混合价十二核锰配合物的合成、结构及磁性研究

合成了2个十二核锰的配合物Mn₁₂O₁₂(3-Cl-C₆H₄CO₂)₁₆(H₂O)₃(3-Cl-C₆H₄CO₂H)]·3-Cl-C₆H₄CO₂H 1, 和Mn₁₂O₁₂(CH₃CO₂)₄(3-Br-C₆H₄CO₂)₁₂(H₂O)₄]·3-Br-C₆H₄CO₂H·H₂O 2。用X-射线衍射单晶分析法测定了配合物1的结构，其中心含有一个类立方体结构的Mn₄⁺⁴O₄]⁺⁸, 这个簇芯被一非共面的8个Mn⁺³环及8个μ₃-O所包围。配体是由16个桥连μ₂-羧基和3个端基水、1个间氯苯甲酸组成。测定了配合物1，2变温直流磁化率，表明配合物1和2在低温时有较大的基态自旋；测定了配合物1，2的不同频率下的变温交流磁化率，以及在1.4K下外磁场从-5T到+5T的磁化强度曲线，在磁滞回线上均出现了2个台阶，表明配合物1和2存在分子自旋的量子隧穿，而且它们的共振磁化隧穿速度不同。简要讨论了配体和溶剂对十二核锰配合物磁性的影响。

Synthesis, Structure and Magnetic Property Study on the Mixed Valence Dodenuclear Manganese Clusters

In order to explore the influence of the ligands and solvents on the magnetic properties of Mn12 complexes, the syntheses and magnetochemical properties of Mn₁₂O₁₂(3-Cl-C₆H₄CO₂)₁₆(H₂O)₃(3-Cl-C₆H₄CO₂H)]·3-Cl-C₆H₄CO₂H 1, Mn₁₂O₁₂(CH₃CO₂)₄(3-Br-C₆H₄CO₂)₁₂(H₂O)₄] 2 have been studied. The crystal structure of the complex 1 has been characterized by X-ray diffraction method. The complex 1 crystallizes in the triclinic, space group of P1 with a=17.5779(3)A°，b=18.2712(3)A°，c=34.3616(5)A°，α=103.515(1)°，β=91.784(1)°，γ=116.25°，V=9508.5(3)A°³，Z=2，D_c=1.294mg·m^-3，μ=1.085mm^-１，F(000)=3696, and S=1.096. It is found that the complex 1 consists of a central cubane-like Mn₄⁺⁴O₄]⁺⁸ held within a nonplanar ring of eight Mn⁺³ ions and eight μ₃-O^2- ions. For both complexes 1 and 2 the χ″_m signals are observed in the region 2～10K, measured at three different frequencies, and exhibit two-frequency dependent of χ″_m AC peaks with a predominant peak in the 4～10K region. The magnetization hyteresis loops for the complexes 1 and 2 show the step-like character. These steps are attributable to the resonant magnetization tunneling. The affect of ligands and solvent on the magnetic properties of the title complexes are briefly discussed.