1. Preparation of Schiff Base Ligands: Preparation of the two ligands, L1 and L2, from their starting materials for use in the formation of coordination complexes.
2. Characterization of the Prepared Ligands: Investigation of the prepared ligands using various spectroscopic techniques, including FT-IR, UV-Vis, C.H.N elemental analysis, mass spectrometry, ¹H-NMR, and ¹³C-NMR, to confirm their structures and physicochemical properties.
3. Preparation of Metal Complexes: Formation of coordination complexes through the reaction of the ligands with transition metal ions: Mn(II), Co(II), Ni(II), Cu(II), and Zn(II).
4. Characterization of the Prepared Complexes: Characterization of the prepared complexes using various techniques, including melting point, FT-IR, UV-Vis spectroscopy, molar electrical conductivity, magnetic susceptibility, C.H.N elemental analysis, and atomic absorption spectroscopy.
5. Proposal of the Geometrical Structures of the Complexes: Determination of the geometrical structures of the complexes based on the obtained spectroscopic and physicochemical data.
6. Evaluation of Biological Activity: Investigation of the biological activities of the ligands and their complexes against selected Gram-positive and Gram-negative bacteria to determine their potential biological activity.
7. Antioxidant Activity: Evaluation of the prepared complexes for their antioxidant activity.

The study was conducted at the University of Baghdad / College of Science for Women / Department of Chemistry, the University of Baghdad / Institute of Laser for Postgraduate Studies, the University of Baghdad / College of Science / Department of Chemistry, and Al-Mustansiriyah University / College of Science / Department of Chemistry, from September 2025 to June 2026. Ten new complexes of the first transition series elements, namely manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II), were prepared and characterized with two Schiff base ligands (L1 and L2). The first Schiff base ligand (L1) was prepared through a condensation reaction between 4-antipyrinecarboxaldehyde and 4-aminoantipyrine in a 1:1 molar ratio. The second Schiff base ligand (L2) was prepared through a condensation reaction between 4-antipyrinecarboxaldehyde and 2-aminobenzohydrazide in a 1:1 molar ratio. The prepared ligands were characterized using Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), C.H.N elemental analysis, mass spectrometry (GC-MS), and nuclear magnetic resonance spectroscopy (¹H-NMR and ¹³C-NMR), in addition to determining their melting points. A new series of chelate complexes was also prepared for each of the two Schiff base ligands (L1 and L2) with a series of first-row transition elements (3d). The proposed structural formulas of the prepared complexes were verified using conventional physical and chemical techniques, including melting point determination, C.H.N elemental analysis, molar electrical conductivity, magnetic susceptibility, electronic spectra, and infrared spectroscopy. The biological activity study showed that the ligands L1 and L2 and their metal complexes exhibited antimicrobial activity against the Gram-positive bacterium Staphylococcus aureus, the Gram-negative bacterium Escherichia coli, and the fungus Candida albicans. In general, the formation of metal complexes enhanced the biological activity compared with the free ligands. The antioxidant activity was investigated using the DPPH assay. The results showed that the ligands L1 and L2 and their metal complexes possessed varying abilities to scavenge free radicals. The antioxidant activity was evaluated based on the IC₅₀ values, where lower IC₅₀ values indicate higher antioxidant efficiency.

• Preparation of new Schiff bases derived from the ligands L1 and L2, with the possibility of preparing new complexes with other metal ions and investigating their structural characteristics using spectroscopic techniques, as well as evaluating their effects, activities, and stability.
• Conducting further studies on the biological activity of the prepared compounds against other types of bacteria and fungi and evaluating their effectiveness.
• Investigating the activity of the prepared compounds as antioxidants and anticancer agents.
• Replacing the metal ions used in the present study with new metal ions, such as cadmium and palladium, to form complexes with the same ligands prepared in this study.
• Investigating the possibility of using the prepared Schiff bases L1 and L2 and their complexes in medical applications and pharmaceutical and antibiotic industries, due to their demonstrated antimicrobial and antioxidant activities.