1. Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85748 Garching, Germany
2. Felix Bloch Institute for Solid State Physics, University Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
3. Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Via G. Quarello 15, I-10135 and Via P. Giuria 7, I-10125 Torino, Italy