Buchwald–Hartwig aminated pyrene-heterocycles with host–guest-enhanced NIR phosphorescence: DFT-guided design toward breast cancer imaging probes

Organic near-infrared room-temperature phosphorescent (NIR-RTP) materials face fundamental challenges from the energy gap law, limiting emission efficiency of wavelengths >600 nm and long-lived triplet states. We report the rational design of Buchwald-Hartwig aminated pyrene-heterocycles embedded in benzophenone host matrices, achieving unprecedented NIR phosphorescence with ultralong lifetimes. The DFT-guided optimization reveals that the heteroatom-induced spin-orbit coupling modulation and host-mediated suppression of non-radiative transitions both overcome traditional efficiency bottlenecks. The O-pyrene/benzophenone (O-pyrene/BPO) system exhibits dual-peak emissions at 609/666 nm with lifetimes up to 275.56 ms-the reported highest value for organic NIR-RTP materials-while the S-pyrene/BPO demonstrates a 243.31 ms lifetime at 613 nm. Crucially, phenoxazine incorporation lowers the T₁ energy level without compromising ISC efficiency, which is validated by SOC calculations. Host-guest confinement also restricts molecular vibrations. This work provides a research foundation for establishing the "heteroatom engineering-host rigidity" paradigm, helpful in the development of therapeutic and diagnostic imaging probes.