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Bis(9-Boraphenanthrene) and Its Stable Biradical.
Samir Kumar Sarkar1, Kimberly K Hollister1, Andrew Molino2
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|September 22, 2023
Summary
Researchers developed novel boron-doped polycyclic aromatic hydrocarbons with unique electronic and photophysical properties. They created the first neutral bis(9-boraphenanthrene) compounds and a rare biradical, showcasing new possibilities in materials science.
Area of Science:
- Organic Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Boron-doping polycyclic aromatic hydrocarbons (PAHs) offers unique redox and photophysical properties not found in carbon-only systems.
- Controlling electronic states in these boron-doped frameworks is crucial for developing advanced materials.
Purpose of the Study:
- To achieve ligand-mediated control over the electronic states of 9-boraphenanthrene systems.
- To synthesize and characterize neutral bis(9-boraphenanthrene) compounds and their corresponding biradicals.
- To investigate the photophysical properties, including intramolecular charge transfer and dual emission.
Main Methods:
- Ligand-mediated synthesis of boron-doped PAHs.
- Structural characterization using advanced spectroscopic techniques.
- Photophysical measurements to determine absorption and emission properties.
Main Results:
- First structurally characterized neutral bis(9-boraphenanthrene) compounds (2-3) and their biradical (4).
- Compounds 2 and 3 exhibit intramolecular charge transfer and dual emission in solution due to excited-state conjugation enhancement (ESCE).
- Biradical 4 is a rare open-shell singlet with 95% biradical character, one of the highest for boron-based polycyclic species.
Conclusions:
- Ligand control enables access to diverse electronic states in boron-doped PAHs.
- These novel compounds demonstrate unique photophysical behaviors, including dual emission.
- The highly biradical compound opens new avenues for radical chemistry and materials applications.
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