1. Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, H-6701 Szeged, P.O. Box 440, Hungary, Biocoordinaton Chemistry Research Group of the Hungarian Academy of Sciences, University of Szeged, H-6701 Szeged, PO Box 440, Hungary, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark, and Department of Natural Sciences, IGV, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark