A Novel Aggregation‐Induced Emission Material, CTRP With Red Emission Based on Coumarin Fluorophore

Abstract A novel aggregation‐induced emission (AIE) material, CTRP , exhibiting red light emission was synthesized by integrating coumarin with triphenylamine through a Knoevenagel condensation reaction. This material demonstrates unique “on‐off‐on” optical switching behavior with its fluorescence intensity initially decreasing by 75% and then increasing by 450% as water content rises, highlighting its excellent AIE properties. CTRP also shows high sensitivity in detecting trace amounts of water, making it a promising fluorescent sensor for organic solvents. Unlike traditional tetraphenylethylene‐based AIE materials, which typically emit blue light and pose risks of photodamage to biological tissues, CTRP ’s red light emission offers a safer and more biocompatible alternative. This advancement in long‐wavelength AIE materials is expected to significantly expand their application scope particularly in biological systems enabling safer bioimaging, biosensing, and in vivo applications.