Poly[diammonium [(μ₄-butane-1,2,3,4-tetra­carboxyl­ato)zincate] tetra­hydrate]

In the title compound, {(NH₄)₂[Zn(C₈H₆O₈)]·4H₂O}_n, the asymmetric unit contains one ammonium cation, half of a butane-1,2,3,4-tetra­carboxyl­ate anion, one Zn²⁺ cation and two water mol­ecules. The butane-1,2,3,4-tetra­carboxyl­ate ligand is located about an inversion centre at the mid-point of the central C—C bond. The Zn²⁺ cation is situated on a twofold rotation axis and is surrounded by four O atoms from four symmetry-related butane-1,2,3,4-tetra­carboxyl­ate anions in a distorted tetra­hedral environment. In turn, each anion coordinates to four Zn²⁺ cations. The bridging mode of the anions leads to a three-dimensional framework structure with channels extending along [110] and [010] in which the ammonium cations and the water mol­ecules are located. N—H...O and O—H...O hydrogen bonding between the cations and water mol­ecules and the uncoordinating O atoms of the carboxyl­ate groups consolidates the crystal packing.

3-(Phenyl­carbamoyl)acrylic acid

In the title compound, C₁₀H₉NO₃, the dihedral angle between the phenyl ring and the amide group is 10.8 (2)°. The C=O and O—H bonds of the carboxyl group adopt an anti orientation and an intra­molecular O—H...O hydrogen bond closes an S(7) ring. In the crystal, N—H...O hydrogen bonds link the mol­ecules into C(7) chains propagating in [101]. The packing is consolidated by C—H...O inter­actions, generating sheets aligned at an angle of ca 60° with the bc plane.

3,3′-(Piperazine-1,4-diium-1,4-di­yl)di­propionate dihydrate

During the recrystallization of 3-[4-(2-carb­oxy­eth­yl)piperazin-1-yl]propionic acid, the carb­oxy­lic acid H atoms were transferred to the piperazine N atoms, forming the title compound, C₁₀H₁₈N₂O₄·2H₂O, in which the zwitterion lies about an inversion center. In the crystal, bifurcated N—H...(O,O) hydrogen bonds connect the zwitterions into a two-dimensional framework parallel to (-102) forming R₄⁴(30) rings. O—H...O hydrogen bonds involving the solvent water mol­ecules connect the two-dimensional framework into a three-dimensional network. In addition, weak C—H...O hydrogen bonds are observed.

3,5,3′,5′-Tetra­methyl-4,4′-bi(1H-pyrazol­yl) hemihydrate

In the title compound, C₁₀H₁₄N₄·0.5H₂O, the amino H atom of one of the two pyrazole rings is disordered over its two N atoms in a 1:1 ratio. The pyrazole rings are aligned at 60.1 (1)°. In the crystal, two bipyrazolyl mol­ecules are linked by an N—H...N hydrogen bond, generating a dimer; the dimer is connected to the water mol­ecule, which lies on a twofold rotation axis, resulting in the formation of a chain that makes an angle of ca 45.3 (1)° with the ab plane. The chains are cross-linked by N—H...O and O—H...N inter­actions, forming a three-dimensional network.

3,5-Dimethyl­pyrazolium 3,5-dinitro­salicylate

In the title mol­ecular salt, C₅H₉N₂⁺·C₇H₃N₂O₇⁻, the roughly planar anion (r.m.s. deviation = 0.120 Å) has been deprotonated at the phenol group. An intra­molecular O—H...O hydrogen bond in the anion generates an S(6) ring. In the crystal, the components are linked by cation-to-anion N—H...O and N—H...(O,O) hydrogen bonds, generating [010] double chains. Weak C—H...O inter­actions consolidate the packing.