Nano-synthesis and spectral, thermal, modeling, quantitative structure-activity relationship and docking studies of novel bioactive homo-binuclear metal complexes derived from thiazole drug for therapeutic applications

Seven novel homo-binuclear Cr(III), Fe(III), Cu(II), ZrO(II), Sn(II), Pb(II) and Ce(III) nanosized complexes of a thiazole drug (H2L) were synthesized for chemotherapeutic applications. H2L was prepared via a condensation reaction between 2-(4-aminobenzenesulfonamido)thiazole and 2-hydroxybenzaldehyde. The structures of H2L and its metal complexes were investigated by various means. These included microanalysis, H-1 NMR, C-13 NMR, Fourier transform infrared, UV-visible, electron spin resonance and mass spectroscopies, transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA) and molar conductivity. The measurements revealed that H2L coordinates with the metal ions through two chelating centers, indicating its behavior as a dibasic tetradentate ligand. The first center involves the nitrogen of azomethine (CHN) and the -hydroxyl oxygen while the other center is the thiazole nitrogen and the sulfonamide oxygen. From spectroscopic and analytical data, the Cr(III), Fe(III) and Ce(III) complexes have octahedral geometries, whereas the Cu(II), ZrO(II), Sn(II) and Pb(II) complexes have tetrahedral geometries. TEM and XRD measurements unambiguously showed the nanometric particle sizes of the complexes. The activation thermo-kinetic parameters, E*, H*, S* and G*, of the various decomposition steps of the complexes were determined mathematically from the TGA curves. Gaussian09 and quantitative structure-activity relationship modeling studies were utilized to verify the biological and structural feature relationships. Docking studies were performed to throw more light on the biological priority of the proposed drugs, using microorganism protein receptors. The antitumor and antimicrobial efficiencies of the H2L drug and its complexes were determined to estimate their potential therapeutic utility. In general, the complexes showed greater antitumor and antimicrobial efficiencies than the H2L drug. The Fe(III) complex exhibited efficient antimicrobial activities against Candida albicans and Staphylococcus aureus and its efficiency is equivalent to that of standard drugs. The Cu(II) complex showed the greatest cytotoxic activity towards HEPG2.