1. Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
2. US DOE Ames Laboratory, Ames, Iowa 50011, United States
3. Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
4. Univ Lyon, ENS Lyon, Université Lyon 1, CNRS, High-Field NMR Center of Lyon, UMR 5082, F-69100 Villeurbanne, France