Title: An Amphoteric Switch to Aromatic and Antiaromatic States of a Neutral Air‐Stable 25π Radical
Abstract: Abstract Ever since the discovery of the trityl radical, isolation of a stable and neutral organic radical has been a synthetic challenge. A (4 n +1)π open‐shell configuration is one such possible neutral radical but an unusual state between aromatic (4 n +2)π and antiaromatic (4 n )π electronic circuits. The synthesis and characterization of an air‐ and water‐stable neutral 25π pentathiophene macrocyclic radical is now described. It undergoes reversible one‐electron oxidation to a 24π antiaromatic cation and reduction to a 26π aromatic anion, thus confirming its amphoteric behavior. Structural determination by single‐crystal X‐ray diffraction studies revealed a planar configuration for the neutral radical, antiaromatic cation, and aromatic anion. In the solution state, the cation shows the highest upfield chemical shift ever observed for a 4 n π system, while the anion adhered to aromatic nature. Computational studies revealed the delocalized nature of the unpaired electron as confirmed by EPR spectroscopy.
Publication Year: 2014
Publication Date: 2014-08-26
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 28
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