An unprecedented Ag–pipemidic acid complex with helical structure: Synthesis, structure and interaction with CT-DNA

• A new Ag–pipemidic acid complex with helical structure was synthesized.
• The complex is a positive example for the study of metal–drug complexes.
• The complex exhibits the higher Kb constant and KSV value than the PPA.

A new Ag–pipemidic acid complex with helical structure has been prepared and structurally characterized by routine technique. Single-crystal X-ray diffraction analysis shows that there are the left- and right-handed helical chains constructed by Ag ions and PPA drugs along the b direction. And two types of helical chains are connected into 2D layer by sharing pseudo-tetra-nuclear clusters, which are stabilized by PPA-1 molecules as scaffolds. UV study of the interaction of the complex with CT-DNA shows that the title complex can bind to the CT-DNA and exhibits the higher binding constant (Kb) than free HPPA drugs. Additionally, its competitive study with ethidium bromide and the relatively high KSV value also indicates that complex can bind to DNA for the intercalative binding sites.