The 1:1 proton-transfer compounds of 4-(phenyldiazenyl)aniline (aniline yellow) with 3-nitrophthalic, 4-nitrophthalic and 5-nitroisophthalic acids

Abstract

The structures of the anhydrous 1:1 proton-transfer compounds of the dye precursor aniline yellow [4-(phenyl-diazenyl)-aniline], namely isomeric 4-(phenyl-diazenyl)-anilin-ium 2-carb-oxy-6-nitro-benzoate, C12H12N3 +·C8H4NO6 -, (I), and 4-(phenyl-diazenyl)-anilinium 2-carb-oxy-4-nitro-benzoate, C12H12N3 +·C8H4NO6 -, (II), and 4-(phenyl-diazenyl)-anilinium 3-carb-oxy-5-nitro-benzoate monohydrate, C12H12N3 +·C8H4-NO6 -·H2O, (III), have been determined at 130 K. In (I) the cation has longitudinal rotational disorder. All three compounds have substructures comprising backbones formed through strong head-to-tail carboxyl-carboxyl-ate hydrogen-bond inter-actions [graph set C(7) in (I) and (II), and..