A new highly efficient tetra-electronic catalyst based on a cobalt porphyrin bound to four mu(3)-oxo-ruthenium acetate clusters

A meso-tetra(4-pyridyl)cobaltporphyrin modified with four [mu (3)-O-Ru-3(Ac )(6)(py)(2)](+) clusters (CoTCP = cobalt tetraclusterporphyrin) has been sy nthesized and characterized by H-1-NMR and UV-Vis spectroscopy, electrochem istry and spectroelectrochemistry. The facility of CoTCP to form adherent a nd durable films on a glassy carbon surface has been exploited in the prepa ration of modified electrodes exhibiting outstanding catalytic activity in the tetraelectronic reduction of dioxygen to water. This finding has been c onfirmed from the linear behavior and the slope of the Levich plots up to 4 000 rpm, as well as from the high current densities, e.g. up to 2.8 mA cm(- 2) obtained for the modified electrodes. The enhanced activity has been int erpreted in terms of the electronic activation of the cobalt porphyrin by t he peripheral triangular ruthenium cluster complexes, as supported by detai led spectroelectrochemical data confirming a significant electronic couplin g between the cobalt porphyrin and [mu (3)-O-Ru-3(Ac)(6)](+) groups. (C) 20 01 Elsevier Science B.V. All rights reserved.