Dimethyl-pyrrolidinum-based salts have been investigated by means of DSC, conductivity, NMR and Raman spectroscopy. The investigation aims to study the effect of the anion on the behaviour of the salt, in terms of plastic properties as well as rotational degrees of freedom of the cation. The materials range from the non-plastic iodide salt to the highly plastic BF4 salt, which flows under its own weight at elevated temperatures. The different rotational and translational motions of the cations, and the difference between rotator and plastic phases are discussed. (c) 2005 Elsevier Ltd. All rights reserved.