Imidazo[1,2-a]pyridine-substituted coumarin as a selective ratiometric sensor for Cu2+ ion

A novel fluorescent chemosensor, (E)-7-(diethylamino)-3-((2-phenylimidazo[1,2-a]pyridin-3-ylimino)methyl)-2H-chromen-2-one 1a, has been synthesised and characterised. This chemosensor displayed an extreme selective fluorescence emission only with Cu2+ ion over all other metal ions examined. The Job’s plot experiment analysis suggested the binding ratio of the chemosensor 1a with Cu2+ was 1:1 metal-to-ligand ratio. The association constant for Cu2+ towards receptor 1a obtained from Benesi–Hildebrand plot was found to be 4.859 × 103 M−1 with a detection limit 4.6 × 10−8 M. Fluorescence enhancement caused by Cu2+ binding with chemosensor 1a attributed to combinational effect of intramolecular charge transfer and chelation-enhanced fluorescence occurred at pH 8.0.