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首页> 外文期刊>Chemistry: A European journal >Theoretical Clues to the Mechanism of Dioxygen Formation at the Oxygen-Evolving Complex of Photosystem II
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Theoretical Clues to the Mechanism of Dioxygen Formation at the Oxygen-Evolving Complex of Photosystem II

机译：在光系统II析氧复合物中形成双氧的机理的理论线索

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摘要

The mechanism of the generation of dioxygen at the oxygen-evolving complex (OEC) of photosystem II (PSII), a crucial step in photosynthesis, is still under debate. The simplest unit present in the OEC that can produce O_2 is a dinuclear oxo-bridged manganese complex within the tetranuclear Mn_4 cluster. In this paper we report a theoretical study of the model complexes [Mn_2(#mu#-O)_2(NH_3)_6(H_2O)]~(n+) (n = 2-5), for which density functional calculations have been carried out for several electronic configurations. The molecular orbital picture deduced from the calculations indicates that one-electron oxidation of the Mn_2~(IV, IV)/(O~(2-)_2 complex (n = 4) mostly affects the oxygen atoms, thus ruling out the existence of a Mn~V oxidation state in this context, while the incipient formation of an O-O bond in the O_2~(3-) transition species evolves exothermally toward the dissociation of dioxygen and a Mn_2~(II, III) couple. These results identify the electronic features that could be needed to enable an intramolecular mechanism of oxygen-oxyen bond formatin to exist at the OEC during photosynthesis.
机译：在光合作用的关键步骤光系统II（PSII）的放氧复合物（OEC）上产生双氧的机制仍在争论中。 OEC中可产生O_2的最简单单元是四核Mn_4簇中的双核氧桥联锰配合物。在本文中，我们报告了对模型配合物[Mn_2（＃mu＃-O）_2（NH_3）_6（H_2O）]〜（n +）（n = 2-5）的理论研究，为此进行了密度泛函计算列出几种电子配置。由计算得出的分子轨道图表明，Mn_2〜（IV，IV）/（O〜（2-）_ 2配合物（n = 4）的单电子氧化主要影响氧原子，从而排除了氧原子的存在。在这种情况下，Mn〜V处于氧化态，而O_2〜（3-）过渡物种中OO键的初期形成则放热地朝着双氧和Mn_2〜（II，III）的离解方向发展。使光合作用过程中的OEC存在氧-氧键甲format的分子内机制所需的电子特征。

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