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Antimicrobial Evaluation of Novel Metals Complexes of n- Isonicotinamido-2-hydroxy-5-methoxybenzalaldimine

Objective: The appearance of resistant bacteria reduces the efficiency of antimicrobial therapies, thereby increasing the need for more efficient drugs for infections treatment. Many studies have shown an enhance in antimicrobial activity after the interaction of many agents with metal ions. Complexes of the metal ions with ligands which are polydentate have been the theme of demanding research as they have interesting spectral, magnetic properties and a miscellaneous spectrum of biological activities.

New isoniazid based compounds and their transition metal complexes (cobalt (II), copper (II), nickel (II) and zinc (II)) were produced using microwave synthesis technique. The All compounds which were synthesized (free ligand and their metal complexes) were fully characterized by many spectroscopic techniques (FT-IR spectra, UV/visible electronic spectra, mass spectra and 13C NMR and 1H NMR spectra). In addition, CHN, XRFA, AAS merged with other spectroscopic data were utilized to allocate the precise ligand to metal ratio and geometry. The synthesized ligands and their complexes were tested for in vitro antimicrobial activity against Candida albicans (ATCC 10231), Aspergillus niger (ATCC 16404), Escherichia coli (ATCC 25922), and Staphylococcus aureus (ATCC 29213) by using agar-well diffusion.

Results: Based on analytical and spectroscopic findings, the ligands proceed as a coordinate and monoanionic tridentate throughout phenolic oxygen, azomethine nitrogen, and carbonyl oxygen. New complexes of nisonicotinamido- 2-hydroxy-5-methoxy benzalaldimine with Cu(II), Co(II) and Zn(II), having a formula of the type [M (L) 2].nH2O, (M = Co(II), n = 1.5; Zn(II), n = 0; Cu(II), n = 6) and with Ni(II), featuring a formula of the type [M (L) (H2O)] (ac).nH2O, (M = Ni(II), n = 0, ac = CH3COO¯) were obtained. Accordingly, octahedral geometries were determined to Zinc(II), Cobalt(II) and Copper(II) complexes and geometry of the tetrahedral was allocate to the Ni(II) complex.

Conclusion: Biological findings indicate that complexation may increase or decrease the antimicrobial activity of some complexes. This could be endorsed to an increase of complexes lipophilicity in comparison to the parent ligand.


Husain I. Alarabi, Sofian S. Mohamed, Wahiba A. Suayed, Inass A. Al-Sadawe, Salah M. Bensaber, Fathi M. Sherif, Anton Hermann, Abdul Gbaj

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