Crystalline Inclusion compounds

Tabic 4. Crystalline inclusion compounds with host 22 5)... 

Considering this variety of crystalline inclusion compounds, 26 is close to 1 (cf. Table 1) and like 1, the stoichiometries (host guest) found for the different aggregates of 26 largely correspond to the expected ratios. Thermal stabilities in most cases are relatively high. 

K. T. Holman, M. D. Ward, Metric Engineering of Crystalline Inclusion Compounds by Structural Mimicry , Angew. Chem. Int. Ed, 2000, 39,1653-1656. 

Crystalline fructose, 23 485-486 Crystalline glycolic acid, 14 127 Crystalline hybrid compounds, 13 546-548 Crystalline inclusion compounds, 14 184 molecular recognition behavior of, 16 796 preparation of, 14 182 Crystalline melting point, of polymers, 20 399... 

CO crystalline inclusion compound were isolated and were shown to contain 1 1 tpcb bta 34 33 with disordered DMSO and water molecules in the supramole-cular channels (Fig. 10). 

Cyclotriveratrylene/1180-60-5] (34) is a cyclocondensation product of veratrole with formaldehyde. It possesses a stable trigonal crown conformation and forms crystalline inclusion compounds with benzene, chlorobenzene, toluene, thiophene, decalin, chloroform, acetone, carbon disulfide, acetic acid, and butyric acid (101). Their structures consist of columns of cyclotriveratrylene molecules that are not amenable to close packing and provide channels into which the guests are accommodated. A number of modified host structures, derived from prototype (34) have been prepared. The hexaphenol analogue cyclotricatechylene also yields well-defined channel inclusions (101). They involve mosdy polar guests and the structures are held by hydrogen bonding. 

Several prominent types of host molecule, such as the steroidal bile acids and the cyclodextrins, are chiral natural products that are available as pure enantiomers. Chemical modification of these parent compounds provides an easy route to the preparation of large numbers of further homochiral substances. Since all these materials are present as one pure enantiomer, it automatically follows that their crystalline inclusion compounds must have chiral lattice structures. It is not currently possible to investigate racemic versions of these compounds, but the examples discussed previously in this chapter indicate that very different behaviour could result. 

Extensive systematic work over the past decade has established that bile acid derivatives have the ability to form crystalline inclusion compounds with various organic substances [1], The accumulated data tell us two notable things. One is that their inclusion behavior varies from one case to another. The other is that their crystals consist of host-inherent or guest-dependent assemblies with different molecular arrangements and hydrogen-bonding networks. These facts force us to direct our attention to separation engineering accompanied by crystallization and... 

The cyclodextrins (cycloamyloses) are torus-shaped molecules that can form crystalline inclusion compounds, recently attracting much attention as enzyme-site models. Their history has been seen in three phases. From 1891 to 1935 they were known as natural products, but with no recognition of their exact chemical structure. This recognition emerged in the second period, to about 1970, when most of their characteristics were also elucidated. The period from 1970 to the present has seen considerable research into their industrial use and production.239 Their inclusion compounds or complexes have found employment in such diverse fields as explosives, insecticides, pharmaceutical products, rust-prevention agents, and even baking powder. 

In principle, the negatively charged, presumably planar network I can be combined with one molar equivalent of tetraalkylammonium ion IGN"1" of the right size as interlayer template to yield a crystalline inclusion compound of stoichiometric formula (IGN+) I C(NIG ) ICO2 that is reminiscent of the graphite intercalates. Anionic network n, on the other hand, needs twice as many monovalent cations for charge balance, and furthermore possesses honeycomb-like host cavities of diameter 700 pm that must be filled by... 

For a long time, Robinson s compound has attracted attention in view of its ability to form crystalline inclusion compounds with certain small molecules. This property was initially mentioned in 1931 by Bhagwat et al. [10], and some of these inclusion complexes were investigated in detail some 25 years later by Caglioti et al. [11] (at the time Robinson s compound was believed to be a hexamer-see Ref. [9]). 

Cyclotriveratrylene (1) and its hexademethylated derivative cyclotricatechylene (16) (Table 2) form crystalline inclusion compounds with a great variety of small to medium-sized molecules. These inclusion compounds have been described in a previous review [9] and will not be further considered here. 

Clathrates are crystalline inclusion compounds formed by the physical reaction between host molecules and low molecular weight gases as guests. In the clathrate structure there are two different types of cages which can entrap guest molecules into the network of host molecules. The three-dimensional clathrate structures can be determined by X-ray diffraction method. 

Undecanone (methyl nonyl ketone), a natural nontoxic insect repellant compound, was recently isolated from the trichomes of wild tomatoes, and is currently being introduced as a replacement for insect repellants containing N,N-diethyl-meta-toluamide or DEET, which are permitted for use only on children older than 2 months. In an effort to improve the delivery of the somewhat volatile liquid 2-undecanone, we have successfully formed the crystalline inclusion compound (IC) between 2-undecanone and a-CD, using a coprecipitation method [69,70],... 

Clathrate hydrates are crystalline inclusion compounds in which the host framework is formed by water molecules linked through hydrogen bonds. The cavities of the framework are occupied by guest molecules of appropriate size and shape. Hydrates composed of gas molecules as guests and water molecules as the host are called gas hydrates. As a rule, there are only van der Waals interactions between the guest and host subsystems. 

Crystalline inclusion compounds containing unsaturated monomers are effective reactive systems for the production of linear polymers (1-6). This process belongs to the wider class of solid state polymerization, but possesses some specific features which make it worthy of a separate description. Throughout this article, the polymerization in inclusion compounds will be referred to as "inclusion polymerization" (other names currently used in the scientific literature are channel, canal or tunnel polymerization), and the terms "clathrate" will be used as synonymous with "inclusion compound". When there is no risk of confusion, the more general term of "adduct" will be used for clathrate in principle a... 

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