Desenvolvimento de modelos para descrição de estrutura e propriedades do diazometano

• Ano de defesa: 2013
• Autor(a) principal: Monteiro, João Guilherme Siqueira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Programa de Pós-graduação em Química; Química
• Palavras-chave em Português: diazometano; CH2N2; GVB; ligação química; VSCF; Propriedade química; Diazometano; Ligação química; Estrutura molecular; diazomethane; chemical bond; chemical compound; molecular Structure; chemical property; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: https://app.uff.br/riuff/handle/1/20730

The electronic and vibrational structures of the diazomethane molecule were studied. The search for a chemical structure representation for this molecule was performed under the premise that an acceptable quantum mechanical based model must yield at least qualitatively correct values for its electronic and vibrational fundamental properties. The wave function GVB-RCI(6,12)/CASSCF(4,5) is the simplest one that is able to correctly reproduces the bonding scheme in diazomethane. Some molecular properties as harmonic frequencies and electric dipole moments computed at this level of theory are in quantitative agreement with experiment. The resulting bonding scheme is the superposition of two diabatic structures, one of the ylide type and the other of biradical type. Anharmonic vibrational levels associated to CH2N2 and CD2N2 were also computed and analyzed under the light of VSCF theory. In particular, some internal modifications were implemented in the code in order to improve our results. For instance, the inclusion of three-mode coupling in the potential energy surface, more flexibility in the generation of configurations for use in the VCI theory and the inclusion of electric anharmonicity in the intensity calculations. Some simulations on the molecular dissociation in ultrafast conditions were also performed using the electronic wave function obtained.