4-Amino-pyridinium 4-amino-benzene-sulfonate 4-ammonio-benzene-sulfonate monohydrate

The ephemeral dihydrate of sulfanilic acid

Evaporation of an aqueous solution of sulfanilic acid (systematic name: 4-aminobenzene-1-sulfonic acid) at 273 K affords a crystalline dihydrate, C₆H₇NO₃S·2H₂O. The organic molecule exists as a zwitterion; two zwitterions are aligned in an antiparallel fashion about a crystallographic centre of inversion. They interact directly via two N-H...O hydrogen bonds between the ammonium group of one zwitterion and the sulfonate group of its symmetry-related counterpart, and their aromatic rings are π-stacked, with an interplanar distance of 3.533 (3) Å. One of the cocrystallized water molecules connects the resulting pairs into layers and the second crosslinks the layers into a three-dimensional network. All H atoms connected to N or O atoms find acceptors in suitable geometries. In the resulting crystal, polar and hydrogen-bond-dominated slabs alternate with stacks of organic arene rings. Although the new dihydrate shows efficient space filling, with a packing coefficient of 75.7%, it is unstable and undergoes fast desolvation at room temperature. In this process, the orthorhombic ansolvate forms as a pure phase.

Crystal structure of di-ethyl-ammonium aniline-4-sulfonate anilinium-4-sulfonate

The title compound, C4H12N+·C6H6NO3S-·C6H7NO3S, consists of an ion pair and a zwitterionic neutral mol-ecule. The cation adopts an extended conformation [C-C-N-C torsion angles = 177.1 (3) and -178.4 (3)°]. In the crystal, the components are linked by N-H⋯O and N-H⋯N hydrogen bonds, generating a three-dimensional network, which is consolidated by weak C-H⋯O inter-actions.

2-Amino-6-methyl-pyridinium trans-di-aqua-dioxalatochromate(III) monohydrate

In the title compound, (C6H9N2)[Cr(C2O4)2(H2O)2]·H2O, the Cr(III) atom adopts a slightly distorted octa-hedral coordination environment defined by two chelating oxalate ligands in the equatorial plane and two water mol-ecules in axial positions. A three-dimensional network is generated by inter-molecular N-H⋯O and O-H⋯O hydrogen-bonding interactions involving the cation, the complex anion and the lattice water molecule.

4-Amino-pyridinium trans-diaqua-dioxalatochromate(III) monohydrate

In the non-centrosymmetric structure of the title compound, (C₅H₇N₂)[Cr(C₂O₄)₂(H₂O)₂]·H₂O, the Cr^III ion has a slightly distorted octa­hedral coordination environment defined by two chelating oxalato ligands in equatorial positions and two water mol­ecules in axial positions. An extensive three-dimensional network of hydrogen bonds involving all the water mol­ecules, the 4-amino­pyridinium cation and some of the oxalate O atoms contributes to the stabilization of the structure. π–π inter­actions between adjacent pyridine rings provide additional stability of the crystal packing, with a closest distance between pyridine mean planes of 3.613 (1) Å.