1. Department of Chemistry Innovative Drug Research Center Shanghai University Shanghai 200444 P. R. China
2. Qianweichang College Shanghai University Shanghai 200444 P. R. China
3. Laboratory for Microstructures and Instrumental Analysis and Research Center Shanghai University Shanghai 200444 P. R. China
4. Key Laboratory of Organofluorine Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032 P. R. China