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Intramolecular hydrogen bonding protects the hydroxyl group from attack by fluctuating solvent forces
1Schulich Faculty of Chemistry and Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel.
The Journal of Chemical Physics
|February 24, 2020
Summary
Pure dephasing rates in chlorophenols reveal how hydrogen bonding affects ultrafast molecular dynamics. Intramolecular hydrogen bonds protect molecules from solvent forces, influencing vibrational energy transfer.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Ultrafast spectroscopy investigates molecular dynamics, particularly pure dephasing of vibrationally excited molecules.
- Hydrogen- (H-) bonding is crucial in many chemical and physical systems, influencing molecular behavior.
Purpose of the Study:
- To determine pure dephasing rates of hydroxyl stretching (νOH) excitations in chlorophenols.
- To correlate dephasing rates with vibrational anharmonicity and understand the role of H-bonding.
Main Methods:
- Employed third-order nonlinear vibrational spectroscopy techniques.
- Utilized polarization-selective transient grating and two-dimensional infrared spectroscopy.
- Analyzed line shape components and pure dephasing rates of νOH excitations.
Main Results:
- Pure dephasing rates correlate with νOH mode anharmonicity in chlorophenols.
- In free hydroxyl groups, dephasing scales linearly with anharmonicity, aligning with Kubo-Oxtoby theory.
- Intramolecular H-bonding reverses this trend, slowing dephasing by ~50% with increased anharmonicity.
Conclusions:
- Intramolecular H-bonding protects molecules from solvent fluctuations, impacting ultrafast dynamics.
- This protective effect is significant for understanding H-bonding's role in complex systems like biomolecules.
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