Carole Duboc

Heterogeneous materials incorporating molecular catalysts hold strong promise for efficient electrocatalytic CO2 reduction to value-added products. While activity and selectivity are traditionally tuned through ligand design, increasing attention is being paid to the second-coordination sphere, which modulates reactivity beyond the metal center. Inspired by enzymatic systems, this outer-sphere environment enhances catalysis through spatial confinement and noncovalent interactions. Here, we report a host–guest strategy to control CO2 reduction using the [bpyMn(CO)3MeCN]+ catalyst encapsulated in an anionic cage. When immobilized on an electrode surface, the assembly selectively produces CO. Mechanistic studies indicate that the cage promotes proton-coupled CO2 binding while preventing catalyst deactivation. This demonstrates that supramolecular second-sphere engineering is a powerful strategy for enhancing electrocatalytic performance and provides a basis for future developments in molecular electrocatalysts.

In order to mitigate superoxide-induced damage, cells rely on superoxide dismutases (SODs), a family of metalloenzymes that catalyze the dismutation of superoxide. These enzymes display a positively-charged substrate entrance channel for superoxide guidance to the active metal center. ATCUN-like Ni(II) complexes have been shown to mimic NiSOD effectively and benefit from versatile peptide structures, which are ideal for introducing positive charges through arginine residues at various positions to modulate catalytic properties. We describe here five novel ATCUN-like Ni(II) complexes, with arginines at various positions in close proximity to the metal center. All the peptides form monometallic square planar Ni(II) complexes in water at pH 7.4, with either a N₂S₂ coordination (S-series) or an equilibrium between N₂S₂ and N₃S₁ coordination modes (N/S-series). The S-series demonstrates a clear beneficial effect of the charge increase from − 2 to + 2 on the pseudo-first order catalytic constant. Furthermore, the data obtained for the N/S complexes demonstrate that introducing an arginine residue in the central position of the ATCUN-like motif does not enhance activity, but actually impedes catalysis. These findings show that both the distance of the charged residues from the metal center and their positioning in space are of prime importance. Graphical abstract The alternative text for this image may have been generated using AI.

A mononuclear Cu complex bearing a pentadentate polypyridylalkylamine ligand mediates four-electron O ₂ reduction in both organic and aqueous media, revealing the key role of ligand fine-tuning in catalytic performance.

A series of phosphine-substituted [FeFe]-hydrogenase model complexes was synthesized and investigated for electrocatalytic CO ₂ reduction, revealing selective formate production and ligand-dependent reactivity.

The selective electrochemical reduction of CO2 to formate is a key challenge in developing carbon-recycling chemical processes, with potential applications in energy storage and renewable feedstock production. Inspired by the active site of [FeFe]-hydrogenases, we synthesized and characterized three derivatives of the [(μ-bdt)-Fe2(CO)6] complex (1, bdt = benzene-1,2-dithiolate), incorporating nitrogen-containing functional groups into the aromatic ring of the bdt ligand. These complexes exhibit 100% Faradaic efficiency for CO2 reduction in the presence of MeOH, with formate selectivity reaching up to 62%, alongside H2 and CO as side products. While bdt ligand functionalization has a minimal impact on the electronic properties of the FeFe core, it moderately enhances turnover frequencies (TOFₘₐₓ) for CO2 reduction. The catalysis depends on the MeOH concentration, with the functionalized complexes reaching their maximum catalytic current at lower MeOH concentrations with respect to complex 1. By combining infrared spectroelectrochemistry (IR-SEC) and density functional theory (DFT) calculations, we revisited the reac-tion mechanism of this class of catalysts, demonstrating the involvement of a key metal-hydride intermediate. Our findings explain the observed selectivity and open the possibility of further design of secondary-sphere interactions to enhance CO2 reduction kinetics.

The excitation of bidentate quinoline/quinoxaline-NHC iron( ii ) complexes at 530 nm produced ³ MC/ ³ MLCT mixed excited states with lifetimes up to 74 ps.