Naphthalimide-based probe as an in situ indicator of photochemical reaction for self-reporting imidazole ring formation

Fluorescent probes were promising ultrasensitive candidates in the sensing area. Herein, a fluorescent indicator bearing an active photochemical reactive site based on naphthalimide was designed and synthesized. Under UV irradiation, the photocyclization reaction to form imidazole occurred through the intramolecular addition reaction between α-amine and imine. This photochemical reaction was dynamically monitored in real time by significant fluorescence and UV spectrum changes. The reaction mechanism was further verified by NMR, MS, IR and free radical quenching reaction. The photocyclization reactions of analogous substrates based on this mechanism were also monitored by self-reporting spectrum changes.