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Accueil > Equipes > Photochimie théorique et computationnelle (PTC) > Projets de Recherche > Mécanismes de photolabilisation de ligands dans des complexes de ruthénium

Ligand photorelease mechanisms in ruthenium complexes

In collaboration with Sylvestre Bonnet’s group (Leiden University, Netherlands), we are working on the rationalization of photolabilization quantum yields in ruthenium complexes of biological interest.

We have shown that the 3MC surface was offering two minima, namely two structures sharing the same electronic configuration. These isomers are involved in the photolabilization of a thioether ligand. We have proposed that a first 3MC minimum, with a reasonably elongated Ru-S distance of ca. 3 angstroms, could bring the system back to its initial state, while a second 3MC isomer, almost degenerate but almost pentacoordinated (Ru-S ca. 4 angstroms), would favor solvent attack and the departure of the sulfur ligand.

In collaboration with Paul Elliott’s group (University of Huddersfield, UK), we are also interested in mechanistic studies related to photolabilization of bidentate ligands, which are intrinsically more complex due to the difficulty to foresee the reaction coordinate. In this context we have identified new 3MC states that possess peculiar geometries : flattened hexacoordinated or truly pentacoordinated. This work has allowed us to refine our knowledge of the 3MC state region, and to propose a multistep mechanism for the formation of Elliott’s original κ1 intermediate photoproduct bearing a singly-coordinated bidentate ligand.

More recently we have extended these studies to the archetypal complex Ru(bpy)32+, for which we also have identified a second local 3MC minimum possessing two main elongations towards the two nitrogen atoms of the same bpy ligand (named 3MCcis, by contrast to 3MCtrans bearing two elongations trans to one another towards two distinct ligands).

We then undertook a thorough theoretical study of the model reaction involving photosolvolysis of Ru(bpy)32+ in acetonitrile. We have described several reaction paths, requiring either one or two photonic excitations, in agreement with the observation (or absence of) intermediate photoproduct.
The microscopic description of the photosolvolysis elementary steps involves internal conversions (3MLCT-3MC and 3MC-3MC) but also triplet-singlet crossing points allowing the system to relax.
Finally we have shown that the coordination of the entering ligand could occur on the metal either in the singlet or in the triplet state.

This project has led to 6 publications :

Inorg. Chem. 2016, 55, 4448 link

PCCP 2017, 19, 27765 link

Inorg. Chem., 2018, 57, 3192 link

Inorganics 2020, 8, 15 link

Coord. Chem. Rev. 2020, 408, 213184 link

Inorg. Chem. 2020, 59, 14679 (Forum Article) link