Síntese, caracterização e reatividade de novos nitrosilo complexos de rutênio, tendo como ligante auxiliar a 2,2-bipiridina

• Ano de defesa: 2004
• Autor(a) principal: Silva, Francisco Ordelei Nascimento da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Oxído Nítrico; Análise espectral
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/1281

In this work were carried out the synthesis, characterization and the reactivity study of the cis-[Ru(bipy)2LNO](PF6)n (L = imidazole, isonicotinamide and sulphite) and trans-[Ru(bipy)2SO3NO](PF6) complexes, aiming the modulation of the nitrosyl complexes that can act as NO donors in biological systems. The infrared spectra of the cis-[Ru(bipy)2LNO](PF6)n and trans-[Ru(bipy)2SO3NO](PF6) complexes presented ν(NO) frequencies latively high indicating that the nitric oxide is coordinated to the metal center in linear form, NO+. These frequencies were utilized as an indicative of the influence of the L ligands according to the decreasing order of the p-acceptor character of the ligand L: Isn > Im > SO3 2–, where cis-[Ru(bipy)2IsnNO](PF6)3 presents the higher value of the ν (NO). The characteristics of the 1H NMR and 13C NMR spectra of the compounds L = Isn, ImN are consistent with the position of the coordination to metal center of such ligands and that the pyridine rings of the bipyridine are in the cis isomeric form. This conclusion is based on the presence of several signs in the 1H NMR and 13C NMR spectra, due to 16 protons and 20 carbon of the two bipyridine. The Resence of only four signals in the 1H NMR spectrum for the trans-[Ru(bipy)2SO3NO](PF6), suggests that the two bipyridine are coordinated to the ruthenium in a trans conformation one each other. The study of the nitrosyl-nitro interconvertion reaction to the cis- [Ru(bipy)2SO3NO](PF6) and trans-[Ru(bipy)2SO3NO](PF6), using the spectrophotometric method reveled that only in the pH values above 9,0 half of the species containing the NO+ fragment suffered nucleuphilic attack by the hydroxide, producing the NO2 species. The equilibrium constants, Keq to the reaction: Cis, trans-[Ru(bpy)2LNO]+n + 2OH- Cis, trans-[Ru(bpy)2LNO2]+n + H2O Were calculated in NaTFA 0,5 Mol L–1 presenting the following values: 1,80 x 1025 L2mol-2, 1,42 x 1016 L2 mol-2, 1,74 x 107 L2 mol-2 for the complexes with the isonicotinamide, imidazole and sulphite, respectively. By the electrochemical study of the nitrosyl complexes it can be concluded that in the potential equal to –300 mV versus Ag/AgCl occurs the reduction of the NO+ ligand, producing NO0. This process is followed by a chemical reaction where occurs the NO05 release and the formation of the aqua complex. It was observed one correlation between the ν(NO) and E1/2 values for the quasi-reversible process centered in this ligand. The preliminary studies of the photochemical behavior of the nitrosyl complexes conducted to the conclusion of the formation of nitric oxide and the cis and trans- [RuIII(bipy)2H2OL]n+ specie, when the complexes are irradiated in aqueous solution andsolid state with white light