期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 17, 期 18, 页码 12168-12174出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5cp00138b
关键词
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资金
- Knut and Alice Wallenberg Foundation
- Beijing Normal University [2014NT10]
In a previous detailed study of all the steps of water oxidation in photosystem II, it was surprisingly found that O-2 release is as critical for the rate as O-O bond formation. A new mechanism for O-2 release has now been found, which can be described as an opening followed by a closing of the interior of the oxygen evolving complex. A transition state for peroxide rotation forming a superoxide radical, missed in the previous study, and a structural change around the outside manganese are two key steps in the new mechanism. However, O-2 release may still remain rate-limiting. Additionally, for the step forming the O-O bond, an alternative, experimentally suggested, mechanism was investigated. The new model calculations can rule out the precise use of that mechanism. However, a variant with a rotation of the ligands around the outer manganese by about 301 will give a low barrier, competitive with the old DFT mechanism. Both these mechanisms use an oxyl-oxo mechanism for O-O bond formation involving the same two manganese atoms and the central oxo group (O5).
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