Stable Intermediate Complex Research Articles

Collaborative Fabrication of High-Quality Perovskite Films for Efficient Solar Modules through Solvent Engineering and Vacuum Flash System.

The vacuum flash solution method has gained widespread recognition in the preparation of perovskite thin films, laying the foundation for the industrialization of perovskite solar cells. However, the low volatility of dimethyl sulfoxide and its weak interaction with formamidine-based perovskites significantly hinder the preparation of cell modules and the further improvement of photovoltaic performance. In this study, we describe an efficient and reproducible method for preparing large-scale, highly uniform formamidinium lead triiodide (FAPbI3) perovskite films. This is achieved by accelerating the vacuum flash rate and leveraging the complex synergism. Specifically, we designed a dual pump system to accelerate the depressurization rate of the vacuum system and compared the quality of perovskite film formed at different depressurization rates. Further, to overcome the limitations posed by DMSO, we substituted N-methylpyrrolidone as the ligand solvent, creating a stable intermediate complex phase. After annealing, it can be transformed into a uniform and pinhole-free FAPbI3 film. Due to the superior quality of these films, the large area perovskite solar module achieved a power conversion efficiency of 22.7% with an active area of 21.4 cm2. Additionally, it obtained an official certified efficiency of 22.1% with an aperture area of 22 cm2, and it demonstrated long-term stability.

Atmospheric chemistry of 2-nitrobenzaldehyde: Initiated by photo-excitation, OH-oxidation, and small TiO2 clusters adsorption catalysis

The fate of 2-nitrobenzaldehyde (2-NBA) is of interest in atmospheric chemistry as it is a semi-volatile organic compound with high photosensitivity. This study presents a quantumchemical study of the gas-phase reactions of 2-NBA photo-excitation and OH-oxidation in the absence and presence of small TiO2 clusters. To further understand the unknown photolysis mechanism, the photo-reaction pathways of ground singlet state and the lying excited triplet state of 2-NBA were investigated including the initial and subsequent reactions of proton transfer, direct CO, NO2, and HCO elimination routes in the presence of O2 and NO. Meanwhile, the OH-mediated degradation of 2-NBA proceeded via five H-extraction and six OH-addition channels by indirect mechanism, which follows a succession of reaction steps initiated by the formation of weakly stable intermediate complexes. The H-extraction from the -CHO group was the dominant pathway with a negative activation energy of -1.22kcal/mol. The calculated rate coefficients at 200-600K were close to the experimental data in literature within 308-352K, and the kinetic negative temperature independence was found in both experimental literature and computational results. Interestingly, 2-NBA was favored to be captured onto small TiO2 clusters via six adsorption configurations formed via various combination of three types of bonds of Ti···O, Ti···C, and O···H between the molecularly adsorbed 2-NBA and TiO2 clusters. Comparison indicted that the chemisorptions of aldehyde oxygen have largest energies. The results suggested adsorption conformations have a respectable impact on the catalysis barrier. This study is significant for understanding the atmospheric chemistry of 2-nitrobenzaldehyde.

Structural and mechanistic basis for protein glutamylation by the kinase fold

The kinase domain transfers phosphate from ATP to substrates. However, the Legionella effector SidJ adopts a kinase fold yet catalyzes calmodulin (CaM)‐dependent glutamylation to inactivate the SidE ubiquitin ligases. The structural and mechanistic basis in which the kinase domain catalyzes protein glutamylation is unknown. Here we present cryo‐EM reconstructions of SidJ:CaM:SidE reaction intermediate complexes. We show that the kinase‐like active site of SidJ adenylates an active site Glu in SidE resulting in the formation of a stable reaction intermediate complex. An insertion in the catalytic loop of the kinase domain positions the donor Glu near the acyl‐adenylate for peptide bond formation. Our structural analysis led us to discover that the SidJ paralog SdjA is a glutamylase that differentially regulates the SidE‐ligases during Legionella infection. Our results uncover the structural and mechanistic basis in which the kinase fold catalyzes non‐ribosomal amino acid ligations and reveal an unappreciated level of SidE‐family regulation.

Associative detachment in anion-atom reactions involving a dipole-bound electron

Associative electronic detachment (AED) between anions and neutral atoms leads to the detachment of the anion’s electron resulting in the formation of a neutral molecule. It plays a key role in chemical reaction networks, like the interstellar medium, the Earth’s ionosphere and biochemical processes. Here, a class of AED involving a closed-shell anion (OH−) and alkali atoms (rubidium) is investigated by precisely controlling the fraction of electronically excited rubidium. Reaction with the ground state atom gives rise to a stable intermediate complex with an electron solely bound via dipolar forces. The stability of the complex is governed by the subtle interplay of diabatic and adiabatic couplings into the autodetachment manifold. The measured rate coefficients are in good agreement with ab initio calculations, revealing pronounced steric effects. For excited state rubidium, however, a lower reaction rate is observed, indicating dynamical stabilization processes suppressing the coupling into the autodetachment region. Our work provides a stringent test of ab initio calculations on anion-neutral collisions and constitutes a generic, conceptual framework for understanding electronic state dependent dynamics in AEDs.

Novel Selection Approaches to Identify Antibodies Targeting Neoepitopes on the C5b6 Intermediate Complex to Inhibit Membrane Attack Complex Formation.

The terminal pathway of complement is implicated in the pathology of multiple diseases and its inhibition is, therefore, an attractive therapeutic proposition. The practicalities of inhibiting this pathway, however, are challenging, as highlighted by the very few molecules in the clinic. The proteins are highly abundant, and assembly is mediated by high-affinity protein–protein interactions. One strategy is to target neoepitopes that are present transiently and only exist on active or intermediate complexes but not on the abundant native proteins. Here, we describe an antibody discovery campaign that generated neoepitope-specific mAbs against the C5b6 complex, a stable intermediate complex in terminal complement complex assembly. We used a highly diverse yeast-based antibody library of fully human IgGs to screen against soluble C5b6 antigen and successfully identified C5b6 neoepitope-specific antibodies. These antibodies were diverse, showed good binding to C5b6, and inhibited membrane attack complex (MAC) formation in a solution-based assay. However, when tested in a more physiologically relevant membrane-based assay these antibodies failed to inhibit MAC formation. Our data highlight the feasibility of identifying neoepitope binding mAbs, but also the technical challenges associated with the identification of functionally relevant, neoepitope-specific inhibitors of the terminal pathway.

Thermodynamics and Kinetic Investigation of Reaction of Acriflavine with L-cysteine in Aqueous Medium

The kinetic investigation of reaction of 3,6-diamino-10-methylacridin-10-ium chloride (acriflavine) with l-cysteine in aqueous acidic medium at maximum absorption = 460 nm, ionic strength (I) = 0.1 mol dm−3 and temperature (T) = 307 K has been carried out spectrophotometrically. Using a pseudo first order approach, the rate of the redox reaction resulted to first order with respect to the [acriflavine, (AF)] and [l-cysteine, (CSH)] and second order total. Stoichiometric determination confirms that a mole of the acriflavine is consumed by a mole of l-cysteine at a time for the attainment of product formation. The reaction followed a one-way acid independence path. The adjustment in ionic strength (NaCl) and solvent polarity (water/acetone mixture) of the reaction system showed no reasonable effect and there was a fairly decrease in the reaction rate, respectively. The reaction rate is also characterised by neither catalysis nor inhibition of added ions. The negative magnitude of entropy of activation, DeltaS‡, (− 151.39 ± 031 J mol−1 K−1) and positive value of enthalpy of activation, DeltaH‡, (+ 31.378 ± 030 kJ mol−1) suggest that the reaction proceeds via an associative pathway and reasonable energy are needed to lower the activation energy for a tangible products formation. Two acridine unit products polymerised afterward forming a dimer as a result of an intramolecular coupling. A determinable intermediate has been observed through a spectroscopic test and confirmed by Michaelis–Menten’s plot. Based on Taube’s inorganic electron transfer reaction, an inner-sphere mechanistic pathway is implicated with a stable intermediate complex formation as shown below;Graphic abstract

Redox reactions of tris-(1,10-phenanthroline)iron(III) complex with thiourea and N-methylthiourea in an aqueous acidic medium: Kinetics and mechanism

• The reactions order of thiourea (TSH) and methylthiourea (MSH) with tris-(1,10-phenanthroline)iron(III) complex is established to be 1st order with rest to their concentrations. • The stoichiometric mole ratio of the reactions of tris-(1,10-phenanthroline)iron(III) complex with TSH and MSH is 1:1 and 2:1 (Oxidant: Reductants) respectively. • The variation in solvent polarity (acetone/water) of the reactions mixtures significantly influences the reaction rate. • The involvement of free radicals in the reaction is paramount in actualizing the products of the reactions. • The Δ H ‡ (+33.19 (TSH) and 36.07 kJmol −1 (MSH)) and Δ G ‡ (+79.13 (TSH) and 79.72 kJmol −1 (MSH)) suggest an ordered activated complex formation that will proceed through an endothermic process. Spectrophotometrically, the redox reactions of tris-(1,10-phenanthroline)iron(III) complex with thiourea (TSH) and N-methylthiourea (MSH) in an aqueous acidified medium have been investigated at maximum absorption of 510 nm and 301 K. The reactions were first order with respect to [Fe III (phen) 3 3+ ], [MSH] and [TSH]. The stoichiometric mole ratio investigations of [Fe III (phen) 3 ] 3+ with [MSH] is 1:1, and with that of [TSH] is 2:1. An enhancement of observed reaction rates by protonation of hydrogen ion was insignificant for both reactions of TSH and MSH with the complex. The variation of the salt concentration (NaCl) and solvent polarity (acetone/water mixture) of the [Fe III (phen) 3 ] 3+ / TSH reaction medium has no substantial effect on the observed reaction rate (k obd ), while there was retardation and enhancement of reaction rate on the change in the salt concentration and solvent polarity of the [Fe III (phen) 3 ] 3+ / MSH system respectively. The participation of added anion (NO 3 − ) and cation (NH 4 + ) aided the reaction of the complex with MSH, and the cation (NH 4 + ) and anion (NO 3 − ) showed no significant effect on the observed reaction rates of the [Fe III (phen) 3 ] 3+ / TSH system. The involvement of free radicals was eminent for the reactions, and it contributed to a meaningful product formation. The investigation of the thermodynamic activation parameters; Δ S ‡ (−152.63 Jmol −1 K −1 ), Δ H ‡ (+33.19 kJmol −1 ), Ea (+35.69 kJmol −1 ), and Δ G ‡ (+79.13 kJmol −1 ) showed that the reaction of the complex with TSH proceeds via an endothermic process as well as the reaction of the complex / MSH with Δ S ‡ (−145.03 Jmol −1 K −1 ), Δ H ‡ (+36.07 kJmol −1 ), Ea (+38.57 kJmol −1 ) and Δ G ‡ (+79.72 kJmol −1 ). The results of Δ S ‡ indicate that the reactions followed an associative route, and although, it was not established by Michaelis Menten’s plot for the reaction of the complex with MSH. The observation of a determinable intermediate complex reinforced the associative route noticed in the reaction of the TSH with the complex, whereas, the absence of a significant intermediate complex in the reaction of the MSH with the complex ruled it out. An inner-sphere mechanistic pathway is implicated for [Fe III (phen) 3 ] 3+ / TSH reaction with a stable intermediate complex formation as shown below;

Structural and mechanistic basis for protein glutamylation by the kinase fold

The kinase domain transfers phosphate from ATP to substrates. However, the Legionella effector SidJ adopts a kinase fold, yet catalyzes calmodulin (CaM)-dependent glutamylation to inactivate the SidE ubiquitin ligases. The structural and mechanistic basis in which the kinase domain catalyzes protein glutamylation is unknown. Here we present cryo-EM reconstructions of SidJ:CaM:SidE reaction intermediate complexes. We show that the kinase-like active site of SidJ adenylates an active-site Glu in SidE, resulting in the formation of a stable reaction intermediate complex. An insertion in the catalytic loop of the kinase domain positions the donor Glu near the acyl-adenylate for peptide bond formation. Our structural analysis led us to discover that the SidJ paralog SdjA is a glutamylase that differentially regulates the SidE ligases during Legionella infection. Our results uncover the structural and mechanistic basis in which the kinase fold catalyzes non-ribosomal amino acid ligations and reveal an unappreciated level of SidE-family regulation.

Plasmodium falciparum SURFIN4.1 forms an intermediate complex with PTEX components and Pf113 during export to the red blood cell.

Plasmodium falciparum malaria parasites export several hundred proteins to the cytoplasm of infected red blood cells (RBCs) to modify the cell environment suitable for their growth. A Plasmodium translocon of exported proteins (PTEX) is necessary for both soluble and integral membrane proteins to cross the parasitophorous vacuole (PV) membrane surrounding the parasite inside the RBC. However, the molecular composition of the translocation complex for integral membrane proteins is not fully characterized, especially at the parasite plasma membrane. To examine the translocation complex, here we used mini-SURFIN4.1, consisting of a short N-terminal region, a transmembrane region, and a cytoplasmic region of an exported integral membrane protein SURFIN4.1. We found that mini-SURFIN4.1 forms a translocation intermediate complex with core PTEX components, EXP2, HSP101, and PTEX150. We also found that several proteins are exposed to the PV space, including Pf113, an uncharacterized PTEX-associated protein. We determined that Pf113 localizes in dense granules at the merozoite stage and on the parasite periphery after RBC invasion. Using an inducible translocon-clogged mini-SURFIN4.1, we found that a stable translocation intermediate complex forms at the parasite plasma membrane and contains EXP2 and a processed form of Pf113. These results suggest a potential role of Pf113 for the translocation step of mini-SURFIN4.1, providing further insights into the translocation mechanisms for parasite integral membrane proteins.

Dual‐Functioning Molecular Carrier of Superoxide Radicals for Stable and Efficient Lithium–Oxygen Batteries

AbstractLow round‐trip efficiency and poor cycle stability remain the major challenges associated with lithium–oxygen (Li–O2) batteries. These issues are primarily triggered by or correlated to the radical species produced during the operation of Li–O2 cells, which lead to significant deterioration of the electrolytes and air electrodes. Regulation of the reactivity of these radical species would thus open up opportunities to suppress such side reactions. Herein, a dual‐functioning molecule that is capable of mitigating the reactivity of radical species produced in a Li–O2 cell by reversibly forming stable intermediate complex during both the discharge and charge processes is introduced. Specifically, 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) is exploited, which has been widely used as a chemical agent to detect oxygen radicals, to induce the reversible formation of an intermediate complex, DMPO–O2−, in the presence of superoxide radicals. It is demonstrated that DMPO mediates the O2−‐involved electrochemical reaction, leading to significant suppression of side reactions and a remarkably improved oxygen efficiency. Unexpectedly, it is also observed that upon charging, DMPO actively scavenges the superoxides from the surface of discharge products, thus substantially lowering the charging overpotential. The combined radical mediation and scavenging of superoxides result in cycle stability of a practical Li–O2 cell over 200 cycles with a specific capacity of 1000 mAh g−1. The findings indicate the importance of controlling the reactivity of radical species and suggest a new pathway toward the realization of stable and efficient Li–O2 batteries.

Rhodium(III)-Catalyzed Direct Coupling of Quinoline-8-Carbaldehydes with (Het)Arylboronic Acids for the Synthesis of 8-Aryloylquinolines.

Herein, we describe a method for the synthesis of aryl-(het)aryl ketones by Rh(III)-catalyzed direct coupling between quinoline-8-carbaldehydes and (het)arylboronic acids. The method has a broad substrate scope, a high functional group tolerance, and uses commercially available starting materials. Scale-up of the reaction and subsequent synthesis of tubulin polymerization inhibitor demonstrated its utilities. A plausible mechanism was proposed on the basis of the fact that a stable cycloacylrhodium intermediate complex could be used as catalyst, and the complex reacted stoichiometrically with (het)arylboronic acids.

Blocking LC3 lipidation and ATG12 conjugation reactions by ATG7 mutant protein containing C572S

Autophagy, a system for the bulk degradation of intracellular components, is essential for homeostasis and the healthy physiology and development of cells and tissues. Its deregulation is associated with human disease. Thus, methods to modulate autophagic activity are critical for analysis of its role in mammalian cells and tissues. Here we report a method to inhibit autophagy using a mutant variant of the protein ATG7, a ubiquitin E1-like enzyme essential for autophagosome formation. During autophagy, ATG7 activates the conjugation of LC3 (ATG8) with phosphatidylethanolamine (PE) and ATG12 with ATG5. Human ATG7 interactions with LC3 or ATG12 require a thioester bond involving the ATG7 cysteine residue at position 572. We generated TetOff cells expressing mutant ATG7 protein carrying a serine substitution of this critical cysteine residue (ATG7C572S). Because ATG7C572S forms stable intermediate complexes with LC3 or ATG12, its expression resulted in a strong blockage of the ATG-conjugation system and suppression of autophagosome formation. Consequently, ATG7C572S mutant protein can be used as an inhibitor of autophagy.

DFT calculation-based study of the mechanism for CO2 formation in the interaction of CO and NO2 molecules

Abstract The paper studies the transfer of the oxygen atom O from the NO2 molecule to the CO molecule, resulting in the formation of CO2. The methods of quantum mechanics are used to obtain transition states, vibrational frequencies and reaction paths CO + NO2 ↔ CO2 + NO, and their key energy characteristics. Two mechanisms of the reaction are determined: a direct one and a stepwise involving the formation of a stable intermediate complex. The rate constants of forward and backward reactions were calculated within the framework of the transition state theory. They are compared with the experimental data available in the references. Their approximations are presented in the form of Arrhenius in a wide temperature range of 300–2500 K.

Surface Ligands As Atomic Valves for Growth of Nanocrystal Quantum Dots

Growth of monodisperse quantum dots (QDs) is a pressing requirement in the context of commercial application as well as academic study, as the size uniformity is directly related to color purity in display products which have been commercialized. In the growth, surface ligands serve not only as a protection layer for QD surface but also controller for reaction kinetics. I will present our recent findings pertaining to these issues on the basis of different material examples. Our study on the colloidal synthesis of InP QDs in the presence of Zn precursors will be discussed, in which size uniformity is markedly enhanced as compared to the case of InP QDs synthesized without Zn precursors. In the presence of zinc carboxylate, intermediate species containing Zn-P bonding appears. The Zn-P intermediate complex with P(SiMe3)3 exhibits lower reactivity than In-P complex. The formation of stable Zn-P intermediate complex results in lower reactivity, hence monodisperse QDs. Insights from the experimental and theoretical studies advance the mechanistic understanding and controlling of nucleation and growth of InP QDs. We investigated diffusion of active species monomers through ligand layers using CdSe nanorods (NRs) as a model system. Colloidal NRs are of special interest for optoelectronic applications because its shape anisotropy leads to unique optical and physical characteristics, expandable with morphological and structural deviation. I present a new answer for detailed growth mechanism of colloidal semiconductor NRs. For this, we developed dual-diameter nanorod (DDNR) structure via colloidal synthesis, where two sections along the long axis in each NR have different diameters at a few nanometer scale. The vivid segmentation is an ideal platform for monitoring the growth process of NRs, presenting important determinants in the reactivity of distinguishable NR facets. By controlling the discovered factors, single-diameter NRs with controllable core position also became available. I will put the findings in perspective by outlining the effect of diffusion of monomers and surface growth reactions.

New Insights into Organic Dye Regeneration Mechanism in Dye-Sensitized Solar Cells: A Theoretical Study

Understanding the regeneration mechanism of an oxidized dye with redox couples is significant in improving the efficiency of dye-sensitized solar cells (DSSCs). However, all the previously considered regeneration mechanisms are failed to match the incident photon-to-current efficiency (IPCE) and the UV-vis absorption spectra. Herein, we propose a new regeneration mechanism for organic dyes by assuming the probability of two electron injection from the stable dye-iodide intermediate complex. Thus, the stability and optoelectronic properties of the dye-iodide intermediate complexes of our elementary steps for the regeneration mechanism have been systematically investigated using density functional theory (DFT) and time-dependent (TD)-DFT calculations. Our results highlight the possibility of two electron injection into the semiconductor surface during dye regeneration mechanism, rather than the conventional one electron injection. In addition, the calculated UV-vis absorption spectra for the considered intermediate complexes clearly indicate blue/redshift (see Fig. 1) compared to that of isolated dye, which reflects the IPCE spectra. Keywords: Dye regeneration mechanism; Organic dye; Electron injection; Dye-sensitized solar cells; Density Functional Theory; UV-vis spectra Figure 1

Cotransporting Ion is a Trigger for Cellular Endocytosis of Transporter-Targeting Nanoparticles: A Case Study of High-Efficiency SLC22A5 (OCTN2)-Mediated Carnitine-Conjugated Nanoparticles for Oral Delivery of Therapeutic Drugs.

OCTN2 (SLC22A5) is a Na+ -coupled absorption transporter for l-carnitine in small intestine. This study tests the potential of this transporter for oral delivery of therapeutic drugs encapsulated in l-carnitine-conjugated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (LC-PLGA NPs) and discloses the molecular mechanism for cellular endocytosis of transporter-targeting nanoparticles. Conjugation of l-carnitine to a surface of PLGA-NPs enhances the cellular uptake and intestinal absorption of encapsulated drug. In both cases, the uptake process is dependent on cotransporting ion Na+ . Computational OCTN2 docking analysis shows that the presence of Na+ is important for the formation of the energetically stable intermediate complex of transporter-Na+ -LC-PLGA NPs, which is also the first step in cellular endocytosis of nanoparticles. The transporter-mediated intestinal absorption of LC-PLGA NPs occurs via endocytosis/transcytosis rather than via the traditional transmembrane transport. The portal blood versus the lymphatic route is evaluated by the plasma appearance of the drug in the control and lymph duct-ligated rats. Absorption via the lymphatic system is the predominant route in the oral delivery of the NPs. In summary, LC-PLGA NPs can effectively target OCTN2 on the enterocytes for enhancing oral delivery of drugs and the critical role of cotransporting ions should be noticed in designing transporter-targeting nanoparticles.

Functional importance of stripping in NFκB signaling revealed by a stripping-impaired IκBα mutant

Stress-response transcription factors such as NFκB turn on hundreds of genes and must have a mechanism for rapid cessation of transcriptional activation. We recently showed that the inhibitor of NFκB signaling, IκBα, dramatically accelerates the dissociation of NFκB from transcription sites, a process we have called "stripping." To test the role of the IκBα C-terminal PEST (rich in proline, glutamic acid, serine, and threonine residues) sequence in NFκB stripping, a mutant IκBα was generated in which five acidic PEST residues were mutated to their neutral analogs. This IκBα(5xPEST) mutant was impaired in stripping NFκB from DNA and formed a more stable intermediate ternary complex than that formed from IκBα(WT) because DNA dissociated more slowly. NMR and amide hydrogen-deuterium exchange mass spectrometry showed that the IκBα(5xPEST) appears to be "caught in the act of stripping" because it is not yet completely in the folded and NFκB-bound state. When the mutant was introduced into cells, the rate of postinduction IκBα-mediated export of NFκB from the nucleus decreased markedly.

The interchange of immunophilins leads to parallel pathways and different intermediates in the assembly of Hsp90 glucocorticoid receptor complexes.

Hormone receptors require participation of the chaperones Hsp40/Hsp70 to form client-transfer complexes with Hsp90/Hop. Interaction with the co-chaperone p23 releases Hop and Hsp70, and the immunophilin FKBP52 mediates transfer of the Hsp90-receptor complex to the nucleus. Inhibition of glucocorticoid receptor (GR) transport by FKBP51, but not by FKBP52, has been observed at the cellular level, but the subunit composition of the intermediates involved has not been deduced. Here we use mass spectrometry to show that FKBP51/52 form analogous complexes with GR/Hsp90/Hop/Hsp70/ATP, but differences emerge upon addition of p23 to client-transfer complexes. When FKBP51 is present, a stable intermediate is formed (FKBP51)1(GR)1(Hsp90)2(p23)2 by expulsion of Hsp70 and Hop. By contrast, in the presence of FKBP52, ejection of p23 also takes place to form the nuclear transfer complex (FKBP52)1(GR)1(Hsp90)2. Our results are therefore consistent with pathways in which FKBP51/52 are interchangeable during the early assembly reactions. Following interaction with p23, however, the pathways diverge with FKBP51 sequestering GR in a stable intermediate complex with p23. By contrast, binding of FKBP52 occurs almost concomitantly with release of p23 to form a highly dynamic transfer complex, primed for interaction with the dynactin transport machinery.

Effect of collision energy on the reaction mechanism of C((3)P) + OH(X(2) Π) → CO(X(1) Σ(+)) + H((2)S).

Quasiclassical trajectory calculations based on a fully global ab initio potential energy surface of the rotational angular momentum polarisation of the product CO in the title reaction are reported. The alignment and orientation of the rotational angular momentum of the CO fragment in the scattering frame were found to be sensitive to the initial collision energy chosen. Differences in the angular momentum polarization at different collision energies were traced to differences in the microscopic reaction mechanism. The results of this study suggest that the title reaction is mainly dominated by an abstraction reaction mechanism (involving the short-lived and metastable intermediate complex COH) at low collision energies; however, at relatively high energies, an insertion reaction mechanism (involving the long-lived and stable intermediate complex HCO) plays a role.

Proton dissociation and transfer in hydrated phosphoric acid clusters

The dynamics and mechanisms of proton dissociation and transfer in hydrated phosphoric acid (H3PO4) clusters under excess proton conditions were studied based on the concept of presolvation using the H3PO4–H3O+–nH2O complexes (n = 1–3) as the model systems and ab initio calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations at the RIMP2/TZVP level as model calculations. The static results showed that the smallest, most stable intermediate complex for proton dissociation (n = 1) is formed in a low local‐dielectric constant environment (e.g., ε = 1), whereas proton transfer from the first to the second hydration shell is driven by fluctuations in the number of water molecules in a high local‐dielectric constant environment (e.g., ε = 78) through the Zundel complex in a linear H‐bond chain (n = 3). The two‐dimensional potential energy surfaces (2D‐PES) of the intermediate complex (n = 1) suggested three characteristic vibrational and 1H NMR frequencies associated with a proton moving on the oscillatory shuttling and structural diffusion paths, which can be used to monitor the dynamics of proton dissociation in the H‐bond clusters. The BOMD simulations over the temperature range of 298–430 K validated the proposed proton dissociation and transfer mechanisms by showing that good agreement between the theoretical and experimental data can be achieved with the proposed rate‐determining processes. The theoretical results suggest the roles played by the polar solvent and iterate that insights into the dynamics and mechanisms of proton transfer in the protonated H‐bond clusters can be obtained from intermediate complexes provided that an appropriate presolvation model is selected and that all of the important rate‐determining processes are included in the model calculations. © 2015 Wiley Periodicals, Inc.