Anticancer activity of large metalla-assemblies built from half-sandwich complexes

A series of octanuclear p-cymene ruthenium and pentamethylcyclopentadienyl rhodium and iridium metalla-assemblies has been prepared from tetrapyridyl porphyrin (tpp) panels and the corresponding dinuclear clips, (η6-MeC6H4Pri)2Ru2(μ4-C6HRO4)Cl2 (R = C11H23) and (η5-C5Me5)2M2(μ4-C6HRO4)Cl2 (M = Rh, Ir). All complexes were isolated in good yield as their triflate salts, (η6-MeC6H4Pri)8Ru8(μ4-tpp)2(μ4-C6HRO4)4CF3SO38 (1), (η5-C5Me5)8Rh8(μ4-tpp)2(μ4-C6HRO4)4CF3SO38 (2) and (η5-C5Me5)8Ir8(μ4-tpp)2(μ4-C6HRO4)4CF3SO38 (3), and fully characterized by spectroscopic methods. The antiproliferative activity of the complexes was evaluated on the cancerous (MCF-7, B16 and A549) and non-cancerous (NIH 3T3) cell lines, showing in all cases IC50 values around 0.1 μM. Further biological studies suggest that apoptosis is induced by the complexes and that interaction with DNA can be in part responsible for the high cytotoxicity.