All-Visible-Light Azobenzene Photoswitches for Controlling Dynamic C—N Bonds†

Abstract

The visible light-driven photoswitches are attracting widespread attention, but it is challenging to leverage their phototriggered structural changes to regulate dynamic bonds, assemblies, and materials. Herein, we incorporated reversible covalent sites of aldehyde ring-chain tautomers into all-visible-light azobenzenes toward a versatile platform for light-controlled formation/exchange of dynamic C—N bonds from secondary amines. The movement of ring-chain equilibrium was attained via manipulating intramolecular multiple hydrogen bonding from E/Z configurational isomers. Such structural regulation further enabled photocontrolled kinetics for the formation and exchange reactions of cyclic hemiaminal ethers from secondary amines exhibiting kinetic rate reversal from E/Z isomers. The varied capability of E/Z configurational isomers in engaging in multiple hydrogen bonds of azo attached carboxylate with ammonium salt accounts for the difference. Moreover, the photoswitching performance of azobenzenes in different solutions was readily regulated by dynamic covalent reactions with amines. The dynamic reactivity control with visible light and associated mechanistic foundation add into the collection of photoswitchable dynamic covalent chemistry and would lay the foundation for subsequent biological and material applications.