Predicting the Open-Shell Character of Polycyclic Hydrocarbons in Terms of Clar Sextets,The Journal of Physical Chemistry A

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Predicting the Open-Shell Character of Polycyclic Hydrocarbons in Terms of Clar Sextets
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-01-18 00:00:00 , DOI: 10.1021/acs.jpca.7b11095
Georges Trinquier ₁ , Jean-Paul Malrieu ₁

Affiliation

Rather unexpected spin-symmetry breakings of mean-field single determinants occur in singlet ground states of many families of alternating conjugated hydrocarbons which accept a full on-bond electron pairing. These symmetry breakings may be seen as an indication of the existence of unpaired electrons. Although qualitative, the concept of disjoint electronic sextets proposed by Clar (hereafter called CS) is at least a heuristic tool for predicting various features of fused polybenzenic hydrocarbons. The present work shows that identifying the preferred CS distribution enables one to rationalize the existence of one or several spin-symmetry breakings, i.e., the existence and the number of unpaired electrons in alternant fused polycyclic hydrocarbons via a simple recipe for the prediction of these features. This recipe is based on comparison between various distributions of CS on the molecular frame, subject to a restriction concerning the fragments of the graph that do not belong to the CS. This rule is successfully confronted to UDFT calculations and to a recently proposed criterion predicting the possible occurrence of spin-symmetry breaking from the topological Hückel Hamiltonian. The confrontation runs on series of rhombuses, periacenes, anthenes, and other graphene flakes or nanoribbons. The CS distribution definitely offers a qualitative guide to look at the possible occurrence of (multiple) symmetry breakings in polycyclic architectures which are commonly seen as closed-shell singlets.

中文翻译：

根据Clar Sextets预测多环烃的开壳特性

相反，平均场单行列式的意外的自旋对称破坏发生在许多交替共轭烃族的单重基态中，这些共轭烃接受完整的键合电子对。这些对称断裂可以看作是存在未成对电子的指示。尽管是定性的，但Clar（以下称为CS）提出的不相交电子六重态的概念至少是一种用于预测熔融聚苯烃的各种特征的启发式工具。目前的工作表明，确定优选的CS分布可以使人们合理地预测一个或多个自旋对称断裂的存在，即通过简单的预测这些特征的方法，交替稠合多环烃中不成对电子的存在和数量。该配方基于分子框架上CS的各种分布之间的比较，并且受关于不属于CS的图形片段的限制。该规则已成功应用于UDFT计算和最近提出的预测自拓扑对称HückelHamiltonian打破自旋对称性可能发生的标准。这种对抗在一系列菱形，海藻油，蒽和其他石墨烯薄片或纳米带上进行。CS分布无疑提供了定性指南，以了解多环体系结构中（多个）对称断裂的可能发生情况，这些结构通常被视为闭壳单线态。该规则已成功应用于UDFT计算和最近提出的预测自拓扑对称HückelHamiltonian打破自旋对称性可能发生的标准。这种对抗在一系列菱形，海藻油，蒽和其他石墨烯薄片或纳米带上进行。CS分布无疑提供了定性指南，以了解多环体系结构中（多个）对称断裂的可能发生情况，这些结构通常被视为闭壳单线态。该规则已成功应用于UDFT计算和最近提出的预测自拓扑对称HückelHamiltonian打破自旋对称性可能发生的标准。这种对抗在一系列菱形，海藻油，蒽和其他石墨烯薄片或纳米带上进行。CS分布无疑提供了定性指南，以了解多环体系结构中（多个）对称断裂的可能发生情况，这些结构通常被视为闭壳单线态。

更新日期：2018-01-18

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