PhD offer (CSOB group) – Evaluation of mass spectrometric activation techniques for the measurement of thermochemical quantities: application to the study of the stabilityof organometallic catalysts

The CSOB group is looking for a candidate for a PhD scholarship on the topic:

Evaluation of mass spectrometric activation techniques for the measurement of thermochemical quantities: application to the study of the stability
of organometallic catalysts

Project overview :  

Reaction mechanisms are governed by thermochemical quantities, for example when the active form of a catalyst is produced by releasing a coordination site on the metal center. Mass spectrometry is a powerful tool for measuring thermochemical quantities in the gas phase. To do this, it relies on ion activation and fragmentation techniques, giving access to dissociation energies. In the literature, there are techniques considered robust and reliable for measuring these thermochemical quantities. They can nevertheless be very difficult to implement and require specific and not very common spectrometers. These include the SPES (Slow PhotoElectron Spectroscopy) technique, which is accessible on synchrotron light lines. The BIRD (Blackbody Infrared Radiative Dissociation) technique, available on very rare FT-ICRs modified for such measurements.

Finally, the TCID (Threshold Collision- Induced Dissociation) technique is carried out on “Guided Ion Beam MS” type prototypes. Nevertheless, these “robust” techniques have very limited fields of application. SPES is suitable for small neutral molecules (M<500u). BIRD can only be easily applied to large fragile systems at thermal equilibrium (M>1500u), and requires highly complex kinetic modeling for smaller systems. TCID is also difficult to master and is more suited to the fragmentation of small solid ions (M<300u).

Over the last ten years, our team has developed expertise in the use of these three techniques. However, they all show limits in the study of complex systems developed by synthetic chemists, and we have therefore interested in the development of new activation approaches. One example is Low-Energy CID, enabling slow collisional heating. We have achieved very good results in the case of “host-guest” chemistry and for the fragmentation of diastereomeric complexes. This method has the advantage of being much quicker to implement than the BIRD technique, and also enables the study of smaller and stronger systems than those accessible in BIRD. Another technique developed, HCD experiments modeling, allows a comparison of the fragmentation of molecules of very variable size and strength. Finally, there is currently no robust model to quantify the energy deposited under RE (Resonant Excitation) activation in an FT-ICR cell.

The aim of this thesis is therefore to better define the limits of validity and accuracy of these new techniques compared to those more commonly used. For example, we will be looking at how the Low- Energy CID and HCD techniques can converge in different fields of application. We will also be interested in the mass and energy limits within which ions are still under rapid energy exchange conditions, and in thermal equilibrium by Low-Energy CID activation. Once the methods have been validated, they will be used to study Fe and Co complexes involved in the electrochemical reduction of CO2. The stability of the reduced forms involved in the reactions is a crucial parameter. The methods developed will enable us to characterize these intermediates, which often escape observation in solution (instability, lifetime in the reaction medium), and thus gain a better understand the nature of metal-organic reagent interactions. A major part of the work will concern the validation of experimental measurements by theoretical chemistry calculations. Synthesis of reference molecules of interest is possible. This work will also rely on instrumental developments that have been part of the team’s know-how for many years.

Profiles : 

– The candidate must hold a Master 2 or an engineering degree in molecular chemistry.
– Scientific curiosity, motivation and the ability to work in a team are essential.

Duration:

36 months from October 2024

Application:

– Send a cover letter
– a detailed CV
– Please note: to be valid, registration must be completed on the Adum website.

Contact : Director D. Lesage, Co-directors H. Dossmann et Y. Gimbert

Key words : Mass spectrometry, Bond dissociation energies, Kinetic modelling, Theoretical chemistry, Ion-molecule reactions

References

  1. Investigation of activation energies for dissociation of host‐guest complexes in the gas phase using low‐energy collision induced dissociation, P Bayat, D Gatineau, D Lesage, S Marhabaie, A Martinez, RB Cole, Journal of Mass Spectrometry, 54 (5), 437-448 2019 https://doi.org/10.1002/jms.4345
  2. Bond-Dissociation Energies to Probe Pyridine Electronic Effects on Organogold(III) Complexes: From Methodological Developments to Application in π‑Backdonation Investigation and Catalysis, L Bourehil, C Soep, S Seng, S Dutrannoy, S Igoudjil, J Forte, G Gontard, D Lesage, B Bertrand, and H Dossmann, Inorganic Chemistry, 62, 13304-13314 2023 https://doi.org/10.1021/acs.inorgchem.3c01584
  3. Enantioselective Reduction of Noncovalent Complexes of Amino Acids with CuII via Resonant Collision-Induced Dissociation: Collision Energy, Activation Duration Effects, and RRKM Modeling, C Chalet, D Lesage, E Darii, A Perret, S Alves, Y Gimbert, JC Tabet, J. Am. Soc. Mass Spectrom., 35, 3, 456–465, 2024 https://doi.org/10.1021/jasms.3c00355