Special Mixing Behavior of Chelate-based Ionic Liquid with Methanol

Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) (C₁₀mim]Cu(hfacac)₃]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate (C₁₀mim]hfacac]) blue-shifted more significantly than that of C₁₀mim]Cu(hfacac)₃], meanwhile the (C=O) red-shifted in C₁₀mim]Cu(hfacac)₃], which is contrast with that in C₁₀mim]hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in C₁₀mim]hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the C₁₀mim]Cu(hfacac)₃] system.