1. Department of Chemistry, Chungnam National University, Taejon 305-764, Korea, Center for Molecular Science, 373-1 Kusung-dong, Yusung-gu, Taejon 305-701, Korea, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea, Agency for Defence Development, Taejon 305-600, Korea, and Department of Industrial Chemistry, Kyungpook National University, Taegu 702-701, Korea