Solvation Structures of Some Transition Metal(II) Ions in a Room-Temperature Ionic Liquid, 1-Ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)amide

Solvation structures of manganese(II), cobalt(II), nickel(II) and zinc(II) ions in 1-ethyl-3-methylimidazolium bis(trifluoro- methanesulfonyl)amide (EMI+TFSA-) have been studied by UV-Vis, FT-IR and FT-Raman spectra. The ionic liquid involves TFSA- conformers with Ci (cis) and C2 (trans) symmetries, and both conformers coexist in equilibrium in the liquid state. The results showed that these metal(II) ions are all six-coordinated with three TFSA- ions, i.e., TFSA- ligates as a bidentate O-donor in the ionic liquid. Although the metal ion strongly prefers the C1 conformer in crystals, the metal ion coordinates both the C1 and C2 conformers in the liquid state, and the conformational equilibrium in the bulk only slightly shifts to the C1 conformer in the coordination sphere. We concluded that the conformational equilibrium in the coordination sphere is strongly temperature-sensitive.