Coumarin-based ‘turn-off’ fluorescent chemosensor with high selectivity for Cu2+ in aqueous solution

Abstract Coumarin-based “turn-off” fluorescent chemosensor, 3-acetoacetyl-7-diethylaminocoumarin ( 1 ), has been synthesized and structurally characterized by IR, 1 H NMR and X-ray crystal structure analysis. The fluorescence behaviors in the presence of various metal ions were investigated in aqueous media. 1 Exhibits highly selective and sensitive absorbance and fluorescence sensing ability for Cu 2+ over other metal ions. Addition of Cu 2+ to the aqueous solution of 1 gave rise to obvious absorbance change and fluorescence quenching. Other competing ions, such as Mg 2+ , Ba 2+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Hg 2+ , induced negligible absorbance and fluorescence changes under the same conditions. The job’s plot showed that the stoichiometry between 1 and Cu 2+ was estimated to be 1:1. The fluorescence intensity varied almost linearly vs. the concentration of Cu 2+ (1.0–7.0 μM), and the detection limit of Cu 2+ was estimated to be 1.81 nM, indicating that 1 can be used as “turn-off” fluorescent chemosensor to selectively detect Cu 2+ in aqueous solution.