Luminescent dihydroquinolines: fluorescence in aqueous media and insights into anticancer activity

Two dihydroquinoline derivatives were synthesized through a modified Doebner reaction, which resulted in stable dihydroquinolines instead of the expected aromatized products. Their photophysical properties were investigated in solution, in the solid state, and in aqueous media, and their anticancer potential was evaluated. Both derivatives exhibited fluorescence and moderate cytotoxicity toward the HL-60 leukemia cell line. Quantum chemical calculations combined with the analysis of experimental ¹H NMR shifts confirmed the formation of an intramolecular hydrogen bond (IHB) in the compound bearing an ortho-phenolic hydroxy group, which appears to reduce its affinity for biological targets. Molecular docking studies on common quinoline-associated targets suggested that both derivatives may act as tubulin depolymerizers and DNA intercalators. Interestingly, both compounds exhibited aggregation-induced emission (AIE), with the unsubstituted derivative exhibiting unusual solvent-dependent luminescence and stable emission near physiological pH. Overall, these findings identify dihydroquinolines as promising luminescent scaffolds with tunable optical behavior and preliminary anticancer activity, providing a foundation for future structural optimization and biological studies.