Preparation, structure and microbial evaluation of metal complexes of the second generation quinolone antibacterial drug lomefloxacin

Lomefloxacinate of Y(III), Zr(IV) and U(VI) were isolated as solids with the general formula; [Y(LFX)2Cl2]Cl·12H2O, [ZrO(LFX)2Cl]Cl·15H2O and [UO2(LFX)3](NO3)2·4H2O. The new synthesized complexes were characterized with physicochemical and diverse spectroscopic techniques (IR, UV–Vis. and 1H NMR spectroscopies) as well as thermal analyses. In these complexes lomefloxacin act as bidentate ligand bound to the metal ions through the pyridone oxygen and one carboxylate oxygen. The kinetic parameters of thermogravimetric (TGA) and its differential (DTG), such as entropy of activation, activation energy, enthalpy of activation and Gibbs free energy evaluated by using Coats–Redfern and Horowitz–Metzger equations for free lomefloxacin and three complexes were carried out. The bond stretching force constant and length of the UO bond for the [UO2(LFX)3](NO3)2·4H2O complex were calculated. The antimicrobial activity of lomefloxacin and its metal complexes was tested against different bacterial species, such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) as Gram-positive and Gram-negative bacterial species and also against two species of antifungal, penicillium (P. rotatum) and trichoderma (T. sp.). The three complexes are of a good action against three bacterial species but the Y(III) complex exhibit excellent activity against Pseudomonas aeruginosa (P. aeruginosa), when compared to the free lomefloxacin.