SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL STUDIES OF ETHYLENEDIAMINE, CHLORO / NITRO BENZALDEHYDE, AMINOBENZOPHENONE DERIVED SCHIFF BASES AND THEIR METAL (II) COMPLEXES

Abstract

Transition metal complexes of Schiff bases have played vital roles in the field of coordination, inorganic and bioinorganic chemistry due to their diverse application in medicine and catalysis. Some biologically active compounds which are used as drugs exhibit pharmacological and toxicological effects when taken in the form of metal-based compounds. In this study, five Schiff bases: N,N1-bis(4-nitrobenzylidene)ethylenediamine (denoted as L1); N,N1-bi(3-chlorobenzyli dene)ethylenediamine (denoted as L2); N-(3-chlorobenzylidene)-N1-(4-nitrobenzylidene) ethyl enediamine(denoted as L3); N-(4-nitrobenzylidene)-N-(2-aminobenzophenylidene) ethylenedi amine(denoted as L4) and N-(3-chlorobenzylidene)-N-(2-aminobenzophenylidene)ethylene diamine (denoted as L5) and their complexes with Co(II), Ni(II) and Mn(II) were synthesised and characterised by NMR, GC-MS, UV-Vis spectroscopy, FTIR, Magnetic susceptibility measurement, Elemental analysis, TGA, Melting point determination and Molar conductance. The results of spectroscopic studies revealed that the Schiff base ligands (L1 - L3) coordinated to metal ions through the (-C=N) nitrogen atoms in a bidentate form with the evidence of new bands due to the v(M-N) vibrations respectively in their metal complexes. Ligands, L4 and L5 coordinated to the metal ion through the (-C=N) nitrogen atoms and amino (NH2) group in a tridentate form with evidence of new bands due to the v(M-N) vibrations in the spectra of their metal complexes. The ligands and their metal complexes were screened against two Gram positive bacteria: staphylococcus aureus, Bascillus subtilis and three Gram-negative bacteria: Escherichia coli, Klebsiella pneumonia and Shigella flexneri. The ligands and their complexes were also screened against two fungi: Candida albicans and Aspergillus fumiigatus. The results revealed that both the Schiff base ligands and their complexes possess good activity against the tested microorganisms. The activity of the ligands are higher than the complexes in Gram negative bacteria but, the activity of the complexes in the Gram-positive bacteria and fungi are higher than the corresponding Schiff base ligands. In addition, the complexes possess higher

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antifungal activity than antibacterial activity. The toxicological studies of the tested ligands and their complexes revealed that the prepared compounds possess low toxicity level in rat, than the standard drug Amoxicillin. The study has developed novel Schiff base ligands and metal complexes, it has further established the structural integrity of the developed compounds. The antimicrobial activity of the prepared ligands on Gram-negative bacteria are higher than the corresponding metal complexes contrary to what is usually reported in the literature. All the prepared compounds possessed strong antifungal activity thus, they can serve as good antifungal agents for pharmaceutical applications.