【作者】 贾丽慧；

【导师】 刘祖黎；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2007， 博士

【摘要】 分子磁体的设计研究是近年来材料领域的研究热点。在这个方面,由金属和有机配体构成的金属配合物由于其结构变化的多样性和磁性行为的丰富性而成为非常重要的一类分子磁体并得到了大量关注和研究。本论文通过超分子化学的自组装方法合成得到了一些具有不同结构和磁性的金属配合物分子磁体,研究了不同有机配体在与金属离子构筑金属配合物分子磁体中配位模式对结构和磁性的影响,讨论了配合物的磁结构关联,并设计合成了具有三维磁有序的分子基磁体,研究了有机配体在自旋倾斜的弱铁磁体中的作用。主要开展了以下几个方面的工作:1、研究了具有螯合结构配合物的磁性。以EDTA(乙二胺四乙酸)为配体合成得到了过渡金属铜(CuⅡ)和锰(MnⅡ)的配合物,详细表征了它们的结构、热稳定性及磁性。结构上分别为单核和三核螯合结构并由氢键形成三维网络结构,磁性为反铁磁耦合。利用相应理论模型和理论公式对磁性测试结果进行了拟合得出了反应实验结果的磁耦合常数J值。讨论了EDTA配体在结构和磁关联上的一些特点。2、研究了配位模式对配合物结构和磁性的影响。首先以反丁烯二酸为配体合成得到了钴(CoⅡ)、锰(MnⅡ)、铜(CuⅡ)三个过渡金属配合物,详细表征了它们的结构和磁性。结构上以反丁烯二酸为长程桥联配位模式形成了一维无限延伸链状结构或零维双核结构,磁性表现为链内或分子内反铁磁耦合作用。讨论了反丁烯二酸配体不同配位模式对配合物结构和磁性的影响。3、研究了羧酸三原子顺-反桥联配位模式配合物的磁性。以顺丁烯二酸为配体合成得到了具有羧酸顺-反三原子桥联模式的一维链状铜(CuⅡ)金属配合物。磁性显示为链内铁磁性交换作用并在理论和实验两个方面对磁性进行了研究。应用基于密度泛函理论(DFT)的全势线性缀加平面波(FPLAPW)方法,采用高度精确的广义梯度近似(GGA),精确计算自旋结构、电子结构并结合磁结构关联分析了具有羧酸顺-反三原子桥联模式磁性系统的铁磁性来源和磁交换作用的机理。4、研究了羧酸三原子顺-顺桥联配位模式配合物的磁性。以邻苯二甲酸单甲酯为配体合成得到了两个金属铜(CuⅡ)配合物,详细表征了它们的结构和磁性。结构上都形成了四羧基桥联双核铜的中心对称结构。磁性上,铜与铜之间通过羧酸三原子顺-顺桥联超交换通道产生强的反铁磁相互作用。结构与磁性分析表明,邻苯二甲酸单甲酯配体中羧酸形成的三原子桥O-C-O的电子结构是控制顺磁中心离子之间反铁磁交换作用大小的主要因素。5、研究了以镧系金属钆(GdⅢ)为顺磁中心的金属配合物磁性。以二氰胺(dca)和羧酸为配体合成得到了镧系金属钆(GdⅢ)的配合物。详细表征了它们的结构,并对二氰胺钆的配合物磁性进行了测试分析。通过与同配体过渡金属配合物比较,讨论了具有4f电子的镧系金属之间的磁交换作用。6、研究了三维磁有序分子磁体的结构和磁性。利用有机化学方法合成得到了一个新的具有确定单晶结构的由两个三唑环构成的有机配体(3.4’-bi-1,2,4-triazole, btr)并对其结构进行了详细的分析。以此btr为配体水热法得到了一个锰MnⅡ的配合物,结构表征为一个少见的三维二元金属配合物。详细的磁性测试表明低温下存在自旋倾斜引起的三维磁有序,为自旋倾斜的弱铁磁体。对三维晶体结构和低温下的三维磁有序进行了分析讨论。更多还原

【Abstract】 The design of molecule-based magnetic materials has been of considerable interest in recent years. In this field, coordination complexes with metal and organic ligands have received intense attention and studies, due to the versatility of the metal coordination complexes in strucrure and the versatility of the complexes in magnetic behavior. In this thesis some metal coordination complexes were obtained by self-assembly method of supermolecular chemistry which have different structure and different magnetic behavior. The impact of bridging conformations in different organic ligands on structure and magnetism has been investigated while the magnetostructural correlation in these complexes has been discussed. Moreover, a molecular magnet with 3D magnetic order state was synthesized and the abilities of a new organic ligand to construct the spin-canting weak-ferromagnet was also discussed. The main results in this thesis are as following:1. The Cu(Ⅱ)-EDTA and Mn(Ⅱ)-EDTA coordination complexes were synthesized and their structures, thermal stabilites and magnetic properties were characterized thoroughly. They are mono and tri metal centre 3D networks built through hydrogen bonds and showing antiferromagnetic coupling interactions. The magnetic data were fitted through the correspondent theoretical model and equations and obtained the value of magnetic coupling constant. The structure and magnetostructural correlations about EDTA ligand were discussed.2. The CoⅡ、MnⅡ、CuⅡcoordination complexes bridged by fumarate ligand were synthesized and their structures and magnetic properties were characterized thoroughly. They are 1D infinite chainlike structure or dimmer structure using fumarate ligand as bridge spacer indicating antiferromagnetic coupling interactions. The impact of bridging conformations in fumarate ligands on structure and magnetism has been investigated.3. A syn-anti triatomic carboxylate-bridged chain-like CuⅡcomplex was synthesized and magnetic properties were investigated experimentally and theoretically which show the weak ferromagnetic intrachain interaction. The magnetic data had been analyzed and interpreted in terms of Heisenberg chain model corrected by a mean molecular field. Density functional theroy (DFT) with generalized gradient approximation (GGA) was applied to calculate the electronic structure and spin distribution of the present complex. The structural and electronic factors controlling the magnetic interactions was also determined:4.Two hydrated tetra-carboxylato-bridged dinuclear CuⅡcoordination complex with 1,2-benzenedicarboxylate monoester ligand has been prepared and characterized by means of X-ray analysis and magnetic measurements. Both complexes adopt dimeric paddle-wheel cage structures. The magnetic data exhibited strong intramolecular antiferromagnetic interaction between the two paramagnetic metal ions. The structural and magnetic results are compared with those for other related dimmers.5. The lanthanide metal GdⅢcoordination complexes with dicyamide or carboxyl ate ligand were prepared and their structures were characterized thoroughly. The magnetic measurement of Gd-dca complex exhibited antiferromagnetic coupling interactions. The magnetic interactions between 4f metal Gd centre was discussed comparing to the transition metal centres.6.A new organic ligand containing two triazole rings was prepared and the single crystal structure was first obtained and discussed thoroughly. Hydrothermal treatment of MnⅡions and btr ligands provided an infrequent 3D binary manganese coordination complex. Detailed magnetic measurement exhibited the occurence of spin canting and spontaneous magnetic order at low temperature as a weak ferromagnet.更多还原