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

****技术摘要****研究将集中在两个协同活动；(a)模型低维（1-和2D）量子磁体的合成，特别是链和方晶格；(b)检查这些化合物中的电荷和自旋密度。我们努力更多地了解电子分布及其影响，以及在选定的Cu(II), Ni（II）和Co（II）基有机磁体中的交换途径。我们的策略将结合由M（II）或Ir（IV）阳离子与嘧啶配体[例如吡嗪（pyz）]之间的配位共价键（CCB）组装的初级结构组分，这些配体以其良好的刘易斯碱度和作为桥接功能和交换介质的能力而闻名。基于强氢键的二次相互作用（例如，F—H—o和F—H—F）将为我们提供进一步的结构控制和可能主导M-pyz-M的额外磁途径，从而实现交换各向异性。最初，我们将专注于我们小组最近开发的几种聚合物，然后转向具有以前未知的辅助配体组合的新系统。后者将允许我们系统地扰动电子态，以便询问各种材料中电荷和自旋密度分布的显著特征。来自不同背景的本科生将进行合成并协助数据分析和样品表征，前往最先进的研究设施，并参加/在专业会议上展示他们的工作。****非技术摘要****金属有机磁体是凝聚态科学的一个重要研究领域。它们的流行源于许多可以合成的变化，然后允许系统地研究它们的磁性。我们的基础研究兴趣在于利用特定化学键的组合来设计不同维度的结构，从而调整重要的磁相互作用。在这个项目中，我们将利用x射线和中子衍射方法以及固态核磁共振来研究设计磁体中的电子密度分布，以评估某些键类型（例如交换各向异性）的效率，这将取决于存在的金属离子。这项工作可能会导致改进材料设计和合成方案，以便更有效地制备多功能材料，即那些包含多种物理性质的材料。我们的材料发现工作将辅以广泛的表征和理论工作。这个项目的高度协作性质利用了几个国内和国际用户设施，并将为本科生提供独特的机会，与PI一起旅行，参加许多计划中的实验以及参加专业会议。学生参与该项目将激发他们的成长和热情，并为将来开始研究生工作或继续从事化学和物理科学的职业提供必要的背景。指导和培训本科生是这个项目的重中之重。

****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.