LLNLの化学者は、放射性物質を研究するための画期的な方法を開発しました。(LLNL chemists double down with breakthrough method to study radioactive materials)


2023-02-27 ローレンスリバモア国立研究所(LLNL)

◆この研究の成果は、Nature ChemistryおよびInorganic Chemistryに掲載され、両雑誌の表紙に掲載されました。また、Nature誌でも紹介されました。今後、LLNLチームはこの研究を継続し、従来の方法では研究できなかった最も珍しいおよび毒性の高い元素に関する化学的知見を拡大することを目指しています。


マイクログラムスケールの希少同位体化合物の合成、分離、特性評価のための配位子としてのポリオキソメタレート Polyoxometalates as ligands to synthesize, isolate and characterize compounds of rare isotopes on the microgram scale

Ian Colliard,Jonathan R. I. Lee,Christopher A. Colla,Harris E. Mason,April M. Sawvel,Mavrik Zavarin,May Nyman & Gauthier J.-P. Deblonde
Nature Chemistry  Published:01 September 2022

LLNLの化学者は、放射性物質を研究するための画期的な方法を開発しました。(LLNL chemists double down with breakthrough method to study radioactive materials)


The synthesis and study of radioactive compounds are both inherently limited by their toxicity, cost and isotope scarcity. Traditional methods using small inorganic or organic complexes typically require milligrams of sample—per attempt—which for some isotopes is equivalent to the world’s annual supply. Here we demonstrate that polyoxometalates (POMs) enable the facile formation, crystallization, handling and detailed characterization of metal–ligand complexes from microgram quantities owing to their high molecular weight and controllable solubility properties. Three curium–POM complexes were prepared, using just 1–10 μg per synthesis of the rare isotope 248Cm3+, and characterized by single-crystal X-ray diffraction, showing an eight-coordinated Cm3+ centre. Moreover, spectrophotometric, fluorescence, NMR and Raman analyses of several f-block element–POM complexes, including 243Am3+ and 248Cm3+, showed otherwise unnoticeable differences between their solution versus solid-state chemistry, and actinide versus lanthanide behaviour. This POM-driven strategy represents a viable path to isolate even rarer complexes, notably with actinium or transcalifornium elements.

溶液状態NMRによるポリオキソメタレートによる3価ランタニドおよびアクチニドの錯形成の対比 Contrasting Trivalent Lanthanide and Actinide Complexation by Polyoxometalates via Solution-State NMR

Christopher A. Colla, Ian Colliard, April M. Sawvel, May Nyman, Harris E. Mason, and Gauthier J.-P. Deblonde
Inorganic Chemistry  Published:December 29, 2022

Abstract Image


Deciphering the solution chemistry and speciation of actinides is inherently difficult due to radioactivity, rarity, and cost constraints, especially for transplutonium elements. In this context, the development of new chelating platforms for actinides and associated spectroscopic techniques is particularly important. In this study, we investigate a relatively overlooked class of chelators for actinide binding, namely, polyoxometalates (POMs). We provide the first NMR measurements on americium–POM and curium–POM complexes, using one-dimensional (1D) 31P NMR, variable-temperature NMR, and spin-lattice relaxation time (T1) experiments. The proposed POM–NMR approach allows for the study of trivalent f-elements even when only microgram amounts are available and in phosphate-containing solutions where f-elements are typically insoluble. The solution-state speciation of trivalent americium, curium, plus multiple lanthanide ions (La3+, Nd3+, Sm3+, Eu3+, Yb3+, and Lu3+), in the presence of the model POM ligand PW11O397– was elucidated and revealed the concurrent formation of two stable complexes, [MIII(PW11O39)(H2O)x]4– and [MIII(PW11O39)2]11–. Interconversion reaction constants, reaction enthalpies, and reaction entropies were derived from the NMR data. The NMR results also provide experimental evidence of the weakly paramagnetic nature of the Am3+ and Cm3+ ions in solution. Furthermore, the study reveals a previously unnoticed periodicity break along the f-element series with the reversal of T1 relaxation times of the 1:1 and 1:2 complexes and the preferential formation of the long T1 species for the early lanthanides versus the short T1 species for the late lanthanides, americium, and curium. Given the broad variety of POM ligands that exist, with many of them containing NMR-active nuclei, the combined POM–NMR approach reported here opens a new avenue to investigate difficult-to-study elements such as heavy actinides and other radionuclides.