Macrocyclic Confined Purely Organic Room-Temperature Phosphorescence Three-Photon Targeted Imaging

摘要

A purely organic supramolecular assembly emitting three-photon room-temperature phosphorescence (RTP) is constructed from a macrocyclic host, cucurbit[8]uril (CB[8]), and 4-bromophenyl pyridine salt having an alkyl chain length of 6 or 12 carbon atoms (6C and 12C, respectively). Benefiting from macrocyclic host confined guests, the encapsulation of 12C and 6C in the CB[8] cavity results in three-photon absorption and subsequent near-infrared (NIR) phosphorescence emission. Notably, secondary assembly with sulfonated beta-cyclodextrin (SCD) further enhances the phosphorescence emission of the multilevel supramolecular assembly. NIR-delayed fluorescence via a light-harvesting phosphorescent energy transfer system is achieved by adding Nile blue as a substrate. Comparison of 12C/CB[8]/SCD and 6C/CB[8]/SCD shows that a long hydrophobic layer is more conducive to stabilizing NIR-delayed fluorescence emission. These findings indicate that multilevel supramolecular assemblies can be used for three-photon-excited NIR-delayed fluorescence and RTP imaging of cancer cells, which greatly expands the biological applications of pure organic RTP materials.

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