title: Dependence of cobaltocenium diffusion in ionic liquids on the alkyl chain length of 1-alkyl-3-methylimidazolium cations.
abstract: The electrochemical behavior of cobaltocenium (Cc(+)) on a Au(111) electrode was investigated in five 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([Cnmim][Tf2N], n = 2, 4, 6, 8, or 10) ionic liquids (ILs) in the temperature range from 293.15 to 343.15 K by cyclic voltammetry and chronoamperometry. The redox couple of Cc(+) exhibited a clear reversible one-electron reaction in all the [Cnmim][Tf2N] ILs. The diffusion coefficients of Cc(+) increased with an increase in the alkyl chain length of [Cnmim](+) and a decrease in the viscosity of the IL upon elevating the temperature. The viscosity of the IL plays an important role in determining the activation energy for the diffusion of Cc(+). The obtained results suggested that the alkyl chain length of [Cnmim](+) affects the strength of the interaction between Cc(+) and the surrounding ion species. The results also clarified that the equation proposed by Sutherland adequately describes the diffusion of Cc(+) in ILs when the effect of the type of IL and the temperature on the product of the Stokes radius of Cc(+) and the Sutherland coefficient is considered.
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ueda
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Soichiro
authors.initials: S
authors.lastname: Yoshimoto