J. Holbrey, W. Reichert, R. Rogers
Jul 26, 2004
Citations
1
Influential Citations
193
Citations
Quality indicators
Journal
Dalton transactions
Abstract
Crystal structures of two examples of an important class of ionic liquids, 1,3-dimethylimidazolium and 1,2,3-triethylimidazolium bis(trifluoromethanesulfonyl)imide have been characterized by single crystal X-ray diffraction. The anion in the 1,3-dimethylimidazolium example (mp 22 degrees C), adopts an unusual cis-geometry constrained by bifurcated cation-anion C-H. . .O hydrogen-bonds from the imidazolium cation to the anion resulting in the formation of fluorous layers within the solid-state structure. In contrast, in the 1,2,3-triethylimidazolium salt (mp 57 degrees C), the ions are discretely packed with only weak C-H. . .O contacts between the ions close to the van der Waals separation distances, and with the anion adopting the twisted conformation observed for all other examples from the limited set of organic bis(trifluoromethanesulfonyl)imide crystal structures. The structures are discussed in terms of the favorable physical properties that bis(trifluoromethanesulfonyl)imide anions impart in ionic liquids.