An iridium(III)-palladium(II) metal−organic cage for efficient mitochondria-targeted photodynamic therapy

Abstract An Ir8Pd4-heteronuclear metal − organic cage (MOC-51) was assembled from bipodal metalloligand [Ir(ppy)2(qpy)(BF4)] (qpy = 4,4':2',2'':4'',4'''-quaterpyridine; ppy = 2-phenylpridine) with Pd(II) salt. The cubic barrel shaped MOC shows one-photon and two-photon excited deep-red emission, as well as large singlet oxygen quantum yields under visible light irradiation, therefore exhibiting great potentials in organelles-targeted cell imaging and photodynamic therapy (PDT). Compared with the Ir(III) metalloligand, the Ir8Pd4-MOC showed less dark toxicity and higher mitochondria-targeting efficiency. The localization in mitochondria overcomes the limitation of short lifetime and diffusion distance of ROS in cell, thus improved PDT effect can be obtained in low light dose usage of the MOC. This study presents the first case of Ir-based metal-organic cages for bio-applications in successful integration of imaging diagnosis and photodynamic therapy