Supramolecular compounds solid-state inclusion hosts

Table 1 An illustrative timeline charting the development of supramolecular chemistry from its roots in solid-state inclusion compounds, through the birth of macrocyclic host-guest chemistry in the 1960s to its modem incarnation in self-assembled materials and nanoscale chemistry.

Recently, we have been investigating the chemistry of a series of racemic diquinoline compounds that form lattice inclusion hosts. The solid-state structures of these involve only rather weak intermolecular attractions. A number of these hosts assemble by means of centrosymmetric supramolecular synthons, and therefore their enantiomer separation is limited in the solid state. 

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... 

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