1. Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Department of Molecular Physics, Wageningen Agricultural University, and Wageningen NMR Center, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands, Department of Chemistry, University of Tennessee, Knoxville, Tennessee, 37996-1600, and Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tenneesee 37831