Département de Chimie Moléculaire

Gold-catalyzed reactions have established as a powerful tool in organic synthesis, offering efficient pathways to construct diverse molecular structures and notably scaffolds with high complexity. Most processes rely on the use of LAuCl precatalysts, which are generally activated, i.e., cationized, by silver salts. In this work, we explore the role of silicon-based Lewis acids based, such as spirosilane, derivatives as alternative activators in lieu of silver salts. It was found that Martin spirosilanes mediate the activation of gold precatalysts, facilitating diverse cyclization and cycloisomerization reactions as well as intermolecular reactions. NMR studies and computational investigations suggest that no real cationization, i.e., formation of an ionic pair, takes place, but rather activation through weak interaction between silicon and the chlorine atom of LAuCl. This preserves the Au─Cl bond and ultimately enables the LAuCl complex to be recovered. On the same line, the LAuCl-silane interaction has also proven to be beneficial for asymmetric catalysis. This work significantly contributes to the expansion of gold-catalyzed transformations by opening up the prospect of a more sustainable gold catalysis. It also opens perspectives on the use of silicon-based Lewis acids as versatile cooperative agents in organometallic chemistry.

This study examines the effect of temperature during pyrolysis on the capacity of cedar wood-derived biochar to be employed as a sustainable electrode material for supercapacitors. Cedar wood-derived biochars were produced at different temperatures of 800 °C, 900 °C, 1000 °C and 1100 °C and fully characterized in terms of their structural, physicochemical and electrochemical properties, including specific surface area, hydrophobicity, electrical conductivity, and surface functional groups. The results indicated that the cedar wood biochar obtained through pyrolysis at 900 °C (BC900) provided optimal electrical conductivity, hydrophobicity, and porosity characteristics relative to the other cedar wood biochars produced by pyrolysis at 800 °C to 1100 °C. Specifically, when compared to commercial activated carbon (AC), BC900 provided half the specific capacitance at a current density of 1 A g−1 and indicated that there is more potential for improvement with further activation and doping. The influence of the binder (either polyvinylidene fluoride (PVDF) or chitosan) in combination with conductive carbon black (CB) was also examined. Electrodes fabricated with PVDF binder showed higher specific capacitance, while biochar electrodes made from CB and chitosan (BC900/CB/chitosan) showed better electrical conductivity, wettability, and good electrochemical stability with >95% capacity retention even after 10,000 cycles.

Glycans are vital macromolecules with diverse biological roles, decoded by lectins - specialized carbohydrate-binding proteins crucial in pathogenesis. The WHO identifies bacterial antimicrobial resistance (AMR) as a critical global health challenge, necessitating innovative strategies that also target non-antibiotic pathways. Recent studies highlight bacterial lectins as key players in pathogenesis and promising therapeutic targets, with early clinical success using glycomimetics and vaccines to treat and prevent AMR-related infections. This review covers the current knowledge on bacterial lectins, their classifications, and roles in host recognition and adhesion, biofilm formation, cytotoxicity, and host immune evasion, with examples of well-characterized lectins. It also explores their therapeutic potential and highlights novel lectins with unknown functions, encouraging further research.

Ruthenium(II) polypyridine compounds often have a relatively long-lived triplet metal-ligand charge transfer (3MLCT) state, making these complexes useful as chromophores for photoactivated electron transfer in photomolecular devices (PMDs). As different PMDs typically require different ligands and as the luminescence lifetime of the 3MLCT is sensitive to the structure of the ligand, it is important to understand this state and what types of photoprocesses can lead to its quenching. Recent work has increasingly emphasized that there are likely multiple competing pathways involved, which should be explored in order to fully comprehend the 3MLCT state. However, the lowest barrier that needs to be crossed to pass over to the nonluminescent triplet metal-centered (3MC) state has been repeatedly found to be a trans dissociation of the complex, at least in the simpler cases studied. This is the fourth in a series of articles investigating the possibility of an orbital-based luminescence index (LI3, because it was the most successful of three) for predicting luminescence lifetimes. In an earlier study of bidentate (N∧N) ligands, we showed that the gas-phase 3MLCT → 3MC mechanism proceeded via an initial charge transfer to a single N∧N ligand, which moves symmetrically away from the central ruthenium atom, followed by a bifurcation pathway to one of two 3MC enantiomers. The actual transition state barrier was quite small and independent, to within the limits of our calculations, of the choice of ligand studied. Here, we investigate the same reaction in acetonitrile, CH3CN, solution and find that the mechanism differs from that in the gas phase in that the reaction passes directly via a trans mechanism. This has implications for the interpretation of LI3 via the Bell-Evans-Polanyi principle.

ZenoTOF is new class of high-resolution mass spectrometer that combines resolution and sensitivity. This mass spectrometer is well designed to perform metabolomics. In this context, we compared the performance of ZenoTOF 7600 system (Sciex) with QTOF6520 (Agilent Technologies) through the leaf metabolome analysis of two Coffea species, namely C. anthonyi and C. arabica. Both species were used to compare both TOF systems. Our results showed that the ZenoTOF 7600 system provided more features (3146 vs 2326 metabolites) and more nodes (1410 vs 379 metabolites) by molecular network in only one injection. These performances were attributed to the scan speed and sensitivity of the ZenotTOF and demonstrates its added value in the context of metabolomics.

This work is a continuation of the series of studies aimed at studying the electronic and structural properties of divalent metal porphyrin complexes, especially zinc(ii) metalloporphyrins. In this perspective, we have prepared the [Zn(TMPP)(4,4'-bpy)]·CHCl3 (I) coordination compound, where TMPP is the meso-tetra(para-methoxyphenyl)porphyrinate and 4,4'-bpy is the 4,4'-bipyridine. The UV/Vis, fluorescence, IR and 1H NMR spectroscopic techniques, ESI-HRMS mass spectrometry investigation as well as a single crystal X-ray diffraction study were used to characterize the title compound. Notably, we demonstrated the ability of this zinc(ii) metalloporphyrin to degrade the methylene blue (MB) dye, examining several influencing factors, including pH, temperature and initial dye concentration. Additionally, complex I exhibited remarkable efficiency in degrading MB under blue LED irradiation. Beyond catalytic applications, this compound was successfully employed as an electrochemical sensor for the detection of dopamine (DA) using the square wave voltammetry (SWV) method, showcasing its multifunctional capabilities.

The active sites of metalloenzymes involved in small molecules activation often contain pendant bases that act as proton relay promoting proton-coupled electron-transfer processes. Here we focus on hydrogenases and on the reactions they catalyze, i. e. the hydrogen evolution and oxidation reactions. After a short description of these enzymes, we review some of the various biomimetic and bioinspired molecular systems that contain proton relays. We then provide the formal electrochemical framework required to decipher the key role of such proton relay to enhance catalysis in a single direction and discuss the few systems active for H2 evolution for which quantitative kinetic data are available. We finally highlight key parameters required to reach bidirectional catalysis (both hydrogen evolution and hydrogen oxidation catalyzed) and then transition to reversible catalysis (both reactions catalyzed in a narrow potential range) as well as illustrate these features on few systems from the literature.