En. Rizkalla et Gr. Choppin, COMPLEXATION OF LANTHANIDE IONS BY DIETHYLENETRIAMINE-N,N',N''-PENTA-BETA-PROPIONATE, Journal of alloys and compounds, 207, 1994, pp. 465-467
The stability constants for the formation of the lanthanide chelates L
nH2DTPP0 and LnH3DTPP+ diethylenetriamine-N,N',N''-penta-beta-propiona
te) have been measured in solutions of 0.50 M (NaClO4) ionic strength
by pH measurement. The similar stabilities of the two complexes indica
te that both species involve similar binding sites of the ligand. The
similarity in their entropy and enthalpy values also support such a mo
del. Fluorescence data indicate that the primary coordination sphere o
f the Eu(III) ion in both complexes contains 5.5 +/- 0.5 water molecul
es compared to the value of 8.8 +/- 0.5 for the free Eu(III)(aq) ion.
This is consistent with binding of the lanthanide ion via three donor
sites of DTPP.