Interaction of E. coli DNA with diazine-bridged late first row transition metal complexes derived from hexadentate compartmental ligands: an approach to DNA cleavage/binding studies

A series of binuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes having mu-1,2 diazine bridging have been prepared and characterized by various physico-chemical methods. The hexadentate ligands were synthesized by condensing 3,5-dichloroformyl-1H-pyrazole with 2-hydrazinobenzothiazole (L(1)H) or 4-aminoantipyrine (L(2)H) in 1:2 ratio. Gel electrophoresis data indicate cleavage of E. coli DNA to a minute extent by both [Co(2)L(2)(mu-Cl)Cl(2)(H(2)O)(2)]center dot H(2)O and [Ni(2)L(2)(mu-Cl)Cl(2)(H(2)O)(2)]. Conversely, the data for the remaining complexes indicated binding but not cleavage. These results were confirmed by viscosity measurements and absorption spectral studies. An intercalative binding mode is predicted when the title complexes interact with DNA.