Electrocarboxylation of chloroacetonitrile by a Cobalt(I) complex of terpyridine

The electrocarboxylation of chloroacetonitrile (NC–CH2–ClRCl) mediated by [CoIIL2]2+ (L = terpyridine) was investigated by cyclic voltammetry. Electrochemical studies under argon atmosphere showed that the monoelectronic reduction of [CoIIL2]2+ yielded a Cobalt(I) complex which after the loss of a terpyridine ligand reacted with chloroacetonitrile. The oxidative addition of chloroacetonitrile on [CoIL]+ gave an alkylCobalt(III) complex [R–CoIIIL]2+ which was reduced into an alkylCobalt(II) complex, highly unstable and decomposed into an alkyl anion and a Cobalt(II) complex. Under carbon dioxide atmosphere, Cobalt(I) complex was shown to be unreactive towards CO2 but CO2 insertion was observed in the alkylCobalt(III) complex [R–CoIIIL] 2+ giving probably a CO2 adduct [R–CoIIIL(CO2)]2+. This adduct presented a strong adsorption at the carbon electrode and was reduced at potential less cathodic than the one of alkylCobalt(III) complex. After reduction, the carboxylate RCO2− (NC–CH2–CO2−) was released and a catalytic bielectronic carboxylation of chloroacetonitrile took place. Controlled potential electrolyses confirmed the catalytic process and gave for cyanoacetic acid faradic yields up to 60% under low overpotential conditions

Electrocarboxylation du chloroacétonitrile assistée par des complexes de coordination

Ce manuscrit porte sur l'électrosynthèse de l'acide cyanoacétique par électrocarboxylation du chloroacétonitrile en phase homogène et en phase hétérogène. Cette réaction est étudiée en présence de complexes métalliques. Ces catalyseurs doivent permettre d'abaisser le potentiel de travail de la réaction envisagée tout en gardant des rendements de synthèse et des rendements faradiques économiquement viables. Cinq catalyseurs ont été étudiés, trois possédant un centre métallique constitué par un cobalt et deux possédant un nickel. Les ligands associés au centre métallique sont des molécules bidentates ou tridentates. Quatre complexes présentent des propriétés électrocatalytiques intéressantes. L'étape clef du processus, dans le cas des complexes de cobalt, est la perte d'un ligand permettant l'addition oxydante du dérivé chloré. Pour les complexes de Nickel, la dissociation du complexe alkyl nickel est l'étape limitante. Les rendements obtenus par électrolyses préparatives montrent des résultats encourageants. Cependant une désactivation des complexes est observée au cours des cycles catalytiques. L'immobilisation des complexes de cobalt afin de réaliser l'électrocarboxylation du cloroacétonitrile en phase hétérogène a montré que les résultats ne sont pas satisfaisants.This manuscript is dedicated to the study the electrosynthesis of cyanoacetic acid by electrocarboxylation of chloroacetonitrile in homogeneous and heterogeneous phases. This reaction has been conducted in presence of metal complexes as catalysts in order to reduce the working potential while maintaining the cyanoacetic acid and faradic yields. Five catalysts were studied: three cobalt complexes and two nickel complexes. The ligands which are associated with the metal ion are bidentate or tridentate. Four catalysts presented interesting electrocatalytic properties. In the case of cobalt complexes, the rate determining step is the loss of a ligand for the oxidative addition of chloroacetonitrile. For the nickel complexes, the dissociation of the alkyl-nickel complex is the limiting step. The yields obtained by electrolyses are very interesting even though the deactivation of the complex has been observed during the process. The immobilization of the cobalt complex on the electrode surface in order to achieve the electrocarboxylation of chloroacetonitrile in heterogeneous phase showed that the results are not satisfactory

Square wave voltammetry measurements of low concentrations of nitrate using Au/AgNPs electrode in chloride solutions

International audienceThe aim of this work is to highlight the potential of using a modified gold electrode with controlled quantity of silver nanoparticles as a working electrode to detect low concentrations of nitrate in chloride solutions. Optimal charge for silver deposition has been determined to obtain the highest signal for the nitrate reduction as the electrocatalytic properties of the bimetallic electrode were directly influenced by its composition. According to the Volcano plot obtained the charge chosen was -52 µC for a 3 mm diameter electrode, corresponding to 4.6 x 1015 Ag atoms cm-2. It has been shown that dioxygen did not participate to the nitrate reduction mechanism. In order to decrease the limit of quantification, square wave voltammetry was preferred to less sensitive cyclic voltammetry. Nitrate was quantified in chloride solutions in the concentration range found in the open ocean, i.e. 0.39-50 µmol L-1 with a good linear regression (R2=0.9969). The stability of the bimetallic Au-Ag systems has been evaluated and showed almost no difference on the signal recorded over a 26 days period which is suitable to consider an in situ sensor development for marine applications

Electrocarboxylation du chloroacétonitrile assistée par des complexes de coordination

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Electrocarboxylation of chloroacetonitrile mediated by a Ni(I) terpyridine complex: Voltammetric and spectroscopic studies

International audienc

Preparation of Ti3C2Tx modified rare earth doped PbO2 electrodes for efficient removal of sulfamethoxazole

Abstract In this study, we deposited Ti3C2Tx-modified, rare-earth-doped PbO2 on the surface of a carbon fabric via electrodeposition. The surface morphology and electronic structure of the electrode were characterized with SEM, XRD and XPS. The layered Ti3C2Tx did not change the structure of β-PbO2, and at the same time, it improved the crystallinity of the material and reduced the grains of PbO2. Electrochemical experiments showed that the addition of Ti3C2Tx increased the electrochemical activity of the electrode and produced more H2O2, which contributed to the degradation of pollutants. The efficiency of sulfamethoxazole (SMX) degradation reached 95% after 120 min at pH 3 with a current density of 50 mA/cm2. Moreover, the electrode has good cycling performance, and the degradation efficiency was still 80% after 120 min after 10 cycles of recycling. Based on the intermediates identified by HPLC‒MS, a mechanism for SMX degradation was proposed. Our results will provide a new idea for the development of efficient electrocatalytic degradation of antibiotics

Unveil the transcriptional landscape at the Cryptococcus-host axis in mice and nonhuman primates.

Pathogens and hosts require rapid modulation of virulence and defense mechanisms at the infection axis, but monitoring such modulations is challenging. In studying the human fungal pathogen Cryptococcus neoformans, mouse and rabbit infection models are often employed to shed light on the disease mechanisms but that may not be clinically relevant. In this study, we developed an animal infection model using the non-human primate cynomolgus monkey Macaca fascicularis. In addition, we systematically profiled and compared transcriptional responses between the infected mice and the cynomolgus monkey, using simultaneous or dual RNA next-generation sequencing. We demonstrated that there are shared but distinct transcriptional profiles between the two models following C. neoformans infection. Specifically, genes involved in immune and inflammatory responses are all upregulated. Osteoclastogenesis and insulin signaling are also significantly co-regulated in both models and disrupting an osteoclastogenesis-associated gene (OC-STAMP) or the insulin-signaling process significantly altered the host tolerance to C. neoformans. Moreover, C. neoformans was shown to activate metal sequestration, dampen the sugar metabolism, and control cell morphology during infection. Taking together, we described the development of a non-human primate model of cryptococcosis that allowed us to perform an in-depth analysis and comparison of transcriptome profiles during infections of two animal models and conceptually identify host genes important in disease responses. This study provides new insights in understanding fungal pathogenesis mechanisms that potentially facilitate the identification of novel drug targets for the treatment of cryptococcal infection

First Deployment and Validation of in Situ Silicate Electrochemical Sensor in Seawater

An electrochemical sensor is proposed to measure silicate concentration, in situ, in the ocean without any addition of liquid reagent. From the analytical principle to the laboratory prototype toward the first in situ, immersible sensor, the evolution of the mechanical design is presented and discussed. The developed in situ electronics were compared to the commercial potentiostat and gave promising results to detect low silicate signals with a limit of quantification of 1 μmol L−1.The flow rate of the pump appeared to be a crucial parameter in order to transfer the silicomolybdic complex formed from the “complexation cell” to the “detection cell” without dilution as well as to fill and rinse the whole circuit. The study of temperature effect revealed no influence on the electrochemical signal between ~7° and ~21°C. Finally the sensor was successfully deployed for the very first time on a mooring off Coquimbo, Chile and also integrated onto a PROVOR profiling float in the Mediterranean Sea off Villefranche-sur-Mer, France. The data collected and/or sent through satellite were in good agreement with the 2 reference samples and previously published values illustrating the great potential of this electrochemical sensor. A 7 days silicate time series from the mooring deployment off Chile is also presented