Crystal structure of a metal ion-bound oxoiron(IV) complex and implications for biological electron transfer
Crystal structure of a metal ion-bound oxoiron(IV) complex and implications for biological electron transfer
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DOI：
10.1038/nchem.731
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发表时间：
2010-09-01
期刊：
影响因子：
21.8
通讯作者：
Nam, Wonwoo
中科院分区：
文献类型：
--
作者：
Fukuzumi, Shunichi;Morimoto, Yuma;Nam, Wonwoo
涉及高价氧代金属化学的关键生物电子转移过程广泛存在，例如血红素蛋白[氧代铁（IV）; Fe-IV（O）]和光系统II。光系统II涉及Ca 2+以及高价oxomanganese簇物种。然而，没有金属离子和氧合铁（IV）络合物之间相互作用的实例。在这里，我们报告的新发现有关的氧化还原惰性的金属离子Ca 2+和Sc 3+的非血红素氧合铁（IV）配合物，[（TMC）Fe-IV（O）]（2+）（TMC = 1，4，8，11-四甲基-1，4，8，11-四氮杂环十四烷）的结合。如通过X-射线衍射分析所确定的，氧代-Sc 3+相互作用导致氧代铁（IV）部分的结构畸变。更重要的是，这种相互作用促进了二茂铁的双电子还原，而在没有金属离子的情况下仅发生单电子还原过程。这种氧化还原行为的控制提供了有价值的机械见解oxometal氧化还原化学，并建议一个可能的关键作用，辅助刘易斯酸金属离子可以在自然界中发挥作用，如在光系统II。
Critical biological electron-transfer processes involving high-valent oxometal chemistry occur widely, for example in haem proteins [oxoiron(IV); Fe-IV(O)] and in photosystem II. Photosystem II involves Ca2+ as well as high-valent oxomanganese cluster species. However, there is no example of an interaction between metal ions and oxoiron(IV) complexes. Here, we report new findings concerning the binding of the redox-inactive metal ions Ca2+ and Sc3+ to a non-haem oxoiron(IV) complex, [(TMC)Fe-IV(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). As determined by X-ray diffraction analysis, an oxo-Sc3+ interaction leads to a structural distortion of the oxoiron(IV) moiety. More importantly, this interaction facilitates a two-electron reduction by ferrocene, whereas only a one-electron reduction process occurs without the metal ions. This control of redox behaviour provides valuable mechanistic insights into oxometal redox chemistry, and suggests a possible key role that an auxiliary Lewis acid metal ion could play in nature, as in photosystem II.