Concerted bond switching mechanism coupled with one-electron transfer for the oxygen-oxygen bond formation in the oxygen-evolving complex of photosystem II

• Published in: Chemical physics letters 2019-01, Vol.714, p.219-226
• Main Authors: Shoji, Mitsuo, Isobe, Hiroshi, Yamaguchi, Kizashi
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2018.10.041

[Display omitted] •O-O bond formation of oxygen-evolving complex of photosystem II was investigated.•Chemical indices derived from the natural orbitals were adapted.•The O-O bond formation proceeds with a Concerted Bond Switching (CBS) mechanism.•The CBS mechanism is a new non-radical mechanism.•The CBS mechanism provides new aspects for the O-O bond formation of PSII-OEC. We here precisely analyzed the electronic structures during the oxygen-oxygen (O-O) bond formation of the oxygen-evolving complex (OEC) in photosystem II (PSII) based on the quantum mechanics/molecular mechanics (QM/MM) calculations. Changes in the spin density and the chemical indices derived from the natural orbitals suggested that the O(5)-O(6) bond formation proceeds with a concerted bond breaking of the Mn4-O(5) coupled with the through-bond one-electron transfer from the O(6) site to the Mn4 site (Mn4(IV) → Mn4(III)). This mechanism can be best described as a Concerted Bond Switching (CBS) mechanism, which is a non-radical reaction of the O(5)-O(6) bond formation.