Tarannum Ibtesham, Singh Saurabh Kumar
Computational Inorganic Chemistry Group, Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana, 502284, India.
Phys Chem Chem Phys. 2025 Feb 19;27(8):4109-4120. doi: 10.1039/d4cp03016h.
Organometallic sandwich complexes of Dy(III) ion are ubiquitous for designing high-temperature single-ion magnets with blocking temperatures close to the liquid nitrogen boiling point. Magnetic bistability at the molecular level makes them potential candidates for nano-scale information storage materials. In the present contribution, we have thoroughly investigated the electronic structure, bonding, covalency, and magnetic anisotropy of inorganic dysprosocene complexes with a general formula of [Dy(E)] (where E = N, P, As, CH) using state-of-the-art scalar relativistic density functional theory (SR-DFT), and a multiconfigurational complete active space self-consistent field (CASSCF) method with the N-electron valence perturbation theory (NEVPT2). Geometry optimization calculations predict stabilization of the [Dy(E)] complexes with a linear geometry and local symmetry Dy(III) ion in [Dy(N)] (1) and [Dy(P)] (2) complexes, while a bent geometry has been observed for the [Dy(As)] (3), [Dy(P(CH))] (4), and [Dy(As(CH))] (5) complexes. Energy decomposition analysis (EDA) and natural bonding orbital (NBO) calculations reveal sizable 5d-ligand covalency followed by 6s/6p and weak 4f-ligand covalency in complexes 1-5. Both the natural localized molecular orbitals (NLMOs) at the DFT level and -based ligand field theory (AILFT) at the NEVPT2 level of theory predict an increase in the Dy-ligand covalency as we move from N to As. Spin-Hamiltonian parameter analysis of complexes 1-5 reveals stabilization of the |±15/2〉 as the ground state with highly axial values ( ∼ ∼ 0 and ∼ 20) and the barrier height of 2902, 1214, 1104, 1845, and 1509 K for 1-5, respectively. The Orbach effective demagnetization barrier () for complexes 1-5 ranges between 2416-1175 K, with a record value of 2416 K observed for 1. In addition, we have explored the role of heavy element effects on the magnetic anisotropy by turning off the spin-orbit coupling of the pnictogens (N, P, and As), and our calculations clearly predict that heavy atoms in the first coordination sphere help in increasing the barrier height for magnetic relaxation. Heavy elements like P and As significantly enhance the SOC contributions, thereby providing a platform for designing and optimizing Dy(III) complexes with tailored magnetic behaviors.
镝（III）离子的有机金属夹心配合物在设计具有接近液氮沸点阻塞温度的高温单离子磁体方面无处不在。分子水平上的磁双稳性使其成为纳米级信息存储材料的潜在候选者。在本论文中，我们使用最先进的标量相对论密度泛函理论（SR-DFT）以及带有N电子价态微扰理论（NEVPT2）的多组态完全活性空间自洽场（CASSCF）方法，深入研究了通式为[Dy(E)]（其中E = N、P、As、CH）的无机镝茂配合物的电子结构、键合、共价性和磁各向异性。几何优化计算预测，[Dy(N)]（1）和[Dy(P)]（2）配合物中具有线性几何结构和局部对称Dy(III)离子的[Dy(E)]配合物会得到稳定，而[Dy(As)]（3）、[Dy(P(CH))]（4）和[Dy(As(CH))]（5）配合物则观察到弯曲几何结构。能量分解分析（EDA）和自然键轨道（NBO）计算表明，配合物1 - 5中存在可观的5d - 配体共价性，其次是6s/6p和较弱的4f - 配体共价性。DFT水平的自然定域分子轨道（NLMO）和NEVPT2理论水平的基于配体场理论（AILFT）均预测，随着我们从N到As移动，Dy - 配体共价性会增加。配合物1 - 5的自旋哈密顿参数分析表明，|±15/2〉作为基态得到稳定，具有高度轴向的值（~ ~ 0和~ 20），1 - 5的能垒高度分别为2902、1214、1104、1845和1509 K。配合物1 - 5的奥尔巴赫有效退磁能垒（）在2416 - 1175 K之间，其中1观察到创纪录的 值2416 K。此外，我们通过关闭氮族元素（N、P和As）的自旋 - 轨道耦合，探索了重元素效应在磁各向异性中的作用，我们的计算清楚地预测，第一配位层中的重原子有助于增加磁弛豫的能垒高度。像P和As这样的重元素显著增强了自旋 - 轨道耦合（SOC）的贡献，从而为设计和优化具有定制磁行为的Dy(III)配合物提供了一个平台。
