Cn. Shi et Fc. Anson, COMPARISON OF THE CATALYTIC REDUCTION OF DIOXYGEN BY NERUTHENINO(II))-4-PYRIDYL)PORPHYRINATO]COBALT(II) IN SOLUTION AND ON GRAPHITE ELECTRODE SURFACES, Inorganic chemistry, 34(18), 1995, pp. 4554-4561
The ammineruthenio(II))-4-pyridylporphinato]cobalt(II) complex that ca
talyzes the four-electron reduction of O-2 at graphite electrode surfa
ces on which it has been assembled has now been prepared in homogeneou
s solution. The preparative procedure for the catalyst is described, a
nd the kinetics of its catalysis of the reduction of O-2 by chemical r
eductants in homogeneous solution are reported. In solution, only two-
electron reductions of O-2 are obtained and the rate of intramolecular
electron-transfer from the four Ru(NH3)(5)-py(2+) centers on the peri
phery of the catalyst molecule to an O-2 molecule coordinated to the C
o(II) center in the porphyrin ring is shown to be quite slow. Possible
reasons for the contrasting mechanistic behavior of the catalyst in s
olution and on graphite electrodes are suggested.