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首页> 外文期刊>Polyhedron: The International Journal for Inorganic and Organometallic Chemistry >Electronic and spin structures of manganese clusters in the photosynthesis II system
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Electronic and spin structures of manganese clusters in the photosynthesis II system

机译：光合作用II系统中锰团簇的电子和自旋结构

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摘要

Electronic and spin structures of manganese clusters, Mn4O4 (1), CaMn3O4 (2), Mn3O4 (3), MnX (4), and CaMn4O4 (5), in the photosynthesis II system are investigated using the classical and quantum Heisenberg models. The molecular orbital calculations by the use of general spin orbitals (GSO) are performed for cubane-type calcium manganese cluster 2 with noncollinear spin alignment, which has also been concluded in our previous studies of 1 and 3. The calculated results, together with available experiments, enable us to propose possible electronic states (from S-0 to S-4) of tetranuclear manganese cluster 5, which is the active site of oxygen evolution center (OEC). The low-spin (LS) ground states of 2-5 are consistent with the ESR and other magnetic observations. A new reaction scheme for oxygen evolution from water is resulted from both theoretical and experimental results for manganese clusters 1-5 in OEC on the basis of the newly determined X-ray structure by Ferreira et al. [Science 303 (2004) 183 1]. In this mechanism, both calcium and manganese ions play important roles for formation of peroxide anion bridge, which is the precursor of molecular oxygen. Implications of computational results are discussed in relation to a key role of the high-valent manganese oxo (Mn(V)=O) species in OEC for oxygen evolution from water. Our previous and present computations conclude that Mn(V)=O plays a crucial role in both native and artificial OEC systems. (c) 2005 Published by Elsevier Ltd.
机译：使用经典Heisenberg模型和量子Heisenberg模型研究了锰团簇的电子和自旋结构Mn4O4（1），CaMn3O4（2），Mn3O4（3），MnX（4）和CaMn4O4（5）。使用普通自旋轨道（GSO）对具有非共线自旋对准的古巴型钙锰簇2进行了分子轨道计算，这在我们之前的1和3研究中也得出了结论。实验使我们能够提出四核锰簇5的可能电子态（从S-0到S-4），这是氧释放中心（OEC）的活性位点。 2-5的低旋转（LS）基态与ESR和其他电磁观测结果一致。基于费雷拉等人新确定的X射线结构，OEC中1-5锰簇的理论和实验结果都提出了一种新的从水中放出氧气的反应方案。 [Science 303（2004）183 1]。在这种机理中，钙离子和锰离子都对过氧化物阴离子桥的形成起重要作用，过氧化物阴离子桥是分子氧的前体。讨论了计算结果的含义，涉及OEC中的高价锰羰基（Mn（V）= O）物种从水中放出氧气的关键作用。我们之前和现在的计算得出结论，Mn（V）= O在天然和人工OEC系统中都起着至关重要的作用。 （c）2005年由Elsevier Ltd.发布。

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