Calix[6]arene-Based [3]Rotaxanes as Prototypes for the Template Synthesis of Molecular Capsules

Abstract

In this work, the ability of several bis-viologen axles to thread a series of heteroditopic tris(N-phenylureido)calix[6]arene wheels to give interwoven supramolecular complexes to the [3]pseudorotaxane type was studied. The unidirectionality of the threading process inside these nonsymmetric wheels allows the formation of highly preorganised [3]pseudorotaxane and [3]rotaxane species in which the macrocycles phenylureido moieties, functionalised with either ester, carboxylic, or hydroxymethyl groups, are facing each other. As verified by NMR and semiempirical computational studies, these latter compounds possess the correct spatial arrangement of their subcomponents, which could lead, in principle, upon proper bridging reaction, to the realisation of upper-to-upper molecular capsules that are based on calix[6]arene derivatives.

Supramolecular Handshakes: Characterization of Urea‐Carboxylate Interactions Within Calixarene Frameworks

“…[21,22] An important group of molecular containers, especially from an application standpoint, are those assembled in water due to the hydrophobic effect. [23,24] Aside from being used in the field of the development of supramolecular capsules, the knowledge of non-covalent pairing of complementary molecular blocks is nowadays exploited in the concepts of supramolecular Velcro (applied as adhesives, [25][26][27][28] LMW and polymer gels [29,30] ), in modelling of biochemically important processes, [31][32][33] and molecular machines (for example, rotaxanes [34,35] ).…”