Macrocyclic Inclusion Complexation

Inclusion complexation has developed to becoming another widely exploited supramolecular interaction for the formation of supramolecular polymer networks, mostly in water [197, 198]. Several classes of macrocycles have been developed, including crown ethers [199, 200], porphyrins [201, 202], cyclophanes [203], catenanes [204], cavitands [205, 206], cryptophanes [207], calix[n]arenes [208], and carcerands [209]. Macrocyclic-based supramolecular gels can either be formed from low molecular weight precursors or from macromolecular building blocks. The following discussion focuses on the latter. 

CD-based hydrogels can be divided into several classes, as shown in Fig. 11 (a) poly(pseudo)rotaxane hydrogels that contain CDs threaded to precursor-polymer chain ends or (b) to precursor-polymer chain branches (c) hydrogels 

Like CD-based hydrogels, CB[/i]-derived hydrogels can also be divided into different classes (1) hydrogels that consist of a three-component system cross-linked by ternary CB[8] inclusion complexes and (2) hydrogels based on a two-component system of CB[6] alkylammonium ion host-guest pairs. At least one example of each hydrogel class is described. 

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A molecule that contains one or more binding sites that can accommodate inorganic or organic ions referred to as guests. The binding site could even be a cavity within a crystal structure. Although enzymes clearly qualify as examples of host molecules, the term is usually restricted to structures such as crown ethers, macrocycles, and cyclodextrins. Nevertheless, these hosts do serve as models for molecular recognition. See also Crown Ethers Macrocycles Inclusion Complexes... 

HORN-BORNIG PLOT HORSERADISH PEROXIDASE HOST-GUEST INTERACTIONS HOST MOLECULE CROWN ETHERS MACROCYCLES INCLUSION COMPLEXES HOCKEL MOLECULAR-ORBITAL CALCULATIONS... 

Kamitori, S., Hirotsu, K., Higuchi, T., Crystal and molecular-structure of double macrocyclic inclusion complexes, gamma-cyclodextrin.12-crown-4.nacl, a model for the transport of ions through membranes. Bull. Chem. Soc. Jpn. 1988, 61, 3825-3830. 

Kamitori S, Hirotsu K, Higuchi T (1987) Crystal and molecular structures of double macrocyclic inclusion complexes composed of cyclodextrins, crown ethers, and cations. J Am Chem Soc 109 2409- 2414... 

Macrocyclic tetraammonium compounds VIII and IX 611 form stable 1 1 inclusion complexes with anionic molecules in aqueous solutions 62). The anions are halides, carbonate, phosphate, AMP, ATP etc. The stability of the inclusion complexes hepends on electrostatic as well as hydrophobic interactions. Whereas the complexes of VIII are dominated by the electfostatic component, the hydrophobic interaction plays the main part in complexes of IX. 

Monocyclic or polycyclic molecules containing binding sites for one or more so-called guest molecules or ions. Examples include the crown ethers as well as numerous macrocycles containing other electronegative atoms besides oxygen. See Inclusion Complexes Host-Guest Interactions Cydodextrins... 

It should be stressed that there is not alwaysjustice in reseach evaluation. The selective formation of inclusion complexes by cyclodextrins (such as 11) was established by Cramer [6] at least 15 years earlier than that by crown ethers. However, cyclodextrin studies forming an independent branch of host-guest chemistry seem underestimated in spite of their considerably greater practical importance at present than that of other host macrocycles (crown ethers 17, calixarenes 18, etc.). Sometimes they are even totally neglected by discussing inclusion phenomena [7]. 

THE MOST INTERESTING MACROCYCLIC LIGANDS WHICH ARE HOSTS FOR INCLUSION COMPLEXES... 

Spherands, hemispherands, and other similar macrocycles capable of inclusion complex formation [33]... 

The antibiotics employed as CSPs generally have macrocyclic structures. These molecules are relatively large and contain several chiral centers and cavities that exhibit enantioselectivity via inclusion-complexation interactions with analytes. Antibiotics have been known to display a broad degree of enantioselectivity [149-153], Vancomycin and teicoplanin are the most widely employed antibiotics for this use. Karlsson et al. [154] used a vancomycin CSP in both polar organic mode and reverse-phase CEC to separate a variety of enantiomers (Table 3). 

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