1. Contribution from the Institute of Chemistry and The Farkas Center for Light-Induced Processes, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, FR 11.2 Organische Chemie, Universität des Saarlandes, 66041 Saarbrücken, Germany, and Engler-Bunte Institut der Universität Karlsruhe, 76128 Karlsruhe, Germany