Above 110 degreesC the symmetric di-methyl-pyrrolidinium iodide salt forms a plastic crystal phase of interest in the area of new electrolyte materials. In this study ab initio calculations of this material has been conducted in order to assign the vibrational spectra. Raman spectroscopy measurements on the solid salt as well as on the salt dissolved in different solvents has been performed and these have been compared to the theoretical spectra. Furthermore, Raman spectra as a function of temperature have been recorded to investigate possible changes in inter-ionic interaction and/or structure through the phase transition. H-1 NMR linewidth measurements as a function of temperature showed a large decrease in linewidth above 100 degreesC, attributed here to an increase in mobility in agreement with a previously reported phase transition at similar to110 degreesC. (C) 2003 Elsevier Science Ltd. All rights reserved.