Terpenes Show Nanomolar Affinity and Selective Binding with Cucurbit[8]uril

Eucalyptol, fenchyl alcohol, and geranylamine were tested for the binding to cucurbit[8]uril. Nanomolar affinities were found, giving rise to a highly selective binding of the terpenes by cucurbit[8]uril when compared to the smaller cucurbit[7]uril. This was rationalized with a better size fit with the larger macrocycle. These notions were supported by the calculation of the packing coefficient and NMR measurements of the free and complexed terpenes. The binding process is mainly enthalpically driven, which is associated with the release of high‐energy water.