Electrochemical and spectroelectrochemical studies of cobalt salen and salophen as oxygen reduction catalysts

Electrochemical and spectroelectrochemical studies of cobalt-Schiff (Co-SB) base complexes, Co(salen) [NN'-bis(salicylaldehyde)-ethylenediimino cobalt(II)] and Co(salophen) [N-N'-bis(salicylaldehyde)-1,2-phenylenediimino cobalt(II)], have been carried out to test them as oxygen reduction catalysts. Both compounds were found to form an adduct with oxygen and exhibit catalytic activities for oxygen reduction. Comparison of spectra obtained from electrooxidized complexes with those from Co-SB complexes equilibrated with oxygen indicates that the latter are consistent with the postulated complex formed with oxygen occupying the coaxial ligand position, namely, Co(III)-SB . O-2(-.) .The catalysis of oxygen reduction is thus achieved by reducing Co(III) in the oxygen-Co-SB adduct, releasing the oxygen reduction product, e.g., O-2(-.),from the Co(II)-SB complex.X1157sciescopu