Electrochemistry and stability studies of oxo-bridged dinuclear ruthenium(III) complexes for water oxidation

Abstract

Electrochemical and water oxidation studies have been carried out for the bridged complexes (1) and (2). [graphic omitted] Three consecutive reversible two-electron processes were shown to occur. Repeated continuous cyclic scans of the redox processes, however, led to the decomposition of the dimers to the monomeric complex. Visible spectra showed that the decomposition leads to the formation of cis-[Ru(bpy)^-₂(H₂O)₂]²⁺. The dimer complexes are stable at a Nifion-coated graphite electrode in their adsorbed state even on repeated cyclic scans of the redox processes. It was shown by gas chromatography as well as by mass spectroscopy that oxygen was evolved by water oxidation on adding Ce^IV ion to an aqueous solution of the dinuclear complex. The turnover number showed that the complexes worked as catalysts for water oxidation, although they suffer partial decomposition during the catalysis. The nitrite complex was more stable than the water complex against decomposition.