Synthesis, crystal structure and DNA cleavage activities of copper(II) complexes with asymmetric tridentate ligands

Two asymmetric tridentate copper(II) complexes, [Cu(dppt)Cl-2].0.25H(2)O (1) (dppt = 3-(1,10-phenanthrolin-2-yl)-5,6-diphenylas-triazine) and [Cu(pta)Cl-2] (2) (pta=3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]acenaphthylene), have been prepared and characterized by elemental analysis, IR and Fast atomic bombardment mass spectra. Complex 1 has also been structurally characterized. The complexes exist as distorted square pyramid with five co-ordination sites occupied by the tridentate ligand and the two chlorine anions. DNA interaction studies suggest that the ligand planarity of the complex has a significant effect on DNA binding affinity increasing in the order [Cu(dppt)Cl-2] < [Cu(pta)Cl-2]. In the presence of ascorbate or glutathione, the two complexes are found to cause significant cleavage of double-strand pBR 322 DNA and [Cu(pta)Cl-2] exhibited the higher cleaving efficiency.