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The dimeric complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) with two new symmetrical ON-NO donor bis bidentate (tetradentate) azo dye ligands, LH2 = 4,4'-bis(4'-hydroxyquinolinolinylazo)diphenylsulphone, and L'H2 = 4,4'-bis(acetoacetanilideazo)diphenylsulphone have been synthesized. The metal complexes have been characterised by elemental analytical, conductance, magnetic susceptibility, IR, electronic spectra, ESR, NMR, thermogravimetry, X-ray diffraction (powder pattern) spectra, and molecular modelling studies. The Co(II) and Ni(II) complexes are found to be octahedral, Cu(II) complexes are distorted octahedral, and a tetrahedral stereochemistry has been assigned to Zn(II), Cd(II), and Hg(II) complexes. The thermogravimetric study indicates that compounds are quite stable. The energy optimized structures are proposed using the semiempirical ZINDO/1 quantum mechanical calculations. The potential antibacterial study of the ligands and some metal complexes has been made with one gram positive bacteria Staphylococcus aureus and one gram negative bacteria E. coli which gives encouraging results. Both the Co(II) complexes are found to possess monoclinic crystal system. [ABSTRACT FROM AUTHOR]