Toward Models for the Full Oxygen-Evolving Complex of Photosystem II by Ligand Coordination To Lower the Symmetry of the Mn3CaO4 Cubane: Demonstration That Electronic Effects Fac

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• 作者：Jacob S. Kanady ; Po-Heng Lin ; Kurtis M. Carsch ; Robert J. Nielsen ; Michael K. Takase ; William A. Goddard ; III ; Theodor Agapie
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：October 15, 2014
• 年：2014
• 卷：136
• 期：41
• 页码：14373-14376
• 全文大小：389K
• ISSN：1520-5126

文摘

Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn<sub>4sub>CaO<sub>nsub> cluster. Herein, low-symmetry Mn<sup>IVsup><sub>3sub>GdO<sub>4sub> and Mn<sup>IVsup><sub>3sub>CaO<sub>4sub> cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant cubane distortions. As a result of increased electron richness and desymmetrization, a specific 渭<sub>3sub>-oxo moiety of the Mn<sub>3sub>CaO<sub>4sub> unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag<sup>+sup>, to the same site gives a Mn<sub>3sub>CaAgO<sub>4sub> cluster that models the topology of the OEC by displaying both a cubane motif and a 鈥渄angler鈥?transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.