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Nicolai Nikishkin (promotion date: 24 January 2013)

Functionalized parazines as ligands for minor actinide extraction and catalysis

Promotion date: January 24.

Promotor: Prof. dr. Jurriaan Huskens

Assistant Promotor: Dr. Willem Verboom

The synthesis of different types of pyrazine-based ligands with specifically tuned donor properties as well as solubility, is based on a newly developed methodology for the palladium-catalyzed P-C cross-coupling of chloropyrazines.

Hydrophilic pyrazine-based extractants revealed a high selectivity for americium over europium and showed a great potential for use in the “innovative selective actinide extraction process (i-SANEX)”, directed towards lanthanide/actinide separation. The same ligand motif being incorporated onto a supramolecular calix[4]arene platform resulted into a series of multivalent ligands, with an outstanding acid resistivity and even higher affinity for americium, than that of monovalent ligands.

The synthesis of novel phosphinopyrazines gave rise to novel, highly active and robust catalytic systems for ketone reduction and polymerization of terminal arylacetylenes in ecologically benign solvents. The above strategies, initially used to design and synthesize novel selective extractants for nuclear waste treatment, proved to be universal and effective in development of ligands for multiple purposes, and uncovered new prospects in the systematic design of novel ligands with improved properties, which are of high demand in industry.

Was your research application driven?

We were a partner of a European consortium working on more safe and effective methods to treat nuclear waste disposals. Extractants directed towards lanthanide/actinide separation can make possible the transmutation of minor actinides, which considerably reduces radiotoxicity of nuclear waste. These ligands must perform under severe conditions and must retain extractability and selectivity in a highly acidic medium, typical for nuclear waste.

The research presented in the thesis comprised a lot of experimental work, from design and synthesis of the ligands to their extraction behaviour study. The ultimate tests were executed at the Forschungszentrum Jülich. There they are specialized and authorized, to carry out the experiments with radioactive materials.

A covalent combination of hard oxygen-donor groups with a soft nitrogen donor unit on a pyrazine scaffold, led to nice results in an early stage of the research already. The extraction values as well as separation factors found in Jülich, successfully fulfilled the demands of the project, after two and a half years of research. Grouping the ligands on a supramolecular calix[4]arene platform increased ligand’s acid resistivity and affinity towards actinides even more.

So, my thesis project was very rewarding. I was very happy to present the results in the Organic Biomolecular Chemistry and in the New Journal of Chemistry. The multidisciplinary nature I rewarded very much so, giving added value to the project. Now I feel like being able to design all kinds of ligands for a multitude of applications.

After successfully completing the minor actinides extraction part of the project, there was some money and time left. Thus we designed and assessed ligands for other important catalytic processes such as ketone hydrogenation and polymerization of arylacetylenes.

The combination of synthesis with physical chemistry methods is an important feature of this work. For example, studying the kinetics of the ketone hydrogenation with our catalytic system, allowed to improve the catalyst performance as well as to get insight into the reaction mechanism. Due to my knowledge and skills on this, I feel I became a broad specialist here, so to say.

What are your future plans?

I like to stay in academic research. I really love the degree of freedom, choosing the topics in which I am interested in. Mesa+ has a great tradition on this, not narrowing down the field of research but looking across disciplinary borders. Here I felt like a highly paid researcher, given a great deal of responsibility. In my opinion, one cannot fail then!

Hopefully I will be able to find a research job in the Netherlands, although the market is a little poor for chemists nowadays.

Did you feel like a Mesa+ member, while working here on your thesis project?

Next to the nice traditional meetings, like the Mesa+ day and X-mas presents and parties with Glühwein, I felt as a part of something big happening here. Colleagues outside Mesa+ recognize it as a highly renowned research institute, opening all doors to me.

I really hope the Dutch government advances in sponsoring the institute, as I am convinced investments in research like this are important for the future of the nation.