1. Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
2. US DOE Ames Laboratory, Ames, Iowa 50011, United States
3. Univ Lyon, ENS Lyon, Université Lyon 1, CNRS, High-Field NMR Center of Lyon, FRE 2034, F-69100 Villeurbanne, France
4. Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
5. Department of Organic Chemistry, University of Geneva, 1211 Geneva, Switzerland
6. Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland