1. Department of Chemistry, University of Patras, 26504 Patras, Greece, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Institute of Materials Science, NCSR “Demokritos”, 15310 Aghia Paraskevi Attikis, Greece, and Laboratoire Louis Néel-CNRS, 38042 Grenoble, Cedex 9, France