Physics Colloquium / Prof. Ulrich Kortz: From Polyoxotungs­tates to Polyoxopallada­tes: Synthesis, Structure and Magnetic Properties

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Abstract: Polyoxometalates (POMs) are discrete, anionic metal-oxo clusters with a diverse compositional range, enormous structural variety, and a multitude of physicochemical properties including magnetism. Examples of classical POMs are the Keggin (e.g. [SiMo₁₂O₄₀]^4-) and Dawson ions (e.g. [P₂W₁₈O₆₂]^6-), but besides polyoxotungstates and - molybdates also polyoxovanadates, -niobates and -tantalates (e.g. [MV₆O₁₉]^8-, M = V, Nb, Ta) are known. A few POMs appear in nature as minerals (such as sherwoodite Ca_4.5[AlV₁₄O₄₀]), whereas the number of POMs synthesized in the laboratory is enormous. For the Keggin- and Dawson-type polyoxotungstes derivatives can be made by the incorporation of d or f block metal ions, including paramagnetic ones, and thereby engineering magnetic POMs. In fact, it was possible to incorporate up to 20 guest metal ions into the wheel-shaped POM host {P₈W₄₈}, resulting in {Cu₂₀P₈W₄₈} and {Fe₁₆P₈W₄₈}. The spin-spin coupling of the oxo/hydroxo-bridged magnetic guest ions can be investigated, and in some cases molecular magnetism was observed (e.g. {Co₁₆P₈W₃₆}). In 2008 the class of polyoxopalladates(II) (POPs) was developed with the discovery of the cube-shaped [Pd₁₃As₈O₄₀]^14-, and then developed further systematically, resulting in different structure types such as star, open-shell, bowl, dumbbell, and some derivatives exhibited interesting magnetic properties.

Short bio: 1983-1986: Study of Chemistry (B.Sc.), Giessen University, Germany / 1986-1989: Study of Chemical Engineering (M.Sc.), Darmstadt University, Germany (thesis title: Encapsulation of Biologically Active Substances in Polyelectrolyte Microparticles) / 1990-1995: Study of Chemistry (Ph.D.), Georgetown University, USA (thesis title: Diphosphate Complexes of Polyoxotungstates and Polyoxomolybdates) / 1995-1996: Postdoc, Universitá di Firenze, Italy / 1996-1997: Postdoc, Université de Versailles, France / 1997-2001: Assistant Professor, American University of Beirut (AUB), Lebanon / 2001-2002: Associate Professor, American University of Beirut, Lebanon / 2002- 2007: Associate Professor, International University Bremen / (IUB)2007-: Professor, Jacobs University Bremen (formerly IUB).