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.
