1. C & C Research Laboratories, Hwasung 445-970, Korea, Department of Chemistry and School of Molecular Science, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea, Department of Chemistry, Dankook University, Seoul 140-714, Korea, School of Chemistry, Seoul National University, Seoul 151-742, Korea, and Department of Chemistry, Dankook University, Cheonan 330-714, Korea