An Amphoteric Switch to Aromatic and Antiaromatic States of a Neutral Air-Stable 25[pi] Radical

Ever since the discovery of the trityl radical, isolation of a stable and neutral organic radical has been a synthetic challenge. A (4n+1)π open-shell configuration is one such possible neutral radical but an unusual state between aromatic (4n+2)π and antiaromatic (4n)π electronic circuits. The synt...

Full description

Saved in:
Bibliographic Details
Published in:Angewandte Chemie 2014-10, Vol.126 (41), p.11164
Main Authors: Gopalakrishna, Tullimilli Y, Reddy, J Sreedhar, Anand, Venkataramanarao G
Format: Article
Language:ger
Subjects:
Chemistry
Crystals
Diffraction
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Ever since the discovery of the trityl radical, isolation of a stable and neutral organic radical has been a synthetic challenge. A (4n+1)π open-shell configuration is one such possible neutral radical but an unusual state between aromatic (4n+2)π and antiaromatic (4n)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 4nπ system, while the anion adhered to aromatic nature. Computational studies revealed the delocalized nature of the unpaired electron as confirmed by EPR spectroscopy. [PUBLICATION ABSTRACT]
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201406893