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

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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.