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Issue 19, 2019
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The influence of metal-complexing macrocycle size on intramolecular movement in rotaxanes

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Abstract

[2]rotaxanes composed of a dibenzo-24-crown-8 wheel (DB24C8) and an axle containing two metal-complexing tetraazamacrocyclic units linked with a p-xylylene bridge, coordinating the same or different metal ions (Ni and/or Cu) are described. A symmetric di-Ni rotaxane crystallizes in the monoclinic P21/c space group with one rotaxane cation and four PF6 counterions in the asymmetric part of the unit cell. In the crystal, the cations and anions of the investigated compound form an intertwined 3D-framework with C–H⋯F and C–H⋯π intermolecular interactions. The NMR ROESY spectrum of the diamagnetic di-Ni rotaxane confirms that at room temperature slow shuttling of the DB24C8 moiety takes place along the symmetric axle. The non-symmetric rotaxane, containing 14- and 16-membered nickel(II)-complexing macrocycles, exists in solution as an equilibrium mixture of two conformers in the ratio of ca. 1 : 7. This rotaxane behaves as a potential-controlled molecular switch: in the major isomer, the DB24C8 moiety is localized in the vicinity of the 14-membered metal-complexing macrocycle, and moves towards the 16-membered unit upon the first oxidation. Reverse translocation occurs after the subsequent oxidation of the 14-membered complex unit. In contrast, no such movements of the DB24C8 moiety were observed upon investigation of the heteronuclear [2]rotaxane, coordinating copper(II) and nickel(II) ions.

Graphical abstract: The influence of metal-complexing macrocycle size on intramolecular movement in rotaxanes

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Publication details

The article was received on 07 Jan 2019, accepted on 10 Apr 2019 and first published on 11 Apr 2019


Article type: Paper
DOI: 10.1039/C9DT00083F
Dalton Trans., 2019,48, 6546-6557

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    The influence of metal-complexing macrocycle size on intramolecular movement in rotaxanes

    M. Woźny, K. M. Tomczyk, A. Więckowska, S. Sutuła, D. Trzybiński, K. Woźniak and B. Korybut-Daszkiewicz, Dalton Trans., 2019, 48, 6546
    DOI: 10.1039/C9DT00083F

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