Spectral, structural, biological and molecular docking studies of a new mixed-valence V(IV)/V(V) ofloxacin complex

Abstract

In this study, a biologically active mixed-valence V(IV)/V(V) complex [VO(Hofloz)2(H2O)][V4O12]0.5.6H2O (1) (Hofloz = zwitterionic isomer of ofloxacin) was synthesized by the reaction of VOSO4 with ofloxacin (Hofloz) in presence of KOH with 1:1:1 ratio. The complex was characterized through the usage of elemental analysis, FT-IR, molar conductivity and single-crystal X-ray diffraction and thermogravimetric analysis (TGA). The results of single crystal X-ray structure determination revealed an ionic structure consisting of [VO(Hofloz)2(H2O)]2+ and [V4O12]4− units with 1:0.5 stoichiometry. The V+4 ion in the cationic unit has octahedral geometry while each V+5 ion of the eight-member cyclic tetravanadate anion is tetrahedrally coordinated. In regards to the crystal structure of 1, the bidentate ofloxacin ligand is coordinated to the V+4 ion in its zwitterionic form (+HN–···–COO-) through the oxygen atoms of the pyridone and carboxylato groups. The thermodynamic stability of two isomeric forms of Hoflo and 1 along with their charge distribution patterns was studied by DFT and NBO analysis. Also, the ability of the ligand to interact with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) was investigated by docking calculations. These studies revealed that this ligand can bind to the proteins and DNA molecule and could be consider as biologically active compound. Finally, the antibacterial activities of the free Hoflo ligand and its vanadium complex have been evaluated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains through the utilization of broth microdilution and well diffusion methods. The complex showed antibacterial effect similar to the free Hoflo ligand on the selected bacterial strains and these compounds were more active against Gram-negative bacteria.