1. Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstraße 4+6, D-53115 Bonn, Germany
2. Kekulé-Institut für Organische Chemie und Biochemie, University of Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
3. Department of Physical Chemistry, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary