研究领域

Anorganische Chemie (Molekularer Magnetismus)

The control and understanding of magnetic interactions of spin centers within discrete molecules as well as within molecular networks are at the core of molecular magnetism. In this context, we aim to address various open questions, for example: Which magnetic phenomena can actually be realized in single molecules (i.e., quasi-zerodimensional spin structures)? This includes e.g. static and dynamic ordering phenomena such as phase transitions or spin glass characteristics. What is the response of these spin structures to changes such as structural distortions, redistribution of spin centers, or changes to the exchange connectivity between the spin centers? What happens when spin clusters are interlinked to result in multidimensional networks? How can magnetic molecules be utilized in the area of molecular spintronics, i.e., the combined exploitation of molecular charge and magnetic states? How can we contact molecules or attach them to conducting as well as non-conducting surfaces for this very purpose? What effects do non-standard ligand fields have on the spin centers? How does the electrostatic environment affect the molecular magnetic characteristics? What theoretical approaches can be used to adequately model these relations? Closely linked to this topic are our projects focusing on the chemistry and physics of polyoxometalates, a class of compounds with an unmatched potential for chemical functionalization and structural complexity. Polyoxometalates allow for a structural and electronic control that far surpasses that known for classical coordination compounds. These molecular metal oxide clusters can even aggregate to ultra-large oligomeres that fill the gap between discrete molecules and molecule-based network structures. This allows us to study the transition from discrete to extended, multi-dimensional structures in terms of electronic and magnetic properties. The chemistry of polyoxometalates still poses several fundamental questions, since the precise reaction mechanisms underlying the self-assembly of these nano-scaled clusters remain unknown. Likewise, their syntheses remain serendipitous and rational synthesis strategies are still rare. We are also interested in the homogeneous catalytic activity of such polyoxometalates. Here, oxidation catalysis, water oxidation, and O2 activation as well as the integration of hydrolytically stable systems in photochemical cells are being explored.

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L. Qin, Z. Zhang, Z. Zheng, M. Speldrich, P. Kögerler, W. Xue, B.-Y. Wang, X.-M. Chen, Y.-Z. Zheng, "Dynamic Magnetism of an Iron(II)-Chlorido Spin Chain and its Hexametallic Segment", Dalton Trans. 2015, 44, 1456-1464. J. van Leusen, M. Speldrich, H. Schilder, P. Kögerler, "Comprehensive Insight into Molecular Magnetism via CONDON: full vs. effective Models", Coord. Chem. Rev. 2015, accepted, DOI:10.1016/j.ccr.2014.10.011. S.A. Adonin, N.V. Izarova, C. Besson, P.A. Abramov, B. Santiago-Schübel, P. Kögerler, V.P. Fedin, M.N. Sokolov, "An Ir(IV)-containing Polyoxometalate", Chem. Commun. 2015, 51, 1222-1225. K.Yu. Monakhov, O. Linnenberg, P. Kozłowski, J. van Leusen, C. Besson, T. Secker, A. Ellern, X. López, J.M. Poblet, P. Kögerler, "Supramolecular Recognition Influences Magnetism in [X@HVIV8VV14O54]6- Self-Assemblies with Symmetry-Breaking Guest Anions", Chem. Eur. J. 2015, 21, 2387-2397.