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β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity

Octaethyltrioxopyrrocorphins unexpectedly show macrocycle-aromatic properties, even though they contain the macrocyclic π-system of the non-aromatic pyrrocorphins (hexahydroporphyrins). Two of the four possible triketone regioisomers were first reported in 1969 by one-pot oxidation of octaethylporph...

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Autores principales: Chaudhri, Nivedita, Guberman-Pfeffer, Matthew J., Li, Ruoshi, Zeller, Matthias, Brückner, Christian
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8480330/
https://www.ncbi.nlm.nih.gov/pubmed/34603659
http://dx.doi.org/10.1039/d1sc03403k
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author Chaudhri, Nivedita
Guberman-Pfeffer, Matthew J.
Li, Ruoshi
Zeller, Matthias
Brückner, Christian
author_facet Chaudhri, Nivedita
Guberman-Pfeffer, Matthew J.
Li, Ruoshi
Zeller, Matthias
Brückner, Christian
author_sort Chaudhri, Nivedita
collection PubMed
description Octaethyltrioxopyrrocorphins unexpectedly show macrocycle-aromatic properties, even though they contain the macrocyclic π-system of the non-aromatic pyrrocorphins (hexahydroporphyrins). Two of the four possible triketone regioisomers were first reported in 1969 by one-pot oxidation of octaethylporphyrin but remained essentially unexplored since. We detail here the targeted preparation of the remaining two triketone isomers and the optical and NMR spectroscopic properties of all isomers. All four regioisomers possess unique electronic properties, including broadly varying degrees of diatropicity that were experimentally determined using (1)H NMR spectroscopy and computationally verified. Structural patterns modulating the aromaticity were recognized. These differences highlight the regioisomerically differentiated influences of the three β-oxo-functionalities. We also present the solid state structure of the two most common isomers (in their free base form or as zinc complexes), allowing further conclusions to be made about the resonance structures present in these triketones. Remarkably, also, the halochromic properties of the triketones differ sharply from those of regular (hydro)porphyrins, providing further support for the proposed 16-membered, 18 π-electron aromatic ring-current. The work conceptually expands the understanding of tris-modified hydroporphyrinoid analogues and the factors that enable and control porphyrinoid aromaticity.
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spelling pubmed-84803302021-10-01 β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity Chaudhri, Nivedita Guberman-Pfeffer, Matthew J. Li, Ruoshi Zeller, Matthias Brückner, Christian Chem Sci Chemistry Octaethyltrioxopyrrocorphins unexpectedly show macrocycle-aromatic properties, even though they contain the macrocyclic π-system of the non-aromatic pyrrocorphins (hexahydroporphyrins). Two of the four possible triketone regioisomers were first reported in 1969 by one-pot oxidation of octaethylporphyrin but remained essentially unexplored since. We detail here the targeted preparation of the remaining two triketone isomers and the optical and NMR spectroscopic properties of all isomers. All four regioisomers possess unique electronic properties, including broadly varying degrees of diatropicity that were experimentally determined using (1)H NMR spectroscopy and computationally verified. Structural patterns modulating the aromaticity were recognized. These differences highlight the regioisomerically differentiated influences of the three β-oxo-functionalities. We also present the solid state structure of the two most common isomers (in their free base form or as zinc complexes), allowing further conclusions to be made about the resonance structures present in these triketones. Remarkably, also, the halochromic properties of the triketones differ sharply from those of regular (hydro)porphyrins, providing further support for the proposed 16-membered, 18 π-electron aromatic ring-current. The work conceptually expands the understanding of tris-modified hydroporphyrinoid analogues and the factors that enable and control porphyrinoid aromaticity. The Royal Society of Chemistry 2021-08-20 /pmc/articles/PMC8480330/ /pubmed/34603659 http://dx.doi.org/10.1039/d1sc03403k Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by/3.0/
spellingShingle Chemistry
Chaudhri, Nivedita
Guberman-Pfeffer, Matthew J.
Li, Ruoshi
Zeller, Matthias
Brückner, Christian
β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title_full β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title_fullStr β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title_full_unstemmed β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title_short β-Trioxopyrrocorphins: pyrrocorphins of graded aromaticity
title_sort β-trioxopyrrocorphins: pyrrocorphins of graded aromaticity
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8480330/
https://www.ncbi.nlm.nih.gov/pubmed/34603659
http://dx.doi.org/10.1039/d1sc03403k
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