Synthesis, π‑Stacking and Application of Tetraethynyl Dioxotriangulenes

Area of Science:

• Organic electronics
• Materials science
• Semiconductor physics

Background:

• 4,8-Dioxotriangulene (DOT) possesses a unique structure with a triangulene core and carbonyl groups.
• This core stabilizes radical anions via charge and spin delocalization across an extended π-framework.

Purpose of the Study:

• To explore DOT derivatives as building blocks for n-type organic semiconductors.
• To synthesize and characterize novel tetraethynyl DOT derivatives.

Main Methods:

• Synthesis of tetraethynyl DOTs (1a-c) using a novel Pd-catalyzed C-(Ar)-O bond activation.
• Single-crystal X-ray diffraction analysis to determine molecular assembly.
• Electrochemical reduction, Electron Paramagnetic Resonance (EPR), and UV-vis spectroscopy to characterize radical anions.
• Fabrication and testing of solution-processed films in field-effect transistors.

Main Results:

• Successful synthesis of tetraethynyl DOTs with varying substituents.
• Distinct solid-state packing observed: discrete π-stacked tetramers (1a) and 1D π-stacks (1b).
• Generation of persistent radical anions in 1b upon electrochemical reduction, confirmed spectroscopically.
• Demonstration of n-type semiconducting behavior in solution-processed films of 1b.

Conclusions:

• DOT derivatives are promising candidates for n-type organic semiconductor applications.
• The synthetic methodology enables access to functionalized DOT building blocks.
• Molecular packing significantly influences electronic properties and device performance.