Pyridalthiadiazole acceptor-functionalized triarylboranes with multi-responsive optoelectronic characteristics

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Triarylboranes are versatile Lewis acids with tunable electronic properties.
• Pyridalthiadiazole (PT) is a strong electron-accepting moiety used in organic electronics.
• Developing new π-conjugated systems with tailored optoelectronic properties is crucial for advanced materials.

Purpose of the Study:

• To synthesize and characterize novel Ar2B-π-A dyads and A-π-B(Ar)-π-A triads incorporating pyridalthiadiazole (PT) acceptors and triarylborane cores.
• To investigate the photophysical properties, electronic structures, and reactivity of these new compounds.
• To explore their potential applications in organic electronics, such as electron-only diodes.

Main Methods:

• Stille cross-coupling reactions were employed for the synthesis of the target molecules.
• Single-crystal X-ray crystallography was used to determine the solid-state structure.
• Photoluminescence spectroscopy was utilized to study emission properties.
• Electrochemical methods and theoretical calculations (DFT) were performed to understand electronic structures and reactivity.
• Fabrication and characterization of electron-only diodes were conducted.

Main Results:

• A new class of Ar2B-π-A dyads and A-π-B(Ar)-π-A triads featuring PT acceptors and triarylborane cores were successfully synthesized.
• The compounds exhibit strong photoluminescence in solution with quantum yields up to 52%, and further conjugation leads to red-shifted emission.
• Chemical reduction induces intramolecular charge transfer (ICT) from PT to boron, causing a blue color change.
• Strong fluoride anion binding to the boron center was observed, leading to an opposite ICT pathway.
• Electron-only diodes fabricated from a hexylthiophene derivative showed an average electron mobility of 6.4 × 10^-5 cm^2 V^-1 s^-1.

Conclusions:

• The synthesized triarylborane-PT compounds possess unique photophysical and electronic properties.
• Their optoelectronic behavior can be tuned through chemical reduction or fluoride binding, enabling color switching.
• The electron-accepting nature of these materials makes them promising candidates for organic electronic devices, particularly electron-only diodes.