title: A schiff-base bibracchial lariat ether forming a cryptand-like cavity for lanthanide ions.
abstract: We report here a structural and photophysical study of lanthanide(III) complexes with the di-deprotonated form of the bibracchial lariat ether N,N'-bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5. The X-ray crystal structures of [Ce(L(2)-2H)](ClO(4)).0.5H(2)O (2) and [Sm(L(2)-2H)](ClO(4)).C(3)H(8)O (5b) show the metal ion being nine-coordinated and deeply buried in the cavity of the dianionic receptor. Thanks to the formation of a pseudomacrocycle through pi-pi interaction between one of the phenol rings and one of the benzyl rings, the complexes present a cryptand-like structure in the solid state. (1)H and (13)C NMR studies on the La(III) complex point that the solid state structure is essentially maintained in acetonitrile solution. High-resolution laser-excited emission spectra of the crystalline Eu(III) complex demonstrate the presence of several coordination sites arising from different conformations of the crown moiety. The ligand-to-Eu(III) energy transfer is relatively efficient at low temperature, but back transfer is implied in the deactivation process, especially at room temperature, because the ligand triplet state lies at very low energy. However, the low energy of the (3)pipi state provides an efficient conversion of the visible light absorbed into near-infrared light emitted by the Nd(III) ion.
authors.affiliation: Departamento de Química Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus de A Zapateira s/n, 15071, A Coruña, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: González-Lorenzo
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.forename: Fernando
authors.initials: F
authors.lastname: Avecilla
authors.forename: Carlos F G C
authors.initials: CF
authors.lastname: Geraldes
authors.forename: Daniel
authors.initials: D
authors.lastname: Imbert
authors.forename: Jean-Claude G
authors.initials: JC
authors.lastname: Bünzli
authors.forename: Andrés
authors.initials: A
authors.lastname: de Blas
authors.forename: Teresa
authors.initials: T
authors.lastname: Rodríguez-Blas