1. Paul Scherrer Institute, Division of Radiopharmacy, CH-5232 Villigen/Switzerland
2. Universität Zürich, Institute of Inorganic Chemistry, CH-8057 Zürich/Switzerland
3. University of Tübingen, Institute of Inorganic Chemistry, D-72076 Tübingen/Germany
4. Oak Ridge National Laboratory, Health Sciences Research Division, Oak Ridge TN 37831