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Investigating Intramolecular H Atom Transfer Dynamics in β-Diketones with Ultrafast Infrared Spectroscopies and
Jessika L S Dean1, Valerie S Winkler1, Mark A Boyer2
1Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States.
The Journal of Physical Chemistry. A
|October 26, 2023
Summary
Ultrafast dynamics of intramolecular hydrogen bonds in beta-diketones were studied using 2D IR spectroscopy. Stronger hydrogen bonds lead to softer potentials, broad vibrational signatures, and distinct orientational dynamics for different isotopes.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Computational Modeling
Background:
- Intramolecular hydrogen bonds play a crucial role in molecular structure and dynamics.
- Understanding the vibrational behavior and ultrafast dynamics of these bonds is key to chemical processes.
Purpose of the Study:
- To investigate the vibrational signatures and ultrafast dynamics of intramolecular hydrogen bonds in beta-diketones.
- To correlate hydrogen bond strength with vibrational properties and molecular dynamics.
Main Methods:
- Two-dimensional infrared (2D IR) spectroscopy was employed to probe vibrational dynamics.
- Computational modeling was used to analyze potential energy surfaces and vibrational couplings.
- Polarization-sensitive transient absorption measurements were performed on isotopologues.
Main Results:
- Strongest intramolecular hydrogen bonds exhibit soft potentials, leading to red-shifted OH frequencies and atomic dislocation upon excitation.
- Broad vibrational signatures were observed, attributed to significant coupling between normal modes.
- Isotopologues showed distinct orientational dynamics, with relaxation times of ~600 fs (H) and ~2 ps (D).
Conclusions:
- The strength of intramolecular hydrogen bonds directly influences their vibrational properties and dynamics.
- Activated hydrogen/deuterium atom transfer events, driven by structural rearrangements, govern the observed orientational dynamics.
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