Promethium is extremely rare, with only about 0.5 kg occurring naturally in the Earth’s crust at any one time.
Conceptual art depicts the rare earth element promethium in a vial surrounded by organic ligands. Image courtesy of Jacqueline DeMink / Thomas Dyke / ORNL.
Named after the mythical Titan who brought fire to mankind, the name symbolizes human endeavor.
Despite their use in medical research and long-life nuclear batteries, some of their properties remain poorly understood.
“The aim of this project was to explore and gain new knowledge about this extremely rare element,” he said. Oak Ridge National Laboratory.
Dr. Ivanov and his colleagues prepared a chemical complex of promethium, allowing them to characterize it in solution for the first time.
Thus, they uncovered the secrets of this element through a series of meticulous experiments.
“Promethium was the last lanthanide discovered and has been the most difficult to study because it has no stable isotopes,” said Dr. Ilya Popovs, also of Oak Ridge National Laboratory.
“There are thousands of papers on lanthanide chemistry without promethium. It was a glaring flaw in the science as a whole,” said Dr. Santa Giansone-Popova of Oak Ridge National Laboratory.
“Scientists could only guess at most of its properties. Now we can actually measure some of them.”
The researchers linked, or chelated, radioactive promethium with a special organic molecule called a diglycolamide ligand.
The researchers then used X-ray spectroscopy to determine the properties of the complex, including the lengths of the chemical bonds between promethium and neighboring atoms — a scientific first and a long-missing part of the periodic table of elements.
Unlike other rare earth elements, synthetic promethium has no stable isotopes and is therefore only available in very small quantities.
For their research, the scientists produced the isotope promethium-147, which has a half-life of 2.62 years, in sufficient quantity and purity to study its chemical properties.
Remarkably, they were the first to demonstrate the signature of lanthanide contraction in solution for the entire lanthanide series, including promethium, atomic number 61.
Lanthanide contraction is a phenomenon in which elements with atomic numbers 57 through 71 become smaller than expected.
As the atomic number of these lanthanides increases, the radius of their ions decreases.
This contraction results in unique chemical and electronic properties as the same electric charge is confined to a shrinking space.
The authors obtained a clear promethium signal, which allowed them to better define the shape of the trend across the series.
“It’s really amazing from a scientific point of view. When I got all the data I was blown away,” Dr Ivanov said.
“This contraction of chemical bonds accelerates along the atomic series, but slows down significantly from promethium onwards.”
“This is a major breakthrough in understanding the chemical bonding properties of these elements and their structural changes along the periodic table.”
“Among other things, this achievement will ease the difficult task of isolating these valuable elements,” said Dr. Jansonne Popova.
“Our team has been working for a long time to isolate the entire series of lanthanides, but promethium was the last puzzle piece. It’s been very challenging.”
“With today’s advanced technology, we can’t use all these lanthanides as a mixture, because we have to separate them first.”
“This is where shrinkage becomes really important. It basically allows you to separate them, which is still pretty difficult.”
“All of the technological marvels of our time contain these rare earth elements in some form,” Dr Popovs said.
“We’re adding the missing link.”
Team paper Published in today’s journal Nature.
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D.M. Driscoll othersObservation of promethium complexes in solution. NaturePublished online May 22, 2024, doi: 10.1038/s41586-024-07267-6
Source: www.sci.news
