Mandal Shuvankar, Pramanik Abhishek, Dey Sourav, Carrella Luca M, Rajaraman Gopalan, Rentschler Eva, Mohanta Sasankasekhar
Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India.
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Dalton Trans. 2022 Oct 4;51(38):14753-14766. doi: 10.1039/d2dt02348b.
The work in this report describes the syntheses, crystal structures, dc/ac magnetic behaviour, and theoretical calculations (both CASSCF and DFT) of three defect dicubane/planar butterfly type tetradysprosium(III) compounds of compositions [DyL(μ-OH)(carboxylate)(dmf)] (carboxylate = formate (1), acetate (2), propionate (3)), where HL = 2-(2-hydroxy-3-ethoxybenzylideneamino)phenol. In the butterfly type structures, two Dy centres (Dy) occupy the body positions while two other (Dy) units occupy the wing positions. SHAPE analyses reveal that the coordination geometries of the Dy and Dy centres, both octacoordinated, are triangular dodecahedron (TDD) and square antiprism (SAPR), respectively. Variable-temperature magnetic susceptibility measurements give an indication of weak antiferromagnetic interactions and variable-field magnetization measurements reveal strong anisotropy in all the three compounds. The variable-temperature/frequency in-phase/out-of-phase AC susceptibility data reveal that all these three compounds are SMMs with two relaxation channels under zero dc field; slow relaxation (SR) and fast relaxation (FR) processes could be assigned to the SAPR (Dy) and TDD (Dy) metal centres, respectively. The simulated and values are: 49.0 cm and 1.76 × 10 s for 1, 30.3 cm and 1.51 × 10 s for 2 and 23.4 cm and 9.64 × 10 s for 3. Furthermore, CASSCF/RASSI-SO/SINGLE_ANISO calculations reveal that the ground state of Dy centres are axial in nature with a dominating contribution from = |±15/2>. The magnetization relaxation occurs the first excited KD resulting in the large computed blocking barrier of Dy (SAPR) centres compared to that of the Dy (TDD) centres which corroborates the experimental measurements. The exchange parameters obtained from DFT calculations are generally in line with those obtained from the fitting of in POLY_ANISO calculations. Interesting structural and magneto-structural correlations have been found, which are the major outcomes of this investigation.
本报告中的工作描述了三种组成为[DyL(μ-OH)(羧酸盐)(dmf)]（羧酸盐 = 甲酸盐(1)、乙酸盐(2)、丙酸盐(3)）的缺陷型双立方烷/平面蝴蝶型四镝(III)化合物的合成、晶体结构、直流/交流磁行为以及理论计算（CASSCF和DFT），其中HL = 2-(2-羟基-3-乙氧基苄叉氨基)苯酚。在蝴蝶型结构中，两个Dy中心（Dy）占据主体位置，而另外两个（Dy）单元占据翅膀位置。SHAPE分析表明，均为八配位的Dy和Dy中心的配位几何形状分别为三角十二面体（TDD）和四方反棱柱（SAPR）。变温磁化率测量表明存在弱反铁磁相互作用，变场磁化测量揭示了所有这三种化合物中都存在强各向异性。变温/频率同相/异相交流磁化率数据表明，所有这三种化合物在零直流场下都是具有两个弛豫通道的单分子磁体；慢弛豫（SR）和快弛豫（FR）过程可分别归因于SAPR（Dy）和TDD（Dy）金属中心。模拟的 和 值分别为：1的49.0 cm和1.76×10 s、2的30.3 cm和1.51×10 s以及3的23.4 cm和9.64×10 s。此外，CASSCF/RASSI-SO/SINGLE_ANISO计算表明，Dy中心的基态本质上是轴向的，主要贡献来自 = |±15/2>。磁化弛豫发生在第一个激发的KD中，导致Dy（SAPR）中心的计算阻挡势垒比Dy（TDD）中心的大，这与实验测量结果相符。从DFT计算获得的交换参数通常与从POLY_ANISO计算中的 拟合获得的参数一致。已发现有趣的结构和磁结构相关性，这是本研究的主要成果。
