The present article discusses the synthesis of tetradentate Schiff base complexes formed by the condensation reaction of 2-hydroxy benzaldehyde and phthalohydrazide. The ligand (LH2) was detected using FT-IR spectra, 1H, 13C-NMR, UV-Vis spectroscopy, elemental microanalysis CHN, and mass spectrometry. The obtained solid complexes have been assessed using physicochemical and spectroscopic techniques, including UV-Vis, FT-IR, nuclear magnetic resonance (1H-NMR, 13C-NMR), mass spectrometry, thermal gravimetric analysis (TGA), and atomic absorption, in addition to complex conductivity and magnetic moment measurements. The infrared results demonstrated that ligands functioning as tetradentate ligands are chelated to metal ions via the phenolic oxygen and nitrogen of the azomethine group. Specific metal ions join with chloride ions (Cu+2, Zn+2) to reach their coordination numbers. The generated compounds' antibacterial effect in vitro was measured towards Candida albicans as a fungal species, Gram-positive Bacilla and pseudomonas, and Gram-negative Staph and E. coli using the agar well diffusion technique. The ligand generated an octahedral geometry around the (Cu+2 and Zn+2) and a tetrahedral form around the Ni+2 metal ion, per the measurement and spectroscopic tests. Ascorbic acid is used as a standard in the phosphomolybdate technique to assess the antioxidant activity of the ligand and complexes. KEY WORDS: Antioxidant activity, Phosphomolybdate, Tetradentate ligand, Coordination number, Condensation reaction Bull. Chem. Soc. Ethiop. 2025, 39(6), 1109-1118. DOI: https://dx.doi.org/10.4314/bcse.v39i6.7
