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Updated: Nov 30, 2025

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Vibrationally Hot and Cold Triplets. Sensitizer-Dependent Dynamics and Localized Vibrational Promotion of a
Kai-Yuan Kuan1, Daniel A Singleton1
1Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States.
Large intramolecular kinetic isotope effects (KIEs) in benzobarrelene rearrangement align with heavy-atom tunneling using low-energy sensitizers. Higher-energy sensitizers yield lower KIEs, indicating hot, nonstatistical dynamics from excess vibrational energy.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Chemical Dynamics
Background:
- The di-π-methane rearrangement is a key organic reaction.
- Kinetic Isotope Effects (KIEs) provide insights into reaction mechanisms.
- Triplet energy transfer is a common method for initiating rearrangements.
Purpose of the Study:
- To investigate the influence of sensitizer energy on the KIEs of the benzobarrelene di-π-methane rearrangement.
- To explore the role of vibrational energy in reaction dynamics.
- To determine if the rearrangement proceeds via statistical or nonstatistical pathways.
Main Methods:
- Measurement of intramolecular 13C KIEs for benzobarrelene.
- Utilizing sensitizers with varying triplet energies.
- Computational trajectory studies to model reaction dynamics.
Main Results:
- Large 13C KIEs were observed with low-energy sensitizers, consistent with heavy-atom tunneling.
- Significantly lower 13C KIEs were obtained with high-energy sensitizers.
- Trajectory studies indicated that excess vibrational energy promotes nonstatistical dynamics.
Conclusions:
- The energy of the sensitizer critically influences the dynamics of the di-π-methane rearrangement.
- High-energy sensitizers lead to "hot" and nonstatistical reaction pathways.
- Heavy-atom tunneling is a significant factor in the rearrangement mechanism under specific conditions.
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