Vibrational spectroscopic and density functional theory studies on ion solvation and ion association of lithium tetrafluoroborate in N,N-dimethylcarbamoyl chloride-based solvents

Solvation and association interactions in solutions of LiBF4/DMCC (DMCC for N,N-dimethylcarbamoyl chloride) and LiBF4/DMCC–DME (DME for 1,2-dimethoxyethane) have been studied as a function of concentration of lithium tetrafluoroborate by infrared and Raman spectroscopy. Strong interactions between Li+ and solvent molecules or BF4− anions are observed. The apparent solvation numbers of Li+ in LiBF4/DMCC solutions were deduced. Band-fitting to the B–F stretching band of BF4− anion permits detailed assess of the ion pairing. Based on the calculations of density function theory, optimal structures of Li+(DMCC)n (n = 1–3) were suggested. It is found that the lithium ion was preferentially solvated by DME in DMCC–DME binary solvents. This finding is supported by quantum chemistry calculations.