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Intramolecular excimer formation and delayed fluorescence in sterically constrained pyrene dimers
Andrew C Benniston1, Anthony Harriman, Sarah L Howell
1Molecular Photonics Laboratory, School of Natural Sciences (Chemistry), Newcastle University, Newcastle upon Tyne, UK.
Researchers synthesized pyrene-based molecular dyads to study through-space communication. Steric bulk modulated fluorescence, with potential applications in molecular imaging via intramolecular triplet-triplet annihilation.
Area of Science:
- Photochemistry and Photophysics
- Supramolecular Chemistry
- Organic Synthesis
Background:
- Molecular dyads with pyrene units are investigated for their photophysical properties.
- Steric interactions play a crucial role in modulating electronic communication between chromophores.
- Understanding through-space communication is key to designing advanced functional molecules.
Purpose of the Study:
- To synthesize and characterize a series of pyrene-based molecular dyads with varying steric bulk.
- To investigate the influence of steric hindrance on the photophysical properties, specifically fluorescence emission.
- To explore the potential of these molecular systems for applications such as molecular imaging.
Main Methods:
- Synthesis of five molecular dyads with pyrene terminals linked by a phenylene spacer.
- Incorporation of bulky moieties at the 6,8-positions of pyrene units to control steric interactions.
- Spectroscopic analysis, including steady-state and time-resolved fluorescence measurements at different temperatures.
- Investigation of laser-induced and delayed fluorescence phenomena.
Main Results:
- All synthesized compounds exhibited a mixture of monomer and excimer fluorescence in solution, and monomer emission in a glassy matrix.
- The ratio of monomer to excimer fluorescence was significantly influenced by the steric bulk of the substituents.
- Compound DP1 (minimal steric hindrance) favored excimer emission, while DP4 (significant steric hindrance) showed enriched monomer fluorescence.
- Delayed fluorescence was observed through both intramolecular and bimolecular pathways occurring on distinct timescales.
Conclusions:
- Steric interactions effectively modulate through-space electronic communication in pyrene-based molecular dyads.
- The observed fluorescence behavior provides insights into the relationship between molecular structure and photophysical properties.
- Intramolecular triplet-triplet annihilation presents a promising avenue for developing novel molecular imaging techniques.
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