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A strategy has been developed for the design, synthesis, and testing of new clathrate hosts that possess relationship complementarity to specific guest-compounds.

Clathrate chemistry today - Some problems and reflections.- Separation of enantiomers by clathrate formation.- Isolation and optical resolution of materials utilizing inclusion crystallization.- Tri-o-thymotide clathrates.- Structural parsimony and structural variety among inclusion complexes (with particular reference to the inclusion compounds of trimesic acid, N-(p-tolyl)-tetrachlorophthalimide, and the heilbron "complexes").- Inclusion properties of tetraphenylene and synthesis of its derivatives.

A strategy has been developed for the design, synthesis, and testing of new clathrate hosts that possess relationship complementarity to specific guest-compounds.

The family of ionophore (cation-carrier) antibiotics can be subdivided into several groups with different chemical constitution [1]. Amino acids are building blocks of the gramicidins, antamanides, alamethicin and some cyclopeptides from mitochondrial membranes while valinomycin, the enniatins and monamycins consist of depsipeptide units. Nonactins are formed by hydroxy acid residues with attached tetrahydrofuran rings and the nigericin antibiotics nigericin, grisorixin, dianemycin, monensin, X-206 and X-537A contain tetrahydrofuran and -pyran groups fused together by spiro and single C-C linkages (Figure 1). In general, the ionophore mol ecules have cyclic structures with the exception of some gramicidins (these are probably helical [2]) and of the nigericin antibiotics. Although diverse from a chemical point of view, the ionophore antibiotics display rather similar biological activities. They show a broad antimicrobial spectrum against Gram-positive bacteria, yeasts and fungi and have found application in the prevention and treatment of several diseases such as coccidiosis in chicken [3].

Das Tris-(p-brommethyl-phenyl)-benzol (I) reagiert mit dem Tris-(p-mercaptomethyl-phenyl)-benzol (II) in 3l%iger Ausbeute zu dem Macrocyclus (IIIa), der mit Wasserstoffperoxid zu dem Trisulfon (IIIb) oxidiert wird.

Selectivity of enclathration and desolvation of xylene isomers by a dicarboxylic host depends on temperature.

A series of singly bridged triarylmethanols, with different substituents and modified bridging units, form crystalline inclusion compounds with dioxane. X-ray diffraction studies revealed hydrogen bonds between host and guest in all these structures, and in one case also a host-to-host hydrogen bond. Most crystals contain either 1 : 1 or 2 : 1 hydrogen-bonded host–dioxane complexes, dependent on the structural parameters of the host molecule. With both host–guest and host–host hydrogen bonds present, 4 : 1, host–dioxane units are formed. Some structures accommodate additional dioxane guests which are held by van der Waals forces. The stabilities of the different dioxane clathrates were studied by thermal analysis.

New fluorinated host compounds, namely, 2,4,6-tris(4-bromo-3-fluorophenoxy) -1,3,5-triazine, 2,4,6-tris(4-bromo-3,5-difluorophenoxy)-1,3,5-triazine, and 2,4,6-tris(4-bromo-2,6-difluorophenoxy)-1,3,5-triazine, were synthesized to investigate the effect of fluorine on the inclusion behavior. The altered electrostatic potential of the channel wall caused by fluorine substituents led to essential differences in host-guest interactions which were demonstrated by the inclusion of large guest molecules such as fullerenes, decamethylferrocene, or bucky-ferrocene. © 2007 American Chemical Society.

The structures of the acetone inclusion compounds of 2,2′-bis(2,7-dichloro-9-hydroxy-9-fluorenyl)biphenyl (compound 1) and 2,2′-bis(2,7-di-tert-butyl-9-hydroxy-9-fluorenyl)biphenyl (compound 2), with host∶guest ratios of 1∶2 and 1∶1, respectively, have been elucidated. Compound 2 desolvates at 175 °C, whereas compound 1 is much less stable and desolvates at 80 °C. Compound 1 desolvates in a single deceleratory step following a three dimensional diffusion kinetic model. The desolvation of compound 2 follows the first-order kinetic model. The activation energies of desolvation have been evaluated.

This study dealt mainly with the structure-reactivity relationship of selected organic inclusion compounds. The crystal structures of the inclusion compounds of three related hosts, 2,2′–bis(2,7–di-tert-butyl-9–hydroxy-9–fluorenyl)biphenyl, 2,2′–bis (2,7–dichloro-9–hydroxy-9–fluoienyl)biphenyl and 2, 2′–bis(2,7-dibromo-9–hydroxy-9–fluorenyl)biphenyl with 1,4–dioxane (Compound 1), 1,3–dioxane (Compound 2) and 1,3–dioxolane (Compound 3) respectively were elucidated, using single crystal X-ray crystallography. It was found that the guests were either located in channels or constricted channels (cavities), formed by the host framework. The kinetics of desolvation of these compounds were studied and their activation energies were compared.

Both the macro-rings in the double-looptitle ligand, which has C2 symmetry, bind one of the water molecules of solvation and an Li+ ion in the same cavity; the metal ion interacts simultaneously with both captured and the free molecules of water of solvation.

The title compound acts as a clathrate host for dimethylformamide (DMF), ethanol, and propan-2-ol; DMF is held inside a rectangular void of the host lattice via hydrogen bonding and steric interaction.

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 840. DOI:10.1002/anie.198308400

New macrocyclic compounds, in which a large cavity is enclosed by three or four aliphatic bridges between two parallel aromatic systems, have been synthesized by making use of the dilution principle.

2 + 4 Cycloaddition of fumaric or maleic acid to anthracene produces the novel host molecules (1) and (2)respectively, which readily form inclusion compounds with a variety of solvents, among which acetic acid, as demonstrated by its crystal structure, give true clathrate formation with encapsulated dimeric guest units.

The tetra-aryl-allenes (1d) and (2) are representatives of a new host design, acting via formation of crystal channels and selective guest inclusion.

A 21-membered macroring (1) incorporating as characteristic building blocks a 2,6-bridged pyridino site and three adjacent catechol moieties is shown to form selectively an inclusion complex with nitromethane, the crystal structure of which demonstrates a completely encapsulated guest molecule.