Superior electrocatalysts for the reduction of O2 by four-electrons in
one step have been prepared by coordinating ammine complexes of Ru(II
) to the pyridine ligand sites in cobalt tetrakis(4-pyridyl) porphyrin
. At least three coordinated Ru(II) centers appear to be required to o
btain the four-electron reduction. When fac-Ru(NH3)3(OH2)3(2+) was use
d to ruthenate the porphyrin, a network structure was obtained in whic
h both terminal and bridging ruthenium centers were present.