Synthesis and properties of novel ammonium-based room-temperature gemini ionic liquids

Abstract

Ammonium-based room-temperature asymmetrical gemini ionic liquids, 1-trimethylammonium-3-(pyridinium)propane bisdicyanamide ([N₁₁₁C₃Py][DCA]₂) and 1-trimethylammonium-3-(1-methylpiperidinium)propane bisdicyanamide ([N₁₁₁C₃MPi][DCA]₂) were respectively synthesized and structurally characterized by ¹H NMR and ¹³C NMR. Thermal stability of the gemini ionic liquids was determined by thermogravimetric analysis under a pure nitrogen atmosphere. Densities and viscosities of pure GILs and their binary mixtures with acetonitrile (MeCN) were investigated over the entire range of mole fractions at various temperatures, from 288.15 to 333.15 K, under atmospheric pressure. Moreover, the excess molar volumes (V^E_m) and the viscosity deviations (Δη) of the binary mixtures were evaluated and well fitted to the Redlich–Kister polynomial expression. The negative values of V^E_m and Δη result from strong self-association and interaction between the gemini ionic liquid molecules and MeCN. Results are discussed in terms of molecular interactions and structures.