LAboratoire de Spectrochimie Infrarouge et Raman – UMR 8516
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Dynamics and elementary photoreactivity in solution

Two research axes are developed:

1. One axis deals with the fundamental study of the structure and dynamics in neat liquids, aqueous solutions and supercritical fluids. The objective is to understand physico-chemical phenomena such as solute solvation, aggregation, diffusion, micro-heterogeneity, conductivity, …, which are related to the major solute effects: solvent destructuration, protein denaturation, bio-protective effects, hydrophobic and hydrophilic interactions. These phenomena involve various spatial scales (molecular scale, intermolecular correlation scale) and time scales (typical relaxation times of the various distance-dependent dynamics), which imposes the use of a wide range of experimental techniques (Raman and IR vibrational spectroscopies, time-resolved optical Kerr effet, neutron diffusion, NMR…) as well as the development of new classical and quantum chemical tools for the analysis of molecular dynamics. Another goal is to optimize supercritical solvent conditions for applications in chemical extraction, synthesis, and waste treatment.

Fig. 6. Schematic potential energy diagram for the excited-state processes of the HOPPy-1 cation in solution. Evolution along two coordinates, torsion α around the interring bond and proton transfer to the solvent (PT) can occur with relative kinetics depending on the solvent (Ref. P 2012-2).

2. We are also interested in the excited-state dynamics of multifunctional molecules which give rise to multiple ultrafast elementary processes upon light excitation. Our goals are to identify, as a function of the solvent, the main factors that control the chronology of the different events, their concerted or competitive character, and the potential synergy effects. There is a particular focus on hydroxylated amphoteric heteroaromatics, which are both « super » photoacids and « super » photobases and combine photoinduced intra- and inter-molecular proton transfer. Also considered are systems combining excited-state proton transfer and cis-trans isomerization (chromophore HBDI of the GFP protein), or excited-state proton transfer and intramolecular charge transfer (phenol-pyridinium betaines).

Fig. 7. Photophysics of the SBPa zwitterion in solution inferred from ultrafast time-resolved spectroscopy and quantum calculation (Ref. P 2012-5).