Petra Drevenšek, Amalija Golobič, Iztok Turel*
University of Ljubljana, Faculty of Chemistry and Chemical Technology, Aškerčeva 5, POB 537, 1000 Ljubljana, Slovenia

Nataša Poklar
University of Ljubljana, Biotechnical Faculty, Department of Food Science and Technology, Jamnikarjeva 101, 1000 Ljubljana, Slovenia

Kristina Sepčić
University of Ljubljana, Biotechnical Faculty, Department of Biology, Večna pot 111, 1000 Ljubljana, Slovenia
 

Abstract
The title compound, ciprofloxacinium(1+) ciprofloxacinium(2+) tetrachlorocuprate(II) chloride hydrate, (cfH2)(cfH3)[CuCl4]Cl.H2O, (1), was isolated and its structure was determined by X-ray crystallography. This is a typical ionic compound with no direct bonds between the quinolone and metal. Both ciprofloxacin (cfH = 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid) molecules are nonequivalent and are protonated thus being unable to coordinate to the copper. The new complex has been characterised by intrinsic fluorescence emission and UV spectroscopy. The title compound as well as two previously isolated copper complexes, [Cu(cfH)(H2O)3]SO4.2H2O, (2) and [Cu(cfH)2]Cl2.6H2O, (3), were tested against the growth of  various Gram positive and Gram negative microorganisms. Antimicrobial activities were evaluated using the agar diffusion test. Since ciprofloxacin alone has the ability to bind to DNA, the binding of a new compound has also been tested by UV spectroscopy. Our results reveal that (cfH2)(cfH3)[CuCl4]Cl.H2O slightly thermally destabilise the linear double stranded DNA at pH 7.0.