COVALENT BINDING OF AQUARUTHENIUM COMPLEXES TO DNA

Thermal denaturation studies were performed on a group of mononuclear mono- and diaqua polypyridyl complexes of Ru(II) covalently bound to c alf thymus DNA. Adducts of monofunctional complexes show small, positi ve values of DELTAT(m) (0.8-3.5). The adducts of difunctional complexe s exhibit much larger values (6-13), and the thermal denaturation is i rreversible, which is consistent with formation of an interstrand diad duct. The dinuclear complex [(bpy)2Ru(OH2)]2O4+ was also studied and f ound to bind stereoselectively to calf thymus DNA (bpy = 2,2-bipyridin e). Circular dichroism spectroscopy showed the filtrate obtained from ultrafiltration of calf thymus DNA and [(bpy)2Ru(OH2)]204+ to be enric hed in one enantiomer. We also report here the synthesis and electroni c properties of the model complex [(bpy)2(EtG)RuOH2]2+ (EtG = 9-ethylg uanine). The complex is stable and possesses all of the characteristic electronic properties of the other polypyridylaquamthenium complexes. Surprisingly, the Ru(IV)O form is accessible via electrochemical oxid ation and is an effective DNA cleavage agent.