Synthesis, spectral characterization and biological studies of Co(II) complexes with Schiff bases derived from sulpha drugs

This study reports the synthesis, spectral characterization, and antimicrobial evaluation of a cobalt(II) complex, [Co(L)₂Cl₂], derived from 4-amino-N-(5-methyl-1,2-oxazol-3-yl)benzenesulfonamide and 2-hydroxy- benzaldehyde. The complex was synthesized via refluxing the Schiff base ligand with Co(II) chloride in ethanol. Spectroscopic and analytical techniques (molar conductance, elemental analysis, IR, UV-Vis, ¹H and ¹³C NMR, and mass spectrometry) confirmed complex formation and bidentate coordination through azomethine nitrogen (-CH=N) and phenolic oxygen (-OH). Electronic spectra and magnetic moment data suggested an octahedral geometry. The electrochemical behavior of the complex was analyzed using cyclic voltammetry, revealing quasi-reversible Co(II)/Co(I) redox behavior. Antimicrobial activity was evaluated using the disc diffusion method against Staphylococcus aureus, Proteus vulgaris, and Candida albicans. The Co(II) complex exhibited enhanced antibacterial and antifungal activity compared to the free Schiff base, attributed to increased lipophilicity and better microbial membrane interaction. Minimum inhibitory concentration (MIC) studies further confirmed its effectiveness. These findings highlight the potential of Schiff base Co(II) complexes as promising antimicrobial agents, supporting further exploration for biomedical applications. KEY WORDS: Schiff base, Co(II) complex, Elemental analysis, Spectral characterization, Redox behavior, Fluorescence, Antibacterial assay, Antifungal activity and MIC studies Bull. Chem. Soc. Ethiop. 2025, 39(6), 1071-1082. DOI: https://dx.doi.org/10.4314/bcse.v39i6.4