Chair of Radiochemistry/Radioecology, Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, 01062 Dresden, Germany.
Central Radionuclide Laboratory, Radiation Protection Office, Technische Universität Dresden, 01062 Dresden, Germany.
Molecules. 2023 May 31;28(11):4469. doi: 10.3390/molecules28114469.
Etidronic acid (1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP, HL) is a proposed decorporation agent for U(VI). This paper studied its complex formation with Eu(III), an inactive analog of trivalent actinides, over a wide pH range, at varying metal-to-ligand ratios (M:L) and total concentrations. Combining spectroscopic, spectrometric, and quantum chemical methods, five distinct Eu(III)-HEDP complexes were found, four of which were characterized. The readily soluble EuHL and Eu(HL) species with log β values of 23.7 ± 0.1 and 45.1 ± 0.9 are formed at acidic pH. At near-neutral pH, EuHL forms with a log β of ~23.6 and, additionally, a most probably polynuclear complex. The readily dissolved EuL species with a log β of ~11.2 is formed at alkaline pH. A six-membered chelate ring is the key motif in all solution structures. The equilibrium between the Eu(III)-HEDP species is influenced by several parameters, i.e., pH, M:L, total Eu(III) and HEDP concentrations, and time. Overall, the present work sheds light on the very complex speciation in the HEDP-Eu(III) system and indicates that, for risk assessment of potential decorporation scenarios, side reactions of HEDP with trivalent actinides and lanthanides should also be taken into account.
依替膦酸（1-羟基亚乙基-1,1-二膦酸，HEDP，HL）是一种被提议的铀（VI）去毒剂。本文在宽 pH 范围内，在不同的金属与配体比（M：L）和总浓度下，研究了其与 Eu(III)（三价锕系元素的非活性类似物）的络合形成。结合光谱、分光光度和量子化学方法，发现了五种不同的 Eu(III)-HEDP 络合物，其中四种进行了表征。在酸性 pH 下，易溶的 EuHL 和 Eu(HL)物种以 logβ 值 23.7±0.1 和 45.1±0.9 形成。在近中性 pH 下，EuHL 以 logβ 值约 23.6 形成，并且还形成一种可能是多核络合物。易溶的 EuL 物种以 logβ 值约 11.2 形成。在碱性 pH 下形成。六元螯合环是所有溶液结构的关键模式。Eu(III)-HEDP 物种之间的平衡受多种参数的影响，例如 pH、M：L、总 Eu(III)和 HEDP 浓度以及时间。总的来说，本工作揭示了 HEDP-Eu(III)体系中非常复杂的形态，表明对于潜在去毒场景的风险评估，还应考虑 HEDP 与三价锕系元素和镧系元素的副反应。
