Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Observation of a promethium complex in solution



Bruce D. Ravel, Darren Driscoll, Frankie White, SUBHAMAY PRAMANIK, Jeffrey Einkauf, Dmytro Bykov, Santanu Roy, Richard Mayes, Laetitia Delmau, Samantha Schrell, Thomas Dyke, April Miller, Matt Silveira, Silveira2 van Cleve, Roy Copping, Sandra Davern, Santa Jansone-Popova, Ilja Popovs, Alexander Ivanov


Lanthanide rare earth metals are ubiquitous in modern technologies, but we know little about chemistry of the 61st element, promethium (Pm), a lanthanide which is highly radioactive and inaccessible. Despite its significance, Pm has conspicuously been absent from the experimental studies of lanthanides, impeding our full comprehension of the so-called lanthanide contraction phenomenon – a fundamental aspect of the periodic table that is quoted in general chemistry textbooks. Here we demonstrate a stable chelation of the 147Pm radionuclide (half-life τ ½= 2.62 years) in aqueous solution by the newly synthesized organic diglycolamide ligand. The resulting homoleptic PmIII complex is studied using synchrotron X-ray absorption spectroscopy and quantum chemical calculations to establish the coordination structure and a bond distance of promethium. These fundamental insights allow a complete structural investigation of a full set of isostructural lanthanide complexes, ultimately capturing the lanthanide contraction in solution solely based on the experimental observations. Interestingly, our results reveal somewhat accelerated shortening of bonds at the beginning of lanthanide series, which can be correlated to the separation trends exhibited by diglycolamides. The characterization of the radioactive PmIII complex in an aqueous environment deepens our understanding of intra-lanthanide behavior and the chemistry and separation of the f-block elements.


EXAFS, lanthanide, promethium, solution chemistry


Ravel, B. , Driscoll, D. , White, F. , PRAMANIK, S. , Einkauf, J. , Bykov, D. , Roy, S. , Mayes, R. , Delmau, L. , Schrell, S. , Dyke, T. , Miller, A. , Silveira, M. , van Cleve, S. , Copping, R. , Davern, S. , Jansone-Popova, S. , Popovs, I. and Ivanov, A. (2024), Observation of a promethium complex in solution, Nature, [online],, (Accessed June 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created May 22, 2024, Updated May 30, 2024