TlxO (x = 2 - 4) contain novel linear di-coordinated, T-shaped tri-coordinated and square-planar tetra-coordinated oxygen
Publication date: Available online 31 March 2017 Source:Computational and Theoretical Chemistry Author(s): Ke Zhou, Soumendra Roy, Cai-bin Zhao The clusters TlxO (x = 2 - 4) were studied using density functional theory (B3PW91). The global minima contain linear di-coordinated, T-shaped, tri-coordinated and square-planar tetra-coordinated oxygen for Tl2O, Tl3O and Tl4O, respectively. The 18-valence electron rule and the preference for planar structure for Tl4 contribute to square structure for Tl4O. The NICS values reveal that the σ and π double aromaticity (especially π aromaticity) contributes to stabilizing ...
Source: Computational and Theoretical Chemistry - March 31, 2017 Category: Chemistry Source Type: research

The guanylated bioamine agmatine – A theoretical investigation of its structure and exceptional high basicity in the gas phase
Publication date: Available online 27 March 2017 Source:Computational and Theoretical Chemistry Author(s): Ewa D. Raczyńska, Jean-François Gal, Pierre-Charles Maria The guanylated bioamine agmatine, H2N(CH2)4–N=C(NH2)2 ⇌ H2N(CH2)4–NH–C(NH2)=NH, formed by decarboxylation of the proteinogenic amino acid arginine, plays an important role in the physiological processes of living organisms. Its structure is marked by the flexibility of the four-carbon chain connecting the two potentially basic amino and guanidino sites. Owing to these noteworthy properties and the questionable literature data on its...
Source: Computational and Theoretical Chemistry - March 28, 2017 Category: Chemistry Source Type: research

Accurate predictions of spectroscopic and molecular properties of 20 low lying electronic states of SiP+ cation
Publication date: Available online 28 March 2017 Source:Computational and Theoretical Chemistry Author(s): Yishi Zhang, Zunlue Zhu, Dan Zhou, Deheng Shi, Jinfeng Sun The potential energy curves (PECs) of 20 low lying electronic states of SiP+ cation are calculated by the internally contracted multi-reference configuration interaction approach. All the 20 low lying electronic states generated by the first two dissociation channels Si+(2Pu)+P(4Su) and Si+(2Pu)+P(2Du). The Davidson correction is taking into account in the calculation. Meanwhile, core-valence correlation and scalar relativistic corrections are included. All t...
Source: Computational and Theoretical Chemistry - March 28, 2017 Category: Chemistry Source Type: research

Electronic structure calculation of the MgAlk (Alk=K, Rb, Cs) molecules for laser cooling experiments
Publication date: 15 May 2017 Source:Computational and Theoretical Chemistry, Volume 1108 Author(s): Dunia Houalla, Wael Chmaisani, Nayla El-Kork, Mahmoud Korek The potential energy curves for the molecules MgK, MgRb and MgCs have been computed by using the ab initio CASSCF/ (MRCI+Q) calculation. For the considered electronic states the static and transition dipole moment curves have been calculated along with the Franck-Condon factor (FCF), the spectroscopic constants Te, ωe, ωexe, Be, Re, and the fraction of ionic character. By using the canonical functions approach, the ro-vibrational constants Ev, Bv, Dv a...
Source: Computational and Theoretical Chemistry - March 28, 2017 Category: Chemistry Source Type: research

Application of Pristine and Ni-decorated B12P12 Nano-clusters as Superior Media for Acetylene and Ethylene Adsorption: DFT Calculations
In this study, density functional theory (DFT) method with B3LYP-D and MPW1PW91 functionals is carried out to explicate the adsorption properties of small unsaturated hydrocarbons (acetylene and ethylene molecules) on the surfaces of pristine and Ni-decorated B12P12 nano-clusters. More specifically, binding energies, natural bond orbital (NBO) charge transfer, dipole moment, frontier molecular orbitals, density of states (DOS), and global indices of activities are analyzed to deeply perceive the fluctuations of electronic and chemical properties of pure and Ni-decorated B12P12 nano-cage upon acetylene and ethylene adsorpti...
Source: Computational and Theoretical Chemistry - March 26, 2017 Category: Chemistry Source Type: research

Donor-Acceptor interactions as descriptors of the free radical scavenging ability of flavans and catechin
Publication date: Available online 24 March 2017 Source:Computational and Theoretical Chemistry Author(s): Erika N. Bentz, Alicia B. Pomilio, Rosana M. Lobayan Interest in food phenolics has increased in recent years largely due to their antioxidant capacity, free radical scavenging, and potential health benefits. In literature two main reaction mechanisms have been proposed for their role as free radical (FR) scavengers, i.e., the mechanism of a hydrogen atom transfer (HAT) governed by the O-H bond dissociation enthalpy (BDE), and the mechanism of single electron transfer (SET) governed by an electron transfer process, t...
Source: Computational and Theoretical Chemistry - March 25, 2017 Category: Chemistry Source Type: research

Theoretical study of Au4 Thymine, Au20 and Ag20 Uracil and Thymine Complexes for Surface Enhanced Raman Scattering
Publication date: Available online 14 March 2017 Source:Computational and Theoretical Chemistry Author(s): Himadri De, Ankan Paul, Ayan Datta A Density Functional Theory (DFT) study using the relativistic effective core potentials (RECPs) is performed with an aim to understand the relative energies and gain deeper insight of the preferential binding of the sites of nucleobases towards particular sites of tetrahedral twenty atom Au and Ag clusters and Au4 cluster using reactivity descriptors. Such calculations carry high values towards understanding the relativistic effects of the Au atom towards the Surface Enhanced Raman...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

A rigorous nonorthogonal configuration interaction approach for the calculation of electronic couplings between diabatic states applied to singlet fission
Publication date: Available online 14 March 2017 Source:Computational and Theoretical Chemistry Author(s): Meilani Wibowo, Ria Broer, Remco W.A. Havenith For the design of efficient singlet fission chromophores, knowledge of the factors that govern the singlet fission rate is important. This rate is approximately proportional to the electronic coupling between the lowest (diabatic) spin singlet state that is populated following photoexcitation state and a so-called 1TT state. The latter state is characterised by two triplets, each localised on one of two neighbouring molecules, which are coupled into a singlet. Here, we s...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Chemical bonding in the pentagonal-pyramidal benzene dication and analogous isoelectronic hexa-coordinate species
Publication date: Available online 18 March 2017 Source:Computational and Theoretical Chemistry Author(s): Felipe Fantuzzi, David Willian Oliveira de Sousa, Marco Antonio Chaer Nascimento The nature of the chemical bond in the pentagonal-pyramidal benzene dication and related species was described by Modern Valence Bond calculations and the Generalized Product Function Energy Partitioning method. The results suggest that the π space of C6H6 2+ is composed of a donor-acceptor bond from a cyclopentadienyl anion moiety, described as a 5c–6e π bonding, to a triply charged Lewis acid CH structure. Similar results w...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Epimeric and anomeric relationship of octyl- α-D-gluco/galactosides: insight from density functional theory and atom in molecules studies
Publication date: Available online 20 March 2017 Source:Computational and Theoretical Chemistry Author(s): Sara Ahmadi, Vijayan ManickamAchari, Zahir Hussain, Rauzah Hashim Density functional theory calculations on three conformers, gt (gauche-trans), gg (gauche-gauche) and tg (trans-gauche) of n-octyl-α-D-glucoside (C8O-α-Glc) and n-octyl-α-D-galactoside (C8O-α-Gal) were performed for geometry optimization at the B3LYP/6-311++G∗∗ level. Both of these molecules are epimers differing only in the orientation of the hydroxyl group at the C4 position. We investigated electronically the ef...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

On the Performance of Generalized Valence Bond Theory in Predicting Magnetic Exchange Coupling Constant in Organic Diradicals: A Comparison with Hartree-Fock Theory
Publication date: Available online 21 March 2017 Source:Computational and Theoretical Chemistry Author(s): Sudip Sarkar, Tamal Goswami, Debojit Bhattacharya, Anirban Misra We have investigated four different already synthesized meta- and para-connected diradicals to get their magnetic exchange coupling constants (J) through generalized valence bond (GVB) approach and also with Hartree-Fock (HF) theory with a view to establish the superiority of GVB method over HF theory for the prediction of J. In doing so, at first optimization of these molecules are done at B3LYP level of density functional theory using the 6-31++g(d) b...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Quantum Investigation into Intermolecular Interactions between Bisphenol A and 2-Vinyl/4-vinylpyridine: Theoretical Insight into Molecular Imprinting Complexes
Publication date: Available online 21 March 2017 Source:Computational and Theoretical Chemistry Author(s): Panpan Zhang, Xiuyan Ji, Hongxing Zhang, Baohui Xia Molecular imprinting complexes of bisphenol A (BPA) templates with the isomeric functional monomers 2-vinylpyridine (2-Vpy, a) and 4-vinylpyridine (4-Vpy, b) in a molar ratio of 1:1 (1a, 1b) and 1:2 (2a, 2b) were investigated by quantum chemical calculations at the B3LYP/6-311++g(d,p) level. The optimized stable geometrical structures of the complexes revealed close contact between the N site of the functional monomer and the –OH group in BPA, with N…H(...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Insight into the function of the key residues in the binding clefts of the substrate with CBM4-2 of xylanase Xyn10A by molecular modeling and free energy calculation
Publication date: Available online 21 March 2017 Source:Computational and Theoretical Chemistry Author(s): Hongsu Wang, Yang Chen, Can Huang, Mengxue Diao, Yan Zhou In this work, it is revealed that the residues of Asn31, Trp69, Glu72, Phe110, Arg115, His117 and Arg142 play the key role in the stabilization of the binding of xylopentaose with carbohydrate binding modules (CBM4-2) of xylanase Xyn10A, which is similar with the result of the previous report. The results were compared with that of mutant type protein, X-2, with xylopentaose. Interestingly, due to the residue mutation of X-2, xylopentaose was deviated from the...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Lowest energy states of hubbard ladder model with infinite electron repulsion
Publication date: Available online 23 March 2017 Source:Computational and Theoretical Chemistry Author(s): V.O. Cheranovskii, E.V. Ezerskaya, D.J. Klein, V.V. Tokarev We apply cyclic spin permutation formalism to the study the lowest energy states of the infinite-repulsion Hubbard model on n-leg ladders. For ladder fragments with the electron densities ρ =1 – (2n)–1 we show that the alternation in the values of one-site energies for neighboring rungs leads to the stabilization of the ground state of ladder fragments with the maximal value of the total spin (S 0=S max) against the increase of the interactio...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Predicting standard reduction potential for anticancer Au(III)-complexes: A DFT study
Publication date: Available online 23 March 2017 Source:Computational and Theoretical Chemistry Author(s): G.Y. Sánchez Delgado, D. Paschoal, H.F. Dos Santos The Au(III) complexes are considered promising for cancer treatment given their structural and electronic similarities to Pt(II) complexes. Different from Pt(II) complexes, the Au(III) compounds are much less stable under physiological conditions, due to their high Au3+/Au+ reduction potential. Therefore, great effort has been done to develop more stable Au(III) complexes in order to explore and improve their biological activity. Density functional theory (DFT...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

DFT investigation of CF bond activation by a low-coordinate cobalt(I) complex
Publication date: 1 April 2017 Source:Computational and Theoretical Chemistry, Volume 1105 Author(s): Quan Jiang, Thomas R. Cundari A low-coordinate cobalt(I) complex, LtBuCo [LtBu =bulky β-diketiminate ligand] was reported to be capable of cleaving the CF bond in fluoroarenes. To investigate the mechanism of CF bond activation, a simplified ligand model (LMeCo) with methyl substituents was first used as a guide before the full LtBuCo complex was calculated. DFT calculations indicate the free energy change of CF oxidative addition is −3.9kcalmol−1 to yield a Co(III) product. When the initial interaction o...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Chiral penta-graphene nanotubes: Structure, bonding and electronic properties
Publication date: 15 May 2017 Source:Computational and Theoretical Chemistry, Volume 1108 Author(s): J.J. Quijano-Briones, H.N. Fernández-Escamilla, A. Tlahuice-Flores In this work, we carry out a computational study on the structure and electronic properties of penta-graphene nanotubes (penta-CNTs), based on a periodic plane wave-pseudopotential approach. We consider chiral structures, among zigzag and armchair structures which were reported previously. Interestingly, the energetic stability (Binding energy per atom or BEA) of chiral penta-CNTs is comparable with (n,n) penta-CNTs. In such manner that chiral (5,10)...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

The electronic and structural responses of B12N12 nanocage toward the adsorption of some nonpolar X2 molecules: X=(Li, Be, B, N, O, F, Cl, Br, I): A DFT approach
Publication date: 15 May 2017 Source:Computational and Theoretical Chemistry, Volume 1108 Author(s): Aidin Bahrami, Mohammad Balooch Qarai, Nasser L. Hadipour Density functional theory calculations at the M06 with 6-311+G(d) and LANL2DZ basis sets were carried out to investigate the adsorption of some nonpolar X2 molecules, X=(Li, Be, B, N, O, F, Cl, Br, I), on the B12N12 nanostructure to analyze the effects and aspects of nonpolarity properties upon adsorption processes. Certain aspects of the interfacial phenomena dependent on both structural and electronic characteristics of B12N12 associated with adsorption processes ...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Relativistic rotation-vibrational energies for the CP molecule
Publication date: 15 May 2017 Source:Computational and Theoretical Chemistry, Volume 1108 Author(s): Chun-Sheng Jia, Teng He, Zheng-Wei Shui We solve the Dirac equation with the improved Tietz potential by using the supersymmetric shape invariance approach, and obtain the relativistic rotation-vibrational energy equation for diatomic molecules. We find that the relativistic effects subject to the relative motion of the ions increase slightly the vibrational energies for the X2∑+ state of the CP molecule. The improved Tietz potential energy model does not show any difference in comparison to the nonrelativistic results...
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

TD-DFT benchmark: Excited states of atoms and atomic ions
Publication date: 15 May 2017 Source:Computational and Theoretical Chemistry, Volume 1108 Author(s): Marcin Gronowski Time-Dependent Density Functional Theory (TD-DFT) calculations in their conventional form, starting from the ground, low-spin state of atoms and atomic ions, have been carried out to examination the precision of excitation energy predictions. Results obtained for several functionals and basis sets have been compared with experimental data and include valence low- and high-spin states. All DFT methods achieve basis sets limits extremely quickly, but produce results that are far from the experimental values....
Source: Computational and Theoretical Chemistry - March 24, 2017 Category: Chemistry Source Type: research

Theoretical investigation of the molecular properties of PtBO and PdBO
Publication date: Available online 11 March 2017 Source:Computational and Theoretical Chemistry Author(s): Jiwon Moon, Joonghan Kim The molecular properties of the ground and low-lying excited states of PtBO and PdBO were calculated using density functional theory and high-level ab initio methods. Spin-orbit coupling was also considered to identify the true ground states of PtBO and PdBO using the state-interaction approach. PBE0 gives reasonable performances for calculating the molecular properties of PtBO and PdBO. The ground states of PtBO and PdBO are the 2Δ5/2 and 2Σ+ 1/2 states, respectively. According t...
Source: Computational and Theoretical Chemistry - March 12, 2017 Category: Chemistry Source Type: research

A possible valence-bond approach to symmetry-adapted perturbation theory
Publication date: Available online 11 March 2017 Source:Computational and Theoretical Chemistry Author(s): P. Reinhardt The multi-configurational ansatz of valence-bond theory may serve as basis for calculating intermolecular interaction energies in a non-orthogonal basis. We look in the present contribution at the possibility to obtain the 1st-order electrostatic interactions from breathing-orbital valence-bond densities, and the 2nd-order dispersion energy from dipole-dipole interactions. The discussion is based on numerical results for the interaction of two N2O molecules. Graphical abstract (Source: Computational and ...
Source: Computational and Theoretical Chemistry - March 12, 2017 Category: Chemistry Source Type: research

Bimetallic PbnCun (n=2 –14) clusters were investigated by density functional theory
Publication date: 15 April 2017 Source:Computational and Theoretical Chemistry, Volume 1106 Author(s): Gaofeng Li, Jiaju Wang, Xiumin Chen, Zhiqiang Zhou, Hongwei Yang, Bin Yang, Baoqiang Xu, Dachun Liu In order to investigate the structural and electronic properties of bimetallic PbnCun (n=2–14) clusters, density functional theory (DFT) were applied. The ground-state structures, average bond distances, binding energies, Mülliken population analysis, vertical ionization potentials, vertical electron affinities, HOMO-LOMO gaps and electronic density of states of PbnCun (n=2–14) bimetallic clusters were cal...
Source: Computational and Theoretical Chemistry - March 12, 2017 Category: Chemistry Source Type: research

Systematic Search of Conformations of Five Tetrapeptides and a Divide and Conquer Strategy for the Predictions of Peptide Structures
Publication date: Available online 10 March 2017 Source:Computational and Theoretical Chemistry Author(s): Bing Yang, Zijing Lin Conformations of biomolecules are the basis for their property studies and the predictions of peptide structures are of high interest in life science but very difficult in practice. The potential energy surfaces of five tetrapeptides, GGGG, GVGG, GTGG, GGYG and GSDG, are thoroughly explored here by considering all combinations of their internal single bond rotamers. The structural features of all the important tetrapeptide conformers are analyzed in detail and are characterized with five hydroge...
Source: Computational and Theoretical Chemistry - March 11, 2017 Category: Chemistry Source Type: research

On the electronic structures and s/p-orbital aromaticity in the Hg3Al3+/ −, Hg3Al3Li, and Hg3Al3Be+ clusters
Publication date: 15 April 2017 Source:Computational and Theoretical Chemistry, Volume 1106 Author(s): Biao Jin, Qiao Jin, Fu-Kai Jin The equilibrium geometries, harmonic vibrational frequencies, stabilities, and chemical bonding of the low-lying states for all-metal Hg3Al3 +/−, Hg3Al3Li, and Hg3Al3Be+ clusters are investigated using 2nd order Møller–Plesset perturbation theory. The extensive search for the global minimum structures of Hg3Al3 +/− at the MP2 level of theory with 6-311++G∗ basis set for Al and CEP-121G basis set for Hg reveals that the ground states of the Hg3Al3 + and Hg3Al3...
Source: Computational and Theoretical Chemistry - March 11, 2017 Category: Chemistry Source Type: research

On the stability of clusters containing all-cis 1,2,3,4,5,6-hexafluorocyclohexane
Publication date: Available online 9 March 2017 Source:Computational and Theoretical Chemistry Author(s): Sean A.C. McDowell A computational study of strongly-bound triad clusters involving the all-cis 1,2,3,4,5,6-hexafluorocyclohexane molecule (F6C6H6) sandwiched between oppositely-charged ions, as well as the constituent ion/F6C6H6 dyad subunits, was undertaken at the B3LYP/6-31++G(d,p) level of theory. The model M+…F6C6H6…X− clusters involve the simultaneous attachment of a cation (M+) to the “negative” face of F6C6H6 (via interaction with the axial F-C bonds) and an anion (X−) to ...
Source: Computational and Theoretical Chemistry - March 10, 2017 Category: Chemistry Source Type: research

Electronic structure calculation of the MgAlk (Alk= K, Rb, Cs) molecules for laser cooling experiments
Publication date: Available online 8 March 2017 Source:Computational and Theoretical Chemistry Author(s): Dunia Houalla, Wael Chmaisani, Nayla El-Kork, Mahmoud Korek The potential energy curves for the molecules MgK, MgRb and MgCs have been computed by using the ab initio CASSCF/ (MRCI+Q) calculation. For the considered electronic states the static and transition dipole moment curves have been calculated along with the Franck-Condon factor (FCF), the spectroscopic constants Te, ωe, ωexe, Be, Re, and the fraction of ionic character. By using the canonical functions approach, the ro-vibrational constants Ev, Bv,...
Source: Computational and Theoretical Chemistry - March 9, 2017 Category: Chemistry Source Type: research

Structure prediction of nanoclusters from global optimization techniques: computational strategies and connection to experiments
Publication date: Available online 8 March 2017 Source:Computational and Theoretical Chemistry Author(s): Philippe Carbonnière, Michel Rérat, Fernand Spiegelman, Ajit J. ThakkarGraphical abstract (Source: Computational and Theoretical Chemistry)
Source: Computational and Theoretical Chemistry - March 9, 2017 Category: Chemistry Source Type: research

Metal-metal multiple bond in low-valent diuranium porphyrazines and its correlation with metal oxidation state: a relativistic DFT study
Publication date: Available online 8 March 2017 Source:Computational and Theoretical Chemistry Author(s): Ning Qu, Dong-Mei Su, Qun-Yan Wu, Wei-Qun Shi, Qing-Jiang Pan To explore the uranium-uranium bonding nature, a ligated diuranium complex that could be experimentally possible would show features with no bridging ligand constraints (i.e. discrete or unsupported ligand), rigid ligand skeleton and suitable U-ligand bond. In this respect, we have designed and examined a series of diuranium diporphyrazines (Um 2Pz2, m = II, III and IV) using relativistic density functional theory. Optimizations on all possible electron-spi...
Source: Computational and Theoretical Chemistry - March 9, 2017 Category: Chemistry Source Type: research

Photoinduced electron transfer from aromatic amino acids to the excited isoalloxazine in single mutated flavin mononucleotide binding proteins: Effect of the dimer formation on the rate and the electrostatic energy inside the proteins
Publication date: Available online 7 March 2017 Source:Computational and Theoretical Chemistry Author(s): Nadtanet Nunthaboot, Kiattisak Lugsanangarm, Arthit Nueangaudom, Somsak Pianwanit, Sirirat Kokpol, Fumio Tanaka, Seiji Taniguchi, Haik Chosrowjan, Takeshi Nakanishi, Masaya Kitamura Conformational changes in the single mutated flavin mononucleotide binding proteins (FBP), E13K (Glu13 of wild type FBP is replaced by Lys), E13R (Glu13 replaced by Arg), E13T (Glu13 replaced by Thr) and E13Q (Glu13 replaced by Gln) upon dimer formations were studied through the phenomena of photoinduced electron transfer (ET) from tryptop...
Source: Computational and Theoretical Chemistry - March 8, 2017 Category: Chemistry Source Type: research

On the electronic structures and s/p-orbital aromaticity in the Hg3Al3+/ –, Hg3Al3Li, and Hg3Al3Be+ clusters
Publication date: Available online 7 March 2017 Source:Computational and Theoretical Chemistry Author(s): Biao Jin, Qiao Jin, Fu-Kai Jin The equilibrium geometries, harmonic vibrational frequencies, stabilities, and chemical bonding of the low-lying states for all-metal Hg3Al3 +/–, Hg3Al3Li, and Hg3Al3Be+ clusters are investigated using 2nd order Møller–Plesset perturbation theory. The extensive search for the global minimum structures of Hg3Al3 +/– at the MP2 level of theory with 6-311++G∗ basis set for Al and CEP-121G basis set for Hg reveals that the ground states of the Hg3Al3 + and Hg3...
Source: Computational and Theoretical Chemistry - March 8, 2017 Category: Chemistry Source Type: research

NO2 sensing properties of a borazine doped nanographene: a DFT study
Publication date: Available online 6 March 2017 Source:Computational and Theoretical Chemistry Author(s): A. Hosseinian, Z. Asadi, L. Edjlali, A. Bekhradnia, E. Vessally Nanographenes are definite segments of graphene whose end atoms are saturated with hydrogens and their properties are different from those of the graphene because of size confinement. Herein, we investigated the structural properties, reactivity and electronic sensitivity of a newly synthesized borazine-like ring doped nanographene (BNG) to NO2 gas by means of density functional theory. We found that the central and peripheral rings of BNG are aromatic, w...
Source: Computational and Theoretical Chemistry - March 7, 2017 Category: Chemistry Source Type: research

Performance of DFT, MP2, and composite ab initio methods for the prediction of enthalpies of formations of CHON compounds using isodesmic reactions
Publication date: Available online 6 March 2017 Source:Computational and Theoretical Chemistry Author(s): Olga V. Dorofeeva, Evgeniya L. Osina This paper assesses the performance of quantum chemical models with regard to the calculation of enthalpy of formation of CHON molecules using isodesmic reactions. The high accuracy of prediction of enthalpy of formation of CHON compounds can be achieved by the combination of isodesmic reaction scheme with composite ab initio methods. The best composite methods, such as G4, G4MP2, CBS-QB3, and CBS-APNO, can attain near chemical accuracy or better depending on reaction type. Other c...
Source: Computational and Theoretical Chemistry - March 7, 2017 Category: Chemistry Source Type: research

Values of ( ΔfHo298.15)(g) and (S°298.15)(g) of the several N,N-ethylenebisalkaneamides calculated using RB3LYP/6-31G(D,P) AND CBS-4M approaches, and their correlation dependencies
Publication date: 1 April 2017 Source:Computational and Theoretical Chemistry, Volume 1105 Author(s): Gregory A. Poskrebyshev In the present work, the thermochemical properties of the several N,N′-ethylenbisalkaneamides are calculated using RB3LYP/6-31G(d,p), UB3LYP/6-311++G(d,p), CBS-4M and CBS-Q approaches. The values of standard enthalpies of their formation ((Δf H o 298.15)(g)) are calculated using thermochemistry of the isodesmic reactions as well as using the group additivity methods. Due to the high uncertainty in the values of (Δf H o 298.15)(g) of the high atomic molecules, calculated using diff...
Source: Computational and Theoretical Chemistry - March 7, 2017 Category: Chemistry Source Type: research

Negative Ion Wolff Rearrangement of Some Diazoketones: A Theoretical Mechanistic Study
Publication date: Available online 4 March 2017 Source:Computational and Theoretical Chemistry Author(s): Ritu Arora, Rita Kakkar The mechanism of the Wolff rearrangement of some deprotonated diazocarbonyl compounds has been studied using density functional calculations, for both the gas and aqueous phases. The anionic rearrangement of the deprotonated analogues proceeds in a similar manner to the neutral counterparts. In the gas phase, the syn and anti conformers form the deprotonated ketene product concertedly. In certain analogues, the reaction of the anti conformer occurs non-concertedly, involving a deprotonated carb...
Source: Computational and Theoretical Chemistry - March 6, 2017 Category: Chemistry Source Type: research

Bimetallic PbnCun (n=2-14) clusters were investigated by density functional theory
Publication date: Available online 3 March 2017 Source:Computational and Theoretical Chemistry Author(s): Gaofeng Li, Jiaju Wang, Xiumin Chen, Zhiqiang Zhou, Hongwei Yang, Bin Yang, Baoqiang Xu, Dachun Liu In order to investigate the structural and electronic properties of bimetallic PbnCun (n=2-14) clusters, density functional theory (DFT) were applied. The ground-state structures, average bond distances, binding energies, Mülliken population analysis, vertical ionization potentials, vertical electron affinities, HOMO-LOMO gaps and electronic density of states of PbnCun (n=2-14) bimetallic clusters were calculated b...
Source: Computational and Theoretical Chemistry - March 4, 2017 Category: Chemistry Source Type: research

Orthogonal Valence Bond Hamiltonians incorporating dynamical correlation effects
Publication date: Available online 2 March 2017 Source:Computational and Theoretical Chemistry Author(s): E. Giner, C. Angeli, A. Scemama, J.-P. Malrieu The Complete Active Space Self-Consistent Field calculations offer a definition of a set of molecularly optimized valence mono-electronic functions and a basis of Orthogonal Valence Bond (OVB) configurations. However this variational description misses important dynamical correlation effects, affecting both the energy and the weights of the various OVB components. The dynamical polarization effects induce for instance an increase of the weight of the ionic VB components. ...
Source: Computational and Theoretical Chemistry - March 3, 2017 Category: Chemistry Source Type: research

Dissociation of Methane on Ni4 Cluster-A DFT Study
Publication date: Available online 1 March 2017 Source:Computational and Theoretical Chemistry Author(s): Ghanashyam Roy, Asoke Prasun Chattopadhyay The sequential four step dissociation of methane on Ni4 cluster has been investigated using density functional theory. The adsorption of CH4, CHx, C and H are exothermic and Gibbs free energy changes are negative on bare cluster. The dissociation of methane on Ni4 cluster is endothermic and thermodynamically not favorable at standard condition (T=298K, P=1atm). The dissociation of CHx(x=1-3) species on bare cluster show higher activation energy barrier than on the hydrogen pr...
Source: Computational and Theoretical Chemistry - March 2, 2017 Category: Chemistry Source Type: research

Complexation of the Zn, Co, Cd, and Pb ions by metallothioneins: A QM/MM simulation
Publication date: Available online 1 March 2017 Source:Computational and Theoretical Chemistry Author(s): © Sergey A. Peshkov, Sergey L. Khursan Complexation of divalent metal ions (Zn, Co, Cd and Pb) with metallothioneins (MT), typical low-molecular proteins of diverse higher organisms, has been theoretically studied within the all-electron approximation B3LYP/DZP. The active site of MT (metal ions and cysteine residues) adopts the structure, in which cadmium, cobalt and zinc ions reveal a tetrahedral location of the sulfur atoms. A pyramidal structure is typical for the coordination environment of the lead complexe...
Source: Computational and Theoretical Chemistry - March 2, 2017 Category: Chemistry Source Type: research

On the structure of the H2CO-HNO dimer: Planar or orthogonal?
Publication date: Available online 1 March 2017 Source:Computational and Theoretical Chemistry Author(s): Alfred Karpfen The potential energy surface of the dimer formed between formaldehyde and nitrosyl hydride has been investigated theoretically at the MP2 and CCSD(T) levels using several extended basis sets. Six low-lying minima, all with Cs symmetry, were detected. Two of them are planar, four are non-planar. All dimers display geometry changes and vibrational frequency shifts characteristic for a formyl group engaged in hydrogen bonding: red shifts of C=O stretches and blue shifts of C-H stretches. In five of the dim...
Source: Computational and Theoretical Chemistry - March 2, 2017 Category: Chemistry Source Type: research

Localized Electron Wave Packet Description of Chemical Bond and Excitation: Floating and Breathing Gaussian with Valence-Bond Coupling
Publication date: Available online 1 March 2017 Source:Computational and Theoretical Chemistry Author(s): Koji Ando A model of localized electron wave packets (WPs) with variable position and width (floating and breathing) that are spin-coupled as per the valence-bond theory is presented. It produces accurate potential energy curves of LiH in the ground singlet and triplet states. Quantization in a mean-field approximation of the motion of a WP that corresponds to the Li 2s electron generates semi-quantitative potential energy curves of low energy excited states. Real-time semiquantal dynamics of the WP induced by an inte...
Source: Computational and Theoretical Chemistry - March 2, 2017 Category: Chemistry Source Type: research

The effects of water microsolvation on the C2O4 −↔CO2·CO2− core switching reaction: Perspective from exploration of pathways on the potential energy surfaces of small [(CO2)2(H2O)n]− (n=1 and 2) clusters
Publication date: 1 April 2017 Source:Computational and Theoretical Chemistry, Volume 1105 Author(s): Manami Kondo, Toshiyuki Takayanagi Water microsolvation effects on the C2O4 − ↔CO2·CO2 − anion core switching reaction in the small [(CO2)2(H2O) n ]− (n =1 and 2) clusters have been computationally studied. All low-energy rearrangement pathways have been explored using global reaction route mapping (GRRM) techniques. Both the C2O4 − dimer anion core and CO2·CO2 − monomer anion core have various hydration structures. The former is stable in [(CO2)2(H2O)1]− while the la...
Source: Computational and Theoretical Chemistry - March 2, 2017 Category: Chemistry Source Type: research

Tuning spin gap in anthracene and tetracene for singlet fission: An exact PPP model study in the VB basis
Publication date: Available online 28 February 2017 Source:Computational and Theoretical Chemistry Author(s): Y. Anusooya Pati, S. Ramasesha We have studied donor-acceptor (D-A) substituted anthracene and tetracene to explore the strength and nature of substitutions that satisfy the energy criteria for singlet fission. We have carried out exact π - electron calculation on symmetrically substituted anthracene and tetracene by employing the Valence Bond technique and exactly solving the PPP model. The singlet manifold for tetracene spans a space of ≈ 450 million VB diagrams while the triplet spans a space of &asymp...
Source: Computational and Theoretical Chemistry - March 1, 2017 Category: Chemistry Source Type: research

Low-lying Ptn cluster structures (n=6 –10) from global optimizations based on DFT potential energy surfaces: Sensitivity of the chemical ordering with the functional
Publication date: Available online 17 February 2017 Source:Computational and Theoretical Chemistry Author(s): Rui Li, Marc Odunlami, Philippe Carbonnière Through the example of the small Pt6 clusters the low-lying structures and their chemical ordering obtained with the four classes of functionals: GGA (PBE), hybrid GGA (PBE0), meta-GGA (TPSS) and hybrid meta-GGA (TPSSh), were investigated with the cc-pVTZpp basis set. Moreover, the spin multiplicities from singlet to nonet were considered. The results yield two different pictures: singlet to septet planar structures are favored with the pure functionals while quin...
Source: Computational and Theoretical Chemistry - February 25, 2017 Category: Chemistry Source Type: research

DFT Investigation of C-F Bond Activation by a Low-Coordinate Cobalt(I) Complex
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): Quan Jiang, Thomas R. Cundari A low-coordinate cobalt(I) complex, LtBuCo [LtBu = bulky β-diketiminate ligand] was reported to be capable of cleaving the C-F bond in fluoroarenes. To investigate the mechanism of C-F bond activation, a simplified ligand model (LMeCo) with methyl substituents was first used as a guide before the full LtBuCo complex was calculated. DFT calculations indicate the free energy change of C-F oxidative addition is -3.9 kcal mol-1 to yield a Co(III) product. When the initial interaction...
Source: Computational and Theoretical Chemistry - February 25, 2017 Category: Chemistry Source Type: research

Adsorption manners of hydrogen on Pt(100), (110) and (111) surfaces at high coverage
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): Qiaocui Shi, Rong Sun Density functional theory (DFT) calculations were performed to investigate hydrogen adsorption on Pt(100), (110) and (111) surfaces at different coverages. It is found that each surface has different hydrogen adsorption strength and saturated coverages, and Pt(111) surface has the weakest adsorption as well as smallest saturated coverage. Thermodynamics method was applied to include the effects of temperature and hydrogen partial pressure on the stable hydrogen coverage, where the built phase...
Source: Computational and Theoretical Chemistry - February 25, 2017 Category: Chemistry Source Type: research

Theoretical investigation effects of anchor groups on photovoltaic properties for the C217-based dye sensitizer
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): Caibin Zhao, Xiaohua Guo, Jianqi Ma, Hongguang Ge, Lingxia Jin, Qiang Zhang Designing and synthesizing high-performable dye sensitizers has kept an important and hot issue in dye-sensitized solar cells (DSSCs). In this work, with the (TiO2)16 cluster, we theoretically investigated the effects of five different anchor groups (-CONHOH, -CSSH, -OH, -PO3H2, and -SO2H) on the photovoltaic properties of the C217 dye by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calcula...
Source: Computational and Theoretical Chemistry - February 25, 2017 Category: Chemistry Source Type: research

Theoretical insights into the phosphorescent process of a series of 2-(2-trifluoromethyl) pyrimidine-pyridine based heteroleptic iridium(III) compounds: The influence of the ancillary ligand
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): Xin Wang, Songyan Feng, Xiaolin Wang, Chunzhang Wang, Li Wang, Jinglai Zhang The structure-property relationship is theoretically elucidated for four heteroleptic Ir(III) complexes with different ancillary ligand (See Fig. 1). Besides the ground state geometric parameters, the different triplet states are finally determined by both the density functional theory (DFT) and time-dependent DFT (TDDFT) methods. On the basis of the respective optimized triplet geometry, the emissive wavelength is determined by the &Delt...
Source: Computational and Theoretical Chemistry - February 25, 2017 Category: Chemistry Source Type: research

Alkyl-Functionalized and Methylidyne-Doped Boron Nitride Fullerene Polymer Precursors
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): Ryan C. Fortenberry Boron nitride fullerenes are stabilized by including methylidyne (CH) groups in place of some of the nitrogen atoms. Such a process also produces carbon atoms in the cage that can subsequently be functionalized. The present work shows that attaching ethyl groups to these carbons destabilizes the fullerene cages somewhat. However, replacing other nitrogen atoms with CH groups returns to a path of stabilization. In fact, the energy minima for inclusion of an ethyl substituted carbon and five CH g...
Source: Computational and Theoretical Chemistry - February 24, 2017 Category: Chemistry Source Type: research

Borophene nanosheet molecular device for detection of ethanol – A first-principles study
Publication date: Available online 24 February 2017 Source:Computational and Theoretical Chemistry Author(s): V. Nagarajan, R. Chandiramouli The electronic and ethanol adsorption properties of hydrogenated 2D borophene nanosheet device are studied through non-equilibrium Green’s function (NEGF) and density functional theory (DFT) method. The adsorption property of ethanol on borophene nanosheet is investigated in terms of average energy gap variation, adsorption energy and Mulliken charge transfer. The variation in the density of states and energy band structure of ethanol adsorbed borophene nanosheet compared with ...
Source: Computational and Theoretical Chemistry - February 24, 2017 Category: Chemistry Source Type: research