A pillar[5]arene/imidazolium [2]rotaxane: solvent- and thermo-driven molecular motions and supramolecular gel formation

Abstract

Based on the pillar[5]arene/imidazolium recognition motif, a [2]rotaxane was effectively prepared. Solvent/temperature triggered molecular motions of the pillar[5]arene ring on the imidazolium axle were successfully realized. By comparison of proton NMR spectra of the [2]rotaxane in different solvents, we found that if we increased the solvent polarity, the pillar[5]arene ring gradually moved away from the imidazolium part. In DMSO, we also could adjust the binding site of the pillar[5]arene ring by changing the temperature. Furthermore, in DMSO, the [2]rotaxane self-assembled to form a supramolecular gel, which showed multiple stimuli-responsiveness.