title: Significant enhancement of electron transfer reduction of NAD(+) analogues by complexation with scandium ion and the detection of the radical intermediate-scandium ion complex.
abstract: 4-Acetyl-N,N-diisopropyl-1-benzylnicotinamidinium ion (ABNA(+)) and 1-benzyl-4-phenylnicotinamidinium ion (PhBNA(+)) were newly synthesized as NAD(+) analogues to examine the electron-transfer reactivity and the effects of metal ions on the reactivity in comparison with those of 1-benzylnicotinamidinium ion (BNA(+)) and 1-methyl-4-phenylpyridinium ion (MPP(+)) which has no amide or acetyl group. A remarkable positive shift in the one-electron reduction potential of ABNA(+) was observed in the presence of Sc(3+) which forms a 1:1 complex with ABNA(+) through both acetyl and amide groups, whereas no such shift in the presence of Sc(3+) was observed for the one-electron reduction of MPP(+) which has no acetyl or amide group. Similar but less positive shifts in the one-electron reduction potentials were observed in the presence of Sc(3+) for the one-electron reduction of BNA(+) and PhBNA(+) both of which have only one amide group. The rate of electron-transfer reduction of ABNA(+) is enhanced significantly by the complexation with Sc(3+) to produce stable ABNA(*)-Sc(3+) complex which has been successfully detected by ESR. The electron self-exchange rates of the MPP(*)/MPP(+) system have been determined from the ESR line width variation and are compared with those of the ABNA(*)/ABNA(+) system.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, CREST, Japan Science and Technology Corporation (JST), Suita, Osaka 565-0871, Japan. fukuzumi@ap.chem.eng.osaka-u.ac.jp
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Osamu
authors.initials: O
authors.lastname: Inada
authors.forename: Naoya
authors.initials: N
authors.lastname: Satoh
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Suenobu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007202:Indicators and Reagents; D007700:Kinetics; D008958:Models, Molecular; D009243:NAD / Q000031:analogs & derivatives* / Q000737:chemistry*; D009538:Nicotine / Q000031:analogs & derivatives / Q000737:chemistry*; D010084:Oxidation-Reduction; D012538:Scandium / Q000737:chemistry*
chemical_list: C464971:1-benzyl-4-phenylnicotinamidinium; D007202:Indicators and Reagents; D009243:NAD; D009538:Nicotine; D012538:Scandium