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Issue 4, 2017
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Radically promoted formation of a molecular lasso

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Two potential viologen-based molecular lasso precursors—both composed of a 4,4′-bipyridinium (BIPY2+) unit as part of a rope appended to a cyclobis(paraquat-p-phenylene) (CBPQT4+) loop—that have been designed to mimic the threading/unthreading motion of lasso peptides, have been synthesised and characterised. Solution and solid-state experiments reveal that, when the BIPY2+ unit in the rope and the CBPQT4+ loop are connected by a bulky linker, no lasso-like conformational transformation is observed between the different redox states on account of steric effects. In sharp contrast, when the linker size is small, the molecule can be switched between (i) a free rope-like conformation in its fully oxidised state and (ii) a self-entangled lasso-like conformation under reducing conditions employing either chemical or electrochemical stimuli: the BIPY˙+ unit in the rope resides inside the cavity of the CBPQT2(˙+) loop, forming a pseudo[1]rotaxane. The switching process is reversible and stereochemically unambiguous. This research shows how tiny structural differences can induce significantly different self-complexing properties and sheds light on designing functional artificial actuators.

Graphical abstract: Radically promoted formation of a molecular lasso

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The article was received on 14 Nov 2016, accepted on 15 Jan 2017 and first published on 16 Jan 2017

Article type: Edge Article
DOI: 10.1039/C6SC05035B
Citation: Chem. Sci., 2017,8, 2562-2568
  • Open access: Creative Commons BY-NC license
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    Radically promoted formation of a molecular lasso

    Y. Wang, J. Sun, Z. Liu, M. S. Nassar, Y. Y. Botros and J. F. Stoddart, Chem. Sci., 2017, 8, 2562
    DOI: 10.1039/C6SC05035B

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