Photosynthetic water oxidation: binding and activation of substrate waters for O–O bond formation
Photosynthetic water oxidation occurs at the oxygen-evolving complex (OEC) of Photosystem II (PSII). The OEC, which contains a Mn4CaO5 inorganic cluster ligated by oxides, waters and amino-acid residues, cycles through five redox intermediates known as Si states (i = 0–4). The electronic and structural properties of the transient S4 intermediate that forms the O–O bond are not well understood. In order to gain insight into how water is activated for O–O bond formation in the S4 intermediate, we have performed a detailed analysis of S-state dependent substrate water binding kinetics taking into consideration data from Mn coordination complexes. This analysis supports a model in which the substrate waters are both bound as terminal ligands and react via a water-nucleophile attack mechanism.
- This article is part of the themed collection: Supramolecular Photochemistry