Synthesis and characterization of trifluoromethylsulfonate choline ionic liquid using NMR, FT-IR, and FT-Raman spectra with DFT calculations

Abstract

In this work, the choline trifluoromethylsulfonate ionic liquid [CHO+][CF3SO3􀀀 ] was synthesized via anion exchangebetween choline chloride and lithium trifluoromethylsulfonate in aqueous medium at room temperature.The metathesis synthesis of the targed ionic liquid was confirmed by NMR spectroscopy measurements. TGAmeasurements revealed that the ionic liquid was stable up to 150 ◦C, while DSC curves indicated a melting pointof +34 ◦C and a glass transition temperature of approximately 􀀀 79 ◦C. The infrared and Raman spectra of thesynthesized ionic liquid were compared with DFT calculations at the B3LYP/6–311++G** level of theory/basisset to achieve complete vibrational band assignment. Differences in band assignment under vacuum or DMSOenvironment were highlighted. Two possible conformations of the ionic pairwere considered, andby comparingwith the experimental results, we were able to show that the most energetically stable conformation involves twointramolecular interactions.