【作者】 王玉霞；

【导师】 程鹏；

【作者基本信息】 南开大学 ， 无机化学， 2013， 博士

【摘要】 本论文以镧系硝酸盐和多羟基配体N，N，N′，N′-四羟乙基乙二胺为原料,设计合成了系列三角形结构的磁、电功能性分子基材料,并对所得到的目标产物进行了详细的结构表征和性质研究。1.利用溶剂热合成方法,得到了首个同时具有单分子磁体行为和铁电体行为的三角形分子基簇合物Dy3-EtOH。低温磁学性质研究表明该单分子磁体具有罕见的两步慢磁弛豫和阶梯状磁滞回线。通过第一性原理计算,定量分析了镝离子间的磁耦合参数和分子内的偶极-偶极相互作用大小。热分析测试证明簇合物Dy3-EtOH具有很高的热稳定性,通过介电性质的表征以及变温单晶数据,说明了Dy3-EtOH铁电相到顺电相的转变温度高达470K。这项工作为多功能材料的研究提供了一种新颖的思路和方法。2.为了进一步确认溶剂分子对Dy3-EtOH对称性和多步慢磁弛豫行为的影响,合成了一例不含溶剂分子的三角形簇合物Dy3。磁学性质表明,它也是具有两步慢磁弛豫行为的单分子磁体,但是慢磁弛豫过程间的相互依赖程度不同。此外,对Dy3-EtOH和Dy3两个三角形单分子磁体进行抗磁离子稀释,实验结果证实了两种慢磁弛豫过程来源于不同配位构型的镝离子,为分析多步慢磁弛豫行为提供了明确方法。3.通过溶剂调控改变已有配合物晶格内的溶剂分子,从而改变其极性,我们成功的将已得到的由镧系离子构筑的四个中心对称的簇合物转变到四个极性的簇合物。通过介电性质的测试,发现极性簇合物Ln3具有很高的铁电相到顺电相的转变温度(488-523K),变温单晶和粉末衍射数据以及热分析测试共同印证了它们的高热稳定性。此外,我们还研究了两个钆簇合物的磁制冷性质,发现两者具有较大的磁熵变值,有望成为良好的磁制冷材料。更多还原

【Abstract】 This thesis focuses on the design and synthesis of functional complexes constructed by lanthanides ions and N,N,N’,N’-tetrakis(2-hydroxyethyl)ethylenediamine. Both the magnetic and electric propertiess of the obtained complexes have been investigated in detail.1. An unprecedented molecule-based Dy3-EtOH cluster, which exhibited single-molecule magnetic properties and dielectric properties simultaneously, was obtained under solvent thermal conditions. Two slow magnetic relaxation processes and magnetization steps were found in the magnetic investigation of Dy3-EtOH. The parameters of dipolar and magnetic exchange interactions of Dy3-EtOH which has the practical toroidal arrangement of the local magnetic moments have been calculated in detail with ab initial calculation. Dielectric data displayed a high paraelectric-ferroelectric phase transition and electric hysteresis loops. This work still sheds light on a synthetic route to generate molecular multifunctional materials.2. As a follow-up research work for multiple relaxation processes of Dy3-EtOH, a new solvent-free triangular Dy3cluster has been successfully synthesized and characterized. Magnetic investigations reveal that the new triangular single-molecule magnet (SMM) exhibiting two independent relaxation processes in the absence of solvent molecules. Besides, the magnetic properties of the two magnetic diluted SMMs were also studied, the results of which provided a proper way to investigate multi-steps slow magnetic relaxations.3. Four ferroelectric lanthanide clusters Ln3were obtained from their non-polar point group analogues via solvent modulation, which presents a facile way to obtain new molecule-based ferroelectric materials. All of them exhibited ferroelectric properties with high thermal stabilities, as confirmed by ferroelectric hysteresis loops and anomalies dielectric peaks as well as varying temperature X-ray diffraction and thermal analyses, respectively. Two Gd clusters exhibit large magneto-caloric effect indicating their potential application as MCE and multifunctional devices.更多还原