Synthesis and Characterization of Kinetically Stabilized Octadehydrobisthieno[12]annulenes
Taishi Mochizuki1, Yuki Okagaki1, Kazukuni Tahara1
1Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan.
The Journal of Organic Chemistry
|December 30, 2025
Summary
Researchers synthesized kinetically stabilized octadehydrobisthieno[12]annulene (ODTA) derivatives, specifically c- and b-isomers. Steric protection influenced isomer reactivity and stability, with anti-b-ODTA exhibiting a narrower energy gap due to antiaromaticity.
Area of Science:
- Organic Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Octadehydrobisthieno[12]annulene (ODTA) derivatives are complex polycyclic aromatic hydrocarbons with potential electronic applications.
- Understanding the synthesis and properties of different ODTA isomers is crucial for designing novel organic materials.
- Kinetic stabilization is a key strategy for isolating strained or reactive molecular architectures.
Purpose of the Study:
- To synthesize and characterize kinetically stabilized beta- (b-) and cis- (c-) isomers of octadehydrobisthieno[12]annulene (ODTA) derivatives.
- To investigate the influence of substituent groups on the stability and reactivity of ODTA isomers.
- To explore the electronic properties, including energy gaps and frontier molecular orbital levels, of synthesized ODTA derivatives.
Main Methods:
- Multi-step organic synthesis involving cyclization reactions to form the ODTA core.
- Characterization using techniques such as NMR spectroscopy, mass spectrometry, and X-ray crystallography.
- Spectroscopic analysis including UV-Vis absorption spectroscopy and electrochemical methods like cyclic voltammetry.
Main Results:
- A tetraaryl-substituted c-ODTA derivative was successfully synthesized and characterized.
- Tetraaryl-substituted b-ODTA derivatives were not obtained under identical conditions, indicating differing reactivity.
- An anti-b-ODTA derivative with n-butyl groups was isolated, while the syn-b-ODTA isomer was unstable and decomposed.
- Anti-b-ODTA exhibited a narrower HOMO-LUMO energy gap and higher HOMO energy level compared to c-ODTA, attributed to enhanced antiaromaticity.
Conclusions:
- The steric bulk of substituent groups significantly impacts the kinetic stabilization and reactivity of b-ODTA isomers.
- The anti-b-ODTA isomer demonstrates distinct electronic properties, including a reduced energy gap, linked to its antiaromatic character.
- This study highlights the importance of substituent design in accessing and controlling the properties of complex ODTA systems.
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