Aggregation-induced emission cyclometallated Iridium(III) complex for multi-photon FLIM imaging-guided photodynamic therapy

Cyclometallated iridium(III) complexes have unique photophysical properties that turn them into promising photosensitizers and potential fluorescence lifetime imaging probes. Herein, we developed a novel cyclometallated iridium(III) complex (Ir–OH) with aggregation-induced emission (AIE) properties for FLIM imaging-guided photodynamic therapy. Studies on photophysical properties show that Ir–OH exhibits excellent fluorescence response to in situ mitochondrial viscosity with varied lifetime. In addition, Ir–OH shows satisfactory multiphoton absorption properties in the near-infrared region (Two-photon: 700–800 nm; Three-photon: 1150–1450 nm). More importantly, changes in mitochondrial viscosity during photodynamic processes can be quantified in real-time by FLIM. Thus, our work illustrates that cyclometallated iridium(III) complexes can simultaneously induce and precisely detect microenvironmental changes at the subcellular level using FLIM, leading to self-reporting PDT outcomes.