Topological Engineering of NIR‐II Emissive Conjugated Oligomers With Unexpected Excited‐State Manifolds for Efficient Phototheranostics and Cancer Immunotherapy

Phototheranostic agents operating in the second near‐infrared (NIR‐II) window hold great potential for precision cancer therapy, yet the rational regulation of excited‐state processes to simultaneously optimize fluorescence and phototherapeutic performances remains a fundamental challenge. Herein, we report a topology‐driven excited‐state engineering strategy for constructing conjugated oligomers with tailored excited‐state manifolds and multi‐channel excitation dynamics. By precisely manipulating molecular topology, conjugated topological oligomers achieve enhanced light‐harvesting capability and optimized exciton utilization, thereby enabling synergistic regulation of excitation dynamics. Under 808 nm laser irradiation, nanoparticles (NPs) derived from TBT‐3 exhibit 2.8‐fold enhanced NIR‐II fluorescence brightness, 2.7‐fold improved photothermal performance, and 7.5‐fold increased total reactive oxygen species (ROS) generation compared with TBT‐1. In vivo studies demonstrate that TBT‐3 NPs enable high‐resolution NIR‐II fluorescence imaging and efficient tumor elimination. Moreover, TBT‐3‐mediated phototherapy induces immunogenic cell death and enhances antitumor immunity, leading to improved therapeutic efficacy when combined with anti‐PD‐1 immune checkpoint blockade. This work provides a molecular topology‐based strategy for manipulating excited‐state landscapes and establishes conjugated oligomers as versatile candidates for NIR‐II phototheranostics and cancer immunotherapy.