Cobalt−Oxo Core of a Water-Oxidizing Catalyst Film

• Published in: Journal of the American Chemical Society Vol. 131; no. 20; pp. 6936 - 6937
• Main Authors: Risch, M, Khare, V, Zaharieva, I, Gerencser, L, Chernev, P, Dau, H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.05.2009
• Subjects: Cobalt - chemistry; Electrochemical Techniques - methods; Fourier Analysis; Models, Molecular; Oxidation-Reduction; Oxides - chemistry; Photosystem II Protein Complex - chemistry; Spectrometry, X-Ray Emission - methods; Water - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja902121f

In photosynthesis, water is oxidized at a protein-bound Mn4Ca complex. Artificial water-oxidation catalysts that are similarly efficient and based on inexpensive and abundant materials are of great interest. Recently, assembly of a catalyst as an amorphous layer on inert cathodes by electrodeposition starting from an aqueous solution of cobalt ions and potassium phosphate has been reported. X-ray absorption spectroscopy on the cobalt catalyst film (CoCF) suggests that its central structural unit is a cluster of interconnected complete or incomplete CoIII−oxo cubanes. Potassium ligation to Co-bridging oxygens could result in Co3K(μ-O)4 cubanes, in analogy to the Mn3Ca(μ-O)4 cubane motif proposed for the photosynthetic Mn complex. The similarities in function and oxidative self-assembly of CoCF and the catalytic Mn complex in photosynthesis are striking. Our study establishes a close analogy also with respect to the metal−oxo core of the catalyst.