Synthesis and strong luminescence of water soluble lanthanide complexes sensitized by a new tridentate organic ligand

Sensitive biological analysis requires optical labels have good water solubility and relative longer excitation wavelength. Herein, two water-soluble lanthanide (Ln) organic complexes, Na3Ln(DIEDPA)3 (Ln=Eu, Tb) have been synthesized with a new tridentate ligand, 4-[2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-ethoxy]-pyridine-2,6-dicarboxylic acid (H2DIEDPA). The two lanthanide complexes showed characteristic emissions of Eu3+ and Tb3+ ions with high quantum yields of 11±1.1% and 13±1.5% respectively. Moreover, compared with those for the europium and terbium complexes with pyridine-2,6-dicarboxy acid as a ligand, the effective excitation wavelengths for the two complexes shifted more than 60 nm to longer wavelengths by decoration of the molecular structure of the organic ligand. The results might provide reference for design and synthesis of organic luminescent lanthanide bioprobes with longer excitation wavelengths.