Department of Chemistry, Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Am Chem Soc. 2013 Jan 9;135(1):315-21. doi: 10.1021/ja309434t. Epub 2012 Dec 21.
Like the larger nonplanar Möbius rings, porphyrinoid aromaticity is not due primarily to the macrocyclic π conjugation of the corresponding annulene perimeters. The block-localized wave function (BLW)-derived aromatic stabilization energies (ASE) of several porphyrinoids reveal that, on a per atom basis, the appended 6π electron heterocycles of porphyrinoids confer aromaticity much more effectively than the macrocyclic 4n+2 π electron conjugations. There is no direct relationship between thermochemical stability of porphyrinoids and their macrocyclic 4n or 4n+2 π electron counts. Porphyrinoids having an "antiaromatic" macrocyclic 4n+2 π electron conjugation pathway (e.g., 4) as well as those having no macrocyclic conjugation (e.g., 9) can be stabilized by aromaticity. Computed nucleus independent chemical shifts (NICS) and the anisotropy of the induced current density (ACID) disclose the intricate local versus macrocyclic circulation interplay for several porphyrinoids.
与较大的非平面 Möbius 环一样，卟啉类芳香性不是主要归因于相应的轮烯周长的大环π共轭。几种卟啉类的块局部波函数 (BLW) 衍生的芳香稳定能 (ASE) 表明，就每个原子而言，卟啉类的附加 6π 电子杂环赋予芳香性的效果比大环 4n+2 π 电子共轭要强得多。卟啉类的热化学稳定性与其大环的 4n 或 4n+2 π 电子计数之间没有直接关系。具有“反芳香性”大环 4n+2 π 电子共轭途径的卟啉类（例如 4）以及没有大环共轭的卟啉类（例如 9）都可以通过芳香性来稳定。计算得到的核独立化学位移 (NICS) 和感应电流密度各向异性 (ACID) 揭示了几种卟啉类的复杂局部与大环循环相互作用。
