Shape-Shifting Tetranuclear Oxo-Bridged Manganese Cluster: Relevance to Photosystem II Water Oxidase Active Site

The redox properties of the “dimer-of-dimers” complex, [{Mn2(μ-O)2(tphpn)}2]4+ (1) (where Htphpn = N,N,N‘,N‘-tetra(2-methylpyridyl)-2-hydroxypropane-diamine) were investigated. The structure changes dramatically to an adamantane-shaped core upon one-electron oxidation. On the other hand, the one-electron reduced product of 1, [Mn4O4(tphpn)2]3+, exhibits a hyperfine-structured multiline EPR signal very similar to the so-called S0 state of the tetramanganese cluster, which resides at the Photosystem II water oxidase active site.

本研究对“双二聚体”配合物[{Mn₂(μ-桥氧)₂(tphpn)}₂]⁴+ (记为化合物1) 的氧化还原性质展开了探究，其中Htphpn为N,N,N',N'-四(2-甲基吡啶基)-2-羟基丙烷二胺。该配合物在经历单电子氧化后，结构会发生显著变化，形成金刚烷构型的核心结构。另一方面，化合物1的单电子还原产物[Mn₄O₄(tphpn)₂]³+ 展现出带有超精细结构的多线电子顺磁共振（Electron Paramagnetic Resonance, EPR）信号，该信号与位于光系统II水氧化酶活性位点处的四锰簇所谓的S₀态极为相似。