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Aromaticity of the triplet states of corannulene and coronene
Journal of Physical Organic Chemistry ( IF 1.9 ) Pub Date : 2022-10-29 , DOI: 10.1002/poc.4464
Dmitrii Govorov 1 , Niroodha R. Pitawela 1 , Anna D. Gudmundsdottir 1
Affiliation  

Sunlight-driven photochemical reactions are an important tool for sustainable organic synthesis. However, compared with ground states, for which the effects of structure on properties and reactivity are well established, the understanding of excited states is limited. In particular, an improved understanding of aromaticity and antiaromaticity in excited states is necessary to develop strategic photochemical methods for synthesizing polycyclic aromatic compounds. Herein, using density functional theory (DFT)-optimized structures, the ground singlet (S0) and lowest triplet (T1) states of coronene and corannulene were compared. Bond length analysis demonstrated that both triplet corannulene and triplet coronene bear a partial resemblance to benzene. Nucleus-independent chemical shift (NICS(0), NICS(1.7)ZZ, NICS scans) and anisotropy of the induced current density (ACID) calculations were carried out to compare the induced magnetic currents in these molecules. This analysis demonstrated rather weak π-conjugation and partial antiaromaticity in the S0 state of each molecule. In contrast, a combination of circular induced currents and pronounced antiaromaticity was found in the T1 state of each molecule. However, the T1 of corannulene exhibited higher stability, which should facilitate functionalization. Consequently, corannulene is considered more suitable for photochemical applications.

中文翻译:

corannulene 和 coronene 三重态的芳香性

阳光驱动的光化学反应是可持续有机合成的重要工具。然而,与基态相比,结构对性质和反应性的影响已得到充分证实,对激发态的理解是有限的。特别是,有必要更好地了解激发态的芳香性和反芳香性,以开发合成多环芳香化合物的战略性光化学方法。在此,使用密度泛函理论 (DFT) 优化的结构,地面单线态 (S 0 ) 和最低三线态 (T 1) 比较了 coronene 和 corannulene 的状态。键长分析表明,三重态环烯和三重态晕苯都与苯具有部分相似性。进行与核无关的化学位移(NICS(0)、NICS(1.7) ZZ、NICS 扫描)和感应电流密度 (ACID) 计算的各向异性,以比较这些分子中的感应磁流。该分析证明了每个分子在 S 0状态下的相当弱的 π 共轭和部分反芳香性。相反,在每个分子的 T 1态中发现了圆形感应电流和显着的反芳香性的组合。然而,T 1的环烯表现出更高的稳定性,这应该有助于功能化。因此,环烯被认为更适合光化学应用。
更新日期:2022-10-29
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