1. Institut für Physikalische und Theoretische Chemie der J.W. Goethe-Universität Frankfurt, Marie-Curie-Strasse 11, 60439 Frankfurt am Main, Germany, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic, J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic, and Center for Complex Molecular Systems and Biomolecules, 182 23 Prague 8, Czech Republic