Structural Characterization and Antimicrobial Studies of Some New Mixed Ligand Complexes of Lomefloxacin and 3‐(Bromoacetyl)coumarin with Some Metals

Abstract

AbstractThe interaction of Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), and Zn(II) (6) with lomefloxacin (LFX) in the existence of 3‐(bromoacetyl)coumarin (BAC) and NaOH in a 1 : 1 : 1 : 1 molar ratio resulted in the formation of unique mixed ligand metal complexes. The ability of two ligands to chelate metal ions was investigated by elemental analysis, molar conductance, effective magnetic moments FT‐IR, ultraviolet‐visible (UV‐Vis), 1H NMR spectra and thermogravimetric analyses (TG‐DTG). FT‐IR spectra of the complexes suggest that LFX reacted with metal ions as bi‐dentate through pyridone oxygen and carboxylate oxygen. BAC also interacts as bi‐dentate through oxygen of α,β‐unsaturated ketone and oxygen of lactone carbonyl of coumarin. These chelates are electrolytes, according to conductivity experiments, with a 1 : 1 ratio for Mn(II), Fe(II), and Zn(II) and a 1 : 2 ratio for Co(II), Ni(II), and Cu(II). Electronic and magnetic data revealed an octahedral shape for all compounds. The thermodynamic parameters of thermal breakdown processes such as Ea, ΔH*, ΔS* and ΔG* were determined from TG and DTG curves using Coats‐Redfern (CR) and Horowitz‐Metzeger (HM) techniques for LFX, BAC and their metal complexes. The structural geometry of the complexes is confirmed by molecular modeling studies. The findings show that the complexes are soft with regard to ligands, with values ranging from 0.058 eV for Fe(II) complex to 0.090 eV for Zn(II) complex and 11.11 to 17.24 eV for LFX and BAC, respectively, and 0.121, 8.26 eV and 0.111, 9.009 eV for LFX and BAC. The ligands and their complexes were tested in vitro for antibacterial activity against a variety of bacterial and fungal strains, and the results revealed that the complexes had significantly higher potency than the parent drug.