单分子磁体[Mn4(CF3COO)4(hmp)6]的合成、晶体结构及磁学性质

以Mn12O12(CF3COO)16(H2O)4]·2CF3COOH·4H2O和2-羟甲基吡啶(hmpH)为起始物, 在四氢呋喃溶液中合成了一种新的四核锰配合物Mn4(CF3COO)4(hmp)6]. X射线单晶衍射结果表明, 该配合物属于单斜晶系, P21/c空间群, 晶胞参数a=1.3663(3) nm, b=1.4705(3) nm, c=1.4734(3) nm, β=98.51(3) °, V=2.9276 nm3, Z=2. 配合物中有两个CF3COO-基团与七配位Mn2中心相连, 其中一个为单齿配体, 另一个是双齿配体. 直流磁化率研究结果表明, 该配合物具有较高的自旋基态, 而交流磁化率依赖于外场频率变化极值的出现表明该配合物是一种单分子磁体.

Synthesis, Crystal Structure and Magnetic Properties of a Single-molecule Magnet [Mn4(CF3COO)4(hmp)6]

The preparation, X-ray structure characterization and magnetic properties are presented for a new mixed-valence tetranuclear manganese complex that functions as a single-molecule magnet(SMM), Mn4(CF3COO)4(hmp)6], where hmp- is the anion of 2-(hydroxymethyl) pyridine and is a N,O bidentate chelate. The compound crystallizes in the monoclinic system, space group P21/c(No.14) with unit cell parameters a=1.3663(3) nm, b=1.4705(3) nm, c=1.4734(3) nm, β=98.51(3)°, V=2.9276 nm3 and Z=2. The structure of the complex shows a novel coordination of the trifluoroacetate(TFA) anions, with one anion acting as a monodentate ligand while the second one coordinating through both oxygens to the same Mn centre. Direct current magnetic susceptibility measurement in the 2—300 K temperature range supports a high-spin ground state. The presence of a frequencey-dependent alternating current susceptibility signal indicates that the individual molecule is acting as the magnet.