Formation of Artificial Mn4YO4-Cluster Mimicking the Oxygen-Evolving Center in Photosynthesis

The oxygen-evolving center (OEC) in photosynthesis is a unique biological Mn4CaO5-cluster that splits water into electrons, protons, and dioxygen. It is a great challenge for chemists to develop a robust and precise mimic of the OEC in the laboratory. Herein, we report the formation of a rare-earth-element-containing Mn4YO4-cluster that represents an excellent and robust model of the OEC. The key synthetic precursor, the Mn3YO2-cluster, is reported for the first time, which possesses an identical mixed-valence MnIII2MnIV metal core and a hydrogen-bonding network coordination sphere. This precursor is very reactive and can convert into various compounds in solution. Importantly, it has been found that the presence of organic bases significantly influences the distribution of intermediates and promotes the formation of the Mn4YO4-cluster. Meanwhile, two Mn4YO4-clusters are described, which closely mimic the main metal-oxide core and peripheral ligands, as well as the oxidation states of the four Mn ions in the OEC, revealing that both the terminal ligands and a bridging carboxylate are variable. This new Mn4YO4-cluster displays a remarkable stability in the presence of water in acetonitrile solution. These findings shed new light on the synthesis of rare-earth-element-containing clusters and the rational design of robust artificial water-splitting catalysts, and provide chemical insights into the dynamic structural changes of both biological and artificial clusters.