Channel-type inclusion compounds

Deoxycholic acid (DCA), apocholic acid (ACA), and cholic acid (CA) form channel-type inclusion compounds with a wide variety of organic molecules. Of these DCA has been extensively investigated. 

Cl-4H2Op [790], on the other hand, are not clathrates but are channel-type inclusion compounds formed from cross-linking nets and ribbons into framework structures, with anions integrated in the water structure. The lower hydrates of... 

K. Miki, A. Masui, N. Kasai, M. Miyata, M. Shibakami, K. Takemoto, New Channel-Type Inclusion Compound of Steroidal Bile Acid Structure of a 1 1 Complex between Cholic Acid and Acetophenone , J. Am. Chem. Soc., 110, 6594 (1988)... 

Miki, K., Masui, A., Kasai, N., Miyata, M., Shibakami, M., and Takemoto, K., New channel-type inclusion compound of steroidal bile acid. Structure of a 1 1 complex between cholic acid and acetophenone, J.Am. Chem. Soc. 110, 6594-6596 (1988). 

We found that some kinds of alcohols form channel-type inclusion compounds with alkaloids such as brucine (72) and sparteine (75), and that the alcohols are easily resolved utilizing inclusion formation. We also found that sparteine can be resolved by inclusion formation with an optically active tertiary acetylenic alcohol. 

Thiourea forms channel-type inclusion compounds with globular molecules.This is partly because the space group E3c lacks a screw axis that the space group of the urea inclusion compounds P6i22 possesses. The larger diameter of the channel than in the urea compounds accommodates cyclohexane and monosubstituted cyclohexane as well as carbon tetrachloride and hexachloro-ethane in the channel. With these more or less spherical molecules as the guest species, thiourea inclusion compounds are rich in their polymorphism, most undergoing two or more phase transitions below room temperature. 

Fig. 1 Polarity formation for channel-type inclusion compounds. where A-D molecules enter channels, while the crystal grows in the direction of the channels. Orientational selectivity for A-D molecules is assumed to occur independently for each channel (A-and D-sites). (View this art in color at www.dekker.com.)...

Packing of the cyclodexthn molecules (a, P, P) within the crystal lattice of iaclusion compounds (58,59) occurs in one of two modes, described as cage and channel stmctures (Fig. 7). In channel-type inclusions, cyclodextrin molecules are stacked on top of one another like coins in a roU producing endless channels in which guest molecules are embedded (Fig. 7a). In crystal stmctures of the cage type, the cavity of one cyclodextrin molecule is blocked off on both sides by neighboring cyclodextrin molecules packed crosswise in herringbone fashion (Fig. 7b), or in a motif reminiscent of bricks in a wall (Fig. 7c). 

To our knowledge, no such effective optical resolution by inclusion formation with an optically active channel-type host compound has been reported so far. 1,2-Bis(2-methyl-1-naphthyl)-l,2-bis(2,4,6-trimethylphenyl)ethane (80) yields a 1 1 crystal inclusion with (+)-a-pinene, but successive recrystallization of 80 from (-i-)-a-pinene gives only a partial optical resolution... 

The host architecture has some gross structural characteristics, which are repeated in a series of its inclusion compounds. Among the most extensively studied channel-type inclusion coinpounds are the conventional urea inclusion compounds (see Urea), in which the urea molecules form an extensive hydrogen-bonded honeycomb network containing parallel helical tunnels (Fig. la) with diameter between 5.5-5.S A and the tunnel centers separated by ca. 8.2 The walls of the tunnels are... 

Fig. 7. Schemes of crystalline cyclodextrin inclusion compounds (a) channel type (b) cage herringbone type (c) cage brick type (58).

Figure 7. Schematic representation of the packing arrangement in cyclodextrin complexes (a) channel type, (b) cage or herringbone type, and (c) brick type. (Reproduced with permission from W. Sanger in Inclusion Compounds, Vol. 2, J. L. Atwood, J. E. D. Davies, and D. D. MacNicol, Eds., Academic Press, New York, 1984, p. 231.)...

Figure 8. A stereoscopic view of the packing in the inclusion compound of 1,1,6,6-tetraphenylhexa-2,4-dyne-1,6-diol, 2, with (a) chalcone and (b) 9-anthraldehyde. 9-Anthraldehyde gives cage-type and chalcone gives channel-type structures. [Reproduced with permission from F. Toda, Topics Curr. Chem. 140, 43 (1987).]...

Another type of inclusion compd is the channel or canal compound. Here the straight chain compds, such as hydrocarbons, acids,esters , alcohols, aldehydes, ketones, etc are enclosed in the channels formed by compds, such as urea, thiourea, choleic acids, cyclodextrins, etc. As examples of channel compds may be cited, the urea-decone compd, [CO(NH2)2] g.C, 2H26, and various zeolites. (See also Ref 10, pp431 ... 

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