Related Experiment Video
Updated: Jun 23, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
New interpretation of the CH stretching vibrations in imidazolium-based ionic liquids
Abstract:
In ionic liquids composed of alkyl-substituted imidazolium cations and weakly coordinating anions such as bis(trifluoromethanesulfonyl)imide, (CF(3)SO(2))(2)N(-), the stretching vibrations of the imidazolium CH groups are shown to interact by Fermi resonance with the overtones and the combination of two in-plane ring vibrations. This new assignment, based on isotopic substitutions and anharmonic frequency calculations for gas phase cations, implies that these imidazolium cations do not establish any strong and directional C-H...anion hydrogen bond.
Related Concept Videos
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
IR Spectroscopy: Molecular Vibration Overview
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
IR Frequency Region: X–H Stretching
IR Frequency Region: Alkyne and Nitrile Stretching
Comparing the stretching vibrational frequency of C≡C triple bonds with that of double and single bonds, it is evident that C≡C triple bonds exhibit a higher stretching frequency than C=C double and C–C single bonds. Similarly, the C≡N triple bond exhibits higher stretching absorption than the C=N...
IR Absorption Frequency: Hybridization
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
IR Absorption Frequency: Delocalization
In IR spectroscopy,...

