Spectroscopic Study of Hydrazone-based Ligands as Calorimetric Reagents for Acetate Anion

Abstract

This study focuses on investigating the chromogenic properties of hydrazone compounds derived from the reaction of 2,4-dinitrophenylhydrazine (2,4-DNPH) with salicyaldehyde and 2-hydroxyacetophenone for anion recognition. Two chromogenic ligands, 2-[[2-(2,4-dinitrophenyl)hydrazone]methyl]phenol (L1) and 1-(2-hydroxy-phenyl)-ethanone-(2,4-dinitro-phenylhydrazone) (L2), were synthesized and characterized using IR and NMR spectroscopy. The complexation abilities of these ligands towards various anions (acetate, chloride, carbonate, nitrate, fluoride, iodide, sulphite) were investigated using UV-Vis spectroscopy. Both ligands showed higher selectivity towards the acetate anion in DMSO compared to the other anions. The complexes exhibited maximum absorptions (λmax) at 502 nm and 499 nm for L1 and L2, respectively. The Job plot results showed a 1:1 stoichiometry between the ligands and the acetate anion. The stability constants for both complexes were found to be 3.77×10-8 and 9.0 ×10-8, respectively. No significant interference from other anions on the complexes was observed.