Aromatic-aromatic interactions and hydrogen bonding in amino acid based ionic liquids

A series of six amino-acid-based imidazolium ionic liquids is computationally investigated using ab initio molecular dynamics. Radial pair and combined distribution functions are employed for the characterization and understanding of the interactions within these complex systems. The analyses reveal that the ionic liquids under investigation experience distinct cation-anion, cation-cation, and anion-anion interactions. It has been shown that cation-anion pairs interact predominantly through π-π interactions. Furthermore, hydrogen bonds are identified between distinct sites, with the interaction between the carboxylic acid group of the anion and the ring hydrogen atoms of the cation being the most dominant. The detailed analyses presented herein shed light on the complete spatial configuration of the investigated systems, as well as the interactions that are responsible for their structural stability. These interactions make ionic liquids particularly interesting as chiral solvents and reagents for the dissolution and stabilization of biomolecules.