Isomerization patterns and proton transfer in ionic liquids constituents as probed by ab-initio computation

Abstract

We have recently shown that some protic ionic liquids (PILs) are characterized by an unexpected complex dynamic of proton transfer (M. Campetella et al., Phys. Chem. Chem. Phys. 19, 11,869, (2017)). These liquids are based on a combination of cholinium cations and amino acid (AA) deprotonated anions. The side chain proton migration, can take place both within the same anion and between different anions. The intra-molecular proton transfer leads to a tautomerization of the AA anion that gives rise to the appearance of an anionic zwitterionic form. The inter-molecular proton transfer is chemically more interesting since it might, at least in principle, point to a way to achieve a dry, fast conduction in materials that are otherwise very viscous and typically poor conductors. We examine here, by means of ab-initio computations, the basic mechanism of proton transfer in a variety of AA anions to find promising candidates as new materials for electrochemistry applications.