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Arylazo-1,2,3-Triazoles: “Clicked” Photoswitches for Versatile Functionalization and Electronic Decoupling
preprintsubmitted on 17.05.2021, 07:40 and posted on 20.05.2021, 07:25 by Dong Fang, Zhao-Yang Zhang, Tao LI
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 arylazo-1,2,3-triazoles. These heteroaryl azoswitches are easily accessed and readily functionalized using click chemistry. Their photoswitch property can be regulated by structural modification, enabling (near-)quantitative E-Z photoconversion and widely 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, benefitting from its cross-conjugated nature. The combination of clickable synthesis, tunable photoswitch property and self-decoupling ability, makes arylazo-1,2,3-triazoles intriguing molecular tools in designing photo-responsive systems with desired performance.