1. Department of Chemistry, AC II, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany, Materials Division, University of Ulm, Albert-Einstein-Allee 47, D-89081 Ulm, Germany, and Institute of Organic Chemistry, University of Erlangen-Nürnberg, Henkestrasse 42, D-91054 Erlangen, Germany