Aplicação de metodologias teóricas para o estudo do processo de solvatação e espectroscopia eletrônica de íons de metais de transição em solução

Abstract

In this work we have studied the chemical process of solvation and solvent effects on spectroscopic and magnetic properties of transition metal ions, employing theoretical methods based on the Computational Chemistry. We have chosen the first and second row transition metal ions to be studies. A sequential Monte Carlo/Quantum Mechanics approach was used to investigate the solvation and solvent effects on d . d transition of the Fe2+ and Ni 2+ ions in aqueous solution and, for the Ni2+ was also a study in ammonia solution. The same approach was also used to investigate the solvent effects on the Metal-to-Ligand Charge Transfer (MLCT) transitions involved in the complex u(Pirazina)(NH3)5]2+. The solvation structure and hydrogen bond analysis for these ions/complex were also investigated. Due to the lack of intermolecular potential parameters reported in the literature, we have developed a set of Lennard-Jones parameters for transition metal ions through the modification of the non-bonded terms of the UFF force field. The electronic spectrum of the ions/complex was obtained within the Time Dependent Density Functional, using several GGA and hybrid GGA exchange-correlation functional. We shown in this study that the intermolecular potential parameters generated for the transition metal ions are suitable to be used in studies involving these ions in solution, providing excellent agreement with the experimental results. We show that the d . d transition is localized on the first solvation shell of the ions and, inclusion of outer solvation shells does not affect these transitions. The analysis of the Metal-to- Ligand Charge Transfer (MLCT) transitions involved in the complex [Ru(Pirazina)(NH3)5]2+ showed that the common used hybrid GGA functional fails in describing these transitions, which pointed out to the need of developing new functional to be used in TD-DFT studies involving charge transfer complexes.