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.
Bibliographical noteFunding Information:
We thank Dr. Xavi Ribas and Dr. Anna Company for reading this work and for helpful comments. We also thank the European Research Foundation for project FP7-PEOPLE-2010-ERG-268445 (J.L.-F), MICINN for project CTQ2009-08464 (M.C.) and for a Ramon y Cajal contract (J.L.-F.), Generalitat de Catalunya for an ICREA Academia Award and the European Research Foundation for Project ERC-2009-StG-239910 (M.C.). The work carried out at the University of Minnesota was supported by US National Institutes of Health grant GM38767 to L.Q. We appreciate financial support from INNPLANTA project INP-2011-0059-PCT-420000-ACT1 to Dr. X. Ribas.