Structural Studies of Lithium 4,5-Dicyanoimidazolate-Glyme Solvates. 2. Ionic Aggregation Modes in Solution and PEO Matrix

In this paper, we present complementary spectroscopic analyses of lithium 2-trifluoromethyl-4,5-dicyanoimidazole adducts with aprotic solvents like dimethyl ethers of poly(ethylene glycols) (i.e., glymes) and crown ethers. Comparing the XRD structures with Raman spectra we have found fingerprints of various structural motifs such as ionic pairs, dimers, free ions, and higher aggregates. Comprehensive analysis of crystalline materials has been performed to correlate molecular structures with spectroscopic data, which give valuable information about the coordination preferences of substituted 4,5-dicyanoimidazolato anions and provide the basis for further developing a model for poly(ethylene oxide) electrolytes. Complementary and systematic X-ray studies of glyme adducts enable precise interpretation of the anion-cation and cation-solvent interactions from experimental Raman spectra. This information provides a convenient tool for the characterization of the ionic association interactions within electrolytes.