Mass Spectrometry : Fundamental Aspect

Mass spectrometry is an ideal tool for studying compounds in the gas phase. In this phase, the molecules are isolated, i.e. they are free of any environmental effects. It is thus possible to study their intrinsic properties, which are then necessary for a better understanding of their behaviour in condensed media. The various projects developed in this research area can be divided into two themes. The first concerns the formation and reactivity of transient species and the second the study of non-covalent interactions within biological systems.

Formation and reactivity of transient species in the gas phase

  • Organometallic catalysts

Industrial processes currently use many chemical reactions that are catalysed by organometallic complexes. In solution, many parameters can play a role in the efficiency of these reactions (effect of solvent, concentrations, counterion, etc.) and thus prevent a precise study of the influence of each of these parameters. We have already been able to show that gas phase studies make it possible to overcome many of these factors and thus to determine precisely the role of the catalyst in each of the elementary stages of the reaction. For this purpose, we use two instruments, a modified triple quadrupole mass spectrometer and an FT-ICR, in which we carry out ion-molecule reactions. This work is done in close collaboration with the MACO team.

Within this theme, we aim to develop a new way of evaluating and linking the electronic and steric properties of ligands with the reactivity they induce in the metal centres to which they are bound. On the other hand, we are interested in highly reactive intermediates such as organolithium aggregates which are at the origin of a chiral entity capable of inducing enantioselectivity when creating a C-C bond with a carbonyl derivative.

  • Kinetic and energy aspects of elementary processes

Our team has been interested in the elucidation of elementary reaction mechanisms in the gas phase for several years. Various questions arise during the study of a reaction, notably in terms of energy cost and speed. We use several approaches such as measurements of appearance energies coupled with quantum chemistry calculations, which allow us to return to the energy aspect of the reaction, and measurements of kinetic constants associated with RRKM calculations, which reveal the kinetics of the reaction.

Recently, we have studied magnesium and carbon dioxide adducts of the HOMgCO2- form (Figure 3) and investigated their reactivity with methyl chloride. We have shown that it is possible to activate carbon dioxide in this reaction by forming a bond with the methyl group (Figure 4). This project was carried out in collaboration with Prof. Einar Uggerud from the University of Oslo.

Current projects in this area involve copper and nickel complexes with interesting carbon-carbon bond activation properties.

  • VUV spectroscopy and reactivity of transient species of biological interest

The fundamental properties of molecules of biological interest are generally poorly known because their determination requires isolation of the molecule which is often very difficult to implement for these systems (large and fragile, they degrade very quickly when put in the gas phase). Different methods have recently been developed to assist in the gas-phasing of intact biological molecules such as aerosol sources. We have developed a collaboration with researchers at the SOLEIL Synchrotron Centre, aiming to study different families of molecules such as vitamins and nitrosamine derivatives in this way. Determining the intrinsic properties of these molecules (in particular their redox properties) allows us to better understand the mechanisms involving antioxidants (in the case of vitamins).