Phosphorogenic dipyrrinato-iridium(III) complexes as photosensitizers for photodynamic therapy

Abstract

We have designed and synthesized a family of Ir(III) metal complexes coordinated with two cyclometalated bisfluorophenylpyridine ligands and an ancillary dipyrromethene which is functionalized with a mesityl group (Ir(dipy)-1), an α-chloroacetyl ester (Ir(dipy)-2) or a chain containing an ammonium cation (Ir(dipy)-3). The Ir (III) complexes feature a high triplet state population enabling red phosphorescence and efficient singlet oxygen generation. Ir(dipy)-2 and Ir(dipy)-3 are demonstrated to stain cells in both one-photon and two-photon confocal imaging. Moreover, Ir(dipy)-2 and Ir(dipy)-3 produce ROS in cells upon irradiation, inducing cell death by apoptosis. Colocalization studies in SK-Mel-103 cells show that Ir(dipy)-3 is partially accumulated in mitochondria and induces upon irradiation a disruption in their morphology. Overall our studies demonstrate that the prepared Ir(III) act as photosensitizers able to kill cells under irradiation, being suitable candidates for photodynamic therapy applications.