Investigation of type-I conformations of A2B4-[26]hexaphyrins(1.1.1.1.1.1) bearing strongly electron-withdrawing aryl substituents at 5,20-positions
Investigation of type-I conformations of A2B4-[26]hexaphyrins(1.1.1.1.1.1) bearing strongly electron-withdrawing aryl substituents at 5,20-positions
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研究 5,20 位具有强吸电子芳基取代基的 A2B4-[26]hexaphyrins(1.1.1.1.1.1) 的 I 型构象
DOI：
10.1142/s1088424621500978
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
M. Suzuki
中科院分区：
文献类型：
--
作者：
Y. Nagano;M. Suzuki
哑铃形I型构象是[26]六卟啉（1.1.1.1.1.1）框架的固有结构，没有来自其外围取代基的任何扰动。相反，矩形II型构象可以被认为是稳定的[26]六卟啉（1.1.1.1.1）中更常见的结构，这不仅是因为合成的限制，而且还因为与间位芳基取代基相关的空间影响。本论文研究了含一系列吸电子基团的[26]六卟啉（1.1.1.1.1.1）的合成及其构象表征。1H NMR谱表明，在5，20-位上带有3，5-二硝基苯基的[26]六卟啉是唯一的I型构象异构体，而大多数其他的[26]六卟啉在I型、II型和II型构象异构体之间处于平衡状态。此外，紫外-可见吸收测量显示，I型构象可以利用其5，20-取代基的电子特征，由于它们与大环的相对共面排列。
The dumbbell-shaped type-I conformation is the inherent structure of the [26]hexaphyrin(1.1.1.1.1.1) framework without any perturbations from its peripheral substituents. Conversely, the rectangular type-II conformation can be regarded as a more general structure seen in stable [26]hexaphyrins(1.1.1.1.1.1) because of not only the synthetic limitations but also the steric influences related to themeso-aryl substituents. In this study, the synthesis of [26]hexaphyrins(1.1.1.1.1.1) bearing a series of electron-withdrawing groups and their conformational characterizations were investigated. The1H NMR spectra showed that [26]hexaphyrin with 3,5-dinitrophenyl groups at the 5,20-positions was obtained as the sole type-I conformer, whereas most other [26]hexaphyrins are in equilibrium between type-I, type-II, and type-IIconformers. Moreover, UV-vis absorption measurements revealed that type-I conformations can utilize the electronic features of their 5,20-substituents owing to their relatively co-planar arrangements with the macrocycles.