1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Material Chemistry and Application, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
2. Department of Chemistry and Key Laboratory of Organic Optoelectronics & Molecular Engineering of the Ministry of Education, Tsinghua University, Beijing 100084, P. R. China
3. Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
4. Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA