title: Lanthanide-to-lanthanide energy-transfer processes operating in discrete polynuclear complexes: can trivalent europium be used as a local structural probe?
abstract: This work, based on the synthesis and analysis of chemical compounds, describes a kinetic approach for identifying intramolecular intermetallic energy-transfer processes operating in discrete polynuclear lanthanide complexes, with a special emphasis on europium-containing entities. When all coordination sites are identical in a (supra)molecular complex, only heterometallic communications are experimentally accessible and a Tb → Eu energy transfer could be evidenced in [TbEu(L5)(hfac)6] (hfac = hexafluoroacetylacetonate), in which the intermetallic separation amounts to 12.6 Å. In the presence of different coordination sites, as found in the trinuclear complex [Eu3(L2)(hfac)9], homometallic communication can be induced by selective laser excitation and monitored with the help of high-resolution emission spectroscopy. The narrow and non-degenerated character of the Eu((5)D0 ↔ (7)F0) transition excludes significant spectral overlap between donor and acceptor europium cations. Intramolecular energy-transfer processes in discrete polynuclear europium complexes are therefore limited to short distances, in agreement with the Fermi golden rule and with the kinetic data collected for [Eu3(L2)(hfac)9] in the solid state and in solution. Consequently, trivalent europium can be considered as a valuable local structural probe in discrete polynuclear complexes displaying intermetallic separation in the sub-nanometric domain, a useful property for probing lanthanido-polymers.
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, 30 quai E. Ansermet, 1211 Geneva 4 (Switzerland).
authors.forename: Amir
authors.initials: A
authors.lastname: Zaïm
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Eliseeva
authors.forename: Laure
authors.initials: L
authors.lastname: Guénée
authors.forename: Homayoun
authors.initials: H
authors.lastname: Nozary
authors.forename: Stéphane
authors.initials: S
authors.lastname: Petoud
authors.forename: Claude
authors.initials: C
authors.lastname: Piguet
mesh_terms: D004735:Energy Transfer; D005063:Europium / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D028581:Lanthanoid Series Elements; D005063:Europium
keywords: energy transfer; lanthanides; photophysics; polynuclear complexes; structural probes