(Hetero)arylazo-1,2,3-triazoles: "Clicked" Photoswitches for Versatile Functionalization and Electronic Decoupling.

The development of light-responsive chemical systems often relies on the rational design and suitable incorporation of molecular photoswitches such as azobenzenes. Linking a photoswitch core with another π-conjugated molecular entity may give rise to intramolecular electronic coupling, which can dramatically impair the photoswitch function. Decoupling strategies have been developed based on additionally inserting a linker that can disrupt the through-bond electronic communication. Here we show that 1,2,3-triazole-a commonly used decoupling spacer-can be directly merged into the azoswitch core to construct a class of "self-decoupling" azoswitches called (hetero)arylazo-1,2,3-triazoles. Such azotriazole photoswitches are easily accessed and modularly functionalized by click chemistry. Their photoswitch property can be optimized by rational design of the substituent groups or heteroaryl rings, allowing (near-)quantitative E⇆Z photoisomerization yields and tunable Z-isomer thermal half-lives from days to years. Combined experimental and theoretical results demonstrate that the electronic structure of the photoswitch core is not substantially affected by various substituents attached to the 1,2,3-triazole unit, benefiting from its cross-conjugated nature. The combination of clickable synthesis, tunable photoswitch property, and self-decoupling ability makes (hetero)arylazo-1,2,3-triazoles intriguing molecular tools in developing photoresponsive systems with desired performance.