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Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
S1-state internal conversion of isolated azulene derivatives
Yasushi Numata1, Satoru Toyoshima, Katsuhiko Okuyama
1Department of Materials Chemistry and Engineering, College of Engineering, Nihon University, Koriyama 963-8642, Japan.
The Journal of Physical Chemistry. A
|August 8, 2009
Summary
This study investigates the internal conversion mechanism in azulene derivatives using hole-burning spectroscopy. We observed vibronic selectivity, where specific vibrational modes compete with relaxation processes, offering insights into molecular dynamics.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Molecular Dynamics
Background:
- Internal conversion is a key process in the photophysics of molecules.
- Understanding internal conversion mechanisms is crucial for predicting molecular behavior after light absorption.
- Azulene and its derivatives are model systems for studying electronic and vibrational dynamics.
Purpose of the Study:
- To investigate the S0-S1 hole-burning spectra of azulene and its methyl and cyano derivatives.
- To elucidate the internal conversion mechanism by analyzing spectral broadening.
- To identify the role of conical intersections and vibronic selectivity in energy relaxation.
Main Methods:
- Measurement of S0-S1 hole-burning spectra under isolated conditions.
- Analysis of spectral band widths (0-0 and vibronic bands).
- Comparison of spectral broadening with vibrational excess energy and transition energy.
Main Results:
- Spectral broadening correlates with vibrational excess energy, indicating normal internal conversion.
- A drastic increase in broadening in the medium-energy region suggests relaxation via conical intersection, observed in methyl but not cyano derivatives.
- Anomalous narrow spectral widths were observed for specific vibronic bands, indicating vibronic selectivity.
Conclusions:
- The study reveals distinct internal conversion pathways influenced by molecular structure (methyl vs. cyano substituents).
- Conical intersection plays a significant role in energy relaxation for certain azulene derivatives.
- Vibronic selectivity demonstrates a competition between relaxation and internal conversion processes, offering a new perspective on molecular photophysics.
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