title: A Mononuclear Nonheme Iron(III)-Peroxo Complex Binding Redox-Inactive Metal Ions.
abstract: Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating reactivities of oxygen-containing metal complexes in a variety of biological and biomimetic reactions, including dioxygen activation/formation and functionalization of organic substrates. Mononuclear nonheme iron(III)-peroxo species are invoked as active oxygen intermediates in the catalytic cycles of dioxygen activation by nonheme iron enzymes and their biomimetic compounds. Here, we report mononuclear nonheme iron(III)-peroxo complexes binding redox-inactive metal ions, [(TMC)FeIII(O2)]+-M3+(M3+= Sc3+and Y3+; TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), which are characterized spectroscopically as a 'side-on' iron(III)-peroxo complex binding a redox-inactive metal ion, (TMC)FeIII-(μ,η2:η2-O2)-M3+(2-M). While an iron(III)-peroxo complex, [(TMC)FeIII(O2)]+, does not react with electron donors (e.g., ferrocene), one-electron reduction of the iron(III)-peroxo complexes binding redox-inactive metal ions occurs readily upon addition of electron donors, resulting in the generation of an iron(IV)-oxo complex, [(TMC)FeIV(O)]2+(4), via heterolytic O-O bond cleavage of the peroxide ligand. The rates of the conversion of2-M to4are found to depend on the Lewis acidity of the redox-inactive metal ions and the oxidation potential of the electron donors. We have also determined the fundamental electron-transfer properties of2-M, such as the reduction potential and the reorganization energy in electron-transfer reaction. Based on the results presented herein, we have proposed a mechanism for the reactions of2-M and electron donors; the reduction of2-M to the reduced species, (TMC)FeII-(O2)-M3+(2'-M), is the rate-determining step, followed by heterolytic O-O bond cleavage of the reduced species to form4. The present results provide a biomimetic example demonstrating that redox-inactive metal ions bound to an iron(III)-peroxo intermediate play a significant role in activating the peroxide O-O bond to form a high-valent iron(IV)-oxo species.
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Lee
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Suhee
authors.initials: S
authors.lastname: Bang
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Yun Mi
authors.initials: YM
authors.lastname: Kim
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea ; Department of Emerging Materials Science, DGIST, Daegu 711-873, Korea.
authors.forename: Jaeheung
authors.initials: J
authors.lastname: Cho
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Seungwoo
authors.initials: S
authors.lastname: Hong
authors.affiliation: Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomura
authors.affiliation: Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogura
authors.affiliation: Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Troeppner
authors.affiliation: Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Ivana
authors.initials: I
authors.lastname: Ivanović-Burmazović
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
authors.forename: Ritimukta
authors.initials: R
authors.lastname: Sarangi
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea ; Department of Material and Life Science, Graduate School of Engineering, ALCA, Japan Science and Technology Agency (JST), Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Nam