A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites
A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites
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DOI：
10.1098/rstb.2007.2226
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发表时间：
2008-03-27
影响因子：
6.3
通讯作者：
Nocera, Daniel G.
中科院分区：
文献类型：
--
作者：
Betley, Theodore A.;Surendranath, Yogesh;Nocera, Daniel G.
氧-氧键的形成和O-2的产生发生在放氧复合物（OEC）的S-4状态。已经提出了几种可能的水氧化机理，这取决于锰原子的形式氧化态。所有这些都属于两个一般分类：AB机制，其中亲核氧（碱，B）攻击Mn 4Ca簇的亲电氧（酸，A）或RC机制，其中自由基样氧物种在OEC内偶联。在任一机制中的关键中间体涉及金属氧代，尽管AB和RC机制的这种氧代的性质是不同的。在AB机理的情况下，需要偶电子数、高价金属氧代接近氢氧化物的组装，而在RC机理中，需要两个奇电子数、高价金属氧代。因此，这两种机制产生了非常不同的设计标准的功能模型的OEC活性位点。本讨论提出了电子计数和配体的几何形状，支持AB和RC O-O键形成反应的金属羰基。的AB和RC方案的范围内，将两个氧功能在一起的架构的建设进行了说明。
Oxygen-oxygen bond formation and O-2 generation occur from the S-4 state of the oxygen-evolving complex (OEC). Several mechanistic possibilities have been proposed for water oxidation, depending on the formal oxidation state of the Mn atoms. All fall under two general classifications: the AB mechanism in which nucleophilic oxygen (base, B) attacks electrophilic oxygen (acid, A) of the Mn4Ca cluster or the RC mechanism in which radical-like oxygen species couple within OEC. The critical intermediate in either mechanism involves a metal oxo, though the nature of this oxo for AB and RC mechanisms is disparate. In the case of the AB mechanism, assembly of an even-electron count, high-valent metal-oxo proximate to a hydroxide is needed whereas, in an RC mechanism, two odd-electron count, high-valent metal oxos are required. Thus the two mechanisms give rise to very different design criteria for functional models of the OEC active site. This discussion presents the electron counts and ligand geometries that support metal oxos for AB and RC O-O bond-forming reactions. The construction of architectures that bring two oxygen functionalities together under the purview of the AB and RC scenarios are described.