Acta Crystallographica Section C

Volume 65, Part 10 (October 2009)

organic compounds

 

Proton transfer versus nontransfer in compounds of the diazo-dye precursor 4-(phenyldiazenyl)aniline (aniline yellow) with strong organic acids: the 5-sulfosalicylate and the dichroic benzenesulfonate salts, and the 1:2 adduct with 3,5-dinitrobenzoic acid

G. Smith, U. D. Wermuth, D. J. Young and J. M. White

Abstract: The structures of two 1:1 proton-transfer red-black dye compounds formed by reaction of aniline yellow [4-(phenyldiazenyl)aniline] with 5-sulfosalicylic acid and benzenesulfonic acid, and a 1:2 nontransfer adduct compound with 3,5-dinitrobenzoic acid have been determined at either 130 or 200 K. The compounds are 2-(4-aminophenyl)-1-phenylhydrazin-1-ium 3-carboxy-4-hydroxybenzenesulfonate methanol solvate, C₁₂H₁₂N₃⁺·C₇H₅O₆S^-·CH₃OH, (I), 2-(4-aminophenyl)-1-phenylhydrazin-1-ium 4-(phenyldiazenyl)anilinium bis(benzenesulfonate), 2C₁₂H₁₂N₃⁺·2C₆H₅O₃S^-, (II), and 4-(phenyldiazenyl)aniline-3,5-dinitrobenzoic acid (1/2), C₁₂H₁₁N₃·2C₇H₄N₂O₆, (III). In compound (I), the diazenyl rather than the aniline group of aniline yellow is protonated, and this group subsequently takes part in a primary hydrogen-bonding interaction with a sulfonate O-atom acceptor, producing overall a three-dimensional framework structure. A feature of the hydrogen bonding in (I) is a peripheral edge-on cation-anion association also involving aromatic C-HO hydrogen bonds, giving a conjoint R¹₂(6)R¹₂(7)R²₁(4) motif. In the dichroic crystals of (II), one of the two aniline yellow species in the asymmetric unit is diazenyl-group protonated, while in the other the aniline group is protonated. Both of these groups form hydrogen bonds with sulfonate O-atom acceptors and these, together with other associations, give a one-dimensional chain structure. In compound (III), rather than proton transfer, there is preferential formation of a classic R²₂(8) cyclic head-to-head hydrogen-bonded carboxylic acid homodimer between the two 3,5-dinitrobenzoic acid molecules, which, in association with the aniline yellow molecule that is disordered across a crystallographic inversion centre, results in an overall two-dimensional ribbon structure. This work has shown the correlation between structure and observed colour in crystalline aniline yellow compounds, illustrated graphically in the dichroic benzenesulfonate compound.

Formula: C₁₂H₁₂N₃⁺·C₇H₅O₆S^-·CH₃OH,C₁₂H₁₂N₃⁺·C₇H₅O₆S^-·CH₃OH and C₁₂H₁₁N₃·2C₇H₄N₂O₆

	Structure factor file (CIF format) (174.9 kbytes) [ doi:10.1107/S0108270109036622/gd3306Isup2.hkl ] Contains datablock I
	Structure factor file (CIF format) (344.6 kbytes) [ doi:10.1107/S0108270109036622/gd3306IIsup3.hkl ] Contains datablock II
	Structure factor file (CIF format) (117.4 kbytes) [ doi:10.1107/S0108270109036622/gd3306IIIsup4.hkl ] Contains datablock III

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