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Hygroscopic single crystals of a new hexagonal high‐temperature modification of Sr[ReO4]2 were prepared from a melt of Sr[ReO4]2 ⋅ H2O and SrCl2 ⋅ 6 H2O. The structure analysis of the obtained crystals by X‐ray diffraction revealed that the title compound crystallizes in the ThCd[MoO4]3‐type structure with the hexagonal space group P63/m and the lattice parameters a=1023.81(7) pm and c=646.92(4) pm (c/a=0.632) for Z=2 in its quenchable high‐temperature form. Two crystallographically independent Sr2+ cations are coordinated by oxygen atoms forming either octahedra or tricapped trigonal prisms, whereas the Re7+ cations are found in the centers of discrete tetrahedral meta‐perrhenate units [ReO4]−. Temperature‐dependent in‐situ PXRD studies of dry powder samples of Sr[ReO4]2 exhibited its thermal dimorphy with a phase‐transition temperature at 500–550 °C from literature‐known m‐Sr[ReO4]2 into the newly discovered h‐Sr[ReO4]2 (hexagonal). [ABSTRACT FROM AUTHOR]

Here, we quantify the relationship between microphase segregation and local structure development in thermoplastic polyurethanes. Samples were prepared with varying ratios of 4,4′‐methylene diphenyl diisocyanate (MDI) and 1,4‐butanediol (BDO) to polytetrahydrofuran (PTHF) and annealed at temperatures Ta between RT–140 °C for 20 h each. Distinct populations of smaller and larger ordered domains are distinguished by pair distribution function analysis. The intermediate‐range order of nanoscale hard domains in the paracrystalline state (form I) is directly extracted and characterized. The results suggest that form I of the MDI‐BDO:PTHF system presents a conformational and packing order similar to the form III structure, typically obtained from stretching/annealing, but with limited spatial coherence of 3–7 nm. Heating above Tg of the hard segments is necessary to achieve a substantial structural response from the annealing treatment. Increasing Ta promotes purification of the soft phase via microphase segregation, coalescence of the hard blocks, and growth of paracrystalline phase, while a minority fraction of longer‐range ordered domains left over from production remains relatively constant. We observe a composition‐dependent decrease in the average nearest‐neighbor distance that can be correlated with the greater number of CC, CN, and CO bonds with increased hard segment content. A non‐linear deviation in the trend is observed to correlate with sample densification. The mechanical and thermal behavior of the samples is intimately tied to the segregation state. [ABSTRACT FROM AUTHOR]

Crystal engineering has exclusively focused on the development of advanced materials based on small organic molecules. We now demonstrate how the cocrystallization of a polymer yields a material with significantly enhanced thermal stability but equivalent mechanical flexibility. Isomorphous replacement of one of the cocrystal components enables the formation of solid solutions with melting points that can be readily fine‐tuned over a usefully wide temperature range. The results of this study credibly extend the scope of crystal engineering and cocrystallization from small molecules to polymers. [ABSTRACT FROM AUTHOR]

The conversion of La2O3 with HCl, subsequent neutralization and precipitation using (NH4)2CO3 in an industrial process leads to the previously unknown La2(CO3)3 ⋅ 5H2O. The phase was characterized by X‐ray powder diffraction leading to an averaged crystal structure model, thermal analysis, vibrational and optical spectroscopy. La2(CO3)3 ⋅ 5H2O crystallizes in space group Pbca(61) with a=9.0167(4) Å, b=12,842(3) Å, c=9.6331(4) Å and V=1115.4(3) Å3. The structure consists of ∞2LaCO34/4+ ${{}_{{\rm { \infty }}}{}^{{\rm { 2}}}\left\{{\left({\rm { La}}{\left({{\rm { CO}}}_{{\rm { 3}}}\right)}_{{\rm { 4/4}}}\right)}^{{\rm { +}}}\right\}}$ zig zag layers and a highly disordered interlayer space occupied by water molecules and carbonate anions. Partially occupied water‐related oxygen positions theoretically allow for a flexible hydrate water content La2(CO3)3 ⋅ xH2O, with x ranging from 1.5 to 5.0. Although a strong structural relationship between La2(CO3)3 ⋅ 5H2O and La2(CO3)3 ⋅ 8H2O and similar substance properties were found, the title compound cannot be obtained by partial dehydration of the octahydrate. Instead, both lanthanum carbonate hydrates transform into strongly disordered La2(CO3)3 in a one‐step dehydration process. [ABSTRACT FROM AUTHOR]

Crystals of Sc2Si2Te6 have been grown and its crystal, micro‐ and electronic structures were investigated. The layered character of the title compound exhibits stacking faults that impede a full structural characterization by single crystal X‐ray diffraction due to diffuse scattering. Based on high resolution transmission electron micrographs and diffraction patterns, the stacking faulted nature of the real structure of Sc2Si2Te6 has been revealed. Different stacking models were derived from the idealized, faultless structure and the stacking disorder was quantitatively analyzed by Rietveld refinement of powder X‐ray diffraction patterns. An energetic comparison of the stacking models by density functional theory is in line with the experimental observations. Further, the bonding situation was investigated by electronic structure calculations. Sc2Si2Te6 is a narrow gap semiconductor with an indirect band gap of 0.65 eV. [ABSTRACT FROM AUTHOR]

A new six‐membered cyclic alkanolamine with chemical formula C6H15N3O3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1H/13C/15N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real‐space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X‐ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit‐cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry‐independent PDF and PDF‐Rietveld co‐refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen‐bonded molecular stacks. Thermal analysis (TG/DTA) and temperature‐dependent XRPD measurements were also performed to determine the thermal behavior. [ABSTRACT FROM AUTHOR]

The Jahn–Teller (JT) theorem constitutes one of the most fundamental concepts in chemistry. In transition‐element chemistry, the 3d4 and 3d9 configurations in octahedral complexes are particularly illustrative, where a distortion in local geometry is associated with a reduction of the electronic energy. However, there has been a lasting debate about the fact that the octahedra are found to exclusively elongate. In contrast, for Na9Bi5Os3O24, the octahedron around Os6+(5d2) is heavily compressed, lifting the degeneracy of the t2g set of 5d orbitals such that in the sense of a JT compression a diamagnetic ground state results. This effect is not forced by structural constraints, the structure offers sufficient space for osmium to shift the apical oxygen atoms to a standard distance. The relevance of these findings is far reaching, since they provide new insights in the hierarchy of perturbations defining ground states of open shell electronic systems. [ABSTRACT FROM AUTHOR]

Cyclic peptoids are macrocyclic N‐substituted oligoglycines, with remarkable structural, chemical and physical properties. The gas adsorption properties of a permanently porous hexameric cyclopeptoid decorated with four propargyl and two methoxyethyl side chains were monitored by in situ X‐ray powder diffraction (XRPD). High‐resolution XRPD data together with Rietveld and density functional based tight binding (DFTB) method allowed us to locate propyne guest molecules inside the host channels, even though the powder sample contains more than one phase. We were able to characterize the host‐guest interactions, providing useful information on the host recognition sites and discuss host adaptiveness and host–guest chemical affinity in comparison with analogous compounds. [ABSTRACT FROM AUTHOR]

Helical motifs are common in nature, for example, the DNA double or the collagen triple helix. In the latter proteins, the helical motif originates from glycine, the smallest amino acid, whose molecular confirmation is closely related to acetic acid. The combination of acetic acid with calcium and water, which are also omnipresent in nature, materializing as calcium acetate hemihydrate, was now revealed to exhibit a collagen‐like triple helix structure. This calcium salt is observed as efflorescence phase on calcareous heritage objects, like historic Mollusca shells, pottery or marble reliefs. In a model experiment pure calcium acetate hemihydrate was crystallized on the surface of a terracotta vessel. Calcium acetate hemihydrate crystallizes in a surprisingly large unit cell with a volume of 11,794.5(3) Å3 at ambient conditions. Acetate ions bridge neighboring calcium cations forming spiral chains, which are arranged in a triple helix motif. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Reaction of Mn(NCS)2 with 4‐picoline (4‐methylpyridine) leads to the formation of [Mn(NCS)2(4‐picoline)4]·0.67·4‐picoline·0.33·H2O (1‐Mn) reported in literature, Mn(NCS)2(4‐picoline)2(H2O)2 (2‐Mn/H2O), and of [Mn(NCS)2(4‐picoline)2]n (2‐Mn/I). 1‐Mn and 2‐Mn/H2O consist of discrete complexes, in which the metal cations are octahedrally coordinated, whereas in 2‐Mn/I the metal cations are linked by pairs of μ‐1,3‐bridging thiocyanate anions into corrugated chains. Measurements using thermogravimetry and differential scanning calorimetry as well as temperature dependent X‐ray powder diffraction on 1‐Mn and 2‐Mn/H2O reveal that upon heating both compounds transform into [Mn(NCS)2(4‐picoline)]n (3‐Mn) via 2‐Mn/I as intermediate. 3‐Mn shows a very rare chain topology in which the metal cations are linked by μ‐1,3,3 (N,S,S) coordinating anionic ligands which was never observed before with MnII. From these investigations there is no hint that a further modification of 2‐Mn can be prepared as recently observed for [M(NCS)2(4‐picoline)2]n (M = Fe, Cd) and such a form is also not available if the metastable forms of the FeII or CdII compounds were used as template during thermal decomposition. Magnetic investigations on 2‐Mn/H2O show only paramagnetic behavior, whereas for 2‐Mn/I antiferromagnetic ordering is observed. Finally, the crystal structure of Mn(NCS)2 was determined from XRPD data, which shows that it is strongly related to that of 3‐Mn. [ABSTRACT FROM AUTHOR]

The microstructures of six stacking‐faulted industrially produced cobalt‐ and aluminium‐bearing nickel layered double hydroxide (LDH) samples that are used as precursors for Li(Ni1−x−yCoxAly)O2 battery materials were investigated. Shifts from the brucite‐type (AγB)□(AγB)□ stacking pattern to the CdCl2‐type (AγB)□(CβA)□(BαC)□ and the CrOOH‐type (BγA)□(AβC)□(CαB)□ stacking order, as well as random intercalation of water molecules and carbonate ions, were found to be the main features of the microstructures. A recursive routine for generating and averaging supercells of stacking‐faulted layered substances implemented in the TOPAS software was used to calculate diffraction patterns of the LDH phases as a function of the degree of faulting and to refine them against the measured diffraction data. The microstructures of the precursor materials were described by a model containing three parameters: transition probabilities for generating CdCl2‐type and CrOOH‐type faults and a transition probability for the random intercalation of water/carbonate layers. Automated series of simulations and refinements were performed, in which the transition probabilities were modified incrementally and thus the microstructures optimized by a grid search. All samples were found to exhibit the same fraction of CdCl2‐type and CrOOH‐type stacking faults, which indicates that they have identical Ni, Co and Al contents. Different degrees of interstratification faulting were determined, which could be correlated to different heights of intercalation‐water‐related mass‐loss steps in the thermal analyses. [ABSTRACT FROM AUTHOR]

Interpenetration in metal–organic frameworks (MOFs) is an intriguing phenomenon with significant impacts on their properties, and functional applications. Herein, we show that a 7‐fold interpenetrated MOF (1) is transformed into an 8‐fold interpenetrated MOF by the loss of DMF in a single‐crystal‐to‐single‐crystal manner. This is accompanied by a giant enhancement of the second harmonic generation (SHG ca. 125 times) and two‐photon photoluminescence (ca. 14 times). The strengthened π–π interaction between the individual diamondoid networks and intensified oscillator strength of the molecules aid the augment of dipole moments and boost the nonlinear optical conversion efficiency. Large positive and negative thermal expansions of 1 occur at 30–150 °C before the loss of DMF. These results offer an avenue to manipulate the NLO properties of MOFs using interpenetration and provide access to tunable single‐crystal NLO devices. [ABSTRACT FROM AUTHOR]

Hygroscopic single crystals of a new hexagonal high‐temperature modification of Sr[ReO4]2 were prepared from a melt of Sr[ReO4]2 ⋅ H2O and SrCl2 ⋅ 6 H2O. The structure analysis of the obtained crystals by X‐ray diffraction revealed that the title compound crystallizes in the ThCd[MoO4]3‐type structure with the hexagonal space group P63/m and the lattice parameters a=1023.81(7) pm and c=646.92(4) pm (c/a=0.632) for Z=2 in its quenchable high‐temperature form. Two crystallographically independent Sr2+ cations are coordinated by oxygen atoms forming either octahedra or tricapped trigonal prisms, whereas the Re7+ cations are found in the centers of discrete tetrahedral meta‐perrhenate units [ReO4]−. Temperature‐dependent in‐situ PXRD studies of dry powder samples of Sr[ReO4]2 exhibited its thermal dimorphy with a phase‐transition temperature at 500–550 °C from literature‐known m‐Sr[ReO4]2 into the newly discovered h‐Sr[ReO4]2 (hexagonal). [ABSTRACT FROM AUTHOR]

Ferrous glycine sulfate pentahydrate [Fe(glycine)(SO4)·5H2O with glycine = C2H5NO2], contained in the supplement for treating iron deficiency anaemia, commercially known as ferro sanol duodenal®, was characterized by laboratory X‐ray powder diffraction (XRPD), scanning electron microscope (SEM), and infrared spectroscopy (IR). The thermal behavior was investigated by thermal analysis (TGA and DTA) and temperature‐dependent in situ XRPD measurements. Furthermore, the phase transitions to a less hydrated form [Fe(glycine)(SO4)·3H2O] and successively to the anhydrous form were demonstrated to occur in the crystalline solid state. Compared to the crystal structure of the pentahydrate, the trihydrate exhibits a different coordination environment of the iron sites where glycine ligands bridge iron forming a 1D polymeric chain structure. From detailed structural comparison, the mechanism of the phase transitions can be concluded. [ABSTRACT FROM AUTHOR]

Strontium phosphates with apatite structure containing cobalt and fluoride atoms in the trigonal channels were synthesized and characterized by magnetic measurements. The compounds exhibit slow magnetization relaxation with two types of relaxing centers with an energy barrier for magnetization reversal of about 55 and 200 cm–1, respectively. On the fluoride incorporation, the nature of the magnetic centers remains the same as in the initial hydroxyapatite, while the quantity of cobalt incorporated in the channels is reduced substantially. In the sample with the highest fluoride content slow relaxation behaviour almost disappears. [ABSTRACT FROM AUTHOR]

Pure anhydrous Cu(CH3COO)2 was obtained both, by thermal dehydration of Cu(CH3COO)2·H2O and by drying a commercially purchased mixture of Cu(CH3COO)2·H2O and Cu(CH3COO)2 in a nitrogen atmosphere using P2O5 as drying agent. The crystal structure was solved ab initio from synchrotron X‐ray powder diffraction (XRPD) data at 150 °C and from laboratory XRPD data at ambient conditions and found to be isotypic to anhydrous chromium(II), molybdenum(II) and rhodium(II) acetate. Cu(CH3COO)2 crystallizes in space group P1 (no. 2) with lattice parameters of a = 5.1486(3) Å, b = 7.5856(6) Å, c = 8.2832(6) Å, α = 77.984(4)°, β = 75.911(8)°, γ = 84.256(6)° at ambient conditions. Cu2(CH3COO)4 paddle wheels with short (2.6 Å) Cu–Cu distances form chains in a direction, which is the main motif in the crystal structure. Due to their identical structural main motif Cu(CH3COO)2·H2O and Cu(CH3COO)2 exhibit a similar bluish‐green color, almost identical UV/Vis spectra and comparable magnetic properties. The temperature dependent magnetic susceptibility also indicates only weak inter‐dimer spin exchange between neighbouring Cu2(CH3COO)4 paddle wheels. [ABSTRACT FROM AUTHOR]

The title compound, Zn4Cu3(Zn1–xCux)6(HCOO)8(OH)18·6(H2O), also denoted as "Zinc C", a previously unknown corrosion phase of brass in contact with glass, was found on four different historic objects stored in three different collections. Model experiments demonstrated that formaldehyde emitted e.g. from wooden cabinets undergoes a Cannizarro reaction in the alkaline surface film on the historic glass making formate available for the formation of this corrosion phase. The crystal structure of "Zinc C" was solved ab initio from X‐ray powder diffraction data. From the crystal structure and EDX analyses, a phase composition of Zn4Cu3(Zn1–xCux)6(HCOO)8(OH)18·6(H2O) was derived. Zinc C crystallizes in a trigonal unit cell in space group R3(148) with lattice parameters of a = 10.9185(1) Å, c = 27.5058(4) Å, and V = 2839.74(6) Å3. Layers of edge sharing MO6/3 octahedra with voids capped by Zn(HCOO) forming Zn(HCOO)(OH)3/3 tetrahedra are the main motif in the structure. The zinc/copper ratio of the corrosion phase "Zinc C" can vary between 10:3 and 4:9, due to a partial occupational disorder between copper and zinc in the crystal structure. A corrosion phase found on historic brass objects was characterized and identified as Zn4Cu3(Zn1–xCux)6(HCOO)8(OH)18·6(H2O). The crystal structure exhibits a layered motif with a partial occupational disorder between copper and zinc. Model experiments demonstrate that the corrosion was induced by partial hydrolysis of the historic glass. [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]

Two hitherto hardly characterized glycine zinc sulfates were identified in the product of a batch production process for glycine zinc sulfates of the BASF Company: Gly·ZnSO4·2H2O and β-Gly-ZnSO4. The crystal structures were solved from high resolution synchrotron X-ray powder diffraction data. Gly·ZnSO4·2H2O is the zinc analogue to an isotypic copper compound with space group P21/c (no. 14) and a = 7.8092(1) Å, b = 12.3979(2) Å, c = 8.3732(1) Å, β = 90.673(1) and V = 810.62(2) Å3. The crystal structure of the hitherto unknown β-Gly-ZnSO4 with space group P21/c (no. 14) and a = 9.2577(1) Å, b = 5.1268(1) Å, c = 12.9926(1) Å, β = 90.267(1) and V = 616.65(1) Å3 was solved ab initio. In both crystal structures the zinc cations exhibit exotic, fivefold coordination arrangements: squared ZnO5-pyramids are present in the structure of the dihydrate, whereas the crystal structure of β-Gly-ZnSO4 contains trigonal ZnO5- bipyramids. [ABSTRACT FROM AUTHOR]

Copyright of Nachrichten aus der Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reaction of Cd(NCS)2 with 3-hydroxymethylpyridine (3-HMPy) leads to the formation of compounds with the composition Cd(NCS)2(3-HMPy)4 ( 1-Cd), Cd(NCS)2(3-HMPy)2 ( 2-Cd) (Cd(NCS)2)2(3-HMPy)3 ( 3-Cd), and (Cd(NCS)2)3(3-HMPy)4 ( 4-Cd). Compound 1-Cd consists of discrete complexes and in 2-Cd the Cd cations are linked into chains by the anionic and the organic co-ligands. In 3-Cd as well as 4-Cd the Cd cations are connected into chains by the thiocyanate anions, which are further linked into layers by the 3-HMPy co-ligands. In contrast, with Zn only one compound with the composition Zn(NCS)2(3-HMPy)2 ·H2O ( 1-Zn-H2O) was characterized by single-crystal X-ray diffraction, which shows a tetrahedral coordination of the Zn cations by two thiocyanate anions and two 3-HMPy ligands. The discrete complexes are arranged to form channels, in which the water molecules are embedded. 1-Zn-H2O cannot be obtained phase pure and detailed investigations reveal, that additional Zn compounds with the composition Zn(NCS)2(3-HMPy)2 · xH2O including an anhydrate ( 1-Zn) can be obtained, which possesses a similar X-ray powder diffraction (XRPD) pattern. 1-Zn was characterized using X-ray powder diffraction analysis. Most compounds were investigated by thermoanalysis, IR and Raman as well as luminescence spectroscopy. [ABSTRACT FROM AUTHOR]

In salient effects, still crystals of solids that switch between phases acquire a momentum and are autonomously propelled because of rapid release of elastic energy accrued during a latent structural transition induced by heat, light, or mechanical stimulation. When mechanical reconfiguration is induced by change of temperature in thermosalient crystals, bursts of detectable acoustic waves are generated prior to self-actuation. These observations provide compelling evidence that the thermosalient transitions in organic and organic-containing crystals are molecular analogues of the martensitic transitions in some metals, and metal alloys such as steel and shape-memory alloys. Within a broader context, these results reveal that, akin to metallic bonding, the intermolecular interactions in molecular solids are capable of gradual accrual and sudden release of a substantial amount of strain during anisotropic thermal expansion, followed by a rapid transformation of the crystal packing in a diffusionless, non-displacive transition. [ABSTRACT FROM AUTHOR]

The solid/liquid equilibria in the ternary system Ni(OH)2-NiCl2-H2O at temperatures of 25 and 200 °C have been investigated by applying equilibration periods of up to 45 months (3 years and 9 months). The equilibration process was studied by isothermal saturation methods using different solids as starting materials. At 200 °C, Ni2Cl(OH)3 and NiCl(OH) occur as stable phases, whereas a solid solution, NiClx(OH)2-x (ss-type-OH), appears as an intermediate phase. At 25 °C, two nickel(II) chloride hydroxide hydrates, Ni3Cl2+x(OH)4-x·4H2O and Ni3Cl(OH)5·4H2O, are formed. The latter phase was characterized for the first time and a structural model was created from a Rietveld refinement of the powder X-ray diffraction pattern. A systematic investigation of the solubilities at 25 °C revealed that Ni2Cl(OH)3 is the solid phase in both dilute and concentrated NiCl2 solutions at this temperature. In general, all stable and metastable phases in the system Ni(OH)2-NiCl2-H2O exhibit very low solubility, but during the very slow phase transformations high hydroxide supersaturations occur that are persistent for years. [ABSTRACT FROM AUTHOR]

Several coordination compounds, based on Cd halides and 2-methylpyrazine (Mepyz) or 2-chloropyrazine (Clpyz) as N-donor coligands, are synthesized and their crystal structures determined by either single-crystal or X-ray powder diffraction (XRPD). In [CdX2(2-Clpyz)2]n (X = Cl: 1-Cl-Clpyz; X = Br: 1-Br-Clpyz; and X = I: 1-I-Clpyz) and [CdX2(2-Mepyz)2]n (X = Cl: 1-Cl-Mepyz; X = Br: 1-Br-Mepyz; and X = I: 1-I-Mepyz), the Cd cations are octahedrally coordinated by two N-donor ligands and are linked into chains by the halide anions that share common edges. In the ligand-deficient compounds [CdX2(2-methylpyrazine)] n (X = Cl: 2-Cl-Mepyz; X = Br: 2-Br-Mepyz; and X = I: 2-I-Mepyz), similar CdX2 chains, which are connected into layers by the N-donor ligands, are observed. Thermal analysis of all 1-Mepyz compounds shows a transformation into 2-Mepyz, which is not observed for the 2-chloropyrazine compounds. On further heating, compounds of composition [(CdX2)2(2-Mepyz)]n (X = Cl: 3-Cl-Mepyz; X = Br: 3-Br-Mepyz) and [(CdI2)3(2-Mepyz)2] (4-I-Mepyz) are observed. A discrete complex, with the composition CdI2(2-Mepyz)2 monohydrate (1-I-Mepyz-H2O), and a hydrate with the composition [(CdI2)(2-Mepyz)]·1.5H2O (2-IMepyz-H2O) with an unknown structure, were also synthesized. Both lose the water molecules upon heating. Luminescence measurements show blue to orange emissions in the range of ca. 22530-16276 cm-1, depending on the halide or pyrazine substituent, as well as the metal halide/ligand ratio. [ABSTRACT FROM AUTHOR]

A sample of pure, artificial hellyerite was synthesized in aqueous solution at 0 °C. The recorded X-ray diffraction pattern completely agrees with the reference data given for natural hellyerite. Laboratory high resolution X-ray powder diffraction, applying global optimization methods and Rietveld refinement, was employed to solve the crystal structure. Synthetic hellyerite was determined to crystallize in the primitive monoclinic space group P2/ m (no. 10) with a = 10.769(2) Å, b = 7.295(2) Å, c = 9.343(2) Å, and β = 94.042(2)°. The crystal structure consists of edge-linked, isolated pairs of Ni2(CO3)2(H2O)8 octahedra and non-coordinating water molecules. According to structure solution and thermal analysis the molecular formula of hellyerite was corrected from NiCO3 ·6H2O to NiCO3 ·5.5H2O. The title compound was characterized by scanning electron microscopy, IR-, Raman-, and UV/Vis spectroscopy. [ABSTRACT FROM AUTHOR]

The previously unknown nickel chloride hydroxide phases Ni3Cl2+ x(OH)4- x ·2H2O ( x = 0.26, 0.48, 0.82) have been synthesized in concentrated aqueous NiCl2 solutions and investigated in detail. Crystal structure determination from X-ray powder diffraction data revealed triple chains of distorted, edge-linked NiO6 and NiO3(O/Cl)3 octahedra as the main building blocks. The chains exhibit a layer-like configuration and therefore great structural similarity to nickel-layered hydroxy halides (Cl, Br, I) and β-Ni(OH)2. Increasing chloride content in Ni3Cl2+ x(OH)4- x ·2H2O leads to a reduction of the space group symmetry from C2/ m (12) for x = 0.26 and 0.48 to P $\bar {1}$ (2) for x = 0.82 and to distinct shifts in their thermal, spectral, and magnetic properties. Each solid exhibits a maximum magnetic susceptibility in the range 5.9-9.7 K, which indicates antiferromagnetic ordering. Positive Curie-Weiss temperatures, θ, were found, which points to predominantly ferromagnetic spin-exchange interactions. In addition, broad maxima of the magnetic susceptibility evidence a low-dimensional magnetic character as the most prominent feature of the magnetic properties of the investigated phases. [ABSTRACT FROM AUTHOR]

The crystal structure of ferrous glycine sulfate (a ferroglycine sulfate complex with chemical formula FeSO4(C2H5NO2), a compound extensively used as an iron dietary supplement, was refined from synchrotron X-ray powder diffraction data. The crystal structure of an (so-far unreported) isostructural manganese analogue was also structurally detailed by a Rietveld refinement against the corresponding X-ray powder diffraction pattern. All studied compounds crystallize in the monoclinic P21 space group, building layers of metal cations coordinated by the oxygen atoms of sulfate groups and glycine ligands. Neighboring layers are parallel packed, bonded by hydrogen bonds. The coordination polyhedra around the cations can be regarded as distorted and elongated octahedral, presumably due to severe strains present in the crystal structure of the layers. [ABSTRACT FROM AUTHOR]

Anhydrous zinc hydroxide sulfates are promising precursors for the preparation of pigments and ZnO nanomaterials. The crystal structure of one such compound 5[Zn(OH)2] ·2[ZnSO4] was determined from high resolution laboratory X-ray powder diffraction data by use of a combination of charge flipping, simulated annealing, and difference Fourier analysis. The material crystallizes in the space group P $\bar{1}$ with the lattice parameters of a = 5.4559(2) Å, b = 8.0528(3) Å, c = 8.9275(3) Å, α = 112.697(2)°, β = 85.219(3)°, γ = 95.441(3)°, and a volume of V = 359.76(2) Å3. The basic crystal structure consists of brucite type Zn(OH)2 layers where every sixth octahedral site is vacant. Tetrahedrally coordinated zinc ions are located above and below these vacancies and consecutive layers are bridged by sulfate molecules. The composition of this layered structure can be written as [Zn5VI□(OH)4 ·Zn2IV(OH)6 ·(SO4)2]. Its thermal decomposition was studied by X-ray powder diffraction and thermal analysis. [ABSTRACT FROM AUTHOR]

A new basic nickel carbonate Ni12(CO3)8(OH)8·(x – 1)H2O or Ni12(CO3)8(OH)6O·xH2O (x = 6–8) was synthesized by two hydrothermal methods. The crystal structure was determined in the cubic space group P43m (215) with a = 8.3814(2) Å by laboratory high-resolution X-ray powder diffraction with the application of global optimization methods and Rietveld refinement. The crystal structure consists of edge-linked [NiO6] octahedra and carbonate units that form cages. The interconnected cages form channels filled with disordered water molecules. This causes a zeolite-like behavior of the water molecules, as shown by thermogravimetric analysis coupled with infrared spectroscopy (TG–IR) and in situ X-ray powder diffraction experiments up to 300 °C. In addition, the title compound was characterized by elemental analysis, scanning electron microscopy, and Raman and UV/Vis spectroscopy. The title compound was proven to be a pure carbonate and not nickel hydrogen carbonate (PDF 15-0782), as was assumed before. [ABSTRACT FROM AUTHOR]

Two samples of pure NiCl(OH) were produced by hydrothermal synthesis and characterized by chemical analysis, IR spectroscopy, high-resolution laboratory X-ray powder diffraction and scanning electron microscopy. Layers composed of edge-sharing distorted NiCl6 x(OH)6−6 x octahedra were identified as the main building blocks of the crystal structure. NiCl(OH) is isostructural to CoOOH and crystallizes in space group R m [ a = 3.2606 (1), c = 17.0062 (9) Å]. Each sample exhibits faults in the stacking pattern of the layers. Crystal intergrowth of ( Aγ B)( Bα C)( Cβ A) and ( Aγ B)( Aγ B) [C6 like, β-Ni(OH)2 related] stacked layers was identified as the main feature of the microstructure of NiCl(OH) by DIFFaX simulations. A recursion routine for creating distinct stacking patterns of rigid-body-like layers in real space with distinct faults (global optimization) and a Rietveld-compatible approach (local optimization) was realized and implemented in a macro for the program TOPAS for the first time. This routine enables a recursive creation of supercells containing ( Aγ B)( Bα C)( Cβ A), ( Aγ B)( Aγ B) and ( Cβ A)( Bα C)( Aγ B) stacking patterns, according to user-defined transition probabilities. Hence it is an enhancement of the few previously published Rietveld-compatible approaches. This routine was applied successfully to create and adapt a detailed microstructure model to the measured data of two stacking-faulted NiCl(OH) samples. The obtained microstructure models were supported by high-resolution scanning electron microscopy images. [ABSTRACT FROM AUTHOR]

Monitoring of mechanochemical thiocarbamoylation by in situ Raman spectroscopy revealed the formation of aryl N-thiocarbamoylbenzotriazoles, reactive intermediates deemed unisolable in solution. The first-time isolation and structural characterization of these elusive molecules demonstrates the ability of mechanochemistry to access otherwise unobtainable intermediates and offers a new range of masked isothiocyanate reagents. [ABSTRACT FROM AUTHOR]

Different temperature conditions in crystal growth of tin(II) bromide, SnBr2, lead to the formation of two modifications of the title compound. Applying a temperature gradient from 650 °C to room temperature along a silica glass ampoule, the stable room-temperature modification, o-SnBr2 crystallizes in the orthorhombic space group Pnma (no. 62), with a = 839.08(4) pm, b = 423.54(2) pm, c = 1052.03(4) pm, and Z = 4. Changing the reaction conditions towards a decreased temperature gradient from 700 °C to 400 °C, a high-temperature form h-SnBr2 crystallizes in the hexagonal space group P63/ m (no. 176), with a = 1228.24(5) pm, c = 435.68(2) pm, and Z = 6. The trigonal coordination of Sn with three Br atoms and the resulting one-dimensional chains of corner sharing units 1∞[SnBrBr2/2] can be assigned as common structural motif of both modifications. In o-SnBr2 pairs of these chains exhibit the motif of a hexagonal rod packing parallel to the crystallographic b axis. In h-SnBr2 the chains are rearranged, which results in a lower packing density and in a change in topology from 63 to 34.6. Utilizing differential scanning calorimetry on o-SnBr2 endothermal processes at 224 °C and 226 °C were assigned as possible phase transition temperatures prior to the melting point at 227 °C, supported by temperature depending powder X-ray diffraction data. [ABSTRACT FROM AUTHOR]

Since the discovery of symplesite mineral in the late 19th century, a number of structural studies were performed. The crystal symmetry of this mineral was debated to be either monoclinic or triclinic. Even though this debate has ended, agreeing on the triclinic symmetry, no detailed crystal structure was reported so far. In the present contribution, we report on the crystal structure of symplesite. The crystal structure was solved and refined from high-resolution laboratory X-ray powder diffraction data, collected on a natural sample. Symplesite is shown to be isostructural to metavivianite (and possibly to ferrostrunzite). [ABSTRACT FROM AUTHOR]

A novel approach for the marking of deposited lithium on graphite anodes from large automotive lithium-ion cells (≥6 Ah) is presented. Graphite anode samples were extracted from two different formats (cylindrical and pouch cells) of pristine and differently aged lithium-ion cells. The samples present a variety of anodes with various states of lithium deposition (also known as plating). A chemical modification was performed to metallic lithium deposited on the anode surface due to previous plating with isopropanol (IPA). After this procedure an oxygenated species was detected by scanning electron microscopy (SEM), which later was confirmed as Li2CO3 by Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). A valuation of the covered area by Li2CO3 was carried out with an image analysis using energy-dispersive X-ray spectroscopy (EDX) and quantitative Rietveld refinement. [ABSTRACT FROM AUTHOR]

Almost a century has passed since the pioneering work of Debye, Scherrer, and Hull and their first powder X-ray diffraction experiments in 1916/17. Although these pioneers and many others discovered most of the fundamental concepts in the field of powder diffraction within the first few years, nobody at that time could foresee the development of the computer and its calculating power in the 21st century. The general availability of computing power changed the field of powder diffraction, as Hugo Rietveld showed with his computer-assisted whole powder pattern fitting concept around fifty years after the first powder diffraction patterns were observed. Nowadays, much more complex algorithms are used to solve and identify crystal structures from powders. The intention of this historical review is to show some of the most important developments from the viewpoint of the authors in the field of powder diffraction in the last century, from the beginnings of the first transmission experiments and the determination of simple cubic crystal structures to the techniques of today allowing for the refinement of thousands of atoms within one unit cell. [ABSTRACT FROM AUTHOR]

The crystal structure of magnesium potassium arsenate hexahydrate, MgKAsO4 ·6H2O, was refined from powder diffraction data. MgKAsO4 ·6H2O crystallizes in the orthorhombic space group Pmn21 with Z = 2, as the biomineral struvite. Complete dehydration of MgKAsO4 ·6H2O proceeds in a single step, with one endothermic peak at 87.9 °C ( Tonset). The infrared and Raman spectra of protiated and deuterated polycrystalline samples were recorded at room temperature and at the boiling temperature of liquid nitrogen (LNT). The assignments of the observed bands are proposed and spectra-structure correlations are made. [ABSTRACT FROM AUTHOR]

Phase-pure ScF[SeO3] and YF[SeO3] were synthesized via solid-state reactions of the corresponding rare-earth metal sesquioxides and trifluorides with selenium dioxide in excess of fluxing cesium bromide at 700 °C for 7 d. To avoid the formation of oxosilicates, these reactions took place in corundum crucibles embedded inside of evacuated fused silica ampoules. Upon cooling down below 13 °C, a pseudo-second-order phase transition ( P21/ m → P $\bar{1}$ or P1) for ScF[SeO3] occurs, which is similar to the high-temperature phase transition of LuF[SeO3]. By heating YF[SeO3] above 319 °C, it undergoes a first-order phase transition ( P21/ c → P21/ m) without passing the intermediate P $\bar{1}$ modification in contrast to LuF[SeO3]. Both the high-temperature phase transition of YF[SeO3] and the low-temperature phase transition of ScF[SeO3] were characterized by in-situ X-ray powder diffraction, X-ray single-crystal diffraction, thermal analysis DSC, and distortion-mode analysis. For both cases the driving forces for the symmetry-breaking phase transitions from the high- to the low-temperature phases are discussed. [ABSTRACT FROM AUTHOR]

Phase transitions recorded using in-situ powder diffraction are typically analysed by Rietveld refinements applying relative atomic coordinates in a least-squares iteration process. Although this choice of relative atomic coordinates gives an intuitive coordinate system, it can be improved by changing to another basis of the atomic configuration space, as the motion of whole atomic groups or polyhedra can be normally described with a smaller set of parameters. Using rotational rigid body symmetry modes as another basis, it is possible to directly describe and refine the rotation of groups of atoms (denoted as constrainable atomic groups). In addition, a reduction of the total number of relevant parameters can occur. In order to explore the capabilities of this new approach, phase transitions in different compounds, namely sodium niobate (NaNbO3), ferrocene (Fe(C5H5)2), and schafarzikite (FeSb2O4) are reinvestigated. [ABSTRACT FROM AUTHOR]

In the course of solid-state photoreactions, a single crystal (SC) of the reactant can be transformed into an SC of the product or it can lose crystallinity and become amorphous. In-between these two scenarios exist the reconstructive phase transformations, where upon irradiation, the reactant SC becomes a powder or an SC with increased mosaicity. We present a detailed description of reconstructive photodimerization, where the structural changes are directly correlated with the disintegration process. The kinetics of the reaction is explained by two kinetic regimes, forming an autocatalytic autoinhibition photoreaction set with high quantum yield. In addition, the photoreaction pathways were studied theoretically. [ABSTRACT FROM AUTHOR]

The extremely rare examples of dynamic single crystals where excitation by light or heat induces macroscopic motility present not only a visually appealing demonstration of the utility of molecular materials for conversion of energy to work, but they also provide a unique opportunity to explore the mechanistic link between collective molecular processes and their consequences at a macroscopic level. Here, we report the first example of a photosalient effect (photoinduced leaping) observed with crystals of three coordination complexes which is induced by a [2+2] photocycloaddition reaction. Unlike a plethora of other dimerization reactions, when exposed to even weak UV light, single crystals of these materials burst violently, whereby they are propelled to travel several millimeters. The results point to a multistep mechanism where the strain energy that has been accumulated during the dimerization triggers a rapid structure transformation which ultimately results in crystal disintegration. [ABSTRACT FROM AUTHOR]

Sequential Rietveld refinements were applied on high-pressure synchrotron powder X-ray diffraction measurements of lanthanum ferrite (LaFeO3) revealing two phase transitions on the room-temperature isotherm up to a pressure of 48 GPa. The first structural phase transition of second order occurs at a pressure of 21.1 GPa, changing the space group from Pbnm to Ibmm. The second transition, involving a isostructural first-order phase transition, occurs at approximately 38 GPa, indicating a high-spin to low-spin transition of the Fe3+ ion. Following the behavior of the volume up to the hydrostatic limit of methanol-ethanol it was possible to use inverted equations of state (EoS) to determine a bulk modulus of B0 = 172 GPa and a corresponding pressure derivative of B′0 = 4.3. In addition, the linearized version of the inverted EoS were used to determine the corresponding moduli and pressure derivatives for each lattice direction. [ABSTRACT FROM AUTHOR]

The application of rotational symmetry modes to quantitative rigid-body analysis is demonstrated for octahedral rotations in Mg(H2O)6RbBr3. Rigidbody rotations are treated as axial-vector order parameters and projected using group-theoretical methods. The high-temperature crystal structure of the Mg(H2O)6RbBr3 double salt consists of a cubic perovskite-like corner-sharing network of RbBr6 octahedra with isolated MgO6 octahedra at the perovskite A sites. A phase transition occurs at 411 K upon cooling, whereupon the MgO6 octahedra experience a substantial rigid-body rotation, the RbBr6 octahedra are translated but not rotated, and both types of octahedra become slightly distorted. The MgO6 rotation has three orthogonal components associated with the X-5, Γ4 + and X1 - irreducible representations of the parent Pm3m space-group symmetry which, given the weakly first-order character of the transition, appear to be strongly coupled. Parametric and sequential refinements of the temperature-dependent structure were conducted using four model types: (1) traditional atomic xyz coordinates for each atom, (2) traditional rigid-body parameters, (3) purely displacive symmetry modes and (4) rigid-body rotational symmetry modes. We demonstrate that rigid-body rotational symmetry modes are an especially effective parameter set for the Rietveld characterization of phase transitions involving polyhedral rotations. [ABSTRACT FROM AUTHOR]

The application of rotational symmetry modes to quantitative rigid-body analysis is demonstrated for octahedral rotations in Mg(H2O)6RbBr3. Rigidbody rotations are treated as axial-vector order parameters and projected using group-theoretical methods. The high-temperature crystal structure of the Mg(H2O)6RbBr3 double salt consists of a cubic perovskite-like corner-sharing network of RbBr6 octahedra with isolated MgO6 octahedra at the perovskite A sites. A phase transition occurs at 411 K upon cooling, whereupon the MgO6 octahedra experience a substantial rigid-body rotation, the RbBr6 octahedra are translated but not rotated, and both types of octahedra become slightly distorted. The MgO6 rotation has three orthogonal components associated with the X-5, Γ4 + and X1 - irreducible representations of the parent Pm3m space-group symmetry which, given the weakly first-order character of the transition, appear to be strongly coupled. Parametric and sequential refinements of the temperature-dependent structure were conducted using four model types: (1) traditional atomic xyz coordinates for each atom, (2) traditional rigid-body parameters, (3) purely displacive symmetry modes and (4) rigid-body rotational symmetry modes. We demonstrate that rigid-body rotational symmetry modes are an especially effective parameter set for the Rietveld characterization of phase transitions involving polyhedral rotations. [ABSTRACT FROM AUTHOR]

The high-temperature phase transition of LuF[SeO3] has been characterized by time-resolved high-resolution synchrotron powder diffraction. On heating, a second-order structural phase transition was found at 393 K, while on cooling the same phase transition occurs at 371 K, showing a large hysteresis typical for a first-order phase transition. Detailed analysis using sequential and parametric whole powder pattern fitting revealed that the coupling between the strain and the displacive order parameter determines the behaviour of the material during the phase transition. Different possible coupling mechanisms have been evaluated and the most probable rationalized. [ABSTRACT FROM AUTHOR]

Parametric refinement is used for the simultaneous modeling of a series of diffraction data, replacing single independent parameters with physical or empirical equations that are valid for the full sequence of data. For the parametric treatment of diffraction data at high pressure, pressure-dependent constraints can be introduced in the form of an equation of state (EoS). However, the parameterization needs inverse functions of the EoS and most of them are not analytically invertible. In order to overcome this drawback, Taylor series expansions of different orders of the Vinet EoS were calculated and analytically inverted. It is shown that the inverted third-order Vinet EoS approximation, in its volume and linearized version, is applicable to a wide range of materials under high pressure. [ABSTRACT FROM AUTHOR]

Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel cement phase 3Mg(OH)2 ·MgCl2 ·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the phases 3Mg(OH)2 ·MgCl2 ·5.4H2O and 3Mg(OH)2 ·MgCl2 ·4.6H2O. The crystal structure of 3Mg(OH)2 ·MgCl2 ·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2 ·MgCl2 ·5.4H2O phase is given. These phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented. [ABSTRACT FROM AUTHOR]

A new chromophore has been identified in copper-doped apatite pigments having the general composition [Sr10(PO4)6(Cu xOH1− x− y)2], in which x=0.1, 0.3 and y=0.01-0.42. By using X-ray absorption spectroscopy, low-temperature magnetization measurements, and synchrotron X-ray powder structure refinement, it has been shown that the oxygenated compounds contain simultaneously diamagnetic Cu1+ and paramagnetic Cu3+ with S=1. Cu3+ is located at the same crystallographic position as Cu1+, being linearly coordinated by two oxygen atoms and forming the OCuO− anion. The Raman spectroscopy study of [A10(PO4)6(Cu xOH1− x− y)2,], in which A=Ca, Sr, Ba, reveals resonance bands at 651-656 cm−1 assigned to the symmetric stretching vibration ( ν1) of OCuO−. The strontium apatite pigment exhibits a strong paramagnetic anisotropy with an unprecedentedly large negative zero-field splitting parameter ( D) of ≈−400 cm−1. The extreme magnetic anisotropy causes slow magnetization relaxation with relaxation times ( τ) up to 0.3 s at T=2 K, which relates the compounds to single-ion magnets. At low temperature, τ is limited by a spin quantum-tunneling, whereas at high temperature a thermally activated relaxation prevails with Ueff≈48 cm−1. Strong dependence of τ on the paramagnetic center concentration at low temperature suggests that the spin-spin relaxation dominates in the spin quantum-tunneling process. The compound is the first example of a d-metal-based single-ion magnet with S=1, the smallest spin at which an energy barrier arises for the spin flipping. [ABSTRACT FROM AUTHOR]

A new magnesium oxysulfate hydrate phase, 5 Mg( OH)2· MgSO4·7 H2 O was synthesized and structurally characterized. The new phase crystallizes in the form of microsized needles and its crystal structure was solved using X-ray powder diffraction. The crystal packing is made of infinite triple MgO6 chains, intercalated with sulfate groups, water molecules, and hydroxide anions. Using vibrational spectroscopy [infrared (IR) and Raman] and Rietveld refinement, the arrangement of water molecules and hydroxide anions were observed to be statistically distributed and dynamically disordered. The high-temperature behavior and decomposition were studied by thermal analyses and in situ X-ray powder diffraction. The high-temperature measurements reveal the presence of five decomposition stages from the new phase to the production of MgO. After the reactions with atmospheric carbon dioxide were analyzed using micro-Raman spectroscopy, two new carbonate phases were detected on the surface of the material. [ABSTRACT FROM AUTHOR]