1. Key Laboratory of Environmentally Friendly Chemistry of the Ministry of Education; College of Chemistry; Xiangtan University; 411105 Xiangtan Hunan P. R. China
2. CAS Key Laboratory of Molecular Recognition and Function; CAS Research/Education Center for Excellence in Molecular Sciences; Institute of Chemistry; Chinese Academy of Sciences (CAS), and University of Chinese Academy of Sciences; 100190 Beijing P. R. China