Addition Of Hydrogen Atoms Research Articles

Protonation of Dppbz- and Binap-Ligated Rhodathiaboranes Yielding Hydron, Hydride, and Hydrogen Exchange.

The reaction of the 11-vertex rhodathiaborane [8,8,8-(H)(PPh3)2-3-(NC5H5)-nido-7,8-RhSB9H10] (1) with 1,2-bis(diphenylphosphine)benzene (dppbz) and (S)-(-)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap) affords [1,1-(η2-dppbz)-3-(NC5H5)-closo-1,2-RhSB9H8] (2) and [1,1-(η2-binap)-3-(NC5H5)-closo-1,2-RhSB9H8] (3). These 11-vertex closo-rhodathiaborane chelates result from PPh3 ligand substitution at the rhodium center and a nido-to-closo structural cluster transformation driven by H2 loss. Treating compounds 2 and 3 with triflic acid (TfOH) leads to the formation of cationic clusters 4 and 5. The hydrons bind to the polyhedral clusters, acquiring hydride character and providing chemical nonrigidity that manifests through metal vertex-to-thiaborane pseudo-rotations and concomitant hydron tautomerisms. The resulting cations react with hydrogen to form mixtures of hydrons, hydrogen, and hydridorhodathiaboranes in equilibrium. The reaction products are the result of heterolytic cleavage of the H-H bond, with full participation of the clusters and the addition of hydrogen atoms to the cages. In these reactions, there is a conversion of electrons and hydrons into hydrogen, and hydrogen into hydride ligands, demonstrating that these boron-based metal compounds act as electron reservoirs, capable of promoting multielectron processes.

Visible‐Light‐Induced Synthesis of γ‐Amino Sulfones from Vinyl Sulfones and Amino Acids

AbstractA method for the synthesis of γ‐amino sulfones through visible light‐induced oxidative decarboxylation and radical reductive addition is described. Various readily available N‐protected natural amino acids react with aromatic/aliphatic vinyl sulfones to directly produce γ‐amino sulfone derivatives. This reaction is also applicable to α‐N(O)‐acids and other aliphatic carboxylic acids, resulting in the corresponding sulfone derivatives. The method operates without the need for sacrificial reducing agents or additional hydrogen atom donors. The sole by‐product is CO2 released from decarboxylation, rendering the process both atom‐ and step‐economical.

How the addition of atomic hydrogen to a multiple bond can be catalyzed by water molecules.

Observational data show complex organic molecules in the interstellar medium (ISM). Hydrogenation of small unsaturated carbon double bond could be one way for molecular complexification. It is important to understand how such reactivity occurs in the very cold and low-pressure ISM. Yet, there is water ice in the ISM, either as grain or as mantle around grains. Therefore, the addition of atomic hydrogen on double-bonded carbon in a series of seven molecules have been studied and it was found that water catalyzes this reaction. The origin of the catalysis is a weak charge transfer between the π MO of the unsaturated molecule and H atom, allowing a stabilizing interaction with H2O. This mechanism is rationalized using the non-covalent interaction and the quantum theory of atoms in molecules approaches.

Kinetics of the thermal decomposition of thermally reduced graphene oxide treated with a pulsed high-frequency discharge in hydrogen atmosphere

Thermal stability and the kinetics of thermal decomposition of the thermally reduced graphene oxide (TRGO) treated by a pulsed high-frequency discharge in a hydrogen atmosphere have been studied. The modified Hummers method was used for obtaining the initial graphite oxide from graphite powder. Thermal exfoliation of the graphene oxide powder has been done in vacuum conditions with a heating rate of 5–7 degrees per minute to a temperature of 300 °С. TRGO has been treated by pulsed high-frequency discharge in a hydrogen atmosphere for partial graphene hydrogenation (chemical addition of atomic hydrogen) that leads to structural changes in the carbon planes and formation of C–H sp3 bonds. The thermogravimetry analysis measurements of the mass loss have been carried from room temperature to 1000 °C in a nitrogen atmosphere with a nitrogen flow rate of 20 mL/min and different heating rates: 50, 75 100, 125, 150, and 200 K/min, respectively. Kissinger’s multiple heating rate method has been used to determine the activation energy for decomposing substances. Activation energies Ea1, Ea2, and Ea3 equal 28, 50, and 148 kJ/mol, respectively, have been compared with the energies of the activation of thermal defunctionalization of multiwalled carbon nanotubes (MWCNTs). The activation energy Ea3 = 148 kJ/mol is close to that of the thermal decomposition of anhydride functional groups in MWCNT. The value of Ea2 = 50 kJ/mol indicates the presence of the keto and hydroxy acid’s function groups on TRGO. Activation energy Ea1 = 28 kJ/mol related with all other groups including the lighter C–H bonds that destructed due to dehydrogenation of the TRGO. Obtained experimental results are useful for further proposing the kinetic model of the mechanism of the most probable reaction of TRGO decomposition.

Hydrogen diffusion in BCC-Fe: DFT study of tensorial stress effects and interactions with point defects

Hydrogen embrittlement is a multifaceted phenomenon that can significantly compromise the toughness of susceptible metals. We study the critical process of hydrogen diffusion within the body-centered cubic lattice of iron (BCC-Fe or α−Fe) using ab-initio density functional theory (DFT). Beyond standard investigations on the effect of hydrostatic stress, we extend our study to incorporate the influence of uniaxial and pure shear stress states. We find substantial alterations in diffusion barriers. Moreover, we study scenarios involving paired point (zero-dimensional) defects, including one vacancy and an additional interstitial hydrogen atom. Calculations comprehend various configurations and transitions between them, providing insight into the interplay between the chemical environment and mechanical fields. The barrier values here determined offer essential data for complementary techniques, including Monte-Carlo models, to accurately describe hydrogen diffusion. This research contributes to a deeper understanding of hydrogen embrittlement, offering insight that can inform the design of safer materials used in structural engineering.

Alternatives to Remdesivir: Drug repurposing for inhibition of SARS-CoV2 RNA dependent RNA polymerase

Background & Objectives: Even after more than a year of the beginning of COVID-19 pandemic, a specific treatment for the disease has not been discovered. Vaccination programmes are being rolled out as the fastest pace possible but achievement of herd immunity will take time. Many drugs like favipiravir, remdesivir and tocilizumab are being used for the treatment of this disease but reports published by the World Health Organization and the New England Journal of Medicine shows that they do not produce any significant clinical results. In this study, by molecular docking a large set of drugs has been used to replace remdesivir in RdRp protein so that they can produce the same action and therefore provide suitable alternatives for clinical trials and emergency use. Materials & Methods: The receptor i.e. the RdRp protein was first processed in Drug Discovery studio by removal of heterogenous atoms, water molecules, prime and template RNA strands and remdesivir. This gave us the clean RdRp molecule. Using PyRx docking software, it was converted automatically into an Autodock macromolecule. Around 750 drug molecules were loaded into PyRx using Open Babel plugin which were then converted into Autodock ligands by minimization of their energies, addition of hydrogen atoms and addition of partial charges. Using Autodock Vina ligands were docked into the restricted search space containing the target amino acids. Results: The drugs identified in the study are saquinavir, cefoperazone, gliquidone, nelfinavir, 5-methyltetrahyrofolate among various others. Conclusion: The drugs obtained above have also been identified in other in-silico studies as potential inhibitors of SARS-CoV2 by different mechanisms. They must be tried in-vitro because of the limitations of in-silico docking.

Hydrogenation of High-Density Polyethylene during Decompression of Pressurized Hydrogen at 90 MPa: A Molecular Perspective.

To investigate changes in the physical and chemical properties of high-density polyethylene (HDPE) upon the rapid release of hydrogen gas at a pressure of 90 MPa, several characterization techniques have been employed, including optical microscopy, scanning electron microscopy, X-ray diffraction, differential scanning thermal analysis, and attenuated total reflectance Fourier-transform infrared spectroscopy. The results showed that both physical and chemical changes occurred in HDPE upon a rapid release of hydrogen gas. Physically, a partial hexagonal phase was formed within the amorphous region, and the overall crystallinity of HDPE decreased. Chemically, hydrogenation occurred, leading to the addition of hydrogen atoms to the polymer chains. Oxidation also occurred, for example, the formation of ester -C=O groups. Crosslinking and an increase in -CH3 end termination were also observed. These changes suggest that structural transformation and chemical modification of HDPE occurred upon the rapid release of hydrogen gas.

Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning.

The high critical superconducting temperatures (Tc s) of metal hydride phases with clathrate-like hydrogen networks have generated great interest. Herein, we employ the Density Functional Theory-Chemical Pressure (DFT-CP) method to explain why certain electropositive elements adopt these structure types, whereas others distort the hydrogenic lattice, thereby decreasing the Tc . The progressive opening of the H24 polyhedra in MH6 phases is shown to arise from internal pressures exerted by large metal atoms, some of which may favor an even higher hydrogen content that loosens the metal atom coordination environments. The stability of the LaH10 and LaBH8 phases is tied to stuffing of their shared hydrogen network with either additional hydrogen or boron atoms. The predictive capabilities of DFT-CP are finally applied to the Y-X-H system to identify possible ternary additions yielding a superconducting phase stable to low pressures.

Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning**

AbstractThe high critical superconducting temperatures (Tcs) of metal hydride phases with clathrate‐like hydrogen networks have generated great interest. Herein, we employ the Density Functional Theory‐Chemical Pressure (DFT‐CP) method to explain why certain electropositive elements adopt these structure types, whereas others distort the hydrogenic lattice, thereby decreasing the Tc. The progressive opening of the H24 polyhedra in MH6 phases is shown to arise from internal pressures exerted by large metal atoms, some of which may favor an even higher hydrogen content that loosens the metal atom coordination environments. The stability of the LaH10 and LaBH8 phases is tied to stuffing of their shared hydrogen network with either additional hydrogen or boron atoms. The predictive capabilities of DFT‐CP are finally applied to the Y−X−H system to identify possible ternary additions yielding a superconducting phase stable to low pressures.

σ versus π-radical: Tuning the electronic nature of neutral carbon (I) compounds with three non-bonding electrons.

The bonding and reactivity of the hypo-coordinated compounds with one, two, and four non-bonding electrons namely, carbon-centered free radical, carbenes, and carbones were well earlier established. Here, we report stability, bonding and reactivity of compounds RCL, where R is one-electron donor group (R=CH3 (a), CHO (b), and NO2 (c)) and L is two-electron donor ligand (L=cAAC (1), CO (2), NHC (3) and PMe3 (4)), having three non-bonding electrons. The ground states of molecules exist in a doublet with a lone pair of electrons and an unpaired electron at the central carbon atom (C1). The spin hops over from π- to σ-type orbitals is observed as the π-acceptor strength of the donor ligand increases. The replacement of the methyl group by CHO and NO2 indicate that the cAAC and CHO substituted compounds gives a σ-radical except in compound 2c. These molecules show very high proton affinity and exothermic reaction energy for the hydrogen atom addition indicating dual reactivity namely, radical and lone pair reactivity.

Synthesis, chemical and physical properties of lanthanide(III) (Nd, Gd, Tb) complexes derived from (E)-ethyl 4-(2-hydroxybenzylideneamino)benzoate

The 1:2 reaction between Ln(NO3)3·6H2O (1) (Ln = Nd (a), Gd (b) or Tb (c)) and ((E)-ethyl 4-((2-hydroxybenzylidene)amino)benzoate) (LN,OH) in ethanol has provided access to the complexes [LnIII(LNH,O)2(NO3)3(H2O)] (2a–c) in good yield. The isomorphous structures of 2a–c have been determined by single-crystal X-ray crystallography. The LnIII ions in 2a–c are coordinated by 9 oxygen atoms: two from the phenolate oxygen atoms of the Schiff bases, six from three chelating nitrato groups and one aqua ligand. The ligands LN,OH behave as monodentate phenolate O–donors, whereby an additional hydrogen atom is bonded to the imino nitrogen atom, resulting in a formally neutral ligand that adopts an exceptionally unusual coordination mode engaging in the zwitterionic form. The nine donor atoms that define the coordination polyhedra surrounding the LnIII ion are best described as capped square antiprisms. The crystal structures are based on a variety of intermolecular interactions. Hirshfeld surface analysis was used to assess the degree of interactions between the molecules. Susceptibility measurements on 2a–2c confirm the occurrence of the free ion ground 2S+1LJ state at room temperature. However, the magnetization measurements at 2 K revealed a lack of saturation at the highest applied field of 70,000 Oe for both 2a and 2c, indicating the presence of substantial magnetic anisotropy in these compounds. On the other hand, 2b exhibits perfect paramagnetic behavior with magnetic saturation at high fields, indicating the absence of significant magnetic anisotropy in this compound. Solid-state IR and UV/VIS data are discussed in terms of the structural features. Solid 2a–c emit in the visible region upon UV-Excitation with the emission exhibiting dopant characteristics.

δ-C-H Halogenation Reactions Enabled by a Nitrogen-Centered Radical Precursor.

Nitrogen-centered radicals are versatile synthetic intermediates with the ability to undergo diverse reactions such as hydrogen atom transfer (HAT), β-scission, and addition across unsaturated systems. A long-standing impediment to the wider adoption of these intermediates in synthesis has been the difficulty of their generation. Herein we disclose a new hydrazonyl carboxylic acid precursor to nitrogen-centered radicals and its application toward remote C-H fluorination and chlorination reactions of sulfonyl-protected alkyl amines via 1,5-HAT.

Reactive molecular dynamic simulations of hydrogenation process of amorphous silicon nitride

Hydrogenated amorphous silicon nitride is useful as an anti-reflection coating on solar cells. The addition of hydrogen atoms to amorphous silicon nitride can reduce the dangling bonds that exist on the surface. The objective of this paper is to clarify on the behavior of hydrogen atoms absorbed in silicon nitride during the hydrogenation process at various temperatures. We investigate, in particular, the silicon and hydrogen bonds that are formed by the transfer of electrons from hydrogen to silicon to form [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] ions. The conversion of [Formula: see text] ions into [Formula: see text] ions and then also into [Formula: see text] and [Formula: see text] occurs during enhancement of the hydrogen atoms absorbed. Hydrogenated amorphous silicon nitride was stabilized through the passivation of dangling bonds of silicon atoms and nitrogen atoms by the absorbed hydrogen atoms. The passivation was indicated by enhancement of over-coordinated silicon and nitrogen atoms as well as the reduction of under-coordinated silicon and nitrogen atoms. It was found that the thermal energy from high hydrogenation temperature was primarily used by hydrogen atoms to diffuse more and to penetrate deeper into silicon nitride rather than being used for the ionization of silicon atoms. Finally, we stress that these reactive molecular dynamic simulations have led to substantial progress in understanding how hydrogen atoms interact with amorphous silicon nitride during hydrogenation.

Electronic structure regulation toward the improvement of the hydrogenation properties of TiZrHfMoNb high-entropy alloy

Active metals, such as platinum and palladium, were doped in TiZrHfMoNb high-entropy alloy to tune its electronic structure. The electronic structure, activation, and kinetic properties were experimentally investigated. The results indicate that electron transfer occurred between the active metal atoms and other metal atoms after platinum or palladium doping, and that the oxide on the surface was destabilized by active metal doping due to improved activation performance. Therefore, TiZrHfMoNbPt0.0025 could reach a maximum hydrogen storage capacity of 1.749 wt% (1.80 H/M) at around 100 s on the first absorption curve. The electron transfer process is believed to aid in optimizing the electron density of interstitial sites, allowing additional interstitial sites to accommodate additional hydrogen atoms. The presented results provide new insights into the hydrogen storage properties of high-entropy alloys, and it is expected that hydrogen storage capacity can be increased by tuning the concentration and type of doping elements.

Experimental and kinetic modeling studies of 2-acetylfuran pyrolysis at atmospheric pressure

Furan-based derivatives are promising biomass fuels that may be used directly in internal combustion engines as alternative fuels or as additives to fossil fuels. In this work, the experimental studies of 2-acetylfuran (AF2) pyrolysis were carried out in a jet-stirred reactor in the temperature range of 770 – 1130 K and at the pressure of 760 Torr, using synchrotron vacuum ultraviolet photo-ionization mass spectrometry, coupled with gas chromatography. Key pyrolysis intermediates such as methane, ethylene, acetylene, ketene, vinylacetylene, cyclopentadiene, ethynylketene, 2-methylfuran, furfural, carbon monoxide and isomers such as allene/propyne, furan/vinylketene, benzene/fulvene, etc., were identified and quantified. The potential energy surfaces of AF2 unimolecular decomposition reactions were calculated at CBS-QB3 level. The temperature- and pressure-dependent rate constants of the relevant reactions were calculated by solving the master equation based on Rice-Ramsperger-Kassel-Marcus theory. A detailed pyrolysis kinetics of AF2 was developed based on the previous combustion models of 2-methylfuran and was validated against the current experimental results. Rate of production and sensitivity analysis showed that the main consumption pathways of AF2 pyrolysis under atmospheric pressure are unimolecular decomposition reactions, leading to 2-furyl + acetyl and furoyl + methyl, and hydrogen atom-addition reaction to C(5), leading to 2,3-dihydro-5-acetyl-3-furyl, accounting at 1070 K for 25.1%, 13.2% and 20.7% of AF2 consumption, respectively (the remaining 41.0% are due to minor reaction channels contributing < 10% each). At this temperature, the total AF2 consumption is 73%. The contributions of ipso-substitution reactions by methyl and by hydrogen atom to AF2 consumption were comparable.

Electrocatalytic N2 Reduction on FeS2 Nanoparticles Embedded in Graphene Oxide in Acid and Neutral Conditions

The development of stable, low-cost, and highly efficient electrocatalysts for the N2 reduction reaction (NRR) process is challenging but crucial for ammonia production. Herein, we demonstrate the synthesis of pyrite nanoparticles wrapped by graphene oxide (FeS2@GO) acting as a highly efficient NRR catalyst in a wide pH range. The FeS2 nanoparticles are uniformly dispersed across the GO nanosheet, thus leading to the fine exposure of active sites, the promotion of charge transfer, and the increment of a contact surface area, which are all beneficial for a desired catalyst. In the meantime, the low-coordinated Fe atoms are activated as highly active sites, which is in favor of the enhanced electrochemical performance for the NRR. Furthermore, density functional theory (DFT) calculations illustrated that the high activity of N2 reduction over the FeS2@GO catalyst arises from the well-exposed Fe active sites and the increment of charge density at the valence band edge. Benefiting from the well-optimized interface, the barrier of the addition of the first hydrogen atom to N2 forming *NNH species as the potential-determining step is as low as 0.93 eV in N2 electroreduction. The electrochemical test results reveal that, as expected, FeS2@GO exhibits high Faradaic efficiencies (4.7% in 0.1 M HCl solution and 6.8% in 0.1 M Na2SO4 solution) and advanced NH3 yields (78.6 and 27.9 μg h-1 mgcat.-1 in 0.1 M HCl and 0.1 M Na2SO4 solutions, respectively) in both acid and neutral conditions. This work offers a new avenue for exploring novel electrocatalysts, which has great promise to accelerate the practical application of the NRR.

Electronically induced defect creation at semiconductor/oxide interface revealed by time-dependent density functional theory

Carrier induced defect creation at the semiconductor-oxide interface has been known as the origin of electronic device degradation for a long time, but how exactly the interface lattice can be damaged by carriers (especially low-energy ones) remains unclear. Here we carry out real-time time-dependent density functional theory simulations on concrete $\mathrm{Si}/\mathrm{Si}{\mathrm{O}}_{2}$ interfaces to study the interaction between excited electrons and interface bonds. We show that the normal interface Si-H bonds are generally resistant to electrons due to the delocalized nature and high energy level of the Si-H antibonding states, and due to the high-energy barrier to break the Si-H bond. However, if an additional hydrogen atom exists by attaching to a nearby oxygen atom (forming a ``Si-H\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}H-O'' complex), the Si-H bond will be greatly weakened, including the reduction of energy barrier for bond breaking, and the lowering of the antibonding state energy level which favors electron injection. Together with the multiple vibrational excitation process, the corresponding Si-H bond can be broken much more easily. Thus we propose that the Si-H\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}H-O complex will be the center for defect creation and device degradation. We also explain why such a center might be relatively easy to form during the hydrogen annealing process.

Competitive Dehydrogenation and Backbone Fragmentation of Superhydrogenated PAHs: A Laboratory Study

Abstract Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) have been suggested to catalyze the formation of H2 in certain regions of space, but it remains unclear under which circumstances this mechanism is viable given the reduced carbon backbone stability of superhydrogenated PAHs. We report a laboratory study on the stability of the smallest pericondensed PAH, pyrene (C16H10+N , with N = 4, 6, and 16 additional H atoms), against photodestruction by single vacuum ultraviolet photons using the photoelectron–photoion coincidence technique. For N = 4, we observe a protective effect of hydrogenation against the loss of native hydrogens, in the form of an increase in the appearance energies of the and C16H8 + daughter ions compared to those reported for pristine pyrene (C16H10). No such effect is seen for N = 6 or 16, where the weakening effect of replacing aromatic bonds with aliphatic ones outweighs the buffering effect of the additional hydrogen atoms. The onset of fragmentation occurs at similar internal energies for N = 4 and 6, but is significantly lower for N = 16. In all three cases, H-loss and C m H n -loss (m ≥ 1, carbon backbone fragmentation) channels open at approximately the same energy. The branching fractions of the primary channels favor H-loss for N = 4, C m H n -loss for N = 16, and are roughly equal for the intermediate N = 6. We conclude that superhydrogenated pyrene is probably too small to support catalytic H2-formation, while trends in the current and previously reported data suggest that larger PAHs may serve as catalysts up to a certain level of hydrogenation.

Homogeneous-like Alkyne Selective Hydrogenation Catalyzed by Cationic Nickel Confined in Zeolite

The selective hydrogenation of alkynes to their corresponding alkenes is an important type of organic transformation, which is currently accomplished by modified palladium catalysts. Herein, we rep...

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

AbstractOximes represent one of the fundamental organic compound classes with a wide range of synthetic applications. In the last decade O‐substituted oximes were recognized as the synthetically available and versatile precursors of iminyl radicals via one‐electron oxidation or one‐electron reduction employing visible light photoredox catalysts, salts of abundant metals (such as Cu or Fe), or other convenient reagents. Iminyl radicals are powerful synthons for various processes of cyclization, ring‐opening, CH‐functionalization, and coupling. The present review is focused on the synthetic methods based on oxime‐derived iminyl radicals developed in the last few years excluding ring opening reactions of cyclic iminyl radicals that were summarized in recent publications. The review consists of two main parts: (1) reactions of iminyl radicals involving 1,n‐hydrogen atom transfer (n=5 in most cases) and (2) reactions involving the addition of iminyl radical to the carbon‐carbon π‐bond.magnified image