Structural and magnetization studies of a new (mu-oxo)bis(mu-carboxylato)dimanganese(III) complex with a terminal hydroxo ligand
Structural and magnetization studies of a new (mu-oxo)bis(mu-carboxylato)dimanganese(III) complex with a terminal hydroxo ligand
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DOI：
10.1021/ic950930x
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发表时间：
1996-03-27
影响因子：
4.6
通讯作者：
Rodriguez, V
中科院分区：
文献类型：
--
作者：
Corbella, M;Costa, R;Rodriguez, V
双核Mn-III配合物[Mn 2 O（PhCOO）（2）（bpy）（2）（OH）（NO3）]。在苯甲酸（PhCOOH）和2，2 '-联吡啶（bpy）存在下，用高锰酸四丁基铵（NH 4）控制氧化硝酸锰制备水。通过单晶X-射线衍射实验确定了其结构，并由一个三联桥[Mn-2（mu-O）（mu-PhCOO）（2）]（2+）双核核组成。每个锰（III）离子带有螯合bpy和终端X阴离子（X = OH-或NO3-）完成扭曲的八面体配位几何。虽然末端阴离子位于无序位置，但键长和空间位阻的分析使我们将络合物分配为不对称结构[（bpy）（OH）Mn-III（mu-O）（mu-PhCOO）（2）Mn-III（bpy）（ONO）（2））]。具有化学式C34 H29 Mn 2N 5 O 10的产物在单斜晶系中结晶，空间群C2/c，其中a = 16.607（4）埃，B = 25.619（6）埃，c = 9.796（3）埃，β = 100.15（3）度，并且Z = 4。对一系列相关化合物进行的磁性研究表明，高自旋d（4）锰（III）离子具有中等的铁磁或反铁磁相互作用和显著的零场分裂，这与强Jahn-Teller畸变一致。在目前的工作中，我们解释了复杂的磁性使用自旋哈密顿量，其中包括海森堡交换，轴向和菱形的自旋，和各向异性的朗德因子，假设的假C-2对称的双核核心。为了以足够的精度确定各向异性参数，我们在2-300 K的范围内，在0.5、1.0、2.5和5 T的磁场下进行了变温变场磁化测量。通过对完整的自旋哈密顿量进行对角化，用一组参数拟合了整个数据集。最佳拟合值J = +1.0（4）cm（-1），D = +4.5（5）cm（-1），E = 0，g（x）= g（y）= 1.96，g（z）= 2.00表明在压缩八面体环境中锰（III）离子之间发生铁磁相互作用。的双核配合物的铁磁行为的Mn（III）的协调领域的压缩（和相反的反铁磁性的伸长率）的磁结构关系，然后提出。它是由扩展的休克尔型的理论分子轨道计算证实。
The dinuclear Mn-III complex [Mn2O(PhCOO)(2)(bpy)(2)(OH)(NO3)]. H2O was prepared by controlled oxidation of manganous nitrate with n-tetrabutylammonium permanganate in the presence of benzoic acid (PhCOOH) and 2,2'-bipyridine (bpy). Its structure was determined in a single-crystal X-ray diffraction experiment, and consists of a triply-bridged [Mn-2(mu-O)(mu-PhCOO)(2)](2+) dinuclear core. Each manganese(III) ion bears a chelating bpy and a terminal X anion (X = OH- or NO3-) completing a distorded octahedral coordination geometry. Although the terminal anions are located in disordered positions, the analysis of bond lengths and steric considerations led us to assign to the complex an asymmetric structure [(bpy)(OH)Mn-III(mu-O)(mu-PhCOO)(2)Mn-III(bpy)(ONO)(2))]. The product, with a chemical formula C34H29Mn2N5O10, crystallizes in the monoclinic system, space group C2/c, with a = 16.607(4) Angstrom, b = 25.619(6) Angstrom, c = 9.796(3) Angstrom, beta = 100.15(3)degrees, and Z = 4. Magnetic studies performed on a series of related compounds have revealed a moderate ferro- or antiferromagnetic interaction and significant zero-field splittings in line with the strong Jahn-Teller distortion of the high spin d(4) manganese(III) ions. In the present work we interpreted the magnetic properties of the complex using a spin Hamiltonian which includes the Heisenberg exchange, axial and rhombic ZFS, and an anisotropic Lande factor, under the assumption of a pseudo-C-2 symmetry of the dinuclear core. In order to determine the anisotropy parameters with enough accuracy, we resorted to variable-temperature variable-field magnetization measurements over the 2-300 K range at fields of 0.5, 1.0, 2.5, and 5 T. The whole set of data was fit with a single set of parameters through diagonalization of the complete spin Hamiltonian. The best fit values J = +1.0(4) cm(-1), D = +4.5(5) cm(-1), E = 0, g(x) = g(y) = 1.96, and g(z) = 2.00 showed that a ferromagnetic interaction occurs between manganese(III) ions in a compressed octahedral environment. A magnetostructural relationship linking the ferromagnetic behavior of the dinuclear complex to the compression of the Mn(III) coordination sphere (and conversely of the antiferromagnetism to the elongation) is then proposed. It is substantiated by theoretical molecular orbital calculations of the extended Huckel type.