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The N-heterocyclic stannylene [Fe{(η5-C5H4)NC6H3-2,6-iPr2}2Sn] (1) has been synthesised from SnCl2 and the lithium amide [Fe{(η5-C5H4)NC6H3-2,6-iPr2}2Li2]. Compound 1 is inert towards H2, CO, CO2, and MeI under ambient conditions. Immediate hydrolysis and ammonolysis was observed with H2O and NH3, respectively. While oxidation reactions of 1 with chalcogens (O2, S8, Se8) afforded only intractable material, the reaction with Ph2Se2 cleanly furnished [Fe{(η5-C5H4)NC6H3-2,6-iPr2}2Sn(SePh)2] (2). Compounds 1 and 2 have been structurally characterised by single-crystal X-ray diffraction. Compound 2 exhibits an intramolecular CH⋯Se contact compatible with a weak hydrogen bond. [ABSTRACT FROM AUTHOR]

The tandem Knoevenagel—Michael—intramolecular ammonolysis—alkylation reaction was used to synthesize functionalized tetrahydropyridones. The molecular and crystal structures of four pyridone derivatives were studied by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Polycrystalline BaTiO 3 , BaTi(O,F) 3 , BaTi(N,O) 3 , and BaTi(N,O,F) 3 powders were synthesized by a solid-state reaction and thermal ammonolysis. By powder X-ray diffraction (XRD) a tetragonal perovskite-type structure with space group P 4 mm was identified for all samples. Thermogravimetric analysis (TGA) revealed a gradual mass increase for the oxynitride BaTi(N,O) 3 and the oxyfluoronitride BaTi(N,O,F) 3 due to the nitrogen-oxygen exchange process. UV–visible diffuse reflectance spectra indicated the nitrogen incorporation into the perovskite lattice, and presumably the presence of large amounts of reduced titanium ions in BaTi(N,O,F) 3 . XANES spectra showed distinctive peak features for BaTi(O,F) 3 and BaTi(N,O,F) 3 . Detailed magnetic property measurements revealed diamagnetism for BaTiO 3 , but weak ferromagnetism for BaTi(N,O) 3 and a ferromagnetic behavior for BaTi(O,F) 3 and BaTi(N,O,F) 3 . Enhanced magnetization of BaTi(N,O,F) 3 is attributed to the synergetic effect of increased concentration of both surface/lattice defects and Ti 3+ . [ABSTRACT FROM AUTHOR]

Nitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO 2 substrate from a ZnO colloidal solution. Zinc peroxide (ZnO 2 ) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H 2 O 2 solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250 °C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV–Visible transmittance spectroscopy. [ABSTRACT FROM AUTHOR]

We report on the single crystal structure of Na2PtF6, which was synthesized from (NH4)2PtCl6 and NaCl in a flow of 10 % F2 in argon. The light yellow compound crystallizes in the Na2SiF6 structure type with the trigonal space group P321 and the lattice parameters a = 9.2981(2), c = 5.1147(1) Å, and V = 382.95(1) Å3 at 123 K with Z = 3. Na2PtF6 reacts with liquid ammonia yielding bis triamminesodium hexafluoridoplatinate(IV) [Na(NH3)3]2[PtF6]. It crystallizes in the monoclinic space group C2/ c with a = 14.0508(4), b = 8.4894(1), c = 12.8820(4) Å, β = 120.495(4)°, and V = 1324.05(6) Å3 at 123 K with Z = 4. In contrast to the aqueous system, the solvolysis in NH3 does not lead to the cleavage of the Pt-F bonds, at least not at the temperatures employed in this study. [ABSTRACT FROM AUTHOR]

Improvements of the two-step reaction sequence starting from γ-Fe2O3 enabled us to synthesize α′′-Fe16N2 in single phase according to the applied diffraction methods. Simultaneous Rietveld refinements were carried out on powder X-ray and neutron diffraction data. Scanning electron microscopy images of the in situ formed α-Fe and α′′-Fe16N2 indicate the formation of pores during reduction and ammonolysis reaction, respectively, resulting in a sponge-like morphology of the α′′-Fe16N2 particles and simultaneously a large surface area facilitating a complete reaction at comparably low temperatures of 125 °C. The large surface area is susceptible to the sorption of impurities and indeed chemical analysis reveals significant oxygen and hydrogen contamination of the sample. From EDX measurements in combination with the results of chemical analysis a sorption of humidity to the surface seems to be more likely to explain this contamination than an incorporation of oxygen into the bulk of the sample. Magnetization measurements on the bulk sample of α′′-Fe16N2 did not reveal any indication for the presence of a proposed giant magnetic effect. [ABSTRACT FROM AUTHOR]

We report on the single crystal structure of Na2PtF6, which was synthesized from (NH4)2PtCl6 and NaCl in a flow of 10 % F2 in argon. The light yellow compound crystallizes in the Na2SiF6 structure type with the trigonal space group P321 and the lattice parameters a = 9.2981(2), c = 5.1147(1) Å, and V = 382.95(1) Å3 at 123 K with Z = 3. Na2PtF6 reacts with liquid ammonia yielding bis triamminesodium hexafluoridoplatinate(IV) [Na(NH3)3]2[PtF6]. It crystallizes in the monoclinic space group C2/ c with a = 14.0508(4), b = 8.4894(1), c = 12.8820(4) Å, β = 120.495(4)°, and V = 1324.05(6) Å3 at 123 K with Z = 4. In contrast to the aqueous system, the solvolysis in NH3 does not lead to the cleavage of the Pt-F bonds, at least not at the temperatures employed in this study. [ABSTRACT FROM AUTHOR]

Improvements of the two-step reaction sequence starting from γ-Fe2O3 enabled us to synthesize α′′-Fe16N2 in single phase according to the applied diffraction methods. Simultaneous Rietveld refinements were carried out on powder X-ray and neutron diffraction data. Scanning electron microscopy images of the in situ formed α-Fe and α′′-Fe16N2 indicate the formation of pores during reduction and ammonolysis reaction, respectively, resulting in a sponge-like morphology of the α′′-Fe16N2 particles and simultaneously a large surface area facilitating a complete reaction at comparably low temperatures of 125 °C. The large surface area is susceptible to the sorption of impurities and indeed chemical analysis reveals significant oxygen and hydrogen contamination of the sample. From EDX measurements in combination with the results of chemical analysis a sorption of humidity to the surface seems to be more likely to explain this contamination than an incorporation of oxygen into the bulk of the sample. Magnetization measurements on the bulk sample of α′′-Fe16N2 did not reveal any indication for the presence of a proposed giant magnetic effect. [ABSTRACT FROM AUTHOR]

A simple process for preparing mesoporouschromium nitride (CrN)by the ammonolysis of a bulk ternary oxide (K2Cr2O7) is reported. The products were characterized by Rietveldrefinement of powder X-ray diffraction patterns, scanning electronmicroscopy (SEM), and nitrogen adsorption/desorption analysis. Poresizes ranging from 10 to 20 nm are easily accessible. The conductivityof mesoporous CrN powder compressed at 35 bar is 54 S/cm. A Pt/CrNcatalyst prepared from the mesoporous CrN shows a negative onset potentialfor methanol electrooxidation (0.20 V vs SCE) similar to that of Pt/C(0.22 V vs SCE). The electrochemically active specific surface area(ECSA) of the Pt/CrN catalyst (82 m2/g) was only slightlyhigher than that of Pt/C (75 m2/g). More importantly, thePt/CrN catalyst demonstrates high tolerance to corrosion and is acandidate to replace carbon black, which is known to corrode underhigh potentials, as a support for fuel cell catalysts. This work providesan efficient method for preparing mesoporous metal nitrides that arepromising supports for the oxidation of small organic molecules infuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite-type La(Ti,Nb)(O,N)3 powders with different Ti and Nb content were synthesized by a thermal ammonolysis of oxide precursors prepared via a soft chemistry route. By X-ray diffraction (XRD), a gradual increase of the unit cell volume was observed with increasing niobium content. The crystallite size calculated with the Scherrer equation displayed a minimum of about 30nm at the intermediate composition. Scanning electron microscopy (SEM) showed morphological changes of the microstructure with increasing niobium content. Thermal re-oxidation studies with thermogravimetric analysis (TGA) revealed that a different amount of nitrogen was substituted into the La (Ti,Nb)(O,N)3 lattice. UV-visible diffuse reflectance spectroscopy (UV-vis DRS) showed that absorption edge wavelengths of the oxynitrides were in the range of 612nm – 744nm, corresponding to the bandgap energy of 2.02eV – 1.67eV. Among all La(Ti,Nb)(O,N)3, LaTiO2N showed the highest photocatalytic activity for water oxidation. One of the determining factors for the photocatalytic water oxidation with La(Ti,Nb)(O,N)3 was found to be the defects concentration. [Copyright &y& Elsevier]

Abstract: Two new oxynitride double perovskites of composition Sr2FeMoO6−x N x (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750°C and 650°C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Mössbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1)Å, c=7.9024(2)Å, V=247.46(2)Å3 for Sr2FeMoO5.7N0.3; and a=5.6202(2)Å, c=7.9102(4)Å, V=249.85(2)Å3 for Sr2FeMoO5N; space group I4/m, Z=2. The nitridation process seems to extraordinarily improve the long-range Fe/Mo ordering, achieving 95% at moderate temperatures of 750°C. The analysis of high resolution NPD data, based on the contrast existing between the scattering lengths of O and N, shows that both atoms are located at (O,N)2 anion substructure corresponding to the basal ab plane of the perovskite structure, whereas the O1 site is fully occupied by oxygen atoms. The evolution of the 〈Fe–O〉 and 〈Mo–O〉 distances suggests a shift towards a configuration close to Fe4+(3d 4, S=2):Mo5+(4d 1, S=1/2). The magnetic susceptibility shows a ferrimagnetic transition with a reduced saturation magnetization compared to Sr2FeMoO6, due to the different nature of the magnetic double exchange interactions through Fe–N–Mo–N–Fe paths in contrast to the stronger Fe–O–Mo–O–Fe interactions. Also, the effect observed by low-temperature NPD seems to reduce the ordered Fe moments and enhance the Mo moments, in agreement with the evolution of the oxidation states, thus decreasing the saturation magnetization. [Copyright &y& Elsevier]

Abstract: We investigated the ammonolysis of β-Ga2O3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a β-Ga2O3 related oxynitride phase was found, and the nitrogen solubility in β-Ga2O3 was found to be below the detection limit of about 2–3at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the β-Ga2O3 phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis. [Copyright &y& Elsevier]

Abstract: Within the ternary system Ga–O–N we performed experimental and theoretical investigations on the thermodynamics, structure and kinetics of new stable and metastable compounds. We studied the ammonolysis of β-Ga2O3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction, and in situ X-ray absorption spectroscopy (XAS). From total diffraction pattern refinement with the Rietveld method we analyzed the anionic occupancy factors and the lattice parameters of β-Ga2O3 during the reaction. Within the detection limits of these methods, we can rule out the existence of a crystalline oxynitride phase that is not derived from wurtzite-type GaN. The nitrogen solubility in β-Ga2O3 was found to be below the detection limit of about 2–3 at.% in the anionic sublattice. The kinetics of the ammonolysis of β-Ga2O3 to α-GaN and of the oxidation of α-GaN to β-Ga2O3 was studied by means of in situ X-ray absorption spectroscopy. In both cases the reaction kinetics could be described well by fitting linear combinations of β-Ga2O3 and α-GaN spectra only, excluding that other crystalline or amorphous phases appear during these reactions. The kinetics of the ammonolysis can be described well by an extended Johnson–Mehl–Avrami–Kolmogorow model with nucleation and growth of GaN nuclei, while the oxidation kinetics can be modeled by a shrinking core model where Ga2O3 grows as a layer. Investigations by means of TEM and SEM support the assumptions in both models. To investigate the structure and energetics of spinel-type gallium oxynitrides (γ-galons) we performed first-principles calculations using density-functional theory. In addition to the ideal cubic γ-Ga3O3N we studied gallium deficient γ-galons within the Constant-Anion-Model. In highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO1.2 we found at a temperature around 670 K an insulator–metal transition, with a conductivity jump of seven orders of magnitude. We demonstrate through experimental studies and density-functional theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric β-Ga2O3 within the metastable oxide matrix. By doping with nitrogen the critical temperature and the conductivity in the highly conducting state can be tuned. [Copyright &y& Elsevier]

Abstract: Thick films of the perovskite-related oxynitrides LaTiO2N, NdTiO2N, SrNbO2N and SrTaO2N were synthesised by nitridation of single crystals of the corresponding oxides with general composition ABO3.5. The oxide crystals were obtained by optical floating zone growth. They correspond to n =4 member of the AnBn O3n+2 family of layered perovskites and were reacted at temperatures between 900°C and 1050°C to form the oxynitrides. Electron probe microanalysis proved the presence of nitrogen in a surface layer of a few micrometer thickness. Cross-section SEM revealed additional thin stripes of oxynitride within the bulk of the crystals, indicating that nitrogen is incorporated preferably parallel to the perovskite-type layers, which in turn are connected in a zipper-type mechanism. The formation of the desired perovskite-type oxynitrides was confirmed by X-ray diffraction. Pole figure measurements proved an epitaxial orientation ABO2N (110)[001]‖ ABO3.5 (001)[100]. The mosaicity of the oxynitrides both in polar and azimuthal direction was very small (<2°) indicating a nearly single crystalline quality of the surface layer. The nitridation of the crystals results in a dramatic change in colour. Optical spectroscopy revealed shifts of the absorption edge by more than 200nm to longer wavelengths with respect to the parent oxides, corresponding to a reduction of the band gap energies by 1.4–1.8eV. [Copyright &y& Elsevier]

Nanocrystalline bimetallic metal oxynitride, Ti0.5Cr0.5OxNy, was synthesized by ammonolysis of the nanosized Cr2O3/TiO2 composite powder at 800 °C for 8 h. The precursor and the resulting oxynitride were characterized by Auger electron spectroscope (AES), X-ray diffraction analysis (XRD), electron probe microanalysis (EP), transmission electron microscopy (TEM), and BET surface area techniques. The result indicated that the as-synthesized oxynitride powder contains only Ti0.5Cr0.5OxNy with cubic structure and the average particle size is about 30 nm. [Copyright &y& Elsevier]

Abstract: In this work studies of the structure and superconducting properties of xVN−(100− x)SiO2 films (where x =90, 80, 70 and 60mol%) are reported. The films were obtained through thermal nitridation (ammonolysis) of sol–gel derived V2O3–SiO2 coatings (in a proper V2O3/SiO2 ratio) at 1200°C. This process led to the formation of a disordered structure with VN metallic grains dispersed in the insulating SiO2 matrix. The structural transformations occurring in the films as a result of ammonolysis were studied using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The superconducting properties of the samples were examined with magnetically modulated microwave absorption (MMMA). All the samples apart from x =90 exhibited superconducting transition above 6K. [Copyright &y& Elsevier]