Photo-oxidation of water to oxygen sensitised by tris(2,2′-bipyridyl)ruthenium(II)

Abstract

Irradiation of tris(2,2′-bipyridyl)ruthenium(II) in aqueous solution containing a sacrificial electron acceptor results in formation of bipy₃Ru³⁺, a powerful oxidant which is able, in the presence of a redox catalyst, to oxidise water to O₂. Both colloidal RuO₂ and simple cobalt(II) ions are effective catalysts for O₂ production and, with [Co(NH₃)₅Cl]²⁺ as sacrificial electron acceptor, the quantum efficiency for formation of O₂ was ca. 12 %. However, when the sacrificial electron acceptor was replaced with Fe³⁺, which is a reversible redox couple, no O₂ was observed upon prolonged irradiation. The absence of O₂ in this latter system can be explained by kinetic considerations.