Detailed Density Functional Theory Calculations Research Articles

Understanding the Decomposition of Dimethyl Methyl Phosphonate on Metal-Modified TiO2(110) Surfaces Using Ensembles of Product Configurations.

The decomposition of dimethyl methyl phosphonate (DMMP), a simulant for the nerve agent sarin, was investigated on Cu4/TiO2(110) and K/Cu4/TiO2(110) surfaces using a combination of near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory calculations (DFT). Mass-selected Cu4 clusters and potassium (K) atoms were deposited onto TiO2(110) as a metal catalyst and alkali promoter to improve the reactivity and recyclability of the TiO2 surface after exposure to DMMP. Surface reaction products resulting from decomposition of DMMP were probed by NAP-XPS measurements of phosphorus (P) 2p and carbon 1s core-level spectra. The Cu4/TiO2(110) surface is found to be very active for DMMP decomposition with highly reduced P-species observed even at room temperature (RT). The codeposition of K atoms and Cu4 clusters further improves the reactivity with no intact DMMP detectable. Temperature-dependent measurements show that the presence of K atoms promotes the removal of residual P-species at temperatures > 600 K. Detailed DFT calculations were performed to determine the surface structures and energetically accessible pathways for DMMP decomposition on Cu4/TiO2(110) and K/Cu4/TiO2(110) surfaces. The calculations show that DMMP and P-containing reaction products preferentially bind to the TiO2 surface, while the molecular fragments, i.e., methoxy and methyl, bind to both the Cu4 clusters and TiO2. The Cu4 clusters make the P-O, O-C, and P-C bond cleavages of DMMP markedly more exothermic. The Cu4 clusters are highly fluxional with atomic structures that depend on the configuration of fragments bound to them. Finally, the manifold of P 2p chemical shifts calculated for a large number of energetically favorable configurations of decomposition products is in good agreement with the observed XPS spectra and provides an alternative way of interpreting incompletely resolved core-level spectra using an ensemble of observed structures.

Density Functional Theory Investigation of Intermolecular Interactions for Hydrogen-Bonded Deep Eutectic Solvents

Examining the interplay between choline chloride (ChCl) and ethylene glycol (EG) in Deep Eutectic Solvents (DES) assumes a pivotal role in designing innovative solvents. According to the literature, the comprehensive analysis of all possible types of conformers of ChCl and EG-based DES was scarce at different ratios, highlighting a gap in understanding at the atomistic level. In this study, we address this gap through a detailed Density Functional Theory calculation with dispersion correction (DFT+D3). Employing Density Functional Theory (DFT) calculations, our investigation delves into intermolecular relationships within DES, particularly focusing on ChCl and EG-based DES. DFT outcomes highlight the 1:2 ChCl to EG based DES ratio as notably more stable than alternative conformers. Key interactions within this DES conformation include: i) choline-chloride charge centers, ii) choline-EG links, and iii) EG-chloride anion associations. These findings provide valuable insights for crafting advanced solvents with tailored attributes. The intricate intermolecular interplay demonstrated here offers a versatile framework for harnessing DES potential across various domains, from chemical engineering to sustainable technologies.

Tailoring a MOF‐based adsorbent with partitioned aliphatic pore spaces for efficient CH4 purification from natural gas

AbstractSeparation of CH4 from natural gas is an essential but extremely challenging process in the petrochemical industry. Here, we tailored a MOF‐based adsorbent with partitioned aliphatic pore spaces through the simultaneous incorporation of the aliphatic sites and the symmetrically matched partition agent. The resulting adsorbent demonstrates exceptional adsorption capacity for C3H8 and C2H6 compared to CH4, along with remarkably competitive adsorption selectivities for C3H8/CH4 and C2H6/CH4. Breakthrough experiments further support the excellent dynamic separation efficiency of the adsorbent for the purification of CH4 from natural gas. Moreover, detailed density functional theory calculations and molecular simulations elucidate the synergistic interactions between the aliphatic sites and the partitioned pore spaces within the adsorbent, which promote the stronger binding affinities for C3H8 and C2H6 over CH4.

Terahertz Vibrational Dynamics and DFT Calculations for the Quantum Spin Chain Linarite, PbCuSO4(OH)2.

The low-dimensional quantum-magnet, linarite, PbCuS4(OH)2, has been investigated using terahertz (THz) spectroscopy coupled with detailed density functional theory (DFT) calculations in order to explore the effects of the temperature on its lattice vibrations. Linarite is characterized by largely isolated CuO chains propagating along the crystallographic b-axis, which at very low temperatures are responsible for exotic, quasi-1D magnetism in this material. To better understand the synergy between the structural bonds and lattice oscillations that contribute to these chains, polarized THz spectroscopic measurements were performed. Consolidating these results with detailed DFT calculations has revealed that the anisotropic vibrational motion for the THz modes is correlated with extreme motion associated with the crystallographic b-axis. An unexpected feature observed in the infrared spectrum is attributed to subtle lattice distortions which break the centro-symmetry in linarite at high temperatures. This phenomenon has not previously been observed in linarite and likely results from anharmonicity in lattice oscillations.

Atomically Dispersed Gold Nanoclusters and Single Atoms Coexisting Chiral Electrode for High‐Performance Enantioselective Electrosynthesis using H2o as Hydrogen Source

AbstractDeveloping chiral electrode catalysts for enantioselective electrosynthesis is a great challenge, as it requires catalysts that possess both high activity and enantioselectivity. Precise synthesis of nanoclusters and single atoms coexisting chiral catalysts provide a promising pathway for enhancing asymmetric catalytic performance. Herein, chiral electrode catalysts are fabricated comprising gold clusters (R‐AuC) and single atoms (R‐AuS) on graphene oxide (R‐AuC/S@GO) through an assembly‐irradiation strategy. Thereinto, the R‐Aus is in situ generated from R‐AuC under light irradiation. The monoatomization process can be precisely regulated by changing the wavelength of the light, resulting in four Au‐based chiral electrode (R‐Au@GO) catalysts with different ratios of nanoclusters and single atoms. These chiral electrodes are applied in the electrocatalytic enantioselective hydrogenation of methyl benzoylformate (MB) to chiral methyl mandelate (S‐MM), and the R‐AuC/S‐2@GO with ≈26% R‐AuC and 74% R‐AuS achieve the highest catalytic activity (35 µmol cm−2 h−1 productivity) and enantioselectivity [97% enantiomeric excess (ee)]. Detailed experimental analysis and density functional theory calculations reveal that the R‐AuS on GO promotes the in situ generation of H* species, and R‐AuC mainly drives the enantioselective conversion of MB by transferring the H* species to the carbonyl group of MB, ultimately yielding chiral S‐MM.

Metallaantiaromaticity of 10-Platinacorrole Complexes.

The aromaticity of cyclic π-conjugated organometallic compounds is known as metallaaromaticity. π-Conjugated metallacycles, such as metallabenzenes and metallapentalenes, have been investigated in order to understand the involvement of the d electrons from the metal center in the π-conjugated systems of the organic ligands. Here, we report the synthesis of Pd(II) 10-platinacorrole complexes with cyclooctadiene (COD) and norbornadiene (NBD) ligands. While the Pd(II) 10-platinacorrole COD complex adopts a distorted structure without showing appreciable antiaromaticity, the corresponding NBD complex exhibits a distinct antiaromatic character due to its highly planar conformation. Detailed density functional theory (DFT) calculations revealed that two d orbitals are involved in macrocyclic π-conjugation. We furthermore demonstrated that Craig-Möbius antiaromaticity is not present in the studied system. The synthesis of 10-platinacorroles enables a systematic comparison of the antiaromaticity and aromaticity of closely related porphyrin analogues, providing a better understanding of π-conjugation that involves d orbitals.

O-Vacancy Mediated Partially Inverted Ferrospinels for Enhanced Activity in the Sulfuric Acid Decomposition for Hydrogen Production.

Understanding the characterization of a tailored Co3O4 spinel with Fe3+ doping poses a challenge due to the surface state complexity in bifunctional catalysts with higher cation diversity. Doping with secondary metal results in a double spinel structure (a hybrid of normal and inverted spinels). This enhances the catalytic properties by generating more active oxygen vacancies. The cobalt-rich (FeCo2O4) hybrid spinel and iron-rich (CoFe2O4) inverted spinel are synthesized using a wet impregnation method, supported over oxidized SiC (SiC-Pretrt) for an improved metal-support interaction. FeCo2O4 on pretreated SiC exhibits the highest catalytic activity (90% conversion at 1173 K) and stability (over 100 h) in sulfuric acid decomposition of the iodine-sulfur process for hydrogen production. This improved performance is attributed to the high electronegativity of Co3+, oxygen vacancies, and strong metal-support interaction. The high electronegativity of Co3+ weakens the S-O bond in M-S-O, enhancing the catalytic activity of the spinels. These results are further corroborated by detailed characterization and density functional theory calculations.

Green synthesis of novel spiropyrazoline-indolinones in neutral deep eutectic solvents and DFT studies

Novel spiropyrazoline-indolinones (4a–t) have been synthesized successfully in neutral deep eutectic solvents by reacting 5-Cl/Br-isatin (1a–b) with aromatic ketones (2a–b) and a variety of substituted hydrazines (3a–e) in good to excellent yields. This eco-friendly straightforward synthetic protocol discloses good functional group compatibility. The conventional synthetic approach was compared with the greener route of microwave-assisted synthesis of spiropyrazolines using ethanol. This approach utilized mild reaction conditions which furnished high yields in short reaction time employing one pot two-step multicomponent. All new compounds were structurally confirmed by detailed spectroscopic analysis and density functional theory calculations. This method provides efficient access to spiropyrazole derivatives using biodegradable and green solvent.

Local Electron Environment Regulation of Spinel CoMn2O4 Induced Effective Reactant Adsorption and Transformation of Lattice Oxygen for Toluene Oxidation.

In contrast to numerous studies on oxygen species, the interaction of volatile organic compounds (VOCs) with oxides is also critical to the catalytic reaction but has hardly been considered. Herein, we develop a highly efficient Pt atom doped spinel CoMn2O4 (Pt-CoMn) for oxidation of toluene at low temperature, and the toluene conversion rate increased by 18.3 times (129.7 versus 7.1 × 10-11 mol/(m2·s)) at 160 °C compared to that of CoMn2O4. Detailed characterizations and density functional theory calculations reveal that the local electron environment of the Co sites is changed after Pt doping, and the formed electron-deficient Co sites in turn strengthen the interaction with toluene. Adsorbed toluene will react with lattice oxygen in Pt-CoMn and CoMn catalysts and convert into benzoate intermediates, and the consumption rate of benzoate is closely related to the activation of gaseous oxygen. Significantly, the abundant bulk defects of Pt-CoMn help to open the reaction channel in the CoMn spinel, which acts as an oxygen pump to promote the transformation of bulk lattice oxygen into surface lattice oxygen at lower temperatures, thus accelerating the conversion rate of benzoate intermediates into CO2 and enhancing low-temperature combustion of toluene. Pt-CoMn developed here emphasizes the regulation of VOCs adsorption strength and lattice oxygen transformation processes on CoMn2O4 by adjusting the local electron environment, which will provide new guidance for the design of efficient oxide catalysts for catalytic oxidation.

Synergistic effect of platinum single atoms and nanoclusters for preferential oxidation of carbon monoxide in hydrogen-rich stream

Despite the maximum atom-utilization efficiency and remarkable activity of single-atom catalysts, further improvement of catalytic activity can be obtained by the synergistic effect of single atoms and nanoclusters in some catalytic systems. Herein, CeFeOx-supported Pt single atoms coupling with subnanometric clusters (Pt1-Ptn) structures are developed via a facile strategy. They are applied as the highly efficient catalysts for the preferential oxidation of CO in H2-rich stream (CO-PROX), which achieve complete elimination of CO at low temperature of 50 °C, with a wide operating temperature window and extraordinary stability for over 500 h without noticeable deactivation. The exceptional performance is attributed to the synergistic effect of distinctive Pt1-Ptn structures, which couple the benefits of Pt single atoms and subnanometric clusters in a remarkable way. The disadvantages of single Pt species catalysts, such as sensibility to strong adsorption of CO or reduced lattice oxygen reactivity due to excessive coordination, can be well mitigated. The results of detailed characterizations and density functional theory calculations confirm that the unique structures possess moderate adsorption strength for CO and create abundant active interfacial oxygen species, because of the absence of bulk metallic Pt0 and appropriate coordination to lattice oxygen, which synergistically facilitate the catalytic performance.

CeNCl‐CeO2 Heterojunction‐Modified Ni Catalysts for Efficient Electroreduction of CO2 to CO

AbstractRenewable‐electricity‐powered electrochemical CO2 reduction (CO2RR) is considered one of the most promising ways to convert exhaust CO2 into value‐added chemicals and fuels. Among various CO2RR products, CO is of great significance since it can be directly used as feedstock to produce chemical products through the Fischer–Tropsch process. However, the CO2‐to‐CO electrocatalytic process is often accompanied by a kinetically competing side reaction: H2 evolution reaction (HER). Designing electrocatalysts with tunable electronic structures is an attractive strategy to enhance CO selectivity. In this work, a CeNCl‐CeO2 heterojunction‐modified Ni catalyst is successfully synthesized with high CO2RR catalytic performance by the impregnation‐calcination method. Benefiting from the strong electron interaction between the CeNCl‐CeO2 heterojunction and Ni nanoparticles (NPs), the catalytic performance is greatly improved. Maximal CO Faradaic efficiency (FE) is up to 90% at −0.8 V (vs RHE), plus good stability close to 12 h. Detailed electrochemical tests and density functional theory (DFT) calculation results reveal that the introduction of the CeNCl‐CeO2 heterojunction tunes the electronic structure of Ni NPs. The positively charged Ni center leads to an enhanced local electronic structure, thus promoting the activation of CO2 and the adsorption of *COOH.

Boosting the Lithium-Ion Transport Kinetics of Sn-Based Coordination Polymers through Ligand Aromaticity Manipulation.

Tin-based compounds are promising anode materials for lithium-ion batteries owing to their low charge/discharge voltage and high theoretical capacity but are plagued by both huge volume expansion during cycling and complex synthetic procedures. Constructing a coordination network between Sn and the lithium-active organic matrix can effectively relieve the volume expansion and increase the lithium storage active site utilization. Herein, we report a facile method to prepare two one-dimensional Sn-based coordination polymers [Sn(Hcta)]n (1) and [Sn(Hbtc)]n (2) (H3cta = 1,3,5-cyclohexanetricarboxylic acid, H3btc = 1,3,5-benzenetricarboxylic acid) for lithium storage, which differ only in the aromaticity of the ligand. 2 with an aromatic ligand provided a reversible capacity of 833 mAh g-1 at 200 mA g-1 over 160 cycles, higher than that of 1 without an aromatic ligand due to the quick charge transfer. The reversible lithium storage reactions of metal centers and organic ligands and the volume expansion rate of Sn-based coordination polymers during cycling were studied by detailed characterization and density functional theory (DFT) calculations. This research revealed that the structural factor of ligand aromaticity in these Sn-based coordination polymers boosted the utilization of active sites and rapid charge transfer, offering a coordination chemistry strategy for the design and synthesis of advanced anode materials.

Binary adsorption isotherms of methylene blue and crystal violet on mandarin peels: prediction via detailed multivariate calibration and density functional theory (DFT) calculations.

The multicomponent adsorption of synthetic dyes has great relevance in the treatment of effluents due to the complexity of the adsorbate-adsorbent interactions. Therefore, this study provides useful information about the adsorption capacity of methylene blue (MB) and crystal violet (CV) in a bioadsorbent (mandarin peels) in a single-component and competitive system using detailed multivariate calibration analysis. The PLS1 multivariate calibration model was used to quantify the adsorbates. In mono and two-component systems, the adsorption capacity of CV (1.26-1.36 mg g-1) was superior when compared to MB (0.925-0.913 mg g-1), characterizing synergistic adsorption for CV and antagonistic adsorption for MB. The Sips model was effective for describing single-component systems, suggesting that adsorption did not occur in the monolayer. For competitive adsorption, modified, unmodified, and extended models were used to understand the interactions between the dyes and the bioadsorbent. The modified Redlich-Peterson (MRP) model was effective in describing the behavior of the binary system, indicating that the interaction forces with the adsorbate were significant. Thus, the bioadsorbent showed promising results for competitive adsorption, thus being of relevance to the industrial sector. Density functional calculations were also performed to characterize the atomic interactions for the removal of both dyes on mandarin peels.

Ligand‐Controlled Regiodivergence in Nickel‐Catalyzed Vinylcyclopropane Rearrangement

AbstractA ligand‐controlled regiodivergence in Ni‐catalyzed rearrangement of vinylcyclopropanes to 1,4‐ or 1,5‐disubstituted cyclopentenes is reported. The 1,4‐ or 1,5‐disubstituted cyclopentene is selectively obtained depending on the choice of ligands. Detailed kinetic studies and density functional theory calculations on the catalytic cycle revealed that the product selectivity is determined at the reductive elimination step from the six‐membered η1‐allyl intermediate.

A Low‐Cost Quasi‐Solid‐State “Water‐in‐Swelling‐Clay” Electrolyte Enabling Ultrastable Aqueous Zinc‐Ion Batteries

AbstractThe poor reversibility of Zn metal anodes arising from water‐induced parasitic reactions poses a significant challenge to the practical applications of aqueous zinc‐ion batteries (AZIBs). Herein, a novel quasi‐solid‐state “water‐in‐swelling‐clay” electrolyte (WiSCE) containing zinc sulfate and swelling clay, bentonite (BT), is designed to enable highly reversible Zn metal anodes. AZIB full cells based on the WiSCE exhibit excellent cyclic stability at various current densities, long shelf life, low self‐discharge rate, and outstanding high‐temperature adaptability. Particularly, the capacity of WiSCE‐based AZIB full cells retains 90.47% after 200 cycles at 0.1 A g−1, 96.64% after 2000 cycles at 1 A g−1, and 88.29% after 5000 cycles at 3 A g−1. Detailed density functional theory calculations show that strong hydrogen bonds are formed between BT and water molecules in the WiSCE. Thus, water molecules are strongly confined by BT, particularly within the interlayers, which significantly inhibits water‐induced parasitic reactions and greatly improves cyclic stability. Compared to the state‐of‐the‐art “water‐in‐salt” electrolytes, the WiSCE can provide a significantly higher capacity at the full‐cell level with a substantially reduced cost, which is promising for the design of next‐generation high‐performance AZIBs. This work provides a new direction for developing cost‐competitive AZIBs as alternatives to grid‐scale energy storage.

Retrofitting Zr-Oxo Nodes of UiO-66 by Ru Single Atoms to Boost Methane Hydroxylation with Nearly Total Selectivity.

Direct selective oxidation of methane (DSOM) to high value-added oxygenates under mild conditions is attracting considerable interest. Although state-of-the-art supported metal catalysts can improve methane conversion, it is still challenging to avoid the deep oxidation of oxygenates. Here, we develop a highly efficient metal-organic frameworks (MOFs)-supported single-atom Ru catalyst (Ru1/UiO-66) for the DSOM reaction using H2O2 as an oxidant. It endows nearly 100% selectivity and an excellent turnover frequency of 185.4 h-1 for the production of oxygenates. The yield of oxygenates is an order of magnitude higher than that on UiO-66 alone and several times higher than that on supported Ru nanoparticles or other conventional Ru1 catalysts, which show severe CO2 formation. Detailed characterizations and density functional theory calculations reveal a synergistic effect between the electron-deficient Ru1 site and the electron-rich Zr-oxo nodes of UiO-66 on Ru1/UiO-66. The Ru1 site is responsible for the activation of CH4 via the resulting Ru1═O* species, while the Zr-oxo nodes undertake the formation of oxygenic radical species to produce oxygenates. In particular, the Zr-oxo nodes retrofitted by Ru1 can prune the excess H2O2 to inactive O2 more than •OH species, helping to suppress the over-oxidation of oxygenates.

Zwitterion Functionalized Graphene Oxide/Polyacrylamide/Polyacrylic Acid Hydrogels with Photothermal Conversion and Antibacterial Properties for Highly Efficient Uranium Extraction from Seawater

AbstractIn this study, graphene oxide (GO) and polyacrylamide/polyacrylic acid (PAM/PAA) are used to prepare hydrogels with photothermal conversion properties for highly efficient uranium extraction from seawater. Zwitterionic 2‐methacryloyloxy ethyl phosphorylcholine (MPC) is introduced in the PAM/PAA/GO hydrogel to obtain PAM/PAA/GO/MPC (PAGM), exhibiting good antibacterial properties. PAGM demonstrates efficient and specific adsorption of uranium (VI) (U(VI)). Under light conditions, the adsorption capacity of PAGM reaches 196.12 mg g−1 (pH = 8, t = 600 min, C0 = 99.8 mg L−1, m/v = 0.5 g L−1). The adsorption capacity is only 160.29 mg g−1 under dark conditions (pH = 8, t = 600 min, C0 = 99.8 mg L−1, m/v = 0.5 g L−1). The adsorption capacity of light is 22.5% higher than that of dark. The adsorption process is fitted using the Langmuir and pseudo‐second‐order models. Furthermore, PAGM exhibits good repeatability and stability after five adsorption–desorption cycles. PAGM exhibits a U(VI) adsorption capacity of 6.1 mg g−1 after storage for one month in natural seawater. The X‐ray photoelectron spectroscopy (XPS) results demonstrate that the coordination of the amino, carboxyl, and hydroxyl groups with U(VI) is the primary mechanism of U(VI) adsorption. The mechanism is confirmed through detailed density functional theory calculations. PAGM demonstrates durability, high efficiency, photothermal conversion properties, and antibacterial properties. Thus, it is a promising candidate for uranium extraction from seawater.

Boosting the Electrocatalytic Formic Acid Oxidation Activity via P-PdAuAg Quaternary Alloying.

Direct formic acid fuel cells (DFAFCs) are considered promising sustainable power sources due to their high energy density, nonflammability, and low fuel crossover. However, serious CO poisoning and activity attenuation of the anodic formic acid oxidation reaction (FAOR) greatly restrict the output and durability of DFAFCs. Inspired by the specific relationship between the composition, type, and property of alloys, in this work, we synthesize a series of hybrid substitutional/interstitial quaternary alloys P-PdAuAg by means of a novel polyphosphide route to address these issues. Due to the simultaneous interstitial P-doping and metal (Au, Ag, Pd) co-reduction, the P-PdAuAg quaternary alloy obtained is only 3 nm in diameter with abundant defects. It not only achieves a new high mass activity of 8.08 A mgPd-1 (6.78 A mgcatalyst-1) but also maintains high stability in the high potential range and harsh reaction conditions. Both the activity and anti-poisoning ability are far exceeding those of the currently reported FAOR catalysts. Detailed density functional theory (DFT) calculations reveal that the superb electrochemical performances originate from the shift of the d-band center of Pd as a result of the synergistic electronic/ligand effects between Pd, Au, Ag, and P. The introduction of interstitial P inhibits the occurrence of an indirect reaction pathway on Pd, while Au and Ag suppress the adsorption of CO and optimize the sequential dehydrogenation steps, leading to boosted reaction kinetics and CO tolerance. This work pioneered a facile way for the synthesis of Pd-based substitutional/interstitial hybrid alloys, providing a promising means of further improving the performance of alloying catalysts.

NMR and DFT studies of monounsaturated and ω-3 polyunsaturated free fatty acids in the liquid state reveal a novel atomistic structural model of DHA

Structures of low-energy conformers of caproleic acid (CA; 10:1 cis-9), oleic acid (OA; 18:1 cis-9), α-linolenic acid (ALA; 18:3 cis-9,12,15 ω-3), eicosapentaenoic acid (EPA; 20:5 cis-5,8,11,14,17 ω-3), and docosahexaenoic acid (DHA; 22:6 cis-4,7,10,13,16,19 ω-3) in the liquid state, based on detailed 1D NOE and density functional theory calculations of 1H NMR chemical shifts are presented. Transient 1D NOE experiments with variable mixing time showed significant through-space proximity of the CH2–COOH protons and the terminal CH3– groups. Variable temperature 1H NMR experiments revealed strong intermolecular centro-symmetric cyclic hydrogen bond interactions of the carboxylic groups of the monounsaturated oleic and caproleic acids (δ(COOH) ∼ 12.0–12.4 ppm), ALA and EPA (δ(COOH) ∼ 11.0 ppm). On the contrary, the carboxylic proton of DHA is strongly shielded with δ(COOH) ∼ 8.5 ppm. DFT calculations were interpreted in terms of aggregates of dimerized fatty acids with parallel and antiparallel interdigitated structures. The antiparallel arrangement was found to be in excellent agreement with experimental 1D NOE NMR data. For the dimeric DHA, a flip-flop process between a classical intermolecular centro-symmetric hydrogen bond through carboxylic groups and a novel intramolecular hydrogen bond between the carboxylic group and the terminal ω-3 double bond is demonstrated.

Mechanistic Insights into the Metal-Free Deoxygenative Borylation of Ketones and Aldehydes with Bis(catecholato)diborane.

The mechanisms of direct deoxygenative borylation of acetone and benzaldehyde with bis(catecholato)diborane (B2 cat2 ) in the solvent N,N-dimethylacetamide (DMA) are investigated through detailed density functional theory calculations. These calculations show that the isomer 1,2-B2 cat2 in situ generated from 1,1-B2 cat2 induced by DMA is the reactive boron intermediate for the reactions. The addition of the B-B bond of 1,2-B2 cat2 to the C=O bond of acetone or benzaldehyde via a concerted [2σ+2π]-cycloaddition-like transition state is the rate-limiting step for both the triboration reaction of acetone and the monoboration reaction of benzaldehyde. DMA not only acts as the solvent but also promotes the structural isomerization of B2 cat2 , the deoxygenation of acetone to form the vinyl boronate intermediate and subsequent diboration of vinyl boronate with 1,2-B2 cat2 , as well as the protodeboronation of the gem-diboronate intermediate in the deoxygenative borylation of benzaldehyde. The presented computational results can explain the observed experimental facts and provide insight into the roles of the isomeric 1,2-B2 cat2 and the solvent DMA in related reactions.