Asymmetric calix[4]-thiacalix[4]arene tubes: Synthesis and ionophore properties

Asymmetric p-tert-butylcalix4]-p-R-thiacalix4]arene tubes (R = tert-Bu, H, 1-adamantyl) were prepared for the first time by reaction of tosyloxyethoxy derivative of p-tert-butylcalix-4]arene and the corresponding p-R-thiacalix4]arenas in acetonitrile in the presence of K₂CO₃. Complex formation of compounds obtained with sodium, potassium, and rubidium iodides in CDCl₃-CD₃OD, 4:1, was studied by means of ¹H NMR. The ionophore properties of the molecule were governed by the character of substituents on the upper rim of the thiacalixarene fragment, and only the molecular tube containing a fragment of the p-(1-adamantyl)-thiacalix4]arene quantitatively bound potassium ions (quickly) and rubidium ions (slowly).