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A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH4)2 and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg3{(Im)BH2(Im)}6(ImH)6] ·CH3CN crystallizes in the space group R¯3, having the unit cell parameters a = 15.1942(2)˚A and c = 28.3157(3)˚A as determined by single crystal X-ray diffraction. The structure was further investigated by solid state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg2+ ions are bridged with {(Im)BH2(Im)}– units, forming inside voids of 4.6˚A in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense 1 Page 1 of 32 ACS Paragon Plus Environment Submitted to Inorganic Chemistry 123456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 ◦C. Using an alternative synthesis method from imidazole melt, an imidazole solvate with the formula [Mg3{(Im)BH2(Im)}6(ImH)6] ·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 ◦C. Upon further heating, it transformed into a layered structure with the formula Mg(Im3BH)2, space group P¯31c, and unit cell parameters a = 8.7442(4)˚A, c = 17.643(2)˚A determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

Understanding the interplay between lattice mismatch and supersaturation in the hydrothermal topochemical transformation from Bi4Ti3O12 to SrTiO3 nanoplatelets in view of nucleation–crystallization theory and atomic scale interfacial analysis.

High-temperature phase relations in the La2O3–TiO2–Nb2O5 ternary system were investigated at 1290 °C using SEM, EDS and XRD, and a subsolidus phase equilibrium diagram was constructed. It was demonstrated that the addition of the La1/3NbO3 to the La2O3:3TiO2 mixture completely stabilizes a perovskite-La2/3TiO3 compound, which is otherwise not stable at stoichiometric composition. On the other hand, a mixture La2O3:TiO2 =1:3 dissolves in La1/3NbO3 up to 15 mol% TiO2. Moreover, a newly defined composition of compound La30Ti16Nb4O87 formed in the La2O3-rich part of the system and a solid solution La3Ti5Nb10O39.5–La2Ti2Nb8O27 were proposed. In the binary subsystem LaTiNbO6-La0.462Ti0.386Nb0.614O3, the components exhibit opposite temperature dependence of resonant frequency in the microwave frequency range. Thus, the dielectric properties of the prepared ceramics can be tailored by varying the component concentration and thermally stable dielectric properties can be achieved for a composition with a LaTiNbO6/La0.462Ti0.386Nb0.614O3 molar ratio of 0.27.

In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of “dirty” superconductors.

Ferroelectric Bi4Ti3O12 nanoparticles can be hydrothermally synthesized in two distinct morphologies, i.e., nanoplatelets and nanowires. The nanowires exhibit a new layered crystal structure that has not been described before.

In this study, we investigate the scandium-containing Sc-Hf-Nb-Ta-Ti-Zr system of refractory high-entropy alloys (HEAs). Using the arc-melting method, we synthesized nine equimolar alloys (five 4-, three 5- and one 6-component), with all of them containing Sc. The alloys were characterized by XRD, electron microscopy and EDS, while superconductivity was investigated via electrical resistivity, specific heat and the Meissner effect. The results were compared to the parent Hf-Nb-Ta-Ti-Zr refractory HEAs, forming a single-phase body-centered cubic (bcc) structure and quite homogeneous microstructure. The addition of Sc produces a two-phase structure in the Sc-Hf-Nb-Ta-Ti-Zr alloys, with one phase being bcc and the other hexagonal close-packed (hcp). The hcp phase absorbs practically all Sc, whereas the Sc-poor bcc phase is identical to the bcc phase in the Hf-Nb-Ta-Ti-Zr parent system. Upon the Sc addition, the microstructure becomes very inhomogeneous. Large bcc dendrites (10–100 µm) are homogeneous in the central parts, but become a fine dispersion of sub-micron precipitates of the bcc and hcp phases close to the edges. The interdendritic regions are also a fine dispersion of the two phases. Superconductivity of the Sc-Hf-Nb-Ta-Ti-Zr alloys originates from the bcc phase fraction, which demonstrates identical superconducting parameters as the bcc Hf-Nb-Ta-Ti-Zr parent alloys, while the Sc-containing hcp phase fraction is non-superconducting.

High-entropy alloys (HEAs) are characterized by a simultaneous presence of a crystal lattice and an amorphous-type chemical (substitutional) disorder. In order to unravel the effect of crystal-glass duality on the electronic transport properties of HEAs, we performed a comparative study of the electronic transport coefficients of a 6-component alloy Al

Mo$_8$O$_{23}$ is a low-dimensional chemically robust transition metal oxide coming from a prospective family of functional materials, MoO$_{3-x}$, ranging from a wide gap insulator $(x=0)$ to a metal $(x=1)$. The large number of stoichometric compounds with intermediate $x$ have widely different properties. In Mo$_8$O$_{23}$, an unusual charge density wave transition has been suggested to occur above room temperature, but its low temperature behaviour is particularly enigmatic. We present a comprehensive experimental study of the electronic structure associated with various ordering phenomena in this compound, complemented by theory. Density-functional theory (DFT) calculations reveal a cross-over from a semi-metal with vanishing band overlap to narrow-gap semiconductor behaviour with decreasing temperature. A buried Dirac crossing at the zone boundary is confirmed by angle-resolved photoemission spectroscopy (ARPES). Tunnelling spectroscopy (STS) reveals a gradual gap opening corresponding to a metal-to-insulator transition at 343 K in resistivity, consistent with CDW formation and DFT results, but with large non-thermal smearing of the spectra implying strong carrier scattering. At low temperatures, the CDW picture is negated by the observation of a metallic Hall contribution, a non-trivial gap structure in STS below $\sim 170$ K and ARPES spectra, that together represent evidence for the onset of the correlated state at $70$ K and the rapid increase of gap size below $\sim 30$ K. The intricate interplay between electronic correlations and the presence of multiple narrow bands near the Fermi level set the stage for metastability and suggest suitability for memristor applications., Comment: 13 pages, 6 figures, pre-print of an article published in Scientific Reports. The final authenticated version is available online at http://dx.doi.org/10.1038/s41598-019-52231-4

Lysosomal cysteine peptidase cathepsin B (catB) is an important tumor-promoting factor involved in tumor progression and metastasis representing a relevant target for the development of new antitumor agents. In the present study, we synthesized 11 ruthenium compounds bearing either the clinical agent nitroxoline that was previously identified as potent selective reversible inhibitor of catB activity or its derivatives. We demonstrated that organoruthenation is a viable strategy for obtaining highly effective and specific inhibitors of catB endo- and exopeptidase activity, as shown using enzyme kinetics and microscale thermophoresis. Furthermore, we showed that the novel metallodrugs by catB inhibition significantly impair processes of tumor progression in in vitro cell based functional assays at low noncytotoxic concentrations. Generally, by using metallodrugs we observed an improvement in catB inhibition, a reduction of extracellular matrix degradation and tumor cell invasion in comparison to free ligands, and a correlation with the reactivity of the monodentate halide leaving ligand., Eleven ruthenium compounds bearing either the clinical agent nitroxoline or its potent cathepsin B (catB) inhibiting derivatives were evaluated as antimetastatic agents. We demonstrated that organoruthenation is a viable strategy for obtaining highly effective and specific inhibitors of catB activities, as shown using enzyme kinetics and microscale thermophoresis. Furthermore, we showed that the novel metallodrugs significantly impair processes of tumor progression in in vitro cell based functional assays at low noncytotoxic concentrations.

This study was designed to better understand the microstructural and phase evolution of lead-free sodium potassium niobate based piezoceramics with a nominal composition (K0.5Na0.5)0.99Sr0.005NbO3 (KNNSr) during pressure-less spark plasma sintering followed by post-annealing in oxygen. The as-sintered samples were dark-coloured and electrically conductive as a result of partial reduction of Nb5+ to Nb4+ and formation of oxygen vacancies confirmed by X-ray photoelectron and Raman spectroscopy. The Rietveld refinement analysis showed that the as-sintered samples contained two perovskite phases with monoclinic Pm unit cell and slightly different unit-cell parameters. The microstructure with sub-micrometre-sized grains unambiguously confirmed that rapid heating and short dwell time hindered the grain growth. We found that post-annealing the samples at 950 °C in oxygen led to improvement in functional properties. The samples became white-coloured, the both perovskite unit cells decreased as a result of re-oxidation, while the microstructure remained essentially unchanged. The KNNSr sintered at nominal sintering temperature of 1300 °C for 3 min and post-annealed possessed a relative density of 88% and dielectric and piezoelectric properties similar to those of the conventionally sintered samples. Our findings contribute to the understanding of pressure-less spark plasma sintering of sodium potassium niobate-based materials and suggest that arrested grain growth and minimisation of alkali evaporation not necessarily lead to dense ceramic.

We present a study of the magnetic phase diagram and the magnetoresistance of a Gd–Tb–Dy–Ho–Lu "ideal" hexagonal high-entropy alloy (HEA), composed of the elements from the heavy half of the rare earth series only. The phase diagram contains an antiferromagnetic (AFM) state, a field-induced ferromagnetic (FM) state above the AFM-to-FM spin-flop transition and a low-temperature spin-glass state. The complex ( H , T ) phase diagram is a result of competition between the periodic potential arising from the electronic band structure that favors periodic magnetic ordering, the substitutional-disorder-induced random local potential that favors spin-glass-type spin freezing in random directions, the Zeeman interaction with the external magnetic field that favors spin alignment along the field direction and the thermal agitation that opposes any spin ordering. The magnetoresistance reflects complexity of the ( H , T ) phase diagram. Its temperature dependence can be explained by a continuous weakening and final disappearance of the periodic potential upon cooling that leads to the destruction of long-range ordered periodic magnetic structures. The magnetoresistance is large only at temperatures, where the AFM and field-induced FM structures are present and exhibits a maximum at the critical field of the AFM-to-FM transition. Within the AFM phase, the magnetoresistance is positive with a quadratic field dependence, whereas it is negative with a logarithmic-like field dependence within the field-induced FM phase. At lower temperatures, the long-range periodic spin order "melts" and the magnetoresistance diminishes until it totally vanishes within the low-temperature spin glass phase. The magnetoresistance is asymmetric with respect to the field sweep direction, reflecting nonergodicity and frustration of the spin system.

In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of “dirty” superconductors.

The CoCrFeMnNi high-entropy alloy (HEA) is a magnetically concentrated crystalline system with all lattice sites magnetic, containing randomness (five different types of spins are randomly positioned on the lattice) and frustration (a consequence of mixed ferromagnetic and antiferromagnetic interactions). The sample material was prepared as a non-equiatomic, fully random solid solution of the five magnetic elements and we have studied experimentally the nature of the magnetic state. Upon cooling, no long-range magnetic ordering takes place, but the spin system undergoes a kinetic freezing transition to a spin glass phase, where below the spin freezing temperature T f ≈ 20 K, ergodicity of the system is broken. The observed broken-ergodicity phenomena include zero-field-cooled – field-cooled magnetization splitting in low magnetic fields, a frequency-dependent cusp in the ac susceptibility, an ultraslow time-decay of the thermoremanent magnetization and the memory effect, where the state of the spin system reached upon isothermal aging at a certain temperature can be retrieved after a reverse temperature cycle. All these phenomena are associated with the out-of-equilibrium dynamics of a nonergodic, frustrated system of coupled spins that approach thermal equilibrium, but can never reach it on a finite experimental time scale, so that we are observing only transient effects of partial equilibration within localized spin domains.

We address the nature of the collective magnetic state in an ideal high-entropy alloy (HEA), representing a magnetically concentrated system with all lattice sites occupied by localized magnetic moments and containing randomness and frustration due to chemical disorder. Being a “metallic glass on a topologically ordered lattice”, HEAs possess simultaneously the properties of an ordered crystal and an amorphous glass. The influence of this crystal-glass duality on the collective magnetic state was studied experimentally on a hexagonal Tb-Dy-Ho-Er-Tm (TDHET) HEA, composed of rare-earth (RE) elements with zero pair mixing enthalpies that assure completely random mixing of the elements and very similar atomic radii that minimize lattice distortions, representing a prototype of an ideal HEA. The TDHET HEA is characterized by probability distributions of the atomic moments P ( μ ) , the exchange interactions P ( J ) , the magnetocrystalline anisotropy P ( D ) , and the dipolar interactions P ( H d ) . Based on the measurements of the static and dynamic magnetization, the magnetization M ( H ) curves, the thermoremanent magnetization, the specific heat and the magnetoresistance, we found that the collective magnetic state of the TDHET is temperature-dependent, forming a speromagnetic (SPM) state in the temperature range between about 140 and 30 K and an asperomagnetic (ASPM) state below 20 K. In the intermediate temperature range between 30 and 20 K, a spin glass (SG) state is formed, representing a transition state between the speromagnetic and asperomagnetic states. The observed temperature evolution of the magnetic ground state in the TDHET HEA upon cooling in the sequence SPM→SG→ASPM is a result of temperature-dependent, competing magnetic interactions. The distribution of the exchange interactions P ( J ) shifts continuously on the J axis from the high-temperature SPM-type with the average interaction biased towards a net negative value, J ‾ 0 , through the SG-type with J ‾ = 0 , to the low-temperature ASPM-type with J ‾ > 0 . This shift is a band-structure effect, closely linked with the crystallinity of the spin system, which the TDHET HEA shares with the topologically ordered crystals. The probability distributions P ( μ ) , P ( J ) , P ( D ) and P ( H d ) are, on the other hand, a consequence of chemical disorder, a property that the TDHET HEA shares with the amorphous magnets. Both features, the topologically ordered lattice and the amorphous-type chemical disorder essentially determine the magnetic state of an ideal, RE-based HEA.

ABO 3 -type perovskite crystallites with symmetrical crystal structures do not show a tendency to grow in the shape of rods and plates, which are of great scientific interest due to their anisotropic physical properties. A topochemical transformation is one of the most convenient approaches for the preparation of such defined-shape perovskite particles, the functional properties of which can be additionally tailored by the formation of solid solutions. In this study a one-step topochemical conversion reaction from a Bi 4 Ti 3 O 12 template to A-site-substituted complex Ba 1-x Sr x TiO 3 perovskite microplates was investigated in order to understand the mechanism and to determine the compositional, structural and morphological correlations between the template and the final plate-like particles. Based on our finding that Sr incorporates in a 2.7-times larger amount than expected from the initial Ba/Sr ratio (0 1-x Sr x TiO 3 solid-solution composition could be prepared using this topochemical transformation. The tetragonal distortion of the Ba 1-x Sr x TiO 3 plates, expressed as the c/a ratio, was found to decrease linearly from 1.0092 (x = 0) to 1.0037 (x = 0.23), while the compositions with higher x were cubic (c/a=1). According to a piezo-response force microscope (PFM) examination, Ba 1-x Sr x TiO 3 plates with 0 ≤x ≤ 0.175 showed ferroelectric and piezoelectric characteristics. The temperature of the ferroelectric-to-paraelectric phase transition, as determined by differential scanning calorimetry (DSC), linearly decreased from 124 °C (x = 0) to 88 °C (x = 0.11). XRD examinations revealed a strong (001) preferential orientation for the plates (0 ≤ x ≤ 0.11) and the typical (001)/(100) peak splitting indicated the presence of c - and a -domains. The successful preparation and design of Ba 1-x Sr x TiO 3 plates increase the potential of this topochemical transformation for the preparation of plates with a variety of solid-solution compositions and controlled characteristics.

The conversion of the biomass-derived lipid, lignocellulosic and carbohydrate resources into renewable platform intermediates, chemicals and biofuels has been lately increasing in interest. The mechanistic reaction pathways, like hydro-deoxygenation, decarboxylation and hydrocracking, of the selected palmitic acid, as a model fatty acid, over Ni/ZSM-5 zeolite catalysts were studied. The ZSM-5 material with different Al/Si molar ratios was synthesized via a green template-free hydrothermal synthesis procedure, treated and subsequent functionalised with various Ni metal loadings. However, Ni/Al molar ratio was kept stoichiometric (Ni/Al = 0.5). The characteristic physicochemical properties of composite catalysts were studied by numerous characterization techniques, such as X-ray powder diffraction (XRD), scanning-, as well as high-resolution transmission electron microscopy (SEM/HRTEM), and X-ray photoelectron spectroscopy (XPS). NiO with an average particle size of 10–20 nm was found on ZSM-5 support. The relative Ni/Al atom fraction in Ni/ZSM-5 systems influenced their Lewis/Bronsted acidic sites, as well as the external exposed area of prepared heterogeneous structures. Furthermore, the mentioned morphological parameters affected predominant catalytic routes. Species’ production mechanism, as a consequence of Lewis/Bronsted centre weak/strong acidity, as well as their integral concentration, was proposed, mirroring the observed process kinetics, selectivity and turnover. It was demonstrated that the main obtained products were esters, aldehydes, alcohols, hydrocarbons and gases (CO2, CO…), produced by deoxygenation (e.g. decarbonylation), hydrogenation and cracking, less, though, through isomerisation.

Two different quaternary ammonium cations, methyltriethyl- (MTEA) and tetraethylammonium cations (TEA) were used as templates in the synthesis of pure-silica as well as aluminosilicate ZSM-12 (MTW-type) frameworks. The distribution of the template cations in the 12-membered rings channels in the 1-dimensional framework topology was studied; thus the as-prepared products were characterized by means of X-ray powder diffraction, Raman, transmission FTIR, solid-state NMR spectroscopy, thermogravimetric and elemental analyses and SEM. It was shown that in pure-silica (PS) ZSM-12, TEA cations are well ordered - a superstructure with three-times longer b edge (in comparison to unit cell of empty framework) along the channel is formed, which can be seen by virtue of a few additional peaks in the X-ray powder pattern. Herein we describe that its aluminosilicate counterpart with TEA also contains ordered TEA cations and is isostructural to PS-ZSM-12. Conversely, in both pure-silica and aluminosilicate ZSM-12 frameworks with MTEA, the cations are disordered and no superstructure is formed.

Reversible colour change of leuco dye-based composites is in general closely related to their phase change, thus the two phenomena should occur at around the same temperature and should be influenced similarly. However, spatial confinement of the analysed sample affects the change in colour differently compared to its phase transition and the most pronounced effects can be observed during cooling. The bulk composite is coloured while still liquid and the colour hysteresis does not exhibit a loop. In an open-porous medium the colouration coincides well with the crystallization and the colour hysteresis widens to about 4 °C. Microencapsulated composite exhibits two crystallization processes, one of them taking place at the bulk crystallization temperature and the other one at about 20 °C lower. Under such conditions the composite is coloured just before the onset of the second crystallization, i.e. about 15 °C below crystallization in the bulk, and the corresponding colour hysteresis widens to 18 °C. The two crystallization forms are thermally independent and have the same crystalline structure. These effects should be taken into account when designing future applications where the phase-changing materials are implemented.

High-temperature reactions during the solid-state synthesis of samples from the (1-x)Na 0.5 Bi 0.5 TiO 3 –xSrTiO 3 system were investigated. Due to the number of chemically different elements, the processing of these ceramics is delicate and requires several firing steps under specific conditions to obtain phase-pure samples. Sintering in an air atmosphere resulted in a macroscopically inhomogeneous microstructure, which is a consequence of incomplete reaction between different secondary phases. However, prolongation of the sintering time aggregated the pores in the sample, while at a higher firing temperature the sample’s secondary phase melted. As a result, the nominal composition was altered, leading to the formation of the Na 2 Ti 6 O 13 secondary phase. Sintering under an increased oxygen pressure of 1 MPa limited the evaporation of the secondary phase. This allowed the completion of the reaction, forming a homogeneous and dense sample. The study provides a set of experimental conditions for the successful preparation of ceramics from the investigated system.

Rare-earth (RE) based hexagonal high-entropy alloys (HEAs) containing elements from the heavy half of the RE series (from Gd to Lu) are considered as prototypes of an ideal HEA, stabilized by the entropy of mixing with completely random distribution of the elements on an almost undistorted hexagonal close-packed (hcp) lattice. Here we present a study of the Ce-Gd-Tb-Dy-Ho hexagonal HEA (abbreviated as HEA-Ce), where a light-RE element Ce is alloyed with four heavy-RE elements. Since the binary mixing enthalpies of Ce with these elements are all zero, random mixing of the elements and an ideal solid solution can also be expected. Contrary to the expectations, a two-phase structure forms in the HEA-Ce, consisting of the majority hcp matrix and the rhombohedral precipitates that occupy a significant fraction of the sample's volume, with both phases having very similar composition. The “ideality” of the HEA-Ce solid solution is very likely compromised by the fact that the crystal structure of Ce is different from the structures of other elements. By performing measurements of the magnetic properties, the specific heat and the electrical resistivity in a magnetic field, we have determined the magnetic state of the HEA-Ce. Long-range-ordered periodic magnetic structures do not form (like they do in the hexagonal HEAs containing heavy-RE elements only), but the magnetic structure breaks up into ferromagnetically (FM) polarized spin domains distributed in size that orient randomly in zero field. The magnetically ordered state of the HEA-Ce can be described as a disordered FM state with a 2nd-order thermodynamic FM phase transition at T C = 140 K. The introduction of Ce did not yield any of the phenomena that are exceptional for the Ce-containing alloys and compounds (mixed valence, heavy-fermion, unconventional superconductivity).

We have investigated the magnetism of CoCrFeNiZr x (x = 0.4–0.5) eutectic high-entropy alloys (HEAs) in relation to their microstructure by XRD, SEM, magnetization, specific heat and electrical resistivity measurements. Two structural phases develop in the CoCrFeNiZr x HEAs, a Zr-free fcc solid solution and a Zr-containing C15 Laves-phase intermetallic compound, where in both phases magnetic transition elements Co, Cr, Fe and Ni substitute each other in a random-like manner. Relative fractions of the two phases change substantially with the Zr concentration. Microstructurally, the two phases form alternatively grown fine lamellar structure typical of eutectic alloys. In addition, bulky dendrites of the fcc solid solution form in large number for the x = 0.40 concentration and in small number for x = 0.45. Two magnetic structures coexist in the CoCrFeNiZr x HEAs. The first is a disordered ferromagnetic (FM) phase that develops in the interior of large dendrites of the fcc solid solution and in some larger lamellas of this phase. The second phase is superparamagnetic-like and originates from the remaining spins of the fcc solid solution fraction, located at the surfaces and in the interfaces, and from all spins of the C15 Laves-phase fraction. The relative magnitude of the disordered FM-state magnetization with respect to the superparamagnetic magnetization in the samples with different Zr concentration is predominantly determined by the volume fraction of the fcc bulky dendrites. There is no one-to-one relation between the two magnetic structures on one side and the two structural components of the CoCrFeNiZr x eutectic mixtures on the other side. The magnetism of multi-phase HEAs containing magnetic elements cannot be described as a compositional average of magnetic properties of the constituent phases.

Vanadium(V) compounds with 3,5-difluoropicolinic acid (HpicFF) and 3-hydroxypicolinic acid (H2hypic) and zinc(II) compounds with HpicFF, H2hypic and 4-methylhydroxypicolinic acid (HpicCH2OH) in the presence or absence of pyridine (py), 4-(dimethylamino)pyridine (DMAP), and 1,10-phenanthroline (phen) have been synthesized and characterized. The crystal structures of NH4[VO2(picFF)2]·1.6H2O (3·1.6H2O), NH4[VO2(hypic)2]·H2O (4·H2O), [Zn(picFF)2(H2O)2] (5), [Zn(picFF)2(py)2]·py (6·py), [Zn(picFF)2(DMAP)2]·H2O (7·H2O), [Zn(picFF)2(phen)]·2CHCl3 (8·2CHCl3), [Zn(Hhypic)2(MeOH)2] (10), [Zn(Hhypic)2(DMAP)(H2O)] (11) and [Zn(Hhypic)2(phen)] (12) were determined by X-ray crystallography. The spatial arrangement of the vanadium(V) complex 3 possesses carboxylate oxygen atoms in a mutual trans orientation while crystal structure 4 represents the first crystallographic evidence for the formation of an isomer with two picolinato nitrogen atoms in a mutual trans position. Two different spatial arrangements were found in the zinc(II) complexes with trans (5, 10 and 11) and cis (6, 7, 8 and 12) octahedral geometry. Insulin-mimetic activity of the selected VIVO, VVO2 and ZnII complexes was studied by in vitro inhibition of the free fatty acid (FFA) release from isolated rat adipocytes treated with epinephrine. All the studied metal complexes showed insulin-mimetic activity. Vanadium complexes 1–4 exhibit activities similar to VOSO4 with the Hhypic complexes being more active than the picFF ones. The zinc complexes also exhibited some insulin-mimetic activity, with the Hhypic complex (9) being more active than the other two, however, the insulin-mimetic activity of these complexes did not show more potent activity than ZnSO4.

We have synthesized a range of novel cyclometallated organoruthenium(II) complexes through ortho-C-H activation of the aryl group in 2-aryl-substituted quinazolines with [RuX2(p-cymene)]2. The beneficial effect of the carboxylate ligand on both the cyclometallation and further arylation reaction step was demonstrated. Mechanistic studies reveal that bromide and iodide anions decelerates the arylation process via in situ ligand exchange reaction. Additionally, a detailed NMR investigation explains some elementary steps in the arylation of 2-(aryl)quinazoline-halido-ruthenacycles.

We present a study of superconductivity in Ta-Nb-Hf-Zr-Ti high-entropy alloys (HEAs) by investigating four samples of different atomic concentrations (equimolar and off-equimolar) and number of components (4 and 5), subjected to different thermal treatments. The structure of the samples varied between a homogeneous random solid solution and a partially ordered nanostructure in the form of a three-dimensional grid of short-range ordered atomic clusters enriched in Zr and Hf that has developed during long-time annealing. Superconductivity was found to be a robust phenomenon, being quite insensitive to the actual structure of the material. All investigated samples were superconducting in the entirety of their volumes. The superconducting transition temperatures T C of the samples are scattered in the range between 5.0 and 7.3 K and this scatter could be related to the degree of structural and chemical inhomogeneity of the samples. In the samples with partially ordered nanostructure, short-range atomic clusters possess a slightly different T C than the Ta- and Nb-rich matrix. Our results also demonstrate the important fact that the formation, stability and structure of a regular (non-ideal) HEA mixture are determined by both, the minimization of the mixing enthalpy that favors local atomic ordering and the maximization of the mixing entropy that favors a random solid solution. The actual equilibrium state achieved during long-time thermal annealing via the atomic diffusion is generally partially ordered, and the resulting nanostructure is a sensitive function of the number of components constituting the HEA, their concentrations, the differences in the atomic radii and the annealing temperature and time. This nanostructure essentially determines the electronic properties of HEA materials.

Vanadium(V) compounds with 5-cyanopicolinato acid (HpicCN), pyrazine-2-carboxylic acid (Hprz) and 3-aminopyrazine-2-carboxylic acid (HprzNH2) and zinc compounds with HpicCN in the presence of 4-aminopyridine (4apy), pyridine (py) and 1,10-phenanthroline (phen) have been synthesized and characterized. The crystal structures of NH4[VO2(picCN)2] (3), NH4[VO2(prz)2] (4), NH4[VO2(przNH2)2]·H2O (5·H2O), [Zn(picCN)2(H2O)2] (6), [Zn(picCN)2(4apy)2]·C7H8 (7·C7H8), [Zn(picCN)2(4apy)] (8), [Zn(picCN)2(py)2] (9) and [Zn(picCN)2(phen)]·C7H8·2MeOH (10·C7H8·2MeOH) were determined by X-ray crystallography. The spatial arrangements of all the vanadium(V) complexes are similar, having carboxylate oxygen atoms in a mutual trans orientation. In the zinc bis(5-cyanopicolinato) complexes three different arrangements were found with trans (6) and a cis (7, 9 and 10) octahedral and square-pyramidal (8) geometries. The insulino-mimetic activity of selected VO(IV), VO2(V) and Zn(II) complexes was studied by in vitro inhibition of the free fatty acid (FFA) release from isolated rat adipocytes treated with epinephrine. All metal complexes showed insulino-mimetic activity and among them the VO(IV)–prz complex 2 was found to have higher insulino-mimetic activity than the positive control. The other vanadium compounds have activities similar to VOSO4. The Zn complexes also exhibited some insulino-mimetic activity. Introduction of the N-donor 4apy to the zinc picCN complex 8 significantly increased inhibition of FFA release compared to 6.

Physicochemical evaluation of polyethylene oxide (PEO) polymers with various molecular weights was performed at molecular (polymeric dispersion) and bulk level (powders, polymeric films, and tablets) with the aim of specifying polymer critical material attributes with the main contribution to drug release from prolonged-release tablets (PRTs). For this purpose, grades of PEO with low, medium, and high viscosity were used for formulating PRTs with a good soluble drug substance (dose solubility volume 15 ml). The results revealed a good correlation (r2=0.88) between in vivo data (pharmacokinetic parameters: Cmax and AUC) and the elastic property of PEO films determined with the nanoindentation method, demonstrating that film level can also be used for the in vivo prediction of drug dissolution. The study confirmed that polymer molecular weight and its viscosity are the most important critical material attributes affecting drug dissolution (in vitro) and in vivo bioavailability (e.g. Cmax and AUC). Our research revealed that the nanoindentation technique can distinguish well between various types of polymers, classifying PEO as the most ductile and polyvinyl alcohol as the most brittle. Finally, our study provides an approach for the determination of exact physical attributes of PEO as a critical material attribute from clinically relevant data, and it therefore fulfills the basic principles of product development by Quality by Design.

Dinuclear ferrocene-based conjugates comprising a small homochiral sequence of two aminoacids (FcCO-Pro-Ala-NHFc) were prepared using stepwise solution-phase coupling techniques. The propensity of these bioorganometallics to form tight turns that resemble those in natural peptides was investigated by means of spectroscopy and the crystal structure was determined by X-ray diffraction analysis. The experimental data were corroborated by DFT calculations. The intramolecular NHFc⋯OCFc hydrogen bond keeps the molecule in the β-turn conformation. Molecules are further organized into bilayers with the inner region containing amino acid parts with relatively strong NHAla⋯OCAla hydrogen bonds, and the outer region linked by relatively weaker ferrocene⋯ferrocene interactions. The current research again confirms the robustness of the β-turn and its persistence in solution and in the solid state of small dinuclear ferrocene peptidomimetics.

This study was supported by the ERA-NET HarvEnPiez project. The authors would like to thank their national funding agencies (Latvian State Education Development Agency, Slovenian Ministry of Higher Education, Science and Technology, Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III – M-ERA NET Program)., The results of experimental and theoretical ab initio study of structural and piezoelectric properties of (Ba,Sr)TiO3 perovskite solid solutions are discussed and compared. Experimentally, plate-like (Ba,Sr)TiO3 particles were synthesized by the topochemical conversion in the molten salt from Bi4Ti3O12 template plates. All dimensions (side length ≈ 1 µm, thickness ≈ 200–400 nm) were well above the critical size necessary for observation of piezo- and ferroelectricity. The first-principles computations of the structural and electromechanical properties of solid solutions were performed with CRYSTAL14 computer code within the linear combination of atomic orbitals (LCAO) approximation, using three advanced hybrid functionals of the density-functional-theory (DFT). Different chemical compositions are considered for the ferroelectric and paraelectric phases. Calculated structural properties of solid solutions in tetragonal and cubic phases are in a very good agreement with experimental data. Experimentally obtained and calculated band gaps are compared for cubic SrTiO3 and tetragonal BaTiO3. BaTiO3/SrTiO3 heterostructures were considered theoretically for different chemical compositions. The calculated piezoelectric properties of solid solutions and heterostructures in ferroelectric phase are compared. It is predicted that both solid solutions and heterostructures improve the piezoelectric properties of the bulk BaTiO3, but solid solutions are more preferable for equal Sr concentrations., ERA-NET HarvEnPiez project; Latvian State Education Development Agency, Slovenian Ministry of Higher Education, Science and Technology, Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III – M-ERA NET Program; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Detailed characterization of calcium aluminate rich secondary steel slag derived from two different refining processes of stainless steel production has been performed in order to gain generic knowledge about this by-product, and its behaviour as a supplementary cementitious material. Additionally, slag blended cement composites were investigated and compared to a limestone filler blended cement composites and to a reference cement composites. The results showed that the investigated slag contained several hydraulic phases, mainly in the form of calcium aluminates. In the case of the slag cement composites, a larger proportion of hydration products was observed than in the case of the limestone cement composites, as well as a higher rate of strength increase.

A precise X-ray crystal structure determination of systems that exist in a polycrystalline form often poses a challenge due to several factors that limit the resolution of the diffraction measurement. The location of atoms is usually determined at significantly lower precision than the unit cell parameters, rendering the complete characterization of the structure difficult. This is particularly pronounced when precise location of hydrogen atoms is required, for instance in ionizable biomolecules or in hydrogen bonds. In such cases periodic quantum (DFT) calculations may crucially assist structure determination, because they can reliably predict the location of atoms, provided that the unit cell parameters, the space group and tentative atomic positions are known. In this work we present DFT-assisted structure determination of pentadecafluorooctanoic acid hydrate, a benchmark system featuring short hydrogen bonds (RO...O ≈ 2.5 Å) between acid and water molecules. While Rietveld refinement based solely on powder diffraction data cannot reliably resolve the location of crystal water molecules and even less so the position of hydrogen atoms in the network of hydrogen bonds, periodic DFT optimization yields several minimum energy structures suitable for further refinement. Due to the low experimental resolution and similarity, comparison between model and experimental powder diffraction pattern can barely distinguish between certain structure candidates provided by DFT calculations, but it can rule out those featuring larger misfits. The proposed structure solution is delivered from a tandem application of structure determination from powder diffraction data and DFT optimization, the former providing the unit cell parameters and estimated atomic positions that are finely tuned by DFT. The present strategy can in principle be generalized to other examples of structure determination at relatively low resolution, such as is often the case with biological macromolecules. This work is licensed under a Creative Commons Attribution 4.0 International License.

Sub-solidus phase relations in the ternary CaO–La2O3–TiO2 system at 1400 °C in air were determined. The multi-phase samples were prepared by a solid-state reaction method, whereas the single-phase samples for the structure analysis of selected solid solutions were prepared by a wet-precipitation method in order to provide good homogeneity of the starting mixtures. The phases in the prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The oxides form seven ternary compounds in the equilibrium state, many solid solutions (which extend across a broad concentration region), and a large, single-phase area based on the CaTiO3 solid solution. The structures of several new phases – solid solutions on the tie lines CaTiO3–Ca3La4Ti3O15 and La2TiO5–Ca3La4Ti3O15 – were determined in detail.

Structural information is crucial for understanding and tailoring the materials properties. When the materials are available only in the polycrystalline form, powder diffraction is the method of choice for structure determination. Compared to the single crystal data, the powder pattern contains less information due to the overlap problem and the reduction of the information content is even larger if only the low resolution data are available. Several data analysis approaches are available to address this problem, including reciprocal, direct and dual space methods. They are discussed and illustrated by a number of examples, including cases where other techniques, such as IR and NMR spectroscopy, electron microscopy and crystal-chemical knowledge have to be applied to solve the structure.

Seven different dioxido(pyridine-2,6-dicarboxylato)vanadate(V) compounds with pyridinium (Hpy+) (1·2H2O and 1), 2-hydroxypyridinium (H2pyon+) (2·H2O), 4-aminopyridinium (H4apy+) (3·H2O and 3), 4-(dimethylamino)pyridinium (Hdmap+) (4·H2O) and imidazolium (Himd+) (5) cations have been prepared via different pathways starting either from pyridine-2,6-dicarboxylic acid or its esters, and were structurally characterized by single-crystal X-ray diffraction. The vanadium metal center in dioxido(pyridine-2,6-dicarboxylato)vanadate(V) anion is pentacoordinated in all of the compounds: having two oxido oxygen atoms in a mutual cis position and a tridentate pyridine-2,6-dicarboxylic ligand. Study of hydrogen bonds and weak interactions in the compounds revealed the relationship between the type of cation and the hydrogen bonding network in the compounds. While in 1·2H2O, 2·H2O and 4·H2O a one-dimensional (band, pillar or chain) hydrogen bonding network via N/O–H⋯O bonds is preferred, anhydrous 3 and 3·H2O favor a two-dimensional hydrogen-bonded framework, and the Himd+ cation facilitates a three-dimensional hydrogen bonding in 5. The unique vanadium coordination environment with two easily accessible oxido oxygen atoms of the VO2+ unit is suitable for the construction of non-covalent metal–organic hybrids. In 2·H2O, 3·H2O, 4·H2O and 5 both oxido oxygen atoms of the VO2+ unit participate as acceptors, however, in 1·2H2O and 3 only one oxido oxygen atom is involved in classical hydrogen bonding. Besides N/O–H⋯O hydrogen bonding, also other weak non-covalent interactions, such as C–H⋯O, π⋯π and C–H⋯π interactions, play an important role in stabilizing the crystal lattices.

Four novel ruthenium organometallic complexes: [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)Cl] (1), [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)pta]PF$_6$ (2), [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)Cl] (3) and [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)pta]PF$_6$ (4) were synthesized and characterized by elemental analysis, infrared (IR), UV-Vis, NMR and mass spectroscopy and single-crystal X-ray diffraction. The crystal structures and spectroscopic data were compared to the previously published complexes [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-chloro-phenyl)-1,3-butanedione)Cl] (5) and [(η$^6$-p-cymene)Ru(4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butanedione)pta]PF$_6$ (6). The pairs of complexes 1 and 3 as well as 2 and 4 are isostructural, with the former crystallizing in triclinic P-1 and the latter in monoclinic P2$_1$/c. The ruthenium(II) ion is found in a pseudo-octahedral “piano-stool” geometry in all compounds. Bond lengths and angles are consistent with other complexes of this type. Complexes 2 and 4 exhibit some moderate dynamic disorder. The lack of hydrogen bonding and major π-π interactions means that most of intramolecular interactions are fairly weak and involve halogen atoms present. This was further confirmed by $^1$H-NMR spectra, where a significant difference is observed only on the ligand near the halogen atom, following an expected trend. The combined data show that the difference in any activity depends substantially on the type of the ligand′s substituted halogen atom.

The presented study describes the deterioration of a traditional pigment, malachite—[Cu2(CO3)(OH)2] in different binders, as a consequence of environmental effects acting on paint layers which were prepared according to traditional Baroque recipes. Malachite has often been reported to be very permanent in all binding media; however, investigations of aged and non-aged paint layers by means of Raman microscopy have shown instability of the carbonate part of the molecule, especially when malachite is present in an egg yolk medium. Decomposition of the pigment and the formation of degradation products such as copper oxide (tenorite—CuO) were observed. The possible formation of another copper oxide, paramelaconite—Cu4O3 was also taken into consideration. In order to obtain additional information on the degradation processes which affect malachite paint layers, supporting analytical methods, such as scanning electron microscopy and X-ray diffraction, were used. Copyright © 2014 John Wiley & Sons, Ltd.