Water‐Soluble Arylazoisoxazole Photoswitches

Azoheteroarenes are emerging as powerful alternatives to azobenzene molecular photoswitches. Herein, we introduce water-soluble arylazoisoxale photoswitches. UV/vis and NMR spectroscopy revealed moderate to very good photostationary states and reversible photoisomerization between the E- and Z-isomers over multiple cycles with minimal photobleaching. Several arylazoisoxales form host-guest complexes with β- and γ-cyclodextrin with significant differences in binding constants for each photoisomer as shown by isothermal titration calorimetry and NMR experiments, indicating their potential for photoresponsive host-guest chemistry in water. One carboxylic acid functionalized arylazoisoxale can act as a hydrogelator, allowing gel properties to be manipulated reversibly with light. The hydrogel was characterized by rheological experiments, atom force microscopy and transmission electron microscopy. These results demonstrate that arylazoisoxazoles can find applications as molecular photoswitches in aqueous media.