Luminescent iminophosphorane gold, palladium and platinum complexes as potential anticancer agents

A series of coordination gold(iii), palladium(ii), and platinum(ii) complexes with a luminescent iminophosphorane ligand derived from 8-aminoquinoline [Ph₃P=N-C₉H₆N] (1) have been synthesized and structurally characterized. The coordination palladium(ii) and platinum(ii) compounds can evolve further, under appropriate conditions, to give stable cyclometalated endo species [M{κ³-C,N,N-C₆H₄(PPh₂=N-8-C₉H₆N)}Cl] (M = Pd, Pt) by C-H activation of the phenyl group of the PPh₃ fragment. Iminophosphorane 1 and the new metallic complexes are luminescent in DMSO or DMSO-H₂O (1:1 mixture) solutions at RT. The compounds have been evaluated for their antiproliferative properties in a human ovarian cancer cell line (A2780S), in human lung cancer cells (A549) and in a non-tumorigenic human embryonic kidney cell line (HEK-293T). Most compounds have been more toxic to the ovarian cancer cell line than to the non-tumorigenic cell line. The new complexes interact with human serum albumin (HSA) faster than cisplatin. Studies of the interactions of the compounds with DNA indicate that, in some cases, they exert anticancer effects in vitro based on different mechanisms of action with respect to cisplatin.