Finbloom, J.A., et al., Rotaxane-mediated suppression and activation of cucurbit[6]uril for molecular detection by (129)Xe hyperCEST NMR. Chem Commun (Camb), 2016. 52(15): p. 3119-22.
http://www.ncbi.nlm.nih.gov/pubmed/26795714
We report a method for blocking interactions between (129)Xe and cucurbit[6]uril (CB6) until activation by a specific chemical event. We synthesized a CB6-rotaxane that allowed no (129)Xe interaction with the CB6 macrocycle component until a cleavage event released the CB6, which then produced a (129)Xe@CB6 NMR signal. This contrast-upon-activation (129)Xe NMR platform allows for modular synthesis and can be expanded to applications in detection and disease imaging.