Ligational behaviour of lomefloxacin drug towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO2(VI) ions: Synthesis, structural characterization and biological activity studies

Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO2(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV–vis, 1H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary complexes have been determined spectrophotometrically in aqueous solution at 25 ± 1 °C and at 0.1 M KNO3 ionic strength. The discussion of the outcome data of the prepared complexes indicate that the lomefloxacin ligand behaves as a neutral bidentate ligand through OO coordination sites and coordinated to the metal ions via the carbonyl oxygen and protonated carboxylic oxygen with 1:1 (metal:ligand) stoichiometry for all complexes. The molar conductance measurements proved that the complexes are electrolytes. The powder XRD study reflects the crystalline nature for the investigated ligand and its complexes except Mn(II), Zn(II) and UO2(II). The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first steps followed by decomposition of the anions, coordinated water and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats–Redfern and Horowitz–Metzger methods. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial effect against one or more bacterial species than the free LFX ligand. The antifungal and anticancer activities were also tested. The antifungal effect of almost metal complexes is higher than the free ligand. LFX, [Co(LFX)(H2O)4]·Cl2 and [Zn(LFX)(H2O)4]·Cl2 were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While, other complexes had been found to be inactive at lower concentration than 100 μg/ml.

Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO2(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV–vis, 1H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary metal complexes have been determined. The antibacterial, antifungal and anticancer activities were also tested.Figure optionsDownload as PowerPoint slideHighlights
► Metal complexes of lomefloxacin were synthesized.
► The complexes were prepared by reacting metal chlorides or uranyl nitrate with the lomefloxacin drug and characterized by different techniques, including: elemental analysis, thermogravimetric analysis (TG), molar conductivity measurements, UV–vis, 1H NMR, X-ray powder diffraction and IR spectroscopic techniques.
► The antibacterial activity of the lomefloxacin ligand and its corresponding complexes was investigated against several pathogenic bacteria (E. coli and Staphylococcus aureus) and fungi (Aspergillus flavus and Candida albicans).
► LFX, [Co(LFX)(H2O)4]·Cl2 and [Zn(LFX)(H2O)4]·Cl2 were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While other complexes had been found to be inactive at lower concentration than 100 μg/ml.