Ruthenium-Cyclopentadienyl-Cycloparaphenylene Complexes: Sizable Multicharged Cations Exhibiting High DNA-Binding Affinity and Remarkable Cytotoxicity.

Two novel sizable multicharged cationic complexes, of the formulae [( η 6 --[12]CPP)[Ru( η 5 --Cp)] 12 ]Χ 12 and [( η 6 --[11]CPP)[Ru( η 5 --Cp)] 11 ]Χ 11 , CPP = cycloparaphenylene, Cp = cyclopentadienyl, X = [PF 6 ] - , ( 1 ), ( 3 ) and [Cl] - , ( 2 ), ( 4 ), were synthesized and characterized using NMR techniques, high-resolution mass spectrometry, and elemental analyses. Complexes ( 1 ) and ( 3 ) were stable in acetone and acetonitrile solutions over 48 h. In contrast, the water-soluble ( 2 ) and ( 4 ) begin to decompose in aqueous media after 1 h, due to the [Cl] - tendency for nucleophilic attack on ruthenium of the {Ru( η 5 --Cp)} units. Fluorescence quenching experiments conducted during the stability window of ( 2 ) with the d(5'-CGCGAATTCGCG-3') 2 -EtBr adducts revealed remarkably high values for K sv = 1.185 × 10 4 ± 0.025 M -1 and K b = 3.162 × 10 5 ± 0.001 M -1 . Furthermore, the cytotoxic activity of ( 2 ) against A2780, A2780res, and MCF-7 cancer cell lines shows that it is highly cytotoxic with IC 50 values in the range of 4.76 ± 1.85 to 16 ± 0.81 μΜ.