Homogeneous catalytic O 2 reduction to water by a cytochrome c oxidase model with trapping of intermediates and mechanistic insights

Zakaria Halime, Hiroaki Kotani, Yuqi Li, Shunichi Fukuzumi, Kenneth D. Karlin

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

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 ( 6LFeCu) or its Cu-free version ( 6LFe) 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 6LFeCu is significantly faster than that for 6LFe, whereas the rates of the O-O bond cleavage of the Fe III-OOH species observed (-60 ° C) with either the 6LFeCu or 6LFe 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.

Original languageEnglish
Pages (from-to)13990-13994
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number34
DOIs
StatePublished - 23 Aug 2011

Keywords

  • Dioxygen reduction
  • Enzyme model
  • Ferric hydroperoxo
  • Heme/copper
  • Kinetic mechanism

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