Aromaticity of giant polycyclic aromatic hydrocarbons with hollow sites: super ring currents in super-rings.
Aromaticity of giant polycyclic aromatic hydrocarbons with hollow sites: super ring currents in super-rings.
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DOI：
10.1002/chem.200501321
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发表时间：
2006-07
期刊：
影响因子：
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通讯作者：
B. Hajgató;M. Deleuze;K. Ohno
中科院分区：
文献类型：
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作者：
B. Hajgató;M. Deleuze;K. Ohno
本文基于半经验、Hartree-Fock （HF）和密度泛函理论（DFT）模型，对一系列具有空心位点的多环芳烃（PAHs）进行了系统的理论研究。在这项研究中，我们特别关注芳香性的磁性标准，即(1)H NMR和核无关化学位移（NICS），以及它们与其他电子性质的关系。计算的位移和NICS指数表明，外磁场在均匀层的多环芳烃甜甜圈中产生了异常强的环形电流，特别是在双层化合物的中心孔直接邻近的层中。这些异常强的环形电流还与特别小的HOMO-LUMO间隙和电子激发能以及异常高的极化率有关，这反过来表明这些化合物具有更明显的金属特性。通过采用拓扑、结构和能量标准，对这些体系和[18]-[66]环的芳构性作了进一步的比较。
We present a systematic theoretical study based on semi-empirical, Hartree-Fock (HF), and density functional theory (DFT) models of a series of polycyclic aromatic hydrocarbons (PAHs) that exhibit hollow sites. In this study we focus particularly on the magnetic criteria of aromaticity, namely (1)H NMR and nucleus-independent chemical shifts (NICS), and on their relationships with other electronic properties. The computed shifts and NICS indices indicate that an external magnetic field induces exceptionally strong ring currents in even-layered PAH doughnuts, in particular in the layer directly adjacent to the central hole of double-layered compounds. These exceptionally strong ring currents also correlate with particularly small HOMO-LUMO gaps and electronic excitation energies and to abnormally high polarizabilities, indicating in turn that these compounds have a more pronounced metallic character. Comparison is made with further depictions of aromaticity in these systems and in [18]-[66]annulene rings by employing topological, structural, and energetic criteria.