1. Institute of Organic Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, D-06120 Halle, Germany.
2. Institute of Physical Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, D-06120 Halle, Germany.
3. Department of Engineering Materials and Centre for Molecular Materials, University of Sheffield, Sheffield S1 3JD, UK.