Paper
Crystal structures of imidazolium bis(trifluoromethanesulfonyl)imide 'ionic liquid' salts: the first organic salt with a cis-TFSI anion conformation.
Published Jul 26, 2004 · J. Holbrey, W. Reichert, R. Rogers
Dalton transactions
194
Citations
1
Influential Citations
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.
The crystal structures of 1,3-dimethylimidazolium and 1,2,3-triethylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids reveal favorable physical properties and unique anion conformations.
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