Novel coumarin fluorescent dyes: Synthesis, structural characterization and recognition behavior towards Cu(II) and Ni(II)

A series of novel coumarin dyes (3-12) were designed and synthesized. The structures of the dyes were characterized by IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS and single crystal X-ray diffraction. 3-(2-Benzoylhydrazonotrifluoroethyl)-7-(N,N-diethylamino)coumarin (11) could recognize Cu²⁺ and Ni²⁺ selectively in aqueous solution. Upon addition of Cu²⁺ or Ni²⁺ to 11 a blue shift or a bathochromatic shift of the absorption band was observed while the emission band blue-shifted with decrease in the fluorescence intensity. Upon addition of Cu²⁺ the color of the solution of 11 changed from orange to red. The results showed that 11 could be used as an optical chemosensor of Cu²⁺ and Ni²⁺.