Estudos teóricos das propriedades vibracionais e eletrônicas dos complexos [Ru(bpy)2(1,4-dt)(L)]n+, onde L = Cl⁻, NO2⁻ e NO⁺

Abstract

The rapid and continuous advancement of computer data processing along with the development of softwares, functionals and basis sets more efficient has made the density functional theory (DFT) an advanced and efficient method for describe chemical systems. DFT allows to calculate, with good approximation, the structural, vibrational, and electronic properties of atoms, molecules and solids, including coordination compounds. Among the different classes of coordination compounds, those that acts as nitric oxide (NO) donor, nitrosyl complexes, have attracted the scientists´ interest. These can be used as tools for studying the NO-release mechanisms. However, the electronic properties of these systems, such as the metal/NO interaction and release mechanisms, are yet not fully understood. Therefore, computational quantum calculations are required for describe the electronic structure of these complexes. In this context, the main aim of this work was to perform computational density functional theory calculations to study the structural, vibrational, and electronic properties of cis-[Ru(bpy)2(1,4-dt)(L)]n+ complexes, where L = Cl⁻ (1), NO2⁻ (2) and NO+ (3). The geometries of the complexes were optimized at the DFT/B3LYP/6-311++g(d,p)/LANL2DZ theory level. From such structures, the energy and nature of the vibrational and electronic transitions were calculated. From the natural transitional orbitals (NTO´s), the nature of electronic transitions was evaluated. For complex 1, the bands of bpy and 1,4-dt ligands are the DFT IR spectrum, while for the complex 2, in addition to these, the bands of NO2⁻ were observed. For 3, an intense band was observed, assigned to the vibrational stretching mode v(NO), at 1960 cm⁻1, indicating a character of NO²⁺ coordinated to Ru²+. In the theoretical UV-Vis spectra, the lowest energy bands at 460 and 411 nm for complexes 1 and 2, respectively, result from metal-ligand charge transfer (MLCT) and interligand (LLTC) transitions. However, complex 3 has two lower energy bands at 408 and 328 nm with interligand charge transfer (LLCT) transitions. In general, the theoretical vibrational and electronic spectra showed great agreement with experimental data previously published. Such results have allowed the assignment of the bands and evaluation of the ligand L effect on the electronic properties of the complexes.