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Published July 13, 2005 | Supplemental Material + Published
Journal Article Open

Linear Artificial Molecular Muscles

Abstract

Two switchable, palindromically constituted bistable [3]rotaxanes have been designed and synthesized with a pair of mechanically mobile rings encircling a single dumbbell. These designs are reminiscent of a "molecular muscle" for the purposes of amplifying and harnessing molecular mechanical motions. The location of the two cyclobis(paraquat-p-phenylene) (CBPQT^(4+)) rings can be controlled to be on either tetrathiafulvalene (TTF) or naphthalene (NP) stations, either chemically (1H NMR spectroscopy) or electrochemically (cyclic voltammetry), such that switching of inter-ring distances from 4.2 to 1.4 nm mimics the contraction and extension of skeletal muscle, albeit on a shorter length scale. Fast scan-rate cyclic voltammetry at low temperatures reveals stepwise oxidations and movements of one-half of the [3]rotaxane and then of the other, a process that appears to be concerted at room temperature. The active form of the bistable [3]rotaxane bears disulfide tethers attached covalently to both of the CBPQT^(4+) ring components for the purpose of its self-assembly onto a gold surface. An array of flexible microcantilever beams, each coated on one side with a monolayer of 6 billion of the active bistable [3]rotaxane molecules, undergoes controllable and reversible bending up and down when it is exposed to the synchronous addition of aqueous chemical oxidants and reductants. The beam bending is correlated with flexing of the surface-bound molecular muscles, whereas a monolayer of the dumbbell alone is inactive under the same conditions. This observation supports the hypothesis that the cumulative nanoscale movements within surface-bound "molecular muscles" can be harnessed to perform larger-scale mechanical work.

Additional Information

© 2005 American Chemical Society. ACS Editors' Choice - Sponsored Access by American Chemical Society. Received February 20, 2005. Publication Date (Web): June 15, 2005. This work was funded in part by a National Science Foundation NIRT grant (ECS-0103559), by NASA's Institute for Cell Mimetic Space Exploration, and by the Defense Advanced Research Projects Agency (DARPA) Biomolecular Motors program. Some of the compound characterizations are supported by the National Science Foundation under equipment grant numbers CHE-9974928 and CHE-0092036. In Denmark, this work was supported by the Danish Natural Science Research Council (SNF, grants 21-03-0014 and 21-03-0317).

Attached Files

Published - ja051088p.pdf

Supplemental Material - ja051088p_si_001.pdf

Supplemental Material - ja051088psi20050228_030428.pdf

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Additional details

Created:
August 19, 2023
Modified:
October 24, 2023