1. Zernike Institute for Advanced Materials, Nijenborgh 4, 9747AG Groningen (The Netherlands), Fax: (+31) 503637208
2. Current Address: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart (Germany)
3. Chair of Organic Chemistry 1, Department of Chemistry and Pharmacy, University of Erlangen‐Nürnberg, Henkestrasse 42, 91054 Erlangen (Germany), Fax: (+49) 9131‐8526865
4. Department of Physics, University of Central Florida, Orlando, Florida 32816 (USA)