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 (-NR2H2+-) and a 4,4'-bipyridinium (BIPY2+) 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 H-1 NMR spectroscopy. The results showed that the supramolecular system can only switch smoothly in CD3CN. The two separated switchable processes can run together smoothly in this supramolecular system.