Issue 7, 2014

Competitive pi interactions and hydrogen bonding within imidazolium ionic liquids

Abstract

In this paper we have explored the structural and energetic landscape of potential π+–π+ stacked motifs, hydrogen-bonding arrangements and anion–π+ interactions for gas-phase ion pair (IP) conformers and IP-dimers of 1,3-dimethylimidazolium chloride, [C1C1im]Cl. We classify cation–cation ring stacking as an electron deficient π+–π+ interaction, and a competitive anion on-top IP motif as an anion–donor π+–acceptor interaction. 21 stable IP-dimers have been obtained within an energy range of 0–126 kJ mol−1. The structures have been found to exhibit a complex interplay of structural features. We have found that low energy IP-dimers are not necessarily formed from the lowest energy IP conformers. The sampled range of IP-dimers exhibits new structural forms that cannot be recovered by examining the ion-pairs alone, moreover the IP-dimers are recovering additional key features of the local liquid structure. Including dispersion is shown to impact both the relative energy ordering and the geometry of the IPs and IP-dimers, however the impact is found to be subtle and dependent on the underlying functional.

Graphical abstract: Competitive pi interactions and hydrogen bonding within imidazolium ionic liquids

Supplementary files

Article information

Article type
Paper
Submitted
05 Nov 2013
Accepted
23 Dec 2013
First published
09 Jan 2014

Phys. Chem. Chem. Phys., 2014,16, 3238-3253

Competitive pi interactions and hydrogen bonding within imidazolium ionic liquids

R. P. Matthews, T. Welton and P. A. Hunt, Phys. Chem. Chem. Phys., 2014, 16, 3238 DOI: 10.1039/C3CP54672A

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