Guest—host interactions

The cage-type packing structure is frequently observed for relatively small guest molecules which can be enclosed in the host cavity. CyD molecules are arranged in a herring-bone fashion and both ends of the host cavity are closed by adjacent molecules to create an isolated cage (Fig. 7.13A). The channel-type structure is 

The layer-type packing structure has been sometimes observed when the guest molecule is so large that a part of the molecule cannot be accommodated within the CyD cavity. CyD rings are arranged in a plane to make a molecular layer and two adjacent layers are shifted with respect to each other by half a molecule, showing a brick-work pattern (Fig. 7.13C). Both ends of the cavity are open to an inter-molecular space of the adjacent layers. A part of the guest molecule not included in the host cavity protrudes into the intermolecular space and is in contact with host molecules of the adjacent layer. 

Guest molecules included in CyDs are noncovalently bound and have some degree of freedom for translational and rotational motion. In the crystal of the 

The channel-type structure is formed with a variety of guest molecules. Generally, anionic guests, such as, acetate [91], 1-propanesulfonate [92], benzenesulfo-nate [93], y-aminobutyrate [94], and Methyl Orange [95] 14 are preferentially included in positively charged cylindrical channels. In contrast, metal cations are 

The layer-type packing structure is observed in the complexes with para-isomers of disubstituted benzenes, such as p-iodoaniline [109], p-iodophenol [110], p- 

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Kuokkanen evaluated a series of constants. Kpeg for substituted diazonium ions with PEG 1000 and found a reaction constant (p = 1.12) comparable to those for complexation with the three crown ethers investigated by Nakazumi et al. (1983), p = 1.18-1.38). It is therefore likely that the host-guest interaction of diazonium ions with acyclic polyethers is basically similar to that with crown ethers. A dual substituent parameter analysis (DSP, see Sec. 8.3) for (Nakazumi et al., 1987)... 

The bonding in these complexes is the result of ion-dipole attractions between the hetero atoms and the positive ions. The parameters of the host-guest interactions can sometimes be measured by NMR." ... 

A regio- and stereoselective Beckmann rearrangement utilized diastereose-lective host guest interactions of the inclusion complexes 225 and 228 in a solid state reaction. Initially, a 1 1 mixture of the chiral host 223 and the racemic oximes 224 and 227, respectively, was treated with ultra sound in the solid state to induce the optical resolution. Then H2SO4 was added to start the Beckmann rearrangement, the corresponding c-caprolactams 226 and 229 were isolated in 68 % and 64 % yields and ee of about 80 % and 69 % (determined by HPLC analysis on chiracel OC) (Scheme 43) [46]. 

Keywords. Rotaxane dendrimers. Host-guest interaction, Recognition, Self-assembly, Supra-molecular chemistry... 

Acceptor guest molecules such as quinone, TCNQ, or toluene can be accommodated in the flexible cavity of face-to-face bismacrocyclic Nin complexes (656). The host-guest interactions decrease the energy gap between the LUMO of the organic acceptors and the HOMO of the complex donors.1664... 

Fig. 6. Diagrammatic (two-dimensional) representation of different modes of lattice inclusions involving coordinative (H-bond) interactions (indicated by broken lines) (a) cross-linked matrix type of inclusion (host-host interaction, true clathrate) (b) coordinatoclathrate type of inclusion (coordinative host-guest interaction, coordination-assisted clathrate)...

The latter could be obtained, if particular donor substituents (e.g. specific functional groups) facing corresponding acceptor groups of the guest molecule are added to the host and vice versa, thus using specific host-guest interactions of polar... 

Akiyoshi K, Ueminami A, Kurumada S et al (2000) Self-association of cholesteryl-bearing poly(L-lysine) in water and control of its secondary structure by host — guest interaction with cyclodextrin. Macromolecules 33 6752-6756... 

Host-guest interactions. The area of host-guest chemistry encompasses the complexation by organic hosts of a range of both organic and inorganic guests. 

With simple crowns, complex formation may involve various degrees of inclusion of the guest into the cavity of the crown and a conformational rearrangement of the crown is almost always necessary for strong complexation to occur. This will normally involve a redirection of the donor electron pairs on complex formation so that their final orientations optimize a particular host-guest interaction. 

In this form sPS can absorb reversibly certain analytes, whose size and shape well fit the nanocavities establishing specific host guest interactions, when exposed to vapor or liquid environment where these compounds are present even in traces. 

Figure 20. Schematic models of host-guest interaction. Host membranes are (a) CsAzoCioN+Br and (b) CgAzoC)oN+Br, respectively.

Abstract This chapter updates but mostly supplements the author s Ange-wandte Review,111 setting in context recent advances based on protein and nucleic acid engineering. Systems qualify as a true enzyme mimics if there is experimental evidence for both the initial binding interaction and catalysis with turnover, generally in the shape of saturation kinetics. They are discussed under five broad headings mimics based on natural enzymes, on other proteins, on other biopolymers, on synthetic macromolecules and on small-molecule host-guest interactions. 

Mimics based on natural enzymes Mimics based on other proteins Mimics based on other biopolymers Mimics based on synthetic macromolecules Mimics based on small-molecule host-guest interactions... 

Mimics Based on Small-Molecule Host-Guest Interactions... 

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