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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
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Torsional barriers for planar versus twisted singlet styrenes
Frederick D Lewis1, Xiaobing Zuo
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA. lewis@chem.northwestern.edu
Journal of the American Chemical Society
|February 20, 2003
Summary
Kinetic modeling reveals temperature-dependent lifetimes of styrenes. Phenyl-vinyl dihedral angle influences C=C torsional barriers and excited-state behavior, impacting intersystem crossing rates.
Area of Science:
- Photochemistry
- Chemical Kinetics
- Organic Chemistry
Background:
- Understanding excited-state dynamics is crucial in photochemistry.
- Styrene derivatives are important chromophores with tunable electronic properties.
Purpose of the Study:
- To investigate the relationship between molecular structure and excited-state behavior in styrene derivatives.
- To determine the torsional barriers for C=C rotation in the singlet state.
- To explore the factors influencing intersystem crossing rates.
Main Methods:
- Kinetic modeling of temperature-dependent lifetimes.
- Computational analysis of torsional barriers.
- Spectroscopic characterization of styrene and methyl-substituted styrenes.
Main Results:
- A correlation was found between the ground-state phenyl-vinyl dihedral angle (φ) and the C=C torsional barrier.
- Planar styrenes exhibit higher torsional barriers (~6.5 kcal/mol) compared to twisted analogs.
- Highly twisted styrenes show exceptionally rapid intersystem crossing.
Conclusions:
- The phenyl-vinyl dihedral angle significantly impacts excited-state dynamics in styrenes.
- A transition from delocalized to localized excited states occurs with increasing twist, affecting intersystem crossing.
- These findings provide insights into structure-property relationships in organic photochemistry.
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