1. Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus, Institut Néel, CNRS/UJF, BP 166, 25 Avenue des Martyrs, 38042 Grenoble, Cedex 9, France, and Department of Chemistry, University of South Florida, Tampa, Florida 33620