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 addn., 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) resp. All cationic metalla-cubes were isolated as triflate salts and characterized by NMR, IR, electro-spray mass spectrometry and UV-visible spectroscopy. Moreover, the formation of unsym. metalla-cubes built using a mixt. 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 mixts. contg. the unsym. metalla-cubes were established on human ovarian A2780 and A2780cisR cancer cell lines. All sym. compds. are equally cytotoxic (IC50=7-15μM) (IC50 being the drug concn. necessary for 50% inhibition of cell viability) against both A2780 and cisplatin-resistant A2780cisR cancer cells, with stronger cytotoxicities (IC50=2-5μM) obsd. for the mixts. contg. the unsym. 2,5-dioxydo-1,4-benzoquinonato metalla-cubes.