Synthesis, characterization and biological activity of mixed ligands complexes of quinolin-8-ol and substituted chromones with Mn(II), Co(II), Ni(II) and Cu(II) metal ions

Abstract

The mixed ligand complexes were synthesized using quinolin-8-ol and substituted chromone derivative with transition metals like Mn(II), Cu(II), Ni(II) and Co(II). These complexes were characterized using elemental analysis by electron dispersive spectroscopy, Fourier transforms infrared, ultraviolet–visible, proton nuclear magnetic resonance, liquid chromatography coupled with mass spectrometry, electron spin resonance spectra, magnetic susceptibility, powder X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The complexes were screened by biological activities such as antioxidant activity by 2, 2-Diphenyl-1-picrylhydrazyl, antimicrobial activity by the agar well-diffusion method and anticancer activity by yellow tetrazolium (3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide methods. The synthesis of mixed ligand complexes were synthesized by using homoleptic complexes of respective metal complexes of chromones. The FTIR spectra show ν_M–O the ν_M–N frequencies are obtained at 515–645 cm⁻¹ and 431–496 cm^{− 1} respectively. The NMR spectra of Ni(II) complexes were indicating the complexes are paramagnetic in nature. The ESR spectra of copper complexes shows singlet signal, and they indicate that the copper has 2 + oxidation state in complexes. The complexes showed a well-defined crystal system indicated by powder-X-ray diffraction patterns. The thermogram studies show formation of metal oxides residues at the end product of decomposition of complexes. The scanning electron microscope showed complexes were nanocrystalline in nature. The mixed ligand complex of Ni(II) shows 80.73% antioxidant activity as compared to both the ligands and other metal complexes. The antibacterial activity result obtained clearly showed that all complexes were effective against all the microorganisms of Staphylococcus aures, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginos. The inhibition of the cancerous cell is more the case of Ni (II) complexes as compared with other complexes.