X-ray crystallographic structure of the two-to-one α-cyclodextrin-acetone. 9H2O compound

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Abstract
An inclusion complex of acetone with α-cyclodextrin (α-CD) has been prepared in aqueous solution containing AG+ ions. The crystal structure of the complex has been determined by single crystal X-ray diffraction. Crystal data: triclinic, space group P1, Z = 1, a = 13.852(1), b = 13.878(1), c = 15.719(1) Å, α = 93.01(1), β = 91.98(1), γ = 119.32(1)° and R = 0.069 for 6092 observed MoKα reflections with I > 3σ(I). This crystalline form is of the dimeric-type structure which normally occurs for ionic guest molecules. The dimers are stacked along the c axis to form an ‘endless head-to-head’ channel. Nine water molecules fill the intermolecular space outside the dimeric cavity and contribute to reinforce the cohesion between the channels which are in a pseudo-hexagonal arrangement. The acetone molecule is encapsulated within the cavity of the dimer. Molecular graphics analysis of difference Fourier maps suggests that the acetone molecule is situated in several partially occupied sites forming an infinite chain lying along the dimer axis. Thus, the stoichiometry for the complex corresponds to 2 α-CD molecules per acetone molecule, but this is not a true 2:1 inclusion compound.