ELECTROCATALYSIS OF THE REDUCTION OF DIOXYGEN BY ADSORBED COBALT 5,10,15,20-TETRAARYLPORPHYRINS TO WHICH ONE-RU, 2-RU, OR 3-RU(NH3)52+ CENTERS ARE COORDINATED

The reactions of Ru(NH3)5OH22+ with the pyridine sites in (5-(4-pyridyl)-10, 15,20-triphenylporphyrinato)cobalt-(II), (5,10-bis(4-pyridyl)-15,20-diphenylporphyrinato)cobalt(II), (5,10-bis(4-pyridyl)-15,20-bis(4-(trifluoromethyl)-phenyl)porphyrinato(cobalt(II), (5,15-bis(4-pyridyl)-10,20-diphenylporphyrinato)cobalt(II), and (5,10,15-tris(4-pyridyl)-20-phenylporphyrinato)cobalt(II) adsorbed on pyrolytic graphite electrodes produce the mono-, di-, and triruthenated complexes. The adsorbed complexes act as catalysts for the reduction of dioxygen. The mono- and diruthenated complexes catalyze the two-electron reduction of dioxygen to hydrogen peroxide, whereas the triruthenated complex catalyzes the four-electron reduction to water. The preparation and electrocatalytic behavior of the catalysts are described. A comparison of the catalysts has provided additional insight into the mechanisms by which they operate in catalyzing the electroreduction of dioxygen.