Synthesis, characterisation, spectral, thermal, XRD, molecular modelling and potential antibacterial study of metal complexes containing octadentate azodye ligands

•Azodye ligands are derived from 4,4′-oxydianiline, and 2,4-dihydroxybenzoic acid, 2,4-dihydroxyacetophenone.•Metal complexes are synthesized and characterised by spectroscopic, thermal and XRD powder pattern.•Molecular modelling of the ligands and Zn complexes are made to draw geometrical and physicochemical parameters.•Biological activity of the ligands and some complexes are studied.

Twelve tetrametallic complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with two new octadentate azodye ligands, 4,4′-bis(2′,4′-dihydroxy-5′carboxyphenylazo) diphenylether (LH6) and 4,4′-bis(2′,4′-dihydroxy-5′-acylphenylazo) diphenylether (L′H4) have been synthesised. The structural elucidation of the complexes was made basing upon analytical, conductance, magnetic susceptibility, IR, electronic spectra, ESR, NMR, ESI-MS, TG, DTG, DTA and X-ray diffraction (powder pattern) data. The cobalt (II) and nickel (II) complexes are found to be octahedral, copper (II) complexes are distorted octahedral and a tetrahedral stereochemistry has been suggested to zinc (II), cadmium (II) and mercury (II) complexes. The thermal analysis data provided the kinetic parameters as order of decomposition reaction, activation energy and frequency factor. The geometry of the ligands and their Co(II), Ni(II), Cu(II) and Zn(II) complexes were optimised and their physicochemical properties were calculated by using molecular modelling procedure. The ESI-MS determination supports the molecular formula and molecular weight of the ligands and the complexes. The Ni(II) complex is found to have a triclinic crystal system. The potential antibacterial study of the two ligands and eight metal complexes was made by cup-plate method against one gram positive and one gram negative bacteria. The results showed increase in the activity of some metal complexes as compare with azodye ligands.

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