1. a Martin Luther University Halle-Wittenberg, Institute of Organic Chemistry , Kurt-Mothes-Straße 2, D-06120 Halle (Saale)
2. b Martin Luther University Halle-Wittenberg, Institute of Organic Chemistry , Kurt-Mothes-Straße 2, D-06120 Halle (Saale)
3. c Institute of Physical Chemistry , Mühlpforte 1, D-06108 Halle (Saale), Federal Republic of Germany
4. d Institute of Physical Chemistry , Mühlpforte 1, D-06108 Halle (Saale), Federal Republic of Germany