• Optical sensitization and upconversion in discrete polynuclear chromium–lanthanide complexes
    L. Aboshyan-Sorgho, M. Cantuel, S. Petoud, A. Hauser and C. Piguet
    Coordination Chemistry Reviews, 256 (15-16) (2012), p1644-1663
    DOI:10.1016/j.ccr.2011.12.013 | unige:21642 | Abstract | Article PDF
Due to its extreme kinetic inertness, trivalent chromium, Cr(III), has been rarely combined with labile trivalent lanthanides, Ln(III), to give discrete self-assembled (supra)molecular polynuclear complexes. However, the plethora of accessible metal-centered excited states possessing variable lifetimes and emissive properties, combined with the design of efficient intramolecular Cr(III)  Ln(III) energy transfer processes open attractive perspectives for programming directional light-conversion within these heterometallic molecules. Efforts made to address this exciting challenge for both light-sensitization and light-upconversion are discussed in this article.
  • Tuning the Decay Time of Lanthanide-Based Near Infrared Luminescence from Micro- to Milliseconds through d->f Energy Transfer in Discrete Heterobimetallic Complexes
    S. Torelli, D. Imbert, M. Cantuel, G. Bernardinelli, S. Delahaye, A. Hauser, J.-C.G. Bnzli and C. Piguet
    Chemistry - A European Journal, 11 (11) (2005), p3228-3242
    DOI:10.1002/chem.200401158 | unige:3273 | Abstract | Article HTML | Article PDF
Inert and optically active pseudo-octahedral CrIIIN6 and RuIIN6 chromophores have been incorporated by self-assembly into heterobimetallic triple-stranded helicates HHH-[CrLnL3]6+ and HHH-[RuLnL3]5+. The crystal structures of [CrLnL3](CF3SO3)6 (Ln=Nd, Eu, Yb, Lu) and [RuLnL3](CF3SO3)5 (Ln=Eu, Lu) demonstrate that the helical structure can accommodate metal ions of different sizes, without sizeable change in the intermetallic MLn distances. These systems are ideally suited for unravelling the molecular factors affecting the intermetallic nd→4f communication. Visible irradiation of the CrIIIN6 and RuIIN6 chromophores in HHH-[MLnL3]5/6+ (Ln=Nd, Yb, Er; M=Cr, Ru) eventually produces lanthanide-based near infrared (NIR) emission, after directional energy migration within the complexes. Depending on the kinetic regime associated with each specific d-f pair, the NIR luminescence decay times can be tuned from micro- to milliseconds. The origin of this effect, together with its rational control for programming optical functions in discrete heterobimetallic entities, are discussed.

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