Presence Of Molecular Nitrogen Research Articles

Chemische Synthese mit Gasförmigen Molekularen Ionen: Gewinnung von [B12Br11N2]− aus einem Massenspektrometer

AbstractIn der Massenspektrometrie werden häufig kurzlebige Ionen in der Gasphase beobachtet, die zuvor nicht in Lösung oder in der Bulkphase synthetisiert worden sind. Diese schwer zugänglichen Ionen werden daher oft primär als analytisch wertvoll für grundlegende Gasphasenstudien angesehen. Hier wird der Nachweis erbracht, dass die Produkte von Ionen‐Molekül‐Reaktionen in Massenspektrometern auf Oberflächen gesammelt werden können, um kondensierte Materie zu erzeugen und somit als Bausteine für die Synthese neuer Verbindungen zu dienen. Das hochreaktive Fragmentanion [B12Br11]− wurde in einem Massenspektrometer erzeugt und in Anwesenheit von molekularem Stickstoff in [B12Br11N2]− umgewandelt, gefolgt von seiner Massenselektion und sanften Deposition auf Oberflächen. Die Molekularstruktur des bisher nie zuvor synthetisierten [B12Br11N2]− wurde mit konventionellen Methoden der Molekularanalyse, einschließlich magnetischer Kernresonanz‐ und Infrarotspektroskopie, bestätigt. Das [B12Br11N2]−‐Ion ist auf Oberflächen und in Lösung bei Raumtemperatur stabil, aber Erhitzen führt zur Abspaltung von N2 und ermöglicht den Zugang zu dem hochreaktiven Zwischenprodukt [B12Br11]− in der kondensierten Phase, das beispielsweise als Reagenz für elektrophile aromatische Substitutionen weiterverwendet werden kann. Die Isolierung von [B12Br11N2]− erweitert somit das Repertoire der verfügbaren Diazo‐Ionen, die als vielseitige Zwischenprodukte bei verschiedenen chemischen Umwandlungen eingesetzt werden können.

Chemical Synthesis with Gaseous Molecular Ions: Harvesting [B12 Br11 N2 ]- from a Mass Spectrometer.

Mass spectrometry frequently reveals the existence of transient gas phase ions that have not been synthesized in solution or in bulk. These elusive ions are, therefore, often considered to be primarily of analytical value in fundamental gas phase studies. Here, we provide proof-of-concept that the products of ion-molecule reactions in mass spectrometers may be collected on surfaces to generate condensed matter and thus serve as building blocks to synthesize new compounds. The highly reactive fragment anion [B12 Br11 ]- was generated in a mass spectrometer and converted to [B12 Br11 N2 ]- in the presence of molecular nitrogen followed by its mass-selection and soft-landing on surfaces. The molecular structure of [B12 Br11 N2 ]- , which has not been synthetically obtained before, was confirmed by conventional methods of molecular analysis, including nuclear magnetic resonance and infrared spectroscopy. The [B12 Br11 N2 ]- ion is stable on surfaces and in solution at room temperature, but thermal annealing induces elimination of N2 and provides access to the highly reactive intermediate [B12 Br11 ]- in the condensed phase, which can be further used as a reagent, for example, for electrophilic aromatic substitutions. Thus, isolation of [B12 Br11 N2 ]- expands the repertoire of the available diazo ions that can be employed as versatile intermediates in various chemical transformations.

The extent of reaction traced by determination of N2 content for synthesised cationic biodegradable polymer flocculant

AbstractBiodegradable “green” and safe substitutes to minimize environmental and health risks are drawing extensive attention for research interest. This research aims to create a water‐soluble cationic starch‐grafted biodegradable polymer that can be used as a flocculant. As polymers are strong molecules that carry charges, they are effective flocculants. Saturated polymer chains do not change the pH value on adding to wastewater. The reactive groups of the starch, i.e., hydroxyls, form a complex with cations present in the reagent. According to the proposed strategy outlined in the research, the mechanism of free radical graft copolymerization of ethyl monomers onto starch should proceed as expected. In presence of molecular nitrogen, H+ may be replaced by reactive group R, i.e., CH2CH2N (Et3) (triethylamine) in a highly alkaline medium. During the work, it was observed that starch‐based flocculant exhibits a high degree of cationic charge. Developed cationic flocculant performs well in a liquid dispersion form, is fast‐acting and effective, and is suitable for treating industrial wastewater. It combines low sludge formation with cost‐effectiveness. The paper will discuss important practical considerations to increase the %N2 by changing the reaction parameters of the polymer produced and its effect on flocculation efficiency.

Synthesis and validation of water-soluble cationic biodegradable starch as a flocculant

All efforts must be made to preserve water's purity for the present and the future because it is necessary for environment's sustenance and for all living things including humans, vegetation and animals. This project is an experiment to synthesize a flocculant for industrial effluent and as a result grafted starch-based biodegradable polymer is created to benefit both natural and synthetic polymers. This research focused on creating water-soluble, cationic, biodegradable starch to use as a flocculant. The reactive groups of the starch, or hydroxyls, combine with the cations in the reagent to produce a complex. The complex can separate creating free radical sites on the polysaccharide backbone. The mechanism of free radical graft copolymerization of ethyl monomers onto starch is anticipated in the presence of molecular nitrogen. H+ may be replaced by Reactive group R i.e. (CH2 CH3)3 N - (Et3)N in highly Alkaline medium. The effect of flocculant is validated on industrial effluent by jar test with various coagulation treatments.

Syntone Chemistry. Theoretical study on the formation of glycine, alannine and serine

Three synthons: methylene, nitrene and carbon monoxide form aziridinone in the presence of molecular nitrogen at low temperatures. This one, in contact with the same three synthons could form the precursors of the first proteinogenic amino acids. This paper is a theoretical, thermodynamically and reactivity study concerning the formation of the three previously named amino acids at low temperature conditions. The key intermediates are identified in the formation of the three amino acids: aziridinone, aziridinonil and methyl-aziridinonil radicals. The quantitative results, enthalpies of formation, reaction enthalpies and free energies were taken from quantum mechanical calculations acquired by density functional method (DFT): B88-LYP.

Mechanism for the formation of nitrogen-filled voids after annealing of GaN on a sapphire substrate

This study investigated the formation of nitrogen-filled voids at the interface between a GaN layer grown on a sapphire substrate by metalorganic vapor phase epitaxy. These voids were formed in the sapphire substrate at the interface after annealing and previous research shows that they can induce an inversion domain in AlN, which affects the film quality and the device performance. We investigated the void formation using scanning electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray spectrometry, and electron energy loss spectroscopy. The voids are known to originate from the decomposition of sapphire in the presence of ammonia and hydrogen. Our analysis confirmed that the outgassing reaction between the decomposing sapphire and the low temperature GaN buffer layer resulted in the diffusion of aluminum and oxygen into the GaN buffer layer. During the annealing process, oxygen ions replaced nitrogen ions and created nitrogen-filled voids at the interface between the GaN buffer layer and the sapphire substrate. The presence of molecular nitrogen in the voids was confirmed by scanning transmission electron microscopy and electron energy loss spectroscopy.

Computational and experimental study of copper–gold nitride formation

This work investigates the formation of a Cu3Au-nitride alloy using experimental and computational methods. For this purpose, we prepared a custom-made Cu–Au target and then hit it with argon ions in the presence of molecular nitrogen that produced a film on Corning glass. This film was analyzed using spectroscopic and diffraction techniques. The four-point-probe method and Tauc plots were applied to determine the electrical and optical properties of this thin film. Using first principle calculations a structural model was constructed that validated our observations. The crystalline system that we used was cubic (Pm3m space group) with half the sites filled with Au randomly. The composition was close to Cu3Au0.5N. In agreement with the electrical measurements and calculations, the Cu3Au0.5N band structure was highly affected by the Au incorporation since the electrical resistance and carrier density were in the 10−3Ωcm and 1022cm−3 ranges, respectively, and the optical gap decreased 0.61eV with respect to the Cu3N. The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature; this should give it great potential for use in the optoelectronics industry.

Numerical prediction of optical lattice-induced gas heating within multipass optical cavities

Direct simulation Monte Carlo was used to investigate the potential of non-resonant optical lattice gas heating in the context of two proposed multipass optical cavity designs. One-dimensional lattices were formed by two 5 ns, 100 mJ, 532 nm simulated laser pulses in the presence of molecular nitrogen. Simulations suggest that these cavity designs are able to facilitate a several fold increases in deposited energy as a result of optical lattice gas heating, with the more efficient of these designs leading to a 14-fold increased temperature change (ΔT ≈ 350 K) for the first ten passes over the single-pass case (ΔT ≈ 25 K).

The Tribological Properties of Low-friction Hydrogenated Diamond-like Carbon Measured in Ultrahigh Vacuum

In this paper, we investigate the sliding friction and wear behavior of a hydrogenated diamond-like carbon (DLC) film in ultrahigh vacuum (UHV) and under partial pressures of water vapor, oxygen, nitrogen and hydrogen. The initial friction coefficient of the film in UHV was ~0.15, but decreased steadily to values as low as 0.03 after about 30 sliding passes. During longer duration tests, the friction coefficient increased again to values as high as ~0.15 and such an increase in friction coincided with hydrogen desorption from the contacting surfaces (as detected by a mass spectrometer). Heating DLC to temperatures higher than 360 K also caused desorption of hydrogen and a resulting marked increase in friction. The presence of molecular nitrogen, oxygen and hydrogen in the test chamber did not have any noticeable effect on friction, but the presence of thermally dissociated or ionized hydrogen within the close proximity of sliding surfaces had a beneficial effect by restoring the low friction behavior of the DLC films. The introduction of water vapor into test chamber had an adverse effect on friction. The results of this study confirm that hydrogen is key to low friction behavior of hydrogenated DLC films and that the presence of water molecules has an adverse effect on their friction behavior.

Formation of Phosphorus−Nitrogen Bonds by Reduction of a Titanium Phosphine Complex under Molecular Nitrogen

The reduction of high oxidation state metal complexes in the presence of molecular nitrogen is one of the most common methods to synthesize a dinitrogen complex. However, the presence of strong reducing agents combined with the poor binding ability of N2 can lead to unanticipated outcomes. For example, the reduction of [NPN]ZrCl2(THF) (where NPN = PhP(CH2SiMe2NPh)2) with KC8 under N2 leads to the formation of the side-on bridged dinuclear dinitrogen complex ([NPN]Zr(THF))2(mu-eta2:eta2-N2) with an N-N bond distance of 1.503(3) A; however, reduction of the corresponding titanium precursor, [NPN]TiCl2, under N2 does not generate a dinitrogen complex, rather the bis(phosphinimide) derivative, ([N(PN)N]Ti)2, is isolated in which the added N2 is incorporated between the titanium and phosphine centers. Performing the reaction under 15N2 results in the 15N label being incorporated in the phosphinimide unit. A suggested mechanism for this process involves an initially formed dinitrogen complex being over reduced to generate a species with bridging nitrides that undergoes nucleophilic attack by the coordinated phosphine ligands and formation of the P=N bond of the phosphinimide.

Reduction of hafnium(IV) complexes in the presence of molecular nitrogen: Attempts to form dinitrogen complexes of the heaviest group 4 element

The reaction of [P2N2]Li2(dioxane)2 with HfCl4(THF)2 (where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)2PPh) results in the formation of the hafnium dichloride complex [P2N2]HfCl2 (1). The behaviour of 1 as a potential precursor in the generation of a dinitrogen coordination complex is described. Reduction of 1 with potassium-graphite (C8K), under dinitrogen, under a variety of conditions led to a number of products, one of which is the dinuclear derivative with bridging P-phenyl groups that has the general formula {[P2N2]Hf}2 (2). Reduction of the hafnium diiodide [P2N2]HfI2 (3) — prepared via the reaction of 1 with excess Me3SiI — with C8K results in the formation of ([P2N2]Hf)2(µ-η2:η2-N2) (4) as the major product of the reaction, while {[P2N2]Hf}2 (2) and [P2N2]Hf(C7H8) (5) appear to be minor products. Reaction of 1 with 2 equiv of MeMgCl gives [P2N2]HfMe2 (6), which, upon exposure to an atmosphere of H2, gives the hafnium tetrahydride {[P2N2]Hf}2(m-H)4 (7).Key words: hafnium, dinitrogen, reduction, coordination chemistry, hydride, mixed donor ligands.

X‐ray absorption spectroscopy in the analysis of GaN thin films

AbstractStoichiometric amorphous GaN thin films have been grown by an ion‐assisted deposition method and examined by x‐ray photoelectron spectroscopy and x‐ray absorption near‐edge spectroscopy (XANES). The crucial question is the nature of the local structure around the N and Ga in the x‐ray amorphous films. The N K edge XANES has been used to determine coordination around the N centre and reveals substantial differences to crystalline GaN. Although the transitions observed mirror those of the crystalline material and are consistent with density of states calculations, the low‐energy peak at ∼402 eV is dominant in all films less than ∼150 nm in thickness. This peak, initially attributed to an sp2 environment, is associated with the presence of molecular nitrogen. For thicker films, a duplex‐type structure is observed with a surface layer much closer to the structure of the crystalline material. Copyright © 2003 John Wiley & Sons, Ltd.

On the presence of molecular nitrogen in nitrogen-implanted amorphous carbon

Hard amorphous carbon (ta-C) films were implanted with 20 keV N+ ions into saturation at two different temperatures. Monitoring the composition ratio [N]/[C] using in situ elastic recoil detection analysis, saturation levels [N]/[C] of 0.35 and 0.16 have been found for implantations at room temperature and 400 °C, respectively. Raman and x-ray photoelectron spectroscopy analyses of the implanted films indicate the presence of N2 molecules inside room-temperature implanted samples, but not for the case of implantation at 400 °C. Cross-section transmission electron microscopy images show the presence of near-surface voids, interpreted as remnants of N2-filled bubbles, in the former case. Annealing experiments show that about 50% of the total N inventory consists of nitrogen only weakly trapped inside the carbon matrix in room-temperature implanted films, this fraction being significantly reduced in samples held at 400 °C during implantation.

Metallo-oxides in nitrogen fixation

Ammonia is released from the metallo-imide trans-[W(NH)(OMe)(Ph2PCH2CH2PPh2)2]+ without degradation of the phosphine ligand assembly by a hydrolysis reaction which gives the oxide trans-[WOCl(Ph2PCH2CH2PPh2)2]+; and this oxide and its Mo analogue are reduced at a mercury cathode in the presence of molecular nitrogen with phenol as a proton source to give trans-[M(N2)2(Ph2PCH2CH2PPh2)2](M = Mo or W); the primary reduction potentials of the Mo and W oxides are substantially positive of those of their isostructural imide counterparts and this suggests a possible role for oxides in biological nitrogen fixation.

Cs+-electron recombination in the presence of N2, O2, and CO2 at 300 K

The mechanism and rate constants associated with three-body recombination of Cs+ and electrons have been determined by monitoring the disappearance of electrons using a movable double Langmuir probe in a flowtube apparatus. The ambipolar diffusion rate constant for the dilute plasma in argon and helium was measured to be 380±30 cm2 s−1 and 650±200 cm2 s−1, respectively. Electron-ion recombination was measured in the presence of molecular nitrogen, oxygen, and carbon dioxide. From the kinetics of the electron disappearance along the flowtube, plasma recombination in nitrogen can be explained by the formation of a complex ion, recombination in oxygen proceeds through the formation of the O−2 followed by dissociative attachment in which the latter step is the rate determining step, and recombination in CO2 can be attributed to a direct three-body process.

Photolysis of Water and Photoreduction of Nitrogen on Titanium Dioxide

The photolysis of chemisorbed water on incompletely outgassed TiO/sub 2/ powder yields H/sub 2/ and O/sub 2/ in the molar ratio of 2 : 1 if conducted under argon. In the presence of molecular nitrogen, O/sub 2/ is still formed but the evolution of H/sub 2/ is inhibited as chemisorbed nitrogen is reduced to NH/sub 3/ and traces of N/sub 2/H/sub 4/ according to N/sub 2/ + 3H/sub 2/O + nhv yields 2NH/sub 3/ + 1.50/sub 2/ and N/sub 2/ + 2H/sub 2/O + mhv yields N/sub 2/H/sub 4/ + O/sub 2/. Iron doping enhances the photocatalytic reactivity of rutile and provides prototypes of solar cells for photochemical ammonia synthesis from N/sub 2/ and H/sub 2/O.

Measurements of vibrationally excited molecules by Raman scattering. I The yield of vibrationally excited nitrogen in the reaction N+NO → N2+O

The reaction of nitrogen atoms with nitric oxide leads to vibrationally excited nitrogen. In the presence of molecular nitrogen, V-V exchange processes rapidly establish a modified distribution for which a measurement of N2(ν=1) is adequate to determine the total vibrational energy yield of the reaction. The measurements of N2 (ν=1) have been made by Raman spectroscopy using the intensity of the Q branch of the anti-Stokes line at 4382 Å (using 4880 Å Ar+ laser radiation). The system sensitivity is determined using heated nitrogen. The measurements have established that 25 ± 3% of the available energy (3.27 eV) appears as vibrational energy and that the vibrationally excited nitrogen is an initial product and does not result from collisions of translationally hot oxygen atoms with nitrogen.