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Published on: March 24, 2018
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Dealing with supramolecular structure for ionic liquids: a DOSY NMR approach
Marcileia Zanatta1, Víctor U Antunes, Cláudio F Tormena
1Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 Porto Alegre 91501-970 RS, Brazil. fpsantos@ufrgs.br marcizanatta@ufrgs.br.
Physical Chemistry Chemical Physics : PCCP
|January 19, 2019
Summary
Diffusion-ordered spectroscopy (DOSY) reveals how ionic liquid structures behave in solution. Ion structure and concentration affect ion pair formation, which can be disrupted by water content in specific cases.
Area of Science:
- Physical Chemistry
- Supramolecular Chemistry
- Analytical Chemistry
Background:
- Ionic liquids (ILs) are versatile solvents with tunable properties.
- Understanding the dynamic-structural behavior of ILs is crucial for their application.
- Diffusion-ordered spectroscopy (DOSY) offers insights into IL molecular dynamics.
Purpose of the Study:
- To investigate the dynamic-structural behavior of imidazolium-based ionic liquids.
- To explore the influence of varying cation and anion structures on IL behavior.
- To assess the impact of IL concentration and solvent polarity on ion pairing.
Main Methods:
- Experimental measurement of 1H diffusion coefficients using DOSY NMR.
- Systematic variation of cation (1-n-butyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tetra-n-butylammonium) and anion (prolinate, acetate, o-trifluoromehtylobenzoate) structures.
- Evaluation of IL concentration effects (0.01–0.5 mol L-1) and solvent type (chloroform, water, DMSO).
Main Results:
- Contact ion pairs and aggregates are maintained in both chloroform and water across the studied concentration range.
- The structure of both cations and anions significantly influences the dynamic-structural behavior of ILs.
- For 1,2,3-trimethylimidazolium imidazolate (TMI·Im) in DMSO, confined water content affects ion pair stability and can disrupt supramolecular structure.
Conclusions:
- DOSY is a powerful technique for analyzing the dynamic-structural behavior of ionic liquids.
- The interplay between ion structure, concentration, and solvent dictates the persistence of ion pairs in IL solutions.
- Water content can play a critical role in destabilizing IL supramolecular structures, particularly in specific solvent systems.
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