Benzothiazole‐Modified Mechanical‐Induced Emission Enhancement Emitter for Mechanical Stimuli and Trace Water Sensing

ABSTRACT A novel multifunctional pyrone derivative based on A’‐D‐π‐A structure was designed and reported. The target fluorophor PID exhibited obvious aggregation‐induced enhanced emission (AIEE) and solvatochromic behavior. Interestingly, the solid sample displayed an unexpected 33 nm hypsochromic mechanochromic property accompanied by mechanical force‐induced luminescence enhancement characteristics. In this case, the above phenomenon may be co‐rationalized by the changes in intermolecular space and packing mode as well as the noncovalent interactions between atoms. Considering its excellent response to polarity, PID may serve as a promising candidate for quantitative monitoring of trace water in water‐miscible organic solvents. Remarkably, the limit of detection (LOD) was calculated to be 0.021%, 0.040%, and 0.020% in THF, acetone, and 1,4‐dioxane, respectively. In contrast to the drastic PL quenching observed in THF‐water and acetone‐water systems, fluorescence intensity displayed an inverted U‐shaped tendency in dioxane‐water mixture. This abnormal performance was ascribed to the formation of intermolecular hydrogen bonds and the transition from intramolecular charge transfer (ICT) to twisted intramolecular charge transfer (TICT) process. The D‐A strategy introduced in this work could facilitate the development and application of multi‐stimuli responsive AIE materials.