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Updated: Jun 13, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
The potential role of hydrogen bonding in aprotic and protic ionic liquids
Koichi Fumino1, Alexander Wulf, Ralf Ludwig
1Institut für Chemie, Abteilung Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, D-18051 Rostock, Germany.
Abstract:
Cohesion energies determine the phase behavior of materials. The understanding of interaction energies is in particular interesting for ionic liquids. Here we show experimentally that, in accord with theoretical work, the intermolecular cation-anion interactions in ionic liquids can be detected by far FTIR spectroscopy. The measured vibrational bands of aprotic and protic ionic liquids in the low-frequency range can be referred to the interaction strength between cations and anions in various combinations. It can be shown by DFT B3LYP calculations that these interactions are described by characteristic ratios between Coulomb forces and hydrogen bonds. These ratios can be tuned towards increasing hydrogen bond contributions which is reflected in important macroscopic properties of ionic liquids such as enthalpies of vaporization and viscosities. This opens a new path for tuning the desired properties of this new class of material.
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