Intermolecular inclusion, cyclodextrin structures

An atypical rotaxane structure is that involving a thread covalently attached to the CyD ring. Such a system acts as both host and guest and it has to be specially designed so that the thread is induded spontaneously in a cavity other than the one bearing it intermolecular inclusion), whereas intramolecular indusion is prevented. The resulting assembly, named a daisy chain by J.F. Stoddart, is either an acyclic supramolecular polymer 8 or a cyclic supramolecular oligomer 9 [50] (Fig. 12.4). Acyclic cyclodextrin polymers were first observed in the solid state in... 

Cgo is extremely hydrophobic thus, some of the initial attempts to capture Cgo molecules were carried out in water. Qo forms a 1 2 complex with a cyclodextrin molecule. Liu et al. synthesized water-soluble double-CD 16 (Figure 7.10). End-to-end intermolecular inclusion complexation of Cgo with double-CD 16 led to the formation of a supramolecular polymer in water. An STM image of the polymer displayed the regular linear arrangement of the Cgo nano-array. TEM observation of the supramolecular polymer confirmed the presence of a linear structure with a length in the range of 150 to 250 nm, suggesting that the polymer consists of 60 to 80 units of the minimum component. 

Owing to the inclusion complex formation cyclodextrins offer an excellent model system to study intermolecular interactions as different substrate molecules can be accommodated into their cavity. In the following some of these complexes are described structurally and the structural data and data from kinetic measurements are combined to derive a picture of the inclusion mechanism and to show which intermolecular interactions are involved in the inclusion process. 

Jaime, C., Redondo, J., Sanchez-Ferrando, R, and Virgili, A. [beta]-cyclodextrin inclusion complex with adamantane Intermolecular 1H 1H NOE determinations and molecular mechanics calculations. J Mol Structure 1991, 248 317-329. 

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