Near‐Infrared Multiple‐Resonance Polycyclic Aromatic Hydrocarbon as Type I Photosensitizer Toward High‐Performance Synergistic Phototherapy

Abstract Type I photosensitization is of particular significance in the anaerobic tumor treatment. Nonetheless, the development of high‐performance type I photosensitizers (PSs) remains challenging, due to weak absorption and inefficient intersystem crossing (ISC) progress. Herein, an effective approach toward a near‐infrared (NIR) type I PS ( NIR‐BN ) is demonstrated using a boron/nitrogen‐embedded polycyclic aromatic hydrocarbon with multiple‐resonance (MR) character, for the first time. A small singlet‐triplet splitting (Δ E ST = 0.09 eV) and high molar extinction coefficient (3.3 × 10 4 M −1 cm −1 ) of the NIR MR‐configured PS supports an efficient ISC for the triplet sensitization. The distorted molecular configurations induce multi‐model structural relaxations after the optical excitation, resulting in a remarkable photothermal conversion efficiency exceeding 50% for NIR‐BN nanoparticles. Of note, the nanoparticles are capable of generating the highly toxic superoxide anion radical (O 2 •− ) under 660 nm laser irradiation, benefiting from the vigorous intramolecular dihedral angle vibrations in the excited states. Consequently, the biocompatible PS demonstrates superior performance for in vivo synergistic photodynamic and photothermal therapies.