Wang Lei, Niu Weiwei, Tian Di, Jiao Tianyu, Zhang Lemin, Hou Xudong, Han Yi, Zou Ya, Wu Jishan, Li Guangwu
Center of Single-Molecule Sciences, Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, 300350, Tianjin, China.
Department of chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore, Singapore.
Angew Chem Int Ed Engl. 2025 Jan 15;64(3):e202415746. doi: 10.1002/anie.202415746. Epub 2024 Nov 26.
High-spin organic radicals are notable for their unique optical, electronic, and magnetic properties, but synthesizing stable high-spin systems is challenging due to their inherent reactivity. This study presents a novel strategy for designing stable high-spin polycyclic hydrocarbons (PHs) by incorporating allylic radical into fused aromatic benzenoid rings. To enhance stability, large steric hindrance groups with a synergistic captodative effect were added to the allylic radical centers. This approach was applied to synthesize derivatives of two open-shell all-benzenoid PHs: benzo[fg]tetracene (1) and dibenzo[fg,lm]heptacene (2). Both compounds exhibited excellent stability, with diradical 2 showing a half-life of up to 17.2 days under ambient conditions. Bond length analysis and theoretical calculations suggest that 1 and 2 predominantly feature Clar's aromatic sextet structures with embedded allylic radicals. Compound 2 was confirmed to have a triplet ground state through DFT calculations and experimental methods, including pulse EPR spectroscopy and SQUID measurements. This work introduces a new design strategy for stable high-spin hydrocarbons, paving the way for future developments in high-spin organic materials.
高自旋有机自由基因其独特的光学、电子和磁性特性而备受关注，但由于其固有的反应性，合成稳定的高自旋体系具有挑战性。本研究提出了一种通过将烯丙基自由基引入稠合芳香苯环来设计稳定的高自旋多环烃（PHs）的新策略。为了提高稳定性，在烯丙基自由基中心添加了具有协同给体-受体效应的大位阻基团。该方法被应用于合成两种开壳全苯型PHs的衍生物：苯并[fg]并四苯（1）和二苯并[fg,lm]庚并四苯（2）。两种化合物均表现出优异的稳定性，双自由基2在环境条件下的半衰期长达17.2天。键长分析和理论计算表明，1和2主要具有嵌入烯丙基自由基的克拉尔芳香六隅体结构。通过DFT计算以及包括脉冲EPR光谱和SQUID测量在内的实验方法，证实化合物2具有三重基态。这项工作为稳定的高自旋烃类引入了一种新的设计策略，为高自旋有机材料的未来发展铺平了道路。
