Metal-radical complexes : design, spectroscopy and reactivity

F. Thomas (Prof.), O. Jarjayes (assist. Prof.), N. Leconte (assist. Prof.), A. du Moulinet dHardemare (assist. Prof), L. Lecarme (PhD), J. Moutet (undergraduate), D. Serre (undergraduate)
    The association of a radical ligand to a metal ion allows for a very efficient catalysis in Nature, as exemplified by Galactose Oxidase (oxidation of alcohols) and Cytochrome P450 (C-H bond activation). There are growing evidence that the inherent inability of some earth abundant d-transition metal ions to catalyze multi-electron transfers can be overcome by combining redox non-innocent ligands with these metals in inorganic complexes. However, the correct description of the electronic structure of such complexes is extremely challenging and requires sophisticated spectroscopic and electrochemical tools. We design and synthesize in our team new putative radical complexes and address their electronic structure by spectroscopy. In addition to this fundamental work, we exploit their reactivity for different purposes (DNA cleavage, molecular motion
  • Description of the electronic structure of complexes involving redox non-innocent ligands:

    One-electron oxidized nickel(II) salophen complexes could be described as either Ni(III) bis(phenolate) or Ni(II)-phenoxyl radical species. Combined EPR, UV-Vis and DFT calculations show that their electronic structure corresponds to the latter electronic isomer.
  • Interaction of metal complexes with DNA:

    We showed recently that tripodal ligands involving pro-phenoxyl ligands promote efficient DNA cleavage and further anti-proliferative activity. In contrast, the salophen complexes do not cleave plasmid DNA, but interact tightly with G-quadruplex DNA.
 Cleavage of plasmid DNA by a copper-phenolate complex.
  • Molecular motions promoted by redox processes centered on the ligand:

    Oxidation of the imino-semiquinone moieties promotes reversible ligand ejection, without change in the metal oxidation state.
Ligand ejection triggered by electron transfer from the ligand.

    Prof. Tim Storr (Simon Fraser University, Burnaby, Canada)
    Prof. Yuichi Shimazaki (College of science, Ibaraki, Japan)
    Prof Xavier Ronot (CaCys, IAB, Grenoble)
    Dr. Nathalie Berthet (I2BM, DCM, Grenoble)
    Dr. Jean-Louis Mergny (IECB, Bordeaux)
    Dr. Dennis Gomez (IPBS, Toulouse)