A novel colorimetric-fluorescent probe for Al 3+ and the resultant complex for F - and its applications in cell imaging.

A novel quinoline-based Schiff-base probe QL had been synthesized, which could sequentially monitor Al ³⁺ and F ^- in MeOH-H ₂ O solution (v/v = 8/1, 0.01 M, HEPES buffer, pH = 7.3). The probe QL expressed a high selective and sensitive "OFF-ON-OFF" fluorescent response for Al ³⁺ and F ^- (excitation at 460 nm and emission at 530 nm) accompanying visible color changed, which was ascribed to intramolecular charge transfer (ICT) process and chelation-enhanced fluorescence (CHEF) mechanism. The binding stoichiometry of QL with Al ³⁺ was 2:1 counting on Job's plot and HRMS, while F ^- could pull Al ³⁺ to depart from the complexation 2QL-Al ³⁺ and released free QL. The limit of detections of probe QL for Al ³⁺ and F ^- ions were calculated to be 0.10 μM and 0.50 μM. The ¹ H NMR experiments and density functional theory (DFT) calculations were carried out to further prove the binding mode between QL and Al ³⁺ . Furthermore, fluorescence imaging studies demonstrated that the probe QL was low cytotoxicity and could be applied to detect Al ³⁺ and F ^- in living PC12cells.
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