7. Lanthanide Complexes of Polyacid Ligands Derived from 2,6-Bis(pyrazol-1-yl)pyridine, Pyrazine, and 6,6′-Bis(pyrazol-1-yl)-2,2′-bipyridine: Synthesis and Luminescence Properties

Article abstract of DOI:10.1002/hlca.19970800108

The synthesis of three novel pyrazole-containing complexing acids, N,N,N′,N′-{2,6-bis[3-(aminomethyl)pyrazol-1-yl]-4-methoxypyridine} tetrakis(acetic acid) (1), N,N,N′, N′-{2,6-bis[3-(aminomethyl)pyrazol-1-yl]pyrazine}tetrakis(acetic acid) (2), and N,N,N′,N′-{6,6′-bist[3-(aminomethyl)pyrazol-1-yl]-2,2′- bipyridine}tetrakis(acetic acid) (3) is described. Ligands 1-3 formed stable complexes with Eu^III, Tb^III, Sm^III and Dy^III in H₂O whose relative luminescence yields, triplet-state energies, and emission decay lifetimes were measured. The number of H₂O molecules in the first coordination sphere of the lanthanide ion were also determined. Comparison of data from the Eu^III and Tb^III complexes of 1-3 and those of the parent trisheterocycle N,N,N′,N′-{2,6-bis[3-(aminomethyl)pyrazol-1-yl]pyridine} tetrakis(acetic acid) showed that the modification of the pyridine ring for pyrazine or 2,2′-bipyridine strongly modify the luminescence properties of the complexes. MeO Substitution at C(4) of 1 maintain the excellent properties described for the parent compound and give an additional functional group that will serve for attaching the label to biomolecules in bioaffinity applications.