Dissociative Adsorption of Water on CaMn 4 O 5 Cationic Clusters.

Water splitting is catalyzed by photosystem II, which comprises an inorganic core (CaMnO) and protein ligands. To understand the evolution of CaMnO after attaching water molecules, an isolated CaMnO cluster was investigated using vibrational spectroscopy and density functional theory calculations. Computational findings suggest that when a water molecule adsorbs on the Ca atom through the O atom of water, one of the OH bonds forms a hydrogen bond with a μ-oxo bridge, which dissociates into two OH groups. This is consistent with the fact that no isomers with molecularly adsorbed water were experimentally observed.