Mechanochemical synthesis of glutamic acid Schiff base ligand and its vanadyl complex: exploration of their anion sensing, photocatalytic and antioxidant activity

Schiff base ligands are attractive for their synthetic ease, stability, and versatility in sensing and catalysis. A glutamic acid–based ligand, (2,4-dihydroxyphenyl)ethylidene amino pentanedioic acid, was synthesized mechanochemically from 2,4-dihydroxyacetophenone and glutamic acid. It effectively recognized carbonate, bicarbonate, chloride, iodide, and acetate anions through colorimetric and absorption studies, showing hypochromic shifts indicative of interaction. The ligand was further employed to prepare a water-soluble vanadyl complex (metal:ligand = 1:2) via mortar–pestle grinding. Characterization was performed by UV-Vis, NMR, and FTIR spectroscopy. The vanadyl complex displayed strong photocatalytic activity toward methylene blue degradation, achieving ~90% removal with a rate constant of 4.24 × 10⁻2 min⁻¹, alongside pH-dependent performance and reusability. Additionally, the complex exhibited notable antioxidant activity, scavenging 88% of DPPH radicals within 15 min. These results highlight the ligand and its vanadyl complex as promising candidates for anion sensing, dye remediation, and antioxidant applications.