Titre : From Fullerene-Donor Conjugates to Luminescent Transition Metal Complexes.
Cette conférence sera prononcée par le Professeur Jean-François Nierengarten du Laboratoire de chimie des matériaux moléculaires de l'Université de Strasbourg (France). Elle sera donnée en anglais.
Résumé : Coordination compounds possessing low-lying metal-to-ligand charge transfer (MLCT) excited states with marked reducing character are excellent partners for C60 in photoactive multicomponent hybrid systems. We have prepared a large number of dyads in which C60 is coupled with photoactive coordination compounds of Ru(II), Re(I), Ir(III) and Cu(I). For most of these systems, the energy of the lowest 3MLCT level lies higher than that of the fullerene singlet and triplet, whereas the charge separated state is intermediate. Upon excitation of the metal- complexed moiety, charge separation followed by charge recombination to the fullerene triplet is generally observed. Practically, since direct excitation of the fullerene moiety results in regular deactivation without intercomponent interactions, the fullerene triplet level is the final energy sink of the dyad, whatever the excitation wavelength. The situation is rather different in the case of Cu(I)-bisphenanthroline fullerene hybrids. Cu(I) complexes are indeed stronger reducing agents than Ru(II), Re(I) or Ir(III) systems, thus the charge separated state is the lowest in the energy level diagram, originating a different pattern of photoinduced processes, also finely depending on the fullerene cage functionalization (e.g. mono- vs. bis-methanofullerenes).
During the photophysical studies carried out on these dyads, we have also systematically investigated the electronic properties of the corresponding model compounds and thus became progressively involved in the field of phosphorescent metal complexes. In particular, we have developed strongly luminescent Cu(I) complexes and shown their potential for light emitting applications. Indeed, such non-toxic Cu(I) complexes are interesting alternatives to the heavy metal complexes (Ir(III) and Pt(II) derivatives) typically used as electrophosphorescent materials in LEDs.
