Synthesis, characterization and crystal structure of copper(II) ternary complex with cinoxacin and histamine

In order to enhance the knowledge of how quinolones may exert their antibacterial action, the synthesis of a new copper(II) mixed ligand, containing histamine complex was carried out. Crystal structure of [Cu(hsm)(cnx)NO3]H2O shows that Cu(II) cation displays a distorted square pyramidal geometry. Cinoxacinate (cnx) acts as bidentate ligand bonded to the Cu(II) ion through the oxygen atoms of the 3-carboxylate and 4-keto groups and histamine (hsm) is coordinated by the aliphatic amino group and the non protonated nitrogen of imidazole. Molar conductivity, elemental analysis, infrared and electronic spectroscopy have been used to characterize the complex. The results here reported indicate that cnx coordination mode is similar to that found in other complexes reported previously, being only found that metal-ligand distances are slightly different because the asymmetry of the coordination environment. This result also, may support the hypothesis that the mechanism of action of quinolones could be through a copper(II) complex carrier with imidazole ligands in their coordination environment. (C) 2003 Elsevier B.V. All rights reserved.