POLYMAG · Magnetic Coordination Cluster Polymers

Magnetic Coordination Cluster Polymers

Coordination cluster polymers (CCPs) built up from magnetic polynuclear coordination clusters have received considerable attention due to potential applications in different fields and the rational preparation of such CCPs, in particular the controlled integration of the individual cluster properties into those of the final, networked system, represents multiple challenges. The main objectives of the project POLYMAG were the design and elaboration of novel cluster-based materials with exceptional magnetic properties by connecting small and nanosized homo- and heterometallic carboxylate clusters using adequate O- and/or N-based organic linkers, and to examine the structural, magnetic, thermal and other properties of both the prepared clusters and coordination polymers based on them. The project has been successful leading to one chapter in the book and five papers published in the international journals and eight abstracts in the proceedings of the conferences. To achieve the goals of the project practical and broadly applicable approaches for the synthesis of clusters and cluster-based coordination polymers were developed. This includes the use of conventional solution chemistry and novel synthetic procedures such as hydro(solvo)thermal synthesis, microwave assisted heating, ultrasonic irradiations and the reactions in solid state. By employing these different synthetic methods an extensive series of both homo- and heterometallic 3d and 3d/4f compounds with different nuclearity ranging from di-, tri-, tetra-, hexa-, hepta-, octa-, undeca-, tetradecanuclear up to hexadecanuclear metallic cores, metal ratio and coordination topology have been obtained. Research has also been ongoing into synthesis of single molecule magnets (SMMs) involving 3d/4f systems. The using of the different O,N-donor ligands leaded to the formation of multidimensional coordination networks (one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D)) by connection the metal-based clusters. The thus-obtained clusters and coordination cluster polymers were investigated and characterised by a range of physico-chemical methods in order to elucidate their chemical composition, and their structural and electronic / magnetic properties. A single-crystal X-ray diffraction analysis was used for the characterisation of structures of all prepared materials. Detailed studies of magnetic properties of a large number of new synthesised clusters and coordination cluster polymers were performed that allowed to establish the nature of magnetic interactions between metal ions in these compounds. Considering that the interpretation of the magnetic characteristics in the CCPs can be complicated by the additional inter-cluster coupling, a new semi-empirical program wxJFinder has been developed (see http://www.ac.rwth-aachen.de/extern/ak-koegerler/wxjfinder.php for details). The program provides accurate prediction the exchange energies in Fe-O-Fe systems. Overall, the achieved results allow us to develop a library of synthetic pathways, and understand the correlation between geometrical and electronic structure, spectroscopic and magnetic properties of clusters and infinite polymetallic cluster-based systems. Therefore, the work comprised fundamental research in pure chemistry but also has connections to the understanding of new molecular magnetic materials. Designed homo- and heteropolynuclear discrete and infinite supramolecular systems can find application in important fields such as catalysis, gas and liquid storages, separation and purification, pharmaceuticals, and solid-state materials used in electronics, optics and telecommunications.

Data: CORDIS, © European Union