Synthesis, photophysical properties and aggregation-induced enhanced emission of bischalcone-benzothiadiazole and chalcone-benzothiadiazole hybrids

Hybrids containing both chalcone and benzothiadiazole (BTD) moieties were synthesized and photophysically characterized. The compounds display either chalcone-BTD-chalcone or aryloxy-BTD-chalcone architectures. The synthesis of these dyes was based on aldol condensations in formyl-substituted BTD-based intermediates. The hybrids presented absorption maxima ranging from 384 to 408 nm with remarkably high extinction coefficient values (1.31-4.04 x 10(4) L mol(-1) cm(-1)). Regarding the emission, all compounds are fluorescent in solution with emission maxima ranging from 481 to 535 nm and Stokes shifts between 81 and 148 nm. The quantum yields of fluorescence (phi(f)) ranged from 0.002 to 0.40 in solution and they were dependent on the architecture of the hybrids as well as the substitution pattern of the chalcone aryl group. In respect to aggregation-induced enhanced emission properties, while the fluorescence of bischalcone-BTD hybrids was not increased by aggregation, the compound with design aryloxy-BTD-chalcone presented AIEEgen properties since a sharp increase (30-fold) in the fluorescence intensity along with a remarkable enhancement of phi(f) values (from 0.0070 to 0.143) were observed upon aggregation.

Automated summary

Hybrids containing both chalcone and benzothiadiazole moieties were synthesized and characterized for their photophysical properties. The compounds exhibited absorption maxima ranging from 384 to 408 nm and high extinction coefficient values. Some hybrids showed aggregation-induced enhanced emission properties, with a significant increase in fluorescence intensity and quantum yields observed upon aggregation.