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

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With the support of the Chemical Synthesis (SYN) Program of the Chemistry Division, Professor William J. Evans, Chemistry Department, University of California – Irvine is studying the chemistry of seven new oxidation states of rare earth elements. Rare earths are heavy metals that have vital roles in electronics, medicine, and others. The rare earth metals most commonly have an oxidation state of +3, but some can have other values such as +2. This project explores the chemistry of seven rare earth elements for which a +2 oxidation state has recently been discovered. Elements with this new oxidation state have properties which make them ideal for applications in energy conservation through magnetism (neodymium in the world’s most powerful magnets) and lighting (europium and terbium in energy efficient lighting) as well as in medicine (gadolinium in magnetic resonance imaging), and catalysis (cerium in automotive catalytic converters). The Evans group is studying how these new oxidation states can impact fundamental chemistry, while training students in the science of these strategically important metals. Professor Evans is also pursuing applications in the development of the smallest, most efficient, magnets that can be designed at a molecular level, namely single-molecule magnets, and in quantum information science to make new types of quantum bits, i.e. qubits. The project provides training and education in the manipulation and application development of the rare earth elements and contains an outreach component that encourages middle and high school students to continue in science.The chemistry of new +2 ions of praseodymium, gadolinium, terbium, holmium, erbium, and lutetium is being explored to evaluate the special reactivity and physical properties that can arise from their unexpected electron configurations which involve not only the valence 4f orbitals but also the higher energy 5d orbitals. These 4fn5d1 ions differ from traditional +2 oxidation states of the lanthanide metals that have 4fn+1 electron configurations. The chemistry of the new +2 rare earth ion of yttrium, a 4d1 system, is also being studied for comparison. The synthesis of new molecular complexes of these ions has led to a rapidly evolving perspective of how these new ions can be utilized. For example, a molecular complex of Lu2+ has been found to have one of the largest electron-nucleus hyperfine coupling constants that provides a stable transition called a clock transition that could be used as a qubit with minimum noise. The project also will seek to discover new small molecule activation reactions, e.g. with nitrogen and nitrogen oxides, and other new oxidation states, e.g. the +1 ions of the rare earth metals. In addition to training students to develop technical expertise of f-block chemistry there is significant outreach to middle and high school students and participation in a University of California - Irvine Chemistry Undergraduate Scholars Program to support first generation, low income and minority students in General Chemistry through peer mentoring.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.