Synthesis, characterization, interactions with the DNA duplex dodecamer d(5'-CGCGAATTCGCG-3') 2 and cytotoxicity of binuclear η 6 -arene-Ru(II) complexes.

The novel binuclear η 6 -arene-Ru(II) complexes with the general formula {[(η 6 -cym)Ru(L)] 2 (μ-BL)}(PF 6 ) 4 , and their corresponding water soluble {[(η 6 -cym)Ru(L)] 2 (μ-BL)}Cl 4 , where cym = p -cymene, L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), BL = 4,4'-bipyridine (BL-1), 1,2-bis(4-pyridyl)ethane (BL-2) and 1,3-bis(4-pyridyl)propane (BL-3), were synthesized and characterized. The structure of {[(η 6 -cym)Ru(phen)] 2 (μ-BL-1)}(PF 6 ) 4 was determined by X-ray single crystal methods. The interaction of {[(η 6 -cym)Ru(phen)] 2 (μ-BL- i )}Cl 4 ( i = 1, 2, 3; (4), (5) and (6) correspondingly) with the DNA duplex d(5'-CGCGAATTCGCG-3') 2 was studied by means of NMR techniques and fluorescence titrations. The results show that complex (4) binds with a K b = 12.133 × 10 3 M -1 through both intercalation and groove binding, while (5) and (6) are groove binders ( K b = 2.333 × 10 3 M -1 and K b = 3.336 × 10 3 M -1 correspondingly). Comparison with the mononuclear complex [(η 6 -cym)Ru(phen)(py)] 2+ reveals that it binds to the d(5'-CGCGAATTCGCG-3') 2 with a K b value two orders of magnitude lower than (4) ( K b = 0.158 × 10 3 M -1 ), indicating that for the binuclear complexes both ruthenium moieties participate in the binding. The complexes were found to be cytotoxic against the A2780 and A2780 res. cancer cell line with a selectivity index (SI) in the range of 3.0-5.9.