Cobalt(III) Schiff base complexes derived from mesostilbenediamine: Synthesis, characterization, crystal structure, electrochemistry and antibacterial studies

Four new N2O2 type tetradentate Schiff base complexes of Co(III), [Co(Lx)(py)2]PF6 (CoLx, x = 1,3–4), and [CoNa(L2)(py)(OAc)(CH3CH(OH)CH3)(H2O)]ClO4·(CH3CH(OH)CH3), (CoNaL2), where Lxs are tetradentate Schiff base ligands derived from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine (mesostilbenediamine) with salicylaldehyde derivatives, were synthesized and characterized by elemental analysis, 1H NMR, IR, and UV–Vis spectroscopy. X-ray crystal structures of CoNaL2 and CoL3were also determined. In CoNaL2, sodium atom is coordinated to CoL2 moiety via two oxygen atoms of 3-OMe groups of salicylaldehyde part. A bridging acetate ion also has bridged the Co and Na centers. Cyclic voltammetry studies revealed that all of the complexes showed a one-electron reversible oxidation wave related to CoIII/IV couple in the anodic region. Two reduction waves for CoIII/II and CoII/I couples were also observed. The in vitro antimicrobial activity of the Schiff base complexes was tested against human pathogenic bacteria such as Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus and Listeria monocytogenes. All of the complexes showed moderate antibacterial activities against both Gram positive and Gram negative bacteria.