Novel Arylazo-1,2,5-oxadiazole Photoswitches: Synthesis, Photoisomerization and Nitric Oxide Releasing Properties

A series of novel molecular photoswitches incorporating an aryldiazenyl moiety linked to a 1,2,5‐oxadiazole (furazan) or 1,2,5‐oxadiazole 2‐oxide (furoxan) subunit was synthesized by a simple and step‐economic chemical route. Upon visible light irradiation, (E)‐arylazo‐1,2,5‐oxadiazoles underwent photoisomerization to the corresponding (Z)‐isomers which are stable under ambient conditions. Structural factors affecting the photoswitching ability were also revealed. Synthesized photoswitches exhibited good performance due to the absence of fatigue or decomposition over at least ten cycles under air in a temperature range of 20–60 °C. NO donor properties of the synthesized arylazofuroxans were also evaluated in vitro and it was found that (Z)‐arylazofuroxans released significantly larger amounts of NO than the corresponding (E)‐isomers, which suggests strong potential of these molecular photoswitches in photopharmacology and other biomedical applications.