Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates
Seongsoo Kang1, Taeyeon Kim1, Yongseok Hong1
1Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 03722, South Korea.
Journal of the American Chemical Society
|June 24, 2021
Summary
Ultrafast dynamics in perylenebisimide (PBI) H-aggregates reveal excimer and delocalized radical anion states. Vibrational coherences serve as key indicators for exciton dynamics in these PBI systems.
Area of Science:
- Photochemistry
- Spectroscopy
- Materials Science
Background:
- Perylenebisimide (PBI) derivatives are widely studied for their optoelectronic properties.
- H-aggregates of PBI exhibit unique excited-state behaviors due to intermolecular interactions.
- Understanding ultrafast dynamics is crucial for designing advanced materials.
Purpose of the Study:
- To investigate the ultrafast photoinduced dynamics and vibrational coherences in PBI H-aggregates.
- To elucidate the formation mechanisms of excimer and delocalized radical anion states.
- To identify key vibrational modes indicative of coherent exciton dynamics.
Main Methods:
- Femtosecond transient absorption (fs-TA) spectroscopy.
- Time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements.
- Analysis of excited-state Raman modes and their temporal evolution.
Main Results:
- Identified the formation of excimer and delocalized radical anion states in excited PBI H-aggregates.
- Demonstrated that intermolecular out-of-plane and core C═C stretch Raman modes are crucial indicators of exciton dynamics.
- Observed stationary peak positions for these excited-state Raman modes during dynamics.
- TR-ISRS provided insights into vibrational coherences linked to excimer and charge-delocalized state formation.
Conclusions:
- Intermolecular interactions in PBI H-aggregates lead to novel excited states.
- Specific vibrational modes act as fingerprints for coherent exciton dynamics.
- TR-ISRS is a powerful tool for probing excited-state vibrational coherences in aggregate systems.
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