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Movers And Shakers

Polly Arnold explores the chemistry of rare earths and radioactive elements

This Lawrence Berkeley National Lab chemist shows how f-block complexes can catalyze important reactions like nitrogen fixation

by Katherine Bourzac
April 8, 2022 | A version of this story appeared in Volume 100, Issue 12


A photo of Polly Arnold.
Credit: Salgu Wissmath
Polly Arnold

Polly Arnold is drawn to challenging problems at the far reaches of the periodic table. “It’s all about the f block,” she says of the work in her group, which is split between the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, where she heads the Chemical Sciences Division.


Hometown: London

Education: BA, University of Oxford, 1994; DPhil, University of Sussex, 1997

Current position: Professor of chemistry, University of California, Berkeley, and director of the Chemical Sciences Division, Lawrence Berkeley National Laboratory

LGBTQ+ identity: Queer woman

Favorite lab tool: A torch. Oops, flashlight. Are there actually crystals forming in the bottom of that dark solution, or is it a pale precipitate to be thrown away?

Go-to stress reliever: A run in the Californian sunshine and 180 bpm hard-core techno

This outpost of the periodic table collects the lanthanides (including most of the rare earth elements) and the actinides. These elements are difficult to separate from one another and challenging to study, and until the past couple of decades, many scientists had assumed it wasn’t possible to do interesting chemistry with the f-block elements. “Now my friends and I are showing you can do redox chemistry with all of them—you just have to choose your ligands carefully,” Arnold says.

Arnold doesn’t mind working in the esoteric realms of chemistry; in fact, untrodden paths are sort of her specialty. She grew up in England, and for the last 2 years of education before attending university, she went to an all-boys’ school that allowed a few girls. “It was like a fishbowl,” she says. One of her summer jobs in college was in Jim Henson’s Creature Shop, where she worked on Muppet fur and eyes. “I loved it. It was making stuff, it was a lot of fun, and the people were weird, in a good way,” she says. “I knew I didn’t want to wear a suit.”

She was ultimately drawn to the research lab. In graduate school at the University of Sussex, she worked on making new molecules by co-condensing volatile organic compounds with vaporized lanthanides. She worked with late transition metals, but it wasn’t as challenging as working with the f-block elements, “so it caught my attention less,” she says. The toughest stuff was what captured her focus.

f-Block chemistry is difficult, but it offers new possibilities. The reactivity of compounds containing f-block elements means they’re promising for activating inert molecules such as carbon dioxide and nitrogen gas without the need for high temperatures and pressures, which require large amounts of energy to generate. In 2020, Arnold showed that a uranium complex can catalyze the reduction of N2 to make ammonia under ambient conditions. Because uranium, an actinide, is radioactive, she hopes to adapt this process to work with one of the lanthanides, which should be safer.

The f block has long been seen as “a weird little island at the bottom of the periodic table,” says Tom Welton, a chemist at Imperial College London and the president of the Royal Society of Chemistry. “Polly is part of a generation of chemists who have changed that idea, to show, ‘No, it’s really interesting.’ ”

Arnold moved her lab to Berkeley from the University of Edinburgh in late 2019. Before the move, Welton says, Arnold helped level the playing field for women and other underrepresented people in science, technology, engineering, and mathematics (STEM) in the UK. “Many people talk about diversity, but she did something,” he says. Among other activities, she made a documentary about female scientists at the University of Edinburgh. She also helped expand the efforts of the Royal Society of Chemistry’s diversity committee.

Many people talk about diversity, but she did something.
Tom Welton, professor, Imperial College London

Arnold was awarded the prestigious Order of the British Empire (OBE) in 2017 for this community service. “For her science to be recognized at such a high level while at the same time doing the diversity stuff that led to her getting the OBE—it’s pretty unique,” Welton says.

Arnold says that now that she’s more established (tongue in cheek, she refers to herself as “the elder scientist”), she’s trying to not only level the playing field in STEM but also be more open about her identity as a queer woman. She says she doesn’t want everyone she works with to know everything about her personal life but that being open helps put students and others at ease. It “makes me less frightening to students, and that’s fantastic.”

Jenifer Shafer, an f-block chemist at the Colorado School of Mines, met Arnold at a conference around 2015, shortly after Shafer had come out herself. She says it’s inspiring to have such a luminary of f-block chemistry as an out, female role model.

Arnold’s work at Berkeley had a slow start because of the pandemic—the campus and national lab went into lockdown before she could get her equipment set up and her students situated. Now that things are up and running, she hopes to use her new role to advocate for more US Department of Energy grants for scientists from underrepresented groups, and she and her team are excited to work on new experiments. One project she’s particularly excited about is the opportunity to work with one of the rarest f-block elements—the radioactive metal berkelium, first made in 1949 at her new home institution. She has received a milligram of a short-lived isotope of the radioactive metal from Oak Ridge National Laboratory this year and is eager to study it.



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