title: Oxidation reaction of [Ni(1,4,7-triazacyclononane)(2)](2+) by [Fe(o-phenanthroline)(3)](3+) in aqueous acidic solution at elevated pressures: determination of the activation and reaction volumes for the Ni(iii)/(ii) couple.
abstract: The reaction volume corresponding to the self-exchange process of the [Ni(tacn)(2)](3+/2+) couple was determined in aqueous acidic solution. Theoretical equations on the basis of the Mean Spherical Approximation were proposed for the estimation of reaction volumes for M(n+/(n- 1)+) couples in solution, and the calculated reaction volumes were compared with the experimentally estimated values. The activation volume for the [Ni(tacn)(2)](3+/2+) couple was determined in the acidic condition from the cross reaction of [Ni(tacn)(2)](2+) and [Fe(o-phen)(3)](3+) at elevated pressures. The agreement of the experimentally estimated activation volume for the [Ni(tacn)(2)](3+/2+) couple, -8.2 +/- 2.4 cm(3) mol(-1), with the theoretically calculated value, -7.5 cm(3) mol(-1), within the allowed uncertainty (+/-1 cm(3) mol(-1)) indicates that the electron self-exchange reaction of this redox couple obeys the Marcusian behavior in aqueous acidic solution.
authors.affiliation: Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8602, Japan. htakagi@chem.nagoya-u.ac.jp
authors.forename: Sumitaka
authors.initials: S
authors.lastname: Itoh
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Koshino
authors.forename: Masumi
authors.initials: M
authors.lastname: Katsuki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Noda
authors.forename: Koji
authors.initials: K
authors.lastname: Ishihara
authors.forename: Masahiko
authors.initials: M
authors.lastname: Inamo
authors.forename: Hideo D
authors.initials: HD
authors.lastname: Takagi