Huang Yanxia, Zhou Laiyun, Zhang Ruiying, Ding Yeda, Shi Dan, Zhu Lingyun, Lin Lisen, Li Yuanming, Wang Qing
Key Laboratory of Advanced Carbon-Based Functional Materials, Fujian Province University), College of Chemistry, Fuzhou University, Fuzhou, 350108, China.
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou, 350207, China.
Angew Chem Int Ed Engl. 2025 Mar 24;64(13):e202424128. doi: 10.1002/anie.202424128. Epub 2025 Jan 17.
Polycyclic aromatic hydrocarbons (PAHs) have attracted significant interest in material chemistry, particularly if they own extremely low band gaps and magnetic properties. However, challenges remain regarding the synthetic accessibility and energy saturation issues. In this study, we introduce NR-11, which consists of eleven aromatic rings in its main conjugation and is separately doped with two electron-rich nitrogen atoms. This unique structure imparts intriguing oxidation characteristics to NR-11. The cationic radical NR-11⋅ exhibits enhanced stability and demonstrates strong absorption in the range of 1250 nm to 3000 nm, peaking at 2570 nm. As a result, the optical energy gap of NR-11⋅ is one of the lowest reported to date. Additionally, X-ray crystal structure analysis reveals that NR-11⋅ displays unusual symmetry-broken charge separation. For the dication, variable-temperature NMR and variable-temperature EPR studies indicate that NR-11 exhibits a high diradical character with a ▵E of approximately -1 kcal/mol. Additionally, its spins are polarized at two ends of the PAH. Meanwhile, its strong absorption in the near-infrared II region suggests promise in photoacoustic (PA) conversion applications. This work underscores the significance of cationic species of extended long PAHs, highlighting their exceptional properties and potential applications.
多环芳烃（PAHs）在材料化学领域引起了广泛关注，特别是当它们具有极低的带隙和磁性时。然而，在合成可及性和能量饱和问题方面仍存在挑战。在本研究中，我们引入了NR-11，其主共轭结构由11个芳环组成，并分别掺杂有两个富电子氮原子。这种独特的结构赋予了NR-11引人入胜的氧化特性。阳离子自由基NR-11⋅表现出增强的稳定性，并在1250 nm至3000 nm范围内表现出强烈吸收，峰值在2570 nm。因此，NR-11⋅的光学能隙是迄今为止报道的最低值之一。此外，X射线晶体结构分析表明，NR-11⋅显示出异常的对称破缺电荷分离。对于双阳离子，变温核磁共振和变温电子顺磁共振研究表明，NR-11具有高双自由基特征，ΔE约为 -1 kcal/mol。此外，其自旋在PAH的两端极化。同时，它在近红外II区域的强烈吸收表明在光声（PA）转换应用中有前景。这项工作强调了长链PAHs阳离子物种的重要性，突出了它们的特殊性质和潜在应用。
