Compounds of Antibacterial Agent Ciprofloxacin and Magnesium - Crystal Structures and Molecular Modeling Calculations

Two novel magnesium complexes of the quinolone antibacterial drug ciprofloxacin (cfH) were isolated and their crystal structures determined. In both compounds, bidentate O,O′‐bonding of quinolone molecules to the metal was observed and it was also found that a very extensive intermolecular hydrogen‐bond framework is present. The structures of both compounds, [Mg(H2O)2(cfH)2](NO3)2·2H2O (1) and [Mg(cfH)3](SO4)·5H2O (2) respectively, were compared with previously isolated compounds (cfH2)2[Mg(H2O)6](SO4)2·6H2O (3) and [Mg(cf)2]·2.5H2O (4) and the appearance of magnesium and quinolone in these structures was analyzed in detail. The lowest energy model structures of the new complexes were determined with molecular modeling calculations and compared with the corresponding structures of 1 and 2 determined by X‐ray crystallography. Though we were not able to isolate the 1:1 magnesium–ciprofloxacin complex, modeling calculations were also performed for such a complex due to its possible importance in biological systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) Crystal structures of isolated Mg complexes of the quinolone antibacterial drug ciprofloxacin (metal–ligand ratio 1:2 and 1:3) were determined. A bidentate O,O′‐bonding was found for both complexes. The crystal structures of several Mg–ciprofloxacin complexes were analyzed. Additionally, molecular modeling calculations in these systems were performed.