Water-soluble pillar[5]arene was synthesized by the introduction of carboxylate anions at both upper and lower rims. When cationic viologen salt was mixed with the water-soluble pillar[5]arene in aqueous media, a very stable 1:1 host-guest complex was formed.

Introduction of bulky substituents such as benzyl and pyrenyl groups using click reactions inhibited or slowed the rotation of the units on the NMR chemical shift timescale. The perpyrenylated pillar[5]arene showed a thermally-responsive excimer emission, but a unit model of the perpyrenylated pillar[5]arene did not exhibit such a response.

We report supramolecular assemblies of a beta-cyclodextrin dimer linked at both ends of a fluorescent phenylethynylpyrene moiety (Py-beta-CD dimer). The Py-beta-CD dimer formed supramolecular associations in aqueous media due to the pi-pi stacking of the hydrophobic phenylethynylpyrene moiety. From tapping mode atomic force microscopy measurements, the Py-beta-CD dimer formed wire-shaped assemblies in aqueous media. By adding sodium adamantane carboxylate to the supramolecular assemblies, the structural change to J-type assemblies was observed. In contrast, upon addition of the electron-deficient guest, the electron transfer from the electron rich phenylethynylpyrene moiety of the supramolecular assemblies to the electron-deficient guest took place.