1. Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
2. School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
3. Beijing Huiwen Middle School, Beijing 100061, P. R. China
4. X-ray Laboratory, China University of Geoscience, Beijing 100083, P. R. China