Institut de Chimie

Cu(I)-bisdiimine complexes, [Cu(NN)2]+ (where NN represents a diimine such as phenanthroline or bipyridine derivatives), are considered promising photosensitizers for various photochemical applications. However, their effectiveness is subject to several key challenges. In particular, controlling steric strain around the copper(I) center by introducing appropriate substituents (R) at the α-position of the nitrogen atoms is crucial for optimizing the excited-state properties of the complex. In brief, increasing the size of R leads to longer emission lifetimes and higher quantum yields. Additionally, the energy of the singlet excited state rises with increasing steric bulk, enhancing photoinduced reactivity. However, excessive steric strain from bulky substituents can significantly destabilize the coordination sphere. To balance complex stability with increased steric bulk around the metal center, we have developed two novel nonsymmetrical ligands featuring branched alkyl chains and benzyl groups at the α-position of the nitrogen atoms. Our findings demonstrate that intramolecular π-stacking interactions between the benzyl group and the opposing phenanthroline ligand contribute to stabilizing the coordination sphere. Furthermore, the flexibility of the benzyl group reinforces the tetrahedral geometry around copper(I), resulting in an increased singlet excited-state energy compared to benchmark complexes. Notably, we show that this enhancement in excited-state energy translates into greater excited-state reactivity.

The development of efficient circularly polarized electrochemiluminescence (CP-ECL) probes is still at its infancy and examples are still very limited. Yet, their achievement would enable gathering a readout that carries privileged information on the probe's chiral environment by monitoring luminescence polarization bias with high signal-to-noise ratio. Notwithstanding, this is a highly challenging task and requires judicious chemical engineering of chiral ECL-active emitters. Herein, we aim at expanding the palette of CP-ECL luminophores by presenting a novel class of enantiopure heterobinuclear Ir(III)-Au(I) complexes, which are investigated thoroughly by means of chemical, structural, and (chiro-)optical techniques. The ground and excited state properties are also elucidated by using density functional theory (DFT) approaches including spin-orbital coupling (SOC) perturbation. The chiral-at-metal complexes display luminescence with a polarization bias of the emitted light that is function of the helical arrangement of the coordination sphere around the Ir(III) center. Overall, the photo- and electro-active complexes unraveled in this work combine unparallelly high photoluminescence quantum yield in the orange region, excellent circularly polarized luminescence (CPL) brightness up to 4.5M-1 cm-1 with a notable ECL activity. Finally, these features provide emitters with CP-ECL efficiency that encompass remarkably by a factor 3.5 that of the well-known benchmark tris-(2,2'-bipyridyl)ruthenium(II).

ABSTRACT Binder‐free electrodes are critical for advancing supercapacitor performance. Here, we explore the development of multi‐wall carbon nanotubes (MWCNTs) electrodes for supercapacitors by replacing conventional non‐conductive polymer binders, such as poly(vinylidene fluoride‐ co ‐hexafluoropropylene) (PVDF‐HFP), with a conductive polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT). PEDOT/MWCNT composite films were synthesized and characterized in an aqueous medium using an electrochemical quartz crystal microbalance (EQCM) and an advanced ac ‐electrogravimetric technique to investigate their charge storage mechanisms and ionic transfer kinetics. Compared to MWCNTs/PVDF‐HFP and pure PEDOT films, the PEDOT/MWCNT composite demonstrates enhanced electrochemical performance, with improved ion concentration and reduced interfacial resistance. The EQCM analysis reveals distinct mass transfer behaviors, highlighting the role of anions, cations, and free water molecules at the interface of electrodes. Ac‐electrogravimetry investigation further identifies the kinetics of ion transfer and the relative concentration of each species, showing that the composite film facilitates efficient charge storage. This work provides a new insight into understanding the interfacial behavior of binder‐free PEDOT/MWCNT electrode.

Titanium (Ti) is widely used in biomedical implants due to its high strength, corrosion resistance, and excellent biocompatibility. However, surface functionalization is essential to enhancing its interaction with biological environments. In this study, monolayers of citrate-stabilized, negatively charged gold nanoparticles (TCAuNPs(−)) were fabricated on Ti substrates precoated with poly(allylamine hydrochloride) (PAH) to facilitate electrostatically driven adsorption. The adsorption behavior of two amino acids, cysteine (Cys) and tryptophan (Trp) on TCAuNPs(−) deposited on the modified Ti surface, was investigated using atomic force microscopy combined with surface-enhanced infrared absorption (AFM-SEIRA) spectroscopy, enabling nanoscale chemical analysis of biomolecular interactions on the modified surface. The AFM-SEIRA spectra revealed characteristic bands associated with COO– and NH3+ groups for both amino acids. In addition, Trp exhibited prominent signals from the aromatic indole ring, suggesting that these molecular fragments were adsorbed onto the TCAuNPs(−)/Ti surface. AFM-SEIRA results indicate that the strongest amino acid signals were localized at the nanoparticle apexes. The results provide insight into the early stage molecular interactions at the bionano interface and offer a framework for designing new functionalized implant surfaces.

Over the last few decades, allenes have evolved from objects of curiosity to central elements of organic synthesis. Among them, N -allenamides, allenes featuring an electron-withdrawing group on the nitrogen, stand out for their great stability and versatility. Their unique reactivity has made them valuable platforms for numerous chemical transformations. Their interest is reinforced by their ability to efficiently lead to multisubstituted enamides, motifs present in many bioactive natural products but notoriously challenging to synthesize with high regio- and stereocontrol. Driven by our deep interest in the reactivity of activated N -allenamides, particularly those with fluorinated units, we present here new transformations leading to the construction of heterocyclic fluorinated structures and complex enamides, two motifs with significant relevance in medicinal chemistry.

This work investigates the performance of numerical optimization algorithms applied to the State-Averaged Orbital-Optimized Variational Quantum Eigensolver for the H2 molecule under various quantum noise conditions. The goal is to assess the stability, accuracy, and computational efficiency of commonly used gradient-based, gradient-free, and global optimization strategies within the Noisy Intermediate-Scale Quantum regime. We systematically compare six representative optimizers, BFGS, SLSQP, Nelder-Mead, Powell, COBYLA, and iSOMA, under ideal, stochastic, and decoherence noise models, including phase damping, depolarizing, and thermal relaxation channels. Each optimizer was tested over multiple noise intensities and measurement settings to characterize convergence behavior and sensitivity to noise-induced landscape distortions. The results show that BFGS consistently achieves the most accurate energies with minimal evaluations, maintaining robustness even under moderate decoherence. COBYLA performs well for low-cost approximations, while SLSQP exhibits instability in noisy regimes. Global approaches such as iSOMA show potential but are computationally expensive. These findings provide practical guidance for selecting suitable optimizers in variational quantum simulations, highlighting the importance of noise-aware optimization strategies for reliable and efficient quantum chemistry computations on current hardware.

The catalytic enantioselective hydrosilylation activity of zinc is investigated in the presence of two ligands derived from cyclohexane‐1,2‐diamine: N,N′‐dibenzylcyclohexane‐1,2‐diamine (1) and a cage‐like structure composed of six cyclohexane‐1,2‐diamine units (2). The reaction proceeds rapidly, achieving complete conversion within minutes and affording alcohol products with enantiomeric excesses of up to 94%. Despite the favorable results with the cage‐like ligand (2), no significant advantage over ligand (1) is observed. In a second part, to gain insight into the reaction mechanism, various mechanistic experiments are conducted alongside density functional theory calculations. The findings suggest that ligand‐selective silylation leads to the formation of a zinc hydride species, which is likely the active catalytic intermediate in this system.

α-N-Pyridylthiosemicarbazones (PTSC) are anticancer agents that can induce oxidative stress in cells, likely through interactions with metal ions. Redox-active Cu and Fe bind strongly to PTSC, forming complexes Cu-PTSC and Fe-PTSC2. These complexes have been proposed to directly catalyze the formation of reactive oxygen species (ROS) and deplete key cellular reductants, thereby exerting oxidative stress. Alternatively, oxidative stress could also arise indirectly through interactions with other cellular targets. Evaluating catalytic rates could help distinguish direct from indirect mechanisms, as ROS production should outpace antioxidant defenses. In this respect, the catalytic activity of the Fe complexes of two PTSCs, Triapine (3AP) and Dp44mT, with the two most abundant reducing agents, ascorbate and glutathione, was evaluated under aerobic conditions. Fe-3AP2 and Fe-Dp44mT2 showed very low catalytic activity in depleting GSH/ascorbate and producing ROS (<4 turnovers per hour). Higher activity appeared with H2O2 and ascorbate, but only for 1:1 Fe-PTSC complexes, not 1:2 Fe-PTSC2. Competition assays with H2O2-degrading enzyme catalase revealed that Fe-PTSC reacted 3 orders of magnitude slower than the enzyme. Thus, Fe-PTSC and Fe-PTSC2 are unlikely to drive ROS production through a direct mechanism. Instead, an indirect mechanism or a site-specific ROS production appears to be more plausible.

International audience

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by progressive decline of cognitive functions, yet its underlying aetiology remains elusive. While amyloid-β (Aβ) and tau pathologies have been extensively studied, emerging evidence suggests that metal and especially copper dyshomeostasis may also play a crucial role in the pathogenesis of AD. This review explores the intricate relationship between copper and AD, shedding light on the multifaceted mechanisms through which copper dysregulation contributes to neurodegeneration. We delve into the impact of copper ions on Aβ aggregation, tau phosphorylation, and oxidative stress, providing a comprehensive overview of the molecular pathways involved. Furthermore, we discuss the interplay between different brain cell types and the impact Cu dysregulation may have on them. The therapeutic implications of targeting copper dysregulation for AD treatment are also addressed, emphasizing the potential of copper-modulating agents in ameliorating cognitive decline. In summary, this review discusses copper dyshomeostasis as a central player in the intricate tapestry of AD pathology, offering new insights and avenues for therapeutic interventions.