Solvent and structural effects on the photo-reduction of cobalt(III) complexes in aquo-organic solvent media possessing different H-bonding properties

Abstract

The photo-reduction of a series of cobalt(III) complexes of the type cis-β-[Co(ampy) 2 (4-R-Py)Cl]Cl 2 where ampy = 2-aminomethylpyridine and R = H, Me, Et, t-Bu, COMe, and CN has been studied in propan-2-ol/water and 1,4-dioxane/water medium. The photo-reduction quantum yield (Φ Co II ) data were correlated with solvent and structural parameters with an aim to shed some light on the mechanism of these reactions. Increase in the percentage of organic co-solvent in both the medium increased the photo-reduction quantum yield. Correlation of Φ Co II with macroscopic solvent parameters viz. relative permittivity indicated that the reactivity is influenced by both specific and non-specific solute-solvent interactions. Kamlet-Taft solvatochromic comparison method was used to separate and quantify these effects. H-bonding property of the mixture was found to dominate the solvation and consequently the magnitude of the quantum yield.