(5,10,15,20-TETRAMETHYLPORPHYRINATO)COBALT(II) - A REMARKABLY ACTIVE CATALYST FOR THE ELECTROREDUCTION OF O-2 TO H2O

Unlike most simple, monomeric cobalt porphyrins, the cobalt tetramethy lporphyrin identified in the title catalyzes the electroreduction of O -2 to H2O instead of H2O2. On graphite electrodes, coatings of the por phyrin prepared by irreversible adsorption from chloroform solutions c atalyze the electroreduction of O-2 in aqueous HClO4 at unusually posi tive potentials. Both the title porphyrin and the corresponding unsubs tituted cobalt porphine are argued to derive their activity as four-el ectron reduction catalysts from their propensity to form dimers (or hi gher aggregates) in solution and, presumptively, on the surface of gra phite electrodes.