Anticancer activity of osmium metalla-rectangles

Abstract

A series of cationic metalla-rectangles of the general formula [(p-cymene)₄Os₄(OO∩OO)₂(N∩N)₂]⁴⁺ have been obtained in methanol from the dinuclear arene osmium precursors [(p-cymene)₂Os₂(OO∩OO)₂Cl₂] (OO∩OO = 2,5-dioxydo-1,4-benzoquinonato (dhbq), 2,5-dichloro-1,4-benzoquinonato (dcbq)) by reaction with bipyridine linkers (N∩N = 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene) in the presence of AgCF₃SO₃. All complexes were isolated as triflate salts and characterised by NMR, IR and UV-visible spectroscopy. The cytotoxicities of the dinuclear and tetranuclear osmium complexes were established using ovarian A2780 cancer cell lines. The most active metalla-rectangle, [(p-cymene)₄Os₄(dhbq)₂(4,4′-bipyridine)₂]⁴⁺, shows an IC₅₀ value of 5.7 μM (comparable to cisplatin) against A2780 cancer cells and 7.5 μM against the cisplatin resistant A2780cisR cells.