Solvent and guest-binding-controlled chiroptical inversion of molecular devices based on pseudo[1]catenane-type pillar[5]arene derivatives

Four pillar[5]arene-based bicyclic compounds, so-called molecular universal joint (MUJ), were synthesized by incorporating a bisamide ring containing N, O, or S-heteroatom groups, which served as stimuli-responsive chiroptical molecular devices. The structure of MUJ was confirmed by 1H NMR spectra and single-crystal X-ray diffraction analysis, and their planar-chiral enantiomers were successfully separated. Chiroptical inversion behaviors from in to out configurations triggered by temperature, solvent, and guest complexation were investigated by circular dichroism spectra. Chiroptical inversion could be realized in the presence of adiponitrile in certain solvents due to the solvation effects on the side ring and the threading of the guest into the pillar[5]arene cavity. However, the stronger self-included interactions between the cavity and the inside ring of certain MUJs led to inhibition of the switching.