title: The crystal structure of the 1:1 inclusion complex of beta-cyclodextrin with squaric acid.
abstract: The crystal and molecular structure of the 1:1 inclusion complex of beta-cyclodextrin (cyclomaltoheptaose) with squaric acid (3,4-dihydroxycyclobutene-1,2-dione) was determined by X-ray diffraction. The complex crystallizes in the monoclinic P2(1) space group and belongs to the monomeric cage-type, characterized by a herringbone-like packing motif. Co-crystallized water molecules are present on seven sites, of which six are fully occupied. The guest molecule is placed inside the beta-cyclodextrin cavity, perpendicular to the plane defined by the glycosidic O-4n atoms, and held in place by direct and water-mediated hydrogen bonds mainly involving symmetry-related beta-cyclodextrin molecules. The accommodation of the planar guest molecule into the beta-cyclodextrin cavity determines a significant distortion of the latter from the sevenfold symmetry.
authors.affiliation: Biopolymer Research Centre, C.N.R., via Marzolo 1, I-35131 Padova, Italy. biop02@chor.unipd.it
authors.forename: M
authors.initials: M
authors.lastname: Crisma
authors.forename: R
authors.initials: R
authors.lastname: Fornasier
authors.forename: F
authors.initials: F
authors.lastname: Marcuzzi
mesh_terms: D002236:Carbohydrate Conformation; D018360:Crystallography, X-Ray; D003503:Cyclobutanes / Q000737:chemistry*; D003505:Cyclodextrins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D047392:beta-Cyclodextrins
chemical_list: D003503:Cyclobutanes; D003505:Cyclodextrins; D047392:beta-Cyclodextrins; C031215:betadex; C030042:squaric acid