Two‐Photon Excited Near‐Infrared Phosphorescence Based on Secondary Supramolecular Confinement

Organic phosphorescence materials have received wide attention in bioimaging for bio‐low toxicity and large Stokes. Herein, a design strategy to achieve near‐infrared (NIR) excitation and emission of organic room‐temperature phosphorescence through two‐stage confinement supramolecular assembly is presented. Via supramolecular macrocyclic confinement, the host–guest complexes exhibit phosphorescence with two‐photon absorption (excitation wavelength up to 890 nm) and NIR emission (emission wavelength up to 800 nm) in aqueous solution, and further nano‐confinement assembly significantly strengthens phosphorescence. Moreover, the nano‐assemblies possess color‐tunable luminescence spanning from the visible to NIR regions under different excitation wavelengths. Intriguingly, the prepared water‐soluble assemblies maintain two‐photon absorption and multicolor luminescence in cells or vivo. A multi‐stage assembly strategy involving macrocyclic confinement and nano‐confinement is reported, which induces and enhances guests’ phosphorescence with two‐photon absorption and NIR emission. Moreover, the assemblies possess excitation‐dependent emission properties, in which luminescence covers the visible and NIR regions under different excitation wavelengths.