Biological activity studies on metal complexes of novel tridentate Schiff base ligand. Spectroscopic and thermal characterization

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.

Synthesis, spectroscopic, thermal and biological activity studies on triazine metal complexes

The coordination behaviour of the triazine ligand with NNO donation sites, derived from 3-benzyl-7-hydrazinyl-4H-[1,3,4]thiadiazolo[2,3c][1,2,4]triazin-4-one (HL), towards some metal ions namely Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) are reported. The metal complexes are characterized based on elemental analyses, IR, (1)H NMR, solid reflectance, magnetic moment, molar conductance and thermal analyses (TG, DTG and DTA). The ionization constants of the organic ligand under investigation as well as the stability constants of its metal chelates are calculated spectrophotometrically at 25°C. The chelates are found to have octahedral geometrical structures. The ligand (HL) and its binary chelates are subjected to thermal analyses (TG, DTG and DTA) and the different activation thermodynamic parameters are calculated from their corresponding DTG curves to throw more light on the nature of changes accompanying the thermal decomposition process of these compounds. The synthesized ligand and its metal complexes were found to have biological activity against the desert locust Schistocerca gregaria (Forsk.) (Orthoptera - Acrididae) and its adult longevities.

2-Chloro-N'-(5-hydr-oxy-2-nitro-benzyl-idene)benzohydrazide

The mol-ecule of the title Schiff base compound, C(14)H(10)ClN(3)O(4), exists in a trans configuration with respect to the acyclic C=N bond. The dihedral angle between the two benzene rings is 62.37 (9)°. An intra-molecular C-H⋯O hydrogen bond is observed. In the crystal structure, adjacent mol-ecules are linked into a ribbon along [10] by O-H⋯O and N-H⋯O hydrogen bonds.