Efeitos do solvente em transições de transferência de carga metal-ligante em complexo de rutênio(II) e suas interações com cisteína, glutationa e guanina

Abstract

In this dissertation a theoretical study of the solvent effects on the structural an spectroscopic properties of the ruthenium complex [Ru(NH3)5L]2+ (L = pyrazine, pyz), was carried out, is employing the hybrid Monte Carlo/Quantum Mechanics simulations in the S-MC/MQ formalism, and Quantum Molecular Dynamics, in DFT/EFP/MD formalism. The electronic spectrum was evaluated by studying the Metal-to-Ligand Charge Transfer (MLCT) band using the Time-Dependent Density Functional Theory (TDDFT) and employing the Effective Fragment Method (EFP) to describe the solvent effects. In the second part of the work, the interaction of the Ru(II) compound with its possible biological targets cysteine (Cys), glutatione (GSH) and guanine was investigated using the Density Functional Theory (DFT). The Gibbs free energy of the interaction process in solution (Gsol.), was obtained using the Polarizable Continuum Model (PCM) to describe the solvent. The excitation energy for the MLCT transition band calculated in the gas phase shows the value of 3,45 eV ( 360 nm ), which is underestimated in comparison with the experimental value 2,64 eV (470 nm ). Including the solvent effects the value obtained was 3.01 ± 0.20 eV (413 ± 20 nm), confirming the strong solvatochromic effect on Ru(II) complex.. We also managed to theoretically evaluate the intermolecular competitions between GSH, GSH and the nucleobase guanine. The coordination processes are thermodynamically spontaneous, except for the adduct formed between the complex and the N3 coordination site of guanine.