Towards a taxonomy of topology for polynuclear aromatic hydrocarbons: linking electronic and molecular structure
Towards a taxonomy of topology for polynuclear aromatic hydrocarbons: linking electronic and molecular structure
复制标题
DOI：
10.1039/c7cp06048c
复制
发表时间：
2017-11-07
影响因子：
3.3
通讯作者：
Miller, J. Houston
中科院分区：
文献类型：
--
作者：
Adkins, Erin M.;Miller, J. Houston
报道了多核芳烃（PAH）的拓扑特征与其电子性质之间的关系。采用6- 31 G * 基组和B3 LYP交换相关泛函，对一系列PAH进行了TD-DFT电子光谱计算，并报告了HOMO-LUMO能隙。CLAR结构提供了一种将分子的物理结构和芳香性联系起来的途径;当通过键长和芳香性分析的谐振子模型进行扩展时，它为理解电子和物理结构之间的联系提供了强有力的工具。这些结果导致的结论是，所有的PAH结构显示作为尺寸的函数的HOMO-LUMO间隙的减小，但该减小的速率与分子的拓扑结构直接相关。PAH分类法的开发，PAH分类成具有相似的拓扑性质的类别，这使得建模的变化HOMO-LUMO间隙与PAH的大小。采用原子对最小化算法计算了多环芳烃均相二聚体的结合能。每个碳原子的BE随着结构的整体尺寸增加到渐近极限，但与HOMO-LUMO间隙一样，拓扑结构起着关键的次要因素。以前发表的，实验确定的光学带隙（OBG）从Tauc/Davis-Mott分析消光光谱在各种层流，非预混火焰产生的HOMO-LUMO间隙之间的相关性高对称性，近圆形D-2 h对称分子的分子大小。这里介绍的工作提供了一个更细致入微的和预测性的评估OBG如何取决于结构和大小。
Trends linking the topological characteristics of polynuclear aromatic hydrocarbons (PAH) to their electronic properties are reported. TD-DFT electronic spectra computations, using the 6-31G* basis set and B3LYP exchange correlation functional, were calculated for a series of PAH, allowing for the HOMO-LUMO gaps to be reported. Clar structures provide an avenue to link the physical structure and the aromaticity of the molecule; which, when extended by bond length and harmonic oscillator model of aromaticity analysis, provide powerful tools to understand the link between electronic and physical structure. These results lead to the conclusion that all PAH structures show a decrease in HOMO-LUMO gap as a function of size, but the rate of that decrease is directly related to the topology of the molecules. A PAH taxonomy was developed that categorizes PAH into categories with similar topological properties, which allows for modelling of changes in the HOMO-LUMO gap with PAH size. An atom-pair minimization algorithm was used to calculate the binding energy (BE) of homogeneous dimers of the studied PAH. The BE per carbon atom increases with the overall size of the structure to an asymptotic limit, but as with the HOMO-LUMO gap, topology plays a critical secondary factor. Previously published, experimentally determined optical band gaps (OBG) from Tauc/Davis-Mott analysis of extinction spectra in various laminar, non-premixed flames produced a correlation between the HOMO-LUMO gaps of high-symmetry, nearly circular D-2h symmetry molecules to molecular size. The work presented here provides a much more nuanced and predictive evaluation of how OBG depends on structure and size.