Highly Specific and Selective Fluorescent Chemosensor for Sensing of Hg(II) by a New Schiff base Ligand

A novel linear tetraamine was synthesized via nitro group reduction, followed by the preparation of its Schiff base derivative (H₂L) through a reaction with 2-hydroxy-1-naphthaldehyde. The chemosensing properties of H₂L were extensively investigated using fluorescence and UV-Vis spectroscopies, revealing a pronounced fluorescence enhancement in response to mercury ions. A comparative study evaluated the impact of various metal cations-including Cr(III), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(I), Cu(II), Zn(II), Cd(II), Gd(III), Na(I), K(I), Ba(II), Mg(II), Al(III), Pb(II), Sn(II), Hg(II), and Ag(I)-on the fluorescence and UV-Vis behavior of H₂L in an aqueous ethanol medium. The binding constant for Hg²⁺-L interactions was determined to be 1.32 × 10⁵ M⁻¹, with a 1:1 stoichiometry. Furthermore, H₂L exhibited a low detection limit of 1.40 × 10⁻⁸ M and a rapid response time. Notably, the presence of Hg²⁺ and Cu²⁺ ions satisfied the criteria for an INHIBIT molecular logic gate.