1. Department of Chemistry, Faculty of Science, Kobe University, Nada, Kobe, 657-8501 Japan, Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739-8526 Japan, and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Honmachi, Kawaguchi, 332-0012, Japan