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Room-Temperature Rh(I)-Catalyzed P(III)-Directed C–H Bond Alkylation: Enhanced Reactivity through Ligand Acceleration
No full textInternational audienceDespite the potential of Rh(I)-catalyzed trivalent phosphorus-directed C–H functionalizations to diversify phosphorus-containing molecules, the requirement for harsh reaction conditions has limited its broader application. In this study, we introduce a ligand-accelerated catalysis approach that enables room-temperature C–H bond alkylation of biarylphosphines using a Rh(I) catalyst. Through kinetic investigation, we identified tris(4-trifluoromethylphenyl)phosphine as a privileged ligand that significantly enhances overall processes including catalyst stability and regeneration. Our NMR mechanistic studies revealed the formation of a Rh–H intermediate, providing direct evidence for an oxidative addition pathway. This work expands the utility of Rh(I)-catalyzed C–H functionalization under mild conditions and lays the groundwork for further development of ligand-accelerated strategies in other challenging catalytic processes, particularly those involving strong σ-donor directing groups, holding significant potential to broaden the chemical space of phosphorus-based compounds, with diverse applications
Negative gas adsorption transitions and pressure amplification phenomena in porous frameworks
No full textInternational audienceNanoporous solids offer a wide range of functionality for industrial, environmental, and energy applications. However, only a limited number of porous materials is responsive, i.e. the nanopore size dynamically alters its size and shape as a response to external stimuli such as temperature, pressure, light or the presence of specific molecular stimuli adsorbed inside the voids deforming the framework. Adsorption-induced structural deformation of porous solids can result in unique counterintuitive phenomena. Negative Gas adsorption (NGA) is such a phenomenon which describes the spontaneous release of gas from an “overloaded” nanoporous solid via adsorption-induced structural contraction leading to a total pressure amplification (PA) in a closed system. Such pressure amplifying materials may open new avenues for pneumatic system engineering, robotics, damping, or micromechanical actuators. In this review we illustrate the discovery of NGA in DUT-49, a mesoporous metal-organic framework (MOF), and the subsequent examination of conditions for its observation leading to a rationalization of the phenomenon. We outline the decisive experimental and theoretical methods development required to establish the mechanism of NGA and derive key criteria for observing NGA in other porous solids. We demonstrate the application of these design principles in a series of DUT-49-related model compounds of which several also exhibit NGA. Furthermore, we provide an outlook towards applying NGA as a pressure amplification material and discuss possibilities to discover novel NGA materials and other counterintuitive adsorption phenomena in porous solids in future
Effect of annealing on oxidation during solid-state recycling of aluminium chips
No full textInternational audienceSolid-state recycling of AA6060 chips by hot extrusion is investigated. This study focuses on understanding the formation of oxides at the former chip boundaries, that could limit sound welding of the chips. The impact of the time and temperature of the annealing treatment prior to extrusion is analysed ex-situ by coupling TGA and XPS. The results show that for temperatures above 400 °C, oxidation kinetics follows a parabolic law. On top of the 10 nm Al2O3 native oxide layer, MgO islands first grow up to a thickness of 60 nm until reaching a covering rate of about 90 %, and then thicken. Limiting time and temperature of the annealing treatment is favourable to reduce oxide formation. During extrusion of the pre-compacted annealed chips, a new oxygen increase is measured. It results in larger oxides, with a thickness between 165 and 300 nm, depending on the annealing conditions. This enhanced oxidation combined with an increase of chip surface results in a covering rate of prior chip boundaries of 25 %. Extrusion was described into two sub-steps: first, densification of the chips in the billet occurs, during which oxides increase their covering rate if it wasn't yet saturated, or thicken; second, an elongation of the billet where oxides mostly grow on newly formed surfaces. A model using results from TGA, XPS, total oxygen concentration and TEM imaging is developed to quantitatively describe the sub-steps, to propose a complete description of the oxide network and to guide future selection of processing parameters
A machine learning tool to investigate lithium-ion battery degradation under real automotive conditions
No full textInternational audienceIn electric vehicle applications, operating conditions heavily affect the battery cell lifetime and cost. The aging process of Lithium-ion Battery (LiB) cells is influenced by numerous interrelated stress factors, making it challenging to predict aging levels accurately and develop effective mitigation strategies. Including machine learning (ML) models in the Battery Management System (BMS) enables real time analysis and informed decision-making process based on multi-factorial data. To limit degradation of LiB cells, it is crucial to scrutinize the effect of each stress factor and explore interdependencies. We propose an ML model designed to classify aging cycling/storing conditions and protocols based on LiB cell capacity degradation. The proposed model is intended for implementation in the BMS and distinguishes itself through training on industrial datasets. The consideration of large number of features and their interactions with a balanced dataset results in greater interpretability of our model. We further advance the model by developing an interactive application leveraging ML outcomes, allowing for real time navigation over the space of parameters
Investigating the effect of particle size distribution and complex exchange dynamics on NMR spectra of ions diffusing in disordered porous carbons through a mesoscopic model
No full textInternational audienceIon adsorption and dynamics in porous carbons are crucial for many technologies, such as energy storage and desalination. Nuclear magnetic resonance (NMR) spectroscopy is a key method to investigate such systems thanks to the possibility of distinguishing adsorbed (in-pore) and bulk (ex-pore) species in the spectra. However, the large variety of magnetic environments experienced by the ions adsorbed in the particles and the existence of dynamic exchange between the inside of the particles and the bulk renders the interpretation of the NMR experiments very complex. In this work, we optimise and apply a mesoscopic model to simulate NMR spectra of ions in systems where carbon particles of different sizes can be considered. We demonstrate that even for monodisperse systems, complex NMR spectra, with broad and narrow peaks, can be observed. We then show that the inclusion of polydispersity is essential to recover some experimentally observed features, such as the co-existence of peaks assigned to in-pore, exchange and bulk species. Indeed, the variety of exchange rates between in-pore and ex-pore environments, present in experiments but not taken into account in analytical models, is necessary to reproduce the complexity of experimental NMR spectra
Benchmarking density functional approximations in nonadiabatic dynamics: trans-cis isomerization in retinal model
No full textInternational audienceAn exhaustive benchmark of density functional approximations (DFAs) for nonadiabatic dynamics is reported on the trans-cis photoisomerization of the protonated Schiff base 3 (PSB3), which presents numerous challenges for time-dependent density functional theory (TD-DFT). We introduce a rigorous protocol for benchmarking DFAs for nonadiabatic dynamics regarding the initialization, the dynamics, and its evaluation. Different families of DFAs were compared with a high-level reference, highlighting that electronic populations are an unsuitable metric for evaluating the accuracy of dynamics. We found that several local functionals showed the best agreement of the population decay with the reference RMS-CASPT2, but strictly passed through a deactivation channel dominated by a single-bond torsion that is not accessible in the reference and in the literature. While using 100% Hartree-Fock exchange in the functional yields the only correct isomerization behaviour, the time scales and quantum yields are far off the reference values, due to an artificial local minimum being predicted along the wrong torsion coordinate. Static energy scans suggest that this issue can be circumvented by double hybrid functionals, in particular those balancing nonlocal exchange and correlation combined with range-separation. Indeed, they predict energy profiles along the two torsion coordinates in close agreement with the RMS-CASPT2 reference. This emphasizes the impact these DFAs will have on the field of nonadiabatic dynamics once analytical gradients are introduced
Mechanochemical Approach for Metal‐Free Regioselective C5‐Sulfenylation of Imidazo[2,1‐b]thiazoles
No full textInternational audienceThe development of sustainable and selective methodologies for heterocyclic functionalization remains a key challenge in organic synthesis. In this study, we report a novel, metal‐free bis(trifluoroacetoxy)iodo]benzene (PIFA)‐mediated strategy for the regioselective C5‐sulfenylation of imidazo[2,1‐b]thiazoles using aryl methyl sulfides under mechanochemical conditions. This solvent‐free approach offers a rapid, efficient, and environmentally friendly alternative to current methods, achieving yields of up to 86% while completely avoiding hazardous solvents. The method exhibits broad substrate scope, with tolerance to both electron‐donating and electron‐withdrawing functional groups. This mechanochemical strategy provides a valuable synthetic tool for the functionalization of imidazo[2,1‐b]thiazole scaffold, with potential applications in medicinal and materials chemistry
Catalytic Silylation of Alkynyl C(sp)–H Bonds with tert ‐Butyl‐Substituted Silyldiazenes
No full textInternational audienceThe deprotonative silylation of terminal alkynes constitutes one of the most privileged strategies to prepare alkynylsilanes owing to the relatively high acidity of C(sp)–H bonds. While the key deprotonation step is usually mediated by stoichiometric amounts of strong Brønsted bases (e.g., n BuLi) followed by the trapping of the corresponding acetylide with electrophilic silylating reagents, such a sequence can also be transposed to a catalytic regime through pro‐base strategies. We herein demonstrate that N ‐ tert ‐butyl‐ N ’‐silyldiazenes ( t Bu–N = N– Si ) widen the repertoire of silylated pro‐bases that can be used to promote the silylation of a range of terminal alkynes. These reactions are initiated with only catalytic amounts of inexpensive potassium hydroxide, proceed rapidly at room temperature, exhibit broad scope, and allow seamless one‐pot integration with downstream transformations of alkynylsilane products
N-heterocyclic carbenes exchange on gold nanoparticles
No full textInternational audienceN-heterocyclic carbenes (NHC) are neutral species containing a divalent carbon atom, which can be stabilized when bounded to a metal. Used as ligands in organometallic chemistry for many years, they have for some years gain interest as surface ligands for metal nanoparticles and surfaces. In addition to their high functional modularity, their main advantage is likely their capability to form strong M-C bonds, which can sustain quite harsh conditions. Actually, in several reports, NHC have been shown to perform better than thiols, the ligands classically used to stabilize gold nanoparticles.Two types of NHC have been mainly used to stabilize gold nanoparticles. The most studied one is based on the 1,3-imidazol-2-ylidene scaffold (ImNHC), which derived from imidazoliums. More recently, mesoionic carbenes (MICS), based 1,2,3-triazol-5-ylidene scaffold, have also been explored.Full exchange of sacrificial surface ligands, eg. thioether, by NHC have been one of the first method reported to prepare NHC stabilized gold nanoparticles, following a top-down approach. But partial exchange of NHC ligands by other NHC ligands to obtain gold nanoparticles stabilized by two different ligands has so far remained undocumented. Yet, such strategy yields mixed ligands AuNPs, which are valuable tools for expanding the utility and fine tuning the properties of nanoparticles, such as stability, functionality and interactions with the surrounding medium.The practicality and efficiency of various exchange strategies involving the reaction of NHC stabilized gold nanoparticles with imidazolium, triazolium, in-situ generated free NHC or NHC-Au(I) complexes has therefore been evaluated. Solution NMR was used to monitor the extend of reaction and identify possible exchange pathways. XPS was used on the isolated gold nanoparticles to quantify the exchange ratio in relation with the experimental conditions
Gold Nanoparticle-Driven Phenylketonuria Monitoring via Colorimetric Biosensing of Phenylalanine
No full textInternational audiencePhenylalanine has long been recognized as a reliable biomarker for the diagnosis and monitoring of phenylketonuria (PKU), a rare genetic disease characterized by the impairment of phenylalanine hydroxylase. As part of the current efforts toward the design of point-of-care devices for the day-to-day management of PKU, we set up a coupled enzymo–plasmonic assay of phenylalanine based on the combination of the nicotinamide adenine dinucleotide (NAD+)-dependent enzyme phenylalanine dehydrogenase and gold nanoparticles to visually detect physiologically meaningful concentrations of phenylalanine and quantify them with a lightweight portable spectrophotometer compatible with smartphone readout. The principle of the assay relies on the dissolution of gold nanoparticles (AuNPs) induced by mixtures of HAuCl4 and cetyltrimethylammonium bromide (CTAB) and its inhibition by (enzymatically produced) NADH, establishing a relationship between optical readout and phenylalanine concentration with a limit of detection of ca. 1 μM. The transposition of this assay to the analysis of serum samples containing phenylalanine concentrations spanning from 60 to 2000 μmol/L was achieved, validating the nanobiosensor as a promising tool for PKU management