Abstract:

The authors detd. the values of Ka for a wide range of host-guest complexes of cucurbit[n]uril (CB[n]), where n = 6-8, using 1H NMR competition expts. referenced to abs. binding consts. measured by UV/visible titrn. The larger homologs-CB[7] and CB[8]-individually maintain the size, shape, and functional group selectivity that typifies the recognition behavior of CB[6]. The cavity of CB[7] is found to effectively host trimethylsilyl groups. Remarkably, the values of Ka for the interaction of CB[7] with adamantane derivs. exceeds 1012 M-1!. The high levels of selectivity obsd. for each CB[n] individually is also obsd. for the CB[n] family collectively. That is, the selectivities of CB[6], CB[7], and CB[8] toward a common guest can be remarkably large. The high levels of selectivity obsd. individually and collectively for the CB[n] family renders them prime components for the prepn. of functional biomimetic self-sorting systems.