四核镧系元素配合物显示出显着的慢磁弛豫，具有开放的磁滞回线和磁热效应,Inorganic Chemistry Frontiers

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四核镧系元素配合物显示出显着的慢磁弛豫，具有开放的磁滞回线和磁热效应
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2023-01-06 , DOI: 10.1039/d2qi02202h
Tian-Tian Wang ₁ , Zi-Wei Che ₁ , Ji-Tun Chen ₁ , Han Yan ₁ , Teng-Da Zhou ₁ , Yi-Quan Zhang ₂ , Wen-Bin Sun ₁

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两个四核镧系元素配合物，分子式为 [Dy ₄ (HL) ₄ (OAc) ₂ (H ₂ O) ₂ ]·2Et ₃ NH·2CH ₃ CN ( 1 ) 和 [Gd ₄ (HL) ₄ (OAc) ₂ (H ₂ O) ₂ ]·2Et ₃ NH·2CH ₃ OH·4CH ₃ CN ( 2 ) ( H ₄ L = N , N'-bis(3-hydroxylsalicylidene)benzene-1,2-diamine) 进行了结构和磁性表征。动态磁学研究表明，配合物1在零直流 (dc) 场下表现出两个截然不同的慢磁弛豫过程，低温和高温弛豫过程的提取能垒 ( U _eff ) 达到 207(2) K 和分别为 353(3) K，这是已报道的四核镝分子纳米磁体中最高的U _eff值。更引人注目的是，对于复数1，在 5 K（稀释样品为 6.5 K）之前检测到开磁滞回线行为，并且在 1.8 K 时观察到 453 Oe 的矫顽场，这在四核镧系元素单分子磁体中不常见。稀释样品的进一步磁学研究结合从头算计算表明，Dy ^III -Dy ^III相互作用在抑制磁化的量子隧穿方面起着至关重要的作用，因此导致了大块磁体的磁滞行为。此外，Gd-congener 2显示磁热效应 (MCE)，磁熵变 (−Δ S _m ) 为 20.8 J kg ⁻¹ K ⁻¹在 2 K 对于 Δ H= 7 吨。

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Tetranuclear lanthanide complexes display significant slow magnetic relaxation with an open hysteresis loop and the magnetocaloric effect

Two tetranuclear lanthanide complexes with the formulas [Dy₄(HL)₄(OAc)₂(H₂O)₂]·2Et₃NH·2CH₃CN (1) and [Gd₄(HL)₄(OAc)₂(H₂O)₂]·2Et₃NH·2CH₃OH·4CH₃CN (2) (H₄L = N,N′-bis(3-hydroxylsalicylidene)benzene-1,2-diamine) were structurally and magnetically characterized. Dynamic magnetic studies revealed that complex 1 exhibits two distinct slow magnetic relaxation processes under a zero direct current (dc) field and the extracted energy barriers (U_eff) of the low-temperature and high-temperature relaxation processes reach 207(2) K and 353(3) K, respectively, which are among the highest U_eff values of reported tetranuclear dysprosium molecular nanomagnets. More strikingly, as for complex 1, the open hysteresis loop behavior is detected until 5 K (6.5 K for the diluted sample), and a coercive field of 453 Oe is observed at 1.8 K, which is unusually seen in tetranuclear lanthanide single-molecule magnets. Further magnetic studies of diluted samples combined with ab initio calculation indicate that the Dy^III–Dy^III interactions play a crucial role in suppressing quantum tunneling of magnetization and consequently resulted in the bulk magnet-like hysteresis behavior. Additionally, the Gd-congener 2 displays the magnetocaloric effect (MCE) with a magnetic entropy change (−ΔS_m) of 20.8 J kg⁻¹ K⁻¹ at 2 K for ΔH = 7 T.

更新日期：2023-01-06

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