Solvation Structure of Imidazolium Cation in Mixtures of [C₄mim][TFSA] Ionic Liquid and Diglyme by NMR Measurements and MD Simulations

Interactions of 1-butyl-3-methylimidazolium cation ([C₄mim]⁺) with bis­(trifluoromethanesulfonyl)­amide anion ([TFSA]⁻) and diethyleneglycol dimethyl ether (diglyme) in mixtures of [C₄mim]­[TFSA] ionic liquid and diglyme have been investigated using ¹H and ¹³C NMR spectroscopy and molecular dynamics (MD) simulations. The results of NMR chemical shift measurements and MD simulations showed that the diglyme oxygen atoms have contact with the imidazolium hydrogen atoms of [C₄mim]⁺ in the mixtures. The contact between the hydrogen atoms of imidazolium and the oxygen atoms of [TFSA]⁻ remains even when the diglyme mole fraction (x_diglyme) increases up to 0.9. However, the coordination numbers of the hydrogen atoms of [C₄mim]⁺ with oxygen atoms of diglyme increase with x_diglyme. The [TFSA]⁻ anions around [C₄mim]⁺ are not completely replaced by diglyme even at x_diglyme > 0.9. The MD simulations revealed that the diglymes also have contact with the butyl group of [C₄mim]⁺. The methyl groups of diglyme prefer to have contact with the terminal methyl group of the butyl group, whereas the diglyme oxygen atoms prefer to have contact with the methylene group connected to the imidazolium ring of [C₄mim]⁺.