Structural effect on physicochemical properties of ethanolamine carboxylate ionic liquids by experimental and theoretical study

Abstract

The hydroxylammonium ionic liquids (ILs) falling within the category of protic ionic liquids (PILs) have garnered attention from researchers, owing to their outstanding solubility properties. A one-step method was employed to synthesize a series of ethanolamine ILs. The thermodynamic properties of the ILs, including surface tension, density, and electrical conductivity, were measured across varying temperatures. Essential parameters such as thermal expansion coefficient, molecular volume, surface entropy, and surface energy were estimated using empirical equations. In order to elucidate the intermolecular interactions within the ethanolamine carboxylate ILs, the sigma profiles of ILs were determined using COSMO-RS. It was observed that the ethanolamine cation has a strong potential as a H-bond donor, while the carboxylate anion demonstrates significant capability as a hydrogen bond acceptor. By DFT calculations, it was observed that the NH in the ethanolamine cation can form H-bonds with the oxygen atom in the carboxylate anion.