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Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):13990-4. doi: 10.1073/pnas.1104698108. Epub 2011 Aug 1.

Homogeneous catalytic O2 reduction to water by a cytochrome c oxidase model with trapping of intermediates and mechanistic insights.

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  • 1Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.


An efficient and selective four-electron plus four-proton (4e(-)/4H(+)) reduction of O(2) to water by decamethylferrocene and trifluoroacetic acid can be catalyzed by a synthetic analog of the heme a(3)/Cu(B) site in cytochrome c oxidase ((6)LFeCu) or its Cu-free version ((6)LFe) in acetone. A detailed mechanistic-kinetic study on the homogeneous catalytic system reveals spectroscopically detectable intermediates and that the rate-determining step changes from the O(2)-binding process at 25 °C room temperature (RT) to the O-O bond cleavage of a newly observed Fe(III)-OOH species at lower temperature (-60 °C). At RT, the rate of O(2)-binding to (6)LFeCu is significantly faster than that for (6)LFe, whereas the rates of the O-O bond cleavage of the Fe(III)-OOH species observed (-60 °C) with either the (6)LFeCu or (6)LFe catalyst are nearly the same. Thus, the role of the Cu ion is to assist the heme and lead to faster O(2)-binding at RT. However, the proximate Cu ion has no effect on the O-O bond cleavage of the Fe(III)-OOH species at low temperature.

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