RUI: CHARGE- AND SPIN-DENSITY STUDY OF EXCHANGE ANISOTROPY IN METAL-ORGANIC QUANTUM MAGNETS

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****Technical Abstract****The research will focus on two synergistic activities; (a) synthesis of model low-dimensional (1- and 2D) quantum magnets, especially chains and square lattices and (b) examination of charge- and spin-density in those compounds. We endeavor to learn more about the electronic distribution and influences thereof, the exchange pathways in selected Cu(II), Ni(II), and Co(II)-based organic magnets. Our strategy will combine primary structural components assembled by coordinate covalent bonds (CCB's) between M(II) or Ir(IV) cations and diazine ligands [e.g., pyrazine (pyz)], with such ligands being well-known for their good Lewis basicity and ability to act as bridging functionalities and exchange mediators. Secondary interactions based on strong hydrogen bonds (e.g., F---H-O and F---H---F) will provide us with further structural control and an additional magnetic pathway that may dominate M-pyz-M, thus enabling exchange anisotropy. Initially, we will focus on several of the polymers recently developed by our group and then shift toward new systems featuring previously unknown combinations of ancillary ligands. The latter will allow us to systematically perturb electronic states in order to interrogate the salient features of charge- and spin-density distributions in a variety of materials. Undergraduates, from all backgrounds, will carry out the syntheses and assist with data analysis and characterization of samples, travel to state-of-the-art research facilities, and attend/present their work at professional conferences.****Non-Technical Abstract****Metal-organic magnets constitute a major research area in the condensed matter sciences. Their popularity stems from the many synthetic variations that can be made which then allows for systematic investigation of their magnetic properties. Our fundamental research interests lie in using combinations of particular chemical bonds to design architectures of varying dimensionalities so as to tune the important magnetic interactions. In this project, we will utilize X-ray and neutron diffraction methods as well as solid state NMR to study the electron density distributions in designer magnets in order to evaluate the efficiency of certain bond types (e.g. exchange anisotropy) which will depend on the metal ions present. This work could lead to improved materials design and synthesis protocols in order to more effectively prepare multifunctional materials, i.e., those that contain multiple physical properties. Our materials discovery effort will be complemented by extensive characterization and theoretical work. The highly collaborative nature of this project makes use of several national and international user facilities and will provide unique opportunities for undergraduate students to travel with the PI to partake in many of the planned experiments as well as to attend professional conferences. Student involvement in the project will stimulate their growth and enthusiasm, and provide the necessary background to begin graduate work in the future or to go on to careers in the chemical and physical sciences. Mentorship and training of undergraduate students is a high priority of this project.