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Substituent-triggered cross-phase inversion of excimer formation
Hua Zhao1, Jinshan Xu1, Wei Chen1
1College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031, China.
Summary
Substituent effects can invert excimer formation between solution and solid states. This study reveals how modifying acridine derivatives alters their aggregation-controlled photophysics, guiding the design of novel excimer emitters.
Area of Science:
- Photochemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Excimer formation mechanisms differ between solution and crystalline states.
- The interplay between these mechanisms and substituent effects is not well understood.
- Acridine derivatives are known for their photophysical properties.
Purpose of the Study:
- To investigate the substituent-triggered inversion of excimer formation across different phases.
- To understand the molecular-level factors governing excimer formation in solution and solid states.
- To explore the design principles for aggregation-controlled photophysics in acridine derivatives.
Main Methods:
- Synthesis of acridine derivatives with varying substituents (unsubstituted, phenyl, 2-methoxy-phenyl).
- Photophysical characterization (emission spectra, quantum yield) in solution and crystalline states.
- Crystallographic analysis to determine solid-state packing and intermolecular interactions.
Main Results:
- In solution, unsubstituted and phenyl-acridines form dynamic excimers, while the methoxy-analogue shows monomeric emission.
- In the crystalline state, the methoxy-acridine derivative forms preorganized dimers, yielding strong excimer emission (PLQY 64.8%).
- The trend is reversed compared to solution: methoxy-acridine exhibits strong excimer emission, while phenyl-acridine shows partial contribution and unsubstituted acridine shows none.
Conclusions:
- Subtle substituent modifications can drastically invert excimer formation propensity across phases.
- Directional interactions (Ar-H···O) and π-π stacking in crystals dictate excimer formation.
- This work provides insights for designing discrete excimer emitters through substituent and phase control.
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