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

在这个由化学系化学结构、动态和机理B计划资助的项目中，加州大学伯克利分校化学系的Jeffrey Long教授正在设计和合成新的单分子磁体。单分子磁体是在低温下表现为纳米级磁体的分子，可以显示出类似于经典和量子系统的磁性。这项工作的一个潜在的直接应用是在磁数据存储、量子计算和自旋电子学领域，然而通过在分子水平上了解磁性而获得的知识适用于各种各样的磁性材料。单分子磁体通常只能在非常低的温度(低于60K)下工作。该项目的目标是合成具有更高工作温度的新分子。该项目位于无机化学、配位化学和物理学的交界处。龙教授和他的小组成员都积极地向广大科学受众传播他们的工作，小组中的研究生参加项目，将他们安排在当地的小学和中学课堂上实践科学课程。单分子磁体是具有磁双稳基态的分子。当热能相对于这些态之间的热障很小时，磁性分子可以在没有外加磁场的情况下保持其磁化。这项拟议的研究采用了三种策略来合成在更高温度下工作的单分子磁体。第一种是设计具有增强磁各向异性的系统，这将增加磁弛豫的热障。过渡金属和稀土配合物都将采用高度轴向配位环境，以获得更高的磁各向异性。第二种策略是利用强的磁耦合来缓解使热障变短的弛豫过程的影响。过渡金属和稀土络合物都将与自由基桥配体偶联，从而促进强烈的金属-自由基磁交换。对于过渡金属络合物，直接的金属-金属相互作用也会导致强耦合的磁中心。此外，将开发混合的3D-4F系统，以利用镧系元素的大磁各向异性和过渡金属的强交换耦合。最后，第三种策略将磁性各向异性部分放置在金属-有机骨架的刚性配位环境中。通过这种方式，有可能最大限度地减少低能晶格振动引起的穿透势垒磁弛豫路径的影响。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。

In this project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Jeffrey Long of the Department of Chemistry at the University of California, Berkeley is designing and synthesizing new single-molecule magnets. Single-molecule magnets are molecules that behave as nanoscale magnets at low temperatures and can display magnetic properties akin to both classical and quantum systems. A potential direct application of this work is in the fields of magnetic data storage, quantum computing, and spintronics, however the knowledge gained by understanding magnetic properties on the molecular level is applicable to a wide variety of magnetic materials. Single-molecule magnets typically only operate at very low temperatures (less than 60 K). The goal of this project is to synthesize new molecules which have even higher operating temperatures. The project lies at the interface of inorganic chemistry, coordination chemistry, and physics. Both Professor Long and the members of his group are active in disseminating their work to a broad scientific audience, and the graduate students in the group participate in programs which place them in local elementary and middle school classrooms for hands-on science lessons. Single-molecule magnets are molecules with magnetically bistable ground states. When thermal energy is small relative to the thermal barrier between these states the magnetic molecule can retain its magnetization in the absence of an applied field. The proposed research adopts three strategies to synthesize single-molecule magnets which operate at higher temperatures. The first is to design systems with enhanced magnetic anisotropy, which will increase the thermal barrier to magnetic relaxation. Highly axial coordination environments will be employed for both transition metal and lanthanide complexes to achieve higher magnetic anisotropy. The second strategy is to utilize strong magnetic coupling to mitigate the effect of relaxation processes which shortcut the thermal barrier. Both transition metal and lanthanide complexes will be coupled with radical bridging ligands that promote strong metal-radical magnetic exchange. For transition metal complexes, direct metal-metal interactions will also lead to strongly coupled magnetic centers. Additionally, mixed 3d-4f systems will be developed to take advantage of both the large magnetic anisotropy of the lanthanides and the strong exchange coupling of the transition metals. Finally, the third strategy will place magnetically anisotropic moieties in the rigid coordination environments of metal-organic frameworks. In this manner it may be possible to minimize the effects of low energy lattice vibrations in causing through-barrier magnetic relaxation pathways.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.