title: A negative temperature dependence of the electron self-exchange rates of zinc porphyrin pi radical cations.
abstract: The one-electron oxidation of ZnT(t-Bu)PP (T(t-Bu)PP2- = 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin dianion) by one equivalent of Ru(bpy)33+ (bpy = 2,2'-bipyridine) results in quantitative formation of ZnT(t-Bu)PP*+ which is detected by ESR. In the presence of excess ZnT(t-Bu)PP, the ESR line width becomes broader with increasing ZnT(t-Bu)PP concentration due to the electron self-exchange between ZnT(t-Bu)PP*+ and ZnT(t-Bu)PP. The line width of the ESR signal of ZnT(t-Bu)PP*+ becomes broader as the temperature is decreased from 313 to 233 K. This indicates that the electron self-exchange reaction becomes faster at a lower temperature. The substituent and solvent effects on such a negative temperature dependence of the electron self-exchange rates are reported.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, CREST, JST, Osaka University, Suita 565-0871, Japan. fukuzumi@ap.chem.eng.osaka-u.ac.jp
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Endo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori