Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

Geometrical cis- and trans- isomers of 2-chloro-, 2-bromo- and 2-fluoro-4-methyl-1,3,2-dioxaphosphorinan-2-thiones were obtained in a diastereoselective way by (a) sulfurization of corresponding cyclic P^III-halogenides, (b) reaction of cyclic phosphorothioic acids with phosphorus pentachloride and (c) halogen–halogen exchange at P^IV-halogenide. Their conformation and configuration at the C₄-ring carbon and phosphorus stereocentres were studied by NMR (¹H, ³¹P) methods, X-ray analysis and density functional (DFT) calculations. The stereochemistry of displacement reactions (alkaline hydrolysis, methanolysis, aminolysis) at phosphorus and its mechanism were shown to depend on the nature of halogen. Cyclic cis- and trans-isomers of chlorides and bromides react with nucleophiles (HO⁻, CH₃O⁻, Me₂NH) with inversion of configuration at phosphorus. DFT calculations provided evidence that alkaline hydrolysis of cyclic thiophosphoryl chlorides proceeds according to the S_N2-P mechanism with a single transition state according to the potential energy surface (PES) observed. The alkaline hydrolysis reaction of cis- and trans-fluorides afforded the same mixture of the corresponding cyclic thiophosphoric acids with the thermodynamically more stable major product. Similar DFT calculations revealed that substitution at phosphorus in fluorides proceeds stepwise according to the A–E mechanism with formation of a pentacoordinate intermediate since a PES with two transition states was observed.

Enhancing Dielectric Strength of Epoxy Polymers by Constructing Interface Charge Traps

Epoxy polymer-based dielectric materials play a crucial role in advanced electronic devices and power equipment. However, high voltage-stress applications impose stringent requirements, such as a high dielectric strength, on epoxy polymers. Previously reported studies have shown promising material architectures in the form of epoxy polymer-nanoparticle dielectrics, which can restrict the movement of high-energy electrons by the interface charge traps associated with the various interfacial regions. However, these high-energy electrons inevitably traverse the epoxy polymer matrix and destroy the molecular structure, thereby creating a weak link for dielectric breakdown. In this study, a general strategy is developed to improve the dielectric strength by constructing interface charge traps in the molecular structure of the epoxy polymer matrix, using the -CF₃ group in partial replacement of the -CH₃ group. The proposed strategy increases the dielectric strength (39.5 kV mm^-1) and surface breakdown voltage (26.9 kV) of the epoxy polymer matrix by 22.08% and 13.3%, respectively, because the interface charge trap hinders the movement of high-energy electrons. At the same time, the strategy does not degrade the mechanical and thermal properties. The results hold potential for wide application in the manufacturing of advanced future electrical and electronic equipment requiring resilience to high-voltage stress.

Evidence of the CH···O HydrogenBonding in Imidazolium-Based Ionic Liquids from Far-Infrared Spectroscopy Measurements and DFT Calculations

Knowledge of all the intermolecular forces occurring in ionic liquids (ILs) is essential to master their properties. Aiming at investigating the weaker hydrogen bonding in aprotic liquids, the present work combined computational study and far-infrared spectroscopy on four imidazolium-based ILs with different anions. The DFT calculations of the ionic couples, using the ωB97X-D functional and considering both the empirical dispersion corrections and the presence of a polar solvent, show that, for all samples, the lowest energy configurations of the ion pair present H atoms, directly bound to C atoms of the cation and close to O atoms of the anion, capable of creating moderate to weak hydrogen bonding with anions. For the liquids containing anions of higher bonding ability, the absorption curves generated from the calculated vibrational frequencies and intensities show absorption bands between 100 and 125 cm⁻¹ corresponding to the stretching of the hydrogen bond. These indications are in complete agreement with the presently reported temperature dependence of the far-infrared spectrum, where the stretching modes of the hydrogen bonding are detected only for samples presenting a moderate interaction and become particularly prominent at low temperatures. Moreover, from the analysis of the infrared spectra, the occurrence of various phase transitions as a function of temperature was detected, and the difference in the average energy between the H-bonded and the dispersion-governed molecular configurations was evaluated.

Photochemical Carbene Transfer Reactions of Aryl/Aryl Diazoalkanes-Experiment and Theory*

Controlling the reactivity of carbene intermediates is a key parameter in the development of selective carbene transfer reactions and is usually achieved by metal complexes via singlet metal-carbene intermediates. In this combined experimental and computational studies, we show that the reactivity of free diaryl carbenes can be controlled by the electronic properties of the substituents without the need of external additives. The introduction of electron-donating and -withdrawing groups results in a significant perturbation of singlet triplet energy splitting of the diaryl carbene intermediate and of activation energies of consecutive carbene transfer reactions. This strategy now overcomes a long-standing paradigm in the reactivity of diaryl carbenes and allows the realization of highly chemoselective carbene transfer reactions with alkynes. We could show that free diaryl carbenes can be readily accessed via photolysis of the corresponding diazo compounds and that these carbenes can undergo highly chemoselective cyclopropenation, cascade, or C-H functionalization reactions. Experimental and theoretical mechanistic analyses confirm the participation of different carbene spin states and rationalize for the observed reactivity.

Theoretical Insight into the Effect of Fluorine-Functionalized Metal-Organic Framework Supported Palladium Single-Site Catalyst in the Ethylene Dimerization Reaction

Ethylene dimerization reaction is one of the most common mechanisms for the production of 1-butene. Recently, metal-organic frameworks (MOFs) have received extensive attention in this area since they combine all the advantages of homogeneous and heterogeneous catalysts in a single compound. Here a computational mechanistic study of MOF-supported palladium single-site catalyst for ethylene dimerization reaction is reported. Catalytic systems with both biphenyl-type backbone as organic ligand and its fluorine-functionalization have been investigated to reveal the origin of ligand effects on the catalytic activity and selectivity. The calculations revealed that the nonfluorinated palladium MOF catalyst undergoes dimerization over isomerization reaction. Then the influence of the fluorine-functionalized organic ligand was compared in the dimerization catalytic cycle, which was strongly favored in terms of activity and selectivity. Catalyst-substrate interactions were analyzed by energy decomposition analysis revealing the critical role of ligand backbone functionalization on the activity. This theoretical analysis identified three chemically meaningful dominant effects on these catalysts; steric, electrostatic and charge transfer effects. The steric effects promote nonfluorinated MOF catalyst, whereas the electrostatic effects are the dominant factor that promotes its fluorinated counterpart. This theoretical study provides feedback with future experimental studies about the role of fluorine ligand functionalization in palladium MOF catalysts for ethylene dimerization reaction.

Development of 19 F-detected 1,1-ADEQUATE for the characterization of polyfluorinated and perfluorinated compounds

Polyfluorinated and perfluorinated compounds in the environment are a growing health concern. ¹⁹ F-detected variants of commonly employed heteronuclear shift correlation experiments such as heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) are available; ¹⁹ F-detected experiments that employ carbon-carbon homonuclear coupling, in contrast, have never been reported. Herein, we report the measurement of the ¹ J_CC and ⁿ J_CC coupling constants of a simple perfluorinated phthalonitrile and the first demonstration of a ¹⁹ F-detected 1,1-ADEQUATE experiment.

Chemically heterogeneous carbon dots enhanced cholesterol detection by MALDI TOF mass spectrometry

A binary system composed of carbon dots (CDs) and N-doped CDs (N-CDs) embedded in an organic matrix was used for the analysis of cholesterol by MALDI (matrix-assisted laser desorption and ionization time-of-flight) mass spectrometry, as a model for detection of small, biologically relevant molecules. The results showed that both CDs are sensitive to the cholesterol and can be used either alone or in a binary system with 2,5-dihydroxybenzoic acid (DHB) to enhance the detection process. It was found that both COOH and NH₂ groups on CDs surface contributed to the enhancement in the cholesterol detection by MALDI mass spectrometry in the presence of inorganic cations. Nevertheless, in the presence of NaCl, N-CDs led to a better reproducibility of results. It was due to the coexistence of positive and negative charge on N-CDs surface that led to a homogeneous analyte/substrate distribution, which is an important detection parameter. The enhancing effect of carbon dots was linked to a negative Gibbs energy of the complex formation between CDs, Na⁺, cholesterol and DHB, and it was supported by theoretical calculations. Moreover, upon the addition of CDs/N-CDs, such features as a low ionization potential, vertical excitation, dipole moment and oscillator strength positively affected the cholesterol detection by MALDI in the presence of Na⁺.

Novel Bis- and Mono-Pyrrolo[2,3-d]pyrimidine and Purine Derivatives: Synthesis, Computational Analysis and Antiproliferative Evaluation

Novel symmetrical bis-pyrrolo[2,3-d]pyrimidines and bis-purines and their monomers were synthesized and evaluated for their antiproliferative activity in human lung adenocarcinoma (A549), cervical carcinoma (HeLa), ductal pancreatic adenocarcinoma (CFPAC-1) and metastatic colorectal adenocarcinoma (SW620) cells. The use of ultrasound irradiation as alternative energy input in Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) shortened the reaction time, increased the reaction efficiency and led to the formation of exclusively symmetric bis-heterocycles. DFT calculations showed that triazole formation is exceedingly exergonic and confirmed that the presence of Cu(I) ions is required to overcome high kinetic requirements and allow the reaction to proceed. The influence of various linkers and 6-substituted purine and regioisomeric 7-deazapurine on their cytostatic activity was revealed. Among all the evaluated compounds, the 4-chloropyrrolo[2,3-d]pyrimidine monomer 5f with 4,4′-bis(oxymethylene)biphenyl had the most pronounced, although not selective, growth-inhibitory effect on pancreatic adenocarcinoma (CFPAC-1) cells (IC₅₀ = 0.79 µM). Annexin V assay results revealed that its strong growth inhibitory activity against CFPAC-1 cells could be associated with induction of apoptosis and primary necrosis. Further structural optimization of bis-chloropyrrolo[2,3-d]pyrimidine with aromatic linker is required to develop novel efficient and non-toxic agent against pancreatic cancer.

High selective gas-phase rearrangement reaction of TCDD induced by excess electron attachment: Theoretical insight on the decomposition mechanism of one of the most toxic chemical known to science

Dioxins are highly toxic chemicals with serious health risks, for which there is no safe level of exposure. Because of the slow decomposition of dioxins, the removal of these persistent environmental pollutants still remains a challenge. Based on theoretical studies, the present work investigates the degradation mechanism of the most toxic type of dioxin-related compounds by low-energy electron irradiation. To explore the rearrangement manner of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced by excess electron attachment, the B3LYP-D3(BJ)/def2-TZVP//B3LYP-D3(BJ)/6-311++G(d,p) level of density functional theory was applied. Electron attachment resulted in a remarkable decrease in the activation barrier of the rearrangement reaction in a thermodynamically preferred reaction. An activation energy as low as 6.6 kcal/mol provides a strong demonstration that this pathway is the most effective in comparison to the neutral or radical rearrangement mechanisms. The attachment of electrons in the above energy range to C-Cl σ∗orbital is more likely than attachment to the LUMO of TCDD with π∗ orbital character. This σ∗ anion then undergoes a C-O σ bond rupture over a small barrier to produce a relatively stable intermediate, n-IM. The formed n-IM is again reactive toward a subsequent C-O bond rupture along with an intramolecular C-C coupling to produce the products, (E)-4,4',5,5'-tetrachloro-[1,1'-bi(cyclohexylidene)]-3,3',5,5'-tetraene-2,2'-dione and (Z)-4,4',5,5'-tetrachloro-[1,1'-bi(cyclohexylidene)]-3,3',5,5'-tetraene-2,2'-dione. The thermodynamic driving force for the anionic mechanism ensures the formation of the products to be irreversible enough to be purified. The purified products, with their active carbonyl groups, can react in many different ways with a wide range of nucleophile compounds.

Fabrication of Highly Textured 2D SnSe Layers with Tunable Electronic Properties for Hydrogen Evolution

Hydrogen is regarded to be one of the most promising renewable and clean energy sources. Finding a highly efficient and cost-effective catalyst to generate hydrogen via water splitting has become a research hotspot. Two-dimensional materials with exotic structural and electronic properties have been considered as economical alternatives. In this work, 2D SnSe films with high quality of crystallinity were grown on a mica substrate via molecular beam epitaxy. The electronic property of the prepared SnSe thin films can be easily and accurately tuned in situ by three orders of magnitude through the controllable compensation of Sn atoms. The prepared film normally exhibited p-type conduction due to the deficiency of Sn in the film during its growth. First-principle calculations explained that Sn vacancies can introduce additional reactive sites for the hydrogen evolution reaction (HER) and enhance the HER performance by accelerating electron migration and promoting continuous hydrogen generation, which was mirrored by the reduced Gibbs free energy by a factor of 2.3 as compared with the pure SnSe film. The results pave the way for synthesized 2D SnSe thin films in the applications of hydrogen production.

1,2- or 1,3-Hydride Shifts: What Controls Guaiane Biosynthesis?

A systematic computational study addressing the entire chemical space of guaianes in conjunction with an analysis of all known compounds shows that 1,3‐hydride shifts are rare events in guaiane biosynthesis. As demonstrated here, 1,3‐hydride shifts towards guaianes can only be realized for two stereochemically well defined out of numerous possible stereoisomeric skeletons. One example is given by the mechanism of guaia‐4(15)‐en‐11‐ol synthase from California poplar, an enzyme that yields guaianes with unusual stereochemical properties. The general results from DFT calculations were experimentally verified through isotopic‐labeling experiments with guaia‐4(15)‐en‐11‐ol synthase.

CO2 Capture by Hydroxylated Azine-Based Covalent Organic Frameworks

Covalent organic frameworks (COFs) RIO-13, RIO-12, RIO-11, and RIO-11m were investigated towards their CO₂ capture properties by thermogravimetric analysis at 1 atm and 40 °C. These microporous COFs bear in common the azine backbone composed of hydroxy-benzene moieties but differ in the relative number of hydroxyl groups present in each material. Thus, their sorption capacities were studied as a function of their textural and chemical properties. Their maximum CO₂ uptake values showed a strong correlation with an increasing specific surface area, but that property alone could not fully explain the CO₂ uptake data. Hence, the specific CO₂ uptake, combined with DFT calculations, indicated that the relative number of hydroxyl groups in the COF backbone acts as an adsorption threshold, as the hydroxyl groups were indeed identified as relevant adsorption sites in all the studied COFs. Additionally, the best performing COF was thoroughly investigated, experimentally and theoretically, for its CO₂ capture properties in a variety of CO₂ concentrations and temperatures, and showed excellent isothermal recyclability up to 3 cycles.

Van der Waals enhanced interfacial interaction in cellulose/zinc oxide nanocomposite coupled by graphitic carbon nitride

In-depth understanding of interfacial property is the key to guiding the synthesis of biomass composites with desired performance. However, the exploration is of great challenge due to limitations of experimental techniques in locating hydrogen, requiring large/good crystals and detecting a weak interaction like van der Waals (vdW). Herein, we experimentally and computationally investigated the composite cellulose/zinc oxide/g-C₃N₄. Hydrothermal synthesis afforded cellulose/ZnO, and then fabricated the ternary composite by adding g-C₃N₄ under ultrasonic condition. Three components are found to co-exist in the composite, and the ZnO nanoparticle is attaching to cellulose and coupling with g-C₃N₄. These experimental findings were corroborated by relativistic DFT calculations. The interfacial coupling is elaborated as contributions of dative bonds, hydrogen bonds and vdW interaction. The vdW is increased by a factor of 4.23 in the ZnO/g-C₃N₄ interface. This improves electron-hole separation and offers prospective application of the composite in photocatalysis, antibacteria and gas sensing.

Experimental and theoretical investigation of the reaction of a 3-amidothiophene derivative with various carbonyl compounds

The reactions of a 3-amidothiophene derivative, which is a partial structure of penthiopyrad, with various carbonyl compounds were investigated. Depending on the carbonyl compound that was used as a reactant, different products (alkenes and bis-products) were obtained from the attack of the carbon at the 2-position of the 3-amidothiophene on the carbonyl compounds. Density functional theory (DFT) calculations revealed that dehydration conditions were important for the first carbonyl addition to shift the reaction toward the product, as the products are more unstable than reactants other than aldehyde. The DFT calculations also suggested that the relative stability of the alkenyl state determined whether the second bis-product formation would proceed; i.e., the relatively unstable disubstituted alkene led to bis-products, and the stable trisubstituted or conjugated alkene yielded alkenyl products.

Chemical ordering as a precursor to formation of orderedδ-UZr2phase: a theoretical and experimental study

A combination of special quasi-random structure (SQS) analysis, density functional theory (DFT) based simulations and experimental techniques are employed in determining the transformation pathway for the disorderedγ-(U, Zr) phase (bcc structure) to transform into the chemically orderedδ-UZr₂phase (C32, AlB₂type structure). A novel Monte-Carlo based strategy is developed to generate SQS structures to study theβ→ωdisplacive phase transformation in A_1-xB_xbinary random alloy. Structures generated with this strategy and using DFT calculations, it is determined that (222)_bccplane collapse mechanism is energetically unfavorable in chemically disordered environment at UZr₂composition. A mechanically and dynamically stable 24 atom SQS structure is derived which serves as a structural model of chemically orderedδ-UZr₂structure. Finally, a thermodynamic basis for the mechanism of theγtoδtransformation has been established which ensures chemical ordering is a precursor to the subsequent displacive transformation to form chemically orderedδ-UZr₂structure.

Solvent-Free Mechanochemical Synthesis of High Transition Biphenyltetracarboxydiimide Liquid Crystals

A series of high temperature alkyl and alkoxy biphenyltetracarboxydiimide liquid crystals have been prepared under ball mill method using solvent-free mechanochemical approach. The thermal properties of the prepared compounds were investigated by deferential scanning calorimetry (DSC) measurements and the textures were identified by polarized optical microscope (POM). The compounds showed smectic mesomorphic behaviour. The results showed the increasing nature of transition temperature Cr-SmC with chain length with increments of the SmC mesophase range. However, the mesophase range of the SmA was decreased with the terminal chain length either for the alkyl or alkoxy terminal groups. Moreover, the DFT theoretical calculations have been conducted give a detailed projection of the structure of the prepared compounds. A conformational investigation of the biphenyl part has been studied. A deep illustration of the experimental mesomorphic behaviour has been discussed in terms of the calculated aspect ratio. A projection of the frontier molecular orbitals as well as molecular electrostatic potential has been studied to show the effect of the polarity of the terminal chains on the level and the gab of the FMOs and the distribution of electrostatic charges on the prepared molecules.

Coordination Behavior of [Cp″2Zr(µ1:1-As4)] towards Lewis Acids

The functionalization of the arsenic transfer reagent [Cp″₂Zr(η^1:1-As₄)] (1) focuses on modifying its properties and enabling a broader scope of reactivity. The coordination behavior of 1 towards different Lewis-acidic transition metal complexes and main group compounds is investigated by experimental and computational studies. Depending on the steric requirements of the Lewis acids and the reaction temperature, a variety of new complexes with different coordination modes and coordination numbers could be synthesized. Depending on the Lewis acid (LA) used, a mono-substitution in [Cp″₂Zr(µ,η^1:1:1:1-As₄)(LA)] (LA = Fe(CO)₄ (4); B(C₆F₅)₃ (7)) and [Cp″₂Zr(µ,η^3:1:1-As₄)(Fe(CO)₃)] (5) or a di-substitution [Cp″₂Zr(µ₃,η^1:1:1:1-As₄)(LA)₂] (LA = W(CO)₅ (2); CpMn(CO)₂ (3); AlR₃ (6, R = Me, Et, ⁱBu)) are monitored. In contrast to other coordination products, 5 shows an η³ coordination in which the butterfly As₄ ligand is rearranged to a cyclo-As₄ ligand. The reported complexes are rationalized in terms of inverse coordination.

Exploration of interaction behavior between spiro[indene-2,2'-[1,3,5]oxathiazine]-1,3-diones and DNA with the help of DFT, molecular docking, and MD simulations

A detailed computational study covering density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulations of some spirocyclic compounds interacting with a B-DNA has been performed. DFT calculations were performed using the B3LYP functional with 6-311++G(d,p) basis set and were used to identify the electrophilic and nucleophilic centers in electrostatic forces. NMR results were in agreement with previous experimental data and approved the reliability of the used method and basis set. The in silico screening results showed that spirocyclic compounds fulfill the Lipinski's rule of five and can be developed as potential oral bioavailable drug candidates. Based on molecular docking results, the binding affinities follow the 4c < 4d < 4a = 4b < 4e < 4g < 4f order and ranged from -8.6 to -9.7 kcal/mol indicating a reasonably favorable interaction between DNA and investigated compounds. The adducts were stabilized by hydrophobic and hydrogen bonding interactions. The MD simulations performed for 100 ns and the results are reported in terms of variables such as root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), center of mass (COM) separation distance between DNA and ligands, intermolecular hydrogen bonds, and radial distribution functions (RDF). The MD simulations demonstrated that compounds 4a and 4d bind into the minor groove of 1BNA and may act as potential biological probes for B-DNA.Communicated by Ramaswamy H. Sarma.

Phosphorus-nitrogen compounds: part 53-synthesis, characterization, cytotoxic and antimicrobial activity, DNA interaction and molecular docking studies of new mono- and dispirocyclotriphosphazenes with pendant arm(s)

Mono-/dispirocyclotriphosphazenes with pendant arm(s) are robust, but they are less investigated inorganic ring systems. In this study, a series of mono (3 and 4)- and dispirocyclotriphosphazenes with 4-chloro-benzyl pendant arm(s) (13-16) was obtained from the Cl exchange reactions of hexachlorocyclotriphosphazene with sodium (N-benzyl)aminopropanoxides (1 and 2). When compound (3) reacted with excess pyrrolidine, morpholine, tetra-1,4-dioxa-8-azaspiro[4,5]decane (DASD) and piperidine, the fully substituted monospirocyclotriphosphazenes (7, 9, 10 and 12) occurred. But, the reactions of 4 with excess piperidine and morpholine produced the gem-piperidino (5)- and morpholino (6)-substituted monospirocyclotriphosphazenes, whereas the reactions of 4 with excess pyrrolidine and DASD gave the fully substituted monospirocyclotriphosphazenes (8) and (11). However, it should be indicated that these derivatives were obtained to be used for the investigation of their spectral, stereogenic and biological properties. The structures of 5, 7 and 14 were determined crystallographically. X-ray data of 5 and 14 displayed that both of compounds were chiral in solid state, and their absolute configurations were assigned as R and RR. Additionally, the antimicrobial activities of phosphazenes were investigated. Minimum inhibitory concentrations, minimal bacterial concentrations and minimum fungicidal concentrations of phosphazenes were determined. The interactions of phosphazenes with plasmid DNA were evaluated by agarose gel electrophoresis. The cytotoxic activities of compounds were studied against L929 fibroblast and DLD-1 colon cancer cells. In addition, density functional theory calculations of 5, 7 and 14 were reported, and their molecular docking studies with DNA, E. coli DNA gyrase and topoisomerase IV were presented.

Insight into electrocatalytic activity and mechanism of bimetal niobium-based oxides in situ embedded into biomass-derived porous carbon skeleton nanohybrids for photovoltaics and alkaline hydrogen evolution

Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm^-2 and Tafel slope (54 mV dec^-1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I₃^-/I^- electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.

Novel 2-Hydroselenonicotinonitriles and Selenopheno[2, 3-b]pyridines: Efficient Synthesis, Molecular Docking-DFT Modeling, and Antimicrobial Assessment

Selenium containing heterocyclic compounds gained great interest as bioactive molecules as of late. This report explores the design, synthesis, characterization, and antimicrobial screening of new pyridine derivatives endowed with selenium moieties. A one-pot multicomponent system with a solvent-free, microwave irradiation environment was employed to afford this series. The spectroscopic techniques were exploited to verify the structures of the synthesized derivatives. Additionally, the agar diffusion method was employed to determine the antimicrobial activity of all the desired compounds. Of all the synthesized molecules, 9b, 12b, 14f, and 16d exhibited well to remarkable antibacterial and antifungal activities. Moreover, derivative 14f demonstrated the most potent antibacterial and antifungal performance. The results were also supported by molecular docking studies, utilizing the MOE (molecular operating environment) which revealed the best binding mode with the highest energy interaction within the binding pocket. Lastly, theoretical DFT calculations were carried out in a gas phase at B3LYP 6-311G (d,p) basis set to predict the molecular geometries and chemical reactivity descriptors. DFT results have been used to illustrate that molecular docking findings and biological activity assessments.

Ruthenium-Catalyzed Enantioselective Propargylic Phosphinylation of Propargylic Alcohols with Phosphine Oxides

The development of transition metal-catalyzed enantioselective propargylic substitution reactions has gained much progress in recent years, however, no successful example with phosphorus-centered nucleophiles has yet been reported until now. Herein, we report the first successful example of ruthenium-catalyzed enantioselective propargylic substitution reactions of propargylic alcohols with diarylphosphine oxides as phosphorus-centered nucleophiles. This synthetic approach provides a new method to prepare chiral phosphorus-containing organic compounds.

Effect of local anesthetic drug procaine hydrochloride on the conformational stability of bovine hemoglobin: Multi-spectroscopic and computational approaches

The interaction between bovine hemoglobin (BHb) and local anesthetic drug procaine hydrochloride (PCH) was examined by spectroscopic and computational studies. Intrinsic fluorescence analysis explored the ground-state complex formation in the binding of PCH with BHb through static quenching mechanism. The binding constants (K_b) are 29.38 × 10³, 22.54 × 10³ and 17.99 × 10³ M^-1 at 288, 298 and 308 K, respectively, and the ratio of BHb:PCH was 1:1 in the interaction mechanism of PCH and BHb. The acquired thermodynamic parameters (ΔH⁰, ΔG⁰ and ΔS⁰) demonstrated that interaction mechanism is spontaneous and enthalpy driven. The van der Waals forces and hydrogen bonding have been played a predominant role in the binding mechanism. The UV-vis spectroscopy validates the ground-state complexation between PCH and BHb and the binding constant (K_b) has been evaluated utilizing Benesi-Hildebrand equation. Fluorescence resonance energy transfer (FRET) results have demonstrated that the distance between donor (BHb) and acceptor (PCH) is very short (2.34 nm) suggesting a significant probability to energy transfer from BHb to PCH. Synchronous fluorescence results revealed that the alteration in the micro-environment of Tyrosine (Tyr) is more than tryptophan (Trp) residues suggesting that PCH molecule is close to Tyr residue. The secondary structure alterations were confirmed by CD, 3-D fluorescence and FT-IR spectroscopic measurements. Moreover, computational analyses further corroborated that PCH molecules are closer to Tyr residues as compared to Trp residues of BHb during the interaction process. The BHb-PCH complexes may contribute to a deeper understanding of the metabolism of drug, blood circulation process and may help to illustrate the relationship between functions and structure of BHb.Communicated by Ramaswamy H. Sarma.

Selenoxide Elimination Triggers Enamine Hydrolysis to Primary and Secondary Amines: A Combined Experimental and Theoretical Investigation

We discuss a novel selenium-based reaction mechanism consisting in a selenoxide elimination-triggered enamine hydrolysis. This one-pot model reaction was studied for a set of substrates. Under oxidative conditions, we observed and characterized the formation of primary and secondary amines as elimination products of such compounds, paving the way for a novel strategy to selectively release bioactive molecules. The underlying mechanism was investigated using NMR, mass spectrometry and density functional theory (DFT).

Chemical stability of caesium iodide deposits in air/steam atmosphere

Iodine compounds that may be released in case of severe nuclear accident will have important radiotoxicity if they are disseminated in air. One of the most important iodine species is CsI that is deposited on the surfaces of the reactor coolant system. However, depending on the conditions, CsI can volatilize or react with oxidants to produce I_2(g). Theoretical and experimental studies demonstrate that the oxidation of iodide depends on the temperature and in the presence of oxidants in the gas. It is also slightly influenced by the crystallinity of the CsI particles and the nature of the support. In case of a high temperature deposition, the iodine release started at temperature lower than 300 °C. For the CsI vapour and aerosol depositions, the iodine is detected only at temperature above 450 °C and become very important above 550 °C.