Navegando por Palavras-chave "Density functional theory"
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- ItemSomente MetadadadosAll-boron fullerene exhibits a strong affinity to inorganic anions(Elsevier Science Bv, 2017) Colherinhas, Guilherme; Fileti, Eudes Eterno [UNIFESP]; Chaban, Vitaly V. [UNIFESP]Experimentally observed all-boron fullerene, B-80, inspires systematic investigation of its physical chemical properties and search for possible applications. We hereby report density functional theory calculations to characterize interactions of B-80 with the selected imidazolium room-temperature ionic liquids (RTILs), dimethylimidazolium nitrate and dimethylimidazolium hexafluorophosphate. Whereas the imidazolium cation exhibits a rather poor affinity to B-80, the inorganic anions form polar covalent bonds with the boron atom occupying a central position within a B-6 hexagon. Attachment of the RTIL ion pairs leads to a significant alteration of the electronic spectra, charge density distribution, valence and conduction molecular orbitals. The total binding energies keeping the RTIL@B-80 complexes together range 200250 kcal mol(-1), being higher than the energies of many interactions in chemistry. The observed phenomenon predicts an excellent solubility of B-80 in the considered RTILs, but may also reveal a poor stability of B-80 in the polar media. Our results motivate further efforts in studying the behavior of the all boron fullerene in polar environments. (C) 2017 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosIonization of cucurbiturils as a pathway to more stable host-guest complexes(Elsevier Science Bv, 2016) Chaban, Vitaly V. [UNIFESP]; Fileti, Eudes Eterno [UNIFESP]; Malaspina, Thaciana [UNIFESP]Cucurbiturils are particularly interesting to chemists, because these macrocyclic molecules are suitable hosts for many neutral and cationic species. Allegedly, the host-guest binding originates from hydrophobic effects and ion-dipole interactions in the case of cationic guests. An elementary unit of cucurbiturils (glycoluril unit) consists of two fused imidazole rings. Each of these rings can be ionized. We report ionized cucurbiturils and discuss their binding to C-60 fullerene using an electronic-structure approach. We assert that the ionization of cucurbiturils fosters C-60- cucurbituril binding due to significant polarization of electron density in C-60. Our results suggest a previously unexplored pathway to additionally increase stability of the host-guest complexes. (C) 2016 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosA joint computational and experimental study of a novel dioxomolybdenum(VI) complex bearing chiral N,N-dimethyllactamide ligand(Elsevier B.V., 2011-09-01) Sensato, Fabricio Ronil [UNIFESP]; Cass, Quezia Bezerra; Lopes, Bianca Rebelo; Lourenco, Tiago Campos; Zukerman-Schpector, Julio; Tiekink, Edward R. T.; Longo, Elson; Andres, Juan; Universidade Federal de São Paulo (UNIFESP); Universidade Federal de São Carlos (UFSCar); Univ Malaya; Univ Estadual Paulista; Univ Jaume 1A new cis-dioxomolybdenum complex MoO2(DMLA)(2) (DMLA = N,N-dimethyllactamide) has been synthesized and characterized by X-ray crystallography, H NMR and IR spectroscopies and electronic structure calculations at DFT/B3LYP level. This compound (chemical formula C10H20MoO6N2) crystallizes in the orthorhombic space group P2(1)2(1)2(1) with Z = 4, a = 6.9357(2) angstrom, b = 11.8761(4) angstrom, c = 17.7251(5), V = 1460.00(8) angstrom(3) and renders a slightly distorted octahedral structure with two long Mo-O bonds (2.253(3) angstrom and 2.257(3) angstrom) trans to each of the Mo=O groups and with two short Mo-O bonds of 1.942(3)4 angstrom cis to them. the Mo=O bond length are 1.715(3) and 1.704(3) angstrom). Each lactamide ligand is bidentate; they are coordinated in their deprotonated form with the carbonyl oxygen occupying a position trans to the Mo=O moiety while the deprotonated hydroxyl oxygen is located cis to them. Structural characterization is complemented by DFT/B3LYP calculations. (C) 2011 Elsevier B.V. All rights reserved.
- ItemAcesso aberto (Open Access)Modelagem molecular aplicada à Engenharia Química: modelagem da reação de hidrólise do anidrido acético(Universidade Federal de São Paulo, 2022-03-02) Francisco, Gustavo Stanev [UNIFESP]; Hirota, Wilson Hideki [UNIFESP]; Moraes, José Ermirio Ferreira de [UNIFESP]; http://lattes.cnpq.br/4692364565124711; http://lattes.cnpq.br/7967631751356969; http://lattes.cnpq.br/2498805234631397Esse estudo busca evidenciar a efetividade da modelagem molecular através de softwares freewares junto a sua aplicabilidade em técnicas de modelagem amplamente empregadas na engenharia química. Para isso, o estudo foi dividido em duas partes. A primeira parte consiste na modelagem da reação de hidrólise do anidrido acético partindo do seu âmbito subatômico/quântico, por meio da análise das partículas em sua esfera vibracional com a utilização de programas computacionais de código aberto, buscando assim, a obtenção de parâmetros da reação química tais como energia de ativação e fator pré-exponencial. Em uma segunda etapa, é feita a modelagem em nível macroscópico da reação em um reator químico do tipo batelada para a comparação dos resultados obtidos com resultados da literatura. Como resultado deste trabalho, pretende-se confirmar a viabilidade da aplicação da modelagem molecular no âmbito da Engenharia Química através de softwares obtidos de maneira não monetizada.
- ItemAcesso aberto (Open Access)Synthesis and Study of Fe-Doped Bi2S3 Semimagnetic Nanocrystals Embedded in a Glass Matrix(Mdpi Ag, 2017) Silva, Ricardo Souza; Mikhail, Hanna Degani; Guimaraes, Eder Vinícius; Gonçalves, Elis Regina; Cano, Nilo Francisco [UNIFESP]; Dantas, Noelio Oliveira; Universidade Federal de São Paulo (UNIFESP)Iron-doped bismuth sulphide (Bi2-xFexS3) nanocrystals have been successfully synthesized in a glass matrix using the fusion method. Transmission electron microscopy images and energy dispersive spectroscopy data clearly show that nanocrystals are formed with an average diameter of 7-9 nm, depending on the thermic treatment time, and contain Fe in their chemical composition. Magnetic force microscopy measurements show magnetic phase contrast patterns, providing further evidence of Fe incorporation in the nanocrystal structure. The electron paramagnetic resonance spectra displayed Fe3+ typical characteristics, with spin of 5/2 in the 3d(5) electronic state, thereby confirming the expected trivalent state of Fe ions in the Bi2S3 host structure. Results from the spin polarized density functional theory simulations, for the bulk Fe-doped Bi2S3 counterpart, corroborate the experimental fact that the volume of the unit cell decreases with Fe substitutionally doping at Bi1 and Bi2 sites. The Bader charge analysis indicated a pseudo valency charge of 1.322| e | on Fe-Bi1 and 1.306 | e | on Fe-Bi2 ions, and a spin contribution for the magnetic moment of 5.0 mu(B) per unit cell containing one Fe atom. Electronic band structures showed that the (indirect) band gap changes from 1.17 eV for Bi2S3 bulk to 0.71 eV (0.74 eV) for Bi2S3: Fe-Bi1 (Bi2S3: Fe-Bi2). These results are compatible with the 3d(5) high-spin state of Fe3+, and are in agreement with the experimental results, within the density functional theory accuracy.