1. Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, Département de Recherche Fondamentale sur la Matière Condensée/SCIB, Laboratoire de Chimie de Coordination (URA CNRS 1194), CEA-Grenoble, 38054 Grenoble, France, and Departments of Physics, Knox College, Galesburg, Illinois 61401, and University of Illinois, Urbana, Illinois 61801