Crystal and Molecular Structure of N-(3,5-Dichloro-2-hydroxybenzylidene)- and N-(2-Hydroxy-3-methoxybenzylidene)aniline Oxides. Delocalisation in the Spacer of the Intramolecular H-Bond and the Problem of Quasi-Aromaticity

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Title:Crystal and Molecular Structure of N-(3,5-Dichloro-2-hydroxybenzylidene)- and N-(2-Hydroxy-3-methoxybenzylidene)aniline Oxides. Delocalisation in the Spacer of the Intramolecular H-Bond and the Problem of Quasi-Aromaticity
Creators:
Krygowski, Tadeusz M.
Stępień, Beata
Anulewicz-Ostrowska, Romana
Cyrański, Michał K.
Grabowski, Sławomir J.
Rozwadowski, Zbigniew
Dziembowska, Teresa
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 64, 11, pp. 1797-1806
Uncontrolled Keywords:<i>Ab initio</i> calculations, X-Ray diffraction, Aromaticity, Chelates, H-bonds, Crystal structure, Schiff bases

Abstract

The hydrogen bond in the title compounds and their analogues with the spacer built of six heavy atoms (O,N,C,C,C,O) between the H-donor OH group and H-acceptor oxygen atom in the oxide group is much stronger than in the case of spacers with five heavy atoms. In spite of that, the delocalisation in the spacer does not depend on the strength of the H-bond, leading to the conclusion that quasi-aromaticity is not a proper term for these kinds of pseudorings. This is supported by analysis of the geometry of <i>N</i>-(3,5-dichloro-2-hydroxybenzylidene)- and <i>N</i>-(2-hydroxy-3-methoxybenzylidene)aniline oxides presented in this study and molecular geometries of five well solved structures retrieved from the CSD. Schleyer's index of aromaticity, NICS, is positive (<i>i.e.</i> indicating nonaromatic behaviour) for a model approximating the title H-bond system spacer indicating no ring current in the pseudoring whereas Li<sup>+</sup>-chelated system exhibits a slightly aromatic property (NICS &lt; 0). <p>

Title:Crystal and Molecular Structure of N-(3,5-Dichloro-2-hydroxybenzylidene)- and N-(2-Hydroxy-3-methoxybenzylidene)aniline Oxides. Delocalisation in the Spacer of the Intramolecular H-Bond and the Problem of Quasi-Aromaticity
Creators:
Krygowski, Tadeusz M.
Stępień, Beata
Anulewicz-Ostrowska, Romana
Cyrański, Michał K.
Grabowski, Sławomir J.
Rozwadowski, Zbigniew
Dziembowska, Teresa
Uncontrolled Keywords:<i>Ab initio</i> calculations, X-Ray diffraction, Aromaticity, Chelates, H-bonds, Crystal structure, Schiff bases
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:64
Number:11
Page Range:pp. 1797-1806
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19991797UNSPECIFIED
ID Code:1597
Item Type:Article
Deposited On:06 Feb 2009 17:10
Last Modified:06 Feb 2009 16:11

Citation

Krygowski, Tadeusz M.; Stępień, Beata; Anulewicz-Ostrowska, Romana; Cyrański, Michał K.; Grabowski, Sławomir J.; Rozwadowski, Zbigniew; Dziembowska, Teresa (1999) Crystal and Molecular Structure of N-(3,5-Dichloro-2-hydroxybenzylidene)- and N-(2-Hydroxy-3-methoxybenzylidene)aniline Oxides. Delocalisation in the Spacer of the Intramolecular H-Bond and the Problem of Quasi-Aromaticity. Collection of Czechoslovak Chemical Communications, 64 (11). pp. 1797-1806. ISSN 0010-0765

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