A new Series of binuclear macrocyclic Schiff base complexes with the general formula [M2LCl4], (M = Mn (Ⅱ), Fe(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ))was synthesized and characterized, the macrocyclic ligand L = (2Z,21Z)-3,10,14,21-tetraaza-1,12(1,4)-dibenzenacyclodocosaphane-2,10,13,21-tetraene)was obtained through a 2:2 condensation reaction of Terephthalaldehyde with Hexamethylenediamine ,forming a stable N₄ macrocycle. The synthesized compounds are characterized by FT-IR, UV–Vis, atomic absorption spectroscopy (AAS), molar conductivity, magnetic susceptibility measurements, and ¹H and ¹³C NMR spectroscopy. The combined spectroscopic, analytical, and magnetic data are consistent with a tetrahedral environment around the metal centers for all complexes except the Cu(Ⅱ)complex which exhibits a square planar geometry. The complexes exhibit non-electrolytic behavior in solution, as inferred from molar conductivity measurements. The disc diffusion method was used to evaluate the antibacterial activity of the Schiff base ligand and its metal complexes. The result demonstrated that metal coordination significantly enhances the ligand's capacity to inhibit the growth of both Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae). Density functional theory (DFT) calculations were performed at the B3LYP level using the LANL2DZ basis set for the metal atoms and 6-311++G(d,p) for the non-metal atoms. The calculations provided optimized geometries, HOMO–LUMO energies, and thermodynamic parameters, which supported the experimental results and offered further insight into the metal–ligand interactions governing the stability and reactivity of the complexes.