Research Articles
Complexes of Co(II) and Zn(II) with Ofloxacin. Crystal Structure of [Co(oflo)2(MeOH)2]·4MeOH

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Abstract

Ofloxacin (oflo) is able to interact with Co(II) and Zn(II) salts to form complexes with the general formula [M(oflo)2] · 4H2O, (M = Co, Zn). Bonding takes place through one of the oxygen atoms of the carboxylate group (acting as a monodentate) and the oxygen atom of the ketonic group. The IR bands of the carboxylic and ketonic group at 1713 and 1622 cm−1, respectively, shift to 1615 and 1575 cm−1 in the complexes. After dissolution in methanol, complex [Co(oflo)2] · 4H2O crystallizes as [Co(oflo)2(MeOH)2] · 4MeOH, where Co(II) ion is in an octahedral environment of oxygen atoms. This compound crystallizes in the triclinic system, spatial group P‐1, with unit cell dimensions a = 9.3670(12), b = 11.4135(17), c = 11.851(2) Å y α = 71.999(14), β = 73.698(12), γ = 83.528(14)°. Magnetic properties (effective magnetic moment 5.02 BM) and visible spectrum (bands at 490, 510, and 1152 nm) are characteristic of such an octahedral geometry. 1H‐ and 13C‐NMR spectra of the Zn(II) complex indicate only small structural changes in ofloxacin upon coordination to the metallic site. © 2002 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2416–2423, 2002

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.

REFERENCES (23)

  • B.V. Nonius

    CAD4‐express software, Ver. 5.1/1.2

    (1994)
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