Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 9 (September 2008)

organic compounds

dn3091 scheme

Acta Cryst. (2008). C64, o474-o477 [ doi:10.1107/S0108270108023421 ]

Two azo pigments based on -naphthol

M. U. Schmidt, J. Brüning, D. Wirth and M. Bolte

Abstract: There has been much discussion in the literature of the azo-hydrazone tautomerism of pigments. All commercial azo pigments with [beta] -naphthol as the coupling compound adopt the hydrazone tautomeric form (Ph-NH-N=C) in the solid state. In contrast, the red pigments 1-[4-(dimethylamino)phenyldiazenyl]-2-naphthol, C₁₈H₁₇N₃O, (1a), and 1-[4-(diethylamino)phenyldiazenyl]-2-naphthol, C₂₀H₂₁N₃O, (1b), have been reported to be azo tautomers or a mixture of azo and hydrazone tautomers in the solid state. To prove these observations, both compounds were synthesized, recrystallized and their crystal structures redetermined by single-crystal structure analysis. Difference electron-density maps show that the H atoms of the hydroxyl groups are indeed bonded to the O atoms. Nevertheless, a small amount of the hydrazone form seems to be present. Hence, the compounds are close to being `real' azo compounds. Compound (1a) crystallizes with a herring-bone structure and compound (1b) forms a rare double herring-bone structure.

Formula: C₁₈H₁₇N₃O and C₂₀H₂₁N₃O


	Structure factor file (CIF format) (203.5 kbytes) [ doi:10.1107/S0108270108023421/dn30911asup2.hkl ] Contains datablock 1a

	Structure factor file (CIF format) (154.2 kbytes) [ doi:10.1107/S0108270108023421/dn30911bsup3.hkl ] Contains datablock 1b

Notes:

To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

Search: From to Advanced search