Dielectric Relaxation and Hydration Interactions for Protic and Aprotic Ionic Liquids using Time Domain Reflectometry
Shrikant P Musale1, Ashok C Kumbharkhane2, Dilip H Dagade1
1Department of Chemistry , Shivaji University , Kolhapur 416004 , India.
The Journal of Physical Chemistry. B
|October 1, 2019
Summary
Ionic liquids (ILs) show varying hydration, with protic ILs exhibiting stronger hydration than aprotic ILs due to hydrogen bonding. This impacts their solvation capabilities for sparingly soluble organic molecules.
Area of Science:
- Physical Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Ionic liquids (ILs) possess unique properties like H-bonding, hydrophobicity, and cooperativity, influencing their hydration numbers.
- These properties enable ILs to dissolve sparingly soluble organic molecules, highlighting their potential in pharmaceutical and medicinal sciences.
- Understanding IL hydration is crucial for optimizing their applications in various technological and academic fields.
Purpose of the Study:
- To investigate the dielectric spectra and hydration behavior of diethylammonium-based protic ionic liquids (PILs) and imidazolium-based aprotic ionic liquids (APILs).
- To analyze the influence of IL structure, viscosity, and hydrogen bonding on their dielectric properties and solvation capabilities in aqueous solutions.
- To determine effective hydration numbers and compare the solvation behavior of PILs and APILs.
Main Methods:
- Dielectric spectra measurements were performed for neat ILs and their aqueous solutions (0.02–0.8 mol·dm-3) using time domain reflectometry over 0.01–50 GHz at 298.15 K.
- Data analysis involved applying the Cole-Cole (CC) model for neat ILs and a combination of Debye and Cole-Cole (D+CC) models for aqueous solutions.
- Apparent concentrations of bulk water (cbwap) and slow water (cswap) were calculated to determine effective hydration numbers.
Main Results:
- Protic ionic liquids (PILs) exhibited higher static permittivity and relaxation times than aprotic ionic liquids (APILs) due to hydrogen bonding and proton transfer.
- Aqueous solutions showed distinct relaxation processes: fast collective relaxation of bulk water (~20 GHz) and slow relaxation (~5–10 GHz) attributed to hydrophobic hydration.
- Hydration number analysis indicated that imidazolium-based APILs are less hydrated compared to diethylammonium-based PILs.
Conclusions:
- The study elucidates the distinct hydration mechanisms of PILs and APILs, driven by differences in hydrogen bonding and ionic mobility.
- Dielectric spectroscopy effectively probes water-solvation interactions in ionic liquid solutions, correlating with viscosity and molecular structure.
- Findings provide insights into ion solvation and hydration numbers, crucial for designing ILs for specific applications in chemistry and medicine.
More Related Videos
Related Concept Videos
02:42Aqueous Solutions and Heats of Hydration
17.5K
Water and other polar molecules are attracted to ions. The electrostatic attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. These attractions play an important role in the dissolution of ionic compounds in water.
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
17.5K
03:13Intermolecular Forces
70.0K
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen...
70.0K