[Ion solvation and ion association in high-concentration of NaBF4/DMF solutions].

Ion solvation and ion association in solutions of NaBF4/DMF were studied by infrared and Raman spectroscopy and ab initio quantum chemistry. It was found that the sodium cation interacts on oxygen atom of C=O group in DMF molecules. The solvation number of Na+, four, was obtained according to the change analysis of CH3 rocking band. The splitting of the nu1 mode of BF4(-) anion indicates the presence of contact ion pairs. Ionic association degree increases with increasing molality of the salt. The solvated structure of Na+ and the geometry of Li+ BF4(-) ion pair were also suggested based on the ab initio calculations.