Solvate Structures and Computational/Spectroscopic Characterization of LiBF4 Electrolytes

Crystal structures have been determined for both LiBF4 and HBF4 solvates: (acetonitrile)(2):LiBF4, (ethylene glycol diethyl ether)(1):LiBF4, (diethylene glycol diethyl ether)(1):LiBF4, (tetrahydrofuran)(1):LiBF4, (methyl methoxyacetate)(1):LiBF4, (succinonitrile)(1):LiBF4, (N,N,N',N '',N ''-pentamethyldiethylenetriamine)(1):HBF4, (N,N,N',N'-tetramethylethylenediamine)(3/2):HBF4, and (phenanthroline)(2):HBF4. These, as well as other known LiBF4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4-center dot center dot center dot Li+ cation coordination. In addition, complementary DFT calculations of BF4-center dot center dot center dot Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.