Nitrosonium Nitrate Research Articles

Nitro-sonium nitrate (NO+NO3 -) structure solution using in situ single-crystal X-ray diffraction in a diamond anvil cell.

At high pressures, autoionization - along with polymerization and metallization - is one of the responses of simple molecular systems to a rise in electron density. Nitro-sonium nitrate (NO+NO3 -), known for this property, has attracted a large interest in recent decades and was reported to be synthesized at high pressure and high temperature from a variety of nitro-gen-oxygen precursors, such as N2O4, N2O and N2-O2 mixtures. However, its structure has not been determined unambiguously. Here, we present the first structure solution and refinement for nitro-sonium nitrate on the basis of single-crystal X-ray diffraction at 7.0 and 37.0 GPa. The structure model (P21/m space group) contains the triple-bonded NO+ cation and the NO3 - sp 2-trigonal planar anion. Remarkably, crystal-chemical considerations and accompanying density-functional-theory calculations show that the oxygen atom of the NO+ unit is positively charged - a rare occurrence when in the presence of a less-electronegative element.

Quantum-chemical modeling of the mechanism for formation of HNO3 from NO2 and water

The B3LYP density functional method with the expanded 6-311++G(3df,3pd) basis was used to calculate the energy profiles of the reaction 2NO2 + H2O→HNO2 + HNO3 in the gas phase and in the presence of water. The acid formation process should proceed through prior dimerization of ∙NO2 radicals to give an asymmetrical trans isomer of ONONO2 in the rate-limiting step with subsequent formation of nitrosonium nitrate $ {\mathrm{N}}{{\mathrm{O}}^{+} }{\mathrm{NO}}_3^{-} $ .

Adsorption and Surface Reaction of NO2 on a Stepped Au(997) Surface: Enhanced Reactivity of Low-Coordinated Au Atoms

The adsorption and surface reaction of NO2 on a stepped Au(997) surface were investigated by temperature-programmed desorption, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. At low NO2 exposures, NO2 chemisorbs molecularly and reversibly on the Au(997) surface at 130 K, but low-coordinated Au atoms on the (111) step sites exhibit enhanced reactivity. NO2(a) chemisorbed on the (111) step sites is thermally more stable than that chemisorbed on the (111) terrace sites. At large NO2 exposures, an amorphous physisorbed N2O4 multilayer forms at 130 K. Subsequent heating causes the isomerization of the physisorbed N2O4 multilayer (O2N–NO2) to nitrite–N2O4 (ONO–NO2) and the subsequent transformation of nitrite–N2O4 into nitrosonium nitrate (NO+NO3–) that further decomposes into NO(g) and NO2(g) at elevated temperatures, forming O(a) on the surface. These surface reactions could be utilized to prepare oxygen adatoms on inert Au surfaces under ultrahigh vacuum conditions. Our results broaden the fundamental understanding of the interaction between small molecules and Au surfaces.

ChemInform Abstract: Raman Studies on Molecular and Ionic Forms in Solid Layers of Nitrogen Dioxide: Temperature and Light Induced Effects.

Raman spectra of zero pressure formed N2O4 solid layers are reported. Sample composition is extremely dependent upon deposition conditions. For ordered and pure solid N2O4(D2h), produced by slow NO2 deposition, temperature cycling over the range in which the solid is stable shows no significant spectral changes and does not result in autoionization, as argued in a previous Raman study. Fast and low temperature deposited layers are amorphous and multicomponent, showing bands of disordered and isomeric molecular N2O4 and of ionic NO+NO−3, nitrosonium nitrate. For nitrosonium nitrate, three solid modifications (two crystalline, one amorphous) can be characterized spectroscopically. In the amorphous phase, a light induced, temperature dependent, reversible transition between molecular and ionic nitrogen tetroxide is observed below 150 K. The paths leading to nitrosonium nitrate formation are examined.

ChemInform Abstract: Nitrosonium Nitrate: A Simple Cryogenic Preparation and Phase Transitions.

A simple method is suggested for the preparation of pure nitrosonium nitrate (NO+ NO3−) thin films, by deposition of nitrogen dioxide from the gas phase onto a cold tip under specified conditions and subsequent warming up of the layer. Fourier-transform infrared spectra were used for its characterization and to determine its purity. The NO+ NO3− solid thus formed was found to be stable up to 230 K. Raman examination of temperature cycling effects on thev(NO+) band and on the phonon region of the thin films indicates one amorphous and two crystalline phases. Amorphous-crystalline and crystalline-crystalline transition temperatures are reported.

Quantum-chemical evidence for the possible existence of a new isomer of dinitrogen tetraoxide

The geometric, electronic, and thermodynamic parameters of six known isomers of the molecular structure of dinitrogen tetraoxide N2O4 were calculated by the quantum-chemical DFT/B3LYP density functional method with the 6-311++G(3df) basis set. The structure of a new isomer of dinitrogen tetraoxide NONO3, which is characterized by a local potential energy minimum and corresponds to a stationary state of the N2O4 isomer, was calculated. The DFT calculations showed that this structure NONO3 is characterized by a significant negative charge on the NO3 fragment and a positive charge on the NO fragment. The calculated dipole moment of nitrosonium nitrate NO+NO 3 − in the gas phase is 4.13 D.

Potential Role of the Nitroacidium Ion on HONO Emissions from the Snowpack

The effects of photolysis on frozen, thin films of water-ice containing nitrogen dioxide (as its dimer dinitrogen tetroxide) have been investigated using a combination of Fourier transform reflection-absorption infrared (FT-RAIR) spectroscopy and mass spectrometry. The release of HONO is ascribed to a mechanism in which nitrosonium nitrate (NO+NO3-) is formed. Subsequent solvation of the cation leads to the nitroacidium ion, H2ONO+, i.e., protonated nitrous acid. The pathway proposed explains why the field measurement of HONO at different polar sites is often contradictory.

High-pressure transformation ofN2∕O2mixtures into ionic compounds

We report the neutral-ionic transformation of ${\mathrm{N}}_{2}∕{\mathrm{O}}_{2}$ mixtures above $5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The reaction is photoinduced with a Nd:YAG laser irradiation. The ionic compounds are characterized by Raman and infrared spectroscopic and synchrotron x-ray diffraction measurements. We show by Raman analysis that the $\mathrm{N}{\mathrm{O}}^{+}\mathrm{N}{\mathrm{O}}_{3}^{\ensuremath{-}}$ compound can trap a large fraction of ${\mathrm{O}}_{2}$ molecules, thus forming an ${\mathrm{O}}_{2}$ clathrate. But no ${\mathrm{N}}_{2}$ molecule can be included in this nitrosonium nitrate compound. We propose an orthorhombic unit cell with 10 $\mathrm{N}{\mathrm{O}}^{+}\mathrm{N}{\mathrm{O}}_{3}^{\ensuremath{-}}$ in it.

High-pressure stability, transformations, and vibrational dynamics of nitrosonium nitrate from synchrotron infrared and Raman spectroscopy

The properties of nitrosonium nitrate (NO+NO3−) were investigated following synthesis by laser heating of N2O and N2O4 under high pressures in a diamond anvil cell. Synchrotron infrared absorption spectra of NO+NO3− were measured at pressures up to 32 GPa at room temperature. Raman spectra were obtained at pressures up to 40 GPa at room temperature and up to 14 GPa at temperatures down to 80 K. For both lattice and intramolecular vibrational modes, a smooth evolution of spectral bands with pressure indicates that NO+NO3− forms a single phase over a broad range above 10 GPa, whereas marked changes, particularly evident in the Raman spectra at low temperature, indicate a phase transition occurs near 5 GPa. NO+NO3− could be recovered at atmospheric pressure and low temperature, persisting to 180 K. The Raman and IR spectroscopic data suggest that the NO+NO3− produced by laser heating of N2O followed by decompression may differ in structure or orientational order–disorder from that produced by autoionization of N2O4.

High-pressure structure and equation of state study of nitrosonium nitrate from synchrotron x-ray diffraction

Several nitrogen oxide compounds transform to nitrosonium nitrate (NO+NO3−) under high pressure. In this study, NO+NO3− was synthesized by laser heating of N2O in a diamond-anvil cell and characterized by x-ray diffraction as a function of pressure at room temperature and low temperature. The unit-cell parameters were refined up to 32.2 GPa at 300 K, resulting in a denser structure than reported previously. The pressure-volume relations for NO+NO3− at 300 K were fitted to both Birch-Murnaghan and Vinet equations of state. The analysis indicates that NO+NO3− is denser than other nitrogen-oxygen assemblages, consistent with the conclusion that formation of the ionic species is driven by density rather than entropic effects. The low-temperature x-ray-diffraction data represent the first in situ measurements for this material, revealing consistent structural information and evolutions under pressure. These observations provide additional information on the stability relations and reaction diagram of N2O and NO+NO3−.

Novel Broken Symmetry Phase fromN2Oat High Pressures and High Temperatures

Simple molecular solids become unstable at high pressures, typically transforming to dense framework and/or metallic structures. We report formation of an unusual ionic solid NO(+)NO(3)(-) (nitrosonium nitrate) from N(2)O at pressures above 20 GPa and temperatures above 1000 K. Synchrotron x-ray diffraction indicates that the compound crystallizes with a structure related to the aragonite form of CaCO(3) and NaNO(3). Raman and infrared spectroscopic data indicate that the structure is noncentrosymmetric and exhibits a strong pressure dependent charge transfer and orientational order.

Reactions of N 2O 4 with ice at low temperatures on the Au(111) surface

Reactions of N 2O 4, formed by condensation of NO 2 gas, with adsorbed water films as models for ice surfaces were studied on a Au(111) substrate at low temperatures under ultrahigh vacuum (UHV) conditions. Two thermal reaction paths were found, primarily by using infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) techniques. One path evolved gas phase HONO (nitrous acid) and HNO 3 (nitric acid) below 150 K, independent of both the crystallinity of the ice film and the exposure of NO 2. In contrast, another reaction pathway depended strongly on these variables and was conveniently monitored by the formation of oxygen adatoms on the Au(111) substrate surface. The latter reactions only occurred following multilayer adsorption of NO 2 (present as N 2O 4) and only if the adsorption was on amorphous ice clusters and not crystalline ice. The extent of these reactions was proportional to the concentration of ‘free-OH’ groups on the ice film, indicating that water molecules with only two hydrogen bonds were required to initiate these reactions by strongly hydrating N 2O 4. Following adsorption of N 2O 4 multilayers on amorphous ice, we propose that isomerization of O 2N–NO 2 (D 2h–N 2O 4) to ONO–NO 2 (nitrite–N 2O 4) occurs upon heating to 130–185 K. Further heating to 200–260 K leads to formation of NO +NO − 3 (nitrosonium nitrate). This compound is stable on the Au(111) surface up to at least 275 K. Decomposition of NO +NO − 3 on the Au(111) surface at 275–400 K evolves gas-phase NO 2, and possibly NO (nitric oxide), and also produces oxygen adatoms that recombine and thermally desorb as O 2 at about 520 K. These investigations provide new data on reactions of nitrogen oxides and condensed phases of water, which are of general importance for several technologies and improved understanding of atmospheric chemistry. In addition, new details are revealed concerning a novel method for producing oxygen adatoms on Au(111) surfaces under UHV conditions.

Nitrosonium Nitrate, an Isomer of N2O4 in IF5

N2O4 dissolves in IF5 as NO+NO3–, as established by n.m.r spectroscopy, and in the solid state the solvate complex NO+NO3– · IF5 is formed. This contains a double chain of alternating NO+ cations and NO3– anions. (a = 483.4(2), b = 773.9(1), c = 932.6(3) pm, (α = 70.18(2)°, β = 80.90(3)°, (γ = 87.34(2)°, space group P1, Z = 2). Nitrosoniumnitrat, ein Isomer des N2O4 in Gegenwart von IF5 N2O4 lost sich in IF5 als NO+NO3–, wie mit der Kernresonanzspektroskopie bewiesen wird. Im festen Zustand bildet sich ein Solvatkomplex der Formel NO+NO3– · IF5, welcher eine Doppelkette alternierender NO+-Kationen und NO3–-Anionen enthalt (a = 483.4(2), b = 773.9(1), c = 932.6(3) pm, (α = 70.18(2)°, β = 80.90(3)°, (γ = 87.34(2)°, Raumgruppe P1, Z = 2).

Photochemical transformations of dinitrogen tetraoxide in a frozen glassy matrix

The presence of minima on the potential energy surface was shown by semiempirical calculations. These minima correspond to five isomers of dinitrogen tetraoxide: two symmetrical structures of the O2N-NO2 type, two nonsymmetrical structures of the O2N-ONO type, and nitrosonium nitrate NO+NO3−. Quantum yields of photochemical reactions of dinitrogen tetraoxide in a matrix of glassy methylcyclohexane (at 77 K) were determined experimentally to be equal to ≈l, ≈0.15, and ≈10−5 for photoisomerization of symmetrical N2O4 into the nonsymmetrical isomer, reverse photoisome rization, and photodissoeiation to form the stabilized pair of NO2 fragments, respectively. Measurements of the degree of orientation of the products of photochemical transformations performed by photolysis with polarized light show that the photoisomerization occurs via the intramolecular mechanism in a matrix cage, and the photodissoeiation is associated with considerable migration of the molecular fragments formed.

Catalytic autoxidation of benzoquinone dioximes with nitrogen oxides: steric effects on the preparation of monomeric dinitrosobenzenes

A convenient catalytic method for the autoxidation of quinone dioximes to dinitrosobenzenes with dioxygen is based on the presence of small amounts of nitrogen oxides. The catalytic cycle is deduced from the facile chemical oxidation of quinone dioxime to dinitrosobenzene with stoichiometric amounts of the 1-electron oxidant, nitrosonium—either as the NO+BF4– salt or the disproportionated ion pair NO+NO3– derived from nitrogen dioxide. The regeneration of NO+ occurs by the subsequent oxidation of nitric oxide (NO) with dioxygen to nitrogen dioxide followed by the disproportionation to nitrosonium nitrate in the presence of electron-rich donors. Indeed, dioximes of various p-benzoquinones are shown to be strong reducing agents by transient electrochemistry. Electrochemical oxidation also leads to dinitrosobenzenes in good yields at anodic potentials of ca. 1.3 V. The substitution of p-dinitrosobenzene with bulky alkyl groups stabilizes the monomeric form, which is otherwise extensively associated.

Fourier transform infrared study of amorphous N2O4 solid: Destabilization with inert impurities

Amorphous N2O4 solid was formed on predeposited oxygen or krypton layers. Evaporation of the underlying layer and redeposition of the inert impurities resulted in decomposition of the ionic nitrosonium nitrate clusters within the solid nitrogen tetroxide. Infrared features indicate NO+NO−3 decomposition to occur via molecular NONO3 , with NO2 monomers as products. Evaporation of the inert impurities and recooling restored the amorphous N2O4 from which NO+NO−3 was formed again.

Raman studies on molecular and ionic forms in solid layers of nitrogen dioxide: Temperature and light induced effects

Raman spectra of zero pressure formed N2O4 solid layers are reported. Sample composition is extremely dependent upon deposition conditions. For ordered and pure solid N2O4(D2h), produced by slow NO2 deposition, temperature cycling over the range in which the solid is stable shows no significant spectral changes and does not result in autoionization, as argued in a previous Raman study. Fast and low temperature deposited layers are amorphous and multicomponent, showing bands of disordered and isomeric molecular N2O4 and of ionic NO+NO−3, nitrosonium nitrate. For nitrosonium nitrate, three solid modifications (two crystalline, one amorphous) can be characterized spectroscopically. In the amorphous phase, a light induced, temperature dependent, reversible transition between molecular and ionic nitrogen tetroxide is observed below 150 K. The paths leading to nitrosonium nitrate formation are examined.

Nitrosonium nitrate: A simple cryogenic preparation and phase transitions

A simple method is suggested for the preparation of pure nitrosonium nitrate (NO+ NO3−) thin films, by deposition of nitrogen dioxide from the gas phase onto a cold tip under specified conditions and subsequent warming up of the layer. Fourier-transform infrared spectra were used for its characterization and to determine its purity. The NO+ NO3− solid thus formed was found to be stable up to 230 K. Raman examination of temperature cycling effects on thev(NO+) band and on the phonon region of the thin films indicates one amorphous and two crystalline phases. Amorphous-crystalline and crystalline-crystalline transition temperatures are reported.

On the intermolecularity or intramolecularity of nitrosonium nitrate formation in thin films of nitrogen dioxide: A Fourier transform infrared study

The question of whether the formation of the NO+NO−3 (nitrosonium nitrate), the ionic form of nitrogen dioxide, via the decomposition of the ON–O–NO2, ‘‘D′’’ isomer, is an inter- or intramolecular process, is addressed via temperature and concentration dependent FTIR studies of mixed films of N2O4 with CCl4. The process of nitrosonium nitrate production, both during deposition of disordered solid films of nitrogen dioxide and during their subsequent warming, is concluded to be intermolecular but not order dependent. A mechanism is tentatively suggested.

Fourier transform infrared and Raman studies on solid nitrogen dioxide: Temperature cycling of ordered, disordered, and multicomponent layers

Fourier transform infrared (FTIR) spectra of nitrogen dioxide layers deposited at various rates and substrate temperatures, are reported. Bands assignable to N2O4(D2h) (ordered and disordered layers), to O=N–O–NO2 ‘‘D’’ and ‘‘D′’’ isomers, to NO+NO−3 nitrosonium nitrate and to the NO2 monomer were observed. The relative amounts of species depends upon deposition conditions. Temperature cycling effects were followed up to 205 K. Solid N2O4(D2h) behaves like a normal, stable molecular solid, its disordered layer exhibiting small frequency shifts, but also being stable with respect to temperature cycling. The observation of NO+NO−3 bands is related to the existence of the D′ isomer and of monomeric NO2. Raman experiments overemphasize the NO+NO−3 form due to resonant enhancement.