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.