Cd₄As₂Br₃

Single crystals of Cd₄As₂Br₃ (tetra­cadmium biarsenide tri­bromide) were grown by a chemical transport reaction. The structure is isotypic with the members of the cadmium and mercury pnictidohalides family with general formula M₄A₂X₃ (M = Cd, Hg; A = P, As, Sb; X = Cl, Br, I) and contains two independent As atoms on special positions with site symmetry -3 and two independent Cd atoms, of which one is on a special position with site symmetry -3. The Cd₄As₂Br₃ structure consists of AsCd₄ tetra­hedra sharing vertices with isolated As₂Cd₆ octa­hedra that contain As–As dumbbells in the centre of the octahedron. The Br atoms are located in the voids of this three-dimensional arrangement and bridge the different polyhedra through Cd...Br contacts.

Propane-1,2-di­ammonium chromate(VI)

In the title mol­ecular salt, (C₃H₁₂N₂)[CrO₄], each chromate anion accepts six N—H...O and C—H...O hydrogen bonds from nearby propane-1,2-di­ammonium cations. Three of the four O atoms of the chromate anion accept these bonds; the remaining Cr—O bond length is notably shorter than the others. In the crystal, the anions and cations stack in layers lying parallel to (100): the hydrogen-bonding pattern leads to a three-dimensional network.

Bis(1-methyl­piperazine-1,4-diium) di-μ-bromido-bis­[tetra­bromido­bismuthate(III)] dihydrate

In the title hydrated salt, (C₅H₁₄N₂)₂[Bi₂Br₁₀]·2H₂O, the com­plete [Bi₂Br₁₀]⁴⁻ biocta­hedron is generated by crystallographic inversion symmetry. The diprotonated piperazine ring adopts a chair conformation, with the methyl group occupying an equatorial position. In the crystal, the tetra­anions and water mol­ecules are linked by O—H...Br and O—H...(Br,Br) hydrogen bonds to generate [100] chains. The chains are crosslinked by N—H...Br, N—H...O and C—H...Br hydrogen bonds originating from the piperazinediium dications, thereby forming a three-dimensional network.

Bis(4-amino­pyridinium) dichromate(VI)

The asymmetric unit of the title salt, (C₅H₇N₂)₂[Cr₂O₇], contains four independent cations and two independent dichromate anions. The crystal structure consists of discrete dichromate anions with an eclipsed conformation stacked in layers parallel to (010) at y = 1/4 and y = 3/4. These layers are linked via 4-amino­pyridinium cations by N—H...O and weak C—H...O hydrogen bonds, forming a three-dimensional supra­molecular network. In addition, π–π inter­actions are present in this structure; the shortest distance separating mean planes through 4-amino­pyridinium cations is 3.679 (6) Å.

m-Xylylenediaminium dinitrate

The asymmetric unit of the title salt, C₈H₁₄N₂²⁺·2NO₃⁻, contains two independent dications and four independent nitrate anions. The crystal structure consists of discrete nitrate ions, three of which stack in layers parallel to (001) at z = 0 and 0.5. These layers are connected via m-xylylenediaminium dications. The fourth anion is sandwiched by the two independent organic cations in the asymmetric unit. In the crystal, the ions are connected by a large number of bifurcated and non-bifurcated N—H...O(O) hydrogen bonds, forming sheets parallel to (100). These sheets are connected by C—H...O hydrogen bonds, forming a three-dimensional network.

Dopaminium nitrate

The asymmetric unit of the title salt [systematic name: 2-(3,4-di­hydroxy­phen­yl)ethanaminium nitrate], C₈H₁₂NO₂⁺·NO₃⁻, contains two independent cations and two independent nitrate anions. The crystal structure consists of discrete nitrate ions stacked in layers parallel to (010). These layers are linked via the dopaminium cations by O—H...O, N—H...O and weak C—H...O hydrogen bonds, forming a three-dimensional supra­molecular network.

trans-2,5-Di­methyl­piperazine-1,4-diium dinitrate

In the structure of the title salt, C₆H₁₆N₂²⁺·2NO₃⁻, the cations are connected to the anions through bifurcated N—H...(O,O) and weak C—H...O hydrogen bonds, generating corrugated layers parallel to the (100) plane. The organic cation is centrosymmetric and the diprotonated piperazine ring adopts a chair conformation, with the methyl groups occupying equatorial positions.