Synthesis, characterization and Bioactivity Evaluation of Heteroleptic Zinc(II) Complexes: Antioxidant and α-Amylase Inhibition Studies

Abstract

A series of four zinc(II) complexes (SH-1 to SH-4) were successfully prepared through the reaction of zinc acetate dihydrate with 4-chlorophenoxyacetic acid (SH-1)  in methanol and further reaction with additional ligands (1,10-phenanthroline, 2,2'-bipyridine, and 4-methylpyridine, respectively). The complexes were obtained in satisfactory yields (66-78%) and thoroughly characterized using elemental analysis and atomic absorption spectroscopy, which verified their proposed structure. FT-IR spectral analysis confirmed bidentate chelation of the carboxylate moiety to the zinc center, demonstrating metal-ligand interaction. UV-Visible spectroscopy showed characteristic absorption bands in the 200-300 nm range, corresponding to ligand-centered π→π* electronic transitions. Biological assessments revealed concentration-dependent antioxidant activity against DPPH radicals and inhibitory effects on α-amylase enzyme, with the 2,2'-bipyridine-containing complex (SH-3) show high performance in both biological assays compared to other complexes. The IC₅₀ value of SH-3 is 5.867 ± 0.066 for biological activity. SH-4 shows a higher yield of 78%.