2,4-Dihydroxy-5-halobenzaldehydes were synthesized by using 4-haloresorcinol as the raw material via formylation reaction. Then five coumarin derivatives were prepared via Knoevenagel condensation reaction. Finally, five coumarin functional derivatives which have not been reported were obtained via Mannich reaction. The structures of the products were characterized by ¹H NMR, IR, MS techniques and elemental analyses. The fluorescent properties and response to metal cations of these fluorescent compounds were studied. Because of photoinduced electron transfer (PET) effect, the fluorescent intensity of the cou-marin functional derivatives obtained by Mannich reaction decreased. When the metal ions were combined with the above functional compounds, the fluorescent intensity of the compounds was enhanced due to weakening of PET effect.

Key words: coumarin-based mannich base, fluorescent functional compound, metal cation, synthesis