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

[Image: see text] 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.