Synthesis, photophysical and anticancer properties of mitochondria-targeted phosphorescent cyclometalated iridium(III) N-heterocyclic carbene complexes

Abstract Metal N-Heterocyclic carbene (NHC) complexes are expected to be new opportunities for the development of anticancer metallodrugs. In this work, two near-infrared (NIR) emitting iridium(III)-NHC complexes Ir1 and Ir2 have been explored as mitochondria-targeted anticancer and photodynamic agents. These complexes are more cytotoxic than cisplatin against the cancer cells screened, and display higher cytotoxicity in the presence of 450 nm and 630 nm LED light. Colocalization and quantitative studies indicated that these complexes could specially localize to mitochondria. Mechanism studies show that these complexes increase intracellular reactive oxygen species (ROS) level, reduce mitochondrial membrane potential (MMP) and induce some degree of early apoptosis. Further studies found that Ir1could induce mitophagy at dark and necrocytosis under the irradiation of 630 nm LED light. The in vitro and in vivo photoxicity studies revealed that Ir1 is a promising photodynamic therapy (PDT) agent and could significantly inhibit tumor growth.