In-depth understanding of the microstructures and interaction mechanisms of BMIMTfO+N4111TFSI double salt ionic liquids: a combination of experimental and theoretical studies

Abstract

Double salt ionic liquids (DSILs) have attracted significant attention in applications like dissolution, separation and extraction due to their unique physicochemical properties. However, the molecular interactions within DSILs have not been extensively explored. In this work, the microstructures, hydrogen bonding interactions, and dynamics between 1‑butyl‑3-methylimidazolium trifluoromethansulfonate (BMIMTfO) and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N4111TFSI) were investigated using spectroscopic methods and theoretical calculations. The datasets yield several conclusions: (1) The interaction between [BMIM]⁺ and [TfO]⁻ is stronger, and C2−H is the main site of [BMIM]⁺. (2) With the addition of N4111TFSI, the hydrogen bonding interactions associated with imidazolium C−Hs on [BMIM]⁺ are weakened, whereas those associated with alkyl C−Hs are enhanced. (3) Complexes including [N4111]⁺[TFSI]⁻-[BMIM]⁺, 2[BMIM]⁺[TfO]⁻-[N4111]⁺, 2[BMIM]⁺[TfO]⁻, and [BMIM]⁺-2[TfO]⁻ were assigned.