Symes, M. , Wilkinson, D., Cioncoloni, G. and Bucher, G. (2020) Attempted characterisation of phenanthrene-4,5-quinone and electrochemical synthesis of violanthrone-16,17-quinone. How does the stability of bay quinones correlate with structural and electronic parameters? RSC Advances, 10, pp. 38004-38012. (doi: 10.1039/D0RA06519F)
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Abstract
In bay quinones, two carbonyl moieties are forced into close proximity by their spatial arrangement, resulting in an interesting axially chiral and nonplanar structure. Two representatives of this little-explored class of compounds were investigated experimentally in this work. Electrochemical oxidation of 4,5-dihydroxyphenanthrene failed to provide evidence for the reversible formation of phenanthrene-4,5-quinone. Even at temperatures as low as T = 229 K, cyclic voltammograms did not show any evidence for reversibility, indicating that phenanthrene-4,5-quinone likely is a reactive intermediate even at low temperatures. Electrochemical oxidation of the larger homologue 16,17-dihydroxyviolanthrone, on the other hand, was reversible, and the quinone could be characterised by spectroelectrochemical means. The results of quantum chemical calculations confirm the experimental findings and indicate that a bay dicarbonyl moiety, also found in a number of angucycline antibiotics, does not necessarily have to confer extreme reactivity. However, in a series of phenanthrene quinones with an equal number (zero) of Clar sextets and a varying number of bay carbonyl groups (zero to two), there was a clear correlation between the triplet energy, taken as a measure of biradical character, and the number of bay carbonyl moieties, with the lowest triplet energy predicted for phenanthrene-4,5-quinone (two bay carbonyl moieties).
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Bucher, Dr Goetz and Cioncoloni, Giacomo and Wilkinson, Dr Dylan and Symes, Professor Mark |
Authors: | Symes, M., Wilkinson, D., Cioncoloni, G., and Bucher, G. |
College/School: | College of Science and Engineering > School of Chemistry |
Journal Name: | RSC Advances |
Publisher: | Royal Society of Chemistry |
ISSN: | 2046-2069 |
ISSN (Online): | 2046-2069 |
Published Online: | 15 October 2020 |
Copyright Holders: | Copyright © The Royal Society of Chemistry 2020 |
First Published: | First published in RSC Advances 10:38004-38012 |
Publisher Policy: | Reproduced under a Creative Commons license |
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