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

The synthesis and characterization of the new solid complexes {[}VO(MOX)(2)H2O]SO4 center dot 11H(2)O, {[}ZrO(MOX)(2)Cl]Cl center dot 15H(2)O and {[}UO2(MOX)(3)](NO3)(2)center dot 3H(2)O formed in the interaction of moxifloxacin (MOX) with VOSO4 center dot H2O, ZrOCl2 center dot 8H(2)O and UO2(NO3)(2)center dot 6H(2)O 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 (HNMR)-H-1) 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. Delta H{*}, entropies, Delta S{*} and Gibbs free energies, Delta G{*}, 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 U=O for the {[}UO2(MOX)(3)](NO3)(2)center dot 3H(2)O 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. (C) 2011 Elsevier B.V. All rights reserved.