Contact

Dr. Solveig Pospiech

Head Thermodynamics of Actinides
s.pospiechhzdr.de
Phone: +49 351 260 2430

THEREDA

RES³T

Smart Kd-concept

Actinide thermodynamics department

Research

The department of “Thermodynamics of Actinides” is hosting a significant part of the analytical backbone of the institutes, e.g. mass spectrometry, atomic emission spectrometry, elemental analyses, powder diffraction, vibrational and nuclear magnetic resonance spectroscopy. This allows us to work on several steps in the thermodynamics value chain.

From a chemical point of view, the focus is set on heavy metal contaminants, namely long-lived radionuclides. The derivation of parameters describing hydrolysis, aqueous complexation, surface reactions or solubilities are combined with structural investigations to validate the species set forming reactions, enabling mechanistic models. Such parameters are fed into respective databases after verification. Gaps still remaining can be closed by applying different estimation methods, from mineral analogies to Linear Free Energy Relationships.

Combined with field data (mineralogical composition, porosity, pH, redox potential, ionic strength, temperature, or CO₂ partial pressure), geochemical speciation patterns and radionuclide retardation can then be computed for complex systems on different scales. To name just a few, we worked on cementitious barriers with organic additives, with real-world crystalline samples or with Chornobyl soils. There, also, geostatistics helps to map the heterogeneities observed, and sensitivity / uncertainty analysis not only increases confidence in computational results but supports also the identification of critical parameters and submodels.

Quite recently, these approaches were complemented by machine learning methods, this will eventually lead to digital twins for nuclear waste repositories. Eventually, this shall bridge the distance between atomistic investigations and the large-scale prognostics required e.g. in performance assessment covering distances of several km over up to one million years.

The actual major research topics of our department can be summarized as follows:

Spectroscopic characterization of heavy metal species in aqueous solutions and at mineral surfaces.
Development and parameterization of models describing surface complexation phenomena in complex systems (e.g. natural clays).
(Radio)chemical analyses of contaminant elements as well as matrix compounds down to the ultratracer level.
Set-up of thermodynamic data bases for prospective deep nuclear waste repositories.

Latest publication

The second nitrogen fits: Development of diazine-based macrocy-clic chelators to stably bind radionuclides used in targeted alpha therapy

Blei, M. K.; Waurick, L.; Drobot, B.; Brühlmann, S. A.; Duchemin, C.; Mamis, E.; Inzamam, M.; Stora, T.; Audouin, N.; Sounalet, T.; Kopka, K.; Stumpf, T.; Stadlbauer, S.; Kretzschmar, J.; Mamat, C.

Abstract

Identifying suitable chelators for 212Pb, 223Ra, and 225Ac and their diagnostic counterparts 131Ba, 133La, and 203Pb remains one of the major challenges in the development of radiopharmaceuticals for targeted alpha therapy. Four novel macrocyclic chelators containing the 2,4- and 2,6-pyrimidine moiety (pym 2,4 and pym 2,6), along with a combination thereof (pym-mix), as well as the pyrazine moiety (pazi), were synthesized and fully characterized. Protonation constants (pKa) were de-termined using 1H NMR spectroscopy. Stability constants (log K) for the complexes with La3+ (11.8–12.6), Ba2+ (10.1–10.3), and Pb2+ (15.3–15.5) are lower compared to macropa. However, pH-dependent binding affinities (pKd,M) with the novel chelators are higher for Ba2+ (8.7–8.9) and comparable or slightly lower for La3+ and Pb2+ at pH 6. DFT calculations enabled comprehensive elucidation of the molecular structures, facilitating in-depth analyses of the coordination environment. The determined 15N NMR chemical shifts of free chelators and complexes help to explain distinct complexation behavior. Final-ly, the novel chelators were radiolabeled with 131Ba, 223Ra, 133La, 225Ac, 203Pb, and 212Pb, and the radiochemical conversions were compared to results with macropa. All 223Ra-complexes were incubated in human serum, pointing out an increased kinetic inertness and stability.

Keywords: barium-131; radium; targeted alpha therapy; actinium-225; macropa

Inorganic Chemistry 65(2026), 22246
DOI: 10.1021/acs.inorgchem.6c01646

Permalink: https://www.hzdr.de/publications/Publ-42963

More publications

Team

Name	Bld./Office	+49 351 260	Email
Head
Dr. Solveig Pospiech	801/P250	2430	s.pospiechhzdr.de
Employees
Name	Bld./Office	+49 351 260	Email
Dr. Frank Bok	801/P202	3551	f.bok@hzdr.de
Prof. Dr. Vinzenz Brendler	801/P250	2430	v.brendler@hzdr.de
Rodrigo Castro Biondo			r.castro-biondohzdr.de
Alexandra Duckstein	801/P153	2774	a.ducksteinhzdr.de
Dr. Jerome Kretzschmar	801/P207	3136	j.kretzschmarhzdr.de
Dr. Elmar Plischke			e.plischkehzdr.de
Dr. Anke Richter	801/P202	2426	anke.richterhzdr.de
Raj Sarkar	801/P103	2720	r.sarkarhzdr.de
Dr. Katja Schmeide	801/P208	2436 2513	k.schmeidehzdr.de
Salim Shams Aldin Azzam	801/P103	2720	s.shamshzdr.de
Claudia Sieber			c.sieberhzdr.de
Susanne Zechel	801/P352	3328	s.zechelhzdr.de
Other employees
Name	Bld./Office	+49 351 260	Email
Liya Tomy	F100/431	4438	l.tomyhzdr.de

Analytics

Name	Bld./Office	+49 351 260	Email
Head
Dr. Harald Foerstendorf	801/P251	3664 2504	h.foerstendorfhzdr.de
Employees
Name	Bld./Office	+49 351 260	Email
Nick Augustin			n.augustinhzdr.de
Sabrina Beutner	801/P203	2429 2528	s.beutnerhzdr.de
Tim Gitzel	801/P316	2025 2517	t.gitzelhzdr.de
Dominik Goldbach	801/P203	3198	d.goldbachhzdr.de
Karsten Heim	801/P201	2434 2504	k.heimhzdr.de
Sylvia Schöne	850/102.1	2526 3198	s.schoene@hzdr.de, s.schoenehzdr.de