Synthesis and characterization of ionic liquids: Viologen bis{tetrakis[3,5-bis(trifluoromethyl)phenyl]borate} salts

Several viologen bis{tetrakis[3,5-bis(trifluoromethyl)phenyl]borate} salts were prepared by metathesis reaction of the corresponding viologen dibromides (diiodide) with sodium bis{tetrakis[3,5-bis(trifluoromethyl)phenyl]borate} salt in a polar organic solvent. They were characterized for their physical and thermal properties by experimental techniques including variable temperature X-ray diffraction. All exhibited low T_g and T_m, and their T_g/T_m (K) ratios were in the range 0.66-0.79. Several exhibited polymorphism and formed isotropic ionic melts at <150°C. They were soluble in many common organic solvents such as ethers, alcohols, acetonitrile and methylene chloride. They exhibited photoluminescence in both 1,2-dimethoxyethane and methanol, as well as in the solid state. In the solid state, the emission spectra exhibited hypsochromic shift when compared with those in solutions of 1,2-dimethoxyethane and methanol.