Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H2S gas. We report indium sulfide (In2S3) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H2S gas sensor. The pristine In2S3 flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In2S3 sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H2S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 degrees C. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory calculations discovered an 8-fold increase in adsorption energy (-1.51 eV) and significant charge transfer (-0.086 e(-)) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H2S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal NPs.

Herein, we report a NiCl2·DPEPhos catalyzed chemoselective activation of the C(acyl)-O bond in functionalized esters toward the synthesis of amino-hydroxy-amides using ambident amino alcohols. [IrCp*Cl2]2 catalyzed intramolecular cyclization of amino-hydroxy-amides via borrowing hydrogenation, afforded therapeutically beneficial 1,4-benzodiazepin-5-ones. A plausible mechanism for both steps has been elucidated. The 1,4-benzodiazepin-5-one frameworks were structurally diversified through postsynthetic modification. This protocol enables access to natural products such as Circumdatin F and Circumdatin H, further underscoring its potential.

Comprehending the kinetics of bimolecular nucleophilic substitution (SN2) reactions involving bigger nucleophiles is crucial for linking fundamental model investigations to more intricate organic systems. In this work, classical trajectory simulations were performed for the CH3O- + CH3I reaction across collision energies ranging from 0.4 to 1.6 eV, corresponding to conditions recently explored in velocity-map imaging experiments. Two major reactive pathways were identified: the substitution channel forming I- + CH3OCH3 products and the proton transfer channel producing CH2I- and CH3OH. In the experimental investigation, the proton transfer channel progresses from indirect to direct scattering as collision energy increases, while the SN2 channel has more complex dynamics, characterized by predominantly direct scattering throughout the assessed collision energy range. Both the forward scattering caused by direct stripping and the backward scattering caused by the direct rebound mechanism were observed. The simulations align closely with the experiments on proton-transfer channels, demonstrating a distinct shift towards direct dynamics, as evidenced by an increased proportion of forward-scattered products. In contrast, the SN2 channel predominantly proceeds through a direct rebound mechanism at all collision energies. The scattering angles and energy distributions of the products were calculated, and comprehensive atomic-level reaction mechanisms are presented.

Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H2S gas. We report indium sulfide (In2S3) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H2S gas sensor. The pristine In2S3flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In2S3sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H2S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 °C. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory calculations discovered an 8-fold increase in adsorption energy (-1.51 eV) and significant charge transfer (-0.086 e-) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H2S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal NPs.

Small inorganic molecules containing sulfur, nitrogen, and oxygen have been extensively studied due to their roles in industrial processes, biological systems, and atmospheric chemistry. is one such molecule, generated via gas-phase pyrolysis of methoxysulfonyl azide (MSA) [CHOS(O)N]. Previous flash-vacuum pyrolysis experiments, supported by CCSD(T)/6-311++G(2df, 2p) electronic structure calculations, indicated that MSA decomposes through two competing pathways involving a methoxysulfonyl nitrene intermediate (CHOS(O)N), ultimately forming , HCHO, and . In the present work, we combine electronic structure theory with Born-Oppenheimer direct classical trajectory simulations to investigate the unimolecular dissociation dynamics of MSA and to elucidate its atomistic reaction mechanisms. Benchmarking against correlated wavefunction methods showed that density functional B3LYP/6-31G** level of theory is best suited to perform the on-the-fly dynamics. Reactant molecules were activated using classical microcanonical sampling and the integrated trajectories were analyzed to characterize product branching, intermediate lifetimes, and mechanistic pathways. The simulations reveal detailed dissociation mechanisms, including Curtius-type rearrangement and 1,4-H shift processes, providing molecular-level insight into the decomposition chemistry of MSA.

Abstract Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H 2 S gas. We report indium sulfide (In 2 S 3 ) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H 2 S gas sensor. The pristine In 2 S 3 flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In 2 S 3 sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H 2 S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 °C. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory calculations discovered an 8-fold increase in adsorption energy (−1.51 eV) and significant charge transfer (−0.086 e - ) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H 2 S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal NPs.

Simulation of chemical reactions to compute reaction energies using variational algorithms remains challenging in achieving chemical accuracy relative to benchmark computational chemistry methods due to limitations such as qubit number, circuit depth, and noise. To address this issue, we propose the definition of different active spaces for studying chemical reactions, incorporating irreducible representations of both ground and excited states by defining the maximum contribution of excitation terms in the ansatz, implemented here within a second-order Trotterized UCCSD-VQE framework. Our results demonstrate that this approach can achieve chemical accuracy for several representative reactions and yields close agreement with benchmark methods across a broader range of reactions. For all reactions studied, the difference in reaction energies between VQE and CCSD remains within 1 kcal/mol. At the same time, comparison with FCI shows chemical accuracy for several cases and close agreement for the remaining systems. Furthermore, our analysis simplifies the selection of active spaces and electrons for each reaction, reducing it to a single optimal combination that supports chemically accurate or near-chemical-accuracy predictions.

Pericyclic reactions provide stringent tests for quantum simulations because their mechanisms are governed by orbital symmetry and involve correlated transition states. In this work, we employ the variational quantum eigensolver (VQE) combined with a previously established symmetry-guided active-space selection protocol based on symmetry-matched fractions (SMF-VQE) to simulate Diel-Alder and Alder-ene reactions in complex systems involving extended pi-conjugation and multiple bonding. Although absolute electronic energies obtained from the current protocol exhibit significant deviations from the values computed using CCSD method, the symmetry-guided active spaces yield substantial cancellation of deviations in the energy differences. As a result, reaction energies are predicted with error (relative to CCSD) less than one kcal per mol, while activation energies are reproduced within about five to six kcal per mol. The symmetry-guided protocol also reduces the large combinatorial space of active-space choices to a single symmetry-consistent selection for each reaction.

Nitroimidazoles represent an important class of compounds due to their distinct biological activities and potential therapeutic applications. Among them, 2-nitroimidazole (2-NI) is known for its radiosensitizing effects in radiation therapy, while 4-nitroimidazole (4-NI) exhibits notable antimicrobial activity. Despite their significance, the fragmentation chemistry of nitroimidazole ions remains poorly understood. In this study, the fragmentation behavior of protonated and deprotonated 2-NI and 4-NI ions was investigated using electronic structure calculations combined with direct dynamics simulations under collision-induced dissociation (CID) conditions. All dynamics simulations were performed at the density functional M06-2X/6-31+G* level of theory. Ion activation was modeled through collisions with an Ar atom, and the resulting fragment ions were thoroughly analyzed. The simulations revealed a wide variety of dissociation pathways and product ions. Notably, the CID trajectories were dominated by a direct, non-statistical shattering mechanism, leading to deviations from experimental fragmentation patterns. To account for these differences, statistical unimolecular dissociation simulations were also conducted at fixed total energies. The resulting product branching ratios showed improved agreement with experimental observations, offering deeper insight into the underlying dissociation mechanisms.

Quantum computing is viewed as a promising technology because of its potential for polynomial growth in complexity, in contrast to the exponential growth observed in its classical counterparts. In the current Noisy Intermediate-Scale Quantum (NISQ) era, the Variational Quantum Eigensolver (VQE), a hybrid variational algorithm, is utilized to simulate molecules using qubits and calculate molecular properties. However, simulating a chemical reaction to compute the reaction energy using VQE algorithm has not yet reached chemical accuracy relative to the benchmark computational chemistry methods due to limitations such as the number of qubits, circuit depth, and noise introduced within the model. To address this issue, we propose the definition of different active spaces for studying chemical reactions, incorporating irreducible representations of both the ground and excited states of the molecules. Our results demonstrate that this approach achieves chemical accuracy in predicting the reaction energy for various reactions. For all reactions studied, the difference in reaction energies between conventional computational chemistry methods and the quantum-classical hybrid VQE algorithm is less than 1 kcal/mol. Furthermore, our analysis simplifies the process of selecting active spaces and electrons for each reaction, reducing it to a single optimal combination that ensures the chemical accuracy for each reaction.

MoS2 has elicited notable interest as a promising material for gas sensing applications. The pristine MoS2 is still encumbered by drawbacks such as low response, large response time, and a propensity for weak adsorption of target gases, which can impede its effectiveness in practical applications. To address these challenges, this study investigates the functionalization of nitrogen-doped MoS2 with silver nanoparticles to improve its sensing performance for NO2 gas. MoS2 nanosheets were synthesized through chemical vapor deposition and subsequently subjected to nitrogen plasma treatment to facilitate doping. We evaluated the gas sensing performance of pristine MoS2, Ag-decorated MoS2, nitrogen-doped MoS2, and Ag-decorated nitrogen-doped MoS2 (Ag-N-MoS2) specifically for NO2 gas sensing. The Ag-N-MoS2 configuration demonstrated a response that was nearly double that of pristine MoS2 at 100 degrees C, demonstrating the benefits of this dual enhancement strategy. Additionally, selectivity tests revealed the sensor's capacity to distinguish NO2 from other gases. To reinforce our experimental results, density functional theory (DFT) calculations were conducted, confirming the improved electronic properties achieved through nitrogen doping and Ag NP functionalization. This research underscores the potential of Ag-NMoS2 as a formidable platform for sophisticated gas sensors, addressing crucial environmental monitoring requirements while surmounting the intrinsic limitations of pristine MoS2.

Hydrochlorofluorocarbons are an important class of organic compounds having a wide variety of applications despite their hazardous effects on nature. Among these molecules, CF3CH2Cl and its structural isomer CF2ClCH2F were the subject of many experimental and theoretical studies exploring various reaction pathways of their unimolecular dissociation. A commonly observed pathway is 1,2-HX (X = Cl, F) elimination resulting in the formation of alkenes through a four-membered transition state. In earlier studies, it was proposed that the formation of CF2═CHF from CF3CH2Cl occurs via 1,1-HCl elimination resulting in CF3CH followed by migration of the F atom between C centers. A chemical activation experimental study indicated that the Cl/F exchange between C centers may play an important role in the dissociation of CF3CH2Cl and CF2ClCH2F. This study pointed toward replacing the earlier mechanism with the Cl/F exchange followed by 1,2-HCl elimination. In the present work, atomistic level mechanisms for the isomerization and dissociation reactions of the CF3CH2Cl ⇄ CF2ClCH2F system were investigated using electronic structure theory, direct dynamics simulations, and Rice-Ramsperger-Kassel-Marcus theory. The dynamics simulations were performed using the global hybrid functional M06-2X with the 6-31+G* basis set in the gas phase. Trajectories were initiated with fixed total energies for the reactants, and product branching ratios were computed. Detailed study of the trajectories revealed that the Cl/F exchange reaction is dominant at low simulation energies, and the traditional mechanism involving the carbene is the most probable reaction pathway at high energies.

The gas-phase dynamics of bimolecular nucleophilic substitution (SN2) reactions have been extensively studied by both experimental and theoretical groups due to their broad applicability and the emergence of new mechanistic insights. The reaction between CN- and CH3I is particularly intriguing, as it can yield two isomeric products (NCCH3 or CNCH3 + I-) owing to the ambident nature of the CN- nucleophile. Previous velocity map imaging experiments revealed predominantly direct rebound dynamics and high internal energy excitation in the reaction products. In another study, direct dynamics simulations were performed employing the PM7 semi-empirical method and B3LYP/aug-cc-pVDZ/ECP density functional theory (DFT); however, these approaches were limited by an insufficient number of DFT trajectories (due to high computational costs) and an overestimation of hydrogen transfer reactions with PM7. In the present study, a high-dimensional neural network-based potential energy surface (PES) was developed using extensive electronic structure data. The PES was rigorously validated using established benchmarks and subsequently employed in quasi-classical trajectory simulations. A substantial number of reactive trajectories were generated, enabling a detailed analysis of the reaction dynamics. The simulation results are consistent with previous findings and provide new insights into the mechanistic pathways of this SN2 reaction.

Dimethyl carbonate (DMC) has been considered as a potential alternate fuel due to the absence of a C-C bond and the presence of high oxygen content. Experimental studies have shown that the dominant decomposition products of DMC are CO2 and dimethyl ether (DME), among others. DME also undergoes decomposition under similar conditions, and a clear experimental distinction of DMC and DME dissociation products is difficult. In the present work, unimolecular decomposition of DMC and DME was investigated under the same reaction conditions using electronic structure theory, Born-Oppenheimer direct dynamics simulations, and Rice-Ramsperger-Kassel-Marcus (RRKM) theory rate constant calculations. The on-the-fly trajectory simulations were performed at the density functional B3LYP/cc-pVDZ level of electronic structure theory. DMC and DME were excited using the same average normal mode energies and subsequent atomic-level dissociation dynamics investigated. In agreement with previous studies, DME + CO2 formation was dominant for the DMC molecule. In addition, another major pathway resulting in :CH2 and carbonic acid monomethyl ester (CAME) was identified in the decomposition of DMC and this might be an important pathway at high temperatures. CAME underwent subsequent dissociation, resulting in other known products. For the DME decomposition, molecular H2 elimination along with various byproducts was found to be dominant. The dissociation products of DMC and DME were separately quantified, and atomic-level dissociation mechanisms were presented.

A quinoline-based pincer Mn catalyst for α-alkylation of methyl ketones using primary alcohols as alkyl surrogates is presented. The C–C bond formation reaction proceeds via a hydrogen auto-transfer protocol, generating water as the only by-product.

Detection of molecular anions in interstellar media implies that negatively charged species play a prominent role in astrochemical reactions. Among the observed species, carbon chain anions are important, as they can be precursors for the production of complex organic molecules. These anions can form either via direct electron attachment to the corresponding neutral species or through chain growth reactions of smaller anions, resulting in longer chains. In a recent study, crossed beam experiments coupled with velocity map imaging techniques were used to investigate the carbon chain growth reaction C-2n(-) + C2H2 -> C2n+2Hm- + H2-m (n = 1-3, m = 0,1). Products and branching ratios were established from experimental data. In the present work, electronic structure calculations and on-the-fly direct dynamics simulations were used to study these reactions. Energy profiles were investigated by using different density functional methods. Direct trajectory simulations were performed at the experimental collision energies using the B3LYP/6-31+G* level of theory. Trajectory analysis showed a variety of reaction pathways, and detailed atomic-level reaction mechanisms are presented.

Catalytic hydrogenation of the potent greenhouse gas carbon dioxide to obtain value-added products represents a much sought after methodology in academia and industry. Hydrogenation of CO2 to formic acid catalyzed by molecular complexes is a highly desirable protocol because of the industrial importance of formic acid and its potential application as a renewable hydrogen storage material. Herein we disclose that the bench-stable, low-valent phosphine-tethered chromium carbonyl complex Cr(DPPP)(CO)(4) (C-3) (DPPP = 1,3-bis(diphenylphosphino)propane) catalyzed efficient hydrogenation of CO2 to formate giving a maximum turnover number (TON) of 259,000 at 130 degrees C in THF/H2O mixture after 24 h at the expense of 40 bar (CO2:H-2 = 10:30) pressure. Biologically relevant sodium bicarbonate and inorganic carbonates were also tested for hydrogenation to sodium formate, furnishing decent yields of the desired products. Mechanistic investigation along with theoretical studies revealed that the reaction proceeded via the formation of a metallacarboxylate intermediate, which was further converted to a formato complex via an anionic hydrido carbonyl intermediate.

Cyclopentanone is a potential bio-fuel which can be produced from bio-mass. Its gas phase dissociation chemistry has attracted several experimental and theoretical investigations. In the photochemical and thermal decomposition studies of cyclopentanone, ethylene and carbon monoxide were found to be dominant reaction products along with several other compounds in smaller quantities. For the formation of ethylene and carbon monoxide, a concerted mechanism has been proposed as the primary reaction pathway. In addition, a step-wise mechanism involving ring-opened radical intermediate has also been considered. The present work reports gas phase thermal decomposition of cyclopentanone at high temperatures investigated using electronic structure theory methods, Rice-Ramsperger-Kassel-Marcus (RRKM) rate constant calculations, and Born-Oppenheimer direct classical trajectory simulations. The trajectory calculations were performed on density functional PBE96/6-31+G* potential energy surface using initial conditions selected from fixed energy normal mode distributions. Simulations showed that ethylene and carbon monoxide formed primarily via the concerted mechanism confirming the earlier predictions. In addition, step-wise pathways were also observed for the same products in lower fraction of trajectories. Furthermore, several other reaction products in smaller quantities and new mechanistic pathways were observed. The computed RRKM rate constants and simulation data are in agreement with experimental results and detailed atomic level dissociation mechanisms presented.

We have devised a highly diastereoselective formal [2 + 1] annulation reaction of arylidene/alkylidine-pyrazolones with in situ-generated supported as well as standard pyridinium ylides to construct spirocyclopropanyl-pyrazolones. The cascade approach exhibits a wide range of functional group tolerance, gram-scale capability, and substrate versatility. A diverse range of spirocyclic cyclopropanes was synthesized extensively with both mediators, and the supported pyridine was reused in subsequent cycles. Density functional theory calculations confirmed the formation of spirocyclopropane as the lower energy pathway.

Bimolecular nucleophilic substitution reactions have been studied for more than a century. Experimental and theoretical investigations of these reactions are extensively going on due to their wide applicability and the discovery of new features of these reactions. The CN- + CH3I nucleophilic substitution reaction can result in two isomeric products (NCCH3/CNCH3 + I-) because the incoming nucleophile has two reactive centers. Velocity map imaging experiments of this reaction have been reported and dominant direct rebound dynamics and high internal energy excitation of the reaction products were found in the experiments. However, it was not possible to directly obtain the isomer branching ratios from the experimental data and statistical ratios were predicted based on a numerical simulation. In the present work, direct chemical dynamics simulations of this reaction were performed using density functional theory and semi-empirical potential energy surfaces. Reactivity was low at all collision energies and direct rebound dynamics was observed in a major fraction of trajectories in agreement with experiments. However, the branching ratios computed from the trajectories were different from the previously reported estimates. Product energy distributions and scattering angles were computed and detailed atomic level reaction mechanisms are presented.