Evolution of the electronic structure in open-shell donor-acceptor organic semiconductors

作者：Chen, Zhongxin; Li, Wenqiang; Sabuj, Md Abdus; Li, Yuan^*; Zhu, Weiya; Zeng, Miao; Sarap, Chandra S.; Huda, Md Masrul; Qiao, Xianfeng; Peng, Xiaobin; Ma, Dongge; Ma, Yuguang; Rai, Neeraj^*; Huang, Fei^*

来源：Nature Communications, 2021, 12(1): 5889.

DOI：10.1038/s41467-021-26173-3

• CLOSED-SHELL
• QUINOIDAL OLIGOTHIOPHENES
• HARTREE-FOCK
• SINGLET
• DESIGN
• PERSISTENT
• CHARACTER
• RADICALS

Most organic semiconductors have closed-shell electronic structures, however, studies have revealed open-shell character emanating from design paradigms such as narrowing the bandgap and controlling the quinoidal-aromatic resonance of the pi-system. A fundamental challenge is understanding and identifying the molecular and electronic basis for the transition from a closed- to open-shell electronic structure and connecting the physicochemical properties with (opto)electronic functionality. Here, we report donor-acceptor organic semiconductors comprised of diketopyrrolopyrrole and naphthobisthiadiazole acceptors and various electron-rich donors commonly utilized in constructing high-performance organic semiconductors. Nuclear magnetic resonance, electron spin resonance, magnetic susceptibility measurements, single-crystal X-ray studies, and computational investigations connect the bandgap, pi-extension, structural, and electronic features with the emergence of various degrees of diradical character. This work systematically demonstrates the widespread diradical character in the classical donor-acceptor organic semiconductors and provides distinctive insights into their ground state structure-property relationship. @@@ The classical narrow bandgap donor-acceptor organic semiconductors show great application potential in organic electronics, bio-imaging and other fields. Here, the authors systematically and rigorously demonstrate their open-shell diradical character via experimental and theoretical investigation.

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