Two novel BODIPY-Ru(ii) arene dyads enabling effective photo-inactivation against cancer cells

BODIPY (boron dipyrromethene) derivatives and Ru(ii) complexes are two types of functional compounds that have found wide applications in the fields of biology and medicine. We herein synthesized two new Ru(ii) arene complexes based on an iodized BODIPY-containing pyridine (py-I-BODIPY) ligand, [(p-cym)Ru(bpy)(py-I-BODIPY)](2+) (2) and [(p-cym)Ru(2-pydaT)(py-I-BODIPY)](2+) (3), where p-cym = para-cymene, bpy = 2,2'-bipyridine, and 2-pydaT = 2,4-diamino-6-(2-pyridyl)-1,3,5-triazine. The photophysical, photochemical and photobiological properties of 2 and 3 were compared with that of [(p-cym)Ru(bpy)(py-BODIPY)](2+) (1). While 1 undergoes efficient monodentate ligand dissociation upon visible light irradiation and therefore may photobind DNA as a potential photoactivated chemotherapy (PACT) agent, 2 and 3 can generate (1)O2 effectively and thus may serve as photosensitizers in photodynamic therapy (PDT). In electrophoresis experiments, 2 and 3 are even able to retard the mobility of plasmid DNA in the dark at high concentrations. More importantly, the cytotoxicities of 2 and 3 against human ovarian adenocarcinoma SKOV3 cells are enhanced about ten times under irradiation, leading to cytotoxicities more than one order of magnitude higher than that of cisplatin, demonstrating an efficient hybridization of the iodized BODIPY chromophore and the Ru(ii) arene complex.