Tris(1,10-phenanthroline)nickel(II) squarate octa­hydrate

In the title mononuclear [Ni(phen)₃]sq·8H₂O complex [phen is 1,10-phenanthroline (C₁₂H₈N₂) and sq is squarate (C₄O₄²⁻)], the Ni^II ion has a distorted octa­hedral coordination geometry composed of six N atoms from three bidentate chelating phen ligands. An extensive three-dimensional network of O_water—H...O, O_water—H...O_water and C—H...O hydrogen-bonding inter­actions is responsible for crystal stabilization.

Poly[[[diaqua­bis(pyridine-4-carboxamide-κN¹)cobalt(II)]-μ₂-squarato-κO:O′] dihydrate]

The title polymeric compound, {[Co(C₄O₄)(C₆H₆N₂O)₂(H₂O)₂]·2H₂O}_n, has two crystallographically independent half-mol­ecules in the asymmetric unit, each Co atom residing on a center of symmetry. The two polymeric chains exhibit similar coordination geometry but display differences with regard to other structural features. Each Co^II center is octa­hedrally coordinated by two mutually trans pyridine-4-carboxamide (or isonicotinamide) ligands, two mutually trans squarate ligands and two trans aqua ligands. The crystal structure contains chains of squarate-1,3-bridged Co^II ions. These chains are held together by N—H...O and O—H...O inter­molecular hydrogen-bond inter­actions, forming an extensive three-dimensional network.

Tris(1,10-phenanthroline-κ²N,N′)iron(II) squarate octa­hydrate

In the title compound, [Fe(C₁₂H₈N₂)₃](C₄O₄)·8H₂O or [Fe(phen)₃]sq·8H₂O, where phen is 1,10-phenanthroline and sq is the squarate dianion (C₄O₄)²⁻, the Fe^II centre has a distorted octa­hedral coordination geometry comprising six N atoms from the three bidentate chelating phen ligands. An extensive three-dimensional network of O_water—H...O, O_water—H...O_water and C—H...O hydrogen-bonding inter­actions is responsible for crystal stabilization.

Bis[N-(2-hydroxy­ethyl)ethyl­enediamine-κ³N,N′,O]nickel(II) squarate monohydrate

In the title compound, [Ni(C₄H₁₂N₂O)₂](C₄O₄)·H₂O or [Ni(Hydet-en)₂](Sq)·H₂O, where Hydet-en is N-(2-hydroxy­ethyl)ethyl­enediamine and Sq is the squarate dianion, the Ni^II centre has a distorted octa­hedral coordination geometry comprising four amine N and two hydroxyl O atoms from two tridentate Hydet-en ligands. All the O atoms of the squarate dianion are involved in N—H...O and O—H...O hydrogen bonding.

A second monoclinic polymorph of 2,9-dimethyl-1,10-phenanthroline dihydrate

A second monoclinic polymorph of the title compound, neocuproine dihydrate, C₁₄H₁₂N₂·2H₂O, is reported. Unlike the first polymorph [Baggio, Baggio & Mombrú (1998). Acta Cryst. C54, 1900–1902], in which the phenanthroline ring system was constrained to lie in a crystallographic mirror plane, here there is no such imposed symmetry. Consequently, the mol­ecule shows small deviations from planarity, the outer rings being twisted slightly in opposite directions from the plane of the central ring. The hydrogen-bonding motifs remain essentially the same as in the first polymorph, involving small rings of four water mol­ecules and large rings containing four water mol­ecules and two neocuproine mol­ecules, but with no H-atom disorder for the water mol­ecules in this case. There are also aromatic π–π stacking inter­actions.