Crystal structure of a cyclomaltoheptaose-4-hydroxybiphenyl inclusion complex

The crystal structure of the inclusion complex of cyclomaltoheptaose (beta-cyclodextrin) with 4-hydroxybiphenyl was determined by single-crystal X-ray diffraction at 150 K. The complex contains two cyclomaltoheptaose molecules, two 4-hydroxybiphenyl molecules, one ethanol molecule and fifteen water molecules in the asymmetric unit, and could be formulated as [2(C42H70O35)center dot 2(C12H10O)center dot(C2H6O)center dot 15(H2O)]. It crystallized in the triclinic space group P1 with unit cell constants a = 15.257(3), b = 15.564(3), c = 15.592(2) angstrom, alpha = 104.485(15)degrees, beta = 101.066(14)degrees, gamma = 104.330(17)degrees, V = 3343.6(10) angstrom(3). In the crystal lattice, two beta-cyclodextrins form a head-to-head dimer jointed through hydrogen bonds. Two 4-hydroxybiphenyls were included in the dimer cavity with their hydroxyl groups protruding from two primary hydroxyl sides of the cyclodextrin molecules. The guest 4-hydroxybiphenyl molecules linked into a chain via a combination of an O-H center dot center dot center dot O hydrogen bond and face-to-face pi-pi stacking of the phenyl rings. The crystal structure supports the calculation results indicating that the 2:2 inclusion complex formed by beta-cyclodextrin and 4-hydroxybiphenyl is the energetically favored structure. (c) 2007 Published by Elsevier Ltd.