Guest inclusion

Reaction Control of Guest Compounds in Host-Guest Inclusion Complexes... 

Table 4. Selective guest inclusion of host compound 13...

According to the coordinatoclathrate predict, the Spiro compound 23 will not allow the formation of inclusion compounds with dimethylformamide and other polar solvents, but with benzene, tetrahydrofuran, and 1-bromopentane (Table 3). Due to the limited number of guest inclusions, a lattice cavity of rather restricted dimensions is suggested for 23 e.g. toluene, cyclohexane or dioxane are not suitable guest partners for 23, whereas lower homologues (cf. benzene, tetrahydrofuran) are readily included 37). The behavior of a reduced analogue of 23, the hydroxymethyl — substituted spiro compound 24, is in some way comparable since an inclusion compound with benzene is the only one known interestingly it is formed exclusively with optically resolved but not with racemic 24 49). 

Table 9. Selective guest inclusions of hosts 47 and 48 from two-component solvent systems...

The formation of crystal inclusion of 47 and 48 with cyclic ketones of suitable ring size (cyclopentanone, cyclohexanone) and with cyclohexene oxide are also important facts. Corresponding inclusion compounds with alcohols or amines could not be obtained. With reference to the heterocyclic guest molecules, the suitability of the ring size is likely to be the decisive factor for guest inclusion. 

Table 19. Crystal data of pure hydrocarbon host-guest inclusions...

The formation of host-guest inclusion compounds in crystals (or in highly ordered membranes or other biological structures) is a phenomenon more organised than simple co-crystallisation of a pair of substances. The special characteristic of inclusion crystallisation is a constant identity of one member in a series of pairs, this member thereby being identified as host, and a constancy of structure type (but not necessarily dimensions) for the host. The higher molecular organisation involved in inclusion... 

When guest molecules are arranged together in the channel of a host-guest inclusion complex, intermolecular reactions of the guest compound may proceed stereoselec-tively and efficiently. An enantioselective reaction is expected when optically active host compounds are used. 

Table 6. Host-guest inclusion complex formation by solid-solid reaction...

The author is grateful to his coworkers whose names appear in the references, especially Dr. Koichi Tanaka, for their many contributions. The author would like to thank Professors Menahem Kaftory of Technion Israel Institute of Technology, Takaji Fujiwara of Shimane University, and Yuji Oohashi of Ochanomizu Womens University for their valuable X-ray analyses of many host-guest inclusion complexes. 

Anionic guest inclusion compounds, 24 170 Anionic halide complexes, 24 540 Anionic initiators, 24 244-265 alkali metals, 24 245-248 alkyllithium compounds, 24 248-255 1,1-diphenylmethylcarbanions as,... 

Figure 10.38 shows modified / - and y-cydodextrins with two identical appended fluorophores that are able to form extimers (Ueno et al., 1997). They have been studied in 10% ethylene glycol aqueous solutions. /J-cyclodextrins with two 2-naphthylsulfonyl moieties linked to the smaller rim (compounds / -CDl, / -CD2, / -CD3), have a cavity that is too small to include both fluorophores one of them is outside the cavity and the other is inside. The latter can be excluded from the cavity upon inclusion of a guest molecule. Therefore, the excimer band in the fluorescence spectrum increases upon guest inclusion. 

In contrast, the fluorescence spectra of the parent y-cyclodextrins (compounds y-CD1, y-CD2, y-CD3, y-CD4) exhibit both monomer and excimer bands in the absence of guests because the cavity is large enough to accommodate both fluorophores (Figure 10.38). The ratio of excimer and monomer bands changes upon guest inclusion. The ratio of the intensities of the monomer and excimer bands was used for detecting various cyclic alcohols and steroids (cyclohexanol, cyclo-dodecanol, i-borneol, 1-adamantanecarboxylic acid, cholic acid, deoxycholic acid and parent molecules, etc.). 

Enantioselective self-assembling of amino acids 209 Host-guest inclusion complexes 213 Reactivity of chiral ion-dipole complexes 233... 

Chiral recognition, see also Host-guest inclusion complexes... 

Host-guest inclusion complexes, 262—263 antibiotic hosts, 231—233 cahxarene hosts, 228—231 chiral crown ether hosts, 213—218 cyclic oligosaccharide hosts, 218—222 cyclodextrin host selectivities, 223/ host molecular size, 221 hnear ohgosaccharide hosts, 222—228 ir- TT stacking interactions, 217 proteic hosts, 231 Human 15-hpoxygenase, 52/... 

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