SPECTROSCOPIC INVESTIGATIONS OF FLUOROQUINOLONES METAL ION COMPLEXES

The complex formation reaction, between fluoroquinolones (FQ): ciprofloxacin (CPX), enoxacin (ENX), enrofloxacin (ENRX), lomefloxacin (LOMX), levofloxacin (LEVX), ofloxacin (OFX), norfloxacin (NFX), sparfloxacin (SPRX) and aluminum(III), iron(III), copper(II) and zinc(II) ions were investigated. The spectrophotometic titration method in a wide range of pH was utilized for estimation of complex formation equilibrium. The application of Bjerrum method allowed to estimate the complex equilibrium of analyzed species in the reaction mixture. The overall stability constants (log beta(pqr)) of fluoroquinolones complexes with metal ions were calculated using HYPRERQUAD program. The most stable complexes FQ were created with iron(III) and aluminum(III) and than copper(II) and zinc(II) ions, respectively. The highest values of calculated log beta(pqr) were obtained for the Me(FQ)(3)H-3 species and the lowest for the Me(FQ)(2)OH forms. Furthermore, an additional studies have been performed. The effect of the polyvalent metal ions on the complex structure has been investigated. The IR and H-1, C-13 and F-19 NMR spectroscopy methods were used for the confirmation of the structure of the FQ-Me complex formations. The most significant shifts of signals of H-1 NMR spectra of the fluoroquinolones and their complexes were found for the protons substituted in the positions 2, 5 and 8, whereas the C-13 NMR spectra showed up the shifts changes for carbon atoms in positions 2, 3, 3a and 4.