Inclusion-type compound

The question that emerges at the climax of this survey relates to the possibility of using crystalline inclusion phenomena for optical resolutions of molecular species. Can this be done effectively with suitably designed host compounds The definitely positive answer to this question has elegantly been demonstrated by Toda 20) as well as by other investigators (see Ch. 2 of Vol. 140). An optically active host compound will always form a chiral lattice. Therefore, when an inclusion type structure is induced, one enantiomer of the guest moiety should be included selectively within the asymmetric environment. 

Where might one find new AC/QC materials Our earlier extensions of the p-element components in Zintl-type compounds to the triels (Al, Ga, In, Tl) (beyond the so-called Zintl boundary ) as well as the inclusions of late transition metals had already given us some significant glimpses of new and appropriate chemistry and structures [46,51]. In addition, some examples were already in the literature for Ga [44], In contrast, the anion or intermetallic chemistry of aluminum [45] stands apart from that of the three heavier group members (Ga, In, and Tl) and will not be considered here significantly. 

CA 72, 113395 (1970) claims thermites and thermates (thermites + flake Al, S, hydrocarbon oil and/or oxidizers such as Ba(N03)2, KMu04, etc) of improved ignitability due to inclusion of 2-50% of ferrocene-type compounds. 

Figure 7. Self-assembly between a wire-type compound and a macrocyclic ring leading to an inclusion complex not showing the expected pseudorotaxane structure [16],...

The hydrogen bonding of ammonium ions to crown ethers has also been used to assemble a range of rotaxanes andp. eMd/orotaxanes. The inclusion of a secondary ammonium thread into dibenzo[24]crown-8 followed by covalent capping to give a rotaxane is shown in Scheme 10.19. This kind of approach can result in some interesting multiply threaded rotaxane type compounds, Figure 10.63. 

An alternative technique for the resolution of enantiomers which lack polar functional groups is a diastereomeric complex formation via non-ionic mechanisms. These complexes may be of the external or the inclusion type. Chiral amino acids, metal complexes or host compounds may serve as useful complexing agents (Table 2) [49-64]. 

Fig. 13. Classification/nomenclature of host-guest-type compounds definitions and relations (1) coordinative interaction, (2) lattice barrier interaction, (3) mono-molecular shielding interaction (I) coordination-type inclusion compound (inclusion complex), (II) lattice-type inclusion compound (multi-molecular inclusion compound), (III) cavitate-type inclusion compound (mono-molecular inclusion compound)...

The high-temperature polymorph of TMA, hypothetical y-TMA, and the polyhalide inclusions [cf. Sect. 4.1 (2) Table 2] are isostructural inclusion compounds. We shall show later that the polyhalide inclusions are channel-type compounds and that the so-called y-polymorph is actually an interstitial (clathrate) inclusion compound with empty channels. Although y-TMA is not a true polymorph in the strict thermodynamic sense, it is more convenient at this stage to be slightly inexact in nomenclature rather than pedantic. 

Discovery of the inclusion properties of many channel-type compounds was mainly made by chance. The creation of crystal lattices with tailor-made properties or even the fine tuning of properties of known crystal architectures represent significant challenges for materials chemists. Worth mentioning here is a large family of alicyclic diols, called helical tubulands. These com-... 

Intercalation compounds (inclusion complexes) are formed by VO PO4 2H2O and structurally related layer-type compounds MO PO4 H20 (M = Mo, W, Nb, Ta, Ti). Foreign metal cations can sometimes be incorporated with the water molecules between the layers, particularly if the V or M has been partially reduced. 

As a natural development of the successful molecular inclusion concept, which involved electrostatic as well as van der Waals forces between the interacting host and guest entities, an increasing interest has been shown in the systematic study of lattice-inclusion type systems. A considerable effort has been devoted to the design of new hosts for the formation of stable crystaUine clathrates and the improvement of selective complexations with potential guests. Suitable examples of clathrates studied in recent years include hosts such as Dianin s compounds , perhydrotriphenylene , cyclotriveratrylene triphenylmethane hexakis-(arylthio) and -(arylthiomethyl)benzenes tri-o-thymotide (TOT) and choleic acids (cf. Fig. 1 in Ch. 1 of Vol. 140). Selected series of such clathrate inclusion systems have particularly been useful in research of photochemical reactions in the solid state and of selective molecular complexation that is central to biological phenomena... 

While Wemer complexes are based on discrete coordination complexes, another type of coordination compound with a distinctive extension into 2D layers through utilization of ditopic bidentate ligands was developed and first reported by K. A. Hofmann in 1897, Ni(NH3)2Ni(CN)4 2(C6H6). Hofmann-type compounds also exhibit inclusion properties of suitably sized guest molecules. Iwamoto and coworkers prepared a number of derivatives of Hofmann clathrates (Figure 2). 

Solid state investigations are of great importance in particular in case of studying calixarene and calix-type compounds due to their great ability to form molecular inclusion complexes, co-crystals and supramolecular assemblies. In CSD (Cambridge Structural Database [1]) over 6000 structures of calix-type compounds are deposited so far. Approximately one-third of the entries are organometallic compounds and two-thirds are classified as organic compounds. 

As mentioned above, the number of calixarene and calix-type compounds structures investigated and deposited so far in CSD is very big it is not possible to discuss all of them in this chapter. So the discussion will be limited mostly to organic inclusion compounds and co-crystals of course having in mind that the monomolecular crystal structures as well as the metalorganic complexes are also a rich source of valuable information about geometries, possible conformations, coordinatiOTi types, intermolecular interactions, etc. 

As became apparent through the discussion of the metastability of the ferroelectric parent phase, crystal growth of these materials does pose very specific problems. In addition to the possible inclusion of a phase, one must also be concerned about precise stoichiometry. Specific problems are the R2M0O6-type compounds which are related to the previously discussed materials via the equation... 

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