Accelerating symmetry-breaking charge separation in a perylenediimide trimer through a vibronically coherent dimer
Chenjian Lin1, Taeyeon Kim1, Jonathan D Schultz1
1Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, IL, USA.
Nature Chemistry
|April 26, 2022
Summary
Investigating molecular π-stacked chromophores reveals how electronic interactions evolve beyond dimers. This study shows ultrafast symmetry-breaking charge separation in trimers due to vibronic coupling, crucial for photonic materials.
Area of Science:
- Photophysics and Photochemistry
- Materials Science
- Organic Electronics
Background:
- Understanding molecular π-stacked chromophores is key for developing advanced photonic materials.
- Previous studies were limited to molecular dimers, not fully capturing interactions in larger systems.
Purpose of the Study:
- To investigate excited-state dynamics and electronic interactions in perylenediimide trimers beyond the dimer limit.
- To elucidate the mechanisms of state mixing and symmetry-breaking charge separation (SB-CS) in higher oligomers.
Main Methods:
- Comparative study of excited-state dynamics in a perylenediimide dimer and trimer.
- Analysis of coherent vibronic coupling, state mixing (Frenkel exciton/charge-transfer), and solvent effects.
Main Results:
- Coherent vibronic coupling drives ultrafast mixing between Frenkel exciton (FE) and charge-transfer (CT) states.
- Solvent fluctuations and low-frequency vibrations enhance CT character in the mixed state.
- In trimers, low-frequency vibronic coupling collapses coherence, leading to ultrafast SB-CS between distal units.
Conclusions:
- The study provides fundamental insights into electronic state mixing and SB-CS in π-stacked systems beyond dimers.
- Findings are critical for designing and optimizing functional organic photonic materials.
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