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Rupturing aromaticity by periphery overcrowding

delete2023-03-06
delete19
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OA
AI
P
Promeet K. Saha
A
Abhijit Mallick
A
Andrew T. Turley
A
Aisha N. Bismillah
A
Andrew Danos
A
Andrew P. Monkman
A
Alyssa‐Jennifer Avestro
D
Dmitry S. Yufit
P
Paul R. McGonigal *
DOI:10.1038/s41557-023-01149-6delete
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Abstract

Abstract

En 中文
The balance between strain relief and aromatic stabilization dictates the form and function of non-planar pi-aromatics. Overcrowded systems are known to undergo geometric deformations, but the energetically favourable pi-electron delocalization of their aromatic ring(s) is typically preserved. In this study we incremented the strain energy of an aromatic system beyond its aromatic stabilization energy, causing it to rearrange and its aromaticity to be ruptured. We noted that increasing the steric bulk around the periphery of pi-extended tropylium rings leads them to deviate from planarity to form contorted conformations in which aromatic stabilization and strain are close in energy. Under increasing strain, the aromatic pi-electron delocalization of the system is broken, leading to the formation of a non-aromatic, bicyclic analogue referred to as 'Dewar tropylium'. The aromatic and non-aromatic isomers have been found to exist in rapid equilibrium with one another. This investigation demarcates the extent of steric deformation tolerated by an aromatic carbocycle and thus provides direct experimental insights into the fundamental nature of aromaticity.
Keywords:
DEWAR BENZENE
PI
ISOMERS
DENSITY
ANTIAROMATICITY
DELOCALIZATION
MOLECULES
TROPYLIUM
ENERGY
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Journal

Nature Chemistry cover
Nature Chemistry
IF:
20.2
Papers:
4.4K
Citations:
4.8W

Organization

D
Durham University
Scholars:
1.3W
Papers: 1.5W
Citations: 2.1W
U
university of york - uk
Scholars:
1.5W
Papers: 1.5W
Citations: 15