The crystal structure of the inclusion complex of cyclomaltoheptaose (beta-cyclodextrin) with 4-tert-butyltoluene.

The crystal of the 1:1 complex of 4-tert-butyltoluene with cyclomaltoheptaose (beta-cyclodextrin, beta CD) is triclinic P1 with a = 15.562(2), b = 15.564(4), c = 15.835(3) A, alpha = 102.11(2), beta = 102.15(1), gamma = 103.64(2) degrees, V = 3505(1) A3, and Z = 2. The two independent beta CD molecules in the asymmetric unit form a dimer by hydrogen bonding involving HO-3, which accommodates two molecules of the guest. The hydrophobic guests are enclosed completely in the beta CD cavities with the tert-butyl groups in the hydrophobic region beneath the primary hydroxyl groups. The aromatic rings have two orientations and their toluene methyl moieties could not be located but were calculated to be at the interface of the two monomers. The dimers form channels along the c axis. The inter-dimer space is filled with 17 molecules of water distributed over 25 sites. A dense network of hydrogen bonds is formed, involving the beta CD hydroxyl groups and water molecules.