title: Interfacial ion pairing at the interface between water and a room-temperature ionic liquid, N-tetradecylisoquinolinium bis(pentafluoroethylsulfonyl)imide.
abstract: The specific interaction of N-tetradecylisoquinolinium (C(14)Iq+) with Cl- and Br- has been detected in the voltammetry of ion transfer and electrocapillarity at the interface between an aqueous solution (W) and a room-temperature ionic liquid (RTIL), N-tetradecylisoquinolinium bis(pentafluoroethylsulfonyl)imide ([C(14)Iq+][C(2)C(2)N-]). This specific interaction also makes the transfer of Cl- and Br- into [C(14)Iq+][C(2)C(2)N-] energetically more favorable in comparison with that of F- and SO(4)(2-). The width of the polarized potential window in ion-transfer voltammetry at the [C(14)Iq+][C(2)C(2)N-]|W interface is significantly narrower because of the transfer of anions from W to RTIL. The degree of affinity of the anion with C(14)Iq+ agrees with the Hofmeister series. Such an ion-pair formation of anions in W with cations in the RTIL is much weaker when the cation constituting the RTIL is a symmetric tetraheptylammonium ion.
authors.affiliation: Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Ishimatsu
authors.forename: Naoya
authors.initials: N
authors.lastname: Nishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kakiuchi