Cyclodextrins as Model Compounds to Study Hydrogen-Bonding Networks

In / -cyclodextrin, the dimers can either stack linearly to produce type C channels or they are displaced laterally so that the cavity of each dimer is closed on both ends in a brick-wall type B motif. In the latter, direct 0(6)H 0(6 ) hydrogen bonding between the dimers is difficult due to their separation, and water molecules are added at the dimer interface to form the indirect 0(6) H20 0(6) interactions. 

The guest molecules located in the channel with fourfold symmetry are, in general, so disordered that the atomic positions cannot be determined from crystal structure analyses, except when the guest molecule itself possesses fourfold symmetry [569]. 

3 Cyclodextrins as Model Compounds to Study Hydrogen-Bonding Networks 

The property of cyclodextrins of primary interest in this text is the formation of hydrogen-bonding networks in the crystalline state. These networks are extensive because the cyclodextrin crystal structures contain not only the three donor hydroxyl groups and five potential acceptor oxygen atoms characteristic of the glucose unit, but also many waters of crystallization. The total number of donors and acceptors respectively is 18 and 30 for a-cyclodextrin, 21 and 35 for /7-cyclodextrin, and 24 and 40 for y-cyclodextrin, to which is added the double donor and double acceptor function of each of the water molecules.3 

In only a few of the many publications on X-ray studies of the cyclodextrin inclusion compounds and of the cyclodextrin hydrates have the hydrogen atoms of 

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