Vaporization and formation enthalpies of 1-alkyl-3-methylimidazolium tricyanomethanides
Thermochemical studies of the ionic liquids 1-ethyl-3-methylimidazolium tricyanomethanide [C2MIM][C(CN)3] and 1-butyl-3- methylimidazolium tricyanomethanide [C4MIM][C(CN)3] have been performed in this work. Vaporization enthalpies have been obtained using a recently developed quartz crystal microbalance (QCM) technique. The molar enthalpies of formation of these ionic liquids in the liquid state were measured by means of combustion calorimetry. A combination of the results obtained from QCM and combustion calorimetry lead to values of gaseous molar enthalpies of formation of [CnMIM][C(CN)3]. First-principles calculations of the enthalpies of formation in the gaseous phase for the ionic liquids [CnMIM][C(CN)3] have been performed using the CBS-QB3 and G3MP2 theory and have been compared with the experimental data. Furthermore, experimental results of enthalpies of formation of imidazolium-based ionic liquids with the cation [CnMIM] (where n = 2 and 4) and anions [N(CN)2], [NO3], and [C(CN)3] available in the literature have been collected and checked for consistency using a group additivity procedure. It has been found that the enthalpies of formation of these ionic liquids roughly obey group additivity rules.
Emel'Yanenko, Vladimir N.,Zaitsau, Dzmitry H.,Verevkin, Sergey P.,Heintz, Andreas,Voss, Karsten,Schulz, Axel