DFT study of the reaction between VO2+ and C2H6

The molecular mechanisms of the reaction VO2+ ((1)A(1)/(3)A'') + C2H6 ((1)A(g)) to yield V(OH)(2)(+) ((1)Sigma(+)/(3)Sigma(-)) + C2H4 ((1)A(g)) and/or VO+ ((1)Delta/(3)Sigma) + H2O ((1)A(1)) + C2H4 (Ag-1) have been investigated with density functional theory (DFT) at the B3LYP/6-311G(2d,p) level. Calculations including geometry optimization, vibrational analysis, and Gibbs free energy for the stationary points on the reactive potential energy surfaces at both the singlet (s) and first excited triplet (t) electronic states have been carried out. The most thermodynamically and kinetically favorable pathway is the formation of t-V(OH)(2)(+) + C2H4 along a four-step molecular mechanism (insertion, two consecutive hydrogen transfers, and elimination). A crossing point between s and t electronic states has been characterized. A comparison with previous works on VO2+ + C2H4 (Gracia et al. J. Phys. Chem. A 2003, 107, 3107-3120) and VO2+ + C3H8 (Engeser et al. Organometallics 2003, 22, 3933-3943) reactions allows us a rationalization of the different reactivity patterns. The catalytic role of water molecules in the tautomerization process between hydrated oxide cation, VO(H2O)(+,) and dihydroxide cation, V(OH)(2)(+), is achieved by a water-assisted mechanism.

Combined (13)C NMR and DFT/GIAO studies of the polyketides Aurasperone A and Fonsecinone A

Structural characterization by NMR spectroscopy and DFT calculations was performed for two dimeric naptho-gamma-pyrones, the polyketides Aurasperone A and Fonsecinone A. Experimental data ((13)C NMR chemical shifts and interatomic geometries) were found to be in reasonable agreement with theoretical ones, obtained at B3LYP level for three different basis sets (6-31G/6-31G(d)/6-31G(d,p)). Additionally, the dipolar moments calculation allowed explaining the different solubility for these molecules. The (13)C NMR theoretical chemical shifts were calculated with the GIAO method and the solvent effects were taken into account by means of the PCM approximation. In this work, the DFT/GIAO methodology shows to be a reliable tool in the assignment of experimental NMR chemical shifts of similar molecules. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 108: 2408-2416, 2008.

DFT Study with Inclusion of the Grimme Potential on Anatase TiO2: Structure, Electronic, and Vibrational Analyses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and Electronic Properties of Lithiated SnO2. A Periodic DFT Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Silver(I) complexes with symmetrical Schiff bases: Synthesis, structural characterization, DFT studies and antimycobacterial assays

Synthesis, structural and spectroscopic characterizations, molecular modeling and antimycobacterial assays of new silver(I) complexes with two Schiff bases - MBDA and MBDB - are reported. The complexes [Ag(MBDA) 2]NO3, or AgMBDA, and [Ag(MBDB)NO3] or AgMBDB, were obtained by the reaction of the respective ligands with silver(I) nitrate in methanol. The Schiff bases were previously obtained by mixing ethylenediamine or 1,3-diaminopropane with p-anisaldehyde. The characterizations of the complexes were based on elemental (C, H and N) and thermal (TG-DTA) analyses and 13C and 1H NMR and FT-IR spectroscopic measurements, as well as X-ray structure determination for AgMBDA. Spectroscopic data predicted by DFT calculations are in agreement with the experimental data for the AgMBDA complex. The AgMBDA complex has a monomeric structure with a molar proportion 1:2 Ag/ligand, while AgMBDB presents a 1:1 proportion. The complexes AgMBDA and AgMBDB showed to be more effective against Mycobacterium tuberculosis than antibacterial agent silver sulfadiazine - SSD. © 2013 Elsevier Ltd. All rights reserved.

Eletrônica molecular via método híbrido DFT/FGNE em anéis fenilas acoplados a eletrodos metálicos de nanotubos de carbono: a regra de conformação e quiralidade molecular

Nesta tese, investigamos detalhadamente as propriedades de transporte eletrônico, conformacional e de simetria de estruturas de Nanotubos de Carbono de Parede Simples zigzag (9,0), NCPS zz9, acopladas a anéis fenilas (2, 3, 4 e 5) sob influência de campo elétrico externo (voltagem) via método híbrido da Teoria do Funcional Densidade (DFT) do tipo B3LYP 6-311G(d,p) combinado com Função de Green de Não Equilíbrio (FGNE) e Teoria de Grupo. Verificamos uma boa relação entre: 1- o índice quiral () por Teoria de Grupo e a lei do cos2 (, ângulo diedral) por geometria sob a influência de campo elétrico externo, pois  só depende das posições atômicas (), das conformações, e também está fortemente correlacionada a corrente que passa através do sistema; 2- a condutância normalizada (G/Go) é proporcional a cos2 na região do gap (EHOMO-ELUMO), isto é, nas regiões onde ocorre a ressonância e a resistência diferencial negativa (RDN); 3- o gráfico Fowler-Northeim (FN) exibe mínimo de voltagem (Vmin) que ocorre sempre que a cauda de um pico de transmissão ressonante entra na janela de voltagem, isto é, quando nessas estruturas ocorre uma RDN, pois o número de RDN na curva I-V está associado ao número de Vmin no gráfico FN e pode ser explicado pelo modelo de transporte molecular coerente; 4- a altura da barreira (EF - EHOMO e ELUMO - EF) como função do comprimento molecular; 5- Vmin como função da altura da barreira (EF - EHOMO) e do comprimento molecular. Assim, 1 implica que a conformação molecular desempenha um papel preponderante na determinação das propriedades de transporte da junção; 2 sugere que a lei do cos2 tem uma aplicabilidade mais geral independentemente da natureza dos eletrodos; 3 serve como um instrumento espectroscópico e também para identificar a molécula na junção; 4 e 5 a medida que o comprimento molecular atinge um certo valor (1,3nm) o Vmin permanece praticamente inalterado. Os resultados mostraram que as propriedades estruturais sofrem alterações significativas com o aumento da voltagem que estão em boa concordância com os valores encontrados na literatura. O comportamento das curvas IxV e G/GoxV perdem sua dependência linear para dar origem a um comportamento não linear com aparecimento de RDN. Tal ponto revela a modificação estrutural sofrida pelo sistema. A curva IxV confirmou as afirmações que foram feitas através da análise estrutural para o sistema considerado e mostrou como se dá o fluxo de carga nos sistemas analisados.

Produção de minitubérculos de batata-semente em sistemas hidropônicos NFT, DFT e Aeroponia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

DFT Study on Ce-Doped Anatase TiO2: Nature of Ce3+ and Ti3+ Centers Triggered by Oxygen Vacancy Formation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Metodologia computacional baseada em DFT, para compreensão de processos eletródicos em fases intermetálicas ordenadas

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Preparation, thermal characterization, and DFT study of the bacterial cellulose

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization, thermal behavior, and DFT calculation of solid 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene of some trivalent lanthanides

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A DFT Study of Structural and Electronic Properties of ZnS Polymorphs and its Pressure-Induced Phase Transitions

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Asymmetric and Symmetric Triazenido Cyclopalladated Complexes: Synthesis, Structural Analysis and DFT Calculations

The reaction of [Pd{dmba}(l-N3)]2 (dmba = N,N-dimethylbenzylamine) with 1-(2-fluorophenyl)-3-(4- nitrophenyl)triazenido (L1 ) or 1,3-bis(4-nitrophenyl)triazenido (L2 ) anions, in methanol, and subsequent treatment with pyridine (py) allows the preparation of the corresponding cyclopalladated compounds [Pd(dmba)(L1 )(py)] (1) and [Pd(dmba)(L2 )(py)]py (2). The acentric mononuclear entities of (1) and (2) are connected by weak intermolecular non-classical CAHC hydrogen bonds, which results in 2-D arrangements by translation, along the [1 0 0] and [0 01] crystallographic directions, respectively.

DFT + U Simulation of the Ti4O7-TiO2 Interface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal, spectroscopic and DFT studies of solid benzamide

Thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and DFT theoretical calculations were used to study benzamide. The TG-DTA and DSC curves provided information concerning the melting point, evaporation and thermal stability of the compound. Using the FTIR technique it was possible to confirm the evaporation of the compound with no degradation. Density functional theory (DFT) at the 6-311++G (3df, 3dp) level, provided information regarding the energies involved in HOMO-LUMO transitions and the chemical stability of the compound.