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III-nitrides are crucial materials for solar flow batteries due to their versatile properties. In contrast to the well-studied MOVPE reaction mechanism for AlN and GaN, few works report gas-phase mechanistic studies on the growth of InN. To better understand the reaction thermodynamics, this work revisited the gas-phase reactions involved in metal–organic vapor-phase epitaxy (abbreviated as MOVPE) growth of InN. Utilizing the M06-2X function in conjunction with Pople's triple-ζ split-valence basis set with polarization functions, this work recharacterized all stationary points reported in previous literature and compared the differences between the structures and reaction energies. For the reaction pathways which do not include a transition state, rigorous constrained geometry optimizations were utilized to scan the PES connecting the reactants and products in adduct formation and XMIn (M, D, T) pyrolysis, confirming that there are no TSs in these pathways, which is in agreement with the previous findings. A comprehensive bonding analysis indicates that in TMIn:NH3, the In-N demonstrates strong coordinate bond characteristics, whereas in DMIn:NH3 and MMIn:NH3, the interactions between the Lewis acid and base fragments lean toward electrostatic attraction. Additionally, the NBO computations show that the H radical can facilitate the migration of electrons that are originally distributed between the In-C bonds in XMIn. Based on this finding, novel reaction pathways were also investigated. When the H radical approaches MMInNH2, MMIn:NH3 rather than MMInHNH2 will generate and this is followed by the elimination of CH4 via two parallel paths. Considering the abundance of H2 in the environment, this work also examines the reactions between H2 and XMIn. The Mulliken charge distributions indicated that intermolecular electron transfer mainly occurs between the In atom and N atom whiling forming (DMInNH2)2, whereas it predominately occurs between the In atom and the N atom intramolecularly when generating (DMInNH2)3. [ABSTRACT FROM AUTHOR]

Autothermal oxidative coupling of methane (OCM) is a highly attractive approach for methane utilization. If platinum-based catalysts are operated in short-contact-time reactors with high space velocities, high methane conversion can be achieved. Using a 1 wt.% Pt/Al2O3 catalyst as a benchmark, the present study elucidates how different dopants, namely Ni, Sn, and V2O5, affect the OCM reaction. Kinetic catalyst tests reveal that acetylene (C2H2) is the predominant C2 product, irrespective of the catalyst formulation or operation conditions. Furthermore, the use of bimetallic catalysts allows either for the maintenance or even the improvement of the C2 selectivity during OCM, which is attributed to synergistic effects that occur when expensive Pt is partially replaced by cheaper dopants. In particular, the 1 wt.% Pt/Al2O3 reference catalyst yielded a maximum C2 selectivity of 8.2%, whereas the best-performing doped sample 0.25 wt.% Pt 0.75 wt.% V2O5/Al2O3 yielded a total C2 selectivity of 11.3%. [ABSTRACT FROM AUTHOR]

In recent years, the electronic structures of organocuprates in general and the complex [Cu(CF3)4]− in particular have attracted significant interest. A possible key indicator in this context is the reactivity of these species. Nonetheless, this aspect has received only limited attention. Here, we systematically study the series of tetra‐alkyl cuprates [MenCu(CF3)4−n]− and their unimolecular reactivity in the gas phase, which includes concerted formal reductive eliminations as well as radical losses. Through computational studies, we characterize the electronic structures of the complexes and show how these are connected to their reactivity. We find that all [MenCu(CF3)4−n]− ions feature inverted ligand fields and that the distinct reactivity patterns of the individual complexes arise from the interplay of different effects. [ABSTRACT FROM AUTHOR]

We report the preparation, isolation, and reactivity of gas‐phase lanthanide nitrate and acetate complexes featuring the elusive trivalent LnIII=O bond. Complexes [LnIII(O)(X)2]− (X=NO3− or CH3CO2−; Ln=La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Tm, Lu) are prepared from [LnIII(CH3CO2)(X)3]− precursors through decarboxylation followed by nitromethane or acetone elimination. The oxo complexes hydrolyze at rates indicating LnIII=O bond stability. The rates for [LnIII(O)(NO3)2]− are essentially invariant, whereas those for [LnIII(O)(CH3CO2)2]− exhibit a moderate decrease across the lanthanide series. The kinetics of lanthanide‐oxo bond hydrolysis are assessed in the context of participation of 5d2 electrons in bonding, changes in covalency via variations in 5d orbital energies and radial extensions, and steric crowding around the lanthanide center. The observed fast hydrolysis rates and lack of correlation to electronic and qualitative covalent considerations confirm the expected strong polarization in LnIII=O bonding, with variations in covalency minimally impacting reactivity. The LnIII=O bond reactivity is compared with previous results for LnIII−O⋅ and LnIV=O, and actinide AnIII=O and AnIV=O; implications for lanthanide/actinide and lanthanide/lanthanide partitioning are discussed. Additionally, nitromethane and acetone elimination are demonstrated as useful for inducing a 2e− O‐atom transfer resulting in non‐oxidative formation of lanthanide‐oxos. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: We detail the generation of a pulsed atomic oxygen (AO) broad beam with a high flux‐density via collision‐induced dissociation of O2 to support practical industrial exploitation of AOs, particularly for facilitating 2‐dimenstional oxidation/etching at a fast rate of one‐monolayer per second in an area ≥ 1000 cm2. This innovation fuses the following interdisciplinary concepts: (a) a high density of O+ can be produced in an electron‐cyclotron‐resonance (ECR) O2 plasma; (b) O+ can be extracted and accelerated with an aperture‐electrode in the plasma; (c) O+ with adequate kinetic energy can initiate a cascade of gas‐phase collisions in the presence of O2; (d) collision‐induced dissociation of O2 yields AOs with adequate kinetic energy which can cause additional collision‐induced dissociation of O2. Computational simulations of such collisions, with both ab initio molecular dynamics and direct simulation Monte Carlo methods, are used to guide the experimental generation of the proposed AO‐beam. We experimentally demonstrate the highest known AO mean flux‐density of about 1.5 × 1016 atoms·cm–2·s–1 in a broad‐beam, and use it to oxidatively modify a self‐assembled molecular layer of siloxane on a silicon wafer. In addition, we also demonstrate the growth of Al2O3 through an AO‐assisted atomic layer deposition process at room temperature. [ABSTRACT FROM AUTHOR]

In recent years, the remarkable progress in exoplanet science has unveiled a stunning diversity of exoplanets. Technological advancements have significantly expanded our capacity to investigate planetary objects beyond our solar system, which exhibit diverse properties including their sizes, compositions, and orbital characteristics. Although understanding the complex chemical-climate responses occurring in planetary-body atmospheres plays a pivotal role in determining potential habitability, much work is still required in this field. To interpret forthcoming spectral measurements obtained from exoplanetary atmospheres, there is a concerted effort to model these worlds. However, model parameters are often inferred from limited data sets. Consequently, laboratory-based atmospheric simulations are necessary for understanding complex gas-phase interactions and to complement atmospheric models through experimental examination of input parameters. In this paper we introduce the new Berlin Atmospheric Simulation Experimental chamber (BASE), present its current capabilities and provide an overview of experimental scenarios with applications ranging from planetary objects in the solar system (e.g. Mars, Venus, Titan) to Earth-like exoplanets. • Exoplanetary science demands experimental validation of atmospheric processes. • Laboratory simulations are fine tuned to a specific set of atmospheric parameters. • UV photons and electrons initiate important chemical reactions in the gas phase. • BASE simulates pressure, composition and radiation levels of planetary atmospheres. • BASE will provide important laboratory data to improve current atmospheric models. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: We detail the generation of a pulsed atomic oxygen (AO) broad beam with a high flux‐density via collision‐induced dissociation of O2 to support practical industrial exploitation of AOs, particularly for facilitating 2‐dimenstional oxidation/etching at a fast rate of one‐monolayer per second in an area ≥ 1000 cm2. This innovation fuses the following interdisciplinary concepts: (a) a high density of O+ can be produced in an electron‐cyclotron‐resonance (ECR) O2 plasma; (b) O+ can be extracted and accelerated with an aperture‐electrode in the plasma; (c) O+ with adequate kinetic energy can initiate a cascade of gas‐phase collisions in the presence of O2; (d) collision‐induced dissociation of O2 yields AOs with adequate kinetic energy which can cause additional collision‐induced dissociation of O2. Computational simulations of such collisions, with both ab initio molecular dynamics and direct simulation Monte Carlo methods, are used to guide the experimental generation of the proposed AO‐beam. We experimentally demonstrate the highest known AO mean flux‐density of about 1.5 × 1016 atoms·cm–2·s–1 in a broad‐beam, and use it to oxidatively modify a self‐assembled molecular layer of siloxane on a silicon wafer. In addition, we also demonstrate the growth of Al2O3 through an AO‐assisted atomic layer deposition process at room temperature. [ABSTRACT FROM AUTHOR]

Studying the direct effects of DNA irradiation is essential for understanding the impact of radiation on biological systems. Gas‐phase interactions are especially well suited to uncover the molecular mechanisms underlying these direct effects. Only relatively recently, isolated DNA oligonucleotides were irradiated by ionizing particles such as VUV or X‐ray photons or ion beams, and ionic products were analyzed by mass spectrometry. This article provides a comprehensive review of primarily experimental investigations in this field over the past decade, emphasizing the description of processes such as ionization, fragmentation, charge and hydrogen transfer triggered by photoabsorption or ion collision, and the recent progress made thanks to specific atomic photoabsorption. Then, we outline ongoing experimental developments notably involving ion‐mobility spectrometry, crossed beams or time‐resolved measurements. The discussion extends to potential research directions for the future. [ABSTRACT FROM AUTHOR]

In contrast to its behavior in solution, the adduct [(LiBr)(tBu)(Ph)Bpin]− (pin=pinacol) transfers its phenyl anion from boron to lithium upon fragmentation in the gas phase. Quantum chemical calculations predict this exceptional transmetalation to be exothermic relative to the separated reactants, [(tBu)(Ph)Bpin]− and LiBr, which we attribute to the high phenyl‐anion affinity of the coordinatively unsaturated LiBr unit. The addition of a single molecule of tetrahydrofuran drastically reduces the phenyl‐anion affinity of LiBr and thereby renders the transmetalation from boron to lithium endothermic. Thus, the probed system highlights the importance of solvation and ligation effects in transmetalations. For correctly predicting the direction, in which these reactions proceed, it is not sufficient to consider the electronegativities or partial charges of the involved metals or metalloids. Instead, the individual coordination states and their changes over the course of the reaction must be taken into account. [ABSTRACT FROM AUTHOR]

The fundamental reaction pathways to the simplest dialkylsubstituted aromatics—xylenes (C6H4(CH3)2)—in high‐temperature combustion flames and in low‐temperature extraterrestrial environments are still unknown, but critical to understand the chemistry and molecular mass growth processes in these extreme environments. Exploiting crossed molecular beam experiments augmented by state‐of‐the‐art electronic structure and statistical calculations, this study uncovers a previously elusive, facile gas‐phase synthesis of xylenes through an isomer‐selective reaction of 1‐propynyl (methylethynyl, CH3CC) with 2‐methyl‐1,3‐butadiene (isoprene, C5H8). The reaction dynamics are driven by a barrierless addition of the radical to the diene moiety of 2‐methyl‐1,3‐butadiene followed by extensive isomerization (hydrogen shifts, cyclization) prior to unimolecular decomposition accompanied by aromatization via atomic hydrogen loss. This overall exoergic reaction affords a preparation of xylenes not only in high‐temperature environments such as in combustion flames and around circumstellar envelopes of carbon‐rich Asymptotic Giant Branch (AGB) stars, but also in low‐temperature cold molecular clouds (10 K) and in hydrocarbon‐rich atmospheres of planets and their moons such as Triton and Titan. Our study established a hitherto unknown gas‐phase route to xylenes and potentially more complex, disubstituted benzenes via a single collision event highlighting the significance of an alkyl‐substituted ethynyl‐mediated preparation of aromatic molecules in our Universe. [ABSTRACT FROM AUTHOR]

Gas‐phase investigations on acetone, under the influence of electric pulsed discharge has provided distinct insight related to its decomposition. Time‐of‐flight mass spectrometry has been utilized to identify different products generated upon dissociation/ionization of acetone, under the influence of electric discharge. In addition to molecular (C3H6O+) and protonated acetone (C3H7O+) ions, predominant ions signal corresponding to C3H4O+, C3O+ and CH3CO+ were observed in the mass spectrum. Under discharge condition, acetone undergoes soft dissociation/ionization producing C3H4O+ and C3O+ ions, which are distinctive from usual fragment ions reported upon decomposition of acetone, in the gas‐phase. Though metastable in nature, significant ion yield has been obtained for C3O+ ions. Computational studies have been carried out to understand the mechanism of acetone decomposition in gas‐phase. Based on experimental and computational findings, generation of these ions (C3O+ and C3H4O+) has been ascribed to step‐wise H2 elimination reaction originating from acetone molecule, followed by ionization of resultant fragments under the influence of electric pulsed discharge. Present studies are of relevance for plasma pyrolysis of volatile organic compounds and laboratory astrochemical investigations. [ABSTRACT FROM AUTHOR]

Hydrogen spillover, involving the surface migration of dissociated hydrogen atoms from active metal sites to the relatively inert catalyst support, plays a crucial role in hydrogen‐involved catalytic processes. However, a comprehensive understanding of how H atoms are driven to spill over from active sites onto the catalyst support is still lacking. Here, we examine the atomic‐scale perspective of the H spillover process on a Pt/Cu(111) single atom alloy surface using machine‐learning accelerated molecular dynamics calculations based on density functional theory. Our results show that when an impinging H2 dissociates at an active Pt site, the Pt atom undergoes deactivation due to the dissociated hydrogen atoms that attach to it. Interestingly, collisions between H2 and sticking H atoms facilitate H spillover onto the host Cu, leading to the reactivation of the Pt atom and the realization of a continuous H spillover process. This work underscores the importance of the interaction between gas molecules and adsorbates as a driving force in elucidating chemical processes under a gaseous atmosphere, which has so far been underappreciated in thermodynamic studies. [ABSTRACT FROM AUTHOR]

The way in which molecules can arrange themselves is at the root of organic chemistry and elucidating the structures present in isomeric mixtures remains a major challenge nowadays. A tantalizing question for chemists is how molecules transform from one structural configuration to another one. This review introduces in details a technique—tunable photoionization chemical monitoring—that couples tandem mass spectrometry and photoionization enabling to answer the two aforementioned questions for molecular ions. It is based on tracking reactivity changes in bimolecular ion–molecule reactions as a function of the internal energy of the ions. This is illustrated with (i) the structural elucidation of ortho‐benzyne distonic cation within a C 6H4+ population and (ii) the tracking of the isomerization from azulene radical cation as it gets gradually energized to naphthalene cation. In both cases, charge transfer reactions have been primarily used because of their universality. Finally, a state‐of‐the‐art of the TPI‐CM technique using the CERISES mass spectrometer is given, indicating current limitations as well as prospects of improvement. [ABSTRACT FROM AUTHOR]

Possible routes for intra‐cluster bond formation (ICBF) in protonated serine dimers have been studied. We found no evidence of ICBF following low energy collision‐induced dissociation (in correspondence with previous works), however, we do observe clear evidence for ICBF following photon absorption in the 4.6–14 eV range. Moreover, the comparison of photon‐induced dissociation measurements of the protonated serine dimer to those of a protonated serine dipeptide provides evidence that ICBF, in this case, involves peptide bond formation (PBF). The experimental results are supported by ab initio molecular dynamics and exploration of several excited state potential energy surfaces, unraveling a pathway for PBF following photon absorption. The combination of experiments and theory provides insight into the PBF mechanisms in clusters of amino acids, and reveals the importance of electronic excited states reached upon UV/VUV light excitation. [ABSTRACT FROM AUTHOR]

The emission control of harmful compounds and greenhouse gases and the development of alternative, sustainable fuel sources is a major focus in current research. A solution for this problem lies in the development of efficient catalytic materials. Here, gas phase model systems represent prominent examples for obtaining fundamental insights on reaction properties of prospective catalytic systems. In this work, we review results from studies of tantalum clusters and their oxides in the gas phase and discuss insights with a potential relevance for applied systems. We focus on reactions that are essential for sustainable chemistry in the future. In detail, we address the activation of methane, which may enable the transformation of a greenhouse gas to a chemical feedstock, and we discuss the activation of NH 3 , which may function as an alternative energy carrier whose unwanted emission needs to be curbed in future applications. Finally, we consider the activation of N 2 as a third reaction, since reducing the high energy demand of ammonia synthesis still bears significant challenges. While tantalum may be an interesting catalytic material, the discussed studies may also serve as benchmark for investigations of other materials., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

The intramolecular migration of three hydrogen atoms from one moiety of a gaseous radical cation to the other prior to fragmentation is an extremely rare type of redox reaction. Within the scope of this investigation, this scenario requires an ionized but electron-rich arene acceptor bearing a para-(3-hydroxyalkyl) residue. The precise mechanism of such unidirectional 3H transfer processes, including the order of the individual H transfer steps, has remained unclear in spite of previous isotope labelling and recent infrared ion spectroscopy (IRIS) studies. Herein, the details of this peculiar process have been investigated for ionized 4-(N,N-dimethylaminophenyl)-2-butanol, 2, by state-of-the-art density functional theory (DFT) calculations. The energetically most favorable pathway consists of a sequence of successive 1,4-, 1,6- and 1,5-H steps. During these steps the secondary alcohol functionality is oxidized to a carbonyl group and the radical-cationic aniline ring is reduced to an ionized 2,3-dihydroaniline unit. Several alternative sequences, such as three successive 1,5-H shifts, could be excluded. A concomitant unidirectional 2H migration reaction of ion 2 was also investigated and the intermediacy of ion-neutral complexes (INCs) enabling sequential hydride and proton transfer was confirmed by the calculations., (© 2025 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

We report here a green methodology for the synthesis of imine from a gas-phase oxidative coupling of benzyl alcohol to aniline in a continuous-flow system. These reactions were performed using LaMNO3 perovskites as heterogeneous catalysts. The catalytic performance of these materials was 98% and remained stable for 8 h of reaction. The prepared catalysts were successfully regenerated and reused in five successive catalytic cycles. No organic solvents were used in this process, which represents an important advantage in terms of the environment, simplicity, and safety. Moreover, this approach reduces the need for subsequent physicochemical extraction and purification steps.

Zirconia‐alumina mixed oxides (Zr+Ce)O2−Al2O3 with various mol. ratios (5, 10, 20, 50, and 75 % alumina) were prepared using the sol‐gel method. The catalysts were characterised via XRD, SEM, DTA/TG, BET, and FT‐IR spectroscopy. The acidities of the catalysts were measured through the absorption of anthraquinone and pyridine probe molecules using EPR and IR spectroscopy, respectively. Catalytic activity and selectivity were investigated for ethanol conversion to acetaldehyde, ethylene, and diethyl ether, which were used as model reactions to identify surface‐active sites. The relationship between the surface structure and the dehydration/dehydrogenation activity was evaluated. Diethyl ether formation is promoted by the presence of the ZrO2 tetragonal phase at a low ZrO2/Al2O3 ratio in the sample composition, at which the Lewis acid site has an aluminum‐oxygen environment. The reaction mechanism was also discussed. In the low‐temperature reaction region, dehydrogenation competes with dehydration; ethylene and acetaldehyde share a common reactive intermediate. [ABSTRACT FROM AUTHOR]

Actinyl chemistry is extended beyond Cm to BkO2+ and CfO2+ through transfer of an O atom from NO2 to BkO+ or CfO+ , establishing a surprisingly high lower limit of 73 kcal mol-1 for the dissociation energies, D[O-(BkO+ )] and D[O-(CfO+ )]. CCSD(T) computations are in accord with the observed reactions, and characterize the newly observed dioxide ions as linear pentavalent actinyls; these being the first Bk and Cf species with oxidation states above IV. Computations of actinide dioxide cations AnO2+ for An=Pa to Lr reveal an unexpected minimum for D[O-(CmO+ )]. For CmO2+ , and AnO2+ beyond EsO2+ , the most stable structure has side-on bonded η2 -(O2 ), as AnIII peroxides for An=Cm and Lr, and as AnII superoxides for An=Fm, Md, and No. It is predicted that the most stable structure of EsO2+ is linear [O=EsV =O]+ , einsteinyl, and that FmO2+ and MdO2+ , like CmO2+ , also have actinyl(V) structures as local energy minima. The results expand actinide oxidation state chemistry, the realm of the distinctive actinyl moiety, and the non-periodic character towards the end of the periodic table.

Criegee intermediates (CIs) are a class of reactive radicals that are thought to play a key role in atmospheric chemistry through reactions with trace species that can lead to aerosol particle formation. Recent work has suggested that water vapor is likely to be the dominant sink for some CIs, although reactions with trace species that are sufficiently rapid can be locally competitive. Herein, we use broadband transient absorption spectroscopy to measure rate constants for the reactions of the simplest CI, CH2 OO, with two inorganic acids, HCl and HNO3 , both of which are present in polluted urban atmospheres. Both reactions are fast; at 295 K, the reactions of CH2 OO with HCl and HNO3 have rate constants of 4.6×10(-11)  cm(3)  s(-1) and 5.4×10(-10)  cm(3)  s(-1) , respectively. Complementary quantum-chemical calculations show that these reactions form substituted hydroperoxides with no energy barrier. The results suggest that reactions of CIs with HNO3 in particular are likely to be competitive with those with water vapor in polluted urban areas under conditions of modest relative humidity.

The IPCC 2021 report predicts rising global temperatures and more frequent extreme weather events in the future, which will have different effects on the regional climate and concentrations of ambient air pollutants. Consequently, changes in heat and mass transfer between the inside and outside of buildings will also have an increasing impact on indoor air quality. It is therefore surprising that indoor spaces and occupant well‐being still play a subordinate role in the studies of climate change. To increase awareness for this topic, the Indoor Air Quality Climate Change (IAQCC) model system was developed, which allows short and long‐term predictions of the indoor climate with respect to outdoor conditions. The IAQCC is a holistic model that combines different scenarios in the form of submodels: building physics, indoor emissions, chemical–physical reaction and transformation, mold growth, and indoor exposure. IAQCC allows simulation of indoor gas and particle concentrations with outdoor influences, indoor materials and activity emissions, particle deposition and coagulation, gas reactions, and SVOC partitioning. These key processes are fundamentally linked to temperature and relative humidity. With the aid of the building physics model, the indoor temperature and humidity, and pollutant transport in building zones can be simulated. The exposure model refers to the calculated concentrations and provides evaluations of indoor thermal comfort and exposure to gaseous, particulate, and microbial pollutants. [ABSTRACT FROM AUTHOR]

Recent advances in our knowledge of heavy Rydberg and ion-pair states are critically reviewed, with emphasis placed on the close kinship between the two. Heavy Rydberg states are long-range vibrational states, reaching far beyond ≫ 10 2 Å for higher levels. Enhanced chemical reactivity and efficient energy transfer are frequently encountered. Unusual physical properties result from the large dipole moments, including laser-induced reactions and amplified spontaneous emission, and are discussed in the context of the underlying electronic structure. Heavy Rydberg states have a rich spectroscopy which is amenable to quantum defect analysis, as illustrated for a wide range of UV and VUV spectra previously analyzed in terms of Dunham coefficients. The lifetimes of heavy Rydberg states can be long, enabling them to be isolated in cryogenic matrices or as high angular momentum states in the gas phase. Heavy Rydberg and electronic Rydberg states often occupy the same energy region and this, together with the high density of heavy Rydberg vibrational levels, leads to vibronic mixing and numerous perturbations that are a fertile field for analysis by multichannel quantum defect theory and reactive scattering calculations. [ABSTRACT FROM AUTHOR]

The transformation of CO 2 into chemical building blocks for various industries is considered a key technology in a net-zero energy future. To realize this, plasma discharges are one of the most promising approaches thanks to their electron-driven reactions and high operational flexibility. Most studies focused on room-temperature and vibrationally-excited discharges, however, lately, the importance of thermal reactions is considered. Therefore, we developed a temperature-dependent plasma-chemical reaction mechanism to investigate the temperature dependence of plasma-based CO 2 conversion. Here, we present the various effects of thermally-driven reactions on the CO 2 conversion as a function of the gas temperature and specific energy input. Our analysis pinpointed the key reactions controlling the plasma-based CO 2 conversion, shifting from an electron-driven to a thermal-driven regime. Additionally, we used the mechanism to verify the theoretical upper boundary of the process' energy efficiency, and discussed how our findings could lead to the further development and optimization of plasma discharges for efficient CO 2 conversion in the future., (© 2024 The Author(s). ChemSusChem published by Wiley-VCH GmbH.)

Stability and kinetics of plasmonic photocatalysts for gas-phase toluene degradation were assessed by monitoring total volatile organic compound (TVOC) concentration versus UV-A illumination time in a recirculating batch reactor (plate-type flow-through). Plasmonic samples were produced by either coating silver on, or layering silica-protected or unprotected silver beneath, the photocatalyst. Samples were modeled using Finite difference time domain simulations, and characterized. Experimental results show that silver-coated photocatalysts, and photocatalysts layered over unprotected silver, exhibit initially high TVOC degradation rates compared to TiO2, but suffer from relatively rapid deactivation attributed to silver oxidation. Photocatalysts layered over silica-protected (i.e., silica-coated) silver exhibited improved stability versus photocatalysts layered over unprotected (i.e., uncoated) silver, and demonstrated more than 50% increase in reaction rate constant and more than a threefold increase in apparent quantum yield over the non-plasmonic control sample (TiO2 over SiO2). The results of this study demonstrate that a silica layer can help slow down fouling of silica nanoparticles, and that silica-coated silver nanoparticles not only help speed up reaction rate overall but also appear to speed up release of adventitious carbon from the photocatalyst surface during the initial phase of a reaction. [ABSTRACT FROM AUTHOR]

The hitherto elusive monobridged Ge(μ‐H)GeH (X1A′) molecule was prepared in the gas phase by bimolecular reaction of atomic germanium with germane (GeH4). Electronic structure calculations revealed that this reaction commenced on the triplet surface with the formation of a van der Waals complex, followed by insertion of germanium into a germanium‐hydrogen bond over a submerged barrier to form the triplet digermanylidene intermediate (HGeGeH3); the latter underwent intersystem crossing from the triplet to the singlet surface. On the singlet surface, HGeGeH3 predominantly isomerized through two successive hydrogen shifts prior to unimolecular decomposition to Ge(μ‐H)GeH isomer, which is in equilibrium with the vinylidene‐type (H2GeGe) and dibridged (Ge(μ‐H2)Ge) isomers. This reaction leads to the formation of cyclic dinuclear germanium molecules, which do not exist on the isovalent C2H2 surface, thus deepening our understanding of the role of nonadiabatic reaction dynamics in preparing nonclassical, hydrogen‐bridged isomers carrying main group XIV elements. [ABSTRACT FROM AUTHOR]

Ammonia synthesis via the high‐temperature and high‐pressure Haber‐Bosch process is one of the most important chemical processes in the world. In spite of numerous attempts over the last 100 years, continuous Haber‐Bosch type ammonia synthesis at room‐temperature had not been possible, yet. We report the development of a mechanocatalytic system operating continuously at room‐temperature and at pressures down to 1 bar. With optimized experimental conditions, a cesium‐promoted iron catalyst was shown to produce ammonia at concentrations of more than 0.2 vol. % for over 50 hours. [ABSTRACT FROM AUTHOR]

Abstract A gas‐phase investigation of the D‐fructose dehydration reaction in the presence of base has been performed by the joint application of mass spectrometric techniques and theoretical calculations. Protonated addition products of D‐fructose and base were generated in the gas phase by electrospray ionization using several bases of different proton affinity. The intermediates, products and decomposition channels were investigated by ion trap mass spectrometry. Electronic structure calculations allowed the identification of the ionic intermediates and products of a selected system containing NH3, helping to rationalize the observed reaction pathways. The obtained results show that the final product, the protonated 5‐hydroxymethyl‐2‐furaldheyde [5‐HMF]H+, is better formed using selected bases and only if these remain clustered until the end of the dehydration process.

Abstract For the first time, the oxidative dehydrogenation of (−)‐menthol to (−)‐menthone and (+)‐isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO2, CuO distributed on a basic support and RuMnCe/CeO2, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag‐based catalyst was 58 % at 64 % selectivity, with a Cu‐based catalyst 41 % at 51 % selectivity and with a Ru‐based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized.

Abstract Calcium hydroxyphosphate, Ca10(PO4)6(OH)2, is commonly known as hydroxyapatite (HAP). The acidic calcium and basic phosphate/hydroxide sites in HAP can be modified via isomorphous substitution of calcium and/or hydroxide ions to enable a cornucopia of catalyzed reactions. Herein, isomorphic substitution of Ca2+ ions by Cu2+ ions especially at very low levels of exchange created new analogs of molecular surface frustrated Lewis pairs (SFLPs) in CuxCa10−x(PO4)6(OH)2, thereby boosting its performance metrics in heterogeneous CO2 photocatalytic hydrogenation. In situ Fourier transform infrared spectroscopy characterization and density functional theory calculations provided fundamental insights into the catalytically active SFLPs defined as proximal Lewis acidic Cu2+ and Lewis basic OH−. The photocatalytic pathway proceeds through a formate reaction intermediate, which is generated by the reaction of CO2 with heterolytically dissociated H2 on the SFLPs. Given the wealth of information thus uncovered, it is highly likely that this work will spur the further development of similar classes of materials, leading to the advancement and, ultimately, large‐scale application of photocatalytic CO2 reduction technologies.

Calcium hydroxyphosphate, Ca10(PO4)6(OH)2, is commonly known as hydroxyapatite (HAP). The acidic calcium and basic phosphate/hydroxide sites in HAP can be modified via isomorphous substitution of calcium and/or hydroxide ions to enable a cornucopia of catalyzed reactions. Herein, isomorphic substitution of Ca2+ ions by Cu2+ ions especially at very low levels of exchange created new analogs of molecular surface frustrated Lewis pairs (SFLPs) in CuxCa10−x(PO4)6(OH)2, thereby boosting its performance metrics in heterogeneous CO2 photocatalytic hydrogenation. In situ Fourier transform infrared spectroscopy characterization and density functional theory calculations provided fundamental insights into the catalytically active SFLPs defined as proximal Lewis acidic Cu2+ and Lewis basic OH−. The photocatalytic pathway proceeds through a formate reaction intermediate, which is generated by the reaction of CO2 with heterolytically dissociated H2 on the SFLPs. Given the wealth of information thus uncovered, it is highly likely that this work will spur the further development of similar classes of materials, leading to the advancement and, ultimately, large‐scale application of photocatalytic CO2 reduction technologies. [ABSTRACT FROM AUTHOR]

Oxymethylene ethers are a diesel additive/alternative, which reduce pollutant emissions. Based on methanol, it is possible to produce them from renewable energy and CO2. Sulfonated ion exchange resins are known to catalyze the synthesis of OME in liquid phase. Here, we report that the sulfonated polymer polyether‐ether‐ketone (S‐PEEK) exhibits outstanding catalytic properties in the gas phase synthesis of OMEn. PEEK was reacted with gaseous SO3 to a degree of 22 % sulfonated monomer units. Using this material as a catalyst in the direct conversion of formaldehyde and methanol, an extraordinary selectivity to OME1 and OME2 of 93 % at equilibrium conversion of 55 % was obtained. Further, it was shown that the catalyst is stable for more than 60 h, and that with increasing reaction time selectivity to OME2 increases. [ABSTRACT FROM AUTHOR]

Modeling adsorption phenomena on surfaces by DFT calculations often involves substantial errors, resulting in inaccurate predictions of catalytic activities. Such errors partly stem from the inaccurate description of the energetics of free molecules. Herein, we use a semiempirical group‐additivity method to correct the DFT‐calculated heats of formation of 106 carbon‐ and nitrogen‐containing gaseous compounds belonging to 15 different chemical families. PBE, PW91, RPBE and BEEF‐vdW initially yield mean absolute errors (MAEs) with respect to experiments in the range of 0.32–0.75 eV. After correcting the systematic errors, the overall MAEs decrease to ∼0.05 eV. Additionally, upon applying the corrections to three types of reaction enthalpies, the resulting MAEs are below 0.10 eV. These functional‐group corrections can be used in (electro)catalysis to correct the gas‐phase references necessary to evaluate equilibrium potentials and adsorption energies, predict error cancellation, and assess conflicting experimental data. [ABSTRACT FROM AUTHOR]

The reaction of Br atoms with toluene was investigated by employing various quantum chemical methods and statistical rate theory calculations. Various composite methods such as CBS‐QB3, G3, and G4 were used to obtain the energy profiles of the Br + toluene reaction. Further single‐point calculations of the stationary points were performed at the CCSD(T)/cc‐pV(D,T)Z level of theory using B3LYP/cc‐pVTZ and MP2/aug‐cc‐pVDZ optimized geometries. Our calculations revealed several reaction pathways in the potential energy surface of the Br + toluene reaction. However, the reaction pathway that abstracts hydrogen atoms from the methyl site of toluene was found to be energetically the most favorable. This reaction pathway appears to proceed via a complex forming mechanism, similar to that seen in the reactions of cyclic ethers with Br atoms. Our calculations reveal that the reaction of a Br atom with toluene proceeds exclusively via intermediate complexes in an overall endothermic addition‐elimination mechanism. Based on the ab initio results, the standard enthalpies of formation of the product radicals and the rate coefficients for the relevant reaction pathways are computed. The calculated values of the enthalpy of formation are found to match excellently with the available literature data. Lowering the barrier height of hydrogen abstraction reaction at the methyl site by less than 4 kJ/mol, the calculated rate coefficients, kov(T) = 1.36 × 10–23T3.687 exp(−4.57 K/T) cm3 molecule–1 s–1, reproduced the experimental data excellently from 200 to 500 K. [ABSTRACT FROM AUTHOR]

Nitro‐functionalized undecahalogenated closo‐dodecaborates [B12X11(NO2)]2− were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X‐diffraction, mass spectrometry, and gas‐phase ion vibrational spectroscopy. The NO2 substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B12X12]2− (X=F–I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum‐chemical calculations. The stabilizing effect decreases from X=F to X=I. Thermogravimetric measurements of the salts indicate the loss of the nitric oxide radical (NO.). The homolytic NO. elimination from the dianion under very soft collisional excitation in gas‐phase ion experiments results in the formation of the radical [B12X11O]2−.. Theoretical investigations suggest that the loss of NO. proceeds via the rearrangement product [B12X11(ONO)]2−. The O‐bonded nitrosooxy structure is thermodynamically more stable than the N‐bonded nitro structure and its formation by radical recombination of [B12X11O]2−. and NO. is demonstrated. [ABSTRACT FROM AUTHOR]

The thermal gas‐phase reactions of S+, S2+ and S22+ with methane have been explored by using quadrupole‐ion trap (Q‐IT) mass spectrometry complemented by quantum chemical calculations. In contrast to the reactiveness of the S+/CH4 and S22+/CH4 couples as identified by experiment and computation, respectively, the S2+/CH4 couple is inert at ambient temperature. Interestingly, the hydrogen‐atom transfer (HAT) prevails for S+/CH4 and proton‐coupled electron transfer (PCET) for S2+/CH4, while both PCET and hydride transfer (HT) are accessible for S22+/CH4. Multiple factors matter for these processes. The electronic origins of the different reactivities of the three ions have been interrogated. [ABSTRACT FROM AUTHOR]

Using fatty acids as renewable sources of biofuels requires deoxygenation. While a number of promising catalysts have been developed to achieve this, their operating mechanisms are poorly understood. Here, model molecular systems are studied in the gas phase using mass spectrometry experiments and DFT calculations. The coordinated metal complexes [(phen)M(O2CR)]+ (where phen=1,10‐phenanthroline; M=Ni or Pd; R=CnH2n+1, n≥2) are formed via electrospray ionization. Their collision‐induced dissociation (CID) initiates deoxygenation via loss of CO2 and [C,H2,O2]. The CID spectrum of the stearate complexes (R=C17H35) also shows a series of cations [(phen)M(R')]+ (where R' < C17) separated by 14 Da (CH2) corresponding to losses of C2H4‐C16H32 (cracking products). Sequential CID of [(phen)M(R')]+ ultimately leads to [(phen)M(H)]+ and [(phen)M(CH3)]+, both of which react with volatile carboxylic acids, RCO2H, (acetic, propionic, and butyric) to reform the coordinated carboxylate complexes [(phen)M(O2CR)]+. In contrast, cracking products with longer carbon chains, [(phen)M(R)]+ (R>C2), were unreactive towards these carboxylic acids. DFT calculations are consistent with these results and reveal that the approach of the carboxylic acid to the "free" coordination site is blocked by agostic interactions for R > CH3. [ABSTRACT FROM AUTHOR]

The silene molecule (H2SiCH2; X1A1) has been synthesized under single collision conditions via the bimolecular gas phase reaction of ground state methylidyne radicals (CH) with silane (SiH4). Exploiting crossed molecular beams experiments augmented by high‐level electronic structure calculations, the elementary reaction commenced on the doublet surface through a barrierless insertion of the methylidyne radical into a silicon‐hydrogen bond forming the silylmethyl (CH2SiH3; X2A′) complex followed by hydrogen migration to the methylsilyl radical (SiH2CH3; X2A′). Both silylmethyl and methylsilyl intermediates undergo unimolecular hydrogen loss to silene (H2SiCH2; X1A1). The exploration of the elementary reaction of methylidyne with silane delivers a unique view at the widely uncharted reaction dynamics and isomerization processes of the carbon–silicon system in the gas phase, which are noticeably different from those of the isovalent carbon system thus contributing to our knowledge on carbon silicon bond couplings at the molecular level. [ABSTRACT FROM AUTHOR]

The silene molecule (H2SiCH2; X1A1) has been synthesized under single collision conditions via the bimolecular gas phase reaction of ground state methylidyne radicals (CH) with silane (SiH4). Exploiting crossed molecular beams experiments augmented by high‐level electronic structure calculations, the elementary reaction commenced on the doublet surface through a barrierless insertion of the methylidyne radical into a silicon‐hydrogen bond forming the silylmethyl (CH2SiH3; X2A′) complex followed by hydrogen migration to the methylsilyl radical (SiH2CH3; X2A′). Both silylmethyl and methylsilyl intermediates undergo unimolecular hydrogen loss to silene (H2SiCH2; X1A1). The exploration of the elementary reaction of methylidyne with silane delivers a unique view at the widely uncharted reaction dynamics and isomerization processes of the carbon–silicon system in the gas phase, which are noticeably different from those of the isovalent carbon system thus contributing to our knowledge on carbon silicon bond couplings at the molecular level. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) has become a promising approach for the industrial production of graphene films with appealing controllability and uniformity. However, in the conventional hot‐wall CVD system, CVD‐derived graphene films suffer from surface contamination originating from the gas‐phase reaction during the high‐temperature growth. Shown here is that the cold‐wall CVD system is capable of suppressing the gas‐phase reaction, and achieves the superclean growth of graphene films in a controllable manner. The as‐received superclean graphene film, exhibiting improved optical and electrical properties, was proven to be an ideal candidate material used as transparent electrodes and substrate for epitaxial growth. This study provides a new promising choice for industrial production of high‐quality graphene films, and the finding about the engineering of the gas‐phase reaction, which is usually overlooked, will be instructive for future research on CVD growth of graphene. [ABSTRACT FROM AUTHOR]

A bimetallic CuPd/TiO2 system has been prepared by a two‐step synthesis and was used for a methanol steam photoreforming reaction. By sequential deposition, palladium is deposited over copper nanoclusters through a galvanic replacement process. Hydrogen production by steam reforming from methanol was achieved by both thermo‐photocatalytic and photocatalytic processes. It appears that H2 production on the bimetallic system is notably higher than the Pd monometallic reference. Moreover this difference in the catalytic performance could be related to the higher CO evolution observed for the monometallic Pd1.0 TiO2 system which is partially inhibited in the bimetallic catalyst. In addition, an important thermal effect can be envisaged in all cases. Nevertheless, this improved effect in the thermo‐photocatalytic process is accompanied by a remarkable CO evolution and SMSI effect (important strong metal‐support interactions) that hindered the efficiency as temperature increases. On this basis, optimal operational conditions for H2 production are obtained for thermo‐photocatalytic reforming at 100 °C, for which the synergetic effect is higher with lower CO production (H2/CO=4). [ABSTRACT FROM AUTHOR]

[V2O]+ remains “invisible” in the thermal gas‐phase reaction of bare [V2]+ with CO2 giving rise to [V2O2]+; this is because the [V2O]+ intermediate is being consumed more than 230 times faster than it is generated. However, the fleeting existence of [V2O]+ and its involvement in the [V2]+ → [V2O2]+ chemistry are demonstrated by a cross‐over labeling experiment with a 1:1 mixture of C16O2/C18O2, generating the product ions [V216O2]+, [V216O18O]+, and [V218O2]+ in a 1:2:1 ratio. Density functional theory (DFT) calculations help to understand the remarkable and unexpected reactivity differences of [V2]+ versus [V2O]+ towards CO2. [ABSTRACT FROM AUTHOR]