The Structure of the Cyclodextrin Complex. XXI. Crystal Structures of Heptakis(2,6-di-O-methyl)-β-cyclodextrin Complexes with p-Iodophenol and p-Nitrophenol

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Abstract
Crystal structures of heptakis(2,6-di-O-methyl)-β-cyclodextrin complexes with p-iodophenol and p-nitrophenol were determined by the X-ray analysis. These two crystals were isomorphous with the space group P212121 and cell dimensions: a=14.796(3), b=18.853(5), and c=28.989(6) Å for the p-iodophenol complex, and a=14.779(2), b=18.965(3), and c=28.741(4) Å for the p-nitrophenol complex. The structures were solved by the heavy atom method combined with the phase refinement by the tangent formula and refined by the blockdiagonal least-squares method to the R-values of 0.12 (p-iodophenol complex) and 0.10 (p-nitrophenol complex). The host molecule has a round shape, which is maintained by the intramolecular hydrogen bonds between the O(3)H hydroxyl group and O(2)CH3 methoxyl group of the adjacent residue. The guest molecules in the both complexes are not included within the host cavity but located in the intermolecular space between host molecules. The host cavity includes water molecules and a methoxyl group of the adjacent host. Hydrogen bonds are formed only within the host cavity.