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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.

Novel polymer complexes of 8‐hydroxyquinoline‐5‐sulfonic acid hydrate (H2L) with Cu2+, Co2+ and Ni2+ chloride were prepared and characterized. Microanalysis, magnetic susceptibility, IR spectra, electron spin resonance, mass spectra, X‐ray, molar conductance, thermal, and UV–Vis spectra studies have been used to confirm the structure of the prepared polymer complexes. The molecular and electronic structures of the hydrogen bond conformers for ligand (H2L) were optimized theoretically and the quantum chemical parameters were calculated. On the basis of elemental and IR data, the chemical structure of metal chelates commensurate that the tri‐dentate (H2L) coordinate to metal chlorides through oxygen atom of phenolic OH and oxygen atom of SO3‐H group by replacing H atoms and nitrogen of the quinoline ring. The magnetic studies suggested the octahedral geometrical structure for all produced polymer complexes with general formula {[ML (OH2)3] .xH2O}n (M = Cu2+, x = 1.; Co2+, x = 2 and Ni2+, x = 2) in molar ratio (1:1). Coats–Redfern and Horowitz–Metzger methods have been used for calculating the activation thermodynamic parameters of the thermal decomposition for H2L and its polymer complexes. The interaction between H2L and its transition metal complexes with the calf thymus DNA (CT‐DNA) was determined by UV–Vis spectra. Binding efficiency between H2L with the receptors of the prostate cancer (PDB code 2Q7L Hormone) and the breast cancer (PDB code 1JNX Gene regulation) was studied by molecular docking. The inhibition behaviour of H2L against the corrosion of carbon steel/HCl (2 M) solution was studied by weight loss, Tafel polarisation, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The adsorption isotherm was found to be Friendlish isotherm. The morphology of inhibited carbon steel̕ s surface was studied using scanning electron microscope (SEM) and energy dispersive X‐ray spectroscopy (EDS).

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Ni(II) or Co(II)). The structures of the polymer complexes were identified using elemental analysis, infrared and electronic spectra, molar conductance, magnetic susceptibility, X-ray diffraction and thermogravimetric analysis. The interaction between the polymer complexes and calf thymus DNA showed a hypochromism effect. HL and its polymer complexes were tested against bacterial and fungal species. Co(II) polymer complex 2 is the most effective against Klebsiella pneumoniae and is more active than penicillin. The results showed that Ni(II) polymer complex 5 is a good antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa. Molecular docking was used to predict the binding between the monomer with the receptors of prostate cancer (PDB code: 2Q7L Hormone) and breast cancer (PDB code: 1JNX Gene regulation). Coats-Redfern and Horowitz-Metzger methods were applied for calculating the thermodynamic parameters of HL and its polymer complexes. The thermal activation energy of decomposition for HL is higher than that for the polymer complexes.

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