1. College of Pharmaceutical Sciences and Innovative Drug Research Centre; Chongqing University; 55 Daxuecheng South Rd., Shapingba Chongqing 401331 P. R. China
2. Department of Chemistry; BioScience Research Collaborative; Rice University; 6500 Main Street Houston TX 77030 USA
3. College of Chemistry and Chemical Engineering; Chongqing University; 55 Daxuecheng South Rd., Shapingba Chongqing 400030 P. R. China