Asymmetry effect of novel per(fluoroalkylsulfonyl)imide anions in pyrrolidinium ionic liquids

Abstract

Ionic liquids based on the N-butyl-N-methylpyrrolidinium, (PYR₁₄)⁺, cation and different per(fluoroalkylsulfonyl)imide anions, having symmetric, (IM₁₁)⁻, moderately asymmetric, (IM₂₄)⁻, highly asymmetric, (IM₁₄)⁻ and (IM_T4)⁻, and cyclic, (IM₃)⁻ structures, were properly synthesized. A few of the presented per(fluoroalkylsulfonyl)imide ions have never been reported in the literature as ionic liquid anions. The thermal and transport properties of the ionic liquid materials, having a common cation, were investigated and correlated with the structure of the per(fluoroalkylsulfonyl)imide anion. The results have indicated that the symmetry as well as the steric hindrance of the anion affect the melting point and the crystallization kinetics as well as the ion conduction and the self-diffusion coefficient of the ionic liquids. The conductivity data are in good agreement with the thermal measurements.