σ-Aromaticity in a Fully Unsaturated Ring
σ-Aromaticity in a Fully Unsaturated Ring
复制标题
Ï-完全不饱和环中的芳香度
DOI：
10.1002/asia.201801279
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发表时间：
2018
影响因子：
4.1
通讯作者：
Jun Zhu
中科院分区：
文献类型：
--
作者：
Jingjing Wu;Xin Liu;Yulei Hao;Hongjiang Chen;Peifeng Su;Wei Wu;Jun Zhu
芳香性是最基本、最令人着迷的化学主题之一，因其多种表现形式而吸引着实验和理论化学家。 σ-和π-芳香性都可以根据环状电子离域的特征进行分类。一般来说，σ-芳香性通过σ-电子离域稳定完全饱和的环，而传统的π-芳香性描述完全不饱和环中的π-共轭。在这里，我们证明了核无关化学位移（NICS）值和额外循环共振能（ECRE）之间的强相关性，用于评估环丙烯不饱和三元环（3MR）中的σ-芳香性，分别通过分子轨道（MO）理论和价键（VB）理论计算。进一步研究表明，亚甲基环丙烯及其金属类似物中的完全不饱和环是σ-芳香族。我们的研究结果彻底改变了 σ 芳香性概念的基础知识，从而为在其他完全不饱和体系中设计 σ 芳香性开辟了一条途径，这些系统传统上被保留为 π 芳香性领域。
Aromaticity is one of the most fundamental and fascinating chemical topics, attracting both experimental and theoretical chemists owing to its many manifestations. Both σ‐ and π‐aromaticity can be classified depending on the character of the cyclic electron delocalization. In general, σ‐aromaticity stabilizes fully saturated rings with σ‐electron delocalization whereas the traditional π‐aromaticity describes the π‐conjugation in fully unsaturated rings. Here, we demonstrate a strong correlation between nucleus‐independent chemical shift (NICS) values and extra cyclic resonance energies (ECREs), which are used to evaluate the σ‐aromaticity in an unsaturated three‐membered ring (3MR) of cyclopropene, which were computed by molecular orbital (MO) theory and valence bond (VB) theory, respectively. Further study shows that the fully unsaturated ring in methylenecyclopropene and its metallic analogy is σ‐aromatic. Our findings revolutionize the fundamental knowledge of the concept of σ‐aromaticity, thus opening an avenue to design σ‐aromaticity in other fully unsaturated systems, which are traditionally reserved as the domain of π‐aromaticity.