1. Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
2. Department of Chemistry, Ludwig-Maximilians-Universität München. Butenandtstrasse 5−13, Haus D 81377 München, Germany
3. Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany
4. Magnetic Resonance Imaging Research Center, Auburn University, Auburn, Alabama 36849, United States