Issue 42, 2011

A comparison between artificial and natural water oxidation

Abstract

Two artificial water oxidation catalysts, the blue dimer and the Llobet catalyst, have been studied using hybrid DFT methods. The results are compared to those for water oxidation in the natural photosystem II enzyme. Studies on the latter system have now reached a high level of understanding, at present much higher than the one for the artificial systems. A recent high resolution X-ray structural investigation of PSII has confirmed the main features of the structure of the oxygen evolving complex (OEC) suggested by previous DFT cluster studies. The O–O bond formation mechanism suggested is of direct coupling (DC) type between an oxygen radical and a bridging oxo ligand. A similar DC mechanism is found for the Llobet catalyst, while an acid–base (AB) mechanism is preferred for the blue dimer. All of them require at least one oxygen radical. Full energy diagrams, including both redox and chemical steps, have been constructed illustrating similarities and differences to the natural system. Unlike previous DFT studies, the results of the present study suggest that the blue dimer is rate-limited by the initial redox steps, and the Llobet catalyst by O2 release. The results could be useful for further improvement of the artificial systems.

Graphical abstract: A comparison between artificial and natural water oxidation

Supplementary files

Article information

Article type
Paper
Submitted
12 Jul 2011
Accepted
19 Sep 2011
First published
30 Sep 2011

Dalton Trans., 2011,40, 11296-11307

A comparison between artificial and natural water oxidation

X. Li, G. Chen, S. Schinzel and P. E. M. Siegbahn, Dalton Trans., 2011, 40, 11296 DOI: 10.1039/C1DT11323B

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