金属配合物分子磁性的理论研究

【作者】 张义权；

【导师】 罗成林；

【作者基本信息】 南京师范大学 ， 理论物理， 2003， 硕士

【摘要】 近几十年来，分子磁学发展迅猛，已成为一个新兴的前沿研究领域，在本论文中，我们选取了三种分子磁性材料，对其磁学性质分别进行了研究。主要内容有：（1）．研究了对氨基苯甲酸阴离子桥联的双核铜配合物Cu₂（2，2’-bpy）₂（4，4’-bpy）₂L₂的磁学性质，分别采用全电子基组SV/TZVP、和价电子基组LanL2DZ，运用混合密度泛函B3LYP并结合Noodleman提出的对称性破损理论计算其磁偶合作用常数J值，结果分别为J=-34.51cm^-1、J=-61.81cm（-1），与实验值J=-40.63cm^-1比较接近，然后，我们分别对端基配体和桥联配体采用简化模型，并运用上述方法和理论计算各简化模型的J值，所计算的J值与全分子的J值相差不大。考虑到计算量及研究目的，在上面的模型中选取了较简单的分子模型5，来研究其磁构效关系，分子的反铁磁性随桥联角O-C-O夹角θ的增大而增强，在θ大于118.623度时，分子的反铁磁性随三重态铜上自旋密度的减小而增强，但当θ小于118.623度，分子反铁磁性随三重态铜上自旋密度的减小反而减小，在文中，我们解释了这种现象。另外，我们还揭示了J三重态两个成单电子所在的分子轨道能量差的平方（ε₁-ε₂）²之间的变化关系。（2）．研究了目前比较热门的氰根桥联金属配合物的磁学性质，采用上述方法和理论分别计算了氰根桥联配合物(V^ⅣO[Cr^Ⅲ（CN）₆]_2/310/3H₂O、氰根桥联配合物[Mo₂（CN）₁₁]⁵的磁偶合作用常数J，所计算的J值分别为J=-42.36cm¹、J=-111.46cm¹，与实验值J=-48cm¹、J=-113cm¹比较接近。然后，分别对这两种配合物自旋密度分布加以分析，两种配合物中金属离子上的成单电子几乎是定域的，其自旋极化占主导作用。考虑到氰根桥联配合物的重要作用，在今后的研究中，我们将继续深入研究各种氰根桥联配合物的磁学性质。更多还原

【Abstract】 In the past several decades, molecular magnetism has been developing so fast and has become a newly arisen front study realm. In this thesis, we selected three kinds of molecular magnetism materials and studied their magnetism, respectively. The key contents: (1). We computed and studied the materials about the p-aminobenzoic-bridged binuclear copper compound. Adopting the whole basis sets "SV/ TZVP" and the valence basis set "LanL2DZ", we computed its’ magnetic exchange coupling constant J values by combining mixed Density Functional Theory B3LYP and Broken symmetry Approach put forward by Noodleman. The J values are equal to -34.51cm-1 and -61.81cm-1, respectively. The experimental Jvalue is equal to -40.63 cm-1. Their differences are small. Immediately after, we used the simplification models which were obtained by replacing the bridging ligand and the bottom ligand using some simple ligand and computed the J values using above method and theory. Their J values are near to the whole molecule J value. In consideration of the calculation measures and the purpose of study, we selected the simple molecule model 5 in the above models and studied the relation between magnetism and structure. The molecular antiferromagnetism increases with the increasing of the bridging angle O-C-O(o). When 0>118.623 degrees, the molecular antiferromagnetism increases with the decreasing of the spin density on the Cu in its triplet state. But when0<l 18.623 degrees, the molecular magnetism decreases with the decreasing of the spin density on Cu in its triplet state. In the thesis, we explained this phenomenon. Moreover, we also studied the relations between the J and (e,-e2)2. (2). We studied the cyano-bridged metal compounds which are very popular today. Using above method with theories, we have computed the magnetic exchange coupling constants J values about (VIVO)Cr[1 (CN)6]2/3. 10/3H2O compound and [Mo2(CN)11]5 compound, respectively. The J values are equal to -42.36cm-1 and -111.46cm-1, respectively. The experimental J values are equal to -48cm-1 and -113cm-1, respectively. Their differences are small. After that, we analysed their spin density maps. The unpaired electrons in each compound are localized. Their spin polarization dominated. Because of the important of cyano-bridged compounds, we will study them in future.更多还原