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Fatin-Rouge, N ; Toth, E ; Perret, D ; Backer, RH ; Merbach, AE ; Bunzli, JCG

Lanthanide podates with programmed intermolecular interactions : Luminescence enhancement through association with cyclodextrins and unusually large relaxivity of the gadolinium self-aggregates

Journal of The American Chemical Society 122 (44) 10810-10820

par Administrateur - publié le

Abstract :

The synthesis of the phenyl anchored podand H4L1 fitted with four 3-carboxylate pyrazole arms and programmed for intermolecular interactions is reported, and its protonation constants are determined. interaction with Ln(3+) ions (Ln = La, Eu, Lu) in dilute aqueous solutions leads to complexes with 1:I and 1:2 metal-ligand stoichiometry. The stability constants are in the range log beta (110) = 12.7-13.5 and log beta (120) = 22.5-23.8 (pLn values in the range 9-10). The podates display a fair sensitization of the metal-centered luminescence with an absolute quantum yield of 5% in case of Tb-III. The average numbers of water molecules coordinated to the Ln(III) ion amount to 3.8 and 4.9 for the 1:1 Eu and Tb podates, respectively, as determined by lifetime measurements.