Physicochemical properties of phenyltrifluoroborate-based room temperature ionic liquids

Novel room temperature ionic liquids (RTILs) were synthesized using phenyltrifluoroborate ([PhBF3]−), which is the simplest aryltrifluoroborate structure. The [PhBF3]−-based RTILs showed desirable transport properties, i.e., viscosity and ionic conductivity, and the anion has a rigid and bulky aromatic ring. The properties of 1-butyl-3-methylimidazolium phenyltrifluoroborate ([C4mim][PhBF3]) are comparable to those of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]). The molecular volume of the RTILs, which was estimated using the appropriate quantum chemical calculations, highly correlated with the transport properties. The cation volume is an important factor that can control the physicochemical properties in this RTIL system. In addition, the basic skeleton structure of the cation determined the electrochemical window.