Effect of fluorosubstitution on the structure of single crystals, Effect of fluorosubstitution on the structure of single crystals,thin films and spectral properties of palladium phthalocyanines

In this work, the crystalline structure of single crystals grown by vacuum sublimation of unsubstituted palladium phthalocyanines (PdPc), its tetrafluorinated (PdPcF4) and hexadecafluorinated (PdPcF16) derivatives have been investigated using X-ray diffraction measurements. Two crystalline phases have been identified for PdPc; the molecules in both phases crystallize in stacks with herringbone arrangement in the monoclinic space groups (C2/c for -PdPc; P21/n for -PdPc). Both PdPcF4 and PdPcF16 crystallize in the triclinic P-1 space group, forming stacks of molecules in columnar arrangement with molecules in adjacent columns are aligned parallel to one another. X-ray diffraction measurements have also been used to elucidate the structural features and molecular orientation of thin films of PdPc, PdPcF4 and PdPcF16, grown by organic molecular beam deposition at different substrate temperatures. The effect of fluorosubstitution on UV-visible optical absorption and vibrational spectra of palladium phthalocyanine derivatives is also discussed

Solid-State Transformations of Mayenite and Core-Shell Structures of C12A7@C Type at High Pressure, High Temperature Conditions

Calcium aluminate of a mayenite structure, 12CaO∙7Al2O3 (C12A7), is widely applicable in many fields of modern science and technology. Therefore, its behavior under various experimental conditions is of special interest. The present research aimed to estimate the possible impact of the carbon shell in core-shell materials of C12A7@C type on the proceeding of solid-state reactions of mayenite with graphite and magnesium oxide under High Pressure, High Temperature (HPHT) conditions. The phase composition of the solid-state products formed at a pressure of 4 GPa and temperature of 1450 °C was studied. As is found, the interaction of mayenite with graphite under such conditions is accompanied by the formation of an aluminum-rich phase of the CaO∙6Al2O3 composition, while in the case of core-shell structure (C12A7@C), the same interaction does not lead to the formation of such a single phase. For this system, a number of hardly identified calcium aluminate phases along with the carbide-like phrases have appeared. The main product of the interaction of mayenite and C12A7@C with MgO under HPHT conditions is the spinel phase Al2MgO4. This indicates that, in the case of the C12A7@C structure, the carbon shell is not able to prevent the interaction of the oxide mayenite core with magnesium oxide located outside the carbon shell. Nevertheless, the other solid-state products accompanying the spinel formation are significantly different for the cases of pure C12A7 and C12A7@C core-shell structure. The obtained results clearly illustrate that the HPHT conditions used in these experiments lead to the complete destruction of the mayenite structure and the formation of new phases, which compositions differ noticeably depending on the precursor used—pure mayenite or C12A7@C core-shell structure

Synthesis and Crystal Chemistry of Octahedral Rhodium(III) Chloroamines

Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhClx(NH3)6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhClx(NH3)6−x] octahedral species are summarized and critically analyzed. Unknown crystal structures of (NH4)2[Rh(NH3)Cl5], trans–[Rh(NH3)4Cl2]Cl⋅H2O, and cis–[Rh(NH3)4Cl2]Cl are reported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH3)5Cl]Cl2 was redetermined. All available crystal structures with octahedral complexes [RhClx(NH3)6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices

Equations of state of rhodium, iridium and their alloys up to 70 GPa

Knowledge of the compressional and thermal behaviour of metals and alloys is of a high fundamental and applied value. In this work, we studied the behaviour of Ir, Rh, and their fcc-structured alloys, Ir$_{0.42}$Rh$_{0.58}>$ and Ir$_{0.26}$Os$_{0.05}$Pt$_{0.31}$Rh$_{0.23}$Ru$_{0.15}$, up to 70 GPa using the diamond anvil cell technique with synchrotron X-ray diffraction. We found that all these materials are structurally stable upon room-temperature hydrostatic compression in the whole pressure interval, as well as upon heating to 2273 K both at ambient and high pressure. Rh, Ir$_{0.42}$Rh$_{0.58}$ and Ir$_{0.26}$Os$_{0.05}$Pt$_{0.31}$Rh$_{0.23}$Ru$_{0.15}$ were investigated under static compression for the first time. According to our data, the compressibility of Ir, Rh, fcc–Ir$_{0.42}$Rh$_{0.58}$, and fcc–Ir$_{0.26}$Os$_{0.05}$Pt$_{0.31}$Rh$_{0.23}$Ru$_{0.15}$, can be described with the 3rd order Birch-Murnaghan equation of state with the following parameters: V$_0$ = 14.14(6) Å$^3$·atom$^1 {−1}$, B$_0$ = 341(10) GPa, and B0' = 4.7(3); V$_0$ = 13.73(7) Å$^3$·atom$^{−1}$, B$_0$ = 301(9) GPa, and B$_0$' = 3.1(2); V$_0$ = 13.90(8) Å$^3$·atom$^{−1}$, B$_0$ = 317(17) GPa, and B$_0$' = 6.0(5); V$_0$ = 14.16(9) Å$^3$·atom$^{−1}$, B$_0$ = 300(22) GPa, B$_0$' = 6(1), where V$_0$ is the unit cell volume, B$_0$ and B$_0$' – are the bulk modulus and its pressure derivative

Face-Centered Cubic Refractory Alloys Prepared from Single-Source Precursors

Three binary fcc-structured alloys (fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50) were prepared from [Ir(NH3)5Cl][PtCl6], [Ir(NH3)5Cl][PtBr6], [Rh(NH3)5Cl]2[PtCl6]Cl2 and [Rh(NH3)5Cl][PdCl4]·H2O, respectively, as single-source precursors. All alloys were prepared by thermal decomposition in gaseous hydrogen flow below 800 °C. Fcc–Ir0.50Pt0.50 and fcc–Rh0.50Pd0.50 correspond to miscibility gaps on binary metallic phase diagrams and can be considered as metastable alloys. Detailed comparison of [Ir(NH3)5Cl][PtCl6] and [Ir(NH3)5Cl][PtBr6] crystal structures suggests that two isoformular salts are not isostructural. In [Ir(NH3)5Cl][PtBr6], specific Br…Br interactions are responsible for a crystal structure arrangement. Room temperature compressibility of fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50 has been investigated up to 50 GPa in diamond anvil cells. All investigated fcc-structured binary alloys are stable under compression. Atomic volumes and bulk moduli show good agreement with ideal solutions model. For fcc–Ir0.50Pt0.50, V0/Z = 14.597(6) Å3·atom−1, B0 = 321(6) GPa and B0’ = 6(1); for fcc–Rh0.66Pt0.33, V0/Z = 14.211(3) Å3·atom−1, B0 =259(1) GPa and B0’ = 6.66(9) and for fcc–Rh0.50Pd0.50, V0/Z = 14.18(2) Å3·atom−1, B0 =223(4) GPa and B0’ = 5.0(3)

[NiEn₃](MoO₄)_0.5(WO₄)_0.5 Co-Crystals as Single-Source Precursors for Ternary Refractory Ni–Mo–W Alloys

The co-crystallisation of [NiEn3](NO3)2 (En = ethylenediamine) with Na2MoO4 and Na2WO4 from a water solution results in the formation of [NiEn3](MoO4)0.5(WO4)0.5 co-crystals. According to the X-ray diffraction analysis of eight single crystals, the parameters of the hexagonal unit cell (space group P–31c, Z = 2) vary in the following intervals: a = 9.2332(3)–9.2566(6); c = 9.9512(12)–9.9753(7) Å with the Mo/W ratio changing from 0.513(3)/0.487(3) to 0.078(4)/0.895(9). The thermal decomposition of [NiEn3](MoO4)0.5(WO4)0.5 individual crystals obtained by co-crystallisation was performed in He and H2 atmospheres. The ex situ X-ray study of thermal decomposition products shows the formation of nanocrystalline refractory alloys and carbide composites containing ternary Ni–Mo–W phases. The formation of carbon–nitride phases at certain stages of heating up to 1000 °C were shown

Efficient MOF-Catalyzed Ortho–Para Hydrogen Conversion for Practical Liquefaction and Energy Storage

Parahydrogen, being one of two nuclear spin isomers of molecular hydrogen, is required in a number of applications, including hydrogen liquefaction for energy storage and transportation. Obtaining pure parahydrogen is vital for these tasks, thus requiring approaches for efficient ortho–para (OP) hydrogen conversion. In this work, we for the first time demonstrate the extraordinary potential of metal–organic frameworks (MOF) as OP-conversion catalysts. In particular, the specific conversion rate constant of Ni-MOF-74 is found 145-fold higher than that of industrially used catalysts (e.g., hydrous ferric oxide), thus opening new horizons in hydrogen liquefaction and storage and, ultimately, in the broad use of hydrogen energy

High compressibility of synthetic analogous of binary iridium–ruthenium and ternary iridium–osmium–ruthenium minerals

Hcp-Ir$_{0.24}$Ru$_{0.36}$Os$_{0.40}$ and fcc-Ir$_{0.84}$Ru$_{0.06}$Os$_{0.10}$ ternary alloys as well as binary hcp-Ir$_{0.33}$Ru$_{0.67}$ and fcc-Ir$_{0.75}$Ru$_{0.25}$ ones were prepared using thermal decomposition of [Ir$_x$Ru$_{1-x}$(NH$_3$)($_5$)Cl][OsyIr$_{(1-y)}$Cl$_6$] single-source precursors in hydrogen flow below 1070 K. These single-phase alloys correspond to ternary and binary peritectic phase diagrams and can be used as synthetic models for rare iridosmine minerals. Thermal decomposition of parent bimetallic precursor [Ir(NH$_3$)($_5$)Cl][OsCl$_6$] has been investigated using in situ powder X-ray diffraction in inert and reductive atmospheres. In reductive atmosphere, [Ir(NH$_3$)($_5$)Cl][OsCl$_6$] forms (NH$_4$)($_2$) [OsCl$_6$] as crystalline intermediate; Ir from its cationic part is reduced by hydrogen with a formation of defect fcc-structured metallic particles; the final product is a metastable hcp-Ir$_{0.5}$Os$_{0.5}$ alloy. In inert atmosphere, the salt decomposes at higher temperature without a formation of any detectable crystalline intermediates; two-phase fcc+hcp mixture forms directly above 800 K. Room temperature compressibility up to 50 GPa has been studied for all prepared alloys in diamond anvil cells. Investigated ternary and binary alloys do not show any phase transitions upon compression at room temperature. In contrast with other investigated ultra-incompressible refractory alloys with osmium and iridium, hcp-Ir$_{0.33}$Ru$_{0.67}$, fcc-Ir$_{0.75}$Ru$_{0.25}$ binary and fcc-Ir$_{0.84}$Ru$_{0.06}$Os$_{0.10}$ ternary alloys show higher compressibility in comparison with pure metals. Fcc-Ir0.75Ru0.25 alloy shows several magnetic phase transitions (at approx. 3.4 K, 135 K and 233 K) that could be related to different magnetic phases

Unique Nanomechanical Properties of Diamond−Lonsdaleite Biphases: Combined Experimental and Theoretical Consideration of Popigai Impact Diamonds

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