Synthesis, spectroscopic and biological studies of metal complexes of an ONO donor pyrazolylhydrazone - Crystal structure of ligand and Co (II) complex

A new pyrazolylhydrazone, 2-(2-(1,5-dimethy-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazolyl-4-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL) and its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were synthesized and structurally characterized by elemental analysis, molar conductance, magnetic measurements and spectral (IR, H-1 NMR, UV-vis, HRMS) measurements. All complexes possess ML2 stoichiometry with L behaving as monoanionic tridentate ONO donor. Single crystal X-ray diffraction reveals that HL and CoL2 crystallize in orthorhombic system with Pbcn space group. Hydrogen bonding interactions between molecules of CoL2 results in the formation of an infinite zig-zag chain extending along the 'b' axis. EPR spectrum of Cu(II) complex at 77 K suggests mononuclear and distorted octahedral geometry for [CuL2]. Antimicrobial activity of HL and its complexes were investigated and minimum inhibitory concentrations identified. Bacterial and fungal organisms used were gram-positive Staphylococcus aureus, gram-negative Escherichia coli, Aspergillus niger and Candida albicans.