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Synthesis, spectral characterization, and biological activities of Cobalt(II) complexes of Schiff bases derived from <i>o</i>-vanillin and <i>p</i>-vanillin with 3-aminopyridine

Rafiu O. Shaibu
Gareth M. Watkins


Two biologically active Schiff base GL1 and GL2 were synthesized in equimolar reaction of 3-aminopyridine with o-vanillin and p-vanillin. The synthesized Schiff bases were reacted with cobalt acetate, cobalt chloride or cobalt chloride with trimethylamine by using a molar ratio of Schiff base: cobalt salt as 2:1. The characterization of Schiff bases and cobalt complexes was done by UV–visible in methanol, diffused reflectance, FTIR (mid and far), mass spectrometry studies while 1H NMR and 13C NMR were used to further characterize the Schiff bases. The FTIR results confirmed the bidentate binding of the Schiff bases with cobalt center after the formation of the complexes. The UV-visible spectra and diffused reflectance spectra data obtained were used to further investigate the electronic structure as well as the properties of Schiff bases and their cobalt complexes. On the basis of the spectral studies, distorted tetrahedral geometry has been assigned for the Co(II) complexes. The antimicrobial activities of the two Schiff bases GL1, GL2 and their cobalt(II) complexes were tested against laboratory isolated Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and one fungus strain, Aspergillus niger. The antimicrobial evaluation demonstrates significant activity of the Schiff bases and the cobalt complexes against the four known human pathogens. The brine shrimps lethality study confirmed that the compounds are concentration and geometry dependent. The studies showed the complexes were higher in biological activity than the corresponding Schiff bases.

Keywords: 3-aminopyridine Schiff bases, cobalt(II), antimicrobial activity, brine shrimps test

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eISSN: 3026-8583
print ISSN: 0794-4896