Artificial Mn 4 -oxido complexes mimic the oxygen-evolving center in photosynthesis

Abstract The understanding of the structure-function relationship of the oxygen-evolving center (OEC), a Mn 4 Ca-cluster, in photosystem II is impeded mainly due to the complexity of the protein environment and lack of rational chemical models as a reference. In this study, two novel Mn 4 -oxido complexes have been synthesized and characterized, in which the peripheral ligands of the [Mn III 4 ] core are provided by eight μ 2 -carboxylate groups and two neutral terminal ligands (pyridine or isoquinoline). This type of peripheral ligation is very similar to the Mn 4 Ca-oxide model complexes recently reported to mimic the OEC. The new Mn 4 -oxide complex can catalyze the oxygen-evolving reaction in the presence of Bu t OOH as an oxidant. The structure and redox properties comparison of the Mn 4 -oxido and Mn 4 Ca-oxido complexes provide important clues to understanding the functional role of Ca in the OEC in natural photosynthesis, and develop more efficient artificial catalysts for the water-splitting reaction in the future.