Electrochemical investigation of dioxygen interaction with two cobalt chelates in solution and at the electrode surface

Abstract

The interaction between molecular oxygen and the metal atom in two Co(II) complexes with bis(diacetylmonoxime-imino)propane-1,3 ( A) and with the related ligand obtained from cobaloxime by substitution of both the O-H ⋯ O bridges with the -BF 2-group ( B) is investigated using electrochemical and spectroelectrochemical techniques. Notwithstanding the stability of the Co(II) complex B in air, the results suggest the formation of a dioxygen adduct as an unstable intermediate in the electrocatalytic reduction of molecular oxygen in the presence of either A or B. Furthermore, the oxygenation ratio at a given pO 2 appears to be quite different for the homogeneous reaction of A in the Co(II) oxidation state in bulk as compared with either the electrogenerated Co(II) (from complex A) on the electrode surface or the Co(II) complex B.