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.

Interface Between Two Immiscible Liquid Electrolytes: A Review

“…Microinterfaces are another useful analytical tool, one already used to build sensors 179 or to be used in the scanning pipette electrochemical microscopy [180][181][182] or in other analytical detection schemes 121,[183][184][185][186] . Ionic liquids which recently gained popularity in chemistry research also show promise for applications in the ITIES work [187][188][189][190][191][192][193] .…”

Mutual Solubility of Hydrophobic Ionic Liquids and Water in Liquid-Liquid Two-phase Systems for Analytical Chemistry

“…At the other end of the ppw, hydrophilic ions such as Cl -and SO4 2-may determine the width of the window. 214 In actual IL-W two-phase systems, the partition problems can be much more complicated than what is expected for simple IL-W two-phase systems.…”

The Solvation of Anions in Propylene Carbonate

“…In particular, Hofmeister studied the precipitation of egg yolk albumin from aqueous dispersions upon the addition of some sodium salts, and discovered that their effect can be ordered according to the following ranking for anions (at fixed cation) [1,2]: SO 4 2-> PO 4 3-> F -> Cl -> Br -> I -> NO 3 -> ClO 4 -Indeed, Hofmeister phenomena are not restricted to aqueous environments. Some studies have shown the occurrence of specific ion effects in water-free systems, for example, the solubility of salts in organic polar solvents [3], the physico-chemical properties of ionic liquids [4,5], the bubble-bubble coalescence in different organic liquids [6], and the activity of enzymes in non-aqueous media [7].…”