Measurement of Magnetic Exchange in Asymmetric Lanthanide Dimetallics: Toward a Transferable Theoretical Framework
Measurement of Magnetic Exchange in Asymmetric Lanthanide Dimetallics: Toward a Transferable Theoretical Framework
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DOI：
10.1021/jacs.7b10714
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发表时间：
2018-02-21
影响因子：
15
通讯作者：
Chilton, Nicholas F.
中科院分区：
文献类型：
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作者：
Giansiracusa, Marcus J.;Moreno-Pineda, Eufemio;Chilton, Nicholas F.
用EPR光谱直接探测了不对称双金属化合物[hqH(2)][Ln(2)(hq)(4)(NO3)(3)]中心点MeOH， （Ln = Er（III）和Yb(III), hqH = 8-羟基喹啉）内的磁交换相互作用，并用自旋哈密顿技术精确地模拟了它们。通过在Y（III）和Lu（III）基质中掺杂实验，利用位点选择性得到了简单的EPR光谱，对应于孤立的克莱默双偶，从而可以确定双金属化合物中单个位点的局部磁性。CASSCF-SO计算以及INS和远红外测量都被用于进一步支持每个站点的局部电子结构的识别和建模。纯双金属化合物的EPR光谱具有高度的特征，对应于最低交换耦合流形内的跃迁，允许确定镧系离子之间的高度各向异性磁交换。我们发现了交换相互作用的独特取向，对应于两个同构类似物的共同拉长氧桥。这表明与磁超交换有微观的物理联系。这些结果对于建立和验证模型微观哈密顿量以理解镧系元素之间磁相互作用的起源以及如何用化学方法控制它们具有重要意义。
Magnetic exchange interactions within the asymmetric dimetallic compounds [hqH(2)][Ln(2)(hq)(4)(NO3)(3)]center dot MeOH, (Ln = Er(III) and Yb(III), hqH = 8-hydroxyquinoline) have been directly probed with EPR spectroscopy and accurately modeled by spin Hamiltonian techniques. Exploitation of site selectivity via doping experiments in Y(III) and Lu(III) matrices yields simple EPR spectra corresponding to isolated Kramers doublets, allowing determination of the local magnetic properties of the individual sites within the dimetallic compounds. CASSCF-SO calculations and INS and far-IR measurements are all employed to further support the identification and modeling of the local electronic structure for each site. EPR spectra of the pure dimetallic compounds are highly featured and correspond to transitions within the lowest-lying exchange-coupled manifold, permitting determination of the highly anisotropic magnetic exchange between the lanthanide ions. We find a unique orientation for the exchange interaction, corresponding to a common elongated oxygen bridge for both isostructural analogs. This suggests a microscopic physical connection to the magnetic superexchange. These results are of fundamental importance for building and validating model microscopic Hamiltonians to understand the origins of magnetic interactions between lanthanides and how they may be controlled with chemistry.