A Schiff base ligand (L) was synthesized via condensation of N-( 1-naphthyl) ethylenediamine dihydrochloride with phthalaldehyde. The ligand was characterized by FT-IR, UV–Vis, 1H NMR, mass spectrometry, and elemental analysis (C, H, N). Five metal complexes (Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)) were prepared with the ligand in a 1:1 (M:L) ratio using an aqueous ethanol solution. The complexes were characterized by FT-IR, UV–Vis, mass spectrometry, and elemental analysis (C, H, N). Additionally, 1H NMR spectroscopy was employed for Cd(II) complex. Antimicrobial activity of the ligand and its metal complexes against pathogenic bacteria (K. pneumoniae, E. coli, S. aureus, and S. epidermidis) and fungus (C. albicans) were evaluated using the agar well diffusion method. All compounds exhibited inhibitory effects with zone diameters ranging from 8 to 16 mm. The ligand and complexes also displayed significant anticancer activity against a mammary carcinoma cell line. Among them, Zn(II) and Cu(II) complexes demonstrated the highest inhibitory effects (70.68% and 70.57%, respectively), followed by the ligand (61.35%) and Co(II), Cd(II), and Ni(II) complexes (60.34%, 58.96%, and 41.63%, respectively). IC50 values followed a similar trend, ranging from 31.69% (Co(II)) to 165.7% (Cd(II)). Molecular docking studies indicated strong binding affinities of the ligand and the Zn(II) complex to the estrogen receptor.
