The diffusion, structural relaxation, and fragility of [VIO2+][Tf2N-]2 ionic liquid
Shikai Tian1, Yi Luo1, Zhongqin Zhao1
1Departments of Physics & Key Laboratory of Photonic and Optical Detection in Civil Aviation, Civil Aviation Flight University of China, Guanghan, 618307, China.
Journal of Molecular Modeling
|February 10, 2020
Summary
Dimethyl-viologen bis-(tetrafluoroborate) ionic liquid exhibits supercooled liquid dynamics at 400 K. Its temperature-dependent dynamics follow a super-Arrhenius law, classifying it as a fragile glass former.
Area of Science:
- Physical Chemistry
- Materials Science
- Computational Chemistry
Background:
- Ionic liquids (ILs) exhibit complex phase behaviors and structural dynamics influenced by temperature.
- Viologen-based ILs are of interest due to their unique electronic and structural properties.
Purpose of the Study:
- To investigate the temperature-dependent dynamics of dimethyl-viologen bis-(tetrafluoroborate) ([VIO2+][Tf2N-]2) ionic liquid.
- To characterize the glass-forming behavior and relaxation dynamics of this specific IL.
Main Methods:
- Molecular dynamics simulations were employed to study the dynamics of [VIO2+][Tf2N-]2 over a temperature range of 400–800 K.
- Analysis included diffusion constants, structural relaxation times, and ion dynamics.
Main Results:
- The ionic liquid displayed supercooled liquid-like diffusion and structural relaxation even at 400 K.
- Dynamics followed a super-Arrhenius law, fitting both two-Arrhenius and Vogel-Fulcher-Tammann (VFT) models, indicating fragile glass former behavior.
- Decoupling of diffusion and relaxation was observed for the [VIO2+] cation but not the [Tf2N-] anion.
Conclusions:
- The temperature dependence of dynamics is linked to ion cage persistence and exchange times.
- [VIO2+][Tf2N-]2 exhibits complex dynamics characteristic of fragile glass formers.
- Understanding these dynamics is crucial for designing ILs with specific properties for various applications.
Related Concept Videos
01:15Theories of Dissolution: Diffusion Layer Model
1.5K
Dissolution, the process by which drug particles dissolve in a solvent, is explained by the diffusion layer model, a theoretical framework that simulates the absorption of oral drugs and allows us to analyze experimental data.
This process starts with a thin layer, saturated with the drug, forming at the interface between the solid and liquid. The solute then diffuses from this layer into the main solution. The Noyes-Whitney equation suggests that the rate of dissolution relies on the diffusion...
This process starts with a thin layer, saturated with the drug, forming at the interface between the solid and liquid. The solute then diffuses from this layer into the main solution. The Noyes-Whitney equation suggests that the rate of dissolution relies on the diffusion...
1.5K
01:09Theories of Dissolution: The Danckwerts' Model and Interfacial Barrier Model
703
Various dissolution theories provide insight into the factors that influence the dissolution rate. Danckwerts' Model suggests that turbulence, rather than a stagnant layer, characterizes the dissolution medium at the solid-liquid interface. In this model, the agitated solvent contains macroscopic packets that move to the interface via eddy currents, facilitating the absorption and delivery of the drug to the bulk solution. The regular replenishment of solvent packets maintains the...
703
02:54Molecular and Ionic Solids
19.7K
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
19.7K
03:13Intermolecular Forces
68.3K
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...
68.3K
02:42Valence Bond Theory
10.9K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
10.9K
01:28Atomic Nuclei: Types of Nuclear Relaxation
830
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
830