Dissociative Adsorption of Water on CaMn₄O₅ Cationic Clusters

Abstract

Water splitting is catalyzed by photosystem II, which comprises an inorganic core (CaMn 4 O 5 ) and protein ligands. To understand the evolution of CaMn 4 O 5 after attaching water molecules, an isolated CaMn 4 O 5 + 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.

Cluster size dependent coordination of formate to free manganese oxide clusters

“…To probe fundamental aspects of the water oxidation reaction, an increasing number of research groups study small metal oxide clusters isolated in the gas phase to model water activation and oxidation catalysts. 20–26 In our project, we investigate gas-phase clusters consisting of elements also contained in the natural OEC, i.e. , Mn, Ca, and O.…”

“…To probe fundamental aspects of the water oxidation reaction, an increasing number of research groups study small metal oxide clusters isolated in the gas phase to model water activation and oxidation catalysts. [20][21][22][23][24][25][26] In our project, we investigate gas-phase clusters consisting of elements also contained in the natural OEC, i.e., Mn, Ca, and O. In the first steps of this approach, we have prepared bare, non-ligated manganese [27][28][29][30] and calcium-manganese oxide clusters [31][32][33] of different size and composition, and studied their water activation and oxidation properties via reactivity measurements and via infrared spectroscopy.…”