The effect of dispersion forces on the interaction energies and far infrared spectra of protic ionic liquids?

Physical Chemistry Chemical Physics Pub Date: 2015-03-31 DOI: 10.1039/C5CP00885A

Abstract

We could show by means of dispersion-corrected DFT calculations that the interaction energy in protic ionic liquids can be dissected into Coulomb interaction, hydrogen bonding and dispersion interaction. The H-bond energy as well as the dispersion energy can be quantified to be 50 kJ mol?1 each representing ten percent of the overall interaction energy. The dispersion interaction could be dissected into two portions. One third could be related to the dispersion interaction within an ion-pair enhancing the H-bond strength, two thirds stem from dispersion interaction between the ion-pairs. This distribution of dispersion interaction is reflected in the far infrared (FIR) spectra. The H-bond band is shifted weaker than the low frequency band where the latter indicates diffuse cation–anion interaction and H-bond bending motions. Finally, we can dissect the different types of interaction energies indicating their characteristic influence on vibrational modes in the FIR.

Graphical abstract: The effect of dispersion forces on the interaction energies and far infrared spectra of protic ionic liquids
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