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Solvation dynamics on the diffusion timescale elucidated using energy-represented dynamics theory
Kazuya Okita1, Natsuumi Ito1, Nozomi Morishita-Watanabe1
1Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. kasahara@cheng.es.osaka-u.ac.jp.
Physical Chemistry Chemical Physics : PCCP
|April 16, 2024
Summary
We developed a new equation to study how solvents relax around molecules after light exposure. This method reveals differences in relaxation dynamics between water and alcohol solvents.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Computational Chemistry
Background:
- Solvation dynamics, the relaxation of solvent structure after photoexcitation, offers insights into local solvent environments.
- The energy-represented Smoluchowski-Vlasov (ERSV) equation was recently developed to analyze solvation dynamics on diffusion timescales.
- The energy coordinate in the ERSV equation accounts for solvent flexibility, enabling its application to diverse solvent systems.
Purpose of the Study:
- To apply the ERSV equation to study the solvation dynamics of 6-propionyl-2-dimethylamino naphthalene (Prodan) in water and various alcohol solvents.
- To elucidate the differences in relaxation processes across these distinct solvent environments.
- To validate the ERSV equation's ability to reproduce molecular dynamics simulation results.
Main Methods:
- Derivation and application of the energy-represented Smoluchowski-Vlasov (ERSV) equation.
- Analysis of solvation dynamics for Prodan in water, methanol, ethanol, and 1-propanol.
- Comparison of ERSV results with molecular dynamics (MD) simulation data.
Main Results:
- The ERSV equation accurately reproduces relaxation time correlation functions from MD simulations on long timescales.
- A linear correlation was found between the relaxation time coefficient and the inverse of translational diffusion coefficients for alcohol solvents.
- Water exhibited a deviation from this linear trend, attributed to differences in collective motion compared to alcohols.
Conclusions:
- The ERSV equation is a valuable tool for analyzing solvation dynamics across different solvent types.
- Solvent relaxation dynamics are influenced by molecular diffusion and collective motion, with distinct behaviors observed in water versus alcohols.
- The study highlights the utility of Prodan as a fluorescent probe for investigating heterogeneous environments through solvation dynamics.
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