Photomechanical Luminescence from Through‐Space Conjugated AIEgens

Abstract Transforming molecular motions into the macroscopic scale is a topic of great interest to nanoscience. The photomechanical effect is a promising strategy to achieve this goal. Herein, we report an intriguing photomechanical luminescence driven by the photodimerization of 2‐phenylbenzo[b]thiophene 1,1‐dioxide (P‐BTO) in molecular crystals and elucidate the working mechanism and substituent effect through crystallographic analysis and theoretical calculations. Striking splitting, hopping, and bending mechanical behaviors accompanied by a significant blue fluorescence enhancement are observed for P‐BTO crystals under UV light, which is attributed to the formation of photodimer 2P‐BTO. Although 2P‐BTO is poorly π‐conjugated because of the central cyclobutane ring, it exhibits prominent through‐space conjugation and aggregation‐induced emission (AIE), affording strong solid‐state blue fluorescence at 415 nm with an excellent quantum yield of up to 96.2 %.