Yu Donghai, Rong Chunying, Lu Tian, Chattaraj Pratim K, De Proft Frank, Liu Shubin
Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, Hunan 410081, P. R. China.
Phys Chem Chem Phys. 2017 Jul 19;19(28):18635-18645. doi: 10.1039/c7cp03544f.
Even though the concept of aromaticity and antiaromaticity is extremely important and widely used, there still exist lots of controversies in the literature, which are believed to be originated from the fact that there are so many aromatic types discovered and at the same time there are many aromaticity indexes proposed. In this work, using seven series of substituted fulvene derivatives as an example and with the information-theoretic approach in density functional reactivity theory, we examine these concepts from a different perspective. We investigate the changing patterns of Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, information gain, Onicescu information energy, and relative Renyi entropy on the ring carbon atoms of these systems. Meanwhile, we also consider variation trends of four representative kinds of aromaticity indexes such as FLU, HOMA, ASE and NICS. Statistical analyses among these quantities show that with the same ring structure of the derivatives, both information-theoretic quantities and aromaticity indexes obey the same changing pattern, which are valid across all seven systems studied. However, cross correlations between these two sets of quantities yield two completely opposite patterns. These ring-structure dependent correlations are in good agreement with Hückel's 4n + 2 rule of aromaticity and 4n rule of antiaromaticity. Our results should provide a novel and complementary viewpoint on how aromaticity and antiaromaticity should be appreciated and categorized. More studies are in progress to further our understanding about the matter.
尽管芳香性和反芳香性的概念极其重要且被广泛应用，但文献中仍存在许多争议，这些争议被认为源于已发现的芳香类型众多，同时还提出了许多芳香性指标这一事实。在这项工作中，以七系列取代富烯衍生物为例，并采用密度泛函反应理论中的信息论方法，我们从不同角度审视这些概念。我们研究了这些体系中环碳原子上的香农熵、费舍尔信息、戈什 - 伯科维茨 - 帕尔熵、信息增益、奥尼塞库信息能和相对雷尼熵的变化模式。同时，我们还考虑了四种代表性芳香性指标（如FLU、HOMA、ASE和NICS）的变化趋势。这些量之间的统计分析表明，对于具有相同环结构的衍生物，信息论量和芳香性指标都遵循相同的变化模式，这在所有研究的七个体系中都是有效的。然而，这两组量之间的交叉相关性产生了两种完全相反的模式。这些与环结构相关的相关性与休克尔芳香性的4n + 2规则和反芳香性的4n规则高度一致。我们的结果应为如何理解和分类芳香性和反芳香性提供一个新颖且互补的观点。更多的研究正在进行中，以进一步加深我们对该问题的理解。
