Industrial-current Ammonia Synthesis by Polarized Cuprous Cyanamide Coupled to Valorization of Glycerol at 4,000 mA cm.

The electrocatalytic nitrate reduction (NORR) holds significance in both NH synthesis and nitrate contamination remediation. However, achieving industrial-scale current and high stability in membrane electrode assembly (MEA) electrolyzer remains challenging due to inherent high full-cell voltage for sluggish NORR and water oxidation. Here, CuNCN with positive surface electrostatic potential V(r) is applied as highly efficient NORR electrocatalysts to achieve industrial-current and low-voltage stable NH production in MEA electrolyzer with coupled anodic glycerol oxidation.

A Copper-Zinc Cyanamide Solid-Solution Catalyst with Tailored Surface Electrostatic Potentials Promotes Asymmetric N-Intermediate Adsorption in Nitrite Electroreduction.

The electrocatalytic nitrite reduction (NORR) converts nitrogen-containing pollutants to high-value ammonia (NH) under ambient conditions. However, its multiple intermediates and multielectron coupled proton transfer process lead to low activity and NH selectivity for the existing electrocatalysts. Herein, we synthesize a solid-solution copper-zinc cyanamide (CuZnNCN) with localized structure distortion and tailored surface electrostatic potential, allowing for the asymmetric binding of NO.

Designing V Single Atom Embedded Carbon Moiety for the Electrocatalytic Nitrogen Reduction Reaction by First Principles Study.

Development of an efficient electrocatalyst for the nitrogen reduction reaction (NRR) to serve as a sustainable alternative to the Haber-Bosch process has proven highly challenging. Single atom catalysts (SACs), which have the maximum atom utilization efficiency, are among the most promising candidates. Single atoms can be incorporated to a catalytic system by doping or substitution or by attaching a molecular coordination complex to a substrate and the different insertion modes allow the chemical environment to be varied.

Kink-Controlled Gold Nanoparticles for Electrochemical Glucose Oxidation.

Enzymes in nature efficiently catalyze chiral organic molecules by elaborately tuning the geometrical arrangement of atoms in the active site. However, enantioselective oxidation of organic molecules by heterogeneous electrocatalysts is challenging because of the difficulty in controlling the asymmetric structures of the active sites on the electrodes. Here, we show that the distribution of chiral kink atoms on high-index facets can be precisely manipulated even on single gold nanoparticles; and this enabled stereoselective oxidation of hydroxyl groups on various sugar molecules.

Interrupted SAr-Alkylation Dearomatization.

Dearomatizations provide powerful synthetic routes to rapidly assemble substituted carbocycles and heterocycles found in a plethora of bioactive molecules. Harnessing the advantages of dearomatization typically requires vigorous reagents because of the difficulty in disrupting the stable aromatic core. A relatively mild dearomatization strategy is described that employs lithiated nitriles or isocyanides in a simple SAr-type addition to form σ-complexes that are trapped by alkylation.

Anomalous π-backbonding in complexes between B(SiR) and N: catalytic activation and breaking of scaling relations.

Chemical transformations of molecular nitrogen (N), including the nitrogen reduction reaction (NRR), are difficult to catalyze because of the weak Lewis basicity of N. In this study, it is shown that Lewis acids of the types B(SiR) and B(GeR) bind N and CO with anomalously short and strong B-N or B-C bonds. B(SiH)·N has a B-N bond length of 1.

The Importance of Electrostatics and Polarization for Noncovalent Interactions: Ionic Hydrogen Bonds vs Ionic Halogen Bonds.

A series of 26 hydrogen-bonded complexes between Br and halogen, oxygen and sulfur hydrogen-bond (HB) donors is investigated at the M06-2X/6-311 + G(2df,2p) level of theory. Analysis using a model in which Br is replaced by a point charge shows that the interaction energy ([Formula: see text]) of the complexes is accurately reproduced by the scaled interaction energy with the point charge ([Formula: see text]).This is demonstrated by [Formula: see text] with a correlation coefficient, R =0.

Machine learning meets mechanistic modelling for accurate prediction of experimental activation energies.

Accurate prediction of chemical reactions in solution is challenging for current state-of-the-art approaches based on transition state modelling with density functional theory. Models based on machine learning have emerged as a promising alternative to address these problems, but these models currently lack the precision to give crucial information on the magnitude of barrier heights, influence of solvents and catalysts and extent of regio- and chemoselectivity. Here, we construct hybrid models which combine the traditional transition state modelling and machine learning to accurately predict reaction barriers.

The local electron attachment energy and the electrostatic potential as descriptors of surface-adsorbate interactions.

Two local reactivity descriptors computed by Kohn-Sham density functional theory (DFT) are used to predict and rationalize interactions of nucleophilic molecules (exemplified by CO and HO) with transition metal (TM) and oxide surfaces. The descriptors are the electrostatic potential, V(r), and the local electron attachment energy, E(r), evaluated on surfaces defined by the 0.001 e Bohr isodensity contour.

Asymmetric Synthesis of Adjacent Tri- and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2-Carbaldehydes.

A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported.

Electrostatics and polarization determine the strength of the halogen bond: a red card for charge transfer.

A series of 20 halogen bonded complexes of the types R-Br•••Br (R is a substituted methyl group) and R´-C≡C-Br•••Br are investigated at the M06-2X/6-311+G(d,p) level of theory. Computations using a point-charge (PC) model, in which Br is represented by a point charge in the electronic Hamiltonian, show that the halogen bond energy within this set of complexes is completely described by the interaction energy (ΔE) of the point charge. This is demonstrated by an excellent linear correlation between the quantum chemical interaction energy and ΔE with a slope of 0.

Theoretical Investigation into Rate-Determining Factors in Electrophilic Aromatic Halogenation.

The halogenation of monosubstituted benzenes in aqueous solvent was studied using density functional theory at the PCM-M06-2 X/6-311G(d,p) level. The reaction with Cl begins with the formation of C atom coordinated π-complex and is followed by the formation of the σ-complex, which is rate-determining. The final part proceeds via the abstraction of the proton by a water molecule or a weak base.

σ-Holes and σ-lumps direct the Lewis basic and acidic interactions of noble metal nanoparticles: introducing regium bonds.

Using local DFT-based probes for electrostatic as well as charge transfer/polarization interactions, we are able to characterize Lewis basic and acidic sites on copper, silver and gold nanoparticles. The predictions obtained using the DFT-probes are compared to the interaction energies of the electron donating (CO, HO, NH and HS) and the electron accepting (BH, BF, HCl [H-down] and Na) compounds. The probes include the local electron attachment energy [E(r)], the average local ionization energy [Ī(r)], and the electrostatic potential [V(r)] and are evaluated on isodensity surfaces located at distances corresponding to typical interaction distances.

Mechanism and regioselectivity of electrophilic aromatic nitration in solution: the validity of the transition state approach.

The potential energy surfaces in gas phase and in aqueous solution for the nitration of benzene, chlorobenzene, and phenol have been elucidated with density functional theory at the M06-2X/6-311G(d,p) level combined with the polarizable continuum solvent model (PCM). Three reaction intermediates have been identified along both surfaces: the unoriented π-complex (I), the oriented reaction complex (II), and the σ-complex (III). In order to obtain quantitatively reliable results for positional selectivity and for modeling the expulsion of the proton, it is crucial to take solvent effects into consideration.

MD Simulations Reveal Complex Water Paths in Squalene-Hopene Cyclase: Tunnel-Obstructing Mutations Increase the Flow of Water in the Active Site.

Squalene-hopene cyclase catalyzes the cyclization of squalene to hopanoids. A previous study has identified a network of tunnels in the protein, where water molecules have been indicated to move. Blocking these tunnels by site-directed mutagenesis was found to change the activation entropy of the catalytic reaction from positive to negative with a concomitant lowering of the activation enthalpy.

Extending the σ-Hole Concept to Metals: An Electrostatic Interpretation of the Effects of Nanostructure in Gold and Platinum Catalysis.

Crystalline surfaces of gold are chemically inert, whereas nanoparticles of gold are excellent catalysts for many reactions. The catalytic properties of nanostructured gold have been connected to increased binding affinities of reactant molecules for low-coordinated Au atoms. Here we show that the high reactivity at these sites is a consequence of the formation of σ-holes, i.

Dehydrogenation of methanol on CuO(100) and (111).

Adsorption and desorption of methanol on the (111) and (100) surfaces of CuO have been studied using high-resolution photoelectron spectroscopy in the temperature range 120-620 K, in combination with density functional theory calculations and sum frequency generation spectroscopy. The bare (100) surface exhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface.

Nucleophilic Aromatic Substitution Reactions Described by the Local Electron Attachment Energy.

A local multiorbital electrophilicity descriptor, the local electron attachment energy [E(r)], is used to study the nucleophilic aromatic substitution reactions of SAr and VNS (vicarious nucleophilic substitution). E(r) considers all virtual orbitals below the free electron limit and is determined on the molecular isodensity contour of 0.004 atomic units.

Local Electron Attachment Energy and Its Use for Predicting Nucleophilic Reactions and Halogen Bonding.

A new local property, the local electron attachment energy [E(r)], is introduced and is demonstrated to be a useful guide to predict intermolecular interactions and chemical reactivity. The E(r) is analogous to the average local ionization energy but indicates susceptibility toward interactions with nucleophiles rather than electrophiles. The functional form E(r) is motivated based on Janak's theorem and the piecewise linear energy dependence of electron addition to atomic and molecular systems.

Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study.

A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium.

Novel approach for identifying key residues in enzymatic reactions: proton abstraction in ketosteroid isomerase.

We propose a computationally efficient approach for evaluating the individual contributions of many different residues to the catalytic efficiency of an enzymatic reaction. This approach is based on the fragment molecular orbital (FMO) method, and it defines the energy of a deletion form, i.e.

Searching for the thermodynamic limit--a DFT study of the step-wise water oxidation of the bipyramidal Cu7 cluster.

Oxidative degradation of copper in aqueous environments is a major concern in areas such as catalysis, electronics and construction engineering. A particular challenge is to systematically investigate the details of this process for non-ideal copper surfaces and particles under the conditions found in most real applications. To this end, we have used hybrid density functional theory to study the oxidation of a Cu7 cluster in water solution.

Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides.

A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the "σ-complex approach", has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics.

In situ investigations of Fe3+ induced complexation of adsorbed Mefp-1 protein film on iron substrate.

A range of in situ analytical techniques and theoretical calculations were applied to gain insights into the formation and properties of the Mefp-1 film on iron substrate, as well as the protein complexation with Fe(3+) ions. Adsorption kinetics of Mefp-1 and the complexation were investigated using QCM-D. The results suggest an initially fast adsorption, with the molecules oriented preferentially parallel to the surface, followed by a structural change within the film leading to molecules extending toward solution.