1. Contribution from the Department of Chemistry and Biochemistry-0358, University of California at San Diego, La Jolla, California 92093-0358, Department of Physics, University of California at San Diego, La Jolla, California 92093, Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, 32310, and Department of Chemistry, Indiana University, Bloomington, Indiana 47405-4001