Synthesis, Characterization, and Antimicrobial Evaluation of Co(II), Mn(II), and Cr(II) Complexes of a Schiff Base Derived from (E)-2-hydroxy-5-nitrobenzylidene-(1,3-benzothiazol-2-yl)amine

Schiff base ligands derived from heterocyclic amines have garnered sustained interest due to their strong coordination capabilities and enhanced biological relevance when complexed with transition metals. In this research, a novel Schiff base ligand was synthesized via the condensation of 2-aminobenzothiazole with 5-nitrosalicylaldehyde, followed by coordination with Co(II), Mn(II), and Cr(II) ions to yield a series of metal complexes. The ligand and its complexes were characterized by FT-IR spectroscopy, UV–Visible spectroscopy, magnetic susceptibility measurements, and solubility studies. FT-IR spectra confirmed bidentate coordination of the ligand through azomethine nitrogen and phenolic oxygen atoms. Electronic spectral data and magnetic moment values indicated high-spin octahedral geometries for all metal complexes. The antimicrobial activities of the ligand and its complexes were assessed against two bacterial strains (Staphylococcus aureus and Escherichia coli) and two fungal strains (Candida albicans and Aspergillus niger). The metal complexes demonstrated significantly enhanced antimicrobial activity compared to the free ligand, with the Co(II) complex exhibiting the most potent inhibitory effect. The improved biological performance of the complexes is attributed to increased lipid affinity and metal–ligand interactions. These results underscore the potential of benzothiazole-based Schiff base metal complexes as promising candidates for antimicrobial applications.