A Simple Isoniazid-Based N-Acylhydrazone Derivative as Potential Fluorogenic Probe for Zn 2+ Ions

This study evaluated three isoniazid-based N -acylhydrazone derivatives ( HL1 , HL2 , and HL3) varying their substituting groups (-H, -N(CH 3 ) 2 , and -NO 2 ) as potential chemosensors for Zn 2+ ions. To this end, the absorption and emission properties of these derivatives were investigated in the presence of Zn 2+ ions. Results point to the derivative HL2 as the best chemosensor for Zn 2+ 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 2+ ions, attributable to PET inhibition and bond isomerization promoted by coordination with this metal. LOD, LOQ, and binding constant values for HL2 + Zn 2+ were 0.43 μmol.l −1 , 0.93 μmol.l −1 , and 5.04 × 10 12 l.mol −1 , respectively. The fluorescence of HL2 with other metal ions (Fe 3+ , Mg 2+ , Na + , Cd 2+ , Cu 2+ , Co 2+ , Ni 2+ , Ca 2+ , and K + ) was also investigated. Zn 2+ yielded the best result without Cd 2+ interferences. Job’s Plot showed that the stoichiometric ratio of the complex formed by HL2 and Zn 2+ 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.