1. National & Local Joint Engineering Laboratory for New Petro-Chemical Materials and Fine Utilization of Resources, Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), Key Laboratory of the Assembly and Application of Organic Functional Molecules of Hunan Province, College of Chemistry & Chemical Engineering, Hunan Normal University, No. 36, South Lushan Road, Changsha, Hunan 410081, P.R. China