Advantage over other inclusion compounds

Shielding and Stabilization. Inclusion compounds may be used as sources and reservoirs of unstable species. The inner phases of inclusion compounds uniquely constrain guest movements, provide a medium for reactions, and shelter molecules that self-destmct in the bulk phase or transform and react under atmospheric conditions. Clathrate hosts have been shown to stabiLhe molecules in unusual conformations that can only be obtained in the host lattice (138) and to stabiLhe free radicals (139) and other reactive species (1) similar to the use of matrix isolation techniques. Inclusion compounds do, however, have the great advantage that they can be used over a relatively wide temperature range. Cyclobutadiene, pursued for over a century has been generated photochemicaHy inside a carcerand container (see (17) Fig. 5) where it is protected from dimerization and from reactants by its surrounding shell (140). 

An important advantage of the inclusion complexes of the cyclodextrins over those of other host compounds, particularly in regard to their use as models of enzyme-substrate complexes, is their ability to be formed in aqueous solution. In the case of clathrates, gas hydrates, and the inclusion complexes of such hosts as urea and deoxycholic acid, the cavity in which the guest molecule is situated is formed by the crystal lattice of the host. Thus, these inclusion complexes disintegrate when the crystal is dissolved. The cavity of the cyclodextrins, however, is a property of the size and shape of the molecule and hence it persists in solution. In fact, there is evidence that suggests that the ability of the cyclodextrins to form inclusion complexes is dependent on the presence of water. Once an inclusion complex has formed in solution, it can be crystallized however, in the solid state, additional cavities appear in the lattice, as in the case of the hosts previously mentioned, which enable the inclusion of further guest molecules. ... 

One of the advantages of this procedure over conventional synthetic methods of azacyclophanes (cyclic amide formation) resides in its brevity and simplicity. In addition, the results obtained reveal this procedure to be an efficient diaza[3.3]cyclophane synthetic method, and an acceptable approach for the synthesis of triazaC3.3.3]cyclophanes and tetraaza[3.3.3.3]cyclophanes as host molecules of inclusion compounds. This synthetic method has been successfully applied to other cyclophane systems, such as 2,ll-diaza[3.3](2,6)-, 2,11,20-triaza[3.3.3](2,6)- and 2,11,20,29-tetraaza[3.3.3.3](2,6)pyridinophane, syn- and anti-2,13-diazaC3.3](1,4)naphthalenophane, 2,13,24-triaza[3.3.3](1,4)- and 2,13,24,35-tetraaza[3.3.3.3](l,4)naphthalenophane. 

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