The first dinuclear copper(II) and zinc(II) complexes containing novel Bis-TACN: syntheses, structures, and DNA cleavage activities

Two novel binuclear complexes [Cu-2(L)]center dot(ClO4)(2) (1) and [Zn-2(L)]center dot(ClO4)(2)(2) were synthesized and crystallographically characterized {L = 1(4),5(4)-dimethyl-1(2),5(2)-dihydroxy-1(1,3), 5( 1,3)-dibenzene-3( 1,4),7(1,4)-di-1,4,7-triazacyclononane}. The cation [Cu-2(L)](2+) structure of 1 is similar to that of [ Zn-2(L)](2+) of 2. The central ion is bridged by the di-phenoxo of L and lies in a close to perfect square pyramidal geometry. 1 and 2 crystallize in the triclinic space group P (1) over bar. The two complexes effectively promote the cleavage of plasmid DNA in the presence of activating agents at physiological pH and temperature. The pseudo-Michaelis-Menten kinetic parameters k(cat) = 1.61 h(-1), Km = 1.35 x 10(-5) M for complex 1 in the presence of mercaptoethanol; k(cat) = 2.48 h(-1), K-m = 5.5 x 10(-5) M for complex 2 in the presence of hydrogen peroxide were obtained. The mechanism of plasmid DNA cleavage was studied by adding standard radical scavengers. DNA cleavage reaction by the binuclear Zn(II)/H2O2 system is a hydrolytic mechanism.