Square-Planar Copper(II) complexes from a Zwitterionic Schiff-Base N₂/N_2/2-Donor Ligand: DNA Interaction and Cytotoxicity

A new tetradentate ligand, namely 3,3′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(pyridin-2-amine) (en2ampy) was prepared and two copper(II) complexes, viz. [Cu(en2ampy)]Cl₂ (1) and [Cu(en2ampy)](NO₃)₂ (2), were obtained through its reaction with copper(II) chloride and copper(II) nitrate, respectively. The single-crystal X-ray structure of the compounds showed that the metal centre was coordinated in a square-planar fashion by a doubly deprotonated en2ampy acting as a tetradentate (Formula presented.) / (Formula presented.) -donor ligand. DNA-binding studies revealed that 1 and 2 were electrostatically binding to DNA, probably in the grooves and cytotoxicity assays showed that the complexes were clearly more efficient than cisplatin against ovarian carcinoma (A2780) cells and the cisplatin-resistant (A2780Cis) ones.