Donor–Acceptor Modulating of Ionic AIE Photosensitizers for Enhanced ROS Generation and NIR‐II Emission

Abstract Photosensitizers (PSs) with aggregation‐induced emission (AIE) characteristics are competitive candidates for bioimaging and therapeutic applications. However, their short emission wavelength and nonspecific organelle targeting hinder their therapeutic effectiveness. Herein, a donor–acceptor modulation approach is reported to construct a series of ionic AIE photosensitizers with enhanced photodynamic therapy (PDT) outcomes and fluorescent emission in the second near‐infrared (NIR‐II) window. By employing dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) and indolium (In) as the strong donor and acceptor, respectively, the compound DTP‐In exhibits a substantial redshift in absorption and fluorescent emission reach to NIR‐II region. The reduced energy gap between singlet and triplet states in DTP‐In also increases the reactive oxygen species (ROS) generation rate. Further, DTP‐In can self‐assemble in aqueous solutions, forming positively charged nanoaggregates, which are superior to conventional encapsulated nanoparticles in cellular uptake and mitochondrial targeting. Consequently, DTP‐In aggregates show efficient photodynamic ablation of 4T1 cancer cells and outstanding tumor theranostic in vivo under 660 nm laser irradiation. This work highlights the potential of molecular engineering of donor–acceptor AIE PSs with multiple functionalities, thereby facilitating the development of more effective strategies for cancer therapy.