1. Key Laboratory of Medicinal Chemistry and Molecular Diagnosis (Ministry of Education), Key Laboratory of Analytical Science and Technology of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, P.R. China
2. Department of Chemistry, Taiyuan Normal University, Jinzhong 030619, P.R. China
3. Department of Chemistry, Tianjin University, Tianjin 300072, P.R. China