ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P83. Influence of Physiological Anions on Spectral Properties of
Lanthanide(III) Complexes with
Ethylenediamine(tetramethylenephosphonic acid) H8EDTMP
R. Janicki, K. Rubka, A. Walkowiak, A. Mondry
Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland,
e-mail: anm@wchuwr.pl
Thermodynamically stable lanthanide(III) complexes with organophosphonate ligands have found a variety of
applications, particularly in the radiopharmaceutical and biomedical NMR fields. Though the complex of
radioactive isotope of 153 Sm(III) with EDTMP, known clinically as Quadramet ® , is in widespread use to relieve
pain from metastatic bone cancer, the mechanism by which it achieves is still unknown. Whereas the uptake by
metastatic tissue in bones of the Sm(III)–EDTMP complex is good, in the case of the Ho(III)–EDTMP is rather
poor. The latter complex also stays longer in blood plasma. To understand these significant differences between
both Ln(III) complexes, we have undertaken studies on spectral properties of light and heavy ions with EDTMP
ligand in the presence of physiological anions.
Previously it was shown that replacement of inner-sphere water molecules and/or hydroxy anions by a carbonate
anion in the Eu(III)–EDTMP complex at physiological pH results in the formation of [Eu(EDTMP)(CO3)] 7–
species [2]. A very good fitting of a carbonate anion into the coordination space vacated by water molecules
and/or hydroxy groups in [Eu(EDTMP)(H2O)2] 5– and [Eu(EDTMP)(H2O)(OH)] 6– species which are in
equilibrium at physiological pH, is a reason that kinetically labile species become inert.
Molecular structure of [Eu(EDTMP)CO3] 7– anion [2].
Therefore in the present work the absorption and/or emission spectra of the mixed Ln(III)–EDTMP–L
complexes (where Ln are Nd, Sm, Eu, Tb, Er, Yb ions and L are carbonate, phosphonate and acetate anions)
have been analyzed and association constants of the Ln(III)–EDTMP–carbonate systems at physiological pH
were determined. The relative stability of various chelates has been discussed.
References:
[1] N.V. Jarvis, J.M. Wagener, G.E. Jackson, J. Chem Soc. Dalton Trans., 1411 (1995).
[2] A. Mondry, R. Janicki, Dalton Trans., 4702 (2006).
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