Uncommon Supramolecular Phosphorescence-Capturing Assembly Based on Cucurbit[8]uril-Mediated Molecular Folding for Near-Infrared Lysosome Imaging

The construction of highly effective phosphorescence energy transfer capturing system still remains great challenge in aqueous phase. Herein, a high-efficiency supramolecular purely organic room temperature phosphorescence (RTP)-capturing system via a secondary assembly strategy by taking advantage of cucurbit[8]uril (CB[8]) and amphiphilic calixarene (SC4AH) is reported. Comparing with free bromonaphthalene-connected methoxyphenyl pyridinium salt (G), G⊂CB[8] exhibits an emerging RTP emission peak at 530 nm. Moreover, G⊂CB[8] further interacts with SC4AH to form the ternary assembly G⊂CB[8]  @  SC4AH accompanied by remarkably enhanced RTP emission. Interestingly, RTP-capturing systems with delayed near-infrared (NIR) emissive performance (635, 675 nm) are feasibly acquired by introducing Nile Red (NiR) or Nile Blue (NiB) as the acceptor into hydrophobic layer of G⊂CB[8] @ SC4AH, possessing ultrahigh antenna effects (352.9, 123.5) at a high donor/acceptor ratio (150:1, 300:1). More importantly, cell experiments indicate that G⊂CB[8]  @  SC4AH/NiB not only hold low cytotoxicity but also can successfully realize NIR lysosome-targeted imaging of A549 cancer cells. This RTP-capturing system of delayed NIR emission via multistage assembly strategy offers a new approach for NIR imaging in living cells.