1. Department of Chemistry, North Carolina Agricultural and Technical State University, Greensboro, North Carolina 27411, United States
2. Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
3. Department of Chemistry, Capital Normal University, Beijing 100048, China
4. Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
5. Department of Chemistry, Drexel University, Philadelphia, Pennsylvania 19104, United States