A second ortho­rhom­bic polymorph of 3,5-diphenyl-4H-1,2,4-triazol-4-amine

The present crystal structure is the second ortho­rhom­bic polymorph of the title compound, C14H12N4. Whereas the structure in Pnma with Z′ = 0.5 is already known [Ikemi et al. (2002 ▶). Heterocycl. Commun. 8, 439–442], the present structure crystallizes in the space group Pbca with Z′ = 1. The dihedral angle between the two phenyl rings is 23.5 (4)° and the dihedral angles between central ring and the phenyl rings are 41.0 (3) and 26.3 (5)°. In the 4-amino-1,2,4-trizole fragment, the C=N distances are 1.321 (3) and 1.315 (3) Å, which are much shorter than the C—N distances of 1.367 (3) and 1.357 (3) Å. In the crystal, adjacent mol­ecules are linked by N—H⋯N hydrogen bonds

Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides

In this paper we explore the magnetic and orbital properties closely related to a tetragonal-orthorhombic structural phase transition in iron pnictides based on both two- and five-orbital Hubbard models. The electron-lattice coupling, which interplays with electronic interaction, is self-consistently treated. Our results reveal that the orbital polarization stabilizes the spin density wave (SDW) order in both tetragonal and orthorhombic phases. However, the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase rather than in the tetragonal one. Magnetic moments of Fe are small in the intermediate Coulomb interaction region for the striped antiferromangnetic phase in the realistic five orbital model. The anisotropic Fermi surface in the SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved photoemission spectroscopy experiments. These results suggest a scenario that the magnetic phase transition is driven by the ODW order mainly arising from the electron-lattice coupling.Comment: 21 pages, 10 figure

Bis[2-(benzimidazol-2-ylsulfan­yl)acetato]bis­(2,2′-bipyridine)cadmium(II)

In the structure of the title compound, [Cd(C9H7N2O2S)2(C10H8N2)2], the complex mol­ecules are located on a crystallographic twofold rotation axis and the CdII ion is octa­hedrally coordinated by two chelating 2,2′-bipyridine ligands and two O atoms from the carboxyl­ate groups of two 2-(benzimidazol-2-ylsulfan­yl)acetate ligands. The two carboxyl­ate ligands adopt a cis configuration with respect to each other. Within each of these ligands, the imidazole fragments are bent back in a loop towards the acetyl groups, forming intra­molecular N—H⋯O hydrogen bonds, which help to stablilize the mononuclear complex. Adjacent mol­ecules are further linked by weak C—H⋯O hydrogen bonds, resulting in a chain along the c axis

Bis(2-fluoro­benzoato-κO)bis­(pyridin-2-amine-κN 1)zinc(II)

In the title compound, [Zn(C7H4FO2)2(C5H6N2)2] or [Zn(fa)2(2-pa)2] (Hfa is 2-fluoro­benzoic acid and 2-pa = pyridin-2-amine), the asymmetric unit contains one ZnII cation, two fa ligands and two 2-pa ligands, wherein the ZnII displays a distorted tetra­hedral geometry, being surrounded by two monodentate fa ligands with Zn—O distances of 1.962 (2) and 1.976 (3) Å, and by two 2-pa ligands with distances involving pyridyl N atoms of 2.069 (2) and 2.056 (2) Å. The F atoms of the fa ligands are equally disordered over two sites, viz. the 2- and 6-positions of fa. The mononuclear complex mol­ecules are joined by N—H⋯O and N—H⋯F hydrogen bonds into a two-dimensional layer, which is further constructed into a three-dimensional supra­molecular network by weak C—H⋯F inter­actions and effective π–π stacking [centroid-centroid separation of 3.74 (3) Å] between the inter­layer aromatic rings and adjacent heterocycles

(Z,Z)-N′′-[Amino­(pyrazin-2-yl)methyl­ene]pyrazine-2-carbohydrazonamide

The title compound, C10H10N8, resides on a crystallographic symmetry center and features an essentially planar mol­ecule [r.m.s. deviation = 0.278 (1) Å]. In the C=N—N=C fragment, the C=N distance is 1.3017 (18) Å and the N—N distance is 1.403 (2) Å. In the crystal, adjacent mol­ecules are linked by N—H⋯N hydrogen bonds into a three-dimensional network