DNA and protein binding, double-strand DNA cleavage and cytotoxicity of mixed ligand copper(II) complexes of the antibacterial drug nalidixic acid

The water soluble mixed ligand complexes [Cu(nal)(diimine)(H2O)](ClO4) 1-4, where H(nal) is nalidixic acid and diimine is 2,2'-bipyridine (1), 1,10-phenanthroline (2), 5,6-dimethyl-1,10-phenanthroline (3), and 3,4,7,8-tetramethyl-1,10-phenanthroline (4), have been isolated. The coordination geometry around Cu(II) in 1 and that in the Density Functional Theory optimized structures of 1-4 has been assessed as square pyramidal. The trend in DNA binding constants (Kb) determined using absorption spectral titration (Kb: 1, 0.79±0.1