Trinuclear half-sandwich Ru^II, Rh^III and Ir^III polyester organometallic complexes: Synthesis and in vitro evaluation as antitumor agents

Schiff base ligands obtained from the condensation of 4-aminophenylmethanol and either 2-pyridinecarboxaldehyde or salicylaldehyde were used to synthesise bidentate trimeric ester ligands. The trimeric ester ligands were used to prepare a new series of trinuclear polyester organometallic complexes by using the dimeric precursors, [Ru(η⁶-p-iPrC₆H₄Me)Cl₂]₂, [Rh(C₅Me₅)Cl₂]₂ or [Ir(C₅Me₅)Cl₂]₂. The Schiff base ligands act as bidentate donors to each metal. All compounds were characterised by NMR and IR spectroscopy, elemental analysis and EI/ESI mass spectrometry. Model mononuclear analogues were prepared, and the molecular structures of selected compounds were determined by single-crystal X-ray diffraction analysis. The mono- and trimeric ligands and the metal complexes were evaluated for inhibitory effects against the human ovarian cancer cell lines, A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant), and the model human skin fibroblast cell line, KMST-6. Polyester-containing trinuclear half-sandwich Ru^II, Rh^III and Ir^III complexes were prepared and characterised. The cytotoxicity was investigated for all compounds. Aqueous stability studies and interactions with model DNA 5′-GMP were performed for the most-active compounds.