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

The synthesis of three novel pyrazole-containing complexing acids, N,N,N′,N′-{2, 6-bis3-(aminomethyl)pyrazol-1-yl]-4-methoxypyridine}tetrakis(acetic acid)( 1 ), N,N,N′,N′-{2, 6-bis3-(aminomethyl)pyrazol-1-yl]pyrazine}-tetrakis(acetic acid) ( 2 ), and N,N,N′,N′-{6, 6′-bis3-(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-bis3-(aminomethyl)pyrazol-l-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.