Interaction between guests

Polar interaction between guest and cyclodextrin molecules, 32 428-432,434-435 Polarized X-ray absorption spectroscopy, 35 15-17... 

The polar interaction between guest and cyclodextrin molecules (44). 

Davidson (1971) determined that the most important rotation inhibition interactions between guest molecules (in adjacent cages) were the dipole-dipole interactions, but even they were of minor importance. Within a single cage, both nonpolar and polar guest molecules such as EO, THF, and acetone have only small barriers to rotational freedom, which approximates that in the vapor phase. The rotational freedom is probably due to the fact that the sum of the cage water dipoles effectively cancel near the center of each cage, and even the quadrupolar fields are relatively small. 

Occupation of hydrate cavities and the hydrate structure is determined to a large degree by the guest size in structures I and II. In structure H both size and shape considerations are necessary for a guest molecule. The repulsive interactions between guests and hosts stabilize the hydrate structure. 

The trends in endohedral research point towards increased synthesis and investigation of systems containing transition-metal ions, either in the form of elemental or inorganic clusters. As the two Sc endohedrals discussed here have shown, the 3d levels are more likely to participate in hybridisation and thus exhibit a range of interactions between guest and host fullerene than their 4f... 

The stepwise construction of self-assembled organic/inorganic multilayers based on multivalent supramolecular interactions between guest-functionalized dendrimers and nanoparticles and host-modified gold nanoparticles has been developed, yielding supramolecular LbL assembly (Fig. 13.8).12 Multilayer thin films composed of... 

In the absence of guest molecules, the water host framework is unstable. The stability stems from van der Waals interactions between guest and host and is dependent on the extent of occupancy of the cages by the guest. 

Clathrate hydrates are crystalline but nonstoichiometric compounds and all the cages are not always occupied. Clathrate hydrates are stable only when the interaction between guest and water molecules dominates over sum of the unfavorable two terms (1) entropy decrease arising from confinement of guest molecules in small void cages, and (2) free energy for formation of empty clathrate hydrate structure from ice or liquid water. 

Corrections to the last two assumptions have been the most beneficial in improving the theory. Together, the two assumptions (4. no interactions between guests, and 5. host molecules energy being independent of cavity occupation) comprise the ideal solid solution theory, which has been satisfactory for almost 40 years. However, a recent study showed that a 0.5% change in the lattice parameter can change the pressure prediction (at F-lOO bar) by 15%. 

From a supramolecular perspective, cyclodextrins offer a preformed cavity of defined size within a water-soluble macrocycle. The interaction between guest molecules, or substituents to the cyclodextrin itself, leads to some useful results. Hydrophobic fluorescent substituents will be self-included by the macrocycle in aqueous solution until they are displaced by guests with even greater affinities [6]. The act of displacement will generate a fluorescent response that lends itself to sensor applications. It is also possible to use the hydrophobic core to induce rotaxane formation. This approach has been used by many groups, for example, Liu has recently used it to prepare water-soluble gold-polypseudorotaxanes that capture fullerenes such as C60 [7]. 

The absorption spectrum of atoms and molecules in low temperature solids is composed of a sharp zero-phonon line and a phonon side band (Table 2.12 ). The phonon side band corresponds to light absorption accompanied by phonon absorption or emission. The absorption shown in bold in Table 2.12 is a zero-phonon line. The sum of the absorption, drawn in a finer line, yields the phonon side band. The phonon side band appears on the higher energy side of the zero-phonon line at low temperatures. A measure of the interaction between guest molecule and host matrix is given by the Debye-Waller factor, DW(T), defined as a function of temperature, T, in Eq. (2.3), using the areas of the zero-phonon line, S0(T), and the phonon side band, SP(T). 

Regular nanosize pores are snitable for confining guest molecules even when the intermolecular interaction between guest and host molecules is governed only by the dispersion force, the so-called van der Waals force. Self-assembly processes... 

The tweezer 8 was introduced as an analogue of echinomycin (vide infra). As such, the distance between the two binding chromophores is 10.4 A, large enough to accommodate two n systems. It was shown that in the solid state, two ti systems can be bound in the cleft of Shown in Fig. 6 are crystal structure data for the inclusion complexes of 7 and 8 with TNB. Both n-stacking and edge-face interactions between guest and host are evident from these structures. The 8/TNB complex indicates clearly that two n systems can be accommodated within the cleft of 8. 

Interactions between guest molecules in adjacent cages are neglected. 

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