Naphthalimide appended isoquinoline fluorescent probe for specific detection of Al ions and its application in living cell imaging.

Herein, a novel Schiff base fluorescent probe NIQ based on naphthalimide and iso-quinoline units has been readily prepared for the selective detection of Al ions. The obviously visible color changes and prominent fluorescence enhancement were observed upon the addition of Al to NIQ, which could be attributed to the complexation of NIQ with Al and thus leading to the inhibition of photo-induced electron transfer (PET) and the chelation-enhanced fluorescence (CHEF) progress. The limit of detection (LOD) was 52 nM that was far below the standard recommended by the WHO. Binding ratio (1:1) of NIQ with Al ions was supported by Job's plot. The binding constant of NIQ for Al were calculated to be 3.27 × 10 M on the basis of benesi-Hildebrand plot. The plausible binding mechanism for NIQ towards Al ions was evidenced by the density functional theory (DFT) and H NMR titration experiment. Furthermore, this "turn-on" probe NIQ has been successfully applied as a biomarker for imaging the Al ions in living cells.