Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Chem Asian J. 2021 Jun 14;16(12):1553-1561. doi: 10.1002/asia.202100398. Epub 2021 May 10.
The singlet open-shell character and antiaromaticity are intriguing features in π-conjugated carbocycles. These two exhibit similar chemical and physical properties. However, they rarely coexist in the same molecule. Understanding the interrelation between the open-shell and antiaromatic characteristics in the same molecule is crucial to control the electronic properties. Herein we describe the synthesis and characterization of a new member of diareno[a,f]pentalene, benzo[a]naphtho[2,3-f]pentalene 6. Unlike its isomer 5 with a closed-shell ground state, 6 exhibits an appreciable open-shell character and a moderate antiaromatic feature. The behaviors of the open-shell index (y ) against the difference of the proton chemical signal (Δδ(H )) between pentalenide dianions/neutral pentalenes for our reported pentalenes 1, 4, 5, and 6 give a thought-provoking conclusion about the interrelation between open-shell and antiaromatic characteristics in this series. The mode of the incorporated quinoidal moiety and the formal molecular symmetry are critical to balance these two characteristics.
单重态开壳特性和反芳香性是π共轭碳环中引人入胜的特征。这两个特性表现出相似的化学和物理性质。然而，它们很少在同一个分子中同时存在。了解同一分子中开壳特性和反芳香特性之间的关系对于控制电子性质至关重要。在此，我们描述了一种新的二芳基[a,f]戊并[def]茚的合成与表征，即苯并[a]萘并[2,3-f]戊并[def]茚 6。与具有闭壳基态的异构体 5 不同，6 表现出明显的开壳特性和适度的反芳香特征。我们报道的戊并[def]茚 1、4、5 和 6 的开壳指数（y）对戊并[def]茚二负离子/中性戊并[def]茚之间质子化学信号（Δδ（H））差的行为，为这一系列中开壳特性和反芳香特性之间的关系提供了一个发人深省的结论。所包含的醌式部分的模式和形式分子对称性对于平衡这两个特性至关重要。
