In this paper, the physicochemical properties of a new series of ionic liquids (ILs) based on nitrile-functionalised imidazolium cations (C 2CN Cnim+) with sulfonate-based anions were studied. The ILs were prepared by reacting imidazole with acrylonitrile, followed by butyl- and decyl bromide. The anions of the resulting bromide salts exchanged by metathesis to dioctylsulfosuccinate (DOSS), dodecylsulfate (DDS), benzenesulfonate (BS) and trifluoromethanesulfonate (TFMS). The densities of these ILs are lower compared to the those of other reported nitrile- functionalised ILs, while on the other hand, the viscosities of the ILs are higher due to the effects of the large anions and the long alkyl chain of the cations. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.