1. Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, Germany
2. DESY Photon Science, Notkestr. 85, 22607 Hamburg, Germany
3. Department of Inorganic Chemistry, University of Yaoundé I, P. O. Box 812, Yaoundé, Cameroon