Nitrosonium nitrite isomer of N<Subscript>2</Subscript>O<Subscript>3</Subscript>: Quantum-chemical data

The geometrical, electronic, and thermodynamic parameters of three known isomers of dinitrogen trioxide N₂O₃ were calculated by the density functional theory DFT/B3LYP method using the 6-311++G(3df) basis. The structure of the new isomer, NONO₂, was calculated. From the calculation of vibrational frequencies it follows that the structure of NONO₂ has a local potential energy minimum and corresponds to the stationary state of the N₂O₃ isomer. The molecular structure of NONO₂ is characterized by a substantial negative charge on the NO₂ fragment and positive charge on the NO fragment. The electronic structure of the NO⁺NO ₂ ^? isomer can be characterized as nitrosonium nitrite, which can be oxidized to nitrite and participate in nitrosylation in accordance with the biogenic characteristics of the NO _x intermediate, assumed to be formed in biological systems during the oxidation of NO.     

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.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 854–858, April, 1996.     

X-ray diffraction analysis: A brief history and achievements of the first century

A DFT/B3LYP method using the 6-311++G(3df) basis set is employed to calculate the geometric, electronic, and thermodynamic parameters of O=NO-ON=O peroxide as an isomer of N₂O₄ dinitrogen tetraoxide. Calculations of the configuration interaction in a system of three paramagnetic particles with open shells have shown for the first time that the formation of cis-cis peroxide in the oxidation reaction of nitrogen oxide 2NO (²Π) + O₂ (³Σ_g) → O=NO-ON=O (¹ A) proceeds without an energy barrier in accordance with recently performed studies. The molecular orbital scheme of the barrierless activation of molecular oxygen and the driving force of the NO oxidation reaction are considered. A spontaneous character of the process is based on the idea of spin-catalysis when the reaction proceeds in the two-triplet state with total zero spin. The obtained results are in agreement with the experimental data on a spontaneous and irreversible process characterized by the observed negative activation energy.     

Quantum-chemical DFT calculations of the molecular structure of N<Subscript>2</Subscript>O<Subscript>5</Subscript> in the gas and solid phases

By functional density quantum-chemical method (DFT/B3LYP using the 6-311++G(3df)) it has been shown that the molecular structures of N₂O₅ with C_s and C₂ symmetries are energetically equivalent. It follows from calculations of the vibrational frequencies that both structures are characterized by potential energy minima and correspond to stationary states of the N₂O₅ molecule. It is proposed, on the basis of a comparison of the calculated and experimental vibrational spectra of N₂O₅, that dinitrogen pentaoxide exists in the gas phase as an equimolecular mixture of N₂O₅ molecules with Cs and C₂ symmetry, while in the solid phase it is characterized by the C₂ molecular structure. __________ Translated from Teoreticheskaya I éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 58–63, January–February, 2007.     

Coulomb explosion dynamics of N2O in intense laser-field: Identification of new two-body and three-body fragmentation pathways

The Coulomb explosion process of N₂O in an intense laser-field (∼5 PW/cm²) has been investigated by the high-resolution time-of-flight (TOF) spectroscopy. Six two-body explosion pathways involving the NO⁺, NO²⁺, N₂ ⁺ molecular ions have been securely identified from the momentum-scaled TOF spectra of the fragment ions. Assuming a linear geometry, three-body explosion pathways were investigated by sequential and concerted explosion models. When the concerted model is adopted, the observed momentum distributions of six atomic ion channels; N⁺, N²⁺, N³⁺, O⁺, O²⁺ and O³⁺, were well fitted using the Gaussian momentum distribution with the optimized bond elongation factor of 2.2(3). From the yields of individual Coulomb explosion pathways determined by the fit, the abundance of the parent ions, N₂O^z+ (z=2–8), prior to the two- body and three-body explosion processes was found to have a smooth distribution with a maximum at z∼3.     

Charge-transfer absorption of olefins with nitrosonium. Structural relevance to the dimethylbutene complex with dinitrogen tetraoxide

The transient electron donor-acceptor (EDA) complexes of various olefins (dimethylbutene, etc.) with the nitrosonium acceptor (NO⁺) show diagnostic charge-transfer absorption bands in dichloromethane solutions at low temperatures. Since the same charge-transfer absorption bands are observed when olefins are exposed to dinitrogen tetraoxide, they are ascribed to analogous EDA complexes [olefin, NO⁺] NO₃ ^? that are derived from the ionic disproportionation of nitrogen dioxide.     

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

Three new squarate salts were synthesized and combined with experimental and theoretical study on molecular, vibrational, and electronical properties. Squaric acid was crystallized as HSQ⁻ [SQ: squarate] monoanion in [(C₁₃H₁₂NO₂)(HC₄O₄)] (I), as uncharged H₂SQ in [(C₅H₅N₃O)(H₂C₄O₄)] (II), and as SQ²⁻ dianion form in [C₆H₉N₂)₂(C₄O₄)] (III). They crystallize in the triclinic and monoclinic crystal system with space group P−1, P2₁/c, and P2₁/c, respectively. Crystal structure analysis reveals that, far from forming discrete ionic species in (I) and (II), it is likely that there is large degree of proton sharing between the two hydrogen squarate anions in (I) and between the neutral moieties in (II), with the H atom lying almost symmetrically between the donor and acceptor sites, as evidenced by the long O–H and N–H bonds and short H···O distances. Ab initio calculations have been carried out for three compounds by using DFT/B3LYP and HF methods at 6-31++G(d,p) basis set. Although the supramolecular interactions have some influences on the molecular geometry in solid state phase, calculated data show that the predicted geometries can reproduce the structural parameters. The results of the optimized molecular structure for three compounds obtained on the basis of two models are presented and compared with the experimental X-ray data. Calculated vibrational frequencies are consistent with each other and experimental IR data. The theoretical electronic absorption spectra have been calculated by both TD–DFT and HF–CIS methods. Molecular orbital coefficients analysis suggest that the electronic transitions are mainly assigned to n → π* and π → π* electronic transitions.     

Aminoxyl Radicals from N-Phenyl-1-(2-oxo-1-azacycloalkyl)-methanesulfonamides

The synthesis and reaction with two oxidation agents is described for N-phenyl-1-(2-oxo-1-azacycloalkyl)methanesulfonamides. Their oxidation was carried out using RO_2^·R{\rm O}_{2^\bullet} radicals and 3-chloroperbenzoic acid. In both cases, the EPR spectra of corresponding aminoxyl radicals were recorded. Their simulation confirmed that the –SO₂– group in the neighbourhood of the – NO^·{{\rm NO}^\bullet} – fragment does not prevent the interaction of the unpaired electron with the methylene protons and the nitrogen atom of the heterocyclic ring.     

Effects of protonation on proton transfer processes in Watson–Crick adenine–thymine base pair

Intermolecular proton transfer processes in the Watson and Crick adenine–thymine neutral and protonated base pairs have been studied using the density functional theory (DFT) with the non-local hybrid B3LYP density functional. Protonated systems subject to study are those resulting from protonation at the main basic sites of the base pair model, namely N₇ and N₃ of adenine and O₂^′ and O₄^′ of thymine. Protonation of adenine induces a strengthening by about 4–5 kcal/mol of the base pair and does not significantly modify the double proton transfer energy profile obtained for the unprotonated system. On the other hand, protonation at the O₄^′ and O₂^′ thymine moiety causes thymine’s N₃ proton to spontaneously transfer to adenine while non-transferred minima disappear at this level of theory. The different behaviour between protonated adenine– thymine and protonated guanine–cytosine is discussed. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Contribution to the Fernando Bernardi Memorial Issue.     

Palladium(II) complexes with R2edda-derived ligands. Part V. Reaction of O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate with K2[PdCl4]

The reaction of K₂[PdCl₄] with [(S,S)-H₂(Et)₂eddv]Cl₂ diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl₂{(S,S)-(Et)eddv-κ² N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (¹H and ¹³C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.     

Low-temperature activation of nitrogen oxide on Cu-ZSM-5 catalysts

The adsorption and activation of NO molecules on Cu-ZSM-5 catalysts with different Cu/Al and Si/Al ratios (from 0.05 to 1.4 and from 17 to 45, respectively) subjected to different pretreatment was studied by ultraviolet-visible diffuse reflectance (UV-Vis DR). It was found that the amount of chemisorbed NO and the catalyst activity in NO decomposition increased with an increase in the Cu/Al ratio to 0.35–0.40. The intensity of absorption bands at 18400 and 25600 cm⁻¹ in the UV-Vis DR spectra increased symbatically. It was hypothesized that the adsorption of NO occurs at Cu⁺ ions localized in chain copper oxide structures with the formation of mono- and dinitrosyl Cu(I) complexes, and this process is accompanied by the Cu²⁺...Cu⁺ intervalence transfer band in the region of 18400 cm⁻¹. The low-temperature activation of NO occurs through the conversion of the dinitrosyl Cu(I) complex into the π-radical anion (N₂O₂)⁻ stabilized at the Cu²⁺ ion of the chain structure, [Cu²⁺-cis-(N₂O₂)⁻], by electron transfer from the Cu⁺ ion to the cis dimer (NO)₂. This complex corresponds to the L → M charge transfer band in the region of 25600 cm⁻¹. The subsequent destruction of the complex [Cu²⁺-cis-(N₂O₂)⁻] at temperatures of 150–300°C leads to the release of N₂O and the formation of the complex [Cu²⁺O⁻], which further participates in the formation of the nitrite-nitrate complexes [Cu²⁺(NO₂)⁻], [Cu²⁺(NO)(NO₂)⁻], and [Cu²⁺(NO₃)⁻] and NO decomposition products.     

First heterobimetallic AgI–CoIII coordination compound with both bridging and terminal –NO2 coordination modes: synthesis,characterization, structural and computational studies of (PPh3)2AgI–(μ‐κ2O,O′:κN‐NO2)–CoIII(DMGH)2(κN‐NO2)

An unusual heterobimetallic bis(triphenylphosphane)(NO₂)Ag^I–Co^III(dimethylglyoximate)(NO₂) coordination compound with both bridging and terminal –NO₂ (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)₂(PPh₃)] (DMGH₂ is dimethylglyoxime or N,N′‐dihydroxybutane‐2,3‐diimine) with excess AgNO₂. In the title compound, namely bis(dimethylglyoximato‐1κ²O,O′)(μ‐nitro‐1κN:2κ²O,O′)(nitro‐1κN)bis(triphenylphosphane‐2κP)cobalt(III)silver(I), [AgCo(C₄H₇N₂O₂)₂(NO₂)₂(C₁₈H₁₅P)₂], one of the ambidentate –NO₂ ligands, in a bridging mode, chelates the Ag^I atom in an isobidentate κ²O,O′‐manner and its N atom is coordinated to the Co^III atom. The other –NO₂ ligand is terminally κN‐coordinated to the Co^III atom. The structure has been fully characterized by X‐ray crystallography and spectroscopic methods. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) have been used to study the ground‐state electronic structure and elucidate the origin of the electronic transitions, respectively.     

Strong visible up-conversion emissions and thermometric applications of Er<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript> codoped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> prepared by the sol–gel method

The Er³⁺–Yb³⁺ codoped Al₂O₃ has been prepared by the sol–gel method using the aluminium isopropoxide [Al(OC₃H₇)₃]-derived Al₂O₃ sols with addition of the erbium nitrate [Er(NO₃)₃ · 5H₂O] and ytterbium nitrate [Yb(NO₃)₃ · 5H₂O]. The phase structure, including only two crystalline types of doped Al₂O₃ phases, θ and γ, was obtained for the 1 mol% Er³⁺ and 5 mol% Yb³⁺ codoped Al₂O₃ at the sintering temperature of 1,273 K. By a 978 nm semiconductor laser diodes excitation, the visible up-conversion emissions centered at about 523, 545, and 660 nm were obtained. The temperature dependence of the green up-conversion emissions was studied over a wide temperature range of 300–825 K, and the reasonable agreement between the calculated temperature by the fluorescence intensity ratio (FIR) theory and the measured temperature proved that Er³⁺–Yb³⁺ codoped Al₂O₃ plays an important role in the application of high temperature sensor.     

Reaction products of methyl tricyclo[4.1.0.02,7]heptane-1-carboxylate and tricyclo[4.1.0.02,7]hept-1-yl phenyl sulfone with dinitrogen tetraoxide

The reaction of methyl tricyclo[4.1.0.0^2,7]hepatne-1-carboxylate with dinitrogen tetraoxide in diethyl ether at ?10 to 0°C, followed by treatment of the reaction mixture with methanol, gave approximately equal amounts of methyl exo,syn-6,7-dinitro-and exo-6-hydroxy-syn-7-nitrobicyclo[3.1.1]heptane-endo-6-carboxylates. Tricyclo[4.1.0.0^2,7]hept-1-yl phenyl sulfone reacted with dinitrogen tetraoxide under analogous conditions to produce a mixture of diastereoisomeric exo,syn-and endo,syn-6,7-dinitro-6-phenylsulfonylbicyclo-[3.1.1]heptanes and 6,6-dimethoxy-endo-7-nitrobicyclo[3.1.1]heptane at a ratio of 4.5:2:1. Probable factors responsible for the different stereoselectivities in the addition of N₂O₄ at the central C¹-C⁷ bond of the initial tricycloheptane compounds were discussed. The structural parameters of the dinitro ester and related dinitro sulfone were compared on the basis of the X-ray diffraction data.     

Structure and DFT calculations of 2-{[3-methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazonomethyl}-phenol

The title compound 2-{[3-Methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazonomethyl}-phenol (C₂₁H₂₁N₃S₁O₁) crystallizes in the P-1 triclinic space group with a = 5.8880(4) ?, b = 9.5618(5) ?, c = 17.0484(10) ?, α = 80.214(5)°, β = 80.532(5)°, γ = 80.116(5)°. In addition to molecular geometry and packing from X-ray experiment, we have also calculated the molecular geometry and vibrational frequencies of the title compound in the ground state using density functional theory DFT (B3LYP) with the 6–31G(d,p) basis set. Apart from this, the structure of the title compound is characterized by ¹H NMR, ¹³C NMR, IR and UV-vis. Spectra, and the experimental emission energies are compared with the HOMO-LUMO energy gaps calculated by the DFT method.     

Nitrite and Nitrate Production by NO and NO2 Dissolution in Water Utilizing Plasma Jet Resembling Gas Flow Pattern

This study investigated the reactive dissolution of nitric oxide (NO) and nitrogen dioxide (NO₂) mixtures in deionized water. The dissolution study was carried out in a flat surface type gas–liquid reaction chamber utilizing a gas flow-pattern resembling plasma jets which are often used in biomedical applications. The concentration of NO and NO₂ in the gas mixtures was varied in a broad range by oxidizing up to 800 ppm of nitric oxide in Ar carrier gas with variable amount of ozone. The production of nitrite (NO₂^?) and nitrate (NO₃^?) in the water was proportional to treatment time up to 50 min. The concentration of NO₃^? was a power function of gas phase NO₂ while the concentration of NO₂^? increased approximately linearly with gas phase NO₂. The formation of NO₂^? and NO₃^? could be described by reactions between dissolved NO₂ and NO in the water while the production rate was determined by diffusion-limited mass transport of nitrogen oxides to the bulk of the liquid. At higher NO₂ concentrations, the formation of dinitrogen tetraoxide (N₂O₄) increased the formation rate of NO₂^? and NO₃^?. The identified mass transport limitation by diffusion suggests that convection of water created by the gas jet is insufficient and dissolution of nitrogen oxides can be increased by additional mixing. In respect of practical applications, the ratio of NO₂^? /NO₃^? in water could be varied from 0.8 to 5.3 with treatment time and gas phase NO₂ and NO concentrations.

     

Synthesis of the Ruthenium Nitrosyl Complex with Coordinated Ammonia and Pyridine at Room Temperature

The reaction of nitrate ruthenium complex, fac-[RuNO(NH₃)₂(NO₃)₃], with pyridine resulted in cis-[RuNO(NH₃)₂Py₂(NO₃)](NO₃)₂ · H₂O with 84 % yield of the product at room temperature. Addition of any solvent leads to the reaction failure; the excess of pyridine fulfilled the role of a solvent. The DFT simulation of the dissociative mechanism reveals that the nitrate loss from cis-position to NO occurs more easily than for trans-coordinated nitrate. This conclusion is in agreement with the X-ray determined structure of the product. In the solid state, the nitrosyl groups of two neighboring complexes are closely positioned to each other. The small available volume around the nitrosyl group, ca. 0.5 ų, leads to the enhanced stability of the photoinduced metastable state. The Ru–ON isomer converts back to the ground N-coordinated state with 0.001 s^–1 rate constant at 257 K. This O-coordinated isomer of the studied complex is one of the ten known most stable Ru–ON isomers ranked by the “decay” temperature.     

Structural conversion of an oxazolidine ligand upon treatment with copper(I) and (II) halides; structural,spectral, theoretical and docking studies

Abstract

In this work, the 2-(2-(pyridin-2-yl)oxazolidin-3-yl)ethanol (AEPC) ligand was prepared under solvent free conditions using ultrasonic irradiation, before reaction with a Cu(NO₃)₂/KSCN mixture, CuCl₂ and CuI, the products of which were characterized by elemental analysis, UV-Vis, FT-IR spectroscopy and single-crystal X-ray diffraction. The X-ray analyses results revealed that AEPC, after reactions with the three copper(I/II) halides, gave structures ([Cu(DEA)Cl₂] (2), DEA?=?diethanolamine, [Cu(BHEG)₂] (3), BHEG?=?bis(2-hydroxyethyl)glycinato); however, it retains its structure on treatment with Cu(NO₃)₂/KSCN mixture ([Cu(AEPC)(NCS)₂] (1)). The geometrical parameters for the complexes were compared with the Cambridge Structural Database (CSD) and coordination modes for thiocyanate ion were extracted. In the crystal structure of 1, the copper ion has a distorted square-pyramidal geometry and a CuN^pyN₂^NCSN^tertO^alc environment in which the AEPC acts as NN'O-donor in a facial coordination mode. In the crystal structure of 2, the copper ion has a Cu(N^sec)(O^alc)₂Cl₂ environment and distorted square-pyramidal geometry in which the DEA ligand is coordinated as a mer-NO₂-donor. The copper ion in 3 has a CuN₂O₄ environment and distorted octahedral geometry. The ability of these compounds to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) was investigated by Docking calculations and compared with that of doxorubicin. The thermodynamic stability of 1 and its isomer and also charge distribution patterns were studied by DFT and NBO analysis, respectively.     

Conversion of ammonia to dinitrogen in wastewater by Nitrosomonas europaea

Because Nitrosomonas europaea contains ammonia-oxidizing enzyme, nitrite reductase, and nitrous oxide reductase, the conversion of ammonia to dinitrogen was tried with different reaction conditions. In aerobic reaction conditions, ammonium was converted to nitrite (NO ₂ ⁻ ), while under oxygen-limiting or oxygen-free conditions, NO ₂ ⁻ -N formed from ammonia oxidation by N. europaea was reduced to N₂O and dinitrogen with 22% conversion. During denitrification, optimal pH for the production of N₂O and dinitrogen was found to be 7.0–8.0. Dinitrogen was not produced in acidic pH<7.0. A low partial oxygen pressure as well as oxygen-free conditions are favorable for high production of dinitrogen.