Syntheses, crystal structures, and magnetic properties of cyano-bridged Mn(II)-Nb(IV) bimetal assemblies
Syntheses, crystal structures, and magnetic properties of cyano-bridged Mn(II)-Nb(IV) bimetal assemblies
复制标题
氰基桥联 Mn(II)-Nb(IV) 双金属组件的合成、晶体结构和磁性能
DOI：
10.1016/j.poly.2012.08.058
复制
发表时间：
2013
期刊：
影响因子：
2.6
通讯作者：
S. Ohkoshi
中科院分区：
文献类型：
--
作者：
K. Nakagawa;K. Imoto;H. Miyahara;S. Ohkoshi
在本文中，我们报告了两种锰(II)-辛酸铌酸根(IV)基磁体的合成、晶体结构和磁性能：MnII2[NbIV(CN)8](3-吡啶甲醇)8·2H2O (1)和MnII2[NbIV(CN)8](3-氨基吡啶)8·2H2O (2)。图1和图2具有3D网络结构，其中一个[Nb(CN)8]4−离子连接到四个Mn离子，并且一个Mn离子通过桥联氰化物连接到两个[Nb(CN)8]4−离子。 1中[Nb(CN)8]的配位几何为正方反棱镜，而2中的配位几何为十二面体。磁性测量表明，1 和 2 是亚铁磁体，居里温度 (TC) 分别为 24 和 43K，尽管 Nb 和 Mn 离子周围桥联 CN 基团的配位数相同。 TC 的差异可以通过考虑 [Nb(CN)8] 配位几何形状的差异来理解。使用离散变分(DV)-Xα方法对[NbIV(CN)8]进行分子轨道计算表明，十二面体几何结构的桥接N上2p轨道的布居量大于方形反棱镜几何结构的桥接N上的2p轨道布居。计算结果表明，氰基氮上2p轨道的电荷布居影响了NbCNMn磁轨道的超交换相互作用，从而决定了TC值。
In this paper, we report the syntheses, crystal structures, and magnetic properties of two manganese(II)–octacyanoniobate(IV)-based magnets: MnII2[NbIV(CN)8](3-pyridinemethanol)8·2H2O (1) and MnII2[NbIV(CN)8](3-aminopyridine)8·2H2O (2). 1 and 2 possess 3D network structures where a [Nb(CN)8]4−ion is connected to four Mn ions, and a Mn ion is connected to two [Nb(CN)8]4−ions via bridged cyanides. The coordination geometry of [Nb(CN)8] in 1 is square antiprism, while that in 2 is dodecahedron. Magnetic measurements show that 1 and 2 are ferrimagnets with Curie temperatures (TC) of 24 and 43K, respectively, although the coordination numbers of the bridged CN groups around Nb and Mn ions are the same. The difference in TCcan be understood by considering the difference in the coordination geometries of [Nb(CN)8]. Molecular orbital calculations of [NbIV(CN)8] using the discrete variational (DV)-Xα method indicate that the population of the 2p orbital on the bridged N with a dodecahedron geometry is larger than that with a square antiprism geometry. The calculation results suggest that the charge population of the 2p orbital on the cyano-nitrogen affects the superexchange interaction for the magnetic orbital of NbCNMn, which determines the TCvalue.