Synthesis, characterization and antimicrobial activities of heteroleptic metal chelates of isoniazid and 2,2’-bipyridine

Abstract

The Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of isoniazid (L1) mixed with 2,2-bipyridine (L2) were synthesized and characterized by solubility studies, percentage metal analysis, UV-Vis spectroscopy, IR spectroscopy, conductivity measurements and magnetic moment measurements. The IR spectra revealed that the isoniazid coordinated as a bidentate ligand. In Co(II) and Ni(II) complex it coordinated  via the carbonyl oxygen (C=O) and the amide nitrogen, while in the Cu(II), Mn(II) and Zn(II) complexes it coordinated using the amide and carbonyl oxygen via enolization. Bipyridine also bonded to the metals as a bidentate ligand through the pyridinic nitrogen atoms. The magnetic data showed that all the complexes were paramagnetic with values ranging from 1.70 to 5.0 B.M., except [Zn(Is)(Bipy)(H2O)Cl2] which was diamagnetic. The conductivity results revealed that the Cu(II), Mn(II), Zn(II) complexes were 1:1 electrolytes while Co(II) was 1:2 electrolyte and [Ni(Is)(Bipy)Cl2] was non-electrolytic in nature. The antibacterial activities of the ligands and the complexes as evaluated via the agar diffusion method showed that the complexes displayed moderately high antimicrobial activity in comparison with the free ligands when tested against ten strains of bacteria.                     KEY WORDS: Isoniazid, Electronic structure, Geometry, Antimicrobial activity, Electrolytic nature, Magnetic moment   Bull. Chem. Soc. Ethiop. 2020, 34(3), 471-478. DOI: https://dx.doi.org/10.4314/bcse.v34i3.4