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.
Highlights
In the last 20 years, ionic liquids (ILs) have been undoubtedly a “hot” topic in the field of sustainable chemistry [1]
ILs exhibit unique properties and potential such as unmatched ability to dissolve several biopolymers [6,7], high thermal stability [8,9], high ability to solubilize gas [10], and high refractive index [11], the reputation of ILs as “green” solvents is certainly ascribable to their negligible vapor pressure, which makes them safe when compared to traditional organic solvents [12,13]
In the present work, we report the study of the thermal and electrical properties of two structurally related series of benzimidazole dicationic ionic liquids (BDILs) with bromide thermal and electrical properties of two structurally related series of BDILs with bromide and bis(trifluoromethane)sulfonimide as anions
Summary
In the last 20 years, ionic liquids (ILs) have been undoubtedly a “hot” topic in the field of sustainable chemistry [1]. To improve ILs’ sustainabilityrelated issues, synthetic procedures for their preparation have been optimized, focusing on the replacement or elimination of polluting organic solvents and on the usage of reagents deriving from renewable sources [15] In parallel to this approach, toxicity and biodegradation assessments pointed to structural elements of the cationic and anionic parts capable of ameliorating the overall impact profile of ILs [16,17] This new type of ILs, often referred to as the fourth generation of ILs, allowed for expanding the portfolio of possible applications in the fields of food science [18,19], medicine [20,21] and pharmaceutics [22,23]
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