Thermal properties, antimicrobial activity and DNA binding of Ni(II) complexes of azo dye compounds

Abstract

A novel series of nickel(II) azo dye complexes of 5-(4-methoxyphenylazo)-2-thioxo-4-thiazolidinone (HL1), 5-(4-methylphenylazo)-2-thioxo-4-thiazolidinone (HL2), 5-(phenylazo)-2-thioxo-4-thiazolidinone (HL3) and 5-(4-nitrophenylazo)-2-thioxo-4-thiazolidinone (HL4) were prepared and characterized elemental analyses, IR, UV–Visible spectra, X-ray diffraction analysis and mass spectrum as well as thermogravimetric analysis (TGA). The magnetic measurements of Ni(II) complexes (1–4) lie in 3.05–3.20 BM., as anticipated for octahedral geometry. Quantum chemical parameters and molecular structures of the complexes were theoretically computed and the results were studied. IR spectra show that HLn ligands (n=1–4) act a monobasic bidentate ligands by coordinating via the oxygen atom of the deprotonated OH group moiety and nitrogen atom of azo group. The interaction between Ni(II) complexes and calf thymus DNA (CT-DNA) shows hyperchromism effect coupled with obvious bathochromic shift. The value of binding constant (Kb) obtained from the absorption spectral technique for Ni(II) complexes (1–4) was calculated and found to be 1.20×105, 1.17×105, 7.22×104 and 6.65×104M−1, respectively. The antimicrobial activities of Ni(II) complexes (1–4) were investigated. It was found that the Ni(II) complexes have low antibacterial activity against Klebsiella pneumoniae. Complex (1) has antifungal activity against Penicillium italicum. All the Ni(II) complexes have more antibacterial activity than the penicillin against Klebsiella pneumoniae. The thermodynamic parameters were calculated using Coats–Redfern and Horowitz–Metzger methods. From the values of the thermal activation energy for decomposition (Ea) of Ni(II) complexes (1–4), it was found that the Ea value for the complex (4) is higher compared to the other complexes. The positive value of Gibbs free energy of decomposition (ΔG⁎) for the Ni(II) complexes is non-spontaneous processes.