1. Beijing National Laboratory for Molecular Sciences, Organic Solid Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China, The Center for Advanced Polymers and Materials Chemistry, Department of Chemistry, Drexel University, Philadelphia, Pennsylvania 19104, and Laboratory of Extreme Conditions Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, People's Republic of China