Spectroscopic characterization of ethylenediaminedi(o-hydroxyphenyl)acetic acid and its complexes with lanthanide(III) ions

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 characterized 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 co-ordination sphere of Tb(III). Energy transfer from Tb(III) to Eu(III) in the Tb(III)-EIIPG-Eu(III) system indicated an existence of only monomeric form of the Tb-EHPG complex. Analysis of the H-1 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 Dh(III)-EIIPG, showing a linear dependence of luminescence intensity (lambda(em)=578 nm) of Dy(III) on its concentration, in the range of 3.3x10(-7) to 1x10(-5) mol . l(-1), can be applied for spectrofluorimetric determination of Dy(III).