Spectroscopic studies, thermal analyses and biological evaluation of new V(IV), Zr(IV) and U(VI) moxifloxacin complexes

Abstract

The synthesis and characterization of the new solid complexes [VO(MOX)2H2O]SO4·11H2O, [ZrO(MOX)2Cl]Cl·15H2O and [UO2(MOX)3](NO3)2·3H2O formed in the interaction of moxifloxacin (MOX) with VOSO4·H2O, ZrOCl2·8H2O and UO2(NO3)2·6H2O in methanol and acetone as a solvents at room temperature were reported. The isolated solid complexes have been characterized with melting points, elemental analysis, molar conductance, magnetic moments studies, spectral (UV–Visible, IR and 1HNMR) as well as thermal analyses (TGA and DTG). The results support the formation of the complexes and indicate that moxifloxacin reacts as a bidentate ligand chelate to the metal ion through the pyridone oxygen and one carboxylato oxygen. The kinetic parameters of thermogravimetric (TGA) and its differential (DTG), such as activation energies, E*, enthalpies, ΔH*, entropies, ΔS* and Gibbs free energies, ΔG*, have been evaluated by using Coats–Redfern (CR) and Horowitz–Metzeger (HM) methods. The proposed structure of the ligand and their complexes were detected by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The bond stretching force constant and length of the UO for the [UO2(MOX)3](NO3)2·3H2O complex were calculated. The antibacterial activity of the free moxifloxacin ligand and their metal complexes have been tested against some selected bacterial strains such as: Streptococcus aureus K1, Bacillus subtilis K22, Brevibacterium otitidis K76, Escherichia coli K32, Pseudomonas aeruginosa SW1 and Klebsiella oxytoca K42. The complexes showed good antibacterial effect to the selected bacterial strains as compared to the free ligand and Zr(IV) complex is very highly significant compared with the other two complexes.