STUDIES OF ELECTROCATALYTIC DNA CLEAVAGE BY OXORUTHENIUM(IV) - X-RAY CRYSTAL-STRUCTURE OF [RU(TPY)(TMEN)OH2](CLO4)2 (TMEN = N,N,N',N'-TETRAMETHYLETHYLENEDIAMINE, TPY = 2,2',2''-TERPYRIDINE)

The interactions of Ru(II)(tpy)(bpy)OH2(2+) (1), Ru(II)(tpy)(phen)OH2(2+) (2), and Ru(II)(tpy)(tmen)OH2(2+) (3) (typ = 2,2',2"-terpyridine, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, tmen = N,N,N',N'-tetramethylethylenediamine) with DNA have been investigated by cyclic voltammetry. The addition of DNA to solutions of these complexes causes a dramatic decrease in current for the Ru(IV/III) and Ru(III/II) couples indicative of binding of the complexes to DNA. From the decrease in current, binding constants 15 x 10(3) M-1, 78 x 10(3) M-1, and 5.3 x 10(3) M-1 can be estimated for 1-3, respectively. Thus, the binding affinity appears to be partly a function of the extended planarity and aromaticity of the bidentate ligands. The previously reported activity of the Ru(IV) state toward DNA cleavage is apparent as a current enhancement in the Ru(IV/III) oxidation wave. As a result of the differential binding affinity of 1 and 2, greater electrocatalytic efficiency for DNA cleavage is observed for 1 upon controlled potential electrolysis at 0.8 V. A single crystal of 3(ClO4)2 suitable for X-ray diffraction was also obtained. X-ray data: C21H29N5O9RuCl2, monoclinic, P2(1)/c, a = 15.314 (5) angstrom, b = 10.754 (4) angstrom, c = 16.150 (8) angstrom, beta = 96.99 (3)-degrees, V = 2640 (2) angstrom 3, Z = 4, R = 0.0699, and R(w) = 0.0718 for 3601 reflections with I > 2-sigma(I). The electronic properties of 2 and 3 are also reported.