Lanthanide complexes of polycarboxylate-bearing dipyrazolylpyridine ligands with near-unity luminescence quantum yields: the effect of pyridine substitution.

The title complexes displayed a marked dependence of their luminescence properties upon pyridine substitution. The ligand with the 4-carbamoyl-substituted pyridine showed a long-lived luminescence of near-unity quantum yield for Tb3- and quite reasonable values for Eu3+, Sm3+ and Dy3-, thus making it an excellent candidate for a luminescent probe to be attached to biomolecules by a peptide-like linkage.