1. Contribution from the Department of Chemistry, University of Florida, Gainesville, Florida 32611, Department of Physics, University of Florida, Gainesville, Florida 32611, Department of Chemistry and Biochemistry, and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, and Laboratoire Louis Néel-CNRS, BP 166, 25 Avenue des Martyrs, 38042, Grenoble, Cedex 9, France