External-stimulus-triggered conformational inversion of mechanically self-locked [1]catenane and -catenanes based on A1/A2-alkyne-azide-difunctionalized pillar[5]arenes.

Herein, we report a methodology for constructing mechanically self-locked molecules (MSMs) through the efficient intramolecular copper(i)-catalyzed alkyne-azide cycloaddition (CuAAC) of self-threaded A1/A2-azido-propargyl-difunctionalized pillar[5]arenes. The obtained monomeric "[1]catenane" and dimeric "-catenane" were isolated and fully characterized using mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and X-ray crystallography. Upon investigation by H NMR spectroscopy in chloroform, the observed motion for the threaded ring in the [1]catenane was reversibly controlled by the temperature, as demonstrated by variable-temperature H NMR studies. Two -catenane stereoisomers were also isolated in which the two pillar[5]arene moieties threaded by two decyl chains were aligned in different topologies. Furthermore, the conformational inversion of [1]catenane and the -catenanes triggered by solvents and guests was investigated and probed using H NMR spectroscopy, isothermal titration calorimetry, and single-crystal X-ray analysis.