Validity and Limitations of the Bridged Annulene Model for Porphyrins
Validity and Limitations of the Bridged Annulene Model for Porphyrins
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DOI：
10.1021/jp310480d
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发表时间：
2012-11-29
影响因子：
2.9
通讯作者：
Makino, Masakazu
中科院分区：
文献类型：
--
作者：
Aihara, Jun-ichi;Nakagami, Yuto;Makino, Masakazu
根据桥接环烯模型，一类卟啉类化合物的大环芳香性可归因于类环烯主大环偶联途径（MMCP）。然而，从理论上讲，大环芳香性是所有大环电路贡献的总和。我们发现每个大环回路的芳香性是由Huckel的[4n + 2]芳香性规则正式而广泛地确定的。吡咯环中的氮原子有效地抑制了沿每个大环电路停留的π电子数量的变化。因此，所有或大多数低聚吡咯大环中的大环电路都与MMCP相形成芳香（或反芳香）。因此，MMCP不是大环芳香性的决定因素，但可以看作是这个量的一个很好的指标。这就是为什么桥接环烯模型似乎适用于许多卟啉。
According to the bridged annulene model, macrocyclic aromaticity of a porphyrinoid species can be attributed to the annulene-like main macrocydic conjugation pathway (MMCP). Macrocyclic aromaticity, however, is given theoretically as a sum of contributions from all macrocyclic circuits. We found that the aromaticity due to each macrocyclic circuit is determined formally but broadly by Huckel's [4n + 2] rule of aromaticity. Nitrogen atoms in the pyrrolic rings effectively suppress the variation in the number of pi electrons staying along each macrocyclic circuit. As a result, all or most macrocyclic circuits in oligopyrrolic macrocycles are made aromatic (or antiaromaitc) in phase with the MMCP. Thus, the MMCP is not a determinant of macrocyclic aromaticity but can be regarded as a good indicator of this quantity. This is why the bridged annulene model appears to hold for many porphyrins.