Photomechanical Luminescence from Through-Space Conjugated AIEgens

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 pi-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 %.