Influence of the Spacer Length on the in Vitro Anticancer Activity of Dinuclear Ruthenium−Arene Compounds

Water-soluble dinuclear Ru−arene complexes were synthesized and found to exert promising cytotoxic effects in human cancer cells, which could be increased to an IC 50 of 0.29 μM by increasing the spacer length between the metal centers. Cytotoxicity could be correlated with lipophilicity (log P values) and water solubility. The most potent dinuclear compound, 1,12-bis{chlorido[3-(oxo-κ O )-2-methyl-4-pyridinonato-κ O4 ](η 6 - p -isopropyltoluene)ruthenium}dodecane, is at least 2−3 orders of magnitude more active than the mononuclear analogue chlorido[3-(oxo-κ O )-2-methyl-4-pyronato-κ O4 ](η 6 - p -isopropyltoluene)ruthenium.