Redox-Induced Structural Change in Artificial Heterometallic-Oxide Cluster Mimicking the Photosynthetic...

The oxygen-evolving center (OEC) in photosynthesis is a unique Mn₄ CaO₅ -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 (Mn₃ XO₄ )₂ O-clusters (X=Sr²⁺ , La³⁺ ) that closely mimic the heterometallic-oxide Mn₃ XO₄ cubane and three different types of μ-oxide bridges (μ₂ -O^2- , μ₃ -O^2- , and μ₄ -O^2- ) 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 μ₄ -oxide or μ₃ -oxide bridges. Our results provide chemical insights into understanding the reactivity of three different types of oxide bridges in the biological Mn₄ CaO₅ -cluster in PSII.