title: Activation of electron-transfer reduction of oxygen by hydrogen bond formation of superoxide anion with ammonium ion.
abstract: A hydrogen bond formed between the superoxide anion and the ammonium ion (NH4+) accelerates electron transfer from the C60 radical anion to oxygen significantly, whereas the tetra-n-butylammonium ion has no ability to form a hydrogen bond with the superoxidie anion, exhibiting no acceleration of the electron-transfer reduction of oxygen. The second-order rate constant of electron transfer from C60*- to O2 increases linearly with increasing concentration of NH4+. This indicates that O2*- produced in the electron transfer from C60 to O2 is stabilized by 1:1 complex formation between O2*- and NH4+. The 1:1 complex formed between O2*- and NH4+ was detected by ESR. The binding of O2*- with NH4+ results in a positive shift of the reduction potential of O2 with increasing concentration of NH4+, leading to the acceleration of electron transfer from C60*- to O2.
authors.affiliation: Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.forename: Hironori
authors.initials: H
authors.lastname: Kitaguchi
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D037741:Fullerenes / Q000737:chemistry*; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*; D011199:Potentiometry; D011789:Quantum Theory; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry*
chemical_list: D037741:Fullerenes; D000644:Quaternary Ammonium Compounds; D013481:Superoxides; D010100:Oxygen