Cyano Radical Research Articles

The Azobis(isobutyronitrile)-Promoted Oxidative Radical α-Cyanation of Imine under Atmospheric O2.

Herein, we report an azobis(isobutyronitrile) (AIBN)-promoted radical α-cyanation of in situ formed imine under atmospheric O2. This oxidative radical addition (ORA) procedure proceeds with the sequential homocleavage of AIBN, extrusion of N2, and capture of O2 toward an O-centered radical, which is converted to a cyano radical by β-scission. Then, the insertion of the cyano radical into the imine C═N bond forms an aminyl radical, leading to α-cyano imine after 1,2-hydrogen atom transfer (HAT) and H abstraction. Such a transition-metal-free procedure features mild reaction conditions and a broad substrate scope, employing molecular O2 as a clean terminal oxidant.

Nitrogen‐Induced Microcrystalline‐to‐Nanocrystalline Structure Transition in Diamond Films Grown by Microwave Plasma Chemical Vapor Deposition: Comparison of N2 and NH3 Precursors

The structure and properties of polycrystalline chemical vapor deposition (CVD) diamond coatings grown by microwave plasma CVD in H2–CH4 mixtures can be effectively controlled by nitrogen admixture in the process gas. Here, a comparative study of adding nitrogen from different precursors, N2 and ammonia NH3, in concentrations up to 0.4%vol on grain size, texture, surface roughness, and sp2/sp3 ratio of the produced films on Si substrates is performed. A transition from microcrystalline to smooth nanocrystalline diamond structure is found to occur at a certain concentration of the precursor, for NH3 this threshold concentration being much lower, 0.02–0.1%, than for N2. The higher activity of ammonia is associated with easier formation of cyano radicals in the plasma as detected with optical emission spectroscopy, in accord with the lower bond‐dissociation energy for NH3 compared to N2. On the contrary, a smaller addition (0.004%) of either N2 or NH3 promotes almost doubling of the growth rate, while preserving the microcrystalline structure of the film. The results establish ammonia as a convenient alternative precursor to commonly used N2 added in the plasma for the diamond film structure modifications.

The study of adsorption mechanisms and kinetics of recovering Ag and Al on the bioleaching of end-of-life crystalline silicon photovoltaic cells

The steady growth of end-of-life (EoL) crystalline silicon (c-Si) photovoltaic (PV) modules requires the development of recycling technologies to guarantee sustainable circular development for the environment. Therefore, we use cyanogenic bioleaching to recover valuable metals from c-Si PV cells. The kinetic mechanism of the leaching process was evaluated. In addition, the complexation of cyanide on the metal surface was further explored from the perspective of adsorption models. The experimental data show that bioleaching can effectively recover Ag and Al, and the leaching process is controlled by chemical reaction and diffusion. On the metal surface, the C-terminal adsorption of CN– is more advantageous than the N-terminal vertical adsorption. CN– is prone to mutual isomerization between the more stable configurations on the metal surface, and rotation is prone to occur between the adsorption configurations. The results of the charge density difference showed that when CN– was adsorbed on the metal surface, the charge was transferred from the metal surface to the cyanide radical, and the electrons were mainly obtained by C, while N lost part of the electrons. Hence, the results of this study confirm that the culture of Pseudomonas fluorescens can recover metals from retired c-Si PV cells.

Electronic structure and spectroscopic properties of some low-lying electronic states of neutral and ionic species CN and CN−

ABSTRACT The present work provides Potential Energy Curves (PECs) of both cyano radical CN and cyanide anion CN − up to the third asymptote of dissociation out of ab initio calculations. The [MRCI+Q] method is the level of theory used here and we have associated it with the Dunning basis set AV6Z (Augmented correlation-consistent polarised Valence sextet Zeta) for geometry optimisation of our systems. Electronic configurations of the states of the two species were explored and based on these configurations and the relative positions of the PECs of CN − against those of the neutral radical CN, stable and metastable states have been found and exhibited. The calculated electron affinity here that proves itself to be positive and the position of the X 1 Σ + state against its corresponding neutral parent state ( X 2 Σ + ) from which it derives led to confirm that this state is a long-lived and stable ground state of the cyanide anion CN − . Spectroscopic constants of both ground and low-lying excited states are calculated and exhibited in this work.

Investigating the adsorption behavior of cyano radical on zigzag aluminum nitride and aluminum phosphide nanotubes: A DFT study

Investigating the adsorption behavior of cyano radical on zigzag aluminum nitride and aluminum phosphide nanotubes: A DFT study

Radiative Heat Transfer Measurements of Titan Atmospheric Entry in a Shock Tube

Measurements were performed in the T6 Stalker facility operating in Aluminum Shock Tube mode for conditions relevant to Titan entry. Spatially and spectrally resolved radiation emitted from a high-temperature test gas behind a normal shock was recorded by means of emission spectroscopy. For Titan atmospheric entry, the main radiator of interest is cyano radical, formed in the nonequilibrium region behind the shock. The tests reported in this work measured radiation at velocities from 3.1 to 8.5 km/s and freestream pressures of 13, 20, and 133 Pa at a nominal composition of 98% N2 and 2% CH4. These shock layer radiation experiments employed an optical emission spectroscopy system on each side of the facility to allow two spectral regions to be measured simultaneously for each test, covering the spectral range of 200–900 nm. The present work provides a new, comprehensive benchmark set of data relevant to Titan entry studies.

Theoretical study of the O(3P) + CN(X2Σ+) → CO(X1Σ+) + N(2D)/N(4S) reactions.

The barrierless exothermic reactions between atomic oxygen and the cyano radical, O(3P) + CN(X2Σ+) → CO(X1Σ+) + N(2D)/N(4S), play a significant role in combustion, astrochemistry, and hypersonic environments. In this work, their dynamics and kinetics are investigated using both wave packet (WP) and quasi-classical trajectory (QCT) methods on recently developed potential energy surfaces of the 12A', 12A,″ and 14A″ states. The product state distributions in the doublet pathway obtained with the WP method for a few partial waves show extensive internal excitation in the CO product. This observation, combined with highly oscillatory reaction probabilities, signals a complex-forming mechanism. The statistical nature of the reaction is confirmed by comparing the WP results with those from phase space theory. The calculated rate coefficients using the WP (with a J-shifting approximation) and QCT methods exhibit agreement with each other near room temperature, 1.77 × 10-10 and 1.31 × 10-10cm3molecule-1s-1, but both are higher than the existing experimental results. The contribution of the quartet pathway is small at room temperature due to a small entrance channel bottleneck. The QCT rate coefficients are further compared with experimental results above 3000K, and the agreement is excellent.

Absorption of Millimeter-band CO and CN in the Early Universe: Molecular Clouds in the Radio Galaxy B2 0902+34 at Redshift 3.4

Using the Karl G. Jansky Very Large Array, we have detected absorption lines due to carbon monoxide, CO(J = 0 → 1), and the cyano radical, CN(N = 0 → 1), associated with radio galaxy B2 0902+34 at redshift z = 3.4. The detection of millimeter-band absorption observed 1.5 Gyr after the Big Bang facilitates studying molecular clouds down to gas masses inaccessible to emission-line observations. The CO absorption in B2 0902+34 has a peak optical depth of τ ≥ 8.6% and consists of two components, one of which has the same redshift as previously detected 21 cm absorption of neutral hydrogen (H i) gas. Each CO component traces an integrated H2 column density of NH2 ≳ 3 × 1020 cm−2. CN absorption is detected for both CO components, as well as for a blueshifted component not detected in CO, with CO/CN line ratios ranging from ≲0.4 to 2.4. We discuss the scenario that the absorption components originate from collections of small and dense molecular clouds that are embedded in a region with more diffuse gas and high turbulence, possibly within the influence of the central active galactic nucleus or a starburst region. The degree of reddening in B2 0902+34, with rest-frame color B − K ∼ 4.2, is lower than the very red colors (B − K > 6) found among other known redshifted CO absorption systems at z < 1. Nevertheless, when including the many nondetections from the literature, a potential correlation between the absorption-line strength and B − K color is evident, giving weight to the argument that the red colors of CO absorbers are due to a high dust content.

An ab initio diabatic study of rovibronic spectra of CN.

An ab initio study of the rovibronic spectra for the cyano radical (CN) based on a diabatic representation is presented. This work considers 17 electronic states, 59 dipole moment curves, 88 spin-orbit coupling curves, and 30 electronic angular momentum coupling curves, which are obtained using the internally contracted multireference configuration interaction method including the Davidson correction (icMRCI + Q) with the aug-cc-pwCV5Z-DK basis set. The diabatic transformations are performed based on a property-based diabatization method to remove the avoided crossings for the D2Π-H2Π and b4Π-24Π pairs. Ab initio potential energy curves of the X2Σ+, B2Σ+, E2Σ+, A2Π, D2Π, H2Π, F2Δ and J2Δ electronic states are shifted to match the experimental electronic excitation energies and the equilibrium internuclear distances. The coupled nuclear motion Schrödinger equations are then solved to obtain the rovibronic spectra of CN for wavenumbers from 0 to 80 000 cm-1. At wavenumbers of 0-30 000 cm-1, our absorption cross sections agree well with available theoretical data. For wavenumbers above 30 000 cm-1, our cross sections are larger than previous data in view of the fact that the transitions involving high-lying electronic states are considered. This work provides an overall prediction of the rovibronic spectrum of CN. Our results are suitable for temperatures below 8000 K and could be useful for the investigations of planetary exploration.

Ultrafast dynamics of CN radical reactions with chloroform solvent under vibrational strong coupling.

Polariton chemistry may provide a new means to control molecular reactivity, permitting remote, reversible modification of reaction energetics, kinetics, and product yields. A considerable body of experimental and theoretical work has already demonstrated that strong coupling between a molecular vibrational mode and the confined electromagnetic field of an optical cavity can alter chemical reactivity without external illumination. However, the mechanisms underlying cavity-altered chemistry remain unclear in large part because the experimental systems examined previously are too complex for detailed analysis of their reaction dynamics. Here, we experimentally investigate photolysis-induced reactions of cyanide radicals with strongly-coupled chloroform (CHCl3) solvent molecules and examine the intracavity rates of photofragment recombination, solvent complexation, and hydrogen abstraction. We use a microfluidic optical cavity fitted with dichroic mirrors to facilitate vibrational strong coupling (VSC) of the C-H stretching mode of CHCl3 while simultaneously permitting optical access at visible wavelengths. Ultrafast transient absorption experiments performed with cavities tuned on- and off-resonance reveal that VSC of the CHCl3 C-H stretching transition does not significantly modify any measured rate constants, including those associated with the hydrogen abstraction reaction. This work represents, to the best of our knowledge, the first experimental study of an elementary bimolecular reaction under VSC. We discuss how the conspicuous absence of cavity-altered effects in this system may provide insights into the mechanisms of modified ground state reactivity under VSC and help bridge the divide between experimental results and theoretical predictions in vibrational polariton chemistry.

The CN(X 2Σ+) + C2H6 reaction: Dynamics study based on an analytical full-dimensional potential energy surface.

The hydrogen abstraction reaction of the cyano radical with molecules of ethane presents some interesting points in the chemistry from ultra-cold to combustion environments especially with regard to HCN(v) product vibrational distribution. In order to understand its dynamics, a new analytical full-dimensional potential energy surface was developed, named PES-2023. It uses a combination of valence bond and mechanic molecular terms as the functional form, fitted to high-level abinitio calculations at the explicitly correlated CCSD(T)-F12/aug-cc-pVTZ level on a reduced and selected number of points describing the reactive process. The new surface showed a continuous and smooth behavior, describing reasonably the topology of the reaction: high exothermicity, low barrier, and presence of intermediate complexes in the entrance and exit channels. Using quasi-classical trajectory calculations (QCT) on the new PES-2023, a dynamics study was performed at room temperature with special emphasis on the HCN(v1,v2,v3) product stretching and bending vibrational excitations, and the results were compared with the experimental evidence, which presented discrepancies in the bending excitation. The available energy was mostly deposited as HCN(v) vibrational energy with the vibrational population inverted in the CH stretching mode and not inverted in the CN stretching and bending modes, thus simulating the experimental evidence. Other dynamics properties at room temperature were also analyzed; cold rotational energy distribution was found, associated with a linear and soft transition state, and backward scattering distribution was found, associated with a rebound mechanism.

Spectroscopic modeling and measurements of the CN Violet and Red systems for the development of nonequilibrium temperature and speciation diagnostics

The uniquely strong radiative properties of the cyano-radical (CN) make it an important species to model in high-enthalpy, nonequilibrium flows containing carbon and nitrogen. In this work, spectroscopic models for the Violet and Red systems of CN have been developed and validated at wavelengths in both the ultraviolet (UV) and near-infrared (NIR) regimes that would provide quantitative CN rovibrational temperature and concentration. The ultraviolet wavelengths chosen probe high-lying (J′′=30.5−40.5) and low-lying (J′′=0.5−5.5) rotational states in the ground vibrational level (v′′=0) of CN along with high-lying rotational states in the third excited vibrational level (v′′=3) of CN. Meanwhile, the NIR wavelengths cover a range of lower rovibrational content, including high-lying and low-lying rotational levels from the ground up to the fourth excited vibrational level of CN. Dilute cyanogen (C2N2) in argon (Ar) mixtures were shock heated to produce stable quantities of CN that could be spectroscopically studied. In the UV, fixed-temperature absorption cross-section measurements at different wavelengths and a fixed-wavelength temperature sweep for the chosen diagnostic wavelengths enabled an evaluation of the different spectroscopic models and their ability to correctly infer the post-shock temperature in mixtures with high Ar dilution. In the NIR, the lasers were scanned at 100 kHz to probe multiple transitions over different rovibrational states over a wide range of temperatures, and both Einstein A’s and relative line positions of observed Red transitions of CN were experimentally quantified.

Is Pseudohalide CN− a Real Halide? A General Symmetry Consideration

Recently, in light of the significant attention devoted to pseudohalide CN− and cyano radical CN physico-chemical property studies and superhalide behavior exploration in CN−-ligated metal compounds, the photoelectron angular distribution nature of pseudohalide CN− has been directly demonstrated via the photoelectron velocity map imaging technique to be comparable to Cl−. For the halide Cl−, photoelectrons were observed at 266 nm (4.66 eV) to peak, perpendicular to the laser polarization associated with the detachment of p-orbital symmetry. For the analogous pseudohalide CN−, photoelectrons were present at a peak in laser polarization at 266 nm, which can be explained as detachment from mainly atomic s-like orbital symmetry. Although both are often regarded as having the same high electron affinity and similarly strong chemical bonding capabilities to stabilize complexes, their photoelectron angular distributions are distinctly different, which indicates their intrinsically different electronic–structure symmetry (HOMO nature). The approach based on symmetry consideration in this work could be utilized to explain the photoelectron angular distributions of pseudohalide and classic halide ligands via the advanced photoelectron velocity map imaging tool.

Analysis of CN emission as a marker of organic compounds in meteoroids using laboratory simulated meteors

Fragments of small solar system bodies entering Earth’s atmosphere have possibly been important contributors of organic compounds to the early Earth. The cyano radical (CN) emission from meteors is considered as potentially one of the most suitable markers of organic compounds in meteoroids, however, its detection in meteor spectra has been thus far unsuccessful. With the aim to improve our abilities to identify CN emission in meteor observations and use its spectral features to characterize the composition of incoming asteroidal meteoroids, we present a detailed analysis of CN emission from high-resolution spectra of 22 laboratory simulated meteors including ordinary, carbonaceous, and enstatite chondrites, as well as a large diversity of achondrites (i.e., ureilite, aubrite, lunar, martian, howardite, eucrite, and diogenite), mesosiderite, and iron meteorites. We describe the variations of CN emission from different classes of asteroidal meteor analogues, its correlation and time evolution relative to other major meteoroid components. We demonstrate that CN can be used as a diagnostic spectral feature of carbonaceous and carbon-rich meteoroids, while most ordinary chondrites show no signs of CN. Our results point out strong correlation between CN and H emission and suggest both volatile features are suitable to trace contents of organic matter and water molecules present within meteoroids. For the application in lower resolution meteor observations, we demonstrate that CN can be best recognized in the early stages of ablation and for carbon-rich materials by measuring relative intensity ratio of CN band peak to the nearby Fe I-4 lines.

Reaction Kinetics of CN + Toluene and Its Implication on the Production of Aromatic Nitriles in the Taurus Molecular Cloud and Titan’s Atmosphere

Reactions between cyano radicals and aromatic hydrocarbons are believed to be important pathways for the formation of aromatic nitriles in the interstellar medium (ISM) including those identified in the Taurus molecular cloud (TMC-1). Aromatic nitriles might participate in the formation of polycyclic aromatic nitrogen-containing hydrocarbons (PANHs) in Titan's atmosphere. Here, ab initio kinetic simulations reveal a high efficiency of ∼10−10 cm3 s−1 and the competition of the different products of the CN + toluene reaction at 30–1800 K and 10−7–100 atm. In the star-forming region of the TMC-1 environment, the product yields of benzonitrile and tolunitriles for CN reacting with toluene are approximately 17% and 83%, respectively. Detections of the main products, tolunitriles, can serve as proxies for the undetected toluene in the ISM due to their much larger dipole moments. Competition between bimolecular and unimolecular products is extremely intense in the warmer and denser PANH-forming region of Titan's stratosphere. Computational results show that the fractions of tolunitriles, adducts, and benzonitrile are 19%–68%, 15%–64%, and 17%, respectively, at 150–200 K and 0.0001–0.001 atm (Titan's stratosphere). Then, benzonitrile and tolunitriles may contribute to the formation of PANHs by consecutive C2H additions. The kinetic information of aromatic nitriles for the CN + toluene reaction calculated here helps to explain the formation mechanism of polycyclic aromatic hydrocarbons or PANHs under different interstellar environments and constrains corresponding astrochemical models.

New prebiotic molecules in the interstellar medium from the reaction between vinyl alcohol and CN radicals: unsupervised reaction mechanism discovery, accurate electronic structure calculations and kinetic simulations.

Vinyl alcohol (VyA) and cyanide (CN) radicals are relatively abundant in the interstellar medium (ISM). VyA is the enolic tautomer of acetaldehyde and has two low-lying conformers, characterized by the syn or anti placement of hydroxyl hydrogen with respect to the double bond. In this paper, we present a gas-phase model of the barrierless reactions of both VyA's conformers with CN employing accurate quantum chemical computations in the framework of a master equation approach based on the transition state theory. Our results indicate that both VyA conformers feature a similar reactivity with CN, starting with a barrierless addition to the double bond and followed by different isomerization, dissociation, and/or hydrogen elimination steps. The rate constants computed for temperatures up to 600 K show that several reaction channels are open even under the harsh conditions of the ISM, with the favoured one providing the first feasible formation route of a prebiotic molecule not yet detected in the ISM, namely cyanoacetaldehyde. This finding suggests looking for cyanoacetaldehyde in regions where both VyA and CN have already been detected, like, e.g., Sagittarius B2N or G+0.693-0.027.

Kinetics of the reaction of chloromethane with cyano radical

Halocarbons play an important role in combustion and stratospheric chemistry and have been an active subject of many studies for a long time. The six reaction channels, between CH3Cl and CN, have been investigated at CCSD(T)/aug-cc-pVTZ//CASSCF(11,10)/6-311++g(2df,p) level of theory. Only two channels dominate noticeably in the temperature range of 298–1000 K. The calculated values of the rate constants to different temperatures are in good agreement with the available experiment data. This reaction has a rate constant of k = 3.50 × 10−10 T−0.5 exp(−7.50 kJ mol−1/RT) over the range 298–1000 K.

The Formation of Monosubstituted Cyclopropenylidene Derivatives in the Interstellar Medium via Neutral–Neutral Reaction Pathways

Five substituted cyclopropenylidene derivatives (c-C3HX, X=CN, OH, F, NH2), all currently undetected in the interstellar medium (ISM), are found herein to have mechanistically viable, gas-phase formation pathways through neutral–neutral additions of ·X onto c-C3H2. The detection and predicted formation mechanism of c-C3HC2H introduces a need for the chemistry of c-C3H2 and any possible derivatives to be more fully explored. Chemically accurate CCSD(T)-F12/cc-pVTZ-F12 calculations provide exothermicities of additions of various radical species to c-C3H2, alongside energies of submerged intermediates that are crossed to result in product formation. Of the novel reaction mechanisms proposed, the addition of the cyano radical is the most exothermic at -16.10 kcal mol−1. All five products are found to or are expected to have at least one means of associating barrierlessly to form a submerged intermediate, a requirement for the cold chemistry of the ISM. The energetically allowed additions arise as a result of the strong electrophilicity of the radical species as well as the product stability gained through substituent-ring conjugation.

Investigation the ability of pure and Al-doped graphene nano materials to detect toxic gases using first principle study

In the present study, the density function theory (DFT) method was used to compute structural, electronic and spectroscopic properties for pure and aluminum (Al) doped graphene materials, 6-13G basis set and hybrid function B3LYP were used in the present study. The structural properties show that pure and Al-doped graphene materials have a plane surface, also all bond lengths are in agreement with experimental results. Energy gap calculation shows that pure and Al-doped graphene materials have having semiconductor nature. When hydro cyanide gas molecule will have interacted on the surface of pure and Al-doped graphene materials, properties belonging to the systems under study will change. The result shows that interaction of HCN gas molecule with Al-doped graphene material the surface will rise up, but in the pure system, the surface remains plane. Adsorption calculation shows that HCN gas molecule can interact with the surface of a system under study. high chemical adsorption appears at a distance 1 Å between the gas molecule and pure and Al-doped graphene materials. Increasing adsorption distance interaction strength will be decreased until reached 0.002 eV. Positive adsorption energy refers to the repulsion force between the gas molecule and the surface. Fourier transformation infrared radiation (FT-IR) spectroscopy has been used to point-free radicals for interacted systems. It is pointed to carbon groups such as C-C, C-H, C-N and C-Al, also results show that all wave numbers results are in agreement with previous reports. Appear cyanide radical is a sign of chemical adsorption between gas molecules and the surface of pure and Al-doped graphene materials.

Molecular Precursors of the RNA-World in Space: New Nitriles in the G+0.693−0.027 Molecular Cloud

Nitriles play a key role as molecular precursors in prebiotic experiments based on the RNA-world scenario for the origin of life. These chemical compounds could have been partially delivered to the young Earth from extraterrestrial objects, stressing the importance of establishing the reservoir of nitriles in the interstellar medium. We report here the detection towards the molecular cloud G+0.693−0.027 of several nitriles, including cyanic acid (HOCN), and three C4H3N isomers (cyanoallene, CH2CCHCN; propargyl cyanide, HCCCH2CN; and cyanopropyne (CH3CCCN), and the tentative detections of cyanoformaldehyde (HCOCN), and glycolonitrile (HOCH2CN). We have also performed the first interstellar search of cyanoacetaldehyde (HCOCH2CN), which was not detected. Based on the derived molecular abundances of the different nitriles in G+0.693−0.027 and other interstellar sources, we have discussed their formation mechanisms in the ISM. We propose that the observed HOCN abundance in G+0.693−0.027 is mainly due to surface chemistry and subsequent shock-induced desorption, while HCOCN might be mainly formed through gas-phase chemistry. In the case of HOCH2CN, several grain-surface routes from abundant precursors could produce it. The derived abundances of the three C4H3N isomers in G+0.693−0.027 are very similar, and also similar to those previously reported in the dark cold cloud TMC-1. This suggests that the three isomers are likely formed through gas-phase chemistry from common precursors, possibly unsaturated hydrocarbons (CH3CCH and CH2CCH2) that react with the cyanide radical (CN). The rich nitrile feedstock found towards G+0.693−0.027 confirms that interstellar chemistry is able to synthesize in space molecular species that could drive the prebiotic chemistry of the RNA-world.