Highly stable pseudo[2]rotaxanes co-driven by crown ether-ammonium and donor-acceptor interactions |
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Authors: | Dai-Jun Feng |
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Institution: | Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China |
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Abstract: | Bis-p-phenylene-34-crown-10 derivatives 1 and 2, bearing one and two dibenzo24]crown-8 units, respectively, and 4,4′-dipyridinium derivatives of 3·3PF6 and of 4·4PF6, bearing one and two ammonium groups, respectively, have been synthesized from readily available starting materials. 1H NMR and UV-vis studies reveal that in polar acetonitrile 1 binds 3·3PF6 to produce pseudo2]rotaxane 1·3·3PF6 by making use of one donor-acceptor and one electrostatic interaction, whereas 2 binds 4·4PF6 to form pseudo2]rotaxane 2·4·4PF6 through one donor-acceptor and two electrostatic interactions. The association constants of the two pseudorotaxanes have been determined by the UV-vis titration method to be 9.1 (±1.0)×103 M−1 and 6.5 (±0.7)×105 M−1, respectively. The high stability of the new pseudo2]rotaxanes has been ascribed to the cooperative interaction of the two different non-covalent forces. |
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Keywords: | Rotaxane crown ether Donor-acceptor interaction |
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