organic compounds
The structures of two ammonium salts of 3-carboxy-4-hydroxybenzenesulfonic acid (5-sulfosalicylic acid, 5-SSA) have been determined at 200 K. In the 1:1 hydrated salt, ammonium 3-carboxy-4-hydroxybenzenesulfonate monohydrate, NH4+·C7H5O6S−·H2O, (I), the 5-SSA− monoanions give two types of head-to-tail laterally linked cyclic hydrogen-bonding associations, both with graph-set R44(20). The first involves both carboxylic acid O—HOwater and water O—HOsulfonate hydrogen bonds at one end, and ammonium N—HOsulfonate and N—HOcarboxy hydrogen bonds at the other. The second association is centrosymmetric, with end linkages through water O—HOsulfonate hydrogen bonds. These conjoined units form stacks down c and are extended into a three-dimensional framework structure through N—HO and water O—HO hydrogen bonds to sulfonate O-atom acceptors. Anhydrous triammonium 3-carboxy-4-hydroxybenzenesulfonate 3-carboxylato-4-hydroxybenzenesulfonate, 3NH4+·C7H4O6S2−·C7H5O6S−, (II), is unusual, having both dianionic 5-SSA2− and monoanionic 5-SSA− species. These are linked by a carboxylic acid O—HO hydrogen bond and, together with the three ammonium cations (two on general sites and the third comprising two independent half-cations lying on crystallographic twofold rotation axes), give a pseudo-centrosymmetric asymmetric unit. Cation–anion hydrogen bonding within this layered unit involves a cyclic R33(8) association which, together with extensive peripheral N—HO hydrogen bonding involving both sulfonate and carboxy/carboxylate acceptors, gives a three-dimensional framework structure. This work further demonstrates the utility of the 5-SSA− monoanion for the generation of stable hydrogen-bonded crystalline materials, and provides the structure of a dianionic 5-SSA2− species of which there are only a few examples in the crystallographic literature.
organic compounds
The structures of the anhydrous proton-transfer compounds of the sulfa drug sulfamethazine with 5-nitrosalicylic acid and picric acid, namely 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2-hydroxy-5-nitrobenzoate, C12H15N4O2S+·C7H4NO4−, (I), and 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2,4,6-trinitrophenolate, C12H15N4O2S+·C6H2N3O7−, (II), respectively, have been determined. In the asymmetric unit of (I), there are two independent but conformationally similar cation–anion heterodimer pairs which are formed through duplex intermolecular N+—HOcarboxylate and N—HOcarboxylate hydrogen-bond pairs, giving a cyclic motif [graph set R22(8)]. These heterodimers form separate and different non-associated substructures through aniline N—HO hydrogen bonds, one one-dimensional, involving carboxylate O-atom acceptors, the other two-dimensional, involving both carboxylate and hydroxy O-atom acceptors. The overall two-dimensional structure is stabilized by π–π interactions between the pyrimidinium ring and the 5-nitrosalicylate ring in both heterodimers [minimum ring-centroid separation = 3.4580 (8) Å]. For picrate (II), the cation–anion interaction involves a slightly asymmetric chelating N—HO R21(6) hydrogen-bonding association with the phenolate O atom, together with peripheral conjoint R12(6) interactions between the same N—H groups and O atoms of the ortho-related nitro groups. An inter-unit amine N—HOsulfone hydrogen bond gives one-dimensional chains which extend along a and inter-associate through π–π interactions between the pyrimidinium rings [centroid–centroid separation = 3.4752 (9) Å]. The two structures reported here now bring to a total of four the crystallographically characterized examples of proton-transfer salts of sulfamethazine with strong organic acids.
organic compounds
The structures of the 1:1 hydrated proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with oxalic acid and adipic acid are three-dimensional hydrogen-bonded constructs involving several different types of enlarged water-bridged cyclic associations.