TY - JOUR
T1 - Stable Organic Diradicals Based on Fused Quinoidal Oligothiophene Imides with High Electrical Conductivity
AU - Yang, Kun
AU - Zhang, Xianhe
AU - Harbuzaru, Alexandra
AU - Wang, Lei
AU - Wang, Yang
AU - Koh, Changwoo
AU - Guo, Han
AU - Shi, Yongqiang
AU - Chen, Jianhua
AU - Sun, Huiliang
AU - Feng, Kui
AU - Ruiz Delgado, M. Carmen
AU - Woo, Han Young
AU - Ortiz, Rocio Ponce
AU - Guo, Xugang
N1 - Funding Information:
X.G. is grateful to the National Science Foundation of China (no. 51573076). L.W. acknowledges the China Postdoctoral Science Foundation (no. 2018M641626). Research at University of Málaga was supported by Junta de Andalucía (UMA18-FEDERJA-080). H.Y.W. is thankful for the financial support from the NRF of Korea (NRF-2016M1A2A2940911 and 2019R1A6A1A11044070). We would like to thank Dr. Yinhua Yang (MCPC, SUSTech) for the kind help with the ESR and VT-NMR measurements as well as the assistance of the SUSTech Core Research Facilities and the technical support from the Computational Science and Engineering Department of the Southern University of Science and Technology. The authors would like to acknowledge the computer resources, technical expertise, and assistance provided by the Supercomputing and Bioinformatics (SCBI) centre of the University of Málaga.
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/3/4
Y1 - 2020/3/4
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85080075967&partnerID=8YFLogxK
U2 - 10.1021/jacs.9b12683
DO - 10.1021/jacs.9b12683
M3 - Article
C2 - 32048836
AN - SCOPUS:85080075967
VL - 142
SP - 4329
EP - 4340
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 9
ER -