An easily synthesizable naphthalene-based sensing platform for Al and Zn ions: theoretical insights and live cells imaging.

A new naphthalene-derived Schiff base probe, 1-((2-(diphenylphosphino)ethylimino)methyl)naphthalen-2-ol (HL), has been demonstrated for fluorometric detection of Al and Zn ions. HL was characterized by elemental analysis, FT-IR, NMR, UV-Vis, fluorescence, and ESI-MS analyses. It exhibited high sensitivity and selectivity toward Al and Zn ions in a semi-aqueous medium (CHCN-HO; 4 : 1, v/v), remaining unaffected by other competing metal ions. As a 'turn-on' fluorogenic probe, HL displayed strong emission enhancements at 430 nm and 450 nm ( 300 nm) upon the addition of Al and Zn ions, respectively, with detection limits of 0.62 μM for Al and 0.54 μM for Zn. The addition of Al caused 20 nm blue-shift in emission and absorption maxima of HL due to strong complex formation. The calculated binding constant values were found to be 1.39 × 10 M and 4.78 × 10 M, respectively, for Al and Zn ions. Job's plot, NMR, ESI-MS, and density functional theory (DFT) studies supported the metal ion binding mechanism with 1 : 1 stoichiometry. Fluorescence imaging experiments further revealed HL's ability to detect intracellular Al in live cells with very low cytotoxicity, highlighting its potential as a selective chemosensory probe.