New fluorescent chemosensor based on quinoline and coumarine for Cu2+

A new fluorescent chemosensor based a coumarin fluorophore and an 8-hydroxyquinoline ionophore was synthesized and characterized by 1H NMR, IR and ESI-HRMS. Its selectivity toward metal ions in acetonitrile (1% water, v/v) was investigated by UV absorption and fluorescence spectroscopy. The results showed that this chemosensor exhibited good selectivity toward Cu2+ over other metal ions by enhancement of fluorescence intensity more than 13-fold, and the fluorescent color change could be observed by naked eyes under the light of 365 nm. The absorption spectra of the sensor (L) toward the concentration of Cu2+ indicated the formation of L–Cu2+ complex, and the complex was 1:1 ratio according to Job plot experiment. Both of photo-induced electron transfer (PET) and intramolecular charge transfer (ICT) mechanisms were considered to be operational for fluorescence enhancement and spectral shift. The detection limit of Cu2+ was determined to be 1.16 μM, a satisfying level to detect Cu2+ in micromolar scale.

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► A new fluorescent chemsensor 3 based on coumarin and 8-hydroxyquinoline was synthesized.
► 3 exhibited good selectivity toward Cu2+ by a strong fluorescence enhancement.
► PET and ICT mechanisms are operational for fluorescence enhancement.