Complexation Between (O-Methyl)6 -2,6-Helic[6]arene and Tertiary Ammonium Salts: Acid/Base- or Chloride-Ion-Responsive Host-Guest Systems and Synthesis of [2]Rotaxane.

Complexation between (O-methyl)6 -2,6-helic[6]arene and a series of tertiary ammonium salts was described. It was found that the macrocycle could form stable complexes with the tested aromatic and aliphatic tertiary ammonium salts, which were evidenced by 1 H NMR spectra, ESI mass spectra, and DFT calculations. In particular, the binding and release process of the guests in the complexes could be efficiently controlled by acid/base or chloride ions, which represents the first acid/base- and chloride-ion-responsive host-guest systems based on macrocyclic arenes and protonated tertiary ammonium salts. Moreover, the first 2,6-helic[6]arene-based [2]rotaxane was also synthesized from the condensation between the host-guest complex and isocyanate.