Structure and Interaction with CT-DNA of Two Quinolone-Metal Complexes Containing Helical Channels

Abstract

Two new complexes based on pipemidic acid (HPPA) and Co2+/Cd2+ ions, [Co(PPA)2]·2H2O (1) and Cd(PPA)2 (2), have been synthesized and structurally characterized. Single-crystal X-ray diffraction analysis shows that complexes 1 and 2 exhibit similar structures containing two-fold meso-helices and 1D supramolecular channels. The interaction of calf-thymus (CT-DNA) with complexes 1 and 2 with was explored by UV spectrum, and competitive studies with ethidium bromide (EB) by fluorescence spectrum. Notably, these results indicate that complexes 1 and 2 possess the higher binding DNA affinity than free HPPA drugs, maybe attributed to the coordinated metal ions and the helical channels. And the resultant hypochromism suggests the tight binding of 1 and 2 with CT-DNA probably by the intercalative mode. Moreover, the relatively high Ksv value also indicates that 1 and 2 can bind to CT-DNA for the intercalative binding sites. Two new complexes based on HPPA were synthesized and structural description, and exhibit similar structures containing two-fold meso-helices. The result of the interaction with CT-DNA indicates that complexes can bind to the CT-DNA by the intercalative mode and possess the higher binding constant to CT-DNA than free HPPA drugs.