Eduards BAKIS1, Kateryna GOLOVIZNINA3, Nicolas SCAGLIONE5, Frederik PHILIPPI2, Toms REKIS1, Margarida COSTA GOMES4, Agilio PADUA5
1University of Latvia, Faculty of Chemistry, Riga, Latvia
2Imperial College London, Department of Chemistry, London, United Kingdom
3Sorbonne Université, CNRS, Physico-chimie des Électrolytes et Nanosystèmes Interfaciaux, Paris, France
4CNRS Lyon, Lyon, France
5Ecole Normale Supérieure de Lyon, Lyon, France
Studies of ionic liquids (ILs) have revealed that these materials have a unique liquid structure and interactions that are not present in any other liquid material. What often seems unsound in molecular liquids can be the case in ILs. Some structural features are passed on to the liquid upon melting of an ionic solid, while others disappear as a result of the isotropic nature of the liquid.
Coulombic forces determine the attraction and repulsion of ions in ILs, where the like-charged particles expel one another from their primary solvation shells. Anions are commonly surrounded by cations and vice versa. Only one literature report demonstrates that some degree of association of ions of the same charge is possible.
In this work, we demonstrate that ILs bearing cyanogroup-rich anions can exhibit a solid-state structure in which anions can neighbour anions. Moreover, such a peculiar feature is also preserved in the liquid state, as confirmed by SAXS, single-crystal X-ray crystallography, and molecular dynamics simulations with a polarisable force field. These findings demonstrate a new pattern of the liquid structure with which ILs are special and sheds light on plausible implications for solvent-solute interactions that might be of importance when cyanogroups are part of the ionic system.
 T. Niemann, A. Strate, R. Ludwig, H. J. Zeng, F. S. Menges, and M. A. Johnson, “Spectroscopic Evidence for an Attractive Cation–Cation Interaction in Hydroxy?Functionalized Ionic Liquids: A Hydrogen?Bonded Chain?like Trimer,” Angew. Chemie Int. Ed., vol. 57, no. 47, pp. 15364–15368, Nov. 2018, doi: 10.1002/anie.201808381.
EB acknowledges PostDoc Latvia for financial support (Grant No. 22.214.171.124/VIAA/3/19/549).