Abstract
The structures of five s-block metal salt forms of three disulfonated monoazo dyes are presented. These are poly[di-μ-aqua-diaqua[μ4-3,3'-(diazane-1,2-diyl)bis(benzenesulfonato)]disodium(I)], [Na2(C12H8N2O6S2)(H2O)4]n, (I), catena-poly[[tetraaquacalcium(II)]-μ-3,3'-(diazane-1,2-diyl)bis(benzenesulfonato)], [Ca(C12H8N2O6S2)(H2O)4]n, (II), catena-poly[[[diaquacalcium(II)]-μ-2-(4-amino-3-sulfonatophenyl)-1-(4-sulfonatophenyl)diazenium] dihydrate], {[Na(C12H10N3O6S2)(H2O)2]·2H2O}n, (III), hexaaquamagnesium bis[2-(4-amino-3-sulfonatophenyl)-1-(4-sulfonatophenyl)diazenium] octahydrate, [Mg(H2O)6](C12H10N3O6S2)2·8H2O, (IV), and poly[[{μ2-4-[2-(4-amino-2-methyl-5-methoxyphenyl)diazen-1-yl]benzene-1,3-disulfonato}di-μ-aqua-diaquabarium(II)] dihydrate], {[Ba(C14H13N3O7S2)(H2O)4]·2H2O}n, (V). Compound (III) is that obtained on crystallizing the commercial dyestuff Acid Yellow 9 [74543-21-8]. The Mg species is a solvent-separated ion-pair structure and the others are all coordination polymers with bonds from the metal atoms to sulfonate groups. Compound (I) is a three-dimensional coordination polymer, (V) is a two-dimensional coordination polymer and both (II) and (III) are one-dimensional coordination polymers. The coordination behaviour of the azo ligands and the water ligands, the dimensionality of the coordination polymers and the overall packing motifs of these five structures are contrasted to those of monosulfonate monoazo congers. It is found that (I) and (II) adopt similar structural types to those of monosulfonate species but that the other three structures do not.
Highlights
Azo compounds have a long history of use as both dyes and pigments
Previous work on the salt forms of monosulfonated dyes and pigments has shown that many structural features can be predicted from knowledge of the cation identity and the position of the sulfonate group (Kennedy et al, 2009, 2012)
Na structures are expected to feature high-dimensionality coordination polymers with both SO3 and H2O groups bridging between Na centres
Summary
Azo compounds have a long history of use as both dyes and pigments. One of the commonest subclasses is that of sulfonated azo species, where the sulfonate group is typically added to aid water solubility and/or to decrease toxicity (Hunger et al, 2003). The only colourant relevant disulfonate structures with sulfonate groups on both the ring systems, at either end of an azo bond, are the Ca lake structures of Pigment Yellow 183 and Pigment Yellow 191 determined by Schmidt and co-workers (Ivashevskaya et al, 2009; Schmidt et al, 2009). These are relatively complex materials with pyrazolone groups between the two sulfonated aryl rings. The monosodium salt of Acid Yellow 9 was purchased from Sigma–Aldrich and recrystallized from water to give fibrous red crystals of (III). IR samples were prepared as KBr discs and spectra were measured using a Nicolet Avatar 360 FT–IR
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