Synthesis, Characterization, and Reactivity Studies of Cerium, Thorium, and Uranium-Ligand Multiple Bonds

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With support from the Chemical Synthesis Program in the Chemistry Division, Professor Eric Schelter at the University of Pennsylvania is investigating the chemistry of cerium, thorium, and uranium compounds. His team is testing new ways that these metals form chemical bonds to nitrogen and phosphorus. The resulting compounds will be evaluated for their relevance to the production of nitrogen- and phosphorus-containing pharmaceuticals and new materials. The project is particularly focused on ways that organic scaffolds can be build to wrap around the metals in ways that stabilize new kinds of bonds. Guidance and insight into the new bonding patterns are obtained by comparing the structures of the various cerium vs thorium vs uranium compounds. Rare earth materials are used extensively in diverse applications such as catalysts, phosphors and polishing compounds as well as for illuminated screens on electronic devices and air pollution control.Professor Schelter supervises a laboratory that provides graduate and undergraduate students with both theoretical and hands-on experimental training in the synthesis and reactivity of the rare earth elements. The effort supports outreach projects for elementary and high school students; Young students are instructed about the technology and strategic importance of rare earth elements.With support from the Chemical Synthesis Program in the Chemistry Division, Professor Eric Schelter at the University of Pennsylvania leads a program aimed at understanding cerium-ligand multiple bonds. The research will establish their d/f bonding patterns and electronic structures using spectroscopy and computation. Comparative reactivity studies with 5f-element congeners will provide fundamental insights into chemical bonding. The central hypothesis is that control of the relatively large 5d- character in the bonding of cerium(IV) will enable isolation of new examples of metal-ligand multiple bonds. Cerium, thorium, and uranium-heteroatom multiple bonds such as nitrides, phosphinidines, and others will be synthesized and their electronic structures compared. Reactivity patterns for cerium-ligand multiple bonds will be established. The fundamental knowledge developed from the research is expected to demonstrate how bonding of elements at the key d-f interface of the periodic table could be understood, and how their chemical and reactivity properties can be leveraged for new applications. Rare earth materials are used extensively in diverse applications such as catalysts, phosphors and polishing compounds as well as for illuminated screens on electronic devices and air pollution control. Advancing the chemistry of rare earths and developing new and distinctive chemical reactions for thorium and uranium contributes to improving beneficiation and separations of those elements, and therefore national security as many of these elements are not mined in the US. This project supports instruction of high school students about the importance of rare earth elements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.