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The tetragonal tungsten bronze (TTB) structure multiferroic fluoride K0.58FeF3 (alternatively K3–xFe5F15 (x ≈ 0.1)) has been studied using variable temperature high-resolution synchrotron powder X-ray diffraction. The as-made sample occurs as a mixture of two closely related TTB phases, one tetragonal (aTTB ≈ 12.68 A, cTTB ≈ 3.98 A) and one orthorhombic (a ≈ 12.70 A, b ≈ 12.66 A, c ≈ 3.98 A). Heating above 340 K produces a single metrically tetragonal phase, but the phase separation reproducibly reappears on cooling. Below 300 K the tetragonal phase undergoes a structural phase transition to a second orthorhombic phase (with a ≈ b ≈ √2 aTTB) and these two different orthorhombic phases continue to coexist down to at least 125 K. These results are discussed in the context of previous studies, which sometimes suggest conflicting structural details within this system.

The crystal structure of the S = 1/2 kagome system Cs2ZrCu3F12 has been determined at both 295 and 125 K via single-crystal X-ray diffraction. A first-order structural phase transition is seen near 225 K, confirmed by variable-temperature synchrotron powder diffraction studies, in which the structure transforms from rhombohedral (R3m) to monoclinic (P21/m). A corresponding abrupt change in dielectric constant is observed near the same temperature. The phase transition is driven by a dramatic change in coordination around the Zr site, which changes from regular octahedral in the rhombohedral phase to a seven-coordinate environment in the monoclinic phase. This leads to a severe buckling of the copper fluoride kagome layers and significant changes in the geometry around the Cu sites, which correlates with both the observed dielectric anomaly and a previously observed anomaly in magnetic susceptibility. It is suggested that this structural phase transition ultimately permits long-range antiferromagnetic ord...

Two nitrate salts of Ni(II) and ethylenediamine (en), trans-diaquabis(ethylenediamine)nickel(II) nitrate (1) and Λ-δδδ-tris(ethylenediamine)nickel(II) nitrate (2), were investigated crystallographically and the nature of the intermolecular interactions in 2 were explored using the quantum theory of atoms in molecules (QTAIM) of Bader from a X3LYP/6–31 + G(d) single point calculation on a portion of the crystal structure. In 1 the two chelate rings, related by inversion, are in the λ and δ conformations, respectively. The metal complex cations are hydrogen bonded to the axial H2O ligands and the amino protons and pack in ribbons along the crystallographic a axis. In 2, which is the enantiometric form of the known Δ-λλλ-tris(ethylenediamine)nickel(II) nitrate, each nitrate is in a distorted tetrahedral site defined by [Ni(en)3]2+ cations. QTAIM analysis indicates that NO3− forms O····HN hydrogen bonds to amino groups of en, as well as a O····HC hydrogen bond to one of the methylene groups of the ligand. In addition, neighbouring [Ni(en)3]2+ ions are connected by a weak H–H bond between en methylene groups.

The three isostructural compounds butyl­ammonium hexa­chlorido­tin(IV), pentyl­ammonium hexa­chlorido­tin(IV) and hexyl­ammonium hexa­chlorido­tin(IV), (CnH2n+1NH3)2[SnCl6], with n = 4, 5 and 6, respectively, crystallize as inorganic–organic hybrids. As such, the structures consist of layers of [SnCl6]2− octa­hedra, separated by hydro­carbon layers of inter­digitated butyl­ammonium, pentyl­ammonium or hexyl­ammonium cations. Corrugated layers of cations alternate with tin(IV) chloride layers. The asymmetric unit in each compound consists of an anionic component comprising one Sn and two Cl atoms on a mirror plane, and two Cl atoms in general positions; the two cations lie on another mirror plane. Application of the mirror symmetry generates octa­hedral coordination around the Sn atom. All compounds exhibit bifurcated and simple hydrogen-bonding inter­actions between the ammonium groups and the Cl atoms, with little variation in the hydrogen-bonding geometries.

The crystal structure of the title system is determined at 295 and 125 K by single crystal XRD.

The crystal structure of the nitrate salt of N,N'-bis(2-hydroxyethyl)-ethane-1,2-diamine (BHEEN), and its complex with Zn(II) and Cd(II) are reported. (H(2)BHEEN)(NO(3))(2) packs in a layered structure with a herringbone pattern within each layer arising from H-bonding between amino and alcohol protons and NO(3)(-) counterions. In [Zn(BHEEN)(2)]Cl(2), each ligand coordinates to Zn(II) through its two N-donors producing a distorted tetrahedral geometry at the metal centre. The two hydroxyethyl arms of each ligand are trans to each other and the crystals obtained contained a racemic mixture of the bis-trans-R,R and the bis-trans-S,S isomers. All four hydroxyl groups are H-bonded to chloride counter ions, creating a layered structure. Whilst distant from the metal ion (average 3.00 A), the four O atoms of the pendent hydroxylamino groups appear positioned to interact with the metal. The orientation of the arms is preserved in a B3LYP gas phase calculation of the structure. An analysis using Bader's Atoms in Molecules indicates that the Zn-N bonds are predominantly ionic with some covalent character and that there is a weak interaction between the metal and the hydroxyl groups. Several other weak interactions including four O...HN, five O...HC and a H-H dihydrogen bond were identified. The Cd(II) complex of BHEEN crystallised as a dimer [(mu-Cl)(2)(Cd(BHEEN)Cl)(2))] with two asymmetrically-bound bridging Cl(-) ligands and a terminally-coordinated Cl(-) on each metal ion. One hydroxyl group of each ligand is coordinated to the metal and the uncoordinated hydroxyl group is H-bonded to the H atom of the coordinated hydroxyl group of the second ligand in the complex. The ESI-MS spectrum shows the presence of di-cadmium complexes, but the most intense peaks are due to mono-cadmium complexes. The gas phase B3LYP structure of the dimer energy-minimises into two monomers and the longer bond between Cd(II) and bridging Cl(-) breaks. Hence, dimerisation may be a consequence of the crystallisation process and the dimer may not be the predominant species in solution.