Shedding Light on the Single-Molecule Magnet Behavior of Mononuclear DyIII Complexes
Shedding Light on the Single-Molecule Magnet Behavior of Mononuclear DyIII Complexes
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DOI：
10.1021/ic402367c
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发表时间：
2013-12-02
影响因子：
4.6
通讯作者：
Ruiz, Eliseo
中科院分区：
文献类型：
--
作者：
Aravena, Daniel;Ruiz, Eliseo
通过CASSCF+RASSI计算对真实系统和模型系统研究了获得Dy-III单分子磁体（SMM）的一般要求。我们考虑使用一组 20 个 Dy-III 配合物的 X 射线晶体结构进行计算。将理论结果与实验慢弛豫数据进行比较，并提出了与 SMM 行为相关的计算关键参数的一般结论。基于对真实系统和模型系统的计算，讨论了配位几何形状和配体性质的影响。我们发现两种不同的模式表现出 SMM 行为：第一种导致配合物中最大的轴向各向异性，显示配体环境的异配性（比对称要求更重要），而第二种对应于具有较小各向异性的夹心形配合物。因此，大多数现有的单核零场SMM采用混合中性和阴离子配体的杂配位模式，在其配体诱导的静电势中表现出相同的模式，具有与阴离子基团相关的高电势背景内中性配体的存在相关的较低电势岛。配体引起的不同静电区域的存在会诱导择优取向，从而减少对 Dy-III 阳离子电子密度的电子排斥，从而产生磁各向异性。
General requirements for obtaining Dy-III single-molecule magnets (SMM) were studied by CASSCF+RASSI calculations on both real and model systems. A set of 20 Dy-III complexes was considered using their X-ray crystal structure for our calculations. Theoretical results were compared with their experimental slow relaxation data, and general conclusions about the calculated key parameters related with SMM behavior are presented. The effect of the coordination geometry and nature of ligands is discussed based on calculations on real and model systems. We found two different patterns to exhibit SMM behavior: the first one leads to the largest axial anisotropy in complexes showing heterolepticity of the ligand environment (more important than symmetric requirements), while the second one corresponds to sandwich-shaped complexes with a smaller anisotropy. Thus, most existing mononuclear zero-field SMMs adopting a heteroleptic coordination mode mixing neutral and anionic ligands present the same pattern in the electrostatic potential induced by their ligands, with a lower potential island related to the presence of neutral ligands inside a high potential background related with anionic groups. The existence of different electrostatic regions caused by the ligands induces a preferential orientation to reduce the electron repulsion for the electron density of the Dy-III cations, resulting in the magnetic anisotropy.