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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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The Lyotropic Nature of Halates: An Experimental Study
Mert Acar1, Duccio Tatini1, Barry W Ninham2,3
1Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, 50019 Firenze, Italy.
Molecules (Basel, Switzerland)
|December 11, 2022
Summary
The kosmotropic nature of halates increases from chlorate to iodate, reversing the trend seen in halides. This study experimentally confirms iodate as a kosmotrope and chlorate as a chaotrope.
Area of Science:
- Physical Chemistry
- Solution Chemistry
Background:
- Halides exhibit decreasing kosmotropicity from fluoride to iodide.
- Halates (XO3-) present a contrasting trend in kosmotropicity compared to halides.
- Understanding anion behavior in aqueous solutions is crucial for Hofmeister phenomena.
Purpose of the Study:
- To experimentally investigate the lyotropic nature of sodium halate solutions (NaClO3, NaBrO3, NaIO3).
- To assess the kosmotropicity/chaotropicity of halate anions (ClO3-, BrO3-, IO3-).
- To confirm previous simulation results and explore the role of anion polarizability.
Main Methods:
- Density, conductivity, viscosity, and refractive index measurements of aqueous sodium halate solutions.
- Measurements conducted across varying temperatures and salt concentrations.
- Evaluation of activity coefficients and salt polarizability from experimental data.
Main Results:
- Iodate (IO3-) acts as a kosmotrope, while chlorate (ClO3-) acts as a chaotrope.
- Bromate (BrO3-) exhibits an intermediate kosmotropic/chaotropic nature.
- The kosmotropic-chaotropic ranking for halates (ClO3- < BrO3- < IO3-) is the reverse of that for halides.
Conclusions:
- Experimental data confirms the reversed kosmotropic-chaotropic ranking of halates compared to halides.
- Anion polarizability plays a significant role in interpreting Hofmeister phenomena for halates.
- The study provides experimental validation for the distinct lyotropic behavior of halate anions.
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