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Encyclopedia of Physical Science and Technology EN007G-334 June 30, 2001 15:23

728 Inclusion (Clathrate) Compounds

FIGURE 32 Cyclidene complex of iron(II) with bonded carbon
FIGURE 30 Schematic view of the structure of the complex of monoxide.
anisole with cyclodextrin.

studies of this type is a new way to catalyze known chem-
ical reactions.

B. Cation Transport
A necessary feature of the life process is the solubiliza-
tion of cations in low dielectric constant media. The way
in which both electrolytes and nonelectrolytes cross mem-
branes has received much study. A useful model of cation
FIGURE 33 Schematic view of U-shaped host. [From Atwood,
transport is the motion of ions affixed to macrocycles.
J. L., Ed. (1990). “Inclusion and Molecular Recognition,” Plenum
Crown ethers and cryptates have been studied the most. Press, New York.]
One of the features of biological transport is selectivity.
The simple crown ethers are particularly suited for exper-
iments on selectivity, since the hole or cavity is of rather

FIGURE 34 Rigid, U-shaped molecule capable of binding chiral
alcohols.

specific size. Thus, 15-crown-5 is better matched to Na +
than to K , while the reverse is true for 18-crown-6.
+

SEE ALSO THE FOLLOWING ARTICLES
FIGURE 31 General cyclidene structure. [From Atwood, J. L.,
Davies, J. E. D., and MacNicol, D. D., eds. (1991). “Inclusion Com- CATALYSIS,INDUSTRIAL • ENZYME MECHANISMS • HY-
pounds,” Vol. 5, Oxford Univ. Press, Oxford, UK.] DROGEN BOND • MICROPOROUS MATERIALS:ZEOLITES,