Design and synthesis of a compact phenoxazine-indolizine fluorophore with shortwave infrared emission beyond 1300 nm.

We report a class of phenoxazine-based organic small-molecule fluorophores synthesized in four steps, achieving peak emission beyond 1300 nm with molecular weights <600 Da, among the lowest reported to date. This compact and concise synthetic strategy provides new fluorophores for the shortwave infrared (SWIR) region, which offer potential feasibility for overcoming metabolic barriers and provide a structurally compact scaffold for future deep-tissue imaging applications.