Silver ion shuttling in the trimer-mimic thiacalix[4]crown tube

Novel 1,3-alternate calix-thiacalix[4] crown trimers bearing crown-5 and crown-6 were prepared. As proven by X-ray diffraction, in a 1:2 mole ratio of ligand to metal ion, the Cs+ and K+ ions prefer to be encapsulated in the trimeric thiacalix[4]crown-6 and crown-5, respectively. On the contrary, the Ag+ ion was found to be entrapped in the central thiacalix spacer as a 1:1 complex confirmed by H-1 NMR spectrosocpy. Variable-temperature H-1 NMR studies for the trimeric thiacalix[4]crown-6 encapsulating the silver ion revealed that the Ag+ ion oscillates through the central thiacalix spacer with the aid of cation-pi interactions.