Arene Ruthenium(II) Complexes with the Bioactive ortho-Hydroxydibenzoylmethane Ligand: Synthesis, Structure and Cytotoxicity

The synthesis of a series of neutral arene ruthenium(II) complexes (arene = p-cymene, hexamethylbenzene and benzene) [(arene)Ru(HDB)Cl] derived from the reaction of the appropriate arene ruthenium(II) dimers and ortho-hydroxydibenzoylmethane (HDBH), a potent inhibitor of cell proliferation, is described. In addition, related ionic complexes [(arene)Ru(HDB)(PTA)][SO3CF3] (PTA = 1,3,5-triaza-7-phosphaadamantane) have been prepared. The structure of three complexes has been confirmed by X-ray crystallography. The cytotoxicity of the complexes has been evaluated against human ovarian carcinoma cells (A2780 and A2780cisR), as well as against non-tumorigenic human embryonic kidney (HEK293) cells and compared to the free ligand and cisplatin. Two of the complexes, i.e. from the first series with p-cymene and hexamethylbenzene, display relevant activities against the cisplatin resistant A2789cisR cancer cell line.