N2O Complex Research Articles

Easy and Effective Method for α-CD:N2O Host-Guest Complex Formation.

α-CD:N2O "host-guest" type complexes were formed by a simple solid-gas reaction (N2O sorption into α-CD) under different gas pressures and temperatures. The new N2O inclusion method applied in the present study was compared with the already known technique based on the crystallization of clathrates from a water solution of α-CD saturated with N2O. A maximum storage capacity of 4.5 wt.% N2O was achieved when charging the cyclodextrin from a gas phase. The amount of included gas decreases to 1.3 wt.% when the complex is stored in air at 1 atm and room temperature, analogous to that achieved by the crystallization of α-CD:N2O. Furthermore, it was shown that the external coordination of N2O to either the upper or lower rim of α-CD without hydration water displacement is the preferred mode of binding, due to hydrogen bonds with neighboring -OH groups from the host macrocycle and three of the hydration water molecules nearby. The capacity of α-CD to store N2O and the thermal stability of the α-CD:N2O complex demonstrated promising applications of these types of complexes in food and beverages.

Nitrous oxide and dinitrogen complexes as intermediates in the decomposition of metal carbonyl nitrosyls: The triruthenium system

The stability of some metal carbonyl nitrosyls is limited by the oxidation of CO groups by adjacent NO groups to eliminate CO2. Theoretical studies show how intermediates in such processes can be trapped as molecular species using the central Ru3 unit found in the stable and experimentally known Ru3(CO)10(µ-NO)2. Two stages of such NO reduction by adjacent CO ligands have been identified in the Ru3 system. The first stage, as demonstrated by conversion of Ru3(CO)10(µ-NO)2 to the N2O complex Ru3(CO)9(µ3-N2O), involves attack of the oxygen atom of an NO group on the carbon atom of an adjacent CO group to eliminate CO2. This leaves a reactive nitride ligand that can couple with a second NO group to form an N2O complex. The oxygen atom on such an N2O ligand can convert an adjacent CO group to CO2 thereby leaving behind a metal dinitrogen complex.

A new ab initio potential energy surface and rovibrational spectra for the N2–N2O complex

We propose a new potential energy surface for the N2–N2O complex, which encompasses the Q3 normal mode for the ν3 antisymmetric stretching coordinate of N2O. The interaction potential energies were obtained at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level with aug-cc-pVTZ basis set plus mid-bond functions. Four-dimensional vibrationally averaged potentials with N2O in the ground and ν3 excited states were generated through integration over the Q3 coordinate. Both potentials exhibit two equivalent skew T-shaped global minima. The rovibrational energies were calculated by employing the radial discrete variable representation/angular finite basis representation approach. The determined fundamental band origin shift of the infrared spectra in the N2O ν3 region, transition frequencies and rotational constants are all consistent with the experimental values.

IR-Spectroscopic Study of Complex Formation of Nitrogen Oxides (NO, N2O) with Cationic Forms of Zeolites and the Reactivity of Adsorbed Species in CO and CH4 Oxidation.

The formation of complexes and disproportionation of nitrogen oxides (NO, N2O) on cationic forms of LTA, FAU, and MOR zeolites was investigated by diffuse-reflectance IR spectroscopy. N2O is adsorbed on the samples under study in the molecular form and the frequencies of the first overtone of the stretching vibrations ν10–2 and the combination bands of the stretching vibrations with other vibrational modes for N2O complexes with cationic sites in zeolites (ν30–1 + ν10–1, ν10–1 + δ0–2) are more significantly influenced by the nature of the zeolite. The presence of several IR bands in the region of 2400–2600 cm−1 (the ν10–1 + δ0–2 transitions) for different zeolite types was explained by the availability of different localization sites for cations in these zeolites. The frequencies in this region also depend on the nature of the cation (its charge and radius). The data can be explained by the specific geometry of the N2O complex formed, presumably two-point adsorption of N2O on a cation and a neighboring oxygen atom of the framework. Adsorption of CO or CH4 on the samples with preliminarily adsorbed N2O at 20–180 °C does not result in any oxidation of these molecules. NO+ and N2O3 species formed by disproportionation of NO are capable of oxidizing CO and CH4 molecules to CO2, whereas NOx is reduced simultaneously to N2 or N2O. The peculiarities in the behavior of cationic forms of different zeolites with respect to adsorbed nitrogen oxides determined by different density and localization of cations have been established.

Side‐on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel

AbstractA nickel complex incorporating an N2O ligand with a rare η2‐N,N′‐coordination mode was isolated and characterized by X‐ray crystallography, as well as by IR and solid‐state NMR spectroscopy augmented by 15N‐labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid‐state structure. Computational studies revealed that η2‐N2O binds to nickel slightly stronger than η2‐CO2 in this case, and comparably to or slightly stronger than η2‐CO2 to transition metals in general. Comparable transition‐state energies for the formation of isomeric η2‐N,N′‐ and η2‐N,O‐complexes, and a negligible activation barrier for the decomposition of the latter likely account for the limited stability of the N2O complex.

Structural characterization of the NO(X2Π)-N2O complex with mid-infrared laser absorption spectroscopy and quantum chemical calculations.

Both positive and negative ions of N3O2 have been observed in various experiments. The neutral N3O2 was predicted to exist either as a weakly bound NO·N2O complex or a covalent molecule. The rovibrational spectrum of the NO(X2Π)-N2O complex has been measured for the first time in the 5.3 µm region using distributed quantum cascade lasers to probe the direct absorption in a slit-jet supersonic expansion. The observed spectrum is analyzed with a semi-rigid asymmetric rotor Hamiltonian for a planar open-shell complex, giving a bent geometry with an a-axis-NO angle of about 21.9°. The vibrationally averaged 2A'-2A″ energy separation is determined to be ε = 144.56(95) cm-1 for the ground state, indicating that the electronic orbital angular momentum is partially quenched upon complexation. Geometry optimizations of the complex restricted to a planar configuration at the RCCSD(T)/aug-cc-pVTZ level of theory show that the 2A″ state is more stable than the 2A' state by about 110 cm-1 and the N atom of NO points to the central N atom of N2O at the minimum of the 2A″ state.

New 3D potential energy surface and infrared spectrum of Ar—N2O complex in the N2O v3 fundamental vibration region

The goal of this paper was to re-evaluate 3D potential energy surface of the Ar–N2O complex containing N2O monomer v3 stretching vibrations. Two vibrational potentials for v3 = 0, 1 were obtained and then used to predict infrared spectra and spectroscopic constants of the Ar–N2O complex, which showed excellent agreement with the experimentally obtained infrared spectra.

Trapping and Reactivity of a Molecular Aluminium Oxide Ion

AbstractAluminium oxides constitute an important class of inorganic compound that are widely exploited in the chemical industry as catalysts and catalyst supports. Due to the tendency for such systems to aggregate via Al‐O‐Al bridges, the synthesis of well‐defined, soluble, molecular models for these materials is challenging. Here we show that reactions of the potassium aluminyl complex K2[(NON)Al]2 (NON=4,5‐bis(2,6‐diiso‐propylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene) with CO2, PhNCO and N2O all proceed via a common aluminium oxide intermediate. This highly reactive species can be trapped by coordination of a THF molecule as the anionic oxide complex [(NON)AlO(THF)]−, which features discrete Al−O bonds and dimerizes in the solid state via weak O⋅⋅⋅K interactions. This species reacts with a range of small molecules including N2O (to give a hyponitrite ([N2O2]2−) complex) and H2, the latter offering an unequivocal example of heterolytic E−H bond cleavage across a main group M−O bond.

Theoretical studies of infrared spectra for the N2-N2O complex: The tunneling effects of fundamental and combination bands.

This study is a continuation of our previously published research for the N2-N2O complex [Journal of Chemical Physics 143 (2015) 154304], and focuses on predicting the quantum tunneling effects of infrared fundamental and combination bands. A new four-dimensional intermolecular potential energy surface (PES) was constructed for the vibrational excited state upon the N2O ν1 excitation at the same calculated level with the previous PES of ground state. Compared with the ground state, two equivalent T-shaped global minima are found to be slightly different in both structural parameters and binding energies. Based on the PESs of ground and vibrational excited states, the vibrational shift of infrared spectrum for the fundamental band in the N2O ν1 region is determined to be a blue shift of 1.29 cm-1 for 14N2-N2O, which is in qualitative agreement with the experimentally observed value of 2.233 cm-1 [Journal of Chemical Physics 140 (2014) 044332]. Furthermore, for the fundamental and disrotation bands, the calculated tunneling splitting is almost the same for the ground and vibrational excited states, so the tunneling effects cannot be observed for these bands using the infrared spectroscopic technique. Nevertheless for the infrared combination bands, our calculated results suggest that the tunneling effects for the torsion and twice disrotation bands are significantly larger, and the predicted infrared spectra display obvious differences for the different sub-states. If the sensitivity of infrared spectrometer is high enough, it is interesting to investigate the quantum tunneling effects experimentally.

Theoretical study of infrared spectra for the Ar–N2O complex: Fundamental and combination bands

In this work, we performed a theoretical study of fundamental and combination bands for the infrared spectra of the Ar–N2O complex based on high-precision potential energy surfaces and bound state calculations. We constructed three two-dimensional potential energy surfaces (PESs) for the ground and excited states of the Ar–N2O complex. The bound state calculations were performed to determine the energies of rotational and intermolecular vibrational levels for this complex. Based on the results of the bound state calculations, we provide predictions for the infrared spectra of the Ar–N2O complex, including the fundamental and combination bands in the ν1 and ν3 regions of the N2O monomer. The theoretical results are in excellent agreement with experimental data, so our predicted results could be helpful to further investigate the infrared spectrum of van der Waals complex Ar–N2O.

Theoretical Insights into the Electron Capture Behavior of H₂SO₄···N₂O Complex: A DFT and Molecular Dynamics Study.

Both sulfuric acid (H2SO4) and nitrous oxide (N2O) play a central role in the atmospheric chemistry in regulating the global environment and climate changes. In this study, the interaction behavior between H2SO4 and N2O before and after electron capture has been explored using the density functional theory (DFT) method as well as molecular dynamics simulation. The intermolecular interactions have been characterized by atoms in molecules (AIM), natural bond orbital (NBO), and reduced density gradient (RDG) analyses, respectively. It was found that H2SO4 and N2O can form two transient molecular complexes via intermolecular H-bonds within a certain timescale. However, two molecular complexes can be transformed into OH radical, N2, and HSO4− species upon electron capture, providing an alternative formation source of OH radical in the atmosphere. Expectedly, the present findings not only can provide new insights into the transformation behavior of H2SO4 and N2O, but also can enable us to better understand the potential role of the free electron in driving the proceeding of the relevant reactions in the atmosphere.

The weakly bound Ar-N2O complex: A new potential energy surface and microwave spectrum

A new potential energy surface for the Ar–N2O complex has been calculated using coupled-cluster singles and doubles calculations with a large basis set containing bond functions. A two-dimensional potential model was obtained by analytically fitting 315 points on the ab initio energy surface. The potential of the Ar–14N2O complex at an approximate T-shaped geometry, which has a global minimum of −216.449 cm−1 with R = 6.44a0 and θ = 88.13°, is reported. In addition, bound state energies up to J = 5 of the two isotopomeric, Ar–14N2O and Ar–15N2O, complexes were calculated. The calculated transition frequencies and spectroscopic constants are in good agreement with the experimentally observed results.

Complex between Formic Acid and Nitrous Oxide: A Matrix-Isolation and Computational Study.

The complex of formic acid (FA, HCOOH) with nitrous oxide (N2O) was studied experimentally and computationally. Eight structures of the trans-FA···N2O complex and nine structures of the cis-FA···N2O complex were found at the density functional theory (M06-2X and wB97XD), MP2(full), and CCSD(T)-F12a levels. Two structures of the trans-FA···N2O complex (1t and 3t) and two structures of the cis-FA···N2O complex (1c and 3c) were identified by infrared spectroscopy in an argon matrix. Structure 1t with the bonded OH group appears in the matrices after deposition. Structures 3t and 3c with the free OH groups were prepared by vibrational excitation of the trans-FA conformer in structures 1t and 3t, respectively. Structure 3t is thermally unstable and relaxes to structure 1t at ∼15 K. Structure 1c with the bonded OH group is made by vibrational excitation of trans-FA monomer combined with thermal annealing. The lifetimes of the cis-FA···N2O complex structures 1c (81.5 min) and 3c (18.7 min) in an argon matrix at 4.3 K are longer than that of cis-FA monomer (6.3 min). This difference agrees with the calculated stabilization barriers of these species.

Improving analysis of infrared spectrum of van der Waals complex with theoretical calculation: Applied to Xe–N2O complex

A section of infrared spectrum for Xe–N2O has been recorded in the N2O monomer ν1 region, but just 5 rotational resolved lines cannot make an effective rovibrational analysis. To improve the analysis of our observed spectrum for Xe–N2O, a new method is developed based on the bound state calculations with three ab initio potential energy surfaces (PESs). The accuracy of this method is validated by the excellent agreement between theoretical and experimental results for 152 rovibrational transition frequencies with a root mean square deviation of 0.00075cm−1 and spectroscopic parameters with the deviation less than 0.6MHz in the N2O monomer ν3 region. The rotational constants for the excited state are derived with the values of A=12716.1, B=1075.2, C=987.9MHz in the ν1 region of N2O monomer. The band origin of the spectrum is determined to be 1284.8760cm−1 with a red shift of 0.0273cm−1 compared with that of N2O monomer in the ν1 region. The excellent agreement between experimental and theoretical results confirms that this new method is extremely helpful to make a rovibrational analysis for the infrared spectrum of van der Waals complex.

The structure of the O2-N2O complex.

We have investigated the lowest energy structures and interaction energies of the oxygen nitrous oxide complex (O2-N2O) using explicitly correlated coupled cluster theory. We find that the intermolecular potential energy surface of O2-N2O is very flat, with two minima of comparable energy separated by a low energy first order saddle point. Our results are able to conclusively distinguish between the two sets of experimental geometric parameters for O2-N2O that were previously determined from rotationally resolved infrared spectra. The global minimum structure of O2-N2O is therefore found to be planar with a distorted slipped parallel structure. Finally, we show that the very flat potential energy surface of O2-N2O is problematic when evaluating vibrational frequencies with a numerical Hessian and that consideration should be given as to whether results might change if the step-size is varied.

The first ab initio potential energy surface and predicted infrared spectra for Xe–N2O in the v3 stretching region of N2O

The first three-dimensional ab initio potential energy surface of the Xe–N2O complex was calculated using the coupled cluster single and double with noniterative treatment of triple excitations [CCSD(T)] level with a large basis set containing bond functions. The potential includes explicit dependence on the v3 stretching coordinate of the N2O molecule. The potential is characterized by a near T-shaped minimum. The global minimum is located at R=7.05a0 and θ=94.50° with a depth of −302.99cm−1. Dynamical calculations are performed to determine the bound state energies. The theoretical results are all in good agreement with the experimental counterparts.

An ab initio potential energy surface and infrared spectra for Kr–N2O in the v3 stretching region of N2O

A three-dimensional ab initio potential energy surface of the Kr–N2O complex was calculated using the CCSD(T) method and avqz-pp+33221 basis set. The potential includes explicit dependence on the v3 stretching coordinate of the N2O molecule. The potential energy surface is characterized by a near T-shaped minimum. The global minimum locates at R=6.70a0 and θ=96.00° with a depth of −270.29cm−1. Using the fitted potential energy surface, we have calculated bound energy levels of the Kr–N2O complexes. The resulting the potential provides a good representation of the experimental data.

A three-dimensional potential energy surface and predicted infrared spectra for Kr–N2O in the v 1 stretching region of N2O

The three-dimensional ab initio potential energy surface of the Kr–N2O complex was developed at the coupled-cluster single and double with non-iterative treatment of triple excitations [CCSD(T)] level. The potential includes explicit dependence on the symmetric stretching coordinate of the N2O molecule. Two vibrationally averaged potentials with the N2O molecule at both the ground and the first vibrational excited states are generated. Dynamical calculations are performed to determine the bound state energies. The resulting potentials provide a good representation of the experimental data: for 119 infrared transitions of the 84Kr–N2O complex, the root mean square deviation is only about 0.078 cm−1. The predicted rotational constants of the four isotopomers are also in good agreement with their experimental counterparts.

Coordinated nitroxyl anion is produced and released as nitrous oxide by the decomposition of iridium-coordinated nitrosothiols

The aqueous decomposition of the iridium coordinated nitrosothiols (RSNOs) trans-K[IrCl4(CH3CN)NOSPh] (1), and K2[IrCl5(NOECyS)] (2, ECyS=cysteine ethyl ester), was studied by MS analysis of the gaseous products, ESI-MS, NMR, and UV–Vis spectroscopy. Bent NO (NO−, nitroxyl anion), sulfenic acids and nitrite were observed as coordinated products in solution, while nitrous oxide (N2O) and nitrogen were detected in the gas phase. The formation of coordinated NO− and N2O, a nitroxyl dimerization product, allows us to propose the formation of free nitroxyl (HNO) as an intermediate. Complex 1 decomposes 300 times slower than free PhSNO does. In both cases (1 and 2) kinetic results show a first order decomposition behavior and a very negative ΔS≠, which strongly indicates an associative rate-determining step. A proposed decomposition mechanism, supported by the experimental data and DFT calculations, involves, as the first step, nucleophilic attack of H2O on to the sulfur atom of the coordinated RSNO, producing an NO− complex and free sulfenic acid, followed by two competing reactions: a ligand exchange reaction of this NO− with the sulfenic acid or, to a minor extent, coordination of N2O to produce an NO−/N2O complex which finally renders free N2 and coordinated NO2−. Some of the produced NO− is likely to be released from the metal center producing nitroxyl by protonation and finally N2O by dimerization and loss of H2O. In conclusion, the decomposition of these coordinated RSNOs occurs through a different mechanism than for the decomposition of free RSNOs. It involves the formation of sulfenic acids and coordinated NO−, which is released from the complexes and protonated at the reaction pH producing nitroxyl (HNO), and ultimately N2O.

The torsional vibration of the CO2–N2O complex determined from its infrared spectrum

The spectra of the weakly bound complex CO(2)-N(2)O are studied in the regions of the nu(1) and nu(3) fundamentals of N(2)O and the nu(3) fundamental of CO(2) using a rapid-scan tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. Five bands are measured and analyzed, of which four have not been previously studied. Two bands at 2225.75 and 1279.58 cm(-1), with a/b-type rotational structure, are assigned to the nu(1) and nu(3) fundamentals of the N(2)O component of the complex. Small perturbations are noted in the nu(3) band, similar to those observed previously for the nonpolar dimer (N(2)O)(2) in the nu(3) and nu(1)+nu(3) regions. The previously known band at 2348.86 cm(-1) in the region of the nu(3) CO(2) stretch is analyzed in improved detail. Weaker c-type bands at 2251.46 and 2374.67 cm(-1) are assigned as combinations of the intermolecular torsional (out-of-plane) vibration plus the N(2)O nu(1) and CO(2) nu(3) stretches, respectively. The resulting torsional frequency of CO(2)-N(2)O is experimentally determined for the first time to be 25.8 cm(-1).