Research ArticlesComplexes of Co(II) and Zn(II) with Ofloxacin. Crystal Structure of [Co(oflo)2(MeOH)2]·4MeOH
Section snippets
INTRODUCTION
Interaction of metal ions, mainly those existing in living organisms, with drugs, especially antibiotics, has been the aim of many research studies since several review papers on this subject were published.1 Quinolones are a group of antibacterial agents currently used in various kinds of infections,2 and for some of the members of this family, especially cinoxaxin, its interactions with several metal ions has been reported.3., 4., 5., 6., 7. However, only a few articles have been reported on
Materials
Ofloxacin was provided by Sigma, and all reagents used were of analytical grade. Chemical analyses for carbon, hydrogen, and nitrogen were performed on a 2400 elemental analyzer from Perkin‐Elmer. Nickel and copper were determined on a ICP spectrometer (Perkin‐Elmer model 2380 Plasma 2).
IR spectra were recorded using KBr mulls and a Perkin‐Elmer FT‐IR instrument. Electronic spectra were recorded on a Hewlett Packard 8452A diode (200–800 nm) and a Perkin‐Elmer Lambda 9 (800–1600 nm)
Thermal Study and Mass Spectrometry
The presence of four water molecules per complex molecule has been assessed by thermogravimetric (TG) and differential thermal analyses (DTA). So, a 8.4% weight loss in the TG curves is associated to removal of four water molecules. These losses occur in the same temperature range (95–100°C) as endothermic peaks in the DTA curves, as expected for a dehydration process.
However, the molecular masses of these compounds are recorded in mass spectrometry analysis at m/z = 780 and 784, respectively,
NMR SPECTRA
Only broad, ill defined, bands were recorded in the spectra of the Co complexes, due to their paramagnetic character. However, the 1H‐ and 13C‐NMR spectra of the pure ofloxacin and of the Zn complex could be recorded; the data and their assignations21 are summarized in Table 4. Both spectra are rather similar, indicating that coordination to the Zn(II) cation does not heavily modify the conformation of the ofloxacin molecule.
Acknowledgements
The authors thank CICYT (grant PM97‐0105‐C02‐02) for financial support. Critical reading of the manuscript by Prof. V. Rives is also acknowledged.
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