Studies on the convenient synthesis, fluorescence properties and bioactivity of chromenonitriles.

The synthesis of chromenonitriles remains largely underexplored, primarily due to the limited availability of suitable substrates and the generally unsatisfactory yields of existing methods. Herein, we report a new method that enables the efficient construction of chromenonitriles under mild, metal-free conditions, using readily accessible chromones and benzoylacetonitriles as starting materials. This transformation is driven by a Knoevenagel condensation co-catalyzed by pyridine and 1,4-diazabicyclo[2.2.2]octane (DABCO), affording the desired products in good yields. In addition to the reported compounds 3a, 3d and 3h, 23 other new compounds are also successfully synthesized. Photophysical characterization reveals that the synthesized compounds exhibit intense yellow-green fluorescence and pronounced aggregation-induced emission (AIE) behaviour, observable both in a dilute solution and the solid state. Dynamic light scattering analysis confirms the correlation between aggregation and fluorescence enhancement, and DFT calculations rationalize the observed photophysical behaviour. Antibacterial activity tests show that they have the potential to become fluorescent probes with antibacterial ability.