Expanding the Chemical Space of Benzimidazole Dicationic Ionic Liquids

Abstract

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts.

A comparative study on the design and application of new nano benzimidazolium gemini ionic liquids for curing interfacial properties of the crude oil–water system

“…These results are in agreement with a previous study on the thermal stability of a number of benzimidazolium Gemini ionic liquids. 31…”

A Specific Interaction between Ionic Liquids’ Cations and Reichardt’s Dye

“…Monocationic and dicationic bis-(trifluoromethylsulfonyl)imide ILs were obtained with two-step procedures reported in previous works [ 34 , 38 ] through a metathesis reaction from bromide precursors 12 – 21 .…”

Recent Advances in Imidazolium-Based Dicationic Ionic Liquids as Organocatalysts: A Mini-Review

“…Ionic liquids (ILs) have received increasing interest from the scientific community, due to their remarkable physicochemical properties (melting point, chemical and thermal stability, negligible vapor pressure, conductivity, solvating power, etc.) and their potential applications [ 1 , 2 ]. An ionic liquid is a salt which consists of a large organic cation associated to a non-coordinating organic or inorganic anion, melting at temperatures equal to or less than 100 °C.…”