Macrocyclic conjugation pathways in porphyrins
Macrocyclic conjugation pathways in porphyrins
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DOI：
10.1021/jp8014996
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发表时间：
2008-06-12
影响因子：
2.9
通讯作者：
Aihara, Jun-ichi
中科院分区：
文献类型：
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作者：
Aihara, Jun-ichi
大环芳香性是类卟啉化学中最重要的概念。键共振能（Bond resonance energy， BRE）是连接相邻的吡啶环或其他环的键的键共振能，表示由于大环芳香性而产生的稳定能。我们发现，与大环芳香性相关的主要共轭途径可以通过在pi网络的每个分叉处选择具有较大BRE的pi键来追踪。所有位于主共轭途径的pi键都比位于旁路的键具有更大的正BREs。另一方面，与大环抗芳香性相关的主要不稳定途径可以通过在pi网络的每个分叉处选择具有较小BRE的pi键来追踪，因此确定的大环共轭途径与附着在大环上的质子的化学位移完全一致。
Macrocyclic aromaticity is the most important concept in porphyrinoid chemistry. Bond resonance energy (BRE) for any pi-bond linking adjacent pyrrolic or other rings represents the stabilization energy due to macrocyclic aromaticity. We found that a main conjugation pathway associated with macrocyclic aromaticity can be traced by choosing a pi-bond with a larger BRE, at every bifurcation of the pi-network. All pi-bonds located along the main conjugation pathway are intensified with large positive BREs compared with those located along the bypasses. On the other hand, a main destabilization pathway associated with macrocyclic antiaromaticity can be traced by choosing a pi-bond with a smaller BRE at every bifurcation of the pi-network, Macrocyclic conjugation pathways thus determined are fully consistent with the chemical shifts of protons attached to the macrocycle.