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Issue 20, 2017
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Site-selective anion recognition of an interlocked dimer

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Interlocked dimer 2, which is composed of two physically interlocked monomers 1, has three cavities (cavity A × 2 and cavity B × 1) and can encapsulate three anions, such as NO3 and BF4, one anion per cavity. There are six possible encapsulation patterns, AF; two (A and F) contain only one kind of anion and the others (BE) contain both NO3 and BF4 at the same time with different ratios and with different positions. Anion competition experiments showed that in addition to F, which encapsulates three NO3 ions, C, in which NO3 and BF4 ions are captured in cavities A and cavity B, respectively, was selectively formed. Detailed investigations have revealed that BE were formed by dimerization, but three of the four were subjected to anion exchange and converged into C or F. This selective formation can be explained by the fact that NO3 is a better anion template than BF4, as well as the molecular structure of the interlocked dimer; cavities A are surrounded by four bridging ligands and can be accessed by free anions, whereas no space available for anion exchange is present around cavity B because this cavity is surrounded by eight bridging ligands. Therefore, the BF4 ions in cavities A are expelled by free NO3, but the BF4 ion in cavity B is not, resulting in the selection of C and F. We have found that the volume of the cavity influenced anion recognition. New interlocked dimer 3, which has smaller cavities than those of 2, captured three NO3 ions to form F, whereas only a small amount of an interlocked dimer that contains both NO3 and BF4 was formed.

Graphical abstract: Site-selective anion recognition of an interlocked dimer

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Publication details

The article was received on 11 Feb 2017, accepted on 20 Apr 2017 and first published on 20 Apr 2017

Article type: Paper
DOI: 10.1039/C7OB00328E
Org. Biomol. Chem., 2017,15, 4328-4335

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    Site-selective anion recognition of an interlocked dimer

    R. Sekiya, M. Fukuda and R. Kuroda, Org. Biomol. Chem., 2017, 15, 4328
    DOI: 10.1039/C7OB00328E

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