1. Department
of Chemistry, Shantou University, Guangdong 515063, P. R. China
2. Department
of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States
3. Graduate
School of EEWS (WCU), KAIST, 373-1, Guseng Dong, Yuseong Gu, Daejeon 305-701, Republic of Korea
4. Department
of Chemistry, University of California—Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, United States