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Torsional disorder and planarization dynamics: 9,10-bis(phenylethynyl)anthracene as a case study
Ina Fureraj1, Darya S Budkina1, Eric Vauthey1
1Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland. eric.vauthey@unige.ch.
Physical Chemistry Chemical Physics : PCCP
|October 20, 2022
Summary
Torsional disorder in conjugated molecules impacts excited-state dynamics. Planarization occurs via inertial motion for excited states but diffusion for ground states, influenced by potential steepness.
Area of Science:
- Photochemistry
- Molecular Dynamics
- Spectroscopy
Background:
- Conjugated molecules with phenylethynyl units exhibit torsional disorder at room temperature.
- Excited states are more rigid due to conjugation, leading to asymmetric absorption and emission spectra.
Purpose of the Study:
- Investigate the effect of torsional disorder on excited-state dynamics.
- Analyze 9,10-bis(phenylethynyl)anthracene in various solvents and polymers.
- Utilize stationary and ultrafast electronic spectroscopies.
Main Methods:
- Temperature-dependent absorption spectroscopy.
- Ultrafast spectroscopy with varying excitation wavelengths.
- Viscosity and polymer matrix studies.
Main Results:
- Absorption spectra show inhomogeneous broadening at room temperature.
- Excitation of planar molecules leads to ground-state re-equilibration.
- Excitation of disordered molecules induces planarization via viscosity-independent inertial motion.
- Ground-state dynamics are purely diffusive.
Conclusions:
- Excited-state dynamics differ significantly from ground-state dynamics.
- The steepness of the potential energy surface along the torsional coordinate governs this dissimilarity.
- Torsional disorder plays a crucial role in molecular excited-state behavior.
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