1. School of Chemistry and Chemical Engineering Shanxi University; Taiyuan 030006 P. R. China
2. Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences; Beijing 100190 P. R. China
3. Departments of Chemistry & Biochemistry and Materials; Center for Polymers and Organic Solids; University of California; Santa Barbara CA 93106-9510 USA