1. GKSS Research Centre, Max Planck Str., D-21502 Geesthacht, Germany; Physical Chemistry II, RWTH Aachen University, Templergraben 59, D-52056 Aachen, Germany; Institute of Organic Chemistry, Organic and Macromolecular Chemistry, Johannes-Gutenberg-University Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany; and Chemistry Department, Konstanz University, Universitätsstr. 10, D-78457 Konstanz, Germany