A Persistent Open-Shell m -QDM-Type Diindenoanthracene Diradicaloid with a Large Diradical Character

作者：Bin Huang, Gaole Wang, Qiong‐Yan Hong, Xiao‐Li Zhao, Hai‐Bo Yang, Xueliang Shi · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c17094 · 被引用次数：4 · 研究领域：Synthesis and Properties of Aromatic Compounds、Magnetism in coordination complexes、Organoboron and organosilicon chemistry

Indenofluorenes (IFs) have received great interest owing to their intrinsic antiaromaticity, open-shell diradical character, and narrow band gaps. Herein, we report the synthesis and comprehensive characterization of a hitherto unknown m -QDM-type IFs-based diradicaloid derived from a diindenoanthracene framework. The relationships among the structure, diradical character, and chemical and physical properties of this novel diradicaloid are systematically investigated. This diradicaloid exhibits pronounced open-shell character with a large diradical character ( y 0 = 0.87), attributed to its unique fusion pattern and extended m -QDM-type structure. Despite its high reactivity, we successfully obtained a crystalline derivative, 2b, by introducing a bulky 9-mesitylanthracene substituent to protect the spin-bearing centers. Remarkably, 2b is stable in the solid state under ambient conditions but gradually decomposes to a ketone in solution with a long half-life of approximately 33 days. Additionally, 2b displays low-energy absorption beyond 1300 nm, a feature arising from its antiaromatic and π-extended electronic structure. The narrow singlet–triplet energy gap (Δ E S-T = −1.9 kcal mol –1 from VT-EPR and −1.4 kcal mol –1 from SQUID) of 2b enables its thermally accessible triplet excited state, resulting in its paramagnetic behavior with moderate magnetic susceptibility (0.59 cm 3 K mol –1 ) at room temperature. This study offers valuable insights into the structure–property rela...