School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala 695551, India.
Chemphyschem. 2022 Jun 3;23(11):e202200045. doi: 10.1002/cphc.202200045. Epub 2022 May 9.
The implication of the potential concept of aromaticity in the relaxed lowest triplet state of azobenzene, an efficient molecular switch, using elementary aromaticity indices based on magnetic, electronic, and geometric criteria has been discussed. Azobenzene exhibits a major Hückel aromatic character retained in the diradical lowest relaxed triplet state (T ) by virtue of a twisted geometry with partial delocalization of unpaired electrons in the perpendicular p-orbitals of two nitrogen atoms to the corresponding phenyl rings. The computational analysis has been expanded further to stilbene and N-diphenylmethanimine for an extensive understanding of the effect of closed-shell Hückel aromaticity in double-bond-linked phenyl rings. Our analysis concluded that stilbene has Hückel aromatic character in the relaxed T state and N-diphenylmethanimine has a considerable Hückel aromaticity in the phenyl ring near the carbon atom while a paramount Baird aromaticity in the phenyl ring near the nitrogen atom of the C=N double bond. The results reveal the application of excited-state aromaticity as a general tool for the design of molecular switches.
使用基于磁、电和几何标准的基本芳香性指数，讨论了在偶氮苯（一种有效的分子开关）松弛的最低三重态中潜在芳香性概念的含义。偶氮苯通过扭曲的几何形状，在垂直于相应苯环的两个氮原子的 p 轨道中，部分离域未配对电子，在最低松弛三重态（T）中保留了主要的休克尔芳香特征。通过扩展到二苯乙烯和 N-二苯甲亚胺的计算分析，进一步了解了闭壳层休克尔芳香性对双键连接的苯环的影响。我们的分析得出结论，二苯乙烯在松弛的 T 态具有休克尔芳香特征，N-二苯甲亚胺在靠近碳原子的苯环中具有相当大的休克尔芳香性，而在靠近氮原子的苯环中具有主要的贝尔德芳香性。这些结果揭示了激发态芳香性作为设计分子开关的通用工具的应用。
