Theoretical study on the structure and cation-anion interaction of triethylammonium chloroaluminate ionic liquid

The structures and interactions between cation and anion or triethylammonium chloroaluminate ([TEA](+)[Al2Cl7](-)) IL were systematically studied using density functional theory. Five stable conformers of ion pairs were obtained. Multiple H-bonds between cation and anion were characterized by geometry, vibrational frequency and interaction energy analysis. The order of interaction energy was obtained. Conformers containing N-H center dot center dot center dot Cl have relatively large interaction energy comparing to the rest of others. Dispersion energy accounts for over 10% of interaction energy for all conformers of interest. Natural bond orbital (NBO) analysis, atoms in molecules (AIM) theory and reduced density gradient (RDG) approach were employed to make a thorough study on the nature of interactions. It is found that medium H-bond interaction, weak H-bond interaction and Van der Waals interaction act together as the determining factor in the cation-anion interactions of [TEA]+[Al2Cl7](-) ion pairs. (C) 2015 Elsevier B.V. All rights reserved.