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Together they are strong. The combination of fast MAS solid‐state NMR experiments and ab initio calculations on 1H chemical shifts allows the resolution and assignment of guest and host protons in a supramolecular complex (as shown here), provides information about motional processes, and identifies the specifics of intra‐ and intercomplex interactions.

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For the formation of the supramolecular complexes between the molecular tweezers 1 and 2 and the aromatic guests 3–5 the volumes of reaction ΔV were determined from the pressure dependence of the association constants K by the use of high‐pressure 1H NMR spectroscopy and the enthalpy ΔH and entropy ΔS of reaction from the temperature dependence of K. The small pressure dependence of K and, hence, the small variation of the reaction volumes around the zero value (ΔV ≈ 0 cm3 mol−1) clearly indicate that the contraction in volume resulting from the host–guest association is compensated for by the expansion in volume resulting from the desolvation of the free host and guest which has to proceed during the complexation. The association and desolvation are expected to have similar effects on ΔS compensating each other. The significant deviations of ΔS from the zero value are, however, good evidence that the size of ΔS not only depends on the processes mentioned above but moreover is influenced by other factors such as the conformational mobility of the guest molecule inside the receptor cavity. Copyright © 2002 John Wiley & Sons, Ltd.