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A double harmonic oscillator model is applied to compute the negative ion photoelectron spectra (NIPES) of the 1- and 2-cyanonaphthalene (CNN) radical anions. The computed Franck–Condon factors utilize optimized structures and harmonic vibrational frequencies obtained using density functional theory with the B3LYP 6-311++G (2d,2p) basis set while considering the mode-mixing Duschinsky effects. To test the accuracy of our model, the NIPES of α and β naphthyl radical anions were computed, and a strong agreement between the slow electron velocity-map ion imaging spectra and the predicted spectra was found. The adiabatic electron affinities (EAs) of the ground singlet states (S0) in 1-CNN and 2-CNN are 0.856 and 0.798 eV, respectively. The origin of the lowest-lying triplet (T1) states in 1-CNN and 2-CNN is found to be 3.226 and 3.266 eV, resulting in singlet–triplet energy splittings (ΔEST) of 2.370 and 2.468 eV, respectively. Both the NIPES for electron detachment to the S0 and T1 states exhibit well-resolved vibrational features, allowing for the assignment of several vibrational fundamental frequencies. Following deprotonation, several isomers are formed, with the most stable deprotonated radical anions in 1-CNN and 2-CNN, corresponding to the removal of the most acidic proton, with EAs of 2.062 and 2.16 eV. The rich spectroscopic and thermochemical data obtained in the current study make the CNN radical anions and their deprotonated species interesting systems for investigation in gas-phase, negative-ion experiments. [ABSTRACT FROM AUTHOR]

In the recently discovered proton-coupled energy transfer (PCEnT) mechanism, the transfer of electronic excitation energy between donor and acceptor chromophores is coupled to a proton transfer reaction. Herein, we develop a general theory for PCEnT and derive an analytical expression for the nonadiabatic PCEnT rate constant. This theory treats the transferring hydrogen nucleus quantum mechanically and describes the PCEnT process in terms of nonadiabatic transitions between reactant and product electron–proton vibronic states. The rate constant is expressed as a summation over these vibronic states, and the contribution of each pair of vibronic states depends on the square of the vibronic coupling as well as the spectral convolution integral, which can be viewed as a generalization of the Förster-type spectral overlap integral for vibronic rather than electronic states. The convolution integral also accounts for the common vibrational modes shared by the donor and acceptor chromophores for intramolecular PCEnT. We apply this theory to model systems to investigate the key features of PCEnT processes. The excited vibronic states can contribute significantly to the total PCEnT rate constant, and the common modes can either slow down or speed up the process. Because the pairs of vibronic states that contribute the most to the PCEnT rate constant may correspond to spectroscopically dark states, PCEnT could occur even when there is no apparent overlap between the donor emission and acceptor absorption spectra. This theory will assist in the interpretation of experimental data and will guide the design of additional PCEnT systems. [ABSTRACT FROM AUTHOR]

8-oxo-7,8-dihydro-2′-dexyoguanine (8-oxo-dG) can be tautomerized to a 6-enolate,8-keto tautomer through nearby-NH deprotonation at elevated pH. In this work, the N3-protonated 8-oxo-dG tautomers in deuterated pH-buffer solutions were studied using steady-state UV/Vis, FTIR, and ultrafast two-dimensional IR spectroscopies. The presence of 6,8-diketo and C6-anionic tautomers at neutral to basic conditions (pD = 7.4–12.0) was revealed by UV/Vis and FTIR results and was further confirmed by 2D IR signals in both diagonal and off-diagonal regions. However, the C6-enol tautomer, which may be an intermediate during the transition from 6,8-diketo to C6-enolate,C8-keto, was not observed appreciably due to its extreme low population. Furthermore, the neutral-to-anionic tautomeric transition of N3H-8-oxo-dG studied in this work occurs under more basic conditions than the N1H-8-oxo-dG reported previously, showing a higher pKa value for N3H than N1H. Finally, vibrational relaxation of the carbonyl stretching mode was found to be both molecular site dependent and pD dependent for 8oxo-dG. Taken together, this work shows that the ultrafast infrared spectroscopic method is effective for examining tautomers and their dynamics in nucleic acids. [ABSTRACT FROM AUTHOR]

We report the development and testing of new integrated cyberinfrastructure for performing free energy simulations with generalized hybrid quantum mechanical/molecular mechanical (QM/MM) and machine learning potentials (MLPs) in Amber. The Sander molecular dynamics program has been extended to leverage fast, density-functional tight-binding models implemented in the DFTB+ and xTB packages, and an interface to the DeePMD-kit software enables the use of MLPs. The software is integrated through application program interfaces that circumvent the need to perform "system calls" and enable the incorporation of long-range Ewald electrostatics into the external software's self-consistent field procedure. The infrastructure provides access to QM/MM models that may serve as the foundation for QM/MM–ΔMLP potentials, which supplement the semiempirical QM/MM model with a MLP correction trained to reproduce ab initio QM/MM energies and forces. Efficient optimization of minimum free energy pathways is enabled through a new surface-accelerated finite-temperature string method implemented in the FE-ToolKit package. Furthermore, we interfaced Sander with the i-PI software by implementing the socket communication protocol used in the i-PI client–server model. The new interface with i-PI allows for the treatment of nuclear quantum effects with semiempirical QM/MM–ΔMLP models. The modular interoperable software is demonstrated on proton transfer reactions in guanine-thymine mispairs in a B-form deoxyribonucleic acid helix. The current work represents a considerable advance in the development of modular software for performing free energy simulations of chemical reactions that are important in a wide range of applications. [ABSTRACT FROM AUTHOR]

This article investigates the relaxation dynamics of the ionized 2a1 state of a water molecule within a water dimer. The study was motivated by findings from two previous pieces of research that focused on the relaxation behaviors of the inner-valence ionized water dimer. The present study discloses an observation indicating that water dimers display specific fragmentation patterns following inner-valence ionization, depending on the position of the vacancy. Vacancies were created in the 2a1 state of the proton-donating water molecule (PDWM) and proton-accepting water molecule (PAWM). Utilizing Born–Oppenheimer molecular dynamics simulations, the propagation of the 2a1 ionized state was carried out for both scenarios. The results revealed proton transfer occurred when the vacancy resided in the PDWM, accompanied by the closing of decay channels for O–H bond distance (RO–H) > 1.187 Å (matching Richter et al.'s findings). Conversely, when vacancy was on PAWM, we observed no closing of decay channels (aligning with Jahnke et al.'s findings). This difference translates to distinct fragmentation pathways. In PDWM cases, 2a1 state ionization leads to H3O+ −OH• formation. In contrast, PAWM vacancies result in decay pathways leading to H2O+–H2O+ products. [ABSTRACT FROM AUTHOR]

Langmuir monolayers of fatty aniline (C16-aniline) were investigated using sum-frequency vibrational spectroscopy at various pH levels and NaCl concentrations. To analyze the sum-frequency generation (SFG) spectra of aniline, a multi-peak Lorentzian model, in accordance with the theory of SFG for a charged interface, was applied. First, SFG spectra of C16-aniline from pH 2 to 6 at a constant ionic strength of 10 mM (where the phase of the complex potential of the dc-induced signal was suppressed to a few degrees) were fitted with the above-mentioned method. The mean-field theory that considers the chemical equilibrium of the aniline headgroup was used to analyze the fitting results to find that the pKa of aniline is 4.4 ± 0.3. The protonation fraction of the aniline headgroup was estimated to be less than 5% at pH 6 and NaCl concentrations were up to 1M. The generalized Poisson–Boltzmann equation in the Gouy–Chapmann model effectively explained the observed SFG spectra in the OH region for fatty aniline at pH as low as 2, even for the systems without addition of any salt. [ABSTRACT FROM AUTHOR]

The photochemical dynamics of the acetic acid and trifluoro-acetic acid dimers in hexane are studied using time-resolved infrared absorption spectroscopy and ab initio electronic structure calculations. The different hydrogen bond strengths of the two systems lead to changes in the character of the accessed excited states and in the timescales of the initial structural rearrangement that define the early time dynamics following UV excitation. The much stronger hydrogen bonding in the acetic acid dimer stabilizes the system against dissociation. Ground state recovery is mediated by a structural buckling around the hydrogen bond itself with no evidence for excited state proton transfer processes that are usually considered to drive ultrafast relaxation processes in hydrogen bonded systems. The buckling of the ring leads to relaxation through two conical intersections and the eventual reformation of the electronic and vibrational ground states on a few picosecond timescale. In trifluoro-acetic acid, the weaker hydrogen bonding interaction means that the dimer dissociates under similar irradiation conditions. The surrounding solvent cage restricts the full separation of the monomer components, meaning that the dimer is reformed and returns to the ground state structure via a similar buckled structure but over a much longer, ∼100 ps, timescale. [ABSTRACT FROM AUTHOR]

Ammonium and carboxylic moieties play a central role in proton-mediated processes of molecular recognition, charge transfer or chemical change in (bio)materials. Whereas both chemical groups constitute acid–base pairs in organic salt-bridge structures, they may as well host excess protons in acidic environments. The binding of excess protons often precedes proton transfer reactions and it is therefore of fundamental interest, though challenging from a quantum chemical perspective. As a benchmark for this process, we investigate proton storage in the amphoteric compound 5-aminovaleric acid (AV), within an intramolecular proton bond shared by its primary amine and carboxylic acid terminal groups. Infrared ion spectroscopy is combined with ab initio Molecular Dynamics (AIMD) calculations to expose and rationalize the spectral signatures of protonated AV and its deuterated isotopologues. The dynamic character of the proton bond confers a fluxional structure to the molecular framework, leading to wide-ranging bands in the vibrational spectrum. These features are reproduced with remarkable accuracy by AIMD computations, which serves to lay out microscopic insights into the excess proton binding scenario. [ABSTRACT FROM AUTHOR]

Understanding the protonation behavior of metal-oxo water oxidation catalysts is essential to improve catalyst efficiency and long-term performance, as well as to tune their properties for specific applications. In this work, we explore the basicity and protonation effects of the highly active water oxidation catalyst [(Mn4O4) (V4O13) (OAc)3]3− using density functional theory. We computed the relative free energies of protonation in a systematic fashion for all symmetry-inequivalent O atoms, where the presence of multiple oxidation states from Mn 4 IV to Mn 4 III and a rich Jahn–Teller isomerism adds a significant amount of complexity. For high oxidation states, the compound behaves like some other polyoxometalates, showing protonation preferably at the terminal and μ2-bridging O atoms of the vanadate cap. However, upon reduction, eventually, the protonation preference switches to the cubane O atoms, mostly driven by a strong increase in basicity for O atoms located along the Jahn–Teller axes. Our work further evidences that protonation can potentially lead to several chemical transformations, like disproportionation and charge transfer to vanadium, dissociation of ligands, or the opening of the cubane structure. Our simulated UV/Vis absorption spectra additionally provide valuable insights about how the protonation of the catalyst could be tracked experimentally. Overall, our analysis highlights the complexity involved in the protonation of heterometallic polyoxometalate clusters. [ABSTRACT FROM AUTHOR]

The iron(III) complexes [Fe(H2O)n(OH)m]3−m (n + m = 5, 6, m ≤ 3) and corresponding proton transfer reactions are studied with total energy calculations, the nudged elastic band (NEB) method, and molecular dynamics (MD) simulations using ab initio and a modification of reactive force field potentials, the ReaxFF-AQ potentials, based on the implementation according to Böhm et al. [J. Phys. Chem. C 120, 10849–10856 (2016)]. Applying ab initio potentials, the energies for the reactions [Fe(H2O)n(OH)m]3−m + H2O → [Fe(H2O)n−1(OH)m+1]2−m + H3O+ in a gaseous environment are in good agreement with comparable theoretical results. In an aqueous (aq) or alkaline environment, with the aid of NEB computations, respective minimum energy paths with energy barriers of up to 14.6 kcal/mol and a collective transfer of protons are modeled. Within MD simulations at room temperature, a permanent transfer of protons around the iron(III) ion is observed. The information gained concerning the geometrical and energetic properties of water and the [Fe(H2O)n(OH)m]3−m complexes from the ab initio computations has been used as reference data to optimize parameters for the O–H–Fe interaction within the ReaxFF-AQ approach. For the optimized ReaxFF-AQ parameter set, the statistical properties of the basic water model, such as the radial distribution functions and the proton hopping functions, are evaluated. For the [Fe(H2O)n(OH)m]3−m complexes, it was found that while geometrical and energetic properties are in good agreement with the ab initio data for gaseous environment, the statistical properties as obtained from the MD simulations are only partly in accordance with the ab initio results for the iron(III) complexes in aqueous or alkaline environments. [ABSTRACT FROM AUTHOR]

Diffusion of electrons over distances on the order of 100 μm has been observed in crystals of a small tetraheme cytochrome (STC) from Shewanella oneidensis [J. Huang et al. J. Am. Chem. Soc. 142, 10459–10467 (2020)]. Electron transfer between hemes in adjacent subunits of the crystal is slower and more strongly dependent on temperature than had been expected based on semiclassical electron-transfer theory. We here explore explanations for these findings by molecular-dynamics simulations of crystalline and monomeric STC. New procedures are developed for including time-dependent quantum mechanical energy differences in the gap between the energies of the reactant and product states and for evaluating fluctuations of the electronic-interaction matrix element that couples the two hemes. Rate constants for electron transfer are calculated from the time- and temperature-dependent energy gaps, coupling factors, and Franck–Condon-weighted densities of states using an expression with no freely adjustable parameters. Back reactions are considered, as are the effects of various protonation states of the carboxyl groups on the heme side chains. Interactions with water are found to dominate the fluctuations of the energy gap between the reactant and product states. The calculated rate constant for electron transfer from heme IV to heme Ib in a neighboring subunit at 300 K agrees well with the measured value. However, the calculated activation energy of the reaction in the crystal is considerably smaller than observed. We suggest two possible explanations for this discrepancy. The calculated rate constant for transfer from heme I to II within the same subunit of the crystal is about one-third that for monomeric STC in solution. [ABSTRACT FROM AUTHOR]

Quantum state-to-state nonadiabatic dynamics of the charge transfer reaction H+ + NO(X2Π, vi = 1, 3, ji = 0, 1) → H + NO+(X1Σ+) has been studied based on the recently constructed diabatic potential energy matrix. It was found that the vibrational excitation of reactant NO inhibits the reactivity, while the rotational excitation of reactant NO has little effect on the reaction probability. These attributes were also observed in the semi-classical trajectory calculations employed in the adiabatic representation. Such an inhibitory effect of the vibrational excitation of reactant NO was owing to lower accessibility of the conical intersection and avoided crossing regions, which are located in the wells with respect to the Π diabat, as evidenced by the analysis of the population of the time-independent wave functions. Calculated vibrational state distributions of the product show that the decrease of the reaction mainly leads to the less formation of low vibrational states (vf < 6), and the product vibrational state distributions are more evenly populated for vi = 1 and 3, suggesting a non-statistical behavior. However, the overall shapes of the product rotational distributions remain unchanged, indicating that the redistribution of energy into the rotation of product NO is sufficient in the charge transfer process between H+ and NO. While the reaction is dominated by the forward and backward scattering in differential cross sections (DCSs), consistent with the complex-forming mechanism, a clear forward bias in the DCSs appears, indicating that the occurrence of the reaction is not sufficiently long to undergo the whole phase space of the interaction configurations. [ABSTRACT FROM AUTHOR]

[Display omitted] Amino acids are among the most commercially promising additive solutions for achieving stable zinc anodes. However, greater attention should be given to the limitation arising from the protonation effects induced by high isoelectric point amino acids in the weakly acidic electrolytes of aqueous zinc-ion batteries (AZIBs). In this study, we introduce histidine (HIS) and ethylenediaminetetraacetic acid (EDTA) as hybrid additives into the aqueous electrolyte. Protonated HIS is adsorbed onto the anode interface, inducing uniform deposition and excluding H 2 O from the inner Helmholtz plane (IHP). Furthermore, the addition of EDTA compensates for the limitation of protonated HIS in excluding solvated H 2 O. EDTA reconstructs the solvation structure of Zn2+, resulting in a denser zinc deposition morphology. The results demonstrate that the Zn||Zn battery achieved a cycling lifespan exceeding 1480 h at 5 mA cm−2 and 5 mAh cm−2. It also reached over 900 h of cycling at a zinc utilization rate of 70 %. This study provides an innovative perspective for advancing the further development of AZIBs. [ABSTRACT FROM AUTHOR]

Density functional theory calculations uncovered a new mechanism for the rhodium-catalyzed decarbonylative annulation of isatoic anhydride with alkynes, in which the acyloxy group formed from the N–H deprotonation and C–O bond cleavage of isatoic anhydride acts as the directing group to assist the ortho C–H activation. From the generated five-membered rhodacycle intermediate, the final aminoisocoumarin product could be formed by subsequent steps of alkyne insertion, reductive elimination, decarbonylation, and protonation. The isocyanate moiety contained in the annulation intermediate was uncovered as a novel internal oxidant for the reaction, which oxidizes the Rh(I) to Rh(III) by decarbonylation. [ABSTRACT FROM AUTHOR]

Selective deprotonation of the amidinate ligand in lutetium dinitrogen complex [{Cp*{MeC(NiPr)2}Lu}2(μ2-η2:η2-N2)][K(crypt)] (Cp* = (C5Me5)−, crypt = 2,2,2-cryptand) afforded the novel Cp*/enolamido lutetium dinitrogen complex [{Cp*{H2C＝C(NiPr)2}Lu}2(μ2-η2:η2-N2)K][K(crypt)]. Due to the skeleton tension, a further rearrangement was confirmed with the formation of [{Cp*K{H2C＝C(NiPr)2}Cp*Lu}2(μ2-η2:η2-N2)][K(crypt)]2. [ABSTRACT FROM AUTHOR]

Delignification of lignocellulose using basic ionic liquids (BILs) such as choline lysinate ([Ch][Lys]) is a promising method due to its high efficiency, mild conditions, and low toxicity. Typically, the following precipitation of lignin by adding acid media makes it challenging to recycle BILs. Herein, we explored a series of low-cost and recyclable alcohols as anti-solvents, including methanol (MeOH), ethanol (EtOH), iso-propanol (i-PrOH), and tert-butanol (t-BuOH), for recovering [Ch][Lys] and precipitating lignin without adding an acid from water-free [Ch][Lys] (case 1) and aqueous [Ch][Lys] (case 2). For case 1, lignin recovery followed the order of EtOH > i-PrOH > t-BuOH (MeOH was not able to recover lignin and [Ch][Lys]), which was negatively correlated with their pKa values, indicating the effect of the inhibited generation of a basic anion (e.g. EtO− from EtOH) from –NH2 in [Ch][Lys] on lignin precipitation. t-BuOH showed the highest lignin recovery of 99.7%, ensuring the high purity of the recovered [Ch][Lys] (recovery of 94.7%). Lignin deprotonation and depolymerization were detected. For case 2, t-BuOH also facilitated the recovery of lignin from an aqueous lignin–[Ch][Lys] system with a nearly quantitative lignin recovery, yet with lower [Ch][Lys] recovery of 81.7% and 64.0% at the [Ch][Lys] : water ratios (w/w) of 7 : 3 and 1 : 9, respectively. The lower recovery of [Ch][Lys] might be due to the poor dispersity of lignin solid in t-BuOH, and water also enhanced the deprotonation of lignin, thus making lignin precipitation more difficult. Based on the results, a deprotonation-based lignin dissolution mechanism has been proposed, which also helps to understand lignin dissolution and precipitation in a [Ch][Lys]-based system. [ABSTRACT FROM AUTHOR]

α-Unsubstituted aromatic N-heterocycles are a family of broadly used building blocks that play an integral role in drugs, agrochemicals, and materials. However, accessing diverse α-unsubstituted N-heteroarenes in a single strategy is challenging but highly desirable. Thus, a novel and unified photoinduced-radical hydrocyclization of 2-isocyanides is described for rapid assembling of various N-heteroarenes. The reaction features mild and sustainable reaction conditions with broad substrate scope and excellent functional group compatibilities. The potential synthetic utilization is highlighted by the facile synthesis of some biologically active natural alkaloids. Moreover, the mechanism studies indicated that the single-electron reduction/protonation is the key process of the transformation. [ABSTRACT FROM AUTHOR]

The reaction of [M(L)]n with H2O2 as an [O2] unit source and NEt3 as a base is a widely used biomimetic transition metal-peroxo and -superoxo complex [M(L)O2]n−1 synthesis method, but the mechanism and accurate stoichiometry of the synthesis remain elusive. In this study, we performed DFT calculations to deeply understand the mechanism, using the synthesis of the cobalt-peroxo complex [CoIII(12-TMC)O2]+ (12-TMC = (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane)) from the reaction of [CoII(12-TMC)]2+ and H2O2 in the presence of NEt3 as an example. The study found that cobalt-peroxo complex formation proceeds via three stages: (Stage I) the conversion of [CoII(12-TMC)]2+ and H2O2 to [CoIII(12-TMC)OH]2+ and OOH˙ radical, (Stage II) the coordination of OOH˙ to [CoII(12-TMC)]2+ to give [CoIII(12-TMC)OOH]2+, followed by deprotonation with NEt3, affording [CoIII(12-TMC)O2]+, and (Stage III) the transformation of [CoIII(12-TMC)OH]2+ which is generated in Stage I to [CoIII(12-TMC)O2]+. The overall stoichiometry of the synthesis is 2*[Co(12-TMC)]2+ + 3*H2O2 + 2*NEt3 → 2*[Co(12-TMC)O2]+ + 2*HNEt3+ + 2*H2O. In addition, compared to its analog [CoIII(TBDAP)O2]+ (TBDAP = N,N-di-tert-butyl-2,11-diaza[3.3](2,6)-pyridinophane) which is synthesized by the same method and has the same Co(III) oxidation state exhibits dioxygenase-like reactivity to nitriles, [CoIII(12-TMC)O2]+ could be inactive towards acetonitrile because the reaction severely deteriorates the coordination of the 12-TMC ligand to the Co center, which results in high reaction barriers. [ABSTRACT FROM AUTHOR]

α‐Silylalkylamines and α‐borylalkylamines are versatile synthetic intermediates and attractive scaffolds found in pharmaceutical drugs and agrochemicals. Despite great progress on synthetic methods for preparation of α‐silylalkylamines or α‐borylalkylamines, there are no general strategies for preparation of α‐boryl‐α‐silylalkylamines and the reactivity has not been explored. Here we report deoxygenative geminal silylboration of amides using silylboronates in the presence of alkoxide base catalyst, producing α‐boryl‐α‐silylalkylamines. The silicon and boron groups in α‐boryl‐α‐silylalkylamines are found to be utilized to chemoselective transformations, such as protonation and alkylation. This protocol serves various α‐silylalkylamines and α‐borylalkylamines from readily available amides. [ABSTRACT FROM AUTHOR]

Interfacial processes involving metal (oxyhydr)oxide phases are important for the mobility and bioavailability of nutrients and contaminants in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning, and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy to study the molecular-scale interfacial processes that influence surface complexation in ferrihydrite-water systems containing aqueous MoO 4 2 - . We validate the utility of this approach by calculating surface complexation models directly from simulations. The reactive force-field captures the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption and proton transfer. We find that upon hydration and adsorption, ferrihydrite restructures into a more disordered phase through surface charge equilibration, as revealed by simulations and high-resolution X-ray diffraction. We observed how this restructuring leads to a different interfacial hydrogen bond network compared to bulk water by monitoring water dynamics. Using umbrella sampling, we constructed the free energy landscape of aqueous MoO 4 2 - adsorption at various concentrations and the deprotonation of the ferrihydrite surface. The results demonstrate excellent agreement with the values reported by experimental surface complexation models. These findings are important as reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions. [ABSTRACT FROM AUTHOR]

Atomic Fe sites enabled electrochemical carbon dioxide (CO2) reduction (ECO2R) to carbon monoxide (CO) at low overpotentials. However, the narrow potential ranges for selective CO2 conversion on atomic Fe sites hindered the CO production at high current densities. Therefore, unveiling the CO2 electroreduction processes and clarifying the catalytic mechanisms on different atomic Fe sites are important for better design of atomic Fe catalysts toward efficient ECO2R. Herein, the ECO2R processes on single‐atom, dual‐atom, and cluster Fe sites are systematically investigated, and clarify that the balanced water dissociation and CO2 protonation on dual‐atom Fe sites promote the efficient CO production. The dual‐atom Fe catalyst achieves Faradaic efficiencies of CO (FECO) above 92% over a wide potential range of −0.4–−0.9 V versus reversible hydrogen electrode and maintains FECO of 91% after 153‐h electrolysis in H‐type cell. Benefitting from the favorable CO2 protonation for ECO2R on dual‐atom Fe sites, pH‐universal CO2 electroreduction is achieved in alkali‐/acid‐/bicarbonate‐fed membrane electrode assembly electrolyzer, with FECO exceeds 98% in strongly acidic/alkaline and neutral mediums. The work reveals a water dissociation‐promoted CO2 electroreduction on dual‐atom Fe sites and presents a feasible regulation of atomic Fe sites for highly active/selective ECO2R. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction reaction (CO2RR) to produce value‐added multi‐carbon chemicals has been an appealing approach to achieving environmentally friendly carbon neutrality in recent years. Despite extensive research focusing on the use of CO2 to produce high‐value chemicals like high‐energy‐density hydrocarbons, there have been few reports on the production of propane (C3H8), which requires carbon chain elongation and protonation. A rationally designed 0D/2D hybrid Cu2O anchored‐Ti3C2Tx MXene catalyst (Cu2O/MXene) is demonstrated with efficient CO2RR activity in an aqueous electrolyte to produce C3H8. As a result, a significantly high Faradaic efficiency (FE) of 3.3% is achieved for the synthesis of C3H8 via the CO2RR with Cu2O/MXene, which is ≈26 times higher than that of Cu/MXene prepared by the same hydrothermal process without NH4OH solution. Based on in‐situ attenuated total reflection‐Fourier transform infrared spectroscopy (ATR‐FTIR) and density functional theory (DFT) calculations, it is proposed that the significant electrocatalytic conversion originated from the synergistic behavior of the Cu2O nanoparticles, which bound the *C2 intermediates, and the MXene that bound the *CO coupling to the C3 intermediate. The results disclose that the rationally designed MXene‐based hybrid catalyst facilitates multi‐carbon coupling as well as protonation, thereby manipulating the CO2RR pathway. [ABSTRACT FROM AUTHOR]

We present the design of an anthracenyl–naphthyl (ANT‐NAPH) dyad and its application as a luminescent 4‐stage photo switch. Both segments can individually react with singlet oxygen to switch off an optical response. In their initial form the larger ANT component reacts significantly faster and thus an ANTO2‐NAPH stage is turned on, observed by optical response of the remaining NAPH. To reduce its reactivity, ANT is substituted with two pyridine rings. This concept is first investigated and quantified on ANT and NAPH as separated molecules. Upon protonation the reaction of ANT becomes significantly slower. For the three possible pyridyl isomers this effect increases along the order meta

Aromatic polyketides are pharmaceutically significant natural products. Product template (PT) domains from fungal non‐reducing polyketide synthases (NR‐PKSs) control the regioselective aldol cyclization of highly reactive polyketide intermediates, whose instabilities have hindered experimental studies. The molecular basis of PT‐catalyzed cyclization and aromatization remain ambiguous. Herein, we conducted MD simulations and QM/MM calculations to explore the catalytic mechanHism and the cyclization pattern of PksA PT specific for C4−C9. The cyclization mediated by PksA PT is initiated by the C4 deprotonation followed by the aldol condensation in C4−C9 register. PTs which evolve from ancient PKS dehydratases (DHs) perform dehydration reactions to aromatize the cyclized intermediates. In PksA PT, the catalytic His1345 and Asp1543 are responsible for aldol cyclization and aromatization steps, respectively. A keto‐enol tautomerism at C3 assists in the elimination reaction catalyzed by Asp1543 with a water molecule network, different from most DHs of PKSs. The C2−C7 aldol cyclization in PksA PT can occur, but the subsequent dehydration step is kinetically unfeasible and thermodynamically unfavorable, suggesting that the aromatization steps determine the C4−C9 cyclization mode of PksA PT. Overall, these computational investigations provide detailed mechanistic insights into the regiospecific intramolecular cyclization and aromatization controlled by fungal PksA PT. [ABSTRACT FROM AUTHOR]

A flexible tripodal pyrrole-imine ligand (H3L) has been used to facilitate the controlled and sequential single-electron reductions of the uranyl dication from the U(VI) oxidation state to U(V) and further to U(IV), processes that are important to understanding the reduction of uranyl and its environmental remediation. The uranyl(VI) complexes UO2(HL)(sol) (sol = THF, py) were straightforwardly accessed by the transamination reaction of H3L with UO2{N(SiMe3)2}2(THF)2 and adopt 'hangman' structures in which one of the pyrrole-imine arms is pendant. While deprotonation of this arm by LiN(SiMe3)2 causes no change in uranyl oxidation state, single-electron reduction of uranyl(VI) to uranyl(V) occurred on addition of two equivalents of KN(SiMe3)2 to UO2(HL)(sol). The potassium cations of this new [UVO2(K2L)]2 dimer were substituted by transmetalation with the appropriate metal chloride salt, forming the new uranyl(V) tetra-heterometallic complexes, [UVO2Zn(L)(py)2]2 and [UVO2Ln(Cl)(L)(py)2]2 (Ln = Y, Sm, Dy). The dimeric uranyl(V)–yttrium complex underwent further reduction and chloride abstraction to form the tetrametallic U(IV) complex [UIVO2YIII(py)]2, so highlighting the adaptability of this ligand to stabilise a variety of different uranium oxidation states. [ABSTRACT FROM AUTHOR]

A facile solution method for the form-controlled synthesis of CsMgPO4·6H2O is reported in this work and the key factor was determined to be the pH value of the solution used. A pure hexagonal phase (P63mc) was obtained at a pH range of 6.9–8.0, whereas a cubic phase (F4¯3m) was obtained at 9.5–11.3. Compared with the cubic phase, the hexagonal phase of CsMgPO4·6H2O possessed a stronger second harmonic generation response of 0.82 pm V−1 due to the distortion of the PO4 motif from a regular tetrahedron. The form-controlled synthesis mechanism was identified with the aid of infrared spectroscopy: the protonation process reduced the symmetry of the PO4 motif when the solution pH decreased, resulting in the crystallization of the hexagonal phase of CsMgPO4·6H2O with the distorted PO4 tetrahedron at a lower pH range. [ABSTRACT FROM AUTHOR]

Near-neutral HCO3– aqueous solution plays an essential role in respiratory, mineralization and catalysis, yet the interconversion between hydrated CO2, HCO3– and CO32– and the associated proton transfer under such proton-deficient conditions remain uncovered. Here we reveal that cation enables HCO3– to self-dissociate into OH– and CO2 through a pH-independent process, where CO2 hydration and subsequent proton transfer in acid-base reactions lead to the overall exchange of oxygen isotopes between HCO3– and H2O tracked by oxygen isotope-labeled Raman spectroscopy. Isolating HCO3– from cations with crown ether impedes HCO3– dissociation and the following reactions. Further molecular dynamics simulations demonstrate that the interplay between HCO3– and hydrated cations drives HCO3– dissociation. This study suggests a natural proton channel upon coupling HCO3– with cations. Unlike the traditional views that HCO3- anions transit to either CO2 or CO32- upon suffering pH changes. Here, the authors report that cation enables HCO3- to self-dissociate into OH- and CO2 through a pH independent process, leading to the formation of acid-base encounter pairs for proton transfer. [ABSTRACT FROM AUTHOR]

Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light‐induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H2 production activity is studied using femtosecond X‐ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time‐dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the FeII photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X‐ray emission at the iron and cobalt K‐edges in a two‐color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled. [ABSTRACT FROM AUTHOR]

Detecting chemical reaction dynamics at solid-liquid interfaces is important for understanding heterogeneous reactions. However, there is a lack of exploration of interface reaction dynamics from the single-molecule perspective, which can reveal the intrinsic reaction mechanism underlying ensemble experiments. Here, single-event protonation reaction dynamics at a solid-liquid interface are studied in-situ using single-molecule junctions. Molecules with amino terminal groups are used to construct single-molecule junctions. An interfacial cationic state present after protonation is discovered. Real-time electrical measurements are used to monitor the reversible reaction between protonated and deprotonated states, thereby revealing the interfacial reaction mechanism through dynamic analysis. The protonation reaction rate constant has a linear positive correlation with proton concentration, whereas the deprotonation reaction rate constant has a linear negative correlation. In addition, external mechanical forces can effectively regulate the protonation reaction process. This work provides a single-molecule perspective for exploring interface science, which will contribute to the development of heterogeneous catalysis and electrochemistry. Direct detection of chemical reactions at solid-liquid interfaces is important for a more complete understanding of interfacial effects. Here, the authors study single-event interfacial protonation reaction dynamics by single-molecule junctions and thereby identify an interfacial cationic state. [ABSTRACT FROM AUTHOR]

Replacing the slow protonation process of oxygen evolution reaction (OER) with the fast protonation of alcohol electro‐oxidation can decrease the driving potentials, thus improving overall efficiency of electrochemical devices. However, the formation of effective catalytic sites for alcohol oxidation remains challenging in accelerating protonation to inhibit metal leaching and improve catalyst stability. Herein, asymmetric Ni‐O‐Cr sites are constructed by alloying Cr into the NiO matrix to optimize coordination environments, showing significantly enhanced stability during alcohol electro‐oxidation. The asymmetric Ni‐O‐Cr can maintain constant valence states of Cr and Ni during alcohol oxidation, efficiently suppressing metal dissolution even at high oxidation potentials. In situ electrochemical characterizations combined with theoretical calculations indicate that asymmetric Ni‐O‐Cr can improve adsorption and activation of OH* and alcohol molecules compared to pure NiO, thus increasing anodic kinetics. The theoretical results also indicate that the smaller gap of Ni 3d‐O 2p in asymmetric Ni‐O‐Cr strengthens charge transfer, leading to fast protonation of catalytic sites with enhanced stability. This work gives insights into boosting anodic protonation using asymmetric sites‐enriched solid‐solution electrocatalysts. [ABSTRACT FROM AUTHOR]

To evaluate bifunctional ligand reactivity involving NH acidic sites in the secondary coordination sphere, complexes where the proton has been substituted with a methyl group (NMe) are often investigated. An alternative strategy involves substitution of the NH group for an O. This contribution considers and compares the merits of these approaches; the synthesis and characterization of cationic square‐planar Rh carbonyl complexes bearing diprotic bispyrazole pyridine ligand L1, and the bis‐methylated pyrazole pyridine ligand L1Me are described. The syntheses and characterization of the novel monoprotic pyrazole isoxazole pyridine ligand L2 and aprotic bisisoxazole pyridine ligand L3, and their corresponding Rh carbonyl complexes are also described. Comparison of the CO stretching frequencies of the four Rh complexes suggest that substitutions of NH with NMe, as well as with O, lead to significant electronic differences. These electronic differences result in different reactivities with respect to ligand addition/substitution of the Rh carbonyl complexes. Overall, the data suggest that electronic differences arising due to the NH substitutions can be significant and should be considered when the NH group is substituted in investigations of the participation of the NH proton in a reaction. [ABSTRACT FROM AUTHOR]

Pyrazole is an omnipresent moiety in many natural products and pharmaceutically active compounds. Here, we have developed a simple and dynamic method for one‐pot synthesis of substituted pyrazoles through the intramolecular cyclization of hydrazides and alkynyl ketones, using a novel sulfonium saltbased iodate (І) reagent system. This method has the advantage that it proceeds in a one‐pot, without isolating a less stable hydrazone intermediate. Hypervalent iodine‐based reagents are an environmentally benign and greener option to toxic metal oxidants; they have an extensive application in metal‐catalyst‐free reactions, and this reaction proceeds in less time with high yields. [ABSTRACT FROM AUTHOR]

The mesogenic behavior and electronic properties of hydrogen bond ferroelectric liquid crystal (HBFLC) complex are studied using experimental and theoretical techniques. HBFLC complex is synthesized from mesogenic 4-hexyloxy benzoic acid (6O BA) as the proton donor and nonmesogenic chiral DL-tartaric acid (DLTA) as the proton acceptor through intermolecular hydrogen bonding. Molecular geometry of DLTA+6O BA HBFLC complex is optimized by density functional theory (DFT) calculation. An interesting observation is that polarizing optical microscope (POM) study confirms that the HBFLC complex exhibits thermochromic behavior in chiral nematic (N ∗) along with induced nontitled smectic G* phases. Another noteworthy observation is the manifestation of tripartite temperature stages. Fourier-transform infrared spectroscopy (FTIR) and natural bond orbital (NBO) analysis elucidate the intermolecular hydrogen bond between mesogenic (6O BA) and nonmesogenic (DLTA) compounds. Further, frontier molecular orbital (FMO) study and electrostatic potential (ESP) analysis explore the reactivity sites, intermolecular charge transfer and electronic behavior of HBFLC complex. [ABSTRACT FROM AUTHOR]

Electroreduction of CO2 into high‐value chemicals and fuels driven is an effective way to alleviate the environmental crisis, but it suffers from poor activity and low selectivity of the catalyst. Single‐atom catalysts have excellent selectivity and the highest atomic efficiency, and are widely used in the 2‐electron transfer to produce CO. However, electroreduction of CO2 to C2+ products involves complex processes such as multi‐electron reaction and competitive adsorption, so single‐atom catalysis is often powerless. Herein, a single‐atom Ga‐anchored F‐doped Cu2O catalyst with dual active sites is reported. The Lewis acid‐base pairs and Ga single atom sites promote the adsorption/activation of CO2 and the dissociation of water molecules, respectively, enhance the coverage of *CO and *H, and their synergy optimizes the reaction path. At a high current density of 600 mA cm−2, the FEC2+ reached 72.8 ± 3.2% with remarkable stability. Experiments and theory calculations demonstrate that the dual sites increase the coverage of *CO and *H, and the key intermediate *CO is transformed into *CHO through protonation reaction, which changes the reaction path from the C─C coupling (*OCCO) to the protonation followed by C─C coupling (*OCCHO) with low energy barrier, greatly improving the selectivity for C2+ products. [ABSTRACT FROM AUTHOR]

Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon‐neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth‐abundant transition metal complex, trans‐[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N‐heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p‐MeOC6H4)3N exhibited a catalytic half‐wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at −20 °C in controlled‐potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N−N bond. [ABSTRACT FROM AUTHOR]

We report an in-depth study of the reductive activation of O2 by the nonheme [FeII(L 25)(MeCN)]2+ complex carried out by cyclic voltammetry. Experimental evidence is obtained for the slow coordination of dioxygen to the ferrous center yielding an FeII/O2 adduct with a strong FeII–O2 character rather than an FeIII–superoxo one. Electron injection in the FeII–O2 species occurs at a potential of ca. −700 mV vs. SCE, i.e. 200 mV above the O2 to O2˙− reduction, leading to the formation of a FeIII–peroxo intermediate and then FeIII–hydroperoxo upon protonation by residual water. The experimental CVs recorded at variable scan rate or variable FeII concentration are well simulated taking into account a detailed mechanism initiated by the competitive reduction of O2 and the FeII–O2 adduct. Analysis of the concentration of the reaction intermediates generated as a function of the applied potential indicates that the FeIII–peroxo intermediate significantly accumulates at a potential of −650 mV. Oxidative bromination of anisole is assayed under electrolytic conditions at this potential to yield bromoanisole products. The low faradaic yields observed reveal that deleterious reactions such as direct reduction of reaction intermediates likely occur. Based on the detailed mechanism elucidated, a number of improvements to achieve more efficient catalytic reactions can be proposed. [ABSTRACT FROM AUTHOR]

Layered vanadium‐based oxides have emerged as highly promising candidates for aqueous zinc‐ion batteries (AZIBs) due to their open‐framework layer structure and high theoretical capacity among the diverse cathode materials investigated. However, the susceptibility to structural collapse during charge‐discharge cycling severely hampers their advancement. Herein, we propose an effective strategy to enhance the cycling stability of vanadium oxides. Initially, the structural integrity of the host material is significantly reinforced by incorporating bi‐cations Na+ and NH4+ as "pillars" between the V2O5 layers (NaNVO). Subsequently, surface coating with polyaniline (PA) is employed to further improve the conductivity of the active material. As anticipated, the assembled Zn//NaNVO@PA cell exhibits a remarkable discharge capacity of 492 mAh g−1 at 0.1 A g−1 and exceptional capacity retention up to 89.2 % after 1000 cycles at a current density of 5 A g−1. Moreover, a series of in‐situ and ex‐situ characterization techniques were utilized to investigate both Zn ions insertion/extraction storage mechanism and the contribution of polyaniline protonation process towards enhancing capacity. [ABSTRACT FROM AUTHOR]

Context: The reaction force constant (κ ), introduced by Professor Alejandro Toro-Labbé, plays a pivotal role in characterizing the reaction pathway by assessing the curvature of the potential energy profile along the intrinsic reaction coordinate. This study establishes a novel link between κ and the reactivity descriptors of conceptual density functional theory (c-DFT). Specifically, we derive expressions that relate the reaction force constant to nuclear softness and variations in chemical potential. Our findings indicate that regions of the reaction pathway where κ is negative match with significant electronic structure rearrangements, while positive κ regions match mostly with geometric rearrangements. This correlation between κ and c-DFT reactivity descriptors enhances our understanding of the underlying forces driving chemical reactions and offers new perspectives for analyzing reaction mechanisms. Methods: The internal reaction path for the proton transfer in SNOH, chemical potential, and nuclear softness were computed using DFT with B3LYP exchange-correlation functional and 6-311++G(d,2p) basis set. [ABSTRACT FROM AUTHOR]

Benzo[a]fluoranthene (4a) is one of non‐alternate polycyclic aromatic hydrocarbons. A reaction of 4a in CF3SO3H yielded a dark yellow solution. Direct NMR observation indicated the exclusive formation of carbocation 4aH+ by protonation at the C(8) position. The most deshielded 1H and 13C signals were observed at 8.99 ppm for H(12) and 8.29 ppm for H(1), 182.6 ppm for C(12b), 155.6 ppm for C(8a), and 149.4 ppm for C(7a). The signals for H(4) and H(5) were significantly more shielded than those of 4a. A reaction of 3‐tert‐butylbenzo[a]fluoranthene (4b) in CF3SO3H afforded carbocation 4bH+ by the protonation at the C(8) position. 4bH+ was gradually converted to 4aH+. The changes in 13C NMR chemical shifts (Δδ13C) suggested that positive charge was delocalized into mainly seven carbons in 4aH+ and 4bH+. The observed cations were found to be the most stable cations among the possible protonation cations by the DFT method. The NICS(1)zz values for the five‐membered rings were calculated to be 35.6 for 4aH+ and 34.4 for 4bH+ by GIAO‐B3LYP/6‐311+G(2d,p). The experimental NMR and the NICS(1)zz data indicated that the five‐membered rings in 4aH+ and 4bH+ exhibited anti‐aromaticity. [ABSTRACT FROM AUTHOR]

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)2 dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton–electron transfer. The first two reduction steps lead to an N2O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co2S2(CO)6 is 109 kJ mol−1, and for Fe2S2(CO)6, it is 133 kJ mol−1. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water. [ABSTRACT FROM AUTHOR]

Thermochromic polymers with tunable thermochromism, high stretchability and mechanical strength are of interests for optical information storage and encryption. In this work, we demonstrate a new design of thermo-fluorochromic carboxylated nitrile butadiene rubber (XNBR) elastomer cross-linked by Eu3+-COOH dynamic coordination with deprotonated imidazole (DPIm) as the ancillary ligand. The presence of DPIm not only improves the mechanical strength and stretchability, but also dramatically intensifies the fluorescence emission and lifetime of the Eu-containing elastomer. The elastomer behaves reversible thermo-fluorochromism with easily tunable transition temperature and emission intensity by the simple change of the deprotonation degree of imidazole. The facile tunable thermo-fluorochromism, exceptional mechanical strength, and high stretchability (up to about 5000%) enable the Eu-containing XNBR elastomer with potential applications in soft electronics where optical information storage and encryption are required. [ABSTRACT FROM AUTHOR]

The local acidity at the anode surface during electrolysis is apparently stronger than that in bulk electrolyte due to the deprotonation from the reactant, which leads to the deteriorated electrocatalytic performances and product distributions. Here, an anode‐electrolyte interfacial acidity regulation strategy has been proposed to inhibit local acidification at the surface of anode and enhance the electrocatalytic activity and selectivity of anodic reactions. As a proof of the concept, CeO2‐x Lewis acid component has been employed as a supporter to load Au nanoparticles to accelerate the diffusion and enrichment of OH− toward the anode surface, so as to accelerate the electrocatalytic alcohol oxidation reaction. As the result, Au/CeO2‐x exhibits much enhanced lactic acid selectivity of 81 % and electrochemical activity of 693 mA⋅cm−2 current density in glycerol oxidation reaction compared to pure Au. Mechanism investigation reveals that the introduced Lewis acid promotes the mass transport and concentration of OH− on the anode surface, thus promoting the generation of lactic acid through the simultaneous enhancements of Faradaic and non‐Faradaic processes. Attractively, the proposed strategy can be used for the electro‐oxidation performance enhancements of a variety of alcohols, which thereby provides a new perspective for efficient alcohol electro‐oxidations and the corresponding electrocatalyst design. [ABSTRACT FROM AUTHOR]

The 2D porous protonated NiSe/g-C 3 N 4 nanosheets are synthesized via a chemical-calcination-etching-acidification-hydrothermal method. The obtained 2D NiSe/g-C 3 N 4 nanosheets (NiSe/HCN-3) exhibit signally enhanced HER (∼1184.74 μmol g−1 h−1)/degradation (∼0.04645 min−1) than the monomer g-C 3 N 4 (∼150/5-folds), including a decent stability (average HER ∼1152.71 μmol g−1 h−1). It mainly attributes to the NiSe/g-C 3 N 4 interface owns appropriate potential gradient can promote the interface carrier driving to optimize efficiency, including increasing carrier transport, extending carrier lifetime, and reducing recombination, as well as the porous nanosheets and surface protonation obtain numerous active sites for decreasing overpotential and promoting electron solid/liquid interfacial diffusion. Additionally, the 2D porous nanosheets can improve the solar efficiency (multiple internal reflections) and shorten the carrier pathway. [Display omitted] • NiSe co-catalyst optimize carrier efficiency by appropriate Fermi level gradient. • Surface protonation increase active sites to promote electron interfacial diffusion. • Porous nanosheets increase active sites/solar efficiency and shorten carrier path. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Chiral α‐tertiary aminonitriles are valuable synthetic intermediates. They are also found in various structures of biologically active molecules. Therefore, numerous reports of catalytic asymmetric synthesis of chiral α‐aminonitriles continuously emerged during the past few decades. Great strides have been made for the synthesis of chiral α‐aryl and α‐branched alkyl aminonitriles. However, efficient methods for catalytic asymmetric synthesis of chiral α‐linear alkyl aminonitriles remain limited. We herein report a new synthetic approach to chiral α‐tertiary alkyl aminonitriles via catalytic asymmetric isomerization of cyanoketimines. The synthetic value of this method was illustrated by application to a concise catalytic asymmetric synthesis of vildagliptin. [ABSTRACT FROM AUTHOR]

We disclose a benzylic C−H oxidative coupling reaction with alcohols that proceeds through a synergistic deprotonation, halogenation and substitution sequence. The combination of tert‐butoxide bases with 2‐halothiophene halogen oxidants enables the first general protocol for generating and using benzyl halides through a deprotonative pathway. In contrast to existing radical‐based methods for C−H functionalization, this process is guided by C−H acidity trends. This gives rise to new synthetic capabilities, including the ability to functionalize diverse methyl(hetero)arenes, tolerance of oxidizable and nucleophilic functional groups, precision site‐selectivity for polyalkylarenes and use of a double C−H etherification process to controllably oxidize methylarenes to benzaldehydes. [ABSTRACT FROM AUTHOR]

Selective CO2 photoreduction to C2 hydrocarbons is significant but limited by the inadequate adsorption strength of the reaction intermediates and low efficiency of proton transfer. Herein, an ameliorative *CO adsorption and H2O activation strategy is realized via decorating bismuth oxychloride (BiOCl) nanostructures with different metal (Pt, Pd, and Au) species. Experimental and theoretical calculation results reveal that distinct *CO binding energies and *H acquisition abilities of the metal cocatalysts mediate the CO2 reduction activity and hydrocarbon selectivity. The relatively moderate *CO adsorption and *H supply over Pd/BiOCl endows it with the lowest free energy to generate *CHO, leading to its highest activity of hydrocarbon production. Specifically, the Pt cocatalyst can efficiently participate in H2O dissociation to deliver more *H for facilitating the protonation of the *CHO and *CHOH, thereby favoring CH4 production with 76.51% selectivity. A lower *H supply over Pd/BiOCl and Au/BiOCl results in a large energy barrier for *CHO or *CHOH protonation and thus a more thermodynamically favored OC─CHO coupling pathway, which endows them with vastly increased C2 hydrocarbon selectivity of 81.21% and 92.81%, respectively. The understanding of efficient C2 hydrocarbon production in this study sheds light on how materials can be engineered for photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

Nucleophilic vinylic substitution (SNV) by carbon nucleophiles allows the formation of vinylic C−C bonds without transition metal catalysts. In this paper, we show that tethering two alkenes together through a urea linkage can lead to the formation of a diene by an intramolecular SNV reaction. The starting materials are fully substituted N,N'‐diallyl ureas; the reaction proceeds in the presence of base, and entails a cascade of deprotonations, reprotonations, and an SNV reaction of an allylic carbanion on a rare electrophile: a vinylic urea. As a result, two allylic substituents couple to form a diene, despite the fact that neither is activated towards electrophilic attack. The reaction is tolerant of significant steric bulk, and exhibits regioselectivity with unsymmetrical diallyl ureas: β‐substituted allyl groups invariably behave as nucleophiles, while electrophilic behavior may be enforced by the use of an E‐vinylic urea substituent that cannot be deprotonated under the reaction conditions. [ABSTRACT FROM AUTHOR]

In solution, analogues of the Breslow intermediate formed during catalysis by benzoylformate decarboxylase (BFDC) undergo rapid, irreversible fragmentation. The ability of BFDC to prevent this reaction and preserve its cofactor is a striking example of an enzyme 'steering' a reactive intermediate towards a productive pathway. To understand how BFDC suppresses the off‐pathway reactivity of this Breslow intermediate, a clear mechanistic understanding of the fragmentation reaction is required. Here, DFT calculations reveal an unexpected mechanism for the solution‐phase fragmentation that involves an intramolecular cyclization and a subsequent retro‐ene reaction to release the final products. Free energy profiles demonstrate that this pathway is significantly more facile than the previously proposed mechanism that invoked Breslow intermediate enolates as intermediates. Additional computations have been performed to understand why related Breslow intermediates do not undergo analogous fragmentation reactions. Calculations performed with two closely related Breslow intermediates suggest that subtle differences in the relative values of ΔG≠ for protonation and fragmentation dictate whether a given intermediate will fragment or not. These differences and the fragmentation mechanism unveiled in this work may have ramifications for the mechanism of BFDC and other thiamin‐dependent enzymes and could provide general lessons related to the control of reactive intermediates by enzymes. [ABSTRACT FROM AUTHOR]

Described herein is a dirhodium(II)‐catalyzed silylation of propargyl esters with hydrosilanes, using tertiary amines as axial ligands. By adopting this strategy, a range of versatile and useful allenylsilanes can be achieved with good yields. This reaction not only represents a SN2′‐type silylation of the propargyl derivatives bearing a terminal alkyne moiety to synthesize allenylsilanes from simple hydrosilanes, but also represents a new application of dirhodium(II) complexes in catalytic transformation of carbon‐carbon triple bond. The highly functionalized allenylsilanes that are produced can be transformed into a series of synthetically useful organic molecules. In this reaction, an intriguing ON‐OFF effect of the amine ligand was observed. The reaction almost did not occur (OFF) without addition of Lewis base amine ligand. However, the reaction took place smoothly (ON) after addition of only catalytic amount of amine ligand. Detailed mechanistic studies and density functional theory (DFT) calculations indicate that the reactivity can be delicately improved by the use of tertiary amine. The fine‐tuning effect of the tertiary amine is crucial in the formation of the Rh−Si species via a concerted metalation deprotonation (CMD) mechanism and facilitating β‐oxygen elimination. [ABSTRACT FROM AUTHOR]