Solvent Tuning Excited State Structural Dynamics in a Novel Bianthryl
Palas Roy1, Faisal Al-Kahtani1, Andrew N Cammidge1
1School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
The Journal of Physical Chemistry Letters
|January 3, 2023
Summary
Investigating 1,9-bianthryl reveals new insights into symmetry breaking charge separation (SBCS) mechanisms. Different solvent environments lead to distinct structural dynamics, offering two potential pathways for photochemical energy conversion.
Area of Science:
- Photochemistry
- Chemical Physics
- Spectroscopy
Background:
- Symmetry breaking charge separation (SBCS) is crucial for photochemical energy conversion.
- The 9,9-bianthryl (9,9'BA) molecule is a well-studied prototype for SBCS.
- The influence of bianthryl structural variations on SBCS dynamics remains underexplored.
Purpose of the Study:
- To investigate the excited state structural dynamics of 1,9-bianthryl (1,9'BA), a molecule with reduced symmetry compared to 9,9'BA.
- To elucidate the role of molecular structure and solvent interactions in driving SBCS.
- To compare the SBCS mechanisms in 1,9'BA with those in the established 9,9'BA system.
Main Methods:
- Ultrafast electronic spectroscopy.
- Vibrational spectroscopy, specifically resonance selective Raman.
- Studies conducted in polar and nonpolar solvents to probe solvent-dependent dynamics.
Main Results:
- Observed disappearance of a Franck-Condon state mode, coinciding with the emergence of radical species' ring breathing modes.
- Confirmed that solvent orientational motion drives charge separation (CS), similar to 9,9'BA.
- Identified multistep structural relaxation in nonpolar solvents, including rapid decay and slower evolution to a distorted polar state.
Conclusions:
- Two distinct pathways for SBCS were proposed: a solvent-driven pathway in polar solvents and an intramolecular reorganization-initiated pathway in nonpolar solvents.
- The findings highlight the significant impact of molecular structure and solvent dynamics on photochemical energy conversion efficiency.
- This study provides a deeper understanding of the fundamental processes governing charge separation in organic molecules.
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