1. Forschungszentrum Karlsruhe, IBG, POB 3640, 76021 Karlsruhe, Germany, National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, Department of Chemistry and Biochemistry, Institute of Biophysics, Florida State University, Tallahassee, Florida 32306, and Institut für Organische Chemie, University of Karlsruhe, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany