Isostructural behavior in ammonium/potassium salt forms of sulfonated azo dyes

What is it about?

The article discusses the structures of five ammonium salt forms of monosulfonated azo dyes, which are derivatives of 4-(2-phenyldiazen-1-yl)benzenesulfonate. All forms have simple layered structures with alternating hydrophobic and hydrophilic layers. Three of the five ammonium salts have isostructural equivalents, two of which are potassium salt forms and one is a rubidium salt form. The article also compares the packing of these structures with literature examples and provides information on the bond lengths and hydrogen bonding in these compounds.

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Why is it important?

This research is important because it provides insights into the structures and packing of ammonium salt forms of monosulfonated azo dyes, which are derivatives of 4-(2-phenyldiazen-1-yl)benzenesulfonate. Understanding the structures of these compounds can help in the selection of the best form of an active organic material for effectiveness and commercialization. The study also contributes to the understanding of the isostructural behavior of ammonium cations with M+ ions, which is important in the field of sulfonated azo colorants. The insights gained from this research can be applied to other areas where salt selection plays a crucial role in material properties. The research provides a basis for understanding the structure of sulfonated azo pigments by studying the structures of similarly functionalized, but easier to manipulate, dyes. This can help in cross-checking any structure-to-property relationships identified against those pigment structures that are known. Key Takeaways: 1. The structures of five ammonium salt forms of monosulfonated azo dyes are presented, with the general formula [NH4]+[Cl], [OH], [CH3COO], [CF3SO3], and [C2O4]. 2. All form simple layered structures with alternating hydrophobic (organic) and hydrophilic (cation, solvent and polar groups) layers. 3. Three out of the five ammonium salts have isostructural equivalents, with two cases having equivalent potassium salt forms and one case having an equivalent rubidium salt form. 4. The isostructurality of ion packing and unit-cell symmetry and dimensions tolerates cases where the ammonium ions form somewhat different interaction types with coformer species than do the potassium or rubidium ions. 5. No sodium salt forms are found to be isostructural with any ammonium equivalent. However, similarities in the anion packing within a single hydrophobic layer are found for a group that consists of the ammonium and rubidium salt forms of one azo anion species and the sodium and silver salt forms of a different azo species.