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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Thioxanthone: on the shape of the first absorption band
Vidisha Rai-Constapel1, Martin Kleinschmidt, Susanne Salzmann
1Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
Physical Chemistry Chemical Physics : PCCP
|July 8, 2010
Summary
Thioxanthone (TX) is planar in its ground state, and its first absorption band arises from vibrational modes, not distinct conformers. This clarifies TX's photophysical behavior and electronic structure.
Area of Science:
- Photochemistry
- Computational Chemistry
- Spectroscopy
Background:
- Thioxanthone (TX) is a significant photosensitizer.
- Understanding its ground state geometry is crucial for predicting its photophysical properties.
Purpose of the Study:
- To investigate the equilibrium ground state geometry of thioxanthone (TX).
- To elucidate the effect of geometry on TX's vertical excitation energies and photophysical behavior.
- To analyze the first absorption band of TX through detailed simulation.
Main Methods:
- Quantum chemical calculations were employed to determine the ground state geometry.
- Simulations of the first absorption band were performed.
- Comparison of calculated vertical excitation spectra with experimental data in non-polar solvents.
Main Results:
- Thioxanthone (TX) exhibits a planar, C(2v) symmetric ground state geometry.
- Excited state energies are largely unaffected by butterfly motion.
- The shoulder in the first absorption band is attributed to vibrational progressions, refuting the existence of distinct photophysical conformers.
Conclusions:
- The planar ground state geometry of TX is confirmed.
- The observed spectral features are explained by vibrational effects, not conformational heterogeneity.
- This study provides a clearer understanding of thioxanthone's photophysical behavior.
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