Anion-tuning of supramolecular gel properties

Abstract

The study of supramolecular gels has developed into a well-recognised field of materials science, pertaining to the general area of soft matter. The use of small molecules that aggregate through supramolecular interactions (such as hydrogen bonds, ππ interactions, coordination bonds and van der Waals interactions) has given materials scientists an alternative to polymeric compounds for the development of practical gels. There have been further attempts to functionalize, activate or control the physical properties of such gels by means of the reversibility of the interactions between the component molecules. Tuning of these characteristics has been accomplished by using mechanical, thermal, electrochemical, electromagnetic and chemical stimuli. The use of anions as a chemical stimulus has been a recent development and is the subject of this Perspective.

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Figure 1: The acetone gel of 1, showing the transitions between the gel and liquid states on addition of chemical stimuli (X = F, Cl or BF4).
Figure 2: Schematic representation of the reversible polymerization and the reversible conversion between folded and unfolded conformations of a coordination chain on counteranion exchange of 5, resulting in state changes from gel to sol and vice versa.
Figure 3: Gels of 6 (11 wt % in acetonitrile) exhibit multi-responsive behaviour, including the chemo-response to formic acid and TBA+ ClO4.
Figure 4: Diagram showing the luminescence profiles of Au(I) pyrazolate complex 8 in hexane as solutions and gels, and the schematics of the self-assembling structures.

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Acknowledgements

We thank the Commonwealth Scholarships Commission and the EPSRC for funding of our work in the fascinating world of supramolecular gels.

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Correspondence to Jonathan W. Steed.

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Lloyd, G., Steed, J. Anion-tuning of supramolecular gel properties. Nature Chem 1, 437–442 (2009). https://doi.org/10.1038/nchem.283

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