfaces is essential to a wide variety of research fields and technologies such as hydrogen storage for transportation, precise localization of hydrogen in electronic devices and the formation of cosmic H-2. For coronene cations as prototypical Polycyclic Aromatic Hydrocarbon (PAH) molecules, the existence of magic numbers upon hydrogenation was uncovered experimentally. Quantum chemistry calculations show that hydrogenation follows a site-specific sequence leading to the appearance of cations having 5, 11, or 17 hydrogen atoms attached, exactly the magic numbers found in the experiments. For these closed-shell cations, further hydrogenation requires appreciable structural changes associated with a high transition barrier. Controlling specific hydrogenation pathways would provide the possibility to tune the location of hydrogen attachment and the stability of the system. The sequence to hydrogenate PAHs, leading to PAHs with magic numbers of H atoms attached, provides clues to understand that carbon in space is mostly aromatic and partially aliphatic in PAHs. PAH hydrogenation is fundamental to assess the contribution of PAHs to the formation of cosmic H-2.

First author: Armakovic, S, Influence of sumanene modifications with boron and nitrogen atoms to its hydrogen adsorption properties, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 2859, (2016)
Abstract: We investigate the influence of sumanene modifications on its adsorption properties towards the hydrogen molecule. The benzylic positions of sumanene were substituted with boron and nitrogen atoms, which changed its hydrogen storage properties. H-2 binding energies were calculated using the LMP2, DFT and DFT-D3 approaches with several exchange-correlation functionals and the results indicate a physisorption mechanism. Physisorption was confirmed by fragment analysis and special attention was paid to non-covalent interactions. All non-covalent interactions, based on reduced density gradient surfaces, were identified and calculated for better understanding of the adsorption mechanism. Moreover, the significance of charge separation by inducing boron and nitrogen atoms is emphasized and special attention is paid to the z-component of the dipole moment of sumanene derivatives.

First author: Dumas, T, The nature of chemical bonding in actinide and lanthanide ferrocyanides determined by X-ray absorption spectroscopy and density functional theory, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 2887, (2016)
Abstract: The electronic properties of actinide cations are of fundamental interest to describe intramolecular interactions and chemical bonding in the context of nuclear waste reprocessing or direct storage. The 5f and 6d orbitals are the first partially or totally vacant states in these elements, and the nature of the actinide ligand bonds is related to their ability to overlap with ligand orbitals. Because of its chemical and orbital selectivities, X-ray absorption spectroscopy (XAS) is an effective probe of actinide species frontier orbitals and for understanding actinide cation reactivity toward chelating ligands. The soft X-ray probes of the light elements provide better resolution than actinide L-3-edges to obtain electronic information from the ligand. Thus coupling simulations to experimental soft X-ray spectral measurements and complementary quantum chemical calculations yields quantitative information on chemical bonding. In this study, soft X-ray XAS at the K-edges of C and N, and the L-2,L-3-edges of Fe was used to investigate the electronic structures of the well-known ferrocyanide complexes K4FeII(CN)(6), thorium hexacyanoferrate (ThFeII)-Fe-IV(CN)(6), and neodymium hexacyanoferrate (KNdFeII)-Fe-III(CN)(6). The soft X-ray spectra were simulated based on quantum chemical calculations. Our results highlight the orbital overlapping effects and atomic effective charges in the Fe-II(CN)(6) building block. In addition to providing a detailed description of the electronic structure of the ferrocyanide complex (K4FeII(CN)(6)), the results strongly contribute to confirming the actinide 5f and 6d orbital oddity in comparison to lanthanide 4f and 5d.

First author: Johnson, PS, Multitechnique Approach for Determining Energy Levels and Exciton Binding Energies of Molecules for Organic Electronics, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 1366, (2016)
Abstract: The energies of the frontier orbitals and their electronhole binding energy are key quantities in organic electronics, such as organic light-emitting diodes (OLEDs) and solar cells. A method is developed for obtaining these quantities from ultraviolet photoelectron spectroscopy (UPS) and optical absorption spectroscopy, combined with calculations of the ionization energy (IE) and the electron affinity (EA). This method provides a more efficient and accurate determination of the lowest unoccupied molecular orbital (LUMO) together with the exciton binding energy. The concept is extended to element-sensitive core-level spectroscopies, such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), in order to obtain core exciton binding energies. Two prototypical organic molecules for OLED applications are used as examples, i.e., N,N’-di(1-naphthyl)-N,N’-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPD) and dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT:CN). These methods have the potential to facilitate the systematic tailoring of molecules for applications in organic electronics. The method devised for determining the LUMO is consistent with previous reports using conventional techniques.

First author: Martinez, JP, (4+2) and (2+2) Cycloadditions of Benzyne to C-60 and Zig-Zag Single-Walled Carbon Nanotubes: The Effect of the Curvature, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 1716, (2016)
Abstract: Addition of benzyne to carbon nanostructures can proceed via (4 + 2) (1,4-addition) or (2 + 2) (1,2-addition) cycloadditions depending on the species under consideration. In this work, we analyze by means of density functional theory (DFT) calculations the reaction mechanisms for the (4 + 2) and (2 + 2) cycloadditions of benzyne to nanostructures of different curvature, namely, C-60 and a series of zigzag single-walled carbon nanotubes. Our DFT calculations reveal that, except for the concerted (4 + 2) cycloaddition of benzyne to zigzag single-walled carbon nanotubes, all cycloadditions studied are stepwise processes with the initial formation of a biradical singly bonded intermediate. From this intermediate, the rotation of the benzyne moiety determines the course of the reaction. The Gibbs energy profiles lead to the following conclusions: (1) except for the 1,4-addition of benzyne to a six-membered ring of C-60, all 1,2- and 1,4-additions studied are exothermic processes; (ii) for C-60 the (2 + 2) benzyne cycloaddition is the most favored reaction pathway; (iii) for zigzag single-walled carbon nanotubes, the (4 + 2) benzyne cycloaddition is preferred over the (2 + 2) reaction pathway; and (iv) there is a gradual decrease in the exothermicity of the reaction and an increase of energy barriers as the diameter of the nanostructure of carbon is increased. By making use of the activation strain model, it is found that the deformation of the initial reactants in the rate-determining transition state is the key factor determining the chemoselectivity of the cycloadditions with benzyne.

First author: Smiles, DE, Use of Se-77 and Te-125 NMR Spectroscopy to Probe Covalency of the Actinide-Chalcogen Bonding in [Th(E-n){N(SiMe3)(2)}(3)](-) (E = Se, Te; n=1, 2) and Their Oxo-Uranium(VI) Congeners, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 814, (2016)
Abstract: Reaction of [Th(I)(NR2)(3)] (R = SiMe3) (1) with 1 equiv of either [K(18-crown-6)](2)[Se-4] or [K(18-crown-6)](2)[Te-2] affords the thorium dichalcogenides, [K(18-crown-6)][Th(eta(2)-E-2)(NR2)(3)] (E = Se, 2; E = Te, 3), respectively. Removal of one chalcogen atom via reaction with Et3P, or Et3P and Hg, affords the monoselenide and monotelluride complexes of thorium, [K(18-crown-6)][Th(E)(NR2)(3)] (E = Se, 4; E = Te, 5), respectively. Both 4 and 5 were characterized by X-ray crystallography and were found to feature the shortest known Th-Se and Th-Te bond distances. The electronic structure and nature of the actinide-chalcogen bonds were investigated with Se-77 and Te-125 NMR spectroscopy accompanied by detailed quantum-chemical analysis. We also recorded the Se-77 NMR shift for a U(VI) oxo-selenido complex, [U(O)(Se)(NR2)(3)](-) (delta(Se-77) = 4905 ppm), which features the highest frequency Se-77 NMR shift yet reported, and expands the known Se-77 chemical shift range for diamagnetic substances from similar to 3300 ppm to almost 6000 ppm. Both Se-77 and Te-125 NMR chemical shifts of given chalcogenide ligands were identified as quantitative measures of the An-E bond covalency within an isoelectronic series and supported significant 5f-orbital participation in actinide-ligand bonding for uranium(VI) complexes in contrast to those involving thorium(IV). Moreover, X-ray diffraction studies together with NMR spectroscopic data and density functional theory (DFT) calculations provide convincing evidence for the actinide-chalcogen multiple bonding in the title complexes. Larger An-E covalency is observed in the [U(O)(E)(NR2)(3)](-) series, which decreases as the chalcogen atom becomes heavier.

First author: Zhang, QN, Carbon Dioxide Activation by Scandium Atoms and Scandium Monoxide Molecules: Formation and Spectroscopic Characterization of ScCO3 and OCScCO3 in Solid Neon, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 425, (2016)
Abstract: The reactions of carbon dioxide with scandium monoxide molecules and scandium atoms are investigated using matrix isolation infrared spectroscopy in solid neon. The species formed are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. The results show;that the ground state ScO molecule reacts With carbon dioxide to form the carbonate complex ScCO3 spontaneously on annealing. The ground state Sc atom reacts with two carbon dioxide molecules to give the carbonate carbonyl complex OCScCO3 via the previously reported OScCO insertion intermediate on annealing. The observation of these spontaneous reactions is consistent with theoretical predictions that both the Sc + 2CO(2) -> OCScCO3 and ScO + CO2 -> ScCO3 reactions are thermodynamically exothermic and are kinetically facile requiring little or no activation energy.

First author: Molina, B, Thiolated Au-18 cluster: preferred Ag sites for doping, structures, and optical and chiroptical properties, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 1397, (2016)
Abstract: Recently, the X-ray determined structure of the thiolated Au-18 cluster has been reported. In this communication, we addressed a study of structures and chiroptical properties of thiolated Au-18 cluster doped with up to ten Ag atoms, which have been calculated by Time Dependent Density Functional Theory (TD-DFT). The number of Ag atoms was steadily varied and more stable isomers showed optical and Circular Dichroism(CD) spectra distinct from that found for the parent Au-18 cluster. Doping with more than four Ag atoms results in enhancement of the oscillator strength of the HOMO-LUMO peak and it is expected that this feature can be exploited for photoluminescence applications.

First author: Lage-Estebanez, I, Self-interaction error in DFT-based modelling of ionic liquids, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 2175, (2016)
Abstract: The modern computer simulations of potential green solvents of the future, involving the room temperature ionic liquids, heavily rely on density functional theory (DFT). In order to verify the appropriateness of the common DFT methods, we have investigated the effect of the self-interaction error (SIE) on the results of DFT calculations for 24 ionic pairs and 48 ionic associates. The magnitude of the SIE is up to 40 kJ mol(-1) depending on the anion choice. Most strongly the SIE influences the calculation results of ionic associates that contain halide anions. For these associates, the range-separated density functionals suppress the SIE; for other cases, the revPBE density functional with dispersion correction and triple-zeta Slater-type basis is suitable for computationally inexpensive and reasonably accurate DFT calculations.

First author: Koshevoy, EI, Electron Paramagnetic Resonance Study of the Interaction of Surface Titanium Species with AIR(3) Cocatalyst in Supported Ziegler-Natta Catalysts with a Low Titanium Content, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 1121, (2016)
Abstract: The electron paramagnetic resonance (EPR) method was used to investigate the formation of alkylated Ti(III) species in superactive titanium-magnesium catalysts with a low titanium content during their interaction with an organoaluminum activator (AlMe3), as well as the interaction of alkylated Ti(III) surface species with carbon monoxide. EPR data on the content of alkylated Ti(III) species in these catalysts agree well with the number of Ti-R bonds that are determined after the interaction of radioactive carbon monoxide ((CO)-C-14) with catalyst activated by triethylaluminum in the absence of monomer. Parameters of EPR spectra of the Ti(III) species having different structure and composition on the surface of titanium-magnesium catalysts were calculated by quantum-chemical simulations. The calculated g-values are consistent with the g-values observed in EPR spectra of the catalysts. Analysis of the literature data and results of our study made it possible to propose the parameters of EPR spectra characterizing the alkylated Ti(III) species that can serve as precursors of the active sites in supported Ziegler-Natta catalysts.

First author: Sadhu, B, Efficient Separation of Europium Over Americium Using Cucurbit-[5]-uril Supramolecule: A Relativistic DFT Based Investigation, INORGANIC CHEMISTRY, 55, 598, (2016)
Abstract: Achieving an efficient separation of chemically similar Am3+/Eu3+ pair in high level liquid waste treatment is crucial for managing the long-term nuclear waste disposal issues. The use of sophisticated supramolecules in a rigid framework could be the next step toward solving the long-standing problem. Here, we have investigated the possibility of separating Am3+/Eu3+ pair with cucurbit-[5]-uril (CB[5]), a macrocycle from the cucurbit-[n]-uril family, using relativistic density functional theory (DFT) based calculations. We have explored the structures, binding, and energetics of metalCB[5] complexation processes with and without the presence of counterions. Our study reveals an excellent selectivity of Eu3+ over Am3+ with CB[5] (ion exchange free energy, Delta Delta G(Am/Eu) > 10 kcal mol(1)). Both metals bind with the carbonyl portals via (5) coordination arrangement with the further involvement of three external water molecules. The presence of counterions, particularly nitrate, inside the hydrophobic cavity of CB[5], induces a cooperative cationanion binding, resulting in enhancement of metal binding at the host. The overall binding process is found to be entropy driven resembling the recent experimental observations (Rawat et al. Dalton Trans. 2015, 44, 42464258). The optimized structural parameters for Eu3+CB[5] complexes are found to be in excellent agreement with the available experimental information. To rationalize the computed selectivity trend, electronic structures are further scrutinized using energy decomposition analysis (EDA), quantum theory of atom in molecules (QTAIM), Mulliken population analysis (MPA), NalewajskiMrojek (NM) bond order, and molecular orbital analyses. Strong electrostatic iondipole interaction along with efficient charge transfer between CB[5] and Eu3+ outweighs the better degree of covalency between CB[5] and Am3+ leading to superior selectivity of Eu3+ over Am3+.

First author: Rodriguez, JI, A QTAIM topological analysis of the P3HT-PCBM dimer, CHEMICAL PHYSICS LETTERS, 644, 157, (2016)
Abstract: In order to cast some light onto the nature of the chemical bonding between a 8-unit oligomer of the poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) in the two stables isomers reported recently [I. Gutierrez-Gonzalez, B. Molina-Brito, A.W. Gotz, F.L. Castillo-Alvarado, J.I. Rodriguez, Chem. Phys. Lett. 612, 234 (2014)], we have performed a Bader’s quantum theory of atoms in molecules (QTAIM) analysis. According to QTAIM, no covalent bonds are formed between P3HT and PCBM, and hydrogen and stacking interactions account for about 90% and 10% of the total number of bonds between P3HT and PCBM, respectively.

First author: Pandey, KK, Theoretical insights into the nature of bonding in group 13-group 15 compounds [RE=E ‘ R] (E = B-Tl; E ‘ = N-Bi; R = Me, Ph, Ar): Bonding energy analysis, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1076, 23, (2016)
Abstract: Molecular geometry, electronic structure and bonding analysis of multiply bonded, monomeric group 13-group 15 compounds [RE-E’R] (E = B-TI; E’ = N-Bi; R = Me, Ph, Ar = C6H3-2,6-Ph-2) were investigated using BP86/TZ2P/ZORA level of theory. The optimized geometrical parameters are in excellent agreement with the experimental values. The Pauling and Mayer bond order of the optimized structures of [RE=E’R] shows that the E=E’ bonds in these compounds are essentially multiple bonds. The electronic structure of the studied compounds, which is obtained by NBO analysis, reveals that the E=E’ sigma-bonding orbitals consist of nearly sp hybridized orbital at group 13 element (E) while the heavier group 15 elements (E’) have >75% p-orbital contribution to the total atomic orbital contributions. The bending of E-E’-C bond angles have been discussed in terms of the percentage s character of group 15 elements along E=E’ and E’-C bonds and a second order Jahn-Teller distortion. The E=E’ pi-bonding orbitals are highly polarized toward the group 15 atom. The contributions of orbital interactions, Delta E-orb, to the E=E’ bonds are larger than the electrostatic interactions, Delta E-elstat indicating greater covalent characters of the E=E’ bonds than the ionic characters. In all studied compounds, the pi-bonding contributions to the total E=E’ bonds are smaller (19.5-37.6%) than the corresponding sigma-bonding contributions. The absolute values of the interaction energy, as well as bond dissociation energy decreases in the order N > P > As > Sb > Bi and B >Al >Ga >In >Tl.

First author: Mulder, JR, Substituent Effects on the Optical Properties of Naphthalenediimides: A Frontier Orbital Analysis Across the Periodic Table, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 304, (2016)
Abstract: A comprehensive theoretical treatment is presented for the electronic excitation spectra of ca. 50 different mono-, di-, and tetrasubstituted naphthalenediimides (NDI) using time-dependent density functional theory (TDDFT) at ZORA-CAM-B3LYP/TZ2P//ZORA-BP86/TZ2P with COSMO for simulating the effect of dichloromethane (DCM) solution. The substituents -XHn are from groups 14-17 and rows 2-5 of the periodic table. The lowest dipole-allowed singlet excitation (S-0-S-1) of the monosubstituted NDIs can be tuned from 3.39 eV for -F to 2.42 eV for -TeH, while the S-0-S-2 transition is less sensitive to substitution with energies ranging between 3.67 eV for -CH3 and 3.44 eV for -SbH2. In the case of NDIs with group-15 and -16 substituents, the optical transitions strongly depend on the extent to which -XHn is planar or pyramidal as well as on the possible formation of intramolecular hydrogen bonds. The accumulative effect of double and quadruple substitution leads in general to increasing bathochromic shifts, but the increased steric hindrance in tetrasubstituted NDIs can lead to deformations that diminish the effectiveness of the substituents. Detailed analyses of the Kohn-Sham orbital electronic structure in monosubstituted NDIs reveal the mesomeric destabilization of the HOMO as the primary cause of the bathochromic shift of the S-0-S-1 transition.

First author: de Almeida, KJ, Methane C-H bond activation by niobium oxides: Theoretical analyses of the bonding and reactivity properties of Nbo(m)(n+) (m=1, 2; n=0, 1, 2), JOURNAL OF ORGANOMETALLIC CHEMISTRY, 802, 49, (2016)
Abstract: The catalytic properties of NbOmn+ (m = 1, 2; n = 0, 1, 2) on the methane C-H bond activation were investigated using B3LYP and CCSD(T) calculations. The spin-orbit relativistic effects were evaluated by means of ZORA approximations. The main results indicate that in agreement with the previous experimental findings only the neutral NbO monoxide is kinetically and thermodynamically feasible via the oxidative addition, whereas the remaining oxides and dioxides show better theoretical predictions in the hydrogen abstraction pathways. In these reactions, a known mechanism described as “Oxidative Hydrogen Migration (OHM)” was found to be more stable for the neutral and singly charged niobium-oxo species, while competitive direct H abstraction (DHA) and OHM pathways were obtained for the doubly charged niobium oxides, with slightly preferential conditions observed in DHA. Overall, the increase of charge on the metal center and the presence of the oxo ligands favors the initial electrostatic interaction between niobium oxides and methane, decreasing the activation barrier heights in the H abstraction pathways due to the electron acceptor nature of oxo ligands. Among the investigated oxides, NbO2+ and NbO22+ show the best performances in the methane activation process, with activation barriers computed to be around 1.5-5.9 kcal mol(-1).

First author: Zanuy, D, Fmoc-RGDS based fibrils: atomistic details of their hierarchical assembly, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 1265, (2016)
Abstract: We describe the 3D supramolecular structure of Fmoc-RGDS fibrils, where Fmoc and RGDS refer to the hydrophobic N-(fluorenyl-9-methoxycarbonyl) group and the hydrophilic Arg-Gly-Asp-Ser peptide sequence, respectively. For this purpose, we performed atomistic all-atom molecular dynamics simulations of a wide variety of packing modes derived from both parallel and antiparallel beta-sheet configurations. The proposed model, which closely resembles the cross-beta core structure of amyloids, is stabilized by pi-pi stacking interactions between hydrophobic Fmoc groups. More specifically, in this organization, the Fmoc-groups of beta-strands belonging to the same beta-sheet form columns of pi-stacked aromatic rings arranged in a parallel fashion. Eight of such columns pack laterally forming a compact and dense hydrophobic core, in which two central columns are surrounded by three adjacent columns on each side. In addition to such Fmoc…Fmoc interactions, the hierarchical assembly of the constituent beta-strands involves a rich variety of intra-and inter-strand interactions. Accordingly, hydrogen bonding, salt bridges and pi-pi stacking interactions coexist in the highly ordered packing network proposed for the Fmoc-RGDS amphiphile. Quantum mechanical calculations, which have been performed to quantify the above referred interactions, confirm the decisive role played by the pi-pi stacking interactions between the rings of the Fmoc groups, even though both inter-strand and intra-strand hydrogen bonds and salt bridges also play a non-negligible role. Overall, these results provide a solid reference to complement the available experimental data, which are not precise enough to determine the fibril structure, and reconcile previous independent observations.

First author: van der Lit, J, Modeling the Self-Assembly of Organic Molecules in 2D Molecular Layers with Different Structures, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 318, (2016)
Abstract: If organic molecules are to be used as the active component in devices, self-assembly represents the most attractive route to control the geometric structure and therefore part of the device performance. High-resolution scanning tunneling microscopy measurement combined with density functional theory and Monte Carlo calculations are used to study the stability of self-assemblies of molecules with bonding motifs spanning (nearly) the entire range of intermolecular interaction strengths. Our atomistic model reproduces the experimentally observed crystal structures with sub-Angstrom precision in all cases. In addition, it is able to identify metastable structures through thermodynamic analysis.

First author: Alkan, F, Effect of Co-Ordination Chemistry and Oxidation State on the Pb-207 Magnetic-Shielding Tensor: A DFT/ZORA Investigation, JOURNAL OF PHYSICAL CHEMISTRY A, 120, 161, (2016)
Abstract: The magnetic shielding tensor of 207Pb is calculated for various solids exhibiting (1) a holodirected lead(II) center containing a stereochemically inactive lone pair, (2) a hemidirected lead(II) center with a stereochemically active lone-pair, or (3) a lead(IV) center. Tensors investigated at the scalar relativistic level are compared with those calculated with the full ZORA/spin-orbit Hamiltonian. The effect of using GGA density functionals is compared to the use of hybrid density functionals.

First author: Nicu, VP, Interplay of Exciton Coupling and Large-Amplitude Motions in the Vibrational Circular Dichroism Spectrum of Dehydroquinidine, CHEMISTRY-A EUROPEAN JOURNAL, 22, 704, (2016)
Abstract: A detailed analysis of the computed structure, energies, vibrational absorption (VA) and circular dichroism (VCD) spectra of 30 low-energy conformers of dehydroquinidine reveals the existence of families of pseudo-conformers, the structures of which differ mostly in the orientation of a single O-H bond. The pseudo-conformers in a family are separated by very small energy barriers (i.e., 1.0 kcal mol(-1) or smaller) and have very different VCD spectra. First, we demonstrate the unreliable character of the Boltzmann factors predicted with DFT. Then, we show that the large differences observed between the VCD spectra of the pseudo-conformers in a family are caused by large-amplitude motions involving the O-H bond, which trigger the appearance/disappearance of strong VCD exciton-coupling bands in the fingerprint region. This interplay between exciton coupling and large-amplitude-motion phenomena demonstrates that when dealing with flexible molecules with polar bonds, vibrational averaging of VCD spectra should not be neglected. In this regard, the dehydroquinidine molecule considered here is expected to be a typical example and not the exception to the rule.

First author: Eriksson, SK, Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed using photoelectron spectroscopy and DFT, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 252, (2016)
Abstract: The effects of alkoxy chain length in triarylamine based donor acceptor organic dyes are investigated with respect to the electronic and molecular surface structures on the performance of solar cells and the electron lifetime. The dyes were investigated when adsorbed on TiO2 in a configuration that can be used for dye sensitized solar cells (DSCs). Specifically, the two dyes D35 and D45 were compared using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The differences in solar cell characteristics when longer alkoxy chains are introduced in the dye donor unit are attributed to geometrical changes in dye packing while only minor differences were observed in the electronic structure. A higher dye load was observed for D45 on TiO2. However, D35 based solar cells result in higher photocurrent although the dye load is lower. This is explained by different geometrical structures of the dyes on the surface.

First author: Mudedla, SK, Interaction of nucleobases with silicon doped and defective silicon doped graphene and optical properties, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 295, (2016)
Abstract: The interaction of nucleobases (NBs) with the surface of silicon doped graphene (SiGr) and defective silicon doped graphene (dSiGr) has been studied using electronic structure methods. A systematic comparison of the calculated interaction energies (adsorption strength) of NBs with the surface of SiGr and dSiGr with those of pristine graphene (Gr) has also been made. The doping of graphene with silicon increases the adsorption strength of NBs. The introduction of defects in SiGr further enhances the strength of interaction with NBs. The appreciable stability of complexes (SiGr-NBs and dSiGr-NBs) arises due to the partial electrostatic and covalent (Si center dot center dot center dot O(N)) interaction in addition to it it stacking. The interaction energy increases with the size of graphene models. The strong interaction between dSiGr-NBs and concomitant charge transfer causes significant changes in the electronic structure of dSiGr in contrast to Gr and SiGr. Further, the calculated optical properties of all the model systems using time dependent density functional theory (TD-DFT) reveal that absorption spectra of SiGr and dSiGr undergo appreciable changes after adsorption of NBs. Thus, the significant variations in the HOMO-LUMO gap and absorption spectra of dSiGr after interaction with the NBs can be exploited for possible applications in the sensing of DNA nucleobases.

First author: Vargas-Caamal, A, How strong are the metallocene-metallocene interactions? Cases of ferrocene, ruthenocene, and osmocene, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 550, (2016)
Abstract: An exhaustive exploration of the potential energy surfaces of ferrocene, ruthenocene and osmocene dimers has been performed. Our computations involving dispersion show that only four different isomers are present in each metallocene dimer. The collective action of small interaction energies of dispersive nature leads to a dissociation energy of 7.5 kcal mol(-1) for the ferrocene dimer. Dispersion has strong effects on the geometrical parameters, reducing the M … M distances by almost 1 angstrom. Our results also reveal that inclusion of entropic factors modifies the relative stability of the complexes. The nature of bonding is examined using the energy decomposition analysis and the non-covalent interaction index. Both analyses indicate that dispersion is the major contributing factor in stabilizing a metallocene dimer.

First author: de Oteyza, DG, Decacyclene Trianhydride at Functional Interfaces: An Ideal Electron Acceptor Material for Organic Electronics, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 90, (2016)
Abstract: We report the interface energetics of decacy-clene trianhydride (DTA) monolayers on top of two distinct model surfaces, namely, Au(111) and Ag(111). On the latter, combined valence band photoemission and X-ray absorption measurements that access the occupied and unoccupied molecular orbitals, respectively, reveal that electron transfer from substrate to surface sets in. Density functional theory calculations confirm our experimental findings and provide an understanding not only of the photoemission and X-ray absorption spectral features of this promising organic semiconductor but also of the fingerprints associated with the interface charge transfer.

First author: Anand, M, Hydrogen Bond-Aromaticity Cooperativity in Self-Assembling 4-Pyridone Chains, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 59, (2016)
Abstract: Self-assembling building blocks like the 4-pyridone can exhibit extraordinary H-bond-aromaticity coupling effects. Computed dissected nucleus independent chemical shifts (NICS(1)(zz)), natural bond orbital (NBO) charges, and energy decomposition analyses (EDA) for a series of hydrogen (H-) bonded 4-pyridone chains (4-py)(n) (n = 2 to 8) reveal that H-bonding interactions can polarize the 4-pyridone exocyclic C=O bonds and increase 4n+2 pi-electron delocalization in the six-membered ring. The resulting H-bonded 4-pyridone units display enhanced pi-aromatic character (both magnetically and energetically) and their corresponding N-H center dot center dot center dot O=C interactions are strengthened. These p-electron polarization effects do not depend on the relative orientations (co-planar or perpendicular) of the neighboring 4-pyridone units, but increase with the number of H-bonded units.

First author: Petraglia, R, Beyond Static Structures: Putting Forth REMD as a Tool to Solve Problems in Computational Organic Chemistry, JOURNAL OF COMPUTATIONAL CHEMISTRY, 37, 83, (2016)
Abstract: Computational studies of organic systems are frequently limited to static pictures that closely align with textbook style presentations of reaction mechanisms and isomerization processes. Of course, in reality chemical systems are dynamic entities where a multitude of molecular conformations exists on incredibly complex potential energy surfaces (PES). Here, we borrow a computational technique originally conceived to be used in the context of biological simulations, together with empirical force fields, and apply it to organic chemical problems. Replica-exchange molecular dynamics (REMD) permits thorough exploration of the PES. We combined REMD with density functional tight binding (DFTB), thereby establishing the level of accuracy necessary to analyze small molecular systems. Through the study of four prototypical problems: isomer identification, reaction mechanisms, temperature-dependent rotational processes, and catalysis, we reveal new insights and chemistry that likely would be missed using static electronic structure computations. The REMD-DFTB methodology at the heart of this study is powered by i-PI, which efficiently handles the interface between the DFTB and REMD codes.

First author: Luo, YF, Exploring the Photodeactivation Pathways of Pt[ONCN] Complexes: A Theoretical Perspective, CHEMPHYSCHEM, 17, 69, (2016)
Abstract: In this article, the influence of the tert-butyl unit on the photodeactivation pathways of Pt[O boolean AND N boolean AND C boolean AND N] (O boolean AND N boolean AND C boolean AND N=2-(4-(3,5-di-tert-butylphenyl)-6-(3-(pyridin-2-l)phenyl) pyridin-2-yl)phenolate) is investigated by DFT/TDDFT calculations. To further explore the factors that determine the radiative processes, the transition dipole moments of the singlet excited states, spin-orbit coupling (SOC) matrix elements, and energy gaps between the lowest triplet excited states and singlet excited states are calculated. As demonstrated by the results, compared with Pt-3, Pt-1 and Pt-2 have larger SOC matrix elements between the lowest triplet excited states and singlet excited states, an indicator that they have faster radiative decay processes. In addition, the SOC matrix elements between the lowest triplet excited states and ground states are also computed to elucidate the temperature-independent non-radiative decay processes. Moreover, the temperature-dependent non-radiative decay mechanisms are also explored via the potential energy profiles.

First author: DiLabio, GA, NONCOVALENT INTERACTIONS IN DENSITY FUNCTIONAL THEORY, REVIEWS IN COMPUTATIONAL CHEMISTRY, VOL 29, 29, 1, (2016)
Abstract: In this article, the influence of the tert-butyl unit on the photodeactivation pathways of Pt[O boolean AND N boolean AND C boolean AND N] (O boolean AND N boolean AND C boolean AND N=2-(4-(3,5-di-tert-butylphenyl)-6-(3-(pyridin-2-l)phenyl) pyridin-2-yl)phenolate) is investigated by DFT/TDDFT calculations. To further explore the factors that determine the radiative processes, the transition dipole moments of the singlet excited states, spin-orbit coupling (SOC) matrix elements, and energy gaps between the lowest triplet excited states and singlet excited states are calculated. As demonstrated by the results, compared with Pt-3, Pt-1 and Pt-2 have larger SOC matrix elements between the lowest triplet excited states and singlet excited states, an indicator that they have faster radiative decay processes. In addition, the SOC matrix elements between the lowest triplet excited states and ground states are also computed to elucidate the temperature-independent non-radiative decay processes. Moreover, the temperature-dependent non-radiative decay mechanisms are also explored via the potential energy profiles.

First author: Gostynski, R, Electronic Influence of Different beta-Diketonato Ligands on the Electrochemical Behaviour of Tris(beta-Diketonato)M(III) Complexes, M = Cr, Mn and Fe, JOURNAL OF NANO RESEARCH, 44, 252, (2016)
Abstract: The reduction of the M-III/M-II metal couple of complexes [Cr(beta-diketonato)3], [Fe(beta-diketonato) 3] and [Mn(beta-diketonato)(3)] is reviewed and compared. The ease of reduction of the M-III/M-II couple of [M(beta-diketonato)(3) complexes increases according to the metal sequence [Cr(beta-diketonato) 3] < [Fe(beta-diketonato)3] < [Mn(beta-diketonato)(3)] (with the most positive reduction potential). Good linear relationships obtained between the reduction potential and different electronic parameters related to the beta-diketonato ligand on these [M-III (beta-diketonato)(3)] complexes, show that the ease of reduction of the M-III/M-II couple increases with decreasing acidic strength (pKa) of the respective beta-diketone ligands. It also increases with increasing total group electronegativity of the R and R’ groups on the respective beta-diketonato ligand (RCOCHCOR’)(-) of the [M(beta-diketonato)(3)] complexes, (chi(R) +chi(R)’), as well as with an increase in the total Hammett sigma meta constants (sigma(R) + sigma(R)’), and also with increasing value of the Lever ligand electronic parameter (E-L)of ligand (RCOCHCOR’)(-).

First author: Izakmehri, Z, Organic pollutant adsorption on pristine, defected and al-doped carbon nanotube: a dispersion corrected DFT study, BULGARIAN CHEMICAL COMMUNICATIONS, 48, 119, (2016)
Abstract: The effective enrichment and detection of organic pollutantsin the environment has been attracted many attentions because of the enormous human health concerns. Using dispersion-corrected density functional theory (DFT-D2), we studied the interactions between 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) and pristine, defected and Al-doped carbon nanotubes. The TCDD molecule physical adsorption a pure and defected CNTs with a binding energy of about 0.52 eV and -0.34 eV. The accuracy of our method was validated by hybrid B3LYP levels of theory and it was shown that there is worthy agreement between two respected methods. However, the binding energy rises to -0.85 eV when TCDD binds to Al-CNT. The increase in binding is due to charge transfer from the TCDD molecule to the Al-CNT. Furthermore, the obtained DOS spectra show that the electronic properties of Al-CNT change considerably by the adsorption of TCDD whereas no such variations are observed for the other considered CNTs. Consequently, the Al-CNT is a promising candidate for the TCDD sensing and detection. Our first-principles results present evidence for a rational benchmark for the applicability of the Al-CNT for TCDD adsorption and detection.

First author: Lara-Astiaso, M, Decoherence, control and attosecond probing of XUV-induced charge migration in biomolecules. A theoretical outlook, FARADAY DISCUSSIONS, 194, 41, (2016)
Abstract: The sudden ionization of a molecule by an attosecond pulse is followed by charge redistribution on a time scale from a few femtoseconds down to hundreds of attoseconds. This ultrafast redistribution is the result of the coherent superposition of electronic continua associated with the ionization thresholds that are reached by the broadband attosecond pulse. Thus, a correct theoretical description of the time evolution of the ensuing wave packet requires the knowledge of the actual ionization amplitudes associated with all open ionization channels, a real challenge for large and medium-size molecules. Recently, the first calculation of this kind has come to light, allowing for interpretation of ultrafast electron dynamics observed in attosecond pump-probe experiments performed on the amino acid phenylalanine [Calegari et al., Science 2014, 346, 336]. However, as in most previous theoretical works, the interpretation was based on various simplifying assumptions, namely, the ionized electron was not included in the description of the cation dynamics, the nuclei were fixed at their initial position during the hole migration process, and the effect of the IR probe pulse was ignored. Here we go a step further and discuss the consequences of including these effects in the photoionization of the glycine molecule. We show that (i) the ionized electron does not affect hole dynamics beyond the first femtosecond, and (ii) nuclear dynamics has only a significant effect after approximately 8 fs, but does not destroy the coherent motion of the electronic wave packet during at least few additional tens of fs. As a first step towards understanding the role of the probe pulse, we have considered an XUV probe pulse, instead of a strong IR one, and show that such an XUV probe does not introduce significant distortions in the pump-induced dynamics, suggesting that pump-probe strategies are suitable for imaging and manipulating charge migration in complex molecules. Furthermore, we show that hole dynamics can be changed by shaping the attosecond pump pulse, thus opening the door to the control of charge dynamics in biomolecules.

First author: Chen, LX, Imaging ultrafast excited state pathways in transition metal complexes by X-ray transient absorption and scattering using X-ray free electron laser source, FARADAY DISCUSSIONS, 194, 639, (2016)
Abstract: This report will describe our recent studies of transition metal complex structural dynamics on the fs and ps time scales using an X-ray free electron laser source, Linac Coherent Light Source (LCLS). Ultrafast XANES spectra at the Ni K-edge of nickel(II) tetramesitylporphyrin (NiTMP) were measured for optically excited states at a timescale from 100 fs to 50 ps, providing insight into its sub-ps electronic and structural relaxation processes. Importantly, a transient reduced state Ni(I) (pi, 3d(x2-y2)) electronic state is captured through the interpretation of a short-lived excited state absorption on the low-energy shoulder of the edge, which is aided by the computation of X-ray transitions for postulated excited electronic states. The observed and computed inner shell to valence orbital transition energies demonstrate and quantify the influence of the electronic configuration on specific metal orbital energies. A strong influence of the valence orbital occupation on the inner shell orbital energies indicates that one should not use the transition energy from 1s to other orbitals to draw conclusions about the d-orbital energies. For photocatalysis, a transient electronic configuration could influence d-orbital energies up to a few eV and any attempt to steer the reaction pathway should account for this to ensure that external energies can be used optimally in driving desirable processes. NiTMP structural evolution and the influence of the porphyrin macrocycle conformation on relaxation kinetics can be likewise inferred from this study.

First author: Gaggioli, CA, Dioxygen insertion into the gold(I)-hydride bond: spin orbit coupling effects in the spotlight for oxidative addition, CHEMICAL SCIENCE, 7, 7034, (2016)
Abstract: O-2 insertion into a Au(I)-H bond occurs through an oxidative addition/recombination mechanism, showing peculiar differences with respect to Pd(II)-H, for which O-2 insertion takes place through a hydrogen abstraction mechanism in the triplet potential energy surface with a pure spin transition state. We demonstrate that the spin-forbidden Au(I)- hydride O-2 insertion reaction can only be described accurately by inclusion of spin orbit coupling (SOC) effects. We further find that a new mechanism involving two O-2 molecules is also feasible, and this result, together with the unexpectedly high experimental entropic activation parameter, suggests the possibility that a third species could be involved in the rate determining step of the reaction. Finally, we show that the O-2 oxidative addition into a Au(I)- alkyl (CH3) bond also occurs but the following recombination process using O-2 is unfeasible and the metastable intermediate Au(III) species will revert to reactants, thus accounting for the experimental inertness of Au-alkyl complexes toward oxygen, as frequently observed in catalytic applications. We believe that this study can pave the way for further theoretical and experimental investigations in the field of Au(I)/Au(III) oxidation reactions, including ligand, additive and solvent effects.

First author: Zabardasti, A, A new approach on diminutive effects for non-covalent interactions: fused bicyclic hydrogen-bonded complexes of hypohalous acids with fluoromethanol, MOLECULAR PHYSICS, 114, 3341, (2016)
Abstract: The computational study of dimer and trimer complexes of fluoromethanol (CH2FOH) with one or two molecules of hypohalous acids (HOX; X = F, Cl or Br) was carried out at the MP2/aug-cc-pVDZ computational level. Also to show the reliability of these results, the binding distance and interaction energy have been compared with large basis set aug-cc-pVTZ level for some systems. The 1:1 ratio gives two different hexagonal and heptagonal ring complexes and the 1:2 ratio of CH2FOH/HOX leads to fused bicyclic hydrogen-bonded trimer adducts constructed from hexagonal and heptagonal rings. The results show diminutive effects in the range of 0.36-0.78 kcal/mol for the trimer bicyclic systems. Redshifts with bond elongations were observed for H-O and C-F bonds, while blueshifts along with bond contractions were seen for the C-H and the X-O bonds. The CH2FOH/HOX complexes were analysed using the Quantum Theory of Atoms in Molecules (QTAIM) and natural bond orbital methodologies.

First author: Gowda, V, DFT calculations in the assignment of solid-state NMR and crystal structure elucidation of a lanthanum(III) complex with dithiocarbamate and phenanthroline, DALTON TRANSACTIONS, 45, 19473, (2016)
Abstract: The molecular, crystal, and electronic structures as well as spectroscopic properties of a mononuclear heteroleptic lanthanum(III) complex with diethyldithiocarbamate and 1,10-phenanthroline ligands (3 : 1) were studied by solid-state C-13 and N-15 cross-polarisation (CP) magic-angle-spinning (MAS) NMR, X-ray diffraction (XRD), and first principles density functional theory (DFT) calculations. A substantially different powder XRD pattern and C-13 and N-15 CP-MAS NMR spectra indicated that the title compound is not isostructural to the previously reported analogous rare earth complexes with the space group P2(1)/n. Both C-13 and N-15 CP-MAS NMR revealed the presence of six structurally different dithiocarbamate groups in the asymmetric unit cell, implying a non-centrosymmetric packing arrangement of molecules. This was supported by single-crystal X-ray crystallography showing that the title compound crystallised in the triclinic space group P1. In addition, the crystal structure also revealed that one of the dithiocarbamate ligands has a conformational disorder. NMR chemical shift calculations employing the periodic gauge including projector augmented wave (GIPAW) approach supported the assignment of the experimental C-13 and N-15 NMR spectra. However, the best correspondences were obtained with the structure where the atomic positions in the X-ray unit cell were optimised at the DFT level. The roles of the scalar and spin-orbit relativistic effects on NMR shielding were investigated using the zeroth-order regular approximation (ZORA) method with the outcome that already the scalar relativistic level qualitatively reproduces the experimental chemical shifts. The electronic properties of the complex were evaluated based on the results of the natural bond orbital (NBO) and topology of the electron density analyses. Overall, we apply a multidisciplinary approach acquiring comprehensive information about the solid-state structure and the metal-ligand bonding of the heteroleptic lanthanum complex.

First author: Kelly, CHW, Choosing the right precursor for thermal decomposition solution-phase synthesis of iron nanoparticles: tunable dissociation energies of ferrocene derivatives, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 32448, (2016)
Abstract: Organometallic coordination compounds in general and metallocenes in particular are convenient precursors for the synthesis of metal nanoparticles through thermal decomposition. The strength of the interaction between the metal ion and its ligands determines the conditions under which decomposition occurs, most importantly the range of temperatures and pressures at which a given compound is useful as a precursor. We show that a comprehensive analysis of all individual contributions to the ligand metal interactions that establishes the nature of the interaction can be used to select compounds that are tuned to a specific dissociation energy with advantageous properties under experimental conditions. To this end, we apply the Morokuma-Ziegler-Energy Decomposition Analysis (MZ-EDA) to a series of ferrocene analogues using high-level density functional theory (DFT). We find that asymmetrically substituted ferrocene derivatives are unlikely to be useful as precursors because of the large energy required to remove the second cyclopentadienyl-derivative from the central iron atom. However, we are able to establish that symmetrically substituted chloroferrocenes exhibit a wide range of relatively low bond dissociation energies for both dissociation steps and are hence good candidates for the synthesis of highly mono-disperse iron nanoparticles.

First author: Niu, XH, Revealing the underlying absorption and emission mechanism of nitrogen doped graphene quantum dots, NANOSCALE, 8, 19376, (2016)
Abstract: Nitrogen-doped graphene quantum dots (N-GQDs) hold promising application in electronics and optoelectronics because of their excellent photo-stability, tunable photoluminescence and high quantum yield. However, the absorption and emission mechanisms have been debated for years. Here, by employing time-dependent density functional theory, we demonstrate that the different N-doping types and positions give rise to different absorption and emission behaviors, which successfully addresses the inconsistency observed in different experiments. Specifically, center doping creates mid-states, rendering non-fluorescence, while edge N-doping modulates the energy levels of excited states and increases the radiation transition probability, thus enhancing fluorescence strength. More importantly, the even hybridization of frontier orbitals between edge N atoms and GQDs leads to a blue-shift of both absorption and emission spectra, while the uneven hybridization of frontier orbitals induces a red-shift. Solvent effects on N-GQDs are further explored by the conductor-like screening model and it is found that strong polarity of the solvent can cause a red-shift and enhance the intensity of both absorption and emission spectra.

First author: Valdez, CE, Predictive methods for computational metalloenzyme redesign – a test case with carboxypeptidase A, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 31744, (2016)
Abstract: Computational metalloenzyme design is a multi-scale problem. It requires treating the metal coordination quantum mechanically, extensive sampling of the protein backbone, and additionally accounting for the polarization of the active site by both the metal cation and the surrounding protein (a phenomenon called electrostatic preorganization). We bring together a combination of theoretical methods that jointly offer these desired qualities: QM/DMD for mixed quantum-classical dynamic sampling, quantum theory of atoms in molecules (QTAIM) for the assessment of electrostatic preorganization, and Density Functional Theory (DFT) for mechanistic studies. Within this suite of principally different methods, there are both complementarity of capabilities and cross-validation. Using these methods, predictions can be made regarding the relative activities of related enzymes, as we show on the native Zn2+-dependent carboxypeptidase A (CPA), and its mutant proteins, which are hypothesized to hydrolyze modified substrates. For the native CPA, we replicated the catalytic mechanism and the rate in close agreement with the experiment, giving validity to the QM/DMD predicted structure, the DFT mechanism, and the QTAIM assessment of catalytic activity. For most sequences of the modified substrate and tried CPA mutants, substantially worsened activity is predicted. However, for the substrate mutant that contains Asp instead of Phe at the C-terminus, one CPA mutant exhibits a reasonable activity, as predicted across the theoretical methods. CPA is a well-studied system, and here it serves as a testing ground for the offered methods.

First author: Cheng, ZP, The redox mechanism of Np-VI with hydrazine: a DFT study, RSC ADVANCES, 6, 109045, (2016)
Abstract: Valence state control and adjustment of neptunium in spent fuel reprocessing is very important for improving the separation efficiency of U/Np and Np/Pu. Hydrazine and its derivatives have been experimentally demonstrated to be effective in the reduction of Np-VI to Np-V. In this work, hydrazine was used as a representative reductant and the reduction mechanisms of Np-VI induced by hydrazine were investigated using density functional theory (DFT) calculations. Three reaction pathways were taken into account and characterized by gradually transferring a hydrogen atom from N2H4 to the “yl”-oxygen of [(NpO2)-O-VI(H2O)(5)](2+) followed by the valence state adjustment from Np-VI to Np-V. The calculated results of the potential energy profiles (PEPs) revealed that Pathway I should be the most likely to occur as the process of forming (N2H3)-N-center dot is considered to be the rate-determining step with the highest energy barrier of 32.02 kcal mol(-1), which is in favor of the experimental results. Pathway II hardly occurs and Pathway III probably occurs. The bonding evolution, along with the reaction pathways, was explored through natural bond orbitals (NBOs), quantum theory of atoms-in-molecules (QTAIM) and electron localization function (ELF) analyses. This work can shed light on the understanding of redox mechanisms of Np-VI with N2H4 and its derivatives and help further attempts to design more efficient reductants for the separation of U/Np and Np/Pu in spent nuclear fuel reprocessing in the near future.

First author: Luo, YF, A cyclometalated ((CC)-C-boolean AND*) platinum(II) NHC complex decorated via different carboranes to tune the photodeactivation mechanism: a theoretical investigation, RSC ADVANCES, 6, 113513, (2016)
Abstract: Unveiling the photodeactivation mechanisms of transition metal complexes is crucial for designing high-efficiency phosphorescent materials. Herein, the photodeactivation mechanisms of cyclometalated ((CC)-C-boolean AND*) platinum(II) N-heterocyclic carbene (NHC) complexes modified by carboranes were systematic study with the help of the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). In order to illustrate the photodeactivation mechanisms, three vital photodeactivation processes, namely radiative decay process, temperature-independent nonradiative decay process and thermally activated nonradiative photodeactivation process, were taken into account. On the basis of calculated results, the emission wavelengths of the cyclometalated ((CC)-C-boolean AND*) platinum(II) N-heterocyclic carbene (NHC) complex can be effectively tuned via the carborane-functionalized ligand structures. Meanwhile, compared with the original (NHC) Pt(II)(acac) complex, the radiative decay processes can be facilitated and the nonradiative decay processes can be managed via attaching distinct carboranes to the main ligand of the (NHC) Pt(II)(acac) complex, indicating that this is a feasible strategy for obtaining high-performance phosphorescence emitters.

First author: Tang, XQ, Theoretical investigations of the small molecular acceptor materials based on oligothiophene – naphthalene diimide in organic solar cells, RSC ADVANCES, 6, 102159, (2016)
Abstract: A series of novel acceptor-donor-acceptor-donor-acceptor (A(2)-D-A(1)-D-A(2)) structured acceptor oligomers with naphthalene diimide (NDI) as centre and acceptor unit (A(1)), oligothiophenes (T = 1, 2, 3, 4) as pi-bridges (D), and 2-(1,1-dicyanomethylene)rhodanine (DCRD) as terminal groups (A(2)) have been investigated using quantum chemistry and Marcus theory in this research. Compared with NDI-2T(1)Me-NDI-2T(4)Me, the NDI-2T(1)DCRD-NDI-2T(4)DCRD exhibit stronger and wider absorption peaks because of the increase of the electron withdrawing ability of the electron deficient units. In particular for the NDI-2T(3)DCRD, the electron mobility (mu(e) = 5.71 x 10(-3) cm(2) V-1 S-1) was accurately predicted quantitatively using first principle simulation. The blend of poly(3-hexylthiophene) with NDI-2T(3)DCRD as an active layer exhibits obviously strong and wide light absorption, which form a perfectly complementary absorption. The results indicate that the incorporation of DCRD as acceptor units into D-A-D type oligomers has been proven to create promising candidates for high efficiency acceptor materials for organic solar cells (OSCs). Overall, this research may provide a theoretical guidance for designing small molecular acceptors for OSC applications.

First author: Wang, X, DFT/TD-DFT study on the spectroscopic properties of zinc(II), nickel(II), and palladium(II) metal complexes with a thiourea derivative, JOURNAL OF THE SERBIAN CHEMICAL SOCIETY, 81, 1263, (2016)
Abstract: The geometries, electronic structures, and spectral properties of three metal complexes Zn(C10H12N3OS)(2) (1), Ni(C10H12N3OS)(2) (2) and Pd(C10H12N3OS)(2) (3) with N-2-pyridinylmorpholine-4-carbothioamide as a ligand were investigated by means of the DFT (density functional theory) and TD-DFT (time-dependent density functional theory) methods. Complex 1 has a distorted tetrahedral geometry, while complexes 2 and 3 present a distorted square-planar coordination environment. In the simulated range, the spectrum of complex 1 has five obvious absorption peaks and one of them has the strongest intensity. The latter two complexes have one more absorption peak and a shoulder with similar intensity. Moreover, the strongest peak of complexes 2 and 3 is blue-shifted as compared with that of complex 1.

First author: Elder, PJW, Te-125 NMR provides evidence of autoassociation of organo-ditellurides in solution, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 30740, (2016)
Abstract: The frequency of the resonance of Te-125 of two organo-ditellurides, R-Te-Te-R (R=4-CH3C6H4 and 2-(CH3)(2)NCH2C6H4), in solution undergoes a low-field shift as the concentration of the sample increases. In sharp contrast, the resonance of a sterically hindered ditelluride (R = (C6H5(CH3)(2)Si)(3)C) and telluric acid display the opposite effect. While the negative concentration coefficients can be explained by the change in magnetic susceptibility, the positive coefficients are consistent with autoassociation of the molecules through tellurium-centred supramolecular interactions. Although the corresponding equilibrium constants are small, the process is shown to be exothermic. However, the influence of autoassociation is much smaller than the effects of solvent polarity and the conformation of the ditelluride bond.

First author: Safin, DA, An intermolecular pyrene excimer in the pyrene-labeled N-thiophosphorylated thiourea and its nickel(II) complex, INORGANIC CHEMISTRY FRONTIERS, 3, 1419, (2016)
Abstract: A new N-thiophosphorylated thiourea (1-pyrene) NHC(S) NHP(S)(OiPr)(2) (HL) has been synthesized. The molecular structure of HL was elucidated by X-ray diffraction revealing a linear intramolecular hydrogen bond. Additionally, its crystal structure is stabilized by two intermolecular hydrogen bonds, which in turn leads to a centrosymmetric R-2(2) (8) dimer formation. These dimers are packed into polymeric chains through pi center dot center dot center dot pi stacking interactions between the pyrene rings. The reaction of the deprotonated HL with Ni-II leads to the Ni-II complex ([NiL2]). The crystal structure of [NiL2] exhibits a centrosymmetric homoleptic structure, where the Ni-II ion is coordinated in a square-planar fashion with the ligands arranged in a trans-N2S2 configuration. The pyreneNH protons in [NiL2] are involved in intramolecular hydrogen bonds of the pyreneN-H center dot center dot center dot S=P type. Molecules of [NiL2] form pi center dot center dot center dot pi stacking interactions between the pyrene rings, yielding 1D polymeric chains similar to those observed in the structure of HL. These pi center dot center dot center dot pi stacked 1D polymeric chains are linked to each other through C-H center dot center dot center dot S and anagostic C-H center dot center dot center dot Ni interactions, yielding 2D sheets. Hirshfeld surface analysis showed that the structures of both HL and [NiL2] are highly dominated by H center dot center dot center dot H, H center dot center dot center dot C, H center dot center dot center dot S and C center dot center dot center dot C contacts and also characterized by H center dot center dot center dot O and H center dot center dot center dot N contacts. The molecular surfaces of HL and [NiL2] also contain O center dot center dot center dot S and H center dot center dot center dot Ni contacts, respectively. Both HL and [NiL2] were found to be emissive in CH2Cl2 solution, which is due to the concentration dependent emission of the pyrene monomer and excimer. It was established that the latter fluorescence is due to the intermolecular excimer formation. The DFT calculations allowed us to confirm the aggregation ability of the synthesized species in solution through the numerous non-covalent interactions C-H center dot center dot center dot S, C-H center dot center dot center dot Ni and C-H center dot center dot center dot pi, which, in turn, might be responsible for the concentration dependent photophysical properties.

First author: Zheng, XJ, Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycle, DALTON TRANSACTIONS, 45, 15910, (2016)
Abstract: The computationally-and experimentally-determined molecular structures of a bis-uranyl(VI) complex of an expanded Schiff-base polypyrrolic macrocycle [(UO2)(2)(L)] are in close agreement only if the pyridine in the fifth equatorial donor site on the uranium is included in the calculations. The relativistic density functional theory (DFT) calculations presented here are augmented from those on previously reported simpler frameworks, and demonstrate that other augmentations, such as the incorporation of condensed-phase media and the changes in the peripheral groups of the ligand, have only a slight effect. Synthetic routes to pure samples of the bis-and mono-uranyl(VI) complexes have been developed using pyridine and arene solvents, respectively, allowing the experimental determination of the molecular structures by X-ray single crystal diffraction; these agree well with the calculated structures. A comprehensive set of calculations has been performed on a series of actinyl AnO(2)(n+) complexes of this macrocyclic ligand. These include both bis-and mono-actinyl adducts for the metals U, Np and Pu, and formal oxidation states VI and V. The reduction potentials of the complexes for U, Np, and Pu, incorporating both solvation and spin-orbit coupling considerations, show the order Np > Pu > U. The agreement between experimental and computed data for U is excellent, suggesting that at this level of computation predictions made about the significantly more radiotoxic Np and Pu molecules should be accurate. A particularly unusual structure of the mononuclear plutonyl(V) complex was predicted by quantum chemical calculations, in which a twist in the macrocycle allows one of the two endo-oxo groups to form a hydrogen bond to one pyrrole group of the opposite side of the macrocycle, in accordance with this member of the set containing the most Lewis basic oxo groups.

First author: Bao, Z, Theoretical investigation of low-valent uranium and transuranium complexes of a flexible small-cavity macrocycle: structural, formation reaction and redox properties, DALTON TRANSACTIONS, 45, 15970, (2016)
Abstract: The flexible small-cavity macrocycle, trans-calix[2] benzene[2] pyrrolide (H2L), has been found experimentally to complexate low-valent U-III and U-IV with binding pockets (BP) of bis(arene) (Ar) and bis(pyrrolide) (Pl), respectively. This switchable coordination of the uranium center has been explored using relativistic density functional theory (DFT) in this work. Systematic calculations of [(BP-L)An(m)(eta-H) nBH4-n)](z+) (BP = Ar and Pl; An = U, Np and Pu; m = III and IV; n = 2 and 3; and z = 0 and 1), labeled as BP-An(m)-nH, were carried out. Energetics and geometrical/electronic-structure analyses reveal that the size matching between actinide ions and the binding pocket plays a significant role in determining the energetic ordering of isomers. The relatively large-size U-III and Np-III ions are selectively preferred by the large bis(arene) pocket, yielding the most stable isomer of Ar-An-2H; simultaneously formed delta(An-Ar-2) bonding helps stabilizing the system. In contrast, the small-size Pu-III and An(IV) are held by the smaller bis( pyrrolide) to show the energetically favored Pl-An-3H isomer. This size argument is further supported by calculations on the related Th and Pa compounds. The formation reactions of BP-An(m)-nH demonstrate an endothermic process when using the H2L ligand reactant. Applying a more basic alkali ligand (A(2)L; A = Li, Na and K) as the reactant significantly reduces the reaction energy and presents thermodynamic possibility to prepare the low-valent actinide complexes. This is in agreement with the experimental synthesis where K2L was utilized. The redox potentials (E-0) from tri-to tetravalent actinides were calculated while including both solvation and spin-orbit coupling effects. The highly reductive nature of the U-III complex was manifested by the calculated E-0 of over 1.1 V.

First author: Mirzaeva, IV, Theoretical study of host-guest interactions in complexes of cucurbit[7]uril with protonated amino acids, SUPRAMOLECULAR CHEMISTRY, 28, 857, (2016)
Abstract: The theoretical study of host-guest interactions in complexes of protonated amino acids (AA=Val, Thr, Ser, Asn) and macrocyclic cavitand cucurbit[7]uril with the focus on characterisation of non-covalent interactions between the host and the guest molecules have been carried out. Host-guest interactions have been described by means of R. Bader’s Atoms in Molecules’ theory and Energy Decomposition Analysis (EDA) as it is implemented in ADF program suit. EDA shows that energies of inclusion and exclusion complexes are very close. The optimised geometries for exclusion complexes of CB[7] with protonated AA are slightly more stable than their inclusion counterparts.

First author: Safin, DA, Polymorphism driven optical properties of an anil dye, CRYSTENGCOMM, 18, 7249, (2016)
Abstract: Red crystals of N, N’-bis.3-methoxysalicylidene)-1,5-diiminonaphthalene were obtained after Schiff base condensation in ethanol. Recrystallization from acetone afforded yellow crystals, a process which is reversible and reproducible. Single crystal X-ray diffraction evidences two polymorphs differing in their space group and dihedral angle between aromatic moieties. DFT periodic calculations further confirmed the existence of two minima on the potential energy surface corresponding to red and yellow crystals. The red polymorph irreversibly (monotropically) transforms at 165-190 degrees C into the yellow one with a 3% increase of the unit cell volume, as shown by X-ray powder diffraction and periodic DFT calculations. Both polymorphs are thermochromic but only the red one displays photochromism upon irradiation at lambda = 365 nm, which is reversible and exhibits a relatively slow thermal relaxation. A temperature induced cis/trans-keto equilibrium is for the first time identified for an N-salicylidene aniline derivative. Static DFT molecular and periodic calculations as well as ab initio Born-Oppenheimer dynamics simulations were performed to characterize the stability of both polymorphs and to determine the relative populations of the enol/cis-keto/trans-keto isomers at various temperatures.

First author: Pan, S, Noble gas bound beryllium chromate and beryllium hydrogen phosphate: a comparison with noble gas bound beryllium oxide, RSC ADVANCES, 6, 92786, (2016)
Abstract: A comparative study is made on the noble gas (Ng) binding ability of beryllium hydrogen phosphate (BeHPO4), beryllium chromate (BeCrO4), and beryllium oxide (BeO) via density functional theory and ab initio calculations. BeO serves as a prototype example of a Be based Lewis acid with remarkable Ng binding capability. Although NgBeHPO(4) and NgBeCrO(4) have lower Ng-Be bond dissociation energy by 1.4-4.6 and 2.4-6.3 kcal mol(-1), respectively, than NgBeO, the corresponding free energy changes at the standard state show that Ar-Rn analogues may be viable even at an ambient condition. The nature of bonding in all these Ng bound complexes is exactly the same, being exclusively a donor-acceptor type of interaction as indicated by the natural bond orbital, electron density and energy decomposition analyses (EDA) in conjunction with natural orbitals for chemical valence calculations. The negative local energy density values at the bond critical points of Ng-Be bonds involving Kr-Rn imply the covalent nature of the bonding which is further supported by the dominant orbital contribution (80-88%) towards the total stabilization as obtained from the EDA. In fact, the variation in the orbital term is responsible for the observed trend of their Ng binding ability in changing either the Ng atoms or the Be system. Further, Ng -> BeY (Y = HPO4, CrO4, O) sigma-donation is the key contributor (70-82%) of the orbital term, whereas Ng <- BeY pi-back donation is responsible only for 15-21% of the total orbital interaction.

First author: Gil, A, A theoretical study of methylation and CH/pi interactions in DNA intercalation: methylated 1,10-phenanthroline in adenine-thymine base pairs, RSC ADVANCES, 6, 85891, (2016)
Abstract: The study of CH/pi interactions in DNA model intercalated systems has been carried out with the popular intercalator 1,10-phenanthroline (phen) and several methyl derivatives, changing number and position, and the adenine-thymine tetramers (AT/TA) where thymine also contains a methyl group. Density Functional Theory (DFT) was used for the calculations, by means of improved functionals including dispersion effects. Our results given by the AIM analysis confirm the existence of these CH/pi interactions and the energy decomposition analysis shows a perfect direct correlation between the number of CH/pi interactions found and their Delta E-int. Moreover, despite the important role of dispersion energy in the systems with more methyl groups, it is not yet enough to compensate the Pauli repulsion term, Delta E-Pauli, and the orbital contribution, Delta E-orb, and the electrostatic contribution, Delta E-elstat, become crucial for the stabilization of the structures in the intercalation process.

First author: Pires, MD, Experimental and theoretical study on the reactivity of maghemite doped with Cu2+ in oxidation reactions: structural and thermodynamic properties towards a Fenton catalyst, RSC ADVANCES, 6, 80830, (2016)
Abstract: In this work, a polymeric method was used to prepare undoped and Cu-doped iron oxide catalysts for the H2O2 decomposition reaction. These catalysts were characterized by powder X-ray diffractometry (XRD), scanning electronic microscopy (SEM) coupled to an energy dispersive X-ray spectrometer (EDX), and H-2-Temperature Programmed Reduction (H-2-TPR). The SEM images show an inhomogeneous particle cluster in both samples, tending to decrease in size with Cu-doping. EDX mapping reveals a good dispersion of Cu2+ in the iron oxide. In addition, Rietveld refinement of the XRD patterns reveals that the samples are constituted of hematite and maghemite, but only maghemite has octahedral Fe3+ ions isomorphically replaced by 2 wt% Cu2+. Cu-doping produces an active catalyst for H2O2 decomposition. Tests using phenol show the strong inhibition of H2O2 decomposition by the Cu-doped catalysts, suggesting that H2O2 may be decomposed via a radical mechanism. Furthermore, phenol degradation kinetics confirm that the doping of maghemite with Cu2+ brings about a significant improvement in catalytic activity. Theoretical calculations reveal that Cu-doping in maghemite produces low electronic density sites, favoring the interactions between the surface oxygens of H2O2 and Cu2+, thus improving the catalytic activity. This strategy can be extended to other materials to design active heterogeneous catalysts for environmental purposes.

First author: Weinhold, F, What is NBO analysis and how is it useful?, INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY, 35, 399, (2016)
Abstract: Natural bond orbital (NBO) analysis is one of many available options for ‘translating’ computational solutions of Schrodinger’s wave equation into the familiar language of chemical bonding concepts. In this Review, we first address the title questions by describing characteristic features that distinguish NBO from alternative analysis methodologies (e.g. of QTAIM or EDA type) and answering criticisms that have been raised in specific chemical applications. We then address the general ‘usefulness’ of NBO analysis in the context of widely accepted philosophical criteria, including (i) broad consistency, both internally and with respect to known experimental data, (ii) multi-faceted predictive capacity, including numerical model predictions of specific properties, general correlative and statistical regression relationships, and ‘risky’ falsifiable predictions of previously unknown chemical phenomena, and (iii) general pedagogical value, promoting organisation, unification, and orderly rationalisation of chemical knowledge. Specific chemical topics chosen for discussion include controversial H center dot center dot center dot H ‘bond lines’ in bay-type hydrocarbon species; carbene ligation of coinage metals; resonance-type bonding of noble gas hydrides; NBO descriptors in Hammett-type quantitative structure-activity relationships; nature of conventional and ‘anti-electrostatic’ hydrogen bonding interactions; multi-centre bonding in ‘aromatic’ Al-4((2-)), Lewis-like hybridisation picture of non-VSEPR geometry and high-order multiple bonding in transition metal species; resonance origin of the ’18e rule’; and localised (symmetry-independent) prediction of Jahn-Teller effects in free radical chemistry. We conclude with hints of some directions for future extensions of NBO methods.

First author: Xu, YY, Theoretical study and design of cyclometalated platinum complexes bearing innovatively a highly-rigid terdentate ligand with carboranyl as a chelating unit, RSC ADVANCES, 6, 78241, (2016)
Abstract: Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were employed to explore the electronic structures and phosphorescence properties of synthesized terdentate Pt(II) complexes bearing highly-rigid 3,6-bis(p-anizolyl)-2-carboranyl-pyridine as a cyclometalated ligand and triphenylphosphine (1) or t-butylisonitrile (2) as ancillary ligand. To understand the marked difference in phosphorescence quantum efficiency between 1 and 2, the relaxation dynamics of excited states were elucidated in detail. Aiming to formulate the radiative relaxation, the zero-field splitting (ZFS) and the radiative decay rate constant (k(r)) were calculated by SOC-perturbed TDDFT (pSOC-TDDFT). Meanwhile, the temperature-independent non-radiative relaxation was analyzed by calculating the Huang-Rhys factor (S), the SOC interaction between the emitting state and the ground state. While the temperature-dependent non-radiative decay mechanism was studied by depicting the thermal deactivation process via a metal-centered excited (MC)-M-3 state. Based on the results, 1 and 2 show a few differences in their temperature-independent non-radiative rates. However, the activation barrier for the population of non-emissive 3MC is greatly raised for complex 2. Therefore, the temperature-dependent non-radiative decay behavior of 2 is considerably suppressed, which ultimately leads to a substantially enhanced phosphorescence quantum efficiency for 2. To further tune the emission wavelength towards blue, four new complexes 3-6 were theoretically designed by modifying the terdentate ligand with azole groups based on the parent complex 2. As a result, pyrazole modified complex 4 stands out with enhanced deep-blue phosphorescence located at 434 nm.

First author: Saha, R, Noble gas supported B-3(+) cluster: formation of strong covalent noble gas-boron bonds, RSC ADVANCES, 6, 78611, (2016)
Abstract: The stability of noble gas (Ng) bound B-3(+) clusters is assessed via an in silico study, highlighting their structure and the nature of the Ng-B bonds. Ar to Rn atoms are found to form exceptionally strong bonds with B-3(+) having each Ng-B bond dissociation energy in the range of 15.1-34.8 kcal mol(-1) in B(3)Ng(3)(+) complexes with a gradual increase in moving from Ar to Rn. The computed thermochemical parameters like enthalpy and free energy changes for the Ng dissociation processes from B(3)Ng(3)(+) also support the stability of Ar to Rn analogues for which the corresponding dissociation processes are endergonic in nature even at room temperature. The covalent nature of the Ng-B bonds is indicated by the localized natural Ng-B bond orbitals and high Wiberg bond indices (0.57-0.78) for Ng-B bonds. Electron density analysis also supports the covalency of these Ng-B bonds where the electron density is accumulated in between Ng and B centres. The orbital interaction energy is the main contributor (ca. 63.0-64.4%) of the total attraction energy in Ng-B bonds. Furthermore, the Ng-B bonding can be explained in terms of a donor-acceptor model where the Ng (HOMO) -> B(3)N(g)2(+) (LUMO) sigma-donation has the major contribution.

First author: Wodrich, MD, Accessing and predicting the kinetic profiles of homogeneous catalysts from volcano plots, CHEMICAL SCIENCE, 7, 5723, (2016)
Abstract: Volcano plots are frequently used as aids in the search for new heterogeneous and electrochemical catalysts. These tools successfully predict catalytic processes based solely on thermodynamic descriptions, which also capably describe many aspects of the catalytic cycles of homogeneous species. However, homogeneous catalysts also frequently depend upon the kinetic influences brought about by steric interactions to promote or prevent specific chemical reactions. Here, a prototypical transformation facilitated by a homogeneous catalysis, the hydroformylation of an olefin using CO and H-2, is examined to establish the viability of creating kinetic volcano plots and to determine their ability to ascertain the influences steric bulk plays on catalytic cycle energetics. Similar to their thermodynamic counterparts, kinetic volcanoes successfully reproduce many experimentally known facets of the hydroformylation reaction. In contrast to thermodynamic volcanoes, kinetic volcanoes emphasize changes in the height of the different activation barriers brought about by steric interactions. This crucial information, however, comes with considerable computational cost, since the transition states of catalysts bearing large bulky ligands must be identified and characterized. To overcome this drawback, a procedure is proposed that relates a simple steric parameter, the Tolman cone angle, with the descriptors used to create the kinetic volcano plots. In this way, the activation barriers of bulky catalysts can be estimated without requiring expensive transition state computations. These newly derived structure-activity relationship volcano plots represent useful tools for identifying new homogeneous catalysts.

First author: Li, WL, Theoretical studies on the bonding and electron structures of a [Au3Sb6](3-) complex and its oligomers, DALTON TRANSACTIONS, 45, 11657, (2016)
Abstract: Recently an all-metal aromatic sandwich compound of a [Sb3Au3Sb3](3-) ion has been synthesized and characterized experimentally, which indicates that there might exist a variety of stable all-metal sandwich complexes. The intralayer and interlayer chemical bonding interaction in this system plays significant roles in their stability, chemical properties and functionalities. Here we report a systematic theoretical study on the geometries, electronic structures, and chemical bonding of the [Sb3Au3Sb3](3-) ion and its congeners of [X3Au3X3](3-) (X = N, P, As, Sb, Bi, Uup) as well as [X3M3X3](3-) (M, X = Cu, As; Ag, Bi; Au, Sb; Rg, Uup) to understand the special stabilities of these species. Additional studies are also performed on the oligomers [Sb-3(Au3Sb3)(n)](3-) (n = 1-4) to explore whether the sandwich compound can form stable extended systems. Through extensive theoretical analyses, we have shown that among the [Au3X6](3-) (X = N, P, As, Sb, Bi, Uup) species, [Sb3Au3Sb3](3-) is most stable due to superb matching of Sb-3 and Au-3 in both geometric size and fragment orbital energies. The significant stability of the [Au3Sb6](3-) ion is determined by the interlayer (p-d-p)sigma interactions between the vertical Au 5d6s hybrid orbitals of Au-3 and Sb 5p(pi) orbitals of the Sb-3 rings. Each Sb-3 ring demonstrates unique sigma aromaticity, which remains when the complex is extended to oligomers. The results suggest that it is likely that there might exist other stable [A(p)M(p)A(p)](x-) (M = transition metals, A = main group elements, p = 3, 4, 5, …) sandwich ions and oligomers.

First author: Nguyen, TAN, A Comparison of Donor-acceptor Interactions in Borane Complexes of Divalent Tetrylenes(II) and Divalent Tetrylones(0) using Energy Decomposition Analysis Method with Natural Orbital for Chemical Valence Theory,SMART SCIENCE, 4, 28, (2016)
Abstract: A scheme for chemical bond analysis by combining the energy decomposition analysis (EDA) method with natural orbitals for chemical valence (NOCV) theory has been investigated. Quantum chemical calculations at the BP86/TZ2P+level of theory are performed for a comparison of chemical bond analysis between tetrylones [BH3-{E(PH3)(2)}] (B3-EP2) and tetrylenes [(BH3-{NHEMe}] (B3-NHE) (E = C to Pb). The EDA-NOCV results suggest that the B-E bond dissociation energies (BDEs) in tetrylones and tetrylenes decrease from the slighter to the heavier homologs. The decrease in the bond strengths from the lighter to the heavier homologs of B3-EP2 comes mainly from the decrease in the electrostatic attractions Delta E-elstat and the orbital interactions Delta E-orb, while the decrease in the bond strength from carbene B3-NHC to plumbylene B3-NHPb strongly correlates with the decrease in electrostatic term Delta E-elstat.

First author: Lukens, WW, The roles of 4f-and 5f-orbitals in bonding: a magnetochemical, crystal field, density functional theory, and multi-reference wavefunction study, DALTON TRANSACTIONS, 45, 11508, (2016)
Abstract: The electronic structures of 4f(3)/5f(3) Cp ” M-3 and Cp ”’ M-3 center dot alkylisocyanide complexes, where Cp ”’ is 1,3-bis-(trimethylsilyl) cyclopentadienyl, are explored with a focus on the splitting of the f-orbitals, which provides information about the strengths of the metal-ligand interactions. While the f-orbital splitting in many lanthanide complexes has been reported in detail, experimental determination of the f-orbital splitting in actinide complexes remains rare in systems other than halide and oxide compounds, since the experimental approach, crystal field analysis, is generally significantly more difficult for actinide complexes than for lanthanide complexes. In this study, a set of analogous neodymium(III) and uranium(III) tris-cyclopentadienyl complexes and their isocyanide adducts was characterized by electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility. The crystal field model was parameterized by combined fitting of EPR and susceptibility data, yielding an accurate description of f-orbital splitting. The isocyanide derivatives were also studied using density functional theory, resulting in f-orbital splitting that is consistent with crystal field fitting, and by multi-reference wavefunction calculations that support the electronic structure analysis derived from the crystal-field calculations. The results highlight that the 5f-orbitals, but not the 4f-orbitals, are significantly involved in bonding to the isocyanide ligands. The main interaction between isocyanide ligand and the metal center is a s-bond, with additional 5f to pi* donation for the uranium complexes. While interaction with the isocyanide p*-orbitals lowers the energies of the 5f(xz2) and 5f(yz2)-orbitals, spin-orbit coupling greatly reduces the population of 5f(xz2) and 5f(yz2) in the ground state.

First author: Cao, GJ, Structures and electronic properties of B2Si6-/0/+:anion photoelectron spectroscopy and theoretical calculations, RSC ADVANCES, 6, 62165, (2016)
Abstract: We measured the photoelectron spectrum of B2Si6- anion and investigated the structures and electronic properties of B2Si6- anion as well as those of its neutral and cationic counterparts with quantum chemical calculations. The vertical detachment energy (VDE) of the B2Si6- anion has been measured to be 2.40 ± 0.08 eV. Through global minimum searches and CCSD(T) calculations, we have identified that the lowest-energy structures of B2Si6q (q = -1, 0, +1) are peculiar structures with a Si atom hanging over a distorted bowl-like B2Si5 framework. Quasi-planar or planar isomers have also been identified for the B2Si6 cluster at -1, 0, and +1 charge states. The quasi-planar and planar isomers are higher in energy than their bowl-like counterparts by at least 0.20 eV. The symmetries of the quasi-planar isomers varied at different charge states, ranging from C-s to C-2h, then to D-2h respectively for the -1, 0, and +1 charge states. The reducing of the symmetry from +1 charge state to -1 charge state is more likely due to the Jahn-Teller effect upon the addition of electrons.

First author: Shi, YR, Research on charge-transport properties of TTF-TTP derivatives and organic interfaces, RSC ADVANCES, 6, S7057, (2016)
Abstract: The electronic and charge transport properties of four derivative groups containing nineteen different tetrathiafulvalene (TTF) and tetrathiapentalene (TTP) derivative compounds were theoretically investigated by density functional theory (DFT) based on the Marcus-Hush theory. In particular, we have considered TTF or TTP systems where some hydrogen atoms are substituted with methoxy or halogen moieties since it is well known that these electron-withdrawing groups are used to reduce the energies of frontier orbitals (HOMO and LUMO) and to increase the stability of the TTF derivative. A comparative analysis of the crystal structures reveals that the face-to-face layer structure and the herringbone structure with slip-stacks of the dimers exhibit higher charge transfer values compared with the disordered structures, and that the face-to-face pi-pi interaction and S-S interactions are favorable for molecular stacking and charge transport behavior. The computed values of the transfer integrals show that variation in calculated transfer integral values is likely along specific directions corresponding to the pi-pi stacking degree of the molecules. The interface charge conduction mechanism between two different molecule crystals is investigated, and we find there are high-conducting interfaces and low resistances of about 10-50 k Omega. Furthermore, the calculated data demonstrate that the TTF derivatives should be candidates for high-performance organic materials with high mobility values and good stability, and that the predicted highest hole and electron mobility values are 1.821 cm(2) V-1 s(-1) and 1.709 cm(2) V-1 s(-1), respectively, at 300 K. The high mobility combined with simple processing make TTF derivatives promising candidate materials for electronic devices where low cost and flexibility are required.

First author: Ruzie, C, Design, synthesis, chemical stability, packing, cyclic voltammetry, ionisation potential, and charge transport of [1]benzothieno[3,2-b][1]benzothiophene derivatives, JOURNAL OF MATERIALS CHEMISTRY C, 4, 4863, (2016)
Abstract: Five new molecular semiconductors that differ from dioctylbenzothienobenzothiophene, by the introduction of ether or thioether side chains, have been synthesized and obtained in good yields. Their availability in sufficient quantities has allowed investigation of their electrochemical behaviour in solution and their electronic properties in solid state. Both ether and thioether compounds oxidise rather easily in solution, but nevertheless, they exhibit rather high ionisation potentials. This is a consequence of their crystal structure. Dioctylthioetherbenzothienobenzothiophene is rather sensitive to oxidation and degrades easily in close to ambient conditions. Dioctyletherbenzothienobenzothiophene is more stable. Its charge carrier mobility remains however rather moderate, on the order of 0.5 cm(2) V-1 s(-1), whereas that of dioctylbenzothienobenzothiophene reached 4 cm(2) V-1 s(-1), in the same conditions. The difference is explained by intrinsic factors as shown by a theoretical modelling.

First author: Sun, WF, Reverse saturable absorbing cationic iridium(III) complexes bearing the 2-(2-quinolinyl)quinoxaline ligand: effects of different cyclometalating ligands on linear and nonlinear absorption, JOURNAL OF MATERIALS CHEMISTRY C, 4, 5059, (2016)
Abstract: To develop broadband reverse saturable absorbing materials, four Ir(III) complexes containing the 2-(2-quinolinyl)quinoxaline (quqo) ligand and different cyclometalating ligands ((quqo) Ir(C<^>N)(2)PF6, where C<^>N = 2-[4-(7-benzothiazolylfluoren-2-yl)phenyl]pyridine (1), 2-(7-benzothiazolylfluoren-2-yl)pyridine (2), 2-[3-(7-benzothiazolylfluoren-2-yl)phenyl]pyridine (3), and 2-[3-(7-naphthalimidylfluoren-2-yl)phenyl]pyridine (4)), were synthesized. Their linear and nonlinear absorption and emission characteristics were systematically investigated via spectroscopic techniques (i.e. UV-vis absorption, emission, and fs and ns transient absorption), nonlinear optical characterization techniques (i.e. Z-scan and the time-resolved pump-probe technique with a phase object (PO pump-probe)), and theoretical calculations. The effect of quqo as a strong electron-withdrawing and extensively pi-conjugated ligand, and the effect of the substitution position (meta versus para) at the 2-phenylpyridine ligand on the lowest-energy charge transfer absorption band and the triplet excited-state lifetimes of these complexes were explored. It was found that all these complexes possess a very weak but broad charge-transfer ground-state absorption band from 450 to 750 nm, where their excited states absorb strongly. Therefore, they exhibit the broadest optical window in the visible to the near-IR region among reverse saturable absorbers reported to date. The strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses was demonstrated for these complexes. In order to maintain the long-lived triplet excited state while red-shifting the charge-transfer ground-state absorption band, attaching the 7-R-fluoren-2-yl substituent at the 4-position of the cyclometalating phenyl ring instead of the 3-position of the cyclometalating phenyl ring is the solution.

First author: Sturzbecher-Hoehne, M, Intramolecular sensitization of americium luminescence in solution: shining light on short-lived forbidden 5f transitions, DALTON TRANSACTIONS, 45, 9912, (2016)
Abstract: The photophysical properties and solution thermodynamics of water soluble trivalent americium (Am-III) complexes formed with multidentate chromophore-bearing ligands, 3,4,3-LI(1,2-HOPO), Enterobactin, and 5-LIO(Me-3,2-HOPO), were investigated. The three chelators were shown to act as antenna chromophores for Am-III, generating sensitized luminescence emission from the metal upon complexation, with very short lifetimes ranging from 33 to 42 ns and low luminescence quantum yields (10(-3) to 10(-2)%), characteristic of Near Infra-Red emitters in similar systems. The specific emission peak of Am-III assigned to the D-5(1) -> F-7(1) f-f transition was exploited to characterize the high proton-independent stability of the complex formed with the most efficient sensitizer 3,4,3-LI(1,2-HOPO), with a log beta(110) = 20.4 ± 0.2 value. In addition, the optical and solution thermodynamic features of these AmIII complexes, combined with density functional theory calculations, were used to probe the influence of electronic structure on coordination properties across the f-element series and to gain insight into ligand field effects.

First author: Ren, LB, Isomeric indacenedibenzothiophenes: synthesis, photoelectric properties and ambipolar semiconductivity, JOURNAL OF MATERIALS CHEMISTRY C, 4, 5202, (2016)
Abstract: A new strategy via double C-H activation cyclization has been developed for the versatile synthesis of IDBT derivatives with quite different photoelectric properties. Single-crystal field-effect transistors based on IDBT-l-TIPSA delivered high and balanced charge carrier mobilities of up to 0.64 cm(2) V-1 s(-1) for holes and 0.34 cm(2) V-1 s(-1) for electrons under ambient conditions.

First author: Viveka, S, Synthesis, characterization, single crystal X-ray diffraction and DFT studies of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 629, 135, (2016)
Abstract: The present study describes the synthesis, spectroscopic, and single crystal X-ray structural analysis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate. The pyrazole ester of formula [C13H14N2O2] was prepared from the three-component one-pot condensation reaction of ethyl acetoacetate, N,N-dimethyldimethoxymethanamine, and phenyl hydrazine. The product was crystallized by using ethanol as solvent. The structure of the compound was confirmed by elemental analysis, Fourier transforms infrared (IR), thermogravimetric analysis, UV-visible (UV-Vis), H-1 NMR, and single-crystal X-ray diffraction studies. The gas-phase molecular geometry and the electronic structure-property of the molecule were calculated at the density functional theory. The frontier molecular orbitals, theoretical UV-Vis, and IR stretching vibrations were also reported. The compound crystallizes in the monoclinic system with the space group P2(1)/c and Z = 4. The unit cell parameters are a = 12.141(3) angstrom, b = 13.934(4) angstrom, c = 7.2777(18) angstrom, and beta = 97.816(14)degrees. The structure is stabilized by an intermolecular interaction of type C-H center dot center dot center dot O and the structure also involves C-H center dot center dot center dot pi interactions.

First author: Rusakova, IL, Theoretical grounds of relativistic methods for calculation of spin – spin coupling constants in nuclear magnetic resonance spectra, RUSSIAN CHEMICAL REVIEWS, 85, 356, (2016)
Abstract: The theoretical grounds of the modern relativistic methods for quantum chemical calculation of spin spin coupling constants in nuclear magnetic resonance spectra are considered. Examples and prospects of application of relativistic calculations of these constants in the structural studies of organic and heteroorganic compounds are discussed. Practical recommendations on relativistic calculations of spin spin coupling constants using the available software are given.

First author: Wolters, LP, d(10)-ML2 Complexes: Structure, Bonding, and Catalytic Activity, COMPUTATIONAL STUDIES IN ORGANOMETALLIC CHEMISTRY, 167, 139, (2016)
Abstract: Our goal in this chapter is to show how one can obtain a better understanding of the decisive factors for the selectivity and efficiency of catalytically active metal complexes. This ongoing research project has been designated the ‘Fragment-oriented Design of Catalysts’ and aims at providing design principles for a more rational development of catalysts. To this end, we have performed a series of studies in which we systematically investigate the effect of a specific variation on the reactivity of the catalyst. Thus, we will summarize previous results on not only how the reaction barrier varies when different bonds are activated by palladium, different ligands are attached to palladium but also how different metal centers perform compared to palladium. In a final section, we present a case study on newly obtained results about the effect of adding substituents with different electronegativity to the phosphine ligands at the metal center. A red thread throughout the chapter, and our methodology in general, is the application of the activation strain model of chemical reactivity. This is a predictive model that provides a quantitative relationship between trends in barrier heights and variation of geometric and electronic properties of the reactants.

First author: Du, JH, Tuning the electronic and photophysical properties of platinum(II) complexes through ancillary ligand modification: a theoretical study, MOLECULAR SIMULATION, 42, 1035, (2016)
Abstract: In this work, six Pt(II) complexes have been studied via density functional theory (DFT)/time-dependent DFT caculations to explore the influence of different ancillary ligand on electron structures, photophysical properties and radiative decay processes. Moreover, the self-consistent spin-orbit coupling TDDFT was used to calculate zero-field splitting, radiative rate and radiative lifetime to unveil the radiative deactivation processes for these complexes. The results indicated that [Pt(ppy)(ppz)] (ppy=2-phenylpyridine and ppz=5-(2-pyridyl)-pyrazole) has a higher radiative decay rate constant and a smaller nonradiative decayrate constant than that of [Pt(ppy)(acac)] (acac=acetylacetonate). Furthermore, complex 5, with dimesityboron added on the 3-position of the pyrazole ring in [Pt(ppy)(ppz)], shows great potential to serve as an efficient blue-green light emitter in OLED.

First author: Wielandt, JW, Self-Assembly of Square-Planar Halide Complexes of Trimethylphosphine-Stabilized Diphenyl-Arsenium, -Stibenium, and -Bismuthenium Hexafluorophosphates, AUSTRALIAN JOURNAL OF CHEMISTRY, 69, 524, (2016)
Abstract: Square-planar halide complexes in which four trimethylphosphine-stabilized diphenyl-stibenitun or -bismuthenium ions surround a central halide ion in discrete centrosymmetrical structures of C-4h, symmetry have been isolated and their structures determined by X-ray crystallography. The structures are stabilized by electrostatic interactions between the halide ion and four positively charged trimethylphosphine-stabilized cliphenyl-stibenium or -bismuthenium ions, as well as four edge -to-face phenyl phenyl embraces above and below the plane containing the nine main group elements. The parent halide -free trirnethylphosphine-stabilized diphenyl-arsenium, -stibenium, and -bisrnuthenium hexaflurophosphate complexes have also been prepared and structurally characterized.

First author: Luo, ZX, What determines if a ligand activates or passivates a superatom cluster?, CHEMICAL SCIENCE, 7, 3067, (2016)
Abstract: Quantum confinement in small metal clusters leads to a bunching of states into electronic shells reminiscent of shells in atoms, enabling the classification of clusters as superatoms. The addition of ligands tunes the valence electron count of metal clusters and appears to serve as protecting groups preventing the etching of the metallic cores. Through a joint experimental and theoretical study of the reactivity of methanol with aluminum clusters ligated with iodine, we find that ligands enhance the stability of some clusters, however in some cases the electronegative ligand may perturb the charge density of the metallic core generating active sites that can lead to the etching of the cluster. The reactivity is driven by Lewis acid and Lewis base active sites that form through the selective positioning of the iodine and the structure of the aluminum core. This study enriches the general knowledge on clusters including offering insight into the stability of ligand protected clusters synthesized via wet chemistry.

First author: Gregson, M, Emergence of comparable covalency in isostructural cerium(IV)- and uranium(IV)-carbon multiple bonds, CHEMICAL SCIENCE, 7, 3286, (2016)
Abstract: We report comparable levels of covalency in cerium- and uranium-carbon multiple bonds in the iso-structural carbene complexes [M(BIPMTMS)(ODipp)(2)] [M = Ce (1), U (2), Th (3); BIPMTMS = C(PPh2NSiMe3)(2); Dipp = C6H3-2,6-Pr-i(2)] whereas for M = Th the M=C bond interaction is much more ionic. On the basis of single crystal X-ray diffraction, NMR, IR, EPR, and XANES spectroscopies, and SQUID magnetometry complexes 1-3 are confirmed formally as bona fide metal(IV) complexes. In order to avoid the deficiencies of orbital-based theoretical analysis approaches we probed the bonding of 1-3 via analysis of RASSCF- and CASSCF-derived densities that explicitly treats the orbital energy near-degeneracy and overlap contributions to covalency. For these complexes similar levels of covalency are found for cerium(IV) and uranium(IV), whereas thorium(IV) is found to be more ionic, and this trend is independently found in all computational methods employed. The computationally determined trends in covalency of these systems of Ce similar to U > Th are also reproduced in experimental exchange reactions of 1-3 with MCl4 salts where 1 and 2 do not exchange with ThCl4, but 3 does exchange with MCl4 (M = Ce, U) and 1 and 2 react with UCl4 and CeCl4, respectively, to establish equilibria. This study therefore provides complementary theoretical and experimental evidence that contrasts to the accepted description that generally lanthanide-ligand bonding in non-zero oxidation state complexes is overwhelmingly ionic but that of uranium is more covalent.

First author: Jacobsen, H, Theoretical Inorganic Chemistry: In Reminiscence of Tom Ziegler, COMMENTS ON INORGANIC CHEMISTRY, 36, 196, (2016)
Abstract: We report comparable levels of covalency in cerium- and uranium-carbon multiple bonds in the iso-structural carbene complexes [M(BIPMTMS)(ODipp)(2)] [M = Ce (1), U (2), Th (3); BIPMTMS = C(PPh2NSiMe3)(2); Dipp = C6H3-2,6-Pr-i(2)] whereas for M = Th the M=C bond interaction is much more ionic. On the basis of single crystal X-ray diffraction, NMR, IR, EPR, and XANES spectroscopies, and SQUID magnetometry complexes 1-3 are confirmed formally as bona fide metal(IV) complexes. In order to avoid the deficiencies of orbital-based theoretical analysis approaches we probed the bonding of 1-3 via analysis of RASSCF- and CASSCF-derived densities that explicitly treats the orbital energy near-degeneracy and overlap contributions to covalency. For these complexes similar levels of covalency are found for cerium(IV) and uranium(IV), whereas thorium(IV) is found to be more ionic, and this trend is independently found in all computational methods employed. The computationally determined trends in covalency of these systems of Ce similar to U > Th are also reproduced in experimental exchange reactions of 1-3 with MCl4 salts where 1 and 2 do not exchange with ThCl4, but 3 does exchange with MCl4 (M = Ce, U) and 1 and 2 react with UCl4 and CeCl4, respectively, to establish equilibria. This study therefore provides complementary theoretical and experimental evidence that contrasts to the accepted description that generally lanthanide-ligand bonding in non-zero oxidation state complexes is overwhelmingly ionic but that of uranium is more covalent.

First author: Umadevi, P, Metal-interacted histidine dimer: an ETS-NOCV and XANES study, RSC ADVANCES, 6, 38919, (2016)
Abstract: We have analyzed the metal coordination in a histidine dimer, hydrated with a water molecule, based on the extended transition state scheme with the theory of natural orbitals for chemical valence (ETS-NOCV). Metal interaction weakens and strengthens the C=O and C-N bonds respectively, which indicates sigma bond formation between the metal and the ligand. Frequency analysis reveals C=O bond exhibits a red shift, which confirms that the pi-back donation of electrons takes place through this bond. From the ETS-NOCV analysis, the electrostatic term is dominant over the orbital term. NOCV analysis indicates that the switching of bond strength between C-N bond and C=O bond in neutral and zwitterionic systems respectively is due to the amount of back donation in TM2+-N and TM2+-O bonds (TM2+ = Cu, Zn, Ca, Mg). K-edge XANES spectra for the metal indicates that oxidation state of Zn and Ca increases while for Cu and Mg it decreases. Oxygen K-edge spectra indicate that metals like zinc and copper back-donate the electrons largely to ligands.

First author: van Niekerk, DME, A DFT study to unravel the ligand exchange kinetics and thermodynamics of Os-VIII oxo/hydroxido/aqua complexes in aqueous matrices, DALTON TRANSACTIONS, 45, 7028, (2016)
Abstract: The Os-VIII oxo/hydroxido complexes that are abundant in mild to relatively concentrated basic aqueous solutions are (OsO4)-O-VIII, [(OsO4)-O-VIII(OH)](-) and two cis-[(OsO4)-O-VIII(OH)(2)](2-) species. Os-VIII complexes that contain water ligands are thermodynamically unfavoured w.r.t. the abovementioned species. (OsO4)-O-VIII reacts with hydroxide in two, consecutive, elementary coordination sphere expansion steps to form the [(OsO4)-O-VIII(OH)](-) complex and then the cis-[(OsO4)-O-VIII(OH)(2)](2-) species. The Gibbs energy of activation for both reactions, in the forward and reverse direction, are in the range of 6-12 kcal mol(-1) and are relatively close to diffusion-controlled. The thermodynamic driving force of the first reaction is the bonding energy of the Os-VIII-OH metal-hydroxido ligand, while of the second reaction it is the relatively large hydration energy of the doubly-charged cis-[(OsO4)-O-VIII(OH)(2)](2-) product compared to the singly-charged reactants. The DFT-calculated (PBE-D3 functional) Delta G(rxn)degrees in the simulated aqueous phase (COSMO) is -2.4 kcal mol(-1) for the first reaction and -0.6 kcal mol(-1) for the second reaction and agree to within 1 kcal mol(-1) with reported experimental values, at -2.7 and 0.3 kcal mol(-1) respectively. From QTAIM and EDA analyses it is deduced that the Os-VIII=O bonding interactions are ionic (closed-shell) and that Os-VIII-OH bonding interactions are polar covalent (dative). In contrast to QTAIM, NCI analysis allowed for the identification of relatively weak intramolecular hydrogen bonding interactions between neighbouring oxo and hydroxido ligands in both [(OsO4)-O-VIII(OH)](-) and cis-[(OsO4)-O-VIII(OH)(2)](2-) complexes.

First author: Kosnik, SC, A zwitterionic triphosphenium compound as a tunable multifunctional donor, DALTON TRANSACTIONS, 45, 6251, (2016)
Abstract: The preparation of a novel triphosphenium zwitterion featuring di-, tri-, and tetra-coordinate phosphorus centres derived from a 1,2,4-tris-(diphenylphoshinyl)cyclopentadienyl framework is described. The reactivity of this potentially multidentate donor with protons, elemental sulfur and gold(I) chloride is examined, and the preferential reactivity of the pendant phosphine group over the P(I) centre is rationalized on the basis of density functional theory investigations.

First author: Lei, YY, High stability of the He atom confined in a U@C-60 fullerene, RSC ADVANCES, 6, 29288, (2016)
Abstract: To understand the confined nature of rare gases in endohedral metallofullerenes (EMFs) encapsulating actinide metals, here we study the interaction between a He atom and uranium metallofullerene U@C-60 in a UHe@C-60 system, using density functional theory (DFT). Analysis of the electron density indicates no observable electron clouds overlap between the He atom and U atom/fullerene cage. Direct contributions from the atomic orbitals to molecular orbitals (MOs), show that the 1s shell electrons of the He atom account for >1% contribution to only three MOs, and they are all far beneath the frontier molecular orbitals. Furthermore, the modulations of the He atom on the UV-Vis, infrared and Raman spectra are almost negligible. Our work highlights the high stability of the He atom in the actinide metallofullerenes, and it can also help to understand the interaction between fission products of actinide elements and the synthesizing process of EMFs.

First author: Herman, A, Propeller-Like Chirality of Methyl-Tris (2,6-diisopropylphenoxy)Silylsulfide, SILICON, 8, 105, (2016)
Abstract: Two new methylsilylsulfides are synthesized. Propeller-like chirality is described for triaryloxysilanethiol and its methyl derivative. S-methylation of the silanethiol lowers the overall symmetry of the unit cell.

First author: Chiweshe, TT, Synthesis and structure of dithizonato complexes of copper(II), antimony(III) and tin(IV), JOURNAL OF COORDINATION CHEMISTRY, 69, 788, (2016)
Abstract: In view of the important role of dithizone in trace metal analyses, new structural aspects and approaches used to probe metal complexes of dithizone are of interest. Three X-ray diffraction structures are reported, dichloridobis(dithizonato) tin(IV), dichlorido(dithizonato) antimony(III), and bis(dithizonato) copper(II). During synthesis of the tin complex, auto-oxidation of (SnCl2)-Cl-II to Sn-IV occurred without chloride liberation. The Sb-III complex revealed a unique distorted see-saw geometry which is, as for the other complexes, predicted by DFT molecular orbital calculations. The computed products of the lowest energy reactions are in agreement with experimentally obtained reaction products, which, together with molecular orbital renderings serve as a tool toward prediction of modes of coordination in these complexes. The S-M-N bond angle in the five-membered coordination ring shows a linear relationship with the corresponding metal ionic radii.

First author: Cabaleiro-Lago, EM, Comment on “Theoretical studies on a carbonaceous molecular bearing: association thermodynamics and dual-mode rolling dynamics” by H. Isobe, K. Nakamura, S. Hitosugi, S. Sato, H. Tokoyama, H. Yamakado, K. Ohno and H. Kono, Chem. Sci., 2015, 6, 2746, CHEMICAL SCIENCE, 7, 2924, (2016)
Abstract: The LC-BLYP functional accompanied with proper calculations leads to unreliable results for systems governed by pi center dot center dot center dot pi interactions. It seems quite clear that a good representation of dispersion interactions is required, so DFT must be supplemented (through the DFT-D formalism or the many-body dispersion method) in order to afford good results.

First author: Zendaoui, SM, Coordination chemistry of mixed M(benzene)(cyclopendadienyl) sandwich complexes: electronic properties and bonding analysis, NEW JOURNAL OF CHEMISTRY, 40, 2554, (2016)
Abstract: DFT calculations using BP86 and B3LYP functionals have been carried out for all the low-energy structures of mixed [M(Bz)Cp](+1/0/-1) (M = Sc-Ni) sandwich complexes of benzene and cyclopentadienyl ligands. The electronic configuration of cationic, neutral and anionic metal-ligand complexes and their structures are discussed, wherein depending on the metal nature, the spin state and the metal valence electrons, a complete rationalization of the bonding has been provided for the [M(Bz) Cp](+1/0/-1) complexes. Benzene and cyclopentadienyl adopt unchanged eta(6) and eta(5) hapticities, respectively, for Sc, Ti, V, Cr and Mn complexes, but various coordination modes for Fe, Co and Ni were emphasized, according to the metal oxidation state and the complex’s spin state, wherein some of them involve full or partial coordination of either benzene or cyclopentadienyl to satisfy the metal’s electron demand. The ionization energy and the electron affinity showed that the neutral 19-electron iron complex is the easiest oxidized and reduced species among all the complexes studied.

First author: Nishiki, K, Preparation of alpha(1)- and alpha(2)-isomers of mono-Ru-substituted Dawson-type phosphotungstates with an aqua ligand and comparison of their redox potentials, catalytic activities, and thermal stabilities with Keggin-type derivatives, DALTON TRANSACTIONS, 45, 3715, (2016)
Abstract: Both the alpha(1) and the alpha 2 -isomers of mono-ruthenium (Ru)-substituted Dawson-type phosphotungstates with terminal aqua ligands, [alpha 1-P2M17O61RuIII(H2O)(7-) (alpha(1)-RuH2O) and [alpha(2)-P2W17O61RuIII(H2O)(7-)(alpha 2-RuH2O), were prepared in pure form by cleavage of the Ru-S bond of the corresponding DMSO derivatives, [alpha(1)-P2W17O61Ru(DMSO)(8-) (alpha(1)-RuDMSO) and [alpha(2)-P2W(17)O(61)Ru(DMSO)](8-) (alpha(2)-RuDMSO), respectively. Redox studies indicated that alpha 1-RuH2O and alpha 2-RuH2O show proton-coupled electron transfer (PCET), and the Rul(H2O) species was reversibly reduced to Ru(H2O) species and oxidized to Ru-IV(=O) species and further to Ru(=O) species in aqueous solution depending on the pH. Their redox potentials and thermal stabilities were compared with those of the corresponding alpha-Keggin-type derivatives (alpha-XW(11)O(3)gRu(H2O)r; X = Si4+ (n = 5), Ge4+ (n = 5), or P5+ (n = 4)). The basic electronic and redox features of Ru(L)-substituted Keggin- and Dawson-type heteropolytungstates (with L = H2O or O2- were analyzed by means of density functional calculations. Similar to the corresponding u-Keggin-type derivatives, both alpha-RuH2O and alpha(2)-RuH2O show catalytic activity for water oxidation.

First author: Liu, L, Structure and bonding of IrB12-: converting a rigid boron B-12 platelet to a Wankel motor, RSC ADVANCES, 6, 27177, (2016)
Abstract: The global minimum of IrB12- is a C-3v symmetric bowl-like structure in which the Ir atomis located on the concave side of the bowl, similar to its lighter congeners, CoB12- and RhB12- clusters. Although all these MB12- (M = Co, Rh, Ir) clusters show dynamical behaviour, analogous to that of the so-called ‘Wankel motors’, the energy barrier for the rotation of the inner B-3 ring within the peripheral B-9 ring is the lowest in the IrB12- case (5.0 kcal mol(-1) only). The geometrical feature along with the lower interaction energy between B-3 and MB9 moieties are responsible for a smaller rotational energy barrier in IrB12- than those in CoB12- and RhB12- clusters.

First author: Mamada, M, Crystal structure and modeled charge carrier mobility of benzobis(thiadiazole) derivatives, NEW JOURNAL OF CHEMISTRY, 40, 1403, (2016)
Abstract: The crystal structures of benzobis(thiadiazole) (BBT)-based organic semiconductors with high electron mobilities were revealed using single-crystal X-ray analyses, followed by density functional theory and hopping modeling to estimate the charge carrier mobility levels. The crystal packings and intermolecular interactions were found to be similar regardless of trifluoromethyl and trifluoromethoxy groups for the corresponding para-substituted or meta-substituted derivatives. Although a compound with ortho-trifluoromethyl groups showed a molecule with a twisted conformation, the ortho-trifluoromethoxy derivative had nearly planar conformation. Since the ortho-trifluoromethyl groups prevent effective intermolecular interactions through short heteroatom contacts between BBT rings, molecules have a one-dimensional charge carrier transport path, resulting in lower overall charge carrier mobility in transistor devices. On the other hand, the ortho-trifluoromethoxy derivative exhibits a herringbone packing with large diffusion coefficients. The para and meta-derivatives showed an unusually large diffusion coefficient between the molecules located in the co-planar and the standard pi-pi stacking directions. The formation of a two-dimensional structure afforded high electron mobilities in actual organic thin-film transistor (OTFT) devices using these BBT-based materials.

First author: Lee, LM, Synthetic, structural, and computational investigations of N-alkyl benzo-2,1,3-selenadiazolium iodides and their supramolecular aggregates, DALTON TRANSACTIONS, 45, 3285, (2016)
Abstract: Despite their versatility, the application of telluradiazoles as supramolecular building blocks is considerably constrained by their sensitivity to moisture. Albeit more robust, their selenium analogues form weaker supramolecular interactions. These, however, are enhanced when one nitrogen atom is bonded to an alkyl group. Here we investigate general methods for the synthesis of such derivatives. Methyl, iso-propyl and tert-butyl benzo-2,1,3-selenadiazolium cations were prepared by direct alkylation or cyclo-condensation of the alkyl-phenylenediamine with selenous acid. While the former reaction only proceeds with the primary and tertiary alkyl iodides, the latter is very efficient. Difficulties reported in earlier literature are attributable to the formation of adducts of benzoselenadiazole with its alkylated cations and side reactions initiated by aerobic oxidation of iodide. However, the cations themselves are resilient to oxidation and stable in acidic to neutral aqueous medium. X-ray crystallography was used in the identification and characterization of the following compounds: [C6H4N2(R) Se](+) X-, (R = CH(CH3)(2), C(CH3)(3); X = I-, I-3(-)], [C6H4N2(CH3) Se](+) I-, and [C6H4N2Se][C6H4N2(CH3)Se](2)I-2. Formation of Se center dot center dot center dot N secondary bonding interactions (chalcogen bonds) was only observed in the last structure as anion binding to selenium is a strong competitor. The relative strengths of those forces and the structural preferences they enforce were assessed with DFT-D3 calculations supplemented by AIM analysis of the electron density.

First author: Correa, S, Synthesis, Structural Characterization, and Thermal Properties of the Poly(methylmethacrylate)/delta-FeOOH Hybrid Material: An Experimental and Theoretical Study, JOURNAL OF NANOMATERIALS, 45, 3285, (2016)
Abstract: The delta-FeOOH/PMMA nanocomposites with 0.5 and 2.5 wt.% of delta-FeOOH were prepared by grafting 3-(trimethoxysilyl) propyl methacrylate on the surface of the iron oxyhydroxide particles. TheFTIR spectra of the delta-FeOOH/PMMA nanocomposites showed that the silane monomers were covalently attached to the delta-FeOOHparticles. Because of the strong interaction between the PMMA and delta-FeOOH nanoparticles, the thermal stability of the delta-FeOOH/PMMA nanocomposites was improved compared to the pure PMMA. The SEM analysis conferred the size agglomerate of particles regarding the morphology of samples. The theoretical study enabled a better understanding of the interaction of the polymer with the iron oxyhydroxide. The DFT-based calculations reinforce the radical trapping mechanism of stabilization of nanocomposites; that is, Fe3+ species might be able to accept electrons coming from the organic phase that decomposes via radical unzipping. The radical scavenge effect delays the weight loss of polymer.

First author: Rocha, MVJ, Structural Characterization, Thermal Properties, and Density Functional Theory Studies of PMMA-Maghemite Hybrid Material, POLYMER COMPOSITES, 37, 51, (2016)
Abstract: Maghemite (gamma-Fe2O3)-poly(methyl methacrylate) (PMMA) nanocomposites were prepared by grafting 3-(trimethoxy-silyl) propyl methacrylate on the surface of maghemite nanoparticles, this process being followed by methyl methacrylate radical polymerization. Three different hybrids with 0.1, 0.5, and 2.5 wt% of maghemite nanoparticles were studied. The results indicate that these nanocomposites consist of a homogeneous PMMA matrix in which maghemite nanoparticles with a bimodal size distribution are embedded. The existence of covalent bonding between silane monomers and atoms on the maghemite surface was evidenced. AFM images showed a clear increase in surface roughness for increasing maghemite content. The thermal stability of PMMA-maghemite nanocomposites is higher than that of pure PMMA and increases for increasing maghemite content. The results of our theoretical studies indicate that the electron density in the maghemite nanoparticle is not homogenous, the low electron density volumes being supposed to be radical trappers during PMMA decomposition, thus acting as a thermal stabilizer.

First author: Izarova, NV, The polyoxo-22-palladate(II), [(Na2Pd22O12)-O-II((AsO4)-O-V)(15)((AsO3OH)-O-V)](25-), DALTON TRANSACTIONS, 45, 2394, (2016)
Abstract: The polyoxo-22-palladate [(Na2Pd22O12)-O-II((AsO4)-O-V)(15)((AsO3OH)-O-V)](25-) (1), which represents a novel polyoxo-noble-metalate structural type, was synthesized by reaction of Pd2+ and AsO43- ions in aqueous solution. Polyanion 1 comprises two {NaPd11} units linked by two arsenate bridges, and hence represents the first example of a defect, monolacunary {Pd-11} polyoxopalladate nanocube with arsenate capping groups. The title polyanion was characterized in the solid state as well as by theoretical calculations.

First author: Liu, R, Comparison of X-ray photoelectron spectroscopy multiplet splitting of Cr 2p peaks from chromium tris(beta-diketonates) with chemical effects, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 206, 46, (2016)
Abstract: X-ray photoelectron spectra (XPS) measurements of a series of chromium(III) beta-diketonato complexes of the Cr 2p spectra was fitted with calculated multiplet peaks. The XPS of these Cr(III) complexes did not exhibit fine structure, however, well-defined line shapes could be fitted to the Cr 2p(3/2) envelope. The splitting patterns obtained for the Cr(III) beta-diketonato complexes compared well with the multiplet splitting predicted by Gupta and Sen for the free Cr(III) ion. The Cr(III) beta-diketonato complexes containing unsymmetrically substituted beta-diketonato ligands, which display both the fac and mer isomers, could be fitted with two sets of multiplets and were useful in determining the ratio between the fac and mer isomers, which was compared with the Boltzman calculated ratio obtained from density functional theory energies. The obtained binding energy of the first multiplet splitting peak of the Cr 2p(3/2) envelope was found to be dependent on the combined Gordy group electronegativity of the R-groups substituted on the beta-diketonato ligand (RCOCHCOR’)(-).

First author: Liu, XR, Theoretical investigations on enhancing the performance of terminally diketopyrrolopyrrole-based small-molecular donors in organic solar cell applications, JOURNAL OF MOLECULAR MODELING, 22, 46, (2016)
Abstract: Diketopyrrolopyrrole (DPP)-based small molecules with acceptor-core-acceptor (A-core-A) type as donor materials have been used successfully in organic solar cells (OSC). In this work, based on the DPP-core-DPP type molecule SM1 consisting of a DPP unit as acceptor and benzene as the core, we replaced the benzene core with more electron-withdrawing groups in SM1 and further designed four new small-molecular donors (SM2-SM5) in order to improve the electrical properties, optical absorption and performance in OSC applications. The calculated results indicate that the designed small-molecular donors SM2-SM5 exhibit better performances in comparison with SM1, such as lower highest occupied molecular orbital (HOMO), narrower energy gap, larger absorption range, better electronic transfer between donor and acceptor and higher hole mobility. Moreover, the decreased HOMO levels and transition energy of small-molecular donors in OSC applications play an important role in the parameters of open-current voltage, fill factor and short-circuit current. Consequently, adjusting the electron-deficient ability of cores in DPP-core-DPP type small-molecular donors is an efficient approach that can be used to obtain high-efficiency DPP-based small-molecular donors for OSC applications.

First author: Miranda-Rojas, S, Theoretical exploration of seleno and tellurophenols as promising alternatives to sulfur ligands for anchoring to gold (111) materials, RSC ADVANCES, 6, 4458, (2016)
Abstract: It is widely known that sulfur ligands, such as alkanethiols or phenothiols and their derivatives, are useful anchor systems for gold materials due to the high affinity of sulfur to gold surfaces. In this study we use DFT calculations and a 42-atom gold cluster model to study the interaction between selenophenol and tellurophenol-derivatives with the Au(111) surface to gain information towards potential new gold-based materials. We modulated the interaction strength by controlling the charge transfer process of a particular interaction by chemically modifying the ligands. To obtain a complete analysis, we studied the ligands in their protonated, anionic and radical states aiming to cover the three possibilities in which these may interact with the gold cluster. In order to get a deeper insight into the nature of the interaction we used several analysis techniques such as energy decomposition analysis (EDA), non-covalent interactions (NCI) and natural population analysis (NPA). Our results reveal that tellurium in the anionic state provides complexes of better thermodynamic stability by similar to 12.0 kcal mol, when compared with the strongest sulfur-gold complex, also in the anionic state. Furthermore, this indicates that the anionic ligand is probably the dominant state for both selenium and tellurium as observed previously for sulfur. The extent to which the interaction strength could be controlled directly depends on the state of the anchor atom. In our case the anionic state is the most suitable for tuning the interaction. Finally, our main findings suggest that exchanging sulfur with selenium or tellurium involves an important increase of the interaction strength, thus, making these selenophenol and tellurophenol derivatives attractive for the development of new functional materials.

First author: Bistoni, G, How pi back-donation quantitatively controls the CO stretching response in classical and non-classical metal carbonyl complexes, CHEMICAL SCIENCE, 7, 1174, (2016)
Abstract: The CO stretching response upon coordination to a metal M to form [(L)(n)M(CO)](m) complexes (L is an auxiliary ligand) is investigated in relation to the sigma donation and pi back-donation components of the M-CO bond and to the electrostatic effect exerted by the ligand-metal fragment. Our analysis encompasses over 30 carbonyls, in which the relative importance of donation, back-donation and electrostatics are varied either through the ligand in a series of [(L)Au(CO)](0/+) gold(I) complexes, or through the metal in a series of anionic, neutral and cationic homoleptic carbonyls. Charge-displacement analysis is used to obtain well-defined, consistent measures of s donation and pi back-donation charges, as well as to quantify the sigma and pi components of CO polarization. It is found that all complexes feature a comparable charge flow of sigma symmetry (both in the M-CO bonding region and in the CO fragment itself), which is therefore largely uncorrelated to CO response. By contrast, pi back-donation is exceptionally variable and is found to correlate tightly with the change in CO bond distance, with the shift in CO stretching frequency, and with the extent and direction (C -> O or C <- O) of the CO pi polarization. As a result, we conclusively show that pi back-donation can be an important bond component also in non-classical carbonyls and we provide the framework in which the spectroscopic data on coordinated CO can be used to extract quantitative information on the pi donor properties of metal-ligand moieties.

First author: Dubrulle, L, A Push-Pull Pd-II Complex with a Ternary Pd-P-C+ Accepting End and a Key N-Heterocyclic Carbene-Imidazoliophosphine Ligand, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 7, 313, (2016)
Abstract: Neutral and cationic PdCl2 complexes based on the neutral frame of a cis-chelating N-heterocyclic carbene (NHC)-imidazolophosphine ligand involving an o-phenylene bridge have been devised for comparison of their relative push-pull character. Both target complexes, which are globally isosteric in the Pd coordination sphere, have been prepared in 58-68 % yield by direct coordination of the corresponding cis-chelating NHC-imidazol(i) ophosphine ” free ligand”, or by extrusion of a Ph2P+ phosphenium moiety from (imidazoliophosphine) PdII complex precursors. The cationic complex has also been obtained in 64 % yield by selective N-methylation of the neutral counterpart. The charge transfer from the NHC donating end (LD) to the imidazol(i) ophosphine accepting end (LA) has been investigated by electronic spectroscopy and by calculations of the first excited states at the time-dependent (TD)-DFT level. Although all the excitations involving the LD and LA ends of the neutral complex converge to the Pd center, the excited states |S-7> (305 nm) and | S-8> (303 nm) of the cationic complex exhibit a net L-D[M]L-A charge-tranfer (CT) character, which is clearly visualized by particle-hole density analysis. The push-pull complex involving a Pd-P-C+ p-accepting end is regarded as a “ternary” counterpart of “binary” phosphine-borane complexes involving two-center Pd-B s-accepting ends.

First author: Chong, DP, Theoretical Study of Structures and Spectra of Small Anticancer Drugs: Fluorouracil, Hydroxyurea, and Tirapazamine, JOURNAL OF THE CHINESE CHEMICAL SOCIETY, 63, 109, (2016)
Abstract: The structures and spectra of anticancer drug molecules fluorouracil, hydroxyurea, and tirapazamine are studied with ab initio methods and density functional theory. We optimize the geometry of the three molecules in gas phase and compute the vibrational spectra, dipole moments, and static dipole polarizabilities. Based on the coupled cluster method with single and double excitations (CCSD) results as standard for comparison for the geometry of fluorouracil and hydroxyurea, we conclude that third-order Moeller-Plesset perturbation (MP3) theory is more reliable than its second-order shortcut (MP2) or the popular method in density functional theory known as Becke three-parameter Lee-Yang-Parr exchange-correlation functional (B3LYP). Using the best methods based on past experience, we also calculate the vertical ionization energies of both valence and core electrons. Most of the results are new predictions, while others compare well with previous calculations and with available experimental data. On the other hand, the absorption spectra of the aqueous solution of three title molecules are studied with time-dependent DFT using the polarizable continuum model in conjunction with the nonequilibrium solvation method. Out of over 30 exchange-correlation functions/models, five are found to be more reliable than the others when compared with the observed UV/visible spectra of fluorouracil and tirapazmine.

First author: Chen, X, Oxygen reduction reaction on cobalt-(n)pyrrole clusters from DFT studies, RSC ADVANCES, 6, 5535, (2016)
Abstract: The oxygen reduction reaction (ORR) catalyzed by Co-(n)PPy (n = 2-10) clusters is investigated in detail at BLYP/DZP level of theory. The calculation results indicate that different O-2 adsorption modes could greatly affect the types of the reduction intermediates. The side-on O-2 adsorption is more likely to yield the intermediate HO-OH, while end-on yields H2O-O. However, the side-on O-2 adsorption could lead to strong intra-molecular strain and result in instability of the clusters, the cobalt ion therefore is more easily to be dissolved from the active site, leading to poor durability of the Co-(n) PPy clusters. The ORR activity might be enhanced with the cluster size increases, based on HOMO and LUMO analysis. From Co-(8) PPy, the electronic structures are hard to be modified by simply increasing the PPy chains. However, further increasing the cluster size might result in an increase of Co-N-2 active site due to that more Co atoms could be captured by the pyrrolic N atoms, the resulting synergistic effect would be more likely to enhance the activity.

First author: Jorge, FE, All-electron double zeta basis sets for the lanthanides: Application in atomic and molecular property calculations, CHEMICAL PHYSICS LETTERS, 643, 84, (2016)
Abstract: Segmented all-electron basis sets of valence double zeta quality plus polarization functions (DZP) for the elements from Ce to Lu are generated to be used with the non-relativistic and Douglas-Kroll-Hess (DKH) Hamiltonians. At the B3LYP level, the DZP-DKH atomic ionization energies and equilibrium bond lengths and atomization energies of the lanthanide trifluorides are evaluated and compared with benchmark theoretical and experimental data reported in the literature. In general, this compact size set shows to have a regular, efficient, and reliable performance. It can be particularly useful in molecular property calculations that require explicit treatment of the core electrons.

First author: Weglowska, D, High birefringence bistolane liquid crystals: synthesis and properties, RSC ADVANCES, 6, 403, (2016)
Abstract: Twenty liquid crystals both symmetrical and non-symmetrical bistolanes with terminal alkyl, alkoxy and alkylsulfanyl chain and lateral methyl or ethyl group have been synthesized via Sonogashira cross-coupling and their mesomorphic properties have been studied. Most compounds exhibit an enantiotropic nematic phase in a broad temperature range (>40 degrees C). Optical properties of selected compounds have been investigated. They exhibit a high value of birefringence (>0.4).

First author: Durango-Garcia, CJ, Back to basics: identification of reaction intermediates in the mechanism of a classic ligand substitution reaction on Vaska’s complex, RSC ADVANCES, 6, 3386, (2016)
Abstract: The mechanism of methylation of Vaska’s complex trans-[ClIr(CO)(PPh3)(2)] by trimethylgallium was studied and the identification of the spectroscopically detected intermediates was achieved with the aid of computational methods. The reaction pathway, computed by means of density functional theory (M05-2X-D3/def2-SVP), involves the initial formation of a chloride-bridged adduct trans-[(Cl center dot GaMe3) Ir(CO)(PPh3)(2)] to then proceeds to a transition state [(mu(2)-Cl,C-ClMeGaMe2) Ir(CO)(PPh3)(2)]. This transition state subsequently evolves to the methylated adduct [MeIr(CO)(PPh3)(2)center dot(GaMe2Cl)] to finally release the alkylated product trans-[MeIr(CO)(PPh3)(2)] together with GaMe2Cl.

First author: Werle, C, New Pd(II) hemichelates devoid of incipient bridging CO center dot center dot center dot Pd interactions, DALTON TRANSACTIONS, 45, 607, (2016)
Abstract: In organometallic chemistry the commonly known Sidgwick-Langmuir 18 electron rule is constantly being probed for further discovery of molecular compounds that arise as exceptions. The present study examines the formation and the structure of three novel hemichelates of Pd(II) derived from the reaction of in situ-formed indene and hydrophenanthrene-based organometallic anions with three different mu-chloro-bridged palladacycles. Electronic structure and interaction behavior have been calculated with methods of the density functional theory at the (ZORA) MetaGGA-D TPSS-D3(BJ), GGA-D PBE-D3(BJ), and hybrid PBE0-dDsC dispersion corrected levels, all with the implementation of all electron triple zeta single polarization basis set. A particular focus of the theoretical investigation was made on the nature of the interaction between the [Cr(CO)(3)] moiety and the Pd(II) centers, which according to X-ray diffraction analyses lack significant incipient bridging CO center dot center dot center dot Pd character. Structures were further assessed-Natural Bonding Orbitals (NBO), Quantum Theory of Atoms in Molecules (QTAIM), and Extended Transition State with Natural Orbitals for Chemical Valence (ETS-NOCV) analysis methods. As a result, intramolecular interactions of interest, primarily around the Pd atom, were analyzed as a measure of natural atomic orbital (NAO) contributions to the natural bonding orbital (NBO) formation, QTAIM analysis with special attention to the bonding critical points (BCPs), as well as energetic analysis of intramolecular interaction forces by Energy Decomposition Analysis (EDA). Theoretical analyses confirm that attractive electrostatics dominate the stabilization of Pd(II) hemichelates. In the case of complexes 1c, 2c and 3c we expand the known amount of 14 electron transition metal complexes that can be synthesized via reliable synthetic methods. However, complex 3c presented some means of stability but was more reactive to moisture and air under laboratory conditions and escaped thorough analytical characterization.

First author: Norheim, HK, Ligand noninnocence in FeNO corroles: insights from beta-octabromocorrole complexes, DALTON TRANSACTIONS, 45, 681, (2016)
Abstract: The first FeNO octabromocorroles have been synthesized including four beta-octabromo-meso-tris(p-X-phenyl)corrole derivatives Fe[Br(8)TpXPC](NO) (X = CF3, H, CH3, OCH3) and the beta-octabromo-meso-tris-(pentafluorophenyl)corrole complex, Fe[Br8TPFPC](NO). The last complex, which proved amenable to single-crystal X-ray structure determination, exhibits the geometry parameters: Fe N(O) 1.643(8) angstrom, N O 1.158(9) angstrom, and a FeNO angle of 176.4(6)degrees. The more electron-deficient complexes exhibit increased instability with respect to NO loss and also higher infrared NO stretching frequencies (nu(NO)). Interestingly, DFT calculations and IR marker bands indicate a noninnocent {FeNO}(7)-(corrole(center dot 2-)) formulation for all FeNO corroles, both beta-H-8 and beta-Br-8, with essentially the same degree of corrole radical character. Instead, an electron-deficient corrole appears to exert a field effect resulting in reduced Fe-to-NO back-donation, which accounts for both the increased instability with respect to NO loss and the higher nu(NO)’s.

First author: Altarawneh, M, Decomposition of ethylamine through bimolecular reactions, COMBUSTION AND FLAME, 163, 532, (2016)
Abstract: Ethylamine (EA) often serves as a surrogate species to represent aliphatic amines that occur in biofuels. This contribution reports, for the first time, the thermochemical and kinetic parameters for bimolecular reactions of EA with three prominent radicals that form in the initial stages of biomass decomposition; namely, H, CH3 and NH2. Abstraction of a methylene H atom from the EA molecule largely dominates H loss from the two other sites (i.e., methyl and amine hydrogens) for the three considered radicals. We demonstrate that, differences in bond dissociation enthalpies of methylene C-H bonds among EA, ethanol and propane reflect their corresponding HOMO/LUMO energy gaps. At low and intermediate temperatures, the rate of H abstraction from the methylene site in EA exceeds the corresponding values for propane and ethanol. As the temperature rises, matching entropic factors induce comparable rate constants for the three molecules.

First author: Rezvani, M, Structural and electronic properties of metalloporphyrin (MP, M = Fe, Co and Zn) adsorbed on single walled BNNT and SiCNT, APPLIED SURFACE SCIENCE, 360, 69, (2016)
Abstract: In the present work, we report a detailed theoretical investigation of a series of metalloporphyrin, MP (M=FeP, CoP and ZnP), molecules interacting with silicon carbide nanotube (SiCNT) by means of density functional theory (DFT) calculations. In all calculations, we used the Perdew-Burke-Erzenhof (PBE) functional as employed in the SIESTA package. The detailed analysis of the structural and electronical properties of various optimized configurations is performed. The results show that among the MPs, adsorption of FeP molecule on the Si site with zigzag orientation is the most energetically preferable with a binding energy of -2.10 eV. Compared to SiCNTs, boron nitride nanotubes (BNNTs) have weaker interaction strength with the FeP molecule with -0.34 eV of binding energy. We have analyzed charge transfer between two interacting species trough well-known Mulliken, Hirshfeld and Voronoi charges analysis for aforementioned systems. The spin-polarized DFT calculations showed that the density of states (DOSs) are spin-polarized for the Fe-BNNT complex while the spin-polarization of the DOS spectra turn out to be less notable for MP-SiCNT complexes. Our results propose that FeP-SiCNT complex could be used for interesting applications in solar cell technology and nano-biosensors while FeP-BNNT complex might be considered for spintronic molecular devices.

First author: Janicki, MJ, STRUCTURE AND SURFACE ENERGY OF BOTH FLUORITE HALVES AFTER CLEAVING ALONG SELECTED CRYSTALLOGRAPHIC PLANES, PHYSICOCHEMICAL PROBLEMS OF MINERAL PROCESSING, 52, 451, (2016)
Abstract: The density functional theory, supported with a commercial software, was used to compute the geometry and surface energy of fluorite cleaved along the (111), (110) and (100) planes. In the case of cleaving a piece of fluorite along the (111) plane the two newly created surfaces are identical consisting of fluorite ions with the surface energy equal to 0.384 J/m(2). Cleaving fluorite along the (110) plane also provides identical halves and, both contain one Ca ion next to two F ions, with the surface energy equal to 0.723 J/m(2). When cleaving takes place along the (100) plane, it creates two corresponding halves with different surface structures. One half, having only surface Ca ions (100(Ca)) has the surface energy equal to 0.866 J/m(2), while the surface energy of the second half, having only F surface ions (100(F)), is 0.458 J/m(2). Different structures and energies of the corresponding fluorite surfaces, that is (100(Ca)) and (100(F)) planes, should have an impact on their chemical properties, including hydrophobicity expressed by contact angle. The calculations performed in the paper also showed that reorganization of fluorite surfaces after cleaving was insignificant for all of the investigated planes.

First author: Migal, YF, Impurity and alloying elements on grain surface in iron: Periodic dependence of binding energy on atomic number and influence on wear resistance, COMPUTATIONAL MATERIALS SCIENCE, 111, 503, (2016)
Abstract: A quantum chemical analysis of interaction of impurity and alloying elements with grain surface in iron is carried out. The elements of the first five periods (from hydrogen to xenon) are considered. The cluster and slab models are used. Within these models the boundary between grains is imitated by a multilayered system including atoms of two neighboring grains of iron and a layer of the impurity (alloying) atoms between them. Grain surfaces with the Miller indices (100) and (110) are considered. The energy needed for disintegration (decohesion) of the system into two parts is determined. It is shown that dependence of decohesion energy of the system on atomic number of the impurity (alloying) atoms is of the same type for different models. It testifies to opportunity of studying such dependence by means of simple models and carrying out on this basis a classification of elements based on their ability to strengthen grain boundaries. The produced estimates of compatibility of the elements with iron on grain boundaries in steel agree with the known experimental data and correspond to Mendeleev’s periodic law. Possibilities of diffusion introduction of the strengthening elements into steel surface layers with a view to increase their wear resistance are discussed. The discovered dependences can be used for the prediction of wear resistance and strength properties of polycrystalline materials with various alloying additives.