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

Abstract

Highlights • Two 3-aminopyridine derived Schiff bases were synthesized. • Six cobalt (II) complexes of the Schiff bases were synthesized. • The Schiff bases and the cobalt (II) complexes were characterized. • Antimicrobial and brine shrimps activities of the complexes and the Schiff bases were examined 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 1 13 far), mass spectrometry studies while H NMR and C 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.

Co (II), Cu (II), Mn (II), Ni (II), Pd (II), and Pt (II) complexes of bidentate Schiff base ligand: Synthesis, crystal structure, and acute toxicity evaluation

“…[ 60,61 ] Our compounds manifested a lower degree of toxicity, as evidenced by the small lethality observed only at first (50 μM) or sometimes second (5 μM) concentration level compared to Islam et al [ 60 ] cytotoxic compounds (LC 50 varying between 32.5 μg/ml). Shaibu et al [ 61 ] reported that complexation of ligand to the central metallic ion decreased the toxicity effect on brine shrimp for a number of complexes.…”

Macrocyclic “tet a”-Derived Cobalt(III) Complex with a N,N′-Disubstituted Hexadentate Ligand: Crystal Structure, Photonuclease Activity, and as a Photosensitizer

“…nauplii gut has noticeable changes as observed by a phase-contrast microscope, as shown in Figure . The results suggested that complex 1 accumulation does not induce mortality after 24 h of exposure. − …”

“…The results suggested that complex 1 accumulation does not induce mortality after 24 h of exposure. 48 − 50 …”

Synthesis, IR, and NMR Study of Some Cu(II), Ni(II), Co(II) Complexes of O-Vanillin and 2- Amino Pyridine.

“…Various bands are grouped into the range between 210-245nm, 280-290nm, 302372nm, and 421nm. The first and second band is due to the π to π* transition of benzene & the band above 400nm displayed by Schiff base is attributed to imino n→π* 6,7 The keto-enol tautomer of Schiff base is implied by the presence of these bands in methanol. The transition of these complexes shifted to a higher wavelength.…”

“…Azomethine moiety forms complexes with a diversity of metals 4,5 . Many Cu (II) complexes have seemed in the literature with various biological activities 6,7 . The presence of a heterocyclic ring in the Schiff base moiety leads to adding stability to the structure of Schiff base metal complexes 8 .…”