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Mise en œuvre de différents plateformes hélicoïdales supramoléculaires pour la catalyse asymétrique
No full textAbstract: Triarylamine trisamide (TATA) monomers have been functionalized in order to provide a new class of helical supramolecular polymers with unique catalytic and chiral properties. A wide range of molecular targets including TATA monomers functionalized with phosphine (ligand for catalysis) or (thio)urea moieties, and non-functionalized monomers (chiral monomers “sergeants”, achiral monomers “soldiers” and additives) have been prepared via a multi-step synthesis. Preliminary studies demonstrated that most of these monomers form hydrogen-bonded self-assemblies in apolar solvents. Two strategies of chirality induction have been used to yield homochiral co-assemblies. The first one consists in using the “sergeants-and-soldiers” (S&S) effect to obtain homochiral TATA coassemblies by mixing chiral and achiral monomers; copolymers functionalized at their periphery by phosphine moieties proved to be enantioselective for the copper-catalyzed hydrosilylation of 4-nitroacetophenone. The selectivity is modest but stems exclusively from the supramolecular nature of the assemblies. One “sergeant', (S)-TPA, exbibits a particular phenomenon: the dichroic signal exhibited by its self- or coassemblies inverts as a function of the temperature. In the copper-catalyzed hydrosilylation reaction, no inversion of selectivity has been observed for the helical catalyst embedding the (S)-TPA monomer. The second strategy consists in inducing the chirality to the supramolecular assemblies by complexing the peripheral (thio)urea moieties with a chiral anion. The couple constituted of the TATA (thio)urea monomer and the TRIP anion has been studied into detail in toluene. It forms hydrogen-bonded stacks and can be used as a supramolecular “sergeant' with many “soldiers” thanks to the orthogonality between the amide and urea functions. This approach also allows to induce the chirality to pre-formed achiral copolymers. The use of a supramolecular “sergeant” provides higher enantioselectivity in catalysis than the conventional strategy via the S&S effect.Keywords: supramolecular polymers, triarylamine trisamide monomers, hydrogen bonds, “sergeants-and-soldiers” effect, helicity inversion, chirality induction, copper-catalyzed hydrosilylation.Des monomères de type triarylamine trisamide (TATA) ont été fonctionnalisés en vue de fournir une nouvelle classe de polymères supramoléculaires hélicoïdaux aux propriétés chirales et catalytiques originales. Une large gamme de molécules cibles incluant des monomères TATA fonctionnalisés avec des groupements phosphine (ligand pour la catalyse), ou (thio)urée et des monomères non fonctionnalisés (monomères chiraux « sergents », monomères achiraux « soldats » et additifs) ont été préparées via une synthèse multi-étape. Les études préliminaires ont démontré que la plupart de ces monomères forment des homoassemblages par liaisons hydrogène dans les solvants apolaires. Deux stratégies d'induction de chiralité ont alors été mises en œuvre pour construire des copolymères homochiraux. La première a consisté à utiliser l'effet « sergents-et-soldats » (S&S) pour obtenir des coassemblages TATA homochiraux en mélangeant des monomères chiraux et achiraux ; les copolymères fonctionnalisés en périphérie avec des motifs phosphine ont montré une énantiosélectivité pour l'hydrosilylation de la 4-nitroacétophénone catalysée au cuivre. Cette sélectivité est modeste mais provient exclusivement de l'assemblage supramoléculaire. Un « sergent », le (S)-TPA, montre un phénomène particulier : le signal dichroïque de ses auto- ou coassemblages hélicoïdaux s'inverse en fonction de la température. Dans la réaction d'hydrosilylation au cuivre, l'inversion de sélectivité du catalyseur hélicoïdal incorporant (S)-TPA n'a pas pu être mis en évidence. La seconde stratégie a consisté à induire la chiralité aux assemblages supramoléculaires par complexation du motif (thio)urée avec des anions chiraux. Le couple constitué du monomère TATA (thio)urée / anion TRIP a été étudié en détail dans le toluène. Ce complexe forme des empilements par liaisons hydrogène et peut être utilisé comme « sergent » supramoléculaire avec de nombreux soldats grâce à l'orthogonalité des fonctions amide et (thio)urée. Cette approche permet d'induire la chiralité in situ à partir d'un copolymère achiral déjà formé. L'utilisation d'un « sergent » supramoléculaire permet d'obtenir une meilleure énantiosélectivité en catalyse que la stratégie conventionnelle via l'effet S&S.Mots-clés : polymères supramoléculaires, monomères triarylamine trisamide, liaisons hydrogène, effet « sergents-et-soldats », inversion d'hélicité, induction de chiralité, hydrosilylation au cuivre
« Layered double hydroxide-assisted calcium tungstate (scheelite) dissolution »
No full textInternational audienceThis work is part of the VARTA project (VAlorization and Remediation of TAillings of W-ores) which aims to reduce the environmental impact of mine tailings while reducing European dependence on the critical resources of tungsten. The goal is to develop a green hydrometallurgical process to recover the valuable metals (tungsten) and manage toxic elements (arsenic in particular) present in a tungsten mine located in the French Pyrenees.First part of the study focuses on the solubilization of a pure scheelite mineral (CaWO4) to extract W(VI) using a Layered Double Hydroxide (LDH), an anion-exchanger material with high surface area. LDH is known for its environmental-friendly composition, high anion-exchange capacities, non-toxicity, ease of synthesis and its compositional flexibility; different anions can be intercalated in between the interlamellar space to extract a specific metal. It is widely studied for environmental remediation due to its low carbon footprint. The LDH, synthesized by the copreciptation method, is of Mg-Al-CO3 type. The solubility of CaWO4 was determined as a function of pH and a value as low as 2.10-5 mol/L at pH 5 was found, in agreement with literature. When LDH is added to the suspension, the dissolution is dramatically increased, showing that an anion exchange effectively takes place between carbonate and heptatungstate ions. We confirmed this mechanism by performing in situ real time Fourier-Transform infrared ATR spectroscopy. In a second stage, the anion exchange reaction being reversible, the stripping of W from the scheelite concentrated tailing via the LDH would take place in alkaline conditions and in a single step, reducing the process footprint. The lability of As present in the tailings will be assessed to prevent the contamination of the process effluent. Literature studies show that Fe-oxyhydroxide has a strong affinity toward As(V) which could prevent its mobilization under chemical conditions of the tungsten extraction process
Perspective sur l'utilisation prospective de l'IA dans la prédiction de la structure protéique
No full textInternational audienceAlphaFold2 (AF2) and RoseTTaFold (RF) have revolutionized structural biology, serving as highly reliable and effective methods for predicting protein structures. This article explores their impact and limitations, focusing on their integration into experimental pipelines and their application in diverse protein classes, including membrane proteins, intrinsically disordered proteins (IDPs), and oligomers.In experimental pipelines, AF2 models aid X-ray crystallography in resolving the phase problem, while complementarity with Mass Spectrometry and NMR data enhances structure determination and protein flexibility prediction. Predicting the structure of membrane proteins remains challenging for both AF2 and RF due to difficulties in capturing conformational ensembles and interactions with the membrane. Improvements in incorporating membrane-specific features and predicting the structural effect of mutations are crucial. For Intrinsically Disordered Proteins, AF2's confidence score (pLDDT) serves as a competitive disorder predictor, but integrative approaches with molecular dynamics simulations or hydrophobic cluster analyses are advocated for accurate dynamics representation. AF2 and RF show promising results for oligomeric models, outperforming traditional docking methods, with AlphaFold-Multimer showing improved performance, however, somes caveats remain in particular for membrane proteins. Real-life examples demonstrate AF2's predictive capabilities in unknown protein structures, but models should be evaluated for their agreement with experimental data. Furthermore, combining AF2 models with molecular dynamics simulations can be used complementarily. In this perspective we propose a "wish list" for improving deep learning-based protein folding prediction models, including using experimental data as constraints and modifying models with binding partners or post-translational modifications. Additionally, a meta-tool for ranking and suggesting composite models is suggested, driving future advancements in this rapidly evolving field.AlphaFold2 (AF2) et RoseTTaFold (RF) ont révolutionné la biologie structurale, servant de méthodes très fiables et efficaces pour prédire les structures protéiques. Cet article explore leur impact et leurs limites, en se concentrant sur leur intégration dans des pipelines expérimentaux et leur application dans diverses classes de protéines, y compris les protéines membranaires, les protéines intrinsèquement désordonnées (IDP) et les oligomères.Dans les pipelines expérimentaux, les modèles AF2 aident la cristallographie radiographique à résoudre le problème de phase, tandis que la complémentarité avec les données de spectrométrie de masse et RMN améliore la détermination de la structure et la prédiction de la flexibilité des protéines. Prédire la structure des protéines membranaires reste difficile pour AF2 et RF en raison de difficultés à capturer des ensembles conformationnels et des interactions avec la membrane. Des améliorations dans l'incorporation de caractéristiques spécifiques à la membrane et la prédiction de l'effet structurel des mutations sont cruciales. Pour les Protéines Intrinsèquement Désordonnées, le score de confiance d'AF2 (pLDDT) sert de prédicteur de désordre compétitif, mais des approches intégratives avec des simulations de dynamique moléculaire ou des analyses de cluster hydrophobes sont préconisées pour une représentation dynamique précise. AF2 et RF montrent des résultats prometteurs pour les modèles oligomériques, surpassant les méthodes d'amarrage traditionnelles, avec AlphaFold-Multimer montrant des performances améliorées, cependant, certaines mises en garde subsistent en particulier pour les protéines membranaires. Des exemples réels démontrent les capacités prédictives de l'AF2 dans des structures protéiques inconnues, mais les modèles devraient être évalués pour leur accord avec les données expérimentales. De plus, la combinaison de modèles AF2 avec des simulations de dynamique moléculaire peut être utilisée de manière complémentaire.Dans cette perspective, nous proposons une "liste de souhaits" pour améliorer les modèles de prédiction du repliement des protéines basés sur l'apprentissage profond, y compris l'utilisation de données expérimentales comme contraintes et la modification de modèles avec des partenaires de liaison ou des modifications post-traductionnelles. De plus, un méta-outil pour classer et suggérer des modèles composites est suggéré, ce qui conduira à de futures avancées dans ce domaine en évolution rapide
Passivation and Localized Corrosion Resistance of Al0.3Cr0.5Fe2MoxNi1.5Ti0.3 Compositionally Complex Alloys: Effect of Mo Content
No full textInternational audienceAl0.3Cr0.5Fe2MoxNi1.5Ti0.3 (x = 0, 0.05, 0.15) FCC+L21 compositionally complex alloys are investigated using electrochemical and surface science methods in 0.1 M Na2SO4 and 0.1 M NaCl at pH 4 and 10. Mo is mainly found in the FCC phase and amplifies Al and Ti partitioning. The passive film is enriched in Cr(III), Ti(IV), Mo(IV)/Mo(VI), and (at pH 4) Al(III) with elemental fates tracked during film formation and dissolution. Mo presence does not enhance Cr or Ni passivation, instead promoting Ti(IV). Pitting and repassivation potentials increase at higher Mo concentrations, suggesting improved resistance to localized corrosion often initiated at FCC-L21 interfaces
Inorganic-polymer composite materials at the positive electrode of Li all solid-state batteries
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Operando Entropy Profiling of Sodium-Ion Batteries via Optical Fiber Sensing for Thermal Management and Ageing Monitoring
No full textInternational audienceBatteries are essential for the electrification of transport and the replacement of internal combustion engines. Thermodynamics was largely established with the development of the engines, and this knowledge has been applied to batteries for years. In particular, entropy profiles are sensitive to structural changes and are useful for diagnosing and understanding battery ageing. However, entropy profiling of aged batteries is mainly limited to the potentiometric method, which makes the technique in situ and time-consuming. Herein, we rely on optical fiber calorimetry to perform operando entropy profiling of commercial sodium-ion cells. Firstly, we directly compare the entropy profile of sodium-ion Na 3 V 2 (PO 4 ) 2 F 3 /hard carbon (NVPF/HC) chemistry against those of commercialized lithium-ion chemistries, highlighting the uniqueness of NVPF/HC chemistry in battery thermal management. Operando entropy profiling of NVPF/HC chemistry further elucidates the structural degradations that take place during cycling and provide features that can be important indicators of the battery’s state of health. This work reintroduces thermodynamic analyses as a valuable tool for batteries and spotlights the new horizons offered by the convergence of battery sensing, thermodynamics, and other disciplines
Incorporation of halogen (Cl, Br, I) in Li-P-S-O system for exploring new sulfide solid electrolytes with high conductivity and superior electrochemical performance in solid-state batteries
No full textInternational audienceThe solid electrolytes (SEs) with high conductivity and better stability against lithium metal are most important requirements for successful commercialization of solid state battery (SSB) technology. Therefore, in the search for new SEs with above mentioned qualities, halogen elements (Cl, Br, I) are explored in Li-P-S-O system to prepare Li10GeP2S12 (LGPS) structured SEs. In all prepared SEs, Li3.3PS3.7O0.3Br0.1 and Li3.3PS3.7O0.3I0.1 compositions show highest conductivities of 0.77 mS cm -1 and 0.93(≈ 1.0) mS cm -1 at 25 °C. These compounds also show superior stability against lithium metal in symmetric cells as well as in full SSB cells tested with LiNi0.8Co0.15Al0.05O2 (NCA) cathode and graphite anode. The instability of sulfide based SEs in ambient environment is a major issue, whereas, our prepared compounds Li3.3PS3.7O0.3Br0.1 and Li3.3PS3.7O0.3I0.1 show 5 times higher stability in ambient environment conditions as compared to non-doped Li3.2PS3.7O0.3. In-situ EIS study performed on full SSB as prepared and after chargedischarge cycles have revealed the contribution of interfacial reactions on impedance. The study also shows higher interfacial resistances in full SSB with Li-metal anode as compared graphite anode. At the end, post-mortem analysis of full SSB cell as well as SE-Li interfacial study was conducted by SEM and elemental mapping to observed the changes in the electrodes and electrolyte before and after charge-discharge cycles. Therefore, the present work reports sulfide based new SEs with high conducting and better stability, and their interfacial studies
Understanding and simulating mechanochromism in dye-dispersed polymer blends: from atomistic insights to macroscopic properties
No full textInternational audienceIn this work, we propose a computational protocol enabling the simulation of mechanochromic responses in dye-dispersed polymer blends. The main objective is the modeling of the molecular-level structural changes responsible for the modulation of the photophysical properties that lead to the mechanochromic phenomenon. In this demonstrative study we focus on predicting the changes in optical absorption displayed by a model system consisting of a dimer of a tetraphenylethylene derivative dispersed in a polyethylene matrix. The blend is subjected to an external stimulus that causes a modulation of the polymer matrix density that translates, in turn, into the emergence of specific mechanical constraints on the optically active dimers. The accurate description of this phenomenon requires the reliable sampling of the dimer configurations induced by the interaction with the matrix under stress. These molecular geometries are associated with modified electronic structures that confer novel absorption responses to the dispersed dyes.Methods : In the present contribution, the sampling of these structures is achieved through classical molecular dynamics (MD) simulations including a model element to apply an anisotropic mechanical force. This element allows the microscopic modeling of the chains and dyes structural rearrangements under stress. After the sampling, we compare the results of two approaches for the prediction of the optical response: i) the calculation of a mean response from a statistical average over quantum chemical calculations on the sampled MD structures and ii) a prediction via a more expensive hybrid scheme allowing the relaxation of the sampled molecular geometries in presence of the matrix constraints
Hydrogen autotransfer with alcohols for alkylations
No full textInternational audienceDespite the advancements enabled by organometallic complexes in organic synthesis, which have led to innovative transformations and tackled issues related to waste and atom economy, concerns have arisen regarding the expense of noble metals and ligands. Expanding on previous work, iron and ruthenium complexes with cyclopentadienone ligands, akin to Knölker catalysts, have demonstrated remarkable efficiency in bond reduction and alkylations using alcohols as proelectrophiles. This review delves into novel alkylation methodologies involving hydrazides or ketones, inventive dehydrogenative coupling reactions yielding highly functionalized structures, and the optimization of metal-catalysed reactions through organometallic complex modifications. Metal-catalysed hydrogen auto-transfer, or hydrogen borrowing,offers a sustainable approach to forming C-C or C-N bonds from eco-friendly alcohols. While transitioning the diaminocyclopentadienone tricarbonyl ligand to first-row transition metals under mild conditions remains challenging, recent findings indicate that blue-light irradiation at room temperature can facilitate this transformation without external photosensitizers. Thus, while conventional studies without light remain demanding, light's additional role can enhance this research domain, where such catalysts may play a pivotal role. Moreover, further exploration of asymmetric catalysis is warranted. This review aims to impact not only the community working with Knölker derivative catalysts but also organic chemists for potential applications and inorganic chemists for catalyst development, ultimately striving to generate catalystsfor asymmetric syntheses. Additionally, its sustainability makes it relevant for chemists dedicated to green chemistry
