Eight salt forms of sulfadiazine

Buist, Amanda and Dennany, Lynn and Kennedy, Alan and Manzie, Craig and McPhie, Katherine and Walker, Brandon (2014) Eight salt forms of sulfadiazine. Acta Crystallographica Section C: Structural Chemistry, 70 (9). pp. 900-907. ISSN 2053-2296

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    Abstract

    Proton transfer to the sulfa drug sulfadiazine [systematic name: 4-amino-N-(pyrimidin-2-yl)benzenesulfonamide] gave eight salt forms. These are the monohydrate and methanol hemisolvate forms of the chloride (2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium chloride monohydrate, C10H11N4O2S+·Cl−·H2O, (I), and 2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium chloride methanol hemisolvate, C10H11N4O2S+·Cl−·0.5CH3OH, (II)); a bromide monohydrate (2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium bromide monohydrate, C10H11N4O2S+·Br−·H2O, (III)), which has a disordered water channel; a species containing the unusual tetraiodide dianion [bis(2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium) tetraiodide, 2C10H11N4O2S+·I42−, (IV)], where the [I4]2− ion is located at a crystallographic inversion centre; a tetrafluoroborate monohydrate (2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium tetrafluoroborate monohydrate, C10H11N4O2S+·BF4−·H2O, (V)); a nitrate (2-{[(4-azaniumylphenyl)sulfonyl]azanidyl}pyrimidin-1-ium nitrate, C10H11N4O2S+·NO3−, (VI)); an ethanesulfonate {4-[(pyrimidin-2-yl)sulfamoyl]anilinium ethanesulfonate, C10H11N4O2S+·C2H5SO3−, (VII)}; and a dihydrate of the 4-hydroxybenzenesulfonate {4-[(pyrimidin-2-yl)sulfamoyl]anilinium 4-hydroxybenzenesulfonate dihydrate, C10H11N4O2S+·HOC6H4SO3−·2H2O, (VIII)}. All these structures feature alternate layers of cations and of anions where any solvent is associated with the anion layers. The two sulfonate salts are protonated at the aniline N atom and the amide N atom of sulfadiazine, a tautomeric form of the sulfadiazine cation that has not been crystallographically described before. All the other salt forms are instead protonated at the aniline group and on one N atom of the pyrimidine ring. Whilst all eight species are based upon hydrogen-bonded centrosymetric dimers with graph set R22(8), the two sulfonate structures also differ in that these dimers do not link into one-dimensional chains of cations through NH3-to-SO2 hydrogen-bonding interactions, whilst the other six species do. The chloride methanol hemisolvate and the tetraiodide are isostructural and a packing analysis of the cation positions shows that the chloride monohydrate structure is also closely related to these.