Expanding Reductive Chemistry and Oxidation State Diversity with the Synthetic Chemistry of the Rare Earth Metals

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The Chemical Synthesis Program of the Chemistry Division supports the project by Professor William J. Evans of the Department of Chemistry at the University of California, Irvine, to investigate chemical compounds that contain the rare earth metals, i.e. scandium, yttrium, and the lanthanides. Molecules and materials that contain these metals are important for technologies such as energy efficient lighting and magnetic devices, and they have been designated strategic materials by the U.S. Government. Professor Evans is using the special properties of the rare earth metals to discover new methods to accomplish one of the most fundamental types of chemical reaction, reduction chemistry. He is also trying to improve the performance of the world's smallest (i.e., molecular) magnets. This project simultaneously involves training the next generation of scientists to study these critically important metals and involves personnel from groups commonly underrepresented in science. The myriad uses of the rare earth elements in everyday technologies are providing an excellent basis for outreach programs at all educational levels. Professor Evans is building upon the recent discovery of new oxidation states for seven rare earth elements in the first molecular complexes of Y2+, Ho2+, Er2+, Tb2+, Pr2+, Gd2+, and Lu2+. The electronic structure of these ions with mixed principal quantum number 4fn5d1 electron configurations is being modeled using computational methods. The generality of obtaining new oxidation states with coordination environments that allow higher-lying orbitals to be populated is being explored synthetically. Because new oxidation states expand opportunities to do redox chemistry, Professor Evans is examining the reaction chemistry and photochemistry of these complexes. The mixed electron configuration of these compounds may lead to an unusual combination of transition metal and rare earth chemistry. The influence of the mixed configuration on physical properties of the compounds is also being studied, because the Ho2+ complex has the highest magnetic susceptibility, 11.4 mu-B, ever observed for a monometallic complex. In general the researchers are using synthetic approaches to explore fundamental aspects of reductive reactivity, oxidation state diversity, and magnetism from new perspectives. Students from diverse backgrounds are currently involved in the project, and the participants are spending time in outreach activities directed towards broadening the participation of underrepresented groups in STEM fields.