A Simple Isoniazid-Based N-Acylhydrazone Derivative as Potential Fluorogenic Probe for Zn Ions.

This study evaluated three isoniazid-based N-acylhydrazone derivatives (HL1, HL2, and HL3) varying their substituting groups (-H, -N(CH), and -NO) as potential chemosensors for Zn ions. To this end, the absorption and emission properties of these derivatives were investigated in the presence of Zn ions. Results point to the derivative HL2 as the best chemosensor for Zn ions because of its comparatively higher sensitivity. The color of this derivative changed from colorless to strong yellow with zinc addition, as indicated by the shift in UV-vis spectrum. Moreover, HL2 was the only derivative to emit fluorescence in the presence of Zn ions, attributable to PET inhibition and bond isomerization promoted by coordination with this metal. LOD, LOQ, and binding constant values for HL2 + Zn were 0.43 μmol.l, 0.93 μmol.l, and 5.04 × 10 l.mol, respectively. The fluorescence of HL2 with other metal ions (Fe, Mg, Na, Cd, Cu, Co, Ni, Ca, and K) was also investigated. Zn yielded the best result without Cd interferences. Job's Plot showed that the stoichiometric ratio of the complex formed by HL2 and Zn ions is 2:1 (ligand:metal). The strip test with adsorbed HL2 indicated fluorescence in the presence of zinc ions under 365 nm UV irradiation.