Un article de l’équipe “Senseurs optiques et sondes oligonucléotidiques pour bioanalyses et imagerie” vient de parâitre dans le journal “Journal of the American Chemical Society”

28 October 2011 par Super Administrateur
Ce travail illustre une approche simple pour optimiser la luminescence des lanthanides dans les complexes moléculaires dinucléaires de lanthanides et identifie un complexe d'europium multidentate particulier comme le meilleur candidat pour une incorporation ultérieure dans des matériaux polymères.

Titre : Optimizing Sensitization Processes in Dinuclear Luminescent Lanthanide Oligomers: Selection of Rigid Aromatic Spacers

Références : J. Am. Chem. Soc., 2011, 133 (40), pp 16219–16234

Auteurs : Jean-François Lemonnier, Laure Guénée, César Beuchat, Tomasz A. Wesolowski, Prasun Mukherjee, David H. Waldeck, Kristy A. Gogick, Stéphane Petoud and Claude Piguet

DOI: 10.1021/ja206806t

Accès pour abonnés portail BiblioVie

Résumé :

This work illustrates a simple approach for optimizing the lanthanide luminescence in molecular dinuclear lanthanide complexes and identifies a particular multidentate europium complex as the best candidate for further incorporation into polymeric materials. The central phenyl ring in the bis-tridentate model ligands L3–L5, which are substituted with neutral (X = H, L3), electron-withdrawing (X = F, L4), or electron-donating (X = OCH3, L5) groups, separates the 2,6-bis(benzimidazol-2-yl)pyridine binding units of linear oligomeric multi-tridentate ligand strands that are designed for the complexation of luminescent trivalent lanthanides, Ln(III). Reactions of L3–L5 with [Ln(hfac)3(diglyme)] (hfac– is the hexafluoroacetylacetonate anion) produce saturated single-stranded dumbbell-shaped complexes [Ln2(Lk)(hfac)6] (k = 3–5), in which the lanthanide ions of the two nine-coordinate neutral [N3Ln(hfac)3] units are separated by 12–14 Å. The thermodynamic affinities of [Ln(hfac)3] for the tridentate binding sites in L3–L5 are average (6.6 ≤ log(β2,1Y,Lk) ≤ 8.4) but still result in 15–30% dissociation at millimolar concentrations in acetonitrile. In addition to the empirical solubility trend found in organic solvents (L4 > L3 L5), which suggests that the 1,4-difluorophenyl spacer in L4 is preferable, we have developed a novel tool for deciphering the photophysical sensitization processes operating in [Eu2(Lk)(hfac)6]. A simple interpretation of the complete set of rate constants characterizing the energy migration mechanisms provides straightforward objective criteria for the selection of [Eu2(L4)(hfac)6] as the most promising building block.