Strong luminescence of novel water-soluble lanthanide complexes sensitized by pyridine-2,4,6-tricarboxylic acid

Sensitive biological analysis requires optical labels have good water solubility and excellent luminescent properties. Herein, two water-soluble lanthanide (Ln) complexes, Na6[Ln(PTA)3] (Ln = Eu and Tb), have been synthesized with a new tridentate ligand, pyridine-2,4,6-tricarboxylic acid (H3PTA). The two-lanthanide complexes showed great characteristic emissions of Eu3+ and Tb3+ ions with high quantum yields of 54.3 ± 0.5% and 20.2 ± 0.2%, respectively. Moreover, they have good water solubility and can be labelled on biological molecules by dehydration reactions between the non-coordinated -COOH groups from the luminescent complexes and the -NH2 groups from the biological molecules.