Intermolecular interactions in tetrabutylammonium chloride based deep eutectic solvents: Classical molecular dynamics studies

Abstract

Deep eutectic solvents (DESs) based on tetrabutylammonium chloride have been studied using atomistic molecular dynamics simulations. Two different hydrogen bond donors (HBDs) glycerol and ethylene glycol were used to explore the effect of HBDs on the structure of DESs. Interaction between the anion and the HBD was found to be the most dominant interaction from the structural analysis using radial and spatial distribution functions. Anions and HBDs interact via hydrogen bonds formed between them. The mean hydrogen bond lifetime for these bonds was found to be relatively shorter in case of ethylene glycol compared to that of glycerol, which agrees with the binding energy of the complexes in the gas phase determined using quantum chemical calculations. Diffusivity of components in DES having ethylene glycol as HBD is higher than that of the DES having glycerol due to the greater extent of hydrogen bonding in the latter. The presence of peaks and anti-peaks in the lower wave vector region in both the DESs signifies the existence of long-range structural ordering. The vapor – liquid interface of both the systems showed enrichment of ions at the interface compared to the bulk region.