A stable open-shell peri-hexacene with remarkable diradical character.

Zhang, Jinji; Fang, Xiaojing; Niu, Weiwei; Yu, Yiming; Hu, Yanlin; Sun, Jiawen; Xu, Ying; Zhou, Zhihua et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

[n]Peri-acenes ([n]PA) have attracted great interest as promising candidates for nanoelectronics and spintronics. However, the synthesis of large [n]PA (n > 4) is extremely challenging due to their intrinsic open-shell radical character and high reactivity. Herein, we report the successful synthesis and isolation of a derivative (1) of peri-hexacene in crystalline form. The structure of 1 is unequivocally confirmed by X-ray crystallographic analysis. Its ground state, aromaticity and photophysical properties are systematically studied by both experimental methods and theoretical calculations. Although the parent peri-hexacene is calculated to have a very large diradical character (y<sub>0</sub> = 94.5%), 1 shows reasonable stability (t<sub>1/2</sub> = 24 h under ambient conditions) due to the kinetic blocking. 1 exhibits an open-shell singlet ground state with a small singlet-triplet energy gap (-1.33 kcal/mol from SQUID measurements). 1 has also a narrow HOMO-LUMO energy gap (1.05 eV) and displays amphoteric redox behavior. This work opens new avenues for the design and synthesis of stable zigzag-edged graphene-like molecules with significant diradical character.