Synthesis and Electronic Structures of Heavy Lanthanide Metallocenium Cations
Synthesis and Electronic Structures of Heavy Lanthanide Metallocenium Cations
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DOI：
10.1021/jacs.7b11535
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发表时间：
2017-12-27
影响因子：
15
通讯作者：
Mills, David P.
中科院分区：
文献类型：
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作者：
Goodwin, Conrad A. P.;Reta, Daniel;Mills, David P.
稀土配合物[Dy（Cp-ttt）（2）][B（C_6F_5）（4）]（Cp-ttt =（C_5H_2Bu_3）-Bu-t-1，2，4，1-Dy）的60 K磁滞现象的起源至今仍是个谜，因此我们设想通过对一系列[Ln（Cp-ttt）（2）]（+）（Ln =镧系）阳离子的分析可以揭示这些性质。本文报道了[Ln（Cp-ttt）（2）]（+）阳离子（1-Ln; Ln = Gd，Ho，Er，Tm，Yb，Lu）的合成和物理性质。1-Ln和2-Ln两个族中的配合物是同构的，分别显示伪线性和伪三角晶场。这导致在原型的电子结构，确定与CASSCF-SO计算和SQUID磁强计和EPR光谱确认，显示磁各向异性取决于Ln离子的选择。磁弛豫动力学的研究表明，它们的拉曼指数非常低，类似于1-Dy，这两个是不同的2-Dy，2-Er，和2-Yb的更大和更规则的拉曼指数。这表明低的拉曼指数来自于孤立的[Ln（Cpttt）2]+阳离子的独特的自旋-声子耦合。至关重要的是，这突出了配体配位模式和自旋-声子耦合之间的直接联系，因此我们提出，1-Dy中的多键配体的独家存在是其显着的磁性的起源。因此，通过配体设计控制自旋-声子耦合对于实现下一代高温单分子磁体至关重要。
The origin of 60 K magnetic hysteresis in the dysprosocenium complex [Dy(Cp-ttt)(2)][B(C6F5)(4)] (Cp-ttt = (C5H2Bu3)-Bu-t-1,2,4, 1-Dy) remains mysterious, thus we envisaged that analysis of a series of [Ln(Cp-ttt)(2)](+) (Ln = lanthanide) cations could shed light on these properties. Herein we report the synthesis and physical characterization of a family of isolated [Ln(Cp-ttt)(2)](+) cations (1-Ln; Ln = Gd, Ho, Er, Tm, Yb, Lu), synthesized by halide abstraction of [Ln(Cp-ttt)(2)(Cl)] (2-Ln; Ln = Gd, Ho, Er, Tm, Yb, Lu). Complexes within the two families 1-Ln and 2-Ln are isostructural and display pseudo-linear and pseudo-trigonal crystal fields, respectively. This results in archetypal electronic structures, determined with CASSCF-SO calculations and confirmed with SQUID magnetometry and EPR spectroscopy, showing magnetic anisotropy depending on the choice of Ln ion. Study of their magnetic relaxation dynamics exhibits an anomalously low Raman exponent similar to 1-Dy, both being distinct from the larger and more regular Raman exponents for 2-Dy, 2-Er, and 2-Yb. This suggests that low Raman exponents arise from the unique spin-phonon coupling of isolated [Ln(Cpttt)2]+ cations. Crucially, this highlights a direct connection between ligand coordination modes and spin-phonon coupling, and therefore we propose that the exclusive presence of multihapto ligands in 1-Dy is the origin of its remarkable magnetic properties. Controlling the spin-phonon coupling through ligand design thus appears vital for realizing the next generation of high-temperature single-molecule magnets.