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06:44
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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Halogen- and hydrogen-bonding catenanes for halide-anion recognition
1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-272690.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|June 4, 2014
Summary
This study demonstrates that halogen bonding (XB) creates more stable anion-templated pseudorotaxanes than hydrogen bonding (HB). These stable structures were used to create novel catenanes with selective halide recognition properties.
Area of Science:
- Supramolecular Chemistry
- Organic Chemistry
- Chemical Crystallography
Background:
- Halogen bonding (XB) is a non-covalent interaction increasingly utilized in molecular assembly.
- Anion-templated synthesis offers a route to complex interlocked molecular architectures.
- Macrocyclic compounds provide pre-organized cavities for guest binding and templation.
Purpose of the Study:
- To investigate the use of halogen bonding in the solution-phase assembly of anion-templated pseudorotaxanes.
- To compare the stability of halogen-bonded (XB) pseudorotaxanes with analogous hydrogen-bonded (HB) systems.
- To synthesize and characterize novel interlocked catenanes using XB interactions and evaluate their anion recognition properties.
Main Methods:
- Solution-phase self-assembly utilizing halogen-bonding interactions.
- Synthesis of isophthalamide macrocycles and pyridinium threading components.
- 1H NMR spectroscopic titration for stability studies.
- Grubbs' catalyst-mediated ring-closing metathesis (RCM) for catenane formation.
- Anion binding studies in competitive solvent mixtures.
Main Results:
- Successful assembly of anion-templated pseudorotaxanes via halogen bonding between macrocycles and pyridinium components.
- Halogen-bonded pseudorotaxane assemblies exhibited enhanced stability compared to hydrogen-bonded analogues.
- Novel interlocked catenanes were synthesized by exploiting the stability of the XB pseudorotaxane intermediates.
- The synthesized catenanes demonstrated selective recognition of heavier halides (iodide and bromide) over chloride and acetate.
Conclusions:
- Halogen bonding provides a robust strategy for constructing stable anion-templated supramolecular assemblies.
- The stability of XB-based pseudorotaxanes is advantageous for the subsequent synthesis of complex interlocked molecules like catenanes.
- The developed catenanes show potential as selective sensors or receptors for specific halide anions.
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