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Hydrogen bond and lifetime dynamics in diluted alcohols
Evgeniia Salamatova1, Ana V Cunha, Keisuke Shinokita
1Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. m.s.pchenitchnikov@rug.nl.
Physical Chemistry Chemical Physics : PCCP
|August 30, 2017
Summary
The hydrophobic tail of alcohols does not significantly alter their hydrogen-bond dynamics when diluted in acetonitrile. Previously observed differences in bulk alcohol dynamics stem from solvent, not solute, properties.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Molecular Dynamics
Background:
- Hydrogen-bonding is fundamental to chemical and biochemical processes.
- Alcohols are key hydrogen-bonding molecules whose properties can be tuned via their hydrophobic tails.
- Previous research indicates hydrophobic tail variations significantly impact bulk alcohol dynamics, but the origin (solvent vs. solute effect) remains unclear.
Purpose of the Study:
- To elucidate the origin of differences in alcohol dynamics by investigating hydrogen-bond dynamics.
- To determine whether alcohol solute properties are influenced by the hydrophobic tail when diluted in a hydrogen-bond accepting solvent.
Main Methods:
- Studied hydrogen-bond dynamics of alcohols (methanol to butanol) diluted in acetonitrile.
- Employed pump-probe and 2D infrared spectroscopy.
- Utilized molecular dynamics-spectral simulations with the OH stretching mode as a reporter.
Main Results:
- The vibrational lifetime of the OH stretching mode was consistently around 3 picoseconds for all studied alcohols.
- Hydrogen-bond dynamics showed a fast initial relaxation (~200 fs) from librational motion.
- A slow relaxation (~4 ps) attributed to hydrogen-bond exchange dynamics was observed.
Conclusions:
- Alcohol solute properties, specifically hydrogen-bond dynamics, are largely independent of the hydrophobic tail length.
- Observed differences in bulk alcohol dynamics are primarily due to solvent property variations influenced by the hydrophobic tail.
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