Lattice inclusion

Extramolecular Cavity Inclusions Lattice-Type Inclusion Compounds, Clathrates... 

Also deoxycholic acid (6) crystallizes in an inclusion lattice with channel-shaped cavities 13). Figure 3 shows that they are formed by facing molecules of deoxycholic acid, 4). This characteristic structural unit is a double layer of head-to-tail linked deoxycholic acid molecules at which specific H-bridges between hydroxy and carboxy groups are the decisive fact. The channels as such (e.g. in case of the orthorhombic crystal, see Fig. 3) are lined with lipophilic groups. Thus only van der Waals contacts are kept between the included guest molecules (also for polar molecules like acetone, Fig. 3) and the molecules of the channel wall. 

Achiral objects can be assembled into chiral solid-state structures, and this is frequently the case for urea 1 when it encloses guests. Other compounds adopt a chiral conformation in solution and therefore may ultimately produce either chiral or achiral host structures. On the other hand, thiourea 2 forms an inclusion lattice that is achiral. This arrangement is nonetheless very effective in enclosing guest molecules. 

Suzuki et al. reported the photochemical reaction of CT crystals, in which cycloaddition reaction of bis(l,2,5-thiadiazolo)tetracyano-quinodimethane 17 (electron acceptor) and 2-divinylstylene 18 (electron donor) is efficiently induced (Scheme 3). [17] A structural feature of the CT crystal is the asymmetric nature of the inclusion lattice because of the adoption of a chiral space group, P2. The [2 + 2] photoadduct 19 was formed via the single crystal-to-single crystal transformation, and the optically active product with 95% ee was obtained. 

A large number of host-guest structures are known, but a reversible guest exchange or chemical transformation of the guest inside a coordination polymer framework has been described for only a few (257, 281-283). In most cases the integrity of the inclusion lattice cannot be effectively maintained in the absence of guest molecules... 

One important field of applications, industrial objectives included, is directed to chemical analysis and molecular separation processes Corresponding to the size, the shape, and the chemical nature of the holes generated in an inclusion lattice, guest molecules may be included selectively. Out of a mixture of compounds the one which... 

The characteristic of crystal lattices is a strict periodical succession of structurally identical molecular units, in the sense of an inclusion lattice also of holes, channels, layers etc. which may include guest molecules in an oriented fashion. This organizing principle makes topochemistry possible. One of the early studies in this area was the inclusion polymerization of dienes in the channels of urea, respectively thiourea, leading to stereoregular polymers (Eq. 1) Although stereodifferentiating inclusion polymerization/co-polymerization has been performed in other host lattices, too, e.g. in the channels of the perhydrotriphenylene host (6) it is still a problem of actual interest... 

In the following, we review a supramolecular con-that demonstrates that the idea of supramolecular interactions, may provide an answer. Essentially, this is aehieved by aligning dipolar molecules into a parallel array provided by an inclusion lattice, in which guest molecules are subjeeted to orientational selectivity of the dipoles... 

R=CH3, X H), with 112°. The angles at the methano bridges are found to be 110 and 111.5°. respectively. Obviously, the inclusion lattices are further improved by alkylation. X-ray crystal analysis of 13a (X=/) 0.5 1,4-dioxane established an enclathration-type inclusion. 

Schlenk. W. Asymmetric urea inclusion lattice. Justus Liebigs Ann. Chem. 1973. 7. 1145 (I. Separation of racements), 1156 (II. Stable configurational lattice coordi-... 

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