13C NMR spin–lattice relaxation and 13C–{1H} nuclear Overhauser measurements were performed on the encapsulation complex between [2.2]paracyclophane and a dimeric capsule known as the hydroxy ‘softball.’ The data were analyzed using the formalism for an isotropically diffusing sphere. The binding constant for the complex is (3.5±0.5)×103 l mol-1 in CDCl3 at 295 K. The average dipole–dipole relaxation time is 0.45±0.04 s for the CH vectors of the encapsulated [2.2]paracyclophane and 0.30±0.03 s for the skeleton of the hydroxy ‘softball.’ The correlation time for the skeleton of the hydroxy ‘softball’ is 2.7×10-10 s. The corresponding correlation time for the encapsulated [2.2]paracyclophane is calculated to be 1.2×10-10 s. This results in an average dynamic coupling constant, χ, of 0.47, indicating shape complementarity and correlated motion between the hydroxy ‘softball’ and the [2.2]paracyclophane.
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Hilmersson et al. (1998) studied this question.