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A new series of transition metal complexes of Cu(II), Co(II), Ni(II), Mn(II) and Cd(II) were prepared from the ligand of 5-(4-benzenesulfonic acid azo)-2thioxo-4-thiazolidinone (H 2 L). The M(II) complexes were structurally elucidated by elemental analysis, infrared spectra, spectral studies, thermal analysis, magnetic measurements and X-ray diffraction analysis. Elemental analysis and IR result suggested the ligand was bonded to the metal ions in monobasic/neutral bidentate through the nitrogen atom of the hydrazone group and oxygen atom of carbonyl group. The bond length, bond angle, HOMO, LUMO and quantum chemical parameters were calculated to confirm the geometry of the ligand and the M(II) complexes. In vitro antimicrobial behavior of ligand (H 2 L) and its M(II) complexes (1-5) was screened with targeted bacterial and fungal strains. Spectroscopic (UV-vis) technique was employed in order to study the binding mode and binding strength of the ligand (H 2 L) and its M(II) complexes to Calf thymus DNA (CT-DNA). Intercalation is the most possible mode of interaction of the ligand (H 2 L) and its M(II) complexes with CT-DNA and the determined binding constants. Molecular docking was used to predict the binding between the starts (4-aminobenzenesulfonic acid (start 1) and 2-thioxo-4-thiazolidinone (start 2)) and tautomers (A-C) of ligand (H 2 L) with the receptors of prostate cancer mutant (PDB code: 2Q7K) and breast cancer mutant (PDB code: 3HB5).

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, 1H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH2 group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).

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5-(4'-substituted phenylazo)-2-thioxothiazolidinone derivatives (HL(n)) have been synthesized and characterized by elemental analysis, spectra (IR, electronic and (1)H NMR). The IR spectral data indicate that the compounds can exist in two resonance structures. The synthesized ligands were screened for their antimicrobial activity against four bacterial species, two Gram positive bacteria (Bacillus cereus and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) as well as against some species various of fungi; Aspergillus niger, Penicillium chrysogenum, Penicillium italicum and Fusarium oxysporium. The results showed that most these ligands are good antibacterial agents against B. cereus and S. aureus and antifungal agents against A. niger and F. oxysporium. HL(3) was found to be the most effect compound against all tested microorganisms. The size of clear zone were ordered as follows p-(OCH(3) < CH(3) < H < Cl < NO(2)) as expected from Hammett's constant σ(R).

Polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) were prepared by the reaction of 3‐allyl‐5‐[(4‐nitrophenylazo)]‐2‐thioxothiazolidine‐4‐one (HL) with metal ions. The structure of polymer complexes was characterized by elemental analysis, IR, UV–Vis spectra, X‐ray diffraction analysis, magnetic susceptibility, conductivity measurements and thermal analysis. Reaction of HL with Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) ions (acetate or chloride) give polymer complexes (1–5) with general stoichiometric [M(L)(O2CCH3)(H2O)2]n (where L = anionic of HL and M = Co(II) (1) or Ni(II) (2)), [Mn(HL)2(OCOCH3)2]n (3), [Cr(L)2(Cl)(H2O)]n (4) and [Cd(HL)(O2CCH3)2]n (5). The value of HOMO–LUMO energy gap (ΔE) for forms (A‐C) of monomer (HL) is 2.529, 2.296 and 2.235 eV, respectively. According to ΔE value, compound has minimum ΔE is the more stable, so keto hydrazone form (C) is more stable than the other forms (azo keto form (A), azo enol form (B)). The interaction between HL, polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) with Calf thymus DNA showed hypochromism effect. The HL and its polymer complexes were tested against some bacterial and fungal species. The results showed that the Cr(III) polymer complex (4) has more antibacterial activity than HL and polymer complexes (1–3 and 5) against Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium.

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