The First Conducting Spin-Crossover Compound Combining a MnIII Cation Complex with Electroactive TCNQ Demonstrating an Abrupt Spin Transition with a Hysteresis of 50 K
The First Conducting Spin-Crossover Compound Combining a MnIII Cation Complex with Electroactive TCNQ Demonstrating an Abrupt Spin Transition with a Hysteresis of 50 K
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DOI：
10.1002/chem.201901792
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发表时间：
2019-07-04
影响因子：
4.3
通讯作者：
Vasiliev, Alexander N.
中科院分区：
文献类型：
--
作者：
Kazakova, Anna, V;Tiunova, Aleksandra, V;Vasiliev, Alexander N.
我们在此介绍自旋交叉盐[Mn(5 - Cl - sal - N - 1,5,8,12)]TCNQ(1.5)·2CH₃CN（I）的合成、晶体结构以及电学和磁学性质，其中5 - Cl - sal - N - 1,5,8,12 = N,N'-双（3 -（2 - 氧代 - 5 - 氯亚苄基氨基）丙基）-乙二胺，它含有不同的导电和磁性单元以及乙腈溶剂分子。具有席夫碱配体的Mn - III配合物[Mn(5 - Cl - sal - N - 1,5,8,12)]⁺作为磁性单元，π电子受体7,7,8,8 - 四氰基对苯醌二甲烷（TCNQ⁻）是导电单元。标题化合物（I）表现出半导体行为，室温电导率σ(RT)约为1×10⁻⁴ Ω⁻¹ cm⁻¹，活化能Δ约为0.20 eV。在73 - 123 K的温度范围内，它经历一个滞后相变，伴随着Mn - III的低自旋S = 1和高自旋S = 2状态之间的交叉以及MnN₄O₂八面体中键长的变化。在自旋交叉时，I中底面Mn - N键的显著收缩表明dx² - y²轨道在这个转变过程中被占据/腾空。有趣的是，标题化合物的溴同构物[Mn(5 - Br - sal - N - 1,5,8,12)]TCNQ(1.5)·2CH₃CN（II）没有显示出自旋交叉现象，并且在2 - 300 K的温度范围内保持高自旋状态。对氯和溴化合物的比较使得能够区分热和自旋交叉对键长总体变化的贡献。这两种盐磁行为的差异归因于分子间超分子效应对自旋转变的影响。在这两种化合物中，阳离子与阳离子以及阳离子与阴离子之间都存在离散的氢键。然而，II晶体中的氢键比I中的强得多。[Mn(5 - Br - sal - N - 1,5,8,12)]⁺阳离子相对紧密的堆积排列可能阻止了它们的自旋转变。
We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin-crossover salt [Mn(5-Cl-sal-N-1,5,8,12)]TCNQ(1.5).2 CH3CN (I), where 5-Cl-sal-N-1,5,8,12=N,N '-bis(3-(2-oxy-5-chlorobenzylideneamino)propyl)-ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The Mn-III complex with a Schiff-base ligand, [Mn(5-Cl-sal-N-1,5,8,12)](+), acts as the magnetic unit, and the pi-electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ(-)) is the conducting unit. The title compound (I) exhibits semiconducting behavior with room temperature conductivity sigma(RT)approximate to 1x10(-4) ohm(-1) cm(-1) and activation energy Delta approximate to 0.20 eV. In the temperature range 73-123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low-spin S=1 and high-spin S=2 states of Mn-III and changes in bond lengths within the MnN4O2 octahedra. The pronounced shrinkage of the basal Mn-N bonds in I at the spin crossover suggests that the dx2-y2 orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5-Br-sal-N-1,5,8,12)]TCNQ(1.5).2 CH3CN (II) of the title compound evidences no spin-crossover phenomena and remains in the high-spin state in the temperature range 2-300 K. Comparison of the chloro and bromo compounds allows the thermal and spin-crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I. The relatively close packing arrangement of the [Mn(5-Br-sal-N-1,5,8,12)](+) cations probably precludes their spin transformation.