1. Contribution from the Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 8, D-72076 Tübingen, Germany, Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany, Dipartimento di Fisica and Istituto Nazionale di Fisica della Materia, Università degli Studi di Cagliari, I-09042 Monserrato (CA), Italy, Laboratory for Chemistry of Novel Materials, Center for Research in Molecular Electronics and Photonics, University...