Abstract
A series of nine different known ionic liquids or low melting salts was synthesised and purified. They are composed of the [NTf(2) ](-) (bis(trifluoromethane)sulfonimide), [OTf](-) (trifluoro-methane-sulfonate), or [B(CN)(4) ](-) (tetracyanidoborate) anion and [Ph(4) P](+) (tetraphenylphosphonium), [Ph(3) BzP](+) (triphenylbenzyl phosphonium), [(n) Bu(4) P](+) (tetra-(n) butylphosphonium), [(n) BuPh(3) P](+) (tri-phenyl-(n) butylphosphonium), [(n) Bu(4) N](+) (tetra-(n) butylammonium), or the [PPN](+) (bis(triphenylphosphine)iminium) cation. Precise vapour pressure data and enthalpies of vaporisation were measured using the Quartz Crystal Microbalance (QCM) method and evaluated. Structure-property relations are established using the obtained data as well as literature known data of ILs with alkyl-substituted imidazolium cations. It turns out that ILs with the tetracyanidoborate anion have even higher values of the enthalpy of vaporisation than those with the common [NTf(2) ](-) or [OTf](-) anion and therefore are even less volatile.