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

本项目的主要目标包括对基于Co（II）和Fe（II）硫代和硒代氰酸盐的1D和2D配位聚合物的合成和性质的研究，这些配位聚合物显示出缓慢的磁化弛豫，就像在单链磁体中观察到的那样。在该项目中，应开发此类化合物的合理途径，并应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，合成了几种具有相同拓扑结构的配位网络的新化合物，它们总是表现出缓慢的磁化弛豫。在Co（II）阳离子的情况下，化合物可以分为两个不同的组：具有反铁磁基态的化合物显示出变磁转变，并且弛豫可以追溯到单链磁性行为，而具有铁磁基态的化合物则不是这种情况。因为这是一个现象学的发现，所以这个项目应该继续下去，以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。这包括合成一些缺失的钴（II）和铁（II）化合物，以及基于硫代和硒氰根阴离子的混合晶体，以更详细地调节此类化合物的磁性。其他一些化合物应该用镉稀释，以确定可以追溯到单个阳离子弛豫的能垒的含量，这可以与相应的离散络合物的值进行比较。最后，确定易轴将是有意义的。因此，将尝试生长适合于定向磁性测量的较大单晶，并合成用于中子衍射的氘代化合物。对于所有这些研究，也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。这包括离散复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，能垒以及这些化合物中易轴的方向。一个特别的重点将放在结构相关性的理解，这将是专门设计的模型系统的基础上解决。

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.