混合价十二核锰配合物的合成、结构及磁性研究

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

合成了 2个十二核锰的配合物 [Mn12 O12 (3 Cl C6 H4 CO2 ) 16 (H2 O) 3(3 Cl C6 H4 CO2 H) ]·3 Cl C6 H4 CO2 H 1,和 [Mn12 O12 (CH3CO2 ) 4 (3 Br C6 H4 CO2 ) 12 (H2 O) 4 ]·3 Br C6 H4 CO2 H·H2 O 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 + 4 O4 ]+ 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的变温直流磁化率 ,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。

In order to explore the influence of the ligands and solvents on the magnetic properties of Mn12 complexes, the syntheses and magnetochemical properties of \[Mn\-\{12\}O\-\{12\}(3\|Cl\|C\-6H\-4CO\-2)\-\{16\}(H\-2O)\-3(3\|Cl\|C\-6H\-4CO\-2H)\]·3\|Cl\|C\-6H\-4CO\-2H 1, \[Mn\-\{12\}O\-\{12\}(3\|Br\|C\-6H\-4CO\-2)\-\{13\}(CH\-3CO\-2)\-3(H\-2O)\-4\] 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) ? ,b= 18.2712(3) ? ,c=34 3616(5) ? ,α=103 515(1)°,β=91 784(1)°,γ=116 25°,V=9508 5(3) ? 3,Z=2,D c = 1 294? mg·m \+\{-3\} ,μ=1 085? mm -1 ,F(000)=3?696, and S=1 096. It is found that the complex 1 consists of a central cubane\|like \[Mn\+\{4+\}\-4O\-4\]\+\{8+\} held within a nonplanar ring of eight Mn\+\{+3\} ions and eight μ\-3\|O\+\{2-\} ions. For both complexes 1 and 2 the χ ″ m signals are observed in the region 2～10?K, measured at three different frequencies, and exhibit two\|frequency dependent of χ ″ m AC peaks with a predominant peak in the 4～10?K 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.