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MSU scientists reach breakthrough in single-molecule magnet design

June 24, 2023
Assistant Professor of Chemistry, Demir Selvan photographed outside on Jun. 23, 2023.
Assistant Professor of Chemistry, Demir Selvan photographed outside on Jun. 23, 2023.

For the longest time, free radicals of chemical elements were thought of as extremely rare chemical species. Scientists believed that they exhibited uncontrollable behavior because of their high reactivity.

Radicals are chemical systems containing an unpaired electron. That electron, because it’s not coupled to anything, zips around very quickly. Compared to neutral molecules, where atoms are bonded through paired electrons with opposite orientations of spins, free radicals can either be electrically neutral, or positively or negatively charged.

“We became really good experts in making new radicals that were entirely unknown yet, not only in the world of lanthanide chemistry,” MSU assistant professor Dr. Selvan Demir said. “Aside from the Bi23- radical, we also made other new radicals, organic radicals, that were published last year and this year.”

Demir and her team have achieved a breakthrough in single-molecule magnet design. They successfully employed the heaviest, non-toxic p-block element bismuth in their research.

Bismuth is a chemical element that finds its main uses in pharmaceuticals, sprinkler systems and cosmetics.

Placing a bismuth radical in between lanthanides results in stronger magnetic communication because it allows for bismuth’s unpaired electrons to couple much more strongly. Accomplishing this task in a laboratory setting comes with immense difficulty.

The team work with the heaviest elements of the periodic table, specifically lanthanides, which are rare earth elements belonging to the F block of the periodic table.  All of their work is new. They’re working to change the electronics of the inner orbital, known as the F orbital.

“If something is very inner core, if you want that electron to somehow interact with something else, you need to be a little more clever in what kind of system you want to design to actually get the electron to interact with something else,” Demir said.

What scientists want is for the electron spins to flip as slowly as possible, because if that happens, they can store information on that spin as the orientation of that spin.

“Lanthanides are very oxophilic, meaning they react very easily with oxygen,” Demir said. “If that happens, you get lanthanide oxides, and those are super robust. You cannot get any chemistry done after that, so that’s why you must protect these metals from oxygen.”

Demir’s lab uses special equipment such as Schlenk Lines, which are glassware that put vacuums on vessels and then introduce a protecting atmosphere around them such as nitrogen or argon.  Nitrogen, for example, is non-harmful and found in plentiful quantities on Earth's atmosphere.

“From every field reaction, you learn something and then you alter the reaction conditions in a way that hopefully will get you the product that you want to have eventually,” Demir said.

Currently, Demir and her lab are looking heavily into magnetism. Once they have created their crystals, they place them into magnetometers and subject them to an external magnetic field. Magnetometers measure the strength and sometimes the direction of magnetic fields.

“When we have unpaired electrons in the system, they will interact with the external magnetic fields, because then you can basically direct with the magnetic field whether they should flip or not,” she said. “When it reacts, we take that response, measure it, and then that's magnetism.”

This process also involves a heavy amount of computational chemistry, because once new compounds have been produced, scientists can investigate their electronic structures to understand the compound’s properties.

“And of course, we do a lot of NMR and X-ray crystallography with the crystals that we grow," Demir said.

NMR stands for Nuclear Magnetic Resonance spectroscopy, which is an analytical chemistry technique meant to observe the molecular structure of a material.  X-ray crystallography determines the atomic and molecular structure of crystals, specifically.

We put in a new sample and then we use radiation, and in this case, molybdenum," Demir said. "We are thus able to find out the exact atomic positions of whatever compound that the crystal consists of. Using that, we can solve it with certain software, and then we know exactly what the identity of the crystal is.”

Demir said this is the ultimate truth for any new compound that is made.

“What's cool about bismuth is it’s a very heavy element, and heavy elements mean you have a lot more electron shells," Demir said. "Therefore, when it interacts with these lanthanide ions, it can actually reach the inner core orbitals of the lanthanides.”

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Synthesis, uranium, organometallic chemistry and quantum bits are also areas of focus in Demir’s lab.

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