Folding of a donor–acceptor polyrotaxane by using noncovalent bonding interactions

doi:10.1073/pnas.0711072105

Folding of a donor–acceptor polyrotaxane by using noncovalent bonding interactions

*California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, 405 Hilgard Avenue, Los Angeles, CA 90095; and
^†Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125

Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved February 26, 2008 (received for review November 21, 2007)

Abstract

Mechanically interlocked compounds, such as bistable catenanes and bistable rotaxanes, have been used to bring about actuation in nanoelectromechanical systems (NEMS) and molecular electronic devices (MEDs). The elaboration of the structural features of such rotaxanes into macromolecular materials might allow the utilization of molecular motion to impact their bulk properties. We report here the synthesis and characterization of polymers that contain π electron-donating 1,5-dioxynaphthalene (DNP) units encircled by cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺), a π electron-accepting tetracationic cyclophane, synthesized by using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The polyrotaxanes adopt a well defined “folded” secondary structure by virtue of the judicious design of two DNP-containing monomers with different binding affinities for CBPQT⁴⁺. This efficient approach to the preparation of polyrotaxanes, taken alongside the initial investigations of their chemical properties, sets the stage for the preparation of a previously undescribed class of macromolecular architectures.

Footnotes

^§To whom correspondence should be sent at the present address:
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208.
E-mail: stoddart{at}northwestern.edu
Author contributions: W.Z., W.R.D., A.Z.S., D.B., J.K.G., J.R.H., and J.F.S. designed research; W.Z., W.R.D., A.Z.S., and D.B. performed research; and W.Z., W.R.D., A.Z.S., D.B., J.K.G., J.R.H., and J.F.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0711072105/DCSupplemental.