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 (xdiglyme) increases up to 0.9. However, the coordination numbers of the hydrogen atoms of [C4mim]+ with oxygen atoms of diglyme increase with xdiglyme. The [TFSA]- anions around [C4mim]+ are not completely replaced by diglyme even at xdiglyme > 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]+.