The crystal structure of the title compound, (C₄H₁₂N₂)[Co(H₂O)₆](SO₄)₂, is built of [Co(H₂O)₆]²⁺ cations, diproton­ated piperazinium cations (each of the two crystallographic­ally independent piperazinium cations occupies a special position on an inversion centre) and sulfate anions. The Co atom is coordinated by six water mol­ecules in a slightly distorted octahedral geometry. The cations are linked to anions by N—HO and O—HO hydrogen bonds, forming an extensive three-dimensional hydrogen-bond network in the crystal structure.

The crystal structure of the title compound, [Zn(H₂O)₆][C₁₀H₄O₈], features a three-dimensional hydrogen-bonded network linking octahedral hexa­aqua­zinc(II) dications, occupying special positions on twofold axes, and di­hydrogen-1,2,4,5-benzene­tetra­carboxyl­ate dianions located on crystallographic inversion centres. There are also intramolecular hydrogen bonds between adjacent carboxyl groups in the dianions.

The title compound, C₁₆H₁₁ClN₃O₂⁺·I₃^-, consists of a bipyridinium cation and a triiodide anion. The two pyridine rings of the cation are not coplanar, with a dihedral angle of 28.83 (4)°. The benzene ring is also twisted out of the mean plane of the adjoining pyridine ring by 64.27 (5)°. The I₃^- anions are slightly bent and asymmetric, with an I-I-I angle of 178.24 (5)° and I-I bond distances of 2.937 (2) and 2.957 (2) Å. The packing shows a columnar arrangement, with parallel stacks of bipyridinium and I₃^- ions along the b axis.

The title compound, poly­[ammonium zinc-μ-benzene-1,2,4,5-tetra­carboxyl­ate octahydrate] {(NH₄)₂Zn[C₆H₂(COO)₄]·8H₂O}_n, forms a three-dimensional network containing one-dimensional nanoporous rhomboid channels along the c axis, accommodating guest water mol­ecules and the ammonium cations. The dimensions of the large channel are 11.555 (2) × 15.00 (1) Å. The network consists of [Zn(C₆H₂(COO)₄]²⁻ anions containing tetrahedral Zn atoms bonded to four carboxyl­ate groups. The ZnO distances range from 1.974 (2) to 1.978 (2) Å. The ammonium cations and the water mol­ecules are associated in a centrosymmetric network by intermolecular hydrogen bonds. The hydrogen bonding is essential to stabilize the crystal structure.

A new cadmium coordination polymer, [Cd(C₅H₂N₂O₄)(H₂O)₂]_n, possesses a one-dimensional zigzag chain structure built from Cd^II centers bridged sequentially by pairs of O and N atoms of the 5-carboxyimidazole-4-carboxylate ligand. The Cd^II center is in a distorted octahedral geometry, being coordinated by two O atoms from two coordinated water mol­ecules [Cd—O = 2.322 (7) and 2.364 (7) Å], and by two N atoms [Cd—N = 2.222 (6) and 2.232 (6) Å] and two carboxyl O atoms [Cd—O = 2.383 (6) and 2.414 (6) Å] from two 5-carboxyimidazole-4-carboxylate ligands.

In the title compound, [Cu(C₂₂H₂₄N₆O₂)], the copper(II) ion is coordinated by five N atoms from the chelating macrocyclic ligand, forming a distorted square-pyramidal geometry. The complexes associate as dimers, disposed about a centre of symmetry, linked through weak intermolecular CuO coordination and N—HO hydrogen bonding.

The title compound, [Co(C₂₂H₂₆N₆O₂)]ClO₄, was prepared from di­formyl­oxanilide, cobalt(II) perchlorate and 1,3-propane­di­amine. The crystal structure contains a complex cobalt(III) cation and a perchlorate anion. Cobalt is coordinated by six N atoms from the anilide ligand in chelating mode, forming a distorted octahedral geometry. Inter-cation hydrogen bonds are present in the crystal structure.

The title compound, guanidinium pyromellitate, 2[C(NH₂)₃]⁺·(C₁₀H₄O₈)²⁻ or 2 CH₆N₃⁺·C₁₀H₄O₈²⁻, comprises a 1,2,4,5-benzene­tetra­carboxyl­ate anion and two guanidinium cations. The carboxyl­ate anions lie on centers of inversion and involve intramolecular O—HO hydrogen bonds. The cations and anions are linked by strong three-dimensional N—HO hydrogen bonds and π–π-stacking interactions into a three-dimensional framework containing a one-dimensional channel along the diagonal of the ca plane. The N—HO hydrogen-bond distances range from 2.899 (6) to 3.068 (5) Å.

The crystal of the title compound, imidazolium tri­hydrogen-1,2,4,5-benzene­tetra­carboxyl­ate, C₃H₅N₂⁺·C₁₀H₅O₈⁻, is built of imidazolium cations and tri­hydrogen-1,2,4,5-benzene­tetra­carboxyl­ate anions. The anions use two of their `active' H atoms to generate hydrogen bonds linking to the neighbouring anions, thus creating a two-dimensional hydrogen-bonding network parallel to the bc plane of the crystal. The third oxy­gen-bound H atom of the anion is involved in an intramolecular hydrogen bond, which closes the six-membered pseudo-ring. The imidazolium cations are linked to the anionic hydrogen-bonded network through N—HO bonds which target two of the O atoms of the carboxyl groups of the anions as acceptors. The mean plane of the imidazolium cation is almost orthogonal to the mean plane of the benzene ring of benzene­tetra­carboxyl­ate, with a dihedral angle of 89.7 (1)°.

The title compound, [Ni(en)(TETA)][GeF₆] or [Ni(C₂H₈N₂)(C₆H₁₈N₄)][GeF₆], was synthesized under mild solvothermal conditions in the presence of triethyl­enetetr­amine (TETA) as a base. It is a new salt composed of [GeF₆]²⁻ anions and [Ni(en)(TETA)]²⁺ cations. The ions are linked together by hydrogen bonding between F atoms and N—H groups. The complex cation and anion lie on twofold axes of the space group Pccn.

The nickel(II) ion in the title complex, [Ni(C₁₉H₁₆N₄O₂)]·H₂O, is coordinated by four N atoms from the 5,6:14,15-dibenzo-1,4,8,12-tetraaza­cyclo­pentadeca-7,13-diene-2,3-dione(2−) ligand in chelating mode, forming a distorted square-planar geometry. The complex molecules are associated into a two-dimensional superamolecular architecture through weak intermolecular O—HO and C—HO hydrogen bonding.

The title compound, [Ni(dien)₂][GeF₆] (dien is diethyl­enetri­amine, C₄H₁₃N₃), synthesized under mild solvothermal conditions, is a novel zero-dimensional material in which [GeF₆]²⁻ building anions are connected to [Ni(dien)₂]²⁺ cations via hydrogen bonds between F atoms and N—H groups. Both metal atoms are located on special positions of site symmetry 2/m. Furthermore, one F and one N atom (including the attached H atom) are located on a mirror plane.

The title compound, {(C₁₂H₁₃N₂)₂[Mo₅O₁₆]}_n, was synthesized under hydro­thermal conditions. The structure contains a two-dimensional layer, constructed from [(Mo₄O₁₄)_n]⁴ⁿ⁻ chains linked through MoO₆ octahedra, which lie across twofold axes. The [(Mo₄O₁₄)_n]⁴ⁿ⁻ chain consists of [Mo₄O₁₄]⁴⁻ clusters connected to one another by sharing their MoO₅ square-pyramidal and MoO₆ octahedral vertices in an anti disposition. The layers are linked by the cation, to which they are connected via N—HO hydrogen bonds.

The structure of the title compound, [Zn₄(C₂O₄)(PO₄)₂(H₂O)₂]_n, which was synthesized under hydro­thermal conditions, consists of zinc phosphate layers joined by bridging oxalate ligands to generate a three-dimensional framework. An extended zinc phosphate layer lies parallel to the ab plane and within this layer there are helical chains, composed of ZnO₆ octahedra and ZnO₅ square pyramids, that run parallel to the b axis and coincide with the 2₁ screw element. The oxalate groups sit on crystallographic inversion centers.