Efficient Green Light-Induced Photoclick Reactions Enabled by Triplet-Triplet Annihilation Photon Upconversion

Photoclick reactions, combining the advantages of photochemistry and classical click chemistry, are highly promising for surface functionalization, polymer conjugation, and biolabeling. Conventional photoclick reactions rely on the use of high-energy ultraviolet (UV) light, which suffers from limited penetration depth and cell toxicity. Herein, we proposed a general strategy of efficient green light-induced photoclick reactions by introducing a triplet-triplet annihilation photon upconversion (TTA-UC) system. The TTA-UC system comprises (octaethylporphyrinato) palladium (II) (PdOEP) as the sensitizer and 9,10-diphenylanthracene (DPA) as the annihilator, and can effectively convert green light into blue light under incoherent and subsolar light intensity, which can further trigger a series of photoclick reactions based on 9,10-phenanthrenequinone and electron-rich alkenes (PQ-ERAs). The pseudo-first-order kinetics (k_obs) can reach up to 0.015 s^-1 under 550 nm LED irradiation (50 mW cm^-2). This study provides a new approach for realizing photoclick reactions under low-power, long-wavelength, and incoherent light excitation, holding great potential for applications in biological and materials systems.