DYNAMIC MOLECULAR RECOGNITION IN SOLIDS - A SYNOPTIC APPROACH TO STRUCTURE DETERMINATION IN P-TERT-BUTYLCALIX[4]ARENE-TOLUENE

Materials in which weak molecular recognition plays a part often are d isordered to an extent that hampers the derivation of reliable structu ral data, Modelling the detailed structure then cannot be done in a cr itical fashion, so that in many cases the molecular recognition proces s itself is not understood very well, Using solid-state NMR methods al ong with newly obtained crystallographic data, we show that p-tert-but ylcalix[4]arene-toluene is a fluxional guest-host material at room tem perature, The new structural model refines down to an R-value of 0.046 instead of the 0.092 value obtained for a model based only on crystal lographic data, Problems with a difficult-to-understand disorder invol ving the tert-butyl groups are resolved, and a number of previously un known structural and dynamical features regarding the nature of the in serted toluene become apparent, Crystal data for C12.75H16O at 290 K: tetragonal P4/n, a = 12.7725(2), c = 13.8068(5) Angstrom, D-c = 1.089 g cm(-3), Z = 8, 1385 observed data I > 2.5 sigma (I), R = 0.046.