【作者】 崔术新；

【导师】 张景萍；

【作者基本信息】 东北师范大学 ， 物理化学， 2006， 硕士

【摘要】 分子磁性材料是近几十年发展起来的新型材料,作为高度有序的分子体系,它具有结构多样性,易于用化学方法对分子进行修饰和剪裁而改变其磁性;磁性能的多样性;可以将磁性和其他如机械、光、电等特性相结合;可以用常温或低温的方法进行合成;易于加工成形,可以制成许多传统磁体难以实现的器件;低密度等特点。正是这些特点使它成了科学家们研究的焦点。分子磁性材料包括纯有机磁性分子、无机-有机杂化磁性材料、无机磁性化合物、单分子磁体、自旋交叉配合物等。其中顺磁离子的金属-有机杂化结构引起很大关注,原因在于它们可以得到在分子磁性和材料化学领域里有潜在应用的新型网络结构。构建这种结构常用的方法是使用桥联配体来形成外延网,同时传递磁相互作用。根据分子设计和功能需要,配体可以是不同的两个或多个。由于有机配体的种类繁多,这类金属有机配合物磁性材料具有广泛的发展前景。迄今为止,报道了许多含有过渡金属CuII, NiII, MnII桥联型配和物磁性材料,但含有CoII的配合物相对少些,而且其分子内相互作用多数为反铁磁性。本论文尝试使用水热方法合成配和物磁性材料。我们的兴趣是含有强的各项异性钴的一维配位聚合物的设计和通过第二配体的晶体设计调节磁性质。在实验中我们使用吡啶-2,6-二羧酸离子pdc2-作为第一配体、2,4′-联吡啶(2,4′-bpy)和5-苯基-2,4′-联吡啶(5-ph-2,4′-bpy)分别作为第二配体构造一维配位聚合物,得到了两种金属钴配位聚合物[Co(pdc)(2,4′-bpy)2·H2O]n (1)和[Co(pdc)(5-ph-2,4′-bpy)2·H2O]n(2)。通过X-射线衍射测量对配合物的结构进行确认,并对所得化合物的磁性进行了研究。在1中可以观察到反铁磁耦合,由于聚合钴链的扭曲结构,配位聚合物2具有铁磁耦合。苯取代基的空间位阻导致了相邻聚合链的扭曲结构。因此,第二配体的位阻效应对调节磁性转变起了重要作用。据我们所知,这是取代基调节磁性转变的第一个例子。本工作将为新的有潜在应用的配位聚合物材料的设计和开发提供一个有前途的方法。此外,我们还尝试了有机材料的水热合成。更多还原

【Abstract】 Molecular magnetic materials were newly developed in past decades. As highly orderedmolecular systems, they are superior to traditional magnetic materials in many fields, such aslow density, solubility, tuning properties, flexibility and so on. Molecular magnetic materialsinclude pure organic molecules, organic-inorganic hybrid structures, inorganic compounds,single molecular magnets and spin crossover complexes.Metal-organic hybrid structures of paramagnetic metal ions are particularly interesting, asthese may give rise to a series of novel framework structures with potential applications in thefields of molecular magnetism and materials chemistry. A commonly used strategy in buildingsuch extended network structures is to employ bridging ligands capable of transmittingmagnetic interactions in addition to propagating.Our interests lie in the design of 1D magnetic polymers containing cobalt (II) ions linkedby first ligands with strong anisotropy and the achievement of tuning the magnetic propertyby crystal engineering of second ligands. Our studies here aimed at constructing such 1Dcobalt polymeric chain using pdc2-as first ligand, namely bridging ligand, and 2,4′-bipyridine(2,4′-bpy) as well as its derivative 5-phenyl-2,4′-bipyridine (5-ph-2,4′-bpy) as second ligands.We have obtained two families of 1D polymeric cobalt complexes in the reaction ofpyridine-2,6-dicarboxylic acid (pdcH2) with Co(NO3)2?6H2O under hydrothermal conditionsin the presence of bipyridyl as second ligands. The structure of [Co(pdc)(2,4′-bpy)2·H2O]n (1)and [Co(pdc)(5-ph-2,4′-bpy)2·H2O]n (2) was confirmed by X-ray measurement. Themagnetism characters for 1 and 2 were investigated. Antiferromagnetic coupling between CoIIions in 1 has been observed, polymer 2 possesses ferromagnetic coupling due to its distortedstructure of polymeric cobalt chains. The steric hindrance of the phenyl substituent results inthe distorted structure of neighbouring polymeric chains. As a result, the steric hindrance insecond ligand plays an important role for tuning magnetic transform. To the best of ourknowledge, this is the first example of substituent tuned magnetic transform. This report mayprovide a promising strategy for design and exploitation of new polymeric coordinationcompounds for useful applications.更多还原