Self-assembly of bis-[1]rotaxanes based on diverse thiourea-bridged mono-functionalized dipillar[5]arenes

The condensation reaction of mono-amido-functionalized pillar[5]arenes with tere- and iso-phthaloyl diisothiocyanates in acetone under ultrasonic irradiation afforded tere- and iso-phthaloylthiourea-bridged dipillar[5]arenes. The similar reaction of mono-amido-functionalized pillar[5]arenes with 1,ω-bis(4-isothiocyanatophenoxy)alkanes also afforded diphenoxyalkylene thiourea-bridged dipillar[5]arenes. 1H NMR and NOESY spectra clearly indicated that bis-[1]rotaxanes were formed by insertion of longer alkylene chains into the cavities of two pillar[5]arenes. On the other hand, the free-forms of dipillar[5]arenes were obtained with the shorter ethylene chains existing on the outside of the cavities of two pillar[5]arenes.