Physicochemical characterisation of novel tetrabutylammonium aryltrifluoroborate ionic liquids

While there have been many studies on the physicochemical characterisation of ILs, little work has previously been reported on the properties unique to the trifluoroborate anion. Here we have characterised the thermal properties, viscosity, liquid nanostructure and intramolecular interactions of 15 novel aryltrifluoroborate ILs. These ILs all contained a tetrabutylammonium cation paired with either meta- or para-substituted aryltrifluoroborate anions, or di-anionic substituted aryltrifluroborate anions. It was found that of the 15 samples analysed, 4 would technically be considered molten salts as they have melting points greater than 100 °C. Overall the structure-property relationship trends of these samples are similar to those previously reported for alkyl and perfluoroalkyltrifluoroborate ILs which contained K+ or Cs+ cations, with the big difference being the ILs in this study having considerably lower melting points.