Exploiting isohexide scaffolds for the preparation of chiral ionic liquids tweezers

New bis-quinolinium chiral ionic liquids (CILs) were synthesized in good yields starting from isomannide and isosorbide by a straightforward procedure that maintains the absolute stereostructure of the isohexide scaffolds. Thermal gravimetric analysis and differential scanning calorimetry, aimed at investigating the short thermal stability and the thermal behaviour of the synthesized ionic compounds are presented. The stereochemical features of both ionic derivatives and their neutral precursors were investigated by electronic circular dichroism (ECD) spectroscopy. ECD spectra of neutral compounds 5 and 6 and their N-methylated cations (5-Me+ and 6-Me+) were theoretically investigated by means of molecular modelling and excited-state calculations. A theoretical conformational analysis suggests the possible use of the isohexide derivatives as tweezers-type hosts in recognition processes toward different kinds of guests. Some of the ionic derivatives were successfully used in the NMR enantiorecognition of TFAE, discriminating the enantiomers through a tweezers-like mechanism.