Assembled structures pillar arenes - crystal states

In this chapter, first, the assembled structures of the cyclic pentamers, pillar[5]arenes, and cyclic hexamers, pillar[6]arenes, in the crystal state are discussed. They have been most widely used because they can be obtained in relatively good yields. Pillar[5]- and pillar[6]arenes possess clear cylindrical pillar-shaped structures when compared with other macrocyclic compounds. Therefore, it is envisioned that the assembled structures of pillar[n]arenes in the crystal state should be easily analyzed and this pre-organized conformation will facilitate the formation of herringbone, one-dimensional channel and slipped-stacked pillar[w]arenes. It has been revealed that the assembled structures of pillar[n]arenes largely depend on the ring size, substituents and solvents used to obtain the single crystal. The assembled structures of pil-lar[ ]arenes contribute to the gas and organic vapor adsorption properties. 

Second, we describe crystal state-assembled structures of pillar[5]arenes, pillar[6]arenes, and larger pillar[n]arene homologs (n = 8, 9, 10). Furthermore, the bulk materials formed using pillar[ ]arenes are discussed. 

Huang et al. also reported the assembled structures of an amphiphilic pillar[5]arene having all five ester groups on the same side (6.20) in the crystal state. The amphiphilic pillar[5]arene also formed onedimensional channels with a rotation angle of 36° (Figure 6.12). The trend is the same as for the non-symmetrical pillar[5]arenes having all five alkoxy groups on the same side, and for a pillar[5]arene with 10 ester moieties. 

In their crystalline state, pillar[5]arenes mainly form three different kinds of assembled structure, including 3D structures (e.g., herringbone), ID channels and slipped-stack structures. The ring size, nature of the substituents on the rims of the pillar[ ]arene structure and type of solvent used for the crystallization aU play a critical role in dictating the assembled structures of pillar[/i]arenes. 

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