Spectral studies on the interaction of yttrium ion with the ligands of phenolic groups: N,N′-Ethylenebis[2-(o-hydroxyphenolic)glycine] and N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid

The interactions of yttrium with N,N′-ethylenebis[2-(o-hydroxyphenolic)glycine] (EHPG) and N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED) are investigated by using UV difference and fluorescence spectra methods in 0.1 M N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (Hepes) at pH 7.4. Yttrium binding produces two UV difference peaks near 240 and 294 nm, respectively, that both are the characteristic of phenolic groups binding to yttrium. The molar extinction coefficient of Y-EHPG and Y-HBED are (15.7 ± 0.40) × 103, (15.8 ± 0.80) × 103 cm−1 M−1 at 240 nm, respectively. Using EDTA as a competitor the obtained conditional equilibrium constants of the complexes are log KY-EHPG = 15.07 ± 0.32 and log KY-HBED = 15.18 ± 0.26, respectively. However, the effects of yttrium binding on the fluorescence intensity of EHPG and HBED are quite different, the former showing a decrease but the latter an increase.