Abstract: | A review of the recent developments in the study and understanding of room temperature ionic liquids are given. An intimate
picture of how and why these liquids are not crystals at ambient conditions is attempted, based on evidence from crystallographical
results combined with vibrational spectroscopy and ab-initio molecular orbital calculations. A discussion is given, based mainly on some recent FT-Raman spectroscopic results on the model ionic liquid system of 1-butyl-3-methylimidazolium (C4
mim]X]) salts. The rotational isomerism of the C4
mim]+ cation is described: the presence of anti and gauche conformers that has been elucidated in remarkable papers by Hamaguchi et al. Such presence of a conformational equilibrium seems to be a general feature of the room temperature liquids. Then the “localized
structure features” that apparently exist in ionic liquids are described. It is hoped that the structural resolving power
of Raman spectroscopy will be appreciated by the reader. It is of remarkable use on crystals of known different conformations and
on the corresponding liquids, especially in combination with modern quantum mechanics calculations. It is hoped that these
interdisciplinary methods will be applied to many more systems in the future. A few examples will be discussed. |