Evidence for hydrogen bonding in solutions of 1-ethyl-3-methylimidazolium halides, and its implications for room-temperature halogenoaluminate(III) ionic liquids

Abstract

Multinuclear NMR spectroscopy and conductivity measurements showed that the 1-ethyl-3-methyl-imidazolium cation, [emim]+, not only forms strong hydrogen bonds (using all three ring protons H2, H4 and H5) with halide ions in polar molecular solvents (e.g. ethanenitrile) and ionic liquids, but that it exists in a quasi-molecular state, [emim]X, in non-polar solvents (e.g. trichloro- and dichloro-methane), showing a conventional aromatic stacking phenomenon.