Supramolecular assemblies from uranyl ion complexes of hexahomotrioxacalix[3]arenes and protonated [2.2.2]cryptand

Abstract

The use of [2.2.2]cryptand as a deprotonating agent during the synthesis of the mononuclear, monoanionic, uranyl ion complexes of p-R-hexahomotrioxacalix[3]arenes (R = tert-butyl, phenyl) results in the formation of supramolecular assemblies, which have been characterized by their crystal structures and ¹H NMR spectra in solution. In the 1∶1 complex–cryptand assembly, the endo monoprotonated cryptand has its ammonium end embedded in the complex cavity, whereas, in the 2∶1 complexes, the endo diprotonated cryptand is encapsulated in a “sandwich” mode by two complexes with convergent concave surfaces. The latter complexes are the first examples of the use of [2.2.2]cryptand as a “connector” to build calixarene supramolecular systems. The importance of cation–π interactions in this assembling process is discussed.