discovered_02_2015

WWW.HZDR.DE discovered 02.15 TITLE The researchers working with Peter Kaden use NMR, or nuclear magnetic resonance spectroscopy, a technique that was developed as early as the 1940s and is used to determine the components of a sample as well as in fields such as medicine. A strong magnetic field is applied to orient the nuclear spin of the elements being studied, while at the same time radio-wave pulses are stimulating them. The behavior of the nuclear spin will change depending on the chemical environment, before ultimately returning to its initial state. This process can be measured and analyzed. Scientists are interested in aspects such as the influence of the actinides on the nuclear spin of nitrogen atoms in organic and inorganic compounds that could serve as bonding partners. "We see a dramatic shift in the signals for the nitrogen, which cannot be fully explained by electrostatic interaction alone," says Peter Kaden. From this researchers conclude that electrons are exchanged between neighboring atoms, meaning that a chemical bond has been established. "This is very recent research, so now what we urgently need is support from theoretical chemistry," the chemist emphasizes. "Not only the experiments, but also the theoretical calculations for actinides are very demanding." Such calculations are incredibly cost-intensive and run for years. From small to large Evidence of this special type of bond in actinide compounds is fundamental. NMR spectroscopy helps researchers to understand the properties of radioactive heavy metals and thus be able to better describe their behavior when they come in contact with organic materials for example. "Once we have successfully understood the interactions on the molecular level, we can later support reliable dispersion calculations," the Helmholtz researcher says. It would then be possible to predict the reactions of radioactive actinides in case of an emergency - What mobilizes them, what do they bond to, and most of all: How can they be immobilized again? Strengthen expertise on-site Actinides are radioactive - and generally remain so for a very long time. Alpha radiation is especially dangerous if it makes it into the body. For this reason, only a handful of research institutions nationwide are allowed to study radioactive heavy metals. "Very strict safety precautions are necessary," says Peter Kaden. "Moreover, the substances themselves, even in the smallest amounts as we use them, are very expensive since even just preparing and purifying them is extremely costly." The chemist has been working in Dresden-Rossendorf for just a few months now. Previously, he was the specialist in charge of NMR spectroscopy of actinide compounds at KIT. Now he brings this expertise to HZDR. "The conditions here are excellent, there are so many opportunities. The HZDR is very interdisciplinary, has just about all relevant measuring devices available, and has an established specialist on-site for every method." In addition to Peter Kaden, institute director Thorsten Stumpf is currently hard at work surrounding himself with more actinide experts from around the country and abroad. "We want to strengthen the expertise we already have here at this location," he emphasizes. The HZDR will then become one of the few institutions worldwide working to shed light on the world of actinide chemistry using a variety of spectroscopy methods. PUBLICATION: P. Kaden et al.: "Evidence for covalence in a N-donor complex of americium(III)", in Dalton Transactions 06/2013 (DOI: 10.1039/ c3dt50953b) _Institute of Resource Ecology at HZDR Dr. Peter Kaden p.kaden@hzdr.de CONTACT PROOF: Doctoral candidate Claudia Wilke analyzes the NMR spectra in order to better understand the properties of radioactive heavy metals and thus be able to better describe the interaction with organic materials. Photo: Oliver Killig

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