X-ray structure of beta-cyclodextrin-2,7-dihydroxy-naphthalene.4.6 H(2)O: an unusually distorted macrocycle

The inclusion complex beta-cyclodextrin.2,7-dihydroxynaphthalene.4.6 H(2)O crystallized in the monoclinic space group P2(1), with a=14.082(3), b=19.079(4), c=12.417(3) A, beta=109.28(3) degrees, V=3149.0(11) A(3), and Z=2. An X-ray study performed at room temperature shows that the crystal packing is of the herringbone type with one 2,7-dihydroxynaphthalene included completely in the beta-CD cavity, its long axis being oriented along the beta-CD molecular axis, and 4.6 water molecules are placed in the interstitial space. The beta-CD macrocycle is elliptically distorted, and the guest molecule is held in the hydrophobic beta-CD cavity by C-H...O and C-H...pi interactions.