Novel pyrene-based Schiff base ligand as a fluorescent sensor for Al3+ and colorimetric sensor for Ni2+ ions detection: Synthesis, photo-physical and cell imaging studies

Abstract

A simple fluorescent and colorimetric pyrene-based ((Z)-4-hydroxy-3-((pyren-1-ylmethylene)amino)benzoic acid (HPMB) chemosensor was synthesized through the condensation reaction between pyrene-1-carboxaldehyde and 3-amino-4-hydroxybenzoic acid. The structure of HPMB was elucidated using 1H NMR, MS, and UV–Visible spectroscopic techniques. The receptor HPMB displayed a detectable, colorimetric colour shift in the presence of Ni2+ and the colour of the solution was observed to be light brown. On the other hand, it also exhibited a fluorescent “turn on” response when Al3+ ions were added in DMSO solution (HEPES 0.01 M, pH = 7.4) at room temperature. Job’s plot showed that HPMB binding ratio to Ni2+ and Al3+ ions was in 1:1 ratio. The detection limit for Ni2+ and Al3+ ions was found to be 0.33 × 10-6 M and 0.26 × 10-6 M, respectively. In addition, HPMB was utilised to create a molecular logic gate, and the fluorescence imaging of HeLa cells was investigated because of HPMB’s low cytotoxicity, indicating that it could be used to detect Al3+ and Ni2+ in living cells.