title: Electronic structure and soft-X-ray-induced photoreduction studies of iron-based magnetic polyoxometalates of type {(M)M5}12Fe(III)30 (M = Mo(VI), W(VI)).
abstract: Giant Keplerate-type molecules with a {Mo72Fe30} core show a number of very interesting properties, making them particularly promising for various applications. So far, only limited data on the electronic structure of these molecules from X-ray spectra and electronic structure calculations have been available. Here we present a combined electronic and magnetic structure study of three Keplerate-type nanospheres--two with a {Mo72Fe30} core and one with a {W72Fe30} core by means of X-ray absorption spectroscopy, X-ray magnetic circular dichroism (XMCD), SQUID magnetometry, and complementary theoretical approaches. Furthermore, we present detailed studies of the Fe(3+)-to-Fe(2+) photoreduction process, which is induced under soft X-ray radiation in these molecules. We observe that the photoreduction rate greatly depends on the ligand structure surrounding the Fe ions, with negatively charged ligands leading to a dramatically reduced photoreduction rate. This opens the possibility of tailoring such polyoxometalates by X-ray spectroscopic studies and also for potential applications in the field of X-ray induced photochemistry.
authors: Institute of Solid State Physics, Ulm University, Albert-Einstein-Allee 11, 89069 Ulm, Germany. kkuepper@uos.de
authors: Karsten
authors: K
authors: Kuepper
authors: Christine
authors: C
authors: Derks
authors: Christian
authors: C
authors: Taubitz
authors: Manuel
authors: M
authors: Prinz
authors: Loïc
authors: L
authors: Joly
authors: Jean-Paul
authors: JP
authors: Kappler
authors: Andrei
authors: A
authors: Postnikov
authors: Wanli
authors: W
authors: Yang
authors: Tatyana V
authors: TV
authors: Kuznetsova
authors: Ulf
authors: U
authors: Wiedwald
authors: Paul
authors: P
authors: Ziemann
authors: Manfred
authors: M
authors: Neumann