Acid-base fluorescence switching and aggregation induced emission (AIE) of phenylene-thienyl chalcones

This work focuses on preparation and optical characterization of the phenylene-thienyl chalcone derivatives with various terminal groups - amino (3a), hydroxyl (3b) and carboxyl (3c). We were able to selectively manipulate the optical behaviour via these functional groups simply by treatment under acidic/basic conditions. The PLQY of the protonated ammonium salt was boosted to 10 % in comparison with 2 % in the neutral form. On the other hand, deprotonation of the alkoxy and carboxy group led to the formation of a non-emissive anions due to the photoinduced electron transfer process. We also studied the behaviour in the aqueous environment that resulted in the aggregation induced emission effect with a bathochromic shift and improved PLQY for all three chalcone compounds. Finally, only the compound 3c showed a fluorescence in the solid -state with a broad emission band at 576 nm with relatively high PLQY (18.6 %).