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Bent and twisted: the electronic structure of 2-azapropenylium ions obtained by guanidine oxidation

New bis-2-azapropenylium ions are obtained by oxidation of guanidino-substituted aromatic compounds. The dications 12+ (1 = 1,4-bis-tetramethylguanidinobenzene) and 22+ (2 = 1,4-bis-guanidinobenzene) exhibit unexpected bent-twisted structures, that differ from the known 2-azapropenylium ion structur...

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Bibliographic Details
Main Authors: Hornung, Julius (Author) , Hübner, Olaf (Author) , Kaifer, Elisabeth (Author) , Himmel, Hans-Jörg (Author)
Format: Article (Journal)
Language:English
Published: 20 Apr 2016
In: RSC Advances
Year: 2016, Volume: 6, Issue: 45, Pages: 39323-39329
ISSN:2046-2069
DOI:10.1039/C6RA04494H
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1039/C6RA04494H
Verlag, lizenzpflichtig, Volltext: https://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra04494h
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Author Notes:Julius Hornung, Olaf Hübner, Elisabeth Kaifer, Hans-Jörg Himmel
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Summary:New bis-2-azapropenylium ions are obtained by oxidation of guanidino-substituted aromatic compounds. The dications 12+ (1 = 1,4-bis-tetramethylguanidinobenzene) and 22+ (2 = 1,4-bis-guanidinobenzene) exhibit unexpected bent-twisted structures, that differ from the known 2-azapropenylium ion structures (linear-orthogonal 2-azaallenium ion or bent-planar 2-azaallylium ion), and resemble the structures of carbodicarbenes. Their electronic structure was analysed by a combination of experiments and quantum chemical calculations. The results indicate that the bent-planar structure is disfavoured for steric reasons, while the allene-type linear-orthogonal structure is also disfavoured due to the electron-donating groups that support the bent form. For these reasons a bent-twisted structure is adopted, in which the nitrogen atom is engaged with two different orbitals in π-bonding with the carbon π-system and in a weaker π-interaction with the CN2 group of the guanidino system.
Item Description:Gesehen am 20.05.2020
Physical Description:Online Resource
ISSN:2046-2069
DOI:10.1039/C6RA04494H

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