Stable Organic Diradicals Based on Fused Quinoidal Oligothiophene Imides with High Electrical Conductivity

Kun Yang, Xianhe Zhang, Alexandra Harbuzaru, Lei Wang, Yang Wang, Changwoo Koh, Han Guo, Yongqiang Shi, Jianhua Chen, Huiliang Sun, Kui Feng, M. Carmen Ruiz Delgado, Han Young Woo, Rocio Ponce Ortiz, Xugang Guo

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Unpaired electrons of organic radicals can offer high electrical conductivity without doping, but they typically suffer from low stability. Herein, we report two organic diradicaloids based on quinoidal oligothiophene derivative (QOT), that is, BTICN and QTICN, with high stability and conductivity by employing imide-bridged fused molecular frameworks. The attachment of a strong electron-withdrawing imide group to the tetracyano-capped QOT backbones enables extremely deeply aligned LUMO levels (from -4.58 to -4.69 eV), cross-conjugated diradical characters, and remarkable ambient stabilities of the diradicaloids with half-lives > 60 days, which are among the highest for QOT diradicals and also the widely explored polyaromatic hydrocarbon (PAH)-based diradicals. Specifically, QTICN based on a tetrathiophene imide exhibits a cross-conjugation assisted self-doping in the film state as revealed by XPS and Raman studies. This property in combination with its ordered packing yields a high electrical conductivity of 0.34 S cm-1 for the QTICN films with substantial ambient stability, which is also among the highest values in organic radical-based undoped conductive materials reported to date. When used as an n-type thermoelectric material, QTICN shows a promising power factor of 1.52 uW m-1 K-2. Our results not only provide new insights into the electron conduction mechanism of the self-doped QOT diradicaloids but also demonstrate the great potential of fused quinoidal oligothiophene imides in developing stable diradicals and high-performance doping-free n-type conductive materials.

Original languageEnglish
JournalJournal of the American Chemical Society
Publication statusAccepted/In press - 2020 Jan 1


ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Yang, K., Zhang, X., Harbuzaru, A., Wang, L., Wang, Y., Koh, C., Guo, H., Shi, Y., Chen, J., Sun, H., Feng, K., Ruiz Delgado, M. C., Woo, H. Y., Ortiz, R. P., & Guo, X. (Accepted/In press). Stable Organic Diradicals Based on Fused Quinoidal Oligothiophene Imides with High Electrical Conductivity. Journal of the American Chemical Society.