Salt forms of sulfadiazine with alkali metal and organic cations

The structures of four salt forms of sulfadiazine (SDH) with alkali metal cations are presented. Three contain the deprotonated SD anion (C₁₀H₉N₄O₂S). These are the discrete complex diaqua{4-[(pyrimidin-2-ylazanidyl-κN¹)sulfonyl-κO]aniline}lithium(I), [Li(SD)(H₂O)₂], (I), and the coordination polymers poly[{μ₃-4-[(pyrimidin-2-ylazanidyl)sulfonyl]aniline}sodium(I)], [Na(SD)]_n, (II), and poly[diaqua{μ₃-4-[(pyrimidin-2-ylazanidyl)sulfonyl]aniline}potassium(I)], [K(SD)(H₂O)₂]_n, (III). Na complex (II) is a three-dimensional coordination polymer, whilst K complex (III) has two crystallographically independent [K(SD)(H₂O)₂] units per asymmetric unit (Z' = 2) and gives a two-dimensional coordination polymer whose layers propagate parallel to the crystallographic ab plane. The different bonding modes of the SD anion in these three complexes is discussed. Structure (IV) contains protonated SDH₂ cations {4-[(pyrimidin-2-yl)sulfamoyl]anilinium, C₁₀H₁₁N₄O₂S} and the Orange G dianion [OG, 7-oxo-8-(phenylhydrazinylidene)naphthalene-1,3-disulfonate, C₁₆H₁₀N₂O₇S₂], namely, 4-[(pyrimidin-2-yl)sulfamoyl]anilinium tetraaqua[7-oxo-8-(phenylhydrazinylidene)naphthalene-1,3-disulfonato]sodium(I) sesquihydrate, (SDH₂)[Na(OG)(H₂O)₄]·1.5H₂O. The [Na(OG)(H₂O)₄]₂ dimers have antiparallel naphthyl ring structures joined through two Na centres that bond to the hydrazone anions through the O atoms of the ketone and sulfonate substituents. The structures of the salts formed on reaction of SDH with 2-aminopyridine and ethanolamine are also presented as 2-aminopyridinium 4-[(pyrimidin-2-ylazanidyl)sulfonyl]aniline, [C₅H₇N₂][SD], (V), and ethanolaminium 4-[(pyrimidin-2-ylazanidyl)sulfonyl]aniline monohydrate, [HOCH₂CH₂NH₃][SD]·H₂O, (VI), respectively. Structure (V) features a heterodimeric R₂²(8) hydrogen-bond motif between the cation and the anion, whilst structure (VI) has a tetrameric core of two cations linked by a central R₂²(10) hydrogen-bonded motif which supports two anions linked to this core by R₃³(8) motifs.