CE07 - Chimie moléculaire

Understanding dioxygen activation by manganese complexes using mass spectrometry – ManOx

Understanding dioxygen activation by manganese complexes using mass spectrometry

Although many biological processes involve manganese complexes to selectively activate oxygen, the complexity of O2 activation makes the development of effective synthetic catalysts extremely challenging. Understanding the oxygen activation mechanism and the characterization of reaction intermediates is therefore essential.

Identification of reactive manganese-oxygen species

The challenging objective of this project is the generation and identification of manganese O2 species by mass spectrometry in order to explain how the activation of oxygen by manganese species occurs and to investigate the connections between different Mn-O2 intermediates.

The characterization of Mn-O2 adducts and the determination of their kinetic and thermodynamic parameters will be carried out by ion-molecule reaction or (photo)dissociation in the gas phase using tandem mass spectrometry techniques. Advanced calculations will be carried out in parallel of this project, from the study of the main manganese intermediates to the study of the different mechanistic pathways of dioxygen activation. Using such approach, combining and comparing information obtained from experimental gas-phase studies and theoretical calculations, we will gain a good understanding of the key factors involved in the activation of O2 by manganese complexes used in solution.

Although many biological processes involve manganese to selectively activate dioxygen, the complexity of this process makes the development of effective synthetic catalysts extremely challenging. It is therefore crucial to understand in detail the role of the metal ion and of the mechanism at a molecular level, particularly through the characterization of intermediate species.
The challenging objective of this proposal is the generation and identification by mass spectrometry of manganese-oxygen species, generated by reacting Mn(II) precursors with O2, in order to understand the mechanistic detail of how O2 activation by manganese occurs and to investigate the connections between different “Mn-O2” intermediates. The characterization of Mn-O2 adducts and the determination of their kinetic and thermodynamic parameters will be carried out by ion-molecule reactions or (photo)dissociation in the gas phase using tandem mass spectrometry techniques.
The first part of the project will focus on the homo- and heterocoupling reaction of aryl lithium or aryl Grignard reagents catalyzed by manganese salts in the presence of dioxygen. The objective is to understand the involvement of O2 in the catalytic activity of manganese complexes by characterizing the reaction intermediates in the gas phase using ion-molecule reaction and obtaining accurate kinetic data. In a second phase, our efforts will aim to elucidate the mechanistic detail of oxygen activation by manganese biomimetic complexes. The last part of the project will concern the determination of the thermochemical properties of O-O or Mn-O bonds by measuring the bond dissociation energy (BDE) and the analysis of the “Mn-O2” compounds by infrared spectroscopy integrated with mass spectrometry (IRMPD). The main intermediates of manganese, the study of the different mechanistic pathways of oxygen activation, will be studied in parallel by theoretical calculations.
Using such complementary approach, combining and comparing information obtained from experimental gas-phase studies and theoretical calculations, we will gain a good understanding of the key factors involved in the activation of O2 by manganese complexes used in solution, with the ultimate goal of proposing new complexes for the development of optimal catalytic systems.

Project coordination

David Gatineau (DEPARTEMENT DE CHIMIE MOLECULAIRE)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

DCM DEPARTEMENT DE CHIMIE MOLECULAIRE

Help of the ANR 191,445 euros
Beginning and duration of the scientific project: December 2020 - 48 Months

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