Copper(II) complexes with sparfloxacin and nitrogen-donor heterocyclic ligands: Structure-activity relationship

Three novel neutral mononuclear copper(II) complexes of the third-generation quinolone antibacterial drug sparfloxacin in the presence of a nitrogen donor heterocyclic ligand 2,2'-bipyridine, 1,10-phenanthroline or 2,2'-dipyridylamine have been prepared and characterized physicochemically and spectroscopically. The resultant complexes are of the type Cu(sparfloxacinato)(N-donor)Cl. Copper(II) is pentacoordinate having a distorted square pyramidal geometry. Molecular modeling calculations have been performed in order to propose the lowest energy model structure of the complexes. The interaction of the complexes with calf-thymus DNA has been investigated with diverse spectroscopic techniques and has shown that the complexes can bind to calf-thymus DNA by the intercalative mode. The antimicrobial activity of the complexes has been tested on three different microorganisms. The Cu(sparfloxacinato)(N-donor)Cl complexes are among the most active ones against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, when compared to the other corresponding copper-quinolone complexes studied by our group and their antimicrobial activity is increased in the order bipyam