Evidence for an oxygen evolving iron-oxo-cerium intermediate in iron-catalysed water oxidation

Abstract

The non-haem iron complex α-[FeII(CF3SO3)2(mcp)] (mcp=(N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with CeIV to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)FeIV (O)(μ-O)CeIV(NO3)3]+, the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive FeIV-O-CeIV adduct may open new pathways to validate mechanistic notions of an analogous MnV-O-CaII unit in the oxygen evolving complex that is responsible for carrying out the key O-O bond forming step.