1. Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, Physical Chemistry Institute, Zurich University, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland, and Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, and Center for Biomolecules and Complex Molecular Systems, Flemingovo nám. 2, 16610 Prague 6, Czech Republic