Experimental and computational studies on the ion dissociation states of 1-butyl-3-methyimidazolium tetrafluoroborate in water and alcohols

Abstract

Herein, we investigated the dissociation states of ion pairs in the prototype ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4), when mixed with water or alcohol, a homologous substituent of water, during experimentation and computation. Specifically, the degree of dissociation of an ion pair was determined through the density, electrical conductivity and self-diffusion coefficient using the Nernst–Einstein equation, and microscopic information regarding the solution was obtained through molecular dynamics simulations. A schematic model was proposed based on the Experimental and computational results. In the region of low IL concentration, [BMIm] and BF4 existed in a loosely aggregated or free ionic state in the [BMIm]BF4/water mixture. However, [BMIm] and BF4 mainly formed ion pairs, and the ion pairs did not aggregate much with each other in the [BMIm]BF4/alcohol mixture.