CAREER: Design Strategies for High-Performance Bismuth- and Lanthanide-Based Single-Molecule Magnets

在化学系化学结构、动力学和机制-B计划的支持下，密歇根州立大学化学系的Selvan Demir正在利用有机金属化学开发具有有趣磁性的新型分子化合物，称为单分子磁体(SMM)。SMM令人兴奋的潜在应用范围从高密度信息存储、量子计算到基于自旋的电子设备，但取决于增加自旋反转势垒、磁阻挡温度和矫顽场-所有这些指标都描述了分子在移除外加磁场后保留信息的能力。该项目将开发新的合理设计策略，以产生由铋和顺磁性稀土元素组成的新型SMM。铋和镧系元素的电学特征的结合可能会带来具有无与伦比的性能特征的新一代SMM。该项目以多种方式将学术研究和教育紧密结合在一起，为公众和所有阶段的学生提供最高水平的教育。这包括一种创造性的方法“科学与艺术相遇”，它利用可视化的力量，促进进入精心设计的基于旋转的科学主题，其中计划在画廊和博物馆举行展览。开发一门带有磁学工具包的实验量子信息科学课程也包括在当地学校的讲座中。单分子磁体(SMM)表现出自旋反转的障碍，在没有量子隧道的情况下，磁滞类似于块状磁体。因此，一个最重要但也是最具挑战性的目标之一是同时增加自旋基态和磁各向异性，这是追求强耦合多核SMM的关键目标。强耦合是需要的，因为它抑制了高温SMM所需的诸如量子隧道之类的快速弛豫路径。此外，必须探索新的化学空间来推动该领域的发展。因此，本项目旨在开发新的合理设计策略，以产生(I)第一个以铋为中心的SMM，(Ii)新的含铋根的稀土SMM，(Iii)由铋和氮给体组成的新的氧化还原活性杂环配体，(Iv)第一个由铋氮杂环桥组成的多核SMM，以及(V)第一个含铋氮杂环自由基的多核SMM。从根本上讲，通过抗磁桥和顺磁桥对磁耦合路径的彻底研究有可能促进对SMM中发生的松弛动力学的了解，并通过这样做，为未来的SMM设计铺平道路。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Selvan Demir of the Department of Chemistry at Michigan State University is employing organometallic chemistry to develop new classes of molecular compounds with interesting magnetic properties, known as single-molecule magnets (SMMs). The exciting potential applications of SMMs span from high-density information storage, quantum computing, to spin-based electronic devices, but hinge on increasing the spin-reversal barrier, magnetic blocking temperature, and coercive field - all metrics that describe the molecule’s ability to retain information after removing an applied external magnetic field. This project will develop new rational design strategies to engender new types of SMMs comprising bismuth and the paramagnetic lanthanides. The combination of the electronic features of bismuth and lanthanide sites could usher in a new generation of SMMs with unparalleled performance characteristics. The project tightly integrates academic research and education in several ways to provide the highest level of education to the public and students at all stages. This includes a creative approach “Science Meets Art” that utilizes the power of visualization to facilitate entry into the elaborate spin-based science subject where exhibitions in a gallery and museums are planned. The development of an experimental quantum information science course accompanied with a magnetism kit is also encompassed alongside lectures at local schools.Single molecule magnets (SMMs) exhibit a barrier to spin reversal and in the absence of quantum tunneling, magnetic hysteresis similar to bulk magnets. Therefore, one of the most important but also challenging goals is to increase simultaneously spin ground state and magnetic anisotropy, critical goals in the pursuit of strongly coupled multinuclear SMMs. Strong coupling is required as it suppresses fast relaxation pathways such as quantum tunneling which is needed for high-temperature SMMs. In addition, new chemical space must be explored to advance the field. Accordingly, this project aims to develop new rational design strategies to engender (i) the first bismuth-centered SMMs, (ii) new lanthanide SMMs containing bismuth radicals, (iii) new redox-active heterocyclic ligands composed of bismuth and nitrogen donors, (iv) the first multinuclear SMMs consisting of bismuth-nitrogen heterocyclic bridges, and (v) the first multinuclear SMMs containing bismuth-nitrogen heterocyclic radicals. From a fundamental point of view, the thorough study of magnetic coupling pathways through diamagnetic and paramagnetic bridges has the potential to advance knowledge of relaxation dynamics occurring in SMMs, and in so doing, pave the way for future SMM design.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.