Self-assembly of a double calix[6]arene pseudorotaxane in oriented channels

Chemistry. 2008;14(1):98-106. doi: 10.1002/chem.200700748.

Abstract

A synthetic study to disclose the more appropriate manner by which two calix[6]arene units could be connected for the construction of an extended tubular structure was undertaken. As a result, a head-to-tail double calix[6]arene having the structure of an oriented nanotube that is about 2.6 nm long and 1.6 nm wide was prepared and characterized. This molecule is able to act as a wheel-type host and forms a supramolecular complex with an axle-type molecule, derived from 4,4'-bipyridinium (viologen), through very efficient self-assembly in solution. The properties of such a pseudorotaxane-type complex, which is stabilized by a combination of noncovalent interactions, were investigated in solution by UV/Vis absorption spectroscopy and voltammetric methods. These observations provide a clue about the location of the bipyridinium unit along the nanotube. In the solid state, the complex undergoes a further stage of self-assembly, thereby initiating extended oriented tubular structures. Crystallographic studies revealed that the positioning of the viologen dication in this asymmetric wheel is addressed by a complicated pattern of cooperative noncovalent intermolecular interactions that involve only one half of the host, whereas the remaining (more polar) half of the host is exploited to create long-range structural order that leads to a "secondary" structure of extended supramolecular channels that, in turn, self-assemble in the lattice, thus giving rise to a "tertiary" structure of parallel sandwiches of nanotubes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calixarenes / chemical synthesis
  • Calixarenes / chemistry*
  • Crystallography, X-Ray
  • Models, Molecular
  • Molecular Structure
  • Phenols / chemical synthesis
  • Phenols / chemistry*
  • Rotaxanes / chemistry*
  • Spectrophotometry

Substances

  • Phenols
  • Rotaxanes
  • calix(6)arene
  • Calixarenes