Compostos de coordenação derivados do disseleneto e disselenoéteres de bis(2-piridina) síntese, caracterização e aplicações

Abstract

This work describes the synthesis and characterization of nineteen compounds derivative of diselenide and diselenoethers of bis(2-pyridyl) with metals of different degree of hardness. Among the nineteen obtained complex, seventeen had their structure elucidated by X-ray crystallography, besides others characterization methods, such as elemental analysis, infrared spectroscopy and mass spectrometry. Six different complexes were obtained when bis(2-pyridyl)diselenide was used as a ligand. These complexes involve metal centers of AuI, CuII, CuI, ReI, ReV and ReIII. Among the rhenium complexes, stands out the ReV complex that has a Se0 atom as a ligand, a rare exemple not previously reported in the literature. Bis(2-pyridyl)diselenoethers with one, three or four methylene groups between selenium atoms were synthesized and characterized. Among these three synthesized diselenoethers two are unprecedented in the literature (L2, L3). The methylene groups act as spacers, and were used in order to evaluate their influence across the complexation with different metals. It was observed that as longer is the carbon chain between the selenium atoms as higher is the tendency to polymer formation. The thirteen complexes obtained with the ligands bis(2-pyridyl)diselenoethers demonstrated follow a trend of complexation which agrees with Pearson's theory of acids and bases, wherein the nitrogen atoms of the ligands coordinate with harder metals and selenium atoms coordinate the softer metals. The obtained complexes were submitted to antioxidant activity tests. Tests of superoxide dismutase (SOD) showed that copper complexes 2, 7, 8, 13 and 18 had good antioxidant activity, with IC50 values less than 0.66 μM. Among these compounds the complex [Cu4I4(L1)2] (8) presented the best IC50 value in 0.08 μM. These results demonstrate that the Cu compounds mentioned have great potential to be used as mimetics of superoxide dismutase enzyme (SOD). In addition, the system CuI/bis(2-pyridyl)diselenoether showed as an efficient catalyst for the formation of a new C-S bond by cross-coupling reactions using glycerol as solvent. Still, the catalytic activity for the complex 8 was also tested for this type of reaction. Both of these catalytic systems provide the desired products in good to excellent yields when compared to the literature.