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Updated: Apr 23, 2026
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Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
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Time-Resolved Laser-Induced Ring-Opening and Dissociation Dynamics in Bromothiophene Isomers.
Noah Frese1, Maximillian Thomas2, Debadarshini Mishra1
1Department of Physics, University of Connecticut, Storrs, Connecticut 06269, United States.
Journal of the American Chemical Society
|April 22, 2026
Summary
Photoinduced ring-opening reactions in 2- and 3-bromothiophene were studied using advanced spectroscopy. The research clarifies fragmentation pathways and dynamics, advancing our understanding of excited-state processes in ring molecules.
Area of Science:
- Photochemistry
- Chemical Dynamics
- Spectroscopy
Background:
- Photoinduced molecular ring-opening reactions are vital in nature and optoelectronics.
- Fundamental mechanisms and excited-state dynamics of these reactions remain debated.
- Nonadiabatic coupling and conical intersections govern these transformations.
Purpose of the Study:
- To investigate the dissociation pathways and fragmentation mechanisms of 2- and 3-bromothiophene after UV photon absorption.
- To elucidate the initial excited states and electronic state dynamics driving ring-opening.
- To understand the isomer-dependent differences in UV absorption and reaction pathways.
Main Methods:
- On-the-fly ab initio molecular dynamics simulations.
- Ultrafast UV pump-IR probe spectroscopy with time-dependent momentum imaging.
- Analysis of fragmentation channels and timescales.
Main Results:
- Identified three dominant fragmentation channels: C-Br bond dissociation and C-S bond cleavage.
- Determined fragmentation times ranging from 600 to 1300 femtoseconds.
- Revealed isomer-specific UV absorption and reaction dynamics, highlighting ultrafast internal conversion and conical intersections.
Conclusions:
- The study clarifies the excited-state dynamics and fragmentation mechanisms of bromothiophene isomers.
- Findings support the crucial role of ultrafast internal conversion in initiating ring-opening.
- Identified specific conical intersections governing the observed ring-opening dynamics.
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