The interaction of xenon with cucurbituril, a synthetic receptor, in aqueou
s solutions is investigated by Xe-129 and H-1 NMR spectroscopy. Xenon is re
versibly trapped into the cavity to form a 1:1 host-guest complex. The exch
ange between the free and the complexed xenon is slow on the Xe-129 NMR che
mical shift time scale but fast on the H-1 NMR chemical shift time scale. T
he apparent association constant of xenon for cucurbituril can be obtained
from analysis of the H-1 spectra and is estimated to be around 200 M-1 at 2
98 K. Interestingly, even though no H-bonding or electrostatic interactions
play a role in the stabilisation of the complex, its stability is comparab
le to the stability of cucurbituril complexes with certain aryl- and alkyl-
ammonium ions.