Yureva E A, Korchagin D V, Anichkin A A, Shilov G V, Babeshkin K A, Efimov N N, Palii A V, Aldoshin S M
Institute of Problems of Chemical Physics, Russian Academy of Sciences, 1, Acad. Semenov prosp., 142432 Chernogolovka, Moscow Region, Russia.
Faculty of Fundamental Physical and Chemical Engineering, Moscow State University, 1-3, Leninskiye Gory, 119991 Moscow, Russia.
Dalton Trans. 2022 Aug 9;51(31):11916-11921. doi: 10.1039/d2dt01336c.
Herein, we report on the synthesis, structure and magnetic properties of a four-coordinate mononuclear Co(II) diiodide complex with the 3,5-dimethylpyrazole ligand. A distorted tetrahedral local coordination environment around the central cobalt ion is formed by the two nitrogen atoms of two monodentate pyrazole ligands and by iodide ions. Direct current (dc) magnetic measurements in combination with SA-CASSCF/NEVPT2 quantum-chemical calculations revealed a strong easy-axis-type magnetic anisotropy with a record value = -30.58(3) cm of the axial zero field splitting parameter for pseudo-tetrahedral Co(II)-based CoLHal complexes. Moreover, it is the only complex in this series demonstrating the slow relaxation of magnetization at zero dc field. The Orbach process is shown to be the dominant mechanism of magnetic relaxations in the high temperature range, while the quantum tunneling of magnetization produces the leading contribution to the overall relaxation at temperatures below 4 K.
在此，我们报道了一种具有3,5 - 二甲基吡唑配体的四配位单核二碘化钴（II）配合物的合成、结构和磁性。两个单齿吡唑配体的两个氮原子和碘离子在中心钴离子周围形成了扭曲的四面体局部配位环境。直流（dc）磁性测量结合SA - CASSCF/NEVPT2量子化学计算表明，对于基于伪四面体Co（II）的CoLHal配合物，具有很强的易轴型磁各向异性，轴向零场分裂参数的记录值为 = -30.58(3) cm。此外，它是该系列中唯一在零直流场下表现出磁化缓慢弛豫的配合物。结果表明，在高温范围内，奥巴赫过程是磁弛豫的主导机制，而在低于4 K的温度下，磁化量子隧穿对整体弛豫起主要贡献。
