New Geometries for Calix[6]arene-Based Rotaxanes

Understanding the role played by the nature, number, and arrangement of binding sites anchored to a macrocycle remains a topic of current interest for the synthesis of new interwoven species. We report the synthesis and detailed structural characterization of a new calix[6]arene derivative decorated with two phenylureido groups anchored at the diametrical position of the calix upper rim that adopts a 1,2,3-alternate conformation in solution and in the solid state. Preliminary data on the ability of this host to form redox-active pseudorotaxanes and rotaxanes are reported.