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Updated: Apr 5, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Cage-Like Local Structure of Ionic Liquids Revealed by a (129)Xe Chemical Shift
Franca Castiglione1, Roberto Simonutti2, Michele Mauri2
1†Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano, Italy.
Abstract:
The chemical shift of xenon (at natural abundance) dissolved in a variety of 1-butyl-3-methylimidazolium-based ionic liquids (ILs) has been measured with (129)Xe NMR spectroscopy. The large chemical shift differences observed are mainly related to the type of anion; the strongest deshielding effect is observed ILs with I(-), Br(-), and Cl(-) anions, and the strongest shielding is found for the bis(trifluoromethanesulfonyl)imide ([Tf2N](-))-based IL. The measured (129)Xe chemical shift variations correlate well with the IL structure organization imposed by the anions and with the size of the empty voids due to charge alternation patterns. Descriptors taken from literature data on X-ray and neutron scattering, as well as single-crystal structures where available, support this interpretation. The proposed methodology adds a new investigating tool to the elucidation of the short-range order in ILs. The observed chemical shift trend provides information about how these solvents are organized.
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