A Dynamic Hydrogen-Bonded Azo-Macrocycle for Precisely Photo-Controlled Molecular Encapsulation and Release.

Abstract

A light-responsive system constructed from hydrogen-bonded azo-macrocycles demonstrates precisely controlled propensity in molecular encapsulation and release process. The marriage of balanced rigidity and flexibility associated with internal hydrogen bonds is responsible for the observed properties in the course of E-Z photoisomerization, as also corroborated by the findings from both the solid state and solution. The slow host-guest exchange via a bi-modular recognition on the NMR timescale accompanied by the distinct shape change of cavity provides accurate and time-resolved control over the release process, underscoring the importance of tunable binding affinities on achieving stepwise release of organic cations with azo-responsive molecules under light irradiation. The light-responsive system established here could advance further design of novel photoresponsive molecular switches and mechanically interlocked molecules in supramolecular chemistry.