Khurana Rishu, Gupta Sameer, Ali Md Ehesan
Institute of Nano Science and Technology, Sector-81, Mohali, Punjab 140306, India.
J Phys Chem A. 2021 Mar 18;125(10):2197-2207. doi: 10.1021/acs.jpca.1c00022. Epub 2021 Feb 22.
With the ongoing effort to obtain mononuclear 3d-transition-metal complexes that manifest slow relaxation of magnetization and, hence, can behave as single-molecule magnets (SMMs), we have modeled 14 Fe(III) complexes based on an experimentally synthesized (PMe)FeCl complex [. , (46), 16474-16477], by varying the axial ligands with group XV elements (N, P, and As) and equatorial halide ligands from F, Cl, Br, and I. Out of these, nine complexes possess large zero field splitting (ZFS) parameter in the range of -40 to -60 cm. The first-principles investigation of the ground-spin state applying density functional theory (DFT) and wave function-based multiconfigurations methods, e.g., SA-CASSCF/NEVPT2, are found to be quite consistent except for few delicate cases with near-degenerate spin states. In such cases, the hybrid B3LYP functional is found to be biased toward high-spin (HS) state. Altering the percentage of exact exchange admixed in the B3LYP functional leads to intermediate-spin (IS) ground state consistent with the multireference calculations. The origin of large zero field splitting (ZFS) in the Fe(III)-based trigonal bipyramidal (TBP) complexes is investigated. Furthermore, a number of complexes are identified with very small Δ values indicating the possible spin-crossover phenomenon between the bistable spin states.
随着人们不断努力获取表现出磁化缓慢弛豫、从而可作为单分子磁体（SMMs）的单核3d过渡金属配合物，我们基于实验合成的(PMe)FeCl配合物[., (46), 16474 - 16477]，通过用第XV族元素（N、P和As）改变轴向配体以及用F、Cl、Br和I改变赤道卤化物配体，对14种Fe(III)配合物进行了建模。其中，9种配合物具有-40至-60 cm范围内的大零场分裂（ZFS）参数。应用密度泛函理论（DFT）和基于波函数的多组态方法（例如SA - CASSCF/NEVPT2）对基态自旋态进行的第一性原理研究，除了少数自旋态近简并的精细情况外，发现结果相当一致。在这种情况下，发现杂化B3LYP泛函偏向高自旋（HS）态。改变B3LYP泛函中精确交换混合的百分比会导致与多参考计算一致的中间自旋（IS）基态。研究了基于Fe(III)的三角双锥（TBP）配合物中大零场分裂（ZFS）的起源。此外，还鉴定出了一些具有非常小的Δ值的配合物，这表明在双稳态自旋态之间可能存在自旋交叉现象。
