Premium
σ‐Aromaticity in a Fully Unsaturated Ring
Author(s) -
Wu Jingjing,
Liu Xin,
Hao Yulei,
Chen Hongjiang,
Su Peifeng,
Wu Wei,
Zhu Jun
Publication year - 2018
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201801279
Subject(s) - aromaticity , delocalized electron , ring (chemistry) , chemistry , chemical shift , computational chemistry , electron delocalization , chemical physics , cyclopropene , molecule , organic chemistry
Aromaticity is one of the most fundamental and fascinating chemical topics, attracting both experimental and theoretical chemists owing to its many manifestations. Both σ‐ and π‐aromaticity can be classified depending on the character of the cyclic electron delocalization. In general, σ‐aromaticity stabilizes fully saturated rings with σ‐electron delocalization whereas the traditional π‐aromaticity describes the π‐conjugation in fully unsaturated rings. Here, we demonstrate a strong correlation between nucleus‐independent chemical shift (NICS) values and extra cyclic resonance energies (ECREs), which are used to evaluate the σ‐aromaticity in an unsaturated three‐membered ring (3MR) of cyclopropene, which were computed by molecular orbital (MO) theory and valence bond (VB) theory, respectively. Further study shows that the fully unsaturated ring in methylenecyclopropene and its metallic analogy is σ‐aromatic. Our findings revolutionize the fundamental knowledge of the concept of σ‐aromaticity, thus opening an avenue to design σ‐aromaticity in other fully unsaturated systems, which are traditionally reserved as the domain of π‐aromaticity.