ELECTROCHEMICAL INVESTIGATION OF DIOXYGEN INTERACTION WITH 2 COBALT CHELATES IN SOLUTION AND AT THE ELECTRODE SURFACE

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 -BF2-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 pO2 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.