Synthesis and optimization of 1D and 2D coordination polymers with a slow relaxation of the magnetization

本项目的主要目标是研究基于Co(II)和Fe(II)硫代和硒氰酸酯的一维和二维配位聚合物的合成和性质，这些配位聚合物表现出像单链磁体一样的缓慢磁化松弛。在这个项目中，应该开发一种合理的途径来获得这些化合物，并且应该研究化学和结构修饰对描述这些材料性能的参数的影响。在我们的研究过程中，合成了几个具有相同配位网络拓扑结构的新化合物，它们的磁化强度总是缓慢松弛。在Co(II)离子的情况下，化合物可以分为两类：具有反铁磁性基态的化合物表现为变磁相变，弛豫可追溯到单链磁性行为，而具有铁磁基态的化合物则不是这样。由于这是一个现象学发现，这个项目应该继续产生更好和更广泛的数据基础，更详细地修改磁性，并调查这种行为的起源。这包括一些缺失的钴(II)和铁(II)化合物的合成，以及基于硫代和硒氰基阴离子的混合晶体的合成，以更详细地调整此类化合物的磁性。其他一些化合物应用镉稀释，以确定可追溯到单个阳离子松弛的能垒含量，并可与相应的离散络合物的值进行比较。最后，容易轴的确定将是有意义的。因此，人们将尝试生长更大的适合于定向磁性测量的单晶，并合成用于中子衍射的氚化合物。对于所有这些研究，还必须研究单离子的磁性(单离子磁性)，这就是为什么这是一个常见的建议。这包括对离散络合物的实验研究以及重要参数的计算，例如，耦合常数、g值、各向异性参数、势垒以及这些化合物中易轴的方向。将特别注重对结构相关性的理解，这将在专门设计的模型系统的基础上加以解决。

The major goal of the present project consists of investigations on the synthesis and properties of 1D and 2D coordination polymers on the basis of Co(II) and Fe(II) thio- and selenocyanates, which show slow relaxations of the magnetization, like observed in single-chain magnets. Within this project, a rational access to such compounds should be developed and the influence of a chemical and structural modification onto those parameters that describe the performance of these materials should be studied. In the course of our investigations several new compounds with an identical topology of the coordination networks were synthesized, that show always slow relaxations of the magnetization. In the case of Co(II) cations, the compounds can be divided into two different groups: The compounds with an antiferromagnetic ground state show a metamagnetic transition and the relaxations can be traced back to single-chain magnetic behavior, which is not the case for the compounds with a ferromagnetic ground state. Because this is a phenomenological finding, this project should be continued to generate a better and broader data basis, to modify the magnetic properties in more detail and to investigate the origin of this behavior. This includes the synthesis of some missing compounds with cobalt(II) and iron(II), and of mixed crystals based on thio and selenocyanato anions to tune the magnetic properties of such compounds in more detail. Some other compounds should be diluted with cadmium to determine the content of the energy barrier that can be traced back to the relaxations of the single cation, which can be compared with the values of the corresponding discrete complexes. Finally, the determination of the easy axis would be of interest. Therefore, it will be tried to grow larger single crystals suitable for oriented magnetic measurements and to synthesize deuterated compounds for neutron diffraction. For all these investigations the magnetic properties of the single ions (single ion magnetism) must also be investigated, which is the reason that this is a common proposal. This includes experimental investigations of discrete complexes as well as calculations of important parameters, like, e.g. coupling constants, g-values, anisotropy parameters, energy barriers as well as the directions of the easy-axis in these compounds. A particular focus will be placed on the understanding of structural correlations which will be addressed on the basis of specifically designed model systems.