A Functional Model Related to Cytochrome c Oxidase and Its Electrocatalytic Four-Electron Reduction of O2
James P. Collman,
*
Lei Fu,
Paul C. Herrmann,
Xumu Zhang
A cytochrome c oxidase model that consists of a cobalt(II)
porphyrin with a copper(I) triazacyclononane macrocycle fastened on the
distal face and an imidazole covalently attached to the proximal face
has been synthesized and characterized. Redox titrations with molecular
oxygen (O2) and cobaltocene were carried out, and O2 was found to bind irreversibly in a 1:1 ratio
to the model compound. This O2 adduct (a bridged peroxide)
can be fully reduced to the deoxygenated form with four equivalents of
cobaltocene. The model compound was adsorbed on an edge-plane graphite
electrode, and rotating ring-disk voltammetry was used to monitor the
electrocatalytic reduction of O2. Four-electron reduction
of O2 was observed at physiological pH.
Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
*
To whom correspondence should be addressed.
