1. Department of Chemistry, Faculty of Science, University of Kragujevac, R. Domanovića 12, P. O. Box 60, 34000 Kragujevac, Serbia, Fax: +381‐34335040
2. Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen‐Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany, Fax: +49‐9131‐8527387