1. Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, D-45141, Essen, Germany
2. EPR Research Group, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, Mülheim an der Ruhr, D-45470, Germany
3. Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Carl-Benz-Straße 199, 47057 Duisburg, Germany