Synthesis and luminescence properties of lanthanide complexes of a novel polyaminopolycarboxylate ligand

Abstract

A novel polyaminopolycarboxylate ligand with many coordination sites, N,N,N1,N1,N2,N2-[( 2,4,6-tri(aminomethyl)-pyridine]hexakis(acetic acid) (TPHA), was designed and synthesized and its lanthanide complexes Na6Tb2(TPHA) Cl6· 14H2O, Na6Eu2(TPHA) Cl6·8H2O, Na6Gd2(TPHA)Cl 6·11H2O and Na6Sm2(TPHA) Cl6·9H2O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, mass, NMR and TG-DTA. The TG-DTA studies indicated that the complexes had a high thermal stability, whose initial decomposition temperature was over 270 oC. The luminescence properties of the complexes in solid state were investigated and the results suggested that Tb3+ and Eu3+ ions could be sensitized efficiently by the ligand, especially the Tb(III) complex displayed a very strong luminescence intensity (> 10000) and only displayed characteristic metal-centered luminescence. Also, the correlative comparison between the structure of ligand and luminescence properties showed how the number of the coordination atoms of ligand can be a prominent factor in the effectiveness of ligand-to-metal energy transfer.