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Issue 22, 2017
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Competition between the donor and acceptor hydrogen bonds of the threads in the formation of [2]rotaxanes by clipping reaction

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Abstract

The synthesis of benzylic amide [2]rotaxanes using 1,2-bis(aminocarbonyl-(1′-tert-butyl-1H-pyrazole-[3′]5′-yl))-ethanes as templates is reported. These templates are equipped with tert-butyl pyrazole-based stoppers and have donor (N–H) and acceptor (C[double bond, length as m-dash]O) hydrogen bond groups. The synthesis of [2]rotaxanes has been shown to be highly dependent on the tert-butylpyrazole stoppers. While the thread with 1′,3′-disubstituted pyrazoles as stopper units was shown to be an excellent template for the synthesis of [2]rotaxanes, the thread with 1′,5′-disubstituted pyrazoles as stopper units did not yield the expected [2]rotaxane. The structure of the synthesized [2]rotaxanes was characterized using NMR experiments and X-ray diffraction, with the latter showing that the macrocycle adopts a distorted chair conformation. An in-depth study of the isolated thread's X-ray structures and concentration-dependent NMR experiments seem to explain the dependence of the rotaxane formation on the substitution pattern of the thread's pyrazole stoppers.

Graphical abstract: Competition between the donor and acceptor hydrogen bonds of the threads in the formation of [2]rotaxanes by clipping reaction

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Publication details

The article was received on 06 Jul 2017, accepted on 04 Oct 2017 and first published on 04 Oct 2017


Article type: Paper
DOI: 10.1039/C7NJ02443F
Citation: New J. Chem., 2017,41, 13303-13318
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    Competition between the donor and acceptor hydrogen bonds of the threads in the formation of [2]rotaxanes by clipping reaction

    M. A. P. Martins, G. C. Zimmer, L. V. Rodrigues, T. Orlando, L. Buriol, M. Alajarin, J. Berna, C. P. Frizzo, H. G. Bonacorso and N. Zanatta, New J. Chem., 2017, 41, 13303
    DOI: 10.1039/C7NJ02443F

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