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Chimeric behavior of excited thioxanthone in protic solvents: I. Experiments
T Villnow1, G Ryseck, V Rai-Constapel
1Institut für Physikalische Chemie and ‡Institut für Theoretische Chemie und Computerchemie, Heinrich-Heine-Universität Düsseldorf , Universitätstrasse 1, D-40225 Düsseldorf, Germany.
The Journal of Physical Chemistry. A
|December 11, 2014
Summary
Thioxanthone (TX) exhibits rapid intersystem crossing between singlet and triplet states in methanol and TFE. This photophysical behavior, observed via time-resolved spectroscopy, influences its excited-state dynamics.
Area of Science:
- Photochemistry and photophysics
- Molecular spectroscopy
- Organic chemistry
Background:
- Thioxanthone (TX) is a photosensitizer with complex excited-state dynamics.
- Understanding its photophysical pathways is crucial for applications in photochemistry.
Purpose of the Study:
- To investigate the ultrafast photophysics of thioxanthone (TX) in methanol (MeOH) and 2,2,2,-trifluoroethanol (TFE).
- To elucidate the role of intersystem crossing and excited-state equilibrium in TX's behavior.
Main Methods:
- Time-resolved fluorescence spectroscopy
- Time-resolved absorption spectroscopy
- ব্যবহার of 1-methylnaphthalene (1-MN) as a quencher
Main Results:
- Stimulated emission amplitude decays within 5-10 ps, significantly faster than fluorescence lifetimes.
- Evidence of reversible intersystem crossing between (1)ππ* and (3)nπ* states was observed.
- Quenching studies confirmed the equilibrium between singlet and triplet excited states.
Conclusions:
- The rapid decay is attributed to reversible intersystem crossing between closely lying singlet and triplet states.
- An activated internal conversion process governs the depopulation of these states to the lowest triplet state on the nanosecond timescale.