Toward Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity

详细信息    查看全文

• 作者：Pan Hu ; Sangsu Lee ; Tun Seng Herng ; Naoki Aratani ; Théo P. Gon?alves ; Qingbiao Qi ; Xueliang Shi ; Hiroko Yamada ; Kuo-Wei Huang ; Jun Ding ; Dongho Kim ; Jishan Wu
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：January 27, 2016
• 年：2016
• 卷：138
• 期：3
• 页码：1065-1077
• 全文大小：1034K
• ISSN：1520-5126

文摘

Open-shell singlet diradicaloids display unique electronic, nonlinear optical, and magnetic activity and could become novel molecular materials for organic electronics, photonics, and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this Article, we report our efforts toward a tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties, and chemical reactivity were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introduction of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/antiaromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.