Abstract
A Mannich base ligand (L) was prepared by reacting 2-mercaptobenzimidazole, diphenylamine and benzaldehyde. This ligand (L) was further used for the preparation of four metal complexes with Co(II), Ni(II), Cu(II) and Zn(II) ions. The reactions were monitored by TLC. The synthesized compounds were structurally characterized using FTIR spectroscopy, UV-Visible spectroscopy, 1H- and 13C-NMR spectroscopy, ICP-OES/atomic absorption spectroscopy. It has been observed that the ligand (L) behaved in a monoanionic bidentate mode and the geometry of resulting complexes was tetrahedral. Conductivity analysis revealed their non-electrolytic nature. Antibacterial activity of the synthesized compounds was assessed through an agar well diffusion method against four strains of Gram-negative bacteria. L-Zn(II) complex showed best activity at all four concentrations against the four strains of Gram-negative bacteria. KEY WORDS: Metal complexes, Mannich bases, 2-Mercaptobenzimidazole, Antibacterial activity Bull. Chem. Soc. Ethiop. 2019, 33(3), 485-492.DOI: https://dx.doi.org/10.4314/bcse.v33i3.9
Highlights
Mannich base is a well known ligand obtained by the condensation of aldehydes, amines and active hydrogen substrates via Mannich reaction [1, 2]
The ligand (L) and its metal complexes were prepared by the general outlines given above in experimental section (Schemes 1 and 2)
Physical properties of ligand and its respective metal complexes are given in experimental section
Summary
Mannich base is a well known ligand obtained by the condensation of aldehydes, amines and active hydrogen substrates via Mannich reaction [1, 2]. The present work includes the synthetic schemes for a Mannich base ligand (L) derived from 2-mercaptobenzimidazole and its transition metal complexes with Co(II), Ni(II), Cu(II) and Zn(II) ions. The resulting ligand solution was added drop wise in the respective solution of metal salt (0.5 mmol) and stirred for 5-6 h followed by evaporation/concentration.
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