Synthesis, Molecular Structure, and Anticancer Activity of Cationic Arene Ruthenium Metallarectangles

Synthesis, Characterization and Anticancer Activity of Porphyrin-Containing Organometallic Cubes

Self‐assembly of 5,10,15,20‐tetra(4‐pyridyl)porphyrin (tpp‐H2) and 5,10,15,20‐tetra(4‐pyridyl)porphyrin‐M(ii) (M = Ni (tpp‐Ni); Zn (tpp‐Zn)) tetradentate panels with the dinuclear p‐cymene ruthenium clips [Ru2(p-cymene)2(C2O4)Cl2] and [Ru2(p-cymene)2(C6H2O4)Cl2] (C2O4 = oxalato; C6H2O4 = 2,5‐dioxydo‐1,4‐benzoquinonato) affords the cationic organometallic cubes: [Ru8(p-cymene)8(tpp‐H2)2(C2O4)4]8+ (1); [Ru8(p-cymene)8(tpp‐Ni)2(C2O4)4]8+ (2); [Ru8(p-cymene)8(tpp‐Zn)2(C2O4)4]8+ (3); [Ru8(p-cymene)8(tpp‐H2)2(C6H2O4)4]8+ (4); [Ru8(p-cymene)8(tpp‐Ni)2(C6H2O4)4]8+ (5); and [Ru8(p-cymene)8(tpp‐Zn)2(C6H2O4)4]8+ (6). In addition, the new dinuclear arene ruthenium 2,5‐dioxydo‐1,4‐benzoquinonato clips [Ru2(indane)2(C6H2O4)Cl2] (7) and [Ru2(nonylbenzene)2(C6H2O4)Cl2] (8) react in methanol with tpp‐H2 in the presence of silver triflate to afford the corresponding cationic cubes [Ru8(indane)8(tpp‐H2)2(C6H2O4)4]8+ (9) and [Ru8(nonylbenzene)8(tpp‐H2)2(C6H2O4)4]8+ (10) respectively. All cationic metalla‐cubes were isolated as triflate salts and characterized by NMR, infrared, electro‐spray mass spectrometry and UV‐visible spectroscopy. Moreover, the formation of unsymmetrical metalla‐cubes built using a mixture of the different porphyrin panels during the self‐assembly of the 2,5‐dioxydo‐1,4‐benzoquinonato metalla‐cubes, [Ru8(p-cymene)8(tpp‐H2)(tpp‐Ni)(C6H2O4)4]8+ (11), [Ru8(p-cymene)8(tpp‐H2)(tpp‐Zn)(C6H2O4)4]8+ (12), and [Ru8(p-cymene)8(tpp‐Ni)(tpp‐Zn)(C6H2O4)4]8+ (13), was studied by electro‐spray mass spectrometry. The cytotoxicities of all metalla‐cubes as well as the mixtures containing the unsymmetrical metalla‐cubes were established on human ovarian A2780 and A2780cisR cancer cell lines. All symmetrical compounds are equally cytotoxic (IC50 = 7–15 μM) (IC50 being the drug concentration necessary for 50% inhibition of cell viability) against both A2780 and cisplatin‐resistant A2780cisR cancer cells, with stronger cytotoxicities (IC50 = 2–5 μM) observed for the mixtures containing the unsymmetrical 2,5‐dioxydo‐1,4‐benzoquinonato metalla‐cubes.

Arene ruthenium complexes as anticancer agents

Neutral or cationic arene ruthenium complexes providing both hydrophilic as well as hydrophobic properties due to the robustness of the ruthenium-arene unit hold a high potential for the development of metal-based anticancer drugs. Mononuclear arene ruthenium complexes containing P- or N-donor ligands or N,N-, N,O- or O,O-chelating ligands, dinuclear arene ruthenium systems with adjustable organic linkers, trinuclear arene ruthenium clusters containing an oxo cap, tetranuclear arene ruthenium porphyrin derivatives that are photoactive, as well as hexanuclear ruthenium cages that are either empty or filled with other molecules have been shown to be active against a variety of cancer cells.