稀土配合物磁弛豫调控

Since the seminal discovery of single molecule magnet (SMM) behavior during the 1990s, the study of SMM has been the focus for chemistry, physics, and materials science, where the quantum world of magnetization for single molecule clusters meets the bulk scale of classical physics. Recent years have seen a flurry of remarkable results, such as the highest relaxation energy barriers and the highest blocking temperature for lanthanide SMMs, which mainly benefit from the significant magnetic anisotropy of lanthanide ions arising from the large, unquenched orbital angular momentum. A strategy combining strong magnetic coupling with f-element single-ion anisotropy has been recently proposed, giving rise to a new record SMM. However, the control of the easy-axis anisotropy represents a major challenge. The objective of the present proposal is to produce and characterize new molecules based on highly anisotropic lanthanide ions with the goal of identifying features relevant to modulating relaxation dynamics of SMMs. As a way to address this challenge, the synthetic strategy is to design new molecules where the anisotropic centers are in fine-tuned local environments and can effectivly communcate with each other by enhancing the coupling between them. Due to the complexity of such systems, it is almost impossible to determine the microscopic nature of the states that control the magnetic relaxation by using routine experimental measurements. In this respect, a combination of experimental efforts (including high frequency ESR and INS) with high level fragment ab initio calculations is applied in order to extract information needed to elucidate the underlying relaxation dynamics. The information extracted from such studies will improve our understanding of the magnetic behaviour of SMMs and facilitate potential applications in data storage and processing, essential for the rational design of new molecular-based materials.

单分子磁体自二十多年前被发现以来，一直是分子功能材料研究的热点领域之一。近年来，人们在高能垒和高阻塞温度稀土单分子磁体的设计上取得了显著进展，同时对其弛豫行为进行了比较深入的研究并且认识到磁各向异性在设计单分子磁体中的重要性，然而如何操控磁各向异性依然是各国科学家面临的一项挑战性课题。针对单分子磁体弛豫机理这一关键问题，本项目选择各向异性显著的稀土离子为自旋载体，设计特定结构的磁性分子，从配体场和金属离子间磁相互作用两个主要方面入手，通过详尽的磁性表征并结合先进的实验方法（如高频高场ESR、非弹性中子散射等）和深入的理论计算，系统研究自旋载体的化学环境与磁各向异性、磁各向异性与慢磁弛豫之间的相关性，揭示稀土单分子磁体弛豫过程的本质，实现有效调控，为制备功能分子材料提供重要的科学数据。

单分子磁体因其独特的性质在高密度信息存储、量子计算及分子自旋电子学方面具有广阔应用前景，一直是分子功能材料研究的热点领域之一。近年来，人们在高能垒和高阻塞温度稀土单分子磁体的设计上取得了显著进展，同时对其弛豫行为进行了比较深入的研究并且认识到磁各向异性在设计单分子磁体中的重要性，然而如何操控磁各向异性以期合理设计单分子磁体依然是各国科学家面临的一项挑战性课题。为此，项目设计合成了特定结构的磁性分子，重点研究了单分子磁体的弛豫调控机制，在稀土单分子磁体设计与磁弛豫调控方面取得了如下主要进展：通过合理设计，得到了首例具有经典赤道配位的Er单分子磁体，实现了对磁各向异性的有效调控；确立了双弛豫和金属中心的对应关系；发现了稀土单分子磁体经由第二激发态的新弛豫途径，为提高稀土单分子磁体能垒和阻塞温度开辟了广阔空间。项目研究成果为进一步开展相关工作打下坚实基础。