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Redox‐Induced Structural Change in Artificial Heterometallic‐Oxide Cluster Mimicking the Photosynthetic Oxygen‐Evolving Center

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To understand the chemical principle of the photosynthetic oxygen-evolving center (OEC), we report two (Mn3XO4)2O-clusters (X=Sr2+, La3+) closely mimicking both the heterometallic-oxide cubane and all types of oxide bridges in OEC. Structural comparison of both oxidized and reduced forms of the (Mn3LaO4)2O-cluster indicates that the reactive site is the μ2 -oxide bridge rather than the μ4 -oxide or μ3 -oxide bridges in the cluster.


Abstract

The oxygen-evolving center (OEC) in photosynthesis is a unique Mn4CaO5-cluster that catalyzes the water-splitting reaction in nature. Understanding its catalytic mechanism for the O=O bond formation is of great challenge and long-standing issue, which is severely restricted by the lack of precise structure and mechanism mimics of this heterometallic-oxide cluster. Herein, we report two synthetic (Mn3XO4)2O-clusters (X=Sr2+, La3+) that closely mimic the heterometallic-oxide Mn3XO4 cubane and three different types of μ-oxide bridges (μ 2-O2−, μ 3-O2−, and μ 4-O2−) simultaneously as seen in the OEC. By resolving the crystal structures of both oxidized and reduced forms of the cluster, we have identified significant redox-induced structural changes that take place on the μ2-oxide bridge, rather than the μ 4-oxide or μ 3-oxide bridges. Our results provide chemical insights into understanding the reactivity of three different types of oxide bridges in the biological Mn4CaO5-cluster in PSII.

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