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Long-term crystallisation from aqueous copper(ii)–acetate solution after the addition of ammonia at 25 °C led to the formation of a hitherto poorly characterised phase in the verdigris pigment system Cu(CH3COO)2–Cu(OH)2–H2O. Laboratory X-ray powder diffraction (XRPD) was successfully employed to solve the crystal structure. The structure solution reveals a phase composition of the Cu3(CH3COO)4(OH)2·5H2O ≡ 2-1-5 phase, which was also confirmed by thermal analysis. The 2-1-5 phase crystallises in space group P21/c (14) with lattice parameters of a = 12.4835(2) Å, b = 14.4246(2) Å, c = 10.7333(1) Å and β = 102.871(1)°. The crystal structure consists of Cu2(CH3COO)2(CH3COO)1/2(OH)4/3H2O1/6+ dimers that are interconnected by Cu(CH3COO)(CH3COO)1/2(OH)2/31/6− squares forming chains running in the c-direction. Non-coordinating hydrate water molecules are intercalated inbetween the chains and mediate the inter-chain interaction. IR and Raman spectroscopy techniques were also employed to confirm selected aspects of the determined crystal structure. The magnetic properties of the 2-1-5 phase decompose into two independent subsystems: a strongly antiferromagnetically spin exchange coupled magnetic Cu–Cu dimer and a significantly weaker coupled Cu monomer. The light blue colour of the sample originates from a reflectance maximum at 488 nm and significantly differs from the known verdigris phases. An investigation of several historic verdigris pigment samples revealed that this phase occurs both as a minor and a major component. Hence, our reference data for the title compound will help to improve the understanding of the multiphase mixtures occurring in historic verdigris samples. [ABSTRACT FROM AUTHOR]

Two different Li/S cathodes are compared in terms of capacity (mA.h.-1gsulfur) and intermediates during discharge and charge. One cathode material is based on fibrous SPAN, a sulfur-containing material obtained via the thermal conversion of poly(acrylonitrile), PAN, in the presence of sulfur. In this material, sulfur is covalently bound to the polymeric backbone. The second cathode material is based on porous activated carbon fibers (ACFs) with elemental sulfur embedded inside the ACFs' micropores. Cyclic voltammetry clearly indicates different discharge and charge chemistry of the two materials. While S-containing ACFs show the expected redoxchemistry of sulfur, SPAN does not form long-chain polysulfides during discharge; instead, sulfide is chopped off the polymer-bound sulfur chains to directly form Li2S. The high reversibility of this process accounts for both the high cycle stability and capacity of SPAN-based cathode materials. [ABSTRACT FROM AUTHOR]

Reaction of Cd(NCS)2 or Zn(NCS)2 with 3-aminomethylpyridine (3-AMPY) leads to the formation of five compounds with the compositions [Cd(NCS)2(3-AMPy)2·(3-AMPy)]n (1-Cd), [M(NCS)2(3- AMPy)2]n [M = Cd (2-Cd), Zn (2-Zn)] [Cd(NCS)2(3-AMPy)]n (3-Cd), and [Zn(NCS)2(3-AMPy)]2 (3-Zn). In 1-Cd the Cd cations are linked by the 3-AMPy ligands into layers that consist of rings, built up of four Cd cations and four 3-AMPy ligands. These layers are stacked to form channels, in which the 3-AMPy solvate molecules are located. In the isotypic compounds 2-Cd and 2-Zn the metal cations are also linked into layers by the 3-AMPy ligands with an identical layer topology as that in 1-Cd, but a completely different conformation of the 3-AMPy ligand. In the most 3-AMPy deficient compound 3-Cd, the Cd cations are linked by μ- 1,3-bridging thiocyanate anions and 3-AMPy ligands into chains, that are further connected into layers by additional anionic ligands. In 3-Zn two Zn cations are linked by pairs of 3-AMPy ligands into discrete dimers. Thermoanalysis and X-ray powder diffraction (XRPD) investigations show that upon heating 1-Cd transforms into 2-Cd and 2-Zn into 3-Zn. The compounds 2-Cd, 3-Cd, 2-Zn and 3-Zn present ligand-based luminescence in the blue-green spectral range with maxima between 21276 and 21795 cm-1. [ABSTRACT FROM AUTHOR]

The impact of a Ni 2+ -influx on formation, stability, solubility and crystal structures of the 3-1-8 (3 Mg(OH) 2 ·MgCl 2 ·8 H 2 O) and the 5-1-8(5 Mg(OH) 2 · MgCl 2 · 8 H 2 O) binder phases of the magnesia cement system was studied by adding MgO, the 5-1-8 and the 3-1-8 phase to Ni 2+ -bearing 4.0 molal MgCl 2 -solutions at 25 °C and applying equilibration periods of more than 2 years (up to 800 days). Nickel was observed to enter the crystal structure of the 5-1-8 phase, yielding solid solutions among this magnesium chloride hydroxide hydrate and its Ni-analog, whereas no incorporation of Ni 2+ ions into the crystal structure of the 3-1-8 phase takes place. The presence of nickel in the access solution inhibits the transformation of the metastable 5-1-8 phase into the thermodynamically stable 3-1-8 phase and prolongs the duration of this process from a few days to more than 2 years. As the final product of the phase formation process a mixture of the 3-1-8 phase and the 2-1-4 Ni-phase (2 Ni(OH) 2 ·NiCl 2 ·4 H 2 O) could be identified. Analyses of the resulting liquid phases confirmed that almost the complete amount of dissolved nickel was removed from the solution by the addition of MgO, the 5-1-8 or the 3-1-8 phase. [ABSTRACT FROM AUTHOR]

A powder sample of pure H3LiIr2O6 was synthesized from α-Li2IrO3 powder by a soft chemical replacement of Li+ with H+. The crystal structure of H3LiIr2O6 consists of sheets of edge sharing LiO6- and IrO6-octahedra forming a honeycomb network with layers stacked in a monoclinic distorted HCrO2 type pattern. Heavy stacking faulting of the sheets is indicated by anisotropic peak broadening in the X-ray powder diffraction (XRPD) pattern. The ideal, faultless crystal structure was obtained by a Rietveld refinement of the laboratory XRPD pattern while using the LiIr2O63−-layers of α-Li2IrO3 as a starting model. The low radial distances of the PDF function, derived from synchrotron XRPD data, as constraints to stabilize the structural refinement. DIFFaX-simulations, structural considerations, high radial distances of the PDF function and a Rietveld compatible global optimization of a supercell were employed to derive a suitable faulting model and to refine the microstructure using the experimental data. We assumed that the overall stacking pattern of the layers in the structure of H3LiIr2O6 is governed by interlayer O–H…O contacts. From the constitution of the layers, different stacking patterns with similar amounts of strong O–H…O contacts are considered. Random transitions among these stacking patterns can occur as faults in the crystal structure of H3LiIr2O6, which quantitatively describe the observed XRPD. [ABSTRACT FROM AUTHOR]

Known synthesis approaches for basic copper(ii) acetates, the main components of historic verdrigis pigments were reinvestigated and revealed to be partially irreproducible. A modification of the reaction conditions led to the successful and reproducible synthesis of the 1–2–0 phase (Cu3(CH3COO)2(OH)4 = 1Cu(CH3COO)2·2Cu(OH)2·0H2O). The phase composition was derived from elemental and thermal analysis and confirmed by the crystal structure solution using synchrotron X-ray powder diffraction (XRPD) data. The 1–2–0 phase crystallises in space group Pbca with lattice parameters of a = 20.9742(1) Å, b = 7.2076(1) Å, and c = 13.1220(1) Å. The crystal structure consists of Cu2(CH3-COO)2(OH)4/3(OH)2/21/3− dimers, which are interconnected by corner sharing Cu(OH)2/3(OH)2/21/3+ squares forming layers perpendicular to the a-axis. The deep blue color of the solid originates from a reflectance maximum at 472 nm and from an absorbance maximum at 676 nm that is comparable with other historic blue pigments like azurite or Egyptian blue. IR- and Raman-spectroscopic properties of the solid were investigated as well, which demonstrated that the obtained product is identical with a previously synthesised verdigris phase that was obtained by applying historical procedures. Therefore, our reference data for the title compound will help to improve the understanding of the multiphase mixtures occurring in historic verdigris samples. The magnetic properties of the 1–2–0 phase were also investigated. At low temperatures the magnetic susceptibility is well described by a spin-1/2 Heisenberg chain with uniform antiferromagnetic nearest-neighbour spin exchange coupling of only one of three Cu magnetic moments. Due to the very strong antiferromagnetic coupling of the Cu2(CH3-COO)2(OH)4/3(OH)2/21/3− dimers their contribution to magnetism becomes relevant above ∼140 K, which results in the presence of two distinct temperature regions where Curie–Weiss behaviour of the magnetic susceptibility with different Curie constants and Weiss temperatures is found. [ABSTRACT FROM AUTHOR]