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Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials

Understanding the stabilization of nitrogen heterocycles is critical in the field of energetic materials and calls for innovative knowledge of nitrogen aromatics. Herewith, we report for the first time that nitrogen lone pair electron (NLPE) delocalization in five-membered nitrogen heterocycles crea...

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Autores principales: Zong, He-Hou, Yao, Chuang, Sun, Chang Q, Zhang, Jian-Guo, Zhang, Lei
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397173/
https://www.ncbi.nlm.nih.gov/pubmed/32679862
http://dx.doi.org/10.3390/molecules25143232
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author Zong, He-Hou
Yao, Chuang
Sun, Chang Q
Zhang, Jian-Guo
Zhang, Lei
author_facet Zong, He-Hou
Yao, Chuang
Sun, Chang Q
Zhang, Jian-Guo
Zhang, Lei
author_sort Zong, He-Hou
collection PubMed
description Understanding the stabilization of nitrogen heterocycles is critical in the field of energetic materials and calls for innovative knowledge of nitrogen aromatics. Herewith, we report for the first time that nitrogen lone pair electron (NLPE) delocalization in five-membered nitrogen heterocycles creates a second σ-aromaticity in addition to the prototypical π-aromaticity. The NLPE delocalization and the attendant dual-aromaticity are enhanced as more carbon atoms in the ring are substituted by unsaturated nitrogen atoms. The presence of adjacent nitrogen atoms in the ring can enhance the aromaticity of the nitrogen heterocycles and improve in-crystal intermolecular binding strength but will decrease the firmness of the individual molecular architecture. Notably, such σ-aromaticity is not present in six-membered nitrogen heterocycles, probably due to the longer bonds and broader regions of their rings; therefore, six-membered heterocycles present overall lower aromaticity than five-membered heterocycles. This work brings new knowledge to nitrogen aromatics and is expected to inspire broad interest in the chemistry community.
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spelling pubmed-73971732020-08-16 Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials Zong, He-Hou Yao, Chuang Sun, Chang Q Zhang, Jian-Guo Zhang, Lei Molecules Article Understanding the stabilization of nitrogen heterocycles is critical in the field of energetic materials and calls for innovative knowledge of nitrogen aromatics. Herewith, we report for the first time that nitrogen lone pair electron (NLPE) delocalization in five-membered nitrogen heterocycles creates a second σ-aromaticity in addition to the prototypical π-aromaticity. The NLPE delocalization and the attendant dual-aromaticity are enhanced as more carbon atoms in the ring are substituted by unsaturated nitrogen atoms. The presence of adjacent nitrogen atoms in the ring can enhance the aromaticity of the nitrogen heterocycles and improve in-crystal intermolecular binding strength but will decrease the firmness of the individual molecular architecture. Notably, such σ-aromaticity is not present in six-membered nitrogen heterocycles, probably due to the longer bonds and broader regions of their rings; therefore, six-membered heterocycles present overall lower aromaticity than five-membered heterocycles. This work brings new knowledge to nitrogen aromatics and is expected to inspire broad interest in the chemistry community. MDPI 2020-07-15 /pmc/articles/PMC7397173/ /pubmed/32679862 http://dx.doi.org/10.3390/molecules25143232 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Zong, He-Hou
Yao, Chuang
Sun, Chang Q
Zhang, Jian-Guo
Zhang, Lei
Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title_full Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title_fullStr Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title_full_unstemmed Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title_short Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials
title_sort structure and stability of aromatic nitrogen heterocycles used in the field of energetic materials
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397173/
https://www.ncbi.nlm.nih.gov/pubmed/32679862
http://dx.doi.org/10.3390/molecules25143232
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