Structure, interaction and hydrogen bond

Abstract

Ionic liquids (ILs), as green solvents, have attracted amazing interest and their potential applications have prompted a large amount of research and investment, and some of the results have been inspiring. In recent years, in combination with cations and anions, some new ILs have been synthesized in the laboratory. However, compared with simple solid salts, the structures of ILs are complicated and their properties vary considerably. It is thus very time consuming to explore ILs experimentally when facing the huge number of ionic combinations. A molecularbased understanding can reveal the quantitative correlation between structures and properties, and is thus an important subject in the study of ILs. The unusual complexity of ionic interactions renders molecular-based interpretations difficult and gives rise to controversies about the structure of the ILs. Herein we discuss the ion-pair, cluster and X-ray crystals structures and their relationship with the properties of many typical ILs, especially imidazolium-based. In the ILs, apart from the strong electrostatic forces, non-covalent H-bonds and van der Waals (dispersion, induce forces) are examined and are shown to have a decisive effect on the properties of ILs.