X-ray structure of β-cyclodextrin-2,7-dihydroxy-naphthalene·4.6 H2O: an unusually distorted macrocycle

The inclusion complex β-cyclodextrin·2,7-dihydroxynaphthalene·4.6 H2O crystallized in the monoclinic space group P21, with a=14.082(3), b=19.079(4), c=12.417(3) Å, β=109.28(3)°, V=3149.0(11) Å3, 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 β-CD cavity, its long axis being oriented along the β-CD molecular axis, and 4.6 water molecules are placed in the interstitial space. The β-CD macrocycle is elliptically distorted, and the guest molecule is held in the hydrophobic β-CD cavity by CH⋯O and CH⋯π interactions.