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Complexes of Cu(II), Ni(II), Co(II), Mn(II) and Fe(II) with an asymmetric tetradentate Schiff base ligand derived from dehydroacetic acid, 4-methyl- o-phenylenediamine and salicylic aldehyde were synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-Vis, IR, 1H-NMR spectroscopy, X-ray diffraction analysis of powdered samples and thermal analysis, and screened for antimicrobial activity. The IR spectral data suggested that the ligand behaves as a dibasic tetadentate ligand towards the central metal ion with an ONNO donor atoms sequence. From the microanalytical data, the stoichiometry of the complexes 1:1 (metal:ligand) was found. The physico-chemical data suggested square planar geometry for the Cu(II) and Ni(II) complexes and octahedral geometry for the Co(II), Mn(II) and Fe(II) complexes. The thermal behaviour (TGA/DTA) of the complexes was studied and kinetic parameters were determined by Horowitz-Metzger and Coats-Redfern methods. The powder X-ray diffraction data suggested a monoclinic crystal system for the Co(II), Mn(II) and Fe(II) complexes. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus niger and Trichoderma viride.

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The solid complexes of Cu(II), Co(II), Mn(II), La(III) and Ce(III) were prepared from bidentate Schiff base, N-benzylidene-2-hydroxybenzohydrazide. The Schiff base ligand was synthesized from 2hyhdroxybenzohydrazide and benzaldehyde. These metal complexes were characterized by molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, FTIR, 1 H-NMR, UV-Vis and mass spectroscopy. The analytical data of these metal complexes showed metal:ligand ratio of 1:2. The physico-chemical study supports the presence of square planar geometry around Cu(II) and octahedral geometry around Mn(II), Co(II), La(III) and Ce(III) ions. The IR spectral data reveal that the ligand behaves as bidentate with ON donor atom sequence towards central metal ion. The molar conductance values of metal complexes suggest their non-electrolyte nature. The X-ray diffraction data suggest monoclinic crystal system for these complexes. Thermal behavior (TG/DTA) and kinetic parameters calculated by Coats-Redfern method are suggestive of more ordered activated state in complex formation. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus niger and Trichoderma.