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 < bipy = phen. We have also shown that two of the Cu(sparfloxacinato)(N-donor)Cl complexes have decreased the viability of human leukemia cells HL-60 in a time-dependent manner.