Article | Published:

Redox-inactive metal ions modulate the reactivity and oxygen release of mononuclear non-haem iron(III)–peroxo complexes

Nature Chemistry volume 6, pages 934940 (2014) | Download Citation

Abstract

Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating the reactivity of oxygen-containing metal complexes and metalloenzymes, such as the oxygen-evolving complex in photosystem II and its small-molecule mimics. Here we report the synthesis and characterization of non-haem iron(III)–peroxo complexes that bind redox-inactive metal ions, (TMC)FeIII–(μ,η22-O2)–Mn+ (Mn+ = Sr2+, Ca2+, Zn2+, Lu3+, Y3+ and Sc3+; TMC, 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). We demonstrate that the Ca2+ and Sr2+ complexes showed similar electrochemical properties and reactivities in one-electron oxidation or reduction reactions. However, the properties and reactivities of complexes formed with stronger Lewis acidities were found to be markedly different. Complexes that contain Ca2+ or Sr2+ ions were oxidized by an electron acceptor to release O2, whereas the release of O2 did not occur for complexes that bind stronger Lewis acids. We discuss these results in the light of the functional role of the Ca2+ ion in the oxidation of water to dioxygen by the oxygen-evolving complex.

  • Compound C14H32FeN4O2+

    [(TMC)FeIII(η2-O2)]+

  • Compound C16H35FeN5O2+

    [(TMC)FeIV(O)]2+

  • Compound C14H32CaFeN4O23+

    [(TMC)FeIII(µ,η2:η2-O2)]+-Ca2+

  • Compound C14H32FeN4O2Sr3+

    [(TMC)FeIII(µ,η2:η2-O2)]+-Sr2+

  • Compound C14H32FeN4O2Zn3+

    [(TMC)FeIII(µ,η2: η 1-O2)]+-Zn2+

  • Compound C14H32FeLuN4O24+

    [(TMC)FeIII(µ,η2:η2-O2)]+-Lu3+

  • Compound C14H32FeN4O2Y 4+

    [(TMC)FeIII(µ,η2:η2-O2)]+-Y3+

  • Compound C14H32FeN4O2Sc4+

    [(TMC)FeIII(µ,η2:η2-O2)]+-Sc3+

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Acknowledgements

The research was supported by KOSEF/MEST of Korea through the CRI (NRF-2012R1A3A2048842 to W.N.), GRL (NRF-2010-00353 to W.N.) and MSIP of Korea through NRF (2013R1A1A2062737 to K-B.C.) and an ALCA project from JST (S.F.) from MEXT of Japan. Stanford Synchrotron Radiation Lightsource (SSRL) operations are funded by the US Department of Energy (DOE) Basic Energy Sciences. The SSRL Structural Molecular Biology program is supported by National Institutes of Health National Center for Research Resources (P41 RR001209) and DOE Biological Environmental Research (R.S.).

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Author notes

    • Suhee Bang
    •  & Yong-Min Lee

    These authors contributed equally to this work

Affiliations

  1. Department of Chemistry and Nano Science, Department of Bioinspired Science, Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea

    • Suhee Bang
    • , Yong-Min Lee
    • , Seungwoo Hong
    • , Kyung-Bin Cho
    • , Mi Sook Seo
    • , Shunichi Fukuzumi
    •  & Wonwoo Nam
  2. Department of Material and Life Science, Graduate School of Engineering, Osaka University and ALCA, Japan Science Technology Agency (JST), Suita, Osaka 565-0871, Japan

    • Yusuke Nishida
    •  & Shunichi Fukuzumi
  3. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

    • Ritimukta Sarangi

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Contributions

W.N. conceived and designed the experiments; S.B., Y-M.L., S.H., K-B.C., Y.N. and M.S.S. performed the experiments; Y-M.L., R.S., S.F., S.B., K-B.C., M.S.S. and S.H. analysed the data; W.N., S.F., Y-M.L., R.S. and K-B.C. co-wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Ritimukta Sarangi or Shunichi Fukuzumi or Wonwoo Nam.

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https://doi.org/10.1038/nchem.2055

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