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Synthesis, characterization, DNA interaction and antibacterial activity of novel tridentate NNs thiosemicarbazone copper (II) and nickel (II) complexes

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Document pages: 14 pages

Abstract: This paper reports the synthesis and detailed characterization of tridentate thiosemicarbazone ligands h2l1 and H2L2 derived from 2-acetylpyrazine with copper (II) and nickel (II). Ligands and their metal complexes were characterized by different physicochemical techniques, including elemental and thermogravimetric analysis; Ultraviolet visible spectrum, infrared spectrum, 1H-NMR and 13C-NMR spectrum; Molar conductance measurement; And mass spectrometry. The crystal structure of h2l1 ligand was determined by single crystal X-ray diffraction. The spectral data show that thiosemicarbazone is a NNs tridentate ligand through the nitrogen atom of methylimino group and pyrazine ring and the sulfur atom of thioamide group. Elemental analysis and thermal analysis showed that Oberdan metal complexes had a 1 : 1 stoichiometry (metal-ligand). The interactions between these complexes and calf thymus DNA (CT-DNA) were studied by electronic absorption and viscosity measurements. The activities of these compounds against oxidative DNA cleavage were examined by agarose gel electrophoresis. Cu(II) and Ni(II) complexes can wind DNA strands through groove interactions and promote strand breakage of the plasmid pmCherry under oxidative stress conditions. Moreover, all the complexes could interact more strongly with DNA than could with the free ligands. Finally, the antibacterial activities of the ligands and their complexes were determined by in vitro tests against Gram-positive bacterial strains (S. aureus ATCC 25923, L. monocytogenes ATCC 19115, and B. cereus ATCC 10876) and Gram-negative bacterial strains (E. coli ATCC 25922, S. typhimurium ATCC 14028, and K. pneumoniae ATCC BAA-2146) using the broth microdilution method. The metal complexes showed greater antimicrobial activities than the precursor ligands against some of the microorganisms.

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