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Halogen-Bonding Heteroditopic [2]Catenanes for Recognition of Alkali Metal/Halide Ion Pairs |
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| Authors: | Hui Min Tay Dr Yuen Cheong Tse Dr Andrew Docker Christian Gateley Dr Amber L Thompson Heike Kuhn Zongyao Zhang Prof Paul D Beer |
| Institution: | 1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA UK;2. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA UK
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China These authors contributed equally to this work. |
| Abstract: | The first examples of halogen bonding (XB) heteroditopic homo2]catenanes were prepared by discrete Na+ template-directed assembly of oligo(ethylene glycol) units derived from XB donor-containing macrocycles and acyclic bis-azide precursors, followed by a CuI-mediated azide-alkyne cycloaddition macrocyclisation reaction. Extensive 1H NMR spectroscopic studies show the 2]catenane hosts exhibit positive cooperative ion-pair recognition behaviour, wherein XB-mediated halide recognition is enhanced by alkali metal cation pre-complexation. Notably, subtle changes in the catenanes’ oligo(ethylene glycol) chain length dramatically alters their ion-binding affinity, stoichiometry, complexation mode, and conformational dynamics. Solution-phase and single-crystal X-ray diffraction studies provide evidence for competing host-separated and direct-contact ion-pair binding modes. We further demonstrate the 2]catenanes are capable of extracting solid alkali-metal halide salts into organic media. |
| Keywords: | Halogen Bonding Heteroditopic Receptors Ion-Pair Recognition Mechanically Interlocked Molecules Solid–Liquid Extraction |