1. Laboratory of Inorganic Chemistry and Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands, Hahn-Meitner Institut, Abteilung Solare Energetik, Glienicker Strasse 100, D-14109 Berlin, Germany, and Debye Institute, Utrecht University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands