Mechanism Insights of Ethane C–H Bond Activations by Bare [Fe^IIIO]⁺: Explicit Electronic Structure Analysis

Alkane C–H bond activation by various catalysts and enzymes has attracted considerable attention recently, but many issues are still unanswered. The conversion of ethane to ethanol and ethene by bare [Fe^IIIO]⁺ has been explored using density functional theory and coupled-cluster method comprehensively. Two possible reaction mechanisms are available for the entire reaction, the direct H-abstraction mechanism and the concerted mechanism. First, in the direct H-abstraction mechanism, a direct H-abstraction is encountered in the initial step, going through a collinear transition state C···H···O–Fe and then leading to the generation of an intermediate Fe–OH bound to the alkyl radical weakly. The final product of the direct H-abstraction mechanism is ethanol, which is produced by the hydroxyl group back transfer to the carbon radical. Second, in the concerted reaction mechanism, the H-abstraction process is characterized via overcoming four/five-centered transition states ^6/4TSH_c5 or ⁴TSH_c4. The second step of the concerted mechanism can lead to either product ethanol or ethene. Moreover, the major product ethene can be obtained through two different pathways, the one-step pathway and the stepwise pathway. It is the first report that the former pathway starting from ^6/4IM_c to the product can be better described as a proton-coupled electron transfer (PCET). It plays an important role in the product ethene generation according to the CCSD­(T) results. The spin–orbital coupling (SOC) calculations demonstrate that the title reaction should proceed via a two-state reactivity (TSR) pattern and that the spin-forbidden transition could slightly lower the rate-determining energy barrier height. This thorough theoretical study, especially the explicit electronic structure analysis, may provide important clues for understanding and studying the C–H bond activation promoted by iron-based artificial catalysts

Versatile Method to Expand the Morphology Library of Block Copolymer Solution Self-Assemblies with Tubular Structures

Self-assembly of block copolymers (BCPs) in solution is a powerful technology to achieve a broad range of structures, such as spheres, cylinders, vesicles, and other hierarchical structures. However, the BCP self-assembly library is limited, especially with respect to tubular structures. Here we show a versatile strategy to expand the morphology library of block copolymer solution self-assemblies with tubular structures (including tubular dumbbells and tubules) via self-assembly of the most common diblock copolymers P4VP-<i>b</i>-PS BCPs in methanol. No special chemistry is needed in this strategy, which proves the universality of this method. The novelty of the strategy is to keep the BCPs both highly asymmetric and with very high molecular weight. The underlying formation mechanism and kinetics of these tubular structures were elucidated. The prepared tubular structures expand the structure library of BCP solution self-assemblies and open up a new avenue for the further applications of a variety of tubular materials

Synthesis of Electron-Deficient Borinic Acid Polymers with Multiresponsive Properties and Their Application in the Fluorescence Detection of Alizarin Red S and Electron-Rich 8‑Hydroxyquinoline and Fluoride Ion: Substituent Effects

Electron-deficient borinic acid monomers and corresponding polymers were synthesized with different substituents via a one-pot reaction of Grignard reagents with trimethoxyborane and reversible addition–fragmentation chain transfer polymerization, respectively. Further investigations of substituent effects of borinic acid polymers (PBAs) were carried out, indicating that the thermoresponsive properties of PBAs benefit from the increase of steric hindrance of PBA substituent, while the binding affinity of PBAs with Alizarin Red S, 8-hydroxyquinoline (HQ), and fluoride ion decreases with the increase of steric hindrance of substituent. Attributed to the strong dative N → B bond and the strongly luminescent boron quinolate, the application of phenyl PBA for fluorescence detection of HQ is realized with high sensitivity at the ppm level. These results therefore confirm that borinic acid-containing polymer is a new type of stimuli-responsive polymer in the field of thermoresponsiveness over a wide temperature range and chemical sensor for diol and electron-rich compounds

A Series of Cd(II) and Zn(II) Coordination Polymers with Helical Subunits Assembled from a Versatile 3‑(4-hydroxypyridinium-1-yl) Phthalic Acid and N‑Donor Ancillary Coligands

A series of coordination polymers with various helical subunits, namely, [Cd­(L)­(CH₃OH)­(H₂O)]_<i>n</i> (<b>2</b>), {[Cd­(L)­(1,4-bbi)]·(H₂O)}_<i>n</i> (<b>3</b>), {[Cd­(L)­(<i>m</i>-bix)­(H₂O)]·(H₂O)₂}_<i>n</i> (<b>4</b>), [Zn­(L)­(4,4′-bpy)_0.5]_<i>n</i> (<b>5</b>), and [Zn­(L)­(bpp)]_<i>n</i> (<b>6</b>) (H₂L = 3-(4-hydroxypyridinium-1-yl) phthalic acid; PA = phthalic acid, a part of 3-(4-hydroxypyridinium-1-yl) phthalic acid)), have been hydro­(solvo)­thermally synthesized through the reaction of 3-(4-hydroxypyridinium-1-yl) phthalic acid with divalent zinc and cadmium salts in the presence or absence of N-donor ancillary coligands (1,4-bbi = 1,1′-(1,4-butanediyl)­bis­(imidazole), <i>m</i>-bix = 1,3-bis­(imidazol-1-ylmethyl)­benzene, 4,4′-bpy = 4,4′-bipyridine, bpp = 1,3-bi­(4-pyridyl)­propane). As a result of various coordination modes of the versatile 3-(4-hydroxypyridinium-1-yl) phthalic acid and different coligands, these compounds exhibit structural diversity. Compound <b>2</b> displays a layered structure containing two kinds of (Cd–L)_<i>n</i> and (Cd–PA)_<i>n</i> helical chains. Compound <b>3</b> features a 3D supramolecular framework embodying a type of supramolecular helical chain. Compound <b>4</b> exhibits a metal–organic ribbon structure with two kinds of helical chains. Compound <b>5</b> features a 3D architecture in which a 1D lemniscate shape pseudo meso-helix chain is observed. Compound <b>6</b> exhibits a 2D achiral layer in which the 1D (Zn–bpp)_<i>n</i> helical chains are alternately arranged in a right- and left-handed sequence. These compounds have been characterized by powder X-ray diffractions (PXRD) and thermal gravimetric analyses (TGA). In addition, their photochemical properties have also been investigated

Histoire d'une faculté sous le prisme de la dérision étudiante

L'ouvrage est une analyse des textes des dix revues satiriques produites par le Cercle des étudiants en médecine de l'Université libre de Bruxelles de 1944 à 2014.Le parti a été pris de considérer ces revues comme un témoignage du regard que les étudiants d'une époque donnée ont porté sur leur professeurs, leur faculté, leur hôpitaux de stages et, d'une manière plus générale, sur leur environnement social et politique.L'analyse des revues est ainsi un moyen de suivre l'actualité de la faculté de médecine et de ses hôpitaux, en tous cas, celle qui a frappé les étudiants.Elle permet aussi d'identifier les quelques personnalités qui, aux yeux des étudiants, ont marqué le vie de la faculté, soit par leur côté particulièrement caricatural, soit par leur rôle politique et de ressentir la perception par les étudiants de ce que fut pour eux les problématiques les plus critiques.info:eu-repo/semantics/publishe

Proteomic Analysis of Endothelial Lipid Rafts Reveals a Novel Role of Statins in Antioxidation

As inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, statins have pleiotropic vascular-protective effects, such as anti-inflammatory and antioxidative effects. We investigated the short-term beneficial effects of statins on modulating the translocation of lipid-raft-related proteins in endothelial cells (ECs). Human umbilical vein ECs were treated with atorvastatin for 30 min or 2 h; lipid-raft proteins were isolated and examined by quantitative proteome assay. Functional classification of identified proteins in lipid rafts revealed upregulated antioxidative proteins; downregulated proteins were associated with inflammation and cell adhesion. Among proteins verified by Western blot analysis, endoplasmic reticulum protein 46 (ERp46) showed increased level in lipid rafts with atorvastatin. Further, atorvastatin inhibited the activation of membrane-bound NADPH oxidase in both untreated and angiotensin II-treated ECs, as shown by reduced reactive oxygen species production. Co-immunoprecipitation and immunofluorescence experiments revealed that atorvastatin increased the association of ERp46 and Nox2, an NADPH oxidase isoform, in lipid rafts, thereby inhibiting Nox2 assembly with its regulatory subunits, such as p47phox and p67phox. Our results reveal a novel antioxidative role of atorvastatin by promoting the membrane translocation of ERp46 and its binding with Nox2 to inhibit Nox2 activity in ECs, which may offer another insight into the pleiotropic functions of statins