Cage-type

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). 

Motors must be generally squirrel cage type and not slip-ring. 

Facile syntheses of highly symmetric cage-type cryptands consisted of pyridine rings and their properties as host molecules 98YGK604. 

The tetrameric zinc anion [Zn4(//-ScPh)r,(ScPh)4]2 has been structurally characterized as the first example of a Zn4Se4 adamantane cage-type structure.594 A further example was characterized by Bochmann and co-workers as part of a study of polymetallic zinc selenophenolates, in this case with chlorides replacing the terminal selenophenolates, [Zn4(/u-SePh)6Cl4]. Octameric zinc species were also characterized with either chloride or phosphine ligands resulting in anionic and neutral complexes respectively, [Zn8(/x-SePh)12Cl4]2 and Zn8(yu-SePh)12(SePh)2 (P Pr3)2.301... 

N. ..N axes parallel to each other) with the trityl groups in contact and the space between the diketopiperazine rings filled by methylene chloride. In the resulting structure every guest moiety is within pseudo-cage-type voids surrounded by four adjacent hosts, representing lattice inclusion which is not assisted by any specific coordination between host and guest. 

The detailed structures of several clathrates have been characterized, and a certain degree of selectivity on complexation with different isomers has been detected 21). Most of these complexes are of the channel type, but some of them have structures which simultaneously qualify for channel and cage type descriptors representative examples are illustrated in Figs. 19-21. The crystal data of the complexes are summarized in Table 1. 

According to Steiner et al. [69], who studied the complex of /TCD with 1,4-butanediol, a monomer model of PTHF, the crystal packing in this complex is the cage type and isomorphous to that of the jS-CD hydrate, and the methylene chain vibrates in the cavity. However, in the /J-CD-PTHF complex, the polymer chain lays fixed inside a column formed by linearly bonded CD molecules. In agreement with this picture, CP/MAS NMR spectra showed the PTHF chain in the complex to be much less flexible than that in its mixture with the CD. 

Figure 2.40 Medium-viscosity cage-type finisher [132]. From Shaw, G., Schaller, R. A., Stikeleather, W. J., Melton, M. D., - ... 

We have previously mentioned the kinetic stabilization toward racemization of methyl methanesulfinate included in the cage-type clathrate of TOT (59). Such an effect may indeed be expected, since the cage wall is fairly rigid and the heat... 

Figure 12.20 shows the structure of the side-window circular cage type and linear focused head-on type of photomultiplier which are both preeminent in fluorescence studies. The lower cost of side-window tubes tends to favor their use for steady-state studies, whereas the ultimate performance for lifetime studies is probably at present provided by linear focused devices. In both types internal current amplification is achieved by virtue of secondary electron emission from discrete dynode stages, usually constructed of copper-beryllium (CuBe) alloy, though gallium-phosphide (GaP) first dynodes have been used to obtain higher gains. 

One of the most signiflcant variables affecting zeolite adsorption properties is the framework structure. Each framework type (e.g., FAU, LTA, MOR) has its own unique topology, cage type (alpha, beta), channel system (one-, two-, three-dimensional), free apertures, preferred cation locations, preferred water adsorption sites and kinetic pore diameter. Some zeolite characteristics are shown in Table 6.4. More detailed information on zeolite framework structures can be found in Breck s book entitled Zeolite Molecular Sieves [21] and in Chapter 2. 

Cage-Type Cyclophanes Embedded in Synthetic Bilayer... 

Fig. 3A-C. Space-filling models of artificial receptors, each being capable of providing a large hydrophobic cavity A octopus cyclophane 4 B steroid cyclophane 6 C cage-type cyclophane 8...

In order to construct a hydrophobic three-dimensional cavity that is in-tramolecularly limited in space, we have prepared cage-type cyclophanes by linking macrocyclic rings. First we prepared a macropolycyclic host, which is constructed with two rigid macrocyclic skeletons of different size, tetraaza[3.3.3.3]paracyclophane as the larger one and tetraazacyclotetradecane as the smaller one, and four flexible hydrocarbon chains that connect the two macrocycles [40]. The flexibility of four hydrocarbon chains connecting the two macrocycles allows the induced-fit host-guest interaction in aqueous media. 

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