Zwei neue basische Yttrium-Nitrate: Y(OH) x (NO3)3−x ·H2O und YO x/2(NO3)3−x (x=1.5)

Summary The intermediate precipitate, resulting by thermal decomposition and stepwise hydrolysis of yttrium-nitrate, was investigated by chemical analysis, TG, IR, and X-ray powderdiagrams and was found to be a definite hydroxynitrate Y(OH)_1.5(NO₃)_1.5·H₂O. Thermal decomposition resulted in the oxynitrate YO_0.75(NO₃)_1.5, stable from 140–280°C, which was characterized in an analogous manner.

     

A Molecular Approach for Unraveling Surface Phase Transitions: Sulfation of BaO as a Model NO(x) Trap

SO(3) -induced surface reconstruction: The SO(3) molecule as a multidentate ligand induces remarkable surface reconstruction phenomena on alkaline earth oxide surface. By using ab initio computations, adsorption properties are derived to elucidate the thermodynamics of the SO(3) -BaO system.     

Sol-gel Preparation of Fluoridated Hydroxyapatite in Ca(NO3)2-PO(OH)3− x (OEt) x -HPF6 System

Fluoridated hydroxyapatite (FHA) has been successfully synthesized via sol-gel method with HPF₆ as the fluorine containing reagent. The chemical reactions induced by HPF₆ addition and the formation process of fluoridated hydroxyapatite (FHA) are investigated. The hydrolysis and alcoholysis of HPF₆ release F ion into the solution which, in turn, reacts with Ca ion to form nanocrystalline CaF₂ (nc-CaF₂). These nc-CaF₂ improves the gelation ability of the system through formation of F‒H hydrogen bonding between F in nc-CaF₂ and H in P precursors. Increasing HPF₆ leads to more nc-CaF₂ thus less Ca(NO₃)₂ in the dried gel, or the presence of nc-CaF₂ in the gel suppresses the formation of Ca(NO₃)₂. At elevated firing temperatures, the P containing groups react with each other to form condensed phosphate. These condensed calcium phosphate, nc-CaF₂/Ca(NO₃)₂, reacts with the rest of the amorphous phase to form FHA phase at above 400°C.     

Reactions of NO2 with BaO/Pt(111) model catalysts: the effects of BaO film thickness and NO2 pressure on the formation of Ba(NOx)2 species

The adsorption and reaction of NO(2) on BaO (<1, ～3, and >20 monolayer equivalent (MLE))/Pt(111) model systems were studied with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRAS) under ultra-high vacuum (UHV) as well as elevated pressure conditions. NO(2) reacts with sub-monolayer BaO (<1 MLE) to form nitrites only, whereas the reaction of NO(2) with BaO (～3 MLE)/Pt(111) produces mainly nitrites and a small amount of nitrates under UHV conditions (P(NO(2))≈ 1.0 × 10(-9) Torr) at 300 K. In contrast, a thick BaO (>20 MLE) layer on Pt(111) reacts with NO(2) to form nitrite-nitrate ion pairs under the same conditions. At elevated NO(2) pressures (≥1.0 × 10(-5) Torr), however, BaO layers at all these three coverages convert to amorphous barium nitrates at 300 K. Upon annealing to 500 K, these amorphous barium nitrate layers transform into crystalline phases. The thermal decomposition of the thus-formed Ba(NO(x))(2) species is also influenced by the coverage of BaO on the Pt(111) substrate: at low BaO coverages, these species decompose at significantly lower temperatures in comparison with those formed on thick BaO films due to the presence of a Ba(NO(x))(2)/Pt interface where the decomposition can proceed at lower temperatures. However, the thermal decomposition of the thick Ba(NO(3))(2) films follows that of bulk nitrates. Results obtained from these BaO/Pt(111) model systems under UHV and elevated pressure conditions clearly demonstrate that both the BaO film thickness and the applied NO(2) pressure are critical in the Ba(NO(x))(2) formation and subsequent thermal decomposition processes.     

Vibronic interaction in europium nitrates Eu(NO3)3 x 4SOR2

Luminescence and excitation of luminescence vibronic spectra of europium nitrates Eu(NO3)3 x 4SOR2 containing sulphoxide derivatives were obtained and analysed. Some factors influencing the intensity distribution in vibronic sidebands are discussed. Significant variation of the intensity distribution in antiStokes sidebands of Eu3+ electronic transitions in series of nitrates results from the difference in effective charges on coordinated oxygen atoms of ligands. Another important detail of the vibronic spectra is a redistribution of intensity in the region of 5D0, 5D1-->7F2 transitions of luminescence spectra originated in overlap of different vibronic transitions. Mixing between the 7F2 electronic state of Eu3+ and vibronic satellites of 7F0 electronic state was studied both under conditions of resonance and in case of significant detuning.     

Polymer micelle-directed growth of BaCO(3) spiral nanobelts

We discovered that micelles of a thermo-responsive polypeptide-based copolymer are able to direct growth of barium carbonate (BaCO(3)) in the form of nanobelts. The BaCO(3) nanobelts tend to grow around a formed crystal, and curl into a spiral superstructure.     

Diffuse reflectance infrared Fourier transform study of NO(x) adsorption on CGO10 impregnated with K2O or BaO

In the present work diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is applied to study the adsorption of NO(x) at 300-500 °C in different atmospheres on gadolinium-doped ceria (CGO), an important material in electrodes investigated for electrochemical NO(x) removal. Furthermore, the effect on the NO(x) adsorption when adding K(2)O or BaO to the CGO is investigated. The DRIFT study shows mainly the presence of nitrate species at 500 °C, whereas at lower temperature a diversity of adsorbed NO(x) species exists on the CGO. The presence of O(2) is shown to have a strong effect on the adsorption of NO, but no effect on the adsorption of NO(2). Addition of K(2)O and BaO dramatically affects the NO(x) adsorption and the results also show that the adsorbed NO(x) species are mobile and capable of changing adsorption state in the investigated temperature range.     

Interactions in the Quinary System H2O-Y(NO3)3-La(NO3)3-Pr(NO3)3-Nd(NO3)3 to Very High Concentrations

Isopiestic measurements have been carried out for the quinary system H₂O-Y(NO₃)₃-La(NO₃)₃-Pr(NO₃)₃-Nd(NO₃)₃ at 298.15 K to near saturation. The measurements can be represented within experimental uncertainty over the full concentration range by a modified Pitzer ion-interaction model extending to the C ⁽³⁾ term. In addition, the system obeys the Zdanovskii–Stokes–Robinson model or partial ideal solution model within the accuracy of the isopiestic measurements, indicating zero interchange energy between the unlike salts, which is consistent with the nature of trivalent rare-earth elements.     

NO adsorption on MoS(x) clusters: a density functional theory study

The density functional theory (DFT) method has been used to investigate NO probe molecule adsorption on the stoichiometric (Mo(16)S(32)) and nonstoichiometric (Mo(16)S(34) and Mo(16)S(29)) clusters. The calculated adsorption energies indicate that the stoichiometric cluster has stronger NO affinity than the nonstoichiometric surfaces. It is also found that mononitrosyl adsorption is favored at low NO coverage, while dinitrosyl (germinal) and (NO)(2) dimer adsorption at high NO coverage are possible. Strong repulsive interaction has been found for the adsorbed dinitrosyl and (NO)(2) dimer species. In addition, the computed NO stretching frequencies for the mononitrosyl and dinitrosyl species agree well with the experimental data, while those of the dimer species are much lower than the suggested experimental data.     

NO2 adsorption on BaO/Al2O3: the nature of nitrate species

Temperature programmed desorption, infrared spectroscopy, and (15)N solid state NMR spectroscopy were used to characterize the nature of the nitrate species formed on Al(2)O(3) and BaO/Al(2)O(3) NO(x) storage/reduction materials. Two distinctly different nitrate species were found: surface nitrates that are associated with a monolayer BaO on the alumina support, and a bulk-like nitrate that forms on this thin BaO layer. The surface nitrates desorb as NO(2) at lower temperatures than do the bulk-like nitrates, which decompose as NO+O(2) at higher temperatures. The amount of NO(x) stored in the monolayer nitrate is proportional to the surface area of the catalyst, while that in the bulk nitrate increases with BaO coverage.     

Competitive adsorption of NO, NO2, CO2, and H2O on BaO(100): a quantum chemical study

Density functional theory (DFT) quantum chemical calculations are used to determine adsorption energies and geometries of NO, NO(2), CO(2), and H(2)O on a barium oxide (100) surface. The study includes two adsorption geometries for NO(2). All species form thermodynamically stable adsorbates, and adsorption strength increases in the order NO(2) < H(2)O < NO 相似文献   

Formation of a high coverage (3 x 3) NO phase on Pd(111) at elevated pressures: interplay between kinetic and thermodynamic accessibility

Using in situ polarization modulation infrared reflection absorption spectroscopy and density functional theory calculations, a new high-coverage monomeric NO adsorption state on Pd(111) was observed and proposed to have a (3 x 3)-7NO structure. Formation of this high coverage NO phase was found to take place only at elevated pressure and temperature conditions showing that some of the accessible thermodynamic equilibrium states at elevated temperatures and pressures are thermodynamically unfavorable or kinetically hindered at lower temperatures and pressures. Our results emphasize the danger of extrapolating results from traditional surface science experiments performed under ultrahigh vacuum to elevated temperature and pressure conditions encountered in heterogeneous catalysis.     

Toward a DFT-based molecular dynamics description of Co(II) binding in sulfur-rich peptides

In this paper, we investigated the reliability of a Car-Parrinello molecular dynamics (CPMD) approach to characterize the binding of Co(II) metal cation to peptide molecules containing cysteine. To this end, we compared pseudo-potentials and DFT plane wave expansion, which are used as key ingredients in the CPMD method, with standard all-electron Gaussian basis set DFT calculations. The simulations presented here are the first attempts to characterize interactions and dynamics of Co(II) metal with the building blocks of phytochelatin peptide molecules. Benchmark calculations are performed on [Co(Cys-H)]+ and [Co(Glutathione-H)]+ complexes, since they are the main fragments of the Co(II)-Cys and Co(II)-glutathione systems found in gas phase electrospray ionisation mass spectrometry (ESI-MS) experiments done in our laboratory. We also present benchmark calculations on the [Co(H2O)6)]2+ cluster with direct comparisons to highly correlated ab initio calculations and experiments. In particular, we investigated the dissociation path of one water molecule from the first hydration shell of Co(II) with CPMD. Overall, our molecular dynamics simulations shed some light on the nature of the Co(II) interaction and reactivity in Co(II)-phytochelatin building block systems related to the biological and environmental activity of the metal, either in the gas or liquid phase.     

Co(x)Cu(1-x)(DDOP)(OH2)(NO3)](NO3): hydrogen bond-driven distortion of cobalt(II) by solid solution 'network mismatch'

Late-first row transition metal nitrate complexes of the tetradentate N-donor ligand cis-3,5-bis[(2-pyridinyleneamino]-trans-hydroxycyclohexane (DDOP) adopt a mono-cationic [M(DDOP)(H(2)O)(NO(3))](+) structure (M = Co, 1; Cu, 2; Zn, 3) in which the DDOP ligand occupies the equatorial plane. The complexes are essentially isostructural and isomorphous, allowing the Co(II) and Cu(II) complexes to co-crystallize in mixed-metal solid solutions with the formula [Co(x)Cu(1-x)(DDOP)(NO(3))(H(2)O)](NO(3)), where x = 0.4 (4), 0.1 (5), and 0.7 (6). For 4, structural and magnetochemical analysis indicate that the geometry of the octahedral Co(II) complex distorts to match that of the dominant Jahn-Teller distorted Cu(II) center. Magnetic susceptibility data of octahedral Co(II) are sensitive to ligand geometry distortions and have been analyzed accordingly, comparing 4 to the reference systems 1 and 2. Bond valence calculations have been used to estimate the relative stabilities of the six hydrogen bonded networks, suggesting that the stretching of the Co(II) coordination sphere 4 in is assisted by adoption of the most stable hydrogen bonded network; but that in 6 this is overcome by a higher loading of Co. This family of complexes therefore represent predictable metal-based tectons which can help probe the influence of secondary non-covalent interactions over metal coordination geometries and properties.     

Low frequency Raman spectra of barium borate glasses in the system (BaCl2)y[(BaO)x(B2O3)1-y-x]1-y for various x and y

Low frequency Raman spectra of glasses of the types (BaO)_x·(B₂O₃)_1−x and (BaCl₂)_y·[(BaO)_x·(B₂O₃)₁-_y-_x]₁-_y have been reported. The temperature reduced Raman spectra show peaks at 67, 116 and 140 cm⁻¹ for the binary glass. The bands at 116 and 140 cm⁻¹ are ascribed to the librational motions of the borate groups and the 67 cm⁻¹ band arises because of the limited structural correlation range (SCR) of the glass network, causing a maximum of the frequency dependent Raman coupling coefficient. Due to addition of BaO in v-B₂O₃, the oxygen are mostly incorporated in the formation of BO₄ units; however large Ba²⁺ ions also enhance the number of non-bridging oxygen at higher concentrations of dopant. These barium ions as well as chlorine ions are accomodated in the interstitial vacancies of the glass network which leads to an expansion of the network structure.     

Synthesis and crystal structures of zirconium(IV) nitrate complexes (NO2)[Zr(NO3)3(H2O)3]2(NO3) 3, Cs[Zr(NO3)5], and (NH4)[Zr(NO3)5](HNO3)

The zirconium nitrate complexes (NO₂)[Zr(NO₃)₃(H₂O)₃]₂(NO₃)₃ (1), Cs[Zr(NO₃)₅] ((2), (NH₄)[Zr(NO₃)₅](HNO₃) (3), and (NO₂)_0.23(NO)_0.77[Zr(NO₃)₅] ((4) were prepared by crystallization from nitric acid solutions in the presence of H₂SO₄ or P₂O₅. The complexes were characterized by X-ray diffraction. The crystal structure of 1 consists of nitrate anions, nitronium cations, and [Zr(NO₃)₃(H₂O)₃]⁺ complex cations in which the Zr^IV atom is coordinated by three water molecules and three bidentate nitrate groups. The coordination polyhedron of the Zr^IV atom is a tricapped trigonal prism formed by nine oxygen atoms. The island structures of 2 and 3 contain [Zr(NO₃)₅]^? anions and Cs⁺ or NH₄ ⁺ cations, respectively. In addition, complex 3 contains HNO₃ molecules. Complex 4 differs from (NO₂)[Zr(NO₃)₅] in that three-fourth of the nitronium cations in 4 are replaced by nitrosonium cations NO⁺, resulting in a decrease in the unit cell parameters. In the [Zr(NO₃)₅]^? anion involved in complexes 2–4, the Zr^IV atom is coordinated by five bidentate nitrate groups and has an unusually high coordination number of 10. The coordination polyhedron is a bicapped square antiprism.