Quinoid‐Engineered Small‐Molecule Photothermal Agents Ignite Deep‐Tissue Tumor Photothermal‐Immunotherapy Driven by 1064 nm Light

Abstract Developing small‐molecule photothermal agents (PTAs) with strong absorption in the NIR‐II window (1000‐1700 nm) remains a significant challenge for effective photothermal therapy (PTT) of deep‐seated tumors. Here, a quinoidal engineering strategy is presented to construct a 1064 nm‐excitable small‐molecule PTA, termed BPT‐FNC, which features a highly quinonized naphthalenedione‐based terminal group, an open‐shell singlet diradical ground state, and thermally accessible triplet states. These electronic characteristics endow BPT‐FNC with pronounced NIR‐II absorption, promoting efficient nonradiative decay and high photothermal conversion efficiency. Under 1064 nm laser irradiation at clinically permissible power densities, BPT‐FNC nanoaggregates enable effective deep‐tissue PTT. Notably, it also triggers pyroptosis and promotes the release of immunogenic damage‐associated molecular patterns (DAMPs), thereby inducing immunogenic cell death (ICD) and stimulating systemic anti‐tumor immune responses. This work showcases a rational molecular design paradigm that integrates quinoidal structure, NIR‐II photothermal functionality, and immune activation, offering a promising platform for synergistic photothermal‐immunotherapy in precision cancer treatment.