Synthesis, characterization and antimicrobial studies of Schiff base derived from 2-Hydroxy Acetophenone and P-Anisidine and its metal (II) complexes

Abstract

Microbial infections remain a major global health challenge due to the rapid emergence and spread of antimicrobial-resistant pathogens. The misuse and overuse of conventional antimicrobial agents have accelerated multidrug resistance, highlighting the need for new therapeutic candidates with improved biological activity. In this study, Mn(II), Co(II), and Ni(II) complexes of a Schiff base derived from p-anisidine and 2-hydroxyacetophenone were synthesized, characterized, and evaluated for antimicrobial activity. The ligand and its complexes were obtained in good yields and characterized using physicochemical and spectroscopic techniques. The ligand exhibited a melting point of 197°C, while the complexes decomposed at 242–263°C, indicating enhanced thermal stability upon complexation. Molar conductivity values (6.23 – 31.40 Ω^-1cm²mol^-1) confirmed their non-electrolytic nature. Magnetic susceptibility measurements and effective magnetic moments of 5.5, 4.3, and 3.2 BM for the Mn(II), Co(II), and Ni(II) complexes, respectively, suggested tetrahedral geometry and paramagnetic behavior. Electronic spectra showed characteristic π→π* (230 – 265 nm) and n→π* (305 – 335 nm) transitions, while FTIR spectra revealed a shift of the azomethine C=N band from 1607 cm^-1 to 1585 – 1592 cm^-1 and disappearance of the phenolic O–H band at 3387 cm^-1, confirming coordination through azomethine nitrogen and phenolic oxygen atoms. Job’s method established a 1:2 metal-to-ligand ratio. The ligand and complexes exhibited concentration-dependent antimicrobial activity against Staphylococcus aureus, Escherichia coli, Salmonella typhi, Candida albicans, Tinea capitis, and Aspergillus flavus. The complexes showed enhanced activity relative to the free ligand but remained less active than the standard drugs amoxicillin and griseofulvin.