A novel supramolecular system: combination of two switchable processes in a [2]rotaxane.

A novel supramolecular system, which is made up of a dibenzo[24]crown-8 (DB24C8) ring component linked with a calix[4]arene derivative, a dumbbell component, containing a secondary ammonium center (-NR(2)H(2) (+)-) and a 4,4'-bipyridinium (BIPY(2+)) unit, and stoppered with two 3,5-di-tert-butylphenyl groups on the two termini of the dumbbell component, has been synthesized. The system displays a combination of two processes: the pH-induced shuttling of a DB24C8 ring and the complexation/decomplexation of K(+) ions. The switching process of this supramolecular system was investigated in detail by (1)H NMR spectroscopy. The results showed that the supramolecular system can only switch smoothly in CD(3)CN. The two separated switchable processes can run together smoothly in this supramolecular system.