1. 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, Department of Theoretical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden, and Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, Prague 6, Czech Republic