2-Hydroxychalcone-β-Cyclodextrin Conjugate with pH-Modulated Photoresponsive Binding Properties.

Stimuli-responsive supramolecular receptors are important building blocks for the construction of self-assembled functional materials. We report the design and synthesis of a pH- and light-responsive 2-hydroxychalcone-β-cyclodextrin conjugate ( 1-Ct ) and its characterization by spectroscopic and computational methods. 1-Ct follows the typical reaction network of trans -chalcone-flavylium photoswitches. Upon light irradiation, 1-Ct can be photochemically converted into the cis -chalcone/hemiketal forms ( 1-Cc / 1-B ) under neutral pH conditions or to the flavylium cation ( 1-AH + ) at acidic pH values. This stimuli-responsive β-cyclodextrin host, 1-Ct , was found to form stronger intramolecular self-inclusion complexes ( K intra = 14) than 1-AH + ( K intra = 3) and weaker than 1-Cc / 1-B (overall K intra = 179), allowing control over their stability and binding properties by combinations of pH and light stimuli.