Synthesis, interaction with DNA and nuclease activity of zinc complexes of 2,2′-bipyridine derivatives with tetraalkylammonium groups

Abstract

Two zinc complexes of disubstituted 2,2′-bipyridine with tetraalkylammonium groups, [Zn(L1)3](ClO4)8 · 12H2O (1) and [Zn(L2)3](ClO4)8 · 2H2O (2) (L1 = [4,4′-(Et3NCH2)2-bpy]2+, L2 = [4,4′-((n-Bu)3NCH2)2-bpy]2+ and bpy = 2,2′-bipyridine), have been synthesized and characterized. Species distributions in aqueous solution of both complexes were determined by potentiometeric titration. The interaction of these complexes with calf thymus DNA was explored by UV spectroscopic titration and CD spectroscopy, suggesting outside electrostatic binding mode. Both complexes were applied to the cleavage of plasmid pBR322 DNA under hydrolytic conditions; 1 can effectively cleave DNA from supercoiled to nicked form, showing quite high nuclease activity, while 2 has limited ability to cleave DNA.