Bending-Induced Vibrational Landscape Reorganization Governs Energy Dissipation in Perylene Bisimides
Wei Zhang1, Di Zhao2, Byeongjoo Kang3
1Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, Republic of Korea.
Angewandte Chemie (International Ed. in English)
|June 26, 2026
Summary
Structural distortion in organic molecules enhances nonradiative decay by altering vibrational dynamics. Bending suppresses key vibrational modes, leading to faster energy loss and reduced light emission.
Area of Science:
- Photochemistry
- Organic Electronics
- Spectroscopy
Background:
- Structural distortion in organic chromophores is known to reduce light emission.
- The precise mechanisms driving this enhanced nonradiative decay are not fully understood.
Purpose of the Study:
- To investigate the structural origins of distortion-enhanced nonradiative relaxation in organic chromophores.
- To elucidate the role of vibrational dynamics in excited-state energy dissipation.
Main Methods:
- Synthesis of perylene bisimide derivatives with controlled structural bending.
- Time-resolved electronic spectroscopy to monitor excited-state decay pathways.
- Time-resolved Raman spectroscopy to probe structural dynamics.
Main Results:
- A clear transition from high emission efficiency to enhanced nonradiative decay was observed with increasing molecular bending.
- Internal conversion was identified as the dominant decay pathway, with negligible intersystem crossing.
- Bending was found to suppress specific vibrational modes, reorganize the vibrational manifold, and accelerate vibrational dephasing.
Conclusions:
- Molecular bending enhances internal conversion by creating a more dissipative excited-state environment, rather than solely reducing the energy gap.
- Vibrational dissipation and loss of coherence are critical factors governing nonradiative decay in these systems.
- A framework linking structure, vibrational dynamics, and energy flow in π-conjugated systems was established.
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