Thermal behaviour of hafnium diethylenetriaminepentaacetate studied using the Perturbed Angular Correlation Technique

Abstract

Polyaminecarboxilic ligands like diethylenetriaminepentaacetic acid form stable complexes with many heavy metal ions, excelling as cation chelants especially in the field of radiopharmacy. The aim of this work is to characterize, by using the Time Differential Perturbed Angular Correlations (TDPAC) technique, the hyperfine interactions at hafnium sites in hafnium diethylenetriaminepentaacetate and to investigate their evolution as temperature increases. TDPAC results for KHfDTPA-3H2O obtained by chemical synthesis yield a well defined and highly asymmetric interaction of quadrupole e frequency Wq = 141 Mrad/s, which is consistent with the existence of a unique site for the metal in the crystal lattice. The thermal behaviour of the chelate is investigated by means of differential scanning calorimetry and thermogravimetrical analyses revealing that an endothermic dehydration of KHfDTPA-3H2O takes place in one step between 80 ° C and 180 ° C. The anhydrous KHfDTPA thus arising is characterized by a fully asymmetric and well defined interaction of quadrupole e frequency Wq = 168 Mrad/s.