Organoruthenium complexes, of the form of [(η6-arene)RuII(YZ)X]+ (Inorg. Chem., 2008, 47, 11470–11486, DOI: 10.1021/ic801361m), are increasingly being studied for use in medicine. The arene is usually a phenyl derivative, YZ is usually a chelating ligand, and X is usually a halide, such as Cl. This type of compound has been studied to be used against cancer. Using the exmple with x=Cl, the Ru-Cl bond can be hydrolyzed and then act as a binding site for DNA, while the arene is a hydrophobic site of the complex, which protects the RuII from oxidizing to RuIII. The chelating ligand provides stability and as the size of the arene increases, the cytotoxicity to the cancer cells increases.
The complex pictured, [(η6-Tha)Ru(bipy(OH)O)(9-EtG-N7)][PF6], contains the bipy(OH)O chelating ligand, and showed a large increase in the cytotoxicity toward human ovarian and human lung cancer cells. The tetrahydroanthracene (tha) “faces” protect the RuII against oxidation. Examining the crystal structures shows CH/π interactions between the bipyridine ligand and tetrahydroanthracene are important for stabilizing the interaction between [(η6-Tha)Ru(bipy(OH)O)(9-EtG-N7)][PF6] and proteins. Although this complex was not tested for activity against ovarian and lung cancer cell lines, A2780 and A549 respectively, other complexes with the tetrahydroanthracene (tha) moity were tested and proved to be most active against the ovarian cancer cell line. Ruthenium complexes such as [(η6-Tha)Ru(bipy(OH)O)(9-EtG-N7)][PF6] have been shown to mimic iron binding in the human body and the ligand, bipy(OH)O, helps the complex bind to DNA in ways that another antitumor compound, cisplatin, cannot. This shows extreme promise as a therapeutic as cisplatin tumor toxicity is not as high with some types of tumors.