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The title metal–organic polymer, catena-poly[[(5,5′-dimethyl-2,2′-bipyridine-κ2 N,N′)iron(II)]-di-μ-azido-κ2 N 1:N 3-[(5,5′-dimethyl-2,2′-bipyridine-κ2 N,N′)iron(II)]-di-μ-azido-κ2 N 1:N 1], [Fe(N3)2(C12H12N2)] n , features alternating μ-1,1 (end-on mode of coordination) and μ-1,3 (end-to-end mode of coordination) double azide bridges, forming chains running in the [100] direction. The octahedral coordination geometry around the FeII centre is completed by a bidentate 5,5′-dimethyl-2,2′-bipyridine ligand. Two polymorphs for this compound were obtained from the crude reaction product, the first in the space group P-1 and the other in P21/c. The molecular and crystal structures are very similar for both forms, the main difference being that the eight-membered Fe(μ-1,3-N3)2Fe metallacycle formed with end-to-end azide ligands has a nearly flat conformation in the triclinic form and a chair conformation in the monoclinic form. In spite of this geometric difference, both forms have the same density, the same packing index and similar arrangements of the one-dimensional chains in the crystal. As a consequence, they also share very similar Hirshfeld surfaces and fingerprint plots. However, a density functional theory (DFT) computational study showed that the monoclinic form is more stable than the triclinic form by ca 30.5 kJ mol−1.

The cocrystal salt tetraaquabis[trans-1,2-bis(pyridin-4-yl)ethene-κN]iron(II) bis(1,1,3,3-tetracyano-2-ethoxypropenide)–trans-1,2-bis(pyridin-4-yl)ethene (1/2), [Fe(C12H10N2)2(H2O)4](C9H5N4O)2·2C12H10N2, is a rare example of a mononuclear FeII compound with trans-1,2-bis(pyridin-4-yl)ethane (bpe) ligands. The complex cation resides on a crystallographically imposed inversion center and exhibits a tetragonally distorted octahedral coordination geometry. Both the symmetry-independent bpe ligand and the cocrystallized bpe molecule are essentially planar. The 1,1,3,3-tetracyano-2-ethoxypropenide counter-ion is nonplanar and the bond lengths are consistant with significant electron delocalization. The extended structure exhibits an extensive O—H...N hydrogen-bonding network with layers of complex cations joined by the cocrystallized bpe. Both the coordinated and the cocrystallized bpe are involved in π–π interactions. Hirshfeld and fingerprint plots reveal the important intermolecular interactions. Density functional theory was used to estimate the strengths of the hydrogen-bonding and π–π interactions, and suggest that the O—H...N hydrogen bonds enhance the strength of the π-interactions by increasing the polarization of the pyridine rings.

In the title compound,catena-poly[bis[(2,2′-bipyridine-κ2N,N′)(1,1,3,3-tetracyano-2-ethoxypropenido-κN)copper(II)]-μ4-hexanedioato-κ6O1,O1′:O1:O6,O6′:O6], [Cu2(C9H5N4O)2(C6H8O4)(C10H8N2)2]n, the adipate (hexanedioate) dianion lies across a centre of inversion in the space groupP\overline{1}. The CuIIcentre adopts a distorted form of axially elongated (4+2) coordination, and the CuIIand adipate components form a one-dimensional coordination polymer from which the 2,2′-bipyridine and 1,1,3,3-tetracyano-2-ethoxypropenide components are pendent, and where each adipate dianion is bonded to four different CuIIcentres. The coordination polymer chains are linked into a three-dimensional framework structure by a combination of C—H...N and C—H...O hydrogen bonds, augmented by a π–π stacking interaction.

In the title compound, [Cu(C2N3)2(C12H10N6)]nor [Cu(dca)2(abpt)]n, where abpt is 4-amino-3,5-bis(pyridin-2-yl)-4H-1,2,4-triazole and dca is the dicyanamide anion, the CuIIcentre is five-coordinate with an approximately square-pyramidal geometry. One of the two dicyanamide ligands is a terminal ligand, but the other one acts as a μ1,5-bridging ligand between pairs of CuIIcentres, so generating a one-dimensional coordination polymer. A combination of N—H...N and C—H...N hydrogen bonds, augmented by π–π stacking interactions, links the coordination polymer chains into a bilayer structure. Comparisons are made with some related CuIIcomplexes containing dca ligands and heteroaromatic co-ligands.