Spectroscopic Characterization of Ethylenediamine-di(o-hydroxyphenyl)acetic Acid and its Complexes with Lanthanide(III) Ions

Abstract

Binding properties of ethylenediaminedi(o-hydroxyphenyl)acetic acid (EHPG) with lanthanide(III) ions were studied using spectroscopic methods. Luminescence intensity and lifetime of the Tb(III) ion were measured in a wide pH range in order to characterize the Ln-EHPG complexation. The calculated hydration number of the Tb-EHPG system proved the replacement of six water molecules by the EHPG ligand in the inner coordination sphere of Tb(III). Energy transfer from Tb(III) to Eu(III) in the Tb(III)-EHPG-Eu(III) system indicated an existence of only monomeric form of the Tb-EHPG complex. Analysis of the 1 H NMR and FTIR spectra of the EHPG ligand and its complexes with lanthanide(III) ions confirmed the hexadentate manner of EHPG complexation with the lanthanides. The system of Dy(III)-EHPG, showing a linear dependence of luminescence intensity (λem = 578 nm) of Dy(III) on its concentration, in the range of 3.3x 10 -7 to 1 x 10 -5 moll-1 , can be applied for spectrofluorimetric determination of Dy(lII).