Nitrogen Insertion Research Articles

ChemInform Abstract: Azidotrimethylsilane-Mediated Schmidt Rearrangement of 2-Aryl-1,2,3,4-tetrahydro-1-methylsulfonyl-4-quinolones: Non-regioselectivity of Carbon Migration.

Azidotrimethylsilane-mediated Schmidt rearrangement of 2-aryl-1-methylsulfonyl-1,2,3,4-tetrahydro-4-quinolones in trifluoroacetic acid was investigated. In contrast to the corresponding 2-aryl-1,2,3,4-tetrahydro-4-quinolone precursors, the N-methylsulfonyl derivatives displayed non-regioselectivity of carbon migration during nitrogen insertion affording the isomeric ring-expanded derivatives via alkyl and aryl migration.

Nitriding of austenitic stainless steel by pulsed low energy ion implantation

Low energy ion implantation (LEII) of nitrogen into austenitic stainless steel was carried out using an electronic beam switch for a defined regulation of nitrogen ion flux and an additional external radiation heating for assuring a constant process temperature of 460 °C with the aim to investigate the influence of a varying ion energy and ion flux, respective particle flux on nitrogen diffusion, phase formation and hardness of the nitrided austenitic stainless steel, grade 1.4301, samples. No influence of both process parameter variations on the layer thickness was found as long as identical temperature profiles were maintained. This implies that the nitrogen diffusion is decoupled from nitrogen insertion at constant temperature for sufficiently high nitrogen supply. It was found that the pulsed mode does not influence the expended austenite formation, hardness of the nitrided layers as well as their corrosion resistance compared with a continuous LEII-mode at the same ion source plasma parameters.

Preparation of Open‐Cage Fullerenes and Incorporation of Small Molecules Through Their Orifices

Open-cage fullerenes can act as hosts for small molecules such as water, nitrogen, or hydrogen, forming endohedral fullerenes. Following a brief summary of carbon, nitrogen, and oxygen insertion in the fullerene framework to form homofullerenes, methods of creating a hole in the fullerene surface are surveyed. Techniques of hole enlargement and the insertion of atoms or molecules through the orifice to form endohedral fullerenes are described. Finally, the possibility of subsequent closure of the hole is considered.

Reduced tribocorrosion of CoCr alloys in simulated body fluid after nitrogen insertion

Tribological studies in air and simulated body fluid (SBF) after surface modification by nitrogen plasma immersion ion implantation of medical CoCr alloys were compared. The PIII treatment temperatures were varied between 390 and 570 °C. Subsequent wear measurements in air exhibit reduced wear rates for the PIII treated specimens. In SBF, a minimum wear rate was observed for a process temperature near 400 °C. For higher PIII temperatures, fretting corrosion leads to an elevated cobalt ion release. Apparently a weakened chemical bonding of cobalt as well as chromium immobilization caused by the nitrogen insertion and a subsequent reduction of passivating oxide layer causes the selective high Co ion release for samples with high process temperatures. A compromise for the PIII treatment temperature must be found as the minimum particle release rate does not correspond to the minimum Co ion release rate.

Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites

N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350–600°C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy analysis, revealed that TiO2 was effectively doped. The thermal treatment induces insertion of nitrogen into TiO2 lattice in the form of nitride anion N−, detected as N by EPR, whose ionic character varies with the temperature of annealing. The amount of N increases till 450°C, then it decreases. Similar trend was observed for the photomineralization of phenol under visible light irradiation (λ>385nm): the photoactivity of N-doped samples becomes maximum for N–TiO2 annealed at 450°C. The overall results suggest that the efficacy of the catalyst depends on the ability of N− centers to trap photogenerated holes. This effect lowers the rate of electron–hole recombination and allows the N (N−+h+) center acts as strong oxidizing agent.

End‐On Nitrogen Insertion of a Diazo Compound into a Germanium(II) Hydrogen Bond and a Comparable Reaction with Diethyl Azodicarboxylate

A happy ending: The germanium(II) hydride [LGeH], where L = [HC{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)], reacts with a diazoalkane to form the hydrazone derivative (see picture). The reaction proceeds through the unprecedented end-on nitrogen insertion of the diazo compound.

Nitrogen-doped and nitrogen–fluorine-codoped titanium dioxide. Nature and concentration of the photoactive species and their role in determining the photocatalytic activity under visible light

Two series of N-doped and N, F-codoped titanium dioxide samples having different loading of impurity were prepared using sol–gel synthesis and successive calcinations in air. Ammonium chloride and ammonium fluoride were used as source of dopants in the two cases. In all cases the insertion of nitrogen is observed which determines the optical absorption in the visible of the materials and their photocatalytic activity under solar light. This was investigated following the decomposition of methylene blue in aqueous phase. Two photoactive species (describable in terms of NO 2− and NO 3− bulk species) determine the optical absorption in the visible range. The former one (paramagnetic) is detectable by Electron Paramagnetic Resonance (EPR) and its intensity in all samples is roughly proportional to the optical absorption at 440 nm. The photocatalytic activity under solar light directly depends on the concentration of the nitrogen photoactive species in the solid till a saturation limit, which in turn, depends on the concentration of ammonium ions in the starting solution and on the heating rate during calcinations. The use of ammonium fluoride in the synthesis promotes N insertion and increments the photocatalytic activity due to the fact that, differently from Cl − ions, F − ions substitutes oxygen in the solid lattice giving rise to electronic effects which favour N photoactive species incorporation in the solid.

Temperature effect on the nitrogen insertion in carbon nitride films deposited by ECR

The impact of the temperature on the local structure of carbon nitride coating a-C 1-x N x:H was investigated by spectroscopic analysis. A set of carbon nitride films were deposited at several substrate temperatures (77 K, 300 K, 673 K and 900 K) by electron cyclotron resonance (ECR) ion gun technique fed of CH 4/N 2 plasma. The films were in situ characterized by X-ray photoelectron spectroscopy (XPS). A drastic decrease of the nitrogen content was observed when increasing the deposition temperature from 77 K to 900 K. Qualitative structural and electronic changes were followed after air exposure by infrared (FTIR), near-edge X-ray absorption fine structure (NEXAFS) and Ultraviolet photoelectron (UPS) spectroscopy. Below 300 K, the films are hydrogenated with aliphatic structure and nitrogen is bonded to carbon in many kind of configuration. Between 300 K and 600 K, the nitrogen amount is reduced while both the aromatic and the aliphatic carbons increase. The local structure of the films radically changes at 900 K, whereas the nitrogen surrounding is the same at 673 K. In that case the hydrogen fraction into the films is reduced to zero. The increase of the sp 3 carbon as well as the ratio π⁎/ σ⁎ on the nitrogen K edge can be observed. This behaviour may be explain by nitrogen substituted to sp 2 carbon which induces local changes in the distribution of the π⁎ states.

Synthesis and characterisation of nitrogen-doped ZnO thin films

Nitrogen doped ZnO thin films were prepared using a DC-Magnetron sputtering technique. The samples were investigated using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS revealed the presence of nitrogen in the films prepared under high oxygen to nitrogen ratio N/O ≥ 5/1. One N 1s peak located at 397 eV binding energy (BE) was assigned to atomic nitrogen. The other located at a BE of 399 eV was assigned to N due to formation of oxynitride. The XRD spectrum of the samples prepared under N/O ratio ≥ 1/5 showed a single peak at 2θ – 33.60 assigned to ZnO (002) plane indicating a strong texture along the c-axis. Both peaks were shifted toward lower angles, as compared to pure ZnO film, indicating an expansion of the unit cell as a result of the insertion of nitrogen in the lattice. The nanostructure of the films was investigated by atomic force microscopy.

Growth of titanium oxynitride layers by short pulsed Nd:YAG laser treatment of Ti plates: Influence of the cumulated laser fluence

Titanium oxynitride layers were formed by surface laser treatment of Ti plates in air using a Nd:YAG laser source of short pulse duration about 5 ns. The cumulated laser fluence was varied in the 100–1200 J cm −2 range and its influence on the composition and the structure of the formed layers was studied by different characterization techniques providing physico-chemical and structural information. It was shown that the laser treatment induces the insertion of light elements as O, N and C in the formed layer with the amount increasing with the laser fluence. The in-depth composition of the layers and the co-existence of different phases were also studied. The way in which the laser parameters such as fluence affect the insertion of nitrogen and oxygen was discussed in connection with the effects of the plasma plume formed above the target.

A novel transformation of 1,2-dithiole-3-thiones into 1,3-thiazine-4-thiones

1,2 Dithiole 3 thiones 1 exhibit a variety of reactivi ties.1 1,3 Dipolar cycloaddition of these compounds is best studied: the reaction involves ring opening with participation of the thione group. Transformations with retention of the thione group are much more uncommon. 1,2 Dithiole 3 thiones have been reported to react with α,β unsaturated nitriles to give thiopyran thiones2 and with amines to give 1,2 thiazole 3 thiones or 1,2 isothiazole 5 thiones.3 We discovered a novel transformation of the dithiole ring. In reactions of 1,2 dithiole 3 thiones 1a—d with 3,4 dihydropyrrolo[1,2 a]pyrazine (2), the imine frag ment of compound 2 is inserted into the 1,2 dithiole ring with extrusion of the S atom (the latter was isolated as elemental sulfur in a nearly quantitative yield) to give fused 1,3 thiazine 4 thiones 3a—d in high yields (Scheme 1). The transformation is possible for both fused (1a—c) and monocyclic 1,2 dithioles (1d). Such reactions in volving the insertion of nitrogen containing fragments into the 1,2 dithiole ring give wide scope for the synthesis of novel heterocyclic systems. The structures of 1,4 thiazine 4 thiones 3a—d were fully confirmed by elemental analysis data and 1H and 13C NMR, IR, and mass spectra. Some of the spectral Scheme 1

PIII nitriding of fcc‐alloys containing Ni and Cr

AbstractFace‐centred cubic (fcc) alloys such as austenitic stainless steel, Ni base alloys and Co base alloys are important materials with a high corrosion resistance. Nitrogen insertion by PIII into all these alloys at moderate temperatures leads to the formation of an expanded austenite structure. A similar activation energy for the thermally assisted diffusion of about 0.75 eV was found for steel and CoCr alloys with CrN precipitates beyond 400 °C in both systems. However, a double layer structure was observed for CoCr, similar to Ni alloys, in contrast to a single layer for austenitic steel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Alumina supported Mo–V–Te–O catalysts for the ammoxidation of propane to acrylonitrile

Abstract The effect of Te addition over Mo–V–O catalysts supported on alumina is discussed for the ammoxidation of propane to acrylonitrile. Catalyst composition and atmosphere of activation are evaluated. Catalysts are characterized before and after catalytic reaction by XPS, XRD and in situ Raman spectroscopies. The absence of Te in catalysts formulation and the presence of a high amount of vanadium induce the presence of V 5+ species and the formation of V 2 O 5 oxide; associated with a decrease in acrylonitrile selectivity. The presence of Mo-based polyacids structures decreases the selectivity to acrylonitrile. V 5+ sites are responsible of propane activation and of the subsequent α-H abstraction to form the intermediate propylene. Then, a Mo–V rutile-like structure in which vanadium species are reduced as V 4+ , is responsible for nitrogen insertion and acrylonitrile formation. The formation of such structure is favoured when Te is added to catalysts and is promoted during propane ammoxidation.

Reactive deposition of TiNx layers in a DC‐magnetron discharge

AbstractTiNx layers have been deposited in ‘balanced mode’ and ‘unbalanced mode’ of a reactive DC‐magnetron plasma (carrier gas argon, reactive gas nitrogen) under different conditions. Discharge power and reactive gas flow have been varied. The layers have been examined by X‐ray photoelectron spectroscopy (XPS), X‐ray reflectometry (XR), and spectroscopic ellipsometry (SE). The results of the layer analyses were combined with plasma investigations carried out by means of energy resolved mass spectrometry under the same conditions. By this method, it is possible to obtain a comprehensive view on the fundamentals of layer deposition, especially on the influence of the ions on the layer properties.Results show that the operation mode of the magnetron has a significant influence on the titanium deposition rate and the incorporation of nitrogen into the layers. The increased energy influx to the growing film in unbalanced mode results in a higher titanium deposition rate despite the lower number of sputtered particles. It also leads to an enhanced nitrogen insertion, since stoichiometric TiN could only be deposited in unbalanced mode. Copyright © 2008 John Wiley & Sons, Ltd.

Charge-Separation in Uranium Diazomethane Complexes Leading to C−H Activation and Chemical Transformation

The reaction of diphenyldiazomethane with [((t-BuArO)3tacn)UIII] (1) results in an eta(2)-bound diphenyldiazomethane uranium complex. This complex exhibits unusual electronic properties as a charge-separated species with a radical anionic open-shell ligand, [((t-BuArO)3tacn)UIV(eta2-NNCPh2)] (2). Treating Ph2CN2 with a uranium complex that contains a sterically more demanding adamantane functionalized ligand, [((AdArO)3tacn)UIII] (3) results in an unprecedented C-H activation and nitrogen insertion to produce a five-membered heterocyclic indazole complex, [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] (5). X-ray crystallography and spectroscopic characterization of these two compounds show that the [((t-BuArO)3tacn)UIV(eta(2)-NNCPh2)] compound is a U(IV) complex with a radical anionic ligand, whereas [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] is a U(IV) f (2) species with a closed-shell ligand.

Influence on the sp 3/sp 2 character of the carbon on the insertion of nitrogen in RFMS carbon nitride films

RFMS carbon nitride films have been elaborated at several substrate temperatures between 150 °C and 450 °C, where they evolve from a highly resistive to highly conductive comportment. Their local structure has been determined from X-ray photoemission, Raman and infrared spectroscopic results. The films composition has been measured by nuclear reaction analysis and elastic recoil detection. We will correlate the strong modifications of the electronic properties of the films to their well characterized structural changes. We will show how the substrate temperature acts on the incorporation of nitrogen in carboneous RFMS films and which is the resulting consequence on the sp 3/sp 2 character of the carbon network.

The influence of laser power and repetition rate on oxygen and nitrogen insertion into titanium using pulsed Nd:YAG laser irradiation

Oxygen and nitrogen insertion in a titanium substrate is performed in air using a Q-switched Nd-YAG laser. This process modifies the surface by the formation of specific layers on the substrate. These layers show different properties, largely influenced by the insertion of elements in the layers. The treatment conditions, especially the laser parameters (fluence and repetition rate), must be known and controlled. Using nuclear analysis, we demonstrate that oxygen insertion is mainly influenced by repetition rate, and that nitrogen insertion is controlled by laser fluence. The physical phenomena involved in the oxygen and nitrogen insertion are discussed.

Microstructure of nitrogen implanted stainless steel after wear experiment

Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation of expanded austenite in the temperature range below 420 °C is a well established phenomena. However, detailed information on the wear mechanism for the modified surfaces is still missing. This paper presents the results of wear experiments performed in a dry oscillating geometry against a WC ball (diameter 3 mm, load 3 N), together with metallographic investigations of the resulting cross-sections, both with and without nitriding. Comparisons with calculated stress distributions indicate that those nitrided samples showing a specific wear reduction by a factor of about 100 were subjected to a combination of stress maxima within the surface layer and below the layer in the bulk material.

The effect of nitrogen insertion on the magnetic and structural properties of Sm2–xGdxFe17 alloys (0 ≤ x ≤ 2)

AbstractThe effect of nitrogen insertion on the structural and magnetic properties of Sm2–xGdxFe17Ny compounds (x = 0‐2) has been investigated. X‐ray diffraction patterns at room temperature show that all our synthesized samples are single phase and crystallize in the rhombohedral Th2Zn17‐type structure with very small amount of impurity. Nitrogen insertion leads to a monotonic increase in the unit cell volume, it leads also to an increase in the Curie temperature Tc from 425 K for SmGdFe17 to 760 K for SmGdFe17N3. Moreover, the nitrogen insertion increases the saturated magnetization Ms. Ms increases from 17.9 µB/mole for SmGdFe17 to 32.7 µB/mole for SmGdFe17N3. X‐ray diffraction measurements on magnetically aligned powder samples of Sm2–xGdxFe17Ny reveal a change in the easy magnetization direction from planar before nitrogen insertion to the c‐axis after nitrogen insertion. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Crystallographic and magnetic properties of a new rare‐earth iron nitride Nd2–xSmxFe17Ny (y ∼ 3)

AbstractThe effect of nitrogen insertion on the structural and magnetic properties of Nd2–xSmxFe17 metallic alloys has been investigated. X‐ray powder diffraction characterizations show that all the nitrides are single phase and crystallize in the Th2Zn17‐type structure. The lattice parameters of the Nd2–xSmxFe17Ny compounds decrease with samarium content. Magnetization studies show that all the samples are ferromagnetic at room temperature. Nitrogen insertion leads to an increase of the Curie temperature Tc. Tc is found to increase from 370 K for NdSmFe17 to 760 K for NdSmFe17N2.8. It leads also to an increase of the saturation magnetization Ms. $ { {{\rm M}_{\rm s}({\rm y}) - {\rm M}_{\rm s}(0)} \over {{\rm M}_{\rm s}(0)} } $ decreases with increasing samarium content from 58% for x = 0 to 45% for x = 2. X‐ray diffraction characterizations on magnetically aligned powder samples of Nd2–xSmxFe17Ny reveal a change in the easy magnetization direction from planar for x = 0 to c axis for x = 2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)