Cobaloxime complexes of diphenylglyoxime with aniline and substituted aniline: Synthesis and antimicrobial study

Abstract

Five cobaloxime complexes represented as [Co(Hdpg)²(R)(SCN)] where H₂dpg is diphenylglyoximato, R = aniline (A), 4-bromoaniline (4BrA), 2-nitroaniline (2NA), 4-nitroaniline (4NA) or 4-anisidine (PA) have been synthesized and characterized by melting point, conductance measurement and infrared spectroscopy. The complexes were obtained in low yields (18 - 25 %) in the order 4BrA > 4NA > A > 2NA when the ligands interacted with cobalt(II) acetate tetrahydrate. However, [Co(Hdpg)²(A)(SCN)] was obtained in good yield (59 %). With the exception of [Co(Hdpg)²(PA)(SCN)]CH₃COO- which is 1:1 electrolyte, these complexes showed low conductivity values (35 – 54 Ω^-1cm²mol^-1), hence non-electrolytic in nature. Furthermore, they are of relatively low thermostability with melting points in the range (70 - 118⁰C). The results from IR spectroscopy indicated coordination of the cobalt ion via the nitrogen of the ligands. An octahedral coordination in which the central cobalt ion is surrounded by four nitrogen atoms of the two diphenylglyoximatemono anions from the equatorial positions and the other two sites occupied by atoms of monodentate neutral ligands and thiocyanate anion from the axial position was proposed. The evaluation of thein vitro antibacterial activity of the cobaloxime complexes were carried out against different strains of bacterial isolates including MRSA(Methiline Resistance Staphylococcus) Staphylococcus aureus, Bacillus subtilis, Streptococcus pneunoniae, and the Gram negative bacteria, Salmonella typhi, Klebsiella pneumoniae, escherichia coli, and Pseudomonas aeruginosa. The resultsrevealed that the zones of inhibition were only noticed in the case of Staphylococcus aureus and Salmonella typhi.