Does Size Really Matter? The Steric Isotope Effect in a Supramolecular Host–Guest Exchange Reaction


  • This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, and the Division of Chemical Sciences, Geosciences, and Biosciences of the U.S. Department of Energy at LBNL under contract no. DE-AC02-05CH11231 and an NSF predoctoral fellowship to J.S.M. We thank M. D. Pluth for helpful discussions and Dr. Ulla Andersen for assistance with mass spectrometry experiments.


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Does size really matter? Inverse kinetic isotope effects of up to 11 % are observed in the guest-exchange process from a highly charged supramolecular host (see picture). While the observed isotope effects can be understood in terms of the smaller steric requirements of deuterium, they are more fully explained in terms of coupling of the host aperture dilation with the guest C[BOND]H/D vibrational modes.