Effects of f–f Interactions on the Single-Molecule Magnet Properties of Terbium(III)–Phthalocyaninato Quintuple-Decker Complexes

Single-molecule magnet (SMM) properties
of terbium­(III)–phthalocyaninato quintuple-decker complex TbCdCdTb
were studied and were compared with those of other multiple-decker
complexes (triple-decker: TbTb, quadruple-decker: TbCdTb) to elucidate
the relationship between magnetic dipole interactions and SMM properties.
From X-ray crystallography performed with synchrotron radiation, the
TbIII–TbIII distance in TbCdCdTb was
determined to be 9.883 Å. From alternating current magnetic studies
on TbCdCdTb, the activation energy for spin reversal (Δ) increased
with an increase in the direct current magnetic field (Hdc). This behavior is similar to that of TbCdTb, although
the increase in Δ for TbCdTb is smaller. On the other hand,
for TbTb, which has shortest TbIII–TbIII distance, Δ did not depend on Hdc, indicating that there is a correlation between SMM properties and
the strength of the TbIII–TbIII interactions.
By comparing the Zeeman diagrams for multiple-decker complexes, we
found that the TbIII–TbIII interactions
affected the magnetic field regions where quantum tunnelling of the
magnetization was active. The results obtained from Zeeman diagrams
are consistent with the results obtained from the magnetic studies.

本研究针对铽(III)–酞菁五重双层配合物（terbium(III)–phthalocyaninato quintuple-decker complex）TbCdCdTb的单分子磁体（Single-molecule magnet, SMM）性能展开系统探究，并将其与其他多重双层配合物（三重双层配合物：TbTb、四重双层配合物：TbCdTb）的对应性能进行对比，旨在阐明磁偶极相互作用（magnetic dipole interactions）与单分子磁体性能之间的构效关系。
通过同步辐射（synchrotron radiation）辅助的X射线晶体学（X-ray crystallography）分析，确定TbCdCdTb中三价铽离子间的间距为9.883 Å。
对TbCdCdTb开展交流磁学研究（alternating current magnetic studies）后发现，其自旋反转活化能（activation energy for spin reversal，Δ）随直流磁场（direct current magnetic field，Hdc）的升高而增大。该变化趋势与TbCdTb的表现相似，不过TbCdTb的活化能增幅相对更小。
与之形成鲜明对比的是，三价铽离子间距最短的TbTb，其自旋反转活化能并不随直流磁场发生变化，这表明单分子磁体性能与三价铽离子间相互作用的强度存在显著相关性。
通过对比多重双层配合物的塞曼图（Zeeman diagrams），我们发现三价铽离子间的相互作用会影响磁化量子隧穿（quantum tunnelling of the magnetization）活跃的磁场区间。塞曼图分析得到的结果与磁学研究的实验结论完全一致。