Carboxylate-phenolate tautomerism in 5-[(nitrophenyl)diazenyl]salicylate anions

Yatsenko, A.V.; Paseshnichenko, K.A.

Авторы: Yatsenko Alexandr V., Paseshnichenko Ksenia A.
Журнал: Acta Crystallographica Section C: Crystal Structure Communications
Том: 72
Номер: 4
Год издания: 2016
Издательство: Blackwell Publishing Inc.
Местоположение издательства: United Kingdom
Первая страница: 274
Последняя страница: 279
DOI: 10.1107/S2053229616003193
Аннотация: Aryldiazenyl derivatives of salicylic acid and their salts are used as dyes. In these structures, the carboxylate groups are engaged in short contacts with the cations and in hydrogen bonds with water molecules, if present. If both O atoms of the carboxylate group take part in such interactions, the negative charge is delocalized over the two atoms. In the absence of hydrogen bonds and contacts with cations, the negative charge is localized on one of the O atoms. In the crystal structures of tetramethylammonium 2-hydroxy-5-[(E)-(4-nitrophenyl)diazenyl] benzoate and tetramethylammonium 2-hydroxy-5-[(E)-(2-nitrophenyl)diazenyl] benzoate, both C4H12N+center dot C13H8N3O5-, all the interactions between the cations and anions are weak, and their effect on the geometry of the anions is negligible. Under these conditions, the 2-nitro-substituted anion is an almost pure phenol-carboxylate tautomer, whereas in the 4-nitro-substituted anion, the phenolic H atom is shifted towards the carboxylate group, and thus the structure of this anion is intermediate between the phenol-carboxylate and phenolate-carboxylic acid tautomeric forms. The probable formation of such an intermediate form is supported by quantum chemical calculations. Being the characteristic feature of this form, a short distance between the phenolic and carboxylate O atoms is observed in the 4-nitro-substituted anion, as well as in the structures of some 3,5-dinitrosalicylates reported in the literature.
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Carboxylate-phenolate tautomerism in 5-[(nitrophenyl)diazenyl]salicylate anionsстатья

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