1. Department of Chemistry; University of Basel; St. Johanns-Ring 19 CH-4056 Basel Switzerland
2. IBM Research - Zurich; Säumerstrasse 4 CH-8803 Rüschlikon Switzerland
3. Institute for Nanotechnology (INT); Karlsruhe Institute of Technology (KIT); P. O. Box 3640 D-76021 Karlsruhe Germany
4. Lehn Institute of Functional Materials (LIFM); School of Chemistry; Sun Yat-Sen University (SYSU); Guangzhou 510275 China