A dual fluorescence probe for Zn2+ and Al3+ through differentially response and bioimaging in living cells

Abstract A novel Schiff base fluorescent probe 7-Hydroxy-8-(((2-(hydroxymethyl)quinolin-8-yl)imino)methyl)-coumarin (XL) consist of formylcoumarin and aminoquinoline moieties was synthesized for dual detection of Zn2+ and Al3+ ions. Probe XL exhibited high selective and sensitive response towards Zn2+ and Al3+ ions through different color changes and significant fluorescence turn-on response (270 fold higher for Zn2+ and 230 fold higher for Al3+) in MeOH-H2O (4/1, v/v) over other cations, with detection limits (LOD) as low as 3.75 × 10−8 and 1.14 × 10−8 M, respectively. Moreover, probe XL exhibited preferential selectivity for Al3+ through displacing Zn2+ from the XL-Zn2+ complex by ligand-to-ligand transfer process. The binding mechanism of intramolecular charge transfer (ICT) were proposed from fluorescence and UV–vis titrations, Job's plot, 1H NMR titration, HRMS and DFT calculations. The probe was proven to be suitable for actual samples detection of Zn2+ and Al3+ ions. The complex XL-Zn2+ and XL-Al3+ exhibited dramatic fluorescent “turn-off” properties for PPi and PPi/F− respectively through snatching metal ions and released free XL. Moreover, probe XL showed low biotoxicity and sequentially “off-on-off” fluorescent bio-imaging of Zn2+/Al3+ and PPi/F− in PC12 cells.