1. Key laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, No. 2 North first Street, Zhongguancun, Beijing 100190, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Department of Chemistry, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan