Dynamical Behavior and Local Interactions in a Binary Mixture between Room-Temperature Ionic Liquid and Organic...

Elucidation of innate interactions between room-temperature ionic liquids (RTILs) and organic solvents can enable the effective use of binary solvent systems, particularly in electrotunable lubricants, electrolytes in energy storage devices, solvents for synthesis, and catalysis, where solubility and ion concentration are key to achieving optimal performance. Molecular dynamics simulations using a polarizable force field and a non-polarizable force field for 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)-imide ([C₂mim]-[NTf₂]) mixed with dimethyl sulfoxide (DMSO) have been carried out. Trends in local structure and dynamics behavior as a function of the mole fraction of DMSO (x _DMSO) were examined. The cis-trans conformational transition around the S-N bonds of RTIL molecules was found to develop a more scattered orientation at a high DMSO concentration range (x _DMSO = 0.70-0.95). The [NTf₂]^- anion and DMSO share the same preferred interaction site at the imidazolium ring of [C₂mim]⁺. Hydrogen bonding interactions are found to predominantly exchange from [C₂mim]⁺···[NTf₂]^- to [C₂mim]⁺···DMSO at around x _DMSO = 0.80.