Versatile Macrocyclic Platform for the Complexation of [(nat)Y/(90)Y]Yttrium and Lanthanide Ions
Résumé
We report a macrocyclic ligand (H) based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing three acetate pendant arms and a benzyl group attached to the fourth nitrogen atom of the macrocycle. The X-ray structures of the Y and Tb complexes reveal nine coordination of the ligand to the metal ions through the six nitrogen atoms of the macrocycle and three oxygen atoms of the carboxylate pendants. A combination of NMR spectroscopic studies (H, C, and Y) and DFT calculations indicated that the structure of the Y complex in the solid state is maintained in an aqueous solution. The detailed study of the emission spectra of the Eu and Tb complexes revealed Ln-centered emission with quantum yields of 7.0 and 60%, respectively. Emission lifetime measurements indicate that the ligand offers good protection of the metal ions from surrounding water molecules, preventing the coordination of water molecules. The Y complex is remarkably inert with respect to complex dissociation, with a lifetime of 1.7 h in 1 M HCl. On the other hand, complex formation is fast (∼1 min at pH 5.4, 2 × 10 M). Studies using the Y-nuclide confirmed fast radiolabeling since [Y]Y is nearly quantitatively formed (radiochemical yield (RCY) > 95) in a short time over a broad range of pH values from ca. 2.4 to 9.0. Challenging experiments in the presence of excess ethylenediaminetetraacetic acid (EDTA) and in human serum revealed good stability of the [Y]Y complex. All of these experiments combined suggest the potential application of H derivatives as Y-based radiopharmaceuticals.
Domaines
Sciences du Vivant [q-bio]
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