Kumari Kusum, Singh Saurabh Kumar
Computational Inorganic Chemistry Group, Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana-502284, India.
Dalton Trans. 2024 Oct 15;53(40):16495-16511. doi: 10.1039/d4dt02090a.
Organometallic dysprosocenium-based molecular magnets are the forefront runners in offering giant magnetic anisotropy and blocking temperatures close to the boiling point of liquid nitrogen. Attaining linearity in the organometallic dysprosocenium complexes is the key to generating giant magnetic anisotropy and blocking barriers. In the present study, we have unravelled the coordination ability of the substituted fullerene (CX) (where X = CCH, B, and N) generated by fencing around the five-membered ring of fullerene towards stabilizing a new family of exohedral dysprosium organometallic complexes showcasing giant magnetic anisotropy and blockade barriers. Eight exohedral mononuclear dysprosium organometallic complexes, namely [Dy(η-CX)(η-CH)] (1), [Dy(η-CX)(η-Cp)] (2), [Dy(η-CX)(η-Cp*)] (3), [Dy(η-CX)(η-CH)] (4), [Dy(η-CX)(η-CH)] (5), [Dy(η-CX)] (6) (where X = CCH), [Dy(η-CB)] (7) and [Dy(η-CN)] (8), were studied using scalar relativistic density functional theory (SR-DFT) and the complete active space self-consistent field (CASSCF) methodology to shed light on the structure, stability, bonding and single-ion magnetic properties. SR-DFT calculations predict complexes 1-8 to be highly stable, with a strictly linear geometry around the Dy(III) ion in complexes 6-8. Energy Decomposition Analysis (EDA) predicts the following order for interaction energy (Δ value): 5 > 1 > 2 ≈ 3 > 6 > 7 > 8 > 4, with sizable 4f-ligand covalency in all the complexes. CASSCF calculations on complexes 1-8 predict stabilization of |±15/2〉 as the ground state for all the complexes except for 5, with the following trend in the values: 6 (1573 cm) ≈ 3 (1569 cm) > 1 (1538 cm) > 8 (1347 cm) > 2 (1305 cm) > 7 (1284 cm) > 4 (1125 cm) > 5 (108 cm). ligand field theory (AILFT) analysis provides a rationale for ordering, where π-type 4f-ligand interactions in complexes 1-4 and 6-8 offer giant barrier height while the large (CH) rings generate δ-type interaction in 5, which diminishes the axiality in the ligand field. Our detailed finding suggests that the exohedral organometallic dysprosocenium complexes are more linear compared to bent [DyCp*] cations and display a giant barrier height exceeding 1500 cm with negligible quantum tunnelling of magnetization (QTM) - a new approach to design highly anisotropic dysprosium organometallic complexes.
基于有机金属镝的分子磁体是提供巨大磁各向异性和接近液氮沸点的阻塞温度的前沿研究对象。在有机金属镝配合物中实现线性结构是产生巨大磁各向异性和阻塞势垒的关键。在本研究中，我们揭示了通过在富勒烯五元环周围构筑围栏生成的取代富勒烯（CX）（其中X = CCH、B和N）对稳定一类新的具有巨大磁各向异性和阻塞势垒的外表面镝有机金属配合物的配位能力。使用标量相对论密度泛函理论（SR-DFT）和完全活性空间自洽场（CASSCF）方法研究了八个外表面单核镝有机金属配合物，即[Dy(η-CX)(η-CH)] (1)、[Dy(η-CX)(η-Cp)] (2)、[Dy(η-CX)(η-Cp*)] (3)、[Dy(η-CX)(η-CH)] (4)、[Dy(η-CX)(η-CH)] (5)、[Dy(η-CX)] (6)（其中X = CCH）、[Dy(η-CB)] (7) 和 [Dy(η-CN)] (8)，以阐明其结构、稳定性、键合和单离子磁性质。SR-DFT计算预测配合物1-8高度稳定，配合物6-8中Dy(III)离子周围具有严格的线性几何结构。能量分解分析（EDA）预测相互作用能（Δ值）的顺序如下：5 > 1 > 2 ≈ 3 > 6 > 7 > 8 > 4，所有配合物中都有可观的4f-配体共价性。对配合物1-8的CASSCF计算预测，除了5之外，所有配合物的基态均为|±15/2〉，其值的趋势如下：6 (1573 cm) ≈ 3 (1569 cm) > 1 (1538 cm) > 8 (1347 cm) > 2 (1305 cm) > 7 (1284 cm) > 4 (1125 cm) > 5 (108 cm)。不对称离子配体场理论（AILFT）分析为排序提供了理论依据，其中配合物1-4和6-8中的π型4f-配体相互作用提供了巨大的势垒高度，而大的(CH)环在5中产生δ型相互作用，这降低了配体场中的轴向性。我们的详细研究结果表明，与弯曲的[DyCp*]阳离子相比，外表面有机金属镝配合物更线性，并且显示出超过1500 cm的巨大势垒高度，同时磁化量子隧穿（QTM）可忽略不计——这是设计高度各向异性镝有机金属配合物的一种新方法。
