Synthesis, Spectral Characterization and Solvent Effects on the Electro-Reduction of Mixed Ligand Cobalt(III) Complexes

A series of cobalt(III) complexes of the type cis-beta-[Co(ampy)(2)(4-R-Py)Cl]Cl-2 where ampy = 2-aminomethylpyridine, R = H, Me, Et, t-Bu, COMe, and CN has been synthesized and characterized spectroscopically. The electro-reduction of these complexes has been studied in propan-2-ol/water and 1,4-dioxane/water media. The redox potential (E (1/2)) data were correlated with solvent and structural parameters with an aim to shed some light on the mechanism of these reactions. Correlation of E (1/2) with macroscopic solvent parameters viz. relative permittivity, indicates that the reactivity is influenced by both specific and non-specific solute-solvent interactions. The Kamlet-Taft solvatochromic comparison method was used to separate and quantify the specific and non-specific solvent effects on the redox process. Increases in the percentage of organic co-solvent in both media makes the electro-reduction of Co(III) to Co(II) easier.