Electronic–Level View of O–O Bond Formation in Nature’s Water Oxidizing Complex

Thomas A. Corry, Patrick J. O’Malley

Research output: Contribution to journalArticlepeer-review


The crucial O-O bond forming step in the water oxidizing complex (WOC) of photosystem II is modeled using density functional theory calculations and compared with structural X-ray free electron laser (XFEL) determinations for the penultimate S 3 state. Concerted electron flow between the Mn 4O5 and Mn 1O6 bonds of the complex and the nascent O-O bond is monitored using intrinsic bond orbital analysis along the reaction path. Concerted transfer to Mn 1 and Mn 4 of two electrons from the reactant oxos, O5 and O6, resulting in an unoccupied antibonding σ 2p∗ orbital is the key to low barrier O-O bond formation. The potential energy surface for O-O bond formation shows a rather broad energy minimum for the oxo-oxo form ranging from 2.4-2.0 Å which may explain the relatively short O5-O6 bond distance reported in experimental structure studies. Alternatively the short O5-O6 bond distance may reflect a dynamic equilibrium model across the whole O-O potential energy surface.

Original languageEnglish
Pages (from-to)4221-4225
Number of pages5
JournalThe journal of physical chemistry letters
Issue number10
Publication statusPublished - 21 May 2020


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