1. Mads Clausen Institute, NanoSYD, University of Southern Denmark, Alsion 2, DK-6400 Sønderborg, Denmark, Institute of Pure and Applied Chemistry, University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany, and Kekulé-Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, D-53121 Bonn, Germany