Department of Chemistry and Biochemistry , University of California-San Diego , La Jolla , California 92093 , United States.
J Am Chem Soc. 2019 Feb 6;141(5):1913-1917. doi: 10.1021/jacs.8b13514. Epub 2019 Jan 25.
Maintaining strong magnetic anisotropy in the presence of collective spin interactions has become a defining challenge in the advancement of single-molecule magnet (SMM) research. Herein we demonstrate effective decoupling of these often competing design goals in a series of new phosphino-supported SMMs containing the anisotropic [Er(COT)] (COT = cyclooctatetraene dianion) subunit. Across this series, a magnetic nuclearity increase from 1 to 2 and subsequent optimization of the relative local anisotropy axis orientation results in dramatic improvements to the long time scale behavior. Specifically, we observe a 6 orders of magnitude increase in relaxation time at 2 K and a consequent open magnetic hysteresis up to 6 K. This drastic scaling of the magnetic dynamics tracks monotonically with the introduction and approach to parallel of the angle between intramolecular anisotropy axes. These results illustrate the powerful implications of fully controlling direction and magnitude of anisotropy in the design of scalable SMMs.
在存在集体自旋相互作用的情况下保持强磁各向异性，已成为推进单分子磁体（SMM）研究的一个决定性挑战。在此，我们在一系列新的膦基支持的 SMM 中证明了这些通常相互竞争的设计目标的有效解耦，这些 SMM 含有各向异性的[Er(COT)]（COT=环辛四烯二阴离子）亚基。在整个系列中，磁核数从 1 增加到 2，随后优化相对局部各向异性轴的取向，导致长时间尺度行为的显著改善。具体来说，我们观察到在 2 K 时弛豫时间增加了 6 个数量级，并且在 6 K 时出现了开放的磁滞。这种磁动力学的急剧缩放与分子内各向异性轴之间夹角的引入和接近平行单调相关。这些结果说明了在可扩展 SMM 的设计中完全控制各向异性的方向和大小的强大意义。
