New Mn(II), Co(II), Ni(II) and Cu(II) homoleptic complexes with 6-chloro-5-7-dimethyl-4oxo-4H-chromene-3-carbaldehydes and its heteroleptic complexes with quinoline-8 ol: synthesis, characterization and antimicrobial activity

Abstract

In the present study, the synthesis of ligand 6-chloro-5-7-dimethyl-4oxo-4H-chromene-3-carbaldehydes by three steps from the substituted phenol. The formed product in the first step was further processed by fries rearrangement reaction and subsequently Vilsmeier–Haack reaction. Then, its homoleptic and heteroleptic complexes with Mn(II), Co(II), Ni(II) and Cu(II) metal ions by using second ligand quinolin-8-ol were synthesized. The ligand and complexes were characterized by different techniques, such as electron dispersive spectroscopy and elemental analysis (CHN), Fourier transform infrared (FTIR), electronic spectroscopy and magnetic susceptibility, 1H-Nuclear magnetic resonance spectroscopy and mass spectra of ligand, electron spin resonance (ESR), thermogravimetric analysis, powder X-ray diffraction, scanning electron microscopy (SEM) and molar conductivity. The spectroscopic analysis like NMR and the FTIR shows that the both ligands are bidentate in nature. The UV–visible spectra show the homoleptic complex of Cu(II) shows square planer, while M = Ni(II), Co(II) and Mn(II) shows octahedral in nature. While the complexes with heteroleptic ligands from square planer geometry with Cu(II) and Ni(II) while Co(II) and Mn(II) show octahedral geometries. The geometry was also supported by magnetic susceptibility and FTIR spectra. The ESR spectra of Cu(II) complexes shows both are square planer geometry and the G-value was more than 4 indicating the absence of exchange interaction between Cu(II) metal ions in the solid state. The powder X-ray diffraction was used to determine the crystal system of all the complexes, while supporting to this X-ray diffraction the SEM was also taken for the nanostructure of complexes was developed or not. Then, the solution state conductivity of the complexes shows electrolytic in nature. Further, these complexes were evaluated for its antimicrobial activity by agar well diffusion method and structure–activity relationship. The ligands show antimicrobial activity against S.typhi. The Ni(II) does not show antibacterial activity, while complexes Cu(II), Co(II) and Mn(II) shows good activity against the gram-positive and the gram-negative bacteria. The heteroleptic ligand complex (6) of Cu(II) shows higher antifungal activity as compared with Ni(II), Co(II) and Mn(II) complexes.