Cyclophane-shaped ionic liquids with planar chirality: effects of bridge unit on thermal properties and chirality-recognition ability

Abstract Six types of cyclophane-shaped imidazolium salts with planar chirality were synthesized in stereopure forms. The cyclophanes were based on a 2-methylimidazolium unit, the two nitrogen atoms of which were connected by a bridge unit with systematically changed structure. Most salts of the chiral cations with fluorinated imide/amide counter anions existed as ionic liquids from −30 °C to >270 °C, the properties and chirality-recognition ability of which were thoroughly investigated. The imidazolium cation with a hydroxymethyl side chain showed the best chirality-recognition ability and was successfully applied as an NMR enantio-differentiating agent and a chiral stationary phase for gas chromatography.