Inclusion organic cations

Organic cations are especially good guests, since their inclusion is favored by cation-7t interactions with the aromatic walls. This enables the encapsulation to be studied by mass spectrometry also [36]. If cations such as tetraethylammonium or cobaltocenium are included [37], the directionality of the hydrogen-bonded belt... 

Inclusion complexing partners are classified as hosts and guests [46]. There are two types of hosts that were successfully employed in the chromatographic separation of enantiomers hosts that have a hydrophobic interior and hosts with a hydrophilic interior. The hydrophilic interior means that the cavity contains heteroatoms such as oxygen, where lone-pair electrons are able to participate in bonding to electron acceptors such as an organic cation (e.g., chiral crown ethers). In contrast, a host with a hydrophobic interior cavity is able to include hydrocarbon-rich parts of a molecule [47]. This type of host is found in the cyclodextrins. 

Pietraszkiewicz O, Kozbial M, and Pietraszkiewicz M. Transport studies of inorganic and organic cations across liquid membranes containing Mannich-base calix[4]resorcinarenes. Molecular recognition and inclusion. In Proceedings of the 9th International Symposium on Molecular Recognition and Inclusion, Francel998 pp. 459 62. 

In summary, we have shown that novel anionic host lattices can be constructed from urea, thiourea, or selenourea molecules and various anions as building blocks, which readily adopt different topologies for the accommodation of tetraalkylam-monium ions of various sizes. By employing organic cations as templates and suitable counter anions as an ancillary host material, with or without neutral molecules such as H2O as a third component, the lattice engineering of new urea, thiourea, and selenourea inclusion compounds by self-assembly may be further explored. 

W. Abraham, Inclusion of organic cations by calix[n]arenes, J. Incl. Phenom. Macrocycl. Chem., 2002, 43, 159-174. 

Abraham. W. Inclusion of organic cations by calix[n]ai enes. J. Inch Phenom. Macrocycl. Chem. 2002, 43, 159-174. Nachtigall, F.F. Lazzarotto. M. Noine, F. Interaction of Calix[4]arene and amines A combined NMR. spectromet-ric and conductimetric investigation. J. Braz. Chem. Soc. 2002, 13. 295-299. 

In the last few years there has been considerable interest in development of new aza and oxa-aza macrocyclic receptors. Macrocyclic molecules containing appropriate binding sites and cavities of suitable size and shape may be designed to form selective inclusion complexes. Actually, the molecular topology of the host molecule can be synthetically modulated in order to bind many different chemical species. To this purpose, aza or oxa-aza macrocyclic receptors able to bind different kinds of substrates, such as inorganic or organic cations,anionic species, " and neutral molecules have been studied to elaborate their use as selective recognizers, molecular carriers and catalysts. 

Inclusion of cationic molecules by hosts in organic solvents is also observed with other host molecules, such as crown ethers and calixarenes. Cat-ion/n and coordination interactions are the main driving forces in these complexes. However, the formation of host-guest complexes with neutral... 

Podates AcycHc analogues of crown ethers /coronands and cryptands (podands, eg, (11) (30) are also capable of forming inclusion compounds (podates) with cations and uncharged organic molecules, the latter being endowed with a hydrogen bond fiinctionahty. Podates normally are less stable than coronates and cryptates but have favorable kinetics. 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

We have not attempted to cover all or even most aspects of crown chemistry and some may say that the inclusions are eclectic. We felt that anyone approaching the field would need an appreciation for the jargon currently abounding and for the so-called template effect since the latter has a considerable bearing on the synthetic methodology. We have, therefore, included brief discussions of these topics in the first two chapters. In chapters 3—8, we have tried to present an overview of the macrocyclic polyethers which have been prepared. We have taken a decidedly organic tack in this attempting to be comprehensive in our inclusion of alkali and alkaline earth cation binders rather than the compounds of use in transition metal chemistry. Nevertheless, many of the latter are included in concert with their overall importance. 

There are several cases that have addressed molecular recognition of chiral drugs by modified CDs127 as well as inclusion complexes of cationic, anionic and neutral organic compounds128 in order to understand the role of hydrophobic and electrostatic interactions between the functional groups on host and guest. 

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