1. Max Planck Institute
for Polymer Research, D-55128 Mainz, Germany
2. Institute
of Organic Chemistry, Johannes Gutenberg-University Mainz, D-55099 Mainz, Germany
3. Institut
für Chemie neuer Materialien, Universität Osnabrück, D-49069 Osnabrück, Germany
4. Department
of Physics, University of Ioannina, P.O. Box 1186, 451 10 Ioannina, Greece