Self-assembling inclusion hosts

Fig. 5 Typical examples of (a-c) self-assembling inclusion hosts (d-f) interlocked and interwoven systems and (g-j) solid state inclusion hosts (a) tennis ball dimer (b) metallamacrocycle (c) ladder-structured metal array (d) catenane (e) rotaxane (f) helicate (g) network lattice host (exemplary host molecule) (h) coorclinatoclathrate host (exemplary hosts) (i) curved framework host molecule and (j) aukward-shape host molecule.

Enantioselective self-assembling of amino acids 209 Host-guest inclusion complexes 213 Reactivity of chiral ion-dipole complexes 233... 

Figure 1.2 Schematic illustrating the difference between a cavitate and a clathrate (a) synthesis and conversion of a cavitand into a cavitate by inclusion of a guest into the cavity of the host molecule (b) inclusion of guest molecules in cavities formed between the host molecules in the lattice resulting in conversion of a clathrand into a clathrate (c) synthesis and self-assembly of a supramolecular aggregate that does not correspond to the classical host-guest description.

Desiraju has reported a crystalline supramolecular wheel-and-axle compound with a structure based on a carboxylic acid dimer.33 Specifically, the group predicted that 4-(triphenylmethyl)benzoic acid would self-assemble to give a homodimer. The dimer was expected, owing to an inability to efficiently pack, to form inclusion compounds that host solvent molecules as guests. Such inclusion would be reminiscent of structurally similar organic molecules that serve as wheel-and-axle compounds in the solid state. The homodimer would, thus, circumvent a covalent synthesis. As predicted, the carboxylic acid formed a homodimer that produced solids that exhibited solvent inclusion (Fig. 15). The packing was dominated by... 

A recent report describes preparation of the monolayers with a permanent inclusion guest. Carceplex molecules having a DMF molecule trapped in the cavity were self-assembled on a gold surface (Figure 29). While the orientation of the host is dictated by the monolayer environment, the guest can adopt different orientations inside the cavity and, in principle, these orientations can be made switchable443. 

As mentioned above, in urea/thiourea-anion inclusion compounds both urea and thiourea molecules adopt various linkage modes not only of self-assembled hydrogen-bonded chains or ribbons but also of composite ribbons with the corresponding anions. The results show that comolecular aggregates of urea or thiourea with other neutral molecules or anionic moieties can be considered as fundamental building blocks for the constructions of various types of novel host lattices. 

In summary, we have shown that novel anionic host lattices can be constructed from urea, thiourea, or selenourea molecules and various anions as building blocks, which readily adopt different topologies for the accommodation of tetraalkylam-monium ions of various sizes. By employing organic cations as templates and suitable counter anions as an ancillary host material, with or without neutral molecules such as H2O as a third component, the lattice engineering of new urea, thiourea, and selenourea inclusion compounds by self-assembly may be further explored. 

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