A Coordination Chemistry Approach to the Synthesis of Single-Molecule Magnets

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The goal of this research project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, is to design and study new single-molecule magnets based upon transition metal and lanthanide elements. The research will be carried out by Professor Jeffrey R. Long and coworkers at the University of California, Berkeley. Single-molecule magnets are a relatively new class of materials that exhibit properties once thought to be relegated to bulk magnetic materials. At very low temperatures, these molecules can retain their magnetization without succumbing to thermal randomization, thus rendering them intriguing candidates for replacing current technologies in applications such as computer hard drives and spintronics devices. The research will depend heavily on synthetic chemistry and physical characterization techniques, enabling graduate students and post-doctoral fellows to learn a wide array of skills in preparation for future careers in academia or industry. Importantly, the project will also devote time to outreach activities at elementary schools in the San Francisco Bay Area, through participation in a program intended to introduce young students to various topics in science and the rewards of higher education. The project will also redesign the Wikipedia Single-Molecule Magnets page to most accurately and comprehensively reflect the state of the field, while also appealing to a broader audience interested in expanding their scientific literacy. This project will seek to further elucidate the structure-function relationship in single-molecule magnets, and how their properties can be most effectively tuned to generate higher operating temperatures necessary for practical applications. The proposed work falls into three broad categories. The primary aim will be to better understand the roles of symmetry and ligand field strength in enhancing magnetic anisotropy. For both transition metals and lanthanides the focus will be directed toward molecules with enhanced magnetic anisotropy that is enforced by high axial symmetry. In the case of transition metals, linear two-coordinate systems will be targeted, while for the lanthanides, axial or equatorial ligand fields will be selectively chosen based on the shape of the magnetic anisotropy for each trivalent metal. Second, magnetic relaxation phenomenon will be correlated with electronic modifications made within these broader ligand field categories to unravel the factors that contribute most to detrimental through-barrier (tunneling) processes, with the ultimate goal of enhancing magnetic blocking temperatures. Isotopically labeled analogues of these new molecules will also be studied to understand the role of hyperfine interactions in through-barrier relaxation processes. A final approach will be to use such highly anisotropic mononuclear complexes as building units in radical-bridged molecules, which can exhibit strong coupling and large spin ground states that greatly minimize the likelihood of rapid relaxation and randomization.