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Modular Synthesis and Dynamics of a Variety of Donor–Acceptor Interlocked Compounds Prepared by Click Chemistry

Authors

  • Adam B. Braunschweig Dr.,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
    2. Current Address: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 92101, Israel
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  • William R. Dichtel Dr.,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
    2. Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA, Tel: (+1) 626-395-8920
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  • Ognjen Š. Miljanić Dr.,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
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  • Mark A. Olson,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
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  • Jason M. Spruell,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
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  • Saeed I. Khan Dr.,

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
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  • James R. Heath Prof. Dr.,

    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA, Tel: (+1) 626-395-8920
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  • J. Fraser Stoddart Prof. Dr.

    1. The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA, Fax: (+1) 310-206-5621
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Abstract

A series of donor–acceptor [2]-, [3]-, and [4]rotaxanes and self-complexes ([1]rotaxanes) have been synthesized by a threading-followed-by-stoppering approach, in which the precursor pseudorotaxanes are fixed by using CuI-catalyzed Huisgen 1,3-dipolar cycloaddition to attach the required stoppers. This alternative approach to forming rotaxanes of the donor–acceptor type, in which the donor is a 1,5-dioxynaphthalene unit and the acceptor is the tetracationic cyclophane cyclobis(paraquat-p-phenylene), proceeds with enhanced yields relative to the tried and tested synthetic strategies, which involve the clipping of the cyclophane around a preformed dumbbell containing π-electron-donating recognition sites. The new synthetic approach is amenable to application to highly convergent sequences. To extend the scope of this reaction, we constructed [2]rotaxanes in which one of the phenylene rings of the tetracationic cyclophane is perfluorinated, a feature which significantly weakens its association with π-electron-rich guests. The activation barrier for the shuttling of the cyclophane over a spacer containing two triazole rings was determined to be (15.5±0.1) kcal mol−1 for a degenerate two-station [2]rotaxane, a value similar to that previously measured for analogous degenerate compounds containing aromatic or ethylene glycol spacers. The triazole rings do not seem to perturb the shuttling process significantly; this property bodes well for their future incorporation into bistable molecular switches.

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