Recently, Associate Professor Yuan Li's group from the School of Materials Science and Engineering / State Key Laboratory of Luminescent Materials and Devices, SCUT, proposed a molecular design strategy of stable narrow bandgap open-shell diradicals based on "donor-acceptor" electronic structure. Relevant results were published in Nature Communications under the title of "Evolution of the Electronic Structure in Open-Shell Donor-Acceptor Organic Semiconductors".
Over the past 30 years, organic semiconductor optoelectronic materials have undergone considerable development, and have shown remarkable application prospects in the fields of organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), organic field-effect transistors (OFETs), infrared organic photodetectors (OPDs), etc. Among them, the classical "donor-acceptor" structure design is one of the most important and effective strategies to realize narrow bandgap organic semiconductors. This kind of "donor-acceptor" organic semiconductors have high stability and are widely used in many frontier fields such as organic optoelectronics, thermoelectricity, photothermal conversion and fluorescent biological imaging. There are abundant theories in organic semiconductor materials and devices, but the development of novel organic optoelectronic materials based on new principles is currently the focus and hotspot in this field.
Due to their unique physical and chemical properties, open-shell free radical molecules have potential applications in many fields such as organic electronics, optoelectronics, and biology. At present, most open-shell radical materials are based on systems such as polycyclic aromatic hydrocarbons, para-quinodimethanes and others. In the past century, the synthesis methods and applications of open-shell radical materials based on this system have made continuous breakthroughs, and most of their electronic ground states are "open-shell singlet ground state".
During the past four years, Professor Yuan Li's research group from SCUT has successfully designed and synthesized open-shell narrow bandgap organic semiconductors based on the "donor-acceptor" structure. They have adopted a variety of research methods to prove their experiment results, including variable temperature nuclear magnetic resonance, variable temperature electron spin resonance, ultra-low temperature and high temperature superconducting quantum interferometer, single crystal X-ray diffraction, sublimation and purification experiment, HPLC purity verification and others. At the same time, with the help of calculation tools of classical free radical theory, the calculation of diradical character index (y0) shows that the y0 value of this organic semiconductor can be effectively adjusted between 20% and 40%, and can be further improved to 66.5% with the extension of conjugation. The research group also conducted calculations of the "singlet-triplet energy gap, ΔEST", NICS, and ACID of the ground state to further prove its open-shell structure. This series of systematic research work proposed a molecular design strategy of stable narrow bandgap open-shell diradicals based on "donor-acceptor" electronic structure.
After years of hard work, Yuan Li's group has put forward a new synthesis and design strategy for stable free radical materials. Relevant results were published online in Nature Communications (2021, 12, 5889) on October 7, 2021.
The first author unit of the paper is the State Key Laboratory of Luminescent Materials and Devices and the Institute of Polymer Luminescent Materials and Devices, South China University of Technology. The corresponding authors of the paper are Associate Professor Yuan Li and Professor Fei Huang of SCUT, and Assistant Professor Neeraj Rai of Mississippi State University. The first author is Dr. Zhongxin Chen from SCUT. This project is supported by the National Key R&D Program (2019YFA0705900), the General Program of the National Natural Science Foundation of China (51973063), the Program of "Guangzhou Pearl River Rising Star in Science and Technology" (201710010194), the "Guangdong Provincial Science and Technology Innovation Program for Young Talents" (2019TQ05C890) and the Guangdong Provincial Key Program of Basic and Applied Research (2019B030302007).
Link of the paper: https://doi.org/10.1038/s41467-021-26173-3
Introduction to Associate Professor Yuan Li:
Dr. Yuan Li received his Ph.D from South China University of Technology in 2010, under the supervision of Academician Yong Cao. From 2010 to 2013, he worked as a postdoctoral researcher in the Department of Chemistry, National University of Singapore, under the supervision of Professor Jishan Wu. In 2013, he came back to SCUT and started to carry out independent research. His main research fields include the synthesis and application of organic radical semiconductors. So far, he has published more than 60 SCI papers as the first and corresponding author in Nature Communications, Joule, Chem, J. Am. Chem. Soc., Angew. Chem. Int. Ed., Adv. Energ. Mater., Adv. Funct. Mater. and others. He has more than 10 authorized patents, and is funded by the "Young Scholars Program" and "General Program" of NSFC, the "Outstanding Youth Fund of Central Universities", “Program of Guangzhou Pearl River Rising Star in Science and Technology", and the "Guangdong Provincial Science and Technology Innovation Program for Young Talents". His current research directions are: 1) Design and synthesis of stable organic radical optoelectronic materials; 2) Electron spin ground state regulation and applications of organic semiconductors.