Synthesis and luminiscence properties of europium(III) and terbium(III) complexes with polyacid chelates derived from 2,6-bis(N-pyrazolyl)pyridine

Abstract

A short and efficient synthesis of N, N, N′, N′-[2,6-bis(3-aminomethyl-1-pyrazolyl)pyridine]-tetrakis(acetic acid)(6), an analogue of terpyridine with additional chelating iminodiacetic groups, is described. Compound 6 forms stable complexes with EuIII and TbIII in water whose relative luminescence yields, excitation maxima and emission decay lifetimes have been measured. The number of water molecules in the first coordination sphere of the europium complex have also been determined. Comparison of data from the EuIII and TbIII complexes of 6 and of the parent trisheterocycle diacid 2,6-bis(3-carboxy-1-pyrazolyl)pyridine shows that the iminodiacetic subunits give extra stabilization to the complexes and are essential to protect the metal from the water environment.