Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity.
New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL(1) and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL(2) derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML((1-2)2) have been synthesized, where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mn<Zn<Cu<Co<Ni. The ligands and their complexes were tested for in vitro antibacterial activity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu>Mn>Ni>Co>Zn.
Department of Chemistry, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana, India.
Jai
J
Devi
Nisha
N
Batra
Rajesh
R
Malhotra
D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D004055:Differential Thermal Analysis; D004578:Electron Spin Resonance Spectroscopy; D007477:Ions; D007700:Kinetics; D008024:Ligands; D060328:Magnetic Phenomena; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D012545:Schiff Bases / Q000737:chemistry* / Q000494:pharmacology*; D013055:Spectrophotometry, Infrared; D013818:Thermogravimetry; D028561:Transition Elements / Q000737:chemistry*; D015032:Zinc / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D007477:Ions; D008024:Ligands; D012545:Schiff Bases; D028561:Transition Elements; D015032:Zinc