Institut de Chimie Moléculaire et des Matériaux d'Orsay

Coupling a photoredox module and a bio-inspired non-heme model to activate O₂ for oxygen atom transfer (OAT) reaction requires a vigorous investigation to shed light on the multiple competing electron transfer steps, charge accumulation and annihilation processes, and the activation of O₂ at the

Understanding the reactivity landscape for the activation of water till the formation of the O-O bond and O₂ release in molecular chemistry is a decisive step in guiding the elaboration of cost-effective catalysts for the oxygen-evolving reaction (OER). Copper (II) complexes have recently caught the attention of chemists as catalysts for the 4e-/4H⁺ water oxidation process. While a copper (IV) intermediate has been proposed as the reactive intermediate species, yet no spectroscopic signature has been reported so far. Copper (III) ligand radical species have also been formulated and supported by theoretical studies. We found, herein, that the reactivity sequence for the water oxidation with a family of Copper (II) o-phenylene bisoxamidate complexes are a function of the substitution pattern on the periphery of the

C4-Symmetrical dirhodium(II) tetracarboxylates are highly efficient catalysts for the asymmetric intermolecular aziridination of substituted alkenes with sulfamates. The reaction proceeds with high levels of efficiency and chemoselectivity to afford aziridines with excellent yields of up to 95% and enantiomeric excesses of up to 99%. The scope of the alkene aziridination includes mono-, di-, and trisubstituted olefins as well as the late-stage functionalization of complex substrates. The reaction

In the context of bioinspired OAT catalysis, we developed a tetra- dentate dipyrrinpyridine ligand, a hybrid of hemic and non-hemic models. The catalytic activity of the iron(III) derivative was investigated in the presence of iodosylbenzene. Unexpectedly, MS, EPR, Mo ̈ssbauer, UV-visible and FTIR spectroscopic signatures supported by DFT calculations provide convincing evidence for the involvement of a relevant FeIII–O–NPy active intermediate.

The evil necessity of sacrificial electron donors (SEDs) in the photoactivation of O₂ can be ousted by the use of a reversible electron acceptor (methylviologen). It intervenes as an electron carrier from the excited photosensitizer to reduce both O₂ and an iron(III) catalyst to form a reactive Fe^III–peroxo species for oxygen atom transfer reactions. Oxidation of an organic substrate closes the photocatalytic cycle.

[Rh₂(Esp)₂]  is a well-established catalyst for intra- and intermolecular C(sp)³􏰂H bond amination. We have prepared and isolated complex I, [Rh₂(Esp)₂(NHTces)₂]₂􏰂, where the catalyst bears sul- fonamidate ligands (􏰂NHTces = 􏰂NHSO₃CH₂CCl₃) as nitrogen sources in the coordination sphere of the rhodium centre. The possibility for light activation instead of chemical activation of the [Rh₂(Esp)₂] catalyst and complex I is demonstrated using [Ru(bpy)₃]²⁺ as the photosensitizer. The oxidation of the two dinuclear Rh complexes occurs through two distinct pathways. On one hand, [Rh₂(Esp)₂] is oxidized in a bimolecular reaction with the RuIII species formed after excitation of the photosensi- tizer in the presence of an electron

A novel monoanionic tetradentate N4 ligand (F₅DPPy) based on a dipyrromethene skeleton as a molecular platform and decorated with pyridine rings at the 1- and 9-positions of the dipyrrin motif has been prepared and characterized. Interestingly, although this ligand is weakly fluorescent, it presents a chelation-enhanced fluorescence effect of around 150 times upon coordination to Zn^II. Time-dependent (TD) DFT calculations reproduce nicely the spectroscopic features of both the ligand and the complex, and analysis of the electron den- sity redistribution in the excited state suggests that a better orbital overlap of the HOMO and LUMO in F₅DPPyZnCl compared with F5DPPy is responsible for the more intense transitions observed with the former system. As such, this ligand opens interesting perspectives in the design of ratiometric sensors.

In the present work we describe the synthesis and study of a Ru^II–Fe^II chromophore–catalyst assembly designed to perform the light-induced activation of an iron bound water molecule and subsequent photo-driven oxidation of a substrate. Using a series of spectroscopic techniques, we demonstrate that excitation of the chromophore unit with 450 nm light, in the presence of a sacrificial electron acceptor, triggers a cascade of electron transfers leading to the formation of a high valent iron(IV)–oxo center from an iron(II)-bound water molecule. The activity of this catalytic center is illustrated by the oxidation of triphenyl phosphine.

Oxidation processes usually necessitate powerful oxidizing reagents such as hydrogen peroxide. As an alternative, we reported the photocatalytic activation of O₂ at a diiron(II) complex - ruthenium(II) photosensitizer dyad where the dinuclear iron complex mimics the methane monooxygenase catalytic center. This biomimetic approach allowed to photooxidize organic substrates in the absence of strong oxidant by using dioxygen as the sole source of O atom.

Despite recent advances in the field of molecular catalysis, noble metals based complexes are still the best candidates to promote water oxidation. We are dedicated to understand the factors that govern the activation of a water molecule at more earth abundant metal centers as in nature. We have shown, for instance, the implication of surrounding water molecules in the formation of highly oxidized Mn-oxo species. As part of the we also managed to photoinduce the activation of a water molecule in a photosensitizer-catalyst dyad to photooxydize a substrate using water as the sole source of O.