基于特殊配位构型和自由基桥联的单分子磁体构筑和磁性研究

Single-Molecule Magnets (SMMs) have attracted considerable attentions in recent years due to its potential applications in high-density information storage and quantum computing. Both the energy barrier and blocking temperature of SMMs have been remarkably increased after decades, however, it should be noted that the quantum tunneling of the magnetization (QTM) still prevails in most systems, as indicated by the butterfly-shaped hysteresis loops for the rare-earth SMMs and field-induced magnetic relaxation for most transition-metal complexes. Experimental and theoretical studies indicate that the QTM can be modestly suppressed by either the regulation of coordination geometry or the intramolecular magnetic interaction. However, molecules containing both the special coordination geometry and strong magnetic correlation are extremely rare due to the difficulties in synthesizing such model complexes. This project aims to construct a series of polynuclear complexes with both the strategies, ie, special coordination geometry and strong intramolecular interaction, and further investigate the corresponding QTM and SMM behavior, yielding the in-depth understanding of magneto-structural correlations and relaxation mechanisms of such complexes, promoting the design and development of high-performance SMMs.

近年来，单分子磁体因其在高密度信息存储和量子计算机等方面的潜在应用而受到广泛关注。经过数十年的发展，单分子磁体的磁各向异性能垒和阻塞温度均得到很大的提高，然而需要注意的是，量子隧穿效应在大多数体系中仍然广泛存在，其中稀土单分子磁体主要表现为蝴蝶状的磁滞回线，而大多数过渡金属配合物仍然需要在外加磁场下才能表现慢磁弛豫行为。实验及理论研究表明配位构型调控或者分子内的磁交换作用均可以在一定程度上抑制量子隧穿效应。然而，同时具有特殊配位构型和强磁交换的分子非常稀有，这主要是因为两者共存的模型化合物的合成极具挑战性。本项目拟从这两种策略同时入手，设计并构筑一系列基于特殊配位构型和强磁交换的多核金属配合物，探索二者共存体系的量子隧穿效应和单分子磁体行为，深入理解这类配合物的磁构关系以及弛豫机理，为获取高性能单分子磁体提供思路和方向。

该项目围绕单分子磁体在高密度信息存储和自旋电子器件的潜在应用，旨在进一步深化理解这类材料的磁构关系，实现单分子磁体的高性能化。通过对螯合配体的裁剪和设计，与钴金属离子组装了一系列基于三棱柱配位构型的单核钴化合物，有效能垒达到276 K，是高配位单分子磁体的记录。在此基础上，进一步引入顺磁金属离子或者自由基作为桥连配体，成功构筑了同时具备三棱柱配位构型和强磁交换作用的多核钴磁性分子，其中金属钴-自由基之间具有强反铁磁交换作用，磁交换常数达到-66 cm-1。系统研究了这类体系中配位构型和磁交换对磁各向异性和量子隧穿效应的影响，探索进一步提高单分子磁体性能的有效策略。