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We discovered superconductivity at 4.8 K in the hexagonal layered compound La2IRu2 comprising a triangular lattice of the La and a honeycomb lattice of the Ru atoms. First-principles calculations reveal a two-dimensional band structure made up of La 5d and Ru 4d electrons and formal oxidation states +1.5 for the La and the uncommon oxidation state −1 for the Ru atoms. The temperature dependence of the specific heat indicates fully gapped superconductivity. Nevertheless, the upper critical field of this compound violates the Pauli limit. We argue that the high upper critical field is ascribed to an antisymmetric spin–orbit coupling in the unique multilayer structure.

Solving the structure of carbon nitrides has been a long-standing challenge due to the low crystallinity and complex structures observed within this class of earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using a molecular precursor route. We present a comprehensive analysis of the in-plane and three-dimensional structure of PHI. Transmission electron microscopy and solid-state NMR spectroscopy, supported by quantum-chemical calculations, suggest a planar, imide-bridged heptazine backbone with trigonal symmetry in both K-PHI and H-PHI, whereas pair distribution function analyses and X-ray powder diffraction using recursive-like simulations of planar defects point to a structure-directing function of the pore content. While the out-of-plane structure of K-PHI exhibits a unidirectional layer offset, mediated by hydrated potassium ions, H-PHI is characterized by a high degree of stacking faults due to the weaker structure directing influence of pore water. Structure-property relationships in PHI reveal that a loss of in-plane coherence, materializing in smaller lateral platelet dimensions and increased terminal cyanamide groups, correlates with improved photocatalytic performance. Size-optimized H-PHI is highly active toward photocatalytic hydrogen evolution, with a rate of 3363 mu mol/gh H-2 placing it on par with the most active carbon nitrides. K- and H-PHI adopt a uniquely long-lived photoreduced polaronic state in which light-induced electrons are stored for more than 6 h in the dark and released upon addition of a Pt cocatalyst. This work highlights the importance of structure- property relationships in carbon nitrides for the rational design of highly active hydrogen evolution photocatalysts.

A previously unknown solid phase in the zinc-imidazole system relevant for the synthesis of ZIF-8 was obtained by adding a small excess of methylimidazole (Hmim) to a diluted zinc chloride solution...

Metal-organic frameworks (MOFs) are promising nanoporous materials for the adsorptive capture and separation of noble gases at room temperature. Among the numerous MOFs synthesized and tested for noble gas separations, Ni(PyC)₂ (PyC = pyridine-4-carboxylate) exhibits one of the highest xenon/krypton selectivities at room temperature. Like lead-optimization in drug discovery, here we aim to tune the chemistry of Ni(PyC)₂, by appending a functional group to its PyC ligands, to maximize its Xe/Kr selectivity. To guide experiments in the laboratory, we virtually screen Ni(PyC-X)₂ (X=functional group) structures for noble gas separations by (i) constructing a library of Ni(PyC-X)₂ crystal structure models then (ii) using molecular simulations to predict noble gas (Xe, Kr, Ar) adsorption and selectivity at room temperature in each structure. The virtual screening predicts several Ni(PyC-X)₂ structures to exhibit a higher Xe/Kr, Xe/Ar, and Kr/Ar selectivity than the parent Ni(PyC)₂ MOF, with Ni(PyC-m-NH₂)₂ among them. In the laboratory, we synthesize Ni(PyC-m-NH₂)₂, determine its crystal structure by X-ray powder diffraction, and measure its Xe, Kr, and Ar adsorption isotherms (298 K). In agreement with our molecular simulations, the Xe/Kr, Xe/Ar, and Kr/Ar selectivities of Ni(PyC-m-NH₂)₂ exceed those of the parent Ni(PyC)₂. Particularly, Ni(PyC-m-NH₂)₂ exhibits a [derived from experimental, equilibrium adsorption isotherms] Xe/Kr selectivity of 20 at dilute conditions and 298 K, compared to 17 for Ni(PyC)₂. According to in situ X-ray diffraction, corroborated by molecular models, Ni(PyC-m-NH₂)₂ presents well-defined binding pockets tailored for Xe and organized along its one-dimensional channels. In addition to discovering the new, performant Ni(PyC-m-NH₂)₂ MOF for noble gas separations, our study illustrates the computation-informed optimization of the chemistry of a "lead" MOF to target adsorption of a specific gas.

Mg(SCN)2·4H2O can be converted into previously unknown compounds Mg(SCN)2·(4 - x) H2O·xTHF with x = 0, 2 and 4 by multiple recrystallization in tetrahydrofuran (THF). The phases were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and their crystal structures were solved from X-ray powder diffraction (XRPD) data. In the crystal structures isolated Mg(NCS)2(H2O)4-x(THF)x units form layered motifs. The thermal behavior of Mg(SCN)2·4H2O and Mg(SCN)2·4THF was investigated by temperature dependent in situ XRPD, where Mg(SCN)2·4THF was found to acquire a room temperature (α-form) and high temperature modification (β-form). The phase transformation is associated with an order-disorder transition of the THF molecules and with a reversion of the stacking order of the layered motifs. Further heating eventually leads to the formation of Mg(SCN)2·2THF. There thiocyanate related sulfur atoms fill the voids in the coordination sphere of magnesium, which leads to the formation of one dimensional electroneutral ∞[Mg(NCS)2/2(SCN)2/2(THF)2] chains. All investigated Mg(SCN)2·(4 - x) H2O·xTHF phases exhibit a remarkable anisotropic thermal expansion, and Mg(SCN)2·4H2O and Mg(SCN)2·2THF were found to show both positive and negative thermal expansion coefficients.

Tb-diluted and Tb-rich apatite-type silicates with compositions Y

Thermally responsive crystals hold great potential for their use as actuating materials by acting as energy transducers to convert heat energy to mechanical work. Control over defined phase transition temperature with rapid reconfiguration is of great advantage for actuation. The thermosalient (TS) effect is a rarely observed phenomenon in coordination polymers (CPs), let alone the reversibility of thermosalience in CPs. Herein, we report the reversible TS effect in a one-dimensional CP due to the martensitic phase transition during both heating and cooling cycles. The TS effect was preceded by anisotropic thermal expansion showing high expansion coefficients. In addition, the nonmolecular crystals show reversible contraction and recovery during multiple heating-cooling cycles due to the self-restorative shape memory effect. The reversible actuation of the CP could be repeated for 20 heating-cooling cycles in differential scanning calorimetry experiments, suggesting its great potential as a multicyclic actuator. Such thermal responsive behavior is unique in metal-organic materials.

Gas capture and sequestration are valuable properties of metal-organic frameworks (MOFs) driving tremendous interest in their use as filtration materials for chemical warfare agents. Recently, the Zr-based MOF UiO-67 was shown to effectively adsorb and decompose the nerve-agent simulant, dimethyl methylphosphonate (DMMP). Understanding mechanisms of MOF-agent interaction is challenging due to the need to distinguish between the roles of the MOF framework and its particular sites for the activation and sequestration process. Here, we demonstrate the quantitative tracking of both framework and binding component structures using in situ X-ray total scattering measurements of UiO-67 under DMMP exposure, pair distribution function analysis, and theoretical calculations. The sorption and desorption of DMMP within the pores, association with linker-deficient Zr6 cores, and decomposition to irreversibly bound methyl methylphosphonate were directly observed and analyzed with atomic resolution. Metal-organic frameworks have been shown to adsorb and decompose chemical warfare agents, but their mechanism of action is not completely understood. Here the authors quantitatively track the binding and decomposition product structures of nerve-agent simulant dimethyl methylphosphonate in host UiO-67 through in situ X-ray total scattering measurements, pair distribution function analysis, and density functional theory calculations. BASF; U.S. Army Research Office [W911NF15-2-0107]; Defense Threat Reduction AgencyUnited States Department of DefenseDefense Threat Reduction Agency [CB3587]; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-SC0012704] Published version M.W.T. gratefully acknowledges support from BASF. A.M.P., D.T., and A.I.F. acknowledge support by the U.S. Army Research Office under grant number W911NF15-2-0107. J.J.M. and W.O.G. thank the Defense Threat Reduction Agency for support under program CB3587. This research used beamline 28-ID-2 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Advanced Research Computing at Virginia Tech is gratefully acknowledged for computational resources.

Summary Precise control over topologically intricate molecular architectures remains an open challenge for chemists due to their inherent structural complexity. We report a simple solvent-free strategy to selectively prepare two multi-component supramolecular crystalline systems based on the halogen bond, endowed with either an unknot topology or a Borromean-type entanglement. Real-time in situ monitoring of the solvent-free mechanochemical synthesis of these three-component halogen-bonded ionic co-crystals reveals that the choice of milling conditions leads to a switch in the supramolecular reaction trajectory, resulting in the selective formation of an open halogen-bonded network or a halogen-bonded Borromean-type assembly.

Chemistry of materials 33(18), 7337 - 7349 (2021). doi:10.1021/acs.chemmater.1c01755, While two-dimensional (2D) materials may preserve some intrinsic properties of the corresponding layered bulk material, new characteristics arise from their pronounced anisotropy or confinement effects. Recently, exceptionally high ionic conductivities were discovered in 2D materials such as graphene oxide and vermiculite. Here, we report on the water-assisted fast conduction of lithium ions in restacked lithium tin sulfide nanosheets. Li$_{0.8}$Sn$_{0.8}$S$_2$ exfoliates spontaneously in water and can be restacked into homogeneous films in which the lithium content is decreased, and a partial substitution of sulfur with hydroxyl groups takes place. Using a recursive supercell refinement approach in reciprocal space along with real-space pair distribution function analysis, we describe restacked lithium tin sulfide as a partially turbostratically disordered material composed of lithium-containing and lithium-depleted layers. In humid air, the material takes up multiple layers of water that coordinate lithium ions in the space between the layers, increasing the stacking distance and screening the interaction between lithium ions and the anionic layers. This results in a 1000-fold increase in ionic conductivity up to 47 mS cm$^{���1}$ at high humidities. Orientation-dependent impedance spectroscopy suggests a facile in-plane conduction and a hindered out-of-plane conduction. Pulsed field gradient nuclear magnetic resonance spectroscopy reveals a fast, simultaneous diffusion of a majority and a minority species for both 7Li and 1H, suggesting water-assisted lithium diffusion to be at play. This study enlarges the family of nanosheet-based ionic conductors and helps to rationalize the transport mechanism of lithium ions enabled by hydration in a nanoconfined 2D space., Published by American Chemical Society, Washington, DC

Covalent organic frameworks (COFs) have emerged as a new class of molecularly precise, porous functional materials characterized by a broad structural and chemical versatility, leading to a diverse range of applications. Despite the increasing popularity of COFs, fundamental aspects of their formation are poorly understood and profound experimental insights into their formation processes are still lacking. Here we use a combination of in situ X-ray powder diffraction and Raman spectroscopy to elucidate the reaction mechanism of mechanochemically synthesized imine COFs, leading to the observation of key reaction intermediates. Real-time monitoring provides experimental evidence of templating effects by the liquid additive for the subsequent pore formation and layer assembly. Moreover, the solid-state catalyst scandium triflate Sc(OTf)3 is revealed to be instrumental in directing the reaction kinetics and mechanism, resulting in products with crystallinity and porosity en par with solvothermally synthesized COFs. This work highlights the potential of mechanochemistry as a green synthetic route towards COF synthesis, and emphasizes the subtle interplay between choice of liquid additives, catalysts, and activation procedure.

Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart-Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks, or directly from corresponding linkers in a one-pot crystallisation-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive-sites on the pore wall, enable further post-synthetic functionalisation to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts.

Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart-Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks, or directly from corresponding linkers in a one-pot crystallisation-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive-sites on the pore wall, enable further post-synthetic functionalisation to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts.

Porphyrin-based metal-organic frameworks (MOFs), exemplified by the prototypical representatives MOF-525, PCN-221, and PCN-224 are among the most promising MOF systems for catalysis, optoelectronics, and solar energy conversion. However, subtle differences between synthetic protocols for these three MOFs give rise to vast discrepancies in purported product outcomes and description of framework topologies. Here, we reveal the type and disorder of the Zr-clusters based on a comprehensive synthetic and structural analysis spanning local and long-range length scales. Our analysis on PCN-221 reveals Zr6O4(OH)4 clusters in four distinct orientations within the unit cell, rather than Zr8O6 clusters as originally published, accompanied by random linker vacancies around 50%. We propose disordered PCN-224 (dPCN-224) as a unified model to understand PCN-221, MOF-525, and PCN-224 by varying the degree of orientational cluster disorder, linker conformation and vacancies, and cluster—linker binding. Our work thus introduces a new perspective on network topology and disorder in Zr-MOFs and pinpoints the structural variables that direct their functional properties.

Dy–Mg silicate Dy8Mg2(SiO4)6O2 has been prepared by high-temperature solid state reaction. It has an apatite type structure (P63/m) with the Dy atoms fully occupying the 6h site and being in random distribution with the Mg atoms at the 4f site. The compound reveals dual magnetization relaxation with widely varying contributions from fast (FR) and slow (SR) relaxation paths controlled by field and temperature. The SR path is stabilized by a strong magnetic field, exhibits a weak dependence of relaxation time τ on field and temperature, and sustains large τ of a few seconds up to a temperature of 40 K and under a field of 50 kOe. The analysis of the electronic structure and comparison with the known Dy-doped phosphate apatites suggests that the Orbach and Raman processes are suppressed.

Structural and morphological interplay between hard and soft phases determine the bulk properties of thermoplastic polyurethanes. Commonly employed techniques rely on different physical or chemical phenomena for characterizing the organization of domains, but detailed structural information can be difficult to derive. Here, total scattering pair distribution function (PDF) analysis is used to determine atomic-scale insights into the connectivity and molecular ordering and compared to the domain size and morphological characteristics measured by AFM, TEM, SAXS, WAXS, and solid-state NMR 1H–1H spin-diffusion. In particular, density distribution functions are highlighted as a means to bridging the gap from the domain morphology to intradomain structural ordering. High real-space resolution PDFs are shown to provide a sensitive fingerprint for indexing aromatic, aliphatic, and polymerization-induced bonding characteristics, as well as the hard phase structure, and indicate that hard phases coexist in both ordered and disordered states.

Powder samples of Ag3LiIr2O6 and Ag3LiRu2O6 were synthesized from alpha-Li2IrO3 and Li2RuO3 respectively by ion exchange in an AgNO3 melt. The crystal structures of the title compounds were solved from high resolution laboratory X-ray powder diffraction (XRPD) patterns and from pair distribution function (PDF) analysis using synchrotron X-ray powder diffraction data. In both crystal structures edge sharing LiO6/3- and (Ir/Ru)O-6/3-octahedra form honeycomb like layers that are stacked in a staggered fashion. Silver cations, situated in-between the layers mediate the interlayer interactions by linear O-Ag-O bonds. Anisotropic peak broadening in the XRPD patterns and diffuse scattering occurring as streaks in the precession electron diffraction (PED) patterns indicate the presence of stacking faults, which could be also visualized by high resolution transmission electron microscopy (HRTEM). Possible alternative stacking sequences were derived from the ideal crystal and incorporated into a microstructure model. By applying a supercell approach that randomly generates and averages stacking sequences based on transition probabilities and combining it with a grid search algorithm, the microstructures, i.e. the degrees of faulting in the structures of the title compounds were refined to the measured XRPD data. In result the crystal structures of Ag3LiIr2O6 and Ag3LiRu2O6 were found to be vastly faulted with almost no coherence of the stacked layers.

During the systematic investigation of the ternary system Ca(CH3COO)2-Ca(HCOO)2-H2O at room temperature, the congruent crystallisation of two solid calcium acetate formates was observed: the hitherto unknown Ca3(CH3COO)4(HCOO)2·4H2O and the poorly characterised Ca(CH3COO)(HCOO)·H2O. The latter is a frequently observed efflorescence phase found on calcareous objects and it could be also identified as a corrosion phase in a natural history collection of birds' eggs. Elemental and thermal analyses were employed to determine the phase compositions and by Raman and IR spectroscopy the presence of acetate and formate anions in both solids was confirmed. Laboratory X-ray powder diffraction data were used to solve the crystal structures. Ca3(CH3COO)4(HCOO)2·4H2O crystallises in a primitive tetragonal unit cell with space group P41212 and lattice parameters of a = 6.8655(1) A and c = 45.5454(6) A, while Ca(CH3COO)(HCOO)·H2O crystallises in a primitive monoclinic unit cell with space group P21/c and lattice parameters of a = 9.2729(1) A, b = 6.8002(1) A, c = 11.2219(2) A and β = 121.232(1)°. Calcium carboxylate zig-zag chains [Ca(μ2-RCOO)+]n (R = CH3 or H) are the main motif of both crystal structures. In Ca3(CH3COO)4(HCOO)2·4H2O these chains are exclusively composed of acetate anions, whereas in Ca(CH3COO)(HCOO)·H2O only formate anions are situated in the chains. The remaining places in the 7-8 fold coordination sphere of the calcium cations are filled by water molecules and additional carboxylate anions that interconnect neighbouring chains, which eventually leads to layered motifs in both structures.

The pyrochlore iridates ${A}_{2}$Ir${}_{2}$O${}_{7}$ are expected to host novel electronic phases due to the interplay of spin-orbit coupling and correlation on a frustrated lattice. Their properties and orbital character are reported to vary as a function of the distortion of IrO${}_{6}$ octahedra, which is scaled by the $A$ cation radius. Here, the authors report a new pyrochlore iridate In${}_{2}$Ir${}_{2}$O${}_{7}$ at the small $A$ cation and large distortion limit. By means of resonant inelastic x-ray scattering and band calculations they show that the orbital character of pyrochlore iridates largely depends on Ir-O-Ir intersite hopping rather than the local distortions. Furthermore, the In-O bond covalency in In${}_{2}$Ir${}_{2}$O${}_{7}$ suppresses this intersite hopping, generating a nearly pure ${J}_{\text{eff}}$=\textonehalf{} state, in contrast to other pyrochlore iridates.

Mechanochemistry provides a highly efficient, but still poorly understood route to synthesize and screen for polymorphs of organic solids. We present a hitherto unexplored approach to control the mechanism and outcome of mechanochemical cocrystallization through changes to the milling assembly, i.e. milling jar and balls. Whereas polymorph control of mechanochemical cocrystallization is typically discussed in terms of liquid additives, real-time synchrotron X-ray diffraction studies reveal a direct impact of the choice of milling media on the rate of formation and interconversion of cocrystal polymorphs. This effect enabled the discovery of a new polymorph of a cocrystal of nicotinamide and adipic acid, whose formation and conversion to the previously known, enantiotropically-related form, was readily controlled by milling in jars made of different materials.

Reaction of Zn(NCS)2 with 4-dimethylaminopyridine (DMAP) leads to the formation of three polymorphic modifications of Zn(NCS)2(DMAP)2 (I–Zn, II–Zn, and III–Zn), of which only the crystal structure of I–Zn is reported in literature. In all three modifications the Zn(II) cations are tetrahedrally coordinated by two terminal N-bonded thiocyanate anions and two DMAP ligands forming discrete complexes, which differ in the dihedral angle between the DMAP ring planes and the arrangement of the complexes in the crystals. All three modifications show melting, and the thermodynamic relations and the transition behavior were investigated by temperature-dependent X-ray powder diffraction, differential scanning calorimetry, thermomicroscopy, and solvent-mediated conversion experiments. These reveal that I–Zn and II–Zn as well as II–Zn and III–Zn are related by enantiotropism, whereas I–Zn and III–Zn are related by monotropism. The thermodynamic transition temperature between I–Zn and II–Zn is much lower than that betw...

SnTiO3 was successfully synthesized for the first time in bulk form by soft chemistry. STEM and Rietveld refinement show that SnTiO3 adopts a structure similar to the archetypical ilmenite-type structure, forming a honeycomb lattice of edge-sharing TiO6-octahedra, which are decorated with Sn2+. Given the formation of a van der Waals gap between the individual layers and hence close energetic minima of different stacking types, SnTiO3 forms multiple stacking orders and twinning domains that we describe by systematic DIFFaX-simulations. The structure is governed by the tin lone pairs, which influence the stacking of the layers as well as local distortions observed by EELS and NMR, potentially leading to a wide range of applications.

Reaction of Cd(NCS)2 with 4-methoxypyridine leads to the formation of four new compounds, of which one crystallizes in two different polymorphs. In Cd(NCS)2(4-methoxypyridine)4·(4-methoxypyridine)2 (1) and Cd(NCS)2(4-methoxypyridine)4 (2-I and 2-II) discrete complexes are found, in which the Cd cations are octahedrally coordinated by four 4-methoxypyridine co-ligands and two terminally N-bonded thiocyanate anions. For the polymorphs 2-I and 2-II no single crystals are available and therefore, the corresponding Mn(II) compound (2-I-Mn) was prepared, which is isotypic to 2-I, as proven by a Rietveld refinement. The crystal structure of 2-II was solved and refined from XRPD data. In [Cd(NCS)2(4-methoxypyridine)2] n (3), the Cd cations are also octahedrally coordinated but linked into linear chains by pairs of thiocyanate anions with all ligands in trans-position. {[Cd(NCS)2]3(4-methoxypyridine)5} n (4) also consists of chains but two different Cd coordination modes are observed. Two of the three crystallographically independent Cd cations show an octahedral coordination with a trans- or cis-arrangement of the N and S atoms of the anionic ligands, whereas the third one is in a distorted square-pyramidal coordination, with cis-coordination of the thiocyanate N and S atoms. Measurements using simultaneous thermogravimetry and differential scanning calorimetry of 2-I and 2-II show different heating rate dependent mass steps, in which the co-ligands are removed. In some of the residues obtained after the respective TG steps compound 3 was detected but no phase pure samples could be obtained.

Iridium(IV) oxides have gained increased attention in recent years owing to the presence of competing spin–orbit coupling and Coulomb interactions, which facilitate the emergence of novel quantum phenomena. In contrast, the electronic structure and magnetic properties of IrIV-based molecular materials remain largely unexplored. In this paper, we take a fresh look at an old but puzzling compound, Na2IrCl6, which can be hydrated to form two stable phases with formulas Na2IrCl6·2H2O and Na2IrCl6·6H2O. Their crystal structures are well illustrated based on X-ray powder diffraction data. Magnetic studies reveal that Na2IrCl6 and Na2IrCl6·2H2O are canted antiferromagnets with ordering temperatures of 7.4 and 2.7 K, respectively, whereas Na2IrCl6·6H2O is paramagnetic down to 1.8 K. First-principle calculations on Na2IrCl6 reveal a Jeff = 1/2 ground state, and the band structures show that Na2IrCl6 is a spin–orbital-induced semiconductor with an indirect gap of about 0.18 eV.

The demand to outperform current technologies pushes scientists to develop novel strategies, which enable the fabrication of materials with exceptional properties. Along this line, lightweight structural materials are of great interest due to their versatile applicability as sensors, catalysts, battery electrodes, and acoustic or mechanical dampers. Here, we report a strategy to design ultralight (ρ = 3 mg/cm3) and hierarchically structured ceramic scaffolds of macroscopic size. Such scaffolds exhibit mechanical reversibility comparable to that of microscopic metamaterials, leading to a macroscopically remarkable dynamic mechanical performance. Upon mechanical loading, these scaffolds show a deformation mechanism similar to polyurethane foams, and this resilience yields ultrahigh damping capacities, tan δ, of up to 0.47.

Supercritical carbon dioxide (CO2) is an established medium for synthesizing molecular compounds and activation of microporous solids, but is much less explored for transformations of high-melting ionic reactants, such as metal oxides. We show that supercritical CO2 enables direct, clean, and rapid transformation of zinc oxide into zeolitic imidazolate frameworks (ZIFs), without requiring toxic or corrosive metal nitrate or chloride precursors, organic or aqueous solvents, additives, or auxiliaries. While recent syntheses of coordination polymers and metal–organic frameworks from supercritical CO2 highlighted the need for specialized metal reagents designed for solubility, we unexpectedly find that ZnO is quantitatively converted into grams of diverse ZIFs in minutes, with hundred grams of popular ZIF-8 accessible within an hour.

White efflorescence crystals grown on the surfaces of a bronze bowl, classical ceramic and ancient wine jugs were investigated. X-ray powder diffraction (XRPD) revealed that in each case an identical, hitherto unknown phase was formed. The crystal structure was solved from high resolution XRPD measurements and revealed a phase composition of Ca 2 (CH 3 COO)(HCOO)(NO 3 ) 2 ·4H 2 O, which is in accordance with the complementary analysis. The overall structural motif of Ca 2 (CH 3 COO)(HCOO)(NO 3 ) 2 ·4H 2 O, one dimensional calcium carboxylate zig zag chains in which acetate and formate ions are arranged in an alternating fashion, is closely related to other naturally occurring or artificial efflorescence salts like thecotrichite or calclacite.

Hydration of anhydrous LiSCN by stoichiometric amounts of water vapor leads to the formation of LiSCN ⋅ 1 H2O. At room temperature, LiSCN ⋅ 1 H2O crystallizes in the monoclinic space group C2/m with a = 15.0271(3) A, b = 7.5974(1) A, c = 6.7070(1) A, β = 96.147(6) ° and V = 761.32(2) A³ (α-phase). At 49 °C, the material transforms into a high temperature β-phase with the orthorhombic space group Pnam and a = 13.2258(2) A, b = 7.0619(9) A, c = 8.1663(1) A and V = 762.72(2) A³. Structural and thermodynamic investigations were conducted using infrared (IR) spectroscopy, ex situ and in situ X-ray powder diffraction (XRPD) while varying temperature or water partial pressure p H 2 O , differential scanning calorimetry (DSC) and direct measurements of equilibrium p H 2 O . The results indicate that LiSCN ⋅ 1 H2O is a special case when compared to LiSCN ⋅ n H2O (n = 0 or 2), both regarding crystal structure and hydration thermodynamics. These results are combined with literature date into an updated phase diagram of the LiSCN – H2O system, showing a detailed picture of the phase formation behavior of the LiSCN ⋅ n H2O hydrates.

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) A, b = 14.4246(2) A, c = 10.7333(1) A 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.

Um Sammlungsguter wie Geschirr, Kruge und Bilder in Museen und Sammlungen sachgemas zu konservieren, mussen die Korrosionsprodukte im Detail bekannt sein. Methoden der Rontgenpulverdiffraktometrie helfen, die Carbonat-, Acetat- und Formiatphasen zu charakterisieren, Einkristalle sind nicht notig.

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.

The reaction of Ni[CO3] with an aqueous solution of the free acid (H3O)2[B12Cl12] leads to green single crystals with the composition Ni(H2O)6[B12Cl12] · 6 H2O. This compound crystallizes in the orthorhombic space group Pnnm with a = 1798.86(9), b = 1312.49(7), c = 1373.63(7) pm for Z = 4. Thermal decomposition studies revealed the possibility for a multi-step dehydration process with the loss of all interstitial and cation-hydrating crystal water molecules. Temperature-dependent X-ray powder diffraction (XRPD) measurements show two characterizable degradation products between 30 and 450 °C. Ni(H2O)6[B12Cl12] was obtained at 30 °C after the loss of all interstitial water molecules as pale green powder with a cubic crystal structure (a = 1700.02(5) pm, Z = 8) and Fm 3 ¯ c as space group, displaying a CsCl-type arrangement. The six water molecules of hydration, which coordinate each Ni2+ cation show fourfold disorder. Above 450 °C all remaining water molecules have left the sample and the color shifts to yellow indicating the formation of anhydrous Ni[B12Cl12]. This water-free salt crystallizes also in the cubic system (a = 986.71(9) pm, Z = 2), but with Im 3 ¯ as space group. In the crystal structure the Ni2+ positions are occupied only by 1/4 and each of them is coordinated by two [B12Cl12]2− anions attached via two faces offering six chlorine atoms in an octahedral shape.

Solid oxides with transition metals ions in unusual oxidation states attract enormous attention due to their electronic, magnetic and catalytic properties. Yet, no crystalline oxide compounds based on purely trivalent iridium have been characterized to date. Here, we present the synthesis and thorough investigation of the properties of the compounds K0.75Na0.25IrO2 and IrOOH, both containing trivalent iridium on a triangular lattice in layers of [IrO2]x-. K0.75Na0.25IrO2 crystallizes in a P2-structure with the space group P63mmc, while the crystal structure of IrOOH adopts the direct maximal subgroup P-3m1. The trivalent state of the iridium ion is discussed with regards to the iridium-oxygen bond length from X-ray diffraction, the chemical composition, the electronic and magnetic behavior of the material as well as X-ray photoemission spectroscopy. The discovery of a new valence state in ternary crystalline iridium oxides is not only of interest from a fundamental perspective, but has far-reaching implic...

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.

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.

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) A, b = 12.3979(2) A, c = 8.3732(1) A, β = 90.673(1) and V = 810.62(2) A³. The crystal structure of the hitherto unknown β-Gly-ZnSO4 with space group P21/c (no. 14) and a = 9.2577(1) A, b = 5.1268(1) A, c = 12.9926(1) A, β = 90.267(1) and V = 616.65(1) A3 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.

A sodium copper formate, first described in 2002, can also form on copper alloys with sodium originating from soda glass hydrolysis. The frequent occurrence (50% of 250 cases of glass-induced metal...

Although carbonyl iron powder (CIP) is an old material for magnetic applications (e.g. inductor cores), the structure of this material is still described controversially in literature. On the first glance a greyish powder exhibiting a spherical structure, CIP reveals on the second glance a nanoscopic crystalline sub-structure. The material itself contains carbon and nitrogen and its structure is described as an onion-type structure. However, the nature of the different shells and clarity on the nature of the involved carbidic and/or nitridic phases, be they crystalline, amorphous or solid solutions has not yet been achieved. In addition, it is known, that CIP transforms in H2-atmosphere to a “soft” grade, consisting of pure Fe. Again, chemical and microstructural knowledge on the transition from the “hard” to the “soft” CIP is lacking. This leads to the motivation of this study: 1. Unambiguously identify the nature and existence of the involved phases in the unreduced and hard carbonyl iron powder and in the reduced and soft iron powder particles 2. Characterize the phase transformations and microstructural changes of CIP during the thermic treatment in a hydrogen atmosphere. Different techniques were used to clarify the above mentioned points like in-situ synchrotron XRPD accompanied by electron microscopy techniques.

Reaction of Co(NCS)2 with 2,6-dimethylpyrazine (2,6-DMPy) leads to the formation of a compound with the composition Co(NCS)2(2,6-DMPy)4 (Co-0D) that consists of discrete complexes, in which the Co cations are octahedrally coordinated. Upon heating, half of the 2,6-DMPy ligands are removed leading to the two-dimensional coordination polymer [Co(NCS)2(2,6-DMPy)2]n (Co-2D), shown by thermogravimetry and X-ray powder diffraction. On further heating, the intermediate Co-2D loses the next 2,6-DMPy ligand and transforms into [Co(NCS)2(2,6-DMPy)]n (Co-3D). The crystal structures of Co-2D and Co-3D were solved and refined using powder X-ray diffraction data. The crystal structure of Co-2D consists of octahedrally coordinated Co cations that are linked by pairs of anionic ligands into dimers, which are further connected by single thiocyanate anions into layers. In Co-3D, octahedrally and tetrahedrally coordinated Co cations are present, that are linked by μ-1,3-bridging single thiocyanate anions into a novel three-...

We prepared trirutile-type polycrystalline samples of CuTa2O6 by low-temperature decomposition of a Cu–Ta–oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure. GGA+U density functional calculations of the spin-exchange parameters as well as magnetic susceptibility and isothermal magnetization measurements reveal that CuTa2O6 is a new 1D Heisenberg magnet with predominant anti-ferromagnetic nearest-neighbor intrachain spin-exchange interaction of ∼50 K. Interchain exchange is a factor of ∼5 smaller. Heat capacity and low-temperature high-intensity neutron powder diffraction studies could not detect long-range order down to 0.45 K.

The investigation of the corrosion of a lid made from a tin–lead alloy of a 200 years old beer jug induced by the degradation of the potash based glass revealed SnO, Cerussite (PbCO3) and K(OH)·2PbCO3 as main corrosion product. A model experiment, simulating the corrosion of lead at room temperature confirmed the formation of K(OH)·2PbCO3 as a corrosion product in alkaline, potassium containing medium. For detailed characterization K(OH)·2PbCO3 was prepared by hydrothermal synthesis, as well. K(OH)·2PbCO3 crystallizes in space group P63/mmc with lattice parameters of a = 5.3389(1) A and c = 13.9295(5) A. The structure consists of Pb(OH)1/2(CO3)6/9[CO3]3/91/2- layers and intercalated K+ and exhibits a close relationship to the crystal structure of hydrocerussite (Pb(OH)2·2PbCO3), also known as “lead white”. A novel structure family, Mn+(OH)n·2PbCO3 (with n = 1,2), was identified by structure solution of K(OH)·2PbCO3, which can be assigned to a 2H-type subspecies and detailed comparison to Pb(OH)2·2PbCO3, w...

Inorganic chemistry 56(10), 5489 - 5492 (2017). doi:10.1021/acs.inorgchem.7b00325, In recent years, continuous process technologies have attracted increasing attention, as a means of overcoming limitations in the repeatability and reproducibility of metal–organic framework (MOF) synthesis. Research in this area, however, has neglected to provide insight into the phenomenon leading to the formation of MOFs. In this work, we report the adaption of high-energy synchrotron powder X-ray diffraction analysis to a continuous ZIF-8 production process for online monitoring of the reaction behavior and crystallite formation during the first seconds of the MOF synthesis. It was confirmed that a diffusion-controlled growth mechanism was accelerated by additional radial diffusion processes in the flow reactor. Kinetic analysis revealed a rapid crystallite formation of ZIF-8, which was completed after 8 s of reaction time and which offers the potential for future process optimization., Published by ACS Publ., Washington, DC

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.

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-I-Mepyz-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.