Radiolytic Evaluation of 3,4,3-LI(1,2-HOPO) in Aqueous Solutions

Abstract

The octadentate hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) (abbreviated as HOPO) has been identified as a promising candidate for both chelation and f-element separation technologies, two applications that require optimal performance in radiation environments. However, the radiation robustness of HOPO is currently unknown. Here, we employ a combination of time-resolved (electron pulse) and steady-state (alpha self-radiolysis) irradiation techniques to elucidate the basic chemistry of HOPO and its f-element complexes in aqueous radiation environments. Chemical kinetics were measured for the reaction of HOPO and its Nd(III) ion complex ([NdIII(HOPO)]-) with key aqueous radiation-induced radical transients (eaq-, H• atom, and •OH and NO3• radicals). The reaction of HOPO with the eaq- is believed to proceed via reduction of the hydroxypyridinone moiety, while transient adduct spectra indicate that reactions with the H• atom and •OH and NO3• radicals proceeded by addition to HOPO's hydroxypyridinone rings, potentially allowing for the generation of an extensive suite of addition products. Complementary steady-state 241Am(III)-HOPO complex ([241AmIII(HOPO)]-) irradiations showed the gradual release of 241Am(III) ions with increasing alpha dose up to 100 kGy, although complete ligand destruction was not observed.