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

本研究计画由化学系化学结构、动力学机制B计画资助，目的是设计与研究以过渡金属与镧系元素为基础的新型单分子磁铁。 这项研究将由杰弗里·R·朗和他在加州大学伯克利分校的同事们说。 单分子磁体是一种相对较新的材料，其表现出的特性曾被认为是块状磁性材料。 在非常低的温度下，这些分子可以保持它们的磁化强度，而不会屈服于热随机化，从而使它们成为替代计算机硬盘驱动器和自旋电子器件等应用中当前技术的有趣候选者。 该研究将在很大程度上依赖于合成化学和物理表征技术，使研究生和博士后研究员能够学习各种技能，为未来在学术界或工业界的职业生涯做准备。重要的是，该项目还将通过参与一项旨在向年轻学生介绍科学和高等教育回报方面各种主题的计划，在旧金山弗朗西斯科的小学开展外展活动。该项目还将重新设计维基百科的单分子磁体页面，以最准确和全面地反映该领域的现状，同时也吸引了更广泛的观众有兴趣扩大他们的科学素养。该项目将寻求进一步阐明单分子磁体的结构-功能关系，以及如何最有效地调节它们的性能以产生实际应用所需的更高的工作温度。拟议的工作分为三大类福尔斯。主要目的是更好地理解对称性和配位场强度在增强磁各向异性中的作用。对于过渡金属和镧系元素，焦点将指向具有增强的磁各向异性的分子，其由高轴对称性强制执行。在过渡金属的情况下，线性双坐标系将被作为目标，而对于镧系元素，轴向或赤道配体场将基于每种三价金属的磁各向异性的形状被选择性地选择。第二，磁弛豫现象将与这些更广泛的配体场类别内的电子修改，以解开的因素，最有助于有害的通过势垒（隧道）的过程，最终目标是提高磁阻断温度。这些新分子的同位素标记的类似物也将进行研究，以了解超精细相互作用在通过屏障弛豫过程中的作用。最后一种方法将是使用这种高度各向异性的单核复合物作为自由基桥接分子中的构建单元，其可以表现出强耦合和大自旋基态，从而大大降低快速松弛和随机化的可能性。

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.