Chemical Reconfiguration via [2 + 2] Cycloaddition: Directing Photobleaching Switching in a Copper Complex

Multifunctional photoresponsive materials exert significant research significance in the field of smart devices and sensors. A new copper-based complex (1) was synthesized via a simple solvothermal method using photoactive 1,2-bis(4-pyridyl)ethylene, multidentate hydroxyethylidenediphosphonic acid, and Cu2+ ions, and it undergoes rapid “single-crystal to single-crystal” transformation via photoinduced [2 + 2] cycloaddition. The structural and chemical reconfiguration triggers second-scale photobleaching (blue-green to pale blue). Moreover, a “one-time write and erase” information encryption system was constructed using a single sample. This work demonstrates a new view of [2 + 2] cycloaddition-driven photobleaching in anticounterfeiting and encryption application.