Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
J Phys Chem A. 2009 Dec 17;113(50):13953-63. doi: 10.1021/jp906126g.
Rotation of pyrrole rings in regular porphyrins and N-confused porphyrins is theoretically investigated by DFT calculations. While the inversion of the pyrrole rings in the regular porphyrins requires high activation energies (36.5-49.1 kcal/mol), the inversion of the confused pyrrole rings in the N-confused porphyrins requires much lower activation energies (18.1-24.5 kcal/mol). This marked difference can be explained by the intramolecular hydrogen bondings and aromatic stabilization due to the [18]annulenic substructures, where confusion and NH tautomerism play an important role. In both of the macrocycles, 360 degrees rotation of their pyrrole rings would be difficult possibly due to the small cavity. Alternatively, a reaction pathway for the production of N-fused porphyrin from N-confused porphyrin is obtained, which is consistent with the experimental observation.
通过 DFT 计算理论研究了规则卟啉和 N-稠合卟啉中环的旋转。虽然规则卟啉中环的反转需要高的活化能（36.5-49.1 kcal/mol），但是 N-稠合卟啉中环的反转需要低得多的活化能（18.1-24.5 kcal/mol）。这种明显的差异可以通过分子内氢键和由于[18]轮烯亚结构引起的芳香稳定化来解释，其中稠合和 NH 互变异构体起着重要的作用。在这两个大环中，由于腔室较小，它们的吡咯环可能难以进行 360 度旋转。或者，得到了从 N-稠合卟啉生成 N-稠合卟啉的反应途径，这与实验观察结果一致。
