Supramolecular cyclodextrins

Karakhanov, E. A., Zhuchkova, A. Y., Filippova, T. Y., Maksimov, A. L. Supramolecular cyclodextrin-based catalyst systems in Wacker oxidation. Neftekhimiya 2003,43, 302-307. 

The main supramolecular self-assembled species involved in analytical chemistry are micelles (direct and reversed), microemulsions (oil/water and water/oil), liposomes, and vesicles, Langmuir-Blodgett films composed of diphilic surfactant molecules or ions. They can form in aqueous, nonaqueous liquid media and on the surface. The other species involved in supramolecular analytical chemistry are molecules-receptors such as calixarenes, cyclodextrins, cyclophanes, cyclopeptides, crown ethers etc. Furthermore, new supramolecular host-guest systems arise due to analytical reaction or process. 

Covalent and noncovalent combination of porphyrins as well as calix[4]arenes, resorcin[4]arenes including macroheterocyclic fragments, and cyclodextrins by construction of supramolecular artificial receptors 98EJ02689. 

The transition state of concerted Diels-Alder reactions has stringent regio- and stereochemical requirements and can assume settled configurations if the reaction is carried out in a molecular cavity. Cyclodextrins, porphyrin derivatives and cyclophanes are the supramolecular systems that have been most investigated. 

Design and Construction of Supramolecular Architectures Consisting of Cyclodextrins and Polymers... 

The application of the techniques discussed above to the binding of guests to DNA or cyclodextrins (CDs) is described below. The intent of this section is not to provide an exhaustive review and analysis of the available data, but the objective is to use examples to show how the different techniques were employed in studies of supramolecular dynamics. The values for rate and equilibrium constants stated below... 

Supramolecular systems, 167, 168 cyclodextrins (CD), study of binding dynamics of guests to, 204-216 DNA, study of binding dynamics of guests to, 186-204... 

In recent years, supramolecular chemistry has produced a number of systems which have been shown to be able to effectively catalyze a Diels-Alder reaction. Most systems selectively afforded only one diastereomer because of a pre-organized orientation of the reactants. These systems include cyclodextrines, of which applications in Diels-Alder chemistry have recently been reviewed89. Some other kinds of non-Lewis acid catalyzed Diels-Alder reactions, including catalysis by proteins and ultrasound, have been discussed by Pindur and colleagues90. 

In principle, there are four basic strategies to compensate for the repulsive effects between the hydrophobic fullerene surface and water (a) encapsulation in the internal hydrophobic moiety of water-soluble hosts like cyclodextrins (Andersson et al., 1992 Murthy and Geckeler, 2001), calixarenes (Kunsagi-Mate et al., 2004) or cyclotriveratrylenes (Rio and Nierengarten, 2002) (b) supramolecular or covalent incorporation of fullerenes or derivatives into water-soluble polymers (Giacalone and Martin, 2006) or biomolecules like proteins (Pellarini et al., 2001 Yang et al., 2007) (c) suspension with the aid of appropriate surfactants and (d) direct exohe-dral functionalization in order to introduce hydrophilic moieties. 

Braun T (1997) Water soluble fullerene-cyclodextrin supramolecular assembles. Preparation, structure, properties (an annotated bibliography). Full Sci Technol. 5 615-626. 

Harada, A. Design and Construction of Supramolecular Architectures Consisting of Cyclodextrins and Polymers. Vol. 133, pp. 141-192. 

This short compilation of the recent literature results convincingly demonstrates the usefulness of water-soluble supramolecular complexing agents in biphasic aqueous organometalHc catalysis. Due to their availability, cyclodextrins play a major role in this field. Thinking of the relatively low price of these chemicals (a few per kg in 1998 [2]) their use on a larger scale can also be envisaged in fine chemicals production. 

Iron figures prominently in a review and a book devoted to supramolecular chemistry, especially in the sections dedicated to siderophores, and also appears in various guises in a book on cyclodextrin chemistry. ... 

A Harada. Design and construction of supramolecular architectures consisting of cyclodextrins and polymers. Adv Polymer Sci 133 141—191, 1997. 

This paper is not a review covering the entire field of carbohydrate-recognition in any organized system. Many excellent papers have already been devoted to supramolecular systems such as cyclodextrins, podands, coronands or cryptants able to entrap carbohydrate molecules [1]. This article only deals with the molecular recognition of mono and oligosaccharides in organized self-assemblies of amphiphilic carbohydrates (possibly blended with other lipids) in aqueous medium i.e. in assemblies mimicking the cell membrane. 

Ferro, S., Jori, G., Sortino, S., Stancanelli, R., Nikolov, P., Tongon, G., Ricchelli, F., and Mazzaglia, A. (2009). Inclusion of 5-[4-(l-dodecanoylpyridinium)-10,15,20-triphenylpor-phine in supramolecular aggregates of cationic amphiphilic cyclodextrines Physic-chemical characterization of the complexes and strengthening of the antimicrobial photosensitizing activity. Biomacromolecules 10(9), 2592-2600. 

Cyclodextrins Szejtli, F., Osa, T, Eds. Comprehensive Supramolecular Chemistry 3 Elsevier Science Oxford, UK, 1996. 

In polar solvents amphiphilic molecules, that is molecules with a polar head and hydrophobic tail , tend to form various aggregates. The structure of micelles is usually much more complicated than that schematically shown in Figure 1.4 (see the pertaining discussion in Section 2.3). Nevertheless, in water they can include nonpolar molecules into their voids acting like surfactants applied in toiletry [15]. Similarly to cyclodextrins such as 11 [6, 16] and liquid crystals [7] discussed in Section 2.6, surfactants are examples of few supramolecular systems which have found numerous practical applications. 

Let us compare the methods applied by Pedersen for establishing the complex formation with a modern approach. Today tedious solubility studies are carried out almost exclusively with practical applications in mind, but they are not performed to prove the complex formation. For instance, one ofthe main reasons for the use of cyclodextrin complexes in the pharmaceutical industry is their solubilizing effect on drugs [8]. There, and almost only there, solubility studies are a must. As concerns spectroscopic methods, at present the NMR technique is one ofthe main tools enabling one to prove the formation of inclusion complex, carry out structural studies (for instance, making use of the NOE effect [9a]), determine the complex stability [9b, c] and mobility of its constituent parts [9d]. However, at the time when Pedersen performed his work, the NMR method was in the early stage of development, and thus inaccurate, and its results proved inconclusive. UV spectra retained their significance in supramolecular chemistry, whilst at present the IR method is used to prove the complex formation only in very special cases. 

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