1. Center for Materials Research (ZfM), Justus-Liebig-University Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
2. Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
3. Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, Universitätsstr. 30, D-95440 Bayreuth, Germany
4. Institute of Experimental Physics I, Justus Liebig University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany