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Updated: Jul 10, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Local structure formation in alkyl-imidazolium-based ionic liquids as revealed by linear and nonlinear Raman
Koichi Iwata1, Hajime Okajima, Satyen Saha
1Research Centre for Spectrochemistry and Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
We show several pieces of Raman spectroscopic evidence that are indicative of local structure formation in imidazolium-based ionic liquids. Low-frequency Raman spectra of C n mimX, where C n mim stands for 1-alkyl(C n H 2 n+1 )-3-methylimidazolium cation and X represents the anion, exhibit broad bands assignable to collective modes of local structures. Spatial distributions of coherent anti-Stokes Raman scattering (CARS) signals from C n mim[PF 6] are consistent with local structures whose size increases with increasing n. Picosecond Raman spectra of S 1 trans-stilbene as a "picosecond Raman thermometer" show microscopic thermal inhomogeneity ascribable to local structure formation in C 2mimTf 2N and C 4mimTf 2N. We also describe two novel phenomena that we believe are relevant to extraordinary nanoenvironments generated by local structures in a magnetic ionic liquid C 4mim[FeCl 4].
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