An Acid–Base Responsive Supramolecular Drawstring with Switchable Fluorescence

Abstract

Supramolecular host–guest complexes offer a versatile platform for stimuli-responsive materials, yet conventional designs rely on macrocyclic hosts derived from non-fluorescent scaffolds (e.g., crown ethers), limiting their photofunctional properties. This work presents a novel acid–base responsive supramolecular drawstring complex consisting of a perylene diimide-imbedded fluorescent bismacrocycle and its complementary linear guest. The self-assembled complex undergoes pH-triggered, reversible conformation changes to effect sensitive fluorescence switching even at physiological pH ranges, which is observable in solution state as well as when covalently integrated into polymer networks. Upon combination with photoacid reagents, the utility of the complex-incorporated polymer is showcased through the development of photosensitive security labels.