Host-guest interactions, cyclodextrin inclusion complexes

Abou-Hamdan, A. Bugnon, P. Saudan, Ch. Lye, P.G. and Merbach, A.E. (2000) High-Pressure Studies as a Novel Approach in Determining Inclusion Mechanisms Thermodynamics and Kinetics of the Host-Guest Interactions for a-Cyclodextrin Complexes, J. Am. Chem. Soc. 122, 592-602. 

Harada and coworkers developed a variety of supramolecular polymers based on the host-guest interaction of cyclodextrin (CD) derivatives with hydrophobic guests, such as the adamantyl and cinnamoyl groups [45,46]. Consequently, various structures were obtained by conjugating cinnamoyl and hydrocinnamoyl groups to a- and/3-CD. When the hydrocinnamoyl group was attached to -CD, the flexibility of the linker resulted in the formation of a self-inclusion complex - in other words. 

A broad range of macrocyclic compounds can be used as chiral selectors for enantioselective HPLC. Besides synthetic crown ethers, derivatized cyclodextrins and cyclic antibiotics are also used as chiral stationary phases. Enantiomer separation employing these compounds is often based on host-guest interactions [15], whereby the cyclic molecules form an inclusion compound or an association complex with the analyte. 

When the materials contain cyclodextrin molecules, the mechanism is due to the formation of an inclusion complex between the CD molecule and the pollutant through host-guest interactions. It has also been reported that the presence of pollutant-pollutant hydrophobic interactions can explain the adsorption properties [35,43]. 

Host-guest inclusion complexes, 262—263 antibiotic hosts, 231—233 cahxarene hosts, 228—231 chiral crown ether hosts, 213—218 cyclic oligosaccharide hosts, 218—222 cyclodextrin host selectivities, 223/ host molecular size, 221 hnear ohgosaccharide hosts, 222—228 ir- TT stacking interactions, 217 proteic hosts, 231 Human 15-hpoxygenase, 52/... 

However, for the positional isomers of phthalate (56-58), the response selectivity was different for the two types of membranes. Whereas membranes 1 and 2 showed responses in the order of 56 (ortho) > 57 (meta) > 58 (para), membrane 53 interestingly showed a different response order, i.e., 57 (meta) > 58 (para) > 56 (ortho), a selectivity which is quite different from that expected on the basis of simple electrostatic effects. Such a difference in the selectivity is possibly due to host-guest complexation involving not only electrostatic interactions but also inclusion into the P-cyclodextrin cavity, which is capable of recognizing differences in the steric structures of the guests. 

The rigid structure of the cyclodextrin host results in well defined but different inclusion and interaction patterns for any potential guest molecule. Treating a mixture of compounds with a dissolved or solid, immobilized CD, leads to the formation of inclusion complexes of different stability and solubility. Consequently separations can be based either on strongly modified solubility in water of the CD-complex of a certain component, or on the... 

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