1. Contribution from the Department of Chemistry, Department of Electrical and Computer Engineering, Department of Materials Science and Engineering, and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113, and Laboratoire de Physique du Solide, Ecole Supérieure de Physique et Chimie Industrielles de la Ville de Paris, CNRS UPR 5, 75321 Paris Cedex 5, France