Journal of the American Chemical Society
ARTICLE
of the U.S. Department of Energy at LBNL under Contract No.
DE-AC02-05CH11231 and an NSF predoctoral fellowship to
J.S.M.
(28) Biros, S. M.; Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc.
2007, 129, 12094–12095.
(29) Hastings, C. J.; Pluth, M. D.; Biros, S. M.; Bergman, R. G.;
Raymond, K. N. Tetrahedron 2008, 64, 8362–8367.
(30) Pluth, M. D.; Johnson, D. W.; Szigethy, G.; Davis, A. V.; Teat,
S. J.; Oliver, A. G.; Bergman, R. G.; Raymond, K. N. Inorg. Chem. 2009,
48, 111–120.
’ REFERENCES
(31) Fiedler, D.; Leung, D. H.; Bergman, R. G.; Raymond, K. N. Acc.
Chem. Res. 2005, 38, 349–358.
(32) Pluth, M. D.; Bergman, R. G.; Raymond, K. N. Acc. Chem. Res.
2009, 42, 1650–1659.
(33) Hastings, C. J.; Pluth, M. D.; Bergman, R. G.; Raymond, K. N.
J. Am. Chem. Soc. 2010, 132, 6938–6940.
(34) Brown, C. J.; Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc.
2009, 131, 17530–17531.
(1) Ditchfield, R. Mol. Phys. 1974, 27, 789–807.
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(35) For monocationic guests, interior-exterior guest exchange in
host 1 is typically much slower than the NMR time scale. For example,
+
the guest exchange rate at room temperature in D2O solution for NEt4
is ∼0.006 sÀ1 and ∼15 sÀ1 for NMe3Bn+. This is significantly slower
1
than the time scale for averaging of interior/exterior guest H NMR
resonances (∼1000 sÀ1).
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Soc. 2010, 132, 1182–1183.
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(10) Patel, D. G.; Paquette, M. M.; Kopelman, R. A.; Kaminsky, W.;
Ferguson, M. J.; Frank, N. L. J. Am. Chem. Soc. 2010, 132, 12568–12586.
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(13) Bal, D.; Kraska-Dziadecka, A.; Gryff-Keller, A. J. Org. Chem.
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(43) It should be noted that encapsulation within host 1 is respon-
sible for switching the relative ordering of the CH2 and CH3 resonances
for PEt4 . The 1H NMR chemical shifts of PEt4+ in free D2O solution
+
(referenced to residual HDO) are as follows: 2.19 ppm (CH2) and 1.21
ppm (CH3).
(18) Ferrer, M.; Mounir, M.; Rossell, O.; Ruiz, E.; Maestro, M. A.
Inorg. Chem. 2003, 42, 5890–5899.
(44) In D2O, CD3OD, and DMSO-d6, guest 2 is quantitatively
encapsulated and its 1H NMR resonances are shifted upfield as would be
expected; only in DMF-d7 is the downfield chemical shift observed. This
is why DMF is chosen as the as the solvent dielectric for subsequent
calculations exploring the chemical shift of PMe4 during guest
exchange.
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Chane-Ching, K.; Lacaze, P. J. Phys. Org. Chem. 2007, 20, 30–43.
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+
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(24) Ajami, D.; Iwasawa, T.; Rebek, J. Proc. Natl. Acad. Sci. U.S.A.
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(25) For recent examples, see:(a) Mal, P.; Breiner, B.; Rissanen, K.;
Nitschke, J. R. Science 2009, 324, 1697–1699. (b) Hatakeyama, Y.;
Sawada, T.; Kawano, M.; Fujita, M. Angew. Chem., Int. Ed. 2009,
48, 8695–8698. (c) Durola, F.; Rebek, J., Jr. Angew. Chem., Int. Ed.
2010, 49, 3189–3191. (d) Pluth, M. D.; Fiedler, D.; Mugridge, J. S.;
Bergman, R. G.; Raymond, K. N. Proc. Natl. Acad. Sci. U.S.A. 2009,
106, 10438–10443. (e) Ferrand, Y.; Kendhale, A. M.; Kauffmann, B.;
Grꢁelard, A.; Marie, C.; Blot, V.; Pipelier, M.; Dubreuil, D.; Huc, I. J. Am.
Chem. Soc. 2010, 132, 7858–7859. (f) Shoji, Y.; Matsuo, T.; Hashizume,
D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2010,
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Wallingford CT, 2009.
(46) 1H NMR chemical shifts for the aromatic host protons were not
calculated at a higher level of theory both to limit computational cost and
because the chemical shifts of these protons are not expected to provide
useful structural information. The chemical shifts for the host protons
change only slightly upon guest encapsulation (0.0À0.1 ppm) and may
also be affected by exterior guest binding.
(47) OriginPro 8.1; OriginLab Corporation: Northampton, MA
01060 USA.
(48) The solid-state coordinates could not be used directly. Since
X-ray diffraction experiments underestimate CÀH bond lengths by
∼0.1 Å (see:Churchill, M. W. Inorg. Chem. 1973, 12, 1213–1214), using
these atom coordinates in the GIAO calculations gives 1H NMR
chemical shifts that are 2À4 ppm different from experimental values.
To solve this problem, the encapsulated guest molecules were mini-
mized (OPLS 2005) with the host atoms frozen, allowing guest CÀH
bonds to assume more accurate lengths. During these minimizations, the
guest conformation and orientation within the host were negligibly
altered.
(26) Caulder, D. L.; Powers, R. E.; Parac, T. N.; Raymond, K. N.
Angew. Chem., Int. Ed. 1998, 37, 1840–1843.
(27) Parac, T. N.; Caulder, D. L.; Raymond, K. N. J. Am. Chem. Soc.
1998, 120, 8003–8004.
(49) MacroModel; Schrodinger: New York, NY, 2010.
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dx.doi.org/10.1021/ja202254x |J. Am. Chem. Soc. 2011, 133, 11205–11212