Effects of Dissolved Water on Li+ Solvation in 1-Ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)amide Ionic Liquid Studied by NMR

Abstract

(1)H and (7)Li NMR chemical shifts of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide-water solutions in the presence and absence of lithium bis(trifluoromethanesulfonyl)amide were determined at 293.2 K over a wide range of water concentrations from 0.0156 to 1.16 mol kg(-1). These results revealed the attractive interaction between water molecule and Li(+) as well as the hydrogen bonding among water molecules. Moreover, self-diffusion coefficients of water, 1-ethyl-3-methylimidazolium cation, Li(+), and bis(trifluoromethanesulfonyl)amide anion in the ionic liquid solutions at various water contents were determined by (1)H, (7)Li, and (19)F NMR techniques. It was found that Li(+) is averagely hydrated by eight water molecules in the ionic liquid solutions. Furthermore, (7)Li longitudinal relaxation times of Li(+) in the ionic liquid solutions at 293.2 K were measured with two different magnetic fields and various water contents. The mean one-jump distances of Li(+) in the ionic liquid solutions were estimated from the correlation times and the self-diffusion coefficients. A comparison between the hydrodynamic radius and the mean one-jump distance of Li(+) suggested the formation of water channels in the ionic liquid solutions.