N-Heterocyclic tridentate aromatic ligands bound to [Ln(hexafluoroacetylacetonate)3] units: thermodynamic, structural, and luminescent properties. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Chemistry - A European Journal Année : 2012

N-Heterocyclic tridentate aromatic ligands bound to [Ln(hexafluoroacetylacetonate)3] units: thermodynamic, structural, and luminescent properties.

Amir Zaïm
  • Fonction : Auteur
Homayoun Nozary
  • Fonction : Auteur
Laure Guénée
Céline Besnard
Stéphane Petoud

Résumé

Herein, we discuss how, why, and when cascade complexation reactions produce stable, mononuclear, luminescent ternary complexes, by considering the binding of hexafluoroacetylacetonate anions (hfac(-)) and neutral, semi-rigid, tridentate 2,6-bis(benzimidazol-2-yl)pyridine ligands (Lk) to trivalent lanthanide atoms (Ln(III)). The solid-state structures of [Ln(Lk)(hfac)(3)] (Ln=La, Eu, Lu) showed that [Ln(hfac)(3)] behaved as a neutral six-coordinate lanthanide carrier with remarkable properties: 1) the strong cohesion between the trivalent cation and the didentate hfac anions prevented salt dissociation; 2) the electron-withdrawing trifluoromethyl substituents limited charge-neutralization and favored cascade complexation with Lk; 3) nine-coordination was preserved for [Ln(Lk)(hfac)(3)] for the complete lanthanide series, whilst a counterintuitive trend showed that the complexes formed with the smaller lanthanide elements were destabilized. Thermodynamic and NMR spectroscopic studies in solution confirmed that these characteristics were retained for solvated molecules, but the operation of concerted anion/ligand transfers with the larger cations induced subtle structural variations. Combined with the strong red photoluminescence of [Eu(Lk)(hfac)(3)], the ternary system Ln(III)/hfac(-)/Lk is a promising candidate for the planned metal-loading of preformed multi-tridentate polymers.

Dates et versions

hal-00726297 , version 1 (29-08-2012)

Identifiants

Citer

Amir Zaïm, Homayoun Nozary, Laure Guénée, Céline Besnard, Jean-François Lemonnier, et al.. N-Heterocyclic tridentate aromatic ligands bound to [Ln(hexafluoroacetylacetonate)3] units: thermodynamic, structural, and luminescent properties.. Chemistry - A European Journal, 2012, 18 (23), pp.7155-68. ⟨10.1002/chem.201102827⟩. ⟨hal-00726297⟩
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