Pyrene Based Schiff Base for Cascade Fluorescent “On‐Off” Detection of Aluminium(III) and Fluoride Ions and its Applications in Live Cells Imaging

Abstract An easy‐to‐prepare pyrene‐based Schiff base PNZ was synthesized by condensing equimolar amount of 1‐pyrenebutyric hydrazide with 2‐hydroxy‐naphthaldehyde, and employed as a fluorescent chemosensor for in‐situ cascade detection of aluminium (Al 3+ ) and fluoride (F − ) ions. In DMSO:H 2 O (1 : 1, v/v), the weakly emissive PNZ showed a significant fluorescence enhancement at 455 nm selectively upon the addition of Al 3+ due to the complexation‐induced formation of a pyrene excimer. Schiff base PNZ and Al 3+ formed a complex in 2 : 1 binding ratio with the estimated binding constants of K 1:1 =9826.01 M −1 and K 2:1 =3188.49 M −1 . The sensing mechanism was explored by performing quantum mechanical calculations and 1 H‐NMR titration of PNZ with Al 3+ . The in‐situ formed PNZ‐Al 3+ complex species enabled the fluorescent turn‐off detection of F − . Using PNZ and PNZ‐Al 3+ , the concentrations of Al 3+ and F − ions can be detected down to 2.89×10 −7 M and 1.88×10 −7 M, respectively. The cytotoxicity of the PNZ and its ability to bioimage Al 3+ and F − ions was examined in the human cervical cancer cell line. Finally, the receptor PNZ was applied for the quantification of Al 3+ and F − ions in various real samples, such as tap water, river water, rainwater, mouthwash, and toothpaste.