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Effects of Donor Rigidity on Coumarin Delayed Emission: New Tricks from Old Materials
Simon Paredis1,2, Tom Cardeynaels1,2,3, Suman Kuila4
1Hasselt University, Institute for Materials Research (imo-imomec), Design & Synthesis of Organic Semiconductors (DSOS), Martelarenlaan 42, B-3500 Hasselt, Belgium.
Researchers explored coumarin laser dyes, discovering new emission mechanisms like thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) by modifying molecular structure.
Area of Science:
- Organic chemistry
- Photophysics
- Materials science
Background:
- Coumarin laser dyes are well-studied fluorescent materials.
- Donor-π-acceptor structures are key for tuning photophysical properties.
Purpose of the Study:
- Design and synthesize a novel donor-π-acceptor emitter based on coumarin.
- Investigate new emission mechanisms in coumarin derivatives.
- Explore structure-property relationships for delayed fluorescence and phosphorescence.
Main Methods:
- Quantum chemistry calculations
- Spectroscopic investigations (photoluminescence, etc.)
- Synthesis of novel coumarin derivatives
Main Results:
- A new twisted phenoxazine donor red-shifts emission and enables TADF.
- Unexpected room temperature phosphorescence (RTP) observed for Coumarin 6.
- Both coumarins exhibit triplet-triplet annihilation (TTA) delayed emission.
Conclusions:
- Molecular structure, particularly donor group flexibility, dictates emission pathways.
- Rotational freedom of the donor enables previously overlooked emission mechanisms.
- New coumarin emitter demonstrates potential for advanced optical applications.
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