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

Abstract

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)₄][CF₃SO₃]₈ (1), [(η⁵-C₅Me₅)₈Rh₈(μ₄-tpp)₂(μ₄-C₆HRO₄)₄][CF₃SO₃]₈ (2) and [(η⁵-C₅Me₅)₈Ir₈(μ₄-tpp)₂(μ₄-C₆HRO₄)₄][CF₃SO₃]₈ (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.