Lanthanide contraction within a series of asymmetric dinuclear [Ln 2] complexes

David Aguilà, Leoní A. Barrios, Verónica Velasco, Leticia Arnedo, Núria Aliaga-Alcalde, Melita Menelaou, Simon J. Teat, Olivier Roubeau, Fernando Luis, Guillem Aromí

    Research output: Contribution to journalArticlepeer-review

    65 Citations (Scopus)

    Abstract

    A complete isostructural series of dinuclear asymmetric lanthanide complexes has been synthesized by using the ligand 6-[3-oxo-3-(2-hydroxyphenyl) propionyl]pyridine-2-carboxylic acid (H3L). All complexes have the formula [Ln2(HL)2(H2L)(NO3)(py) (H2O)] (Ln=La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14), Y (15); py=pyridine). Complexes of La to Yb and Y have been crystallographically characterized to reveal that the two metal ions are encapsulated within two distinct coordination environments of differing size. Whereas one site maintains the coordination number (nine) through the whole series, the other one increases from nine to ten owing to a change in the coordination mode of an NO3- ligand. This series offers a unique opportunity to study in detail the lanthanide contraction within complexes of more than one metal. This analysis shows that various representative parameters proportional to this contraction follow a quadratic decay as a function of the number n of f electrons. Slater's model for the atomic radii has been used to extract, from these decays, the shielding constant of 4f electrons. The average of O×××O distances within the coordination polyhedra shared by both metals and of the Ln×××Ln separations follow also a quadratic decay, therefore showing that such dependence holds also for parameters that receive the contribution of two lanthanide ions simultaneously. The magnetic behavior has been studied for all nondiamagnetic complexes. It reveals the effect of the spin-orbit coupling and a weak antiferromagnetic interaction between both metals. Photoluminescent studies of all the complexes in the series reveal a single broad emission band in the visible region, which is related to the coordinated ligand. On the other hand, the Nd, Er, and Yb complexes show features in the near-IR region due to metal-based transitions.

    Original languageEnglish
    Pages (from-to)5881-5891
    Number of pages11
    JournalChemistry - A European Journal
    Volume19
    Issue number19
    DOIs
    Publication statusPublished - 2013 May 3

    Keywords

    • X-ray diffraction
    • contraction
    • lanthanides
    • luminescence
    • magnetic properties

    ASJC Scopus subject areas

    • Catalysis
    • Organic Chemistry

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