Lanthanide Shift Reagents. Paper 18. Equilibrium Binding Constants for Europium Shift Reagent with Nitrogen Heterocycles

Paper 16 in this series^{1, 2, 3} was concerned with the equilibrium binding constants (K) of the shift reagent Europium tris (2, 2, 6, 6-tetramethylheptane-3, 5-dionate), Eu(thd)₃, with primary, secondary and tertiary amines. One nitrogen heterocycle, pyridine, and two of its derivatives (see Table) were included. In the present paper we describe the binding constants for a further 9 nitrogen containing heterocycles and relate these to basicity and steric effects.